Seminar Topics

The Loop Emulation Sevice for Public Switch Telephone Network

2008-08-04T21:29:00.001-07:00

It is a protocol that supports the delivery of POTS over the loop emulation service which helps to convey analog supervisory signaling states is commonly used by IWFs (interworking functions to support CCS ( Common Chanel Signalling). To avoid the signaling analog line states this protocol uses the simiar message set as the V5-PSTN (ETSI EN 300/324-1) thus covering the risk due to the variations seen in individual national implementation of analog POTS

FLUORESCENT MULTILAYER DISC (FMD)

2008-08-04T21:09:00.000-07:00

Today the need for digital storage capacity is on increase, with a rate growth of 60% per annum. There is strong requirement for more storage facility for the amenities like the storage area networks, data warehouses, supercomputers and e-commerce related data mining as the volume of data to be processed is ever rising. The arrival of high bandwidth Internet and data-intensive applications such as high-definition TV (HDTV) and video & music on-demand, even smaller devices such as personal VCRs, PDAs, mobile phones etc will require multi-gigabyte and terabyte capacity in the next couple of years. This ever-increasing capacity demand can only be only managed by the steady increase in the areal density of the magnetic and optical recording media. In future, this density increase is feasible only by taking advantage of the shorter wavelength lasers, higher lens numerical aperture (NA) or by employing near-field techniques. This increase is best achieved with optical memory technologies. Fluorescent multiplayer disc (FMD) is a three dimensional storage that can store a large volume of data and is also capable of increasing the capacity of a given volume with an aim to achieve a cubic storage element having the dimensions of writing or reading laser wavelength. The current wavelength of 650 Âµm should be sufficient enough to store up to a Terabyte of data.

DIGITAL HUBBUB

2008-07-01T22:47:00.000-07:00

UNDER THE HOOD

This topic brings out the elements which makes up digital hubbub. Just like a personal computer it also got a hardware side and a software side.

HARDWARE
At the core of a home entertainment hub are
Central Processing Unit
Digital signal processing chips
Hard disk drive
Universal serial bus port
PCMCIA connector
Ethernet jack
All these components are shown in the figure ( page )

· Central processing unit :- As in a computer system , CPU is the master of the hub. It deals with the data transfer that takes between different peripherals and hub. It checks on the parallel operations taking place in hub. It enroutes data packages to different operating units. t receives signals regarding the function to be done from the control panel or from a remote control Functions are like recording a video or writing an MP3 in a CD or retrieving the stored data. Based on the received signal the central processing unit generate signals which control other peripherals to perform the concerned operation.

· Digital signal processing chips :- The analog signals from various peripherals like a tv set or a tape recorder is received by analog to digital convertors . These digitized data is accessed by digital signal processing chips via their serial ports. These data streams are compressed for storage .For displays these stop data is expanded by the same digital signal processing chips. This processor has parallel operating functional units and this help in real time processing of data .

· Hard Disk Drive :- The hard disk drive is under a direct control of CPU via disk controller. As in any device a hard disk drive is used to store the data .The compressed data from the digital signal processing chips is written onto the hard disk drive and for displays the same data is accessed via CPU. It will require a capacity of several giga bytes even more than a 20 GB because a good video require a giga byte for an hour and good audio needs about a megabyte a minute.

· Universal Serial Bus (USB) :- The USB is a synchronous protocol that supports isochronous and asynchronous data and messaging transfers. This universal serial bus port is used to communicate data with portable MP3 music players , digital cameras etc.

· Personal Computer Memory card International Association (PCMCIA) :- PCMCIA cards are credit card size adapters which fit into PCMCIA slots found in most handheld and laptop computers. In order to fit into these small size drives, PCMCIA cards must meet very strict physical requirements. It is used in transferring data with non volatile memory cards or other devices.

· Ethernet Jack :- Hub requires communication with other personal computers as in a local area network.. Ethernet jack is the hardware used for the above said interface.

a magnifying look on

· dsp processor
· usb
· pcmcia

A436 PARALLEL VIDEO DSP CHIP
Features
· Overview
o Highly optimized and efficient, general purpose, very high performance, 512b advanced imaging parallel DSP and 32b RISC processor (no MMU) in a single chip in a single instruction stream
o Performance of 50,000 RISC MIPS for motion estimation and 3 billion MACS with only 100 MHz CPU clock
o Achieves very high performance with moderate CPU clock rate and main-stream fabrication
o Fully C software-programmable, parallel image processor optimized for real-time image/video processing/compression and RTOS
o Much faster, more efficient and easier to understand, optimize and use than other fast DSPs
o Directly software programmable in C as universal compressor (encoder)/decompressor (decoder) for multi-format, standards-based or proprietary image/video compression / streaming / decompression
o Provides fully software programmable video compression in real-time
o Provides powerful, flexible, fully software programmable, autonomous "smart" cameras that "watch" images themselves so people don't have to, providing "scene content analysis"
o Enhanced version (fourth generation Ax36 core) of proven A236 Video DSP Chip
o Scaled-down and reduced pin-count versions can be built on demand to satisfy less demanding applications requiring even-lower price points
· Easy to program - use C not microcode!
o Full software development environment includes C compiler, assembler, linker, loader, simulator and debugger
o Develop code using our parallel-enhanced ANSI-standard C compiler with assembly language output
o Simple parallel programming model supports parallel operations on structures using embedded parallel data types
o Use C for what it was intended for -- to provide tight control of the code generated
o You are in control - no need to embed assembly language in C programs or rely on precompiled subroutine libraries
o Evaluation board and evaluation "smart" camera board integrated with software development environment
o Supports modular development, licensing and protection of code by third-parties
o Open architecture with simple pipeline so efficient code can be written easily
o Simple but powerful 32b instruction set provides quick interrupt response time
o Tools automatically pack two scalar instructions into one 32b word when no parallel processing is needed, further reducing program size
o Three internal DMA controllers automatically build circular, multi-frame image/video buffers with programmable sizes in memory, providing a standardized format for video capture, processing and display
o uCLinux RTOS with TCP/IP and UDP/IP for Internet connectivity, and file system and device drivers (video input/output, IDE, USB, ethernet, PCMCIA)
· Very high useful performance (figures @ 100 MHz CPU clock)
o 32, 8b x 16b, or 16b x 16b, multiply-adds per CPU clock with 32b accumulation (3.2B MACS)
o 32 histogram, table look-up or zero-detection operations per CPU clock
o 32 x 16b, or 64 x 8b, plus one 32b, ALU operations per CPU clock
o 32 x 32b bit-realignment and 32 x 16b storage operations per CPU clock
o 64-point motion-estimation / pattern matching operation per CPU clock (50,000 RISC MIPS)
o Eight 4-point matrix-vector multiplies or convolutions per CPU clock (3.2B MACS)
o Four pairs of convolutions per CPU clock for implementing wavelets (3.2B MACS)
o 66 or 100 MHz CPU clock, and 100 or 133 MHz SDRAM clock
· Enhanced ports for imaging, multimedia and device control
o Three independent, asynchronously clocked, glueless, video-aware and packet capable, double-buffered parallel DMA ports, each data path is programmable as 8- or 16-bits wide, has video sync signals and supports live digitized video input or output, including all video buffering required, and also enable multiple A436's to work together for even higher performance
o Able to receive images from up to four image sensors, and produce a video output from them, simultaneously
o Able to provide high speed refresh to video output devices including video encoder chips, and field sequential color LCD microdisplays
o Bit-Programmable I/O port has 8 bit-programmable I/O pins for interface to switches, actuators, keypad and other devices; interrupts are fully programmable

o Buffered, full-duplex, Stereo Audio DMA Port provides handles 4-, 8- and 16-bit samples in little-endian and big-endian formats
o Buffered, full-duplex, programmable 2-wire/3-wire, Serial DMA Port controls/accesses external low speed and high speed devices including image sensors, video encoders and decoders, serial EEPROMs and flash memory cards
o Supports two video encoder/decoder chips and two audio CODECs simultaneously
o Two UART ports are fully programmable
o Two programmable interrupt timers
o Real time clock and CPU clock counter
o Internal debug device provides a built-in logic analyzer with trace capability for program debugging
o 32 MB address space; memory configuration is dynamically specified at boot-up
o Memory interface provides clock to SDRAM
o 5v-tolerant I/O and 3.3v SDRAM interface
USB BUS
The motivation behind the selection of USB for the Macintosh architecture is simple.
USB is a low-cost, high-speed peripheral expansion architecture that provides data transfer rates up to 12 Mbps.
The USB is a synchronous protocol that supports isochronous and asynchronous data and messaging transfers.
USB provides considerably faster data throughput for devices than does the Apple Desktop Bus (ADB) and the Macintosh modem and printer ports. This makes USB an excellent replacement solution for not only the existing slower RS-422 serial channels in the Macintosh today, but also the Apple Desktop Bus, and in some cases slower speed SCSI devices.
In addition to the obvious performance advantages, USB devices are hot pluggable and as such provide a true plug and play experience for computer users. USB devices can be plugged into and unplugged from the USB anytime without having to restart the system. The appropriate USB device drivers are dynamically loaded and unloaded as necessary by the Macintosh USB system software components to support hot plugging.

Better Device Expansion Model
The USB specification includes support for up to 127 simultaneously available devices on a single computer system. (One device is taken by the root hub.) To connect and use USB devices, it isn't necessary to open up the system and add additional expansion cards. Device expansion is accomplished with the addition of external USB multiport hubs. Hubs can also imbedded in USB devices like keyboards and monitors which provides device expansion in much the same way that the Apple Desktop Bus (ADB) is extended for the addition of a mouse through the keyboard or monitor. However, the USB implementation won't have the device expansion or speed limitations that ADB does.

Compact Connectors and Cables
USB devices utilize a compact 4-pin connector rather than the larger 8- to 25-pin connectors typically found on RS-232 and RS-422 serial devices. This results in smaller cables with less bulk. The compact USB connector provides two pins for power and two for data I/O. Power on the cable relieves hardware manufacturers of low-power USB devices from having to develop both a peripheral device and an external power supply, thereby reducing the cost of USB peripheral devices for manufacturers and consumers.

PCMCIA
Founded in 1990, the Personal Computer Memory Card International Association (PCMCIA), of which Quatech is a member, developed a set of standards by which additional memory could be added to portable systems. It soon became apparent that this same interface could be used to add I/O devices and hard disk drives as well, thereby dramatically increasing functionality of laptop computers.
Physical Characteristics
The PCMCIA specification 2.0 release in 1991 added protocols for I/O devices and hard disks. The 2.1 release in 1993 refined these specifications, and is the standard around which PCMCIA cards are built today.
PCMCIA cards are credit card size adapters which fit into PCMCIA slots found in most handheld and laptop computers. In order to fit into these small size drives, PCMCIA cards must meet very strict physical requirements as shown in Figure 6 below. There are three types of PCMCIA cards, Type I generally used for memory cards such as FLASH and STATIC RAM; Type II used for I/O peripherals such as serial adapters, parallel adapters, and fax-modems (this is the type of card Quatech manufactures); and Type III which are used for rotating media such as hard disks. The only difference in the physical specification for these cards is thickness.
.

SOFTWARE
As in a normal personal computer software checks on user interface , applications etc . Software of digital hubbub can be considered as a series of layers. In the innermost is an operating system that manages resources such as storage or CPU timing . The next layer is the middle ware that handles such house keeping details as displaying text and graphics on TV screens. The middleware interpret the input from different panel or remote control and it enables the CPU to generate signals according to the concerned function. It also deals with the communication with the cable that supplies the digital video and data strings . The outermost layer handles several applications .These applications includes recording controls program guides and onscreen signup for additional services and games and even web browsers. It provides a search engine that with only a few button pushes could find all movie musical starring, for instance Elvis Presley, or action dramas with Jackiechan, or new episodes of your favourite home improvement show.Software for digital hubbub is provided by mediabolic Inc (SAN FRANCISCO).

MIDDLE
WARE
INNER MOST LAYER
OUTER
LAYER
SOFTWARE

NEOLOGISM IN DIGITAL HUBBUB
As far as an electronic component market is considered the success of a product relies on the compactness and cheapness of the product. As any electronic device digital hubbub is also required to be compact and cheap. Compactness is brought about by implementing chips with multi-functions or in other way it can be said as compactness can be brought by merging 2 or 3 chips to do a single function. There fore several electronics firm are doing lot of research and development to bring about a much compact and cheap digital hubbub. A few affords to make the digital hubbub compact and cheap as illustrated below.
In April, Conexant Systems Inc. (Newport Beach, Calif., formerly Rockwell Semiconductor Systems) announced a chip that combines digital TV reception with a cable modem. It lets cable operators sell broadband interactive services in a low-cost package that includes 100-plus TV channels.
In another effort, Cirrus Logic Inc. (Austin, Texas) has among its chips a combined DVD and digital-video chipset that powers Samsung's PVR. And on the computercentric side, there's Linksys Group Inc. (Irvine, Calif.). Best known for its pocket routers (units that connect small home or office networks to the Internet), it has a new chip that combines routing circuitry with a cable modem and a wireless network access point. Such a chip could be built into a stand-alone digital hub or slotted into a PC acting as a home server.
Still, how do engineers cram what used to be thousands of dollars worth of video and computer equipment into an under-$500 box? By designing chips to do multiple duty, points out Anthony Simon, director of marketing for chip maker Conexant. For example, adding cable-modem functions to a video chip cuts between $20 and $40 from the cost of a set-top box.
And at PVR maker TiVo Inc. (Alviso, Calif.), product marketing director Ted Malone is proud of the subtle economies the company engineered into its custom disk-controller chip. The chip can read data streams from the disk surface in whatever order is most efficient for the head and then reassemble the information before handing it off to the video section.
Meanwhile, the price of hard-disk drives has put enormous volumes of storage within reach of even a run-of-the-mill set-top box. Currently, a 40-GB drive, which stores more than 50 hours of video, sells for about $80 retail and much less wholesale. Even a small fraction of that disk space can store dozens of hours of audio and thousands of digital photos
The evolving interface

A first step is an interface like TiVo’s where you peck out the name of the show on a virtual on- screen board: as you type each letter, an adjacent display of potential matching titles gets shorter until only a few choices remain. Once the right show is found,recording its eposides is a matter of pressing just a button or two.
Mox is simplifying matters further by mapping the letters most likely to be typed next to the numbers 1 through 9 on the remote’s keypad. Typing text on a numeric keypad will be familiar to the millions of people who send text messages by cellular phone.

Dream versus reality
Any build-up to a single home gateway that controls your television, air conditioning, and e-mail will not come overnight, according to Jakob Nielsen. People won't replace their VCR, DVD player, and home network all at once, he points out.
Thus far, barring a few exceptions such as "universal" remote controls and serial control inputs for some cable boxes, manufacturers still seem focused on locking consumers into a single supplier. Whether that philosophy can stand up to the ultimate purpose of a digital hub—connecting all the disparate entertainment devices a consumer may own and even replacing some of them—is probably the crucial question for the evolution of this new technology

REFERENCES

1. WWW.SPECTRUM.IEEE.ORG/DIGITAL HUBBUB
2. Www.oxfordmicrodevices.com/A436_summary.html
.FEATURES
3. IEEE SPECTRUM MAGAZINE JULY 2002

Aspect Oriented Programming

2008-07-01T22:41:00.000-07:00

Introduction

“A project's efficiency increases if all the concerns are well modularized”
- Law of Demeter

Object-oriented programming (OOP) has been presented as a technology that can fundamentally aid software engineering, because the underlying object model provides a better fit with real domain problems. However most software systems consist of several concerns that crosscut multiple modules. Object-oriented techniques for implementing such concerns result in systems that are invasive to implement, tough to understand, and difficult to evolve. This forces the implementation of those design decisions to be scattered throughout the code, resulting in “tangled” code that is excessively difficult to develop and maintain. The new aspect-oriented programming (AOP) methodology facilitates modularization of crosscutting concerns. Using AOP, you can create implementations that are easier to design, understand, and maintain. Further, AOP promises higher productivity, improved quality, and better ability to implement newer features.

Evolution of the software process

Software design processes and programming languages exist in a mutually supporting relationship. Design processes break a system down into smaller and smaller units. Programming languages provide mechanisms that allow the programmer to define abstractions of system sub-units, and then compose those abstractions in different ways to produce the overall system. A design process and a programming language work well together when the programming language provides abstraction and composition mechanisms that cleanly support the kinds of units the design process breaks the system into.
In the early days of computer science, developers wrote programs by means of direct machine-level coding. Unfortunately, programmers spent more time thinking about a particular machine's instruction set than the problem at hand. Slowly, we migrated to higher-level languages that allowed some abstraction of the underlying machine. Then came structured languages; we could now decompose our problems in terms of the procedures necessary to perform our tasks. However, as complexity grew, we needed better techniques. Object-oriented programming (OOP) let us view a system as a set of collaborating objects. Classes allow us to hide implementation details beneath interfaces. Polymorphism provided a common behavior and interface for related concepts, and allowed more specialized components to change a particular behavior without needing access to the implementation of base concepts.

Programming methodologies and languages define the way we communicate with machines. Each new methodology presents new ways to decompose problems: machine code, machine-independent code, procedures, classes, and so on. Each new methodology allowed a more natural mapping of system requirements to programming constructs. Evolution of these programming methodologies let us create systems with ever increasing complexity. The converse of this fact may be equally true: we allowed the existence of ever more complex systems because these techniques permitted us to deal with that complexity.
Currently, OOP serves as the methodology of choice for most new software development projects. Indeed, OOP has shown its strength when it comes to modeling common behavior. However, as we will see shortly, and as you may have already experienced, OOP does not adequately address behaviors that span over many -- often unrelated -- modules. In contrast, AOP methodology fills this void. AOP quite possibly represents the next big step in the evolution of programming methodologies.

What is a concern

A concern is a particular goal, concept, or area of interest. In technology terms, a typical software system comprises several core and system-level concerns. For example, a credit card processing system's core concern would process payments, while its system-level concerns would handle logging, transaction integrity, authentication, security, performance, and so on. Many such concerns -- known as crosscutting concerns -- tend to affect multiple implementation modules. Using current programming methodologies, crosscutting concerns span over multiple modules, resulting in systems that are harder to design, understand, implement, and evolve.

Aspect-oriented programming (AOP) separates concerns better than previous methodologies, thereby providing modularization of crosscutting concerns.

