聚合电场频率对聚合物稳定胆甾相液晶光电性能的影响

研究了聚合时外加电场对聚合物稳定胆甾相液晶(PSCT)光电性能的影响。采用紫外光聚合诱导相分离法(PIPS)制备了聚合物稳定胆甾相液晶,通过改变光聚合时的外加电场频率控制聚合物网络结构,改善PSCT的光电性能。结果表明:电场频率影响聚合单体的扩散,从而影响聚合物网络形貌。聚合电场频率低,聚合单体扩散快,形成的聚合网络疏松,网孔较大,响应速度慢,关态透过率大,阈值和饱和电压小;聚合电场频率高,阻碍单体的扩散,形成的聚合物网络致密,网孔较小,响应速度快,关态透过率低,阈值电压和饱和电压大。

交变电场频率对电凝并影响的理论及实验研究

根据碰撞理论，推导出偶极行电尘粒在突变电场中的电凝并系数，并利用Williams求声凝并的方法，将其简化。电凝并除烟实验在2，4，6Hz三种频率下进行，结果表明：三种频率下的除尘效率比较接近，但频率为6Hz时除尘效果较好。

交变电场频率对弱导电液滴变形及融合的影响

基于相场方法和电荷守恒模型,在OpenFOAM框架下发展了考虑电荷输运的两相流数值方法,系统研究了不同电物性参数条件下交变电场频率对弱导电的单个液滴变形和双液滴融合的影响。结果表明,交变电场频率对单个液滴变形具有显著影响,同时也会影响双液滴的融合时间。当介电常数比Q和导电率比R相等时,单个液滴在交变电场中的平均变形率和等效直流电场中液滴的稳态变形率相等,双液滴融合时间随着频率增加而增加。当Q>R时,随着频率增大,单个液滴的平均变形率不断增大,双液滴融合时间减少。当Q<R时,电场频率增大会导致单个液滴平均变形率的减小以及双液滴融合时间增加。

介质阻挡放电中离子浓度与电场频率的关系

影响介质阻挡放电离子浓度的因素有很多,用实验方法探讨外加电场频率变化对离子浓度的影响。研究结果显示,离子浓度随着高压电源频率增大而增大,变化率随着频率增大而逐渐减小。

交流电场频率对柳树-东南景天混栽修复镉污染土壤的影响

单一植物吸收的方法修复镉(Cd)污染土壤效果欠佳,交流电场联合植物可以更好地提高土壤Cd污染的治理效率。通过优化电场频率等参数可以提高土壤Cd的移动性,促进植物吸收土壤Cd。采用土壤盆栽试验的方法,研究交流电场频率(50、300 Hz)对竹柳3号和东南景天混种条件下土壤理化性质、Cd有效性、植物生长和Cd吸收积累能力的影响。与对照(没有施加电场)相比,300 Hz电场处理的土壤pH值显著降低了0.13。电场频率的提高显著提升了土壤Cd的有效性,300 Hz频率电场处理的土壤有效态Cd质量分数显著高于对照35.00%。交流电场促进了植物生长,柳树和东南景天的株高、生物量、叶片SPAD值及根系形态指标在外加50、300 Hz交流电场时均得到提高。交流电场降低了柳树各部分和东南景天地下部Cd质量分数,其中50 Hz处理柳树叶片、枝条、树干、根系和东南景天地下部Cd质量分数较对照分别降低22.16%、29.82%(P<0.05)、1.49%、15.91%(P<0.05)、31.81%(P<0.05)。相反,电场频率的提高有利于东南景天地上部Cd质量分数增加,50、300 Hz处理东南景天地上部Cd质量分数较对照分别增加43.37%、55.18%(P<0.05)。交流电场提高了植物对土壤Cd吸收积累,但不同的电场频率对植物Cd修复效率影响不同,50、300 Hz交流电场下植物地上部分总Cd积累量较对照分别显著增加24.04%、21.24%。从这2种植物上看,50 Hz交流电场更能提高柳树Cd修复效率,300 Hz交流电场更提高能东南景天Cd修复效率。本试验装置成本较低,修复效果较好,对于电场频率增强植物修复Cd效率具有很大参考价值,有较好的应用前景。

