语言类
公务员类
工程类
语言类
金融会计类
计算机类
医学类
研究生类
专业技术资格
职业技能资格
学历类
党建思政类
英语证书考试
大学英语考试
全国英语等级考试(PETS)
英语证书考试
英语翻译资格考试
全国职称英语等级考试
青少年及成人英语考试
小语种考试
汉语考试
多选题The intensive work of materials scientists and solid-state physicists has given rise to a class of solids known as amorphous metallic alloys, or glassy metals. There is a growing interest among theoretical and applied researchers alike in the structural properties of these materials. When a molten metal or metallic alloy is cooled to a solid, a crystalline structure is formed that depends on the particular alloy composition. In contrast, molten nonmetallic glass-forming materials, when cooled, do not assume a crystalline structure, but instead retain a structure somewhat like that of the liquid—an amorphous structure. At room temperature, the natural long-term tendency for both types of materials is to assume the crystalline structure. The difference between the two is in the kinetics or rate of formation of the crystalline structure, which is controlled by factors such as the nature of the chemical bonding and the ease with which atoms move relative to each other. Thus, in metals, the kinetics favors rapid formation of a crystalline structure, whereas in nonmetallic glasses the rate of formation is so slow that almost any cooling rate is sufficient to result in an amorphous structure. For glassy metals to be formed, the molten metal must be cooled extremely rapidly so that crystallization is suppressed. The structure of glassy metals is thought to be similar to that of liquid metals. One of the first attempts to model the structure of a liquid was that by the late J.D. Bernal of the University of London, who packed hard spheres into a rubber vessel in such a way as to obtain the maximum possible density. The resulting dense, random-packed structure was the basis for many attempts to model the structure of glassy metals. Calculations of the density of alloys based on Bernal-type models of the alloys metal component agreed fairly well with the experimentally determined values from measurements on alloys consisting of a noble metal together with a metalloid, such as alloys of palladium and silicon, or alloys consisting of iron, phosphorus, and carbon, although small discrepancies remained. One difference between real alloys and the hard spheres used in Bernal models is that the components of an alloy have different sizes, so that models based on two sizes of spheres are more appropriate for a binary alloy, for example, the smaller metalloid atoms of the alloy might fit into holes in the dense, random-packed structure of the larger metal atoms. One of the most promising properties of glassy metals is their high strength combined with high malleability. In usual crystalline materials, one finds an inverse relation between the two properties, whereas for many practical applications simultaneous presence of both properties is desirable. {{U}}One residual obstacle to practical applications that is likely to be overcome is the fact that glassy metals will crystallize at relatively low temperatures when heated slightly.{{/U}} The author's attitude toward the prospects for the economic utilization of glassy metals is one of ______. A. disinterest B. impatience C. optimism D. apprehension E. skepticism
进入题库练习
多选题Halle Berry"s portrayal of Dorothy Dandridge is a powerful ______: it calls forth the qualities that made Dandridge a legend.
进入题库练习
多选题The university"s aggressive transformation from a teaching-centered college to a major research institution has brought ______ that teaching is now being ______.
进入题库练习
多选题Although the administration repeatedly threatened to use its authority in order to ______ the student protestors into submission, they refused to be intimidated.
进入题库练习
多选题In order to ______ the lose of natural wetlands used by mig rating snow geese, conservationists in the 1960"s and 1970"s ______ wetland refuges in the northern prairies.
进入题库练习
多选题Although condemned by the review panel, to film critic Pauline Kael the movie seemed entirely ______ and unlikely to offend.
进入题库练习
多选题Some teachers worry that history courses will become ______ for students due to curricular pressures that are ______ the subject.
进入题库练习
多选题The deterioration of the ozone layer is ______, with the loss of penguin habitats being just one of the ______ results.
进入题库练习
多选题Keats"s poetry was called ______ by those critics who noted that he indulged in sensuous imagery and luxuriant diction.
进入题库练习
多选题Thomas Hardy"s novels are described as ______ because of their preoccupation with daily life in rural and agricultural settings.
进入题库练习
多选题The instructor"s voice was so ______ that most students preferred taking a test over listening to its grating sound.
进入题库练习
多选题Not only was the science of Hildegard of Bingen ______ her theology, but her religious visions helped give her scientific works ______ by winning her the support of medieval church authorities.
进入题库练习
多选题"Foamy" viruses cause cells cultured in laboratories to swell but produce no such ______ in cells of living organism.
进入题库练习
多选题When limitations were in effect on nuclear-arms testing, people tended to save more of their money, but when nuclear-arms testing increased, people tended to spend more of their money. The perceived threat of nuclear catastrophe, therefore, decreases the willingness of people to postpone consumption for the sake of saving money. The argument above assumes that A. the perceived threat of nuclear catastrophe has increased over the years. B. most people supported the development of nuclear arms. C. people's perception of the threat of nuclear catastrophe depends on the amount of nuclear-arms testing being done. D. the people who saved the most money when nuclear-arms testing was limited were the ones who supported such limitations. E. there are more consumer goods available when nuclear-arms testing increases.
进入题库练习
多选题The general was so widely suspected of ______ during the war that his name eventually became synonymous with disloyalty.
进入题库练习
多选题Displaying a heightened sense of ______, many of author Maria Cristina Mena"s characters exemplify a dignified and polite society.
进入题库练习
多选题Isadora Duncan's masterly writings on the dance reveal the depth of her determination to create a lyric form of the art which was free of characterization, storytelling, and the theatrical exhibition of skills. She wished to discard the traditional methods and established vocabularies of such dance forms as ballet and to explore the internal sources of human expressiveness. She shunned bodily ornamentation and strove to use only the natural movements of her body, undistorted by acrobatic exaggeration and stimulated only by internal compulsion. In her recitals Duncan danced to the music of Beethoven, Wagner, and Gluck, among others, but, contrary to popular belief, she made no attempt to visualize or to interpret {{U}}the music{{/U}}; rather, {{U}}she simply relied on it to provide the inspiration for expressing inner feelings through movement.{{/U}} She did not regard this use of music as ideal, however, believing that she would someday dispense with music entirely. That day never came. The author implies that Duncan relied on music in her recitals in order to A. interpret musical works solely by means of natural body movements. B. foster the illusion that music serves as an inspiration for the dance. C. inspire the expression of inner feeling when she danced. D. validate the public belief that music inspires the expression of feeling through movement. E. counter the public belief that she made no attempt to visualize music.
进入题库练习
多选题Although he felt that Steven was ______, Mark did not sense that Steven"s ill will amounted to outright ______.
进入题库练习
多选题Believing that scientists should ______ the public about important scientific issues, marine ecologist Jane Lubchenco has urged the research community to abandon its usual ______ in favor of more effective communication.
进入题库练习
多选题Some Tibetan nomads used yak butter as a ______, one that often took the place of money in commercial transactions.
进入题库练习