压电声透传输新模型

压电声透传输是近年来声载波传输的一个研究热点,通过将电信号转换成声波穿透金属障碍物,可实现其两侧的信号能量传输。一般采用的是由两个正对的压电换能器和中间金属夹层构成的“三明治型”结构。相比较于电感耦合,该方式不需要电磁场作为能量传输的载体,因此适用于传输距离远大于换能器尺寸的情况以及其他电磁屏蔽的应用场景。近十年来,各国的科学家分别从不同的方面对压电声透传输的各个部分进行了建模,但一直没有一个较为完善的统一整体模型。     

单载波频域均衡压电声透通信研究

研究了单载波频域均衡压电声透通信技术,将系统复杂度集中至介质一侧,并实现高速压电声透通信。分析了压电声透系统信道特性,通过变步长自适应滤波器,有效降低了信道响应的计算量并提高了收敛速度。提出一种改进的单载波频域均衡相关同步算法,可涵盖已有的多种同步方案并提出最佳同步的帧结构判决方案。在此基础上,结合训练序列信息和能量判决方法,提出了针对压电声透通信系统的综合同步算法。同时针对实际应用中的采样起始点偏移和频率偏差累积问题,提出了相应的优化策略。实验中采用中心频率为500 kHz的换能器,在4 cm厚钢板两侧可达到1.298 Mbps的最大传输速率,表明该算法能有效抑制码间干扰,降低误比特率。     

跨金属厚壁的视频超声无线通信系统

视频无线传输作为高速通信技术的重要应用场景之一,目前在跨金属超声无线通信领域还鲜见报道,为此,基于FPGA芯片采用单载波时域均衡技术(SC-TDE)搭建了一套高速的跨金属超声无线通信系统。系统以工作频率10 MHz的PZT超声换能器作为超声波的发射端和接收端,基于符号LMS算法在FPGA中构建自适应时域均衡器以实现回波消除。以系统摄像头所采集现场视频数据作为信号源,开展了在厚度50 mm铝板双侧之间的超声无线通信试验。结果表明在穿透厚铝板时,SC-TDE让系统接收信噪比由原来的12 dB提高到26 dB,使得实时视频无线传输得以实现。     

基于IIC和云服务器的智能家居控制系统设计

智能家居普遍采用无线通信技术对家居进行互联,不同的通信方法对智能家居系统的稳定性、便捷性、可靠性有很大的影响;针对智能家居的访问方式,通过对比不同的无线通信技术,选择合适的技术运用在智能家居系统的设计中,实现局域网和广域网两种访问方式；在无线传输的智能家居基础上,使用IIC总线进行功能扩展,使用云服务器来替代传统计算机服务器,增加了系统的灵活性和手机访问的快捷性,更好地实现家庭住宅管理与监测,为我们平时的生活提供便利和保护。     

压电陶瓷超声波马达

压电陶瓷超声波马达是利用压电陶瓷材料激发超声波实现驱动的一种新型电机,同传统的电磁马达和静电马达比较,它具有低速下大力矩输出、无电磁干扰、静音操作、保持力矩大、响应速度快、结构简单等特点.在国外,它已经在精密仪器、航天航空、自动控制、办公自动化、微型机械系统、微装配、精密定位等领域得到了实际应用.文章系统地总结了压电陶瓷声马达的特点,简略介绍了国内外相关技术的发展情况及前沿性研究方向,并提出进一步开发研究的几点建议,希望会对我国压电陶瓷声马达的研究以及相应产品的开发起到积极的促进作用.     

