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.     

Nd-Fe-B速凝铸片显微组织控制及低成本烧结磁体制备

利用片铸工艺制备了低稀土含量的钕铁硼合金铸片。对铸片显微特征进行表征,对比分析了不同厚度铸片的微观组织。发现厚度小于0.35mm时,铸片具有细小均匀的片状晶组织,无α-Fe产生;当厚度超过0.35mm,铸片的近自由端存在α-Fe树枝晶。调节辊轮线速度为2.5m/s时,获得了集中在0.2~0.35mm的厚度分布。通过添加低熔点晶界合金粉末,制得了具有较优显微结构和磁性能的低成本烧结稀土磁体。     

Scattering characteristics of FSSs with triangular conducting elements

In this paper, scattering characteristics of dielectric backed frequency selective surfaces (FSSs) having triangular conducting elements are investigated for both transverse magnetic and transverse electric incident plane waves. Since triangular conducting elements are etched periodically on such a surface, incident and scattered fields are expressed as Floquet modes. Using Floquet’s theorem and satisfying the required boundary conditions an integral equation is obtained for the induced current density on the surface of a triangular conducting element in one periodic cell. This induced current density is expressed as a finite sum of piecewise triangular basis functions having unknown coefficients. The resulting integral equation is then converted to a linear matrix equation by using the Method of Moments. Taking the inverse transform of the matrix equation yields the unknown current coefficients which are finally used to compute the reflection and transmission coefficients. Since there are no theoretical or experimental results for FSSs comprising of triangular conductors, verification of the algorithm developed is carried out by comparing the numerical results obtained using this algorithm with the experimental and theoretical results in the literature for FSSs composed of strips and L-shaped conductors. For this, in the algorithm, appropriate arms of the triangles are removed to conform them into strips or L-shaped conductors. Results obtained for strips and L-shaped apertures by using this algorithm are in excellent agreement with the results in the literature.     

碱锰电池钢壳用镀镍钢带的力学和耐腐蚀性能

利用SEM、XRD等方法,分析了不同碱锰电池钢壳用镀镍钢带.比较了它们的力学性能,详细讨论了它们在40%KOH环境中的耐腐蚀行为.利德公司样品的表面硬度、抗拉强度略高于德国及日本的样品,延伸率为39.57%,低于德国(41.53%)及日本(42.44%)的样品.它们的腐蚀电流相差不大.     

Improvements in the security of the inverting mode of a thyristor-controlled electric drive used in rolling strips of extended range

Rolling heavy strips on hot rolling mills involves considerable line-voltage deviations, which results in the threat of emergency conditions in electric drives with two-region speed control. A method for correction of setting the motor EMF as the line voltage is proposed to improve stability. Experiments have proved the feasibility of reducing the margin of the rectified thyristor converter EMF while maintaining high reliability characteristics of the electric drive.     

基于积分方程的T接线输电线路零序参数带电测量方法

提出了一种基于积分方程的T接线输电线路零序参数带电测量新方法,给出了该方法的数学模型,列写出T接线输电线路积分方程组的离散表达式,并利用最小二乘方法求解其零序阻抗参数.为获得足够多的独立方程,给出T接线线路在带电测量时的6种运行方式.获取测量源与利用全球定位系统(GPS)作为异地测量的同步信号是2个关键技术.给出了T接...     

Efficient analytical-numerical modelling of ultra-wideband pulsed plane wave scattering

Ultra-wideband (UWB) pulsed plane wave scattering from a large but finite strip grating in free space is analysed in the frequency domain via decomposition into plane wave spectra, implemented numerically by the method of moments, and then inverted into the time domain (TD). To make this procedure practical under UWB conditions, closed form expressions are derived for interaction integrals involving widely separated expansion and testing functions. These closed forms are based on a judicious choice of the basis functions, and on asymptotic methods for reducing the integrals. Although large separation distances are assumed, the expressions have been found to be accurate for separations as small as 0·1 wavelengths. The TD self terms can also be evaluated efficiently. To test the frequency domain algorithm, comparisons are made with available data in the literature for surface currents and far-field scattering from multiple strips. New short pulse TD results are shown as well.     