Crosscutting concern problems
Although crosscutting concerns span over many modules, current implementation techniques tend to implement these requirements using one-dimensional methodologies, forcing implementation mapping for the requirements along a single dimension. That single dimension tends to be the core module-level implementation. The remaining requirements are tagged along this dominant dimension. In other words, the requirement space is an n-dimensional space, whereas the implementation space is one-dimensional. Such a mismatch results in an awkward requirements-to-implementation map.
Symptoms
A few symptoms can indicate a problematic implementation of crosscutting concerns using current methodologies.
Code tangling: Modules in a software system may simultaneously interact with several requirements. For example, oftentimes developers simultaneously think about business logic, performance, synchronization, logging, and security. Such a multitude of requirements results in the simultaneous presence of elements from each concern's implementation, resulting in code tangling.
Code scattering: Since crosscutting concerns, by definition, spread over many modules, related implementations also spread over all those modules. For example, in a system using a database, performance concerns may affect all the modules accessing the database.
Implications
Combined, code tangling and code scattering affect software design and developments in many ways:
Poor traceability: Simultaneously implementing several concerns obscures the correspondence between a concern and its implementation, resulting in a poor mapping between the two.
Lower productivity: Simultaneous implementation of multiple concerns shifts the developer's focus from the main concern to the peripheral concerns, leading to lower productivity.
Less code reuse: Since, under these circumstances, a module implements multiple concerns, other systems requiring similar functionality may not be able to readily use the module, further lowering productivity.
Poor code quality: Code tangling produces code with hidden problems. Moreover, by targeting too many concerns at once, one or more of those concerns will not receive enough attention.
More difficult evolution: A limited view and constrained resources often produce a design that addresses only current concerns. Addressing future requirements often requires reworking the implementation. Since the implementation is not modularized, that means touching many modules. Modifying each subsystem for such changes can lead to inconsistencies. It also requires considerable testing effort to ensure that such implementation changes have not caused .

The current response
Since most systems include crosscutting concerns, it's no surprise that a few techniques have emerged to modularize their implementation. Such techniques include mix-in classes, design patterns, and domain-specific solutions.
With mix-in classes, for example, you can defer a concern's final implementation. The primary class contains a mix-in class instance and allows the system's other parts to set that instance. For example, in a credit card processing example, the class implementing business logic composes a logger mix-in. Another part of the system could set this logger to get the appropriate logging type. For example, the logger could be set to log using a filesystem or messaging middleware. Although the nature of logging is now deferred, the composer nevertheless contains code to invoke logging operations at all log points and controls the logging information.
Behavioral design patterns, like Visitor and Template Method, let you defer implementation. However, just as in case with mix-ins, the control of the operation -- invoking visiting logic or invoking template methods -- stays with the main classes.
Domain-specific solutions, such as frameworks and application servers, let developers address some crosscutting concerns in a modularized way. The Enterprise JavaBeans (EJB) architecture, for example, addresses crosscutting concerns such as security, administration, performance, and container-managed persistence. Bean developers focus on the business logic, while the deployment developers focus on deployment issues, such as bean-data mapping to a database. The bean developer remains, for the most part, oblivious to the storage issues. In this case, you implement the crosscutting concern of persistence using an XML-based mapping descriptor.
The domain-specific solution offers a specialized mechanism for solving the specific problem. As a downside to domain-specific solutions, developers must learn new techniques for each such solution. Further, because these solutions are domain specific, the crosscutting concerns not directly addressed require an ad hoc response
The architect's dilemma
Good system architecture considers present and future requirements to avoid a patchy-looking implementation. Therein lies a problem, however. Predicting the future is a difficult task. If you miss future crosscutting requirements, you'll need to change, or possibly reimplement, many parts of the system. On the other hand, focusing too much on low-probability requirements can lead to an overdesigned, confusing, bloated system. Thus a dilemma for system architects: How much design is too much? Should I lean towards underdesign or overdesign?
In summary, the architect seldom knows every possible concern the system may need to address. Even for requirements known beforehand, the specifics needed to create an implementation may not be fully available. Architecture thus faces the under/overdesign dilemma.

The fundamentals of AOP
The scenario so far suggests that it can be helpful to modularize the implementation of crosscutting concerns. Researchers have studied various ways to accomplish that task under the more general topic of "separation of concerns." AOP represents one such method. AOP strives to cleanly separate concerns to overcome the problems discussed above.
AOP, at its core, lets you implement individual concerns in a loosely coupled fashion, and combine these implementations to form the final system. Indeed, AOP creates systems using loosely coupled, modularized implementations of crosscutting concerns. OOP, in contrast, creates systems using loosely coupled, modularized implementations of common concerns. The modularization unit in AOP is called an aspect, just as a common concern's implementation in OOP is called a class.

View the system as a set of concerns

We can view a complex software system as a combined implementation of multiple concerns. A typical system may consist of several kinds of concerns, including business logic, performance, data persistence, logging and debugging, authentication, security, multithread safety, error checking, and so on. You'll also encounter development-process concerns, such as comprehensibility, maintainability, traceability, and evolution ease. Figure 1 illustrates a system as a set of concerns implemented by various modules.
Figure 1. Implementation modules as a set of concerns

Figure 2 presents a set of requirements as a light beam passing through a prism. We pass a requirements light beam through a concern-identifier prism, which separates each concern. The same view also extends towards development-process concerns.
Figure 2. Concern decomposition: The prism analogy

Crosscutting concerns in a system
A developer creates a system as a response to multiple requirements. We can broadly classify these requirements as core module-level requirements and system-level requirements. Many system-level requirements tend to be orthogonal (mutually independent) to each other and to the module-level requirements. System-level requirements also tend to crosscut many core modules. For example, a typical enterprise application comprises crosscutting concerns such as authentication, logging, resource pooling, administration, performance, and storage management. Each crosscuts several subsystems. For example, a storage-management concern affects every stateful business object.

Development steps in AOP
1. Aspectual decomposition: Decompose the requirements to identify crosscutting and common concerns. Separate module-level concerns from crosscutting system-level concerns.
2. Concern implementation: Implement each concern separately. For the credit card processing example, you'd implement the core credit card processing unit, logging unit, and authentication unit.
3. Aspectual recomposition: In this step, an aspect integrator specifies recomposition rules by creating modularization units -- aspects. The recomposition process, also known as weaving or integrating, uses this information to compose the final system. For the credit card processing example, you'd specify, in a language provided by the AOP implementation, that each operation's start and completion be logged. You would also specify that each operation must clear authentication before it proceeds with the business logic.
AOP development stages
AOP differs most from OOP in the way it addresses crosscutting concerns. With AOP, each concern's implementation remains unaware that other concerns are "aspecting" it. For example, the credit card processing module doesn't know that the other concerns are logging or authenticating its operations. That represents a powerful paradigm shift from OOP.
Weaving example
The weaver, a processor, assembles an individual concern in a process known as weaving. The weaver, in other words, interlaces different execution-logic fragments according to some criteria supplied to it.
To illustrate code weaving, let's consider a our credit card processing system example. For brevity, consider only two operations: credit and debit. Also assume that a suitable logger is available.
Consider the following credit card processing module:
public class CreditCardProcessor { public void debit(CreditCard card, Currency amount) throws InvalidCardException, NotEnoughAmountException, CardExpiredException { // Debiting logic } public void credit(CreditCard card, Currency amount) throws InvalidCardException { // Crediting logic }}
Also, consider the following logging interface:
public interface Logger { public void log(String message);}
The desired composition requires the following weaving rules, expressed here in natural language (a programming language version of these weaving rules is provided later ):
1. Log each public operation's beginning
2. Log each public operation's completion
3. Log any exception thrown by each public operation
The weaver would then use these weaving rules and concern implementations to produce the equivalent of the following composed code:
public class CreditCardProcessorWithLogging { Logger _logger; public void debit(CreditCard card, Money amount) throws InvalidCardException, NotEnoughAmountException, CardExpiredException { _logger.log("Starting CreditCardProcessor.credit(CreditCard,Money) " + "Card: " + card + " Amount: " + amount); // Debiting logic _logger.log("Completing CreditCardProcessor.credit(CreditCard,Money) " + "Card: " + card + " Amount: " + amount); } public void credit(CreditCard card, Money amount) throws InvalidCardException { System.out.println("Debiting"); _logger.log("Starting CreditCardProcessor.debit(CreditCard,Money) " + "Card: " + card + " Amount: " + amount); // Crediting logic _logger.log("Completing CreditCardProcessor.credit(CreditCard,Money) " + "Card: " + card + " Amount: " + amount); }}

Anatomy of AOP languages
Just like any other programming methodology implementation, an AOP implementation consists of two parts: a language specification and an implementation. The language specification describes language constructs and syntax. The language implementation verifies the code's correctness according to the language specification and converts it into a form that the target machine can execute.
The AOP language specification At a higher level, an AOP language specifies two components:
Implementation of concerns: Mapping an individual requirement into code so that a compiler can translate it into executable code. Since implementation of concerns takes the form of specifying procedures, you can to use traditional languages like C, C++, or Java with AOP.
Weaving rules specification: How to compose independently implemented concerns to form the final system. For this purpose, an implementation needs to use or create a language for specifying rules for composing different implementation pieces to form the final system. The language for specifying weaving rules could be an extension of the implementation language, or something entirely different.

AOP language implementation
AOP language compilers perform two logical steps:
1. Combine the individual concerns
2. Convert the resulting information into executable code
An AOP implementation can implement the weaver in various ways, including source-to-source translation. Here, you preprocess source code for individual aspects to produce weaved source code. The AOP compiler then feeds this converted code to the base language compiler to produce final executable code. For instance, using this approach, a Java-based AOP implementation would convert individual aspects first into Java source code, then let the Java compiler convert it into byte code. The same approach can perform weaving at the byte code level; after all, byte code is still a kind of source code. Moreover, the underlying execution system -- a VM implementation, say -- could be aspect aware. Using this approach for Java-based AOP implementation, for example, the VM would load weaving rules first, then apply those rules to subsequently loaded classes. In other words, it could perform just-in-time aspect weaving.

AspectJ: An AOP implementation for Java
AspectJ, a freely available AOP implementation for Java from Xerox PARC, is a general-purpose aspect-oriented Java extension. AspectJ uses Java as the language for implementing individual concerns, and it specifies extensions to Java for weaving rules. These rules are specified in terms of pointcuts, join points, advice, and aspects. Join points define specific points in a program's execution, a pointcut is the language construct that specifies join points, advice defines pieces of an aspect implementation to be executed at pointcuts, and an aspect combines these primitives.
In addition, AspectJ also allows the "aspecting" of other aspects and classes in several ways. Indeed, we can introduce new data members and new methods, as well as declare a class to implement additional base classes and interfaces.
AspectJ's weaver -- an aspect compiler -- combines different aspects together. Because the final system created by the AspectJ compiler is pure Java byte code, it can run on any conforming JVM. AspectJ also features tools such as a debugger and selected IDE integration.
Below an AspectJ implementation of the logging aspect for the weaver described in natural language previously
public aspect LogCreditCardProcessorOperations { Logger logger = new StdoutLogger(); pointcut publicOperation(): execution(public * CreditCardProcessor.*(..)); pointcut publicOperationCardAmountArgs(CreditCard card, Money amount): publicOperation() && args(card, amount); before(CreditCard card, Money amount): publicOperationCardAmountArgs(card, amount) { logOperation("Starting", thisjoin point.getSignature().toString(), card, amount); } after(CreditCard card, Money amount) returning: publicOperationCardAmountArgs(card, amount) { logOperation("Completing", thisjoin point.getSignature().toString(), card, amount); } after (CreditCard card, Money amount) throwing (Exception e): publicOperationCardAmountArgs(card, amount) { logOperation("Exception " + e, thisjoin point.getSignature().toString(), card, amount); } private void logOperation(String status, String operation, CreditCard card, Money amount) { logger.log(status + " " + operation + " Card: " + card + " Amount: " + amount); } }
AOP benefits
AOP helps overcome the aforementioned problems caused by code tangling and code scattering. Here are other specific benefits AOP offers:
Modularized implementation of crosscutting concerns: AOP addresses each concern separately with minimal coupling, resulting in modularized implementations even in the presence of crosscutting concerns. Such an implementation produces a system with less duplicated code. Since each concern's implementation is separate, it also helps reduce code clutter. Further, modularized implementation also results in a system that is easier to understand and maintain.
Easier-to-evolve systems: Since the aspected modules can be unaware of crosscutting concerns, it's easy to add newer functionality by creating new aspects. Further, when you add new modules to a system, the existing aspects crosscut them, helping create a coherent evolution.
Late binding of design decisions: Recall the architect's under/overdesign dilemma. With AOP, an architect can delay making design decisions for future requirements, since she can implement those as separate aspects.
More code reuse: Because AOP implements each aspect as a separate module, each individual module is more loosely coupled. For example, you can use a module interacting with a database in a separate logger aspect with a different logging requirement.
In general, a loosely coupled implementation represents the key to higher code reuse. AOP enables more loosely coupled implementations than OOP.

AOP statistics
1. On reengineering a particular image processing program the following results were obtained

2. In the original FreeBSD v3.3 code, the implementation of prefetching is both scattered and tangled. The code is spread out over approximately 260 lines in 10 clusters in 5 core functions from two subsystems. On using AOP the resulting code was spread over two pages of 50 lines each.

AOP applications
a-kernel is an effort to apply AOP techniques to operating system kernel code.
FACET is a framework for a customizable real-time event channel that uses aspects.
Lasagne is an aspect-oriented architecture for context-sensitive and run-time weaving of aspects--prototypes have been developed in Java and Correlate.
QuO is a middleware framework and toolkit which includes aspect-oriented languages for developing quality of service enabled, adaptive distributed object applications.
SoC+MAS is a research project whose main focus is the application of advanced separation of concerns techniques to handle the complexity of designing and implementing multi-agent OO software.
SADES is a customizable and extensible object database evolution system implemented using AOP techniques

2008-05-05T03:19:00.000-07:00

Chameleon chip (civil)

2008-01-22T22:05:00.000-08:00

Chameleon Systems Inc, San Jose, California is one of the new breed of reconfigurable processor makers who claim that Chameleon chip which is its first Reconfigurable Communications Processor (RCP) is a reconfigurable processor which provides a design environment that allows customer to convert their algorithms to hardware configuration on the fly.

Advantages

1. Early and fast designs
2. Enabling Field upgrades
3. Creating product differentiation for suppliers
4. Creating flexible & adaptive products
5. Reducing power
6. Reducing manufacturing costs
7. Increasing bandwidths

Disadvantages

1. Inertia – Engineers slow to change
2. RCP designs requires comprehensive set of tools
3. 'Learning curve' for designers unfamiliar with reconfigurable logic

Applications

1. Wireless Base stations
2. Packetized voice(VOIP)
3. Digital Subscriber Line(DSL)
4. Software Defined Radio(SDR)

Quantum Dots

2008-01-22T21:35:00.000-08:00

Quantum Dot fabrication techniques for QD diode lasers employ self-organized growth of uniform nanometer-scale islands of InGaAs on the surface of GaAs or InP. Under the proper choice of deposition conditions, a layer of material with a lattice constant different from that of the substrate may spontaneously transform to an array of three-dimensional islands. The size of these islands provides quantization in all three directions making them Quantum Dots.

Diode lasers based on InAs/GaAs Quantum Dots developed by Innolume and Zia Lasers (acquired by Innolume in December 2006) are uniquely positioned to serve silcon photonics as light sources in order to bring optical interconnect technologies to the mainstream computer applications.

Three-dimensional nature of quantization of electrons and holes in these islands provides significantly improved temperature stability of laser output power basic characteristics. Fully temperature independent operation has been demonstrated eliminating the need of expensive control schemes.
QD lasers demonstrate extremely low intensity noise, being an ideal CW source of light for high speed external modulation.
Owing to inhomogeneous broadening caused by size distribution of QDs, the effect of spectral hole burning can be controllably used to form very broad lasing spectrum (>80 nm) with uniform intensity distribution. These broad-band or “white” lasers can be used in WDM silicon photonics systems.
Another effect of broad gain spectrum of QD lasers is very stable mode-locking regime with high peak power, which has been unachievable. Mode-locked laser is a source of clocking in future silicon chips with high clocking frequency enabled by optical clock technology.
The emission range of InGaAs/GaAs QD lasers of 1.064 – 1.31 micrometer fits well the window of transparency of silicon based waveguides.

QD lasers arm Silicon Photonics to deliver cost efficient solutions for future Optical Interconnect and Optical Clock Systems.

Innolume has also developed a wide portfolio of laser

for specific wavelength range between 1.064 and 1.31 micron for medical, sensing and other applications.

Silicon Photonics

2008-01-22T21:33:00.000-08:00

As computing and networking performance continue on their exponential growth track, defined by Moore’s Law, the exponentially increasing communication needs will soon exceed the limits of copper wiring. Communications links, or interconnects, are the biggest bottleneck in networks and computers. For example, the next generation of Ethernet runs at 10 Gb/s, and at this speed electrical signals in copper wires can only travel a small distance before fading out completely.

Optical fiber on the other hand is the ideal medium for communications over most distances. The fiber itself is very cheap, and light travels through it for miles even when launched with tiny amounts of power. Optical fiber also has the capability to carry data at rates up to one thousand times faster than 10Gb/s. At each end of the fiber, an optical transmitter/receiver (“transceiver”) is required to interface to the computer or switch. Unfortunately, these optical transceivers currently are extremely expensive. The typical cost of data communications today runs about $100/Gb/s. As a result, optical fiber communication has been largely confined to the capital-intensive long distance telecommunications infrastructure.

Fortunately, Silicon Photonics technology shows promises of delivering low cost seamless optical connectivity from hundreds of meter distances at the network level all the way down to millimeters distances for inter and intra-chip communication. The cost of Silicon Photonics is expected to reach well under $1/Gb/s, many times cheaper than typical data communication links.
Within 10 years, the established approach of using electricity in copper wiring just won’t work, and the ideal approach of using light in optical fiber is just simply too expensive. Only low cost disruptive technology can tip the balance from copper wiring to fiber optics to allow the computing and networking performance to continue on an exponential growth path. Silicon Photonics can fulfill this role.

Since silicon is not an efficient electrically pumped laser material, most silicon photonic solutions need a steady source, or Continuous Wave (CW), of laser light to power the interconnection. This source can be a typical laser based on III-V substrates such as GaAs and InP. The data transfer from electrical to optical occurs in a modulator, in which a voltage applied to a silicon photonic modulator will change the amount of light transmitted. Similarly, data on a light stream is converted back into an electrical current in a silicon photonic detector. Electronic drivers and receivers on each end of the path help with the signal quality. Finally, for increased total data rate and lower cost, it’s best to have many communication channels combined or wavelength division multiplexed (WDM), onto one fiber or waveguide. These modulator, detector and WDM elements can be integrated together on one Si photonic chip for best performance and lowest cost.

