|Главная Случайная страница
Разделы: Автомобили Астрономия Биология География Дом и сад Другие языки Другое Информатика История Культура Литература Логика Математика Медицина Металлургия Механика Образование Охрана труда Педагогика Политика Право Психология Религия Риторика Социология Спорт Строительство Технология Туризм Физика Философия Финансы Химия Черчение Экология Экономика Электроника
Б.Н. Небритов. The word «scientist» was introduced only in 1840 by a Cambrige professor of philosophy who wrote: «We need a name for describing a cultivator of science in
The word «scientist» was introduced only in 1840 by a Cambrige professor of philosophy who wrote: «We need a name for describing a cultivator of science in general. I should be inclined to call him a scientist». «The cultivators of science» before that time were known as «natural philosophers». They were curious, often eccentric, persons who poked inquiring fingers at nature. In the process of doing so they started a technique of inquiry which is now referred to as the «scientific method».
Briefly, the following steps can be distinguished in this method. First comes the thought that initiates the inquiry. It is known, for example, that in 1896 the physicist Henri Becquerel, in his communication to the French Academy of Sciences, reported that he had discovered rays of an unknown nature emitted spontaneously by uranium salts. His discovery excited Marie Curie, and together with her husband Pierre Curie she tried to obtain more knowledge about the radiation. What was it exactly? Where did it come from?
Second comes the collecting of facts: the techniques of doing this will differ according to the problem which is to be solved. But it is based on the experiment in which anything may be used to gather the essential data — from a test-tube to an earth-satellite. It is known that the Curies encountered great difficulties in gathering their facts, as they investigated the mysterious uranium rays.
This leads to step three: organizing the facts and studying the relationships that emerge. It was already noted that the above rays were different from anything known. How to explain this? Did this radiation come from the atom itself? It might be expected that other materials also have the property of emitting radiation. Some investigations made by Mme Curie proved that thiswas so. The discovery was followed by further experiments with «active» radioelements only.
The theory of plate tectonics describes the motions of the lithosphere, the comparatively rigid outer layer of the earth that includes all the crust and part of the underlying mantle. The lithosphere is divided into a few dozen plates of various sizes and shapes; in general the plates are in motion with respect to one another. A mid-ocean ridge is a boundary between plates where new lithosphere material is injected from below. As the plates diverge from a mid-ocean ridge they slide on a more yielding layer at the base of the lithosphere.
Since the size of the earth is essentially constant, new lithosphere can be created at the mid-ocean ridges only if an equal amount of lithosphere material is consumed elsewhere. The site of this destruction is another kind of plate boundary: a subduction zone. There one plate dives under another and is reincorporated into the mantle. Both kinds of plate boundary are associated with fault systems, earthquakes and volcanism, but the kinds of geologic activity observed at the two boundaries are quite different.
The idea of sea-floor spreading actually preceded the theory of plate tectonics. The sea-floor spreading hypothesis was formulated chiefly by Harry H. Hess of Princeton University in the early 1960s. In its original version it described the creation and destruction of ocean floor, but it did not specify rigid lithosphere plates. The hypothesis was soon substantiated by the discovery that periodic reversals of the earth’s magnetic field are recorded in the oceanic crust. An explanation of this process devised by F. J. Vine and D.H. Matthews of Princeton is now generally accepted. As magma rises under the mid-ocean ridge, ferromagnetic minerals in the magma become magnetized in the direction of the geomagnetic field. When the magma cools and solidifies, the direction and the polarity of the field are preserved in the magnetized volcanic rock. Reversals of the field give rise to a series of magnetic stripes running parallel to the axis of the rift. The oceanic crust thus serves as a magnetic tape recording of the history of the geomagnetic field. Because the boundaries between stripes are associated with reversals of the magnetic field that can be dated independently, the width of the stripes indicates the rate of sea-floor spreading. (Precisely how the earth’s magnetic field reverses at intervals of from 10, 000 to about a million years continues to be one of the great mysteries of geology).
It follows from the theory of sea-floor spreading that many of the most interesting geologic features of the earth’s surface are to be found on the ocean floor. The investigation of such features has been furthered in recent years by the development of deep-diving manned submersibles. In particular the U.S. research submersible Alvin, operated by the Woods Hole Oceanographic Institution, has proved to be a valuable tool for studies of the sea bed. A geologist in the Alvin can collect rock samples and document in detail the setting of each rock. For the first time a marine geologist can have maps of a site as precise as those of a geologist on land.
Our suspicion that the earth’s climate changes in leaps comes from the evidence recorded in deep-sea sediments and in ice. The most studied of these records is the amount of heavy oxygen found in the preserved shells of microscopic animals on the ocean floor. The heavy form of oxygen in water vapor tends to be lost as atmospheric moisture is transported to the icecaps. The larger the icecap, the more heavy oxygen remains behind in seawater. Thus, in eras when the icecaps were large, shelled organisms contained more heavy oxygen than they did when the icecaps were small; the shells therefore contain a history of the ice ages.
