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41.
本文为实现全球海量地形数据的实时可视化,提出了一种新算法。算法不使用几何数据而是利用球面特征进行地形多分辨率模型初建,然后基于视锥与节点关系对初建结果进行扩展来得到完整的地形网格。此外设计了能消除具有复杂邻接关系的节点间裂缝的拼接方式,构造了简洁的方法消除GPU32位浮点精度导致的"wob-bling"现象。实现的算法在普通微机上平均漫游速度达每秒95帧以上。 相似文献
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The urban environment has been dramatically changed by artificial constructions. How the modified urban geometry affects the urban climate and therefore human thermal comfort has become a primary concern for urban planners. The present study takes a simulation approach to analyze the influence of urban geometry on the urban climate and maps this climatic understanding from a quantitative perspective. A geographical building database is used to characterize two widely discussed aspects: urban heat island effect (UHI) and wind dynamics. The parameters of the sky view factor (SVF) and the frontal area density (FAD) are simulated using ArcGIS-embedded computer programs to link urban geometry with the UHI and wind dynamic conditions. The simulated results are synergized and classified to evaluate different urban climatic conditions based on thermal comfort consideration. A climatic map is then generated implementing the classification. The climatic map shows reasonable agreement with thermal comfort understanding, as indicated by the biometeorological index of the physiological equivalent temperature (PET) obtained in an earlier study. The proposed climate mapping approach can provide both quantitative and visual evaluation of the urban environment for urban planners with climatic concerns. The map could be used as a decision support tool in planning and policy-making processes. An urban area in Hong Kong is used as a case study. 相似文献
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浙江东南印支晚期的构造伸展事件:来自诸暨大爽岩体的证据 总被引:1,自引:0,他引:1
出露于浙江省东南部的大爽岩体为黑云母二长花岗岩,LA-ICP-MS锆石U-Pb年代学研究表明该岩体形成于227±2Ma,属印支晚期岩浆作用的产物。地球化学分析显示该岩石低Na2O、富K2O,A/CNK=1.26~1.49(大于1.1),为强过铝质、钾玄质系列花岗岩;岩石稀土总量较高,富Sr(Sr=874.6×10-6~1158×10-6),贫Yb(Yb=3.00×10-6~3.92×10-6),富轻稀土而亏损重稀土,具轻微的负铕异常(δEu=0.68~0.70);相对富集Rb、Th等大离子亲石元素,而亏损Nb、Ta等高场强元素;Sr-Nd同位素分析表明岩石具有较高的初始锶比值(I Sr=0.710718~0.711008)和较低εNd(t)值(εNd(t)=-10.9~-11.1),上述地球化学特征指示该岩体岩浆源区为古老的地壳物质。综合分析认为大爽岩体是古老地壳部分减压熔融的产物,受控于印支造山后的伸展应力作用。 相似文献
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全省上表铁矿111处,总储量32.16亿吨,其中有11.27亿吨暂不能使用.而且,富铁矿少,难选矿多,分布边远,难以满足经济发展需求.必须解决菱铁矿、高磷矿选矿问题,以及有远景磁异常补充深部找矿问题,可望取得突破. 相似文献
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城市化进程加快导致街道安全性问题突出,已有研究利用城市视觉要素刻画街道安全感空间分布,忽略了街道真实安全性与安全感间的差异。该文利用街景影像和手机信令数据,结合K-means聚类算法与笛卡尔积运算模型减少“安全感知差异”,以长沙市主城区为研究案例,得到白天、夜晚及总体城市街道安全性分布:1)长沙市主城区安全感指数随圈层数增加呈波动递减趋势,主要原因是建筑视觉要素占比下降较快以及天空视觉要素占比逐步上升;2)长沙市主城区呈双圈层结构,白天高安全性、夜晚低安全性以及总体安全性最低的区域主要分布在主城区中心,具有明显的聚集现象。该研究通过对城市街道安全性和低安全性街道的分析提出街道优化建议,为城市规划提供参考。 相似文献
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Copper-based antifoulant paints and the sea lice treatment Slice® are widely used, and often detectable in the sediments beneath farms where they are administered. Ten-day, whole sediment mesocosm experiments were conducted to examine how increasing sediment concentrations of copper or Slice® influenced final water column concentrations of ammonium-nitrogen (NH4-N), nitrate + nitrite-nitrogen (NOX-N) and phosphate-phosphorus (PO4-P) in the presence of the non-target, benthic organisms Corophium volutator and Hediste diversicolor. Nominal sediment concentrations of copper and Slice® had significant effects on the resulting concentrations of almost all nutrients examined. The overall trends in nutrient concentrations at the end of the 10-day incubations were highly similar between the trials with either copper or Slice®, irrespective of the invertebrate species present. This suggests that nutrient exchange from the experimental sediments was primarily influenced by the direct effect of copper/Slice® dose on the sediment microbial community, rather than the indirect effect of reduced bioturbation/irrigation due to increased macrofaunal mortality. 相似文献
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Wasim Shoman 《国际地球制图》2017,32(12):1352-1366
This paper introduces a new hierarchy for cartographic generalisation processes, applied in street networks. The aims of implementing this hierarchy are to emphasise on significant street features, and to provide more free spaces between street features. The hierarchy is obtained from the functional classes of the features and four centrality measures in a street network, i.e. betweenness, reach, straightness and closeness extracted from a primary graph. The values of centrality measures change in every zoom level by calculating a radius parameter, which depends on the users’ field of view. The coefficients for the measures are constructed using a decision-making technique called fuzzy analytical hierarchy process (FAHP). The weights for each of the centrality measures are computed and normalised to form the proposed hierarchy. The hierarchy is applied and used later in the thinning process to omit insignificant features from the street network in medium scales. 相似文献