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簡述無線電通信按所用波段可分為哪幾類?

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答:無線電通信按所用波段可分為長波通信、中波通信、 短波通信、超短波通信和微波通信等。

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試題分類: 初級(口語)
練習次數(shù):0次
試題分類: 安全員
練習次數(shù):1次
Bernard Bailyn has recentlyreinterpretedthe early historyof the United States by applyingnew socialresearchfindingson theexperiencesofEuropean migrants.Inhisreinterpretation,migrationbecomes the organizingprinciplefor rewritingthe historyofpreindustrial North America. His approach rests on four separate propositions.The firstof these asserts that residentsof early modern England moved regularlyabouttheir countryside; migrating to the New World was simply a natural spillover. Although atfirstthe colonies held littlepositiveattractionfor the English D they would rather havestayed home D by the eighteenth century people increasingly migrated to America becausethey regarded it as the land of opportunity. Secondly, Bailyn holds that, contrary to thenotion that used to flourish in America history textbooks, there was never a typical NewWorld community.For example, the economic and demographiccharacterof early New Englandtowns varied considerably.Bailyn's third proposition suggest two general patterns prevailing among the manythousands of migrants:one group came as indenturedservants,another came to acquire land.Surprisingly,Bailyn suggests that those who recruitedindentured servants were the drivingforces of transatlanticmigration.These colonialentrepreneurshelped determine the socialcharacterof people who came to preindustrialNorth America.At first,thousands ofunskilled laborers were recruited; by the 1730's, however, American employers demandedskilled artisans.Finally, Bailyn argues that the colonies were a half-civilized hinterland of theEuropean culture system. He is undoubtedly correct to insist that the colonies were partof an Anglo-American empire. But to divide the empire into English core and colonialperiphery, as Bailyn does, devalues the achievements of colonial culture. It is true, asBailyn claims, that high culture in the colonies never matched that in England. But whatof seventeenth-century New England, where the settlers created effective laws, built adistinguished university, and published books Bailyn might respond that New England wasexceptional. However, the ideas and institutions developed by New England Puritans hadpowerful effects on North American culture.Although Bailyn goes on to apply his approach to some thousands of indenturedservantswho migrated just prior to the revolution, he fails to link their experience with thepolitical development of the United States. Evidence presented in his work suggests howwe might make such a connection. These indentured servants were treated as slaves for theperiod during which they had sold their time to American employers. It is not surprisingthat as soon as they served their time they passed up good wages in the cities and headedwest to ensure theirpersonal independence by acquiringland. Thus, it is in the west thata peculiarly American political culture began, among colonists who were suspicious ofauthority and intensely anti-aristocratic. 1.Which of the followingstatements about migrants to colonialNorth America is supportedby information in the text [A] A larger percentage of migrants to colonial North America came as indenturedservants than as free agents interested in acquiring land. [B] Migrants who came to the colonies as indentured servants were more successful atmaking a livelihood than were farmers and artisans. [C] Migrants to colonialNorth America were more successfulat acquiringtheir own landduring the eighteenth century than during the seventeenth century. [D] By the 1730's,migrants already skilled in a trade were in more demand by Americanemployers than were unskilled laborers. 2.The author of the text states that Bailyn failed to [A] Give sufficient emphasis to the cultural and political interdependence of thecolonies and England. [B] Describe carefully how migrants of different ethnic backgrounds preserved theirculture in the United States. [C] Take advantage of social research on the experiences of colonists who migrated tocolonial North America specifically to acquire land. [D] Relate the experience of the migrants to the politicalvalues that eventuallyshapedthe character of the United States. 3.Which of the following best summarizes the author's evaluation of Bailyn's fourthproposition [A] It is totally implausible. [B] It is partially acceptable. [C] It is highly admirable. [D] It is controversial though persuasive. 4.According to the text,Bailyn and the author agree on which of the followingstatementsabout the culture of colonial New England [A] High culture in New England never equaled the high culture of England. [B] The culturalachievements of colonialNew England have generallybeen unrecognizedby historians. [C] The colonistsimitatedthe high cultureof England , and did not develop a culturethat was uniquely their own. [D] The southern colonies were greatly influenced by the high culture of New England. 5.The author of the text would be most likely to agree with which of the followingstatements about Bailyn's work [A] Bailyn underestimates the effects of Puritan thought on North American culture. [B] Bailyn overemphasizes the economic dependence of the colonies on Great Britain. [C] Bailyn'sdescriptionof thecoloniesas part of an Anglo-American empireis misleading and incorrect. [D] Bailyn failedto test his propositionson a specificgroup of migrants to colonialNorth America.
