Üds a can coal ever become a friend of the environment? Coal-fired power stations supply
Yüklə 0,75 Mb.
|
particularly has tempted men from early times to explore all parts of the world and this has promoted a close link between exploration and botanic gardens. One well-known botanic garden is the Royal Botanic Garden at Edinburgh which was founded in 1670 by "'Obert Sibbald for the cultivation of medical plants. Since that date it has been removed to several different sites. It is now one of the major botanic gardens in Britain with an area of over 60 acres .
ÜDS F The Royal Society is the national academy of science for Great Britain and Northern Ireland but, unlike other national academies, is and always has been independent of state control; it is not maintained by grants from public funds and manages its own affairs. Since its foundation however, kings, statesmen and government departments have regularly sought its advice on scientific matters; it has never hesitated to assist governments when convinced that the national interest called for official scientific action. Within ten years of its foundation the society, at the invitation of Charles I and his ministers, grappled with problems of national food supply, arboriculture, naval architecture and navigation. Throughout the 18. century It worked with the admiralty on what was then called "the problem of the longitude' in the solution of which are associated the names of the astronomers Edmond Halley and Maskelyne, the chronometer maker John Harrison and the navigator James Cock. It found a cure for jail-fever and advised on th. protection of ships of war against lightning: it organized a geodetic survey of the British isies and appointed scientific personnel to several arctic and antarctic expeditions.
The first flight by a power driven manned aeroplane took place in 1903 and its subsequent development as a military weapon was so rapid that all the belligerents entered World War I totally unprepared to defend themselves against it. The first bombing raids, however, compelled the consideration of anti-aircraft measures, and Britain, in particular, attacked by Zeppelin airships and Gotha aircraft was forced to develop a range of Specialized anti-aircraft equipment, which came to include guns, searchlights, sound locators and predictors, giving it a qualitative ascendancy in this field retained until the end of World War II. Indeed, the first night attack on London caused such public consternation that its gun defences had to be doubled within forty-eight hours and, though they hit few planes, their presence was of great psychological value.
Scientists can now speed up the process of genetic change through biotechnology. Farmers need no longer wait patiently for breeding to yield improved crops and animals, nor must they even respect natural lines of reproduction among species. Laboratory scientists can now select desirable traits from any of a number of species and insert those traits into the genetic material of crops and animals. Among the new products of biotechnology are tomatoes that stay fresh much longer than the usual ones and so promise less waste and higher profits." Normally, tomatoes produce a protein that softens them after they have been picked. Scientists introduce into a tomato plant a gene that is a mirror image of the one that codes for the "softening" enzyme. This gene fastens itself to the RNA of the native gene and breaks its action. A vine-ripe tomato ….this special gene rots more slowly than a normal tomato, allowing , growers to harvest at the most flavourful and nutritious red stage. The tomatoes will still last much longer during shipping and marketing than regular tomatoes harvested when green.
To obtain power from the sun's rays is to use nuclear power developed at no expense in a laboratory 93 million miles away. For the radiant energy of the sun is maintained by nuclear transformation of chemical elements occurring in the sun's interior at temperatures of many million degrees, and at pressures of many million atmospheres. The resources of solar power are enormous. If 100 per cent efficiency could be secured in the transformation of radiant solar energy into mechanical work, a horsepower per square yard of ground surface would be available under cloudless skies. The expense of collecting solar energy still prevents its competition with the usual power Sources. Yet, unless the vague promise of safe thermonuclear power from oceans becomes realized, solar power must supply the enormous and growing requirements of posterity within two centuries. Because the ground sources (coal, oil and uranium) as they near exhaustion will become more costly than solar power.
The design of ships is governed by scientific principles and economic considerations but in practice it has many of the qualities of an art. The designer may be supplied with the precise and detailed requirements of an owner or he may receive only the barest outline of requirements such as the weight of cargo to be carried and the speed. The dimensions chosen and the main characteristics of the ship are governed by the trade in which the vessel is to compete. High-density cargoes such as iron are require little cubic capacity; low density cargoes such as bananas require vast cubic capacity. The ports which the vessel must enter may impose restrictions on length and draught. Passage through canals may restrict both draught and breadth. The nature of the cargo may determine the size of cargo holds and of the hatchways through which the cargo is loaded and unloaded. Available facilities at the ports to be entered affect the loading and unloading apparatus to be installed in the vessel.