微通道内电场频率对电渗流影响的数值模拟

为研究二维微通道内交变电场电渗流速度特性,以双电层P-B方程和粘性不可压缩流体N-S方程为基础,建立交变电场电渗流的数学模型。应用有限元方法,对不同频率的交变电场电渗流进行数值模拟。结果表明,交变电场电渗流速度分布呈"波浪状",微通道中心区域速度滞后于壁面附近,当流体离壁面距离增大时,流体流速的滞后量增大。电场频率小于1 000 Hz时,交变电场电渗流与稳定电场电渗流具有相似的速度分布。随着电场频率的增大,"波浪状"速度流型更为明显,并且双电层滑移速度减小,尤其当电场频率大于3 000 Hz时,双电层滑移速度迅速下降。

混沌频率电场激励乳化油液滴动力学仿真与响应

运用混沌脉冲调制方法构建混沌频率脉冲电场,建立乳化油液滴在混沌频率电场中的振动动力学仿真模型,通过数值计算,得到油中液滴在混沌频率脉冲电场作用下的振动动力学响应,并对响应输出进行了相轨图分析和最大Lyapunov指数计算。结果发现,混沌频率脉冲电场存在最佳脉宽,激励液滴剧烈振动;液滴在高频段获得较大拉伸变形量,在低频段则拉伸变形量相对较小,且波动稳定;可定性和定量地识别液滴振动响应的混沌特征。

不同电场波形下液滴极化变形规律研究

为了深入研究电场波形对液滴变形的影响,基于相场方法,建立了互不相融两流体中液滴变形的仿真模型,实现了流场和电场的耦合。模拟研究了直流脉冲、半正弦波、半三角波和半锯齿波4种电场波形对液滴变形的影响。模拟结果显示,液滴变形度曲线与电场波形相似,且液滴振荡变形的频率与电场频率相同。此外,还研究了以上4种波形电场的场强幅值和频率对液滴变形度的影响。结果显示,电场的均方根RMS越高,液滴变形度越大;随着场强幅值的增加,4种波形条件下液滴变形度近似呈指数增加;随着频率的增加,直流脉冲和半正弦波电场条件下液滴变形度呈先增加后减小的趋势,存在最佳频率40 Hz,半三角波和半锯齿波电场条件下液滴变形度近似呈线性减小。

GIS开关操作空间瞬态辐射电场的特性研究

为清楚了解全封闭式气体绝缘变电站开关操作空间特快速瞬态电磁场的骚扰特性,在550kV全封闭式气体绝缘变电站真型试验平台上开展特快速瞬态辐射电磁场的试验研究,测量空间辐射电场骚扰波形。论文介绍了试验测量系统,包括特快速暂态过电压、电磁场联合测量系统的快速暂态过电压测量、电磁场测量、同步触发系统和光纤传输控制系统。给出了试验操作流程,并对测量结果进行了统计分析。得到了瞬态辐射电场脉冲群持续时间、脉冲个数,微脉冲持续时间、电场幅值等骚扰特性。对电场微脉冲波形进行频谱分析,并统计主要频点出现的概率。试验结果表明,电场脉冲群持续时间的范围为59ms-157ms,脉冲个数为40个-83个,微脉冲持续时间为4.584μs-9.592μs;辐射电场频率成分非常丰富,1MHz、7.5MHz、15MHz、20MHz和46.5MHz等频率出现概率较高。

