洪水演算理论与计算方法的若干进展与评论   总被引：2，自引：0，他引：2       下载免费PDF全文

芮孝芳  姜文斌 《水科学进展》1998,9(4):389-395

从洪水波运动的小扰动分析、水力学洪水演算方法及新技术在洪水演算中的应用等方面,总结了近20年来国内外洪水演算理论与计算方法研究的若干进展,并作了简要的评论.  相似文献   

Drainage density changes during rainfall     

D. G. Day 《地球表面变化过程与地形》1978,3(3):319-326

Observations of stream behaviour during rainfall indicate that previous notions of a simple expanding and contracting network need review and refinement. In a small rural catchment near Armidale, N.S.W. changes in flowing stream length during rainfall have been depicted on flow length graphs which indicate a varied network response to similar rainfall amounts. Channel flow phenomena include discontinuous flow, the generation of flow points within the channel and movement of water downslope from saturated depression sources. Localized physical controls have a significant effect on stream growth which is a sensitive indicator of the catchment response to rainfall. During rapid changes in stream length total flowing length and discharge are highly correlated. A model of the pattern of network expansion and contraction involves several phases of flow contraction.  相似文献   

A fuzzy dynamic flood routing model for natural channels     

R. Gopakumar  P. P. Mujumdar 《水文研究》2009,23(12):1753-1767

A fuzzy dynamic flood routing model (FDFRM) for natural channels is presented, wherein the flood wave can be approximated to a monoclinal wave. This study is based on modification of an earlier published work by the same authors, where the nature of the wave was of gravity type. Momentum equation of the dynamic wave model is replaced by a fuzzy rule based model, while retaining the continuity equation in its complete form. Hence, the FDFRM gets rid of the assumptions associated with the momentum equation. Also, it overcomes the necessity of calculating friction slope (S_f) in flood routing and hence the associated uncertainties are eliminated. The fuzzy rule based model is developed on an equation for wave velocity, which is obtained in terms of discontinuities in the gradient of flow parameters. The channel reach is divided into a number of approximately uniform sub‐reaches. Training set required for development of the fuzzy rule based model for each sub‐reach is obtained from discharge‐area relationship at its mean section. For highly heterogeneous sub‐reaches, optimized fuzzy rule based models are obtained by means of a neuro‐fuzzy algorithm. For demonstration, the FDFRM is applied to flood routing problems in a fictitious channel with single uniform reach, in a fictitious channel with two uniform sub‐reaches and also in a natural channel with a number of approximately uniform sub‐reaches. It is observed that in cases of the fictitious channels, the FDFRM outputs match well with those of an implicit numerical model (INM), which solves the dynamic wave equations using an implicit numerical scheme. For the natural channel, the FDFRM outputs are comparable to those of the HEC‐RAS model. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Role of hypsometry and planform in basin hydrologic response     

Alan D. Howard 《水文研究》1990,4(4):373-385

The effects of variations of drainage basin morphometry and relief characteristics on flood peak magnitude and time-to-peak are investigated using simulated stream networks. The networks are produced by three models: headward growth, systematic capture, and minimum power relaxation. Translational and kinematic wave flood routing were used to generate synthetic hydrographs. Peak discharge and time-to-peak are predictable to a high degree by five different sets of morphometric-relief parameters. In order of decreasing order of importance in predictive ability the parameters characterize basin size, relative relief, basin concavity, and basin shape. Both simulated and natural stream networks exhibit strong dependence of planimetric morphometry upon basin concavity. The effect of this dependency is to increase the effect of basin concavity upon flood hydrographs.  相似文献   

车辆路径问题:从时间地理学的视角   总被引：2，自引：0，他引：2  

戚铭尧  吴涛  张新 《地球信息科学学报》2015,(1):22-30

车辆路径问题具有典型的时空分布特征,受到众多时空约束条件的制约。在车辆路径规划中,综合考虑时间和空间因素是非常必要的。本文从时间地理学这一全新的视角来研究车辆路径问题,提出一套完整的时间地理学分析框架,阐述了时间地理学的基本概念,提出了车辆路径问题中的时空约束、时空路径、时空棱柱、时空可达性、时空距离等概念,并给出了图示或定量化的度量方法。论文提出的时空距离度量方法综合考虑了顾客在空间位置和时间窗口2个方面的特征,可更科学地判定顾客之间的"邻近性"。论文通过设计一种求解大规模软时间窗车辆路径问题的算法,证明了时空距离的价值,并展望了时间地理学在求解动态车辆路径规划问题、移动设施路径规划问题等方面的应用。本文的贡献在于,通过时间地理学所提供的一系列概念和方法,实现了在统一的框架下同时考虑车辆路径问题(VRP)的时间和空间特征的构想,挖掘了传统时间地理学理论在车辆路径领域中的应用潜力,这将有利于更快或者更好地求解VRP问题。  相似文献   