The cost of most silicon photonic devices can be relatively low, like that of silicon electronics. Therefore, the majority of the cost of silicon photonic interconnects will be in the source lasers that must meet tough specifications. These lasers will need to emit high power with low noise at wavelengths that are transparent in Silicon, above 1.1 micrometers. Also, for increased total bandwidth and cost efficiency, a preferred solution would send multiple data channels on multiple wavelengths on one fiber, called wavelength division multiplexing, or WDM. The laser also must operate in a very harsh environment, perhaps from below 0 C to over 100 C.

Innolume’s lasers based on are uniquely qualified to address these needs for silicon photonics.

Quantum cryptography becomes a reality [civil]

2008-01-07T22:53:00.000-08:00

According to reliable sources from NEC, Commercial quantum cryptography, a revolutionary system that can produce quantum keys at a speed of 100Kbit/s and then broadcast it up to 40 kilometres along the commercial fibre optic lines will be available in the markets by the second half of 2005. Speaking in line with Kazuo Nakamura, senior manager of NEC's quantum information technology group at the company's Fundamental and Environmental Research Laboratories, it can be considered as a world record as it is a rare blend of speed and distance. As put by Akio Tajima, the assistant manager at the laboratory, this innovative concept has gone through several improvisations after it was successfully tested in April at the company’s laboratories in Tokyo.

The system permits the users to swap the keys with a prior idea that they have not been disordered up during the transmission. The whole system works on the concept that the system works by implanting the encryption key on photons, which can be either in the receiver end or with an eavesdropper, as the photons cannot be cracked. Akio Tajima said that until last April the round-trip’ quantum cryptography method at NEC where it had a laser as well as a receiver at one end and also a mirror at the other end, faced some troubles regarding the high speed over long distances.

Earlier the detector that turns the photons to electrons once they collide with it functioned very slowly. This created a problem in registering these photons, as there will be an avalanche of electrons with every collision. The team lead by Tajima has rectified that disadvantage now by developing a new detector that can work reliably at 100Kbit/s. This fast pace helps in clearing this whole bunch of electrons produced by the collision from the device, quickly so that they can register the next photon. The NEC scientists have also rectified the problem with the mirror used earlier in the system called the faraday mirror. The performance of this mirror, which can reflect the light in a 90-degree rotation from the input light, changes with temperature leading to quality loss. NEC today has improvised this concept of mirror, by producing a mirror that works efficiently with temperature variations.

Another advantage of NEC system is that it has a conventional laser, which can transmit the photons through the fibre optic cables over a long distance with very less noise. Although there were powerful lasers that could trigger the propagation of photons over long distances, they all resulted in more noises leading to efficiency loss. According to Nakamura 'This is the world's fastest key generation technology at 40 kilometres'. He confirms his statement with various proofs. He said that the University of Geneva has achieved quantum transmission over a distance of over 60 kilometres, but at a much lower speed, while a system developed by Japan's National Institute of Advanced Industrial Science and Technology, a major government laboratory, has achieved nearly the same speed as NEC's system, but only at about half the distance.

According to Toshiyuki Kanoh, chief manager of the company's System Platforms Research Laboratories, this break through system invented in collaboration with the Japan Science and Technology Agency's Exploratory Research for Advanced Technology and Japan's National Institute of Information and Communications Technology, will take an year to be launched in the commercial market as it’s software is still on the developing stage. He also added that they are going to create a commercial market for the system which it lacks now and is expecting the police, banks and financial institutions etc to be it’s clients by the mid of 2005. There is also a move to demonstrate this system in various exhibitions and seminars.

FLUORESCENT MULTILAYER DISC (FMD) [civil]

2008-01-07T22:52:00.001-08:00

Today the need for digital storage capacity is on increase, with a rate growth of 60% per annum. There is strong requirement for more storage facility for the amenities like the storage area networks, data warehouses, supercomputers and e-commerce related data mining as the volume of data to be processed is ever rising. The arrival of high bandwidth Internet and data-intensive applications such as high-definition TV (HDTV) and video & music on-demand, even smaller devices such as personal VCRs, PDAs, mobile phones etc will require multi-gigabyte and terabyte capacity in the next couple of years.

This ever-increasing capacity demand can only be only managed by the steady increase in the areal density of the magnetic and optical recording media. In future, this density increase is feasible only by taking advantage of the shorter wavelength lasers, higher lens numerical aperture (NA) or by employing near-field techniques. This increase is best achieved with optical memory technologies.

Fluorescent multiplayer disc (FMD) is a three dimensional storage that can store a large volume of data and is also capable of increasing the capacity of a given volume with an aim to achieve a cubic storage element having the dimensions of writing or reading laser wavelength. The current wavelength of 650 Âµm should be sufficient enough to store up to a Terabyte of data.

FLUORESCENT MULTILAYER DISC (FMD) [civil]

2008-01-07T22:52:00.000-08:00

ZFS [civil]

2008-01-07T22:51:00.000-08:00

Todays file systems, which the system administrators observe to be always in the verge of data corruption and more over find it extremely difficult to manage due to its slow rate of execution has enabled ZFS to emerge as one of the most powerful file system. Used in Suns Solaris 10 Operating System (Solaris OS), ZFS finds its edge over the other file systems by its unique features of

Cutting short the administrative difficulties by 80 percent by automating and combining complicated storage administration concepts.
It ensures the data integrity and safety of all data with 64-bit checksums that can detect and correct silent data corruption.
It offers more scalability by providing 16 billion times storage of 32 or 64 bit systems.
High performance gains are achieved by using the concept of transactional object model that removes most of the traditional constraints on the order of issuing I/Os.

Smart materials and Smart structures [civil]

2008-01-07T22:49:00.000-08:00

A new generation of materials called smart materials is changing the way a structural system is going to be designed, built and monitored. Advances in composite materials, instrumentation and sensing technology (fiber-optic sensors) in combination with a new generation of actuator systems based on Piezoelectric ceramics and shape Memory Alloys have made this possible.

Shape memory alloys have found applications in a variety of high performance products, ranging from aircraft hydraulic coupling and electrical connectors to surgical suture anchors. Since the material can generate high actuation forces in response to temperature changes, shape memory alloys have the potential to serve as an alternative to solenoids, special significance in the area of smart structures because it offers significant advantages over conventional actuations technologies in number of ways.

Large amounts of recoverable strains offer very high work densities. This is very attractive in situations where the work output to weight ration is critical.
Direct actuation without moving part there by increasing the efficiency.
Large available strains permits long strokes with constant force output.
The actuation can be linear or rotatory.

The Effect of Prior Heavy Exercise On Progressive Exercise To Fatigue [MEDICINE]

2007-10-01T05:00:00.000-07:00

At the onset of constant-load exercise in healthy humans, the rate of muscle metabolism increases to a steady state. However, when exercise is preceded by a bout of high-intensity or 'heavy exercise' several minutes prior, steady state is typically achieved more quickly. The aim of the present study was to study the metabolic effects of prior heavy exercise on a progressive exercise protocol, in which steady state is not achieved.

Scientific Abstract:

At the onset of constant-load exercise, the rate of muscle metabolism increases to a steady state. When exercise is preceded by a bout of heavy intensity (HVY) exercise, steady state is typically achieved more quickly. The effects of a prior HVY bout on a progressive exercise protocol, in which a steady state is not achieved, are unknown. The present study, therefore, was designed to study the effects of a prior HVY bout on a progressive plantar flexion exercise protocol in healthy humans. Subjects (n=5 males, age 25 Â± 4 years) completed two randomized exercise protocols that included a progressive exercise protocol (RAMP) and a progressive exercise protocol preceded 6 min prior by 6 min of HVY (HVY-RAMP). Exercise involved repeated isotonic plantar flexion (0.5 Hz, ~ 40Â° ROM) against an incremental resistance (~1.0 W/min) and was performed inside a 3.0 Tesla magnet for data collection using 31P-MRS (15s time acquisition per spectrum). All subjects had previously completed at least one familiarization RAMP trial, from which the steady state workload in HVY was calculated as the power output halfway between the onset of intracellular acidification and volitional fatigue. Our findings were, compared to the RAMP protocol, HVY-RAMP resulted in an increased (p <>

HVY exercise, the onset of the rapid fall in pHi is delayed, but once initiated, occurs at the same rate as in the RAMP protocol. This delay may be the result of an increased contribution of xidative metabolism suggested by the delayed onset of rapid increases in [Pi]/[PCr].

Ion Chamber Dosimetry: Accuracy in Small X-Ray Field Measurements [MEDICINE]

2007-10-01T04:57:00.001-07:00

Modern radiation therapy techniques, such as stereotactic radiotherapy and tomotherapy, deliver the total treatment dose to the patient using many small fields. This helps to construct a dose distribution which delivers a high dose to the tumour, while minimizing the dose to normal tissue. When considering a single small field, the dose resulting from that small field is usually reported as a relative dose factor (RDF). The RDF is the percentage of dose in a small field as compared to a large reference field. Task group report #51 from the American Association of Physicists in Medicine (AAPM) provides the protocol according to which absolute dose measurements using an ion chamber must be taken, all with respect to measurements at a reference point in a large reference field. In the case of RDF measurements several assumptions are made which allows for the simplification of the TG-51 protocol, but attention is not necessarily paid to the fact that the conditions in a large reference field differ considerably from those ina small field. In this study we have used experimental measurements with plane-parallel ion chambers and theoretical simulations (Monte Carlo BEAMnrc code) to investigate the validity of the assumptions made in the determination of RDFs for small fields. Four custom-made plane parallel ion chambers, as well as other common high resolution radiation dosimeters, were used to measure the dose response in circular 6MV stereotactic radiotherapy fields. BEAMnrc was then used to simulate the experimental conditions and determine the validity of the assumptions mentioned previously. The assumptions were determined to be invalid for use in small radiation fields. Corrections

were calculated from Monte Carlo results and applied to the experimental measurements. Care needs to be taken when applying existing protocols to non-reference conditions.

Longitudinal 31P Magnetic Resonance Spectroscopy Study of Schizophrenia [MEDICINE]

2007-10-01T04:48:00.000-07:00

Schizophrenia affects one in a hundred Canadians at some point in their life. This disorder is characterized by auditory hallucinations, delusions, lack of motivation and thought disorder. Antipsychotic drugs improve some of these symptoms, but there is no cure and the cause of schizophrenia is still unknown. Current models suggest that a brain lesion in-utero, in conjunction with neurodegeneration, may result in the symptoms of the disease. These processes may result in abnormal brain function, manifested as changes in brain metabolism.

In our past studies of first-episode and chronic schizophrenia, we used 31P MRS, a noninvasive technique, to measure the changes in brain metabolism. These studies revealed significant changes between patients and normals in several regions, including the thalamus, and the anterior cingulate. In order to determine the location of significant changes in metabolites as the disease progresses, more measurements between the initial and chronic stages of the disease are required.

In this longitudinal study of schizophrenia, the same subjects undergo 2 separate scans, the first at disease onset and the second at 30 months. Presently 24 schizophrenic patients and 15 matched controls have undergone the initial scan at disease onset and 6 schizophrenic patients and 6 controls have undergone the 30 month scan. Once complete, this study may reveal locations where significant membrane abnormalities occur in the early progression of the disease. This information will help to confirm that degeneration continues after schizophrenia is diagnosed clinically and may also help to target drug treatments to prevent this degeneration.

Babbitt metal [MECH]

2007-10-01T04:37:00.000-07:00

Babbitt metal, also called white metal, is an alloy used to provide the bearing surface in a plain bearing. It was invented in 1839 by Isaac Babbitt in Taunton, Massachusetts, USA. The term is used today to describe a series of alloys used as a bearing metal. Babbit metal is characterized by its resistance to gall.

Common compositions for Babbitt alloys:

90% tin 10% copper
89% tin 7% antimony 4% copper
80% lead 15% antimony 5% tin

Originally used as a cast in place bulk bearing material, it is now more commonly used as a thin surface layer in a complex, multi metal structure.

Babbitt metal is soft and easily damaged, and seems at first sight an unlikely candidate for a bearing surface, but this appearance is deceptive. The structure of the alloy is made up of small hard crystals dispersed in a matrix of softer alloy. As the bearing wears the harder crystal is exposed, with the matrix eroding somewhat to provide a path for the lubricant between the high spots that provide the actual bearing surface.

BlueTec [mech]

2007-10-01T04:32:00.000-07:00

BlueTec is DaimlerChrysler's name for its two nitrogen oxide (NO_x) reducing systems, for use in their Diesel automobile engines. One is a urea catalyst called AdBlue, the other is called DeNO_x and uses an oxidising catalytic converter and particular filter combined with other NO_x introduced the systems in the reducing systems. Both systems were designed to slash emissions further than ever before. Mercedes-BenzE-Class (using the 'DeNO_x' system) and GL-Class (using 'AdBlue') at the 2006 North American International Auto Show as the E 320 and GL 320 Bluetec. This system makes these vehicles 45-state and 50-state legal respectively in the United States, and is expected to meet all emissions regulations through 2009. It also makes DaimlerChrysler the only car manufacturer in the the US committed to selling diesel models in the 2007 model year.

CVCC [mech]

2007-10-01T04:31:00.000-07:00

CVCC is a trademark by the Honda Motor Company for a device used to reduce automotive emissions called Compound Vortex Controlled Combustion. This technology allowed Honda's cars to meet the 1970s US Emission requirements without a catalytic converter, and first appeared on the 1975 ED1 engine. It is a form of stratified charge engine.

Honda CVCC engines have normal inlet and exhaust valves, plus a small auxiliary inlet valve which provides a relatively rich air / fuel mixture to a volume near the spark plug. The remaining air / fuel charge, drawn into the cylinder through the main inlet valve is leaner than normal. The volume near the spark plug is contained by a small perforated metal plate. Upon ignition flame fronts emerge from the perforations and ignite the remainder of the air / fuel charge. The remaining engine cycle is as per a standard four stroke engine.

This combination of a rich mixture near the spark plug, and a lean mixture in the cylinder allowed stable running, yet complete combustion of fuel, thus reducing CO (carbon monoxide) and hydrocarbon emissions.

stratified charge engine [mech]

2007-10-01T04:29:00.001-07:00

The stratified charge engine is a type of internal-combustion engine, similar in some ways to the Diesel cycle, but running on normal gasoline. The name refers to the layering of fuel/air mixture, the charge inside the cylinder.

In a traditional Otto cycle engine the fuel and air are mixed outside the cylinder and are drawn into it during the intake stroke. The air/fuel ratio is kept very close to stoichiometric, which is defined as the exact amount of air necessary for a complete combustion of the fuel. This mixture is easily ignited and burns smoothly.

The problem with this design is that after the combustion process is complete, the resulting exhaust stream contains a considerable amount of free single atoms of oxygen and nitrogen, the result of the heat of combustion splitting the O₂ and N₂ molecules in the air. These will readily react with each other to create NO_x, a pollutant. A catalytic converter in the exhaust system re-combines the NO_x back into O₂ and N₂ in modern vehicles.

A Diesel engine, on the other hand, injects the fuel into the cylinder directly. This has the advantage of avoiding premature spontaneous combustionâ€”a problem known as detonation or ping that plagues Otto cycle enginesâ€”and allows the Diesel to run at much higher compression ratios. This leads to a more fuel-efficient engine. That is why they are commonly found in applications where they are being run for long periods of time, such as in trucks.

E85 [mech]

2007-10-01T04:28:00.000-07:00

E85 is an alcohol fuel mixture of 85% ethanol and 15% gasoline, by volume. ethanol derived from crops (bioethanol) is a biofuel.

E85 as a fuel is widely used in Sweden and is becoming increasingly common in the United States, mainly in the Midwest where corn is a major crop and is the primary source material for ethanol fuel production.

E85 is usually used in engines modified to accept higher concentrations of ethanol. Such flexible-fuel engines are designed to run on any mixture of gasoline or ethanol with up to 85% ethanol by volume. The primary differences from non-FFVs is the elimination of bare magnesium, aluminum, and rubber parts in the fuel system, the use of fuel pumps capable of operating with electrically-conductive (ethanol) instead of non-conducting dielectric (gasoline) fuel, specially-coated wear-resistant engine parts, fuel injection control systems having a wider range of pulse widths (for injecting approximately 30% more fuel), the selection of stainless steel fuel lines (sometimes lined with plastic), the selection of stainless steel fuel tanks in place of terne fuel tanks, and, in some cases, the use of acid-neutralizing motor oil. For vehicles with fuel-tank mounted fuel pumps, additional differences to prevent arcing, as well as flame arrestors positioned in the tank's fill pipe, are also sometimes used.

FADEC - Full Authority Digital Engine Control.[mech]

2007-10-01T04:27:00.000-07:00

FADEC is the acronym for Full Authority Digital Engine Control. It is a system consisting of a digital computer (called EEC /Electronic Engine Control/ or ECU /Electronic Control Unit/) and its related accessories which control all aspects of aircraft engine performance. FADECs have been produced for both piston engines and jet engines, their primary difference due to the different ways of controlling the engines.

Electronics' superior accuracy led to early generation analogue electronic control first used in Concorde's Rolls-Royce Olympus 593 in the 1960s. Later in the 1970s NASA and Pratt and Whitney experimented with the first experimental FADEC, first flown on an F-111 fitted with a highly modified Pratt & Whitney TF-30 left engine. The experiments led to Pratt & Whitney F100 and Pratt & Whitney PW2000 being the first military and civil engines respectively fitted with FADEC and later the Pratt & Whitney PW4000 as the first commercial 'Dual FADEC' engine.

The aircraft's thrust lever sends electrical signals (pilot's command, may also be the autothrottle) to the FADEC. The FADEC digitally calculates and precisely controls the fuel flow rate to the engines giving precise thrust. In addition to the fuel metering function, the FADEC performs numerous other control and monitoring functions such as Variable Stator Vanes (VSV's) and Variable Bleed Valves (VBV's) control, cabin bleeds and power off-takes control, control of starting and re-starting, turbine blade and vane cooling and blade tip clearance control, thrust reversers control, engine health monitoring, oil debris monitoring and vibration monitoring. The inputs come from various aircraft and engine sensors. Apart from the key parameters that are monitored for a safe thrust control (shaft rotational speeds, pressures and temperatures at various points along the gas path) the FADEC also monitors hundreds of various analog, digital and discrete data coming from the engine subsystems and related aircraft systems, providing a fully redundant and fault tolerant engine control.