面向探地雷达应用的活立木木材介电常数受主要应用条件的影响

【目的】目前,探地雷达常被应用于活立木缺陷、健康水平以及根系分布等的检测,检测系统中通常默认介电常数为固定值,但经初步研究发现,活立木的介电常数受环境及自身性质等的影响并不是一成不变的,在检测中使用默认的介电常数值会降低检测的准确性。因此,探究在不同应用条件下的活立木木材介电常数变化,建立各因素与介电常数值相关模型可为后续探地雷达检测活立木的应用中提供高精度的参考依据。【方法】本研究选用从黑龙江省星火林场采集的红松、樟子松、大青杨和水曲柳原木试件,根据探地雷达的应用条件,采用Agilent 4294A型介质频谱测试仪测量试件在不同含水率(范围为10%~100%)、不同温度(范围为-15~20℃)、不同外电场频率(范围为40 Hz~110 MHz)下的介电常数。分析不同应用条件下木材介电常数的变化趋势,并基于SPSS软件进行相关性分析,建立介电常数和各因素间的回归模型。【结果】木材含水率、外电场频率和环境温度对4种木材介电常数的影响规律相似。1)随着木材含水率的增加,介电常数呈现出增大的趋势。当含水率低于纤维饱和点时,介电常数缓慢增加;含水率高于纤维饱和点时,介电常数增加的速率变快。2)随着环境温度的增加,木材的介电常数整体呈现出增大的趋势。当含水率高于纤维饱和点时,介电常数值在0℃处出现突变。3)介电常数与外电场频率呈负相关关系,且随着频率的增大介电常数的下降趋势逐渐趋于平缓。4)在此温度区间内,介电常数与频率和含水率呈较为显著的相关性。通过回归分析,建立了介电常数的回归方程。【结论】实验结果表明环境温度、木材含水率和外电场频率均会对木材的介电常数造成影响。介电常数与含水率、环境温度呈正相关,与外电场频率呈负相关关系。含水率和外电场频率对木材的介电常数影响较大,环境温度次之。在实际应用中,可通过建立的回归方程来修正活立木的介电常数以提高探地雷达的检测精度,为活立木的精确腐朽检测提供依据。

具有分形结构掺入物的二维复合材料三阶光学非线性性质的计算

利用傅里叶展开和退耦合近似方法 ,在二维金属 -绝缘体复合材料中 ,当金属掺入物形成具有分形结构的聚集物集团时 ,计算其三阶光学非线性电极化率 χe与外电场频率 ω的关系 .结果表明 ,在一些特定的频率值 ,Re(χe) -ω曲线出现了显著的放大峰 .与以正方点阵规则排列的柱型掺入物的情况相比 ,掺入物形成具有分形结构的聚集物集团时 ,原有放大峰的强度明显减弱 ,但有新的放大峰出现 ,其峰强非常敏感地依赖于金属材料的特征驰豫时间

Lattice-Matched InP-Based HEMTs with T^T of 120GHz

Lattice matched InP based InAlAs/InGaAs HEMTs with 120GHz cutoff frequency are reported.These devices demonstrate excellent DC characteristics:the extrinsic transconductance of 600mS/mm,the threshold voltage of -1 2V,and the maximum current density of 500mA/mm.

A Novel Polysilicon and Oxide Sandwich Deep Trench with Field Limiting Ring for RF Power Transistors

A vertical sandwich deep trench with a field limiting ring is proposed to improve the breakdown voltage of power devices and high voltage devices.Simulation result shows that nearly 100% breakdown voltage of the plane junction can be realized.

相位共轭、自聚焦等相关效应

O437 2000042574外加交变电场对光折变基频空间电荷场瞬态特性的影响=Effect of external applied alternating fieldon transients behaviour of fundamental harmonicof photorefractive space-charge field[刊,中]/周忠祥,冯玉文,姜永远,孙秀冬,许克彬(哈尔滨工业大学应用物理系.黑龙江,哈尔滨(150001))//光学学报.—1999,19(12).—1608—1614利用"跳跃模型"讨论外加交变电场对光折变基频空间电荷场建立的影响,给出了空间电荷场基频分量时间、外加交流电场振幅频率等变化的通解表达式。发现基频空间电荷场虚部和实部的振荡频率分别是外加交流电场振荡频率的2倍和1倍。当外加交变电场频率较大时光折变光栅是相移型的。这和基于"带导模型"

超短激光脉冲测量技术的发展

文章综述了超短激光脉冲测量技术的发展历程,特别详细地介绍了目前国际上公认的测量飞秒脉冲的频率分辨光学开关法(FROG)和光谱相位相干电场重构法(SPIDER),并概述了处于实验室阶段的阿秒脉冲产生的基本原理及测量方法。

