E-cigarette (Electronic Cigarette)

   An electronic cigarette, e-cigarette or vaporize cigarette, is a battery-powered device that provides inhaled doses of nicotine or non-nicotine vaporized solution. It is an alternative to smoked tobacco products, such as cigarettes, cigars, or pipes. In addition to purported nicotine delivery,[1] this vapor also provides a flavor and physical sensation similar to that of inhaled tobacco smoke, while no smoke or combustion is actually involved in its operation.

 

An electronic cigarette takes the form of some manner of elongated tube, though many are designed to resemble the outward appearance of real smoking products, like cigarettes, cigars, and pipes. Another common design is the "pen-style", so named for its visual resemblance to a ballpoint pen. Most electronic cigarettes are reusable devices with replaceable and refillable parts. A number of disposable electronic cigarettes have also been developed.

The electronic cigarette was invented by a Chinese medicine practitioner Hon Lik in China in 2003 and introduced to the market the next year. The company he worked for, Golden Dragon Holdings, later changed its name to Ruyan (meaning "to resemble smoking") and started selling abroad.[2]

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OLED VIDEOS

OLED-PRINCIPLE

History

     The first observations of electroluminescence in organic materials were in the early 1950s by A. Bernanose and co-workers at the Nancy-Université, France. They applied high-voltage alternating current (AC) fields in air to materials such as acridine orange, either deposited on or dissolved in cellulose or cellophane thin films.  The proposed mechanism was either direct excitation of the dye molecules or excitation of electrons.^[2][3][4][5]

      In 1960, Martin Pope and co-workers at New York University developed ohmic dark-injecting electrode contacts to organic crystals.^[6][7][8] They further described the necessary energetic requirements (work functions) for hole and electron injecting electrode contacts. These contacts are the basis of charge injection in all modern OLED devices. Pope's group also first observed direct current (DC) electroluminescence under vacuum on a pure single crystal of anthracene and on anthracene crystals doped with tetracene in 1963^[9] using a small area silver electrode at 400V. The proposed mechanism was field-accelerated electron excitation of molecular fluorescence.

     Pope's group reported in 1965^[10] that in the absence of an external electric field, the electroluminescence in anthracene crystals is caused by the recombination of a thermalized electron and hole, and that the conducting level of anthracene is higher in energy than the exciton energy level. Also in 1965, W. Helfrich and W. G. Schneider of the National Research Council in Canada produced double injection recombination electroluminescence for the first time in an anthracene single crystal using hole and electron injecting electrodes,^[11] the forerunner of modern double injection devices. In the same year, Dow Chemical researchers patented a method of preparing electroluminescent cells using high voltage (500–1500 V) AC-driven (100–3000 Hz) electrically-insulated one millimetre thin layers of a melted phosphor consisting of ground anthracene powder, tetracene, and graphite powder.^[12] Their proposed mechanism involved electronic excitation at the contacts between the graphite particles and the anthracene molecules.

    Device performance was limited by the poor electrical conductivity of contemporary organic materials.     However this was overcome by the discovery and development of highly conductive polymers.^[13] For more on the history of such materials, see conductive polymers.

    Electroluminescence from polymer films was first observed by Roger Partridge at the National Physical Laboratory in the United Kingdom. The device consisted of a film of poly(n-vinylcarbazole) up to 2.2 micrometres thick located between two charge injecting electrodes. The results of the project were patented in 1975^[14] and published in 1983.^{[15][16][17][18]}

      The first diode device was reported at Eastman Kodak by Ching W. Tang and Steven Van Slyke in 1987.^[19] This device used a novel two-layer structure with separate hole transporting and electron transporting layers such that recombination and light emission occurred in the middle of the organic layer. This resulted in a reduction in operating voltage and improvements in efficiency and led to the current era of OLED research and device production.

Research into polymer electroluminescence culminated in 1990 with J. H. Burroughes et al. at the Cavendish Laboratory in Cambridge reporting a high efficiency green light-emitting polymer based device using 100 nm thick films of poly(p-phenylene vinylene).^[20]

Working principle

Schematic of a bilayer OLED: 1. Cathode (−), 2. Emissive Layer, 3. Emission of radiation, 4. Conductive Layer, 5. Anode (+)

       A typical OLED is composed of a layer of organic materials situated between two electrodes, the anode and cathode, all deposited on a substrate. The organic molecules are electrically conductive as a result of delocalization of pi electrons caused by conjugation over all or part of the molecule. These materials have conductivity levels ranging from insulators to conductors, and therefore are considered organic semiconductors. The highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of organic semiconductors are analogous to the valence and conduction bands of inorganic semiconductors.

     Originally, the most basic polymer OLEDs consisted of a single organic layer. One example was the first light-emitting device synthesised by J. H. Burroughes et al., which involved a single layer of poly(p-phenylene vinylene). However multilayer OLEDs can be fabricated with two or more layers in order to improve device efficiency. As well as conductive properties, different materials may be chosen to aid charge injection at electrodes by providing a more gradual electronic profile,^[21] or block a charge from reaching the opposite electrode and being wasted.^[22] Many modern OLEDs incorporate a simple bilayer structure, consisting of a conductive layer and an emissive layer.

    During operation, a voltage is applied across the OLED such that the anode is positive with respect to the cathode. A current of electrons flows through the device from cathode to anode, as electrons are injected into the LUMO of the organic layer at the cathode and withdrawn from the HOMO at the anode. This latter process may also be described as the injection of electron holes into the HOMO. Electrostatic forces bring the electrons and the holes towards each other and they recombine forming an exciton, a bound state of the electron and hole. This happens closer to the emissive layer, because in organic semiconductors holes are generally more mobile than electrons. The decay of this excited state results in a relaxation of the energy levels of the electron, accompanied by emission of radiation whose frequency is in the visible region. The frequency of this radiation depends on the band gap of the material, in this case the difference in energy between the HOMO and LUMO.

