微波/电热板组合消解-电感耦合等离子体质谱(ICP-MS)法测定土壤中重金属元素

为提高土壤检测的重金属得率,采用了微波消解/电热板组合预处理-电感耦合等离子体质谱法(ICP-MS)测定土壤重金属含量。分析了硝酸(HNO3)、氢氟酸(HF)、高氯酸(HClO4)和盐酸(HCl)组合消解液及赶酸温度对土壤预处理影响。结果显示：在硝酸和盐酸混合消解液中,硝酸占比越高,铬(Cr)、钴(Co)、铜(Cu)、镉(Cd)得率更高;消解液体系中加入氢氟酸可使消解更加彻底,提高铬与铜的得率。最优预处理消解条件为硝酸 6ml+ 氢氟酸 2ml消解液组合进行微波消解,1ml 高氯酸于155℃电热板上赶酸。经土壤标准样品GBW07401(GSS-1)和GBW07452(GSS-23)实际应用,预处理条件优化后测试准确度和稳定性均显著提高。此外使用元素铑(Rh)作为内标物时,其方法稳定性和准确性高于内标物钪(Sc)和锗(Ge)。可为相关国家土壤重金属测定标准的修制订提供方法学参考。     

Nonlinear thickness-shear vibration of an infinite piezoelectric plate with flexoelectricity based on the method of multiple scales

This paper presents a nonlinear thickness-shear vibration model for onedimensional infinite piezoelectric plate with flexoelectricity and geometric nonlinearity. The constitutive equations with flexoelectricity and governing equations are derived from the Gibbs energy density function and variational principle. The displacement adopted here is assumed to be antisymmetric through the thickness due to the thickness-shear vibration mode. Only the shear strain gradient through the thickness is considered in the present model. With geometric nonlinearity, the governing equations are converted into differential equations as the function of time by the Galerkin method. The method of multiple scales is employed to obtain the solution to the nonlinear governing equation with first order approximation. Numerical results show that the nonlinear thickness-shear vibration of piezoelectric plate is size dependent, and the flexoelectric effect has significant influence on the nonlinear thickness-shear vibration frequencies of micro-size thin plates. The geometric nonlinearity also affects the thickness-shear vibration frequencies greatly. The results show that flexoelectricity and geometric nonlinearity cannot be ignored in design of accurate high-frequency piezoelectric devices.     

基于声子晶体带隙特性的薄板减振设计

基于平面波展开法和薄板振动方程,计算了薄板型声子晶体的带隙和减振特性,通过与有限元软件的计算结果验证带隙计算的正确性,并进一步讨论了散射体几何形状及填充率、弹性模量比、密度比等对薄板型声子晶体带隙特性和减振的影响.结果表明正多边形散射体随边数的减小,第一带隙宽度逐渐增加,正方形散射体薄板减振效果明显.填充率对声子晶体带隙特性的影响不是线性的.随散射体基体弹性模量比数量级增大,第一带隙趋于低频,宽度降低.散射体基体弹性模量比较大时,密度比越大,第一带隙宽度越大,对应的薄板结构减振特性越好.     

石英晶体板非线性高频振动的拓展伽辽金法分析

针对考虑几何和材料非线性的石英晶体板厚度剪切振动和弯曲振动的方程组,利用扩展伽辽金法对该方程组进行转化和求解,分别获得了强烈耦合的厚度剪切振动模态和弯曲振动模态的频率响应关系,绘制了不同振幅比和不同驱动电压影响下的频率响应曲线图。数值计算结果表明可以选取石英晶片的最佳长厚比尺寸来避免两种模态的强烈耦合。驱动电压的变化将引起石英晶体谐振器厚度剪切振动频率的明显改变,必须将振动频率的漂移值控制在常用压电声波器件的允许值之内。扩展伽辽金法对石英晶体板非线性振动方程组的求解为非线性有限元分析和偏场效应分析奠定了基础。     

基于均匀化理论的多孔板弯曲问题新解

由于订型分布孔的存在,通常的有限元法不能有效地分析多孔板的弯曲问题。该文基于均匀化理论建立了该类问题的新解法。对含密集型分布的阶梯型圆孔板的分析结果,说明了该文方法是有效的。     

New solution system for circular sector plate bending and its application

Instead of the biharmonic type equation, a set of new governing equations and solving method for circular sector plate bending is presented based on the analogy between plate bending and plane elasticity problems. So the Hamiltonian system can also be applied to plate bending problems by introducing bending moment functions. The new method presents the analytical solutions for the circular sector plate. The results show that the new method is effective. Project supported by National Natural Science Foundation (No. 19732020) and the Doctoral Research Foundation of China.     

正交各向异性厚板的边界元解法

本文利用 Hormander 算子法和平面波分解法导出了计入剪切变形的正交各向异性厚板的基本解。建立了计入剪切变形的正交各向异性厚板的边界积分方程。文中详细地讨论了基本解的数值计算,并用边界元法分析了一些算例。     

阶梯式矩形板的振动

用奇异函数建立阶梯式矩形板自由振动和强迫振动的微分方程并求得其通解，用Ｗ算子给出振型函数的表达式及常见支承条件下板的频率方程，本文解可用于多种边界条件的板。     

Elastoplastic Analysis with Limited Plastic Deformations and Displacements*

ABSTRACT

This paper presents solution methods for elastoplastic and shakedown analysis of linearly elastic, perfectly plastic bodies for which the conventional classical formulations of these problems are completed by constraints on overall plastic deformation and elastoplastic displacement. The methods are described in terms of nonlinear mathematical programming and provide solutions when the plastic reserves of the body are not fully exhausted, and the plastic performance and the plastic deformations are controlled. Application of the method is illustrated by an example.