航天器中精密器件布局的保结构优化

航天器中精密器件的稳定性和工作精度决定于器件布置位置的局部结构振动特性,而航天器局部振动特性又受到精密器件布局的影响.因此,航天器中精密器件的布局优化是确保其稳定高效工作的前提条件.该文建立了粘接精密器件的航天器局部柔性薄板结构的动力学模型,发展保结构分析方法模拟了薄板结构的局部振动特性.考虑精密器件形状和尺寸、散热间...     

二维气体动力学中压差方程的特征分解和简单波

利用直接的方法讨论了在自相似平面上气体动力学中二维压差方程的特征分解理论,得到了压强P和特征值A±的特征分解.进一步地,若流动来自常状态,还可得到速度（u,v）的特征分解.由此,可以得到与常状态流动相邻的流动是简单波,并说明了简单波的流动区域是被一族直线所覆盖,且沿着每条直线, （P,u,v）为常数.     

Riemann problem for a geometrical optics system

The paper solves analytically the Riemann problem for a nonstrictly hyperbolic system of conservation laws arising in geometrical optics,in which the flux contains the nonconvex function possessing an infinite number of inflection points.Firstly,the generalized Rankine–Hugoniot relations and entropy condition of delta shock waves and left(right)-contact delta shock waves are proposed and clarified.Secondly,with the help of the convex hull,seven kinds of structures of Riemann solutions are obtained.The solutions fall into three broad categories with a series of geometric structures involving simultaneously contact discontinuities,vacuums and delta shock waves.Finally,numerical experiments confirm the theoretical analysis.     

Globally Hyperbolic Regularization of Grad's Moment System

In this paper, we propose a globally hyperbolic regularization to the general Grad's moment system in multidimensional spaces. Systems with moments up to an arbitrary order are studied. The characteristic speeds of the regularized moment system can be analytically given and depend only on the macroscopic velocity and the temperature. The structure of the eigenvalues and eigenvectors of the coefficient matrix is fully clarified. The regularization together with the properties of the resulting moment systems is consistent with the simple one‐dimensional case discussed in ¹. In addition, all characteristic waves are proven to be genuinely nonlinear or linearly degenerate, and the studies on the properties of rarefaction waves, contact discontinuities, and shock waves are included. © 2014 Wiley Periodicals, Inc.     

非线性Kirchhoff型波动方程全局吸引子的存在性

非线性Kirchhoff型波动方程描述了竖直方向上的波动.利用近似FaedoGalerkin的方法通过先验估计和一种新的验证紧性的方法(条件C)讨论了这类波动方程强解的全局吸引子.     

考虑非傅立叶效应的瞬态导热过程的波动响应分析

瞬态导热分析需要考虑非傅立叶效应.通过对抛物型及双曲型热传导方程,以及耦合热传导方程后的波动方程的数值求解,研究了非傅立叶效应下导热过程中的波动响应.结果表明,双曲型热传导过程具有明显的波动特性,所引起的波动响应前沿值成倍提高,且呈现显著的跃变行为,而波动峰值外的部位围绕着初始值小幅波动.     

基于Gristensen算法的砂岩储层横波速度计算方法

由于横波测量成本高,大部分油田测井资料中仅有少部分横波数据,则依据常规测井资料准确构建横波曲线已成为关键.考虑到横波构建理论方法更多地依赖实验室分析资料,提出在Gristensen经验公式基础上,以研究区横波测量曲线为约束,通过优化反演确立公式系数是一种好的研究思路.优化方法实现中采用阻尼型高斯牛顿法,保障了多参数优化迭代的收敛性和精度.将研究方法用于卫星油田横波数据构建中,取得好的计算结果.     

On the stability of two new two-step explicit methods for the numerical integration of second order initial value problem on a variable mesh

We present two novel two-step explicit methods for the numerical solution of the second order initial value problem on a variable mesh. In the case of a constant mesh the method is superstable in the sense of Chawla (1985). Numerical experimentation is provided to verify the stability analysis.