Lower Hearing Threshold by Noise

We demonstrate that noise can be a benefit factor that enables us to hear weaker signals. We measured the hearing thresholds of subjects for pure tone in different noise levels. The results show that pure tone thresholds with noise of some levels are lower than that without noise. The largest down-shift of the threshold by noise among the examined subjects is 5.7 dB, and the smallest is 1.7 dB.     

Sound Field Calculations of Elliptical Pistons by the Superposition of Two—Dimensional Gaussian Beams

We present an alternative approach to calculate the sound field of ultrasonic transducers.The distribution function of sources is expanded into the superposition of a series of two-dimensional Gaussian functions.The corresponding radiated sound field is expressed as the superposition of these two-dimensional Gaussian beams and is then reduced to the computation of these simple functions.This treatment does not require the condition that the shape of the source is of circular axial symmetry.A numerical example is presented for the uniform elliptical piston transducer and this is in good agreement with the results given by complicated computation.     

新型AFM探针的制备及应用

采用熔拉 -腐蚀复合方法 ,将普通单模石英光纤制成直锥形光纤探针。利用自制工具将探针打弯 ,制成悬臂式光纤探针 ,在AFM上取得了较理想的测试结果。将自制光纤探针和商用硅材料探针获得的两种扫描图像进行了对比 ,分析了悬臂式光纤探针的特点     

科学出版社物理类新书推荐

比利时的物理学家使用高速摄像机首次观察到液体中“反气泡”的形成、运动和崩溃过程(DorboloSetal.NewJ.Phys .,2 0 0 4 ,5 :1 61 ) .众所周知,气泡是一球形的液体薄膜,里面包着空气,外面又被空气包围着.而反气泡,顾名思义,则是一球形的空气壳,里面包着液体,外面又为液体所包围.在液体中气泡会升到液面上来,而反气泡则沉到液体底部.比利时Liege大学的StephaneDorbolo等缓慢地将肥皂水倒入一个装有同样肥皂水的玻璃容器中.他们观察到在液面下产生了一注液体小球,然后,这注小球破裂成一系列反气泡.反气泡存在了两分钟之久.反气泡崩溃的方…     

流场显示激光扫描仪的研究

本文介绍一种多功能激光扫描仪,并介绍研究该仪器的关键技术问题。最后阐述了采用该仪器对产生的散射粒子流从低速到亚跨音速的多种运动模型的脱体涡系结构进行流动观测。     

一种新型有机非线性光学材料的Z扫描研究

ＰＤＡＢＳ－１［５－（２－硫甲基－４－甲基）－嘧啶基－戊二炔－１－醇－４－Ｎ，Ｎ二甲氨基偶氮苯－４＇－磺酸酯］ＴＨＦ溶液的三阶光学非线性极化率χ＾（３）的Ｚ－扫描测试显示在单光子吸收区附近该材料的非线性由饱和吸收所支配。在波长为５３２ｎｍ，脉宽为１００ｐｓ的激光作用下，其非线性极化率实部Ｒｅχ＾（３）为－４．２００×１０＾－９ｅｓｕ，对应的非线性折射率值ｎ２为－１．２９９×１０＾－１１ｅｓｕ〈０，     

一种用于卫星电视接收的FZP天线

本文用物理光学法对ＦＺＰ反射器的聚焦场、聚焦效率及偏轴扫描特性等进行初步分析，并由此提出一种使用ＦＺＰ天线实现多颗卫星信号同时接收的技术方案。原理性样机实际接收结果证实了其可行性