伯努利定理适用条件分析

本文分析了以理想流体的运动微分方程推导伯努利定理时所利用的限制条件,对有势力作用下不可压缩流动的流场中应用伯努利定理的矢径微分量、速度、涡量之间的关系进行了深入讨论. 分析结果表明当流动为无旋流动或螺旋流时,伯努利常数在流场各点取相同值;伯努利常数在流涡面上各点取值相等,沿流线或涡线积分均为在流涡面上积分的特殊情况.     

一端外伸梁对称弯曲弹性位移的置换法确定

置换法应用于求解一端外伸梁,在对称弯曲的条件下,根据直梁挠曲线所在平面内其与切线所成图形的边角几何关系,推导出求解该形梁的挠度和转角的置换法位移方程,其变量是相应的置换梁自由端的挠度、梁长、梁轴线位置坐标等. 对具体载荷梁的求解过程是：先以具体量值填充左、右置换梁自由端的挠度,再将其代入该置换法位移方程的统一表达式,即得到所求梁段的挠度、转角的方程全解. 所用的计算为代数方程的分式四则运算,只需挠曲线和叠加原理概念,无需积分,一般无需查挠度表,结果精确. 给出工程背景的算例.     

低约束试件断裂韧性测试方法研究进展 1)

低约束试件断裂韧性测试对油气管道安全运营具有重要意义。本文回顾了低约束试件断裂韧性测试方法及发展过程,介绍了裂纹尖端张开位 移(crack tip opening displacement, CTOD)和J积分等常用断裂韧性表征参数,并对断裂韧性测试中应力强度因子、J积分塑性因子、J积分与CTOD转换因子、裂纹尺寸测量方法、数 字图像相关方法等关键问题进行对比分析,总结需要深入研究的问题,为低约束试件断裂韧性测试发展提供一定依据。     

TRANSIENT TORSIONAL WAVE IN FINITE HOLLOW CYLINDER WITH INITIAL AXIAL STRESS

An analytical solution is obtained for transient torsional vibration of a finite hollow cylinder with initial axial stress. The cylinder is subjected to dynamic shearing stress at the internal surface and is fixed at the external surface. The basic equations are presented and the solution is obtained by means of Fourier series expansion technique and the separation of variables method. The effects of the initial stress on the natural frequencies and transient torsional responses are presented and discussed.     

标准圆筒试验技术与数据处理方法研究

 对标准圆筒试验技术与数据处理方法进行了深入研究,在狭缝扫描实验中建立了新型、高效的照明技术、底片判读方法以及数据处理方法,得到了精度高、信息丰富的圆筒壁质点上的位移、速度、加速度和比动能结果。同时,通过VISAR技术直接测量了圆筒外表面径向膨胀速度-时间曲线,进而积分得到位移-时间曲线,与狭缝扫描结果相互印证和补充,进一步提高了测试可靠性。     

Some results on regularity in vector optimization

In this paper we suggest an approach to regularity in, vector optimization which extends the one given in [9]; some necessary or sufficient regularity conditions are given for a wide class of nondifferentiable vector optimization problems which embraces the convex ones.     

The efect of the couple stress parameter and Prandtl number on the transient natural convection flow over a vertical cylinder

An analysis is performed to study transient free convective boundary layer flow of a couple stress fluid over a vertical cylinder, in the absence of body couples. The solution of the time-dependent non-linear and coupled governing equations is carried out with the aid of an unconditionally stable Crank–Nicolson type of numerical scheme. Numerical results for the steady-state velocity, temperature as well as the time histories of the skin-friction coefcient and Nusselt number are presented graphically and discussed. It is seen that for all flow variables as the couple stress control parameter, Co, is amplified, the time required for reaching the temporal maximum increases but the steady-state decreases.     

Exact solution of functionally graded thick cylinder with finite length under longitudinally non-uniform pressure

Elastic analysis of a functionally graded thick-walled cylindrical pressure vessel is analytically studied in the present research. Gradation is considered for all mechanical properties along the thickness direction based on a power function. The constitutive relations are developed in the general cylindrical coordinate system for an axisymmetric pressurized cylinder. For simulation of these two deformation components, first order shear deformation theory is considered. The FG cylinder is subjected to longitudinally non-uniform pressure along the length of the cylinder. The present problem is applicable for simulation of non-uniform pressurized cylinder by fluids or gases.     

蒸发器支撑板板孔精密测量系统

建立了蒸发器支撑板板孔精密测量系统,并提出了基于边缘约束条件的轮廓参量测量方法.首先采用图像处理技术将待测目标转化为二维离散坐标点,计算其最小外接矩形并对轮廓进行预定位;然后将轮廓分割成相互重合的"扩展邻域轮廓",建立以曲率角为原则的边缘约束算法对各轮廓段精确定界,实现对轮廓参量的精密测量.实验和误差分析表明,该系统测量准确度优于0.02mm,对具有复杂轮廓的零件参量测量有参考价值.     

Optimality theory for semi-infinite linear programming ∗

This paper presents an exhaustive approach to optimality theory in semi-infinite linear programming, placing a special emphasis on generality. After surveying optimality conditions for general problems, a detailed analysis is made of problems in which the coefficients are continuous functions of a parameter which varies on a compact set, adopting a feasible directions approach. Lastly, the case of analytical coefficients over an interval is considered in some detail.