As the Ebola virus outbreak continues to run amok in West Africa, scientists are looking ahead to the possibly pivotal use of experimental drugs and vaccines against the disease. It will take months to test, produce and deploy the therapies. But researchers hold out hope that these products — even incompletely vetted — might help to turn the tide against an illness that has defied public health efforts to bring it under control.

## Monday, 24 December 2012

### TurboProp

turboprop engine is a type of turbine engine which drives an aircraft propeller usi and play only a minor role in the propulsion of the aircraft.
The propeller is coupled to the turbine through a reduction gear that converts the high RPM, ng a reduction gear.
The gas turbine is designed specifically for this application, with almost all of its output being used to drive the propeller. The engine's exhaust gases contain little energy compared to a jet enginelow torque output to low RPM, high torque. The propeller itself is normally a constant speed (variable pitch) type similar to that used with largerreciprocating aircraft engines.
Turboprop engines are generally used on small subsonic aircraft, but some aircraft outfitted with turboprops have cruising speeds in excess of 500 kt(926 km/h, 575 mph). Large military and civil aircraft, such as the Lockheed L-188 Electra and the Tupolev Tu-95, have also used turboprop power. The Airbus A400M is powered by four Europrop TP400 engines, which are the third most powerful turboprop engines ever produced, after the Kuznetsov NK-12 and Progress D-27.
In its simplest form a turboprop consists of an intake, compressorcombustorturbine, and a propelling nozzle. Air is drawn into the intake and compressed by the compressor. Fuel is then added to the compressed air in the combustor, where the fuel-air mixture then combusts. The hot combustion gases expand through the turbine. Some of the power generated by the turbine is used to drive the compressor. The rest is transmitted through the reduction gearing to the propeller. Further expansion of the gases occurs in the propelling nozzle, where the gases exhaust to atmospheric pressure. The propelling nozzle provides a relatively small proportion of the thrust generated by a turboprop.
Turboprops are very efficient at flight speeds below 450 mph (390 knots; 725 km/hr) because the jet velocity of the propeller (and exhaust) is relatively low. Due to the high price of turboprop engines, they are mostly used where high-performance short-takeoff and landing (STOL) capability and efficiency at modest flight speeds are required. The most common application of turboprop engines in civilian aviation is in small commuter aircraft, where their greater reliability than reciprocating engines offsets their higher initial cost. Turboprop airliners now operate at near the same speed as small turbofan-powered aircraft but burn two-thirds of the fuel per passenger. However, compared to a turbojet (which can fly at high altitude for enhanced speed and fuel efficiency) a propeller aircraft has a much lower ceiling. Turboprop-powered aircraft have become popular for bush airplanes such as the Cessna Caravan and Quest Kodiak as jet fuel is easier to obtain in remote areas than is aviation-grade gasoline (avgas).

## Monday, 5 November 2012

### Parallel Universe

parallel universe is a hypothetical or fictional self-contained separate reality coexisting with one's own. A specific group of parallel universes is called a "multiverse", although this term can also be used to describe the possible parallel universes that constitute reality. While the terms "parallel universe" and "alternative reality" are generally synonymous and can be used interchangeably in most cases, there is sometimes an additional connotation implied with the term "alternative reality" that implies that the reality is a variant of our own. The term "parallel universe" is more general, without any connotations implying a relationship, or lack of relationship, with our own universe. A universe where the very laws of nature are different – for example, one in which there are no relativistic limitations and the speed of light can be exceeded – would in general count as a parallel universe but not an alternative reality. The correct quantum mechanical definition of parallel universes is "universes that are separated from each other by a single quantum event.

by wikipedia

## Monday, 29 October 2012

### Tubocharger

you may have heard about turbochargers in cars..

Turbocharger is a Device which is attached to exhaust valve of the engine and when the engine(in car) runs at high rpm the exhaust from it rotates the turbine of charger which force more air and fuel is forced to the chamber.

Sometimes it is very dangerous to use turbo charger as it starts at only fixed speed

For example :- i am running my car at a speed of 150 kmph if i will accelerate my car to 160 turbocharger will starts and my car will attain a speed 210 within a second.This can disbalance the car.

