利用马尔柯夫过程预测锡林河流域草原退化格局的变化

以我国北方典型草原模式地段之一的锡林河流域草原为研究对象,根据研究区两个时期遥感影像解译的植被类型图衍生出草原植被退化图。在对草原退化图统一网格化后,计算各网格草原退化指数,并加以分级,确定不同草原退化等级之间转移概率,并应用马尔柯夫模型预测锡林河流域草原退化格局的演变趋势。结果表明:如果不采取防止草地退化的根本性措施,草原退化态势还将继续下去。以每个网格草原退化指数值为各网格草原退化状况划分依据,以3km×3km网格为统计单元,在流域总面积为10701km₂情况下,预测结果是:2005年,锡林河流域草原退化为3级的网格总面积是3776km₂,占流域总面积的35.29%;4、5级网格面积之和为5427km₂,达到流域总面积的50.71%。2025年,锡林河流域草原退化为3级的网格面积总和是3389km₂,占流域总面积的31.67%;4、5级网格面积之和为6406km₂,达到流域总面积的59.86%。     

Probabilistic risk assessment for pedestrian–vehicle collision considering uncertainties of pedestrian mobility

Objectives: The uncertainties of pedestrian mobility are important factors affecting the accuracy and robustness of an active pedestrian protection system. This study is to provide the means for probabilistic risk evaluation of pedestrian–vehicle collision by counting the uncertainties in pedestrian motion.

Method: The pedestrian is modeled by a first-order Markov model to characterize the stochastic properties in mobility according to field experiments of pedestrians crossing an uncontrolled road. Based on the assumption of Gaussian distribution, unscented transformation (UT) is employed to predict the collision risk probability with the symmetric σ-set constructed on the basis of discrete trajectory simulation. Simulation experiments were carried out with 10,000 Monte Carlo (MC) simulations as the reference.

Results: The probability density distributions of time-to-collision, minimal distance, and collision probability estimated by UT coincide with the reference ones under various vehicle–pedestrian conflict scenarios, and the maximal deviation of collision probability from the reference is 5.33%. The UT method is about 600 times faster than the MC method (10,000 runs), which means that the proposed method has the potential for online application.

Conclusions: This article presents an effective and efficient algorithm to estimate the collision probability by using a UT method to solve the nonlinear transformation of uncertainties in pedestrian motion. Simulation results show that the UT-based method achieves accurate collision probability estimation and higher computation efficiency than MC and provides more valuable information concerning collision avoidance than the deterministic methods in the design of a pedestrian collision avoidance system.     

基于区间概率优势决策模型的滑坡治理方案优选研究

滑坡灾害治理初步设计阶段的方案优选和科学处置,对于避免或减少生命财产损失具有重要的科学和工程意义。针对滑坡治理决策指标信息属性的复杂性、区间性与不确定性等特征,首先借鉴博弈决策论的Minimax算法优化思路,结合概率优势关系及粗糙集相关理论,提出滑坡灾害治理方案优选的区间概率优势关系决策模型,该模型考虑治理方案与理想方案之间的优势度及其属性值的概率测度,与方案属性值大小之间存在着等价关系;然后利用属性值优势关系求得权重量化值,同时基于离差最大化算法和推论2对治理方案进行排序和反演;最后通过工程案例仿真模拟进行验证。研究结果表明:优选方案可为滑坡工程项目治理提供借鉴和参考。     

考虑等待位置的航空器交叉滑行冲突概率模型

为解决交叉道口冲突范围定义不完整等问题,提出了航空器交叉滑行冲突概率模型。该模型针对交叉滑行道结构特点,以T型交叉口为例,综合等待位置、机身长度、喷流范围等要素,扩展冲突区域,基于实时速度、位置变化构造冲突概率模型,并利用速度分布密度函数对模型求解。仿真验证表明:模型能计算不同运动状态的中型机在T型交叉口处的冲突概率,T型道口等待位置对冲突概率影响较大,等待位置较近将造成冲突判断延迟,等待位置较远会产生虚警误判,致使滑行中断。利用实际滑行轨迹验证,结果表明:模型能够再现T型道口上2架中型机滑行冲突产生、发展及解脱过程,计算结果与实际运行情况一致,能为管制员、飞行员提前判断冲突,及时采取措施提供依据。     

基于钻孔数据煤矿开采地表沉陷预计

开采沉陷引起的环境损害评价是环评工作中的重要内容,现有预计软件基本不适应在大面积环评工作中开展沉陷预计工作。针对现有问题,以矿区钻孔数据为基础,基于Delaunay三角形剖分算法建立了煤层开采地表沉陷预计模型。通过设计对比试验,验证了新建模型预计结果较传统的预计方法更加符合实际地表沉陷情况,预计结果的可靠性较高。将该模型运用到工程实例中,可以节省人力资源,使煤矿生态环评从原来以定性分析、半定量预计为主的状况,提高到以定量预测为主的高度,更好地为矿区生态环境保服务。     

Flood inundation uncertainty: The case of a 0.5% annual probability flood event

Aging coastal defences around the UK are challenging managers to redesign schemes to be resilient to extreme events and climate change, be cost-effective, and have minimal or beneficial environmental impact. To enable effective design, reduced uncertainty in the assessment of flood risk due to natural variability within the coastal forcing is required to focus on conditions that pose highest threat. The typical UK standard of protection for coastal defences is to withstand a 0.5% annual probability event, historically also known as a 1 in 200 year return period event. However, joint wave-water level probability curves provide a range of conditions that meet this criterion. We examine the Dungeness and Romney Marsh coastal zone, a region of high value in terms of habitat and energy assets, to quantify the uncertainty in flood depth and extent generated by a 0.5% probability event, and to explore which combinations of wave and water levels generate the greatest threat.     

人员密度和出口宽度的不确定性对疏散行动时间的影响

基于Kikuji Togawa所提出的常用人员疏散行动时间经验公式，使用拉丁超立方抽样法，研究房间人员密度和出口宽度的不确定性对疏散行动时间的影响。得出二者服从均匀分布和正态分布条件下，疏散行动时间的概率密度直方图和累积概率曲线。结果表明，人员密度和出口宽度的不同分布形式对疏散行动时间都有显著影响，二者服从正态分布时，计算得到的疏散行动时间范围比服从均匀分布小，且较为集中。而服从均匀分布时，计算得到的疏散行动时间在其范围内则较为均匀、分散。在小概率0～0．1区间范围内，人员密度和出口宽度服从正态分布时，计算得到的疏散行动时间累计概率值明显较均匀分布小，说明二者服从正态分布得到的疏散行动时间值偏于保守。二者均为不确定参数时，假定人员密度服从均匀分布，出口宽度服从正态分布时计算得出的疏散行动时间值偏于保守。     

地下铁矿扩界开采地表影响范围预测

矿山开采活动形成的地下空区往往会对地表造成一定的影响,为确保矿山的安全生产并提供地表影响范围计算的科学依据,现根据某铁矿采用下向胶结充填法采矿需进行扩界开采的工程实际,将该矿的地表影响范围运用概率积分法进行预测。在已知该矿9条勘探线矿体形状的基础上,根据图件可得矿体的埋深、倾角、产状等基础资料,对于较薄矿体以及尖灭部位需做适当的处理,提供更为客观正确的计算数据。以地表沉陷数值的大小为参考标准运用概率积分法计算出地表移动边界和需监测范围,并计算倾斜、曲率和水平应变判断地表建筑物是否位于安全区。可得矿区周边房屋均处于安全区内和地表移动边界之外,扩界开采对地表影响较小,为同类工程提供参考和建议。