    As electrons and holes are fermions with half integer spin, an exciton may either be in a singlet state or a triplet state depending on how the spins of the electron and hole have been combined. Statistically three triplet excitons will be formed for each singlet exciton. Decay from triplet states (phosphorescence) is spin forbidden, increasing the timescale of the transition and limiting the internal efficiency of fluorescent devices. Phosphorescent organic light-emitting diodes make use of spin–orbit interactions to facilitate intersystem crossing between singlet and triplet states, thus obtaining emission from both singlet and triplet states and improving the internal efficiency.

      Indium tin oxide (ITO) is commonly used as the anode material. It is transparent to visible light and has a high work function which promotes injection of holes into the HOMO level of the organic layer. A typical conductive layer may consist of PEDOT:PSS^[23] as the HOMO level of this material generally lies between the workfunction of ITO and the HOMO of other commonly used polymers, reducing the energy barriers for hole injection. Metals such as barium and calcium are often used for the cathode as they have low work functions which promote injection of electrons into the LUMO of the organic layer.^[24] Such metals are reactive, so require a capping layer of aluminium to avoid degradation.

     Single carrier devices are typically used to study the kinetics and charge transport mechanisms of an organic material and can be useful when trying to study energy transfer processes. As current through the device is composed of only one type of charge carrier, either electrons or holes, recombination does not occur and no light is emitted. For example, electron only devices can be obtained by replacing ITO with a lower work function metal which increases the energy barrier of hole injection. Similarly, hole only devices can be made by using a cathode comprised solely of aluminium, resulting in an energy barrier too large for efficient electron injection 

^{VIDEOS: OLED}               

ORGANIC LED-OLED-FUTURE TREND

Defnition:

  Organic LED (light-emitting diode) is a display technology based on the use of an organic substance, typically a polymer, as the semiconductor material in light-emitting diodes (LEDs). A polymer can be a natural or synthetic substance and macro or micro in size. Examples of organic polymers include proteins and DNA. OLED technology was pioneered at Kodak, by Dr. Ching W. Tang. 

   An OLED display is created by sandwiching organic thin films between two conductors. When an electrical current is applied to this structure, it emits a bright light. Because OLED displays don't require backlighting, they can be thinner and weigh less than other display technologies. OLED displays also have a wide viewing angle -- up to 160 degrees even in bright light -- and use only two to ten volts to operate.
OLED displays are used in televisions, laptop and desktop computers, cellular phones, digital video cameras, DVD players, PDAs (personal digital assistants) and car stereos. New technologies that build on the OLED include the FOLED (flexible organic light-emitting display), which promises to bring portable, roll-up displays to the consumer market within the next few years. According to market analysts DisplaySearch, OLED display revenues will grow to $4.5 B by 2011, up from $0.5 B in 2006.

  Wouldn't you like to be able to read off the screen of your laptop in direct sunlight? Your mobile phone battery to last much, much longer? Or your next flat screen TV to be less expensive, much flatter, and even flexible? Thanks to a breakthrough technology called Organic Displays, this could soon be reality.

  Although the technology behind Organic LED (OLED) displays is pure chemistry, the applications are much more everyday - mobile telephone and television screens, laptop and stereo displays, car navigation systems, or even billboards.

  This OLED technology is based on a revolutionary discovery that light-emitting, fast switching diodes could be made from polymers as well as from semiconductors. Starting from a standard LCD glass covered with structured ITO (Indium-Tin-Oxide), the polymer materials are applied by precision ink jet printing. Using this technology, pixels of red, green, and blue material are applied. After the patterned cathode has been applied via metal evaporation, the cell is sealed.

  Philips states that the big advantage of the manufacturing process is its simplicity and therefore its potential for low cost; only a very limited number of process steps are needed. This procedure requires fewer manufacturing steps than the manufacturing of LCDs, and, more importantly, fewer materials are used. In fact, the whole display can be built on one sheet of glass or plastic, so it should be cheaper to manufacture. Philips' thin-film PolyLED technology will enable the production of full-color displays less than 1 mm thick. Combined with a large viewing angle, high brightness and contrast, and full video capability, PolyLED displays are ideal for the next generation of information displays.

  The Kodak EasyShare LS633 zoom digital camera uses Kodak's innovative, award-winning AM OLED technology to display bright, sharp images for better on-camera viewing and sharing from virtually any angle.

  The LS633 camera represented a major milestone in the development and manufacture of OLED displays exhibiting more vivid images and crisper video to consumer electronics. The Kodak display AM550L features 165-degree viewing on a 2.2-inch screen that is up to 107 percent larger than the LCDs on most cameras.

  OLED display technology from Kodak is already found in car audio components manufactured by Pioneer and cellular phones marketed by Motorola and Sanyo . With ongoing research conducted by Kodak and its technology licensees, the applications for OLEDs continue to expand, making it clearly the display technology of the future.

  Not only can they provide brighter, better images at a lower cost, but best of all: Organic Displays use a material with self-luminous properties that eliminates the need for a backlight. While backlighting is a crucial component to improving brightness in LCDs, it also adds significant cost as well as requiring extra power - which, for instance, translates into the heavy batteries in your laptop. With an organic display, your laptop might be less heavy to carry around, or your battery lasts much longer compared to a laptop equipped with a traditional LCD screen.

Polymer LEDs have several inherent properties that afford unique possibilities, such as:

* All colors of the visible spectrum are available

* High brightness is achieved at low drive voltages/current densities

* No viewing angle dependence

* Operating lifetime exceeding 10,000 hours

* High response speeds allow display of high quality video

Advantages of Plastic Electronics

  One big advantage of plastic electronics is that there is virtually no restriction on size. Conventional semiconductor components have become smaller and smaller over the course of time. Silicon is the base material of all microelectronics and is eminently suited for this purpose. However, the making of larger components is difficult and therefore costly. The silicon in semiconductor components has to be mono crystalline: it has to have a very pure crystal form without defects in the crystal structure. This is achieved by allowing melted silicon to crystallize under precisely controlled conditions. The larger the crystal, the more problematic this process is. Plastic does not have any of these problems, so that semi-conducting plastics are paving the way for larger semiconductor components.