Erosion is regarded not merely as the physical removal of soil by water and wind, out rather as the deterioration of all the component parts of the habitat in which man and his crops and livestock have to exist. Since there is no conclusive evidence for any major climatic change in historic times to explain this deterioration, we must conclude that the eroding of the total environment has been due primarily to thoughtless destruction of the vegetative cover. This has led to deterioration of the microclimate above and below the surface, generally in the direction of a general drying out of the soil which has exposed it to erosive action of wind and rainfall of high intensity or frequency, and to the loss of organic matter in the soil, Thus reducing its capacity to resist erosion by conserving the water that falls on the surface. If everything possible is done within the total environment to conserve the naturally planted or cultivated vegetation, this will also ensure optimal conservation of soil and water.
The world's nuclear plants have accumulated vast stocks of highly radioactive waste. Worldwide, high-level waste is currently stored above ground, and no government has a clear policy on its eventual disposal. While most experts believe that burying the waste is the safest bet in the long term, the problem is finding sites that everyone can agree are geologically stable. Decaying radioactive isotopes release heat. As a result, high level waste must be constantly coded, otherwise, it becomes dangerously hot. This is why many experts want to stote waste above ground until it has decayed and is cool enough 10 be stored safely in sealed repositories several hundreds of metres below ground. According to one recent theory, however, waste should be lowered down boreholes drilled to 4 kilometres. The trick is to explore heat generated by the waste to fuse the surrounding rock and contain any leaking radioactivity.
Sounds produced by continuous vibration tones are spread as waves of compression through the air. Where there is a solid boundary such as the walls of a room, the sound waves are reflected so that the sounds within the room are prolonged beyond what they would be in the open. The sounds produced by the voice or by a musical instrument then reverberate through the room after the actual tone production has ceased. When the sound waves strike the walls some of the sound energy travels on and is either absorbed in the material or may penetrate to the other side; but with the usual hard, unyielding walls of which most buildings are made, more than 90% of the sound energy is reflected back into the room at each impact, so that some time must elapse before all is spent. It is this reverberation which, in its excess, is the prime cause of the faulty acoustics of many pre-20. century buildings
ÜDS G Florida's more than 1,000 miles of coastline contain about 150 drawbridges, more than are found in any other state. As these bridges age and Florida grows and changes, many of them now have to be replaced. But replaced with what? Recently there have been very many controversies over drawbridges. One involved the Belleair Beach Causeway, which was built in 1950. When it approached the end of its 50-year lifespan, the choice for a replacement came down to three options: a drawbridge the same height as the existing span (21 feet above high tide) but wider, to accommodate modern traffic levels; a draw bridge with a height of 45 feet; and a fixed span 65 feet tall. Each choice had its advantages and disadvantages. The two draw bridges would have created the least disruption in nearby communities. Opening a draw bridge inconveniences motorists, however, and can cause a dangerous delay for ambulances or in other emergencies. A drawbridge also costs more to build and maintain. A high fixed span would be cheaper and eliminate the delays, but it would require extensive property acquisition to accommodate its ap proaches. It would also tower over the area and block the views of many residents, and some tall boats would be unable to fit under neath. However after much debate and many hearings, the country board settled on a high fixed span.
A new and quicker method to check or prove the existence of weapons of mass destruction (WMO) is being developed. First, on needs to know where they may be hidden and then a high-velocity projectile can be fired at the target. High-tech sensors packed into the projectile will then instantly beam back confirmation that the weapons are there if Indeed they are. It's a high-risk concept that raises many questions, not least its techno logical feasibility and the political protests that would follow if such a device were ever built or used. But the US military is taking the idea seriously. Last year, in a two-page re search paper commissioned by army, experts from the institute for Advanced Technology detailed real test results of a prototype projectile designed to verify the existence of WMOs. They say such a device offers a way to inspect for weapons without permission or cooperation. To inspect reinforced concrete bunkers or factory buildings suspected of housing WMOs, the researchers designed a projectile that can penetrate several meters of hardened concrete, without damaging its load of sensors. Its casing is built from Aer Met 100, a nickel-cobalt steel with traces of molybdenum and chromium. Heat-treating the casing after it is made gives it an extremely hard surface. The tapering projectile is 230 millimeters long, with a maximum cali bre of 45 millimeters
To engineers, design typically has less to do with aesthetics and appearance and more to do with fabrication and performance. Engineers tend to focus on the structure behind the façade. They worry about how the building will be built, how it will stand, whether it will sway too much in the wind, whether it will survive an earthquake, whether it will crack or leak. Engineers designing the structural frame of hotel buildings take into account the strength and stiffness of ballroom floors, where large crowds will gather and rhythmic dancing will occur. Engineers are expected to think about how a building will be heated and cooled" how air will circulate among its spaces, how energy efficient it will be. In the ideal world, the design efforts of architects and engineers complement each other, resulting in a building that is both a joy to look at and a pleasure to use. But all too often in practice, things do not work out like that, and the users of the building pay the price. In most buildings, the work of the architect masks, cloaks and hides the work of the engineer. Engineering criticism is almost un heard of in public discussions of building de sign, although it does sometimes come to the fore when buildings fall down, as in the case of the collapse of the World Trade Center towers
At one point, during what was still a time of hopeful experimentation with nuclear technology, the US considered using atomic bombs to blow a trench through the isthmus of Panama. The idea was to replace the 50 year-old Panama Canal, whose locks were too narrow for the world's growing fleet of super-tankers and aircraft carriers, with one that would be more suited to modem conditions. The problem was not just the size of the locks but their very existence. Ships don't simply sail through the Panama Canal; they have to be lifted 85 feet to the elevation to the highest paint along the way and then brought down to sea level again. Each ship's trip through requires 52 million gallons of fresh water, more than most American cities use in a day, all of it flowing through huge gravity-fed tubes. The source of this water supply is a vast artificial lake whose Dam also provides the electrical power for the whole operation. To fill up and empty a single lock takes 40 minutes on averaged, and when any one of the 12 locks shuts down for mainte nance, ship traffic can back up for days. Finally, with all that complicated machinery, if the canal were to be sabotaged (as had hap pened to the lockless Suez Canal in 1956), correcting the damage might take years.
