磁场有限元后处理中等势线和彩色云图的实现

 磁场有限元的数值解是节点矢量磁位,应将其转化为工程物理量．为了直观观察磁场分布情况,需要用图例定性地表示磁场的分布．使用面向对象的程序设计方法实现了磁场的矢量磁位等势线图和磁通量密度彩色云图,在云图中提出了光滑过渡处理方法,分布图反映的磁场性质与实际测得结果相一致．     

基于ObjectArx开发等高线地形图三维立体化的研究

介绍利用ObjectArx开发工具包装在AutoCAD环境中的平面等高线矢量图生成三维立体图,利用本方法开发的三维成形程序具有小巧实用、开发周期短、易于维护、三维效果逼真的特点。     

Evaluation of the stress field around a notch tip using contour integrals

The mode I and mode II asymptotic stresses around a notch tip are in general governed by different orders of singularity. Direct computation of the mixed-mode near-tip stress field therefore appears to be difficult. In this paper, we propose a pair of contour integrals J_kR. The integrals are shown to be path-independent in a modified sense and so they can be accurately evaluated with finite element solutions. As an aside, by defining a pair of generalized stress intensity factors (SIFs) (K_I)_β and (K_II)_β, the relationship between J_kR and the SIFs is derived and expressed as functions of the notch angle β. Once the J_kR-integrals are accurately computed, the generalized SIFs and, consequently, the asymptotic mixed-mode stress field can then be properly determined. The feasibility of our formulation is demonstrated in two numerical examples, where various instances with different notch angles are considered. No particular singular elements are used in this study.     

Fluidization of microparticles in electric field

The results of statistical modeling of the electrodynamic fluidization of microparticles in an electric field are outlined. The dependence of the current density and charge distribution function of the microparticles on the microparticle concentration is discussed. The limiting attainable microparticle concentration in the interelectrode space is considered. The dependence of the concentration of fluidized microparticles on their bulk concentration is considered.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 60, No. 1, pp. 64–72, January, 1991.     

Three-dimensional observation of nanoscale ferroelectric domains using scanning nonlinear dielectric microscopy with electric field correction by Kelvin probe force microscopy

An advanced technique for the measurement of three-dimensional ferroelectric domain structure is described. Scanning nonlinear dielectric microscopy is used to measure the polarization components both perpendicular and parallel to the specimen surface. A nanoscale electric field correction is devised and performed using Kelvin probe force microscopy to allow more precise measurement of the nanoscale polarization component parallel to the specimen surface. Using this electric field correction, three-dimensional imaging of the ferroelectric polarization orientation is demonstrated.     

Analytic preconditioners for the electric field integral equation

Since the advent of the fast multipole method, large‐scale electromagnetic scattering problems based on the electric field integral equation (EFIE) formulation are generally solved by a Krylov iterative solver. A well‐known fact is that the dense complex non‐hermitian linear system associated to the EFIE becomes ill‐conditioned especially in the high‐frequency regime. As a consequence, this slows down the convergence rate of Krylov subspace iterative solvers. In this work, a new analytic preconditioner based on the combination of a finite element method with a local absorbing boundary condition is proposed to improve the convergence of the iterative solver for an open boundary. Some numerical tests precise the behaviour of the new preconditioner. Moreover, comparisons are performed with the analytic preconditioner based on the Calderòn's relations for integral equations for several kinds of scatterers. Copyright © 2004 John Wiley & Sons, Ltd.     

Three-dimensional field distribution in the focal region of low-Fresnel-number axicons

Three-dimensional intensity and phase distributions generated by microaxicons are evaluated in the low-Fresnel-number regime. Apertured and nonapertured conical wavefronts may generate transverse patterns with notable deviations from the expected nondiffracting Bessel beam. First-order analytical expressions are proposed for the evaluation of the wave field produced by axicons of different Fresnel number in the focal region.     

外推电离室内部电场模拟研究

目前国际上将空气比释动能强度作为近距离治疗125I粒子源剂量计算及评价粒子源强度的物理量。测量粒子源空气比释动能强度的标准装置拟采用外推电离室,外推电离室结构设计会影响内部电场,内部电场的均匀性对电离电荷有效收集产生一定的影响。该文利用Maxwell软件建立电离室结构,研究有无保护电极以及栅极个数和栅极尺寸对内部电场均匀性的影响,对模拟得到的电场图进行分析,得到结论为当保护电极半径大于收集极半径时,增加栅极的个数,并且当栅极中心间距小于保护电极环宽的1/10时,有利于增加电离室内部电场的均匀性,对外推电离室的设计提供一定的参考。     

Singularities in the magnetic field map of type II pure superconductors

The magnetic field distribution in pure type II superconductors is calculated in the limit of a magnetization4M, small compared with the inductionB, i.e., at low temperature nearly the whole magnetic field region betweenH _c2 andH _c1. Because the Ginsburg-Landau equations are invalid in this case, we find a magnetic field distribution which has no simple, local relation with the square of the order parameter (r)² as is the case nearT _c . We find atT=0 and very near toH _c2 that the magnetic field map (see Fig. 2) has two singularities at the maximum fieldH _v and minimum fieldH _m . These singularities have a conical shape, instead of the parabolic shape found nearT _c . We find a finite temperature derivative of these fieldsdH _v /dT=–dH _m /dT0 atT=0 in the limitH=H _c2; this result is in agreement with those of Kung.⁸ We compare our results with the intensity of Bragg lines of neutron diffraction found by Cribier, Simon, and Thorel. The amplitude of variation of the magnetic field is 5.3 times the magnetization atT=0 nearH _c2.This paper is based on a thesis to be submitted to the Faculty of Orsay by the author in partial fulfillment of the requirements for the doctorat d'état ès Sciences Physiques.     

