MEMS or micro-electro-mechanical system a miniaturized mechanical device built with the materials and techniques used to make integrated circuits for computers. These microscopic materials are of the order of a few micrometers (a micrometer is one millionth of a meter). Micromachines combine sensors, levers, gears, and electronic elements such as transistors to perform various tasks. The extremely thin layers of silicon which are only few millionths of a meter thick are used to fabricate Micromachine Gearing Micromachines and can be shaped into can be shaped into levers, gears, and other mechanical devices. With the initiative of Sandia National Laboratories' Intelligent Micromachine, this technology is currently used in imaging systems and motion sensors, and is being developed for applications in biomedicine, computers, and telecommunications.

MEMS technology is currently used in devices such as air bag sensors and certain types of video screen systems. It is being adapted for uses in many other fields, such as medicine, computers, and communication as it has several benefits over larger machines in sensitivity, pace and energy consumption.

According to this phenomenon of the 1940's two clean, flat surfaces of similar metal would strongly adhere if brought into contact under vacuum. Its lately known that by pressing the metals tightly together, increasing the duration of contact, raising the temperature of the workpieces, or any combination of the above could add on to the first contact. As per research, even for the very smooth metals, only the high points of each surface, called 'asperites,' touch the opposing piece which means that as little as a few thousandths of a percent of the total surface is involved in the adhesion and these small areas of taction develop strong molecular connections. If the surfaces are sufficiently smooth the metallic forces between them ultimately draw the two pieces completely together and eliminate even the macroscopic interface. Electron microscope investigations of contact points reveal that an actual welding of the two surfaces takes place after which it is impossible to separate the former asperitic interface. the cold welding effect is eliminated or reduced when exposed to oxygen or certain other reactive compounds which produces surface layers, for example, a metal oxide which has mechanical properties similar to those of the parent element (or softer), here surface deformations will not crack the oxide film.

Applications

Powders in powder metallurgy present large surface areas over which vacuum contact can occur and they use cold welding to best advantage. For instance, a 1 cm cube of metal comminuted into 240?100 mesh-sieved particles (60?149 μm) yields approximately 1.25ױ06 grains having a total surface area of 320 cm2. This powder, reassembled as a cube, would be about twice as big as before since half the volume consists of voids.

it is important to obtain minimum porosity (that is, high starting density) in the initial powder-formed mass if a sturdy final product is preferred. Minimum porosity results in less dimensional change upon compression of the workpiece as well as lower pressures, decreased temperatures, and less time to prepare a given part. Careful vibratory settling reduces porosity in monodiameter powders to less than 40%. Large increase in net grain area will enhance the contact welding effect and noticeably improve the 'green strength' of relatively uncompressed powder whereas decrease in average grain size does not decrease porosity. In space applications moulds may not even be required to hold the components for subsequent operations such as sintering because cold welding in the forming stage is adequate to produce usable hard parts
Hard monodiameter spheres packed like cannonballs into body-centered arrays gives a porosity of about 25%, much lower than the ultimate minimum of 35% for vibrated collections of monodiameter spheres. (The use of irregularly shaped particles produces even more porous powders.) Selected range of grain sizes, typically 3?6 carefully chosen gauges in most terrestrial applications reduces porosity. Such mixtures theoretically permit less than 4% porosity in the starting powder but it becomes 15?20% more with binary or tertiary mixtures. powders containing particles in a wide range of sizes can approach 0% porosity as the finest grains are introduced. Even the introduction of vibration or shaking to free movement cannot induce closest configuration in powder mixtures. Sizeable theoretical and practical analyses exist to assist in understanding the packing of powders. Its seen that gravitational differential settling of the mixture tends to segregate grains in the compress, and some degree of cold welding occurs immediately upon formation of the powder compress which generates internal frictions that strongly impede further compaction. Moderate forces applied to a powder mass immediately cause grain rearrangements and superior packing. Specifically, pressures of 105 Pa (N/m2) decrease porosity by 1?4%; increasing the force to 107 Pa adds only an additional 1?2%. greater force is required mechanically to close all remaining voids by plastic flow of the compressed metal and distinct physical effects of particle deformation and mass flow become significant at still higher pressures or by the application of heat.

