Effects of rapid thermal annealing on surface acoustic wave ultraviolet sensors using ZnO nanorods grown on AlN/Si structures

In this study, we demonstrate a high sensitivity of surface acoustic wave (SAW) ultraviolet (UV) sensor based on ZnO nanorods (NRs) grown on an aluminum nitride (AlN)/silicon (Si) layered structure. The one-dimensional ZnO NRs act as a high-UV sensing material due to their large surface-to-volume ratio. The fabrication of SAW UV sensor is entirely compatible with micro/nano electromechanical (M/NEMS) process with conventional lithography and synthesized ZnO NRs by hydrothermal method at low temperature. The rapid thermal annealing (RTA) process effectively improved the optical properties of ZnO NRs and the sensitivity of the SAW UV sensors. The resulting SAW UV sensors responded to various UV light intensities, and the RTA-processed samples showed high sensitivity. The SAW UV sensor after RTA treatment at 600 °C showed the highest sensitivity with a 130 kHz frequency shift at a UV light intensity of at 0.6 mW/cm², a 5-fold increase in sensitivity compare with as-grown sample.     

Application of TiO<Subscript>2</Subscript> thin film with nanorods to surface acoustic wave type ultraviolet photo detection

TiO₂ thin films with nanorods grown on 128° Y?cut LiNbO₃ and 90° rotated 42°45′ ST?cut quartz were used to fabricate surface acoustic wave ultraviolet photodetectors. TiO₂ thin film was deposited by radio?frequency magnetron sputtering and TiO₂ nanorods were then synthesized on the thin film via the hydrothermal method. 128° Y?cut LiNbO₃ is a Rayleigh wave substrate with a high electromechanical coupling coefficient, whereas 90° rotated 42°45′ ST?cut quartz is a surface skimming bulk wave substrate with a high wave velocity. The effects of substrate characteristics and TiO₂ nanorod morphology on the ultraviolet sensitivity of the surface acoustic wave photodetectors were investigated. The variations of insertion loss, phase, resistance, and capacitance under ultraviolet illumination were examined. The performance of the TiO₂ thin film with nanorods deposited on 128° Y?cut LiNbO₃ is much greater than that of the film deposited on 90° rotated 42°45′ ST?cut quartz, which can be attributed to the former’s high electromechanical coupling coefficient.     

基于ICA盲源分离的声表面波无线传感器信号抗干扰方法

针对声表面波传感器无线信号易受环境中同频信号干扰的问题,设计了基于独立分量分析(ICA)盲源分离的抗干扰算法.该算法对传感器和同频干扰的混合信号进行分离,然后基于分离信号波形的衰减和等幅特征对信号进行判别.MATLAB仿真结果表明,算法能够有效分离混合信号并且保留了源信号的时域波形特征和频域信息.将抗干扰算法在基于数字...     

声表面波无源无线温度传感器产品研究进展

声表面波（SAW）温度传感器可以实现无线无源检测,满足高温、高压、强电磁辐射和强电磁干扰等恶劣环境下正常工作,属于高水平传感器。首先介绍了应用SAW技术的无源无线温度传感器谐振型和延迟线型2种结构的基本工作原理,着重描述了目前国内外高温和低温SAW无源无线温度传感器的产品性能,对各产品进行了比较和分析,提出了SAW温度传感器询问距离的优化方法。询问距离的优化研究对SAW温度传感器在更广泛领域的应用将有深远意义。     

基于声波信号分析的电气设备故障诊断新方法

针对电气设备运行环境复杂这一特点,提出将声波分析技术应用到其故障诊断中,可克服高电压和强电磁场给故障检测带来的诸多难题.设计了基于声波识别的电气设备故障诊断专家系统的总体方案,故障诊断系统由信号采集、特征提取、状态识别和诊断决策4个部分组成,简要介绍了各部分的工作原理:阐述了一种使用分层阈值处理声音信号的消噪算法,将该方法与传统消噪方法作对比,证明了该算法在对非平稳信号分析中具有较高的精确性.给出小波包提取电气设备实测声波信号特征向量的算法,以此作为知识获取和推理的依据,为电气设备运行状态诊断专家系统的实现奠定了基础.     

基于凸优化算法的水声传感器阵列综合

稀疏基阵成像技术已在水下探测领域广为研究。针对稀疏基阵的分布特性带来的波束旁瓣电平升高、成像对比度降低等问题,提出一种基于加权范数最小化的阵列综合方法用于水下超声传感器阵列,设定目标函数及约束条件,进行多次的迭代,同时优化阵元位置与阵元激励,最后将20×20的面阵综合优化成51个阵元的稀疏基阵,旁瓣电平在-15 dB以下,并将凸优化阵列综合得到的稀疏基阵的波束图与切比雪夫阵列综合得到的波束图性能进行比较,且进行成像仿真,结果表明,采用凸优化获得的基阵在保证成像质量的同时,可以大幅减少发射阵元的数目,降低系统复杂性,并获得预期的旁瓣电平。     

基于声传感器阵的舰船被动定向研究

在被动声探测设备中声传感器阵对舰船目标宽带噪声源的精确定向取决于时延估计的精度,针对这一问题,将自适应参量模型算法与变步长的 LMS算法相结合,提出了一种可高精度估计任意时延,且收敛速度快的时延估计算法.结合舰船辐射宽带噪声,以正四面体声传感器定向阵列为例进行了计算机仿真,仿真结果表明：该方法估计所得的方位角误差小于0.1°,俯仰角误差小于1°,实现了对舰船目标宽带噪声源的精确定向,具有很好的工程实用价值.     