### Common Rail Engine

Common rail direct fuel injection is a modern variant of direct fuel injection system for petrol and diesel engines.
On diesel engines, it features a high-pressure (over 1,000 bar or 15,000 psi) fuel rail feeding individual solenoid valves, as opposed to low-pressure fuel pump feeding unit injectors(Pumpe/Düse or pump nozzles). Third-generation common rail diesels now feature piezoelectric injectors for increased precision, with fuel pressures up to 1,800 bar or 26,000 psi.

## Sunday, 29 July 2012

### Higgs Boson - God's Particle

The Higgs boson or Higgs particle is a proposed elementary particle in the Standard Model of particle physics.  The Higgs boson's existence would have profound importance in particle physics because it would prove the existence of the hypothetical Higgs field—the simplest of several proposed explanations for the origin of the symmetry-breaking mechanism by which elementary particles acquire mass. The leading explanation is that a field exists that has non-zero strength everywhere—even in otherwise empty space—and that particles acquire mass by interacting with this so-called Higgs field. If this theory is true, a matching particle—the smallest possible excitation of the Higgs field—should also exist and be detectable, providing a crucial test of the theory. Consequently, it has been the target of a long search in particle physics. One of the primary goals of the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland—the most powerful particle accelerator and one of the most complicated scientific instruments ever built—is to test the existence of the Higgs boson and measure its properties which would allow physicists to confirm this cornerstone of modern theory.
The Higgs boson is named for Peter Higgs who, along with two other teams, proposed the mechanism that suggested such a particle in 1964 and was the only one to explicitly predict the massive particle and identify some of its theoretical properties. In mainstream media it is often referred to as "the God particle", after the title of Leon Lederman's book on the topic (1993). Although the proposed particle is both important and elusive, the epithet is strongly disliked by physicists, who regard it as inappropriate sensationalism since the particle has nothing to do with God nor any mystical associations,and because the term is misleading: the crucial focus of study is to learn how the symmetry breaking mechanism takes place in nature - the search for the boson is part of, and a key step towards, this goal.
According to the Standard Model, the Higgs particle is a boson, a type of particle that allows multiple identical particles to exist in the same place in the same quantum state. It has no spin, electric charge, or colour charge. It is also very unstable, decaying into other particles almost immediately. Some extensions of the Standard Model predict the existence of more than one kind of Higgs boson.
Proof of the Higgs field (by observing the associated particle), and evidence of its properties, are likely to greatly affect human understanding of the universe, validate the final unconfirmed part of the Standard Model as essentially correct, indicate which of several current particle physics theories are more likely correct, and open up "new" physics beyond current theories. If the Higgs boson were shown not to exist, other alternative sources for the Higgs mechanism would need to be considered. On 4 July 2012, the CMS and the ATLAS experimental teams at the LHC independently announced that they each confirmed the formal discovery of a previously unknown boson of mass between 125–127 GeV/c2, whose behaviour so far has been "consistent with" a Higgs boson, while adding a cautious note that further data and analysis were needed before positively identifying the new particle as being a Higgs boson of some type.

## Saturday, 28 July 2012

### Thermistor

thermistor is a type of resistor whose resistance varies significantly with temperature, more so than in standard resistors. The word is a portmanteau of thermal and resistor. Thermistors are widely used as inrush current limiters, temperature sensors, self-resetting overcurrent protectors, and self-regulating heating elements.
Thermistors differ from resistance temperature detectors (RTD) in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response is also different; RTDs are useful over larger temperature ranges, while thermistors typically achieve a higher precision within a limited temperature range, typically −90 °C to 130 °C.

