从实验教学策略看高中物理教师的教学观念

通过问卷调查的方式,对高中物理教师的实验教学策略进行调查,进而对其所持的实验教学观进行分析研究．研究结果表明：大部分物理教师对物理实验的教育功能认识不深刻,教育教学观相对落后,导致他们不能采取有效的实验教学策略．     

SOME PROBLEMS AND THEIR SOLUTIONS IN MECHANICS EDUCATION

当前,力学教育迫切需要加强学生的基础科学素养,提升创新能力。虽然我国力学教育界对此已有共识,但在实践中仍有若干尚待解决的问题。本文基于人才成长规律、认知学习规律、实践创新规律,对课程体系优化、力学教材建设、实践创新拓展等三个问题进行分析,提出若干思考和建议。部分建议已经过实践,可望作为解决问题的方案。     

Energetics and conserved quantity of an axially moving string undergoing three-dimensional nonlinear vibration

Nonlinear three-dimensional vibration of axially moving strings is investigated in the view of energetics. The governing equation is derived from the Eulerian equation of motion of a continuum for axially accelerating strings. The time-rate of the total mechanical energy associated with the vibration is calculated for the string with its ends moving in a prescribed way. For a string moving in a constant axial speed and constrained by two fixed ends, a conserved quantity is proved to remain unchanged during three-dimensional vibration, while the string energy is not conserved. An approximate conserved quantity is derived from the conserved quantity in the neighborhood of the straight equilibrium configuration. The approximate conserved quantity is applied to verify the Lyapunov stability of the straight equilibrium configuration. Numerical simulations are performed for a rubber string and a steel string. The results demonstrate the variation of the total mechanical energy and the invariance of the conserved quantity.     

观念建构为本的化学教学设计研究

以提高学生的科学素养为核心的新课程向以事实为本的课堂教学设计提出了挑战,也为观念建构为本的教学设计提供了展现的平台。在王磊和范晓琼2005年"观念建构为本教学的理论研究"的基础上,提出了观念建构为本的教学设计模型。结合具体教学案例"电离平衡",对如何进行观念建构为本教学设计进行了详细阐述,并提供了电离平衡一节的教学设计。     

Noether-Lie Symmetry of Generalized Classical Mechanical Systems

In this paper, the Noether Lie symmetry and conserved quantities of generalized classical mechanical system are studied. The definition and the criterion of the Noether Lie symmetry for the system under the general infinitesimal transformations of groups are given. The Noether conserved quantity and the Hojman conserved quantity deduced from the Noether Lie symmetry are obtained. An example is given to illustrate the application of the results.     

Weakly Noether Symmetry for Nonholonomic Systems of Chetaev＇s Type

In the paper [J. of Beijing Institute of Technology 26 （2006） 285] the authors provided the definition of weakly Noether symmetry. We now discuss the weakly Noether symmetry for non-holonomic system of Chetaev＇s type, and present expressions of three kinds of conserved quantities by weakly Noether symmetry. Finally, the application of this new result is shown by a practical example.     

Weak Noether Symmetry and non-Noether Conserved Quantities for General Holonomic Systems

A new kind of weak Noether symmetry for a general holonomic system is defined in such a way that the methods to construct Hojman conserved quantity and new-type conserved quantity are given. It turns out that we introduce a new approach to look for the conserved laws. Two examples are presented.     

试谈目前中学化学实验教学中存在的问题和对策

通过实证调查研究,从演示实验、分组实验、教师对学生实验的要求、教师进行探究性实验的能力4个方面分析中学化学实验教学中存在的问题和不足,同时结合教学实践提出相应的解决策略.     

脊状表面减阻特性的风洞试验研究

利用热线风速仪,对光滑表面和多个脊状表面在低速风洞中进行了表面流场测试。基于测得的边界层速度分布数据,利用对数律区速度分布公式,编程分别计算出光滑表面和脊状表面的壁面摩擦速度和虚拟原点。研究发现,脊状表面最大减阻量达13．5％;有减阻效果的脊状表面使边界层速度曲线上移、湍流强度下降;与光滑表面相比,脊状表面的位移厚度和动量损失厚度明显减小,也表明脊状表面具有减阻效果;位移厚度和动量损失厚度减少量随槽间距s^＋的增加呈现先变大后变小的趋势,在S^＋=12时达到最大。