辐射力法测量超声功率的误差分析

辐射力法测量超声功率的误差分析白力军朱云（河北省计量测试研究所，石家庄市０５００５１）本文介绍了采用辐射力法测量毫瓦级超声功率的误差分析方法，对建立“医用超声源”计量标准进行误差分析具有实用价值。超声功率的测量方法很多，但国内计量部门超声功率的测量均...     

聚焦超声的辐射力计算与高强度聚焦超声功率测量实验

本文研究聚焦超声场的辐射力计算，应用几何声学方法，推导了聚焦超声作用于测试靶上的辐射力的通用公式，讨论全反射靶和全吸收靶上的辐射力，最后给出了应用辐射力法测量高强度聚焦超声装置的声功率的实例，其结果与量热法测量的声功率接近，偏差不大于３％。     

浮力变化的量热法与辐射力天平法测量超声功率比较研究

辐射力天平法测量超声功率,一般只适合测量较小功率的平面波超声功率。根据介质吸收热量发生体积变化、浮力变化的原理,设计并实现了蓖麻油吸收靶,建立了采用天平的量热法超声功率测量装置,解决了传统量热法需精确测量温度场分布的问题。经与辐射力天平法装置的比较,验证了所建立超声功率测量装置的有效性,并将进一步推广至大功率、非平面波超声功率的测量。     

聚焦超声的辐射力计算与高强度聚焦超声功率测量实验

研究聚焦超声场的辐射力计算。应用几何声学方法,推导了聚焦超声作用于测试靶上的辐射力通用公式,讨论了全反射靶和全吸收靶上的辐射力。最后给出了应用辐射力法测量高强度聚焦超声装置的声功率的实例,其结果与良热法测得的声功率接近,偏差不大于3%。     

超声功率测量现状及大功率超声测量研究进展

超声功率是超声设备的一项重要量化指标。本文首先介绍了目前国内外超声功率测量和国际比对现状,以及国内外有关大功率超声测量的研究水平。介绍新建立的大功率平面超声源和大功率聚焦超声源,测量并比较了几种吸收靶的吸声系数,利用研制的吸收靶对大功率平面超声源和大功率聚焦超声源进行了功率测量。实验表明,基于吸收靶的大功率超声测量是稳定的、可行的。     

使用辐射力天平的超声治疗换能器的电声特性测量方法研究

论述和规范了工作于200 kHz~10 MHz频率范围内的超声治疗换能器的基本电声特性和参数定义,诠释了它们的物理意义和相互关系,研究并提出了一套基于辐射力和有效面积测量的发射换能器的电声参数的测量方法。对平面活塞型、球面聚焦型和圆柱面聚焦型换能器实施了测量,给出了实测结果。     

超声换能器的自易校准法及其在功率测量中的应用和它与辐射力法的关系(英文)

论述了电声互易原理和用于平面活塞型与球面聚焦换能器校准的自易法(Self Reciprocity Method,SRM)。介绍了一系列的定义和发送电压(电流)响应与电压灵敏度。阐述了SRM与辐射力天平(Radiation Force Balance,RFB)法之间的关系。在1~25 MHz频率范围内,对超声换能器校准和输出功率测量的实验显示,两种方法具有相近的准确度。SRM法比RFB法测量具有更高的信噪比和更好的稳定性。     

一种新颖高温超声测厚实验系统研究（Ⅱ）—测控系统与信号处理技术

本文介绍了一种新颖高温超声测厚实验系统的测控系统和信号处理技术。着重介绍超声系统设计方案,接收发射电路,显示控制电路方案及信号处理技术等。     

超声换能器表面振动和声场测量及其与经典超声换能器的仿真比较

超声换能器广泛应用于声学测量,其工作性能主要取决于它的振动与声特征。然而,多数研究中的换能器被认为是经典的活塞或高斯型,经典与常用的真实换能器之间的差异容易被忽视。基于此,首先用激光测振和传声器测声方法测量了某厂家换能器产品的表面振动与声场特征。然后设计有限元方案,分别仿真经典与真实换能器的声场。最后从辐射面振速分布、声场声压和相关系数等方面,综合比较经典与真实超声换能器之间振动与声场的异同。结果表明,换能器间的辐射面振速分布差别明显,所研究的真实换能器的声场特征接近于活塞,而与高斯型差别较大。     

利用超声回波跟踪技术测量血流速度的实验研究

文章主要介绍了利用超声回波跟踪技术进行血流速度测量的原理和方法,通过对运动弦线速度的测量实验,比较了这种方法和传统的超声多谱勒技术在血流速度测量上的性能差异。     

辐射力天平法测量相控阵超声换能器的声功率

超声换能器相控阵已用于聚焦超声治疗的研究和应用已有20多年历史,但其声功率P的测量仍缺乏方便有效简易的测量方法。文章旨在提出一种基于凸球面吸收靶的辐射力天平（Radiation Force Balance,RFB）方法,测量其声功率。理论推导了这种RFB在各种阵元组合下的比值r=P/cF（c为水中声速,F为阵的声束轴方向的总辐射力）。论述了测量各种组合的发射声功率的实施方法和测量程序。为实际的测量系统设计和应用建立了良好的工作基础。     

基于管内平面波分解的热声谐振管声功测量方法

提出了通过平面声波分解测量热声谐振管中单频压力波声功的方法.在该方法中,只要测量沿程两点的声压,便可将管内平面驻波声场分解为入射波和反射波两种分量.由这种分解可以求出入射波的声功和反射波的声功,二者之和决定了总声功.该方法考虑了粘性耗散和热传导带来的损失,即使在高频、高驻波比情况下也能得到准确的测量结果.由于这种平面波分解的方式可以对整个谐振管内的声场参数进行重构,与以往的双传感器声功测量方法相比,显著优点是不仅能够获得两个压力测点中点的声功,还能得到整个谐振管上沿程各点的声功,这对于分析热声系统各部分的声功耗散是非常有用的,这种方法在原理上也更易于理解.     

