HOW A HOVERCRAFT WORKS
hovercraft is a wonderful machine as it neither fully flies like a plane neither floats liks a ship nor it oves on ground like a road vehicle .
This air-cushion vehicle (ACV), craft designed to travel close to but above ground or water. It is also called a ground-effect machine or Hovercraft. These vehicles are supported in various ways. Some of them have a specially designed wing that will lift them just off the surface over which they travel when they have reached a sufficient horizontal speed (the ground effect). Others are supported by fans that force air down under the vehicle to create lift. In a plenum chamber vehicle the rate of leakage of this air from underneath the vehicle is reduced by placing a skirt around the lower edge of the craft. In an annular jet vehicle the rate of leakage is reduced by directing the air downward and inward from the outer edges of the vehicle. Air propellers, water propellers, or water jets usually provide forward propulsion.
Air-cushion vehicles can attain higher speeds than can either ships or most land vehicles and use much less power than helicopters of the same weight. Air-cushion suspension has also been applied to other forms of transportation, in particular trains, such as the French Aerotrain and the British Hovertrain
In the early 1950s the British inventor Christopher Cockerell began to experiment with such vehicles, and in 1955 he obtained a patent for a vehicle that was "neither an airplane, nor a boat, nor a wheeled land craft." He had a boat builder produce a two-foot prototype, which he demonstrated to the military in 1956 without arousing interest. Cockerell persevered, and in 1959 a commercially built one-person Hovercraft crossed the English Channel. In 1962 a British vehicle became the first to go into active service on a 19-mi (31-km) ferry run. The maximum size of air-cushion vehicles is now over 100 tons; some of them travel at over 100 mi (160 km) per hr. Although air-cushion vehicles of several thousand tons have been under development for many years, it is in small vehicles, usually called flarecraft, that the greatest current potential market exists; current flarecraft can carry one to eight people at 150 mi (240 km) per hr.
Hovercraft are so versatile that their applications are as diverse as the people who use them. They are most often used to reach areas that are inaccessible on foot or by conventional vehicles. A partial listing of present uses includes:
â€¢ Exploring the vast number of shallow and narrow waterways that cannot be reached by boat â€¢ Rescue work on swift water, ice, snow, mud flats, deserts, wetlands, shallow water, swamps, bogs, marshes and floodwaters. â€¢ Affordable, safe way to fly without a pilot's license. â€¢ Transport in environmentally sensitive areas where habitat, erosion and soil compaction are a concern â€¢ Wildlife conservation and research â€¢ Transportation or "island-hopping" with clients for real estate purposes â€¢ Fishing anywhere ... including ice fishing
THE RISING PRICES OF FUEL HAS LIMITED THE USE OF HOVERCRAFT BUT STILL THEY FIND APPLICATION WHERE BOATS AND VEHICLES CAN'N MOVE
Welcome to Topic of the WEEK section.The topic we are going to discuss today is about articial organs.Organ implantation is increasing day by day and so is the need of organs.But demand for organs is much more than supply beause of which many people die.The solution to this problem is Artificial organs.
An artificial organ is a man-made organ that is implanted in a human to replace a natural organ.
HOW ARTIFICIAL ORGANS WORK
This technology is new and not fully implemented for all organs.Resarch is going on.Artifical heart has been successfully made and implanted.Although it is not as effective as natural heart but still can support for day to day actions.This artificial heart works with the help of batteries and pump.Battery provides power to pump the motor. The AbioCor Implantable Replacement Heart is the first completely self-contained artificial heart and is expected to at least double the life expectancy of heart patients. Artificial kidney can be said a dialyser which supports the patients temperorily awaiting a donor.Similiarly Artificial larynx is also developes which matches the mechanism of human larynx.
artificial organs lived on.
Artificial skin is perhaps the most mature specialty in the development of artificial organs. Photo courtesy of Integra Lifesciences (Plainsboro, NJ)
THE ARTIFICIAL BODY
Some current research into artificial organs represents new ways of considering old bioengineering problems. The artificial pancreas, for example, has long been the subject of intensive research, thanks to the large market that would be served by such a device. The traditional model seeks to combine a permanent glucose monitor with some sort of insulin-delivery device. But some biotech firms are taking a different tack. For example, Islet Technology, Inc. (North Oaks, MN), is developing a process for encapsulating healthy pancreatic islets to permit implantation. Encapsulation would allow diffusion of small molecules like glucose and insulin but prevent passage of larger immunogenic molecules. Islet Technology president and CEO Bill Drake likens the encapsulation material to a chain-link fence. "I envision glucose as the size of marbles and immunoglobins as basketballs," he explains.
