一种非超声波测声速的方法

介绍用简单器件在可闻声波范围内测量声速的方法,以及如何解决在实验过程中遇到的问题。     

一种高精度超声波声速自动测量仪

利用现代电子技术研制成功了脉冲式声速自动测量仪，它采用过零检测数字平均方法，声时测量精度达纳秒量级，可测绝对声速．本文着重介绍了仪器的原理结构，并给出了关键部分的详细电路．对固体及液体进行的若干实测结果表明，该声速仪不仅可用于实验室研究工作，更重要的是它在超声工业测量领域有广阔的推广应用价值．     

圆周运动加速度一种新的推导方法

主要从加速度的基本定义出发, 给出了一种新的推导方法, 用以推导圆周运动的加速度. 这种推导方法 紧扣加速度的基本定义, 浅显易懂, 有助于学生加深对加速度的理解     

测声速的一种新方法

本文介绍了利用听音乐的方式判断超声光栅衍射斑点最强位置的方法,进而准确地测量出超声波在光介质中的传播速度。     

一种测声速的新装置

声速的测定是物理学中一个基础实验, 就目前而言已有多种测定方法可以供我们选择, 本文中介绍一 种测声速的简单新装置, 本装置通过声波的反射、 叠加, 利用钢管中液体的振动来测定声音在液体中的传播速度, 该 实验操作简单, 实验仪器精度高, 可行性高, 可以在物理教学中推广使用     

推导平方反比有心力场中质点轨道的一种方法

根据动量定理和角动量定理，通过直角坐标系和平面极坐标系单位矢量的变换，给出了推导平方反比有心力场中轨道的一种新方法．     

高压下声速温度系数的一种新算法

 从声速的定义出发,由热力学基本关系给出了声速温度系数（偏微商）的一种计算方法,以顽火辉石为例,计算结果显示,在40～140 GPa压力范围内,其纵波、剪切波和体波的温度系数随压力的增大而逐渐减小,分别由40 GPa时的-0.386、-0.251、-0.255 m/(s·K)降至80 GPa时的-0.298、-0.188、-0.204 m/(s·K),120 GPa时的-0.244、-0.148、-0.175 m/(s·K)和140 GPa时的-0.197、-0.131、-0.162 m/(s·K)。将这一规律内推至零压得到(dK/dT)₀=-0.027 9 GPa·K^-1,与静高压下的实验值吻合很好。     

一种低声速沉积层海底参数声学反演方法

软泥底环境下沉积层参数的声学反演是国际水声领域的一个研究热点.浅海中,当高声速基底和海水之间存在一层低声速(小于海水声速)的沉积层时,小掠射角情况下不同频率声传播损失会出现周期性增大现象.基于此现象,提出一种适用于低声速沉积层的海底参数声学反演方法.首先,推导给出小掠射角情况下传播损失周期增大的频率间隔与沉积层声速、厚度及近海底海水声速之间的解析表达式;其次,利用一次黄海实验中软泥底环境下的宽带声传播信号,提取了小掠射角下传播损失增大的频率周期;再次,把该解析表达式作为约束条件,结合Hamilton密度与声速的经验公式,采用匹配场处理反演给出沉积层的声速、密度、厚度及基底的声速、密度;然后,利用声传播损失数据反演得到泥底环境下不同频率的声衰减系数,通过拟合发现泥底声衰减系数随频率近似呈线性关系;最后,给出了双层海底模型和半无限大海底模型等效性的讨论.反演结果为低声速沉积层海底声传播规律研究与应用提供了海底声学参数.     

高压下材料弹性声速的一种经验表达式

 将铝、铁、铜等七种材料弹性声速的实测数据进行分析处理发现，其弹性声速随压力的变化均可以用一下关系：ln c=A₀+A₁ln p+A₂ln²p，很好的拟合。拟合结果与实测值的相对误差小于5%。     

声速测量实验的探讨

对声速测量的共振干涉法中的相关问题进行了理论探讨,使学生对此实验的物理图像有更清楚的认识.     

A new derivation of the Silin-Severne-Balescu-Misguich equation

Using the projection-like technique for classical systems, a rederivation of the Silin-Severne-Balescu-Misguich equation is presented.I wish here to express my gratitude to Dr. J. uczka for his interest and valuable aid in the elaboration of this paper. The author is also indebted to the referee for remarks which permitted to improve the presentation.     

A new derivation of the photoelectric effect

A first order time dependent electronic wave function is obtained by summing contributing terms through complex integration in momentum space. The angular dependence of the current found from this wave function agrees exactly with known results for the surface effect, whereas the volume effect is found to be proportional to the second power of the penetration depth l.     

声速测量实验

介绍了2个有趣的测量声速的实验:在室内,采用驻波法结合电脑来测量声速;在室外,利用不同的传播途径结合电脑来测量声速.2个实验可以让学生直接参与实验操作,激发了学生学习的兴趣.     

A new derivation of surface waves in crystal

It is shown that the theory of grain boundaries developed by the present authors gives a new derivation of surface waves in crystal.     

A method for calculating the speed of sound in seawater

A method of calculating the salt concentrations in seawater from known ion concentrations is proposed. Data on the salt concentrations allow one to determine the values of the solvent activity a _s and the concentrations of binary solutions, each of which consists of the solvent and one of the dissolved components, as well as the properties of binary solutions corresponding to the value of a _s of a mixed solution. The use of the concentrations of binary solutions and their corresponding properties makes it possible to calculate the speed of sound in seawater by the formula for the speed of sound in a mixed solution. The deviation of the calculated sound speed value from the experimental one is relatively small.     

Causality and the speed of sound

A usual causal requirement on a viable theory of matter is that the speed of sound be at most the speed of light. In view of various recent papers querying this limit, the question is revisited here. We point to various issues confronting theories that violate the usual constraint.     

声速测量及声波的波动学规律研究

声速除了可利用共振干涉法和相位比较法测量外,还可以用干涉、衍射及“洛埃镜”反射等方法测量．声速实验的改进,不仅可扩展声速测量的方法,而且也可加深学生对波动学规律和本质的理解．     

A new derivation of loop amplitudes by direct integration

The multi-loop amplitude of the general dual-resonant model is derived rigorously from the N-reggeon vertex of Lovelace by direct integration. Methods for the direct integral, the inversion of a complicated matrix and the evaluation of its determinant are developed. The identification with Abelian integrals is straight forward and instructive. These methods will also be very helpful for more general dual-resonant models.     

Measuring the speed of sound of quintessence

Quintessence, a time-varying energy component that may account for the accelerated expansion of the universe, can be characterized by its equation of state and sound speed. In this paper, we show that if the quintessence density is at least 1% of the critical density at the surface of last scattering the cosmic microwave background anisotropy can distinguish between models whose sound speed is near the speed of light versus near zero, which could be useful in distinguishing competing candidates for dark energy.