Size dependence of the thermo-electrodynamics states of composite high-Tc superconductors and its effect on the current instability conditions

The effect of transverse geometries of the slab of composite high-T_c superconductors on their stable and unstable thermal and electrodynamics transient states in the incomplete and complete penetration modes during the current charging are discussed. The transient period when the electric field that is induced by the charged current becomes more homogeneous during the initial stage of the complete penetration mode in the sub-critical voltage range is studied. In the over-critical voltage range, the cross-section shape of the slab affects its stable and unstable temperature variation. As a result, the current instability condition is not identical for high-T_c superconducting composite tapes that have the same cross-sectional area with various shapes of the cross-section. The condition depends on their thickness: the less thickness, the more stable the current distribution in the composite superconductors with the same cross-sectional area. This feature is a result of the unavoidable reduction of the current-carrying capacity of a high-T_c superconducting composite by the temperature increase. This reduction is caused by the relevant temperature dependence of electrodynamics states of the composite. This temperature dependence happens even during a stable stage of the current charging. These mechanisms must be considered during experiments at which the critical or quenching currents are defined.     

A model of peasant labor in China

Nowadays in the rural areas of China, peasants can make their own choices to go to the city for a new job or stay in the rural area. A decision is made based on working ability and the information a peasant gets. A multivariate evolutionary model of this problem is established and the numerical simulation shows that going to the city brings about a rise in the peasants’ income, and also that such a rise, as well as the number of peasants going to the city, is influenced by the capacity of the cities and income gap between agricultural and non-agricultural industries.     

导电媒质中圆柱天线电流分布及地电参数对绝缘天线特征量的影响

本文给出了导电媒质中裸圆柱天线和绝缘圆柱天线的电流分布。通过数值计算,分析研究了地电参数对圆柱绝缘天线的电流分布和天线特性阻抗的影响,所得结果对工程应用有一定意义。     

Bitter型环向场线圈电流分布的研究

本文简述了用数值方法研究Ｂｉｔｔｅｒ型环向场线圈中电流分布情况，给出了不同时刻线圈中电流分布的形式以及线圈电感、电阻随时间的变化，也对电磁力的分布作了分析。     

D形截面环流器中的磁面及LHCD的研究

本文利用环形系统的Ｇｒａｄ－Ｓｈａｆｒａｎｏｖ方程得到了Ｄ形截面的托卡马克磁面位形，并利用射线追踪技术研究了Ｄ形磁面位形下低杂波的运动形态。定性地研究了Ｄ形磁面位形下利用低杂波驱动电流的可行性，优化地给出了驱动电流的最佳方式。     

Selective lumping finite element method for nearshore current

A finite element method for the analysis of nearshore current, which is one of the principal currents in coastal seas, is presented in this paper. Because the nearshore current is induced by the variable distribution of the surface waves, it is necessary to analyse two main characteristics of the wave, i.e. direction and height. The current can be computed using the resulting wave characteristics. The present method makes it possible to employ procedures for which the same methods of solution are applicable for all basic equations of wave direction, height and current flow. The linear interpolation function is used for the discretization of spatial variables and a selective lumping two step explicit scheme is employed for the numerical integration in time. The numerical solutions obtained are compared with analytical, experimental and observed ones. From these comparative studies, it is concluded that the present finite element method provide a useful tool for the analysis of nearshore current.     

Intrinsic surface binding energy shifts in Yb metal

We report on the four-peak structure observed in the region of 4f photoemission in Yb metal, using synchrotron radiation in the energy range 70–200 eV. We conclude, contrary to previous reports, that the doublet associated with surface emissions results from an intrinsic surface shift on clean regions of the surface. We also demonstrate that the observed structure is consistent with earlier XPS measurements, and we set an upper limit on the width of the bulk peaks.     

Determination of electron density in an atomic plasma by least-squares fit to the Stark profile

The measurement of electron density by a unique, one-parameter least-squares fit to the Stark-broadened hydrogen emission line is presented. The curve-fit approach utilizes approximately 60–80 points, and provides improved precision in the measurement.A comparison of data obtained by measurement of the width at half-height and by least-squares analysis indicates that the half-width method exhibits substantial systematic errors, generally over-estimating electron density by a factor of 2–3.     

General considerations of numerical stability and accuracy in inviscid,compressible flow calculations employing primitive variables

The numerical stability of a number of computation schemes currently used for three-dimensional, inviscid, compressible flow is analysed using one-dimensional Fourier analysis. Whereas Reference 1 analysed schemes which were modified to render them amenable to simple analysis, the present work analyses the stability of schemes as actually used by Highton,³ Ahrabian,¹ Denton² and Spalding.⁶ The use of current values of the variables as they become available is shown to bring a general improvement to stability margin. The manner of damping introduced by the time marching formulation is shown to be deleterious to modifications which reduce truncation error. Staggered grid schemes can be formulated to second order accuracy with better stability margin than the corresponding first order scheme. While unstaggered grid schemes can be formulated to second order error and remain stable, their stability margin becomes very small. Agreement of the theory with numerical experiments continues to be of a high order for both one and three-dimensional disturbances.     

我院公共体育课程现状分析与思考

比较分节了我院公共体育课程教学与《全国普通高等学校体育课程教学指导纲要》对高校体育课程教学的要求之间存在的差距,阐述了这些差距存在的原因,提出缩小差距、深化我院公共体育课程教学改革的基本思路。