Numerical modeling of frequency influence on the electromagnetic stirring of semiconductor melts

Alternating magnetic fields can be used in order to increase the level of convection and to mix the doped semiconductor alloys. A numerical analysis of the electromagnetic induced convection in GaInSb semiconductor melts is performed by using the software package CrysVUn. The magnetic field parameters are varied in order to obtain a maximum efficiency of the induced convection with a minimum quantity of the heat released in the melt. The influence of the electrical current frequency on the convection intensity is analyzed for samples with various radii (R = 0.5 – 3cm). Numerical procedure is validated by comparing the numerical results obtained in mercury samples with the experimental data given from the literature, which show a maximum stirring for a magnetic skin depth δ = 0.2R , in the case of a mercury sample with the radius R = 10 cm. This maximum corresponds to a shielding parameter R _ω = 40. Our numerical results show that the value of the shielding parameter for which the convection intensity reaches the maximum depends on the sample radius and increases when the sample radius increases. The results of this analysis are important in the case of samples with small radius, when a good mixing of the melt can be obtained for frequencies much lower than those corresponding to a shielding parameter R_ω = 40. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Propagation of electromagnetic wave in the three phases soil media

IntroductionItisofparamountimportancetogetgeotechnicalparameterssuchasmoisture ,compactness,andshearstrengthforgeotechnicalengineeringtransaction .Butthemethodtofetchthesoilsamplesforlaboratorytestcannotavoidbringingthedisturbance ,andmakethetestresultsinconsistenttotheactualstatusofsoil.Inrecentyears,theapplicationofEMwaveinthedetectinghiddentroublesindamsandundergroundfoundationsdevelopedrapidly .Buttherearestillsomefactorsthatrestricttheadvanceofapplication .Firstly ,thesoilconstitutesthr…     

Wave shaping through finite electromagnetic bandgap structure

Transmission mechanisms and wave steering under localized feeding conditions through a finite electromagnetic bandgap structure are investigated both experimentally and theoretically. The artificial propagating medium consists of a two-dimensional metallic wire structure dimensioned for millimetre wave operation. By analogy with electron propagation in semiconductor heterostructures, the signatures of ‘modal‘ and ‘fluid‘ propagation regimes are experimentally demonstrated. Data are then analysed through electric field patterns calculated by means of a three-dimensional solver of Maxwell‘s equations.     

菲涅耳公式的几何图示与应用

电磁波通过两种透明介质的分界面时,反射波、折射波和入射波的电矢量分量的大小和方向之间的关系可由菲涅耳公式说明,作通过分析和推导,给出了菲涅耳公式的几何图示,这使得在分析光学问题时,谱得简单和直观。     

微机在LC电磁振荡演示中的应用

介绍一种通过微机实时采集数据演示LC电磁振荡的方法,给出了接口电路及应用软件。     

圆棒介质波导的电磁波传播特性

通过简单的数学分析,推导圆棒介质波导的导模传播条件及特征方程,讨论电磁波在圆棒介质波导中的传播特性。     

光纤中的电磁对偶变换与导波的模式分析

讨论了麦克斯韦方程在各向同性均匀电介质中的电磁对偶变换不变性,定义了电磁混合比,求出了对偶场的充要条件.把上述不变性和充要条件应用于阶跃光纤,分析其导波模式,证明在非轴对称情况下,阶跃光纤中不存在具有色散的受导简正模.存在的解只有临界折射模(n=n₂时的特解).求出了它的分立频谱.受导简正模只存在于轴对称情况中.以上结论与实验事实不矛盾,并由此解释了基模的特性 关键词： 光纤光学 光波导 电磁对偶变换 受导波     

电子线路多级过电压保护电路的分析

本文基于电子线路的多级过电压保护装置的设计原则,提出了把低通滤波器件和限幅器件组合在一起的组合防雷系统,并采用电磁暂态计算程序EMTP分析了低虎波器元件参数对保护性能的影响和其幅频特性。同时,本文还提出了过电压冲击自动报警与计数系统设计的可行性方案。     

Rigorous electromagnetic analysis of resonant sub-wavelength metallic gratings by parametric Fourier modal method

Electromagnetic TM modes of metallic lamellar reflection or transmission gratings are analyzed by means of the parametric fourier modal method. We show that the resonant optical response of such devices is due to the excitation of guided waves inside the slits. Our rigorous methods allows us to define a resonance condition number and to calculate the field everywhere inside the grating layer.