地铁车站人员疏散离散时间模型研究

疏散时间对于保证地铁车站这类复杂建筑结构内人群的安全至关重要,本文借鉴群集流动理论建立了用于计算地铁车站人群移动时间的疏散离散时间模型（EDTM）,模型中的人群流动系数取值不同于传统计算公式中的常量,依据的是经典的车站人群密度与速度函数关系式。将此模型用于某地铁车站站台层,求解楼梯出口疏散人数与时间的关系,并与Building EXODUS疏散软件的模拟结果以及传统地铁车站疏散时间计算公式的计算结果进行了对比,分析表明,EDTM计算结果与EXODUS疏散模拟结果非常接近,且比传统公式计算更为精确和符合实际情况。该计算模型可以为地铁车站人群疏散时间计算、建筑出口性能化设计,以及地铁车站事故应急预案的制定提供更有效的工具。     

基于Car(p,q)模型和数学形态学理论的LiDAR点云数据滤波

在分析现有的LiDAR点云数据后处理方法的基础上,本文提出了一种点云数据“分步”滤波方法。首先对LiDAR点云数据进行数学形态学“粗”滤波,得到“地面点假设”和“非地面点假设”。然后引入顾及因果关系的自回归模型（car）对两类点云数据假设进行模型化处理和假设检验,根据假设检验的结果判断地面点和非地面点,最终得到可靠的分类结果。与单纯的“最小二乘拟合预测法”或“数学形态学”方法相比,这种“分步”处理的思想用于LiDAR点云数据分类处理的结果更可靠。     

基于布尔交运算的三维流形单元生成研究

三维流形单元的生成是进行三维数值流形分析的首要问题之一。详细研究了三维流形单元的生成过程,并采用C++语言编写了相应的程序。借鉴二维流形单元的形成技术,基于拓扑学的“有向性”原理,将点、有向边、有向环、有向面和有向壳等作为三维块体的基本数据结构。将材料体和数学网格进行布尔交运算,并对形成的流形块体进行有效性检测,满足要求后即形成新的三维流形单元。每个数学网格的顶点作为新流形单元的数学覆盖,再对数学覆盖进行细分,形成流形单元的物理覆盖。分别选取凹形体、空心体和包含有限结构面的材料体与数学网格进行布尔交运算,并选取一个典型工程来检查该方法和程序的可行性。计算结果表明,该方法可以对复杂块体（凹形体、空心体和包含有限结构面的体）进行处理,为今后进行复杂结构计算和分析奠定基础,具有较强的适应性和可靠性。     

Morphological response of a barrier island system on a catastrophic event: the AD 1634 North Sea storm

The AD 1634 North Sea storm is one of the most catastrophic storms along the Wadden Sea coast of Denmark. In this study we show how pre‐1634 storm morphology exerted a strong control on the resulting post‐storm coastal morphology. Erosional responses associated with the storm were barrier breaching, dune scarping and shoreface erosion and accretionary responses were washover deposition, shoreface healing and barrier‐island formation. Local sediment sources appeared to have a particularly strong influence on post‐storm coastal evolution and allowed a very rapid formation of a barrier shoal which resulted in several kilometres of coastal progradation. Sediment budgets suggest that formation of the barrier shoal was possible, but the sediment transport rates in the decades after the 1634 storm, must have been two to three times higher than present‐day rates. The study demonstrates that catastrophic storms are capable of moving large amounts of sediments over relatively short time‐periods and can create barrier shoals, whereas moderate storms mostly rework the shoal or barrier and create more local erosion and/or landward migration. Catastrophic storms substantially influence long‐term and large‐scale coastal evolution, and storms may positively contribute to the sediment budget and promote coastal progradation in coastal areas with longshore sediment convergence. Copyright © 2015 John Wiley & Sons, Ltd.     

