Electromagnetic scattering from thin strips. I. Analytical solutions for wide and narrow strips

Electromagnetic scattering from thin resistive strips is formulated using an integral equation approach. Analytical expressions for the electric current density over wide and narrow strips are derived based on the physical optics and quasistatic approximation of the pertinent integral equations, respectively. The solutions are used to find closed form expressions for the echo width of the strip.     

Electromagnetic scattering from thin strips. II. Numerical solution for strips of arbitrary size

Electromagnetic scattering from thin resistive strips is formulated using an integral equation approach. The formulation is then specialized to strips of constant curvature and arbitrary size allowing the employment of the method of moments to solve the scattering problem.     

Electromagnetic Emission from Electric Propulsions under Ground Conditions

Analysis and methodological generalization of available methods used for determining characteristics of intrinsic emission from electric propulsions (EP) in a radio-frequency range that can be the interference for the “Earth-spacecraft (SC)” channel of the space communication system are the subjects of this paper. Intrinsic emission from the electric propulsion in a radio-frequency range is examined in detail by the example of a measuring complex developed in RIAME MAI and the measurement results are presented. The electric field intensity distribution in a radio-frequency range for the vertical and horizontal polarizations of the received emission is considered as the main characteristics. Measurements performed for the EP intrinsic emission by using the developed complex and measurements performed in metal vacuum chambers are compared and comparative results are presented in the paper.     

空气针尖负电晕放电的特征辐射谱

为得到针尖负电晕放电的辐射特征,采用针-环结构对不同空气条件下负电晕放电的辐射谱进行了实验测试。结果表明,在给定电极件下,空气负电晕放电具有一定的特征辐射谱,频率〈100MHz。这种特征辐射谱的位置不随放电电压（电流）和气体等条件变化;特征辐射强度与放电电压无关,但与空气的气压和气流有关。空气负电晕放电的特征辐射与Trichel脉冲的形成过程相关,电流脉冲的上升沿决定特征频谱的位置和幅度。     

Three-dimensional computation of light scattering from cells

Using the finite-difference time-domain method, three-dimensional scattering patterns are computed for cells containing multiple organelles. The scattering cross section and average cosine of the scattering angle are computed for cells as a function of volume fraction of melanin granules and mitochondria. Results show that small organelles play a significant role in light scattering from cells, and the volume fraction of organelles affects both the total amount of scattered light and the angular distribution of scattered light     

用铁砂研制的铁氧体电波吸收材料

以铁砂为原料制备一种尖晶石型铁氧体电波吸收材料，在７－１２Ｈｚ范围，发现有两个吸收峰，吸收量在９－１３ｄＢ，将铁氧体吸收体和铁砂吸收体组成复合电波吸收材料，亦有两个吸收峰，一峰向低频区偏移，吸收量增至１４．６ｄＢ；以复合吸收体为基础材料，在其中添加六角铁氧体和稀土元素，可改变吸收峰位置，提高吸收量，阳大可达２７ｄＢ。     

Shadow-corrected bistatic scattering from randomly very rough surfaces

Contents  The like- and cross-polarized scattering coefficients of electromagnetic waves from random rough surfaces corrected by shadowing functions are studied in this paper. Due to the use of approximate tangential surface fields in the derivative of all the wave scattering from randomly rough surfaces, the shadowing functions should be added to correct the scattering especially from surfaces with large rms surface slope. For correct prediction to the scattering characteristics we apply the suitable angular shadowing function to the single and multiple scattering coefficients respectively. The comparisons of scattering coefficients with or without shadowing functions are shown in this paper to evaluate the conditions of angular shadowing functions and the effect of shadowing function for the scattering from random very rough surfaces. We also compare the shadow-corrected scattering coefficients with the measured data and find the good agreements between them. Received: 12 December 2000     

Electromagnetic interference from digital signal transmission onpower line carrier channels

