Analysis of the Shielding Characteristics of Saturable Ferromagnetic Cable Shields

A numerical technique is developed that may be used to analyze the shielding characteristics of a cable with a saturable ferromagnetic outer sheath in an intense low-frequency environment. The solution relates the center conductor current to the total current exciting a coaxial cable with a ferromagnetic sheath. Several examples are given to illustrate how saturation effects the shielding properties of a ferromagnetic sheath.     

Design of Shielded Cables Using Saturable Ferromagnetic Materials

Previously, a numerical solution was evolved that may be used to analyze the effect of material saturation on the low frequency shielding characteristics of a thin ferromagnetic cable shield. Numerical solutions are difficult to employ in design problems and so a simplified theory has also been developed. This supplemental theory, described here, yields simple equations useful in the design of ferromagnetic cable shields to provide protection against some anticipated intense low frequency environment.     

Development of ferromagnetic semiconductors for applications in spin electronics: State and outlook

The state and outlook of works on the creation of ferromagnetic semiconductor materials for applications in spin electronics and informatics units are considered. The obtained results on promising ferromagnetic semiconductor material classes??doped elementary semiconductors, A^IIIB^V compounds, and semiconductor oxides??are given. Unsolved problems in the considered area are indicated and possible ways of their solutions are outlined.     

Three-dimensional-simulation of arc motion between arc runners including the influence of ferromagnetic material

The behavior of the moving electric arc in low-voltage switching devices is determined by the complex interactions of magnetic forces, current flow, gas flow, heat conduction, and radiation. In this paper three-dimensional simulations of arc motion between parallel arc runners are presented, which consider all these interactions. These simulations are carried out with a computational fluid dynamics (CFD) finite volume code. Based on earlier simulations by Frank Karetta the magnetic field, expressed as vector potential formulation, is now treated by the same type of general transport equations as the other processes, which allows the direct implementation into the CFD package used. This enables one to include the effect of ferromagnetic material in the arc chamber, such as ferromagnetic flux concentrators or steel splitter plates. Typical simulation examples are presented for different design details.     

Diffraction by a terminated semi-infinite parallel-plate waveguidewith three-layer material loading

The plane wave diffraction by a terminated semi-infinite parallel-plate waveguide with three-layer material loading is rigorously analyzed for E polarization using the Wiener-Hopf technique. Introducing the Fourier transform for the scattered field and applying boundary conditions in the transform domain, the problem is formulated in terms of the simultaneous Wiener-Hopf equations, which are solved via the factorization and decomposition procedure. The scattered field is evaluated by taking the inverse Fourier transform and applying the saddle point method. Representative numerical examples of the radar cross section (RCS) are given for various physical parameters and the backscattering characteristics are discussed in detail. Some comparisons with a high-frequency technique are also given to validate the present method     

A numerical method for transient analysis of coupled antennas

A numerical method for finding the transient response induced on coupled thin cylindrical antennas excited by an electromagnetic pulse (EMP) is introduced. Numerical examples are given for two coupled thin antenna that are broadside incident by an idealized EMP. Applications of the method are made to calculate the induced currents on corner reflector antennas, and numerical examples are given to illustrate how the transient responses are modified by coupling effects. Examples of applying the method to include the effects of the time-varying medium on the responses are also shown with an assumed time-varying air conductivity.     

Moment method with isoparametric elements for three-dimensionalanisotropic scatterers

A new method for computing the frequency-domain electromagnetic fields scattered from, and penetrating into, arbitrarily shaped, three-dimensional, lossy, inhomogeneous anisotropic scatterers is presented. The method is based on a general volume integro-differential formulation of the scattering problem, and consists of the numerical solution of the coupled integral equations by the moment method and point matching. A particularly powerful feature of this method is that the numerical model of the scatterer is obtained by parametric volume elements and the basis functions used to represent the field within each element are the same used in the finite-element method. Element integration problems due to the singular kernel of the integral equations are treated in some detail. Numerical results for both the isotropic and the anisotropic spherical scatterer are presented, including comparisons with results obtained by different numerical methods for the isotropic cases considered. The capability of the numerical code presented here to deal with cases where the material parameters of the scatterer are given by singular matrices is discussed for two particular examples     

New method for determining the permeability tensor of magnetizedferrites in a wide frequency range

To provide a broadband method for measuring the complex permeability tensor components of magnetized ferrites we have realized a nonreciprocal rectangular waveguide cell. A network analyzer setup is used to measure the scattering parameters of the cell over a wide range of frequencies. The nonreciprocity of the cell permits the determination of the permeability tensor components in a single experimental phase. Complex permittivity and complex components of the permeability tensor are computed from a data-processing program, taking into account higher order modes excited at the cell discontinuities and using a numerical optimization procedure to match calculated and measured values of the S-parameters. We have studied the convergence of the calculated S-parameters as the number of modes taken into account in the calculations. Sensitivity to the input parameters for the optimization algorithm is discussed. A thru-reflect-line calibration in conjunction with a specific sample holder is used to eliminate systematic errors inherent in the S-parameter measurements. Measured complex permeability tensor components data for microwave ferrites are presented at X-band frequencies (8-12 GHz). Experimental results are in good agreement with theoretical results given by the ferromagnetic material theory     

