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从课标、概念组织结构、教学资料对新旧人教版选修“反应热”内容进行对比分析,研究发现:(1)新课标在内容上更加强调“反应热”概念的学科理解,渗透变化观与守恒观等基本观念,突出学习素材的重要性;(2)新教材在内容组织上厘清了“反应热”“焓变”“能量转化”等核心概念之间的关系,重视对“反应热”内容的结构化认识;(3)新教材在图片、实验、习题增强了情境性与科学性。建议教师在教学中增进对“反应热”的学科理解,运用概念构图策略促进学生知识结构化,创设真实情境提高学生的问题解决能力,培养化学学科核心素养。 相似文献
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本文运用理论分析、实验与计算的结果对引进的美国SMS公司的结构动力修正软件SDM3.0作了比较详细的探讨,指出了SDM3.0的优点、局限性与使用范围.提出了改进这一软件的方法,研制了相应的软件.结果表明:改进后的方法及相应的软件是有效和成功的. 相似文献
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固有频率集聚时处理振型的一个方法 总被引:10,自引:0,他引:10
1.前言现在作固有振动分析的结构愈来愈复杂了。由此带来的困难不仅在于自由度众多,还在于常有频率集聚现象,即在很小一段频率区间内有很多个固有频率。当频率集聚在一起时,相应的固有振型对结构的某些物理参数变化很敏感。在正问题中,例如用有限元模型计算固有频率和振型,由于这种敏感性,刚度阵与质量阵的某些误差就会导致计算所得的集聚组振型有更大的误差;在反问题中,集聚组对应的振型对测量误差很敏感,因而也难 相似文献
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The article deals with the problems of controllability.obser-vability and stabilizability of an elastic-structural systemtreated by the finite element method. The results obtained hereagree with that obtained in distributed parameter-system model,nevertheless,they are more convenient than those in carrying outthe computation with a computer, at the same time the method ap-pears much easier than the conventional one. In section one, thesystem’s controllability and observability are studied and someconditions which are easier to be justified by computer are givenIn section two,the problem of stabilizing an elastic object bythe use of linear feedback is fully discussed. As the attainedresults there show that, so far as an elastic-structural systemis concerned,it is possible to assign arbitrary frequencies ofvibration only by the use of displacement feedback. however, itis impossible to stabilize the system while the system is com-pletely controllable. while the velocity feedback can stabilizethe system, b 相似文献
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陈德成;于年才;郑万泔 《力学与实践》1987,9(5):27-29
本文是从教学与工程的角度,阐述具有粘性阻尼模型的多个自由度系统两种不同的解耦特性,讨论了两种解耦法的物理意义与几何形象。 相似文献
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The article deals with the problems of controllability, observability and stabilizability of an elastic-structural system treated by the finite element method. The results obtained here agree with that obtained in distributed parameter-system model, nevertheless, they are more convenient than those in carrying out the computation with a computer, at the same time the method appears much easier that the conventional one. In section one, the system's controllability and observability are studied and some conditions which are easier to be justified by computer are given. In section two, the problem of stabilizing an elastic object by the use of linear feedback is fully discussed. As the attained results there show that, so far as an elastic-structural system is concerned, it is possible to assign arbitrary frequencies of vibration only by the use of displacement feedback, however, it is impossible to stabilize the system while the system is completely controllable. While the velocity feedback can stabilize the system, but its ability is limited. The case of rigid body motion involved in the system equation has also been discussed. In section three, the control of a straight beam is treated by the finite element method. The whole system of a beam can be decomposed into four irrelevant subsystems of tension-compression, torsion, bending in two directions, their controllability and observability are also analyzed respectively. The controllability and observability of segment-shaped beam are discussed in the end. 相似文献