Wireless Intellegent Network

Introduction

The intelligent network (IN) is an architectural concept that enables the real time execution of network services and customer applications in a distributed environment consisting of interconnected computers and switching systems. Beginning in the early 1980’s, the IN was applied to the development of new services in wireline telephone networks. Notable successes were achieved in the United States long distance telephone industry and virtual private network (VPN) services contributed strongly to growth in traffic and revenue.

As we know that the wireless market is becoming increasingly competitive, rapid development of enhanced services become critical to a successful wireless strategy. Rapid creation and deployment of services has become the hallmark of a wireline network based on IN concepts. The WIN will bring those same successful strategies into the wireless networks.

Data-Service Capabilities

Handset displays allow customers to use various massaging services. One, called short message service (SMS), works much like a pager. It allows phones to send and receive messages in addition to making or taking telephone calls. SMS require many SS7 messages just to set up the signaling and the mechanism to get the data through the wireless network. It requires a significant amount of checks and balances, finding the database, pulling up the message, encapsulating it with the right header information to route it to the correct user, and finally sending it out like a phone call.

Calling Name Presentation

CNP displays the name of the calling party on the called party’s terminal. When a call comes in for a wireless subscriber, the subscriber’s home MSC receives the call. The home MSC queries the HLR to determine where the mobile is located. The HLR sends a route request to the MSC serving the subscriber and receives from the serving MSC a temporary local directory number (TLDN), which is routed back to the home MSC. The home MSC uses the TDLN to route the call over the public switched telephone (PSTN) to the serving MSC. When the call is delivered to the serving MSC, the caller’s number is also delivered.

Abstract

Wireless Intelligent Network (WIN) is a concept being developed by the Telecommunications Industry Association (TIA) Standards Committee TR45.2. The motive of WIN is to drive intelligent network (IN) capabilities, based on interim standard (IS)-41, into wireless networks WIN is defined as an architecture that separates the service logic and feature functionality from the wireless network switch and places that functionality in other platforms of the network. . Not only are subscribers insisting on more functionality, not only are subscriber bases growing at tremendous rate, but as subscribers become increasingly accustomed to using wireless phones, they are becoming more mobile and require more services. Expectations for services have gone beyond the need for emergency assistance; people require the same functionality that they are using on their landline phones.

Win Services

Enhanced services are increasing in popularity. At this point, various carriers within different serving areas are implementing them using available IN protocols and concepts.

 Voice Controlled Services

        Hand free services are the most sought after services today. They need features like voice activated dialing and feature activation which requires special technology that converts voice into data.

Conclusion

        The movement to develop a WIN strategy was originally triggered by wireless network operators under the auspices of the Cellular Telecommunications Industry Association (CTIA). They developed a set of requirements calling for industry standards that defined new network architecture incorporating the service flexibility of INs with the mobility aspects of wireless networks.

Super Capacitor

Abstract        

                  

                               Super capacitors also known as Electric double-layer capacitors, or electrochemical double layer capacitors (EDLCs), or ultracapacitors, are electrochemical capacitors that have an unusually high energy density when compared to common capacitors, typically on the order of thousands of times greater than a high capacity electrolytic capacitor. For instance, a typical electrolytic capacitor will have a capacitance in the range of tens of millifarads. The same size super capacitor would have a capacitance of several farads, an improvement of about two or three orders of magnitude in capacitance but usually at a lower working voltage. Larger, commercial electric doublelayer capacitors have capacities as high as 5,000farads.

                            Super capacitor technology is based the electric double layer phenomenon that has been understood for over a hundred years. However, it has only been exploited by commercial applications for about ten years. As in a conventional capacitor, in an ultracapacitor two conductors and a dielectric generate an electric field where energy is stored. The double layer is created at a solid electrode-solution interface - it is, then, essentially a charge separation that occurs at the interface between the solid and the electrolyte. Two charge layers are formed, with an excess of electrons on one side and an excess of positive ions on the other side. The polar molecules that reside in between form the dielectric. In most ultracapacitors, the electrode is carbon combined with an electrolyte.  

 Consumer Electronics

                        Super capacitors can be used in PC Cards, flash photography devices in digital cameras, flashlights, portable media players, solar power calculator, electronic toy, internet equipments and in automated meter reading, particularly where extremely fast charging is desirable.

Fuel Cell Vehicles

In the future the combustion engine mechanical energy obtained from the fuel combustion could be replaced electrical engine supplied by electricity produced by a fuel cell. The promise of fuel cell technology has had a recent resurgence due to new advancements not in fuel cells, but in the double-layer capacitors. Indeed, high power energy storage is required in all types of fuel cell applications and double-layer capacitors are ideally suited to provide it. These improvements open up opportunities for the development of new power train and subsystem architectures utilizing both double-layer capacitors and fuel cells which can improve performance, efficiency, and cleanliness in electric and hybrid vehicle technology.

