基于开源pgRouting的WebGIS最短路径算法实现研究

pgRouting作为开源PostGIS空间数据库扩展路径规划项目,是对开源WebGIS中路径规划的创新.本文提出了如何在开源平台,将Dijkstra算法应用到WebGIS最短路径查询的方法.利用PostGIS开源项目pgRouting,结合Openlayers调用和Geoserver发布地图,利用OSM数据实现起始点定位查询最短路径的方法策略,并给出相关流程和配置安装的步骤.最后以昆明市道路数据验证了WebGIS中最短路径的方法.     

基于WSR框架的《开发区土地集约利用评价规程》指标体系分析

旨在剖析我国《开发区土地集约利用评价规程》中指标体系存在的问题并提出改进建议。在界定开发区土地集约利用内涵基础上,从要素特征(W维)、利用目标(R维)和评价过程(S维)等3个维度阐述了开发区土地集约利用评价的系统要求,构建关联分析矩阵,对《规程》中评价指标体系的特征差异化、层次完整性和目标关联性等3个方面进行了分析讨论。针对当前《规程》中存在的评价对象混杂、开发区类型需要细化、指标体系不完整、计算方法需修正等问题提出了相应修改建议。     

改进Moser法射线追踪

地震波场正演模拟、层析成像、偏移成像经常需要用到射线追踪,本文在基于图形理论的Ｍｏｓｅｒ法基础上,改进其网格节点的划分、追踪时路径的选取,并增加直射线追踪以消除在速度变化不大时射线受节点布置影响出现不合理的折曲现象．     

青海东昆仑哈陇休玛钼多金属矿床成矿流体特征及成矿模式

哈陇休玛钼多金属矿床是东昆仑成矿带东段目前仅有的中型斑岩型矿床。为了查明其成矿流体性质及成矿物质来源,构建矿床成矿模式,本文进行了详细的流体包裹体和H-O-S同位素研究。流体包裹体显微测温显示,哈陇休玛矿床发育气液两相和含CO₂三相两种类型包裹体,成矿流体呈现中高温(集中于280～340℃)、高盐度(w(NaCl),集中于6.00%～18.00%)和中等密度(集中于0.64～0.92 g/cm³)特点,成矿深度为2.4～4.1 km,形成于中浅成环境。H-O同位素显示,成矿流体具有岩浆水和大气降水混合的特征,但主体以岩浆水为主;S同位素显示,成矿物质主要来自于深部岩浆。结合区域构造演化认为,哈陇休玛矿床成矿模式为印支晚期东昆仑地区发生强烈壳幔混合作用,形成富含成矿元素的混合岩浆,含矿流体在随混合岩浆上升的过程中发生流体沸腾,并与大气降水混合冷却,导致成矿物理化学条件发生变化,促使成矿物质沉淀成矿。     

南海夏季风爆发日期和强度的短期气候预测方法研究

利用合成及相关统计方法，研究冬季南海季风指数与850hPa风场、500hPa高度、海表温度、OLR等环境场的相互关系及其影响南海夏季风活动的可能机制。指出冬季南海季风指数及环境场的异常特征可以作为预测南海夏季风活动的前兆信号。在此基础上建立了预测南海夏季风爆发日期和强度的概念模型，1998－2001年的预测试验取得了较好成绩。     

木本植被覆盖岸坡上波浪爬升过程的数值模拟研究

近岸木本植物构成的生态缓冲带作为新型的海岸软防护结构,兼具功能性和生态友好性,在沿海工程建设中愈发受到关注,如何深入开展其防护效果的机理研究是目前亟待解决的问题。本文采用数值模拟方法,在N-S方程中分别考虑树枝和树干的拖曳力影响,提出了木本植被作用下波浪沿斜坡爬升的表面波衰减的连续介质等效模型,并采用MAC法来跟踪自由曲面上的水颗粒轨迹。本文以波浪沿1/30的斜坡爬升为算例,对比讨论了有无植被作用下波浪的传播过程,并将算例结果与以往试验结果规律进行对照,验证了数值模型的有效性。最后,分别讨论了植物枝干的高度、密度、树枝倾斜角度等植被特性和波浪因素对植被消浪效果的影响,得到植被消浪的基本规律。文中的计算结果也可为实际的护岸工程和生态景观设计提供参考。     

Occurrence and characteristics of sporadic sodium layer observed by lidar at a mid-latitude location

