拱形波导中电磁波传播特性的分析

用有限元方法研究了拱形波导中的电磁场问题,根据计算结果,分析了UHF电磁波衰减常数随波导横截面尺寸、相对介电常数、电导率和工作频率的变化规律.     

基于有限元方法的运动磁体电磁场的计算

由于导体与磁体发生相对运动,会在导体中激发出电动势。假如在同等情况下撤去导体,即磁体相对周围空间发生相对运动,运动磁体必然引起周围磁场的变化,从而激发出电场。麦克斯韦方程组是求解电磁场问题的基本依据,而有限元方法凭借其自身特点广泛应用于电磁场计算仿真中。本文在麦克斯韦方程组的基础上,推导出应用于运动磁体电磁场的理论模型,利用有限元软件ANSYS对磁体电磁场进行仿真计算,并对结果进行了详尽的分析。     

非惯性系中非轻质弹簧的弹性力分布

应用圆柱形弹簧的劲度系数公式和胡克定律,导出非惯性系中形变前后非轻质静止弹簧上同一点相对于弹簧固定端的距离关系式,给出弹簧非均匀形变的数学表述,推导非惯性系中静止弹簧形变量与弹簧两端所受外力的关系式和弹簧上任意处弹性力的计算公式,讨论非惯性系中非轻质静止弹簧形变后的弹性力分布问题.     

二维动画中图层相对运动的计算与应用——以一点透视的等物距运动为例

图层相对运动原理是二维动画设计的重要基础理论,对图层相对运动和一点透视的等物距运动进行阐述,明确二维动画中图层相对运动的重要作用。利用摄像机成像原理和几何学,以一点透视的等物距运动为例,对二维动画中图层相对运动的重要参数进行计算,并推导其计算公式。图层相对运动的计算原理和影响因素既是计算公式的理论基础,也决定了其适用的范围。通过典型的水平跟拍镜头实例,分析制作过程,并应用计算公式分别对图层相对运动速度、相对位移距离,以及各图层总画幅的尺寸进行了演示计算。总结了定量计算与其它因素结合的要点,为今后的二维动画创作提供一定的参考。     

有限元-边界元法计算电磁响应

提出了用有限元-边界元法计算三维电磁场感应问题. 首先阐述了棱边单元法的基本性质, 并且根据基函数的几何平面特性推导出对于任意位置面的表面棱边单元法基本公式, 然后用棱边单元法离散数学模型. 用此方法模拟地下金属军事目标的电磁响应, 计算了目标的最低谐振频率及表面电流密度, 和单一目标的频率特性及位移特性, 计算结果和实验结果一致, 因此这种数值方法对计算三维电磁场问题行之有效.     

"圆的周长"教学设计及反思

一、教学圆的周长计算方法与应用 二、教学目的： 1.使学生理解圆周率的意义,推导出圆周长的计算公式,并能正确地进行简单的计算。 2.培养学生的观察、比较、分析、综合及动手操作能力。     

电磁场边值关系的形式及其独立性分析

电磁场边值关系是麦克斯韦方程组的另一种形式,对于解决实际电磁场问题十分有效.从电磁场边值关系的物理起源入手,详细地阐述了不同介质分界面上电磁场边值关系式的推导过程及其表达式,并对各自的独立性进行了讨论.     

钢筋混凝土圆形截面受弯构件正截面强度计算方法

探讨了钢筋混凝土圆形截面受弯构件正截面非均匀配筋的计算方法,推导了有关计算公式,并应用MathCAD软件进行了计算.与现行<混凝土结构设计规范>公式计算结果进行对比分析,该计算方法具有明显的经济效益.     

炸药反应率的理论分析和数值计算

依据爆轰建立过程的唯一迹线原理,结合三个守恒方程及状态方程.推导了炸药在冲击栽荷下起爆的一系列关系式及计算公式,编制了计算炸药起爆率的程序.计算分析中,采用了JWL状态方程描述未反应炸药及其爆轰产物,应用梯度迭代法求解了非线性方程组,获得了合理的炸药起爆率数据.研究表明,唯一迹线原理是描述炸药爆轰建立过程的一种有效方法.     

外包钢-混凝土组合梁正截面极限抗弯承载力的试验研究

基于外包钢混凝土组合梁的试验研究和塑性理论,按照钢梁和混凝土塑性中和轴相对位置的不同,分别推导了完全剪切连接和部分剪切连接的外包钢混凝土组合梁的正截面极限抗弯承载力的计算公式,并对外包钢混凝土组合梁进行了非线性有限元分析,分析中重点考虑了材料非线性和接触非线性.8根完全剪切连接和3根部分剪切连接试件的正截面极限抗弯承载力的计算结果及有限元分析结果与试验结果吻合良好.     

A new energy harvester using a piezoelectric and suspension electromagnetic mechanism

This study presents a new design of a piezoelectric-electromagnetic energy harvester to enlarge the frequency bandwidth and obtain a larger energy output. This harvester consists of a primary piezoelectric energy harvesting device, in which a suspension electromagnetic component is added. A coupling mathematical model of the two independent energy harvesting techniques was established. Numerical results show that the piezoelectric-electromagnetic energy harvester has three times the bandwidth and higher power output in comparison with the corresponding stand-alone, single harvesting mode devices. The finite element models of the piezoelectric and electromagnetic systems were developed, respectively. A finite element analysis was performed. Experiments were carried out to verify the validity of the numerical simulation and the finite element results. It shows that the power output and the peak frequency obtained from the numerical analysis and the finite element simulation are in good agreement with the experimental results. This study provides a promising method to broaden the frequency bandwidth and in- crease the energy harvesting power output for energy harvesters.     

