海水中稳恒电流电场的点电极计算模型

根据点电极基本假设，利用均匀介质中稳恒电流场与静电场的相似性，分别采用分离变量法和镜像法计算了点电极稳恒电流场在空气-海水-海床三层介质平行界面模型下的电位分布。从而得到了海水中稳恒电流电场的计算模型．计算结果表明：点电极的电场分布具有明显的特征，可作为舰船电场电极阵列模拟的计算单元。     

乳状液电磁场破乳法的研究

提出了一种利用电磁感应原理产生涡旋电场进行破乳的新方法。将螺线管、磁芯构成的电感器与电容器串联组成Ｌ－Ｃ谐振电路。在此电路中通过高频电流，使其在破乳器内产生高频磁场，从而感生出高频涡旋电场。在此电场的作用下，乳状液滴极化并加速其运动与碰撞，达到破乳的目的。该法在输入信号电压约３００Ｖ、电流几＋ｍＡ、频率２０ｋＨｚ的条件下，可感应出强度为几十＋ｋＶ／ｃｍ的涡旋电场，５ｍｉｎ内静态破乳率大于９８％。在     

基于印刷工艺的介质层绝缘特性研究

绝缘介质层是三极场致发射显示器的重要组成部分,本文通过丝网印刷技术与一次烧结和重复烧结两种烧结工艺制备不同膜厚的介质层,利用台阶仪和扫描电子显微镜分别对介质层膜厚和形貌进行表征,并对介质层的绝缘耐压性能进行了测试。结果表明,在重复烧结工艺下制备的膜厚约为34μm的介质层的耐压特性较好,电场强度达0.15 MV/cm,可耐压421 V,漏电流小,且重复性好,基本上可以满足后栅型FED栅极调控电压对介质层耐压性能的要求。同时在电场较弱时,介质层漏电流的输运符合欧姆输运机制;随着电场的升高,介质层漏电流的输运以Schottky发射机制为主,Frenkel-Poole发射机制对漏电流的影响很小。     

改善有机片式固体钽电解电容器性能工艺研究

研究了在被膜过程中表面活性处理及掺杂对聚合物片式钽电容器容量、耐压、等效串联电阻(ESR)等特性的影响。研究结果表明表面活性处理后可以有效改善Ta2O5/PEDOT界面间的匹配,提高电容器容量引出效率;通过添加中间阻隔层(硅烷偶联剂)可以有效地阻挡杂质氧化性离子进入介质膜Ta2O5层,降低聚合物片式钽电容器的漏电流,提高耐压特性;实验结果表明在掺杂剂溶液的浓度为3%,补形成电压为赋能电压的70%时,能有效降低电容器ESR及漏电流。     

LCR测量仪电容器损耗角正切测量不确定度的评定

电容器介质损耗是电容器的重要质量指标之一,是电容器介质损耗角正切的简称。LCR测量仪是测量电容值、电容损耗因数tanδ(或D值)等功能的测量仪器,本文采用电容器介质损耗的典型表示,对其进行测量不确定度的评定。一、校准条件1.校准依据JJF1095-2002《电容器介质损耗测量仪校准规范》。2.环境条件     

碳纳米管与活性炭超级离子电容器的频率响应

分别采用碳纳米管和活性炭作用超级离子电容器的电极材料，应用交流阻抗频谱法，研究了两类超级离子电容器的频率响应特性。结果表明，用碳纳米管作电极，超级离子电容器地频率250mHz以下出现“电荷饱和”；而用活性炭作电极，超级离子电容器在频率为100mHz时仍未出现“电荷饱和”，说明碳纳米管超级离子电容器的频率响应特性优于活性炭超级离子电容器的频率响应特性，但是上述两类超级离子电容器的频率响应特性均比传统介质电容器的频率响应特性差。     

用二次谐波检测舰船电场的研究

提出一种测量舰船电场的新方法，即用二次谐波方法测量大轴周围磁场，从而确定大轴电流，进而分析由大轴电流带来的舰船电场，理论和实验均表明，该方法结构简单，构思精巧，是检测舰船电场的方法之一。     

液体灌封高压蓄能电容器失效机理的研究

研究了高压能电容器放置后,其浸渍剂,有机介质性能的变化,分析了浸渍剂,有机介质在电容器失效过程中的变化机理,提出解决高压能电容器失效的方法。     

舰船极低频电场的产生机理及其防护

舰船极低频电场由于能在海水中传播到很远的距离，而且很容易被探测到，已成为舰船的一个重要目标特性，螺旋桨转动调制舰船腐蚀电流和外加电流阴极保护系统在海水中产生的电流是舰船极低频电场的2个重要来源．质量较差的阴极保护系统(ICCP)中的电源滤波器也会导致极低频电场的产生，电磁场防护结构工艺、被动轴接地系统、主动轴接地系统和电场抵消系统是目前降低舰船极低频电场的主要方法。     