Insights into rock avalanche emplacement processes from detailed morpho‐lithological studies of the Tschirgant deposit (Tyrol,Austria)

Large, rapid rockslope failures generate deposits with complex morphologies due to a number of causal and influencing factors. To investigate these, we conducted a detailed case study at the carbonate Tschirgant deposit (Tyrol, Austria). It preserved evidence of simultaneous rock sliding (very large, coherent hummocks) and rock avalanche spreading (smaller, more scattered hummocks and ridges). Motion indicators, such as longitudinal ridges furthermore pinpoint the transition between linear sliding and radial spreading. The lithological distribution in the Tschirgant deposit shows that it retained source stratigraphy despite being split into two accumulation lobes by a high bedrock ridge. Furthermore, lithology had a very strong control on the final deposit morphology in that the different lithologic units form individual deposit surfaces. River erosion has created fortuitous outcrops that reveal the basal rock avalanche contact. The underlying valley‐fill sediments (substrates) have been intricately involved in shaping the rock avalanche morphology and, where entrained, highlight internal rock avalanche deformation features. This study shows that intrinsic dynamic properties of granular media (e.g. tendency for longitudinal alignments), emplacement mode, lithology (and source predisposition), runout path topography, and substrates form the quintet of causal factors that shape rock avalanche morphology. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of transect location,transect spacing and interpolation methods on river bathymetry accuracy

Digital elevation models (DEMs) of river channel bathymetries are developed by interpolating elevations between data collected at discrete points or along transects. The accuracy of interpolated bathymetries depends on measurement error, the density and distribution of point data, and the interpolation method. Whereas point measurement errors can be minimized by selecting the most efficient equipment, the effect of data density and interpolation method on river bathymetry is relatively unknown. Thus, this study focuses on transect‐based collection methods and investigates the effects of transect location, the spacing between transects, and interpolation methods on the accuracy of interpolated bathymetry. This is accomplished by comparing four control bathymetries generated from accurate and high resolution, sub‐meter scale data to bathymetries interpolated from transect data extracted from the control bathymetries using two transect locating methods and four interpolation methods. The transect locating methods are a morphologically‐spaced and an equally‐spaced model. The four interpolation methods are Ordinary Kriging, Delaunay Triangulation, and Simple Linear, which are applied in curvilinear coordinates (Delaunay Triangulation is also applied in Cartesian coordinates), and Natural Neighbor only in Cartesian Coordinates. The bathymetric data were obtained from morphologically simple and complex reaches of a large (average bankfull width = 90 m) and a small (average bankfull width = 17 m) river. The accuracy of the developed DEMs is assessed using statistical analysis of the differences between the control and interpolated bathymetries and hydraulic parameters assessed from bankfull water surface elevations. Results indicate that DEM accuracy is not influenced by the choice of transect location method (with same averaged cross‐section spacing) or a specific interpolation method, but rather by the coordinate system for which the interpolation method is applied and the spacing between transects. They also show negligible differences between the mean depths and surface areas calculated from bathymetries with dense or coarse spacing. Copyright © 2016 John Wiley & Sons, Ltd.     

基于数学形态学的高分遥感影像地震重点目标信息提取

重点目标是抗震救援的关键, 重点目标的破坏大多与目标本身的破坏或破坏前后的形态变化有关。 本文利用数学形态学方法对地物形态特征(包括形状、 大小、 方向等)处理的优势和思路, 构建了重点目标信息提取流程和算法, 并利用海地地震的高分辨率遥感影像, 对震后油罐破损状态的分离和提取、 以及对机场跑道旧损状态的提取。 试验结果表明, 对于形态上能够明显区别于背景的重点目标, 可以利用灰度和结构信息通过数学形态学进行提取。 而且数学形态学算法构造灵活, 处理速度快, 便于硬件实现, 对应急救援的快速处理有一定应用前景。     

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The estimation of estuary dimensions using a simplified form model and the exogenous controls

The most common definition of an equilibrium condition for estuaries and inlets makes use of the well documented relationship between tidal prism and the cross‐sectional area of the channel. However, the tidal prism is itself a function of the morphology of the tidal basin. It would therefore be useful to be able to define the key dimensions of estuaries and inlets based on properties that are external to the estuary itself. This would then provide a more rigorous basis for understanding how systems are being ‘perturbed’ by developments, or other influences such as climate change. An idealized representation of the three–dimensional (3D) form of an estuary has been proposed and is here applied to a wide range of UK estuaries to explore its ability to predict the gross properties of a range of different estuary types. When considering just tidal flow, the model was found to provide an adequate representation, however, the inclusion of wave action was found to significantly improve the predictive power of the model. The exogenous parameters therefore provide a basis for determining the estuary dimensions and how they are likely to change over time. This in turn provokes a broader definition of an estuary than those commonly cited. Copyright © 2012 John Wiley & Sons, Ltd.