試題分類: 專業(yè)英語八級
練習次數(shù):1次
Passage 3 Questions 11 to 15 are based on the following passage: The idea of a special day to honor mothers was first put forward in America in 1907. two years later a woman, Mrs. John Bruce Dodd, in the state of Washington proposed a similar day to honor the head of the family—the father. Her mother died when she was very young, and her father brought her up. She loved her father very much. In response to Mrs. Dodd’s idea that same year—1909, the state governor of Washington proclaimed (宣布) the third Sunday in June Father’s Day. The idea was officially approved by President Woodrow Wilson in 1916. in 1924, President Calvin Coolidge recommended national observance of the occasion “to establish more intimate (親密) relations between fathers and their children, and to impress upon fathers the full measure of their obligations.” The red or white rose is recognized as the official Father’s Day flower. Father’s Day took longer to establish on a national scale than Mother’s Day, but as the idea grained popularity, tradesmen and manufacturers began to see the commercial possibilities. They encouraged sons and daughters to honor their fathers with small thank-you presents, such as a tie or pair of socks, as well as by sending greeting cards. During the Second World War, American servicemen stationed in Britain began to request Father’s Day greeting cards to send home. This generated a response with British card publishers. Though at first the British public was slow to accept this rather artificial day, it’s now well celebrated in Britain on the third Sunday in June in much the same way as in America. Father’s Day seems to be much less important as occasion than the Mother’s Day. Not many of the children offer their fathers some presents. But the American fathers still think they are much better fated than the fathers of many other countries, who have not even a day for their sake in name only. 11. When did Father’s Day officially begin to have national popularity? A. 1907 B. 1909 C. 1916 D. 1924 12. Who first started the idea of holding the Father’s Day? A. Mrs. John Bruce Dodd B. Mrs. John Bruce’s Mother C. The government of Washington. D. Some businessmen. 13. What flower will be popular on Father’s Day? A. Lily B. Water Lily C. Red rose or white rose D. Sunflower. 14. Which statement is true, a according to this passage? A. It took even longer for Mother’s Day to gain national popularity. B. The businessmen helped to make Father’s Day popular. C. Father’s Day is only celebrated in America. D. Father’s Day is only a trick of the businessmen to make money. 15. What was the first reaction of the British publishing towards Father’s Day? A. They thought highly of it and accepted it at once. B. They just accepted it at once without any hesitation. C. They just thought it a joke. D. They thought it was too artificial and took a long time to accept.
試題分類: 大學英語四級
練習次數(shù):1次
California is a land of variety and contrast. Almost every type of physical land feature , sort of arctic ice fields and tropical jungles can be found within its borders. Sharply contrasting types of land often lie very close to one another. People living in Bakersfield , for instance,can visit the Pacific Ocean and the coastal plain , the fertile San Joaquin Valley , the arid Mojave Desert , and the high Sierra Nevada, all within a radius of about 100 miles. In other areas it is possible to go snow skiing in the morning and surfing in the evening of the same day , without having to travel long distance. Contrast abounds in California. The highest point in the United States (outside Alaska ) is in California , and so is the lowest point (including Alaska )。 Mount Whitney , 14,494 feet above sea level,is separated from Death Valley , 282 feet below sea level,by a distance of only 100 miles. The two areas have a difference in altitude of almost three miles. California has deep , clear mountain lakes like Lake Tahoe , the deepest in the country, but it also has shallow, salty desert lakes. It has Lake Tulainyo , 12,020 feet above sea level, and the lowest lake in the country , the Salton Sea, 236 feet below sea level. Some of its lakes , like Owens Lake in Death Valley , are not lakes at all: they are dried up lake beds. In addition to mountains ,lakes, valleys,deserts, and plateaus,California has its Pacific coastline, stretching longer than the coastlines of Oregon and Washington combined. 1. Which of the following is the lowest point in the United States? A. Lake Tulainyo B. Mojave desert C. Death Valley D. The Salton Sea 2. Where is the highest point in the United States located ? A. Lake Tahoe. B. Sierra Nevada. C. Mount Whitney. D. Alaska. 3. How far away is Death Valley from Mount Whitney? A. About 3 miles. D. 14,494 feet. 4. Which of the following is NOT mentioned in the passage as being within a radius ofabout 100 miles of Bakersfield ? A. The Pacific Ocean. B. San Joaquin Valley. C. Mojave Desert. D. Oregon andWashington. 5. Which statement best demonstrates that California is a land of variety and contrast ? A. The highest lake in California is Lake Tulainyo. B. It is possible to go surfing and snow skiing in some parts of California without having totravel long distance. C. Sierra Nevada, San Joaquin Valley, Mojave Desert and the Pacific Ocean all lie withina radius of about 100 miles. D. Owens Lake , in Death Valley , is not really a lake at all.
試題分類: 專業(yè)英語八級
練習次數(shù):1次
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