The 4th International Symposium on HIGH POWER LASER SCIENCE AND ENGINEERING

正Postponed Suzhou,ChinaCo-Chairs Xian-Tu He China Academy of Engineering Physics,China Dianyuan Fan Shanghai Institute of Optics and Fine Mechanics,CAS/Shenzhen University,China Colin Danson AWE/CIFS,Physics Department,Imperial College London,UKPlenary Speakers Patrick Audebert LULI,France Michael Campbell University of Rochester,USA Colin Danson AWE/CIFS,Physics Department,Imperial College London,UK Constantin Haefner Lawrence Livermore National Laboratory,USA Xian-Tu He CAEP,China     

INTER-NOISE 2017

<正>INTER-NOISE 2017,the 46th International Congress and Exposition on Noise Control Engineering,will be held in Hong Kong,China,between 27 and 30 August 2017.The Congress is organized by the Hong Kong Institute of Acoustics and the Hong Kong Polytechnic University,in conjunction with NVH Branch,Society of Automotive Engineering China and the Acoustical Society of China(ASC).Prof.Jun YANG,Director of the Key Laboratory of Noise and     

School of Physics&Microelectronics,Zhengzhou University

Location School of Physics&Microelectronics,Zhengzhou University,Zhengzhou 450052,China Futher Information:http://www5.zzu.edu.cn/wuli/Overview School of Physics and Microelectronics of Zhengzhou University was founded in 1995,and its predecessor was the former Department of Physics of Zhengzhou University that was founded in 1956.The founder of this school is Prof.Bingquan Huo,a famous physicist on high-energy physics and cosmic ray physics of China.Currently,the school has 220 staffs.     

Acoustical news Acoustical Events 1990—1992

1990February…,l 990,Rostock IVth CONfernence on Hydro.and Geophysical Acoustics Details to be announcedAprill7—20,1990,Wien DAGA’90 * l 6.Gemeinschaftstagung der Deutschen Arbeitsgemeinschafl fur Akustik(DAGA) Details to be announced.May2l～25,1990,State College,Pennsylvania Meeting of the Acoustical Society of America Chairman:Sabih I.Hayek。Department of Engineering Science and Mechanics and the Applied Research Loboratory,The Pennsylvania State University,University Pa…     

Department of Physics Renmin University of China

Location Renmin University of China 59 Zhongguancun Ave.,Beijing 100872,China Futher Information:http:www.phys.ruc.edu.cn/Location Renmin University is one of top universities in China.The Department of Physics was founded in the fall of 2005.The Department has 35 full-time faculty members,including 20 professors,12 associate professors,and 3 lecturers.Their orientation is high-quality research combined with physics instruction across the full spectrum of core subjects.The activities of the department are designed to exploit the intrinsic synergy of innovative research teaching and academic exchanges in physics and related disciplines all of which are pursued at an internationally recognized standard.     

School of Physics at Peking University

No. 209, Chengfu Road, Haidian District, Beijing School of Physics, Peking University, Beijing Further Information http：//www.phy.pku.edu.cn Key Contact Professor XinCheng Xie Dean, School of Physics, Peking University Emaih xcxie@pku.edu.cn, xincheng.xieokstate.edu Overview 5Pcking Universii;y： Peking University has a long and rich history. Founded as the Imperial University of Peking in 1898, it is the first established modern national university of China. In 1912, it was renamed National Peking University. With Tsinghua Univerity and Nankai University in Kunming, it formed the National Southwestern Associated University in 1938. In 1952, after merging with Yenching Univer sity, it moved to its present campus and was renamed Peking University. The main campus of Peking University, known as Yan Yuan （the garden of Yan）, is situated in Haidian District in the northwestern part of Beijing, with a total area of 2 743 532 square metres （274 hectares）. It is near the Yuanmingyuan Garden and the Sum mer Palace and is especially renowned for the beauty of its traditional Chinese architecture. Today, Peking University is frequently placed as one of the best comprehensive universities in China by many national and international rankings. The University consists of 30 colleges and 12 departments. It embraces diverse branches of learning in natural sciences, engineering, medical sciences, management, social sciences and humanities.     

