共查询到20条相似文献,搜索用时 78 毫秒
1.
2.
通过对第五届全国超声波治疗学术会议(2000年12月1-5日于重庆)论文的综合介绍,本文报道我国超声波疗法临床应用方面近期取得的成就。 相似文献
3.
超声是频率高于20 000Hz的声波,由于它遇到障碍物能发生反射、透射,同时具有方向性好、穿透能力强等特征,很快在医学诊断中得到重要应用.本文着重阐述如何利用超声在人体各种组织内的传播特性不同而形成影像,对病理作出诊断提供依据。 相似文献
4.
2013年5月2日至5日,第4届国际超声大会(ICU)在新加坡召开。本次会议在国际声学委员会的组织下,由新加坡声学学会主办,由澳大利亚声学学会、印度声学学会、香港声学学会和印度无损检测学会联合承办。会议致力于促进超声不同领域,包括基础研究、工程技术以及生物医学应用等方面的国际交流与合作。 相似文献
6.
7.
8.
9.
提出了一种光通过超声驻波及超声行波后能产生高衬比度相干条纹的新术,利用超声驻波调制光束与超声行波作用后的相关衬比度来选定相干波束.从理论上分析了其相关叠加的结果,并在实验中得到了证实. 相似文献
10.
一、引 言 用工程技术方法研究生命科学大有发展前途.现代生物医学超声工程学正是这方面的一支生力军.它是超声物理学、现代电子检测技术和生物医学在发展中相互渗透的产物.是理、工、医相结合的边缘学科. 现代生物医学超声工程学主要包括基础理论研究、仪器工程开发和临床应用三个相互联系和相互促进的方面.它以超声波与生物组织 相似文献
11.
This paper describes the ultrasonic degradation of oxalic acid. The effects of ultrasonic power, H2O2, NaCl, external gases on the degradation of oxalic acid were investigated. Reactor flask containing oxalic acid was immersed in the ultrasonic bath with water as the coupling fluid. Representative samples withdrawn were analysed by volumetric titration. Degradation degree of oxalic acid increased with increasing ultrasonic power. It was observed that H2O2 has negative contribution on the degradation of oxalic acid and there was an optimum concentration of NaCl for enhancing the degradation degree of oxalic acid. Although bubbling nitrogen gave higher degradation than that for bubbling air, both gases (for 20 min before sonication and during sonication together) could not help to enhance the degradation of oxalic acid when compared with the degradation without gas passage. 相似文献
12.
This paper presents a system that accurately measures the distance travelled by ultrasound waves through the air. The simple design of the system and its obtained accuracy provide a tool for non-contact distance measurements required in the laser’s optical system that investigates the surface of the eyeball. 相似文献
13.
14.
In this paper, the effects of ultrasonic wave on the removal of inorganic scaling and plugging in cores and the influence of the key wave field parameters, process parameters and core physical parameters on the plugging removal efficiency are systematically studied. The main dynamic mechanism of ultrasonic plugging removal is also systematically analyzed. Results show that the transducer frequency, transducer power, ultrasonic treatment time and initial permeability of core have great influence on the effect of ultrasonic scale removal. When the cumulative treatment time of ultrasonic wave exceeds 60 min, the recovery rate of core permeability tends to be stable. Best effect can be achieved when processing for 80–120 min cumulatively; the plugging removal effect is improved with the increase of ultrasonic transducer power and ultrasonic frequency, but the effect of plugging removal is not obvious with the further increasing of them. In addition, it is proved that the effect of removing calcium carbonate plug from near wellbore by hydrochloric acid solution is slightly better than that by ultrasonic treatment alone. Finally, the micro dynamic mechanism of removing inorganic scale plug by high-power ultrasonic treatment is discussed in view of ultrasonic inorganic scale body crushing, ultrasonic cavitation, ultrasonic friction, ultrasonic peristaltic transport operation and ultrasonic fracture-making and permeability-increasing effect. 相似文献
15.
16.
17.
18.
Measurements of coating density using ultrasonic reflection coefficient phase spectrum 总被引:1,自引:0,他引:1
A nondestructive method to determine the density of coating has been proposed in this paper based on the ultrasonic reflection coefficient phase spectrum (URCPS). A model was set up first to represent the ultrasonic waves reflected from a coating system at normal incident, and the relation between the extremum of URCPS and the coating density was established to provide the principle of determining the density. The ultrasonic method was validated on a series of ZrO2-7 wt.%Y2O3 (YSZ) coatings with various density. The specimens were prepared by electric beam physical vapor deposit (EB-PVD). After deposition, the specimens were irradiated using high-intensity pulsed ion beam (HIPIB) at different ion current density of 100 and 200 A/cm2 to change coating density. The coating densities of as-deposited and post irradiation by HIPIB were derived to be 4940-5030, 5200-5320 and 5390-5470 kg/m3, respectively. The relative error between the coating density measured by the ultrasonic method and Archimedean principle ranging from 2.53% to 6.11%, indicates that the proposed ultrasonic quantification method provides a reliable nondestructive way to determine coating density. 相似文献
19.
Ultrasonic critical angle reflectivity method is used to measure the phase velocity of generalized Lamb waves in cadmium and
zinc platings. In addition to the free propagating modes, leaky-wave modes are also observed. Leaky waves are considered using
principles familiar from the discussion of surface waves in anisotropic media and a relatively good agreement is obtained
between the theoretical computations and measured data. 相似文献
20.
Many sparse signal representation (SSR) algorithms have been developed in the past decade. The advantages of SSR such as compact representations and super resolution lead to the state of the art performance of SSR for processing ultrasonic non-destructive evaluation (NDE) signals. Choosing a suitable SSR algorithm and designing an appropriate overcomplete dictionary is a key for success. After a brief review of sparse signal representation methods and the design of overcomplete dictionaries, this paper addresses the recent accomplishments of SSR for processing ultrasonic NDE signals. The advantages and limitations of SSR algorithms and various overcomplete dictionaries widely-used in ultrasonic NDE applications are explored in depth. Their performance improvement compared to conventional signal processing methods in many applications such as ultrasonic flaw detection and noise suppression, echo separation and echo estimation, and ultrasonic imaging is investigated. The challenging issues met in practical ultrasonic NDE applications for example the design of a good dictionary are discussed. Representative experimental results are presented for demonstration. 相似文献