宁夏一次短时暴雨天气的跟踪预报分析

用卫星云图、雷达对2008年8月7日强对流天气产生的暴雨过程跟踪观测资料,结合自动站地面降水实况和WRF模式风场资料进行短时预报分析.结果表明:扩散东移冷空气和副热带高压边缘偏南暖湿气流的共同影响下,大气层结不稳定发生强烈的强对流天气;利用卫星云图,新一代天气雷达基本反射率强度图、0.5°仰角基本速度图和风廓线产品跟踪监测,综合分析预报短时暴雨天气是有效的方法.     

基于图像处理的自动野外救援系统设计

针对野外救援的不及时性,结合人工智能等技术的应用,提出了一种新的自动野外救援系统.人类在野外和海上活动中受困后,除了依靠自身能力和装备进行求生之外,外部的有效及时救援是提高生存几率的关键.自动野外救援系统,由自动报警装置、手动报警装置实现报警,触发整个系统的运行.自动救援装置可以通过定位模块实现定位,通过执行器移动到随身装置附近实现救援,随身装置还可以发出信标导引信号;自动救援装置还可以通过传感器检测信标,通过相位检测技术等计算待救者的坐标并规划路径,实现更精准的定位与救援.     

Traction image method for irregular free surface boundaries in finite difference seismic wave simulation

In this study, we propose a new numerical method, named as Traction Image method, to accurately and efficiently implement the traction-free boundary conditions in finite difference simulation in the presence of surface topography. In this algorithm, the computational domain is discretized by boundary-conforming grids, in which the irregular surface is transformed into a 'flat' surface in computational space. Thus, the artefact of staircase approximation to arbitrarily irregular surface can be avoided. Such boundary-conforming gridding is equivalent to a curvilinear coordinate system, in which the first-order partial differential velocity-stress equations are numerically updated by an optimized high-order non-staggered finite difference scheme, that is, DRP/opt MacCormack scheme. To satisfy the free surface boundary conditions, we extend the Stress Image method for planar surface to Traction Image method for arbitrarily irregular surface by antisymmetrically setting the values of normal traction on the grid points above the free surface. This Traction Image method can be efficiently implemented. To validate this new method, we perform numerical tests to several complex models by comparing our results with those computed by other independent accurate methods. Although some of the testing examples have extremely sloped topography, all tested results show an excellent agreement between our results and those from the reference solutions, confirming the validity of our method for modelling seismic waves in the heterogeneous media with arbitrary shape topography. Numerical tests also demonstrate the efficiency of this method. We find about 10 grid points per shortest wavelength is enough to maintain the global accuracy of the simulation. Although the current study is for 2-D P-SV problem, it can be easily extended to 3-D problem.     

北京城市居民的空间感知与意象空间结构

对北京城市居民的空间感知进行了问卷调查,从323份感知地图中提取和统计相关数据,并据此分析北京城市居民空间感知的基本类型、构成和发展阶段,以及各种差异性特征。研究表明,北京城市居民的空间感知类型与西方的研究结果大体一致,但存在一定差异;居民居住地域、性别、学历、收入以及出生地的不同,感知地图类型的级别也不相同。感知空间的构成要素在居住地域、年龄、收入和出生地方面差异明显,而发展阶段主要与性别、收入和出生地有关,社会角色和经济收入水平在决定居民感知空间发展阶段方面起到巨大作用。文章最后还根据各种地物和构成要素出现的频率,概括了北京城市意象的空间结构,并发现它与现实中北京城市空间布局的重点极为相似。     

1993～2003年厦门市湿地动态变化及其驱动因素分析

通过对厦门市1993年TM遥感影像和2003年ETM 遥感影像的解译分析和数据统计,从湿地面积动态变化和湿地消长情况等方面,用单一土地利用动态度等指标对1993~2003年期间厦门市的湿地变化进行了研究。结果表明,1993~2003年期间厦门市天然湿地面积减少了2103hm2,其中有954hm2(滩涂864hm2)转变为非湿地,有1149hm2转变为人工湿地;而人工湿地面积增加了2775hm2,其中养殖场面积从1993年的5778hm2迅猛增加到2003年的9768hm2,年均增长率为6.91%,水库与水塘和盐田则分别减少了961hm2和254hm2。有27.74%、11.41%、9.33%和3.63%的养殖场面积分别是由非湿地、滩涂、盐田和水库与水塘转变而来的;有54.37%的盐田转变成了养殖场,有33.24%、30.24%的红树林转变为非湿地、养殖场,有10.35%、8.64%的滩涂转变为养殖场、非湿地。对社会经济驱动因素的分析表明,经济发展、人口增长和农业生产比较利益因素极大影响着厦门市湿地的动态变化。     

黄土丘陵沟壑区典型村域土地利用变化及对区域乡村转型发展的启示

深入开展乡村地域土地利用变化和聚落发展规律的研究对于探究乡村地域系统优化、推进城乡融合与乡村可持续发展具有重要意义。论文以延安市碾庄流域为例,基于ENVI和GIS等软件技术,结合Landsat卫星影像、马尔科夫链模型和实地调查,从土地利用转移与交换变化、建筑用地空间转移、社会响应等角度探讨了黄土丘陵沟壑区典型村域土地利用变化特征以及对区域乡村发展转型的影响。研究表明：① 在一系列生态工程措施作用下,碾庄流域生态覆被发生明显改观,主要表现为大量的坡耕地及稀疏生态用地转化为林地,其中,林地面积占比由32.34%(2009年)增加至50.88%(2018年);② 在社会经济发展和延安新城“边缘效应”的影响下,碾庄建设用地呈现向流域的东南和西南方向拓展的趋势,10 a间建设用地面积增加了近75%;③ 在人类活动的主导作用下,黄土丘陵沟壑区的乡村正在朝着生态化和集约化的方向转型发展。研究结果有望为深入理解黄土丘陵沟壑区乡村地域系统结构和优化提供新参考。     

