微波晶体管放大器的图解设计法

在对线性两端口网络Ｓ参量分析的基础上，给出了利用史密斯圆图设计微波晶体管放大器的一般方法。并与解析设计法进行了比较     

微波成像生命探测仪地震模拟环境测试方法研究

破坏性地震发生后,埋压人员的快速搜索是地震救援工作成功的重要因素。微波成像生命探测仪作为当前废墟搜索的装备之一,近年来得到了广泛应用。但救援队利用现有综合训练场地进行该类装备的测试方法,在装备针对性测试和深度功能认知方面存在着一定局限性,影响了微波成像生命探测仪的现场使用效率和技术发展。为此,本文在充分调研国内外主流地震模拟废墟训练场地的基础上,提出了相关的改进意见,结合汶川地震废墟三维采集数据和队伍实战经验,给出微波搜索装备综合测试方法,并在国家地震紧急救援训练基地完成了测试平台的搭建,取得较好的装备测试效果,为应急救援装备电子化和标准化测试提供参考。     

微波超快速吸收现象

对１９８８年６月２９日云南天文台高时间分辨率射电望远镜观测到的微波超快速吸收现象进行了分析研究。在世界时０７ｈ３８ｍ５０ｓ至０７ｈ３８ｍ５８ｓ超快速吸收现象出现在太阳活动区ＮＯＡＡ／ＵＳＡＦ５０６０上空的４００ＧＨｚ上,而在２８４ＧＨｚ和１４２ＧＨｚ上空出现的是ｓｐｉｋｅ辐射。当时,该活动区呈现出极其活跃的双极磁场位形。在世界时０７ｈ３８ｍ至０８ｈ４７ｍ先后产生了３Ｂ级和２Ｂ级的Ｈα耀斑,并出现了Ｍ６５Ｘ射线爆发。根据电子回旋脉泽谐波吸收峰的特性,我们计算了三个波段的二次、三次谐波的磁场强度,并采用偶极磁场模型进行分析。对于４００ＧＨｚ上出现的超快速吸收现象,可能是产生的三次谐波脉泽辐射,在穿过吸收区时被吸收掉了。     

Towards the estimation root-zone soil moisture via the simultaneous assimilation of thermal and microwave soil moisture retrievals

The upcoming deployment of satellite-based microwave sensors designed specifically to retrieve surface soil moisture represents an important milestone in efforts to develop hydrologic applications for remote sensing observations. However, typical measurement depths of microwave-based soil moisture retrievals are generally considered too shallow (top 2–5 cm of the soil column) for many important water cycle and agricultural applications. Recent work has demonstrated that thermal remote sensing estimates of surface radiometric temperature provide a complementary source of land surface information that can be used to define a robust proxy for root-zone (top 1 m of the soil column) soil moisture availability. In this analysis, we examine the potential benefits of simultaneously assimilating both microwave-based surface soil moisture retrievals and thermal infrared-based root-zone soil moisture estimates into a soil water balance model using a series of synthetic twin data assimilation experiments conducted at the USDA Optimizing Production Inputs for Economic and Environmental Enhancements (OPE³) site. Results from these experiments illustrate that, relative to a baseline case of assimilating only surface soil moisture retrievals, the assimilation of both root- and surface-zone soil moisture estimates reduces the root-mean-square difference between estimated and true root-zone soil moisture by 50% to 35% (assuming instantaneous root-zone soil moisture retrievals are obtained at an accuracy of between 0.020 and 0.030 m³ m⁻³). Most significantly, improvements in root-zone soil moisture accuracy are seen even for cases in which root-zone soil moisture retrievals are assumed to be relatively inaccurate (i.e. retrievals errors of up to 0.070 m³ m⁻³) or limited to only very sparse sampling (i.e. one instantaneous measurement every eight days). Preliminary real data results demonstrate a clear increase in the R² correlation coefficient with ground-based root-zone observations (from 0.51 to 0.73) upon assimilation of actual surface soil moisture and tower-based thermal infrared temperature observations made at the OPE³ study site.     

