静电电荷的测量

静电测量是生产、科研中的一个重要课题,静电学是电磁学中的一个重要部分。而在电磁学实验中一般没有静电测量的实验,因此我们试制了静电电荷测量仪,进行了摩擦带电的测量和空气中电荷密度的测定,效果良好。一、静电电荷测量仪静电电荷测量仪由(?)准电容和静电电压表组成,如图1所示。由于使用了静电电子管     

二静电体系相互作用力与相互作用能一般关系的正确表达式

指出二静电体系的相互作用力的普遍表达式F=-↓△w1=-↓△w并不恰当。正确的表达式应当是Fj=δW1/δqj=-δW1/δqj，其中Fj是沿广义坐标qj方向的广义力，W1是静电场总能量，W1是二静电体系的相互作用能，qj为表征二静电体系相对位移的某一广义坐标。     

Mn位W掺杂对La0.3Ca0.7MnO3体系磁结构的影响

通过对La_0.3Ca_0.7Mn_1-xW_xO₃(x=0.00，0.04，0.08，0.12，0.15)多晶样品M-T曲线、M-H曲线及ESR谱的测量，研究了Mn位W掺杂对电荷有序体系La_0.3Ca_0.7MnO₃磁结构的影响.结果表明，当掺杂量为0.00≤x≤0.08时，体系存在电荷有序(CO)相，AFM/CO态共存于相变温度以下，电荷有序温度T_CO随着W掺杂量的增加而增加；x＝0.04时，样品在低温下为FM相与AFM/CO相共存，在CO相建立前、后均有FM从PM中分离出来；当x≥0.12时，CO态融化，在极低温度下存在顺磁-铁磁(PM-FM)相变. 关键词： 磁结构 电荷有序 融化 Mn位掺杂     

浅谈静电火灾的成因

 任何物体内部都带有电荷,一般状态下,其正、负电荷数量相等,对外不显出带电现象,但当两种不同物体接触或摩擦时,物体中的电子会越过界面,进入另一种物体内,产生静电。因它们所带电荷发生积聚时产生了很高静电压,当带有不同电荷的两个物体分离或接触时出现电火花,这就是静电放电现象。静电火灾是由静电放电而形成的,静电火灾成因非常复杂,给预防静电火灾发生带来了困难;但如明确其产生的条件,对静电火灾的防止具有一定的意义。静电火灾的形成主要由于同时具备以下条件而引起。一、产生静电的条件静电起电是物质在相互接触过程中电荷的分离和转移造成的。     

有关导体球带电问题的探究

新课标《物理3-1》"静电现象的应用"这节,课后有一道有关导体球带电问题的习题.教师在讲解这道题时常常会提出与此类题相类似的问题,假设有半径为R的金属球与地相连接,在与球心相距d＝2R处放一个带正电的点电荷q(q＞0),则球上感应电荷带何种电荷?带电荷量多少?前一个问题用电场中导体的特点及电场线的知识可以得出结论,球带负电且电荷量小于q.那么球带多少电荷量,下面用电磁学知识和数学知识探讨一下这个问题.     

孤立带电导体的电荷分布

本文就孤立导体面电荷密度与表面的曲率的关系进行定性地分析．带电导体处于静电平衡状态时，导体内部电场强度必定处处等于零，即Ｅ内＝０．由Ｅ内＝０，可以直接导出如下几点推论：（１）导体是等势体，表面是等势面；（２）导体表面场强处处与表面垂直；（３）由高斯定...     

使验电器带电

1前言 验电器是静电实验的必备仪器,在对静电现象的研究以及对验电器的大量使用和研究中,常常需要给验电器带上一定量或一定种类的电荷.譬如,用验电器辨别电荷的种类时,要先使验电器带上某种已知电荷,金箔箔片的张角宜在40°～60°左右.再将待测带电体渐渐移近验电器的金属球,根据金箔张角的增减判断带电体电荷的性质[1],这也就是说要先使验电器带上一定量和一定种类的电荷.在做静电实验时,通常通过接触传导法和感应法给验电器带电.     

静电及其应用

 建国以来,随着国民经济的迅速发展,我国静电科学研究已取得了很大的进展,并广泛应用于多个领域。如何进一步防止静电的危害、利用静电造福于人类社会对于我们具有十分重要的意义。一、静电现象与研究人们通常将运动的电荷或导体中的电流叫做动电,而把相对静止的电荷或者物体上处于相对平衡的电荷称做静电。静电现象在自然界,在我们的日常生活中广泛地存在着,如:当你拿起梳子梳头时,你会听到噼啪的声响;在炎热的夏季阴雨天气里,你会看到耀眼的闪电;如果你用一块绸子摩擦一根玻璃棒时,你会发现玻璃棒能够吸引许多小纸屑……这些奇妙的现象,就是静电。     

La0.3Ca0.7Mn1-xWxO3体系电荷有序的建立与融化

用标准的固相反应法制备了La0.3Ca0.7Mn1-xWxO3(0.00≤X≤0.15)多晶样品.通过对样品磁化强度-温度(M-T)曲线、磁化强度-磁场强度(MH)曲线及ESR谱的测量,研究了Mn位W掺杂对La0.3Ca0.7Mn1-xWxO3体系的磁相变的影响.结果表明,随着W掺杂量的增加,体系磁相变发生了复杂的变化过程.当掺杂量为0.00≤X≤0.08时,体系存在电荷有序(CO)相,反铁磁(AFM)/C0态共存于相变温度以下,电荷有序温度(Tco)随着W掺杂量的增加而增加.x≥0.12时,体系电荷有序态逐渐减弱并融化,在极低温度下存在顺磁-铁磁(PM-FM)相变.     

