纳米金红石型TiO2催化超声降解亚甲基蓝溶液

水溶性染料是印染工业中污染治理的主要对象,由于它们大多含有苯环,目前所使用的化学和生物等处理方法效果均不佳。而以半导体为催化剂的光催化处理方法对单一染料和实际印染废水处理效果较好。本文采用高温处理过的纳米TiO2作催化剂对亚甲基蓝溶液进行降解,大大缩短了降解时间,提高了降解率,60min降解率即可达66．8％,120min降解率则可达80％以上。而且发现利用超声波来替代紫外光对亚甲基蓝进行降解时,     

超高效液相色谱-串联质谱法同时快速测定卷烟烟丝中的6种生物碱

建立了超高效液相色谱-串联质谱( UPLC - MS/MS)同时快速测定烟草中6种生物碱的方法.对样品前处理条件和仪器分离条件进行了优化,样品经去离子水超声提取后,于UPLC BEH C18色谱柱上分离,在多反应监测模式下采用同位素内标法定量以排除基质效应.结果表明,6种生物碱的线性范围为0.1～8 000 μg/L,...     

基于粒子群算法的稀疏阵列超声相控阵全聚焦成像

为降低相控阵超声检测全聚焦算法的成像数据量及阵列稀疏优化的计算时间,研究了一种用于稀疏阵列全聚焦成像的阵列优化算法,并通过实验对其成像效果进行了验证。针对目前超声相控阵检测的全矩阵采集数据量大、全聚焦算法成像时间长的难点,该文通过构建稀疏阵列,在保证成像质量的同时显著降低成像数据量,提高了全聚焦算法的成像效率。通过以主瓣宽度、旁瓣峰值以及主瓣峰值作为约束条件构建适应度函数,采用粒子群算法得到稀疏阵元位置分布并进行阵元权重修正,并将其用于稀疏全聚焦成像。相比全阵元成像,使用粒子群算法所得的稀疏阵列的阵元个数降低了56.25%、65.62%,数据使用量降低了80.86%、88.18%。在阵列优化方面,相比遗传算法减少了84.86%的计算时间。     

利用激光多普勒测振仪的空气耦合超声声场测量*

进行了空气耦合超声声场测量的实验研究。使用激光多普勒测振仪测量由声波引起的激光路径上的介质折射率变化,进而得到空气和固体材料内部的时域瞬态声压。通过直接测量空耦换能器的辐射声功率,给出对单个空耦换能器灵敏度的直接评价方法。用空耦换能器激励K9玻璃板的漏兰姆波,观测到空气中的直达波和反射波、固体板内和空气中的漏兰姆波,实现了空气和固体中微弱声波的非侵入式实验测量,为空耦换能器的特性评估和空耦检测系统的声场测量提供了实验方法。     

10 kV交联聚乙烯电缆中超声波传播规律*

电缆局放会产生超声波,利用超声波可以进行局放定位和大小估计。为了研究电缆中局放超声波的传播规律,利用COMSOL建立了基于10 kV交联聚乙烯电力电缆本体的声压场仿真模型,探究了超声波在电缆中的扩散过程和电缆表面超声波峰峰值随传播距离的变化规律之间的关系,并在真实10 kV单相交联聚乙烯电缆上进行了超声波衰减实验,探究了真实电缆表面超声波峰峰值随传播距离的衰减规律。结果表明：电缆表面声波峰峰值随传播距离的衰减符合指数规律,衰减系数?=0.07 Np/mm(或0.62 dB/mm),并且是电缆内部声波的扩散过程导致了电缆表面声波峰峰值的严重衰减。据此,针对10 kV 交联聚乙烯电缆,建议将局放超声传感器安装在距离局放易发位置100 mm以内,还提出了判断电缆中局放超声波扩散过程结束位置的方法,为确定其他类似型号电缆安装超声传感器的位置提供参考。     

Nonlinear dynamics of a cavitation bubble pair near a rigid boundary in a standing ultrasonic wave field

The dynamics of a micrometer-sized bubble pair in water near a rigid boundary under standing ultrasonic wave excitation is investigated in this study. The viscous effect in the boundary layer at the air-water interface is considered following the viscous correction model. The evolution of the bubble surface at the collapsing stage of the bubble pair is presented for different parameter sets. The field pressure near the rigid boundary, which is induced by the oscillating bubble pair, and the high-speed water jet at the collapse stage, form the main focus of the analysis. This reveals that a horizontal configuration of the bubble pair retards the strength of the bubble jet towards the boundary, whilst a vertical configuration, especially with differently-sized bubbles, can enhance the bubble collapse. This study may help to understand the interaction of multiple bubbles in an acoustic field and its application to surface cleaning.     

利用激光超声技术研究表面微裂纹缺陷材料的低通滤波效应

利用激光激发声表面波的理论模型,研究了被激发宽带声表面波在具有表面微裂纹缺陷金属材料上的传播特性.对具有不同形状的表面缺陷模型进行了数值分析.结果表明:表面微裂纹缺陷有明显的低通效应,缺陷深度越大高频截止频率就越低,缺陷深度与低通滤波的截止频率呈近似线性关系;缺陷的宽度增大对表面波透射能量有明显的衰减作用. 关键词： 激光超声 声表面波 有限元方法 低通滤波器     

光速测定中激光调制频率选择性的研究

对激光经过超声晶体光栅调制从而利用相位差和光程差进行光速测定进行了理论分析和实验研究。结果表明,在光速测定时超声波频率的选择并不影响测量结果,但在晶体谐振频率附近进行测量更有利于光强波形的观察和结果的测定。这一结论在同类实验问题的操作上具有一定的指导意义。     

Transmission circuits for thick-transducer ultrasound transmission test systems

Pulse techniques for the measurement of ultrasonic absorption over a wide frequency bandwidth are limited by the narrow band nature of conventional piezoelectric transducers. This problem can be overcome if the piezoelectric devices are operated as thick elements. In this paper the insertion characteristics of transducers operating in this mode are determined. The compromise between system sensitivity, bandwidth and noise generation in receiving circuits is examined.It is shown that high voltage generators with rise times of a few nanoseconds are required to drive thick transmission transducers. The design of suitable generators, based on avalanche operation of one or more bipolar transistors is described in detail. It is concluded that exciting signals of sufficient amplitude and short enough rise-time could be generated for absorption measurements to be made over at least two decades of frequency with a dynamic range of 100 dB without a change of transducer.     

Resonance tracking and vibration stablilization for high power ultrasonic transducers

Resonant frequency shift and electrical impedance variation are common phenomena in the application of high power ultrasonic transducers, e.g. in focused ultrasound surgery and in cutting. They result in low power efficiency and unstable vibration amplitude. To solve this problem, a driving and measurement system has been developed to track the resonance of high power transducers and to stabilise their vibration velocity. This has the ability to monitor the operating and performance parameters of the ultrasonic transducers in real time. The configuration of the system, with its control algorithm implemented in LabVIEW (National Instruments, Newbury, UK), ensures flexibility to suit different transducers and load conditions. In addition, with different programs, it can be utilised as a high power impedance analyser or an instantaneous electrical power measurement system for frequencies in the MHz range. The effectiveness of this system has been demonstrated in detailed studies. With it, high transducer performance at high power can be achieved and monitored in real time.