一台转枢式三相同步发电机，电枢以转速n逆时针方向旋转，对称负载运行时，电枢磁动势对电枢的转速及转向如何？对定子的转速又是多少？

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高等继续教育 / 电机学

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电机学

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9、Engineering design aims to link economic, social, environmental and of course safety factors to produce the best solution. This is especially true in earthquake engineering where it is possible to design a building that is “safe” for all types of earthquakes but does not fit the design brief. For example, it is not economically feasible to design buildings in Bristol to withstand a large earthquake as the chances are very small. Similarly a square concrete structure that has small windows and thick walls may be the ideal design for a particular area; however, it wouldn’t fit a design brief asking for a modern high-tech design. This balance of factors can only be achieved by engineers combining experience and knowledge of the area where the structure is to be located. Design practice has been changing over the last few years. The older design requirements used to insist that in an earthquake the building should maintain enough structural integrity to remain standing. This meant that if the serviceability limit state was passed the structure would have to be demolished, as it would be no longer safe to use. Although this concept saves lives as people can escape from buildings, it does nothing to prevent the huge financial cost of a large earthquake as a large proportion of buildings have to be demolished and rebuilt. Thus the new design requirements demand that the structure should remain standing in an earthquake and additionally not have to be demolished. The other factor often left unconsidered is the effect of after shocks. These shocks generally have little effect on undamaged buildings; however, on damaged ones they can have destructive effect and stop rescue operations. In the assessment of buildings the energy from an aftershock should be considered. Apparently the damage caused by earthquakes is almost entirely associated with man-made structures. Earthquakes only cause death by the damage they induce in structures such as buildings, dams, bridges and other works of man. And this is one of the reasons why earthquake engineering is so important. 1. What is the main idea of the passage? A) Earthquake engineers with experience and knowledge. B) Some factors for building design in earthquake engineering. C) Buildings to withstand all possible earthquakes. D) Equal consideration in earthquake engineering. 2. The word “demolish” in the second paragraph means _ _ _ _ _ _ _ _ _ _ _ _ . A) pull down B) pull up C) pull away D) pull apart 3. Which of the following is not true about the new design requirement? A) Building should remain integrated in an earthquake. B) Building should be reconstructed after an earthquake. C) Building should let people escape in an earthquake. D) Building should be made to avoid rebuilding after an earthquake. 4. The damage of all the following causes the death of people except _ _ _ _ _ _ _ _ _ _ _ _ . A) dams and bridges B) buildings and dams C) bridges and buildings D) some works like steel works and brick works 5. When assessing buildings, we should take into account the _ _ _ _ _ _ _ _ _ _ _ . A) undamaged buildings B) man-made structures C) effect of aftershocks D) rescue operations英语(二)

【单选】关于废名的《放猖》与《三竿两竿》，较正确的分析是 a. 《放猖》基本是虚写，《三竿两竿》是实写。b. 《放猖》题材与《女吊》、《水里的东西》相类，文字也相类。c. 《放猖》结尾借景抒情，《三竿两竿》结尾似结非结。d. 《放猖》是刻意为文，《三竿两竿》不经意而成。中国现当代文学名著导读(2)

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在普通碳素钢基础上，（）能明显提高钢材的强度、细化晶粒、改善可焊性。高层建筑施工

非处方药不得采取有奖销售、附赠药品或礼品的销售方式。错误正确药事管理学(专)

主板的灵魂与核心是什么？计算机组装与维护