《声学技术》2003年总目录

论文与报告·色散介质中积累二次谐波的发生邓明晰 (0 3.1.1)……………………………………………………………水中目标强度的一致性时域有限差分计算冯玉田 ,王荣庆 ,王朔中 (0 3.1.4 )………………………………一种采用两个相干累加器提高自适应谱线增强器性能的方法王　彦 ,马章勇 ,黄建人 (0 3.1.8)…………HIFU聚焦探头声场功率测量的凹锥面反射靶设计分析　　　　　…………………………………………　　霍彦明 ,吴　敏 ,宋文章 ,叶兆雄 ,王智彪 (0 3.1.11)………………………………………………………用超声脉冲反射谱评价圆管厚度…     

用锥面靶测量大口径聚焦换能器声功率的计算讨论

辐射压力法是超声功率测量中常采用的方法，用辐射压力法测量声动功率中对于不同反射靶面的功率与压力之间的换算关系是非常重要的。文章从能量守恒基础出发，推导了大口径聚焦换能器声场作用于锥面反射靶的功率与压力的换算关系，并将结果应用于凹锥面反射靶计算。     

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％。     

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%。     

高强度聚焦超声肿瘤治疗系统专项技术研究

本文通过对高强度聚焦超声治疗基本原理介绍,对HY2900聚焦超声肿瘤治疗系统实际工作几项特色专项技术HIFU声场分布参数测量、HIFU温度场测量、三维重建技术中任意方位切面图像浏览及边界轮廓的实现方法等进行讨论,介绍相关技术及方法.     

基于反射探针的聚焦超声测量传感器设计和方法研究

基于钨钢探针和PVDF压电薄膜材料,设计研制了一种用于聚焦超声测量的新型传感器。同时,通过理论分析和有限元分析软件建立了传感器物理模型,并对传感器的内部声场及反射状况进行了模拟仿真,获得传感器输出信号的波形和幅值。最后,利用研制的传感器对聚焦换能器焦域声压和声强进行检测,并将检测结果与理论仿真结果对比,在10W的声功率范围内,证明了新型传感器及其测量理论和方法在聚焦超声测量中的可行性与可靠性。该新型反射探针传感器将为高强度聚焦超声声场的测量提供一种新的方法。     

高强度治疗超声（HITU）测量标准化的进展

高强度聚焦超声（HIFU）的医学应用研究和临床实践,经过20多年的发展,不断提高,逐步完善,取得长足进步。各种高强度治疗超声（HITU）设备产品纷纷涌现。促成了2005年我国国家标准《GB/T19890—2005高强度聚焦超声（HIFU）声功率和声场特性的测量》的制定,也引起了国际电工委员会（IEC）87技术委员会（TC87：超声学）第六工作组（WG6：聚焦换能器）和第八工作组（WG8：超声场测量）以及国际同行专家的重视。     

聚焦换能器声强和声功率测量方法研究

针对聚焦声场的特点,以及辐射力天平(RFB)只能获得单一功率指标的缺点,提出一种基于近场测量法的聚焦换能器声强和声功率评价方法。通过声场测量系统对聚焦换能器预聚焦区域中两个平面上的声压扫描测量,运用声强法得到聚焦换能器的声强分布以及辐射声功率。采用活塞换能器的远场测量法与近场测量法进行比对,两种方法得到的声功率误差不超过12%。比较预聚焦区域声功率值和焦点处声功率值,分析声功率评价方法的准确性。发现聚焦声场中不同位置处的声功率值一致性误差5%,同一位置处的声功率值重复性误差2%。结果表明,近场测量法适用于对聚焦换能器声强和声功率的评价,可有效避免直接测量对测量设备的损坏,同时还克服双水听器声强互谱法频率上限低以及测量系统相位不匹配的缺点。     

CMM测量中基于确定采样策略的圆锥面拟合方法

为解决三坐标测量机测量软件开发中存在的圆锥面拟合参数初值计算不理想而导致的拟合结果不准确的问题,本文研究基于采样策略的圆锥面拟合算法.在利用一种参数化方法建立圆锥面距离函数后,确定圆锥面采样策略,并据此计算圆锥面几何参数初值,最后利用非线性最小二乘法优化圆锥面距离函数,实现圆锥面精确拟合.设计实验,对圆锥面拟合方法进行验证,实验数据表明本文采用方法可以有效地解决三坐标测量软件中圆锥面拟合几何参数初值计算不准确的问题,实现圆锥面的精确拟合.     

