三维横观各向同性介质界面裂纹的边界积分方程方法

基于两相三维横观各向同性介质的基本解和Somigliana恒等式,对三维横观各向同性介质中的任意形状的平片界面裂纹,以裂纹面上的不连续位移为待求参量建立了超奇异积分_微分方程,界面平行于横观各向同性面.根据发散积分的有限部积分理论,应用积分方程方法研究得到裂纹前沿的位移和应力场的表达式、奇性指数以及应力强度因子的不连续位移表达式.在非震荡情形下,超奇异积分_微分方程退化为超奇异积分方程,与均匀介质的超奇异积分方程形式完全相同.     

Passive and active interior noise control of box structures using the structural intensity method

This paper presents passive and active vibro-acoustic noise control methods for attenuating the interior noise level in box structures which can be an analogy of cabins of vehicle and aircraft. The structural intensity (SI) approach is adopted to identify the predominant vibration panels and interior noise sources for box structures. In the study, the finite element method is used to determine the structural vibration and structural intensity in the box surfaces. According to structural intensity vectors plot and structural intensity stream lines presentation, the possible effective control positions where the dampers may be attached and the active control forces may act to reduce vibration and interior noise, are identified. From the study, it can be demonstrated that the structural intensity approach and stream line presentation are possible methods for identifying the vibro-acoustic interior noise source and predominant panels which may be modified to reduce the interior noise level. The structural intensity methodology, passive and active noise control results can be extended to the further study of the vibration and interior noise control of actual cabins of vehicles and aircraft.     

Sn+1(1)中的极小超曲面的等谱问题

设M为Sn 1(1)中紧致极小超面Mn1,n2= Sn1nn1×Sn2nn2 Sn 1(1)为Sn 1(1)中的Clifford极小超曲面如果Specp( M) =specp( Mn1,n2) ,Specq( M) =specq( Mn1,n2) ,其中0≤p 相似文献   

Dynamic fracture mechanics analysis for composite material with material non-homogeneity in thickness direction

The problem considered here is the response of a non-homogeneous composite material containing some cracks subjected to dynamic loading. It is assumed that the composite material is orthotropic and all the material properties depend only on the coordinatey (along the thickness direction). In the analysis, the elastic region is divided into a number of plies of infinite length. The material properties are taken to be constants for each ply. By utilizing the Laplace transform and Fourier transform technique, the general solutions for plies are derived. The singular integral equations of the entire elastic region are obtained and solved by the virtual displacement principle. Attention is focused on the time-dependent full field solutions of stress intensity factor(SIF) and strain energy release rate. As a numerical illustration, the dynamic stress intensity factor of a substrate/functionally graded film structure with two cracks under suddenly applied forces on cracks face are presented for various material non-homogeneity parameters.     

HT—6B托卡马克上的MHD扰动模式分析

利用磁探针对ＨＴ－６Ｂ托卡马克上的Ｍｉｒｎｏｖ扰动的大环模数进行了分辨，发现在一次放民过程中ｎ＝１，２，３，４，的模数同时存在，对各模的频谱分析表明，当扰动较小时，各模扰动具有同为２０ｋＨｚ的单一频率，当扰动增大时，各模在２０ｋＨｚ的基础上出现４０ｋＨｚ的倍频，倍频出现的合理解释是磁岛岛宽的振荡。     

基于无约束最优化理论解析溶液自由基EPR波谱的计算机算法

描述了一种基于无约束最优化理论，采用蒙特卡洛方法与非线性最小二乘法相结合的方法，对溶液自由基ＥＰＲ波谱进行解析的计算机算法。本算法对ＥＰＲ实验谱进行自动拟合，并给出较精确的解析结果，此程序已在我所最近研制的ＥＰＲ波谱仪通用ＰＣ微机数据系统中使用，获得较满意的效果。     

THE ESTIMATE AND MEASUREMENT OF TRANSVERSE WAVE INTENSITY

Transverse waves are a type of structural waves and should be considered in the analy-sis of high frequency vibration because the energy carried by transverse waves increases with the in-crease of frequency and becomes important at high frequencies. This paper studies the estimate theoryand measuring technique of the transverse wave intensity in two dimensional homogeneous structures.In general, the intensity vector is the sum of the effective intensity vector and the intensity variationvector. Each axial intensity component is proportional to two imaginary parts of cross spectral densitiesand its estimate is complicated. For the special case where transverse waves propagate in one direction,the intensity variation is zero and the estimate of the intensity is simplified. The intensity technique isformed based on the finite difference principle. Transverse wave intensity can be measured using a pairof two-transducer arrays lying in the orthogonal direction for the general case or a two-transducer ar-ray lying in the propagating direction for the special case. In order to assess the measurement accuracyof transverse wave intensity, the coupling loss factors from bending to transverse waves in buildingstructures were measured using the intensity technique and compared with the results predicted andmeasured using the conventional method. It is shown that the agreement between the results measuredusing the intensity technique and that by the conventional method is good.     

两片掺铒玻璃样品级联荧光光谱的实验研究

介绍一种掺铒玻璃样品的制作方法，实验测量了单片及两片掺铒玻璃样品的荧光特性.结果表明：两片掺铒玻璃样品级联的荧光强度比单片掺铒玻璃样品的荧光强度高，半值宽度与高浓度单片样品的半值宽度近似相等；在两片掺铒玻璃样品级联的形式中，浓度高的样品靠近抽运光源时的荧光强度比浓度低的样品靠近抽运光源时的荧光强度高；两种低浓度样品组合的荧光强度相对于其单片样品荧光强度的增幅比两种高浓度样品组合的荧光强度相对于其单片样品荧光强度的增幅要高. 关键词： 掺铒玻璃样品 级联 荧光光谱强度 半值宽度     

A comparison of the vectorial nonparaxial approach with Fresnel and Fraunhofer approximations

Based on the vectorial Rayleigh diffraction integrals, a nonparaxial propagation equation of vectorial plane waves diffracted at a circular aperture is derived. The nonparaxial far-field expression, Fresnel and Fraunhofer diffraction formulae are given and treated as special cases of our general expression. The theoretical formulation permits us to study and compare the transversal and axial intensity distributions of diffracted plane waves both analytically and numerically. Illustrative numerical examples are given. It is shown that the vectorial nonparaxial approach has to be used if the aperture size is comparable with or less than the wavelength, and the knowledge of both transversal and axial intensity distributions is required to provide a comprehensive comparison of the paraxial and nonparaxial results.