基于灰色-马尔科夫链理论的建筑施工事故预测研究

我国建筑事故预测中具有统计数据少、数据波动性大等特点,缺乏具有高精度、可操作性强的预测模型。将灰色系统理论和马尔可夫原理相结合,充分发挥了灰色系统理论适用于小样本数据拟合和马尔可夫适合处理数据波动大的系统过程的优势,通过GM(1,1)模型的建立,提出一种适合建筑事故统计数据特点的灰色马尔可夫预测方法。将该方法应用于1994—2007年建筑施工事故次数分析,以此为基础对2008—2009年的建筑施工事故次数进行预测。研究结果表明:基于灰色马尔可夫理论建筑事故预测结果精度可达90%以上。     

DROUGHT INDICATORS AND TRIGGERS: A STOCHASTIC APPROACH TO EVALUATION1

ABSTRACT: Drought management depends on indicators to detect drought conditions, and triggers to activate drought responses. But determining those indicators and triggers presents challenges. Indicators often lack spatial and temporal transferability, comparability among scales, and relevance to critical drought impacts. Triggers often lack statistical integrity, consistency among drought categories, and correspondence with desired management goals. This article presents an approach for developing and evaluating drought indicators and triggers, using a probabilistic framework that offers comparability, consistency, and applicability. From that, a multistate Markov model investigates the stochastic behavior of indicators and triggers, including transitioning, duration, and frequency within drought categories. This model is applied to the analysis of drought in the Apalachicola‐Chattahoochee‐Flint River Basin in the southeastern United States, using indicators of the Standardized Precipitation Index (for 3, 6, 9, and 12 months), the Palmer Drought Severity Index, and the Palmer Hydrologic Drought Index. The analysis revealed differences among the performance of indicators and their trigger thresholds, which can influence drought responses. Results contribute to improved understanding of drought phenomena, statistical methods for indicators and triggers, and insights for drought management.     

环鄱阳湖区分区土地利用景观格局变化模拟研究

依据水环境约束力的大小,将环鄱阳湖区划分为核心、边缘和外围3个影响区。以该地区2005~2010年间土地利用情况为基准,通过构建CA-Markov-Logistic模型模拟2015年该地区土地利用格局情景,并采用景观格局指数进一步分析3个影响区土地利用景观格局变化趋势。研究表明:(1)从土地利用类型变化来看,覆盖环鄱阳湖区约82%土地面积的耕地和林地将有较大幅度的减少,而城建用地所占比重将大幅上升,对环鄱阳湖区的开发在逐渐加快;(2)从土地利用影响力来看,地类分布概率与人口城市化率、生活城市化率以及经济城市化率的空间分布有着一定的相关关系;(3)从模拟结果来看,环鄱阳湖区核心区耕地范围将缩小而水体范围将扩大,边缘区其他建设用地和农村居民点面积增加,外围区水体范围将大幅缩减,土地景观破碎化程度依次从边缘区-外围区-核心区的顺序下降,表明对鄱阳湖保护的作用正在显现,整个土地利用景观格局取向更为合理。     

基于灰色马尔科夫模型的2A12铝合金腐蚀预测方法研究

目的研究飞机结构件的腐蚀随时间的变化规律,为其寿命预测及可靠性分析提供参考。方法以2A12铝合金试件为对象,利用加速腐蚀试验设备,对其进行7个周期的加速腐蚀,以获得蚀坑深度的原始数据。在此基础上,将灰色GM(1,1)模型与马尔科夫链模型相结合,建立起能够预测蚀坑深度的灰色马尔科夫模型。结果将预测值与试验值进行对比,结果表明,灰色马尔科夫模型预测精度在0~4.5%之间,预测结果比较准确。结论该灰色马尔可夫模型能够较好地反映该型铝合金在腐蚀过程中蚀坑深度的变化趋势,建立起了一种新的腐蚀预测方法。     

A model for supply chains environmental performance analysis and decision making

The need to include environmental criteria in the analysis of supply chains is increasingly recognized as a result both of limitations that are posed by legislation and regulations as well as of various motivations that a company may have. A decision model is proposed in this paper based on environmental performance indicators, which may support decision making in the case of supply chains in the presence of environmental considerations. The model uses a set of principles applicable to supply chains design and operation available from previous research work.     

