土地利用现状图概括中的两类问题探讨     

杨毅  王卫安  乔刚 《测绘与空间地理信息》2011,(6):246-248

传统的土地利用现状图概括自动化程度较低,需要大量人工处理,通常借助ArcGIS桌面软件提供的空间处理（Geoprocessing）工具,但对于狭长多边形以及最小锐角检查等地图概括问题,没有提供较好的解决方案。本文正是研究处理狭长多边形以及最小锐角检查的地图概括问题。由实验结果可知,利用ArcGIS Engine对最小锐...  相似文献   

“8·18”暴雨过程中的地面自动站中尺度风场分析     

青泉 《四川气象》2011,(4):24-28

用尺度分离方法对自动站风场进行处理,结合多普勒雷达对2010年8月18日四川盆地西部暴雨过程进行分析,结果表明：强风暴影响地区的地面风场从非常零乱逐渐变得有组织性,这个组织性表现在风向的一致性和风速的增强;对流回波生成的源地是在地形的作用下,中尺度辐合线长时间存在的地区和中尺度正涡度长时间维持的地区,这些地区有利于对流回波的发展加强;对流回波移入辐合区,有利于回波加强,强回波移入辐散区,则回波属于减弱趋势。  相似文献   

1955—2006冬半年中国极端低温的时空变化特征   总被引：4，自引：2，他引：2  

付冬雪  孙照渤  李忠贤  倪东鸿 《气象科学》2011,31(3):274-281

采用1955—2006年全国275个台站冬半年逐日最低气温资料,对中国冬半年极端低温的时空特征和变化趋势进行了分析。结果表明：在全国范围内冬半年极端低温频数变化一致,均呈减小趋势,1983年前后发生了明显的突变;近52 a来最显著的减小趋势位于华北、长江中下游及江南地区,最不显著的减小趋势位于河套地区,较弱的减小趋势位于四川盆地和云贵高原地区;中国冬半年年极端低温事件频数的空间差异明显,各区域极端低温频数突变的年份均不一致,各区域突变前后的极端低温频数存在较大差异,但近年来,各区域冬半年极端低温频数变化均趋于稳定。  相似文献   

Investigation of the scale-dependent variability of radar-rainfall and rain gauge error covariance   总被引：1，自引：0，他引：1  

Bong-Chul SeoWitold F. Krajewski 《Advances in water resources》2011,34(1):152-163

There is a significant spatial sampling mismatch between radar and rain gauge data. The use of rain gauge data to estimate radar-rainfall error variance requires partitioning of the variance of the radar and rain gauge difference to account for the sampling mismatch. A key assumption in the literature pertaining to the error variance separation method used to partition the variance is that the covariance between radar-rainfall error and the error of rain gauges in representing radar sampling domain is negligible. Our study presents the results of an extensive test of this assumption. The test is based on empirical data and covers temporal scales ranging from 0.25 to 24 h and spatial scales ranging from 1 to 32 km. We used a two-year data set from two high quality and high density rain gauge networks in Oklahoma and excluded the winter months. The results obtained using a resampling procedure show that covariance can be considerable at large scales due to the significant variability. As the variability of the covariance rapidly increases with larger spatial and shorter temporal scales, applications of the error variance separation method at those scales require more caution. The variability of the covariance and one of its constituting variables, the variance ratio of radar and gauge errors, shows simple scaling behavior well characterized by a power-law.  相似文献   

Hydrograph separation and precipitation source identification using stable water isotopes and conductivity: River Ganga at Himalayan foothills   总被引：3，自引：0，他引：3  

A. S. Maurya  Miral Shah  R. D. Deshpande  R. M. Bhardwaj  A. Prasad  S. K. Gupta 《水文研究》2011,25(10):1521-1530

The observed retreat of several Himalayan glaciers and snow packs is a cause of concern for the huge population in southern Asia that is dependent on the glacial‐fed rivers emanating from Himalayas. There is considerable uncertainty about how cryospheric recession in the Himalayan region will respond to climate change, and how the water resource availability will be affected. As a first step towards quantifying the contribution of glacier‐melt water, hydrograph separation of River Ganga at Rishikesh into its constituent components, namely (i) surface runoff, (ii) glacial ice‐melt and (iii) groundwater discharge has been done in this paper. A three‐component mixing model has been employed using the values of δ¹⁸O and electrical conductivity (EC) of the river water, and its constituents, to estimate the time‐varying relative fraction of each component. The relative fraction of the surface runoff peaks (70–90%) during winter, due to the near‐zero contribution of glacial ice‐melt, essentially represents the melting of surface snow from the catchment. The contribution of glacial ice‐melt to the stream discharge peaks during summer and monsoon reaches a maximum value of ～40% with an average of 32%. The fraction of groundwater discharge varies within a narrow range (15 ± 5%) throughout the year. On the basis of the variation in the d‐excess values of river water, it is also suggested that the snow‐melt and ice‐melt component has a significant fraction derived from winter precipitation with moisture source from mid‐latitude westerlies (also known as western disturbances). Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Limit equilibrium method based on an approximate lower bound method with a variable factor of safety that can consider residual strength     