Introduction

This paper offers a concise review on the use of a super capacitor in various energy storage applications. Super capacitor is also known as Electric/electrochemical double layer capacitor (EDLC) is a unique electrical storage device, which can store much more energy than conventional capacitors and offer much higher power density than batteries. Electric double-layer capacitor would have a capacitance of several farads, an improvement of about two or three orders of magnitude in capacitance, but usually at a lower working voltage.

Conclusion      

                           

In this paper the use of super capacitor for various energy storage applications is described. They would have a capacitance of several farads, an improvement of about two or three orders of magnitude in capacitance, but usually at a lower working voltage. The specific Power of the super capacitors and its lifetime (1 million of Cycles) is very high. These peculiarities make it very attractive for various energy storage applications and the startup of the automobiles etc.

Stealth Technology

History Of Stealth Aircraft

With the increasing use of early warning detection devices such as radar by militaries around the world in the 1930's the United States began to research and develop aircraft that would be undetectable to radar detection systems. The first documented stealth prototype was built out of two layers of plywood glued together with a core of glue and sawdust. This prototype's surface was coated with charcoal to absorb radar signals from being reflected back to the source, which is how radar detection systems detect items in the air.

Introduction

Stealth means now observable. The very basic idea of Stealth Technology in the military is to 'blend' in with the background. The quest for a stealthy plane actually began more than 50 years ago during World War II when RADAR was first used as an early warning system against fleets of bombers. As a result of that quest, the Stealth Technology evolved. Stealth Technology is used in the construction of mobile military systems such as aircrafts and ships to significantly reduce their detection by enemy, primarily by an enemy RADAR. The way most airplane identification works is by constantly bombarding airspace with a RADAR signal.

 Design

The surfaces and edge profiles are optimized to reflect hostile radar into narrow beam signals, directed away from the enemy radar detector. All the doors and opening panels on the aircraft have saw-toothed forward and trailing edges to reflect radar. The aircraft is mainly constructed of aluminum, with titanium for areas of the engine and exhaust systems. The outer surface of the aircraft is coated with a radar-absorbent material (RAM). The radar cross-section of the F-117 has been estimated at between 10-100cm2. The entire stealth fleet will be stripped of the sheet-coated, radar-absorbing materials on the wings, rudders and fuselage.

Radar Absorbent Material (Ram)

As its name implies, RAM is intended to reduce the scattered signal by absorbing some part of the incident radiation. Microwave energy is converted into heat energy with hardly any noticeable temperature rise because the energies involved are extremely small. Various kinds of materials can be made to absorb microwave energy by impregnating them with conducting materials such as carbon and iron.

Heat Radiation Reduction

Infrared radiation (heat) should be minimized by a combination of temperature reduction and masking. The main body of the airplane has its own radiation, heavily dependent on speed and altitude, and the jet plume can be a most significant factor, particularly in after burning operation. The engines are buried deep in the fuselage These have got shallow 'platypus' exhausts, which cool and deflect the exhaust gases upward to minimize heat emissions.

Radar

Currently the way to detect and even identify an aircraft is the use of RADAR (radio detection and ranging). This system invented during World War II, simply works by constantly sending bursts of radio waves of certain frequencies and measures the echoes of each burst. Objects are reflecting parts of the energy of radio waves.

Abstract

Stealth or low observability (as it is scientifically known) is one of the most misunderstood and misinterpreted concepts in military aviation by the common man. Stealth aircraft are considered as invisible aircraft, which dominate the skies. With an additional boost from Hollywood action movies, stealth is today termed as the concept invincibility rather than invisibility.

Conclusion

Imagine you can electronically change the color of a given surface in such a way it can match the terrain below it. Looking from above, the surface appears to match the terrain. Fly over forest, and the surface takes on a green like hue. A cloudy day adds clouds to match what sensors see underneath and the aircraft becomes a chameleon and disappears. This may sound like science fiction, but then think of the LCD display of notebooks and it may not seem so far fetched all of a sudden.

  

Spin Valve Transistor

Evolution Of Spintronics

        Spintronics came into light by the advent of Giant Magneto Resistance (GMR) in 1988. GMR is 200 times stronger than ordinary Magneto Resistance.  It results from subtle electron – spin effects in ultra multilayers of magnetic materials that cause a huge change in electrical resistance.

A spin valve multilayer serves as a base region of an n silicon metal base transistor structure.  Metal base transistors have been proposed for ultrahigh frequency operations because of 1.  Negligible base transport time. 2. Low base resistance, but low gain prospects have limited their emergence.  The first evidence of a spin valve effect for hot electrons in Co/Cu multilayers is the spin valve transistor. In this we see a very large change in collector current (215% at 77K) under application of magnetic field of 500 Oe.

