徐闻县西部珊瑚礁的分布与保护   总被引：4，自引：4，他引：0  

赵焕庭  王丽荣  宋朝景 《热带地理》2006,26(3):202-206

雷州半岛属热带北缘季风气候,沿岸海洋属热带海洋,生长浅水造礁石珊瑚,但只有雷州半岛西南部沿岸形成珊瑚礁,是中国大陆(不含岛屿)沿岸唯一的礁区.主要为岸礁,有个别为斑礁.徐闻县西部沿岸有16段珊瑚礁,初步统计总长约37.5 km,面积30.1 km2.由于人类不当的开发导致珊瑚不断死亡,珊瑚礁生态退化.现已成立的珊瑚礁自然保护区,应予加强管理.海水养殖珍珠与珊瑚礁自然保护事业是可以协调发展的.  相似文献   

近50a来民勤沙尘暴的环境特征   总被引：19，自引：6，他引：13  

张克存  屈建军  马中华 《中国沙漠》2004,24(3):257-260

根据民勤县气象局近50a来观测的1436次沙尘暴资料, 系统地分析了这一时段沙尘暴发生的时间特性。从沙尘暴发生的机制出发, 并结合当地的其他气象要素, 初步确定沙尘暴和与之对应的气象要素之间的关系, 为该地区治理沙害、恢复生态提供理论依据。  相似文献   

湖南凤凰"南方长城之旅"的开发设计   总被引：3，自引：0，他引：3  

王亚力 《热带地理》2003,23(1):80-84

以"南方长城之旅"为主题对凤凰旅游的形象进行了明确定位,以民族文化的分合为线索对凤凰人文旅游资源进行有机整合,在此基础将凤凰的民族文化景观划分成3大区:民族文化分界区、民族文化分离区、民族文化融合区,提出了旅游产品组合开发的新方案.  相似文献   

高速铁路CPⅢ网平差起算点兼容性研究     

闫广峰  高山 《测绘工程》2014,(8):50-53

起算点的兼容性直接影响约束平差成果的质量,CPⅢ测量工作中要联测大量的已知点,区段搭接时要以重叠区段的部分上段成果作为约束点,因此,对起算点进行兼容性分析是十分重要和必要的.文中提出适用于CPⅢ网的平差起算点兼容性检验方法和兼容性较差起算数据探测方法,并在理论分析的基础上通过实测数据,计算分析并验证这些方法的合理性与科学性.  相似文献   

关于地震灾害快速评估系统的思考   总被引：5，自引：0，他引：5  

杨天青  姜立新 《地震》2005,25(3):123-128

基于地震快速评估经济损失结果与地震现场调查得到的经济损失结果有较大的差异现象, 为了进一步提高地震快速评估经济损失结果的精确性, 笔者通过对地震快速评估经济损失结果和实际现场调查得到的经济损失结果进行对比研究, 并从建筑物单价和建筑物损失比的角度对快速评估结果进行修正, 以发生在云南境内的10次典型地震为例, 初步得出了对地震经济损失快速评估结果粗略的修正系数。 在一定程度上较大提高了地震快速评估经济损失的精确性。 为地震救援指挥工作提供了更加可靠的依据。  相似文献   

基于边坡单元的公路沿线滑坡危险度概率分析     

邱骋  王纯祥  江崎哲郎  谢漠文 《岩土力学》2005,26(11):1731-1736

公路沿线发生的滑坡、泥石流等自然灾害是造成交通停滞的主要原因。对公路沿线边坡进行稳定性评价及滑坡灾害分析对于公路管理和灾害防治具有重要意义。为了能对大范围边坡应用三维力学模型进行稳定性评价,研究中将较大研究区域划分为多个边坡单元（slope unit）,并介绍了边坡单元划分方法。对每个边坡单元,采用随机生成许多假想滑动面并通过一个基于GIS的边坡稳定性三维分析模型计算其安全系数的方法,找出具有最小安全系数的危险滑动面,同时求出在试算过程中安全系数小于某临界值（通常设为1.0）的结果出现的比率,作为该边坡单元的滑坡发生概率,以此作为指标对研究区域进行危险度评价。通过对日本49号国道沿线边坡中的应用对该方法的实用性进行了验证。  相似文献   