《发光学报》第12届编辑委员会委员名单

正(2016.05-2019.05)名誉主编徐叙2)院士北京交通大学E-mail:xrxu@bjtu.edu.cn范希武研究员中国科学院长春光学精密机械与物理研究所E-mail:xiwufan@163.com王立军院士中国科学院长春光学精密机械与物理研究所E-mail:wanglj@ciomp.ac.cn顾问Prof.MELTZER Richard S Department of Physics and Astronomy,University of Georgia,USA Prof.YOKOYAMA Meiso Department of Electronic Engineering,I Shou University,Taiwan,China     

《发光学报》第9届编辑委员会委员名单

国际顾问Advisory BoardProf.YAN Willims M Department of Physics and Astronomy,University of Georgia,USAProf.MELTZER Richard S Department of Physics and Astronomy,University of Georgia,USAProf.YOKOYAMA Meiso Department of Electronic Engineering,Taiwan I-Sho…     

《发光学报》第8届编辑委员会委员名单

顾问Advisory BoardProf.YEN William M Department of Physics and Astronomy,The University of Georgia,USAProf.MELTZER Richard S Department of Physics and Astronomy,The University of Georgia,USAProf.YOKOYAMA Meiso Department of Electronic Engineering,I-Shou U…     

微波在带电沙粒中的衰减效应

 根据沙粒的等效介电常数模型和Rayleigh近似下带电球形粒子的前向散射振幅函数,给出了对数分布模型下的带电沙尘粒子引起微波的衰减计算模型,并进行了分析和仿真计算。结果表明:带电沙粒比不带电沙粒对微波信号衰减的影响明显增大,带电沙粒所带表面电荷越集中,对微波的衰减影响越大;微波衰减随能见度的增大而减小;对于相同含水量,频率小于35 GHz时,沙尘对电磁波衰减的影响较小,频率大于35 GHz时,沙尘对电磁波的衰减影响增大。     

不同模态沙尘暴对太赫兹波的衰减分析

太赫兹波空间传输特性研究对于太赫兹波在空间中的应用具有重要意义.为研究太赫兹波在沙尘暴天气中的传输特性,本文根据沙尘粒子尺度的对数正态分布,应用Mie散射理论和Monte Carlo方法,分析了国内不同地域的六种干沙模态沙尘暴对1—10 THz频段太赫兹波的衰减特性,给出了消光参量和衰减率与频率的关系.结果表明,随着频率的增大,1—10 THz频段太赫兹波的衰减率呈先增加后减小的趋势,沙尘暴的模态不同,太赫兹波衰减较强的频段范围有所不同.为了分析沙粒含水量对太赫兹波传输衰减的影响,计算了不同尺寸的沙尘粒子3个效率因子与含水量的关系,发现粒子尺寸不同,含水量对消光的影响也不同;应用Monte Carlo方法计算了两种湿沙模态的沙尘暴对1—10 THz频段太赫兹波的衰减,给出了衰减率与含水量及频率的关系.结果表明,随沙粒含水量增大,沙尘暴对太赫兹波衰减较强的频段向低频方向移动,含水量小于5%时,太赫兹波衰减率随含水量增大显著增强,湿度较大的沙尘暴天气对太赫兹波的传输衰减影响更大.     

沙尘大气电磁波多重散射及衰减

为了使干旱沙漠地区的电子系统能够全天候的工作, 必须开展沙尘大气的电磁波多重散射及衰减特性研究. 根据Mie理论、沙尘大气粒子尺寸分布和能见度的关系得到了电磁波沙尘大气传播衰减的计算方法, 计算了不同沙尘大气能见度的37 GHz电磁波的衰减, 与其他经验公式及文献中的实验结果进行比较, 文中方法得到的结果更接近于测量结果. 为了研究较低能见度沙尘暴中电磁波的传播特性, 需研究沙尘大气的多重散射效应. 应用Monte Carlo模拟方法, 在沙尘粒子为干燥和5%水含量时, 模拟了37 GHz和93 GHz电磁波在沙尘大气中传播时考虑多重散射效应的衰减, 并与基于Mie理论的计算结果进行比较, 结果显示, 在37 GHz时, 沙尘大气的多重散射对衰减的影响小, 在93 GHz时多重散射显著, 沙尘大气能见度越低, 多重散射的影响越显著. 粒子水含量增加使电磁波的衰减显著增大, 对多重散射的影响不明显. 因此, 在相同大气能见度下, 沙尘天气越干燥, 多重散射影响越大, 电磁波衰减减小越显著.     

Attenuation of electromagnetic wave propagation in sandstorms incorporating charged sand particles

A theoretical approach for predicting the attenuation of microwave propagation in sandstorms is presented, with electric charges generated on the sand grains taken into account. It is found that the effect of electric charges distributed partially on the sand surface is notable. The calculated attenuation is in good agreement with that measured in certain conditions. The distribution of electric charges on the surface of sand grains, which is not easy to measure, can be approximately determined by measuring the attenuation value of electromagnetic waves. Some effects of sand radius, dielectric permittivity, frequency of electromagnetic wave, and visibility of sandstorms on the attenuation are also discussed quantitatively. Finally, a new electric parameter is introduced to describe the roles of scattering, absorption and effect of charges in attenuation.     

