面向带洞面状对象间的拓扑关系描述模型   总被引：1，自引：1，他引：0  

沈敬伟  周廷刚  朱晓波 《测绘学报》2016,45(6):722-730

为研究带洞面状对象间的拓扑关系,提出了一种25IM(25交集模型)。以点集拓扑理论为基础,对带洞面状区域的内部、边界和外部进行定义。分析了9IM(9交集模型)在表达带洞面状对象间拓扑关系方面存在的问题,将带洞面状对象分为内部、外边界、内边界、外边界外部、内边界外部共5部分,提出了一种5×5的矩阵模型,即25IM。基于点集拓扑理论,定义了8条规则来排除不符合逻辑的拓扑关系。基于25IM,对8种基本拓扑关系:相离、相接、重叠、覆盖、包含、相等、被覆盖和被包含,进行细分描述。结果表明,本文提出的25IM能够更为详细地表达带洞面状对象间的拓扑关系。  相似文献   

江汉平原地下水化学特征及水流系统分析          下载免费PDF全文

梁杏  张婧玮  蓝坤  沈帅  马腾 《地质科技通报》2020,39(1):21-33

江汉平原水质性缺水问题日益突出,识别江汉平原地下水流系统分布模式,对地下水资源的合理利用与保护具有重要意义.选取江汉平原典型区域,综合水文地质条件、水动力场及水化学同位素指标深入分析地下水补给过程、水岩作用及滞留时间.得出由于碳酸盐岩的溶解,研究区的地下水化学类型属于HCO3-Ca (Mg)型.地下水中典型离子随深度增加逐渐降低,同位素随深度增加逐渐偏负,表现出地下水流系统呈局部与区域水流系统的特点,系统深度界限在10~20m.独立而复杂的局部水流系统在平枯水期地下水向河渠地表水排泄.根据3H的含量,局部水流为现代水,水循环交替迅速.受地形控制,中深层地下水总体由西和西北向东和东南径流,汇入汉江和长江,为区域水流系统.由于补给源的高程效应,区域水流的18O值存在明显分区,指示不同的补给来源与水流路径.山前丘陵区基本为现代水,向平原腹地纵深至汉江和长江排泄区,地下水年龄在几百年至6000a不等,水循环交替缓慢.研究发现江汉平原低洼排泄区存在区域水流的顶托补给,可为原生劣质水的分布与聚集研究提供依据.  相似文献   

The effects of slope shape and polyacrylamide application on runoff,erosion and nutrient loss from hillslopes under simulated rainfall     

Chang Ao  Wenzhi Zeng  Peiling Yang  Weimin Xing  Guoqing Lei  Jingwei Wu  Jiesheng Huang 《水文研究》2021,35(4):e14130

Natural hillslopes are mostly composed of complex slope shapes, which significantly affect soil erosion. However, existing studies have mainly focused on uniform slopes to simplify complex hillslopes, and the mechanisms responsible for the influence of slope shape on soil and nutrient losses are still not well understood, especially in the application of soil improvers to reduce soil loss. To investigate the effects of slope shape and polyacrylamide (PAM) application on runoff, soil erosion and nutrient loss, this study conducted artificial field rainfall experiments involving two PAM application rates and nine slope shapes. The results indicate that the average amount of soil loss from convex slopes was 1.5 and 1.3 times greater than that from concave and uniform slopes, respectively, and the average amount of ammonia nitrogen loss and phosphate loss increased by 24.0%–58.6%. Soil and nutrient losses increased as the convexity of the convex slopes increased. For runoff, there was little difference between concave and convex slopes, but the runoff amount for both slopes was greater than that for uniform slopes. After PAM application, the soil loss decreased by more than 90%, and the nutrient loss decreased by 28.2%–68.1%. The application of PAM was most effective in reducing soil erosion and nutrient loss from convex slopes, and it is recommended to appropriately increase the PAM application rate for convex slopes. A strong linear relationship between ammonia nitrogen and phosphate concentrations and sediment concentrations was found in the runoff on slopes with no PAM application. However, this linear relationship weakened for slopes with PAM application. The findings of this study may be valuable for optimizing nonpoint source pollution management in basins.  相似文献   

High Resolution ID-TIMS Redefines the Distribution and Age of the Main Mesozoic Lacustrine Hydrocarbon Source Rocks in the Ordos Basin,China     

CUI Jingwei  ZHU Rukai  ZHANG Zhongyi  Jahandar RAMEZANI  LI Yang 《《地质学报》英文版》2023,97(2):581-588

Using high-precision zircon U-Pb ID-TIMS geochronology, tuffs from the Chang 9 shale and the Chang 7 shale were dated. The tuff in the Chang 9 shale is 241.47 ± 0.17 Ma, which falls between the top tuff age of 241.06 ± 0.12 Ma and the bottom tuff age of 241.558 ± 0.093 Ma in the Chang 7 shale. These reveal that the Chang 9 and Chang 7 shales are contemporaneous, belonging to the Ladinian stage of the Middle Triassic. This insight expands the region of the main source rock of Chang 7 to the north...  相似文献   

Hydrochemistry of the natural low pH groundwater in the coastal aquifers near Beihai,China     

Zhou  Xun  Shen  Ye  Zhang  Hua  Song  Chao  Li  Jingwei  Liu  Yan 《中国海洋大学学报(英文版)》2015,14(3):475-483