Abstract

        In a world of ubiquitous presence of electrons can you imagine any other field displacing it? It may seem peculiar, even absurd, but with the advent of spintronics it is turning into reality. In our conventional electronic devices we use semi conducting materials for logical operation and magnetic materials for storage, but spintronics uses magnetic materials for both purposes. These spintronic devices are more versatile and faster than the present one. One such device is spin valve transistor.

Temperature Effects

        Transport property of hot electron is not fully understood at very low energy regime at finite temperatures. So, It is necessary to probe the temperature dependence of the hot electron transport property in relation to the SVT. The collector current across the spin valve changes its relative orientation of magnetic movements at finite temperature. Surprisingly the collector current showed different behaviors depending on the relative spin orientation in Ferro Magnetic layers. The parallel collector current is increasing up to 200 K and decreasing after that, while anti-parallel collector current is increasing up to room temperature. Actually in ordinary metals, the scattering strength increases with temperature T.

Introduction

        Two experiments in 1920’s suggested spin as an additional property of the electron.  One was the closely spaced splitting of Hydrogen spectralines, called fine structure.  The other was Stern –Gerlach experiment, which in 1922 that a beam of silver atoms directed through an inhomogeneous magnetic field would be forced in to two beams.  These pointed towards magnetism associated with the electrons.

         Spin is the root cause of magnetism that makes an electron tiny magnet.  Magnetism is already been exploited in recording devices. 

Conclusion

Now it is clear that, Spinvalve transistor is more versatile and more robust but it needs further fabrication methods to improve magnetic sensitivity of collector current. The greatest hurdle for spintronic engineers may be controlling all that spin. To do it on a single transistor is already feasible while to do it on a whole circuit will require some clever ideas.

SPECT

What Is SPECT?

        SPECT is short for single photon emission computed tomography. As its name suggests (single photon emission) gamma rays are the sources of the information rather than X-ray emission in the conventional CT scan.

Image Acquisition

        Nuclear medicine images can be acquired in digital format using a SPECT scanner. The distribution of radionudide in the patient’s body corresponds to the analog image. An analog image is one that has a continuous distribution of density representing the continuous distribution of radionuclide amassed in a particular organ. The gamma ray counts coming from the patient’s body are digitized and stored in the computer in an array or image matrix. Typical matrix sizes used in SPECT imaging are 256x256, 128x128, 128x64 or 64x64. The third dimension in the array corresponds to the number of transaxial, coronal or sagittal slices used to represent the organ being imaged.

 Data filtering

        Once the data has been transformed to the frequency domain, it is then filtered in order to smooth out the statistical noise. There are many different filters available to filter the data and they all have slightly different characteristics. For instance, some will smooth very heavily so that there are not any sharp edges, and hence will degrade the final image resolution other filters will maintain a high resolution while only smoothing slightly .

Introduction

        Emission Computed Tomography is a technique where by multi cross sectional images of tissue function can be produced , thus removing the effect of overlying and underlying activity. The technique of ECT is generally considered as two separate modalities. SINGLE PHOTON Emission Computed Tomography involves the use single gamma ray emitted per nuclear disintegration. Positron Emission Tomography makes use of radio isotopes such as gallium-68, when two gamma rays each of 511KeV, are emitted simultaneously where a positron from a nuclear disintegration annihilates in tissue. SPECT, the acronym of Single Photon Emission Computed Tomography is a nuclear medicine technique that uses radiopharmaceuticals, a rotating camera and a computer to produce images which allow us to visualize functional information about a patient’s specific organ or body system.

Positron Emission Tomography (Pet)

        The distribution of activity in slices of organs can be obtained in a more accurate way using PET. In the simplest PET camera two modified sophisticated cameras called Anger cameras are placed on opposite sides of the patient. This increases the collection angle and reduces the collection times which are the limitations of SPECT .In PET, radiopharmaceuticals are labeled with positron emitting isotopes. A positron combines rather quickly with an electron. As a result the two gamma quanta are emitted almost in opposite directions .In PET scanners, rings of gamma ray of gamma ray detectors surrounding the patient are used. Each detector interacts electronically with the other detectors in the field of view. When a photon arrives within a short time frame, it is clear that a pair of quanta was generated and that these were created somewhere along the path between the detectors. Conventional PET tomography makes use of standard filtered back projection techniques used in computed tomography and SPECT.

Abstract

        SPECT, the acronym for Single Photon Emission Computed Tomography, is a nuclear medicine imaging modality, giving information about a patient’s specific organ or body system. The patient is injected with a radiopharmaceutical, which will emit Gamma rays.

Conclusion

        It is reasonable to speculate about a constant by perhaps a slower rate of increase of clinical applications of SPECT. It is safe to conclude that SPECT has reached the stage where it will be a valuable and also an unavoidable asset to the medical world.