With the increasing popularity of LCD screens to replace the conventional picture (cathode ray) tube, PolyLED should emerge as another suitable candidate. A screen based on PolyLEDs has obvious advantages: the screen is lightweight and flexible, so that it can be rolled up. With plastic chips you can ensure that the electronics driving the screen are integrated in the screen itself. Other applications of the PolyLED are luminous information screens of almost unlimited size, for example alongside motorways or at train stations.

Philips and PolyLed

Since the discovery of polymer-based light emitting diode (LED) in 1989, Philips has been working on PolyLED. Today, Philips is the first to ship monochrome PolyLED displays in mass production. Philips Research is now concentrating on the development of PolyLED technologies for next-generation full-color displays and on ways of integrating PolyLEDs into flexible displays.

State-of-the-art

Launched in September 2002, the Sensotec Philishave is the first ever product equipped with a display based on superior PolyLED technology and is prominently featured in the latest James Bond movie, Die Another Day.

In 2002, SANYO, Kodak, and SKD shipped 300 OLED displays for trial use in mobile phones. In order to increase production of low temperature poly-silicon TFT LCD displays, the demand for which currently exceeds capacity and in order to establish a mass production infrastructure required for full scale mass production startup of OLED displays, a factory of Tottori SANYO Co., Ltd. was placed under the control of SANYO LCD Engineering Co., Ltd. in February of 2003. The manufacturing line used for the production of amorphous silicon TFT displays is was shifted over to the production of low temperature poly-silicon TFT displays. Production of Low temperature poly-silicon TFT displays on the converted line began in April of 2003.

Some of the challenges OLEDs have to face:

* Entering a market already dominated by a large CRT-to-LCD panel conversion process

* Breaking into the consumer mindset where viewers are still struggling to understand new technologies

* Ensuring competitive refresh rates, contrast ratios, black levels and overall performance

* Quickly m eeting and exceeding price points set by current LCD/plasma technology leaders

While the last issue may be quickly resolved due the nature of the OLED manufacturing process itself, the first three items have yet to be proven and undertaken. OLED technology has to go from novelty to practical competitor in a market that is constantly evolving to exceed and extend beyond its current boundaries. LCD screens are getting faster and faster, while Plasma displays continue to drop in price and go up in performance (check out some of the latest "real-world" contrast ratios achieved by Pioneer and other manufacturers - they rival or exceed that of many high-end direct view CRTs and RPTVs).

We're not sure how fast OLEDs targeted towards home theater or computer display are going to flood the market (Kodak is banking on it happening quickly), but the dam is under stress and the onslaught of consumer devices, once the manufacturing processes are firmly established and optimized, should make for a fantastic "display" of products - one we're looking forward to monitoring.

videos:

Failure of GSLV D3

GSLV failure: Work on cryogenic engine to continue

 Snapping of 10 connectors led to GSLV failure: ISRO sources:

As many as ten connectors between the second and cryogenic third stage had snapped, resulting in non-receipt of commands from onboard computers to strap-on motors in the first stage leading to disintegration of the Geostationary Satellite Launch Vehicle (GSLV-F06) mission which was destroyed within a minute of launch on on Christmas Day.

ISRO sources, speaking on condition of anonymity, said analysis of the data revealed the GSLV-F06, which was meant to put India's heaviest and most advanced communication satellite GSAT-5P in orbit, went out of control due to snapping of ten connectors.

"The take-off was smooth and the flight was normal till 47 seconds. But trouble arose in the next three seconds, when 10 connectors located between the second and third stage (cryogenic stage) got separated, leading to the vehicle losing controllability," the sources said.

The heat shield capsule of the cryo-engine, where the satellite is located, broke first followed by the strap-on motors in the first stage.

As the vehicle started disintegrating, the mission was destroyed by the Range Safety Officer by pressing the "destruct" button, to prevent the debris from falling in human habitations.

The sources said they believed that the area near the connectors, which were like mini-plugs and sockets to take the command from on- board computers at the top portion of the vehicle right down to the strap-on in the first stage, would have received sudden heavy loads between the second and third stage, leading to their snapping.

The sources stoutly denied that increase in the weight of the satellite by nearly 100 kg had led to the disaster.

Analysis of the data showed that snapping of connectors had led to the disintegration of the vehicle and it had nothing to do with the increase in the weight of the satellite, which was only marginal, the sources said.
The government is seeing the GSLV failure on Thursday as a setback, but there is resolve that development of the indigenous cryogenic engine will continue, sources have told NDTV.
Work on cryogenic engine to continue:
India has no choice but to master this technology in the long run as it is technology that has been denied to the country, the sources said.

It took the country more than 15 years to develop the cryogenic engine as technology for this was denied when, in the 1990s, America put pressure on Russia and forced the cancellation of an Indo-Russian technology transfer deal. The argument given was that India would use these engines to make missiles. Two decades later, none of the Indian missiles uses a cryogenic engine. A team of hundreds of scientists toiled day and night to master this technology.

There will now be a thorough probe into why the cryogenic engine failed.

Minister of State for Science and Technology Prithviraj Chauhan is also expected to make a statement on the GSLV failure. (Read: Disappointment. India's GSLV D3 mission fails)

On Thursday, immediately after a much-awaited launch of the Geosynchronous Satellite Launch Vehicle (GSLV), the indigenous cryogenic engine underperformed and the rocket deviated from its path.

ISRO chairman, K Radhakrishan, announced that the rocket had spun out of control and that the cryogenic engine may have ignited. He promised another attempt next year. (Read: ISRO statement on GSLV's failure)

"Sorry to inform you that the cryogenic stage was not successful. The countdown was eventless. We are not very sure that the cryogenic main engine did ignite. The vehicle was tumbling, it lost its control and altitude and splashed down in the sea," Radhakrishan said.

The cost of the mission was Rs 330 crore. The tall and majestic GSLV, if launched successfully, would have marked India's entry into the multi-billion dollar commercial launcher market on a fully indigenous rocket. A sophisticated new Indian technology called the cryogenic engine was being flown for the first time. In the five earlier flights, India had used pre-used imported Russian made cryogenic engines. It was this engine that underperformed.