磁场积分法在永磁步进球形电动机场分析中的应用

用积分方程法建立了永磁步进球形电动机磁场的；学模型，导出了用于计算其磁场分布的离散计算公式。计算结果与有限元法结果比较，表明积分方程法对于永磁步进球形电动机场分析是行之有效的。     

Start-up circuit upgrading to reduce the erosion of the rotor blades of the last stages of steam turbines and prevent the mass strips of stellite plates

At turbine starts with low steam flow rates in idle mode, the low-pressure rotor blades consume energy, causing the ventilation heating of the stages and creating higher depression in them than in the condenser. This leads to the return steam flows in the exhaust of the low-pressure cylinder (LPC), reducing the heat due to the moisture of starting steam damps and cooling injections. It is shown that, as a result of upgrading with the transition to fully milled shroud platforms of rotor blades, the depression in the stages decreases and their cooling efficiency is reduced due to the removal of an elastic turn of the rotor blades under the action of centrifugal forces and seal of them by periphery. Heating the rotor blades of the last stages exceeds the temperature threshold of soldering resistance of stellite plates (150°C), and their mass strips begin. The start-up circuit providing both the temperature retention of the last stages lower the soldering resistance threshold due to overwetting the steam damps up to saturation condition and the high degree of removal from the dump steam of excessive erosive-dangerous condensed moisture was proposed, applied, and tested at the operating power unit. The investment in the development and application of the new start-up circuit are compensated in the course of a year owing to guaranteed prevention of the strips of stellite plates that lengthens the service life of the rotor blades of the last stages as well as increase of the rotor blade efficiency due to the sharp decrease of erosive wear of the profiles and reduction of their surface roughness. This reduces the annual consumption of equivalent fuel by approximately 1000 t for every 100 MW of installed capacity.     

Numerical analysis of waveguide bandpass filters using singular integral equations and construction of simple design formulas

A powerful numerical solution is presented for bandpass filters in rectangular waveguides. The filters are composed of cascading of perfectly conducting inductive obstacles with zero thickness: asymmetrical windows, symmetrical windows, or symmetrical strips. The problem is reduced to a set of singular integral equations, which is solved by an extension of Lewin's quasi‐static procedure. After the accuracy of the classical formulas for the equivalent reactance is investigated, the simple inverse formulas are constructed to yield proper window widths for desired equivalent parameters. Their effectiveness is demonstrated by designing practical filters having maximally flat or equal‐ripple characteristics. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(4): 17–25, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10251     

Transient electromagnetic plane wave reflection from a dielectricslab

Reflection of a transient plane wave normally incident upon a lossless dielectric slab is analyzed via the Fourier transform. The exact expression for the time-harmonic field is used in the inverse Fourier transform to obtain the transient response to a class of exponential exciting functions. Cauchy's integral theorem and the Poisson sum formula yield closed-form expressions for the unit step and impulse response functions     

银铜复合带材生产工艺的研究

采用快冷雾化制粉技术和可控气氛复合技术生产高性能的银铜复合带材，可以连续大卷重进行生产，所生产的复合带材厚度比均匀，复合介面清洁、复合强度高，电性能良好，并可根据客户的要求生产不同厚度比和机械性能的带材。     

水平分层土壤中点电流源电流场的计算

为解决地网仿真计算中多层土壤点电流源的格林函数计算复杂问题,以典型4层水平分层土壤模型为例,对点电流源格林函数公式进行了化简。因为格林函数的计算中涉及到含有贝塞尔函数的广义积分,被积函数高速振荡,难以数值积分。通过对被积函数的分析,提取衰减较慢的成分,给出了级数形式的解析表达式;对剩余部分,按照贝塞尔函数的零点分区间进行积分,收敛很快,提高了计算效率。最后使用数值方法给出了地电流的分布图像。     

Basic parameters of coplanar-strip waveguides on multilayer dielectric/semiconductor substrates. Part 2: Low permittivity superstrates

For Part 1 see ibid., vol.4, pp.67-70 (2003). In Part 1, closed-form formulas were proposed for basic parameters of coplanar-strip (CPS) waveguides on multilayer dielectric substrates. In Part 2, a new partial capacitance technique is proposed to deal with the case where the permittivity of the substrate layers increase away from the strips, and the magnetic wall approximation between the dielectric layers used in Part 1 is not valid. CPS on a SiO/sub 2//Si substrate is a typical example. Conformal mapping technique is also used for the evaluation of the line inductance (including internal) of the strips. The line capacitance, inductance, and conductance are then used to evaluate the frequency-dependent complex impedance, effective dielectric permittivity, and losses. The results are in good agreement with experiments and numerical simulations. The computation time is at least an order of magnitude shorter in comparison with the available commercial software (e.g., Momentum, Sonnet).     