APPLICATIONS OF ARTIFICIAL INTELLIGENCE TECHNIQUES TO REMOTE SENSING*

Remote sensing is a geographic analysis tool capable of producing large quantities of data in the spectral, temporal and spatial domains. Techniques for automating the image analysis process would be advanced by the inclusion of artificial intelligence techniques in the design of image processing systems. The remote sensing application which show promise for successful implementation of artificial intelligence techniques are intelligent onboard processing, advanced database interrogation, and the automated analysis of multispectral imagery.     

BOOK REVIEWS

Book Reviewed in this article: Marine Resources of Kuwait: Their Role in the Development of Non-oil Resources . Fatimah H. Y. al -Abdul -Razzak Recollections of a Revolution: Geography as Spatial Science . Mark Billinge , Derek Gregory and Ron Martin Entre l'Eden et l'Utopie . Luc Bureau Developments in Political Geography . M. A. Busteed The Elements of Graphing Data . William S. Cleveland Rural Resource Management . Paul J. Cloke and Chris C. Park Third World Atlas . Ben Crow and Alan Thomas Exploitation, Conservation, Preservation: A Geographic Perspective on Natural Resource Use . Susan L. Cutter , Hilary Lambert Renwick, and William H. Renwick . Wine Regions of the Southern Hemisphere . Harm Jan de Blij Regional Development: Problems and Policies in Eastern and Western Europe . George Demko The Geographer at Work . Peter R. Gould Change in the Amazon Basin . John Hemming Geography Since the Second World War . R. J. Johnston and P. Claval Urbanization in China: Town and Countryside in a Developing Economy 1949–2000 A.D. , R. J. R. Kirkby Transport and Communications for Pacific Microstates: Issues in Organisation and Management . Christopher C. Kissling Fluvial Forms and Processes . David Knighton The Urban Millennium . Josef W. Konvitz Technological Transition in Cartography . Mark Stephen Monmonier Field Guide to Soils and the Environment: Applications of Soil Surveys . Gerald W. Olson Northern Australia: The Arenas of Life and Ecosystems on Half a Continent . Don Parkes A Killing Rain: The Global Threat of Acid Rain . Thomas Pawlick From the Family Farm to Agribusiness: The Irrigation Crusade in California and the West, 1850–1931 . Donald J. Pisani Hybrid Maize Diffusion in Kenya . Franz -Michael Rundquist Warning and Response to the Mount St. Helens Eruption . Thomas F. Saarinen and James L. Sell Coastal Geomorphology in Australia . B. G. Thom Tropical Rain Forests of the Far East , 2nd ed . T. C. Whitmore The Dark Side of the Earth . Robert Muir Wood Categorical Data Analysis for Geographers and Environmental Scientists , Neil Wrigley     

Spatial uniformity of sediment accumulation in varved lake sediments in northern Sweden

As part of an investigation aimed at assessing the potential of northern Swedish varved lake sediments for fine-resolution reconstruction of past climatic conditions, the following questions were addressed; how representative is a single core, does the appearance of varves change as the sediment ages, and how can varve thickness and within-varve structures be digitized? Analyses of replicate cores from Kassjön, using sample sequences of seasonal, annual and centennial time resolution, show that spatial variability of sediment accumulation in the varved sediment is very low. Comparisons of intensity curves from image analysis of freeze cores of recent sediments from Lake Nylandssjön, sampled in 1980 and 1985, indicate that the varves acquire their appearance at the sediment-water interface during sedimentation and that the varve structures are preserved during diagenetic processes. Measurement of varve thicknesses with a tree-ring microscope and with image analysis gave similar results. However, with image analysis, within-varve structures such as colour variations and thicknesses of seasonal layers, can also be recorded, increasing the possibilities for palaeolimnological and palaeoclimatic inferences.     

Comparative assessment of semantic-sensitive satellite image retrieval: simple and context-sensitive Bayesian networks

In recent years, Bayesian networks using unsupervised extracted image features have been applied in many remote sensing information mining systems to enable semantic-sensitive image retrieval. However, a simple Bayesian network insufficiently accounts for the spatial information, that is, the relations among image regions, for the semantic inference process. This drawback significantly impacts the retrieval performance, especially if the utilised features contain no or little spatial information. Therefore, this article proposes a context-sensitive Bayesian network, which infers semantic concepts of image regions based on the spectral and textural characteristics of the regions themselves as well as their contexts, that is, the adjacent regions. In order to compare the context-sensitive Bayesian network with the simple Bayesian network, comprehensive experiments were conducted based on high-resolution multispectral IKONOS imagery. The results show that the incorporation of the image regions' spatial relations not only significantly improves the accuracy of the semantic concepts inference, but also allows more flexibility in choosing the type of low-level features.