The failure will impact India's efforts at launching its own communication satellites, its first manned space flight and the planned launch of Chandrayan 2 in 2012.

It's the second major setback months after the failure of Chandrayaan-1 - India's maiden mission to the moon. But on a positive note, ISRO has been able to come back with a bang in the past. It plans to attempt another launch in a year.

Scientists also point out that cryogenic engines are a difficult technology to master and even countries like the US and Japan failed in their maiden attempts.

The Indian-made Geosynchronous Satellite Launch Vehicle, at 50 meters tall would be as high as a 25-storey building, and weighing a whopping 416 tons. It is a three-stage rocket.
At lift-off, the first stage ignites using one of the world's largest solid fuel motors and strap on boosters. (Read: GSLV - India's big launch)

The first stage separates and the second stage, powered by a liquid engine takes over, while the heat shield is shed.

At an altitude of about 130 kilometres, the second stage separates and the all-important cryogenic engine takes over. Using very cold liquid oxygen and liquid hydrogen as fuel, this special engine helps launch heavier satellites into space.

After a 17-minute flight, the satellite was to have been put into its designated orbit above Earth.

This mission was to have hoisted a sophisticated communications satellite called G-Sat, an Indian-made experimental satellite that weighs 2200 kg and would improve the global positioning system. It was also to have tested a new electrical propulsion system to keep the satellite in its orbit. It was also carrying a set of Ka band transponders, which would have increased the quality of television coverage.

video:

Prof Yashpal on the failure of GSLV

Mininimun Phase Filter

      In control theory and signal processing, a linear, time-invariant system is said to be minimum-phase if the        system and its inverse are causal and stable.^[1][2][3]

      For example, a discrete-time system with rational transfer function H(z) can only satisfy causality and stability requirements if all of its poles are inside the unit circle. However, we are free to choose whether the zeros of the system are inside or outside the unit circle. A system is minimum-phase if all its zeros are also inside the unit circle. Insight is given below as to why this system is called minimum-phase.

Inverse system

A system is invertible if we can uniquely determine its input from its output. I.e., we can find a system such that if we apply followed by , we obtain the identity system . (See Inverse matrix for a finite-dimensional analog). I.e.,

Suppose that is input to system and gives output .

Applying the inverse system to gives the following.

So we see that the inverse system allows us to determine uniquely the input from the output .

Discrete-time example

Suppose that the system is a discrete-time, linear, time-invariant (LTI) system described by the impulse response . Additionally, has impulse response . The cascade of two LTI systems is a convolution. In this case, the above relation is the following:

where δ(n) is the Kronecker delta or the identity system in the discrete-time case. Note that this inverse system is not unique.

Non-minimum phase

      Systems that are causal and stable whose inverses are causal and unstable are known as non-minimum-phase systems. A given non-minimum phase system will have a greater phase contribution than the minimum-phase system with the equivalent magnitude response.

Maximum phase

A maximum-phase system is the opposite of a minimum phase system. A causal and stable LTI system is a maximum-phase system if its inverse is causal and unstable. That is,

• The zeros of the discrete-time system are outside the unit circle.
• The zeros of the continuous-time system are in the right-hand side of the complex plane.

Such a system is called a maximum-phase system because it has the maximum group delay of the set of systems that have the same magnitude response. In this set of equal-magnitude-response systems, the maximum phase system will have maximum energy delay.

For example, the two continuous-time LTI systems described by the transfer functions

have equivalent magnitude responses; however, the second system has a much larger contribution to the phase shift. Hence, in this set, the first system is the minimum-phase system and the second system is the maximum-phase system.

Mixed phase

A mixed-phase system has some of its zeros inside the unit circle and has others outside the unit circle. Thus, its group delay is neither minimum or maximum but somewhere between the group delay of the minimum and maximum phase equivalent system.

For example, the continuous-time LTI system described by transfer function

is stable and causal; however, it has zeros on both the left- and right-hand sides of the complex plane. Hence, it is a mixed-phase system.

Linear phase

A linear-phase system has constant group delay. Non-trivial linear phase or nearly linear phase systems are also mixed phase.

Group delay and phase delay:

All signal components are delayed when passing through a device such as an amplifier or a loudspeaker. The signal delay can be (and often is) different for different frequencies. The delay variation means that signals consisting of different frequency components suffer delay (or time) distortion. A small delay variation is usually not a problem, but larger delays can cause trouble such as poor fidelity and intersymbol interference. High speed modems use adaptive equalizers to compensate for group delay.

In physics, and in particular in optics, the term group delay has the following meanings:

1. The rate of change of the total phase shift with respect to angular frequency,

through a device or transmission medium, where is the total phase shift in radians, and is the angular frequency in radians per unit time, equal to , where is the frequency (hertz if group delay is measured in seconds).

2. In an optical fiber, the transit time required for optical power, traveling at a given mode's group velocity, to travel a given distance.

Note: For optical fiber dispersion measurement purposes, the quantity of interest is group delay per unit length, which is the reciprocal of the group velocity of a particular mode. The measured group delay of a signal through an optical fiber exhibits a wavelength dependence due to the various dispersion mechanisms present in the fiber.

It is often desirable for the group delay to be constant across all frequencies; otherwise there is temporal smearing of the signal. Because group delay is , as defined in (1), it therefore follows that a constant group delay can be achieved if the transfer function of the device or medium has a linear phase response (i.e., where the group delay is a constant). The degree of nonlinearity of the phase indicates the deviation of the group delay from a constant.

All-pass filter

     The allpass filter is an important building block for digital audio signal processing systems. It is called ``allpass'' because all frequencies are ``passed'' in the same sense as in ``lowpass'', ``highpass'', and ``bandpass'' filters. In other words, the amplitude response of an allpass filter is 1 at each frequency, while the phase response (which determines the delay versus frequency) can be arbitrary.

      We have high-pass and low pass filters, and it turns out that we can create both filter effects using a single piece of hardware called a tunable filter. Tunable filters rely on a device called an allpass filter to create other types of filter outputs.