Hybrid Synergy Drive (HSD)

2007-10-01T04:26:00.000-07:00

Hybrid Synergy Drive (HSD) is a set of hybrid car technologies developed by Toyota and used in that company's Prius, Highlander Hybrid, Camry Hybrid, Lexus RX 400h, and Lexus GS 450h automobiles. It combines the characteristics of an electric drive and a continuously variable transmission, using electricity and transistors in place of toothed gears. The Synergy Drive is a drive-by-wire system with no direct mechanical connection between the engine and the engine controls: both the gas pedal and the gearshift lever in an HSD car merely send electrical signals to a control computer.

HSD is a refinement of the original Toyota Hybrid System (THS) used in the 1997â€“2003 Toyota Prius. As such it is occasionally referred to as THS II. The name was changed in anticipation of its use in vehicles outside the Toyota brand (Lexus).

When required to classify the transmission type of an HSD vehicle (such as in standard specification lists or for regulatory purposes), Toyota describes HSD-equipped vehicles as having E-CVT (Electronically-controlled Continuously Variable Transmission).

regenerative brake

2007-10-01T04:17:00.000-07:00

A regenerative brake is an apparatus, a device or system which allows a vehicle to recapture part of the kinetic energy that would otherwise be lost to heat when braking and make use of that power either by storing it for future use or feeding it back into a power system for other vehicles to use.

It is similar to an electromagnetic brake, which generates heat instead of electricity and is unable to completely stop a rotor.

Regenerative brakes are a form of dynamo generator, originally discovered in 1832 by Hippolyte Pixii. The dynamo's rotor slows as the kinetic energy is converted to electrical energy through electromagnetic induction. The dynamo can be used as either generator or brake by converting motion into electricity or be reversed to convert electricity into motion.

Using a dynamo as an regenerative brake was discovered co-incident with the modern electric motor. In 1873, ZÃ©nobe Gramme attached the wires from two dynamos together. When one dynamo rotor was turned as a regenerative brake, the other became an electric motor.

It is estimated that regenerative braking systems in vehicles currently reach 31.3% electric generation efficiency, with most of the remaining energy being released as heat; the actual efficiency depends on numerous factors, such as the state of charge of the battery, how many wheels are equipped to use the regenerative braking system, and whether the topology used is parallel or serial in nature.^{[citation needed]} The system is no more efficient than conventional friction brakes, but reduces the use of contact elements like brake pads, which eventually wear out. Traditional friction-based brakes must also be provided to be used when rapid, powerful braking is required.

Enhanced Data rates for Global Evolution

2007-06-11T21:51:00.000-07:00

The first stepping stone in migration path to third generation wireless mobile services (3G) is the General Packet Radio Services, GPRS, a packet-switched technology that delivers speeds of up to 115kbps. If GPRS is already in place, Enhanced Data rates for Global Evolution (EDGE) technology is most effective as the second stepping stone that gives a low impact migration. Only software upgrades and EDGE plug-in transceiver units are needed. The approach protects operators' investments by allowing them to reuse their existing network equipment and radio systems.

The EDGE technology will enable GSM and TDMA operators to deliver third-generation mobile multimedia services using existing network frequencies, bandwidth, carrier structure and cell planning process. By using a more efficient air-modulation technology optimized for data communications, EDGE increases end-user data rates up to 384kbit/s and potentially higher in good-quality radio environments

Vertical Cavity surface Emission Lasers

2007-06-11T21:49:00.000-07:00

Vertical Cavity surface Emission Lasers (VCSEL) are lasers that emit light from their surface in contrast with regular â€˜edge emittersâ€™. Also they have got a vertical cavity , as the name suggests, which enables surface emission.â€Vixelsâ€ , as they are commonly called ,have several superior characteristics compared to their edge emitting counter parts.

VCSEL â€“ Semiconductor micro laser diodes which emit light perpendicular to their PN junction in a cylindrical beam vertically from the surface of a fabricated wafer and feature circular low divergence beam

Earliest reported in 1965 by Melngailis

VCSEL was first demonstrated in 1979 at Tokyo Institute of Technology

Epitaxial mirrors for GaAs/ AlGaAs VCSELs

pioneered in 1983

Distributed Bragg Reflection

If layers of alternating semiconductors are stacked periodically , each layer having a thickness

λo n , the reflections from each of the boundaries will be added in phase to produce a large reflectivity

Brag reflection condition

Periodicity of cladding layer is chosen so that

n1d1 + n2d2 = λo/2

n1 , n2 refractive indices

d1 , d2 thickness of layer

λo free space wavelength of the optical beam

Epitaxial growth of VCSEL

There are two methods

1 . Molecular beam epitaxy ( MBE )

2 . Metal Organic Vapour Phase Epitaxy (MOVPE)

Inverse Multiplexing over ATM

2007-06-11T21:48:00.002-07:00

Local Area Networks are now being used to transport voice and video traffic together with traditional data traffic that they have already supported. And in the case of voice and video applications, not only is these is a need for more bandwidth, but there is also a need for guaranteed levels of receive because these applications are very sensitive to latency and delay.

Inverse multiplexing can be proved as technology that overcomes the bandwidth gap that exists between LAN and WAN. Inverse multiplexing is exactly the opposite of traditional multiplexing. In traditional multiplexing, multiple streams of data are combined into one single but larger data pipe, where as inverse multiplexing combines multiple circuits into single logical data pipe.

Asynchronous Transfer Mode (ATM) has compelling business as a WAN technology and is on a steep growth curve both in public carrier networks and in private organisations with requirements for networking video, voice and data traffic.

Inverse multiplexing over ATM (IMA) is a breakthrough standard that enables â€˜right sizing and right pricing of enterprise access solutions for organisations with low to mid range WAN traffic requirements and offers the benefits of ATMâ€™s quality of service and statistical bandwidth optimisation capabilities. IMA divides an aggregate stream ATM cells across multiple WAN links on a cell by cell basis and hence the name inverse-multiplexing. In combination with ATM, IMA simplifies and reduces WAN cost of ownership.

XMax

2007-06-11T21:48:00.001-07:00

The correct title of this article is xMax. The initial letter is capitalized due to technical restrictions.

xMax developed by xG Technology is a wireless communications technology whose developers claim is low power and provides a high data rate over a distance of about 13 miles.

â€œA fundamental paradigm shift in the way radio signals are modulated and demodulated.â€

Developed by xG Technology in Florida Rather than transmitting many RF cycles for each bit of data to be sent, xMax does it in a single RF cycle.

Power is saved not only in the transmission, but because receivers will only recognize single-cycle waveforms, power isn't wasted on un-intended RF signals

Automated eye-pattern recognition systems

2007-06-11T21:41:00.000-07:00

Privacy of personal data is an illusion in todayâ€™s complex society. With only passwords, or Social Security Numbers as identity or security measures every one is vulnerable to invasion of privacy or break of security. Traditional means of identification are easily compromise and enyone can use this information to assume anotherâ€™s identity. Sensitive personal and corporate information can be assessed and even criminal activities can be performed using another name. Eye pattern recognition system provides a barrier to and virtually eliminates fraudulent authentication and identity privacy and safety controls privileged access or authorised entry to sensitive sites, data or material. In addition to privacy protection there are myriad of applications were iris recognition technology can provide protection and security. This technology offers the potential to unlock major business opportunities by providing high confidence customer validation. Unlike other measurable human features in the face, hand, voice or finger print, the patterns in the iris do not change overtime and research show the matching accuracy of iris recognition systems is greater than that of DNA testing. Positive identifications can be made through glasses, contact lenses and most sunglasses. Automated recognition of people by the pattern of their eyes offers major advantages over conventional identification techniques. Iris recognition system also require very little co-operation from the subject, operate at a comfortable distance and are virtually impossible to deceive. Iris recognition combines research in computer vision, pattern recognition and the man-machine interface. The purpose is real-time, high confidence recognition of a persons identity by mathematical analysis of the random patterns that are visible with in the iris. Since the iris is a protected internal organ whose random texture is stable throughout life, it can serve as a â€˜living passwordâ€™ that one need not remember but one always carries.

Zigbee Networks

2007-06-11T21:37:00.001-07:00

ZigBee is a published specification set of high level communication protocols designed to use small, low-power digital radios based on the IEEE 802.15.4 standard for wireless personal area networks (WPANs). The relationship between IEEE 802.15.4-2003 and ZigBee is analogous to that existing between IEEE 802.11 and the Wi-Fi Alliance. The ZigBee 1.0 specifications were ratified on December 14, 2004 and are available to members of the ZigBee Alliance. An entry level membership in the ZigBee Alliance costs US$ 3500 and provides access to the specifications. For non-commercial purposes, the ZigBee specification is available to the general public at the ZigBee Alliance homepage.
The technology is designed to be simpler and cheaper than other WPANs such as Bluetooth. The most capable ZigBee node type is said to require only about 10% of the software of a typical Bluetooth or Wireless Internet node, while the simplest nodes are about 2%. However, actual code sizes are much higher, more like 50% of Bluetooth code size. ZigBee chip vendors announced 128-kilobyte devices.
As of 2005, the estimated cost of the radio for a ZigBee node is about $1.10 to the manufacturer in very high volumes. Most ZigBee solutions require an additional micro controller driving the price further up at this time. In comparison, before Bluetooth was launched (1998) it had a projected price, in high volumes, of $4-$6. The price of consumer-grade Bluetooth chips are now under $3.
ZigBee has started work on version 1.1. Version 1.1 is meant to take advantage of improvements in the 802.15.4b (still in draft) specification, most notably that of CCM* as an alternative to CCM(CTR + CBC-MAC)CCM mode. CCM* enjoys the same security proof as CCM and provides greater flexibility in the choice of Authentication and Encryption.

Zigbee Networks

2007-06-11T21:35:00.000-07:00

Blue Eyes

2007-06-11T21:34:00.000-07:00

Is it possible to create a computer which can interact with us as we interact each other? For example imagine in a fine morning you walk on to your computer room and switch on your computer, and then it tells you â€œHey friend, good morning you seem to be a bad mood today. And then it opens your mail box and shows you some of the mails and tries to cheer you. It seems to be a fiction, but it will be the life lead by â€œBLUE EYESâ€ in the very near future.

The basic idea behind this technology is to give the computer the human power. We all have some perceptual abilities. That is we can understand each others feelings. For example we can understand ones emotional state by analyzing his facial expression. If we add these perceptual abilities of human to computers would enable computers to work together with human beings as intimate partners. The â€œBLUE EYESâ€ technology aims at creating computational machines that have perceptual and sensory ability like those of human beings.

Mesotechnology

2007-06-11T21:28:00.000-07:00

Mesotechnology describes a budding research field which could replace nanotechnology in the future as the primary means to control matter at length scales ranging from a cluster of atoms to microscopic elements. The prefix meso- comes from the Greek word mesos, meaning middle, hence the technology spans a range of length scales as opposed to nanotechnology which is concerned only with the smallest atomic scales.

describes very well phenomena on the atomic to nanoscale while classical Newtonian Mechanics describes the behavior of objects on the microscale and up. However, the length scale in the middle ( Although the term itself is still quite new, the general concept is not. Many fields of science have traditionally focused either on single discrete elements or large statistical collections where many theories have been successfully applied. In the field of physics for example, Quantum Mechanicsmesoscale) is not well described by either theory. Similarly, psychologists focus heavily on the behavior and mental processes of the individual while sociologists study the behavior of large societal groups, but what happens when only 3 people are interacting, this is the mesoscale.

Brain-Computer Interface

2007-06-06T22:38:00.000-07:00

Brain-Computer Interfacing is an attention-grabbing, dynamic and highly inter-corrective explore issue at the interface between medicine, psychology, neurology, therapy-engineering, man-machine interaction, machine learning and signal processing.
BRAIN-COMPUTER INTERFACE SYSTEM :
In this system, Signals from the brain are acquired by electrodes on the scalp, the cortical surface, or from within the brain and are processed to extract specific signal features that reflect the userâ€™s intent. Features are translated into commands that operate a device (e.g., a simple word processing program, a wheelchair, or a neuroprosthesis).
These BCI systems measure specific features of brain activity and translate them into
device control signals
BCI system

Give answer of the simple questions rapidly

Manage the environment
Perform time-consuming word processing.

At the same time, the act of this new technology, measured in rate and accuracy, or in the complete measure, information transfer rate (i.e., bit rate), is self-effacing. Current systems can reach no more than 25 bits/min, even under finest conditions. The eventual value of this new technology will depend largely on the degree to which its information transfer rate can be increased.

Z-Wave

2007-06-06T22:37:00.000-07:00

Z-Wave is the interoperable wireless communication standard developed by Danish company Zensys and the Z-Wave Alliance. It is designed for low-power and low-bandwidth appliances, such as home automation and sensor networks
Radio specifications
Bandwidth: 9,600 bit/s or 40,000 bit/s, fully interoperable
Radio specifics
In Europe, the 868 MHz band has a 1% duty cycle limitation, meaning that a Z-wave unit can only transmit 1% of the time. This limitation is not present in the US 908 MHz band, but US legislation imposes a 1 mW transmission power limit (as opposed to 25 mW in Europe). Z-wave units can be in power-save mode and only be active 0.1% of the time, thus reducing power consumption dramatically.

Topology and routing
Z-wave uses an intelligent mesh network topology and has no master node. A message from node A to node C can be successfully delivered even if the two nodes are not within range providing that a third node B can communicate with nodes A and C. If the preferred route is unavailable, the message originator will attempt other routes until a path is found to the 'C' node. Therefore a Z-wave network can span much further than the radio range of a single unit. In order for Z-wave units to be able to route unsolicited messages, they cannot be in sleep mode. Therefore, most battery-operated devices will opt not to be repeater units. A Z-wave network can consist of up to 232 units with the option of bridging networks if more units are required.

Application areas
Due to the low bandwidth, Z-wave is not suitable for audio/video applications but is well suited for sensors and control units which typically only transmits a few bytes at a time.

Graphics tablet

2007-06-06T22:36:00.000-07:00

A graphics tablet is a computer peripheral device that allows one to hand-draw images directly into a computer, generally through an imaging program. Graphics tablets consist of a flat surface upon which the user may 'draw' an image using an attached stylus, a pen-like drawing apparatus. The image generally does not appear on the tablet itself but, rather, is displayed on the computer monitor.

It is interesting to note that the stylus, as a technology, was originally designed as a part of the electronics, but later it simply took on the role of providing a smooth, but accurate 'point' that would not damage the tablet surface while 'drawing'.

Tablet PC

2007-06-06T22:35:00.000-07:00

A tablet PC is a notebook- or slate-shaped mobile computer. Its touchscreen or digitizing tablet technology allows the user to operate the computer with a stylus or digital pen instead of a keyboard or mouse.

The form factor presents an alternate method of interacting with a computer, the main intent being to increase mobility and productivity. Tablet PCs are often used in places where normal notebooks are impractical or unwieldy, or do not provide the needed functionality.

The tablet PC is a culmination of advances in miniaturization of notebook hardware and improvements in integrated digitizers as methods of input. A digitizer is typically integrated with the screen, and correlates physical touch or digital pen interaction on the screen with the virtual information portrayed on it. A tablet's digitizer is an absolute pointing device rather than a relative pointing device like a mouse or touchpad. A target can be virtually interacted with directly at the point it appears on the screen.

Light Pen

2007-06-06T22:34:00.000-07:00

A light pen is a computer input device in the form of a light-sensitive wand used in conjunction with the computer's CRT monitor. It allows the user to point to displayed objects, or draw on the screen, in a similar way to a touch screen but with greater positional accuracy. A light pen can work with any CRT-based monitor, but not with LCD screens, projectors or other display devices.

A light pen is fairly simple to implement. The light pen works by sensing the sudden small change in brightness of a point on the screen when the electron gun refreshes that spot. By noting exactly where the scanning has reached at that moment, the X,Y position of the pen can be resolved. This is usually achieved by the light pen causing an interrupt, at which point the scan position can be read from a special register, or computed from a counter or timer. The pen position is updated on every refresh of the screen.

The light pen became moderately popular during the early 1980s. It was notable for its use in the Fairlight CMI, and the BBC Micro. However, due to the fact that the user was required to hold his or her arm in front of the screen for long periods of time, the light pen fell out of use as a general purpose input device.

Serial Attached SCSI

2007-06-06T22:33:00.001-07:00

In computer hardware, Serial Attached SCSI (SAS) is a computer bus technology primarily designed for transfer of data to and from devices like hard disk, cd-rom and so on. SAS is a serial communication protocol for direct attached storage (DAS) devices. It is designed for the corporate and enterprise market as a replacement for parallel SCSI, allowing for much higher speed data transfers than previously available, and is backwards-compatible with SATA. Though SAS uses serial communication instead of the parallel method found in traditional SCSI devices, it still uses SCSI commands for interacting with SAS End devices. SAS protocol is developed and maintained by T10 committe. The current draft revision of SAS protocol can be downloaded from SAS 2 draft

Low voltage differential signaling (LVDS)

2007-06-06T22:31:00.000-07:00

Low voltage differential signaling, or LVDS, is an electrical signaling system that can run at very high speeds over cheap, twisted-pair copper cables. It was introduced in 1994, and has since become very popular in computers, where it forms part of very high-speed networks and computer buses.
LVDS uses the difference in voltage between two wires to signal information. The transmitter injects a small current, nominally 3.5 milliamperes, into one wire or the other, depending on the logic level to be sent. The current passes through a resistor of about 100 to 120 ohms (matched to the characteristic impedance of the cable) at the receiving end, then returns in the opposite direction along the other wire. From Ohm's law, the voltage difference across the resistor is therefore about 350 millivolts. The receiver senses the polarity of this voltage to determine the logic level. (This is a type of current loop signaling).

MAC address

2007-06-06T22:30:00.002-07:00

In computer networking a Media Access Control address (MAC address) is a unique identifier attached to most forms of networking equipment. Most layer 2 network protocols use one of three numbering spaces managed by the IEEE: MAC-48, EUI-48, and EUI-64, which are designed to be globally unique. Not all communications protocols use MAC addresses, and not all protocols require globally unique identifiers. The IEEE claims trademarks on the names 'EUI-48' and 'EUI-64'. (The 'EUI' stands for Extended Unique Identifier.)

ARP/RARP is commonly used to map the layer 2 MAC address to an address in a layer 3 protocol such as Internet Protocol (IP). On broadcast networks such as Ethernet the MAC address allows each host to be uniquely identified and allows frames to be marked for specific hosts. It thus forms the basis of most of the layer 2 networking upon which higher OSI Layer protocols are built to produce complex, functioning networks.