Effect of pulsed electromagnetic frequency on the microstructure, wear and solid erosion resistance of CrAlN coatings deposited by arc ion plating

In this work,the chromium aluminum nitride(CrAlN)coatings were prepared on TC11 titanium alloy by composite magnetic field cathodic arc ion plating with controllable pulse electromagnetic combined with permanent magnet.The effects of electromagnetic frequency on the morphology,microstructure,nano-hardness and elastic modulus of the coatings were investigated by scanning electron microscope(SEM),X-ray diffraction(XRD)and nano-indenter.This paper has mainly studied the influence of CrAlN coatings which are prepared at various electromagnetic frequencies on the wear and erosion resistance through a series of wear and solid particle erosion experiments.It was found that the deposition rate of CrAlN coatings increases with the increase of electromagnetic frequency.And CrAlN coatings all preferentially grew along the(111)crystal plane.At 16.7 Hz,with the increase of pulsed electromagnetic frequency,the hardness is the highest(23.6 GPa)and the adhesion is the highest(41.5 N).In addition,the coating deposition exhibited the best wear and solid erosion resistance at 16.7 Hz and 33.3 Hz,the friction coefficient is about 0.35,and the erosion rate is about 0.2μm/g at 30°and less than 1μm/g at 90°,respectively.These results indicate that the CrAlN coating formed at an appropriate pulsed electromagnetic frequency can achieve excellent mechanical properties,wear and solid erosion resistance.

Effective Response of Nonlinear Composite under External AC and DC Electric Field

A perturbation method is used to study effective response of nonlinear Kerr composites, which are subject to the constitutive relation of electric displacement and electric field, Dα=εαE＋xα｜E｜^2E. Under the external AG and DC electric field Eapp = Eα（1 ＋ sinωt）, the effective nonlinear responses and local potentials are induced by the cubic nonlinearity of Kerr materials at all harmonics. As an example in three dimensions, we have investigated this kind of nonlinear composites with spherical inclusions embedded in a host. At all harmonic frequencies, the potentials in inclusion and host regions are derived. Furthermore, the formulae of the effective linear and nonlinear responses are given in the dilute Iimit.

Analytical Solutions of Electromagnetic Fields from Current Dipole Moment on Spherical Conductor in a Low-Frequency Approximation

We analytically derive the solutions for electromagnetic fields of electric current dipole moment, which is placed in the exterior of the spherical homogeneous conductor, and is pointed along the radial direction. The dipole moment is driven in the low frequency f = 1 kHz and high frequency f = 1 GHz regimes. The electrical properties of the conductor are appropriately chosen in each frequency. Electromagnetic fields are rigorously formulated at an arbitrary point in a spherical geometry, in which the magnetic vector potential is straightforwardly given by the Biot- Savart formula, and the scalar potential is expanded with the Legendre polynomials, taking into account the appropriate boundary conditions at the spherical surface of the conductor. The induced electric fields are numerically calculated along the several paths in the low and high frequeny excitation. The self-consistent solutions obtained in this work will be of much importance in a wide region of electromagnetic induction problems.

影响静电除尘器效率的控制因素

静电除尘器通常用来处理锅炉尾部烟气。具有高效、节能、维护量小的优点。静电除尘器在长期使用后效率会下降，达不到设计值要求。为保障烟尘达标排放，需要找出并解决除尘效率下降的因素。

Analysis on Application of Wavelet Neural Network in Wind Electricity Power Prediction

Wind electricity power has fluctuation, and accurate and reasonable wind electricity power prediction is very important for solving wind electricity network and combination. This paper takes an analysis of a lot of actual data of a certain wind electricity field. Through wavelet neural network and time series method rolling, it can predict the overall power of wind electricity field. The result shows that for the original data of sampling time length and large sampling frequency, the model constructed by this paper has very good prediction effect. Because of the fan installation position, wind electricity fan flow effect and other random factor influence, wind electricity field overall power and single unit power distribution have difference. Through comparing with the time series parameters, it puts forward that single wind electricity unit power has smooth effect for overall power of wind electricity field. Finally, it summarizes the prediction effect and puts forward some reasonable suzestions for wind electricity network troblems.