     An all-pass filter is a signal processing filter that passes all frequencies equally, but changes the phase relationship between various frequencies. It does this by varying its propagation delay with frequency

The operational amplifier circuit shown in Figure 1 implements an active all-pass filter with the transfer function

     which has one pole at -1/RC and one zero at 1/RC (i.e., they are reflections of each other across the imaginary axis of the complex plane). The magnitude and phase of H(iω) for some angular frequency ω are

       As expected, the filter has unity-gain magnitude for all ω. The filter introduces a different delay at each frequency and reaches input-to-output quadrature at ω=1/RC (i.e., phase shift is 90 degrees).

This implementation uses a high-pass filter at the non-inverting input to generate the phase shift and negative feedback to compensate for the filter's attenuation.

• At high frequencies, the capacitor is a short circuit, thereby creating a unity-gain voltage buffer (i.e., no phase shift).
• At low frequencies and DC, the capacitor is an open circuit and the circuit is an inverting amplifier (i.e., 180 degree phase shift) with unity gain.
• At the corner frequency ω=1/RC of the high-pass filter (i.e., when input frequency is 1/(2πRC)), the circuit introduces a 90 degree shift (i.e., output is in quadrature with input; it is delayed by a quarter wavelength).

      In fact, the phase shift of the all-pass filter is double the phase shift of the high-pass filter at its non-inverting input.

video link: ALL PASS FILTER

தலைவன் இருக்கிறான்

The History of Airbags

   Airbags are a type of automobile safety restraint like seat belts. They are gas-inflated cushions built into the steering wheel, dashboard, door, roof, or seat of your car that use a crash sensor to trigger a rapid expansion to protect you from the impact of an accident.

Allen Breed - History of the Airbag

   Allen Breed was holding the patent (U.S. #5,071,161) to the only crash sensing technology available at the birth of the airbag industry. Breed invented a "sensor and safety system" in 1968, the world's first electromechanical automotive airbag system.   However, rudimental patents for airbags go back to the 1950s. Patent applications were submitted by German Walter Linderer and American John Hedrik as early as 1951.
Walter Linderer's airbag was based on a compressed air system, either released by bumper contact or by the driver. Later research during the sixties proved that compressed air could not blow the bags up fast enough. Linderer received German patent #896312.
   John Hedrik received U.S. Patent #2,649,311 in 1953 for what he called a "safety cushion assembly for automotive vehicles."

Airbags Introduced

   In 1971, the Ford car company built an experimental airbag fleet. General Motors tested airbags on the 1973 model Chevrolet automobile that were only sold for government use. The 1973, Oldsmobile Toronado was the first car with a passenger air bag intended for sale to the public. General Motors later offered an option to the general public of driver side airbags in full-sized Oldsmobile's and Buick's in 1975 and 1976 respectively. Cadillacs were available with driver and passenger airbags options during those same years. Early airbags system had design issues resulting in fatalities caused solely by the airbags. Airbags were offered once again as an option on the 1984 Ford Tempo automobile. By 1988, Chrysler became the first company to offer air bag restraint systems as standard equipment. In 1994, TRW began production of the first gas-inflated airbag. They are now mandatory in all cars since 1998.

Types of Airbags

  There are two types of airbags; frontal and the various types of side-impact airbags. Advanced frontal air bag systems automatically determine if and with what level of power the driver frontal air bag and the passenger frontal air bag will inflate. The appropriate level of power is based upon sensor inputs that can typically detect: 1) occupant size, 2) seat position, 3) seat belt use of the occupant, and 4) crash severity. Side-impact air bags (SABs) are inflatable devices that are designed to help protect your head and/or chest in the event of a serious crash involving the side of your vehicle. There are three main types of SABs: chest (or torso) SABs, head SABs and head/chest combination (or "combo") SABs.

Sorce:

How do Transistors Work?

Thousands of textbooks have been written to explain electronics and I haven't found a single one that can explain the operation of a transistor. They all make it seem so complicated!

         Let's see if I can do better. Here is a picture of a transistor. My transistor runs on water current. You see there are three openings which I have labelled "B" (Base), "C" (Collector) and "E" (Emitter) for convenience. By an amazing coincidence, these also happen to be the names used by everyone else for the three connections of a transistor!

    

 We provide a reservoir of water for "C" (the "power supply voltage") but it can't move because there's a big black plunger thing in the way which is blocking the outlet to "E". The reservoir of water is called the "supply voltage". If we increase the amount of water sufficiently, it will burst our transistor just the same as if we increase the voltage to a real transistor. We don't want to do this, so we keep that "supply voltage" at a safe level.

If we pour water current into "B" this current flows along the "Base" pipe and pushes that black plunger thing upwards, allowing quite a lot of water to flow from "C" to "E". Some of the water from "B" also joins it and flows away. If we pour even more water into "B", the black plunger thing moves up further and a great torrent of water current flows from "C" to "E".

So what have we learned?:

1. A tiny amount of current flowing into "B" allows a large amount to flow from "C" to "E" so we have an "amplification effect". We can control a BIG flow of current with a SMALL flow of current. If we continually change the small amount of water flowing into "B" then we cause corresponding changes in the LARGE amount of water flowing from "C" to "E". For example, if we measure the current flow in gallons/minute: Suppose 1 gallon/minute flowing into "B" allows 100 gallons/minute to flow from "C" to "E" then we can say that the transistor has a "gain" or "amplification" factor of 100 times. In a real transistor we measure current in thousandths of an Ampere or "milliamps". So 1mA flowing into "B" would allow 100mA to flow from "C" to "E".

2. The amount of current that can flow from "C" to "E" is limited by the "pipe diameter". So, no matter how much current we push into "B", there will be a point beyond which we can't get any more current flow from "C" to "E". The only way to solve this problem is to use a larger transistor. A "power transistor".

3. The transistor can be used to switch the current flow on and off. If we put sufficient current into "B" the transistor will allow the maximum amount of current to flow from "C" to "E". The transistor is switched fully "on".

       If the current into "B" is reduced to the point where it can no longer lift the black plunger thing, the transistor will be "off". Only the small "leakage" current from "B" will be flowing.

