Generation of pulsed pressure in a liquid by means of a metallic plasma and measurement of its characteristics

Certain characteristics of pulsed pressure generated in a liquid by means of a metallic plasma are investigated experimentally. The problem of increasing the duration of the pressure pulse by plasma-chemical reaction is discussed. Zh. Tekh. Fiz. 69, 41–43 (April 1999)     

具有大指向性开角及高发射电压响应的发射换能器

应用复合变幅杆及夹心式换能器结构,研制了一种指向性开角较大且发射电压响应较高的发射换能器。应用有限元方法对换能器的工作频率,发射电压响应及指向性进行了理论计算。并与实验结果进行了比较,结果较吻合。本文研制的换能器工作频率为75.6kHz,发射电压响应级达到1 56dB(基准值1V/μPa),-3dB发射指向性开角100°     

大功率超声功率计的研制及高强度聚焦超声肿瘤治疗头功率检测

研制一种将机械天平、辐射压力法和智能控制结合在一起的大功率超声功率计,该功率计可以安装不同种类的反射靶面或吸收靶面对多种超声换能器进行功率测量;用砝码对该功率计进行校准和误差分析,结果显示该功率计具有稳定性好、精度高、测量范围大的特点。用锥面反射靶和吸收靶对高强度聚焦超声肿瘤治疗头的输出功率进行测量,实验结果表明:一方面该功率计可以满足大功率、高精度测量要求,另一方面被测量的临床治疗用高强度聚焦超声肿瘤治疗头的驱动电压在600-2200 V之间,其功率输出稳定、可靠,在此范围之外功率输出误差变大,超过5%。     

自聚焦换能器的声场研究

高强度聚焦超声（HIFU）治疗局部肿瘤是一项无创伤的新技术,有着很好的应用前景,因此对其声场的研究是有实际的价值的。对声场的研究不仅有利于换能器的设计,提高治疗的效果;而且有助声场测量方案的设计,提高对治疗超声剂量的安全保证。本文采用时域有限差分法研究了自聚焦换能器的声场,分别对简谐波,脉冲波进行了研究。比较清楚地看出在焦区的声场可以认为是平面波,这对光纤端面法声场测量提供了有力的支持。     

Bolt axial stress measurement based on a mode-converted ultrasound method using an electromagnetic acoustic transducer

A method is proposed to measure the stress on a tightened bolt using an electromagnetic acoustic transducer (EMAT). A shear wave is generated by the EMAT, and a longitudinal wave is obtained from the reflection of the shear wave due to the mode conversion. The ray paths of the longitudinal and the shear wave are analyzed, and the relationship between the bolt axial stress and the ratio of time of flight between two mode waves is then formulated. Based on the above outcomes, an EMAT is developed to measure the bolt axial stress without loosening the bolt, which is required in the conventional EMAT test method. The experimental results from the measurement of the bolt tension show that the shear and the mode-converted longitudinal waves can be received successfully, and the ratio of the times of flight of the shear and the mode-converted longitudinal waves is linearly proportional to the bolt axial tension. The non-contact characteristic of EMAT eliminates the effect of the couplant and also makes the measurement more convenient than the measurement performed using the piezoelectric transducer. This method provides a promising way to measure the stress on tightened bolts.     

一种拓宽凸球面压电换能器指向性的方法

利用有限元和边界元耦合的方法对涂环氧树脂后的压电陶瓷凸球面换能器进行了指向性仿真计算,发现这种形式的换能器具有较宽的指向性开角。实验测量结果证明了上述结论。     

Ultrasonic anechoic chamber qualification: accounting for atmospheric absorption and transducer directivity

Qualifying an anechoic chamber for frequencies that extend into the ultrasonic range is necessary for research work involving airborne ultrasonic sound. The ANSI S12.55/ISO 3745 standard which covers anechoic chamber qualification does not extend into the ultrasonic frequency range, nor have issues pertinent to this frequency range been fully discussed in the literature. An increasing number of technologies employ ultrasound; hence the need for an ultrasonic anechoic chamber. This paper will specifically discuss the need to account for atmospheric absorption and issues pertaining to source transducer directivity by presenting some results for qualification of a chamber at Brigham Young University.     

PIV applied to eckart streaming produced by a medical ultrasound transducer.

Particle image velocimetry (PIV) is applied for the first time to study Eckart streaming induced by a medical ultrasonic transducer operating at a frequency of 3.3 MHz and effective acoustic intensities of 0.25 and 3 Wcm(-2). A temporal series of velocities in a two-dimensional plane were recorded resulting in an experimental set comprising over half a million velocity data points. These enabled average and fluctuating properties to be determined and clearly indicated the quasi-steady nature of the flow. The average large scale velocity fluctuations along the axis caused by this quasi-steady property were calculated to be 2 and 20 m ms(-1) at effective intensities of 0.25 and 3 Wcm(-2) respectively corresponding to approximately 25% of the peak flow velocity in both cases. Furthermore averaged shear rates were calculated with peak values of 1 and 8 s(-1) for the low and high intensities respectively. The present investigation indicates the usefulness of PIV for such studies and serves as a prelude to investigations of streaming in biological type fluids.     