Cadaver or autogenous bone grafts could become a thing of the past if Interpore International (Irvine, CA) continues to have success with its Pro Osteon bone graft substitute made from processed sea coral. The processing technique converts the coral to hydroxyapatite, the same mineral found in human bone. The resulting product is nonimmunogenic and is easily sculpted by surgeons for various implant applications. The geometrical structure is similar to that of human cancellous bone. As Interpore president David Mercer explains, "The patient's own osteoblasts are attracted to and grow into the hydroxyapatite graft." Conservationists need not worry. "Less than 1% of the world's coral supply will ever be used for grafts," reassures Mercer.
Artificial skin may be the most mature specialty in the development of artificial organs, and there is definitely no lack of players in this crowded field. Organogenesis (Canton, MA) hopes to stand out from the pack by positioning its Apligraf as entirely natural skin. Organogenesis believes that Apligraf is the first living manufactured organ—unlike competing products, which are made from collagen or protein matrices. According to Carol Hausner, director of investor and public relations, "Our organotypic cell-culture technique actually achieves the three-dimensional organization of living skin." Hausner, who refers to Apligraf as "skin in a dish," also notes that the living tissue product has the added benefit of being able to actively contribute to the wound-healing process.
Research continues in trying to find artificial substitutes for almost every organ in the human body. Many systems are external, like kidney dialysis and liver-assist machines. Some organs—like the eyes—require electronic and optic technology that we can grasp conceptually but not yet command. Although fully implantable organs are still mostly science fiction, the technology is rapidly making that fiction our future.
Because the supply of natural organs is very less so artifical organs have proved very helpful in many cases.But they have a draw back of being very costly.Medical science is constantly trying to develop well functioning organs which can fully replace natural organs.The day they are fully developed few people will die of organ failures.
Some claim that this land bridge is the site of the famous Rama's Bridge, making it a historical, religious and cultural monument of great significance. For this reason, many, including chief ministers of states, oppose the project.Several claims and estimates have been made regarding the age of Rama's bridge and its relation to the Indian epic Ramayana.
Possibly conceived in 1860 by Commander A. D. Taylor of the Indian Marines, the project has been reviewed many times over the years but no decision was ever made. It was part of the election manifestos of all political parties during elections. The Union Government of India appointed the Sethu Samudram Project Committee in 1955, headed by Dr. A. Ramasamy Mudaliar, which was charged with the duty of examining the desirability of the project. After evaluating the costs and benefits, this committee found the project feasible and viable. Several reviews of the proposals followed. Finally, the United Progressive Alliance Government of India headed by Prime Minister Manmohan Singh announced the inauguration of the project on June 2, 2005.
The strategic advantages to India derive from obtaining a navigable sea route close to the coast, with a reduction in travel distance of more than 350 nautical miles (650 km) (for larger ships). The project is expected to provide a boost to the economic and industrial development of coastal Tamil Nadu. The project will be of particular significance to Tuticorin harbour, which has the potential to transform itself into a nodal port. The State Government has announced its proposal to develop 13 minor ports, including Ennore, Cuddalore, Nagapattinam, Thondi, Valinokam, Kolachel and Kanyakumari.
Development of the canal and ports is also expected to provide increased maritime security for Tamil Nadu.
Though there has been a demand from various quarters for the implementation of the project, there is also opposition to it from environmentalists. They point out that the dredging of the Palk Strait and the Gulf of Mannar could affect the ecology of the zone by changing currents, which could:
They also point out that dredging the canal could stir up the dust and toxins that lie beneath the sea bed, affecting marine life. The emptying of bilge water from ships travelling through the hitherto impassable areas could diperse invasive species through the ecosystems of the area.
These effects could endanger precious marine species and wealth. The Gulf of Mannar has 3,600 species of plants and animals and is India's biologically richest coastal region. Mammal species which abound in the area are sperm whales, dolphins and dugongs. The Gulf of Mannar is especially known for its corals: the portion in Indian territorial waters has 117 species of corals, belonging to 37 genera. Associated with these ecosystems are many varieties of fish and crustaceans. Marine life on the Sri Lankan side, which is better protected, is even richer. The Bar Reef off the Kalpitiya peninsular alone has 156 species of coral and 283 of fish; there are two other coral reef systems around Mannar and Jaffna. There are extensive banks of oysters, as well as Indian Chank and Sea Cucumbers, especially in the seas adjacent to Mannar. The pearl fisheries south of Mannar, which inspired Georges Bizet's opera Les Pêcheurs de Perles, have not been productive for many years, indicating the fragility of these ecosystems in the face of overfishing and of relatively minor changes in the habitat.