片式化高压电容器的内电极结构及优化

耐高压片式化多层陶瓷电容器(MLCC)要求其内电极具有特殊的结构以保证产品的可靠性。本文对比了普通MLCC和高压MLCC的内电极结构，用有限元方法对两种ML—CC中若干典型位置的电场分布进行了分析，从电学角度对高压MLCC中内电极结构尺寸进行了优化，建立了高压MLCC内电极结构尺寸和所选用陶瓷介质材料的电学性能、MLCC的额定工作电压等参数之间的关系，这对中、高压MLCC的设计和制造具有指导意义。     

Modeling of charge switching in ferroelectric capacitors

To simulate charge switching in ferroelectric capacitors, a pair of exponential growth and decay currents is mapped to the process of polarization reversal. This is based on the fact that these exponential currents [i.e., i = I(m) e(t/tau) (t < or = 0) and i = I(m) e(-t/tau) (t > or = 0)], are completely specified by two constants I(m) and tau and each accommodates an integral charge Q = I(m) x tau. Equating this charge to the remanent spontaneous polarization allows for the modeling of switching current. For practical circuit simulations for charge switching, this modeling of switching current is simplified to an exponential decay current whose integral charge is set equal to the total reversed spontaneous polarization. This is because an exponential decay current can be conveniently implemented by charging a series resistor and capacitor (RC) circuit with a pulse-voltage source. The voltage transitions of the pulse source are associated with the polarization reversal and can be controlled with a noninverting Schmitt trigger that toggles at the positive and negative coercive voltages of a ferroelectric capacitor. The final circuit model incorporates such electrical and geometrical parameters as capacitance, remanent spontaneous polarization, coercive field, electrode area, and film thickness of a ferroelectric, thin-film capacitor.     

Photoelectret and electrophotographic properties of barium titanate-polyvinylidene fluoride composite film

Photoferroelectric barium titanate (BaTiO₃)-polyvinylidene fluoride (PVDF) composite films in the ratio 7030 are found to possess good photosensitivity in the visible region of the spectrum. Results on investigations of charge generation, trapping, recombination, discharge and retention properties of the composite film are presented in this paper. Photoinduced polarization is obtained in a BaTiO₃-PVDF composite film by the simultaneous application of a d.c. field and illumination from an argon-ion laser or by white light. The dark (photo) polarization and the dark (photo) depolarization current decay characteristics of the polarized films have been studied under different experimental conditions. The studies show that the composite film retains good polarization for a fairly long time in the dark condition, and the magnitude of the depolarization current is comparable with that of BaTiO₃ single crystal. Under illumination, the decay is fast enough to make use of the film for electro-photographic applications.     

Scattering, absorption, and extinction by thin fibers

For electromagnetic wave incidence on a thin fiber at an angle theta i with the fiber axis, induced currents are described by linear combinations of driven and traveling waves exp(+/-ikz cos theta i) and exp(+/-imkz), where the complex factor m serves to remove singularities in the normalizing constants of the currents. The fiber may be solid, hollow, or coated, with quite general constitutive parameters. Results are given for scattering, absorption, extinction, and radar cross sections, using energy conservation and reciprocity as consistency checks, and compared with independent computations, including the Born approximation for tenuous conductors and dielectrics. In addition, the far field amplitude of a 50 wavelength conductor is obtained and compared with the well-known long-wire approximation.     

Spectral and polarization characteristics of the nonspherically decaying radiation generated by polarization currents with superluminally rotating distribution patterns

We present a theoretical study of the emission from a superluminal polarization current whose distribution pattern rotates (with an angular frequency omega) and oscillates (with a frequency Omega) at the same time and that comprises both poloidal and toroidal components. This type of polarization current is found in recent practical machines designed to investigate superluminal emission. We find that the superluminal motion of the distribution pattern of the emitting current generates localized electromagnetic waves that do not decay spherically, i.e., that do not have an intensity diminishing as RP(-2) with the distance RP from their source. The nonspherical decay of the focused wave packets that are emitted by the polarization currents does not contravene conservation of energy: The constructive interference of the constituent waves of such propagating caustics takes place within different solid angles on spheres of different radii (RP) centered on the source. For a polarization current whose longitudinal distribution (over an azimuthal interval of length 2pi) consists of m cycles of a sinusoidal wave train, the nonspherically decaying part of the emitted radiation contains the frequencies Omega +/- momega; i.e., it contains only the frequencies involved in the creation and implementation of the source. This is in contrast to recent studies of the spherically decaying emission, which was shown to contain much higher frequencies. The polarization of the emitted radiation is found to be linear for most configurations of the source.     

