Based on radiant sound field expression for single rectangular piezoelectric wafer,this paper gives analysis the infection each factor causing to sound pressure intensity and directivity,concrete methods to minimize major lobe while narrowing side lobes is put forward.As an example,the paper derives superimposed sound field formula for 16-wafer phased array probe,analyzes relationship of superimposed sound pressure and distance between focus and transducer,simulates and discusses influence on the quality of synthetic sound beam of phased array probe by factors such as element number,distance of adjacent elements.Simulation result is considerably consistent to related theory,which provides reference for evaluation and measurement for sound distribution and production of high-quality phased array probes.

Based on the research of principle of grayscale power transformation image enhancement combining grayscale distribution characteristics, this paper introduces a self-adaptive criterion for obtaining the transform coefficient. We process several images by power transformation with this criterion. The result shows that for images with continuous grayscale histogram distribution, the method can highlight image details, improve the image contrast effectively. Meanwhile, it has a brightness moderation function for images extremely bright or dark, which markedly improves the image visual effect. Experimental results show that compared with other methods such as grayscale histogram equalization, this method compensates the shortage of grayscale histogram equalization that causing image extremely bright and detail lost. © 2011 IEEE.

Compared with the traditional ultrasound imaging methods,the synthetic aperture focusing imaging technology can obtain better resolution by lower frequency and smaller transducer aperture,so it is widely used in the nondestructive testing.With the advancement of science and technology,the synthetic aperture focusing algorithm is increasingly mature.The principles of three common synthetic aperture focusing algorithms are analyzed in this paper.The advantages of each algorithm are summarized.A rational selection of imaging algorithms in practical application can effectively improve the imaging quality.

Due to different parameters of different mediums,electromagnetic waves incidencing on the interface between mediums will produce the phenomenon of reflection and transmission.This paper discusses amplitude,direction characteristics of reflected wave transmission wave versus angle the of incidence through analyzing the formula.

New ideas of reforming for fluid mechanics experimental teaching in engineering course were expounded.The development for individualization experimental installation,and the practical process for opening the individualization experiment were mainly introduced.The practice shows that it is possible to establish the upgraded experiment for excellent students by reforming experimental installation,although the fund of experiment is not enough,and it is efficient to develop cultivation of innovative talents.

Reynolds experiment is an important experiment which shows the laminar flow and turbulent flow.This paper introduced a new design of Reynolds experimental installation based on the tradition Reynolds experimental installations.The new Reynolds experimental installation has some virtues of circle water system,water head stabilization and color dissolving automatically.It exhibits more advantage than tradition installations in the experimental teaching,and overcomes the limitations of tradition installations,therefore,this new installation can be used widely in experimental teaching of fluid mechanics.