To turn it fully off, we must stop all current flowing into "B".

       In a real transistor, any restriction to the current flow causes heat to be produced. This happens with air or water in other things: for example, your bicycle pump becomes hot near the valve when you pump air through it. A transistor must be kept cool or it will melt. It runs coolest when it is fully OFF and fully ON. When it is fully ON there is very little restriction so, even though a lot of current is flowing, only a small amount of heat is produced. When it is fully OFF, provided we can stop the base leakage, then NO heat is produced. If a transistor is half on then quite a lot of current is flowing through a restricted gap and heat is produced. To help get rid of this heat, the transistor might be clamped to a metal plate which draws the heat away and radiates it to the air. Such a plate is called a "heat sink". It often has fins to increase its surface area and, thereby, improve its efficiency.

PNP and NPN:

                              

Getting Technical

      The difference between PNP and NPN transistors is that NPN use electrons as carriers of current and PNP use a lack of electrons (known as "holes"). Basically, nothing moves very far at a time. One atom simply robs an electron from an adjacent atom so you get the impression of "flow". It's a bit like "light pipes". In the case of "N" material, there are lots of spare electrons. In the case of "P" there aren't. In fact "P" is gasping for electrons. Clear as mud isn't it?

OK, bear in mind that the Base is only a few atoms in thickness - almost a membrane - so any electrons allowed into the base "membrane" act as a catalyst to allow other electrons to break through from emitter to collector.

Imagine a pool of water near the edge of a table. It rests there with surface tension holding it in place. Now put one tiny drop of water on the table edge and let it touch the pool of water. Suddenly, the pool drains onto the floor as gravity takes over! Your tiny drop provided the catalyst to get it moving. So the base electrons do a similar job for the "pool" of electrons in the emitter - helped by the "gravity suction" of the power supply voltage on the collector.

      A transistor doesn't "increase" current. It simply allows power supply current to pass from collector to emitter* - the actual amount depends on the (small) current allowed to flow into its base. The more electrons you allow into the base, the more (x 100) that flow from collector to emitter . I put "x 100" because that is the typical gain (amplification factor) of a transistor. For example, one electron put into the base could allow 100 to escape from collector to emitter.

The best way to understand this is to get your soldering iron and start building!

* The purist might argue that current flows from emitter to collector - dependent on whether we are discussing electron flow or "hole" flow. I don't want to get involved in the physics of

we are discussing electron flow or "hole" flow. I don't want to get involved in the physics of current flow. You don't need to know this to design a circuit.

* This discussion relates to Bipolar transistors. Other types of transistor such as "FETs" (Field Effect Transistors) are in common use and work in a slightly different way in that the voltage applied to the "gate" terminal controls the current flowing from "cathode" terminal to "anode" terminal. In effect, a FET is simply a semiconducting (one-way) resistor whose value is controlled by the voltage applied to its "gate".

* OK, having told you all that, I now have to point out that the above description is basically WRONG! What I've described is based on what is called "the beta model" of a transistor. A transistor actually relies on base voltage input - the current input is incidental. If you are at college, your teacher will explain this fully with lots of mathematical equations that will let you design anything at all. However, my description will let you design simple circuits with a minimum of effort and they will almost certainly work. Unless you are going to take up design as a profession, this is all you need to know.

Source:::: link

Do u know why we call 'e' as natural no??

e was invented by Leonard Euler, and is sometimes called Euler's constant, but it's proper name is still 'e'. Euler is pronounce "Oiler".

Take the formula a^x, where a is some number. Say 2^x.

2^0 is 1

2^1 is 2

2^2 is 4

2^3 is 8

and so on.

You can draw this on a graph. It starts fairly flat but rises very quickly and quickly goes off the top of the paper.

You can draw a tangent line to this curve (a line which touches the curve). The steepness or slope of this line measures the rate at which the formula is increasing at the place where the line touches the curve.

A remarkable thing happens. For the 2^x graph, at every point on the graph, the rate of increase of 2^x is 0.693 2^x. The rate is proportional to the height of the graph. Positive feedback!

Try the same thing with 10^x. The rate of increase is 2.3 10^x

Same idea.

So if 2^x rises at 0.693 2^x which is less than 2^x

and 10^x rises at 2.3 10^x which is more than 10^x

then is there a number a between 2 and 10 for which

a^x rises at exactly a^x?

Yes there is. That number is e.

You can take logs to any base, but no base seems better than any other. Is there a base which is somehow more natural than 2 or 10? Yes: base e.

The natural log of x is written ln(x)

In my examples above, the mysterious 0.693 is ln(2)

the mysterious 2.3 is ln(10)

Because e^x is that magic function whose rate is equal to itself, it pops up all over the place where there are problems to do with rates.

for More Study click here....

Can We Store Electricity from Lightning?

It is theoretically possible to store and harness the electricity from lightning, and several proposals have been advanced to show how this could be done. There are a number of reasons which make these proposals impractical, however. Lightning is simply not a good source of energy, and there are numerous alternatives which are safer, less energy-intensive, more effective, and readily available. In other words, just because humans can potentially and highly theoretically store electricity from lightning doesn't mean that they should.

On the surface, lightning seems to have a lot of potential as an energy source. It is totally renewable, which is a definite advantage, and it is readily available in some regions of the world. Furthermore, lightning has a lot of energy; a single bolt can power 150 million light bulbs. The idea of harnessing so much energy and storing it is immensely appealing.

There are a number of problems with trying to harness the tremendous energy of lightning bolts. The first is that lightning is highly unpredictable. There is no way to know exactly where and when lightning will strike, so it would be difficult to find a location to turn into a facility for processing lightning for energy. Lightning also delivers its energy all at once, which would require huge batteries and capacitors. Otherwise, the energy would simply blow out any systems established to capture it.

The potential instability in the supply of electricity from lightning is far less of an issue than the infrastructure which would be needed to support the energy collection process. Lightning is so powerful that it would overload all but the most sophisticated and heavy-duty systems, and the wisdom of building and installing such a system would be questionable if it could only harvest the energy from a few lightning bolts a year. Even in areas where lightning is frequent, the cost of the system would probably outweigh the benefit of getting electricity from lightning.