瓦级超声功率标准装置

为了测定压电换能器向水中辐射的总声功率输出,研制了一套测量装置。该装置由电子微量天平、消声水槽和反射靶悬吊系统组成。在1～5MHz频率范围和输出声功率0.2～20W范国内,测量不确定度优于±5％。     

Statistical estimation of ultrasonic propagation path parameters for aberration correction

Parameters in a linear filter model for ultrasonic propagation are found using statistical estimation. The model uses an inhomogeneous-medium Green's function that is decomposed into a homogeneous-transmission term and a path-dependent aberration term. Power and cross-power spectra of random-medium scattering are estimated over the frequency band of the transmit-receive system by using closely situated scattering volumes. The frequency-domain magnitude of the aberration is obtained from a normalization of the power spectrum. The corresponding phase is reconstructed from cross-power spectra of subaperture signals at adjacent receive positions by a recursion. The subapertures constrain the receive sensitivity pattern to eliminate measurement system phase contributions. The recursion uses a Laplacian-based algorithm to obtain phase from phase differences. Pulse-echo waveforms were acquired from a point reflector and a tissue-like scattering phantom through a tissue-mimicking aberration path from neighboring volumes having essentially the same aberration path. Propagation path aberration parameters calculated from the measurements of random scattering through the aberration phantom agree with corresponding parameters calculated for the same aberrator and array position by using echoes from the point reflector. The results indicate the approach describes, in addition to time shifts, waveform amplitude and shape changes produced by propagation through distributed aberration under realistic conditions.     

基于凹面反射的超声风速测量系统设计与实现

时差法是超声风速风向测量系统的基本方法。在介绍时差测量原理的基础上,分析了系统测量误差的来源;构建了增大测量范围的凹面反射模型;结合该模型,在系统结构、电路系统、控制流程及数据处理算法等方面进行了全面的设计和实现,并制成了原理样机。风洞试验结果表明,凹面反射结构可以增加系统的测量范围,提高大风条件下测量数据的稳定性。原理样机具有体积小、可靠性高、测量范围大的优点,已在风力发电方面获得了实际应用,并取得了较好的应用效果。     

A Microwave–Ultrasonic Cell for Sound-Speed Measurements in Liquids

In this work preliminary results obtained in developing a prototype cylindrical ultrasonic cell designed to apply a microwave resonance technique to the determination of its internal dimensions are described. Since the apparatus is intended for speed-of-sound measurements in pressurized liquid-phase media, the cell design is such that a double reflector pulse-echo technique can be used for time-of-flight measurements. The main absorption and dispersion effects that influence the acoustic measurement in this interferometer-like configuration and the values of the corresponding corrections are considered and discussed. The performance of the experimental apparatus and method in terms of achievable precision and accuracy was tested by measuring the speed of sound in water on a single isotherm at 325 K between 0.1 and 90 MPa. Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A.     

Bandwidth and resolution enhancement through pulse compression

A novel pulse compression technique is developed that improves the axial resolution of an ultrasonic imaging system and provides a boost in the echo signal-to-noise ratio (eSNR). The new technique, called the resolution enhancement compression (REC) technique, was validated with simulations and experimental measurements. Image quality was examined in terms of three metrics: the eSNR, the bandwidth, and the axial resolution through the modulation transfer function (MTF). Simulations were conducted with a weakly-focused, single-element ultrasound source with a center frequency of 2.25 MHz. Experimental measurements were carried out with a single-element transducer (f/3) with a center frequency of 2.25 MHz from a planar reflector and wire targets. In simulations, axial resolution of the ultrasonic imaging system was almost doubled using the REC technique (0.29 mm) versus conventional pulsing techniques (0.60 mm). The -3 dB pulse/echo bandwidth was more than doubled from 48% to 97%, and maximum range sidelobes were -40 dB. Experimental measurements revealed an improvement in axial resolution using the REC technique (0.31 mm) versus conventional pulsing (0.44 mm). The -3 dB pulse/echo bandwidth was doubled from 56% to 113%, and maximum range sidelobes were observed at -45 dB. In addition, a significant gain in eSNR (9 to 16.2 dB) was achieved.     

Modeling of received ultrasound signals from finite planar targets

Presents a computational solution to the ultrasonic target-dependent spectral distortion for a finite planar target (FT-SD). The FT-SD predicts the spectrum of the output signal from the receiving transducer generated in response to the insonification of a finite planar specular target, as a function of incident angle. The transducer is assumed to be operating in pulse-echo mode. The development is made via scalar diffraction theory, in terms of the angular spectrum decomposition of the acoustic source field. Numerical simulations of the FT-SD are presented for several reflector sizes and orientations, insonified by a planar circular piston transducer. Experimental verification of results for a finite square planar reflector is given for a range of reflector orientations     

