并联电容器型式试验或耐久性试验的合格有效性覆盖

并联电容器设计参数的改变是否需要重新对产品进行型式试验或耐久性试验,一般认为应重新试验,但不是绝对的,文章以2膜产品改变为3膜产品为例,从标准规定和试验结果分析方面论证,得出设计参数仅从2膜改为3膜在总厚不变条件下不需再进行型式试验或耐久性试验,具体情况,具体对待。

Singularity-free Green's function for EM sources embedded in a stratified medium

We present a method to unify the calculation of Green＇s functions for an electromagnetic（EM） transmitting source embedded in a homogeneous stratified medium.A virtual interface parallel to layer interfaces is introduced through the source location.The potentials for Green＇s function are derived by decomposing the partial wave solutions to Helmholtz＇s equations into upward and downward within boundaries.The amplitudes of the potentials in each stratum are obtained recursively from the initial amplitudes at the source level.The initial amplitudes are derived by coupling with the transmitting sources and following the discontinuity of the tangential electric and magnetic fields at the source interface.Only the initial terms are related to the transmitting sources and thus need to be modified for different transmitters,whereas the kernel connected with the stratified media stays unchanged.Hence,the present method can be easily applied to EM transmitting sources with little modification.The application of the proposed method to the marine controlled-source electromagnetic method（MCSEM） demonstrates its simplicity and flexibility.

Effects of negative index medium defect layers on the transmission properties of one-dimensional photonic crystal

The photonic band gap structure of 1D photonic crystal with a negative index medium defect layer is studied by using the transfer matrix method. Investigations show that the introdufion of negative index medium defect layer and the increase of the negative index value will result in an extension of the band gap. Moreover, by increasing the negative index, the width of defect layer and the numbers of period photonic crystal, the width of defect modes will be narrowed, which is advantaged to obtain optical filters with narrow band. Finally, the effects of absorption on the properties of band gap and on defect modes have been discussed.

2-D elastic wave modeling with frequency-space 25-point finite-difference operators

Numerical simulation in the frequency-space domain has inherent advantages, such as： it is possible to simulate wave propagation from multiple sources simultaneously; there are no cumulative errors; only the interesting frequencies can be selected; and it is more suitable for wave propagation in viscoelastic media. The only obstacle to using the method is the requirement of huge computer storage. We extend the compressed format for storing the coefficient matrix. It can reduce the required computer storage dramatically. We get the optimal coefficients by least-squares method to suppress the numerical dispersion and adopt the perfectly matched layer （PML） boundary conditions to eliminate the artificial boundary reflections. Using larger grid intervals decreases computer storage requirements and provides high computational efficiency. Numerical experiments demonstrate that these means are economic and effective, providing a good basis for elastic wave imaging and inversion.

NUMERICAL SIMULATION OF ATTENUATION OF LOVE-TYPE CHANNEL WAVES IN VISCOELASTIC MEDIA

Proceeding from wave equations, the paper strictly deduced the dispersion relation equation of Love-type channel waves in Standard Linear Solid model. The e quation is a complex one with its real part signifying the dispersion characteristics of the channel wave while the imaginary part, the attenuation characteristics. In calcu lating the attenuation value, the author has set up a mathematical model of a horizon tal symmetric sequence (a three layer sequence of rock-coal-rock), given out some physical parametersl and adopted the dichotomy method that is more of ten used in root resolving of an equatlon. The calculation indicates that the influence of non-elas tic absorption on the attenuation of the propagation of channel wave varies with the frequency. In the frequency band of the Airy phase, the attenuation increases steep like, which is unfavorable for the channel wave seismic prospecting. The study of channel wave attenuation has provided a theoretical basis for the compensation of at tenuation.