陶瓷真空室镀膜工艺改进及脉冲磁场时间特性测量

 介绍了合肥光源二期工程注入段陶瓷真空室的改进情况,采用新的镀膜技术,大大改善了脉冲磁场的延时特性,减少了储存环注入时的轨道扰动,提高了注入束流累积效速率。改进了原来的点线圈磁场测量方法,采用带有积分电路及抗干扰措施的双线圈测量装置测量了真空室内的脉冲磁场延时特性,使脉冲磁场延时误差测量的分辨率达到ns量级,给出了测量结果。     

陶瓷真空室镀膜工艺改进及脉冲磁场时间特性测量

介绍了合肥光源二期工程注入段陶瓷真空室的改进情况,采用新的镀膜技术,大大改善了脉冲磁场的延时特性,减少了储存环注入时的轨道扰动,提高了注入束流累积效速率。改进了原来的点线圈磁场测量方法,采用带有积分电路及抗干扰措施的双线圈测量装置测量了真空室内的脉冲磁场延时特性,使脉冲磁场延时误差测量的分辨率达到ns量级,给出了测量结果。     

Directional reception of broadband signals by means of ultrasonic transducer arrays

This paper presents a new approach to the theory and technique of ultrasonic transducer arrays, which makes it possible to obtain their directional beam patterns for receiving broadband acoustical signals.The general formulae were derived for the beam pattern of the array, and as an example the beam patterns of the end-fire array have been computed and plotted, for signals of different correlation function.For experimental verification of the theory the simple processor solution is proposed. This technique is based on spatial/temporal signal processing for beamforming of the directional response of an end-fire array.     

Ratcheting up energy by means of measurement

The destruction of quantum coherence can pump energy into a system. For our examples this is paradoxical because the destroyed correlations are ordinarily considered negligible. Mathematically the explanation is straightforward and physically one can identify the degrees of freedom supplying this energy. Nevertheless, the energy input can be calculated without specific reference to those degrees of freedom.     

Optimization of the piezoelectric transducer response by means of electrical correcting circuits

A method of shortening the transient response of a piezoelectric transducer is described. It can be applied to thickness mode piezoelectric transducers of arbitrary electromechanical coupling. The system incorporates electrical correcting circuits and can produce a transient response with a duration much shorter than the transit time of an ultrasonic wave travelling through the piezoelectric plate.     

压电薄膜超声换能器的特性研究

从KLM机电耦合等效电路出发,同时考虑机械损耗和介电损耗的影响,分析和研究了压电薄膜材料和背村材料对换能器输入功率损耗及输出波形的影响.在此基础上,设计和制作了PVDF高频超声聚焦换能器,理论和实验结果进行了对比.     

Vibration attenuation by means of piezoelectric transducer shunted to synthetic negative capacitance

This paper deals with vibration attenuation by use of piezo-actuators connected to a Negative Capacitance circuit, generally formed by a synthetic impedance based on operational amplifiers.The goal of this paper is to investigate the means to improve vibration attenuation performances and to avoid instability applying proper choices of the values of the electric elements composing the Negative Capacitance. This is accomplished using an analytic-numerical approach, which furthermore affords a full understanding of this technique. The paper also illustrates the mentioned instability problems at low-frequency and provides indications on how to avoid them. The results this way obtained are finally validated through experimental tests.     

利用PVDF传感器检测激光超声的实验研究

简要介绍了激光超声技术以及声表面波的基本特点、激光超声产生和接收的基本原理及激光超声技术的应用。概述了聚偏二氟乙烯（PVDF）压电薄膜材料的结构、性质和应用，以及薄膜压电性产生的机理。对PVDF换能器的设计思路和实验方法进行了简单讨论。具体实验采用脉冲激光器激发声表面波，利用PVDF传感器接收实验信号，调试实验信号，得出波形，并对实验现象作出初步分析。证实了该实验装置应用于激光超声无损检测的可行性与可靠性。     

Low-intensity pulsed ultrasound enhances cell killing induced by X-irradiation

To determine the effect of pulsed ultrasound (US) on radiation-induced cell killing, U937 and Molt-4 cell lines were exposed to 1.0 MHz US with 50% of duty factor at 0.3 W/cm² and pulsed at 1 Hz immediately after exposure to X-rays at 0, 0.5, 2.5 and 5 Gy. The cells were assayed 24 h after the treatments. The result showed significant enhancement of cell killing in the combined treatments. However, the ratio of apoptotic cells induced either by X-rays or US alone did not significantly change. These findings suggest that pulsed US can enhance the anticancer effect of X-irradiation due to US streaming under non-inertial cavitational condition. This combined treatment can potentially enhance the therapeutic effect of radiation therapy.     

弯张壳体装配位移的理论计算及实验测量

精确地控制施加于驱动元件上的预应力，对换能器设计有着重要意义，本文结合我们的课题研究工作，用有限元方法，计算了Ⅶ型水声弯张换器壳体给驱动元件施加一定预应力时，壳体所需的装配位称的大小，并通过初步实验作了验证，本文的计算及装配方法，可以推广到其它类型的弯张换能器中。