* Growing demand for electricity
* Limited energy source
* Unavailability of land due to high population

Floating solar power stations

* Availability of solar energy
* Direct conversion into electrical energy
* Rich water logged areas
* Requires minimal land area
* Reduction in evaporation of water

* Expense can be minimized by using reservoirs of hydel stations
* 6-10 hours of electricity generation per day

Electricity generation by solar cells
Solar cells which are made of semi conductor material absorbs light which falls on it. This energy knocks the electron loose and it starts flowing freely. But the electric field in PV cells forces the free electrons to move in a certain direction which is current and this current is tapped by placing metal contacts on top and bottom of PV cell. The current together with cells voltage is called the power of a solar cell.

Building an economical and competent resource for energy storage, plays a key role in energy conservation as it can cut down the time radically, for both energy supply and energy demand. This innovative concept as crucial as locating fresh sources of energy, can actually enhance the output of the whole energy system there by escalating its consistency.

In phase change materials (PCM?s) like the salt hydrates, paraffin?s, non-paraffin?s and eutectics of inorganic, the storage of solar heat energy, leads to compactness and delivering of heat energy at steady temperatures.

The world first came to know about these tiny tubes of rolled up sheets of carbon hexagons in 1991. Born at the research labs of NEC, the size of these miniature tubes, which is 10,000 times slimmer than a human hair doesn?t have any comparison to its potential uses.

By the regulated manoeuvring of carbon nanotubes, mega teeny-weeny electronic devices can be designed. This nanotubes also can be used as microscopic wires.

Recent experiments by the IBM scientists to develop a method for changing the position, shape and orientation in addition to, finding a way for cutting the tiny tubes, have been fruitful using an atomic force microscope (AFM).

Flywheel energy storage is all about the conversion of energy generated by motion, the kinetic energy into the most expensive energy, the electricity. Kinetic energy gets accumulated in the flywheel energy storage system by the continuous rotation of a small motor in a low-friction background. This accumulated kinetic energy gets converted to electricity by the continuous gyrating of rotor, once an interim back-up power is needed due to power failure or oscillations in power.

The incorporation of the tasks of a motor, flywheel rotor and a generator into a single built-in system is the basic theory behind the Active Power's CleanSource? Flywheel Technology. As per it?s working, motor draws power from the electric supply to continuously revolve the flywheel, the constant source of kinetic energy. This kinetic energy gets translated to electricity by the generator. The advantage of all-in-one technology is that the cost can be cut down drastically as well as the product efficiency can be improved.

Synthetic polymers that include the polyethylene, nylon etc are often called by the term ?plastics?. They are broadly organized under three different classes namely, thermoplastics, thermosets and elastomers.

These set of artificial polymers finds its use in almost all walks of our everyday life, be it related to the food packaging industry, the film industry, fibre, tube or pipe industry etc. Personal care industry also takes advantage from this plastic revolution related to areas like the texture of products, binding and moisture retention. The term plastic explosion refers to the manufacturing of polymers like the Acrylic, polyethylene etc.

Propulsion subsystems in a spacecraft aid in preserving the three-axis stability and the control spin. In addition to it, they also help in carrying out manoeuvres and to bring about slight alterations in trajectory. The superior ones called ?engines? can infact, generate an acceleration of large torques in volume to sustain the stability of a solid rocket motor during burning phase. The delta-V for simple tasks like the interplanetary trajectory correction manoeuvres, orbit trim manoeuvres, reaction wheel de-saturation manoeuvres and the routine three-axis stabilization or spin control, are arranged with the support of rather smaller engines that can provide with a force between 1N and 10N. While AACS, kick-off many of regular actions of the propulsion subsystems, all these actions are regulated by CDS.

Magellan spacecraft had four rocket engine modules, where each module housed two 445 -N engines, one gold-colored 22-N thruster, and three gold colored 1-N thrusters.

Each engines had different tasks to fulfil. The 445 -N engines had to manage the mid flight course corrections and take care of orbit-trim corrections also had to steer the spacecraft during the burning of solid rocket motor on entering the venus orbit. While the 22-N thrusters protected the spacecraft from undulating on the manoeuvres, the 1-N thrusters gave the necessary acceleration for wheel de-saturation and small manoeuvres.