多维离散富氏变换法开关电容网络符号分析

本文基于多维离散富氏变换,提出了一种对多相开关电容网络(SCN)进行符号分析的算法,并已在IBM—PC/XT上实现.该法易于编程,可有效地获得不含对消项的符号网络函数.并提出了一种通过新的SCN建模方法获得最小化的系统矩阵,且其中z变量元素最少,使计算量大为减少。

唯一地确定矢量场的边界条件

本文讨论了矢量场唯一性边界条件与场域边界形式的关系．分别给出了以边界法向分量和以边界切向分量作为唯一性边界条件对场域边界形式的要求．

定态电磁场只有两个独立边值关系的一般证明

本文先将电荷守恒定律边值关系推广到有面电流分布情况下的边值关系，然后证明边值关系只有两个是独立的．

Effect of grain size of primary α phase on bonding interface characteristic and mechanical property of press bonded Ti-6Al-4V alloy

The effect of grain size of primary α phase on the bonding interface characteristic and shear strength of bond was investigated in the press bonding of Ti-6Al-4V alloy. The quantitative results show that the average size of voids increases from 0.8 to 2.6 μm and the bonding ratio decreases from 90.9% to 77.8% with an increase in grain size of primary α phase from 8.2 to 16.4 μm. The shape of voids changes from the tiny round to the irregular strip. The highest shear strength of bond can be obtained in the Ti-6Al-4V alloy with a grain size of 8.2 μm. This is contributed to the higher ability of plastic flow and more short-paths for diffusion in the alloy with smaller grain size of primary α phase, which promote the void closure process and the formation of α/β grains across bonding interface.

对用高斯定理解释带电球壳上场强的探讨

对解释带电球壳上场强问题方法很多。本文所采用的方法较为简捷易懂.首先对高斯定理用于高斯面上有电荷存在的方法进行理论上的推证,然后对所得结果给出了定性的物理解释。

“坡印亭”定理的证明

电磁场在传播过程中伴随有能量的传播,电磁能量在传播时,要变成其它形式的能量,但能量总是守恒的,这就是所谓的“坡印亭”定理.电场是一种特殊物质,因此有关能量的转换当然应服从电磁场的基本方程.从理论上说用麦克斯韦尔两方程证明是有关各种书中采用的一般方法.

关于电位移矢量'非汉字符号'的问题

在学习电磁学中有这样一个重要公式(?)=∑qi,这是介质中高斯定理表示式.在n式中只出现了(?)、(?)和qi,有的同学就认为电位移矢量(?)仅与自由电荷有关,而与极化电荷无n关.其实,这只说明(?)的通量与闭合面内电荷qi有关,并非说明被积函数——电位移矢量n(?)仅与自由电荷有关.应该注意,场量(?)本身与(?)的通量是两个不同的概念.例如:(?)n=∑qi/εo式中闭合曲面的(?)通量仅与闭合面内电荷有关,面上各点(?)的应是面内、电荷共同n激发的总场,而不仅仅是面内电荷所激发的.这是一个说明场量与它的通量是两个截然不n同概念很好的例子,从(?)=ε((?)+(?))可知,式中(?)是自由电荷激发的电场,(?)是极化电荷激n发的电场,既然与极化电荷有关,因此一般地说(?)也应与极化电荷有关.

电磁学教学中的体会

电磁学内容比较抽象在学生学习时不易接受.因此我在教学中采用抓重点、攻难点进(?)教学,本文就个人具体做法提出粗浅意见.1 抓重点首先由教学大纲和具体教材内容来确定.备课中,既看教材又不脱离大纲以免造成文不对题的不良后果.确定了静电场这章的重点是:1.1 三个定律:库仑定律、电量守恒定律。

对电磁场能流矢量的另一种表达式

电磁场能流矢量的另一种表达式是从玻印亭矢量中舍弃△×（φＨ）项而得到的。能流矢量的这种新形式与我们通常的直觉相符。而且它能得出一个加速电荷的拉莫尔（Ｌａｒｍｏｒ）辐射公式。

关于电磁场边界条件的另一种合适推求

本文在两个层次上(首先,在一般小直圆柱状盒子面或小长方形回路上,其次,在任意形状小闭合面或小闭合回路上),摒弃不必要的假设,充分利用各个相应矢量在微元范围内为一恒矢量这一特点,从而,合乎逻辑地推得电磁场边界条件。

Closure behavior of rock joint under dynamic loading

The normal compression tests on intact samples and artificial joints with different saw-tooth shape under cyclic loading and half-sine waves of different frequencies were performed by using Instron1342 servo-controlled material testing machine. The specimens were made artificially with mortar. The loading frequency ranged from 0.005 Hz to 0.1 Hz. The experimental results show that joint closure curves are non-linear and concave up. The stress-deformation curves under cyclic loading exhibit hysteresis and permanent set that diminish rapidly and keep constant finally on successive cycles. Normal displacement successively decreases from the joint J1 to J2, to J3 under the same normal loads regardless of frequency. Considering the loading frequency effect, normal displacement of joint J1 decreases with increasing the loading frequency except that the loading frequency is 0.05 Hz. Normal displacement of joint J2 increases with increasing the loading frequency. Normal displacement of joint J3 increases with increasing the loading frequency when the frequency ranges from 0.005 Hz to 0.05 Hz. Its normal displacement, however, becomes least when the loading frequency is 0.1 Hz.