Na lidar observations of SSL during the past 5 years at a mid-latitude location (Wuhan, China, 31°N, 114°E) are reported in this paper. From 26 SSL events detected in about 230 h of observation, an SSL occurrence rate of 1 event/9 h at our location was obtained. This result, combined with that reported by Nagasawa and Abo (Geophys. Res. Lett. 22 (1995) 263) at Tokyo, Japan, reveals that the SSL occurrence can be relatively frequent at some mid-latitude locations. The statistical analyses of main parameters for the 26 SSL events were made, and the results were compared with those previously reported. By examining the corresponding data from a nearby ionosonde, it was found that there was a fairly good correlation between SSL and Es. Of the 18 pairs of SSL and Es events checked, 15 of SSL were accompanied by Es, and 8 pairs of them were correlated within 1 h in time and within 5 km in altitude. From the analyses of observed perturbations during SSL development, the role of dynamic processes of atmosphere in the SSL formations were emphasized.     

Tests and applications of an approach to absorbing reflected waves towards incident boundary

If the upstream boundary conditions are prescribed based on the incident wave only, the time-dependent numerical models cannot effectively simulate the wave field when the physical or spurious reflected waves become significant. This paper describes carefully an approach to specifying the incident wave boundary conditions combined with a set sponge layer to absorb the reflected waves towards the incident boundary. Incorporated into a time-dependent numerical model, whose governing equations are the Boussinesq-type ones, the effectiveness of the approach is studied in detail. The general boundary conditions, describing the down-wave boundary conditions are also generalized to the case of random waves. The numerical model is in detail examined. The test cases include both the normal one-dimensional incident regular or random waves and the two-dimensional oblique incident regular waves. The calculated results show that the present approach is effective on damping the reflected waves towards the incident wave boundary.     

A bio-optical inversion model to retrieve absorption contributions and phytoplankton size structure from total minus water spectral absorption using genetic algorithm

We propose a bio-optical inversion model that retrieves the absorption contributions of phytoplankton and colored detrital matter(CDM),as well as the phytoplankton size classes(PSCs),from total minus water absorption spectra.The model is based on three-component separation of phytoplankton size structure and a genetic algorithm.The model performance was tested on two independent datasets(the NASA bio-Optical Marine Algorithm Dataset(NOMAD) and the northern South China Sea(NSCS) dataset).The relationships between the estimated and measured values were strongly linear,especially for aCDM(412),and the Root Mean Square Error(RMSE) of the CDM exponential slope(SCDM) was relatively low.Next,the inversion model was directly applied to in-situ total minus water absorption spectra determined by an underwater meter during a cruise in September 2008,to retrieve the phytoplankton size structure in the seawater.By comparing the measured and retrieved chlorophyll a concentrations,we demonstrated that total and size-specific chlorophyll a concentrations could be retrieved by the model with relatively high accuracy.Finally,we applied the bio-optical inversion model to investigate changes in phytoplankton size structure induced by an anti-cyclonic eddy in the NSCS.     

南极半岛东北海域表层沉积有机质来源及其沉积环境

采用气相色谱-质谱技术对南极半岛东北海域海底表层沉积物的总有机碳、有机质碳同位素(δ13 Corg)和生物标志化合物等进行了测试分析。研究区表层沉积物总有机碳TOC平均值高于现代深海沉积物中的平均含量。δ13 Corg的变化说明该海域有机碳来源呈海洋水生生物来源和陆源混合的特征。正构烷烃的峰型分布、主峰碳、饱和烃轻重比C-21/C+22和(C21+C22)/(C28+C29)、甾烷组合和藿烷组合证实研究区西部表层沉积物有机质来源以陆源高等植物为主,其陆源可能来自于附近的南极半岛和南舍得兰群岛;研究区东部表层沉积物有机质来源偏以海源为主,且以低等浮游生物、藻类及细菌生物等海源输入为主。碳优势指数(Carbon preference index,CPI)、奇偶优势指数(Odd-even Predominance,OEP)和甾烷C29ααα20S/(20S+20R)比值显示研究区D1-7站位和D5-9沉积物有机质演化程度较高,D5-2和D2-4站位的有机质演化程度低,其他站位介于中间状态。饱和烃中姥鲛烷、植烷及其比值(Pr/Ph)等组合显示研究区西部以氧化-弱还原的沉积环境为主,其可能是受高温低盐别林斯高晋海水流和附近火山喷发的影响所致;研究区东部以还原—强还原沉积环境为主,可能是受低温高盐的威德尔底层水(WSBW)和威德尔海深层水(WSDW)影响所致。