Simultaneous Exact Controllability of Wave Sound Propagations in Multilayer Media

In this work we study one problem of mathematical interest for their applications in several topics in Applied Science. We study simultaneous controllability of a pair of systems which model the evolution of sound in a compressible flow considered as a transmission problem. We show the well posed of the problem. Furthermore provided appropriate conditions in the geometry of the domain are valid and suitable assumptions on the fluid, is possible to conduce the pair of systems to the equilibrium in a simultaneous way using only one control.

Seismic Waves in Layered Media

This paper is organized as follows. After a discussion of the differential equations for wave propagation in the horizontally stratified medium and of the initial and boundary conditions, the displacements are derived on the free surface of the layered medium for plane waves when a point source is located on the s-th imaginary boundary at the depth -s （physical parameters of the layers s and （s ＋ 1） are put to be identical）. Then, the source will be represented as a single force of arbitrary orientation and a general moment tensor point source. Further, ＂a primary field＂ for a point source will be introduced. Matrix method for the solution of the direct seismic problem is considered based on the matrix method of Thomson-Haskell and its modifications.

Magnetohydrodynamic Effect on Free Convection of Three Dimensional Laminar Flow in Porous Annulus

A numerical study has been carried out to investigate heat transfer by free convection under the effect of MHD （magnetohydrodynamic） for steady state three-dimensional laminar flow in horizontal and vertical cylindrical annulus filled with saturated porous media （sand silica） with fins attached to the inner cylinder. A single electric coil placed around the inner cylinder to generate a magnetic field. The governing equations which used are continuity, momentum （using Darcy＇s law） and energy equations which are transformed to dimensionless equations. The finite difference approach is used to obtain all the computational results using Fortran 90 program. The parameters affected on the system are Rayleigh number ranging within （102 ~ Ra＊ 〈 104）, and MHD （Mn） （0 〈_ Mn 〈_ 100） and radius ratio Rr （0.225, 0.338 and 0.435）. The results obtained are presented graphically in the form of streamline and isotherm contour plots and the results show that heat transfer decrease with the increase of magnetohydrodynamic. It was found that the average Nusselt number increase with Ra＊ and decrease with H~ Mn and Rr. A correlation for the average Nusselt number in terms of Ra＊ and Mn, has been developed for the inner cylinder.

Atomic layer deposited high-k Hf_xAl_(1-x)O as an alternative gate dielectric for 4H-SiC MIS based transistors

HfxAl(1-x)O film grown by atomic layer deposition(ALD) on n-type 4H-SiC(0001) epitaxial layer has been studied.Measurements show that it has relatively high breakdown electric field of 16.4 MV/cm,high dielectric constant of 16.3 and low gate leakage current of 2.47×10-5 A/cm2 at E=5 MV/cm,which makes ALD HfxAl(1-x)O a great potential candidate gate dielectric for 4H-SiC MIS based transistors.

Fast integral equation solver for Maxwell's equations in layered media with FMM for Bessel functions

The paper presents a new fast integral equation solver for Maxwell＇s equations in 3-D layered media. First, the spectral domain dyadic Green＇s function is derived, and the 0-th and the 1-st order Hankel transforms or Sommerfeld-type integrals are used to recover all components of the dyadic Green＇s function in real space. The Hankel transforms are performed with the adaptive generalized Gaussian quadrature points and window functions to minimize the computational cost. Subsequently, a fast integral equation solver with O（N2zNxNy log（NzNy）） in layered media is developed by rewriting the layered media integral operator in terms of Hankel transforms and using the new fast multipole method for the n-th order Bessel function in 2-D. Computational cost and parallel efficiency of the new algorithm are presented.

Comment on “A numerical investigation of the acoustic mode waves in a deviated borehole penetrating a transversely isotropic formation”

In the paper"A numerical investigation of the acoustic mode waves in a deviated borehole penetrating a transversely isotropic formation"by Liu et al.[1]numerical experiments are reported for a dipole sonic logging scenario with a deviated borehole penetrating a VTI anisotropic medium.In such a situation it is important to clearly define the meaning of group and phase velocities as this has led to much confusion in the literature as discussed by Miller,Horne and Walsh[2].