Y.M. Cheng  D.Z. Li  L. Li  Y.J. Sun  R. Baker  Y. Yang 《Computers and Geotechnics》2011

In this paper, the factor of safety for a prescribed slip surface will be determined from an equivalent lower bound method (extremum principle), which can satisfy all equilibrium conditions without an interslice force function. This approach will give an overall factor of safety close to that from the classical methods for normal problems, while the thrust line, the local factor of safety for individual slice/block and the progressive yielding phenomenon can be estimated, which will be useful for some special cases. The force and moment equilibrium of every slice will be satisfied, while the location of the thrust line will always be acceptable in the present formulation. To solve the difficult optimisation problem, an innovative coupled particle swarm/harmony search algorithm is proposed in this paper, and a practical engineering problem for which the factor of safety is close to 1.0 is used to illustrate the consideration of the residual strength in the limit equilibrium slope stability analysis.  相似文献   

金锑共生矿石中金的测定方法   总被引：1，自引：1，他引：0  

钟蓓 《贵州地质》2011,28(1):76-78

对于金锑共生的矿石,在进行金测试时锑的干扰比较严重.本文根据金的性质,常温下金与单独的无机酸(如硝酸、盐酸或硫酸)均不起作用的原理,在测金前先除去锑,然后再测金,可得到好的结果.  相似文献   

河南省鲁山石墨矿浮选工艺研究   总被引：4，自引：0，他引：4  

李艳  魏祥松  逄思宇 《化工矿产地质》2011,33(1):61-64

河南鲁山石墨矿属区域变质型矿床.根据矿石性质,进行了粗选条件试验,阶段磨矿阶段选别试验和阶段磨矿阶段选别预先分目试验,研究结果表明阶段磨矿是保护石墨大鳞片的有效方法,同时,结合预先分目能更好地提高石墨大片率.阶段磨矿阶段选别预先分目工艺闭路试验获得的指标为:当原矿品位为3.65%时,获得的技术指标为精矿品位C90.62...  相似文献   

声跃层结构变化对深海汇聚区声传播的影响   总被引：1，自引：0，他引：1  

张旭  张永刚  董楠  张健雪 《台湾海峡》2011,30(1):114-121

根据射线理论建立了线性声速结构条件下的声跃层强度与深海汇聚区关系模型,用最小位移角讨论了海洋环境变化（如声跃层强度变化、声跃层位置变化及季节性跃层生消等）与汇聚区距离和宽度变化的相关性.结果表明,声跃层的结构变化对汇聚区特征影响很大.声跃层强度增大使汇聚区向远离声源的方向变化,跃层强度每增加0.01 s-1对应的汇聚区位移增大约为3.5～5.0 km.声跃层位置变化对汇聚区的影响小于声跃层强度,与两层结构的声速剖面相比,上行结构使汇聚区向靠近声源的方向变化,声跃层上升200 m对应的汇聚区位移减小约为1.0～1.5 km,声跃层越浅,汇聚区距离越近;下行结构使汇聚区向远离声源的方向变化,混合层加深200 m对应的汇聚区位移增大约为1.0～1.5 km,混合层越深,汇聚区距离越远.季节性跃层的生消使近表层有负梯度、零梯度和正梯度的变化.负梯度结构的变化规律与两层结构条件下的声跃层强度变化类似,但对汇聚区的影响程度相对较小;正梯度结构使汇聚区在近表层出现表面声道,梯度值的增强将使汇聚区向靠近声源的方向变化.  相似文献   

四川盆地强暴雨过程诊断及中尺度分析   总被引：2，自引：1，他引：1  

司林青  白爱娟 《成都信息工程学院学报》2011,26(5):508-516

为了探索四川盆地暴雨天气发生发展的机制,利用云图和美国环境预报中心的全球再分析资料,针对2010年8月18—19日出现的暴雨过程进行环流形势、物理量场及中尺度特征分析,结果表明：暴雨过程中不断有低压槽东移,西太平洋副高西伸至盆地东部,暖湿气流通过低层绕流等方式进入盆地;在低层辐合高层辐散和热力不稳定的条件下,随着干冷空气入侵,对流运动异常强烈,促使强降水发生,湿位涡等值线密集带对暴雨落区预报有较好的指示意义。中尺度对流系统各阶段特征明显,与中尺度气旋演变有很好的相关性。  相似文献