实时/时变路网环境下城市出救点选择与救援车辆路径的集成动态优化

为了提升城市突发公共事件应急资源调配效率,考虑实时/时变路网环境下出救点选择与救援车辆路径的集成优化问题(CERFSVRP),设计了一种实时/时变交通信息的结合策略,并提出了满足先进先出原则的路段行驶时间计算方法.在此基础上,综合考虑出救点选择、供应能力以及车辆路径连续性等约束条件,以应急响应时间最短为目标,基于虚拟出救点概念和滚动时域策略建立了CERFSVRP动态优化模型.针对该模型的特点,设计了一种改进遗传算法和线性规划法相结合的两阶段算法.算例分析结果表明该模型和算法可以有效解决实时/时变路网环境下城市突发公共事件CERFSVRP动态优化问题.     

震后应急物资配送的模糊定位-路径问题研究

从系统集成优化的角度研究震后应急物资配送的一种新模糊定位-路径问题(LRP),综合考虑救灾点所在地理位置和地形导致的应急车辆行驶时间的随机性、救灾点应急物资需求量的不确定性与应急物资配送的时间紧迫性,以应急物资总运达时间最短与总配送成本最小为目标,构建一个基于机会约束规划的多目标模糊LRP优化模型,并根据模型的特点设计了一种混合免疫遗传算法予以求解。最后,通过算例验证了本文方法能有效解决震后应急物资配送的模糊多目标LRP,实现了震后应急物流中心定位和应急车辆路径规划的联合决策。     

震后应急物资多方式供应的模糊动态LRP

研究震后应急物资多方式供应中的多层次设施定位-路线规划问题(LRP),综合考虑应急物流网络中的多周期应急物资模糊需求、时间窗限制、部分路网损毁与动态恢复、车辆随机行驶时间、大需求点采用需求分割策略同时进行运输与配送等特性,以应急物资总供应时间最短为目标,构建了一个震后应急物资多方式供应的多周期模糊LRP优化模型,并根据模型特点设计了一种贪婪算法结合蚁群算法的混合启发式算法予以求解.最后,通过算例验证了本文模型和算法的可行性与有效性.     

震后初期应急物资配送的模糊多目标选址-多式联运问题

针对震后初期应急物资配送系统优化问题,考虑应急物资需求模糊情况下应急物资配送中心选址和应急物资多式联运安排的集成决策,以应急物资配送总时间最短和受灾点应急物资未满足的总损失最小为目标,建立了一个震后应急物资配送的多目标选址-多式联运问题优化模型,设计了一种采用二维编码的非支配排序多目标遗传算法,并对该算法进行了复杂性分析。算例分析结果表明:该算法可以在得到Pareto前沿的同时,根据决策者偏好在Pareto前沿面上给出各种优化决策方案。     

基于信息更新的两阶段鲁棒-随机优化调配模型研究

在突发事件的应对中,应急决策过程的灾情信息具有动态性、不确定性等特征,从而使得整个应急救援过程中的决策都必须随信息更新而不断调整,本文在调研国内外相关研究的基础上,以地震为背景提出了基于信息更新的资源调配决策问题。文章结合灾情信息更新的特征,给出了应急救援响应的阶段划分;以此为基础建立了两阶段鲁棒-随机优化模型,通过虚拟储备库点及虚拟临时分发中心点的设计,实现了第一阶段调配结果对第二阶段调配决策的后效性调整决策;根据鲁棒优化及随机优化的特点,设计了相应的原始-对偶及L-Shaped Method算法对模型进行求解;最后,通过CPLEX软件编程求解,并进行情景生成下的算例分析,与其他方法比较分析,证明了文章所设计的模型在灾情信息更新下的优势。     

考虑时效与公平性的震后应急物资动态配送优化研究

大规模地震后应急物资的高效保障是应急救援有效开展的必要前提。震后应急物资运输与配送包括从区域储备仓库和外围物资集散地运输到区域应急配送中心、由区域应急配送中心配送到各个受灾点两个阶段。应急物资保障具有持续时间长、需求紧迫性强和物资相对短缺等特点。本文以应急物资保障时效性与分配公平性为目标,建立了考虑多种运输方式、多时段动态的应急物资配送中心选址与运输配送路径优化的多目标规划模型,并基于此模型设计了一种带精英策略的非支配排序的遗传算法,以九寨沟地区地震灾难情景对模型进行实证研究,验证了模型和算法的有效性,以期为震后应急物资保障提供理论指导与决策支持。     

