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经过初一的学习，初二学生已经具备了初步的中学学习能力，但长期单一性的教学模式，使学生易产生思维惰性，在身心发展的整体把握上存在欠缺。因此，应采取一系列方法去激发学生学习与钻研物理的兴趣，启发他们的思维，帮助他们树立科学严谨的思维方法，培养与提高观察、分析、综合，以及解决实际问题的能力。联系生活，引发兴趣。教师应紧扣课本知识，利用生活实际问题来促进学生思维，让学生有真实感，亲切感。物理与日常生活关系紧密，教师要有意识地引导学生在学课本知识的同时，联系生活实际，让他们利用所掌握的知识去解决实际生活中… 相似文献
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The magnetorheological (MR) fluid damper-based semiactive control systems have received considerable attention for protecting structures against natural hazards such as strong earthquakes and high winds. In this paper, a novel modal controller using wavelet packet transform (WPT) is proposed for the vibration control of distributed structures. In the proposed control system, the WPT method is utilized to decompose the acceleration measurement and select the modes containing most of the WPT energy component as the dominant modes. Then, a modal controller is designed to control the dominant modes and the optimal active control force is solved. Finally, Clipped-optimal con- trol law is adopted to determine the voltage applied to each MR damper. A Kalman-filter observer, which estimates the full controlled modal states from local accelerometer feedbacks, is designed for rendering the controller to be more applicable to distributed structures with a large number of degrees of freedom. A numerical example of a stadium roof structure installed with MRF-04K damper is presented. The effectiveness of the controller is evaluated under both Tianjin and El Centro earthquake excitations. The superior performance and adaptability of the controller for versatile loading conditions are demonstrated through the comparison with traditional truncated modal controller. 相似文献
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