受力腓肠肌剪切波速度的超声检测

肌肉组织受力时的弹性特征变化,是其功能特性、健康状态的重要评估参量.该文利用在离体肌肉组织表面施加低频振动引起组织发生形变,在组织内部产生剪切波的方法,经过快速超声成像,通过剪切波图像估计剪切波的传播速度.研究结果表明顺肌纤维方向传播的剪切波速度快于垂直肌纤维方向传播的剪切波速度,剪切波的传播速度随受力的增加而变大,且...     

超声波在液体中相速与群速的测量

简要叙述了相速与群速的定义,并用实验测量了超声波在不同液体中的相速与群速.     

Ultrasonic SH wave velocity in textured aluminium plates

Neutron diffraction has been used to measure the crystallite orientation distribution function for a sample of rolled aluminium plate. Based on this study an expression is given for the ultrasonic velocity of the fundamental horizontally polarized shear (SH) wave propagating in the plane of the plate at an angle θ to the rolling direction. This expression is correct to second order in the leading texture component and is compared with the exact numerical result and with measurements of the SH wave velocity for this plate. In textured materials the group and phase velocities are not, in general, parallel and an expression for the angle between them is derived. Inclusion of this effect leads to better agreement between experiment and theory. The results have application to the texture-independent determination of stress with ultrasonics recently proposed by MacDonald and Thompson et al.     

超声波探测技术原理实验

介绍了超声波测距和超声波测速的基本原理及应用。根据超声波探测技术中的测距和测速原理设计制作了相关实验组件。利用数据采集系统对超声波测距、超声波测速中的时间延迟、距离、频移量进行了测量,给出了声速、计算距离,相对速率等结果及误差分析。     

超声波流量计测量流体声速的实验方法

为获取液体介质的声速值,设计了一种测定流体声速的实验方法,该方法利用时差式超声波流量计和标准流量校验设备同时对封闭管道中的液体进行流速测量,分别得到流速的测量值和真实值,从而计算出超声波流量计的仪表系数,并以此导出了一定条件下液体介质的声速值随仪表系数的变化关系式.利用该方法测量给出了0.17 MPa下四氧化二氮(N₂O₄)在7.6-19.4 ℃、偏二甲肼((CH₃)₂NNH₂)在6.5-25.2 ℃范围内的流体声速值,并为其他液体介质的声速测量提供了借鉴. 关键词： 超声波流量计 声速 仪表系数 温度     

Ultrasonic velocity of binary systems at elevated pressures

Various empirical theories of ultrasonic velocity have been applied to three binary liquid mixtures, under pressures up to 200 MPa and their validity have been tested. A pressure dependent study of ultrasonic velocities has been made at 303.15 K. The agreement between theory and experiment is found to be quite satisfactory.     

超声波专题实验开展及其传播特性研究

开设了超声波专题设计综合实验,测量得空气、水和白油中超声波传播速度,研究了同一介质中接收到的交变电压随传播距离的变化规律,空气、水和白油中超声波的损耗系数,水中超声波的损耗系数最大。使用Origin软件直线拟合,对实验结果进行分析和评价。     

Ultrasonic study of binary mixtures of acetylacetone with polar diluents at 303.16 K vis-a-vis molecular interaction

The ultrasonic velocity (C) and density (p) of binary mixture of acetylacetone with polar diluents have been measured at temperature 303.16 K and frequency of 2 MHz. The data of C and p have been used to evaluate, isentropic compressibility (β), acoustic impedence (Z) and intermolecular free length (L _f ) to study the molecular interaction. The study reveals that interaction is maximum in bromo-benzene acetylacetone mixture.      

驻波法测量声速实验的讨论

根据声波在2个换能器之间多次反射和声波在空气中的衰减,研究了驻波法测量声速实验中接收器输出信号随接收器到发送器间距离的变化.理论推导结果表明:声波在一般情况下不是严格的驻波,但是当反射比接近-1时则是双曲函数形式的驻波,这与实验测量结果一致.只有接收器到发送器的距离比较远,反射比接近-1时,才能得到几乎理想的驻波.     

Ultrasonic velocity and amplitude characterization of magnetorheological fluids under magnetic fields

Variations in velocity of sound and amplitude of the signal of a commercial magnetorheological fluid under different magnetic fields are studied experimentally. Different factors such as orientation, uniformity, geometry and intensity of the magnetic field are investigated. An increase in the change of MR fluid acoustical properties is obtained when the magnetic field intensity is risen. In addition, these properties show an opposite behavior when a magnetic field is applied parallel or perpendicular to the ultrasound propagation. Experiments using an electromagnet and permanent magnets as the source of magnetic field are also compared. Properties such as anisotropy in sound velocity and amplitude make these materials interesting regarding applications.     

Ratiometric detection of Raman hydration shell spectra

The micro‐structure of hydration shell of solute in water is significant for understanding the properties of aqueous solutions. However the spectra of hydration shell are difficult to be obtained. Herein, a novel Raman ratio spectra, which is obtained through dividing the Raman spectra of aqueous solutions from the spectrum of water, was applied to deduce the spectra of hydration shell of organic (acetone‐D6) and inorganic compounds (NaNO₃, NaSCN, NaClO₄, Na₂SO₄, NaCl) in water. Those spectra of the hydration shell were employed to study the micro‐structures of the first hydration shells of anions, the number of water molecules in the first hydration shell of free anions and acetone‐D6, and the aggregation behavior of ions in the concentrated aqueous NaNO₃. The number of water molecules in the hydration shell was supported by our molecular dynamic simulations. The Raman ratio spectra can be widely employed to obtain the spectra of the first hydration shell, and it is helpful to understand the micro‐structure of aqueous solutions. Copyright © 2016 John Wiley & Sons, Ltd.     