An animal movement model incorporating home range and habitat selection

Wildlife biologists are often interested in how an animal uses space and the habitat resources within that space. We propose a single model that estimates an animal’s home range and habitat selection parameters within that range while accounting for the inherent autocorrelation in frequently sampled telemetry data. The model is applied to brown bear telemetry data in southeast Alaska. This article is based on a portion of this author’s Ph.D. dissertation completed in 2003 at the University of Iowa.     

An application of Markov Decision Programming to ecologico-cybernetics—A decision method applied to the antifrost of winter wheat

Modern ecologico-cybernetic principle is of importance to decreasing damages in relation to agricultural productions. As an illustration of this, the authors studied some of the questions about the optimal policy of choosing actions for the antifrost measures of winter wheat by means of the finite-stage model of Markov Decision Programming (MDP). The related data came from the investigation results of the investigated region in the northeastern part of Henan, China. First, the authors give the states, ecologico-cybernetic action measures, transition probabilities and reward values in relation to these antifrost action measures of winter wheat crop. Second, the authors describe the principles and computational procedures of the ecologico-cybernetic decision-makings based on the finite-stage model of MDP. Third, a simple table applicable to the decision-making practice is given. Finally, we evaluate the results of this study, point out their shortcomings and suggest that this method is applicable to the other fields in relation to decreasing damage ecologico-cybernetics.     

煤矿百万吨死亡率动态无偏灰色马尔科夫预测

为掌握我国煤炭行业整体安全生产状况,构建动态无偏灰色马尔科夫模型,通过处理我国1999—2008年度煤矿百万吨死亡率数据,对2009—2011年度煤矿百万吨死亡率数据进行预测。用无偏灰色GM(1,1)模型代替传统灰色GM(1,1)模型,拟合得到煤矿百万吨死亡率数据的变化趋势,在此基础上应用马尔科夫模型进行预测,并在每一次预测中更新原始数据,最后对预测结果进行对比分析。计算结果表明:动态无偏灰色马尔科夫模型既能消除传统灰色GM(1,1)模型的固有偏差,又能提高预测精度尤其是中长期预测精度。其中,平均绝对误差为3.35%,平均相对误差为3.85%,均低于传统灰色GM(1,1)模型和一般灰色马尔科夫模型。动态无偏灰色马尔科夫模型对于煤矿百万吨死亡率数据的平均预测精度超过96%。     

城市埋地燃气管道危险性SPA-Markov链评价预测模型

为对城市埋地燃气管道系统危险性进行动态评价及预测,为管理者提供更客观的、可靠的管理依据,将集对分析(SPA)理论和马尔科夫链相结合用于城市埋地燃气系统的动态评价中。针对城市埋地燃气管道系统存在不确定性和动态变化的特点,提出集状态评价和预测分析于一体的城市埋地燃气系统动态危险性评价预测方法。该方法利用SPA的多元联系数对系统的危险等级进行划分,运用马尔科夫链的遍历性,并将结果与集对势相结合,预测城市埋地燃气管道系统最终的危险水平。     

基于马尔可夫方法的水下防喷器可靠性研究

水下防喷器是保障海上钻井安全的关键设备,对其可靠性进行定量评价对井控作业有重要的指导意义.为了弥补现有水下防喷器可靠性评价方法的不足,将水下防喷器的工作状态分为四种,包括无故障可用、关井、井控关键失效及关井时失效.利用Markov方法建立了水下防喷器的Markov模型.通过水下防喷器系统的状态转换图找出了各工作状态的转换关系.通过分析墨西哥湾83口深水井水下防喷器的失效数据,定义了影响水下防喷器可靠性的井控关键失效,并对深水钻井水下防喷器防喷功能的可靠性进行了定量计算.将计算结果与不考虑关井期间的井控关键失效相比较发现,防喷器的防喷失效概率增加了65％.因此传统的定量评价方法可能会得出相对乐观的结论,应在实际生产中给予重视.