山西省农民家庭消费水平和结构分析

本文利用统计计量学方法对山西省农民家庭消费水平和消费结构的变化及原因进行了实证分析。建立了山西省农民人均消费的消费函数和山西省农民总消费支出与食品、衣着、住房、日用品、燃料及文化生活服务支出的关系模型，并通过模型分析解释了农民的消费结构，也为决策者提供一些有效的参考资料。     

浅析二阶齐次线性变系数微分方程的一个可积类型

本文讨论了二阶齐次线性变系数微分方程的特殊形式，给出了这种微分方程的一个可积类型．     

对一个力学碰撞问题的讨论

对普通物理力学中有关碰撞的一个问题,从恢复系数e的取值角度出发,进行了详细求解和讨论,得到了更完整的结果.     

ZnSe及ZnSe/GaAs异质结构中压力导致的直接禁带向间接禁带的转变

用经验赝势方法计算了体ZnSe以及ZnSe/GaAs单异质结系统中ZnSe外延层г、X、L等特殊对称点导带底能量随压力的变化。结果表明，同Si、Ge、GaAs等半导体材料不同，ZnSe的X点导带底具有正的压力系数，但比г点的压力系数小，这是ZnSe材料以及ZnSe基异质结构材料发生直接禁带向间接禁带的转变时所需转变压力较大的根本原因。研究了ZnSe/GaAs异质结构中晶格失配造成的应变对外延层г、X、L对称点压力系数的影响，表明这种晶格失配造成的应变可以极大地减小ZnSe外延层材料由直接禁带向间接禁带的转变压力。     

用毛细管测量纯水表面张力系数的误差讨论

通过用毛细管测量纯水表面张力系数实验，得到管内径d与接触角θ的相对误差之间的关系曲线，由此说明实验测得的表面张力系数α和理论公式相比呈现一定的偏差，并简单地讨论了实验的理想状态与实际情况的差别．     

Reference values for drag and lift of a two‐dimensional time‐dependent flow around a cylinder

This paper presents a numerical study of a two‐dimensional time‐dependent flow around a cylinder. Its main objective is to provide accurate reference values for the maximal drag and lift coefficient at the cylinder and for the pressure difference between the front and the back of the cylinder at the final time. In addition, the accuracy of these values obtained with different time stepping schemes and different finite element methods is studied. Copyright © 2004 John Wiley & Sons, Ltd.     

行波管内不连续性的简易模型分析

 根据行波管内微波信号在输能装置和切断衰减器处两个不连续性之间来回反射的物理现象，建立行波管输出段的简易网络串模型，并对行波管输出段传输特性参数的幅频特性、相频特性进行计算分析。结果表明：输能装置和切断衰减器的不连续性是造成幅相一致性行波管相位不可补偿的重要因素之一。     

Linear and Nonlinear Optical Properties Of Racemic (±)2-(α-Methylbenzylamino)-5-Nitropyridine Single Crystals

Linear and nonlinear optical properties of racemic (±)2-(α-methylbenzylamino)-5-nitropyridine ((±)MBANP) single crystals have been comprehensively investigated and compared with those of the enantiomorph (–)2-(α-methylbenzylamino)-5-nitropyridine ((–)MBANP) crystals. (±)MBANP crystal exhibits very high chemical and physical stability, but relatively small nonlinear optical coefficients (d₃₁ = 6.8 pm/V, d₃₂ = 4.7 pm/V, d₃₃ = 0.84 pm/V). A comparison between the nonlinear optical coefficients of (±)MBANP and (–)MBANP demonstrates the validity of the oriented-gas model in molecular crystals that neglects all the contributions from intermolecular interaction.     

Assessing the Error Probability of the Model Selection Test

The asymptotic error probability of Linhart's model selection test isevaluated, and compared with the nominal significance level. We examine thecase where the expected discrepancies of the candidate models from the truemodel are asymptotically equal. The local alternatives method is employed inthe limiting operation of the asymptotic evaluation. Although the errorprobability under the null hypothesis is actually shown to be equal to orless than the level for most situations, intolerable violations of the errorcontrol are observed for nested models: It is often erroneously concludedthat the smaller model is significantly better than the larger model. Toprevent this violation, a modification of Linhart's test statistic isproposed. The effectiveness of the proposed test is confirmed throughtheoretical analysis and numerical simulations.     

Mathematical modelling and analytical solution for workpiece temperature in grinding

This paper deals with modelling the workpiece temperature field produced during the grinding process. The proposed model is given in terms of a two-dimensional boundary-value problem where the interdependence among the grinding wheel, the workpiece and the coolant is described by two variable functions in the boundary condition. An explicit integral form solution is constructed using the Laplace and Fourier transforms and the Green’s function method.