Ni-Cr合金超声导波温度传感器的设计

为了实现在高温环境下对温度的精准测量,基于超声导波测温原理,设计了一种镍铬合金超声导波温度传感器。镍铬合金具有抗氧化性好、高温环境下强度高、热膨胀系数小、导热性能好以及长期使用不变形等优点。经过分析,选用长为1 m,直径为0.8 mm,区截长度为30 mm的Ni-Cr合金丝作为敏感元,采集超声回波信号,利用互相关计算渡越时间,实现对温度的测量,并对传感器的测温范围、灵敏度以及重复性进行了分析,实验结果表明该传感器在1 100℃的强氧化环境下准确度达到了1%。     

Bulk acoustic wave RF technology

RF filtering in mobile terminals is dominated by surface acoustic wave (SAW) and bulk acoustic wave (BAW) based filters due to their high performance, small size, and low cost. As compared to SAW filter technology, BAW filter solutions can provide lower insertion loss, better selectivity, higher power handling, higher operation frequency, and better ESD protection. With these advantages, BAW filter technology has been gaining more market share in wireless communication application.     

Modelling of chemical surface acoustic wave sensors and comparative analysis of new sensing materials

Comparative analysis of different, new gas sensing materials in surface acoustic wave chemical sensors is presented. Different gas sensing materials as polyaniline (PANI), Teflon AF 2400, polyisobutylene (PIB), polyepichlorohydrin (PECH) are considered. They are chosen according to the type of gas to be detected and the desired accuracy: Teflon AF 2400 thin film for the detection of CO₂, PANI nanocomposites film that belongs to the group of conductive polymers for the detection of CO, NO₂ and phosgene (COCl₂), and PECH and PIB for the detection of dichloromethane (CH₂Cl₂, DCM). In the analysis, the simple and useful method of the complete analyses of gas chemical sensors is used. The method is based on the electrical equivalent circuit of the surface acoustic wave sensor. The method is very efficient and can be used for the optimal design of CO₂ sensors. The results are compared with those presented in public literature and good agreement is obtained, demonstrating the validity of modelling. Copyright © 2012 John Wiley & Sons, Ltd.     

基于MEMS惯性传感器的波浪测量系统设计与实现

波浪测量系统能够在固定海域、全天候、全天时地自动监测海洋的波高、周期和波向。设计了基于STM32F429处理器和MTI-3-8A7G6T惯性传感器的波浪测量系统。完成波浪测量系统的算法及软件设计,其中波高和波周期的测量采用在频域内对加速度进行二次积分,可以有效避免直流分量对积分结果的影响,同时在频域内进行数字滤波,滤除加速度计零偏误差和低频随机噪声;波向的测量是利用水平合成加速度与磁航向的夹角获得。通过软件设计将测波算法成功移植到STM32F429处理器中,实现波浪测量功能。经实验验证,针对不同波高和波周期的波浪,波浪测量系统的测量误差都在规定范围内。系统对波浪特征值解算准确,长时间运行稳定,满足高精度和高可靠性的测量要求。     

基于毫米波雷达传感器RAI图像的手势识别方法

针对现有的手势识别方法存在数据集过少、利用特征信息较少和神经网络部分提取信息不充分的问题,提出一种基于毫米波雷达传感器RAI图像的手势识别方法。首先使用TI公司的IWR1443毫米波雷达传感器采集10类手势数据构建数据集,再通过对手部反射的雷达信号进行时频分析,获取固定帧数的RDI和RAI。为了充分提取手势特征并精确分类,在卷积神经网络基础上,引入了残差块和通道注意力块。实验结果表明,相较其他特征如RDI,RAI能更准确的表征手势,所提出的网络相比于CNN方法准确率提高了12.72%,相比于VGG16-Net和单参数VGG16-Net方法准确率提高了8.93%与10.41%,参数量降低了90.68%,时间复杂度降低了17.2%。     

基于无线声发射传感器系统的活立木含水率诊断方法研究

水分在活立木的生长代谢过程中起着至关重要的作用,实时准确的含水率测量对于立木培育及林木经营具有关键指导意义。以无损检测活立木树干含水率为主要目标,设计并实现了一套基于无线声发射传感器网络(WASN)的木材含水率诊断系统。首先WASN节点高速采样树干表皮的声发射信号,接着计算其特征参数并无线传输至网关,然后采用最大相关最小冗余(mRMR)判据从中筛选出最优特征组合,并经由麻雀算法优化的支持向量机(SSA-SVM)建立含水率辨识模型,最后即可进行在线实时的长期监测诊断。分别在水杉、杨树、松树和山毛榉四类树种上进行了实测,结果表明,诊断准确率最低为95.5%,所设计WASN完全具备长期部署观测树木蒸腾作用的功能。     