Natural weak acidic groundwater occurs in the unconfined and confined aquifers consisting of Quaternary and Neogene unconsolidated sediments near Beihai in southern Guangxi, China. Under natural conditions the groundwater has low TDS(less than 200 mg L-1) and low concentrations of trace elements(less than 100 μg L-1) with a deceasing tend in contents of the Lanthanides(rare earth elements, less than 1 μg L-1) towards higher atomic number. The groundwater ranges in p H from 3.33 to 7.0 with an average value of 5.12(even lower than that of local rainwater, 5.88). p H values in the groundwater are a bit higher in rainy seasons than those in dry seasons and do not show significant increasing or decreasing trend with time. The average p H value in groundwater in the confined aquifers is even a bit lower than that in the unconfined aquifer. Comprehensive analyses of the groundwater environment suggest that H+ in the groundwater may be derived from dissociation of H2CO3, release of the absorbed H3O+ in clay layers and the acidity of rainwater. The H2CO3 in the groundwater may be formed by dissolution of CO2(g). Minerals in the unconsolidated sediment are predominated by quartz with small amount of clay minerals. The sediments undergoing a long-term weathering contain low levels of soluble constitutes. Lack of alkaline substances in the groundwater system is also helpful in the accumulation of acidity of the groundwater.  相似文献   

南海中沙群岛海域表层沉积物粒度特征及其输运趋势     

陈俊锦  张经纬  刘时桥  陈万利  秦永鹏  吴时国 《海洋地质与第四纪地质》2022,42(2):15-27

对南海中沙群岛海域232个表层沉积物样品进行了粒度分析,以探讨研究区沉积物来源、沉积环境和输运趋势.根据Folk沉积物命名法,将研究区沉积物划分为砂、粉砂质砂、砂质粉砂、砂质泥、粉砂和泥等6种类型,以砂质泥和泥为主,粒径较粗、分选较好的沉积物主要分布在中沙台地海域.通过对组分含量、粒度参数和水深进行聚类分析和主成分分析...  相似文献   

一次伴随强沙尘暴天气飑线的多普勒雷达回波特征     

韩经纬  孟雪峰  宋桂英 《气象》2006,32(10):57-63

利用斯一代天气雷达和T213数值预报产品资料对2005年4月1日发生在内蒙古中部偏南地区的一次局地强沙尘暴和雷雨大风天气过程进行了连续的监测和分析。诊断分析表明：局地强沙尘暴发生前，动力、热力场条件和系统结构有利于强对流天气的发生发展，沙尘暴发生区域，低层散度的辐合中心和垂直运动的上升中心有很好的对应关系，并与雷达资料的逆风区相对应。物理量场的强度达到甚至超过了当地暴雨或强对流天气的强度，而在沙尘暴发生区域上空整层的相对湿度均特小，低层尤为干燥。进一步结合新一代天气雷达的探测结果，在对雷达回波逆风区沿入流方向（SWNW）的空间剖面分析表明，沙尘暴区域的低层850hPa有强辐合中心，高层存在辐散中心，700hPa附近存在强上升中心，且上升高度一直达到350hPa附近。局地强沙尘暴和强风主要是雷暴内中-γ尺度系统强的辐合旋转造成的，反射率最大区与正负速度最大区接近或重叠，并由正速度区过渡到负速度区，产生了强烈的风切变，使中-γ尺度系统的辐合旋转加强，加之低层较强的垂直运动，造成了局地强沙尘暴天气。沙尘暴区域以外的强风是雷暴系统外部产生的，其最大风速出现在弓形回波突出的部位、出流回波区域及径向速度图上速度模糊区域，而强沙尘暴天气却出现在中-γ尺度的逆风区中。  相似文献   

An Experimental Styudy on Gold Solubility in Amino Acid Solution and Its Geological Significance     

张景荣  陆建军等 《中国地球化学学报》1996,15(4):296-302

The experiments on gold solubility in amino acid solution mdicate that gold is very intensively soluble in amino acid(or other organic acids),which is extensively present in geological bodies,and is most soluble in histidine.The temperature and concentration,acidity and type of amino acid in the solution are important factors affecting gold-amino acid complexing. The solubility of gold in amino acid is different under different conditions of temperature, amino acid concentration and pH value of the solution,At 80℃ and pH=6-8,gold is most soluble in amino acid.Gold dispersed in water and rocks could be concentrated and transported by amino acid and then precipitated in favorable loci.Amino acids might have played an important role in metallogenesis as well as in the formation of source beds of gold.Nitrogen,oxygen and sulfur in amino acid might have reacted with gold to form soluble complex ions.  相似文献   

周口坳陷早白垩世沉积相与沉积格局   总被引：1，自引：0，他引：1       下载免费PDF全文

李文厚  陈景维  邵磊 《沉积与特提斯地质》1996,16(1):44-50

周口坳陷早白垩世主要发育冲积扇相、河流相、湖泊相、扇三角洲相和三角洲相等类型，其中谭庄－沈丘凹陷沉积相带呈东西向狭长展布，是一个典型的断陷盆地．本文在讨论了湖盆的物源、古地形、古水流、水介质条件及古气候条件的基础上，提出了早白垩世时周口坳陷的沉积格局。  相似文献   

声雷达探测在大气扩散研究中的应用(2)——混合层深度及对应的地面浓度     

肖经纬  吕乃平  周明煜 《大气科学》1984,8(4):373-381

本文介绍如何将声雷达探测的混合层深度的变化应用于大气扩散问题.并用实例说明当某一天气过程引起混合层结构的特殊变化时,通常的模式计算不能合理地描述地面浓度特征,而利用声雷达探测的信息则能给出较合理的结果。  相似文献