The effect of bone structure on ultrasonic attenuation and velocity

The relationship between the structure of bovine cancellous bone, and its ultrasonic propagation parameters is investigated by means of a novel technique involving the application of large static loads, thereby changing the porosity in a controlled manner. The results show that for frequencies in the range 0.4 to 1 MHz, porosity decreases up to 35% are associated with a reduction in attenuation of up to 500%, whereas the velocity increases by roughly 35% for the same changes. The data taken overall suggest that in determining the ultrasonic attenuation coefficient at these frequencies, the amount of material in a given bone section is significantly less important than the distribution of that material.     

基于时差法的超声波测速向仪设计与实现

介绍了超声波时差法风速测量的基本原理,以及基于MSP430微控制器和MAG3110的风速风向测量系统的实现方法。给出了以MSP430芯片为核心的硬件设计的总体框架图。详细地阐述了各个外围接口电路的设计,以及超声波风速风向测量的软件设计。系统具有结构简单、精度高、功耗低和扩展方便等特点,能够满足大学物理实验教学的风况信息测量。     

新型声速测定仪的研制

论述了新型声速测定仪的结构、工作原理和实验内容，阐述了几种测媒质中超声波波速的方法。     

A molecular dynamics study of uranyl hydration

Molecular dynamics calculations were carried out in order to investigate the hydration structure of uranyl in aqueous solution. The CF1 model of flexible water molecules is used. This model allows one to investigate a hydrolysis reaction for water molecules in the first uranyl hydration shell. Charge redistribution effects on hydrolysis products are also taken into account. We found five ligands in uranyl hydration shell, which is of bipyramidal pentacoordinated structure. The charge redistribution effects resulted in ligands of four water molecules and one hydroxyl, which was found closer to uranium than the other ligands.     

探究性学习在声速测量实验课中的运用

为了进一步提高大学物理实验课堂教学的质量,根据探究性学习的特点,构建声速测量实验课的实验教学过程,采用创建探究方向、拓展探究方向和加大探究自由度及激励机制,从而提高了大学物理实验课堂教学的自主性、实践性、开放性和激励性。     

LaCoO3中自旋态转变现象的超声研究

测量了LaCoO₃单相多晶样品的纵波与横波超声声速和衰减随温度的变化关系, 在材料的自 旋态转变温度附近（≈90K），纵波声速出现明显的软化并伴随一个尖锐的衰减峰，但是在 横波的测量中却没有出现类似的超声异常，分析认为LaCoO₃在90K附近的自旋态 转变是由于Co³⁺离子是从低自旋态(LS,t⁶_2ge⁰ _g)转变到中等自旋态(IS,t⁵ _2ge¹_g )，而不是高等自旋态(HS,t⁴_2ge²_g).随着温度的升高，在 200K附近纵波和横波测量上都观察到一个伴随着微小声速软化的宽大的衰减峰，这可能是随 机分布的IS态Co³⁺离子的Jahn-Teller效应导致的局域晶格扭曲所造成的. 关键词： 超声声速与衰减 自旋态转变 Jahn-Teller效应     

超声光栅测声速实验方法的探索

对实验室现有的超声光栅测声速实验装置加装反射镜及利用激光光源进行改进,通过对样品纯净水的测试比较,改进后的实验装置对实验测量结果精度有明显提高。测试样品的范围扩大,实现了物理实验技术和方法与石油专业相结合,有利于提高实验教学效果。     

A theoretical study on calculation of absolute hydration enthalpies for some univalent ions

Using the total radius of alkaline fluorides and sodium halides and their experimental total enthalpy values, absolute hydration enthalpies of sodium and fluoride ions ( and ) were previously calculated. Also, by the help of data of sodium and fluoride ions for all alkaline metal ions and halides absolute hydration enthalpies were determined.

Ultrasonic distance and velocity measurement using a pair of LPM signals for cross-correlation method: improvement of Doppler-shift compensation and examination of Doppler velocity estimation

Real-time distance measurement of a moving object with high accuracy and high resolution using an ultrasonic wave is difficult due to the influence of the Doppler effect or the limit of the calculation cost of signal processing. An over-sampling signal processing method using a pair of LPM signals has been proposed for ultrasonic distance and velocity measurement of moving objects with high accuracy and high resolution. The proposed method consists of cross correlation by single-bit signal processing, high-resolution Doppler velocity estimation with wide measurement range and low-calculation-cost Doppler-shift compensation. The over-sampling cross-correlation function is obtained from cross correlation by single-bit signal processing with low calculation cost. The Doppler velocity and distance of the object are determined from the peak interval and peak form in the cross-correlation function by the proposed method of Doppler velocity estimation and Doppler-shift compensation. In this paper, the proposed method of Doppler-shift compensation is improved. Accuracy of the determined distance was improved from approximately within ±140 μm in the previous method to approximately within ±10 μm in computer simulations. Then, the proposed method of Doppler velocity estimation is evaluated. In computer simulations, accuracy of the determined Doppler velocity and distance were demonstrated within ±8.471 mm/s and ±13.87 μm. In experiments, Doppler velocities of the motorized stage could be determined within ±27.9 mm/s.