基于小波再分配尺度谱的Lamb波时频特性研究

基于声—超声技术,对铝板中Lamb波的时频特性进行理论和实验研究,采用小波再分配尺度谱方法对铝板中Lamb波的时频特性进行实验研究和深入探讨,并对铝板中有无模拟损伤的情况做了对比研究和分析,研究相应Lamb波的信号特征,从而实现了铝板结构损伤监测的定性研究。

Applying sub-band energy extraction to noise cancellation of ultrasonic NDT signal

In ultrasonic non-destructive tests, the echo signal at the flaw is highly complex due to the interference of multiple echoes with random amplitudes and phases, and is disturbed by all kinds of noises, such as thermal noise, digitalization noise, and structure noise. In this paper, the ultrasonic signal was decomposed by empirical mode decomposition (EMD) to obtain the in-trinsic mode function (IMF) components according to ultrasonic defect echo signals occuring at the corresponding time, and the energy of the ultrasonic signal was concentrated. The IMF component selection criterion based on sub-band energy extraction was proposed to extract the ultrasonic signal component accurately and automatically from IMF components. When the selected IMF components were filtered by a band pass filter, the signal-to-noise ratio (SNR) was enhanced greatly.

Diagnosis and Treatment Value of Ultrasound for Hepatobiliary and Pancreatic Disease

As an innovative technology, ultrasound has been applied to agriculture, medical, military, aerospace, machinery and other fields widely, as well as the medical industry, such as ultrasound diagnosis, ultrasound therapy. Ultrasonic technology has many advantages, and it certainly will promote the progress in medical area as a new method.

Application of ultrasound in the diagnosis of clinical anesthesia

During the past 10 years, the rapid development of ultrasound technology in clinical anesthesia has become one of the hot clinical researches. Researches in this area home and abroad also made great progress. On the one hand due to improved high-resolution portable ultrasound instrument and probe technology, ultrasound changed from a purely clinical diagnostic into the operating room; on the other hand, with the traditional method of anesthesia increasingly unable to meet the clinical requirements, it is an objective need of technological innovation for clinical anesthesia. And ultrasound has non-invasive, real-time, visible and repeatable characteristics which are able to provide accurate data and rich means for preoperative assessment, intraoperative monitoring and treatment of pain in pre-clinical anesthesia

Effects of Precipitation on Sonic Anemometer Measurements of Turbulent Fluxes in the Atmospheric Surface Layer

Effects caused by precipitation on the measurements of three-dimensional sonic anemometer are analyzed based on a field observational experiment conducted in Maoming, Guangdong Province, China. Obvious fluctuations induced by precipitation are observed for the outputs of sonic anemometer-derived temperature and wind velocity components. A technique of turbulence spectra and cospectra normalized in the framework of similarity theory is utilized to validate the measured variables and calculated fluxes. It is found that the sensitivity of sonic anemometer-derived temperature to precipitation is significant, compared with that of the wind velocity components. The spectra of wind velocity and cospectra of momentum flux resemble the standard universal shape with the slopes of the spectra and cospectra at the inertial subrange, following the-2/3 and-4/3 power law, respectively, even under the condition of heavy rain. Contaminated by precipitation, however, the spectra of temperature and cospectra of sensible heat flux do not exhibit a universal shape and have obvious frequency loss at the inertial subrange. From the physical structure and working principle of sonic anemometer, a possible explanation is proposed to describe this difference, which is found to be related to the variations of precipitation particles. Corrections for errors of sonic anemometer-derived temperature under precipitation is needed, which is still under exploration.

Ultrasonic Resonator Techniques for Broad-band Spectroscopy and for High-resolution Sound Velocity Measurement of Liquids

This review gives a short introduction into the principles of ultrasonic measurement techniques for liquids, using cavity resonators. Guidelines for the resonator design in broad-band ultrasonic stxctroscopy as well as in high-resolution single-frequncy or narrowband applications are presented. Deviations of the field configuration in real cells frtxn that in an ideal resonator are discussed and relations for the mode spectrum of cavity fields are given. Recent resonator measurement procedures and methods of data evaluation are mentioned briefly. Some examples of measurements show the extended usability of ultrasonic resonator techniques in basic science and in a wide range of applications for rrkaterials characterization, in manufacturing processes, as well as in control routines.

Experimental Research on Antiscale and Scale Removal by Ultrasonic Cavitation

Aiming at the scale problem in heat-transfer equipments, experimental investigation on antiscale and scale removalby ultrasonic cavitation is performed. By means of microscopic magnifying photography system, thesedimentary phenomenon can be observed. The experimental research reveals the influencing rule of acoustic intensity,cavitational distance, liquid temperature and solution concentration. The experimental results indicate thatliquid temperature has different effects on antiscale and scale removal. Different experimental liquids are used forantiscale and scale removal experiments. The results show that every liquid has a respective Cavitational activetemperature. When ultrasonic is used for antiscale, the smaller acoustic intensity is, the better effect is. But, whenultrasonic is used for scale removal, acoustic intensity has a reverse influence. In addition, biggish solution concentrationis propitious to antiscale for long-time running. Distance of test sample to ultrasonic transducer alsohas certain influence on antiscale and scale removal. The smaller the distance to ultrasonic transducer is, the bettereffects antiscale and scale removal have.

Scanning near-field acoustic microscope and its application

Scanning near-field acoustic microscope （SNAM） combines the ultrasonic detection technology with scanning near-field microscopy. The main characteristic of such microscope is that the acoustic wave is produced or detected in near-field area whether ultrasonic transducer acts as generator or detector. The resolution of SNAM can reach to nanometer scale. First, two typical SNAMs, scanning electron acoustic Inicroscope and scanning probe acoustic microscope, will be introduced in this paper. The working principle of our homemade SNAM based on a commercial scanning probe microscope will be reported, together with some recent results from this homemade SNAM.