Native Command Queuing (NCQ)

2007-06-06T22:30:00.001-07:00

Native Command Queuing (NCQ) is a technology designed to increase performance of SATAhard disks by allowing the individual hard disk to receive more than one I/O request at a time and decide which to complete first. Using detailed knowledge of its own seek times and rotational position, the drive can compute the best order to perform the operations. This can reduce the amount of unnecessary seeking (going back-and-forth) of the drive's heads, resulting in increased performance (and slightly decreased wear of the drive) for workloads where multiple simultaneous read/write requests are outstanding, most often occurring in server-type applications.

Tagged Command Queuing (TCQ)

2007-06-06T22:28:00.002-07:00

TCQ stands for the Tagged Command Queuing technology built into certain PATA and SCSI hard drives. It allows the operating system to send multiple read and write requests to a hard drive. TCQ is almost identical in function to Native Command Queuing (NCQ) used by SATA drives.

Before TCQ, an operating system was only able to send one request at a time. In order to boost performance, it had to decide the order of the requests based on its own, possibly incorrect, idea of what the hard drive was doing. With TCQ, the drive can make its own decisions about how to order the requests (and in turn relieve the operating system from having to do so). The result is that TCQ can improve the overall performance of a hard drive.

Differential signaling

2007-06-06T22:28:00.001-07:00

Differential signaling is a method of transmitting information over pairs of wires (as opposed to single-ended signalling, which transmits information over single wires).

Differential signaling reduces the noise on a connection by rejecting common-mode interference. Two wires (referred to here as A and B) are routed in parallel, and sometimes twisted together, so that they will receive the same interference. One wire carries the signal, and the other wire carries the inverse of the signal, so that the sum of the voltages on the two wires is always constant.

At the end of the connection, instead of reading a single signal, the receiving device reads the difference between the two signals. Since the receiver ignores the wires' voltages with respect to ground, small changes in ground potential between transmitter and receiver do not affect the receiver's ability to detect the signal. Also, the system is immune to most types of electrical interference, since any disturbance that lowers the voltage level on A will also lower it on B.

HyperTransport (HT)

2007-06-06T21:34:00.000-07:00

HyperTransport (HT), formerly known as Lightning Data Transport (LDT), is a bidirectional serial/parallel high-bandwidth, low-latency computer bus that was introduced on April 2, 2001[1]. The HyperTransport Technology Consortium is in charge of promoting and developing HyperTransport technology. The technology is used by AMD and Transmeta in x86 processors, PMC-Sierra, Broadcom, and Raza Microelectronics in MIPS microprocessors, ATI Technologies, NVIDIA, VIA, SiS, ULi/ALi, AMD, Apple Computer and HP in PC chipsets, HP, Sun Microsystems, IBM, and IWill in servers, Cray, Newisys, and PathScale in high performance computing, and Cisco Systems in routers. Notably missing from this list is semiconductor giant Intel, which continues to use a shared bus architecture.

FireWire

2007-05-29T03:53:00.002-07:00

FireWire (also known as i.Link or IEEE 1394) is a personal computer (and digital audio/digital video) serial bus interface standard, offering high-speed communications and isochronous real-time data services. FireWire has replaced Parallel SCSI in many applications due to lower implementation costs and a simplified, more adaptable cabling system.

Almost all modern digital camcorders have included this connection since 1995. Many computers intended for home or professional audio/video use have built-in FireWire ports including all Macintosh, Dell and Sony computers currently produced. FireWire was also an attractive feature on the Apple iPod for several years, permitting new tracks to be uploaded in a few seconds and also for the battery to be recharged concurrently with one cable. However, Apple has eliminated FireWire support in favor of Universal Serial Bus (USB) 2.0 on its newer iPods due to space constraints and for wider compatibility.

Telestrator

2007-05-29T03:53:00.001-07:00

The telestrator is a device that allows its operator to draw a freehand sketch over a motion picture image.

The telestrator was invented by physicist Leonard Reiffel, who used it to draw illustrations on a series of science shows he did for public television in the late 1960s. The user interface for early telestrators required the user to draw on a TV screen with a light pen, whereas modern implementations are commonly controlled with a touch screen or tablet PC.

Today telestrators are widely used in broadcasts of all major sports. They have also become a useful tool in televised weather reports.

Digital Micromirror Device

2007-05-29T03:52:00.001-07:00

A Digital Micromirror Device, or DMD is an optical semiconductor that is the core of DLP projection technology, and was invented by Dr. Larry Hornbeck and Dr. William E. 'Ed' Nelson of Texas Instruments (TI) in 1987. The DMD project began as the Deformable Mirror Device in 1977, using micromechanical, analog light modulators. The first analog DMD product was the TI DMD2000 airline ticket printer that used a DMD instead of a laser scanner. A DMD chip has on its surface several hundred thousand microscopic mirrors arranged in a rectangular array which correspond to the pixels in the image to be displayed. The mirrors can be individually rotated Â±10-12Â°, to an on or off state. In the on state, light from the bulb is reflected onto the lens making the pixel appear bright on the screen. In the off state, the light is directed elsewhere (usually onto a heatsink), making the pixel appear dark. To produce greyscales, the mirror is toggled on and off very quickly, and the ratio of on time to off time determines the shade produced (binary pulse-width modulation). Contemporary DMD chips can produce up to 1024 shades of gray. See DLP for discussion of how color images are produced in DMD-based systems. The mirrors themselves are made out of aluminum and are around 16 micrometres across. Each one is mounted on a yoke which in turn is connected to two support posts by compliant torsion hinges. In this type of hinge, the axle is fixed at both ends and literally twists in the middle. Because of the small scale, hinge fatigue is not a problem and tests have shown that even 1 trillion operations does not cause noticeable damage. Tests have also shown that the hinges cannot be damaged by normal shock and vibration, since it is absorbed by the DMD superstructure. Two pairs of electrodes on either side of the hinge control the position of the mirror by electrostatic attraction. One pair acts on the yoke and the other acts on the mirror directly. The majority of the time, equal bias charges are applied to both sides simultaneously. Instead of flipping to a central position as one might expect, this actually holds the mirror in its current position. This is because attraction force on the side the mirror is already tilted towards is greater, since that side is closer to the electrodes. To move the mirror, the required state is first loaded into an SRAM cell located beneath the pixel, which is also connected to the electrodes. The bias voltage is then removed, allowing the charges from the SRAM cell to prevail, moving the mirror. When the bias is restored, the mirror is once again held in position, and the next required movement can be loaded into the memory cell. The bias system is used because it reduces the voltage levels required to address the pixels such that they can be driven directly from the SRAM cell, and also because the bias voltage can be removed at the same time for the whole chip, meaning every mirror moves at the same instant. The advantages of the latter are more accurate timing and a more filmic moving image.

VIRTUAL SURGERY

2007-05-29T03:51:00.001-07:00

Virtual surgery is a computer based simulated surgery, which can teach the surgeons new procedures and can determine their level of competence before they operate on patients. Virtual surgery is based on the concept of virtual reality.A simulated model of the human autonomy which look, feel and respond like a real human body is created for the surgeon to operate on.The virtual reality simulators consists of force feed back devices,a real time hapticcomputer, haptic software ,dynamic simulator and 3D-graphics.Using the 3D visualization technologies and thehaptic devices a surgery can be performed which enable the surgeon to reach into the virtual patient with their hands to touch, feel, grasp and manipulate the simulated organs.

Plasma Television

2007-05-29T03:50:00.001-07:00

Television has been around since 19th century and for the past 50 years it held a pretty common place in our leaving room. Since the invention of television engineers have been striving to produce slim & flat displays that would deliver as good or even better images than the bulky C.R.T. Scores of research teams all over the world have been working to achieve this. Plasma television has achieved this goal. Technologies inside it are plasma and hi-definition which are just two of the latest technologies to hit stores. The main contenders in the flat race are PDP (Plasma Display Panel) and flat CRT with LCD and FED (Field Emission Display) To get an idea of what makes a plasma display different it needs to understand how a conventional TV set works. Conventional TVâ€™s used CRT to create the images we see on the screen. The cathode is a heated filament, like the one in a light bulb. It is housed inside a vacuum created in a tube of thick glassâ€¦.that is what makes your TV so big and heavy. The newest entrant in the field of flat panel display systems is Plasma display. Plasma display panels donâ€™t contain cathode ray tubes and pixels are activated differently.

Femtotechnology

2007-05-29T03:49:00.000-07:00

Femtotechnology is a term used by some futurists to refer to structuring of matter on a femtometre scale, by analogy with nanotechnology and picotechnology. This involves the manipulation of excited energy states within atomic nuclei to produce metastable (or otherwise stabilized) states with unusual properties. In the extreme case, excited states of nucleons are considered, ostensibly to tailor the behavioral properties of these particles (though this is in practice unlikely to work as intended).

Practical applications of femtotechnology are currently considered to be unlikely. The spacings between nuclear energy levels require equipment capable of efficiently generating and processing gamma rays, without equipment degradation. The nature of the strong interaction is such that excited nuclear states tend to be very unstable (unlike the excited electron states in Rydberg atoms), and there are a finite number of excited states below the nuclear binding energy, unlike the (in principle) infinite number of bound states available to an atom's electrons. Similarly, what is known about the excited states of individual nucleons seems to indicate that these do not produce behavior that in any way makes nucleons easier to use or manipulate, and indicates instead that these excited states are even less stable and fewer in number than the excited states of atomic nuclei.

The hypothetical hafnium bomb can be considered a crude application of femtotechnology.

Free space laser communication

2007-05-29T03:47:00.000-07:00

Lasers have been considered for space communication since their realization in 1960. It was soon recognized that, although the laser had potential for the transfer data at potentially high rates.

Features of laser communication

Extremely high bandwidth and large information throughput available many times greater than RF communication. Modulation of helium-Neon laser (frequency 4.7 x 1014) results in a channel bandwidth of 4700 GHz, which is enough to carry a million simultaneous TV channel.

Small antenna size requires only a small increase in weight and volume of the satellite. This reduces blockage of fields of view of most desirable areas on satellites. Laser satellite communication equipment can provide advantages of 3:1 in mass and 2:1 in power relative to microwave systemsNarrow beam divergence affords interference free and secure operation. The existence of laser beams cannot be detected with spectrum analyzers. Antenna gain made possible by narrow beam, enables small telescope aperture to be used. The 1550nm-wavelength technology has added the advantage of being inherently eye-safe at the power levels used in the free space systems, alleviating the health and safety concerns often raised with using lasers in an open environment where human exposure is possible.Laser technology can meet the needs of a variety of space missions, including intersatellite links, Earth to near-space links, and deep space missions. The vast distances to deep space make data return via conventional radio frequency techniques extremely difficult.

Microphotonics

2007-05-29T03:46:00.000-07:00

Microphotonics is a branch of technology that deals with directing light on a microscopic scale. It is used in optical networking.
Microphotonics employs at least two different materials with a large differential index of refraction to squeeze the light down to a small size. Generally speaking virtually all of microphotonics relies on Fresnel reflection to guide the light. If the photons reside mainly in the higher index material, the confinement is due to total internal reflection. If the confinement is due many distributed Fresnel reflections, the device is termed a photonic crystal. There are many different types of geometries used in microphotonics including: optical waveguides, optical microcavities, Arrayed Waveguide Gratings
Light bounces off the small yellow square that MIT physics professor John Joannopoulos is showing off. It looks like a scrap of metal, something a child might pick up as a plaything. But it isn't a toy, and it isn't metal. Made of a few ultrathin layers of non-conducting material, this photonic crystal is the latest in a series of materials that reflect various wavelengths of light almost perfectly. Photonic crystals are on the cutting edge of microphotonics: technologies for directing light on a microscopic scale that will make a major impact on telecommunications.

In the short term, microphotonics could break up the logjam caused by the rocky union of fiber optics and electronic switching in the telecommunications backbone. Photons barreling through the network's optical core run into bottlenecks when they must be converted into the much slower streams of electrons that are handled by electronic switches and routers. To keep up with the Internet's exploding need for bandwidth, technologists want to replace electronic switches with faster, miniature optical devices, a transition that is already under way Because of the large payoff-a much faster, all-optical Internet-many competitors are vying to create such devices. Large telecom equipment makers, including Lucent Technologies, Agilent Technologies and Nortel Networks, as well as a number of startup companies, are developing new optical switches and devices. Their innovations include tiny micromirrors, silicon waveguides, even microscopic bubbles to better direct light.
But none of these fixes has the technical elegance and widespread utility of photonic crystals. In Joannopoulos' lab, photonic crystals are providing the means to create optical circuits and other small, inexpensive, low-power devices that can carry, route and process data at the speed of light. 'The trend is to make light do as many things as possible,' Joannopoulos says. 'You may not replace electronics completely, but you want to make light do as much as you can.'
Conceived in the late 1980s, photonic crystals are to photons what semiconductors are to electrons, offering an excellent medium for controlling the flow of light. Like the doorman of an exclusive club, the crystals admit or reflect specific photons depending on their wavelength and the design of the crystal. In the 1990s, Joannopoulos suggested that defects in the crystals' regular structure could bribe the doorman, providing an effective and efficient method to trap the light or route it through the crystal.
Since then, Joannopoulos has been a pioneer in the field, writing the definitive book on the subject in 1995: Photonic Crystals: Molding the Flow of Light. 'That's the way John thinks about it,' says MIT materials scientist and collaborator Edwin Thomas. 'Molding the flow of light, by confining light and figuring out ways to make light do his bidding-bend, go straight, split, come back together-in the smallest possible space.'
Joannopoulos' group has produced several firsts. They explained how crystal filters could pick out specific streams of light from the flood of beams in wavelength division multiplexing, or WDM, a technology used to increase the amount of data carried per fiber ' TR March/April 1999). The lab's work on two-dimensional photonic crystals set the stage for the world's smallest laser and electromagnetic cavity, key components in building integrated optical circuits.
But even if the dream of an all-optical Internet comes to pass, another problem looms. So far, network designers have found ingenious ways to pack more and more information into fiber optics, both by improving the fibers and by using tricks like WDM. But within five to 10 years, some experts fear it won't be possible to squeeze any more data into existing fiber optics.
The way around this may be a type of photonic crystal recently created by Joannopoulos' group: a 'perfect mirror' that reflects specific wavelengths of light from every angle with extraordinary efficiency. Hollow fibers lined with this reflector could carry up to 1,000 times more data than current fiber optics-offering a solution when glass fibers reach their limits. And because it doesn't absorb and scatter light like glass, the invention may also eliminate the expensive signal amplifiers needed every 60 to 80 kilometers in today's optical networks Joannopoulos is now exploring the theoretical limits of photonic crystals. How much smaller can devices be made, and how can they be integrated into optical chips for use in telecommunications and, perhaps, ultrafast optical computers? Says Joannopoulos: 'Once you start being able to play with light, a whole new world opens up.'
Referance :
Wikipedia, Technology Review (MIT)

Astrophotography

2007-05-29T03:45:00.000-07:00

Astrophotography is a specialised type of photography that entails making photographs of astronomical objects in the night sky such as planets, stars, and deep sky objects such as star clusters and galaxies.

Astrophotography is used to reveal objects that are too faint to observe with the naked eye, as both film and digital cameras can accumulate and sum photons over long periods of time.

Astrophotography poses challenges that are distinct from normal photography, because most subjects are usually quite faint, and are often small in angular size. Effective astrophotography requires the use of many of the following techniques:

Mounting the camera at the focal point of a large telescope
Emulsions designed for low light sensitivity
Very long exposure times and/or multiple exposures (often more than 20 per image).
Tracking the subject to compensate for the rotation of the Earth during the exposure
Gas hypersensitizing of emulsions to make them more sensitive (not common anymore)
Use of filters to reduce background fogging due to light pollution of the night sky.

Microvia Technology

2007-05-29T03:44:00.000-07:00

Microvias are small holes in the range of 50 -100 Âµm. In most cases they are blind vias from the outer layers to the first innerlayer.
The development of very complex Integrated Circuits (ICs) with extremely high input/output counts coupled with the steadily increasing clock rates has forced the electronic manufacturer to develop new packaging and assembly techniques. Components with pitches less then 0.30 mm, chip scale packages, and flip chip technology are underlining this trend and highlight the importance of new printed wiring board technologies able to cope with the requirement of modern electronics.
In addition, more and more electronic devices have to be portable and consequently systems integration, volume and weight considerations are gaining importance.
These portables are usually battery powered resulting in a trend towards lower voltage power supplies, with their implication in PCB (Printed Circuit Board) complexity.
As a result of the above considerations, the future PCB will be characterized by very high interconnection density with finer lines and spaces, smaller holes and decreasing thickness. To gain more landing pads for small footprint components the use of microvias becomes a must.

DNA Based Computing

2007-05-29T03:42:00.002-07:00

Biological and mathematical operations have some similarities, despite their respective complexities:

1. The very complex structure of a living being is the result of applying simple operations to initial information encoded in a DNA sequence;

2. The result f(w) of applying a computable function to an argument w can be obtained by applying a combination of basic simple functions to w.

For the same reasons that DNA was presumably selected for living organisms as a genetic material, its stability and predictability in reactions, DNA strings can also be used to encode information for mathematical systems.

To solve the Hamiltonian Path problem, the objective is to find a path from start to end going through all the points only once. This problem is difficult for conventional computers to solve because it is a 'non-deterministic polynomial time problem' (NP). NP problems are intractable with deterministic (conventional/serial) computers, but can be solved using non-deterministic (massively parallel) computers. A DNA computer is a type of non-deterministic computer. Dr. Leonard Adleman (1994) was struck with the idea of using sequences of stored nucleotides (Adenine (A), Guanine (G), Cytosine (C), Thymine (T)) in molecules of DNA to store computer instructions and data in place of the sequences of electrical, magnetic or optical on-off states (0, 1 â€“ Boolean Logic) used in todayâ€™s computers. The Hamiltonian Path problem was chosen because it is known as 'NP-complete'; every NP problem can be reduced to a Hamiltonian Path problem.

The following algorithm solves the Hamiltonian Path problem:

1. Generate random paths through the graph.

2. Keep only those paths that begin with the start city (A) and conclude with the end city (G).

3. If the graph has n cities, keep only those paths with n cities. (n = 7)

4. Keep only those paths that enter all cities at least once.

5. Any remaining paths are solutions.

Unrestricted model of DNA computing is the key to solve the problem in five steps in the above algorithm. These operations can be used to 'program' a DNA computer.

o Synthesis of a desired strand

o Separation of strands by length

o Merging: pour two test tubes into one to perform union

o Extraction: extract those strands containing a given pattern

o Melting/Annealing: break/bond two ssDNA molecules with complementary sequences

o Amplification: use PCR to make copies of DNA strands

o Cutting: cut DNA with restriction enzymes

o Ligation: Ligate DNA strands with complementary sticky ends using ligase

o Detection: Confirm presence/absence of DNA in a given test tube

Since Adleman's original experiment, several methods to reduce error and improve efficiency have been developed.The Restricted model of DNA computing solves several physical problems with the Unrestricted model. The Restricted model simplifies the physical obstructions in exchange for some additional logical considerations. The purpose of this restructuring is to simplify biochemical operations and reduce the errors due to physical obstructions.

