Prediction of the acoustic behavior of a parallel assembly of hollow cylinders

In this paper, an approach to predict the sound absorption coefficient and sound transmission loss of a parallel assembly of hollow cylinders is presented. This approach is based on image processing and the Parallel Transfer Matrix Method (PTMM) using four Johnson–Champoux–Allard effective fluids. First, effective parameters of each fluid are identified using geometrical considerations and numerical simulations. Then, the approach is validated for a stack of uniform plastic straws, and used to model a natural stack of non-uniform switchgrass straws. Finally, two parametric studies are conducted to evaluate the effects of the geometric parameters of the straws on the acoustic behavior of their stack. It is shown that there are optimal parameters that maximize the acoustic behavior at specific frequencies.     

基于哈德曼-夏克传感器测量眼镜片像差的方法

哈德曼-夏克传感器(Hartmann-Shack Sensor,HSS)是一种测量波前像差的仪器。提出了一种利用4F系统实现光瞳衔接,与哈德曼-夏克传感器相结合测量眼镜片的光焦度和像差分布情况的方法。阐述了该系统的工作原理,研究了哈德曼-夏克传感器所得到的检测值与实际被测光学系统的光焦度与像差之间的转换关系。考虑到人眼实际观察不同方向物体时视轴是在不断变化的,采用多光轴测量眼镜片的方法。实现了利用哈德曼-夏克传感器对于眼镜片的光焦度和像差进行精密测量。     

有变高度圆柱干扰的平板表面流谱拓扑结构

采用分区方法和Roe三阶流通量差分分裂格式数值求解雷诺平均N-S方程,湍流附加粘性系数由修正的Baldwin-Lomax模型计算,数值模拟了高超声速绕变高度圆柱流动,进而根据拓扑学理论给出了有变高度圆柱干扰的平板表面流谱拓扑结构,并结合对称截面流谱进行了简要的分析与探讨,指出了需要进一步深入研究的问题。     

The solution of integral equations with strongly singular kernels applied to the torsion of cracked circular cylinder

In this paper,the functions of warping displacement interruption defined on the crack lines are taken for the fundamental unknown functions.The torsion problem of cracked circular cylinder is reduced to solving a system of integral equations with strongly singular kernels.Using the numerical method of these equations,the torsional rigidities and the stress intensity factors are calculated to solve the torsion problem of circular cylinder with star-type and other different types of cracks.The numerical results are satisfactory.     

The generalized variational principles about blending energy form of non-linear elasticity

First of all, this paper gives Legendre transformation for the so-called partial corresponding variables of strain energy function Σ(E_ij) and complementary strain energy function Σc(S_ij) of the elastic materiel, and introduces the corresponding blending complementary strain energy function Σch_k! and blending strain energy function Σh_k!. Moreover, a series of generalized variational principles of the corresponding blending energy form of non-linear elasticity is given. As a special case, there exist corresponding results[1] in linear elasticity.     

无解的模糊关系方程的最优近似解

对无解的模糊关系方程给出了最优近似解的定义,证明了最优近似解的存在性,给出了求最优近似解的算法     

圆柱绕流三维不稳定性的低维Galerkin法分析

利用低维Ｇａｌｅｒｋｉｎ方法及Ｆｌｏｑｕｅｔ稳定性分析理论,计算分析了圆柱绕流的三维线性不稳定性．分析中构造了能较好描述尾迹区流动的周向基函数,建立了完备的合理的基函数组,改进了计算机算法．结果证实圆柱二维周期流对展向小扰动为不稳定的,正确地预计了出现三维长波不稳定性的临界雷诺数Ｒｅｃ＝１９０;扰动展向波长为λｃ一３．６ｄ．对雷诺数Ｒｅ为１８０,１９０两种工况下的圆柱三维绕流流场的计算进一步证实了这种流动的整体不稳定性．本文所预计的临界值比Ｎｏａｃｋ等人的结果更为精确,与Ｂａｒｋｌｅｙ等人的ＤＮＳ解一致,与Ｗｉｌｌｉａｍｓｏｎ的实验相符．     

The perturbation parameter in the problem of large deflection of clamped circular plates

In the problems of large deflection of clamped circular plates under uniformly distributed loads, various perturbation parameters relating to load, deflection, slope of deflection, membrane force, etc, are studied. For a general perturbation parameter, the variational principle is used for the solution of such a problem. The applicable range of these perturbation parameters are studied in detail. In the case of uniformly loaded plate, perturbation parameter relating to central deflection seems to be the best among all others. The method of determination of perturbation solution by means of variational principle can be used to treat a variety of problems, including the large deflection problems under combine loads. This paper is completed under the guidance of Prof. Chien Wei-zang.     

Stress concentration and stress intensity factors fop an infinite plane with several rows of elliptic holes and cracks

This paper deals with the stress concentration in plane with swveral arbitrarily distributed elliptic holes. By using the functions of complex variables, the stress functions in which the interactions of neighbouring holes are taken into consideration can be constructed. By applying the conformed mapping method to satisfy the boundary conditions of each hole, the governing equations can then be transformed into a set of simultaneous equations through boundary integrals. Moreover, the problems with crack can be derived by changing the elliptical rates of the ellipses, thereby an approximate solution of cracking problem may be obtained. Some computing examples are given in the paper.     

受限薄膜中不对称两嵌段共聚高分子的微相形态

用强分凝理论方法研究了组分不对称(f≈0.25)的两嵌段共聚高分子在受限薄膜中的微相形态--层状相、平行柱状相和垂直柱状相.发现对中性基底,无论薄膜厚度为多少,垂直柱状相总是最稳定的相;而对亲少数相的基底,嵌段高分子的平均组成以及基底和两嵌段之间的相互作用能对薄膜体系的相行为有决定性影响.随着薄膜厚度的增加,层状相(包括奇数和偶数层数)、平行柱状相和垂直柱状相都有可能交替出现.