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91.
Quasi-3D Numerical Simulation of Tidal Hydrodynamic Field 总被引:2,自引:0,他引:2
SONG Zhiyao XUE Hongchao YAN Yixin MAO Lihua XU Fumin
Doctor Senior Engineer College of Harbor Waterway Coastal Engineering Hohai University 《中国海洋工程》1999,(3)
Based on the 2D horizontal plane numerical model,a quasi-3D numerical model is establishedfor coastal regions of shallow water.The characteristics of this model are that the velocity profiles can be ob-tained at the same time when the equations of the value of difference between the horizontal current velocityand its depth-averaged velocity in the vertical direction are solved and the results obtained are consistent withthe results of the 2D model.The circulating flow in the rectangular area induced by wind is simulated and ap-plied to the tidal flow field of the radial sandbanks in the South Yellow Sea.The computational results fromthis quasi-3D model are in good agreement with analytical results and observed data.The solution of the finitedifference equations has been found to be stable,and the model is simple,effective and practical. 相似文献
92.
点光源照射的亮度不均匀使获得的海底视像图像的灰度分布极不均匀 ,给海底多金属结核矿物的颗粒自动识别、粒径测量、储量的计算带来误差。本文针对点光源照射的多金属结核海底视像图像 ,提出了 3种方法进行灰度不均匀校正 ,并作了比较。实验结果表明 ,统计原图灰度值的二维分布特性 ,用二阶三次多项式函数拟合此灰度分布 ,再逐像元进行灰度位伸的方法能更有效地消除点光源对海底视像图像灰度的影响。 相似文献
93.
The stability problem is a very important aspect in seismic wave numerical modeling. Based on the theory of seismic waves and constitutive equations of viscoelastic models, the stability problems of finite difference scheme for KelvinVoigt and Maxwell models with rectangular grids are analyzed. Expressions of stability conditions with arbitrary spatial accuracies for two viscoelastic models are derived. With approximation of quality factor Q≥?5, simplified expressions are developed and some numerical models are given to verify the validity of the corresponding theoretical results. Then this paper summarizes the influences of seismic wave velocity, frequency, size of grid and difference coefficients, as well as quality factor on stability condition. Finally the prerequisite conditions of the simplified stability equations are given with error analysis. 相似文献
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95.
An Overview of the Semi-arid Climate and Environment Research Observatory over the Loess Plateau 总被引:17,自引:2,他引:17
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98.
利用多种测高数据反演中国南海海域重力异常 总被引:1,自引:0,他引:1
联合Geosat/GM、ERS-1/168和Envisat 3种测高数据,基于高精度地球重力模型EGM2008,采用垂线偏差方法和逆Vening-Meinesz公式,利用移去-恢复技术确定了中国近海及邻近海域(0°N~42°N,102°E~138°E)分辨率为2′×2′的重力异常.在中国南海海域,测高重力异常与船测重力... 相似文献
99.
Xuke Hu Hongchao Fan Alexey Noskov Zhiyong Wang Alexander Zipf Fuqiang Gu Jianga Shang 《Transactions in GIS》2021,25(1):71-111
Semantically rich maps are the foundation of indoor location‐based services. Many map providers such as OpenStreetMap and automatic mapping solutions focus on the representation and detection of geometric information (e.g., shape of room) and a few semantics (e.g., stairs and furniture) but neglect room usage. To mitigate the issue, this work proposes a general room tagging method for public buildings, which can benefit both existing map providers and automatic mapping solutions by inferring the missing room usage based on indoor geometric maps. Two kinds of statistical learning‐based room tagging methods are adopted: traditional machine learning (e.g., random forests) and deep learning, specifically relational graph convolutional networks (R‐GCNs), based on the geometric properties (e.g., area), topological relationships (e.g., adjacency and inclusion), and spatial distribution characteristics of rooms. In the machine learning‐based approach, a bidirectional beam search strategy is proposed to deal with the issue that the tag of a room depends on the tag of its neighbors in an undirected room sequence. In the R‐GCN‐based approach, useful properties of neighboring nodes (rooms) in the graph are automatically gathered to classify the nodes. Research buildings are taken as examples to evaluate the proposed approaches based on 130 floor plans with 3,330 rooms by using fivefold cross‐validation. The experiments conducted show that the random forest‐based approach achieves a higher tagging accuracy (0.85) than R‐GCN (0.79). 相似文献
100.
提出了一个鲁棒高效的内存矢量地图叠加分析算法,采用改进的平面扫描算法计算交点,解决了重叠边、交点位于端点等所有特殊情形。利用交点及其携带的信息来构造结果环,并且将没有产生交点的输入环忽略,或者增加到结果的外环(或内环)集合中去。所有结果环都带有标识码,增加该标识码信息可以简化后续的两个过程-内外环的匹配以及属性的继承。与一一循环方法相比,本文方法对任何叠加操作可以一次计算得到所有的交点。此外还实现了叠加分析操作,并且用一组真实地理数据的不同操作与ESRI的ArcGIS的叠加分析操作进行了比较,计算结果的要素数完全一致;计算时间耗费约为ArcGIS时间耗费的50%-60%。 相似文献