The Restricted model of DNA computing:

o Separate: isolate a subset of DNA from a sample

o Merging: pour two test tubes into one to perform union

o Detection: Confirm presence/absence of DNA in a given test tube

Despite these restrictions, this model can still solve NP-complete problems such as the 3-colourability problem, which decides if a map can be coloured with three colours in such a way that no two adjacent territories have the same colour. Error control is achieved mainly through logical operations, such as running all DNA samples showing positive results a second time to reduce false positives. Some molecular proposals, such as using DNA with a peptide backbone for stability, have also been recommended.

DNA computing brings great optimism to revolutionize the computer industry in the use of molecules of DNA in a computer, in place of electronics, circuits and magnetic or optical storage media. Obviously, to perform one calculation at a time (serial logic), DNA computers are not a viable option. However, if one wanted to perform many calculations simultaneously (parallel logic), a computer such as the one described above can easily perform 10¹⁴ million instructions per second (MIPS). DNA computers also require less energy and space. In DNA computers data are entered and coded into DNA by chemical reactions and retrieved by synthesizing a key data and make them react with existing strands. Here the key DNA will stick to the required DNA strands containing data.

In short, in a DNA computer, the input and output are both strands of DNA. Furthermore, a computer in which the strands are attached to the surface of a chip (DNA chip) can now solve difficult problems quite quickly

Direct to Home Television (DTH)

2007-05-29T03:42:00.001-07:00

Direct to home (DTH) television is a wireless system for delivering television programs directly to the viewerâ€™s house. In DTH television, the broadcast signals are transmitted from satellites orbiting the Earth to the viewerâ€™s house. Each satellite is located approximately 35,700 km above the Earth in geosynchronous orbit. These satellites receive the signals from the broadcast stations located on Earth and rebroadcast them to the Earth.

The viewerâ€™s dish picks up the signal from the satellite and passes it on to the receiver located inside the viewerâ€™s house. The receiver processes the signal and passes it on to the television.

The DTH provides more than 200 television channels with excellent quality of reception along with teleshopping, fax and internet facilities. DTH television is used in millions of homes across United States, Europe and South East Asia.

Global System for Mobiles

2007-05-29T03:41:00.001-07:00

A GSM network is composed of several functional entities, whose functions and interfaces are specified. Figure 1 shows the layout of a generic GSM network. The GSM network can be divided into three broad parts. The Mobile Station is carried by the subscriber. The Base Station Subsystem controls the radio link with the Mobile Station. The Network Subsystem, the main part of which is the Mobile services Switching Center (MSC), performs the switching of calls between the mobile users, and between mobile and fixed network users. The MSC also handles the mobility management operations. Not shown is the Operations and Maintenance Center, which oversees the proper operation and setup of the network. The Mobile Station and the Base Station Subsystem communicate across the Um interface, also known as the air interface or radio link. The Base Station Subsystem communicates with the Mobile services Switching Center across the A interface.

Free Space Optics

2007-05-29T03:40:00.002-07:00

Mention optical communication and most people think of fiber optics. But light travels through air for a lot less money. So it is hardly a surprise that clever entrepreneurs and technologists are borrowing many of the devices and techniques developed for fiber-optic systems and applying them to what some call fiber-free optical communication. Although it only recently, and rather suddenly, sprang into public awareness, free-space optics is not a new idea. It has roots that go back over 30 years--to the era before fiber-optic cable became the preferred transport medium for high-speed communication. In those days, the notion that FSO systems could provide high-speed connectivity over short distances seemed futuristic, to say the least. But research done at that time has made possible today's free-space optical systems, which can carry full-duplex (simultaneous bidirectional) data at gigabit-per-second rates over metropolitan distances of a few city blocks to a few kilometers.

FSO first appeared in the 60's, for military applications. At the end of 80's, it appeared as a commercial option but technological restrictions prevented it from success. Low reach transmission, low capacity, severe alignment problems as well as vulnerability to weather interferences were the major drawbacks at that time. The optical communication without wire, however, evolved! Today, FSO systems guarantee 2.5 Gb/s taxes with carrier class availability. Metropolitan, access and LAN networks are reaping the benefits. FSO success can be measured by its market numbers: forecasts predict it will reach a USS 2.5 billion market by 2006.

The use of free space optics is particularly interesting when we perceive that the majority of customers does not possess access to fibers as well as fiber installation is expensive and demands long time. Moreover, right-of-way costs, difficulties in obataining government licenses for new fiber installation etc. are further problems that has turned FSO into the option of choice for short reach applications.

FSO uses lasers, or light pulses, to send packetized data in the terahertz (THz) spectrum range. Air, ot fiber, is the transport medium. This means that urban businesses needing fast data and Internet access have a significantly lower-cost option.

An FSO system for local loop access comprises several laser terminals, each one residing at a network node to create a single, point-to-point link; an optical mesh architecture; or a star topology, which is usually point-to-multipoint. These laser terminals, or nodes, are installed on top of customers' rooftops or inside a window to complete the last-mile connection. Signals are beamed to and from hubs or central nodes throughout a city or urban area. Each node requires a Line-Of-Sight (LOS) view of the hub.

RFID

2007-05-29T03:40:00.001-07:00

Radio Frequency Identification (RFID) is an automatic identification method, relying on storing and remotely retrieving data using devices called RFID tags or transponders. An RFID tag is a small object that can be attached to or incorporated into a product, animal, or person. RFID tags contain silicon chips and antennas to enable them to receive and respond to radio-frequency queries from an RFID transceiver. Passive tags require no internal power source, whereas active tags require a power source.

RFID tags can be either passive, semi-passive (also known as semi-active), or active.

Passive

Passive RFID tags have no internal power supply. The minute electrical current induced in the antenna by the incoming radio frequency signal provides just enough power for the CMOS integrated circuit (IC) in the tag to power up and transmit a response. Most passive tags signal by backscattering the carrier signal from the reader. This means that the aerial (antenna) has to be designed to both collect power from the incoming signal and also to transmit the outbound backscatter signal. The response of a passive RFID tag is not just an ID number (GUID): tag chip can contain nonvolatile EEPROM(Electrically Erasable Programmable Read-Only Memory) for storing data. Lack of an onboard power supply means that the device can be quite small: commercially available products exist that can be embedded under the skin. As of 2006, the smallest such devices measured 0.15 mm Ã— 0.15 mm, and are thinner than a sheet of paper (7.5 micrometers).[4] The addition of the antenna creates a tag that varies from the size of postage stamp to the size of a post card. Passive tags have practical read distances ranging from about 2 mm (ISO 14443) up to a few meters (EPC and ISO 18000-6) depending on the chosen radio frequency and antenna design/size. Due to their simplicity in design they are also suitable for manufacture with a printing process for the antennae. Passive RFID tags do not require batteries, and can be much smaller and have an unlimited life span. Non-silicon tags made from polymer semiconductors are currently being developed by several companies globally. Simple laboratory printed polymer tags operating at 13.56 MHz were demonstrated in 2005 by both PolyIC (Germany) and Philips (The Netherlands). If successfully commercialized, polymer tags will be roll printable, like a magazine, and much less expensive than silicon-based tags.

Because passive tags are cheaper to manufacture and have no battery, the majority of RFID tags in existence are of the passive variety. As of 2005, these tags cost an average of Euro 0.20 ($0.24 USD) at high volumes.

Semi-passive

Semi-passive RFID tags are very similar to passive tags except for the addition of a small battery. This battery allows the tag IC to be constantly powered. This removes the need for the aerial to be designed to collect power from the incoming signal. Aerials can therefore be optimized for the backscattering signal. Semi-passive RFID tags are faster in response and therefore stronger in reading ratio compared to passive tags.

Active

Unlike passive and semi-passive RFID tags, active RFID tags (also known as beacons) have their own internal power source which is used to power any ICs and generate the outgoing signal. They are often called beacons because they broadcast their own signal. They may have longer range and larger memories than passive tags, as well as the ability to store additional information sent by the transceiver. To economize power consumption, many beacon concepts operate at fixed intervals. At present, the smallest active tags are about the size of a coin. Many active tags have practical ranges of tens of meters, and a battery life of up to 10 years.

TETRA

2007-05-29T03:39:00.000-07:00

Terrestrial Enhanced(changed from European) Trunked Radio (TETRA) is a specialist Professional Mobile Radio and walkie talkie standard used by police, fire departments, ambulance and military. Its main advantage over technologies such as GSM are:
the much lower frequency used, which permits very high levels of geographic coverage with a smaller number of transmitters, cutting infrastructure cost.
fast call set-up - a one to many group call is generally set-up within 0.5 seconds compared with the many seconds that are required for a GSM network.
the fact that its infrastructure can be separated from that of the public cellphone network, and made substantially more diverse and resilient by the fact that base stations can be some distance from the area served.
unlike most cellular technologies, TETRA networks typically provide a number of fall-back modes such as the ability for a base station to process local calls in the absence of the rest of the network, and for 'direct mode' where mobiles can continue to share channels directly if the infrastructure fails or is out-of-reach.
gateway mode - where a single mobile with connection to the network can act as a relay for other nearby mobiles that are out of contact with the infrastructure.
TETRA also provides a point-to-point function that traditional analogue emergency services radio systems didn't provide. This enables users to have a one-to-one trunked 'radio' link between sets without the need for the direct involvement of a control room operator/dispatcher.
unlike the cellular technologies, which connects one subscriber to one other subscriber (one-to-one) then Tetra is built to do one-to-one, one-to-many and many-to-many. These operational modes are directly relevant to the public safety and professional users.
Radio aspects
TETRA uses a digital modulation scheme known as PI/4 DQPSK which is a form of phase shift keying. TETRA uses TDMA (see above). The symbol rate is 18,000 symbols per second, and each symbol maps to 2 bits. A single slot consists of 255 symbols, a single frame constist of 4 slots, and a multiframe (whose duration is approximately 1 second) consists of 18 frames. As a form of phase shift keying the downlink power is constant. The downlink (i.e. the output of the basestation) is a continuous transmission consisting of either specific communications with mobiles, synchronisation or other general broadcasts. Although the system uses 18 frames per second only 17 of these are used for traffic channel, with the 18th frame reserved for signalling or synchronisation. TETRA does not employ amplitude modulation. However, TETRA has 17.65 slots per second (18000 symbols/sec / 255 symbols/slot / 4 slots/frame), which is the cause of the PERCEIVED 'amplitude modulation' at 17Hz.

Orthogonal Frequency Division Multiple Access (OFDMA)

2007-05-29T03:38:00.000-07:00

Orthogonal Frequency Division Multiple Access (OFDMA) is a multiple access scheme for OFDM systems. It works by assigning a subset of subcarriers to individual users.

OFDMA features

OFDMA is the 'multi-user' version of OFDM
Functions by partitioning the resources in the time-frequency space, by assigning units along the OFDM signal index and OFDM sub-carrier index
Each OFDMA user transmits symbols using sub-carriers that remain orthogonal to those of other users
More than one sub-carrier can be assigned to one user to support high rate applications
Allows simultaneous transmission from several users ⇒ better spectral efficiency
Multiuser interference is introduced if there is frequency synchronization error
The term 'OFDMA' is claimed to be a registered trademark by Runcom Technologies Ltd., with various other claimants to the underlying technologies through patents. It is used in the mobility mode of IEEE 802.16 WirelessMAN Air Interface standard, commonly referred to as WiMAX.

The SIDAC

2007-05-29T03:37:00.001-07:00

The SIDAC, or SIlicon Diode for Alternating Current, is a semiconductor of the thyristor family. Also referred to as a SYDAC (Silicon thYristor for Alternating Current), bi-directional thyristor breakover diode, or more simply a bi-directional thyristor diode, it is technically specified as a bilateral voltage triggered switch. Its operation is identical to that of the DIAC; the distinction in naming between the two devices being subject to the particular manufacturer. In general, SIDACs have higher breakover voltages and current handling capacities than DIACs. The operation of the SIDAC is quite simple and is functionally identical to that of a spark gap or similar to two inverse parallel Zener diodes. The SIDAC remains nonconducting until the applied voltage meets or exceeds its rated breakover voltage. Once entering this conductive state, the SIDAC continues to conduct, regardless of voltage, until the applied current falls below its rated holding current. At this point, the SIDAC returns to its initial nonconductive state to begin the cycle once again. Somewhat uncommon in most electronics, the SIDAC is relegated to the status of a special purpose device. However, where part-counts are to be kept low, simple relaxation oscillators are needed, and the voltages are too low for practical operation of a spark gap, the SIDAC is an indispensable component.

DYNODE

2007-05-29T03:36:00.000-07:00

A dynode is one of a series of electrodes within a photomultiplier tube. Each dynode is more positively charged than its predecessor. Secondary emission occurs at the surface of each dynode. Such an arrangement is able to amplify the tiny current emitted by the photocathode by typically one million.

Trisil

2007-05-29T03:35:00.002-07:00

A Trisil is an electronic component designed to protect electronic circuits against overvoltage. Unlike a Transil it acts as a crowbar device, switching on when the voltage on it exceeds its breakover voltage.A Trisil is bipolar, behaving the same way in both directions. It is principally a voltage-controlled triac without gate. In 1982, the only manufacturer was Thomson SA. This type of crowbar protector is widely used for protecting telecom equipment from lightning induced transients and induced currents from power lines. Other manufacturers of this type of device include Bourns and Littelfuse. Rather than using the natural breakdown voltage of the device, an extra region is fabricated within the device to form a zener diode. This allows a much tighter control of the breakdown voltage. It is also possible to make gated versions of this type of protector. In this case, the gate is connected to the telecom circuit power supply (via a diode or transistor) so that the device will crowbar if the transient exceeds the power supply voltage. The main advantage of this configuration is that the protection voltage tracks the power supply, so eliminating the problem of selecting a particular breakdown voltage for the protection circuit.

Active pixel sensor

2007-05-29T03:35:00.001-07:00

An active pixel sensor (APS) is an image sensor consisting of an integrated circuit containing an array of pixels, each containing a photodetector as well as three or more transistors. Since it can be produced by an ordinary CMOS process, APS is emerging as an inexpensive alternative to CCDs.
Architecture
Pixel
The standard CMOS APS pixel consists of three transistors as well as a photodetector.
The photodetector is usually a photodiode, though photogate detectors are used in some devices and can offer lower noise through the use of correlated double sampling. Light causes an accumulation, or integration of charge on the 'parasitic' capacitance of the photodiode, creating a voltage change related to the incident light.
One transistor, Mrst, acts as a switch to reset the device. When this transistor is turned on, the photodiode is effectively connected to the power supply, VRST, clearing all integrated charge. Since the reset transistor is n-type, the pixel operates in soft reset.
The second transistor, Msf, acts as a buffer (specifically, a source follower), an amplifier which allows the pixel voltage to be observed without removing the accumulated charge. Its power supply, VDD, is typically tied to the power supply of the reset transistor.
The third transistor, Msel, is the row-select transistor. It is a switch that allows a single row of the pixel array to be read by the read-out electronics.
Array
A typical two-dimensional array of pixels is organized into rows and columns. Pixels in a given row share reset lines, so that a whole row is reset at a time. The row select lines of each pixel in a row are tied together as well. The outputs of each pixel in any given column are tied together. Since only one row is selected at a given time, no competition for the output line occurs. Further amplifier circuitry is typically on a column basis.

hydrophone

2007-05-29T03:33:00.000-07:00

A hydrophone is a sound-to-electricity transducer for use in water or other liquids, analogous to a microphone for air. Note that a hydrophone can sometimes also serve as a projector (emitter), but not all hydrophones have this capability, and may be destroyed if used in such a manner.The first device to be called a 'hydrophone' was developed when the technology matured, and used ultrasonic waves, which would provide for higher overall acoustic output, as well as increasing detection. The ultrasonic waves were produced by a mosaic of thin quartz crystals glued between two steel plates, having a resonant frequency of about 150 kHz. Contemporary hydrophones more often use barium titanate, a piezoelectric ceramic material, giving higher sensitivity than quartz. Hydrophones are an important part of the SONAR system used to detect submarines by both surface vessels and other submarines. A large number of hydrophones were used in the building of various fixed location detection networks such as SOSUS.

Mesotechnology

2007-05-29T03:32:00.000-07:00

Brain Computer Interface

2007-05-29T03:31:00.000-07:00

Brain-Computer interface is a staple of science fiction writing. Init's earliest incarnations nomechanism was thought necessary, as the technology seemed so far fetched that no explanation was likely. As more became known about the brain however, the possibility has become more real and the science fiction more technically sophisticated. Recently, the cyberpunk movement has adopted the idea of 'jacking in', sliding 'biosoft' chips into slots implanted in the skull (Gibson, W. 1984).

Although such biosofts are still science fiction, there have been several recent steps toward interfacing the brain and computers. Chief among these are techniques for stimulating and recording from areas of the brain with permanently implanted electrodes and using conscious control of EEG to control computers.

Some preliminary work is being done on synapsing neurons on silicon transformers and on growing neurons into neural networks on top of computer chips.The most advanced work in designing a brain-computer interface has stemmed from the evolution of traditional electrodes. There are essentially two main problems, stimulating the brain (input) and recording from the brain (output).

Traditionally, both input and output were handled by electrodes pulled from metal wires and glass tubing.Using conventional electrodes, multi-unit recordings can be constructed from mutlibarrelled pipettes. In addition to being fragile and bulky, the electrodes in these arrays are often too far apart, as most fine neural processes are only .1 to 2 Âµm apart.

Pickard describes a new type of electrode, which circumvents many of the problems listed above. These printed circuit micro-electrodes (PCMs) are manufactured in the same manner of computer chips. A design of a chip is photoreduced to produce an image on a photosensitive glass plate. This is used as a mask, which covers a UV sensitive glass or plastic film.

A PCM has three essential elements:

1) the tissue terminals,

2) a circuit board controlling or reading from the terminals

3) a Input/Output controller-interpreter, such as a computer.