The oxygen isotope record tells us that over the last million years the polar icecaps have changed in a cyclic fashion, going from the rather small size of the current warm period to the very large size at the maximum of the last glaciation. More important, these fluctuations in ice volume have been shown to be in tune with periodic changes in the earth’s orbit around the sun, generated by gravitational interactions among the objects making up our solar system. Because the timing of the oxygen isotope changes (as determined by age measurements on deep-sea sediment cores) matches what would be expected if the changes were driven by earth’s changing orbit, scientists are reasonably certain of the cause-and- effect relationship.
While the oxygen isotope record in the deep-sea sediments provided evidence pointing to the earth’s orbital cycles as the pacemaker of glaciation, it also tended to lull scientists into concluding that the earth’s climate responds gradually when pushed. This conclusion was drawn despite the realization that the response of polar icecaps to changing climate would to be sluggish that a smooth oxygen isotope record would be expected no matter how abrupt changes in environmental conditions might be. So lulled were we that other clues paleoclimatic records that pointed to abrupt response were largely disregarded.
The awakening came in the early 1980s when Hans Oeschger and his group at the university of Bern, Switzerland, carried out detailed measurements of the CO2 content of air trapped in the ice from a deep boring made at a site in southern Greenland. These measurements concentrated on a section of the core on which earlier studies made by the Danish group of Willi Dansgaard had shown repeated leaps in Greenland’s air temperature. To everyone’s surprise’ each of Dansgaard’s jumps was accompanied by a 20 percent change in the CO2 content of the air trapped in bubbles in the ice (and hence in the CO2 content of the air above Greenland at the time the ice formed).
Eyebrows were raised by Oeschger’s CO2 jumps because while temperature jumps could be written off as a curiosity of Greenland, the CO2 changes could not. The atmosphere’s CO2 is well mixed with its other gases; hence a measurement in Greenland typifies the entire globe. Furthermore, the changes in CO2, content found by the Oeschger group occurred in times as short as a few hundred years. To bring about these changes in CO2 requires some extraordinary change in the earth’s chemical cycles, particularly those operating in the ocean. Scientists were therefore forced to the realization that the leaps in Greenland’s climate were far-reaching, involving the workings of the ocean as well as those of the atmosphere.
Developments in the blast furnace ironmaking process and advances in material sciences have improved the productivity, fuel consumption, product quality and campaign life of the blast furnace.
The duration of a blast furnace campaign was, until the start of the 1990s, influenced mainly by the lifetime of the lower shaft, i.e., the area of the highest thermal load.
This area was protected either by densely spaced copper plates or by cast-iron staves of different generations.
For the majority of large capacity blast furnaces operating today, design engineers have decided in favour of using staves for the cooling system because they enable intensive and, above all, uniform cooling of the furnace vessel. Classically, staves are made from nodular cast iron, which is cast around the cooling water pipes. They are installed over the entire furnace shell, from the bottom plate up to the throat. Frequently, however, the states are subjected to heavy stresses caused by high heat loads, particularly in the bosh and belly areas, which can limit the length of a furnace campaign.
This can lead to loss of the entire stave body, with only the water-conducting pipes remaining. It is believed that both the thermal conductivity of the cast iron material and the heat transfer between the piping and cast body may be the problem.
Even with the best known cooling systems, the lower shaft area remained the weak point of the blast furnace.
Producing staves from copper, using either drilled water passages in place of pipes or providing suitable channels when casting the copper slabs, has proven to be a significant step in the design of the modern blast furnace. The cooling effect is so intense that a protective layer forms within a few minutes, even in front of an unprotected stave. The insulating effect of such layers maintains the heat losses at a minimum.
These staves proved to be so successful that today the use of copper staves in the areas of high thermal load is state-of-the-art blast furnace technology. The lower stack is no longer considered to be a limiting factor to campaign life. Instead, the status of the hearth dictates the campaign life of the furnace.
1. Качалова К.Н., Израилевич Е.Е. - Практическая грамматика английского языка. – М., 2006
2. Комиссаров В.Н. Общая теория перевода. – М., 2000
3. Шеремет Л.Г. Основы теории перевода. – Чита, 2005
4. Learn to Read Science. – М., 1980
5. Swan M. Practical English Usage. – Oxford Univ. Press, 2002
6. Thompson A.J., Martinet A.V. A Practical English Grammar – Oxford University Press, 2000.
 Обратите внимание на употребление Subjunctive Mood в данном предложении.
ПЛАНИРОВАНИЕ НА ПРЕДПРИЯТИИ СТРОИТЕЛЬСТВА
МИНИСТЕРСТВО ОБРАЗОВАНИЯ И НАУКИ РОССИЙСКОЙ ФЕДЕРАЦИИ
Федеральное агентство по образованию
Государственное образовательное учреждение
высшего профессионального образования
«РОСТОВСКИЙ ГОСУДАРСТВЕННЫЙ СТРОИТЕЛЬНЫЙ УНИВЕРСИТЕТ»