A novel electrode‐area‐weighted method of implementing wavelet transform processor with surface acoustic wave device

The objective of this research was to investigate the possibility of a novel electrode‐area‐weighted (EAW) method of implementing wavelet transform processor (WTP) with surface acoustic wave (SAW) device. The motivation for this work was prompted by a diffraction problem of the WTP using SAW device. In this paper, we propose a novel EAW method in order to solve the diffraction problem. When the electrode areas of the EAW wavelet interdigital transducer (IDT) (i.e. the input IDT) are designed according to the envelope areas of the wavelet function, the impulse‐response function of the EAW wavelet IDT is equal to the wavelet function, so that the novel EAW WTP using SAW device can be fabricated. In this study, we also present the diffraction problem, the substrate material, and the electrode number of the output IDT as three key problems, and the solutions to the three key problems are implemented. Copyright © 2016 John Wiley & Sons, Ltd.     

无线传感网络在冲击波场中的应用

主要介绍了无线ZigBee传感网络的星型结构（一个主节点和多个从节点）在冲击波测试技术中的应用,利用无线传感网络触发的同步性使冲击波电路几乎同时进入工作状态并且通过单片机MSP430控制电路实时传回具体位,置的测试数据。     

A fast acoustic field mapping approach based on fabry–perot sensor with high‐speed camera

A Fabry–Perot (FP) interferometer‐based ultrasound sensor provides an inherently broadband response and excellent detection sensitivity compared to piezoelectric zirconate titanate (PZT) or polyvinylidene difluoride (PVDF) transducers. It is therefore expected to be used for medical ultrasound imaging and photoacoustic imaging. However, at present, mapping acoustic fields takes much time for scanning, which hinders real‐time measurement. We propose a new approach that utilizes a high‐speed camera (HSC) to map acoustic fields without mechanical scanning and to sample signals of acoustic waves with the shutter of the HSC. Experimental results indicate that acoustic field at the focus of a pulsed 1‐MHz PZT ultrasound transducer can be detected and mapped by using the FP sensor with the HSC. By improving the uniformity of the FP sensor and the exposure time, the frame rate of HSC can be further developed, and this approach should be able to provide a fast acoustic field mapping for high‐resolution biomedical photoacoustic and other ultrasonic imaging. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

The effect of nano‐ZnO on corona aging and photo aging in low‐density polyethylene

In this paper, space charge distributions as well as dielectric properties, such as volume resistivity and AC breakdown strength, were studied in low‐density polyethylene (LDPE) and its composite obtained by adding nano‐ZnO nanofiller, before and after photo‐oxidation or corona aging for several days. It was found that a small amount of ZnO nanoparticles could effectively improve both the photostabilization and corona stabilization of the LDPE matrix. Fourier transform infrared (FTIR) spectra of the specimens were investigated to reveal the change of the microstructures. The results showed that a weaker carbonyl absorption peak appeared in LDPE/ZnO nanocomposite than in LDPE. A proper explanation is given according to the photodegradation and corona degradation theory of polyethylene. The results also showed that there was a certain similarity between photo aging and corona aging. IEEJ Trans 2010 DOI: 10.1002/tee.20600     

基于紫外激光对硅基微通道刻蚀分析

紫外激光具有波长短、速度快、加工精度高、热影响区小以及无损加工等优点,针对紫外激光加工过程中,不同参数对刻蚀结果产生不同的影响,实验中通过控制单一变量法,设计了扫描速度、扫描次数、能量密度、重复频率、离焦量等不同参数对刻蚀结果的影响。实验结果表明,刻蚀宽度随能量密度的增加而增加,但是增加率不断降低;减小扫描速度,可以刻蚀出深度较深并且边缘工整的微通道;随着扫描次数的增大,激光刻蚀的深度不断增大,但增大率在不断的减小,刻蚀深度过深,激光将不会对沟道再进行刻蚀。实验中通过优化激光刻蚀参数,得到了刻蚀宽度为146μm、刻蚀深度为25.665μm、微通道边缘整齐,边缘粗糙度为7μm,沟道的垂直度将近90°的L型硅基微通道。     

基于LFMCW的L_(CR)波切向正应力检测方法的研究

以LFMCW（linear frequency modulated continuous wave）时间间隔测量原理为基础,针对LCR波（the critically refracted longitudinal wave）声弹性应力检测脉冲激发方式时存在的问题,提出了一种基于LFMCW方式激发LCR波的切向正应力检测系统,使用新的检测方法通过发射信号和接收信号形成的拍频信号来反映波的传播时间,用抛物线插值与最小二乘相结合的数字测频方法准确测量拍频频率。实验结果证明了该系统对LCR波传播声时检测的有效性。