The Application of GIS in Education Administration: Protecting Students from Hazardous Roads     

Fatemah Admadi Nejad Masouleh  Yuji Murayama  Todd Wendell Rho'Dess 《Transactions in GIS》2009,13(1):105-123

Though enrolment by proximity is an official educational policy in Iran, the lack of clearly defined school attendance areas has resulted in an informal open enrolment system where parents may choose public schools outside their residential areas. Two major consequences of parental choice are longer commutes to schools and increased use of motor vehicle transport. To delineate school attendance areas for public female junior high schools in the city of Rasht in Northern Iran, this research used the multiplicatively weighted Voronoi diagram (MWVD) technique to construct school attendance areas. The approach was shown to be useful in developing countries like Iran where accident fatalities are not only disproportionately high but the public school system lacks sufficient educational diversity to offset the societal costs of opting out of neighbourhood schools. A GIS-based specialist package was used for constructing the proposed school attendance areas. Given the MWVD utility in demarcating spaces so that all journeys within them are closest to a chosen point, the research concluded that proposed school attendance areas can result in shorter and more convenient commutes on foot for students. This can eliminate the need to travel by vehicle for the overwhelming majority of students and thus make their journeys more convenient and safer.  相似文献   

空间最近目标查找算法分析及其高性能Web实现   总被引：1，自引：1，他引：0  

田锋  蒋许锋 《测绘与空间地理信息》2009,32(3):108-109,113

讨论了空间最近目标查找的基本算法和相关的空间索引机制,简单地比较了几种算法和索引机制的优缺点.详细地介绍了在Windows IIS和.Net下,建立多级空间格网索引,实现空间最近目标查找的实现方法.  相似文献   

侵入砂体对深水油气勘探的研究意义   总被引：2，自引：0，他引：2  

秦志亮  王大伟  吴时国  马玉波  曹全斌  许建华 《海洋地质与第四纪地质》2009,(2)

侵入砂体是指深水沉积砂体在超压流体作用下侵入至上覆泥质沉积物中形成的砂体,它是深水盆地松散沉积物变形构造中常见的地质现象。侵入砂体由于其特殊的形成特点,可以明显改变原生沉积地层的几何形态和深水沉积物的物性参数,进而使储层复杂化,影响深水油气的勘探与开发,主要表现在:①侵入砂体改变了深水储层的性质及分布;②侵入砂体可能形成油气运移或散失的通道,并且改变了深水油气储层的垂向连通性;③大规模的侵入砂体本身也可以作为良好的油气储层;④侵入砂体的研究可以揭示未固结砂的流动机理,对于研究深水环境中广泛出现的浅水流的成因具有重要的借鉴意义。  相似文献   

Remote sensing of turbidity in seawater intrusion reaches of Pearl River Estuary – A case study in Modaomen water way,China     

Shuisen Chen  Ligang Fang  Lixin Zhang  Wenrui Huang 《Estuarine, Coastal and Shelf Science》2009

Based on field experiments and analysis, the study examined the spectral characteristic and spatial variability of turbidity in the Pearl River Estuary by using the EO-1 ALI satellite imagery collected on December 18, 2005. A negative regression model (turbidity = −439.52 × R (570) + 22.913, R² = 0.9042, n = 11) between the in-situ turbidity and the reflectance at 570 nm (maximum correlation spectral band between 350 and 2500 nm), resulting from increasing of organic matters in suspended solids, was built and applied to ALI band 4 (0.525–0.605 nm). Simple in-water spectral pairs calibration method of bright and dark targets provided the good atmospheric correction of ALI with a root mean square error of 0.00061, and mean absolute percentage error of 2.04%. The study also found the seawater turbidity is a more accurate indicator of Chl_a concentration (R² = 0.7442) than TSS (R² = 0.7061). Also, there is a large correlation between TSS and the turbidity (R² = 0.86, N = 22) for Modaomen watercourse. The model-deduced turbidity distribution from ALI band 4 exhibited distinctive spatial variability of turbidity in the dry season, accordant with seasonal in-situ investigation. The ALI data provides accurate estimates of the mean water clarity conditions in the PRE (RMSE = 1.878 and MAPE = 11.7%) and has potential importance for water quality monitoring of optical remote sensing in the similar estuaries and its future operation.  相似文献   

