远东热点:朝鲜半岛形势分析   总被引：1，自引：0，他引：1  

刘养洁 《世界地理研究》2002,11(3):86-91

朝鲜半岛独特的地理位置，无论对周边的中，俄，日三国，还是对大洋彼岸的美国都具有十分重要的地缘战略意义。如果说这里是四大国利益相互交错的唯一地区，那么解决朝鲜半岛问题便不仅取决于半岛内部北，南双方的互动关系，而且取决于四大四的立场及东北亚政治地理格局的演变态势。近年来随着朝鲜北，南双方首脑的成功会晤，朝鲜半岛的和平统一进程迈出了实质性步伐。但由于朝鲜半岛问题牵涉面广，影响因素复杂，从而使半岛的和平统一进程出现了一波三折的复杂局面，本文从政治地理学角度对半岛形势进行了分析。供关心朝鲜半岛局势的同仁参考。  相似文献   

Present land use and cover patterns and their development potential in North Ningxia     

WU Weicheng  ZHANG Wenfeng 《地理学报》2003,13(1):54-62

With the objectives to acquire the fundamental data of the territorial resource, understand the impacts of human activities on the land use and cover patterns and evaluate the potential of the future exploitation, an intensive land cover classification with an accuracy of 93% has been completed for North Ningxia by remote sensing technique based on the adoption of a combination method composed of texture training, maximum likelihood classification and post-processing such as re-allocation and aggregation. This classification result was incorporated with the contemporaneous socio-economic and meteorological data for cross-sectional regression modelling to reveal the spatial determinants of the land cover patterns and understand the human-environmental relationships. A tentative evaluation on the potential of soil exploitation in the near future was carried out in combination with our land use and cover change detection results aiming at supplying some useful references for the central and local governments in their sustainable land use planning.  相似文献   

b值在地震预测中的三类应用及其物理基础与须注意的问题   总被引：1，自引：0，他引：1  

韩渭宾 《四川地震》2003,(1):1-5

将b值在地震预测中的直接应用归为三类：1）根据b值的动态变化预测地震。2）根据G－R律求出各级地震平均复发周期或年均发生率，推测未来一定时段如50年或100年内发生各级地震的危险性。3）根据G－R直线在横轴的截距，预测强余震的震级。讨论了这三种用法的物理基础及现有工作中容易出现的问题。  相似文献   

Verteilung und Wanderung von Neunaugen im Elbeästuar (Deutschland)     

Ralf Thiel  Volker Salewski 《Limnologica》2003,33(3):214-226

From March 1989 until May 1995 overall 675 hauls were performed using a commercial stow net vessel to get information concerning spatial and seasonal distribution, length frequency distribution, stock situation and migration patterns of lampreys in the Elbe estuary in northern Germany.2217 river lampreys (Lampetra fluviatilis) and 10 sea lampreys (Petromyzon marinus) were caught during the whole study period. The river lamprey occurred in 40.3% of the performed stow net hauls. The catch success was highest in the western main channel, whereas the frequency of occurrence of river lampreys was only about 10.9% at the most upstream site in the southern marginal area. In 1989 and 1990 significantly more than 50% of the hauls contained river lampreys. In contrast, from 1991 to 1995 their frequency of occurrence was lower than 40%, in 1991 even lower than 20%. Sea lampreys occurred only at 6 from 9 sampled sites and were only observed in 1990 and 1992-1994.Total lengths of river lampreys varied between 7 and 46 cm. Based on the length frequency distribution, the following three size classes of river lampreys were separated: LF I (7 to 16 cm), LF II (17-26 cm) and LF III (27-46 cm). The majority of the caught individuals could be grouped in size class LF III. Total lengths of sea lampreys ranged between 69 and 85 cm and were restricted to only one size class (PM III).70% of all sea lampreys were caught in April and May. Most of the sea lampreys were observed in the eastern main channel. The maximum average abundance of river lampreys was observed with 6.75 Ind · m⁻³ · 10⁻⁶ in the same area in 1992. However, in 1993 and 1994 the highest average abundances of river lampreys occurred in the western main channel.Based on redundance analysis, a significant correlation between the abundances of lampreys and the environmental variables autumn, spring, summer, salinity, water temperature, grain size, new moon and first moon quarter was found. The downstream migrating river lampreys of size class LF I und the sea lampreys during their anadromous spawning migration showed highest abundances mainly in spring, whereas high abundances of river lampreys of size class LF II in the feeding phase occurred in summer. The presence of both size classes LF I and LF II confirms the successful reproduction of river lampreys in the catchment area of the Elbe. The observation of river lampreys of size class LF III during their anadromous spawning migration was closely correlated with the variable autumn. A spring spawning migration of river lampreys was not observed.  相似文献   

