Modulation of low-frequency oscillations in GaAs MESFETs’ channel current by sidegating bias

Low-frequency oscillations in channel current are usually observed when measuring the GaAs MESFET‘s output characteristics. This paper studies the oscillations by testing the MESFET‘s output characteristics under different sidegate bias conditions. It is shown that the low-frequency oscillations of channel current are directly related to the sidegate bias. In other words, the sidegate bias can modulate the oscillations. Whether the sidegate bias varies positively or negatively, there will inevitably be a threshold voltage after which the low-frequency oscillations disappear. The observation is strongly dependent upon the peculiarities of channel-substrate (C-S) junction and impact ionization of traps-EL2 under high field. This conclusion is of particular pertinence to the design of low-noise GaAs IC‘s.     

垂直主振系冲击消振运动过程分析及仿真研究

提出一种垂直主振系冲击消振力学模型，在此基础上对该模型的典型运动过程进行了定性分析，并使用MATLAB的Simulink组件建立了仿真模型，对系统的运动性状进行的初步研究，为以后的相关理论研究打下了一定基础。     

Unusual discrepancy between TOMS and ground-based measurements of the total ozone in 2002—2003

Monitoring the atmospheric ozone is one of the key projects in the atmospheric and environmental sciences, and the decrease of ozone in stratosphere has aroused the interests of governments and public in the world. Mainly two methods are used to measure the total atmospheric ozone in the globe: ground-based observation mainly including Dobson and Brewer ozone instruments, and satellite measurement. The popular satellite products are the Total Ozone Mapping Spectrometer (TOMS) data provided by the National Aeronautics and Space Administration (NASA) of the United States of America.     

Research advances in the catalysts for the selective oxidation of ethane to aldehydes

Selective oxidation of ethane to aldehydes is one of the most difficult processes in the catalysis researches of low alkanes. The development of selective oxidation of ethane to aldehydes (formaldehyde, acetaldehyde and acrolein) is discussed. The latest progress of the catalysts, including bulk or supported metal oxide catalysts, highly dispersed and isolated active sites catalysts, and the photo-catalytic ethaneoxidation catalysts, partial oxidation of ethane in the gas phase, and the proposed reaction pathways from ethane to aldehydes are involved.     

THz time-domain spectroscopy of amino acids

The optical characteristics of four kinds of amino acids （tyrosine, arginine, histidine and glutamine） filled with nitrogen at room temperature were studied by THz time-domain spectroscopy （THz-TDS）. Well-resolved absorption and refractive spectrums between 0.I and 2.8 THz were obtained based on the physical model for extracting the optical parameters of materials in THz range. The results not only fill up the spectra gap of amino acids in far-infrared range, supply data for amino acid molecular identification and conformation analysis, but also demonstrate significantly potential to promote the research and application of biological materials in bio-chemical and medical fields by THz-TDS.     

Synthesis, characterization and properties of diamidodisilanes and azocyclosilane

Organosilicon compounds have been widely researched and have the maximum species besides hydrocarbons. In the progress of the research work, many scientists pay attention to the organic silicon compounds that have vari-ety reactive functional groups[1,2]. The difunctional disi-lanes are very active; they could react with not only the compounds containing reactive hydrogen atoms, but also the reactive polymers. Therefore, the disilanes with di-functional groups could be used as disilane substit…     

晋华宫矿高产高效矿井建设

晋华宫矿为大同煤矿集团公司特大型矿井之一。近年来，围绕“双高”矿井建设，针对现有的客观不利条件．积极采用煤体松动和人工强制放顶技术，并结合管理创新。加快“双高”矿井建设步伐，使全矿安全、生产、效益等方面取得了良好效果。     

天线精密测量支撑台架结构分析与优化

在紧缩场中进行天线测量,天线定位结构型式及整体刚度性能非常重要.根据天线测量中心运动范围及精度要求,为减小部件之间的错位公差,采用分段整体结构封闭设计,设计了一种新的天线支撑台架结构方案,详细进行了结构变形刚度分析,提出以比刚度高和系统重量低为双指标的优化函数.最后,以结构尺寸为基本变量,采用模拟退火算法,得出了天线支撑台架的具体结构尺寸.     

双跨连拱隧道掘进及初期支护工艺介绍

结合客塘双跨连拱隧道的施工经验,阐述高速公路双跨连拱隧道应用三导洞法掘进及初期支护的施工工艺,以及监控量测在施工中的应用。     

从经济发展的视点谈财政政策的作用

明确了经济发展概念的内涵和外延;从经济增长的持续稳定性、公平性和平衡性三个方面,对经济发展和经济增长的关系进行了探讨;对微观和宏观经济主体在经济发展中的作用进行了阐述。