LTE宽带无线通信系统在探测器网络中的应用

为提高探测器网络的数据传输能力,适应其网络化、协同化的工作方式,采用基于LTE标准的宽带无线通信系统来构建高速信息链路;为验证LTE宽带无线通信系统的传输能力,分别进行了内场和外场测试;测试结果表明,通过合理选择部署地点,该通信系统满足现有探测器网络更高数据传输容量和更低差错率的要求,同时实现了对通信资源的高效合理利用;LTE宽带无线通信系统具有数据速率高、设备精简、易于快速展开等优点,最后对LTE在专网中的应用前景作了展望。     

压电陶瓷超声波马达

压电陶瓷超声波马达是利用压电陶瓷材料激发超声波实现驱动的一种新型电机，同传统的电磁马达和静电马达比较，它具有低速下大力矩输出、无电磁干扰、静音操作、保持力矩大、响应速度快、结构简单等特点。在国外，它已经在精密仪器、航天航空、自动控制、办公自动化、微型机械系统、微装配、精密定位等领域得到了实际应用。文章系统地总结了电压陶瓷声马达的特点，简略介绍了国内外相关技术的发展发问及前沿性研究方向，并提出进一步开发研究的几点建议，希望会对我国压电陶瓷声马达的研究以及相应产品的开发起到积极的促进作用。     

基于跳频通信的移动机械遥控系统

为解决在同一个工作区域多个无线通信网络容易彼此干扰无法协同工作的问题,以移动机械工程车辆为控制对象,设计JRCJ500无线遥控系统,由用户手持终端接收用户操作指令,现场控制器驱动远程设备动作,实现对车辆的远程操作控制与状态信息反馈;采用STM32L低功耗处理器设计无线通信模块,选择公用通信频段,基于跳频扩频通信技术,约定无线通信数据格式与跳频频点,通过简单高效的跳频图案生成算法,在每一帧数据中添加同步字头,实现了无线通信网络的快速同步组网,保证了通信的稳定性,实现了在限定工作区域多台无线通信设备同时工作的应用需求。由于采用模块化设计,系统具有良好的通用性和可移植性,能够在多种复杂恶劣工作场合实现远程控制功能。     

基于UVC LED的小型化紫外无线通信技术

紫外光通信技术具有低窃听、低位辨、全方位、全天候、抗干扰等优点,而基于紫外光灯的通信系统存在光源体积大、易碎、调制困难、通信速率低、功耗大等问题。设计了一种基于紫外C波段(UVC)LED的小型化无线通信系统方案,并对系统性能进行了理论分析。系统光源采用UVC LED,探测器采用日盲光电倍增管(PMT)和窄带紫外滤光片,通信系统采用开关键控(OOK)和脉冲位置调制(PPM)调制方案。仿真结果表明所设计的紫外无线通信系统可在200mW发射光功率情况下实现直径200m范围内的非视距语音通信和100mW发射光功率情况下实现250m的64Kbps准视距通信。     

基于无线通信的激光超声测量系统

激光超声测量技术是一种重要和先进的非接触式超声测量技术.为了减少测量系统各构成部分间的电缆连接,将无线通信技术与激光测量技术的特点相结合,研究了一种激光超声无损测量系统,分析了该测量系统的原理及构成.系统用掺钕钇铝石榴石固体激光器在材料中激励超声波,压电换能器接收超声信号.该信号经系统级芯片MSP430F2274单片机放大、模数转换成数字信号,然后由单片机控制nRF905芯片进行信号的无线传输.接收部分的单片机采用RS-232-C接口标准实现与计算机的串行通信,把信号送入计算机显示记录存储和处理.结果表明该系统实现了激光超声的近程无线测量, 简化了系统的结构,传输性能稳定,对周围电子仪器干扰小,显示了很好的应用前景.     