Modeling Angle Beam Ultrasonic Testing Using Multi-Gaussian Beams

This paper proposes a new approach to modeling angle beam ultrasonic testing that can predict pulse-echo signals, in an absolute and computationally efficient manner, from various reflectors in steel welded joints. This approach relies on a model of the entire ultrasonic measurement process, a model which requires one to solve three subsidiary problems; 1) determination of a system efficiency factor, 2) evaluation of the ultrasonic beam field around the flaw, and 3) calculation of the scattering from the reflector. Here, solutions are offered for each of those three subsidiary problems. To solve the first problem we employ the specular reflection from the cylindrical part of a STB-A1 (Standard Test Block in compliance with Japanese Industrial Standards Z 2347) (equivalently IIW (International Institute of Welding) type 1) standard block to determine the system efficiency factor. To solve the second problem, we calculate the ultrasonic wave field at the flaw with a highly efficient multi-Gaussian beam model. For the third problem, we treat the scattering from a reflector by high frequency approximations. We explicitly give the solutions to all three of these subsidiary problems for counter bore, crack, and side-drilled hole reflectors. Experimental results that validate this approach are also given.     

Using a Single Transducer Ultrasonic Imaging Method to Eliminate the Effect of Thickness Variation in the Images of Ceramic and Composite Plates

This article describes a single transducer ultrasonic imaging method based on ultrasonic velocity measurement that eliminates the effect of thickness variation in the images of ceramic and composite plate samples. The method is based on using a reflector located behind the sample and acquiring echoes off the sample and reflector surfaces in two scans. As a result of being thickness-independent, the method isolates ultrasonic variations due to material microstructure. Its use can result in significant cost savings because the ultrasonic image can be interpreted correctly without the need for precision thickness machining during nondestructive evaluation stages of material development. Velocity images obtained using the thickness-independent methodology are compared with apparent velocity maps and c-scan echo peak amplitude images for monolithic ceramic (silicon nitride), metal matrix composite and polymer matrix composite materials having thickness and microstructural variations. It was found that the thickness-independent ultrasonic images reveal and quantify correctly areas of global microstructural (pore and fiber volume fraction) variation due to the elimination of thickness effects. A major goal achieved in this study was to move the thickness-independent imaging technology out of the lab prototype environment and into the commercial arena so that it would be available to users worldwide. The method has been implemented on commercially-available ultra-sonic can systems manufactured by Sonix, Inc. via a formal technology transfer agreement between NASA and Sonix.     

Measurement Models and Scattering Models for Predicting the Ultrasonic Pulse-Echo Response From Side-Drilled Holes

A side-drilled hole (SDH) is a commonly used reference reflector in ultrasonic nondestructive evaluation. In this paper, we will develop reciprocity-based measurement models along with scattering models that allow us to predict the ultrasonic response from a SDH in a pulse-echo immersion setup. Two measurement models will be derived, one suitable for large SDHs where variations of the incident fields over the cross section area of the SDH are considered, and a second model which neglects those variations. Two scattering models are also used along with these measurement models. These include an explicit model based on the Kirchhoff approximation, as well as an exact model obtained using the separation of variables method. Examples of the model-based received waveforms and peak-to-peak voltage responses are presented for a number of SDHs of different sizes and compared with experimentally determined SDH responses.     

The deposition of amorphous carbon thin films for hard mask applications by reactive particle beam assisted sputtering process

In this work, amorphous carbon thin films for hard mask applications were deposited by a reactive particle beam (RPB) assisted sputtering system at room temperature. The deposition characteristics of the films were investigated as functions of operating parameters such as reflector bias voltage and RF plasma power. By spectroscopic ellipsometry, the decrease in the refractive index of films at the wavelengths of 633 and 248 nm was observed with the increasing plasma power. In Raman spectra, the positions of G line shifted to higher wavenumbers with increasing plasma power. When the reflector bias voltage increases, the deposition rate was increased but the positions of G line remained nearly unchanged.     

Ultrasonic measurement of density of liquids flowing in tubes

This paper presents the implementation of the relative reflection method for the ultrasonic measurement of the density of liquids, which may be flowing in pipelines, at different temperatures. This technique will be shown to be valid for large-diameter tubes containing flowing liquids. It employs a double-element transducer, consisting of a piezoelectric ceramic transmitter and a large aperture PVDF membrane receiver, separated by a polymethylmethacrylate buffer rod. Between the receiver and the liquid is a PMMA reference rod. The density is obtained from the reflection coefficient of the reference rod-liquid interface and the transit time between this interface and a reflector placed in the opposite wall of the tube. The DET is calibrated once to account for temperature effects. The calibration is incorporated during signal processing, so that the actual density measurement is temperature compensated. In testing this method, a system was implemented and measurements of several liquids, stationary and flowing in a pipeline, were conducted. The error of measurements obtained by this method for distilled water, tap water, castor oil, and ethanol, when compared to data in the literature or obtained by a pycnometer, is less than 1.5%