## Basic operation

Thermistor symbol
Assuming, as a first-order approximation, that the relationship between resistance and temperature is linear, then:
$\Delta R=k\Delta T \,$
where
$\Delta R$ = change in resistance
$\Delta T$ = change in temperature
$k$ = first-order temperature coefficient of resistance
Thermistors can be classified into two types, depending on the sign of $k$. If $k$ is positive, the resistance increases with increasing temperature, and the device is called a positive temperature coefficient (PTC) thermistor, or posistor. If $k$ is negative, the resistance decreases with increasing temperature, and the device is called a negative temperature coefficient (NTC) thermistor. Resistors that are not thermistors are designed to have a $k$ as close to zero as possible, so that their resistance remains nearly constant over a wide temperature range.
Instead of the temperature coefficient k, sometimes the temperature coefficient of resistance $\alpha_T$ (alpha sub T) is used. It is defined as[2]
$\alpha_T = \frac{1}{R(T)} \frac{dR}{dT}.$
This $\alpha_T$ coefficient should not be confused with the $a$ parameter below.

### LDR - Light Dependent Resistor

 Symbol of LDR

Photoresistor or Light Dependent Resistor (LDR) is a resistor whose resistance decreases with increasing incident light intensity; in other words, it exhibits photoconductivity.
A Photoresistor is made of a high resistance semiconductor. If light falling on the device is of high enough frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electron (and its holepartner) conduct electricity, thereby lowering resistance.
A Photoelectric device can be either intrinsic or extrinsic. An intrinsic semiconductor has its own charge carriers and is not an efficient semiconductor, e.g. silicon. In intrinsic devices the only available electrons are in the valence band, and hence the photon must have enough energy to excite the electron across the entire bandgap. Extrinsic devices have impurities, also called dopants, added whose ground state energy is closer to the conduction band; since the electrons do not have as far to jump, lower energy photons (i.e., longer wavelengths and lower frequencies) are sufficient to trigger the device. If a sample of silicon has some of its atoms replaced by phosphorus atoms (impurities), there will be extra electrons available for conduction. This is an example of an extrinsic semiconductor. Photoresistors are basically photocells.

## Saturday, 16 June 2012

### Rectifier

A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The process is known as rectification. Physically, rectifiers take a number of forms, including vacuum tube diodes, mercury-arc valves, solid-state diodes, silicon-controlled rectifiers and other silicon-based semiconductor switches. Historically, even synchronous electromechanical switches and motors have been used. Early radio receivers, called crystal radios, used a "cat's whisker" of fine wire pressing on a crystal of galena (lead sulfide) to serve as a point-contact rectifier or "crystal detector".
Rectifiers have many uses, but are often found serving as components of DC power supplies and high-voltage direct current power transmission systems. Rectification may serve in roles other than to generate direct current for use as a source of power. As noted, detectors of radio signals serve as rectifiers. In gas heating systems flame rectification is used to detect presence of flame.
The simple process of rectification produces a type of DC characterized by pulsating voltages and currents (although still unidirectional). Depending upon the type of end-use, this type of DC current may then be further modified into the type of relatively constant voltage DC characteristically produced by such sources as batteries and solar cells.
A device which performs the opposite function (converting DC to AC) is known as an inverter.

## Thursday, 14 June 2012

### Construction of Electric Bell

 ELECTRIC BELL MAIN COMPONENT OF ELECTRIC BELL Important parts of an electric     bell are :     1. Electromagnet     2. Armature     3. Spring     4. Armature rod     5. Hammer     6. Gong CONSTRUCTION One end of armature winding is connected to terminal T1 and the other to a spring, which is mounted on     a soft iron strip. A rod is attached to the armature and the free end of the rod carries a small hammer,     which strikes a bell. A very light spring is attached to a screw, which is joined to terminal T2. WORKING OF ELECTRIC BELL The electric circuit is completed through a battery and push switch button connected to the terminal T1     and T2. When the push button is pressed the electric circuit is completed and the armature is attracted     towards the electromagnet as a result, the small spring gets detached from the screw due to which the     electric circuit is broken and the electromagnet is demagnetized. Hence, the attraction disappears and     the armature is brought back by the spring to its original position. Contact of the spring with the screw is     now remade, which completes the electric circuit. The action is repeated over and over again     consequently. The armature vibrates and hammer attached to it strikes the gong and the bell rings and     sound is produced.