Einstein Gravity Explorer–a medium-class fundamental physics mission

The Einstein Gravity Explorer mission (EGE) is devoted to a precise measurement of the properties of space-time using atomic clocks. It tests one of the most fundamental predictions of Einstein’s Theory of General Relativity, the gravitational redshift, and thereby searches for hints of quantum effects in gravity, exploring one of the most important and challenging frontiers in fundamental physics. The primary mission goal is the measurement of the gravitational redshift with an accuracy up to a factor 10⁴ higher than the best current result. The mission is based on a satellite carrying cold atom-based clocks. The payload includes a cesium microwave clock (PHARAO), an optical clock, a femtosecond frequency comb, as well as precise microwave time transfer systems between space and ground. The tick rates of the clocks are continuously compared with each other, and nearly continuously with clocks on earth, during the course of the 3-year mission. The highly elliptic orbit of the satellite is optimized for the scientific goals, providing a large variation in the gravitational potential between perigee and apogee. Besides the fundamental physics results, as secondary goals EGE will establish a global reference frame for the Earth’s gravitational potential and will allow a new approach to mapping Earth’s gravity field with very high spatial resolution. The mission was proposed as a class-M mission to ESA’s Cosmic Vision Program 2015–2025.

Inferring land surface parameters from the diurnal variability of microwave and infrared temperatures

This study investigates the properties of the diurnal cycle of microwave brightness temperatures (TB), namely the phase and the amplitude, and their variability in time and space over the globe to infer information on key land surface parameters like changes in soil texture spatial distribution, soil moisture conditions, and vegetation density. The phase corresponds to the lag between Land Surface Temperature (LST) and TB diurnal cycles. The amplitude is determined as the difference between the maximum and the minimum of TB diurnal cycle. The diurnal cycle of TB was constructed using observations from the Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) and the Special Sensor Microwave/Imager (SSM/I). The latter offer a series of sensors, namely, F13, F14, and F15 that were used in this study for a higher temporal coverage and more accurate diurnal cycle determination. LST estimates, which are available every 3 h from the International Satellite Cloud Climatology Project (ISCCP) database were used to build the LST diurnal cycle. ISCCP LST data is an infrared-based temperature with almost no penetration and is the representative of top skin temperature.The analyses of the diurnal cycles showed that the diurnal amplitude of TB decreases as the vegetation density increases, especially in the case of low frequencies which penetrate deeper into the canopy which makes them more sensitive to changes in vegetation density. The interannual variations of TB diurnal amplitudes were also in agreement with the seasonality of the vegetation cover. Over desert and rain forest regions where surface conditions do not vary significantly throughout the year, the changes in diurnal amplitudes were the lowest. A relationship between phase and amplitude values was established. It was found that the amplitude of TB diurnal cycle decreases when the phase lag increases. The spatial distribution of the determined diurnal properties, namely, phase and amplitude of TB, showed an agreement with lithology maps in desert areas. Lower TB amplitudes were observed over regions with loose siliceous rocks. Phase lag values between 1.5 and 3 h corresponded to 83% of the class “loose siliceous rocks” in the Sahara Desert, which corroborates the potential of using the diurnal properties of TB as an indicator of land surface parameters.     

多通道地基微波辐射计在0713号"韦帕"台风登陆前后探测性能及特征分析

利用上海市气象局2007年9月进行的"韦帕"台风探测试验资料和地面常规观测资料,对多通道地基微波辐射计在0713号"韦帕"台风登陆前后探测性能及特征进行了分析。结果表明:多通道地基微波辐射计探测的温度和相对湿度趋势与GPS探空得到的基本一致,尽管二者之间存在一些小的差异,但也表明了微波辐射计对台风具有一定的探测能力。0713号"韦帕"台风登陆前后温度和水汽密度场上,甚短生命史的冷暖气柱和高水汽密度柱十分活跃,体现了"韦帕"台风登陆前后的阵性特征。     

Introduction to plasma astrophysics and cosmology

The year 1996 marks the Centennial Celebration of the founding of Plasma Astrophysics and Cosmology; its origins may be traced to the seminal research first published by Kristian Birkeland in 1896. This special workshop issue reports on advances in issues of importance to the plasma universe; topics as timely as when first raised a century ago.     

高速扩频微波组网技术在防震减灾中的应用

扩频微波技术是近几年发展起来的高新技术,是目前发展宽带网络技术的主要手段之一。采用扩频微波方式组网在地震系统还尚属首次。“京区扩频微波高速链路建设”是采用2－3Mbp/s速率扩频微波技术将中国地震局京区主要直属单位及北京市地震局的计算机网络互联起来,构成中国地震局北京城区计算机网络互联的计算机广域网扩频微波网络平台及中国地震局北京城区计算机网络信道骨干网。同时利用扩频微波建立了与中国科技网相连的信道,将京区各单位和全国各省（市）地震局的计算机网络接入因特网。     

水面油膜微波辐射特性的研究

用36GHz和9.2GHz微波辐射计测量了不同厚度的水面油膜的亮度温度,应用并矢格林函数及起伏逸散定理进行了理论模式的数值计算,同实验取得了基本一致的结果。