Synthesis of general impurity profiles using a two-step diffusion process

By optimizing selected characteristics, the performance of modern semiconductor devices and integrated circuits could be improved if it were possible to control the impurity profile in given regions of the material. However, present methods used for fabricating planar devices by diffusion techniques invariably produce profiles which are approximately either Gaussian or complementary error functions. The purpose of this paper is to demonstrate the feasibility of obtaining a general impurity profile in semiconductor material compatible with the two-step diffusion process. The general boundary value problem for the two-step diffusion process is solved and the impurity concentration in the solid is determined as a function of the impurity concentration of the carrier gas in the diffusion tube. An optimization routine using linear programming techniques is developed which, for a given diffusion time, determines the necessary control function producing a best-fit approximation to the desired impurity profile. The optimum control functions governing the diffusion of boron in silicon for two examples are synthesized. The numerical results clearly indicate that a best-fit approximation to a given impurity profile can be realized by controlling the impurity concentration in the carrier gas during the gaseous phase of a two-step diffusion process.     

Rigorous Numerical Solution to Complex Transcendental Equations

The Kuhn algorithm is introduced firstly and the numerical methods for resolving the complex transcendental equations in the electromagnetic theory are researched. The numerical examples are given to confirm the validity and efficiency of the numerical methods.     

电磁理论中复超越方程的数值解法研究

简要介绍Ｋｕｈｎ法，并以多个数值计算实例研究如何应用Ｋｕｈｎ法来解决电磁场与微波领域中遇到的复超越方程的数值求解问题。     

Characteristic lengths for steady-state transport in illuminated,intrinsic a-Si:H

The steady-state transport equations are solved for a general small-signal case. This solution leads to the spatial distribution of the carriers in the bulk of undoped hydrogenated amorphous silicon (a-Si:H) under illumination. The general small-signal differential equations for electrons and holes, including a local and/or external electric field, are first established. Subsequently, the analysis is restricted to the case with a negligible external electric field. Two characteristic lengths appear in the analytical solution. They are interpreted for the lifetime regime as the ambipolar diffusion length and the dielectric relaxation length. Depending on the material parameters, one or the other of these lengths dominates the transport. Illustrative numerical examples for typical solar-cell-quality a-Si:H are given     

Distribution of a random walk with an application to a truncated nonparametric sequential test

Explicit expressions for the probability of reaching a given position at each stage of a random walk are derived for the case of absorbing boundaries. Utilizing these results, exact expressions for the power function and the average sample number function of a truncated nonparametric sequential test are obtained. Some numerical examples are also given.     

Force on current coils moving over a conducting sheet with application to magnetic levitation

The use of Fourier-transform techniques provides exact integral expressions for the forces on polygonal dc current coils moving over a conducting sheet. These expressions are applied to investigate magnetic levitation of proposed high-speed transportation. Extensive numerical data have been analyzed to determine the performance dependence of the system parameters such as velocity, coil shape, array configuration, clearance, and track thickness, conductivity and permeability. In terms of potential applications, a comparison between the superconducting repulsive and ferromagnetic attractive systems is given.     

Active microwave imaging of inhomogeneous bodies

A numerical method and experimental technique for microwave imaging of inhomogenous bodies is presented. This method is based on the interpretation of the diffraction phenomena and leads to tomographic reconstruction of the body under investigation. Various numerical examples are given on spatial impulse response, recognition of dielectric rods, inhomogeneous bodies, and simulated human arm. Different experimental results on dielectric rods and isolated animal organs are also given.     

铁磁性基体与金属线阵列复合体系的双负材料特性

基于铁磁性基体与金属线阵列复合结构等效电磁参数的长波近似模型,设计了一种应用铁磁性基体的二维双负材料。根据带有介质包裹层的金属线的散射特性,采取多重散射方法计算了铁磁性基体与金属线阵列复合结构的传输谱;还通过全波仿真提取了单元结构的等效电磁参数。这些数值结果与长波近似模型的理论结果取得了很好的一致,确认了该模型的正确性。通过仿真周期复合体系中的电磁场分布,在所设计的双负频带内观察到了反向波现象,进一步验证了所设计的复合体系的双负特性。     

Analysis of fin-line structure containing magnetised ferrite slab smaller than height of waveguide

An analysis has been carried out for a fin-line structure containing a small ferrite slab magnetised parallel to its broad side. The method is based on a mode-matching procedure and leads to an infinite set of homogeneous linear equations which is used for numerical solution. Convergence of the propagation constant is shown by numerical examples. Computed dispersion diagrams are given and compared with those of other authors.     

A probe antenna for in situ measurement of the complex dielectricconstant of materials

A new probe for the in situ measurement of the complex dielectric constant of materials in the microwave frequency region is described. The probe uses two stub antennas mounted on a cylinder. The cylinder is inserted in the material and the transmission coefficient between the two antennas is measured. By comparing this signal with that predicted from a numerical model of the probe obtained by the finite-difference time-domain (FDTD) method we can determine the dielectric constant of the material. The measurement setup and numerical model of the probe are described and several measurement examples in natural and artificial media are presented     

CONFORMAL TRANSFORMATION SOLUTION FOR THE ATTENUATION CONSTANT OF TEM TRANSMISSION LINES

The conformal transformation solution is presented for the attenuation constant ofTEM transmission lines which can be mapped into the coaxial or the parallel plate lines by certainconformal transformations including the numerical ones.The analytic and numerical results ofsome examples are also given.