Evaluation of landscape changes and ecological degradation by GIS in arid regions: a case study of the terminal oasis of the Shiyang River,northwest China

The development and utilization of water and land resources in the Shiyang River basin are the highest among the inland rivers in northwestern China. Using GIS and the landscape structure analysis program FRAGSTATS, landscape metrics of a study area in the lake-district in Minqin Oasis in the lower reaches of Shiyang River basin were calculated and analyzed based on TM images from 1987 to 2001 at class level and landscape level, respectively. Transformation matrix of the landscape mosaics was also examined. The driving forces of landscape changes were analyzed, including the dynamics of runoff and groundwater resources and their exploitation, and influences of policies and market economy. The results showed that: (1) Patch number of farmland and desert decreased, but their mean patch area increased, indicating that reclamation and desertification was very serious in the study area. Contagion index for oasis increased and edge density and landscape diversity were reduced. (2) Farmland and desert areas have enlarged by 1,520.46 and 4,941.27 hm², respectively. This increase was at the cost of woodland and grassland, which shrank by 1,520.46 and 4,941.27 hm², respectively. (3) The net utilization of surface water decreased by 50% in the last 10 years, and dropped to 22.3 × 10⁶ m³ in the later 1990s. Exploitation of groundwater increased remarkably, up to 80 × 10⁶ m³ per year in the last 5 years. (4) The capability of the economic structure to withstand pressures of the market economy has depressed distinctly because of the simplified planting pattern, which is dominated by salinity-enduring cash crops, such as cotton. Based on the above analysis, strategies of ecological reconstruction in the lake-district were suggested.     

闽西一次冰雹过程的雷达产品分析

以闽西一次典型冰雹过程为例，对这次冰雹过程的雷达基本反射率和基本速度特征进行了定性分析，对回波强度、回波顶高、强回波核高度、垂直积分液态含水量和多普勒速度等进行了定量分析。通过分析发现了一些冰雹雷达产品的重要指标和判据，这些结论在龙岩市日常的天气预报业务工作中对判断是否为冰雹回波和降雹时段、地点有很好的作用。     

Applications of Lodrigues Matrix in 3D Coordinate Transformation

Three transformation models (Bursa-Wolf, Molodensky, and WTUSM) are generally used between two data systems transformation. The linear models are used when the rotation angles are small; however, when the rotation angles get bigger, model errors will be produced. In this paper, we present a method with three main terms: ① the traditional rotation angles θ , φ ,ψ are substituted with a , b, c which are three re-spective values in the anti-symmetrical or Lodrigues matrix; ② directly and accurately calculating the formula of seven parameters in any value of rotation angles; and ③ a corresponding adjustment model is established. This method does not use the triangle function. Instead it uses addition, subtraction, multiplication and division, and the complexity of the equation is reduced, making the calculation easy and quick.     

基于RTCM数据格式的虚拟参考站技术算法研究

虚拟参考站技术是网络RTK的一种,它以众多的优势代表了网络RTK的主要发展趋势。本文介绍了VRS系统的工作原理,详细推导了VRS的数学模型,针对差分改正信息,提出了综合误差内插算法,分析了RTCM数据格式的特点及其在VRS技术中的应用,并做了实验验证,结合编程计算,证明了本文中VRS数学模型的正确性,为虚拟参考站系统的进一步研究提供依据。     

全数字摄影测量室内判调方法的应用

本文阐述了航测法成图制作1:1万地形数据工作过程中,采用全数字摄影测量工作站对地物进行室内判调“先内后外”的作业方法,并通过对获取的成果与常规方法的对比,证明此法在实际生产中具应用价值。     

利用数值模拟方法对类星体-星系团引力透镜成因的再考察

利用星系团形成的数值模拟技术所得到的星系团以及大尺度结构,本文研究了星系团和其周围环境物质的引力透镜效应对背景类星体计数的影响,以期解释最近观测到的类星体星系团成协现象．然而,得到的结果却是：用星系团及所遵循的大尺度结构的引力透镜效应,不能解释所观测到的类星体数密度．这与解析方法所得结论一致．分析表明：目前所观测到的类星体与星系团成协,如果不是统计涨落,则无法用引力透镜效应来解释。     

三颗河外射电源第一历元的VLBI图像

本文给出利用上海、乌鲁木齐、意大利ＮＯＴＯ和南非ＨａｒｔＲＡＯ射电望远镜,对三颗河外射电源（１５３２＋０１６,２３２００２０,２３５１１５４）,在５ＧＨｚ频率上的第一历元ＶＬＢＩ观测成图结果     

气球天文观测计算机测控系统设计

球栽STD总线数据采集与控制系统是为气球X射线天文观测研制的新一代计算机控制系统。它采用了多项新技术与新方法,是一个模块化的多CPU多任务并行处理系统。本文详细描述了它的结构和各种工作组态,并给出了地面实测结果。     

IODINE CONTENT OF SARCASSUM IN SOUTHERN CHINA

SeaweedsareAnownas"elementaccUrnulabe",eSPeCiallyforiwhneandbrodrine.AiIgassumwasusedtoPreVntgoiterinancientChina.TheSpeCiesreconledinMQteriaMedica,SampsumthunbergiiandSampsum~lhaun,arewidelydistributedinNorth-ernChina.Chinesescientistsdetendnedtheiwhnecontentsinsomeseaweedsincludinghampsum(Jietal.,lwn).forumresoareesinSOuthernChinaaremoreabundantthanthoseintheNorth.MorethanoosPeCiesaremeOnledinliterathe.Mostspecieslist-edin"CommnSeaWeedsOfChina"(TSeng,l983)aresouthemsPeCies.Iwh…     

ELEMENT COMPOSITION OF SARGASSUM THUNBEGII

ImODUcrIONSa~ll)lisalargegenerabelongingtothedassofFucales,Whosemembersaremorethan250.SargassumthunbopiiisthemostabundantwhdspedesintheYell0wScacoast,andisWdelydistributedalongtheentireChinacoastcyseng,1983).AlthoughsornestudiesonelemetSinseawtalshavebenTnadebyvariousauth0rspeanetal.,l995,Fanetal.,l996;Yamamotoetal.,l983,Whyte&Englar,l98O)theelementalcomPositioninseawedhasrareybenstudiedindetail.NeutronActivationAnalysis(NNA)isanidealmeth0dforinvestigatingtheelementalcompositioninmar…