低频声音在水雾中衰减的测量

一.引言 低频声音在霧气中的衰减的测量可以在充霧的混响室中行之,但是这种测定方法只限制在一些分立的低频率——即相当于混响室的低简正振动方式。为了使这种测量能够在较广的连续频程中进行,作者採取了阻抗管的驻波分析方     

自相似声压驱动下气泡的振动

单泡声致发光来自于气泡经过缓慢膨胀之后的急剧塌缩的过程,而这种急剧塌缩是高阶谐波振动的结果。基于线性叠加的思想,提出了自相似驱动的概念,即用与半径振动相似的声压来驱动气泡。数值模拟表明,自相似驱动声压能够有效地加剧气泡的塌缩过程。与正弦驱动比较,包含基波和二次谐波的自相似驱动显著地提高光辐射强度。这为多频最优化驱动提升发光强度提供了一个直观的物理图景,也给出了一种可用于实验的提升声致发光的方法。     

不均匀等离子体中孤子的反射与透射

用一种新的方法从理论上研究了非均匀等离子体中孤子在不连续点处的反射与透射波.在低阶近似条件下，反射波与透射波均可由KdV方程来描述，并给出了低阶近似情况下，当入射波为单孤子时，反射孤子与透射孤子的个数及其大小. 关键词：     

听觉模拟的语音增强方法

本文通过分析听觉系统的信号提取方法，提出了适合于信号提取的动态多阈值的概念，并以此提出了实现语音增强的方法。实验结果表明，与传统的语音增强方法相比，听觉模拟的语音增强方法有更好的增强效果。     

Experimental Observation of Kink in a Perfect Bidimensional Granular System

The kink formation in a vertical vibrated granular layer has been widely studied in three-dimensional systems, but there are few if any experimental reports on bidimensional granular layers. We report the kink formation newly found in a perfect bidimensional granular system. We measure the range of the driving frequencies and dimensionless accelerations for kinks. Furthermore, we observe a heaping process, which is caused by co-operative action of the kink-associated convection and the sidewall=associated convection.     

汉语的平均频谱:应用现场和实验室语噪声测量的结果

语言是一个物理现象。从物理的角度来研究语言的工作有着多方面的内容,其中最主要的一项是语音能谱的分析——包括各个音素的频谱分析和整个语言的平均频谱分析。所谓“平均”频谱,就是人们日常谈话时声压按频率的统计分布。它是设计传送语言的系统(电话、广播、电影录音等)时很重要的参考资料。本文所述的是测量汉语中的普通话和上海方言平均频谱的结果。测量时采取的是分析语噪声的方式,包括在万人以上的大会中的现场测量和在消声窒中的测量。语噪声方式比别的方式有着一定的优越性。文中列出了普通话和沪语的平均谱曲线,并将汉语(普通话)与     

扫描激光探针检测声脉压线声场

本文讨论了晶体表面存在金属线条时的声光相互作用理论,改进了原来的激光探针测量系统,新的系统能够对弱表面波声场进行成像,实验上,还对制作在YZ-LiNbO_3晶体上的声表面波脉压线声场进行了测试,并对结果进行分析和讨论。     

在液氮及水中声次谐波的实验观察

在液氮及水中进行了有限振幅声波的实验,观察到了次谐波分岔现象,得出了分岔谱。 关键词：     

PARTICULAR SOLITONS IN NONLINEAR LATTICE

One soliton of particle velocity and its amplitude (maximum particle velocity of one soliton) in Toda lattice is given analytically. It has also been known numerically that the maximum particle velocity (when the collision of two solitons reaches their maximum, we define V_n at this time as its maximum particle velocity) during the collision of two solitons moving in the same direction is equal to the difference between the amplitudes of two solitons if the difference is large enough; however, the maximum particle velocity is equal to the adding up of the amplitudes of two solitons moving in the opposite directions. The relationship between the maximum value of e^-(r_n)-1 and their initial amplitude of e^-(r_n)-1 is also given analytically in Toda lattice if the amplitudes of the two solitons are the same and their moving directions are opposite. Compared with the Boussinesq equation, there are differences between the Toda lattice equation and the Boussinesq equation for solitons during the collision.     

NONLINEAR WAVES PROPAGATING IN AN INHOMOGENEOUS BLOOD VESSEL

A model for describing blood pressure propagation wave in artery is proposed. Considering blood viscosity, slowly varying arterial parameters and arterial bifurcations, we obtain the dynamical equation of blood flow. We show that the blood viscosity attenuate the nonlinear blood wave amplitude mainly in small artery. On the other hand, the variation of arterial parameters (such as radius and Young's modulus) amplify the amplitude of the nonlinear blood wave in large arteries. We also investigate how the nonlinear blood wave (or a soliton) is reflected and transmitted at the arterial bifurcations. It can be concluded that the parameters at the bifurcation determine whether there is substantial reflection or not, but the transmission in each bifurcation is approximately the same as the incident wave.