排序方式: 共有41条查询结果,搜索用时 15 毫秒
21.
利用JGYW-2型双-单摆振动示波装置对两个相互垂直方向的同频率欠阻尼振动的合成进行了实验研究和理论分析,得到了欠阻尼振动合成的部分图形和表达式。当两个相互垂直、同频率、同振幅、位相差为π/2的欠阻尼振动合成时,振动曲线为等角螺线,从而揭示了数学上等角螺线的物理意义。 相似文献
22.
以一道证明偶函数在零点处导数为零的习题为例,分别使用链式法则、导数定义,带Peano型余项的泰勒公式等知识,给出6种解法,旨在培养学生分析问题和解决问题的能力。 相似文献
23.
24.
25.
Optical parameters of Nd3+:Er3+:yb3+ co-doped borosilicate glasses and their energy transfers at high temperature 下载免费PDF全文
This paper reports that a series of Nd3+:Er3+:Yb3+ co-doped borosilicate glasses have been prepared and their absorption spectra measured. The J--O intensity parameters Ωk (k=2, 4, 6), spontaneous radiative lifetime τrad, spontaneous transition probability A, fluorescence branching ratio β and oscillator strength fed of the Nd3+ ions at room temperature are calculated based on Judd--Ofelt (J--O) theory. The temperature dependence of the up-conversion photoluminescence characteristics in a Nd3+:Er3+:Yb3+ co-doped sample is studied under a 978 nm semiconductor laser excitation, and the energy transfer mechanisms among Yb3+, Er3+ and Nd3+ ions are analysed. The results show that the J--O intensity parameters Ω2 increase when the Nd3+ concentration of the Nd3+:Er3+:Yb3+ co-doped borosilicate glasses increases. The possibility of spontaneous transition is small and lifetimes are long at levels of 4F5/2 and 4F3/2. The intensity of Nd3+ emissions at 595, 691, 753, 813 and 887 nm are markedly enhanced when the sample temperature exceeds 400 K. The reasons being the cooperation of the secondary sensitization from Er3+ to Nd3+ and the contribution of a multi-phonon. 相似文献
26.
27.
演示实验可以不受空间和时间的限制,把某些自然环境再现,深刻地揭示出物理量之间的关系,从而启发学生深入思考,进一步寻求其变化规律.因此物理知识的讲授离不开课堂演示实验.演示实验又是启发学生思维,调动学生学习积极性,培养学生观察能力和思维能力的重要手段.本文谈谈增强演示实验效果和培养学生能力的几种方法.1 分析演示法分析演示法是让学生先从整体观察获得一个轮廓印象,然后再从几个方面仔细观察,找出局部特征,用分析的方法找出各局部特征的内在联系,最后获得一个全面而深刻的认识.例如用波动演示器演示横波.第一… 相似文献
28.
29.
两体碰撞问题广泛存在于日常生活、生产和科学研究中.根据碰撞过程中内力远大于外力的特点,力学中一般将碰撞的两个物体简化为两个不受外力约束的自由质点.解决自由质点的非完全弹性碰撞问题,除了应用动量守恒外,还需要给出恢复系数.由牛顿碰撞定律给出的恢复系数的定义为碰撞过程的恢复冲量与压缩冲量之比,即 相似文献
30.