Humans may at some point develop a system which can cheaply and effectively collect and store electricity from lightning. Technological innovation is a natural part of human societies, and advances are constantly being made. 18th century humans would have been astounded by the things developed in the 19th century, for example. Such a development is likely to occur in the distant future, however, making it more important to focus on accessible sources of alternative energy like sunlight, wind, and water.

SOURCE:

Can We Store Electricity from Lightning?

It is theoretically possible to store and harness the electricity from lightning, and several proposals have been advanced to show how this could be done. There are a number of reasons which make these proposals impractical, however. Lightning is simply not a good source of energy, and there are numerous alternatives which are safer, less energy-intensive, more effective, and readily available. In other words, just because humans can potentially and highly theoretically store electricity from lightning doesn't mean that they should.

On the surface, lightning seems to have a lot of potential as an energy source. It is totally renewable, which is a definite advantage, and it is readily available in some regions of the world. Furthermore, lightning has a lot of energy; a single bolt can power 150 million light bulbs. The idea of harnessing so much energy and storing it is immensely appealing.

There are a number of problems with trying to harness the tremendous energy of lightning bolts. The first is that lightning is highly unpredictable. There is no way to know exactly where and when lightning will strike, so it would be difficult to find a location to turn into a facility for processing lightning for energy. Lightning also delivers its energy all at once, which would require huge batteries and capacitors. Otherwise, the energy would simply blow out any systems established to capture it.

The potential instability in the supply of electricity from lightning is far less of an issue than the infrastructure which would be needed to support the energy collection process. Lightning is so powerful that it would overload all but the most sophisticated and heavy-duty systems, and the wisdom of building and installing such a system would be questionable if it could only harvest the energy from a few lightning bolts a year. Even in areas where lightning is frequent, the cost of the system would probably outweigh the benefit of getting electricity from lightning.

Humans may at some point develop a system which can cheaply and effectively collect and store electricity from lightning. Technological innovation is a natural part of human societies, and advances are constantly being made. 18th century humans would have been astounded by the things developed in the 19th century, for example. Such a development is likely to occur in the distant future, however, making it more important to focus on accessible sources of alternative energy like sunlight, wind, and water.

SOURCE: WWW.wisegeek.com

TESLA INVENTED RADIO?

   
> In all of the mass comm books I have used over the past 20 years, credit
> for early development in radio goes to Marconi, Fessenden, De Forest
> and Armstrong.  On occasion, and seldom at that, Tesla is mentioned. But
> he is never discussed as a major player in the beginnings of radio.

The books don't mention that the powerful spark transmitters used by Marconi were Tesla coils, nor do they point out that Marconi's central radio patents were later struck down because of Tesla's prior art. Marconi won the Nobel for inventing radio, and if this was a mistake, the whole science community (as well as numberless historians and textbook authors) would have to eat lots of crow before deciding to correct it. Or even admitting it.

Tesla's main problem was that he set his sights too high. He didn't bother with simple and low-cost radio communication between transmitter and receiver. Instead he was aiming for a high power centralized *worldwide* radio communication system and wireless power distribution system. His device more resembled a power plant than a cellphone. He failed at this. Another major problem was that Tesla apparently did not take Marconi seriously as an opponent, and so Tesla did not fiercely defend his work when it was being stolen. The history of invention is written by the winners, and since the winners' success in Radio was based on their use of Tesla's transmitter invention and grounded antennas, they certainly avoided mentioning Tesla! In his Nobel Prize speech, would Marconi give credit to the inventor on which his system was based? Also, people assume that a victim will fiercely fight against theives, and since Tesla didn't fight, they decide that there must not have been theft. And finally, Tesla's ideas were used to make money by far more people than just Marconi. When people steal ideas, they try to make themselves feel better; they justify their theft by ridiculing and marginalizing the ideas even as they profit from them. They pretend that the ideas were "in the air," or were "obvious methods" which anyone could see. Historians reading the material written by such people will not see all their lying and subterfuge. It takes a historian with rare insight (or perhaps one with paranoid distrust of fellow humans) to cut through the dishonesty and interpret the evidence without that bias.

Initially Tesla rejected fame and wealth, and freely gave away his ideas via public science lectures, rather than employing the secrecy and courtroom patent-battles of fellow inventors. Perhaps his upbringing as a minister's son gave him too much trust and altruism to be a sharp businessman or secretive inventor. And not being a professional scientist, Tesla didn't preserve his priority by publishing his research papers in physics journals. He also made the mistake of attempting to perfect his entire system before releasing it to the world, rather than releasing crude versions immediately and then improving it over time. He made radio possible, but his own dreams failed. He invented modern radio, but made such serious business mistakes that the recognition (to say nothing of the money!) all went to others.

The simplified history: Tesla, the expert in high frequency power systems, follows a vision of worldwide instantaneous communication and invents a radio SPARK TRANSMITTER whose output power far outstrips anything of the period. This spark transmitter is based on several key Tesla techniques: rotary spark gap, lumped resonance (rather than antenna resonance,) capacitor energy storage, and an antennea with a ground connection. Tesla also invents a mechanical AC generator or "alternator" capable of broadcasting high power radio waves. Of course radio recievers already existed: the coherer, (NOT invented by Marconi but by Branly and others.) Earlier radio systems such as that of Hertz and Stubblefield also existed, but they had extremely limited range. Tesla's amazing spark transmitter put out 1000 to 10,000 times the power of existing transmitters, and made worldwide communication feasible.

Today we call this transmitter by the name "Tesla Coil."
This was the status in 1893, with several patents granted to Tesla in 1898 and on. Besides the spark transmitter, the high frequency alternator, and the grounded antenna, Tesla's inventions also included the four tuned circuits of all modern radio systems: a transmitter and receiver at both ends of a radio link, all four using tuning.