A domain decomposition method for discontinuous Galerkin discretizations of Helmholtz problems with plane waves and Lagrange multipliers

A nonoverlapping domain decomposition (DD) method is proposed for the iterative solution of systems of equations arising from the discretization of Helmholtz problems by the discontinuous enrichment method. This discretization method is a discontinuous Galerkin finite element method with plane wave basis functions for approximating locally the solution and dual Lagrange multipliers for weakly enforcing its continuity over the element interfaces. The primal subdomain degrees of freedom are eliminated by local static condensations to obtain an algebraic system of equations formulated in terms of the interface Lagrange multipliers only. As in the FETI‐H and FETI‐DPH DD methods for continuous Galerkin discretizations, this system of Lagrange multipliers is iteratively solved by a Krylov method equipped with both a local preconditioner based on subdomain data, and a global one using a coarse space. Numerical experiments performed for two‐ and three‐dimensional acoustic scattering problems suggest that the proposed DD‐based iterative solver is scalable with respect to both the size of the global problem and the number of subdomains. Copyright © 2009 John Wiley & Sons, Ltd.     

基于声辐射模态的粘弹性阻尼板声功率最小化研究*

为了减小薄板结构振动辐射的噪声,在重量约束下进行了声功率最小化研究。利用有限元振动模型来处理结构振动环节,利用声辐射模态模型来处理声辐射环节,用可行方向法进行了优化设计研究。以一矩形粘弹性阻尼板为例,得到了阻尼重量约束下板的声功率最小化模型,结果表明在满足重量约束条件下能够达到明显的降噪效果。     

Parameter measurement for the acoustic output of hand-held ultrasonic fetal heartbeat detectors

Methods and instruments are considered for measuring the parameters of the acoustic output from a Doppler ultrasonic detector for fetal heartbeat frequency as corresponding to the specifications of international and national standards. __________ Translated from Izmeritel’naya Tekhnika, No. 11, pp. 55–59, November, 2006.     

A dislocation and point force approach to the boundary element method for mixed mode crack analysis of plane anisotropic solids

Abstract

This study investigates the feasibility of enhancing steam‐driven ejector performance. Initially, a one‐dimensional ejector theory is used to examine the effects on ejector performance of three isentropic efficiencies: nozzle efficiency η_m , mixing efficiency η_m, and diffuser efficiency η_m . Theoretical analysis demonstrates that mixing efficiency profoundly affects ejector performance, but that the other two efficiencies have slightly influenced ejector performance. This finding suggests that efficient mixing can promote ejector performance. This study also attempts to improve mixing efficiency using a petal nozzle. The behavior and characteristics of a petal nozzle are investigated by testing the nozzle under various operating conditions, i.e. primary pressure, secondary pressure, and back pressure. In addition, the study compares the experimental and theoretical results. These results prove that using a petal nozzle can improve ejector performance. The shadowgraph method was used to visualize the inner flow field of an ejector. The flow patterns observed should help to further improve ejector performance.     

Boundary integral equation analysis for radiation and scattering of elastic waves in three dimensions

Abstract

In this paper, the boundary integral equation (BIE) method is employed to investigate the radiation and scattering of time‐harmonic elastic waves by obstacles of arbitrary shape embedded in an infinite medium. Based on the vector BIE, entirely free of Cauchy principal value integrals, an efficient numerical scheme using quadratic isoparametric boundary elements is proposed. Furthermore, the difficulty of non‐uniquess of a solution inherent with BIE formulations for exterior elastodynamic problems is studied numerically and analytically. The counterparts of the combined Helmholtz integral formulation method for elastodynamics together with the least‐square or Lagrange‐multiplier technique are derived and applied to overcome this difficulty successfully. In addition, the elastic‐wave fields radiated or scattered by either a spherical cavity or a rigid sphere in an infinite medium are calculated and the results are compared with the analytical solutions to demonstrate the accuracy and versatility of the proposed numerical scheme.     

Solution of the second-order one-dimensional hyperbolic telegraph equation by using the dual reciprocity boundary integral equation (DRBIE) method

In this paper, we use a numerical method based on the boundary integral equation (BIE) and an application of the dual reciprocity method (DRM) to solve the second-order one space-dimensional hyperbolic telegraph equation. Also the time stepping scheme is employed to deal with the time derivative. In this study, we have used three different types of radial basis functions (cubic, thin plate spline and linear RBFs), to approximate functions in the dual reciprocity method (DRM). To confirm the accuracy of the new approach and to show the performance of each of the RBFs, several examples are presented. The convergence of the DRBIE method is studied numerically by comparison with the exact solutions of the problems.