The pointwise estimates to solutions for 1-dimensional linear thermoelastic system with second sound

In this paper, we study the thermoelastic system with second sound in one space variable. The mathematical model is a hyperbolic partial differential system with damping term which brings about some parabolic properties. The pointwise estimates of the solution are obtained and from which the generalized Huygens' principle is shown. Our approach is based on detailed analysis on the Green function of the system.     

吉林球粒陨石（H5）的高压声速实验研究

 叙述了以透明材料作窗口，用辐射法测量吉林陨石的高压声速的原理、实验技术和实验结果，实验压力范围为42.2~113.2 GPa，得到了吉林陨石的高压声速随冲击压力的变化关系，并由此判断出吉林陨石在约65 GPa时发生相变。     

Ultrasonic parameters of concentric laminated uric acid stones

Recently a new idea for the disintegration of urinary calculi based upon the large difference of the acoustic impedance inside urinary calculi was suggested. This large difference of acoustical impedance between the two main components of kidney stones, is confirmed in this paper for smooth laminated uric acid stones by two different experimental techniques measuring sound velocities: a surface contact and a submersion technique. Our measured values correlate well with the large differences of the earlier reported measured sound velocities. In general, the disintegration of a urinary stone can be described as follows: a urinary calculus is an inhomogeneous geometrical structure, and its structure plays an important role in the disintegration process.     

Experiments with narrow movable beams of pulsed sound waves at 35 GHz

Only the study of absorption and angular dependent scattering of GHz and THz sound can give us detailed information about interaction processes of acoustical phonons. Therefore, the necessary techniques of sound generation, detection and undisturbed transmission to the target must be improved or to a large extent must still be developed. Corresponding attempts at 35 GHz are described. Sound-beam topography allowed to study crystal defects and also showed us where transmission without scattering occurred. For the piezoelectric generation a reflex klystron was used feeding a planar Hertzian resonator. The needle-like sound beams appeared as a double beam, each showing a minimum diameter of 35 μm for longitudinal polarized sound at an acoustic wavelength of 165 nm in X-cut quartz and 320 nm in a-cut sapphire. To obtain the smallest possible beam diameter for high resolution work, model calculations are presented for an excited fundamental Gaussian sound beam in an isotropic medium.     

黄土层内的声波传播衰减

通过对声波在黄土层内传播的实验研究，本文分析了黄土介质中声波传播的强烈衰耗特性，得出了声波的衰减，这可为浅层地下声探设备的研制提供依据，黄土的声学特性依赖于其结构形状等多种因素而有所不同，而我们的实验环境和所获数据有限，因而我们的研究结果只是该问题的一个特例。     

材料吸声的单值评价和分级方法──ISO/CD11654简介

本文根据吸声评价的国际标准初稿，介绍了从实测的１／３倍频带吸声系数确定吸声性能单值表示的评价方法，以及利用这些单值评价对吸声材料进行分级的方法。     

利用多普勒效应测定声速

本介绍了一种利用超声波的多普勒效应和拍现象简单有效的测量声速的方法。     

Ultralight porous metals: From fundamentals to applications

Over the past few years a number of low cost metallic foams have been produced and used as the core of sandwich panels and net shaped parts. The main aim is to develop lightweight structures which are stiff, strong, able to absorb large amount of energy and cheap for application in the transport and construction industries. For example, the firewall between the engine and passenger compartment of an automobile must have adequate mechanical strength, good energy and sound absorbing properties, and adequate fire retardance. Metal foams provide all of these features, and are under serious consideration for this applications by a number of automobile manufacturers (e.g., BMW and Audi). Additional specialized applications for foam-cored sandwich panels range from heat sinks for electronic devices to crash barriers for automobiles, from the construction panels in lifts on aircraft carriers to the luggage containers of aircraft, from sound proofing walls along railway tracks and highways to acoustic absorbers in lean premixed combustion chambers. But there is a problem. Before metallic foams can find a widespread application, their basic properties must be measured, and ideally modeled as a function of microstructural details, in order to be included in a design. This work aims at reviewing the recent progress and presenting some new results on fundamental research regarding the micromechanical origins of the mechanical, thermal, and acoustic properties of metallic foams. The project supported by the U.S. Office of Naval Research (ONR/ONRIFO grant number N000140110271), the U.K. Engineering and Physical Sciences Research Council (EPSRC grant number EJA/U83), and the Chinese State Key Lab. Foundation of Xi'an Jiaotong University     

头部尺寸对虚拟声像定位的影响

本利用立体声像的相关理论分析方法，分析了用扬声器重发虚拟声时，倾听的头部尺寸对声像定位的影响。结果表明,当实际倾听的头部尺寸与虚拟声信号处理所用头部模型的尺寸有差别时，前方范围内的声像位置畸变较小，但侧向的声像位置畸变较大，因而本特别指出，倾听头部尺寸的不同是虚拟声重发时侧向的声像位置畸变的重要原因，声像定位实验证实了理论分析。     

对5通路3/2环绕声系统缺陷的分析

本文利用环绕声重发的声像定位理论，对一种受到重视、很可能将被国际上广泛应用的通用环绕声系统—5通路3／2系统的声像特性进行了分析，并对系统进行了声像定位实验．理论和实验结果表明，按目前的信号馈给方式，系统可在倾听者前方产生稳定而明晰的声像；但在侧向和后方只能产生模糊和不稳定的声像（扬声器方向除外）；将别是在侧向，存在着一个声像的死区，并且对侧向和后方声像来说，听音区域片不宽阔，因而作为一种通用的系统，虽然将其用作伴随图像的重发时，可获得较好的效果；但用作不伴随图像的重发时，系统并不能很好地再观原声场的空间感。由于系统存在这种不容忽视的缺陷，文中着重强调应设法在这方面对系统加以改进