Artificial passenger

2007-05-29T03:30:00.000-07:00

An artificial passenger (AP) is a device that would be used in a motor vehicle to make sure that the driver stays awake. IBM has developed a prototype that holds a conversation with a driver, telling jokes and asking questions intended to determine whether the driver can respond alertly enough. Assuming the IBM approach, an artificial passenger would use a microphone for the driver and a speech generator and the vehicle s audio speakers to converse with the driver.

The conversation would be based on a personalized profile of the driver. A camera could be used to evaluate the driver s facial state and a voice analyzer to evaluate whether the driver was becoming drowsy. If a driver seemed to display too much fatigue, the artificial passenger might be programmed to open all the windows, sound a buzzer, increase background music volume, or even spray the driver with ice water.

ShotCode

2007-05-29T03:28:00.002-07:00

ShotCode is a circular barcode created by OP3. It uses a dartboard-like circle, with a bulls eye in the centre and datacircles surrounding it. The technology reads databits from these datacircles by measuring the angle and distance from the bulls eye for each.

ShotCodes are designed to be read with a regular camera (including those found on mobile phones and webcams) without the need to purchase other specialised hardware. Because of the circular design, it is also possible for software to detect the angle from which the barcode is read. ShotCodes differ from matrix barcodes in that they do not store regular data - rather, they store an encoded URL which the reading device can connect to in order to download said data.

Serial ATA (SATA)

2007-05-29T03:28:00.001-07:00

In computer hardware, Serial ATA (SATA, IPA: /ˈsÃ¦ta/ or /ˈseɪˌtə/) is a computer bus technology primarily designed for transfer of data to and from a hard disk. It is the successor to the legacy AT Attachmentretroactively renamedParallel ATA (PATA) to distinguish it from Serial ATA. Both SATA and PATA drives are IDE (Integrated Drive Electronics) drives, although IDE is often misused to indicate PATA drives.

standard (ATA). This older technology was

Serial ATA innovations

SATA drops the master/slave shared bus of PATA, giving each device a dedicated cable and dedicated bandwidth. While this requires twice the number of host controllers to support the same number of SATA devices, at the time of SATA's introduction this was no longer a significant drawback. Another controller could be added into a controller ASIC at little cost beyond the addition of the extra seven signal lines and printed circuit board (PCB) space for the cable header.

Features allowed for by SATA but not by PATA include hot-swappingnative command queueing. and

To ease their transition to SATA, many manufacturers have produced drives which use controllers largely identical to those on their PATA drives and include a bridge chip on the logic board. Bridged drives have a SATA connector, may include either or both kinds of power connectors, and generally perform identically to native drives. They may, however, lack support for some SATA-specific features. As of 2004, all major hard drive manufacturers produce either bridged or native SATA drives.

SATA drives may be plugged into Serial Attached SCSI (SAS) controllers and communicate on the same physical cable as native SAS disks. SAS disks, however, may not be plugged into a SATA controller.

Physically, the SATA power and data cables are the most noticeable change from Parallel ATA. The SATA standard defines a data cable using seven conductors and 8 mm wide wafer connectors on each end. SATA cables can be up to 1 m (39 in) long. PATA ribbon cables, in comparison, carry either 40- or 80-conductor wires and are limited to 46 cm (18 in) in length. The reduction in conductors makes SATA connectors and cables much narrower than those of PATA, thus making them more convenient to route within tight spaces and reducing obstructions to air cooling. Unlike early PATA connectors, SATA connectors are keyed â€” it is not possible to install cable connectors upside down without considerable force.

The SATA standard also specifies a power connector sharply differing from the four-pin Molex connector used by PATA drives and many other computer components. Like the data cable, it is wafer-based, but its wider 15-pin shape should prevent confusion between the two. The seemingly large number of pins are used to supply three different voltages if necessary â€” 3.3 V, 5 V, and 12 V. Each voltage is supplied by three pins ganged together (and 6 pins for ground). This is because the small pins cannot supply sufficient current for some devices, so they are combined. One pin from each of the three voltages is also used for hotplugging. The same physical connections are used on 3.5-in (90mm) and 2.5-in (70mm) (notebook) hard disks. Some SATA drives include a PATA-style 4-pin Molex connector for use with power supplies that lack the SATA power connector. Also, adaptors are available to convert a 4-pin Molex connector to SATA power connector.

External SATA

eSATA was standardized in mid-2004, with specifically defined cables, connectors, and signal requirements for external SATA drives. eSATA is characterized by:

Full SATA speed for external disks (115MB/s have been measured with external RAID enclosures)
No protocol conversion from PATA/SATA to USB/Firewire, all disk features are available to the host
Cable length is restricted to 2m, USB and Firewire span longer distances.
Minimum and maximum transmit voltage decreased to 400mV - 500mV
Minimum and maximum receive voltage decreased to 240mV - 500mV

USB and Firewire require conversion of all communication with the external disk, so external USB/Firewire enclosures include a PATA or SATA bridge chip that translates from the ATA protocol to USB or Firewire. Drive features like S.M.A.R.T. cannot be exploited that way and the achievable transfer speed with USB/Firewire is only about half of the entire bus data rate of about 50MB/s. This limited effective data transfer rate becomes very visible when using an external RAID array and also with fast single disks which may yield well over 70MB/s during real use.

Currently, most PC motherboards do not have an eSATA connector. eSATA may be enabled through the addition of an eSATA host bus adapter (HBA) or bracket connector for desktop systems or with a Cardbus or ExpressCard for notebooks.

Note: Prior to the final eSATA specification, there were a number of products designed for external connections of SATA drives. Some of these use the internal SATA connector or even connectors designed for other interface specifications, such as FireWire. These products are not eSATA compliant.

eSATA does not provide power, which means that external 2.5' disks which would otherwise be powered over the USB or Firewire cable need a separate power cable when connected over eSATA.

Night vision technology

2007-05-29T03:26:00.000-07:00

Night vision technology was developed by the US defense department mainly for defense purposes ,but with the development of technology night vision devices are being used in day to day lives. In this seminar of mine I wish to bring out the various principles of working of these devices that have changed the outlook both on the warfront and in our common lives. Night Vision can work in two different ways depending on the technology used. 1.Image enhancement- This works by collecting the tiny amounts of light including the lower portion of the infrared light spectrum, those are present but may be imperceptible to our eyes, and amplifying it to the point that we can easily observe the image. 2:Thermal imaging- This technology operates by capturing the upper portion of the infrared light spectrum, which is emitted as heat by objects instead of simply reflected as light. Hotter objects, such as warm bodies, emit more of this light than cooler objects like trees or buildings.

RAID

2007-05-29T03:25:00.002-07:00

In computing, the acronym RAID (originally redundant array of inexpensive disks, now also known as redundant array of independent disks) refers to a data storage scheme using multiple hard drives to share or replicate data among the drives. Depending on the version chosen, the benefit of RAID is one or more of increased data integrity, fault-tolerance, throughput or capacity compared to single drives. In its original implementations, its key advantage was the ability to combine multiple low-cost devices using older technology into an array that offered greater capacity, reliability, speed, or a combination of these things, than was affordably available in a single device using the newest technology.

At the very simplest level, RAID combines multiple hard drives into a single logical unit. Thus, instead of seeing several different hard drives, the operating system sees only one. RAID is typically used on server computers, and is usually (but not necessarily) implemented with identically sized disk drives. With decreases in hard drive prices and wider availability of RAID options built into motherboard chipsets, RAID is also being found and offered as an option in more advanced personal computers. This is especially true in computers dedicated to storage-intensive tasks, such as video and audio editing.

The original RAID specification suggested a number of prototype RAID levels , or combinations of disks. Each had theoretical advantages and disadvantages. Over the years, different implementations of the RAID concept have appeared. Most differ substantially from the original idealized RAID levels, but the numbered names have remained. This can be confusing, since one implementation of RAID 5, for example, can differ substantially from another. RAID 3 and RAID 4 are often confused and even used interchangeably.

Quantum computer

2007-05-29T03:25:00.001-07:00

A Quantum Computer is a computer that harnesses the power of atoms and molecules to perform memory and processing tasks. It has the potential to perform certain calculations billions of times faster than any silicon-based computer In both the search for ever smaller and faster computational devices, and the search for a computational understanding of biological systems such as the brain, one is naturally led to consider the possibility of computational devices the size of cells, molecules, atoms, or on even smaller scales.

Indeed, it has been pointed out that if trends over the last forty years continue, we may reach atomic-scale computation by the year 2010. This move down in scale takes us from systems that can be understood (to a good enough approximation) using classical mechanics alone, to those which require a quantum mechanical understanding. Thus, it should not be surprising to find that the idea of quantum computation is not new. However, most if not all work so far has been understandably speculative.

QR Code

2007-05-29T03:23:00.002-07:00

A QR Code is a matrix code (or two-dimensional bar code) created by Japanese corporation Denso-Wave in 1994. The QR is derived from Quick Response , as the creator intended the code to allow its contents to be decoded at high speed. QR Codes are most common in Japan, and are currently the most popular type of two dimensional code in Japan.

Although initially used for tracking parts in vehicle manufacturing, QR Codes are now used for inventory management in a wide variety of industries. More recently, the inclusion of QR Code reading software on camera phones in Japan has led to a wide variety of new, consumer-oriented applications, aimed at relieving the user of the tedious task of entering data into their mobile phone. QR Codes storing addresses and URLs are becoming increasingly common in magazines and advertisements in Japan. The addition of QR Codes on business cards is also becoming common, greatly simplifying the task of entering the personal details of a new acquaintance into the address book of one s mobile phone.

Sun Spot

2007-05-29T03:23:00.001-07:00

Sun Spot (Sun Small Programmable Object Technology) is a wireless sensor network (WSN) mote developed by Sun Microsystems. The device is built upon the IEEE 802.15.4 standard. Unlike other available mote systems, the Sun SPOT is built on the Java 2 Micro Edition Virtual Machine (JVM).

Hardware
The completely assembled device should be able to fit in the palm of your hand.
Processing

180 MHz 32 bit ARM920T core - 512K RAM - 4M Flash
2.4 GHz IEEE 802.15.4 radio with integrated antenna
USB interface
Sensor Board
2G/6G 3-axis accelerometer
Temperature sensor
Light sensor
8 tri-color LEDs
6 analog inputs
2 momentary switches
5 general purpose I/O pins and 4 high current output pins

Networking
The motes communicate using the IEEE 802.15.4 standard including the base-station approach to sensor networking. This implementation of 802.15.4 is not ZigBee-compliant.
Software
The device s use of Java device drivers is particularly remarkable as Java is known for its ability to be hardware-independent. Sun SPOT uses a small J2ME which runs directly on the processor without an OS.

Swarm Intelligence

2007-05-29T03:22:00.000-07:00

(SI) is an artificial intelligence technique based around the study of collective behavior in decentralized, self-organized systems. The expression swarm intelligence was introduced by Beni & Wang in 1989, in the context of cellular robotic systems.

SI systems are typically made up of a population of simple agents interacting locally with one another and with their environment. Although there is normally no centralized control structure dictating how individual agents should behave, local interactions between such agents often lead to the emergence of global behavior. Examples of systems like this can be found in nature, including ant colonies, bird flocking, animal herding, bacteria molding and fish schooling.

Application of swarm principles to large numbers of robots is called as swarm robotics.

Honey pot

2007-05-29T03:21:00.000-07:00

A honeypot is an information system resource whose value lies in unauthorized or illicit use of that resource.

A honeypot is a closely monitored network decoy serving several purposes: it can distract adversaries from more valuable machines on a network, can provide early warning about new attack and exploitation trends, or allow in-depth examination of adversaries during and after exploitation of a honeypot. Deploying a physical honeypot is often time intensive and expensive as different operating systems require specialized hardware and every honeypot requires its own physical system.

Honeypots are a powerful, new technology with incredible potential. They can do everything from detecting new attacks never seen in the wild before, to tracking automated credit card fraud and identity theft. In the past several years the technology is rapidly developing, with new concepts such as honeypot farms, commercial and open source solutions, and documented findings released.

A great deal of research has been focused on identifying, capturing, and researching external threats. While malicious and dangerous, these attacks are often random with attackers more interested in how many systems they can break into then which systems they break into. To date, limited research has been done on how honeypots can apply to a far more dangerous and devastating threat, the advanced insider. This trusted individual knows networks and organization. Often, these individuals are not after computers, but specific information. This is a risk that has proven far more dangerous, and far more difficult to mitigate.

WarDriving

2007-05-29T03:20:00.002-07:00

Wardriving is searching for Wi-Fi wireless networks by moving vehicle. It involves using a car or truck and a Wi-Fi-equipped computer, such as a laptop or a PDA, to detect the networks. It was also known (as of 2002) as WiLDing (Wireless Lan Driving, although this term never gained any popularity and is no longer used), originating in the San Francisco Bay Area with the Bay Area Wireless Users Group (BAWUG). It is similar to using a scanner for radio.

Many wardrivers use GPS devices to measure the location of the network find and log it on a website (the most popular is WiGLE). For better range, antennas are built or bought, and vary from omnidirectional to highly directional. Software for wardriving is freely available on the Internet, notably, NetStumbler for Windows, Kismet for Linux, and KisMac for Macintosh.

Wardriving was named after wardialing (popularized in the Matthew Broderick movie WarGames) because it also involves searching for computer systems with software that would use a phone modem to dial numbers sequentially and see which ones were connected to a fax machine or computer, or similar device.

Boids

2007-05-29T03:20:00.001-07:00

Boids, developed by Craig Reynolds in 1986, is an artificial life program, simulating the flocking behaviour of birds.

As with most artificial life simulations, Boids is an example of emergent behaviour; that is, the complexity of Boids arises from the interaction of individual agents (the boids, in this case) adhering to a set of simple rules. The rules applied in the simplest Boids world are as follows:

separation: steer to avoid crowding local flockmates

alignment: steer towards the average heading of local flockmates

cohesion: steer to move toward the average position of local flockmates

More complex rules can be added, such as obstacle avoidance and goal seeking.

The movement of Boids can either be characterized as chaotic (splitting groups and wild behaviour) or orderly. Unexpected behaviours, such as splitting flocks and reuniting after avoiding obstacles, can be considered emergent.

The boids framework is often used in computer graphics, providing realistic-looking representations of flocks of birds and other creatures, such as schools of fish or herds of animals.

Boids work in a manner similar to cellular automata, since each boid acts autonomously and references a neighbourhood, as do cellular automata.

Epistemology

2007-05-29T03:19:00.000-07:00

Epistemology or theory of knowledge is the branch of philosophy that studies the nature and scope of knowledge. The term epistemology is based on the Greek words episteme (meaning knowledge) and logos (meaning account/explanation); it is thought to have been coined by the Scottish philosopher James Frederick Ferrier.

Much of the debate in this field has focused on analyzing the nature of knowledge and how it relates to similar notions such as truth, belief, and justification. It also deals with the means of production of knowledge, and skepticism about different knowledge claims. In other words, epistemology addresses the questions, What is knowledge? How is knowledge acquired? and, What do people know? Although approaches to answering any one of these questions frequently involve theories connected to others (i.e. some theories of what knowledge is being influenced by broad views as to what people know, with restrictive definitions of knowledge thereby dismissed), there is enough particularized to each that they may be treated of separately.

There are many different topics, stances, and arguments in the field of epistemology. Recent studies have dramatically challenged centuries-old assumptions, and it therefore continues to be vibrant and dynamic.

SemaCode

2007-05-29T03:16:00.002-07:00

Semacode is a private company and also this company s trade name for machine-readable ISO/IEC 16022 Data Matrix symbols which encode internet Uniform Resource Locators (URLs). It is primarily aimed at being used with cellular phones which have built-in cameras. The Data Matrix specification is given by the ISO/IEC 16022 standard.

Using Semacode SDK software, a URL can be converted into a type of barcode resembling a crossword puzzle, which is called a tag . Tags can be quickly captured with a mobile phone s camera and decoded to obtain a Web site address. This address can then be accessed via the phone s web browser.

Real Time Operating System

2007-05-29T03:16:00.001-07:00

A real time system is defined as follows - A real-time system is one in which the correctness of the computations not only depends upon the logical correctness of the computation but also upon the time at which the result is produced. If the timing constraints of the system are not met, system failure is said to be occurred.

Two types Hard real time operating system Strict time constraints Secondary storage limited or absent Conflicts with the time sharing systems Not supported by general purpose OS Soft real time operating system Reduced Time Constraints Limited utility in industrial control or robotics Useful in applications (multimedia, virtual reality) requiring advanced operating-system features. In the robot example, it would be hard real time if the robot arriving late causes completely incorrect operation. It would be soft real time if the robot arriving late meant a loss of throughput. Much of what is done in real time programming is actually soft real time system. Good system design often implies a level of fe/correct behaviour even if the computer system never completes the computation. So if the computer is only a little late, the system effects may be somewhat mitigated.

Hat makes an os a rtos?

1. A RTOS (Real-Time Operating System) has to be multi-threaded and preemptible.

2. The notion of thread priority has to exist as there is for the moment no deadline driven OS.

3. The OS has to support predictable thread synchronisation mechanisms

4. A system of priority inheritance has to exist

5. For every system call, the maximum it takes. It should be predictable and independent from the number of objects in the system

6. the maximum time the OS and drivers mask the interrupts. The following points should also be known by the developer:

1. System Interrupt Levels.

2. Device driver IRQ Levels, maximum time they take, etc.

An Introduction to Artifical Life

2007-05-29T03:14:00.000-07:00

Artifical Life also known as alife or a-life, is the study of life through the use of human-made analogs of living systems. Computer scientist Christopher Langton coined the term in the late 1980s when he held the first 'International Conference on the Synthesis and Simulation of Living Systems' (otherwise known as Artificial Life I) at the Los Alamos National Laboratory in 1987.

The focus of this seminar is Artificial Life in software. Topics which will be covered include: what Artificial Life (ALife) is and is about;

open research problems in Alife;

presuppositions underlying Alife in software;

basic requirements of an Alife software system and some guidelines for designing Alife in software. A few Alife software systems will also be introduced to help concretize the concepts

Cryptovirology

2007-05-29T03:13:00.001-07:00

Cryptovirology is a field that studies how to use cryptography to design powerful malicious software. It encompasses overt attacks such as cryptoviral extortion where a cryptovirus, cryptoworm, or cryptotrojan hybrid encrypts the victim's files and the user must pay the malware author to receive the needed session key (that is encrypted under the author's public key that is contained in the malware). The field also encompasses covert attacks in which the attacker secretly steals private information such as private keys. An example of the latter type of attack are asymmetric backdoors. An asymmetric backdoor is a backdoor (e.g., in a cryptosystem) that can only be used by the attacker even after it is found. There are many other attacks in the field that are not mentioned here.

