高温高压声接收换能器的研制和校准

我们研制了一种带毛细孔的能耐150℃和1420atm的高温高压声接收换能器(水听器),并在直径为70mm,高为290mm的圆筒形腔体内用就地互易法在上述高温高压条件下进行了校准.在频带为10Hz—10kHz的频率范围内,接收电压灵敏度为—195±1.5dB(0dB为1V/μPa),水平方向性的不均匀度小于±1.5dB.在常压到1420atm的压力范围内,接收电压灵敏度随压力的变化小于1dB;在150℃时的接收电压灵敏度,较常温下的接收电压灵敏度,只降低3dB.     

第三讲 让声纳系统耳目一新：新型水声换能器与换能器新技术

文章综述了新型水声换能器设计与换能器新技术的重要进展.主要涉及：稀土超磁致伸缩材料、弛豫铁电材料、压电聚合物薄膜等新材料的发展及其水声换能器的新设计,基于新结构的新型水声换能器,利用不同能量转换机理的新型水声换能器,宽带换能器新技术等等;对于接收型换能器着重介绍了光纤水听器和矢量水听器.     

第三讲让声纳系统耳目一新:新型水声换能器与换能器新技术

文章综述了新型水声换能器设计与换能器新技术的重要进展.主要涉及：稀土超磁致伸缩材料、弛豫铁电材料、压电聚合物薄膜等新材料的发展及其水声换能器的新设计,基于新结构的新型水声换能器,利用不同能量转换机理的新型水声换能器,宽带换能器新技术等等;对于接收型换能器着重介绍了光纤水听器和矢量水听器.     

检测超声换能器的校准与性能测量

检测超声换能器的性能是设计制造者和使用者都十分关心的问题。本文就超声换能器的几个主要整体性能——灵敏度、时间响应(传输函数)、空间响应(指向性和声场分布)以及等效电阻抗的测量与校准技术作了简要的综述。其中以灵敏度和时间响应的测量和校准为重点介绍了各种方法的原理和适用范围,并对其特点和局限性作了分析。     

基于PULSE系统的矢量水听器实时校准

基于对PULSE系统的应用开发研究,建立了矢量水听器实时校准可视化系统,利用ActiveX技术解决了PULSE系统与MATLAB实时通讯问题,这是实时校准的基础。并以矢量水听器理论基础为依据,用比较校准法原理通过MATLAB语言完成编程,同时解决了数据转化问题,通过建立的可视化界面实现对矢量水听器实时校准,提高了校准精度和可靠性,为矢量水听器使用前进行快速高效的校准创造了条件,同时也为其它声学设备校准提供了测量平台。     

数值计算法实现同振式矢量水听器驻波管中灵敏度修正

大尺寸的矢量水听器在驻波管中进行灵敏度校准时会引起校准声场分布不均匀, 使得灵敏度校准结果出现较大误差。在无法获取校准声场准确的解析表达式情况下, 以实际驻波管校准装置为原型, 建立声场仿真分析模型, 通过数值计算得到矢量水听器和参考标量水听器的声压和加速度量值, 并结合灵敏度校准公式和参考值导出灵敏度修正因子。利用修正因子, 对不同尺寸矢量水听器灵敏度测试结果修正以后, 与参考值最大绝对误差减小到2.0 dB下。结果表明数值计算法能有效减小非均匀声场引起的大尺寸矢量水听器灵敏度校准误差, 扩展了矢量水听器驻波管校准装置的测试对象。     

声发射研究中的宽频带接收换能器

文章总结了作者在宽频带声发射换能器方面的一些工作和体会,并给出了若干换能器灵敏度估算的数学推导。     

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.     

失谐驻波管及其极高纯净驻波场性质的研究

由直径不同的两级直圆管连接而成的两级突变截面驻波管具有失谐性,即高阶共振频率不是一阶共振频率的整数倍. 两级突变截面驻波管的失谐性质能够很好地抑制一阶共振频率激励下的大振幅非线性驻波畸变产生的高次谐波,从而获得大振幅纯净驻波场. 通过对两级突变截面驻波管失谐性质的研究,采用大功率扬声器正接等措施,利用两级突变截面驻波管的失谐性质在一阶共振频率激励下获得了184 dB的极高纯净驻波场,并对二至五阶共振频率激励下的声场进行了相应的实验研究. 在二阶、四阶共振频率激励下分别获得了180和166 dB波形比较规整的大振幅非线性驻波,并在三阶、五阶共振频率激励下观察到了谐波饱和现象和锯齿波.关键词：失谐驻波管大振幅驻波畸变饱和     

Dipole-induced grating in a waveguide-coupled photonic crystal microcavity embedding a driven three-level emitter

We study optical transmission characteristics of a waveguide-coupled photonic crystal microcavity embedding a driven three-level dipole emitter. By spatially modulating the control field, alternating regions of high transmission and absorption can be produced in two waveguide channels which can be used for an amplitude grating.     