Three-dimensional magnetostatic field calculation using boundaryelement method

The boundary-element calculation of three-dimensional magnetostatic field problems using the reduced and total magnetic scalar potential formulation is described. The method is based on a boundary integral equation that can be derived from Green's theorem. Two regions, a current-free iron region and an air region including the source domains, are considered. The material properties of the iron are assumed to be linear and either isotropic or anisotropic (orthotropic). Two examples are investigated: a C-shaped magnet and an iron cylinder of finite length immersed in the magnetic field of a cylinder coil     

Reverse electric field in spherical striations

We have experimentally studied the floating potential distribution in a spherical stratified dc discharge. A nonmonotonic potential profile is observed in the region of striations, which is indicative of the existence of regions with a reverse electric field.     

Bubble deformation in an electric field

The problem of expansion of bubbles in a compressible liquid upon application of an electric field is solved. The effect of the electric field on phase transition is evaluated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 36, No. 5, pp. 882–884, May, 1979.     

Pulsed electric field assisted assembly of polyaniline

Assembling conducting polyaniline (PANi) on pre-patterned nano-structures by a high rate, commercially viable route offers an opportunity for manufacturing devices with nanoscale features. In this work we report for the first time the use of pulsed electric field to assist electrophoresis for the assembly of conducting polyaniline on gold nanowire interdigitated templates. This technique offers dynamic control over heat build-up, which has been a main drawback in the DC electrophoresis and AC dielectrophoresis as well as the main cause of nanowire template damage. The use of this technique allowed higher voltages to be applied, resulting in shorter assembly times (e.g.,?17.4?s, assembly resolution of 100?nm). Moreover, the area coverage increases with the increase in number of pulses. A similar trend was observed with the deposition height and the increase in deposition height followed a linear trend with a correlation coefficient of 0.95. When the experimental mass deposited was compared with Hamaker's theoretical model, the two were found to be very close. The pre-patterned templates with PANi deposition were subsequently used to transfer the nanoscale assembled PANi from the rigid templates to thermoplastic polyurethane using the thermoforming process.     

Effects of electric field on nanocrack propagation

The present work is concerned with the application of Atomistic Field Theory (AFT) in modeling and simulation of dynamic nanocrack propagation under electrical and mechanical loadings. AFT enables us to express an atomic scale local property of a multi-element crystalline (which has more than one kind of atoms in the unit cell) system in terms of the distortions of lattice cells and the rearrangement of atoms within the lattice cell, thereby making AFT suitable to fully reproduce both atomic-scale and continuum level phenomena. Atomistic Field Theory and its corresponding finite element (FE) implementation are briefly introduced. Taking both efficiency and accuracy into account, we adopt a cluster-based summation rule for atomic force calculations in the FE formulations. Single crystal MgO under electrical/mechanical loading is modeled and simulated. Numerical results show that electric fields can serve as a tool to shield the crack initiation and propagation in the ionic crystal materials, thereby offering new perspectives on fracture mechanics at nano scale.     

Investigation of the dispersion of liquids in an electric field

The results of an investigation of the dependence of the dispersion potential on the liquid flow rate, distance between electrodes, and different parameters are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 57, No. 2, pp. 275–280, August, 1989.     

基于电/磁转换的海洋电场检测方法

传统的直接电测量方法受1/f噪声限制,在低频处信号与噪声发生混叠,难以实现高水平低噪声测量。该文提出一种基于电/磁转换的海洋电场低噪声检测方法,将电信号转化为磁信号,通过微机械的方法将磁信号调制到高频,有效避开低频1/f噪声影响。设计一种实现电/磁转换功能的微机械结构,利用TMR电阻构成惠斯通电桥测量磁信号,实现海洋电场的高水平低噪声检测。仿真与实验结果在1 Hz处噪声分别达到1.16 nV/(Hz)~(1/2)和1.41 nV/(Hz)~(1/2),优于传统电测量方案的噪声水平,验证该方法的有效性。     

Superconducting-coil-resistor circuit with electric field quadratic in the current

It is shown for the first time that the observed [Phys. Lett. A 162, 105 (1992)] potential difference Θ_t between the resistor and the screen surrounding the circuit is caused by polarization of the resistor because of the kinetic energy of the electrons of the superconducting coil. The proportionality of Θ_t to the square of the current and to the length of the superconducting wire is explained. It is pointed out that measuring Θ _t makes it possible to determine the Fermi quasimomentum of the electrons of a metal resistor. Pis’ma Zh. Tekh. Fiz. 24, 7–11 (January 26, 1998)     

Three-dimensional analog of the Cauchy integral formula for solvingmagnetic field problems

Lately, the three-dimensional (3-D) analog of the Cauchy integral formula was used for several studies in geophysics and magnetism. In this paper, a simple demonstration of the expression of the 3-D analog of the Cauchy integral formula is given using only the usual rules of vector calculus, whereas the demonstrations given in references such as journal papers, treatises, or textbooks require complicated mathematical proceedings and lack clearness. Further on in the paper it is shown that some formulas obtained in references by using the analog of the Cauchy integral formula include inadequate results. The ways to avoid these inadequate results are also shown     

Enhancement of the steel quenching process by an electric field

An electric field is known to be able to increase considerably the heat flux during the boiling process by suppressing the occurrence of film boiling. This field enhancement technique can be applied to the steel quenching process to accelerate the cooling rate and thus increase the effective hardenability of the steel. This report describes a quench experiment performed with an electric field. The effective hardenability (depth of high hardness) of the samples quenched with the field was measured to be significantly higher than those quenched without the field. Examination of the microstructures showed that the application of the electric field increased the depth to which martensite formed in the sample.