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 河南成教 / 检测技术及应用
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4[单选题]
光敏二极管工作时，其上( )


A.加正向电压

B.加反向电压

C.不需加电压

D.加正向、反向电压都可以


  积分
检测技术及应用
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  • 6[单选题] 三相对称交流电路的瞬时功率为 A.个随时间变化的量 B.一个常量，其值恰好等于有功功率 C.0 D.以上都不对电路原理
  • 6、         Long after the 1998 World Cup was won, disappointed fans were still cursing the disputed refereeing (裁判)decisions that denied victory to their team. A researcher was appointed to study the performance of some top referees.        The researcher organized an experimental tournament (锦标赛)involving four youth teams. Each match lasted an hour, divided into three periods of 20 minutes during which different referees were in charge.        Observers noted down the referees‘errors, of which there were 61 over the tournament. Converted to a standard match of 90 minutes, each referee made almost 23 mistakes, a remarkably high number.        The researcher then studied the videotapes to analyse the matches in detail. Surprisingly, he found that errors were more likely when the referees were close to the incident. When the officials got it right, they were, on average, 17 meters away from the action. The average distance in the case of errors was 12 meters. The research shows the optimum (最佳的)distance is about 20 meters.       There also seemed to be an optimum speed. Correct decisions came when the referees were moving at a speed of about 2 meters per second. The average speed for errors was 4 meters per second.        If FIFA, football‘s international ruling body, wants to improve the standard of refereeing at the next World Cup, it should encourage referees to keep their eyes on the action from a distance, rather than rushing to keep up with the ball, the researcher argues.        He also says that FIFA‘s insistence that referees should retire at age 45 may be misguided. If keeping up with the action is not so important, their physical condition is less critical.     1.The experiment conducted by the researcher was meant to _ _ _ _ _ _ _ _ .A) review the decisions of referees at the 1998 World CupB) analyse the causes of errors made by football refereesC) set a standard for football refereeing    D) reexamine the rules for football refereeing2.The number of refereeing errors in the experimental matches was _ _ _ _ _ _ _ _ .A) slightly above averageB) higher than in the 1998 World CupC) quite unexpectedD) as high as in a standard match 3.The findings of the experiment show that _ _ _ _ _ _ _ _ .A) errors are more likely when a referee keeps close to the ballB) the farther the referee is from the incident, the fewer the errorsC) the more slowly the referee runs, the more likely will errors occurD) errors are less likely when a referee stays in one spot4.The word “officials”(Line 2, Para. 4)most probably refers to _ _ _ _ _ _ _ _ .A) the researchers involved in the experimentB) the inspectors of the football tournamentC) the referees of the football tournamentD) the observers at the site of the experiment5.What is one of the possible conclusions of the experiment?A) The ideal retirement age for an experienced football referee is 45.B) Age should not be the chief consideration in choosing a football referee.C) A football referee should be as young and energetic as possible.D) An experienced football referee can do well even when in poor physical condition.    大学英语2
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  • 22、在世界的本原上，意识比物质更加基本。毛泽东思想和中国特色社会主义理论体系概论
  • 混凝土立方体试块的尺寸越大，强度越高。工程结构
  • 14[填空题] 稀溶液的依数性是指蒸气压降低、                       、沸点升高、产生渗透压。物理化学

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