CDCC Approaches and Roles of Closed Channels in d-Nucleus Reactions

The effect of deuteron breakup in d-nucleus reaction is treated with the continuum discretized coupled channels （CDCC） approach, and the effects on the total reaction cross sections and elastic scattering angular distributions are studied by comparing the calculations of CDCC and spherical optical model with our global deuteron optical potential [Phys. Rev. C 73 （2006） 054605] below 200 MeV, for target nuclei ranging from ^12C to ^208Pb. The contributions from the closed channels to the total reaction and breakup cross sections, and angular distributions of elastic scattering are also seriously discussed.

Biaxial mechanical behavior of closed-cell aluminum foam under combined shear-compression loading

Combined shear-compression tests and simulations were performed on a closed-cell aluminum foam over a wide range of loading angles in order to probe their yield behaviors under biaxial loading conditions.Combined shear-compression tests were carried out by using a pair of cylindrical bars with beveled ends.The yield surfaces were experimentally measured and compared with various theoretical yield surface models.The cellular structures of closed-cell aluminum foams were modeled as tetrakaidecahedrons and their biaxial crushing behaviors were simulated by the finite element method.The results show that,yield initiates from the stress-concentrated corners in the specimens under combined shear-compression loading and the stress distribution is no longer uniform at the specimen/bar interfaces.In the range of cell sizes studied,the larger the foam cell size is,the higher the yield stress is.Aluminum foam density is found to be the dominant factor on its mechanical properties compared with the cell size and is much more significant in engineering practice.

Photodetachment of H^- Near a Dielectric Surface

Using the closed orbit theory, the photodetachment cross section of H- near a dielectric surface has been derived and calculated. The results show that the dielectric surface has great influence on the photodetachment process of negative ion near the ionization threshold. Above the ionization threshold, the photodetachment cross section starts to oscillate. With the increase of the energy, the oscillating amplitude decreases and the oscillating frequency increases. The oscillation in the photodetachment cross section of H- in the presence of a dielectric surface is either larger or smaller than the photodetachment of H- without the surface. As the photon energy is larger than the critical value Epc, the oscillatory structure disappeared and the cross section approaches to the case of the photodetachment of H- without any external fields. For a given detached-electron energy, the photodetachment cross section becomes decreased with the increase of the ion-surface distance. Besides, the dielectric constant has great influence on the photodetachment of H-. With the increase of the dielectric constant, the oscillation in the cross section becomes increased. As the dielectric constant increases to infinity, the cross section is the same as the photodetachment of H- near a metal surface. This study provides a new understanding on the photodetachment process of H- in the presence of a dielectric surface.

惯性力演示三则

一阿基米德的推理也可以推广到作加速运动的密度均匀的液体中去。图1说明一力正作用在一定体积的密度均匀的液体上,此液体完全充满在一个正在作加速运动的刚体容器中。作用在这个体积上的净力与液体的加速度有关,可由 f=Vρα给出,式中 L 是体积,ρ是密度。如果这部分体积内充满与液体密度相同的另外物体(图1 b),净力仍是一样。

Analytical estimation of mixing coefficient induced by surface wave-generated turbulence based on the equilibrium solution of the second-order turbulence closure model

Based on the equations of motion and the assumption that ocean turbulence is of isotropy or quasi-isotropy, we derived the closure equations of the second-order moments and the variation equations for characteristic quantities, which describe the mechanisms of advection transport and shear instability by the sum of wave-like and eddy-like motions and circulation. Given that ocean turbulence generated by wave breaking is dominant at the ocean surface, we presented the boundary conditions of the turbulence kinetic energy and its dissipation rate, which are determined by energy loss from wave breaking and entrainment depth respectively. According to the equilibrium solution of the variation equations and available data of the dissipation rate, we obtained an analytical estimation of the characteristic quantities of surface-wave-generated turbulence in the upper ocean and its related mixing coefficient. The derived kinetic dissipation rate was validated by field measurements qualitatively and quantitatively, and the mixing coefficient had fairly good consistency with previous results based on the Prandtl mixing length theory.

BIFURCATION OF PERIODIC ORBITS OF A THREE-DIMENSIONAL SYSTEM

Consider a three-dimensional system having an invariant surface. By using bifurca- tion techniques and analyzing the solutions of bifurcation equations, the authors study the spacial bifurcation phenomena of a k multiple closed orbit in the invariant surface. The su?cient conditions of the existence of many closed orbits bifurcate from the k multiple closed orbit are obtained.

Re-examining Photodetachment of H^- near a Spherical Surface using Closed-Orbit Theory

Photodeachment of H^-near a reflective spherical surface was studied by Haneef et al.[J.Phys.B:At.Mol.Opt.Phys.44(2011)195004]using a theoretical imaging method.The total cross section displays interesting oscillations.Here we re-examine the total photodetachment cross section of this system by directly applying the standard closed-orbit theory.Our result for the total cross section differs from the result obtained by Haneef et al.The difference between the two results vanishes in the limit of large radius of the reflective sphere.We argue that the theoretical imaging method developed originally for photodetachment near a Hat surface can not be directly applied to the present system.