Investigation into the Effect of Dielectric Loss on RF Characteristics of Helical SWS

A general theory has been developed to account for the effect of the dielectric loss of discrete rods on the performance characteristics of an actual helical slow wave structure (SWS). The effect of the lossy dielectric rods has been studied on various propagation parameters, namely, phase propagation constant, interaction impedance and attenuation constant at different operating frequency. It is clearly shown that the influence of dielectric loss on RF characteristics is much larger at the millimeter frequency band than that at the microwave frequency band, especially on interaction impedance and attenuation constant. The general theory developed here has been further confirmed by comparing the results with those obtained elsewhere for some special cases.     

Attenuation characteristics of obliquely incident electromagnetic wave in weakly ionized dusty plasma based on modified Bhatnagar–Gross–Krook collision model

The attenuation characteristics of obliquely incident electromagnetic(EM) wave in L-Ka frequency band in weakly ionized dusty plasma are analyzed based on the modified Bhatnagar-Gross-Krook(BGK) collision model.According to the kinetic equation and the charging theory,the total complex dielectric constant of the weakly ionized dusty plasma is derived by considering that the minimum velocity of the electron accessible to the dust particle surface is non-zero and the second potential part of the collision cross-section contributes to the charging.The attenuation characteristics within the modified model are compared with those within the traditional model.The influence of the dusty plasma parameters and the incident angle of EM waves on the attenuation in weakly ionized dusty plasma is further analyzed.Finally,the influence of different reentry heights on the attenuation characteristics of the obliquely incident EM wave is discussed.The results show that the effect of the minimum electron velocity and the second term of the collision cross-section on the attenuation characteristics of EM waves cannot be ignored.When the dust density and dust radius are changed,the trends of the attenuation of obliquely incident EM waves are consistent,but the influence of dust density is weaker than that of dust radius due to the constraint of orbit-limited motion(OLM) theory.The plasma thickness,electron density,and incident angle are proportional to the attenuation amplitude of EM waves.The effect of different reentry heights on the attenuation obliquely incident EM waves is related to the electron density and plasma thickness.     

电流变液的微波透射调控行为

依据外电场作用下电流变液结构由各向同性转变为各向异性及介电性能改变的实验事实,建立了微波穿透电流变液样品的理论模型,导出了微波透射率的基本表达形式.理论模拟显示:当电流变液的介电常量小于所处环境的介电常量时,透射率随电场的增加而增加;反之则减小.实验研究表明:电流变液的微波衰减(透射率)的变化可以通过电场来调控.分析认为在外加电场作用下,电流变液结构转变和介电性能的变化是导致微波透射率可调控的主要原因.     

基于极化强度叠加模型的高功率微波混合气体传播特性

 基于气体极化强度叠加模型,推导了混合气体的介电常数,得到了高功率微波在混合气体中传播时的折射指数和衰减系数。研究发现,高功率微波大气电离产生的混合气体是快速时变的色散有耗介质。根据其色散性分析了微波在混合气体中的传播速度以及微波脉冲在其中的展宽效应,同时,根据其有耗性对微波脉冲在混合气体中传播时的缩短效应进行了研究。研究结果均能自洽地过渡到对流层或电离层电波传播理论。     

Model of a microwave beam coupling to CO2 laser plasma

We have designed a transmission line model of the microwave coupling mechanism for a microwave pumped CO₂ laser. The model is a total loss ridge waveguide transmission line having nonuniform impedance. The laser plasma is modeled as a frequency-dependent lossy dielectric and acts as a distributed resistance in the length of the microwave cavity. The coupling structure of the microwaves is designed not to be resonant at the microwave source frequency of 2.45 GHz at 1 kW and propagating the total microwave field energy to be absorbed without internal reflection. An exact solution to this general transmission line propagation constant for a shunt resistance along length of the guide is found. The measurements and predictions of the parameters of the plasma conductivity as a function of the attenuation constant agree closely.     

Microwave Propagation in Saline Dust Storms

Dielectric constant of sand-powder sampled from saline dust area have been measured at W band by means of wave-guide method. Based on the analysis of the characteristics of saline dust storms, the microwave and millimeter wave attenuation and phase shift in saline dust storms are investigated.