Simulation of braided river flow using a new cellular routing scheme

Results are presented from a numerical simulation of two-dimensional flow patterns in a braided river using a simple cellular routing scheme. The results of the routing scheme are compared with field measurements of discharge per unit width obtained within the study reach at low flow and, for higher flows, with the predictions of a more sophisticated hydraulic model that solves the two-dimensional shallow water form of the Navier–Stokes equations. An assessment is made of the sensitivity of the routing scheme to variations in the values of its main parameters, and appropriate values are determined based on the physical characteristics of the study site and available flow measurements. It is shown that despite the simple approach adopted by the cellular routing scheme to simulate processes of water redistribution, it is able to replicate accurately both the field data and the results of the more sophisticated hydraulic model. These results indicate that the routing scheme outlined here is able to overcome some of the limitations of previous simple cellular automata models and may be suitable for use in modelling bedload transport and channel change in complex fluvial environments. As such this research represents a small and ongoing contribution to the field of numerical simulation of braided river processes.     

基于空间的生态足迹与生态承载力预测模型——以甘肃省河西走廊地区为例

介绍了测度可持续发展的生态足迹分析的计算方法,在此基础上提出了生态足迹和生态承载力的预测模型:在生态足迹的预测方面采用消费预测模型和人口模型相结合的方法,在生态承载力的预测方面采用地理元胞自动机和地理信息系统技术相结合的方法。以甘肃省河西走廊地区为例,采用以上模型方法计算了1995、2000年的生态足迹和生态承载力,预测了2005年的生态足迹和生态承载力,结果表明:河西走廊地区的生态足迹在逐年上升,生态承载力前5年上升后5年下降。采用该模型方法计算与预测生态足迹和生态承载力,具有快速、准确、可操作性强的特点,但预测具有一定的局限性。     

地理学基础理论研究的方法变革及其发展前景

西方科学赖以发展的两大基础可以归结为源于欧氏几何学的形式逻辑和通过系统实验寻找因果关系。地理学如果不将自身作为一门“例外主义”的学科，无疑也要借助形式逻辑和系统实验发展基础理论体系。遗憾的是，逻辑思想只有借助数学方法才能发挥理论演绎的威力，而传统数学不适宜于地理系统空间结构与功能的描述；另一方面，系统实验必须是可以重复的受控试验，由于地理系统的不可控性，地理研究无法利用常规的实验方法寻找因果关系。地理学的理论研究如今正在经历着方法的变革：一方面，分形等后现代数学理论为地理学提供了有效的定量描述手段；另一方面，细胞自动机等仿生科学理论为地理学提供了模拟实验工具。不仅如此，由于新方法的引入，传统的实证研究方法也重新焕发生机。将数学、实证和计算机模拟三种方法有效结合，地理学的基础理论体系必将建立起来，发展前景将十分广阔。     

Incorporation of intra-city human mobility into urban growth simulation: A case study in Beijing

Journal of Geographical Sciences - The effective modeling of urban growth is crucial for urban planning and analyzing the causes of land-use dynamics. As urbanization has slowed down in most...     

基于Logistic回归的CA模型改进方法——以广州市为例

基于Logistic回归的CA模型因其结构简单和数据要求相对较小的优势,被广泛应用于城市模拟领域,但数据的空间自相关性影响了模型机制挖掘与模拟精度。通过将影响城市发展演变的各种约束条件划分为强制和普通约束条件,以及运用主成分分析降低普通约束条件的数据相关性,构建了改进型Logistic回归CA模型,并在2000~2008年广州市城市增长模拟研究中进行应用。结果表明:与传统型Logistic回归CA模型相比,改进型Logistic回归CA模型在模型拟合度和精度上均有4%左右的提高。其中约束条件划分对非城市像元模拟精度约有6%的提高,对整体精度有3%的提高。更为重要的是,降低数据相关性后,Logistic回归CA模型对于城市扩展机制的解释更符合实际。本研究旨在寻求一种简单可行且易于构建的CA模型,探求城市发展机理,为城市规划管理提供更为准确的科学依据。     

Model construction of urban agglomeration expansion simulation considering urban flow and hierarchical characteristics

Journal of Geographical Sciences - Since the launch of China’s reform and opening up policy, the process of urbanization in China has accelerated significantly. With the development of...     

Flood evacuation simulations using cellular automata and multiagent systems -a human-environment relationship perspective

ABSTRACT

A flood evacuation represents a complex geographic phenomenon that includes comprehensive interactions among humans, the flood and urban environments; thus, the simulation of flood evacuations requires crowd simulation models to be coupled with flood models. This paper studies the human-environment relationship during flooding and promotes a simulation model that combines cellular automata and a multiagent system to simulate crowd evacuations in flood disasters. A case study of Niaodao Island was used to evaluate the performance of flood evacuation experiments, and real-participant experiments based on the virtual reality (VR) environment were employed for bench-mark comparisons. The integrated model can provide a comprehensive solution to assist flood risk analysis.