A procedure is presented to evaluate the electromagnetic field generated by a digital transmission system on multiconductor power-line carrier channels. The vertical component of the electric field and the horizontal component of the magnetic field are defined by approximate formulaes of varying accuracy, depending on the frequency and the distance from phase conductors. Field sources are the currents traveling along the line, which are evaluated by means of an accurate simulation model of the transmission system and a rigorous wave propagation algorithm. Frequency spectra and lateral profiles of the field components are computed for single-phase and two-phase couplings on a horizontal power line. Digital channel capacity is shown to increase as the pulse repetition interval T decreases. However, if T increases, the harmonic content of the input signal code increases and, consequently, electromagnetic pollution rises for a given carrier channel. It is concluded that the EMI (electromagnetic interference) level is an important constraint which must be taken into account when choosing T and, more generally, in the design of the digital transmission system     

电爆炸丝断路开关的电磁辐射研究

为研究电爆炸丝开关切断时产生的强度在近距离内可对效应物产生严重破坏的电磁辐射,在TomaChan系统装置中用拉杆天线测得了所产生的电磁辐射信号波形并经FFT变换后得到其频谱也得到了通过电爆炸丝开关的电流。结果表明电爆炸丝开关所产生的信号是一个主频在75 MHz频谱较宽的电磁波。所测电流峰值约为19 kA,其随时间变化过程可以分为3个阶段。分析讨论了开关运行的辐射干扰现象以及产生机理,为辐射干扰进行屏蔽防护提供参考,可供带有电爆炸丝切断开关的脉冲功率系统产生辐射的研究参考。     

开关电源电磁干扰的分析及抑制

本文分析了开关电源产生电磁干扰的主要原因。给出了相应的抑制措施，以提高开关电源的电磁兼容性。     

换流站阀厅电磁骚扰强度的计算分析

从时域和频域两个方面总结了应用矩量法计算阀厅内金属导体结构产生的电磁骚扰水平的方法。直接时域方法以电流为激励源进行计算,考虑因素少,计算简单;而直接频域方法由于可以同时考虑线路、金属架构等多种复杂结构的影响,模型更为准确,但是计算速度慢,建模复杂。考虑到常用的矩量法计算软件如NEC、FEKO等,不适合建立大量电流源模型,因此以电压源、导线、金属板和负载为基本元件的直接频域法就非常适合借助于成熟的软件进行工程计算。首先将±500 kV阀塔的元器件、金属导线和金属框架分别用阻抗、线天线和面天线模型进行等效。对一±500 kV换流站阀厅建立了电磁计算模型,研究了换流站在正常工作情况下由阀厅内金属导体结构产生的电磁骚扰特性,主要讨论阀厅墙体附近的辐射电磁场,阀厅外的无线电干扰水平。通过与测试结果和其它相关报告的结果对比验证了该计算方法和模型的有效性和正确性。应用该方法分析了±800 kV换流站阀厅内金属导体结构产生的电磁骚扰水平,并结合相关标准提出了阀厅墙体应具备的屏蔽效能。该研究既可以用来预测换流站内的电磁场分布,也可为阀厅的屏蔽设计提供依据。     

Electromagnetic hydrodynamics

A broad survey has been conducted of electrohydrodynamic phenomena in which the electric field may be simply static or electrodynamic in nature. Recent developments of new materials have made it possible for relatively high electromagnetic fields to penetrate flow tubes and containers, thus emphasising the need for an electrodynamic approach to the subject. Some engineering problems are introduced in which electromagnetic hydrodynamics plays an important role. The review of the current state of the art is intended to supplement earlier ones and to broaden the scope of the topic to include two-phase flow and electrodynamic field effects     

Electromagnetic visualization

The author begins by discussing visualization in general terms before going on to discuss the visualization of computational electromagnetics and EM visualization theory. Frequency domain visualizations are considered in particular     