Comparison Between Full-Scale and Model Experiments of Oil Fences     

Tae Ho KIM  Duck Jong JANG  Kyong Uk YANG  Sun Chol NA  Dae An KIM 《中国海洋工程》2009,23(4):657-668

  相似文献   

珠江河口咸潮期间浮游植物的群落特征   总被引：4，自引：0，他引：4       下载免费PDF全文

李开枝  黄良民  张建林  尹健强  罗琳 《热带海洋学报》2010,29(1):62-68

根据2007年底至2008年初珠江河口咸潮入侵期间大潮和小潮的两次调查资料, 对浮游植物的种类组成、种数和细胞密度的分布等群落特征进行了分析, 并探讨环境因素对浮游植物群落的影响。共鉴定浮游植物76种, 包括38种硅藻、18种绿藻、14种甲藻、4种蓝藻和2种裸藻。浮游植物种数分布有明显的空间变化, 一般从河口上段至下段种数减少; 大潮时浮游植物的种数低于小潮时, 并且各水层之间浮游植物种数分布不均匀。优势种以淡水硅藻为主, 如颗粒直链藻Melosira granulata、颗粒直链藻最窄变种 Melosira granulata v. angustissima、小环藻 Cyclotella sp.和海链藻Thalassiosira sp.等; 河口上段的站优势种突出, 密度分布不均匀, 均匀度值比较低。大潮和小潮期间浮游植物细胞密度的平均值分别为53.80×104个.L-1和62.21×104个.L-1, 变化范围为(1.48— 290.41)×104个-L-1和(1.52—283.62)×104个.L-1; 二者的平面分布趋势基本相同, 由河口上段至下段呈递减的格局; 硅藻类的细胞密度占明显优势。浮游植物的种类组成、种数和细胞密度的分布受盐度、营养盐等环境因子的影响, 并且具有明显的潮周期性。  相似文献   

渤海湾海岸带开发对近海水环境影响分析   总被引：13，自引：0，他引：13  

聂红涛  陶建华 《海洋工程》2008,26(3)

应用水动力学、水质数学模型,以渤海湾海岸带的几种典型开发活动--围海造地、海水淡化和河口建闸为例,模拟分析海岸带开发活动对渤海湾近岸海域水环境的影响.研究沿海围垦造成的潮通量、近岸流场水动力条件和污染物输移的变化;分析海水淡化工程浓缩海水的排放,高盐度高浓缩污染物对局部生态环境的影响;分析河口建闸后蓄积的污水排放方式对河口及近岸海域造成的影响,大量污水一次性排放会增大河口及近岸海域污染面积和污染程度.  相似文献   

挡潮钢闸门金属热喷涂材料及工艺选择     

朱锡昶  朱雅仙  葛燕  李岩 《海洋工程》2008,26(3)

通过对沿海挡潮闸所处环境特点及金属热喷涂的机理分析,比较热喷涂锌、铝的优越性,对热喷涂工艺进行对比以及封闭涂层的选择,阐述和推荐挡潮闸钢闸门金属热喷涂防腐蚀方案.  相似文献   

热带气旋活动对陕西2007年两次大暴雨影响的综合分析     

侯建忠  许新田  张小玲  李明  段昌辉 《成都信息工程学院学报》2008,23(5):537-543

通过2007年陕西两次区域性大暴雨的分析发现,台风远距离的影响作用明显。在对流层中低层,台风西行发展和加强时,台风低压的东侧或东北侧的风场出现显著增强现象,为暴雨区输送大量能量和提供充沛的水汽。台风在海南附近时,其径向特征表现明显,大暴雨出现在秦岭以南;台风在台湾附近时,其纬向特征表现明显,大暴雨出现在秦岭以北。垂直运动分析表明,台风低压系统的存在、维持、发展和加强对副热带高压有一定的维持、加强作用,有利于强降水的形势能够稳定和维持。  相似文献   

滨州市海（咸）水入侵灾害及发展趋势   总被引：2，自引：1，他引：1       下载免费PDF全文

薛令轩  王兵  卢政峰 《山东国土资源》2008,24(9)

近年来,山东省滨州市地下水位下降迅速,且已引起无棣-沾化-带海（咸）水入侵。通过对滨州市海（咸）水入侵现状、原因、危害及发展趋势的分析,提出限采深层地下水、合理增采浅层淡水、回灌补源、抽咸补淡、开辟新的水源和强化用水管理、全面节约用水等防治海（咸）水入侵灾害的对策措施。  相似文献