结合引力场理论的道路自动选取方法     

韩远  王中辉  徐智邦  余贝贝 《测绘科学》2021,46(1):189-195

针对复杂网络模型被广泛应用于道路选取的研究中,少有方法顾及道路网对偶图中多级邻居节点的影响,导致对道路的重要性评价缺乏准确性和可靠性的问题。该文将道路网对偶图节点的结构特征值视作质量,将节点间的最短距离视作距离,结合引力场方程实现道路自动选取,较好地将道路网对偶图中多级邻居节点的影响纳入到道路重要性的计算中,从而实现对道路重要性的准确评估。通过对兰州市城关区的路网进行实验,结果表明本文方法所选取的路网较好地保持了原始道路网的整体结构、覆盖范围、密度分布、拓扑特征和连通性。  相似文献   

基于ALBERT模型的园林植物知识实体与关系抽取方法     

陈晓玲  唐丽玉  胡颖  江锋  彭巍  冯先超 《地球信息科学学报》2021,23(7):1208-1220

园林植物知识图谱可为顾及区域适应性、观赏性和生态性等因子的绿化树种的选型提供知识支持。植物描述文本的实体识别及关系抽取是知识图谱构建的关键环节。针对植物领域未有公开的标注数据集,本文阐述了园林植物数据集的构建流程,定义了园林植物的概念体系结构,完成了园林植物语料库的构建。针对现有Word2vec、ELMo和BERT等语言模型存在无法解决多义词、融合上下文能力差、运行速度慢等缺点,提出了嵌入ALBERT（A Lite BERT）预训练语言模型的实体识别和关系抽取模型。ALBERT预训练的动态词向量能够有效地表示文本特征,将其分别输入到BiGRU-CRF命名实体识别模型和BiGRU-Attention关系抽取模型中进行训练,进一步提升实体识别和关系抽取的效果。在园林植物语料库上进行方法的有效性验证,结果表明ALBERT-BiGRU-CRF命名实体识别模型的F₁值为0.9517,ALBERT-BiGRU-Attention关系抽取模型的F₁值为0.9161,相较于经典的语言模型（如Word2vec、ELMo和BERT等）性能有较为显著的提升。因此基于ALBERT模型的实体与关系抽取任务能有效提高识别分类效果,可将其应用于植物描述文本的实体关系抽取任务中,为园林植物知识图谱自动构建提供方法。  相似文献   

Computing least air pollution exposure routes     

Monir H. Sharker 《International journal of geographical information science》2014,28(2):343-362

Personalized routing counts on traveler’s preferences which are usually based on different criteria, such as shortest, fastest, least traffic, or less expensive (e.g., less fuel cost, toll free). However, people are increasingly becoming concerned about the adverse health effects of exposure to air pollution in chosen routes. Exposures to elevated air pollution concentrations particularly endanger children, pregnant women, elderly people, and people with asthma and other respiratory conditions. Choosing routes with least air pollution exposure (APE) is seen as one approach to minimize the level of pollution exposed, which is a major public health issue. Routing algorithms use weights on segments of road networks to find optimum routes. While existing weights are commonly distance and time, among a few others, there is currently no weight based on APE to compute least APE routes. In this paper, we present a weight function that computes weight based on APE. Two different approaches, geostatistical and non-geostatistical, were used to compute APE weight. Each approach was evaluated, and the results indicate that the APE weight is suitable for computing least APE routes.  相似文献   

Cycle graph analysis for 3D roof structure modelling: Concepts and performance     

《ISPRS Journal of Photogrammetry and Remote Sensing》2014

The paper presents a cycle graph analysis approach to the automatic reconstruction of 3D roof models from airborne laser scanner data. The nature of convergences of topological relations of plane adjacencies, allowing for the reconstruction of roof corner geometries with preserved topology, can be derived from cycles in roof topology graphs. The topology between roof adjacencies is defined in terms of ridge-lines and step-edges. In the proposed method, the input point cloud is first segmented and roof topology is derived while extracting roof planes from identified non-terrain segments. Orientation and placement regularities are applied on weakly defined edges using a piecewise regularization approach prior to the reconstruction, which assists in preserving symmetries in building geometry. Roof corners are geometrically modelled using the shortest closed cycles and the outermost cycle derived from roof topology graph in which external target graphs are no longer required. Based on test results, we show that the proposed approach can handle complexities with nearly 90% of the detected roof faces reconstructed correctly. The approach allows complex height jumps and various types of building roofs to be firmly reconstructed without prior knowledge of primitive building types.  相似文献   

一种结合地理知识的遥感影像目标实体关联方法北大核心CSCD     

黄梓航  蒋秉川  王自全 《测绘通报》2022,(10):28-36

遥感影像目标识别技术已广泛应用于目标动态监测与定位等领域。但影像目标识别的结果缺乏与目标属性信息的链接,导致分析人员只能依据影像特征进行分析,难以进行更复杂的目标数据关联分析与挖掘。针对遥感影像目标识别语义属性信息缺失的问题,本文利用知识图谱相关技术将影像判别的目标信息与知识语义网链接。首先,提出了一种遥感影像目标知识图谱构建框架;其次,针对遥感影像目标不同的数据类型,构建遥感影像目标知识抽取模型,提出了基于相似度目标实体识别和预定义模式的关系抽取方法;然后,基于多特征Logistic模型的影像目标实体链接方法,实现了遥感影像目标实体与百科知识库的知识关联;最后,针对预定试验区域进行试验,验证了本文方法的可行性。  相似文献