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关键词： 非线性共轭梯度   三维反演   预处理   并行计算  

摘要： 本文改进并验证了大地电磁测深数据的三维反演算法和并行计算程序,程序对计算机物理内存和CPU速度及数量要求较低,使普通家用机进行三维反演计算成为可能.本文在Newman和Alumbaugh(2000)提出的三维非线性共轭梯度算法和Rodi和Mackie(2001)给出的大地电磁场二维NLCG反演预处理方法的基础上实现了大地电磁场NLCG三维反演算法,改进了的预处理方法,将反演计算对初始模型的依赖性降到最低,并且通过理论模型验证了程序的正确性,并根据日本KAYABE地区实测数据的反演结果验证了算法的实用性.

关键词： 电磁场分析   电力设备   软件   分析水平   参考价值  

摘要： 本文针对目前几种重要的电力设备电磁场分析软件的性能、应用及发展方向，进行了对比讨论，对提高电力设备电磁场分析水平，具有一定的参考价值。

关键词： 电磁场与电磁波   教学现状   教学改革  

摘要： 电磁场与电磁波课程是通信、电子类学科的专业基础课。近些年来,该程组教师积极从事《电磁场与电磁波》课程的教改活动,致力于将课程中复杂、晦涩的理论进行深入浅出的分析讲解,培养学生正确思维的方法。本文针对兰州交通大学精品课程评价体系,结合该课程实际情况,提出《电磁场与电磁波》精品课程教学模式建设的观点、看法,阐述了课程建设侧重与教材、综合实验、科研的建设。

关键词： 健康   技术产品   电磁场  

摘要： 有研究表明，手机、电脑：电视等现代技术产品，在给人们带来方便的同时，也会产生电磁场，进而辐射人体而损害健康。

关键词： direct chill casting   low frequency electromagnetic field   refinement   ZK60 magnesium alloy billets  

摘要： The low frequency electromagnetic field was applied during direct chill (DC) semi-continuous casting of the 2K60 magnesium alloy billets. Effects of low frequency electromagnetic field on surface quality, microstructure and hot-tearing tendency of 0500 mm ZK60 magnesium alloy billets were investigated. The results showed that with the application of the low frequency electromagnetic field, the surface quality of the ZK60 magnesium alloy billets is markedly improved and the depth of cold fold is decreased. The microstructure of the billets is also significantly refined. Besides, the distribution of the grain size is relatively uniform from the billet surface towards its center, where the average grain size is 42 μm at surface and 50 um at center. It also shows that the hot-tearing tendency of DC semi-continuous casting ZK60 magnesium alloy billets is significantly reduced under low frequency electromagnetic field. [ABSTRACT FROM AUTHOR]

关键词： 预条件   偏移Laplace   稀疏近似逆   电磁场  

摘要： 针对矢量有限元分析三维电磁问题得到的大型复对称且高度非正定的线性系统的求解,提出了一种新型预条件算法N-AINV,其构造是基于复偏移Laplace算子结合带主元补偿的AINV稀疏近似逆算法,该算法能改善系数矩阵特征谱并避免主元崩溃。数值结果表明,提出的新型预条件算法能获得比其它常规预条件法更稳定的求解,并同时有效提高求解效率,缩短仿真用时。

关键词： Four wave mixing   Fourier transforms   Interference   Optical fibers   Phase conjugation   Self phase modulation  

摘要： Current experimental investigations about time reversal (TR) electromagnetic (EM) fields always depended on TR mirror (TRM). However, EM fields can perform reversal operation invariance in four domains connected by Fourier Transform. A multiplication table and an appropriate operating figure about EM fields' invariance are derived to describe a series of dual combined operations in the four domains, in which there are at least 10 dual-combination operations different from current TRM operations which can equivalently actualize TR symmetry. Theoretically, centrosymmetric operations of spatial position vector and spatial spectrum vector may have the potential to promote different reversal mirrors.

关键词： Electromagnetic radiation   Energy transfer   Erbium doped fiber amplifiers   Finite difference time domain   Optical amplifiers   Optical materials  

摘要： A new algorithm based on auxiliary differential equation and finite difference time domain method (ADE-FDTD method) is presented to model a waveguide whose active layer is constituted of a silica matrix doped with rare-earth and silicon nanograins. The typical lifetime of rare-earth can be as large as some ms, whereas the electromagnetic field in a visible range and near-infrared is characterized by a period of the order of fs. Due to the large difference between these two characteristic times, the conventional ADE-FDTD method is not suited to treat such systems. A new algorithm is presented so that the steady state of rare earth and silicon nanograins electronic levels populations along with the electromagnetic field can be fully described. This algorithm is stable and applicable to a wide range of optical gain materials in which large differences of characteristic lifetimes are present. (C) 2013 Optical Society of America

关键词： 选频法   天然电场   地下水   电磁场  

摘要： 在实地探测的基础上,主要是从理论模型的角度研究天然电场选频法异常的形成原因。首先在已知的充水岩溶上开展实地探测工作,获取实测异常曲线;从麦克斯韦方程组和边界条件出发,求取均匀垂直谐变一次磁场中良导球体和圆柱体内、外磁场矢量位,推导出球外和圆柱体外感应二次电场的解析计算式;对理论模型的各个参数进行假定,计算获得地表主剖面上良导球体和圆柱体的感应二次电场异常曲线。通过实测曲线与理论模型上的模拟计算结果对比分析可知,二者曲线形态相似、特征相同,由此推知天然电场选频法在含水低阻体上方测得异常的起因之一可能是由天然感应二次电场所致。

关键词： 音圈电机   建模   电磁仿真   优化  

摘要： 本文提出了应用于半导体封装设备固晶机焊头的音圈电机建模与设计方法。音圈电机输出力与电场、磁场和机械结构成非线性关系。通常情况下,基于几何结构和所使用材料的导出磁密分布的建模技术是相当复杂的,特别是当磁轭材料存在孔洞时。所以本文基于机械结构和使用材料,提出通过使用电磁仿真软件COMSOL Multiphysics而发展的一种特殊的设计音圈电机的建模过程。一种迭代优化设计过程旨在使音圈电机在一定的容积下最大化其输出推力。仿真结果分析表明所提出音圈电机的设计方法是有效的,能为音圈电机的研制与测试提供良好的理论基础。