On instability of excited states of the nonlinear Schrödinger equation

We introduce a new notion of linear stability for standing waves of the nonlinear Schrödinger equation (NLS) which requires not only that the spectrum of the linearization be real, but also that the generalized kernel be not degenerate and that the signature of all the positive eigenvalues be positive. We prove that excited states of the NLS are not linearly stable in this more restrictive sense. We then give a partial proof that this more restrictive notion of linear stability is a necessary condition to have orbital stability.     

关于热声压缩机原理的讨论

回顾了驻波、行波热声机械的发展历史 ,分析了行波与驻波热声压缩机的优缺点。介绍行波驻波混合型热声压缩机的工作原理及结构 ,指出了今后研究的重点和方向。     

Experimental investigation on finite-amplitude standing waves:Ⅰ. The properties of second harmonic

I.IntroductionInrecentyears,theresearchworkonnonlinearacousticshasbeendcvelopedrapid1ybe-causethehigh-intensitysoundismoreandmoreimportantincontcmporarytechnology.Aerodynamicnoiseemittedbyrockctorjetengines,noisetestofairframcs,u1trasonicpro-cessing,andothcrs,a1linvo1vefinitc-amplitudesoundwavesand,mostlystandingwaves.Athcoryofonc-dimensiona1finitc-amp1itudestandingwavesinlosslessmediahasbeenproposedbyMAAonthebasisofthcfundamenta1principlesofhydrodynamics['l,inwhichformulasofstcadywavcformsa…     

Physical forces exerted by microbubbles on a surface in a traveling wave field

The effect of a wave with a varying traveling component on the bubble activity as well as the physical force generated by microbubbles on a surface has been studied. The acoustic emission from a collection of bubbles is measured in a 928 kHz sound field. Particle removal tests on a surface, which actually measures the applied physical force by the bubbles on that surface, indicate a very strong dependence on the angle of incidence. In other words, when the traveling wave component is maximized, the average physical force applied by microbubbles reaches a maximum. Almost complete particle removal for 78 nm silica particles was obtained for a traveling wave, while particle removal efficiency was reduced to only a few percent when a standing wave was applied. This increase in particle removal for a traveling wave is probably caused by a decrease in bubble trapping at nodes and antinodes in a standing wave field.     

电动声源热声致冷机声学和计算实例

我们将各种热声致机简化为一包括声学终端在内的声管道系统,并通过实例讨论了致冷机的声学特性,该管道系统与一般声管道不同：１．在热声堆中热波和粘滞波不可不计。２．在热声堆与声管连接时,必需考虑合成波的体积流;而热声堆内只需考虑传播波的体积流。本文对此提出了阻抗连接条件的修正。实例使用电动扬声器为声源,给出了热声行波和驻波致冷的声学计算方法以及它们的声学特性,所用扬声器的标称伏安为１００ＶＡ,可为热声致     

Two-dimensional probe absorption in coupled quantum dots

We investigate the two-dimensional (2D) probe absorption in coupled quantum dots. It is found that, due to the position-dependent quantum interference effect, the 2D optical absorption spectrum can be easily controlled via adjusting the system parameters. Thus, our scheme may provide some technological applications in solid-state quantum communication.     

Coherent control of position-dependent probe absorption spectrum in a solid

We investigate the two-dimensional (2D) probe absorption spectrum in a four-subband coupled double quantum-well system driven by two orthogonal standing-wave lasers. It is found that, due to the quantum interference effect of interacting dark resonances, the 2D spatial distribution of probe absorption spectrum can be easily controlled via adjusting the system parameters. Thus, our scheme shows the underlying probability for the formation of the 2D electron localization in a solid.     

Controlling two-dimensional electron localization via phase-controlled absorption and gain in the three-coupled quantum wells

We investigate two-dimensional (2D) electron localization via phase-controlled absorption and gain of a weak probe field in an asymmetric semiconductor three-coupled quantum well (TCQW) with a closed loop under the action of two orthogonal standing-wave fields. It is found that we can achieve high-precision and high-resolution 2D electron localization via properly varying the parameters of the system. The influences of direct one-photon transition and indirect three-photon transition on the precision of probe absorption–gain spectra are also discussed in details. Thus, the proposed scheme shows the underlying probability for the formation of the 2D electron localization in a solid.     

基于分形理论的驻波声场中颗粒团运动特性数值预测*

基于分形理论,建立驻波声场中颗粒团动力学模型,对颗粒团的夹带系数、相位滞后和漂移系数进行数值预测。将预测结果和实验进行对比,二者吻合良好。在此基础上,研究了组成颗粒团的原生颗粒半径、数目以及排列情况对于颗粒团运动特性参数的影响。结果表明,对于由两个原生颗粒组成的颗粒团,原生颗粒半径越接近,颗粒团与等体积球形颗粒运动特性的差异越大;在分形维数一定时,随着原生颗粒数目的增多,颗粒团的夹带系数减小,相位滞后增加,漂移系数先增大后减小,颗粒团与等体积球形颗粒的动力学行为存在显著差异;原生颗粒排列趋于致密时,颗粒团的夹带系数增大,相位滞后减小,漂移系数发生单调变化,与等体积球形颗粒运动特性的差异缩小。