基于图形处理器的海浪仿真研究   总被引：3，自引：0，他引：3  

杜莹  武玉国  王晓明 《海洋测绘》2005,25(3):12-16

提出了一种新的海浪数学模型构造算法,利用基本噪音函数构建Perlin噪音函数,并利用Perlin噪音函数生成的高度场为海浪中的水质点提供高度采样源。同时针对海浪仿真中计算量大的问题,以及依赖CPU完成图形运算的不足,提出用图形处理器(GPU)中的顶点着色器和像素着色器实现海浪的仿真,以平衡CPU和GPU的负载,确保仿真实时和逼真的视觉效果。  相似文献   

湖南沅陵唐浒坪矿田成矿条件分析     

方向阳  戴平云  吴世华 《华南地质与矿产》2005,(1):41-46

矿田位于上扬子地块与华南裂陷槽的结合部,多次构造运动造就了武陵、雪峰、加里东、印支和燕山五个构造层。区内广布的元古界地层中Au,Sb,W,Cu,Pb和Zn的平均含量明显高于上部大陆地壳的平均值,形成一个巨大的微量元素资源库,为区内矿源层。唐浒坪复背斜、沃溪-冷家溪断层、滴水坪-明溪口断层等为区内控矿构造。矿田处于兴安 -太行 -武陵巨型重力梯度带上,在通道-溆浦-安化航磁负异常带北东段和常德幔隆与麻阳幔隆的鞍部。区内发现分散流金异常 26处,面积 2 ~32km2,金峰值 (500 ~4350)×10-9,沃溪金矿最高达4900×10-9;铜异常 5处,面积 2~22.5km2,铜峰值 (40 ~200)×10-6,最高达 316×10-6。研究认为该矿田具良好的找矿前景,可划分为Ⅰ、Ⅱ、Ⅲ级成矿远景区。  相似文献   

A new analytical model for consolidation with multiple vertical drains          下载免费PDF全文

Mengmeng Lu  Scott W. Sloan  Buddhima Indraratna  Hongwen Jing  Kanghe Xie 《国际地质力学数值与分析法杂志》2016,40(11):1623-1640

Various analytical theories of consolidation for soils with vertical drains have been proposed in the past. Most conventional theories are based on a cylindrical unit cell that contains only a single vertical drain. This paper described a new analytical model where a vertical drain located at the centre (the ‘inner vertical drain’) and is surrounded by two or three vertical drains (the ‘outer vertical drains’), the number of which depends on whether the configuration is triangular or rectangular. Both types of drains are combined into a cylindrical unit cell, and the water is assumed to flow both inwards to the inner vertical drain and outwards to the outer vertical drains distributed around the circumference. The outer radial boundary of the unit cell is regarded as a permeable boundary, with a drainage capacity of two or three separate vertical drains for triangular and rectangular configurations, respectively. The smear effects and the drainage resistances for both the inner and outer vertical drains are considered in the analysis as well. In this way, the equations governing the consolidation process with multiple vertical drains are derived, and the corresponding analytical solutions are obtained for instantaneously loading, ramp loading and multi‐stage of instantaneously loading and multi‐stage of ramp loading. The present solutions are finally compared with several conventional solutions for a single vertical drain in the literature. The results show that the present model predicts the same average degree of consolidation as conventional models do, which verifies the correctness of this new model. Finally, the settlement predicted by the present solution is compared with the measured settlement from a field test at the Port of Brisbane, Australia, which shows a good agreement between them. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

The impact of spatial scale: exploring urban butterfly abundance and richness patterns using multi-criteria decision analysis and principal component analysis     

Emily C. Hazell  Claus Rinner 《International journal of geographical information science》2020,34(8):1648-1681

ABSTRACT

Modelling changes in biodiversity have become a necessary component of smart urban planning practices. However, concepts such as biodiversity are often evaluated using area-based composite indices, the results of which are heavily reliant on specific parameters chosen. This paper explores the design and implementation of a butterfly biodiversity index by comparing two widely accepted modelling techniques: principal component analysis and spatial multi-criteria decision analysis (MCDA). A high degree of scale dependency has been demonstrated in previous studies exploring the use of area-based composite measures. To evaluate the impact of scale, each model was assessed at two different spatial resolutions. The outcomes were analyzed, mapped and compared using ordinary least squares, geographically weighted regression and global Moran’s I to evaluate relative biodiversity patterns across the City of Toronto, Canada. Findings indicate that the impact of spatial scale was significant, whereby the coarser resolution models were found to be more highly correlated with biodiversity, compared to the finer resolution models. The results of this study contribute to a growing body of literature that explores key conceptual questions regarding the robustness of GIS-based MCDA, the impact of scale in urban ecology studies, and the use of composite indices to manage spatial ecological data.  相似文献