电机齿压条与端板点焊工艺改进

分析电机齿压条脱落的原因，改进齿压条点焊工艺，从而保证齿压条点焊质量，提高电机运行的可靠性。     

Unified performance bounds for generalized selection diversity combining in independent generalized fading channels

The cumulative distribution function (cdf) and the moment generating function (mgf) of a linear sum of ordered random variables (RVs) are needed for characterizing the performance of a generalized selection combining (GSC) receiver. Unfortunately, in all but a few cases, the mgf and the cdf either are not in closed form or exist only as multidimensional integrals. Consequently, analyzing the GSC performance in a generalized fading environment is difficult and time-consuming, especially when the number of diversity branches, L, is large. This paper therefore derives new upper and lower bounds for the cdf of the GSC output signal-to-noise ratio (SNR) in generalized fading channels. These bounds are either closed-form or single finite integral expressions. New bounds are also derived for the average symbol error rates (SERs) for a multitude of binary and M-ary digital modulations in a variety of fading channel models that heretofore had resisted simple solutions.     

Estimation of Efficiency of the Cooling Channel of the Nozzle Blade of Gas-Turbine Engines

The main direction of improvement of gas-turbine plants (GTP) and gas-turbine engines (GTE) is increasing the gas temperature at the turbine inlet. For the solution of this problem, promising systems of intensification of heat exchange in cooled turbine blades are developed. With this purpose, studies of the efficiency of the cooling channel of the nozzle blade in the basic modification and of the channel after constructive measures for improvement of the cooling system by the method of calorimetry in a liquid-metal thermostat were conducted. The combined system of heat-exchange intensification with the complicated scheme of branched channels is developed; it consists of a vortex matrix and three rows of inclined intermittent trip strips. The maximum value of hydraulic resistance ξ is observed at the first row of the trip strips, which is connected with the effect of dynamic impact of airflow on the channel walls, its turbulence, and rotation by 117° at the inlet to the channels formed by the trip strips. These factors explain the high value of hydraulic resistance equal to 3.7–3.4 for the first row of the trip strips. The obtained effect was also confirmed by the results of thermal tests, i.e., the unevenness of heat transfer on the back and on the trough of the blade is observed at the first row of the trip strips, which amounts 8–12%. This unevenness has a fading character; at the second row of the trip strips, it amounts to 3–7%, and it is almost absent at the third row. At the area of vortex matrix, the intensity of heat exchange on the blade back is higher as compared to the trough, which is explained by the different height of the matrix ribs on its opposite sides. The design changes in the nozzle blade of basic modification made it possible to increase the intensity of heat exchange by 20–50% in the area of the vortex matrix and by 15–30% on the section of inclined intermittent trip strips. As a result of research, new criteria dependences for the complicated systems of heat exchange intensification were obtained. The design of nozzle blades can be used when developing the promising high-temperature gas turbines.     

Kerr electro-optic theory and measurements of electric fields withmagnitude and direction varying along the light path

Differential equations that govern light propagation in Kerr media are derived when the applied electric field direction and magnitude vary along the light path. Case studies predict Kerr electro-optic fringe patterns for the specific case of point/plane electrodes. We apply the characteristic directions theory of photoelasticity to understand these fringes. We also study birefringent media with small Kerr constant, in particular transformer oil. For this case we show that simplifications in the characteristic parameter theory is possible, resulting in simple integral relationships between the characteristic parameters and the applied electric field. We use these simple relationships to extend the ac modulation method to measure the characteristic parameters for small Kerr constant media. Measurements of the characteristic parameters using the ac modulation method are presented for point/plane electrodes in transformer oil. The measurements agree reasonably well with space charge free theory for infinite extent electrodes for which analytical expressions are available. We finally employ the `onion peeling' method to reconstruct the axisymmetric electric field magnitude and direction from the measured characteristic parameters and compare the results to the analytically obtained electric field