Flexoelectricity in Solid Dielectrics: From Theory to Applications

Flexoelectricity phenomenologically describes the universal electromechanical coupling effect between electric polarization and strain gradient, and electric field gradient and elastic strain. In contrast to piezoelectricity which is invalid in materials with inversion symmetry, flexoelectricity exists, commonly, in all solid dielectrics. In this paper, a summary of the research on flexoelectricity is presented to illustrate the development of this topic. Flexoelectricity still have many open questions and unresolved issues in the developing field, although it has attracted a surge of attention recently. Here we review the theoretical investigations and experimental studies on flexoelectricity, and the aim of the current paper is to look into the potential applications of this electromechanical coupling effect.     

Electrocaloric Materials for Solid‐State Refrigeration

The electrocaloric effect (ECE) in dielectric materials has great potential in realizing solid‐state cooling devices with compact size and high efficiency, which are highly desirable for a broad range of applications. This paper presents the general considerations for dielectric materials to achieve large ECE and reviews the experimental efforts investigating ECE in various polar dielectrics. For practical cooling devices, an ECE material must possess a large isothermal entropy change besides a large adiabatic temperature change. We show that polar dielectrics operated at temperatures near order–disorder transition have potential to achieve large ECE due to the possibility of large change in polarization induced by electric field and large entropy change associated with the polarization change. We further show that indeed the ferroelectric poly(vinylidene fluoride–trifluoroethylene)‐based polymers display a large ECE, i.e., an isothermal entropy change of more than 55 J (kgK)^?1 and an adiabatic temperature change of more than 12 °C, at temperatures above the order–disorder transition.     

固态电介质的物理特性及其应用前景

本文综述了固态电介质的特征、极化的基本过程、极化弛豫过程中的表征及其各种物理特性和相关的技术应用，介绍了固态电介质介电特性研究的最新进展，明确指出开发性能优异的铁电器件关键在于设法获得具有高介电特性、低损耗、高稳定性和抗疲劳等综合物理特性的固态电介质材料。     

Control of threshold voltage of organic field-effect transistors by space charge polarization

We demonstrate organic field-effect transistors (OFETs) with an ion-dispersed polymer for the gate dielectrics. By applying external electric field (V_ex), the dispersed ions can migrate by electrophoresis and separated ion pairs form space charge polarization in the gate dielectrics. After V_ex was applied, the drain current is increased over 7 times and threshold voltage is decreased from − 12.9 V to − 2.9 V. The shift direction of V_th is controllable by the polarity of the V_ex. Results of ultraviolet/visible differential absorption study reveal that the active layer of OFETs is charged not only electrostatically but electrochemically with increasing the time after V_ex was applied.     

A “permanent” high-temperature superconducting magnet operated in thermal communication with a mass of solid nitrogen

A new design for a portable “permanent” superconducting magnet system is explored. The design involves a persistent-mode high-temperature superconducting (HTS) magnet that is cooled by a solid heat capacitor. The system is an alternative to permanent low-temperature superconducting (LTS) magnet systems where the magnet is cooled by a bath of liquid helium.An apparatus was constructed to demonstrate stable operation of a permanent magnet wound with Bi2223/Ag conductor while in thermal communication with a mass of solid nitrogen. The apparatus includes a room-temperature bore and can function while it stands alone, detached from its cooling source, power supply, and vacuum pump. The magnet is operated in the 20–40 K temperature range. This apparatus is the first to demonstrate the operation of a superconducting magnet with a permissible temperature variation exceeding a few degrees kelvin. Models are developed to predict the experimental system's warming trend and magnetic field decay. The models are validated with a good agreement between simulations based on these models and experimental results. The results indicate that present HTS conductor critical current and index are not yet sufficient to provide field strengths and field decay time constants that are required for typical persistent-mode applications.     

A strain-gradients theory of elastic dielectrics with spatial dispersion

Balance equations and the boundary conditions of elastic dielectrics are derived through a variational principle in which, to include the spatial and frequency dispersion effects, the first and second gradients of the deformation gradient and the polarization gradient are chosen as independent variables in addition to the deformation gradient and polarization. The polarization inertia effect is also included in the functional. The coupling of soft-optic modes with the displacement field is investigated and the results are particularized for potassium tantalate (KTaO₃). The numerical values of some of its material constants and its polarization inertia are calculated. Using an approximate strain energy density function for -quartz, the material coefficient matrices are obtained and tabulated. The acoustical, optical and infrared activities of -quartz are examined and the results are compared with those available in the literature.