多普勒效应测量声速实验的设计

介绍了设计性实验"多普勒效应测量声速."该实验要求学生理解多普勒效应测量声速的原理,利用气垫导轨实验和声速的测定实验仪器,设计出一套多普勒效应测量声速的实验装置,并利用该实验装置测量声速.     

超声多普勒效应测量声速实验设计

利用多普勒效应来测量声速是大学物理中的一个重要的实验。本文介绍了设计性实验"超声多普勒效应测量声速",利用多普勒效应综合实验仪,设计出一套超声多普勒效应测量声速的实验装置,并利用该实验装置测量声速。     

爱因斯坦-德哈斯实验的现代设计

提出并设计了基于爱因斯坦-德哈斯实验的多功能教学实验装置。该实验装置集成了角度传感和磁滞回线测量模块,能够在验证爱因斯坦-德哈斯实验的基础上,进一步测量磁性材料的磁化曲线和磁滞回线。经过实验测试,该装置可以实现教学实验功能,进一步的应用开发可为精密实验测量提供可行的教学科研设备。     

基于霍尔效应直流电表的设计与制作

基于安培环路定理和霍尔效应,设计制作了一种电流测量装置.该装置利用线性霍尔元件,提供了一种间接测量电流的方法,并对0～20A的直流电流进行了实验验证.实验结果表明：该装置的测量精度满足测量要求.     

一种改进激光偏振主动成像的建模及理论分析

提出一种改进激光偏振主动成像的实验方法,给出实验装置原理图,详细分析实验装置的成像原理。在分析目标Mueller矩阵测量方法的基础上,给出改进后激光偏振成像装置偏振度和强度的计算公式,从理论上证明了该方法的可行性。然后针对实验仪器的要求分析了实验装置存在的误差,以及Cassegrain望远镜对目标散射光的消偏现象。该方法与利用双旋转波片技术（DRRT）测量目标散射光的偏振度和强度相比可以降低对实验装置的精度要求,同时可以提高测量速度,不需要进行16次测量,只需1次就可以测量出目标散射光的偏振度和强度,进而得到偏振度和强度图像。     

微纳电流表的设计与制作

利用集成运放的方法,设计了一个微纳电流的制取和测量方案并搭建了实验装置。在自制装置的基础上,用高精度的标准电阻和纳伏表对装置进行了对比测试,测试结果表明,装置的测量结果与纳伏表的测量结果非常接近,且测量的精度可达纳安量级,可靠性和稳定性都达到了实验预期。     

液滴微粒直径分布的激光散射法测量

本文利用氦氖激光器为光源在自行设计的光散射实验装置上对球形微粒群进行了粒径平均直径及直径分布的理论研究和测量.实验结果表明,本实验装置具有测量精度高、适用范围广和测量粒径范围宽等特点.     

电容率测量仪的改进

针对现有的电容率测量实验教学装置中存在的精度较低等问题,重新设计了电容率实验装置.将平行板电容的上极板设计为T型结构,用一限位螺母的转动来带动上极板上下移动,且不发生转动,用千分表实时测出上极板移动的距离.使用改进后的实验装置测量空气的电容率,测量结果与空气的标准电容率ε相比,误差在1%以内.实验结果表明改进后的电容率实验装置性能可靠,实验测量精度较高.     

弯曲共振法测量材料的杨氏模量实验改进

针对共振法测量杨氏模量实验中存在精确度和获取共振频率上的不足,在原装置中增加高度调节装置和水平仪,通过实验操作对共振阶数进行判断.实验结果证明选用共振二阶型态测量杨氏模量较有优势.     

“用单摆测重力加速度”实验教具优化研究

通过分析"用单摆测量重力加速度的大小"实验中摆长、摆角、摆线与摆球等因素对实验结果精度的影响,探讨了传统实验装置的不足,在此基础上设计并制作了可用于测量重力加速度的双线摆装置,并对装置的构成与应用进行了详细阐述.     

水平线列阵方位—相速度联合的卡尔曼滤波方法*

传统的水下被动测向方法通过波束形成估计目标角度,水平线列阵波束形成中的参考声速应使用声传播的相速度,在被动测向中,由于声源距离未知,因此在对目标角度估计时选取的参考声速与接收阵处的相速度往往存在偏差,从而影响测向精度。本文提出了一种水平线列阵方位-相速度联合的纯方位扩展卡尔曼滤波方法,该方法引入相速度作为估计状态量以此校准参考声速,提高测向精度,进而改善了由于测向误差较大引起的纯方位扩展卡尔曼滤波算法跟踪结果发散的问题。浅海传播条件下的数值仿真结果表明,改进方法较常规纯方位扩展卡尔曼滤波算法具有更高的跟踪精度及稳健的跟踪性能。     

求解水中加肋板声辐射特性的虚拟声源法*

发展一种利用虚拟声源离散声场的方法求解加肋板在水中的声振耦合问题。由波叠加原理和单元体积速度匹配的原则,根据离散的结构单元满足的动力方程和结构与介质的交界相容性条件,确定虚拟声源强度,计算结构的声辐射功率。本文以简支矩形加肋板为例,在不获得结构表面振速和声压的情况下,计算了结构在水中的声辐射功率,并与解析方法计算的结果进行了比较,表明了该方法具有较好的计算精度。     

Effect of operating parameters on noise emission from individual road vehicles

A noise survey has been undertaken on over 1000 vehicles operating on public roads. By the use of a remote device, vehicle velocity and acceleration have been measured and related to the instantaneous sound pressure level emission from the vehicle. The relationship is expressed in terms of A-weighted sound pressure level as a function of both velocity and acceleration. Octave band sound pressure levels are also expressed as functions of these variables. Light and heavy vehicle groups are considered separately.     