Artificial Intelligence for Speech Recognition

2007-05-29T03:12:00.000-07:00

Artificial Intelligence (AI) involves two basic ideas. First, it involves studying the thought processes of human beings. Second, it deals with representing those processes via machines (computers, robots, etc). AI is the behavior of a machine, which, if performed by a human being, would be called intelligent. It makes machines smarter and more useful, is less expensive than natural intelligence. Natural Language Processing (NLP) refers to Artificial Intelligence methods of communicating with a computer in a natural language like English. The main objective of a NLP program is to understand input and initiate action.

The input words are scanned and matched against internally stored known words. Identification of a keyword causes some action to be taken. In this way, one can communicate with computer in oneâ€™s language. One of the main benefits of speech recognition system is that it lets user do other works simultaneously

Softwear Computing

2007-05-29T03:11:00.002-07:00

In this talk, we introduce computational aspects of softwear, specifically fabric and body-based gestural controllers for realtime, time-based media.

Softwear is part of our approach to wearable computing that leverages the naturalized affordances and the social conditioning that fabrics, furniture and physical architecture already provide to our everyday interaction. We exploit physical plus computational materials and rely on expert craft from experimental performance, music and plastic arts in order to make a new class of personal and collective expressive media. In this talk, I will survey Topological Media Lab research areas including gesture tracking, realtime video synthesis, realtime audio synthesis, and media choreography based on continuous state evolution.

Traffic Pulse Technology

2007-05-29T03:11:00.001-07:00

The Traffic Pulse network is the foundation for all of Mobility TechnologiesÂ® applications. This network uses a process of data collection, data processing, and data distribution to generate the most unique traffic information in the industry. Digital Traffic PulseÂ® collects data through a sensor network, processes and stores the data in a data center, and distributes that data through a wide range of applications.

Unique among private traffic information providers in the U.S. , Mobility Technologies real-time and archived Traffic Pulse data offer valuable tools for a variety of commericial and governmental applications:

* Telematics - for mobile professionals and others, Mobility Technologies traffic information complements in-vehicle navigation devices, informing drivers not only how to get from point A to point B but how long it will take to get there â€” or even direct them to an alternate route.
* Media - for radio and TV broadcasters, cable operators, and advertisers who sponsor local programming, Traffic Pulse Networks provides traffic information and advertising opportunities for a variety of broadcasting venues.
* Intelligent Transport business solutions (ITS) - for public agencies, Mobility Technologies applications aid in infrastructure planning, safety research, and livable community efforts; integrate with existing and future ITS technologies and deployments; and provide data reporting tools.

Clockless Chips

2007-05-29T03:09:00.000-07:00

Clock speeds are now in the gigahertz range and there is not much room for speedup before physical realities start to complicate things. With gigahertz clock powering a chip, signals barely have enough time to make it across the chip before the next clock tick. At this point, speeding up the clock frequency could become disastrous.

This is where a chip that is not constricted by clock comes in to action.

Clockless approach, which uses a technique known as asynchronous logic, differs from conventional computer circuit design in that the switching on and off of digital circuits is controlled individually by specific pieces of data rather than by a tyrannical clock that forces all of the millions of the circuits on a chip to march in unison.

A major hindrance to the development of the clockless chips is the competitiveness of the computer industry. Presently, it is nearly impossible for companies to develop and manufacture a Clockless chip while keeping the cost reasonable. Another problem is that there arenâ€™t much tools used to develop asynchronous chips. Until this is possible, Clockless chips will not be a major player in the market.

In this seminar the topics covered are â€“ general concept of asynchronous circuits, their design issues and types of design. The major designs discussed are Bounded delay method, Delay insensitive method & the Null Conventional Logic (NCL).

The seminar also does a comparison of synchronous and asynchronous circuits and the applications in which asynchronous circuits are used.

Blue Tooth

2007-05-29T03:07:00.000-07:00

Bluetooth wireless technology is a cable replacement technology that provides wireless communication between portable devices, desktop devices and peripherals. It is used to swap data and synchronize files between devices without having to connect each other with cable. The wireless link has a range of 10m which offers the user mobility. There is no need for the user to open an application or press button to initiate a process. Bluetooth wireless technology is always on and runs in the background. Bluetooth devices scan for other Bluetooth devices and when these devices are in range they start to exchange messages so they can become aware of each others capabilities. These devices do not require a line of sight to transmit data with each other. Within a few years about 80 percent of the mobile phones are expected to carry the Bluetooth chip. The Bluetooth transceiver operates in the globally available unlicensed ISM radio band of 2.4GHz, which do not require operator license from a regulatory agency. This means that Bluetooth technology can be used virtually anywhere in the world. Bluetooth is an economical, wireless solution that is convenient, reliable, and easy to use and operates over a longer distance.

The initial development started in 1994 by Ericsson. Bluetooth now has a special interest group (SIG) which has 1800 companies worldwide. Bluetooth technology enables voice and data transmission in a short-range radio. There is a wide range of devises which can be connected easily and quickly without the need for cables. Soon people world over will enjoy the convenience, speed and security of instant wireless connection. Bluetooth is expected to be embedded in hundreds of millions mobile phones, PCs, laptops and a whole range of other electronic devices in the next few years. This is mainly because of the elimination of cables and this makes the work environment look and feel comfortable and inviting.

Holographic Memory

2007-05-29T03:06:00.000-07:00

Devices that use light to store and read data have been the backbone of data storage for nearly two decades. Compact discs revolutionized data storage in the early 1980s, allowing multi-megabytes of data to be stored on a disc that has a diameter of a mere 12 centimeters and a thickness of about 1.2 millimeters. In 1997, an improved version of the CD, called a digital versatile disc (DVD), was released, which enabled the storage of full-length movies on a single disc.

CDs and DVDs are the primary data storage methods for music, software, personal computing and video. A CD can hold 783 megabytes of data. A double-sided, double-layer DVD can hold 15.9 GB of data, which is about eight hours of movies. These conventional storage mediums meet today's storage needs, but storage technologies have to evolve to keep pace with increasing consumer demand. CDs, DVDs and magnetic storage all store bits of information on the surface of a recording medium. In order to increase storage capabilities, scientists are now working on a new optical storage method called holographic memory that will go beneath the surface and use the volume of the recording medium for storage, instead of only the surface area. Three-dimensional data storage will be able to store more information in a smaller space and offer faster data transfer times.

Holographic memory is developing technology that has promised to revolutionalise the storage systems. It can store data upto 1 Tb in a sugar cube sized crystal. Data from more than 1000 CDs can fit into a holographic memory System. Most of the computer hard drives available today can hold only 10 to 40 GB of data, a small fraction of what holographic memory system can hold. Conventional memories use only the surface to store the data. But holographic data storage systems use the volume to store data. It has more advantages than conventional storage systems. It is based on the principle of holography.

Scientist Pieter J. van Heerden first proposed the idea of holographic (three-dimensional) storage in the early 1960s. A decade later, scientists at RCA Laboratories demonstrated the technology by recording 500 holograms in an iron-doped lithium-niobate crystal and 550 holograms of high-resolution images in a light-sensitive polymer material. The lack of cheap parts and the advancement of magnetic and semiconductor memories placed the development of holographic data storage on hold.

WiFiber

2007-05-29T03:04:00.000-07:00

A new wireless technology could beat fiber optics for speed in some applications.

Atop each of the Trump towers in New York City, there s a new type of wireless transmitter and receiver that can send and receive data at rates of more than one gigabit per second -- fast enough to stream 90 minutes of video from one tower to the next, more than one mile apart, in less than six seconds. By comparison, the same video sent over a DSL or cable Internet connection would take almost an hour to download.

This system is dubbed WiFiber by its creator, GigaBeam, a Virginia-based telecommunications startup. Although the technology is wireless, the company s approach -- high-speed data transferring across a point-to-point network -- is more of an alternative to fiber optics, than to Wi-Fi or Wi-Max, says John Krzywicki, the company s vice president of marketing. And it s best suited for highly specific data delivery situations.

This kind of point-to-point wireless technology could be used in situations where digging fiber-optic trenches would disrupt an environment, their cost be prohibitive, or the installation process take too long, as in extending communications networks in cities, on battlefields, or after a disaster.
Blasting beams of data through free space is not a new idea. LightPointe and Proxim Wireless also provide such services. What makes GigaBeam s technology different is that it exploits a different part of the electromagnetic spectrum. Their systems use a region of the spectrum near visible light, at terahertz frequencies. Because of this, weather conditions in which visibility is limited, such as fog or light rain, can hamper data transmission.

GigaBeam, however, transmits at 71-76, 81-86, and 92-95 gigahertz frequencies, where these conditions generally do not cause problems. Additionally, by using this region of the spectrum, GigaBeam can outpace traditional wireless data delivery used for most wireless networks.

Because so many devices, from Wi-Fi base stations to baby monitors, use the frequencies of 2.4 and 5 gigahertz, those spectrum bands are crowded, and therefore require complex algorithms to sort and route traffic -- both data-consuming endeavors, says Jonathan Wells, GigaBeam s director of product development. With less traffic in the region between 70 to 95 gigahertz, GigaBeam can spend less time routing data, and more time delivering it. And because of the directional nature of the beam, problems of interference, which plague more spread-out signals at the traditional frequencies, are not likely; because the tight beams of data will rarely, if ever, cross each other s paths, data transmission can flow without interference, Wells says.

Correction: As a couple of readers pointed out, our title was misleading. Although the emergence of a wireless technology operating in the gigabits per second range is an advance, it does not outperform current fiber-optic lines, which can still send data much faster.

Even with its advances, though, Gigabeam faces the same problem as other point-to-point technologies: creating a network with an unbroken sight line. Still, it could offer some businesses an alternative to fiber optics. Currently, a GigaBeam link, which consists of a set of transmitting and receiving radios, costs around $30,000. But Krzywicki says that improving technology is driving down costs. In addition to outfitting the Trump towers, the company has deployed a link on the campuses of Dartmouth College and Boston University, and two links for San Francisco s Public Utility Commission.

Secure And Fast Encryption Routine (SAFER)

2007-05-29T03:03:00.002-07:00

n cryptography, SAFER () is the name of a family of block ciphers designed primarily by James Massey (one of the designers of IDEA) on behalf of Cylink Corporation. The early SAFER K and SAFER SK function, but differ in the number of rounds and the designs share the same encryptionkey schedule. More recent versions â€” SAFER+ and SAFER++ were submitted as candidates to the AES process and the NESSIE project respectively. All of the algorithms in the SAFER family are unpatented and available for unrestricted use.

The first SAFER cipher was SAFER K-64, published by Massey in 1993, with a 64-bit block size. The K-64 denotes a key size of 64 bits. There was some demand for a version with a larger 128-bit key, and the following year Massey published such a variant incorporating new key schedule designed by the Singapore Ministry for Home affairs: SAFER K-128. However, both Lars Knudsen and Sean Murphy found minor weaknesses in this version, prompting a redesign of the key schedule to one suggested by Knudsen; these variants were named SAFER SK-64 and SAFER SK-128 respectively â€” the SK standing for Strengthened Key schedule , though the RSA FAQ reports that, one joke has it that SK really stands for Stop Knudsen , a wise precaution in the design of any block cipher . Another variant with a reduced key size was published, SAFER SK-40, to comply with 40-bit export restrictions.

All of these ciphers use the same round function consisting of four stages, as shown in the diagram: a key-mixing stage, a substitution layer, another key-mixing stage, and finally a diffusion layer. In the first key-mixing stage, the plaintext block is divided into eight 8-bit segments, and subkeys are added using either addition modulo 256 (denoted by a + in a square) or XOR (denoted by a + in a circle). The substitution layer consists of two S-boxes, each the inverse of each other, derived from discrete exponentiation (45^x) and logarithm (log₄₅x) functions. After a second key-mixing stage there is the diffusion layer: a novel cryptographic component termed a pseudo-Hadamard transform (PHT). (The PHT was also later used in the Twofish cipher.)

Symfony

2007-05-29T03:03:00.001-07:00

Symfony is a web application framework for PHP5 projects.

It aims to speed up the creation and maintenance of web applications, and to replace the repetitive coding tasks by power, control and pleasure.

The very small number of prerequisites make symfony easy to install on any configuration; you just need Unix or Windows with a web server and PHP 5 installed. It is compatible with almost every database system. In addition, it has a very small overhead, so the benefits of the framework don t come at the cost of an increase of hosting costs.

Using symfony is so natural and easy for people used to PHP and the design patterns of Internet applications that the learning curve is reduced to less than a day. The clean design and code readability will keep your delays short. Developers can apply agile development principles (such as DRY, KISS or the XP philosophy) and focus on applicative logic without losing time to write endless XML configuration files.

Symfony is aimed at building robust applications in an enterprise context. This means that you have full control over the configuration: from the directory structure to the foreign libraries, almost everything can be customized. To match your enterprise s development guidelines, symfony is bundled with additional tools helping you to test, debug and document your project.

Last but not least, by choosing symfony you get the benefits of an active open-source community. It is entirely free and published under the MIT license.

Symfony is sponsored by Sensio, a French Web Agency.

Gecko

2007-05-29T03:02:00.001-07:00

Gecko is the open source, free software web browser layout engine used in all Mozilla-branded software and its derivatives, including later Netscape releases. Written in C++, Gecko is designed to support open Internet standards. Originally created by Netscape Communications Corporation, its development is now overseen by the Mozilla Foundation.

Gecko offers a rich programming API that makes it suitable for a wide variety of roles in Internet enabled applications, such as web browsers, content presentation and client/server [1]. Primarily it is used by Mozilla browser derivatives, such as Mozilla Firefox, K-Meleon and Netscape, to render websites and the browser user interface (written in XUL), but it is used elsewhere as well. Gecko is cross-platform and works on a number of different operating systems, including Microsoft Windows, BSD s, GNU/Linux and Mac OS X.

Gecko is generally considered to be the second most-popular layout engine on the Web, after Trident (used by Internet Explorer for Windows since version 4), and followed by KHTML (used by Konqueror), WebCore (used by Safari), Presto (used by Opera) and Tasman (used by Internet Explorer for Mac).

Genetic programming (GP)

2007-05-29T03:01:00.000-07:00

Genetic programming (GP) is an automated methodology inspired by biological evolution to find computer programs that best perform a user-defined task. It is therefore a particular machine learning technique that uses an evolutionary algorithm to optimize a population of computer programs according to a fitness landscape determined by a program's ability to perform a given computational task. The first experiments with GP were reported by Stephen F. Smith (1980) and Nichael L. Cramer (1985), as described in the famous book Genetic Programming: On the Programming of Computers by Means of Natural Selection by John Koza (1992).

Computer programs in GP can be written in a variety of programming languages. In the early (and traditional) implementations of GP, program instructions and data values were organized in tree-structures, thus favoring the use of languages that naturally embody such a structure (an important example pioneered by Koza is Lisp). Other forms of GP have been suggested and successfully implemented, such as the simpler linear representation which suits the more traditional imperative languages [see, for example, Banzhaf et al. (1998)]. The commercial GP software Discipulus, for example, uses linear genetic programming combined with machine code language to achieve better performance. Differently, the MicroGP uses an internal representation similar to linear genetic programming to generate programs that fully exploit the syntax of a given assembly language.

GP is very computationally intensive and so in the 1990s it was mainly used to solve relatively simple problems. However, more recently, thanks to various improvements in GP technology and to the well known exponential growth in CPU power, GP has started delivering a number of outstanding results. At the time of writing, nearly 40 human-competitive results have been gathered, in areas such as quantum computing, electronic design, game playing, sorting, searching and many more. These results include the replication or infringement of several post-year-2000 inventions, and the production of two patentable new inventions.

Developing a theory for GP has been very difficult and so in the 1990s genetic programming was considered a sort of pariah amongst the various techniques of search. However, after a series of breakthroughs in the early 2000s, the theory of GP has had a formidable and rapid development. So much so that it has been possible to build exact probabilistic models of GP (schema theories and Markov chain models) and to show that GP is more general than, and in fact includes, genetic algorithms.

Genetic Programming techniques have now been applied to evolvable hardware as well as computer programs.

Meta-Genetic Programming is the technique of evolving a genetic programming system using genetic programming itself. Critics have argued that it is theoretically impossible, but more research is needed.

Cake PHP

2007-05-29T03:00:00.000-07:00

CakePHP is a web application framework written in PHP, modeled after the concepts of Ruby on Rails.

Features:

Model, View, Controller Architecture

View Helpers for AJAX, Javascript, HTML Forms and more

Built-in Validation

Application Scaffolding

Application and CRUD code generation via Bake

Access Control Lists

Data Sanitization

Security, Session, and Request Handling Components

Flexible View Caching

Active, Friendly Community - Just join our IRC channel to see who s in. We d love to help you get started.

Flexible License - Cake is distributed under the MIT License

Clean IP - Every line of code was written by the CakePHP development team

Extremely Simple - Just look at the name...It s Cake

Rapid Development - Build apps faster than ever before

Best Practices - Cake is easy to understand and sets the industry standard in security authentication, and session handling, among other features.

OO - Whether you are a seasoned object-oriented programmer or a beginner, you ll feel comfortable

No Configuration - Set-up the database and watch the magic begin

OWL

2007-05-29T02:59:00.000-07:00

OWL is an acronym for Web Ontology Language, a markup language for publishing and sharing data using ontologies on the Internet. OWL is a vocabulary extension of the Resource Description Framework (RDF) and is derived from the DAML+OIL Web Ontology Language (see also DAML and OIL). Together with RDF and other components, these tools make up the Semantic Web project.

OWL represents the meanings of terms in vocabularies and the relationships between those terms in a way that is suitable for processing by software.

The OWL specification is maintained by the World Wide Web Consortium (W3C).

OWL currently has three flavors: OWL Lite, OWL DL, and OWL Full. These flavors incorporate different features, and in general it is easier to reason about OWL Lite than OWL DL and OWL DL than OWL Full. OWL Lite and OWL DL are constructed in such a way that every statement can be decided in finite time; OWL Full can contain endless loops .

Ruby on Rails

2007-05-29T02:58:00.001-07:00

Ruby on Rails, often called RoR, or just Rails written in , is an open source web application frameworkRuby that closely follows the Model-View-Controller (MVC) architecture. It strives for simplicity and allowing real-world applications to be developed in less code than other frameworks and with a minimum of configuration.

The Ruby programming language allows for extensive metaprogramming, which Rails makes much use of. This results in a syntax that many of its users find to be very readable. Rails is primarily distributed through RubyGems, which is the official packaging format and distribution channel for Ruby libraries and applications.