Electromagnetic compatibility

Electromagnetic compatibility (EMC) is achieved when a device functions satisfactorily in its electromagnetic environment without introducing intolerable disturbances. Electromagnetic interference (EMI) is the degradation in a device's performance due to these fields which make up the electromagnetic environment. Sources of EMI are identified, and the three common means used to control or suppress it, namely, grounding, shielding, and filtering are discussed. Other useful techniques for minimizing and controlling EMI are outlined     

废旧锂离子蓄电池正极材料回收研究

从废旧锂离子蓄电池中回收钴酸锂有两种方法,即直接回收钴酸锂,以及先回收钴和锂然后再合成得到钴酸锂。比较了这两种方法所得产品的电化学性能。通过热重-差热分析曲线确定保温温度和时间,采用X射线衍射分析(XRD)、扫描电子显微镜(SEM)、嵌入-脱嵌循环曲线、循环容量曲线和效率-循环次数曲线进行分析,发现后一方法回收的钴酸锂样品循环性能良好,在0.1C和0.5C放电条件下首次放电比容量分别为130.3mAh·g-1和113.9mAh·g-1;当循环10次以后充放电比容量基本稳定在123mAh·g-1和112mAh·g-1;循环20次之后,放电比容量仍有122.85mAh·g-1和111.80mAh·g-1。     

一种计算旋转对称目标散射的有限元算法

本文给出了一种混合使用有限元和圆柱完全匹配层计算旋转对称目标散射的有限元算法。使用矢量棱边基函数表示横向场分量,用标量节点基函数表示角度场分量。矢量基函数的使用消除了伪解问题,圆柱坐标完全匹配层(PML)的使用缩减了有限元网格,从而避免了无用的计算。这种方法能够处理大型的实际雷达目标,同时与标准目标的计算结果符合得很好。     

电磁辐射污染与电磁环境监测

电磁辐射污染直接影响环境及人体健康。本文对电磁辐射污染的分类、危害及防护措施进行了论述,并指出了进行电磁环境监测的重要性。     

Electromagnetic field radiated from broadband signal transmissionon power line carrier channels

A rigorous procedure is presented for the evaluation of the rectangular components of the electromagnetic field radiated by excited carrier channels on multiconductor overhead power lines above a lossy ground. The proposed full wave approach, based on the use of Hertz potentials, allows the high-frequency analysis of a spread spectrum transmission system. Field sources are the current traveling along the line, which are evaluated by means of an accurate line simulation model including the ground return parameters, obtained by removing the Carson quasi-static hypotheses. The frequency-spectra and the lateral profiles of the field components radiated from wire-to-ground and wire-to-wire channels on a three-conductor distribution line are computed in a frequency-range up to 20 MHz     

针-板局部放电辐射电磁波频率特性的实验研究

高压设备局部放电时会辐射出具有一定频率的电磁波.设计了一种典型的针-板电极放电实验模型,搭建一局部放电试验装置,用以模拟高压设备局部放电,对辐射出的电磁波频率特性进行研究.结果表明,在50 MHz-1 GHz测试频率范围内,这种局部放电能够辐射出能量较强的电磁波信号,并且连续分布于整个测试频段(包括超高频段0.3-1 GHz);通过比较屏蔽装置内外测得的放电频谱,证实辐射出的电磁波可通过开孔处耦合到设备外部,并能被检测,特征也基本不变.这些特性为高压设备局部放电非接触式超高频检测技术和此种放电类型的识别提供了实验依据.     

废旧三元正极材料中选择性提锂

对废旧三元正极材料(LiNi0.5 Co0.2 Mn0.3 O2)进行硫酸化焙烧-水浸选择性提锂研究.在98％硫酸用量为6 ml、焙烧温度为650℃、焙烧时间为2 h、研磨样品d50为6μm、固液比为1 g/7 ml和加水20℃浸出2 h的条件下,20 g三元材料所得浸出液中的Li浓度为5.65 g/L,回收率为93....