Next stage: Marconi takes the Branly coherer and Tesla's spark transmitter and antenna inventions, commercializing them. But Tesla ignores this threat, believing that his completed "world system" will be far superior to Marconi's ocean-spanning demonstration. Therefore Tesla pursues centralized power transmission rather than simple communications alone. He says something to the effect "good luck to Marconi, he's using seventeen of my patents." Perhaps Tesla had a point, since Marconi did see his own patents rejected numerous times by the US Patent Office. The patent officer thought it ridiculous that Marconi claimed not to know about Tesla Coils. But then mysteriously Marconi's patents were suddenly accepted.

Tesla also remained aloof from the community of early radio developers while single-mindedly pursuing his own vision. Nearly twenty years later Tesla finally takes Marconi to court. He can't afford powerful lawers and a long court case. He loses! As many other inventors have found, the winner in a patent battle is usually the side with the deeper pockets. Tesla couldn't afford to continue the court case. Also, though Tesla's patents were prior to Marconi, Marconi had the press behind him. Marconi also had both the US government as well as big business behind him. The country wanted point-to-point radio, while the inventor of the spark transmitter wanted only centralized power broadcast stations. Tesla also wanted to keep control of radio by patenting his work. One can imagine that the government and commercial sectors would search for a way to get such an important invention loose from Tesla's hands by breaking the patents. This probably was the reason why Marconi's US radio patents suddenly went through in the first place after being rejected. Finally, Tesla was an unknown in Radio when compared to Marconi, and the judge was very probably not a technical expert.

Tesla loses his R&D financing in later decades, while Marconi's international companies are wildly successful. It's not a conspiracy theory to say "whoever has the gold, makes the rules." Tesla is not vindicated until 1943, when the US Supreme court reverses the old decision, strikes down the Marconi patents, and awards priority to Tesla #645,576. This was no altruism, since large amounts of money rode on the possibility that Marconi's existing companies could lose their patents.

See also:
Just Who Invented Radio?, radio author, B. E. Rhodes, 1998
Who Invented Radio?, AARL, S. Horzepa, 2003

Also: "Tesla, Man out of Time", Margaret Cheney, especially "The Great Radio Controvery." This book references as a thorough account an article "Priority of Invention of Radio - Tesla vs. Marconi", from The Antique Wireless Association No. 4, March 1980. (I haven't tracked this down.)

Why is Tesla ignored today? Of course there's the old saw that "history is written by the winners". This remains true even if the winners used dishonest means. But there are better explanations. First, names have immense power, and we don't call the Spark Transmitter by it's real name: the Tesla coil. We might have Edison lamps, but nobody says that a grounded radio antenna is a "Tesla antenna." Tesla's mechanical generator also aquired the name "Alexanderson alternator" (Twenty years after Tesla's invention, Alexanderson of Edison's General Electric company patented an improvement which reached above 100KHz, while Tesla's version only ran at up to 50KHz.)

There is another reason why Tesla is ignored today. Tesla lectured about his discoveries, and in a very short time his ideas were incorporated into the technical culture of the period. When this happens, people of the time tend to deny that a single inventor originated the ideas. They can't benefit from historical hindsight, of seeing their own times from the viewpoint of an outsider. Instead they tend to believe that the ideas simply arose spontaneously in many places, or by unnoticed team effort. Historians of much later decades are particularly prone to this mastake. The history of the Wright Brothers followed a similar path; the Wrights published articles about their boxkite-winged glider, and within a few years everyone was copying it and assuming that biplanes were the "natural way to proceed." Only in hindsight does the overwhelming influence of the Wrights' wing-warping biplane become obvious. And so with radio, inventors copied Tesla without realizing it; assuming that his methods of resonant coil and grounded antenna were simply the "obvious way" it should be done. High-power transmitter systems, high frequency resonanant tuning and grounding, the keys to successful radio, were thought to be "in the air." Only through modern hindsight can we see that Tesla, and not Marconi, was the one who put them there.

I'm going to indulge in some unsupported speculation. My own experience as a textbook consultant points to another reason why Tesla is ignored: reference books support each other. Groups of Reference books in many ways strive for consistency rather than for truth. They try not to contradict each other or raise critical questions about apparently well-known history. To an extent they are "inbred", and to an extent their information is not absolute truth, but rather is a consensus perception of the truth. However, most authors would vigorously deny this embarrassing view, and would prefer to believe that reference books contain only truth. In other words, since most books say the same thing, they must all be correct, no? No, not if their authors place the goal of consensus higher than the goal of accuracy or even honesty. If concensus is more important than fact, then the books would be expected to all agree with each other, whether their concensus facts were correct or not.

For this reason it is nearly impossible to alter the contents of text and reference books, even if the material in them is clearly erroneous. If all the books say the same thing, no single author is willing to buck the majority and stand out from the crowd. After all, that many books couldn't be wrong! Yet if they *are* wrong, then acknowledging this fact would rub our noses in the fragility of the foundations of our whole system of knowledge. And so we maintain a unified front of "illusory truthfulness." Maintaining the illusion becomes more important to us than the correcting of any mistakes. If we must maintain respect for reference books at any cost, then whenever they all make the same major flub, we don't correct that flub. We don't even see it, since we automatically indulge in unsupported disbeliefs which lead to blindness and denial.

If a major mistake regarding Tesla's priority to inventing Radio is made in 1915, and if this mistake is not officially righted until 1943, then reference books and textbooks had thirty years to mistakenly elevate Marconi as the inventor of radio. How many decades do you think it would take before the thirty years of Marconi-worship finally wears off, before the textbook concensus shifts and begins to recognize Tesla? Well, fifty years have passed, and clamor to recognize Tesla is finally starting to be heard. PBS even presented Tesla's radio history in the recent "Tesla: Master of Lightning." However, the major players currently dismiss the Tesla revision as "conspiracy theories" coming from fringe groups and "Tesla worshippers." I suspect that it will take far longer than fifty years before all the new textbooks finally reverse themselves. It can only happen slowly, so nobody is threatened or embarrassed. Politics and face-saving becomes far more important than historical accuracy! The real story must invade the books slowly, so no one is directly forced to confront the staggering extent of this historical error.