利用复合网格进行电磁场分析

本描述了对有需要看重分析的局部区域的电磁场进行有限元分析的复合网格法．这种方法基于通常的有限元方法，有总体分析，局部分析和修正后的总体分析3个基本步骤．在前2步中，利用较粗的网格进行总体分析，得到节点的电势，将其作为后续进一步分析的局部区域的人工边界条件．将这些有了边界条件的局部区域用更精细的网格进行分析，得到更为精确的电势与密度分布．在第3步中，进行修正后的总体分析，通过迭代不断改进结果，直到满足给定的求解精度，得到更好的电势与密度分布的结果．数值实验表明，与通常的有限元方法相比，复合网格法在得到同样求解精度的结果时所耗的计算时间要少得多．     

Design and analysis of the hybrid excitation rail eddy brake system of high-speed trains

Compared to the current eddy braking patterns using a single magnetic source, hybrid excitation rail eddy brakes have many advantages, such as controllability, energy saving, and various operating models. Considering the large braking power consumption of the high-speed train, a hybrid excitation rail eddy brake system, which is based on the principle of electromagnetic field, is proposed to fulfill the needs of safety and reliability. Then the working processes of the mechanical lifting system and electromagnetic system are demonstrated. With the electromagnetic system analyzed using the finite element method, the factors such as speed, air gap, and exciting current have influences on the braking force and attractive force. At last, the structure optimization of the brake system is discussed.     

3D Magnetic Field Computation of a Permanent MagnetDisc-Type Generator Using Scalar Potential Method

The three-dimensional magnetic field of a permanent magnet (PM) disc-type generator is analyzed by the scalar potential method. In the analysis the permanent magnets are taken as magnetic charges. Hexahedron element meshes are automatically generated by a pre-processing program developed by the authors. The flux density is computed by a 3D scalar potential method program. Based on the finite element analysis the induced emf, current, armature reaction effects and electromagnetic torque of the disc machine are all calculated.     

工程车辆驾驶室声学特性预测研究

建立某型工程车辆驾驶室的结构有限元模型、空腔声学有限元模型。对驾驶室结构和室内空腔声场进行模态分析,得到结构振动特性和声学特性。计算分析驾驶室声-结构耦合模型在特定频率激励下的噪声分布情况,同时考虑吸声材料对驾驶员耳旁声压级值的影响,总结出在新车型开发阶段进行车内噪声预测和控制研究的有效方法。     

基于Ansoft的自动门用永磁无刷直流电机的设计和分析

对用于自动门控制系统的永磁无刷直流电动机,采用基于等效磁路法的RMxprt软件和基于电磁场有限元分析法的Maxwell软件对样机进行设计、分析和计算,并用＂场路结合＂的设计思路,完成了一台12槽/8极无刷直流电机的电磁设计任务。     

The finite element method magnetics (FEMM) freeware package: May it serve as an educational tool in teaching electromagnetics?

Finite Element Method Magnetics (FEMM) is an open source finite element analysis software package for solving electromagnetic problems. The program addresses 2D planar and 3D axisymmetric linear and nonlinear harmonic low frequency magnetic and magnetostatic problems and linear electrostatic problems. It is a simple, accurate, and low computational cost freeware product, popular in science and engineering. However its educational value has been underestimated. Use of the package in education is quite rare. The aim of this paper is to explore the capability of FEMM to meet as a complementary tool the needs of teaching electromagnetics in higher education. In order to demonstrate its use and exhibit the aid it offers in the teaching of electromagnetics illustrative examples are given. Evaluations in both qualitative and quantitative data have also been conducted and presented. Useful conclusions about its usage and potential applications in the teaching of electromagnetics in higher education are finally drawn.     

表面磁钢永磁无刷电机电磁转矩的解析法分析

With the air gap magnetic field distribution of surface mounted permanent magnet （PM） motors obtained using an analytical technique, the instantaneous electromagnetic torque and its corresponding components are investigated with the Maxwell stress tensor method. Accurate results can easily be achieved using the proposed method without using the tedious finite element analysis （FEA）. In this paper, the electromagnetic torque of a surface mounted PM motor with two phases energized is decomposed into four torque components. This technique is useful not only for the design and optimization of the permanent magnet motor, but also for the choice of control strategy.     

表面磁钢永磁无刷电机电磁转矩的解析法分析

With the air gap magnetic field distribution of surface mounted permanent magnet (PM) motors obtained using an analytical technique, the instantaneous electromagnetic torque and its corresponding components are investigated with the Maxwell stress tensor method. Accurate results can easily be achieved using the proposed method without using the tedious finite element analysis (FEA). In this paper, the electromagnetic torque of a surface mounted PM motor with two phases energized is decomposed into four torque components. This technique is useful not only for the design and optimization of the permanent magnet motor, but also for the choice of control strategy.