However official environmental clearance has been given for the project. The contention that the Sethusamudram Canal will cut through coral reefs and disturb the ecology has been dismissed as a mistaken fear.
The Indian government has conducted various environmental studies which has concluded that such issues are overblown and not based on science. Nevertheless, the fundamental environmentalist objections remain, that
After environmental objections were made in Sri Lanka, the Indian government belatedly decided to carry out modelling, but this had not been done before clearance was given for the project. A modelling exercise carried out by Sri Lanka's National Aquatic Resources Research and Development Agency (NARA) indicated that the project would increase the water flow from the Bay of Bengal to the Gulf of Mannar, disturbing the inland water balance as well as the eco-systems in the Gulf.  There have also been judicial observations against this project .
On July 2, 2005, the Indian Prime Minister Manmohan Singh unveiled the Sethusamudram Shipping Canal Project amidst protests from fishermen and environmentalists. Nearly 600 were arrested.
There have been concerns that the dredging would increase the water flow, thus eroding and even submerging the western Jaffna coastline. However as the project is nearly 50 km from the coastline of Sri Lanka few geologists believe it will have any serious harm. Moreover some have chipped in saying that the economic benefits will be mutual for Sri Lanka as much as it is for India by reviving minor ports in Sri Lanka.
The underdeveloped region of Northern Srilanka is currently occupied by LTTE. Sethusamudram project could potentially allow economic benefits to this region. This is being viewed with mutual suspsicon of both Sri Lankan and Tamil leaders. Further it is expected that in addition to Colombo, new ports to be developed near Jaffna.
There has also been criticism expressed, on the basis that the project could damage relations with SriLanka.
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Television (often abbreviated to TV, T.V.; sometimes called , telly or the tube, bloob tube or boob tube, or idiot box in British English) is a widely used telecommunication system for broadcasting and receiving moving pictures and sound over a distance. The term may also be used to refer specifically to a television set, programming or television transmission. The word is derived from mixed Latin and Greek roots, meaning "far sight": Greek tele (τῆλε), far, and Latin vision, sight (from video, vis- to see, or to view in the first person).
Since it first became commercially available from the late 1930s, the television set has become a common household communications device in homes and institutions, particularly in the first world, as a source of entertainment and news. Since the 1970s, video recordings on VCR tapes and later, digital playback systems such as DVDs, have enabled the television to be used to view recorded movies and other programs.
A television system may be made up of multiple components, so a screen which lacks an internal tuner to receive the broadcast signals is called a monitor rather than a television. A television may be built to receive different broadcast or video formats, such as high-definition television, or preferably referred to as (HDTV).
The elements of a simple broadcast television system are:
Practical television systems include equipment for selecting different image sources, mixing images from several sources at once, insertion of pre-recorded video signals, synchronizing signals from many sources, and direct image generation by computer for such purposes as station identification. The facility for housing such equipment, as well as providing space for stages, sets, offices, etc., is called a television studio, and may be located many miles from the transmitter. Communication from the studio to the transmitter is accomplished via a dedicated cable or radio system.
Television signals were originally transmitted exclusively via land-based transmitters. The quality of reception varied greatly, dependent in large part on the location and type of receiving antenna. This led to the proliferation of large rooftop antennas to improve reception in the 1960s, replacing set-top dipole or "rabbit ears" antennas, which however remained popular. Antenna rotors, set-top controlled servo motors to which the mast of the antenna is mounted, to enable rotating the antenna such that it points to the desired transmitter, would also become popular.
In most cities today, cable television providers deliver signals over coaxial or fiber-optic cables for a fee. Signals can also be delivered by radio from satellites in geosynchronous orbit and received by parabolic dish antennas, which are comparatively large for analog signals, but much smaller for digital. Like cable providers, satellite television providers also require a fee, often less than cable systems. The affordability and convenience of digital satellite reception has led to the proliferation of small dish antennas outside many houses and apartments.
Digital systems may be inserted anywhere in the chain to provide better image transmission quality, reduction in transmission bandwidth, special effects, or security of transmission from reception by non-subscribers. A home today might have the choice of receiving analog or HDTV over the air, analog or digital cable with HDTV from a cable television company over coaxial cable, or even from the phone company over fiber optic lines. On the road, television can be received by pocket sized televisions, recorded on tape or digital media players, or played back on wireless phones (cell or "mobile" phones) over a high-speed or "broadband" internet connection.
Thanks to the advances in display technology, there are now several kinds of video displays used in modern TV sets:
Each has its pros and cons. Flat panel LCD and plasma displays have a wide viewing angle (around 178 degrees) so they may best suited for a home theatre with a wide seating arrangement. Rear projection screens do not perform well in daylight or well-lit rooms and so are only suited to darker viewing areas.