固体声速温变特性实验室探究

基于良导体导热系数的测温原理和声速测量实验原理,利用高灵敏度温差热电偶测温,采用时差法测量固体中声速,设计并搭建了一套可以测量不同温度下金属材料中纵波声速的实验装置。在注意了各种实验操作细节的基础上,研究了A3钢合金材料中超声纵波声速在30～100℃范围内的变化规律,并对本实验的误差来源进行了探究,提出一些减小误差的措施方法。结果表明,使用此套装置研究固体超声纵波声速温变特性,操作过程简单易行,立足于实验室的需求,适合于在实验室推广使用。     

Predicting the path of a changing sound: velocity tracking and auditory continuity

Three studies demonstrate listeners' ability to use the rate of a sound's frequency change (velocity) to predict how the spectral path of the sound is likely to evolve, even in the event of an occlusion. Experiments 1 and 2 use a modified probe-signal method to measure attentional filters and demonstrate increased detection to sounds falling along implied paths of constant-linear velocity. Experiment 3 shows listeners perceive a suprathreshold tone as falling along a trajectory of constant velocity when the frequency is near to the region of greatest detection as measured in Experiments 1 and 2. Further, results show greater accuracy and decreased bias in the use of velocity information with increased exposure to a constant-velocity sound. As the duration of occlusion lengthens, results also show a downward shift (relative to a trajectory of constant velocity) in the frequency at which listeners' detection and experience of a continuous trajectory are greatest. A preliminary model of velocity processing is proposed to account for this downward shift. Results show listeners' use of velocity in extrapolating sounds with dynamically changing spectral and temporal properties and provide evidence for its role in perceptual auditory continuity within a noisy acoustic environment.     

Theory of transit time ultrasonic flowmeters

A theory of transit time ultrasonic flowmeters for clean fluids is developed from the equations of fluid mechanics applied simultaneously to the fluid and the sound vibrations. These equations are linearized (weak sound) and use is made of the electroacoustic reciprocity theorem to give a relation between the voltages and currents at the transducer terminals and the fluid velocity. The technique of “reciprocal operation” of a transit time ultrasonic flowmeter is described and the way this technique eliminates zero drift is explained. The theory can be applied to meters with broad sound beams (which provide a better average over velocity profiles) or meters in which the wavelength of sound is not necessarily small compared with the duct diameter. Small modificaition of the sound field (due to flow) is assumed and the resulting phase (or amplitude) shift of the received signal is expressed as an integral throughout the fluid of the dot product of the fluid velocity and a weight vector defined in terms of the sound fields in the stationary fluid. Simple flowmeter designs which approach the ideal of complete immunity to velocity distribution are described.     

Tomographic inversion of measured cross-correlation functions of ocean noise in shallow water using ray theory

Based on experimental data obtained in 2012 in the Florida Strait, we study the feasibility of employing ray tomography to retrieve sound speed and flow velocity profiles from measured noise cross-correlation functions. We describe the results of numerical experiments that characterize the inversion errors resulting from peculiarities of the ray structure in shallow water, difficulties in unambiguous identification of ray arrivals, and a decrease in accuracy of ray theory at low frequencies. We show that under conditions of low-mode sound propagation, the use of the classical ray tomography scheme can yield only a rough estimate of the sound speed profile, but it allows approximate reconstruction of the current velocity profile. Application of passive ray tomography to the experimental data yields the current velocity profile in the Straits of Florida, which agrees with independent measurements within the inversion error limit.     

使用脉冲声和矢量传声器的现场测量吸声系数

使用不同声源利用矢量传声器对毛毡材料进行现场吸声系数测试,研究了不同背景下不同声源的抗噪能力。矢量传声器可以同时测得声压和质点振速信号,进而可计算得到阻抗,利用自由空间和材料表面的阻抗可计算得到材料的吸声系数。在此次实验中,使用不同声源分别在无干扰和有一白噪声干扰源的两种情况下进行测试。结果表明,使用对数扫频脉冲和巴特沃斯脉冲测试所得的吸声系数曲线更平滑,说明脉冲声可以有效降低环境反射的影响,在高噪声背景下使用对数扫频脉冲测试所得的结果基本没有受到背景噪声的影响,说明对数扫频脉冲的抗噪能力更强。因此,使用对数扫频脉冲作为声源进行测试可有效减弱环境反射和背景噪声的影响。     

Sound velocity in silver chalcogenides

The shift of sound velocity due to the excess ions and electrons in the nonstoichiometric state of silver chalcogenides is investigated theoretically by making use of a continuum model.