Effects of the pump-circuit acoustic coupling on the blade-passing frequency perturbations

Centrifugal pumps are a source of pressure and flow rate perturbations in hydraulic pumping systems. In particular, a significant excitation is usually induced at the blade-passing frequency and harmonics as a consequence of the fluid-dynamic interaction between the rotor and the stator. The magnitude of this excitation is very dependent on the internal geometry of the pump and on its point of operation, but it depends also on the acoustic response of the hydraulic network to the perturbations. The induced and transmitted perturbations can be either amplified or reduced depending on the pump-circuit acoustic coupling, and thus they can lead to excessive levels of noise and vibration under certain conditions. The purpose of the present investigation is the theoretical and experimental characterization of the perturbations induced in a laboratory pumping system, as a function of the acoustic impedance of the pipelines. For different points of operation, the blade-passing frequency impedance is changed by varying the speed of rotation and, additionally, by modifying a closed side branch of the hydraulic system (that is, in the absence of net flow through it). For the theoretical calculations an acoustic model, based on matrix formulation, is applied to obtain the influence of different acoustic impedances of the suction side on the pressure fluctuations at the pump. Test measurements with a fast-response piezoelectric pressure transducer situated at the tongue region of the pump under the same system configurations confirm the significant effect of the pump-circuit acoustic coupling on the pressure perturbations.     

Manipulation with sound and vibration: A review on the micromanipulation system based on sub-MHz acoustic waves

Manipulation of micro-objects have been playing an essential role in biochemical analysis or clinical diagnostics. Among the diverse technologies for micromanipulation, acoustic methods show the advantages of good biocompatibility, wide tunability, a label-free and contactless manner. Thus, acoustic micromanipulations have been widely exploited in micro-analysis systems. In this article, we reviewed the acoustic micromanipulation systems that were actuated by sub-MHz acoustic waves. In contrast to the high-frequency range, the acoustic microsystems operating at sub-MHz acoustic frequency are more accessible, whose acoustic sources are at low cost and even available from daily acoustic devices (e.g. buzzers, speakers, piezoelectric plates). The broad availability, with the addition of the advantages of acoustic micromanipulation, make sub-MHz microsystems promising for a variety of biomedical applications. Here, we review recent progresses in sub-MHz acoustic micromanipulation technologies, focusing on their applications in biomedical fields. These technologies are based on the basic acoustic phenomenon, such as cavitation, acoustic radiation force, and acoustic streaming. And categorized by their applications, we introduce these systems for mixing, pumping and droplet generation, separation and enrichment, patterning, rotation, propulsion and actuation. The diverse applications of these systems hold great promise for a wide range of enhancements in biomedicines and attract increasing interest for further investigation.     

Generation and detection of nano ultrasound waves with a multiple strained layer structure

In this paper a multiple strained layer structure with multiple quantum wells as a piezoelectric transducer is proposed for generating and detecting nano ultrasound waves with nanometer wavelength and tera hertz frequency. By inducing femtosecond optical pulses at this strained structure, internal piezoelectric field is changed. As a result longitudinal acoustic phonon oscillations can be treated as nano acoustic waves. It could be noticed in simulated cases that detection of nano ultrasound waves can be used in non destructive testing and high accuracy measurements with this structure. It is also shown that the MQW structure design how influences in generated nano acoustic waves.     

Acoustic manipulation of active spherical carriers: Generation of negative radiation force

This paper examines theoretically a novel mechanism of generating negative (pulling) radiation force for acoustic manipulation of spherical carriers equipped with piezoelectric actuators in its inner surface. In this mechanism, the spherical particle is handled by common plane progressive monochromatic acoustic waves instead of zero-/higher- order Bessel beams or standing waves field. The handling strategy is based on applying a spatially uniform harmonic electrical voltage at the piezoelectric actuator with the same frequency of handling acoustic waves, in order to change the radiation force effect from repulsive (away from source) to attractive (toward source). This study may be considered as a start point for development of contact-free precise handling and entrapment technology of active carriers which are essential in many engineering and medicine applications.     