静电危害及其防护

 静电是一种常见的自然现象;一方面静电现象可造福于人类,例如我们熟知的静电复印、静电除尘、静电分离、静电防腐、静电造纸、静电养殖……这些有关静电技术的应用,遍及人类生产、生活、科研的各个行业和领域;另一方面静电现象也会在极为广泛的范围内给人类带来各种各样的危害;因此,认识静电和防止静电危害对于我们是非常重要的。静电基本知识我们通常把相对观察者静止的电荷叫做静电。静电现象广泛地存在于自然界和我们日常生活之中,比如我们每时每刻呼吸的空气,每立方厘米就含有100～500个带电粒子,我们居住的地球就是一个巨大的带电体,地壳上带有5×10⁵C的电荷.     

On the energy spectra of one-dimensional anharmonic oscillators

In this paper we present explicit and simple analytical formulae for the energy eigenvaluesE _n (λ) of one-dimensional anharmonic oscillators characterized by the potentials 1/2mω ² x ²+λx ^2α withα=2, 3 and 4. A simple intuitive criterion supplemented by the requirement of correct asymptotic behaviour, has been employed in arriving at the formulae. Our energy values over a wide range ofn andλ are in good agreement with the numerical values computed by earlier workers through very elaborate techniques. To our knowledge this is the first time that formulae of such wide validity have been given. The results for pure power oscillators are trivially obtained by going over to theω→0 limit. Approximate analytic expressions for the low order even moments ofx are also given.     

利用透射系数研究周期势的能带结构

利用一维方位势透射系数的递推公式研究了周期势的能带结构,文中考察了能 结构与垒宽、阱宽及位势个数的关系。     

Statistical thermodynamics of fluid hydrogen at high energy density

By using the available knowledge about the thermodynamic functions for the low-temperature Wigner region (lattice formulae and Gell-Mann-Brueckner formulae) as well as for the high-temperature Debye region (limiting law with quantum corrections) Pade approximations are constructed. The formulae cover the whole nonrelativistic region of density and temperature except the region of ionic lattice and of bound states.     

On the electronic energy spectrum of linear models for disordered systems

In this paper the basic relations for describing the electronic structure of linear models for monatomic and diatomic disordered systems are derived using a F.E.N. theoretical approach. Elegant three terms recurrence formulae between the wavefunctions at three successive atomic sites are established and their relation is discussed with recurrence formulae obtained previously by means of Green's function techniques.     

关于几个能量公式的适用范围

利用能量公式中交换积分项符号的正负，给出产生交换作用的电子间的自旋特征。据此判断出几个能量公式的适用范围     

Mechanism of polymer drag reduction using a low-dimensional model

Using a retarded-motion expansion to describe the polymer stress, we derive a low-dimensional model to understand the effects of polymer elasticity on the self-sustaining process that maintains the coherent wavy streamwise vortical structures underlying wall-bounded turbulence. Our analysis shows that at small Weissenberg numbers, Wi, elasticity enhances the coherent structures. At higher Wi, however, polymer stresses suppress the streamwise vortices (rolls) by calming down the instability of the streaks that regenerates the rolls. We show that this behavior can be attributed to the nonmonotonic dependence of the biaxial extensional viscosity on Wi, and identify it as the key rheological property controlling drag reduction.     

Sc+18离子的跃迁能和振子强度

用全实加关联方法计算了Sc⁺¹⁸离子1s²2s--1s²np (2≤n≤9) 和1s²2p--1s²nd (3≤n ≤9)的跃迁能和振子强度。1s²np和1s²nd 态的精细结构劈裂通过计算自旋-轨道及自旋-其他轨道相互作用算符的期待值加以确定。还得到了这两个里德堡系列的量子亏损（作为能量的函数）。依据三种规范的振子强度公式得到的计算结果相当好的一致。将这些计算结果与量子亏损理论相结合，进一步得到电离阈附近的分立态-分立态跃迁的振子强度和分立态-连续态跃迁的振子强度密度。     

Simplified formulae to investigate flexural vibration characteristics of piezoelectric tubes in ultrasonic micro-actuators

Based on the Rayleigh energy theory combining with Timoshenko beam model, the flexural vibration characteristics of piezoelectric tubes in ultrasonic micro-actuators are investigated. Additionally, the simplified formulae are derived to study the fundamental flexural resonance frequencies of the piezoelectric tubes with free-free ends and cantilevers. By changing the sizes of the tubes and the mass loads at the free ends, the variations of the flexural resonance frequencies of the piezoelectric tubes and cantilevers are calculated theoretically. To verify accuracy of the simplified formulae, by changing the lengths of the tubes and the mass loads the flexural resonance frequencies of the piezoelectric tube with free-free ends are measured experimentally. The theoretical results agree well with the experimental measurements, which demonstrate that the simplified formulae are accurate and effective for analyzing the flexural vibration characteristics of the piezoelectric tubes in the ultrasonic micro-actuators.     

Topological resonance energy,bond resonance energy,and circuit resonance energy

Circuit resonance energy (CRE) is a key quantity that links energetic and magnetic criteria of aromaticity for a polycyclic π‐system. Topological resonance energy (TRE) correlates well with the sum of CREs for an entire π‐system. We found that bond resonance energy (BRE), so far defined to estimate the degree of kinetic stability for a polycyclic π‐system, also correlates very well with the corresponding quantity defined with CREs. These findings justify the view that graph‐theoretical quantities, such as TRE and BRE, can be used safely even though they rely on unrealistic reference structures. Copyright © 2007 John Wiley & Sons, Ltd.