GPS弦距与常规光电测距弦距的比较与分析     

付培义 《测绘工程》2003,12(2):47-48,58

比较GPS弦距与常规光电测距弦距的差别，对分析GPS测量误差问题，解决GPS与地面数据联合平差中权的确定问题，以及检核GPS网的解算结果具有重要意义。本文利用一多期复测成果，对其中的一些问题作了初步探讨。  相似文献   

党政机关电子政务建设的若干问题   总被引：1，自引：4，他引：1  

任锦华 《测绘科学》2003,28(1):12-16

以从事政务信息化建设的实践经验为基础 ,对电子政务建设的基本问题进行了系统分析 ,内容包括 :信息关系和信息控制、信息分类、数据库结构、软件系统开发思路、电子政务的工作目标、服务对象、服务模式、电子政务建设的技术措施等。  相似文献   

Recent Precipitation Trends in Hungary in the Context of Larger Scale Climatic Changes   总被引：1，自引：0，他引：1  

Domonkos  Peter 《Natural Hazards》2003,29(2):255-271

The time series of monthly precipitation totals from 14 Hungarian observing stations (1901–1998) were analysed to reveal the long term changes in precipitation characteristics occurred in the 20th century. A particular attention was given to the changes in the recent decades and their links with the larger scale climatic and circulation changes over Europe and the Atlantic.The statistical significancesof systematic changes are controlled by linear trend analysis and the Mann–Kendall test. The long term fluctuations are illustrated applying a 15-point Gaussian filter on the time series. The Standardised Precipitation Index is used to evaluate the changes in the drought event frequency. The relationships with larger scale changes are mostly discussed relying on contemporary papers, and the Grosswetterlagen Catalogue is used as well.The annual precipitation total decreased by 15–20% in Hungary during the 20th century. The decline is substantial in both halves of the century, but the precipitation sums in the transition seasons declined in the first 50 years, and the winter precipitation decreased in the latest decades. The precipitation total of the period November–February declined significantly in the last 50 years. In the same time the mean winter value of the North Atlantic Oscillation Index (NAOI) increased, the positions of the main pressure patterns over the Atlantic are shifted northeastward, and lot of other coherent changes detected in the winter climate of the European–Atlantic region. The mean summer precipitation total has hardly changed, but the frequency of summer drought events increased. There are some signs of a shift of the Hungarian summer climate towards a Mediterranean like climate.  相似文献   

基桩有效桩长几个问题的探讨   总被引：5，自引：1，他引：5  

曾友金  章为民  王年香  徐光明 《岩土力学》2003,(Z2)

从离心模型试验成果、超长单桩静载试验成果、工程实践及其他学者研究成果中,论证了普通单桩存在有效桩长。深入解释了有效桩长的含义,指出了与临界桩长概念有区别。在分析目前有效桩长定义基础上,提出了合理的有效桩长定义。明确了研究普通单桩有效桩长的意义及存在的问题,并提出了在一定条件下,合理确定有效桩长就是合理设计桩长。  相似文献   

脑卒中与气象要素关系的探讨   总被引：10，自引：4，他引：10       下载免费PDF全文

陆晨 《气象科技》2003,31(6):397-399

1994年1月至2000年12月北京地区若干社区脑卒中发病人数与同期气象资料分析结果表明：北京地区脑卒中发病有明显的季节性，冬春季高发，夏秋季低发；出血性脑卒中发病是春秋季高发，夏季低发；缺血性脑卒中发病是夏季高，秋季低。脑卒中发病与气温、气压和相对湿度有密切关系；寒冷与高温，气温、气压的剧烈变化等，可能是诱发脑卒中的重要气象因素。  相似文献   

荒漠戈壁下垫面表面动量和感热湍流通量参数化研究   总被引：9，自引：0，他引：9  

ZHANG Qiang  HUANG Ronghui  TIAN Hui 《大气科学进展》2003,20(1):111-118

用合理筛选以后的野外观测资料，研究了荒漠戈壁地表湍流通量参数化的问题。首先，分析了Monin-obukhov相似函数的特征，并拟台出了其经验公式。结果表明，风速和温度相似性函数随稳定度参数的变化曲线与典型经验曲线差异较小，并且在经验曲线分布范围以内，但中性时的值有所不同。同时，还用该资料给出了动量和标量粗糙度(感热粗糙度)长度的平均值及其标量粗糙度随摩擦速度的变化关系。发现标量粗糙度的平均值大约比动量粗糙度的小一个量级，并且随摩擦速度的增大而减小，但明显比其理论预测值要大。  相似文献