用压电聚合物构成的单极性声脉冲发生器

本文介绍了用阶跃电压的快速下降沿作用在PVDF压电膜上而产生的单极性声脉冲。实验结果表明，声脉冲的波形和脉冲宽度取决于PVDF压电膜的厚度，阶跃电压的下降沿宽度，以及背衬材料和声传播媒质的形状等多个因素。该声脉冲发生器所产生的压力波脉冲的宽度约为50ns，不仅适用于固体中空间电荷的测量，也可以用于其他方面的应用，例如超声医学诊断，对材料的非破坏性的检测等。文章以该声脉冲发生器在压电压力波中的应用为例进行论述，并且所有测量结果都是通过压电压力波测试系统获得的。     

Proposed method of partial discharge allocation with acoustic emission sensors within power transformers

Employing acoustic emission sensors for detection of partial discharge, PD, introduces many advantages. Besides easy installation and replacement, they are non-invasive and immune to electromagnetic noise and interference and their sensitivity does not vary with object capacitance. For PD allocating utilizing AE sensors, distance calculations are based on the arrival time of acoustic waves to the sensors. Considering structure-borne waves of higher speed, the peaks of some of indirect path AE signals with significant contribution are mistakenly considered as peaks of direct path AE signals. Furthermore, the acoustic signals are propagating through certain parts of the transformer, such as the windings, and this complicates the partial discharge detection and allocation. These would imply an incorrect distance between the source and sensor. A method based on a heuristic algorithm has been proposed which considering all possible indirect paths with the relevant propagation times and all the barriers on the travel path of acoustic signal, calculates the more precise arrival times to sensors. A test chamber has been utilized and artificial PD signals are produced at various points. Output results of algorithm have been compared with results of classic method. It has been shown that proposed method significantly reduces the positioning errors.     

一种用于变压器局部放电在线监测的光纤声发射传感器实验研究

提出了一种光纤声发射传感器并构建传感系统实现变压器局部放电在线监测,利用传感光栅体积小,重量轻,灵敏度高和抗电磁干扰的特点,将传感器置于变压器内部实现局部放电声发射信号的测量。研究了传感光栅实现声发射应力波测量的机理,声发射信号引起传感光栅反射光谱发生漂移,导致特定频点处反射光强发生变化,通过反射光强的变化实现声发射信号的测量。构建声发射传感系统实验模型并提出了一种系统性能优化策略,使系统工作在传感光栅反射光谱上升或下降沿的半峰值频点处,从而保障传感系统具有良好的线性输出特性;研究传感系统工作点稳定技术,设计信号反馈回路自动跟踪反射光谱的漂移,保证系统稳定工作在传感光栅半峰值频点处,消除温度变化对传感系统测量精度的影响。将封装好的传感器用于变压器局部放电现场检测,结果表明,光纤光栅声发射传感器与压电传感器相比具有灵敏度高、动态范围宽等优点,可以实现变压器局部放电在线监测。     

Picosecond acoustics in vegetal cells: Non-invasive in vitro measurements at a sub-cell scale

A 100 fs laser pulse passes through a single transparent cell and is absorbed at the surface of a metallic substrate. Picosecond acoustic waves are generated and propagate through the cell in contact with the metal. Interaction of the high frequency acoustic pulse with a probe laser light gives rise to Brillouin oscillations. The measurements are thus made with lasers for both the opto-acoustic generation and the acousto-optic detection, and acoustic frequencies as high as 11 GHz can be detected, as reported in this paper. The technique offers perspectives for single cell imaging. The in-plane resolution is limited by the pump and probe spot sizes, i.e. ∼1 μm, and the in-depth resolution is provided by the acoustic frequencies, typically in the GHz range. The effect of the technique on cell safety is discussed. Experiments achieved in vegetal cells illustrate the reproducibility and sensitivity of the measurements. The acoustic responses of cell organelles are significantly different. The results support the potentialities of the hypersonic non-invasive technique in the fields of bio-engineering and medicine.     

低声阻抗复合压电陶瓷的研究及应用

本文研究了我们所配制夹心结构复合压电材料低声阻抗的特性。实验表明，夹心复合压电陶瓷材料的声阻抗，与所用陶瓷材料的种类，气孔率，孔径，样品厚度以及工艺制备过程有关。实验证明，研制特定阻抗的材料是可行的，最后，用研制的新材料成功地应用于混凝土、Ｃ／Ｃ复合材料等非金属材料的超声检测中。