If the solar company's claims are borne out, its high-efficiency cells will bring solar power closer to becoming a practical option for home owners. The averaged power demand of a household is 2,000 to 3,000 watts. With solar cells around 20 per cent efficient, this demand can be met with about 15 square meters of solar panels, which is compact enough to fit on a roof top. It has been estimated that ready-to install arrays will sell for around $10 per watt. That cost may eventually fall Further. For, as one spokesman for the company said: "The trend is towards higher efficiency ". Others agree, but say silicon may not be the material that ultimately delivers it. Thin films of cadmium telluride, for instance, are showing promise in the lab. One London-based solar energy systems supplier is very impressed with some new solar cells that have just come on the mar ket, both on account of their efficiency and also because they are practical. "They are very easy to connect together," he points out, you can just put tabs on the sides of the back contacts and connect one cell to another without wires.
Smoke is clouding our view of global warming, protecting the planet from perhaps three quarters of the greenhouse effect. That might sound like good news, but experts say that, as the cover diminishes in coming decades, we're in for a dramatic escalation of warming that could be two or even three times as great as official best guesses. This was the dramatic conclusion reached last week at a workshop in Berlin. Scientists have suspected or a decade that aerosols of smoke and other particles from burning rainforest, crop waste and fossil fuels are blocking sunlight and counteracting the warming effect of carbon dioxide emissions. Until now, they reckoned that aerosols reduced greenhouse warming by perhaps a quarter, cutting in creases by 0.2°C. So the 0.6°C e of warming over the past century would have been 0.8°C without aerosols. But the Berlin workshop concluded that the real figure is even higher aerosols may have reduced global warming by as much as. three-quarters cutting in creases by 1.Boe. If so, the good news is that aerosols have prevented the world getting almost two degrees warmer than it is now. But the bad news is that the climate system is much more sensitive to greenhouse gases than previously guessed. In fact, warming could go up by 7 to 10°C.
ÜDS H On 31 October 1994, a turboprop airliner heading for Chicago, Illinois, crashed into a soybean field at Roselawn in Indiana. All 68 people aboard died. Although the weather was cold and damp that day, no one could believe it when investigators revealed that the crash was caused by a build-up of ice on the wings. Not only did this modern plane have a fully functional de-icing system, but according to US Federal Aviation Administration (FAA) standards, the French-built ATR-72 should have had no problems flying in the cold, damp conditions. The pilots even knew their craft was icing up and at tempted to clear it, following de-icing procedures exactly.
It cannot be denied that buying locally grown food really does offer big advantages, not just in freshness, but also in environmental savings. İmported foods, especially those flown in from the opposite hemisphere, use up huge amounts of jet fuel-127 calories of fuel.,per calorie of Californian lettuce flown to Britain, and 66 calories of fuel per calorie of South African carrot; that at least is what a green re search group based in London has estimated. Much of that cost is hidden from consumers, because air fuel attracts no tax-an advantage guaranteed by international treaty. And under the Kyoto Protocol, carbon emissions from international Transports aren't added to national carbon-emission tallies, because nobody can agree whose account to charge them to. But the fuel used to import food and drink to Britain continues to account for four million tones of CO2 emissions annually, which is about 2.5 per cent of the national total.
When it came to replacing the bridge at John's Pass, there were certain special problems to be taken into consideration. The previous bridge had had a life span of only 30 years, but in that time the currents had caused extensive damage. But a more serious problem connected with the currents is that the bridge has to open on demand, rather than on a fixed schedule. Currents at the inlet are Yüklə 0,75 Mb. Dostları ilə paylaş:
|