国家血液战略储备库选址——库存问题

建立血液战略储备库是应对大规模突发事件应急血液保障问题的重要途径之一.为提高应急血液保障能力,以灾后应急血液保障时效性最高及日常条件下血液战略储备库运营总成本最低为目标,基于非线性混合整数规划方法建立了一个考虑多情景、多阶段、多血型、随机需求、库存补充提前期、容量限制及协同定位等因素的血液战略储备库多目标选址—库存问题优化模型.根据该模型的性质,设计了一种基于小生境技术的多目标非支配排序遗传算法进行求解.算例分析结果表明,该算法能够有效获得Pareto前沿,产生一簇Pareto解,因而决策者可根据偏好与实际需要权衡应急血液保障成本与时效性,选择合适的血液战略储备库选址—库存决策方案.     

城市灾害应急目标管理及动态管理模型研究

根据城市灾害应急目标管理工作的实际需要,提出了城市应急目标管理的概念,从城市灾害预防、安全保障和应急救援三个方面,构建城市灾害应急目标管理的框架结构体系,提出了城市应急目标动态管理模型,并运用动态管理的方法,实现城市灾害应急目标的自我管理和自我完善,以达到城市应急管理目标的实现.     

社区应急疏散动态协作调度优化研究

针对灾民数量和路网通行时间的动态性以及灾民疏散反应系数的随机性，本文提出了社区应急疏散协作调度优化流程，并以疏散灾民数量最大化和疏散成本最小化为目标，构建了社区应急疏散多种运输方式协作调度优化模型，并给出了求解该模型的改进多目标遗传算法。然后，论文使用Tansmodeler模拟社区应急疏散协作调度优化过程，加载疏散灾民动态需求和历史出行时间表，并对模型和算法进行验证。结果表明，该模型和算法可以在有效刻画疏散灾民数量和路网通行时间的基础上，为不同时刻的交通工具配置及疏散路径选取提供决策。     

时变随机网络下基于成功和风险的应急路径选择研究

现实生活中,当发生紧急事件时,应急中心需要对某地需要服务的紧急事件出车.由于交通管理、交通流量、天气变化等因素的影响,导致了路网中各个路段上的行驶时间可能是一个与出发时间相关的随机变量.通常,对于所发生紧急时间需要在一定的应急限制期内到达.由于路网的时变随机特性,使得所选择路径可能不能完全满足应急限制期的需求.首先,定义了时变随机网络下可行应急路径中不满足应急限制的风险和满足应急限制的成功.然后,分别考虑了成功和风险两个目标,建立了时变随机网络下多目标应急路径选择模型,并设计了求解时变随机网络下应急路径选择算法,讨论了算法的计算复杂性.最后,给出了一个应用算例,并与单独考虑成功所获得的应急路径进行了对比.     

Introduction to Special Section on Sensitivity Analysis and Summary of NCSU/USDA Workshop on Sensitivity Analysis

This guest editorial is a summary of the NCSU/USDA Workshop on Sensitivity Analysis held June 11–12, 2001 at North Carolina State University and sponsored by the U.S. Department of Agriculture's Office of Risk Assessment and Cost Benefit Analysis. The objective of the workshop was to learn across disciplines in identifying, evaluating, and recommending sensitivity analysis methods and practices for application to food‐safety process risk models. The workshop included presentations regarding the Hazard Assessment and Critical Control Points (HACCP) framework used in food‐safety risk assessment, a survey of sensitivity analysis methods, invited white papers on sensitivity analysis, and invited case studies regarding risk assessment of microbial pathogens in food. Based on the sharing of interdisciplinary information represented by the presentations, the workshop participants, divided into breakout sessions, responded to three trigger questions: What are the key criteria for sensitivity analysis methods applied to food‐safety risk assessment? What sensitivity analysis methods are most promising for application to food safety and risk assessment? and What are the key needs for implementation and demonstration of such methods? The workshop produced agreement regarding key criteria for sensitivity analysis methods and the need to use two or more methods to try to obtain robust insights. Recommendations were made regarding a guideline document to assist practitioners in selecting, applying, interpreting, and reporting the results of sensitivity analysis.     

Distinguishing traumatic, vicarious and routine operational stressor exposure and attendant adverse consequences in a sample of police officers

Problems in studying occupational stress within the police service are identified and the paucity of work on operational duties as potential stressors are discussed. The present study reports the results of a factor analysis of operational stressors (N = 601 serving British police officers) that revealed three factors: exposure to death and disaster; violence and injury; sexual crime. These were demonstrated to be reliable scales and were included in logistic regression models together with a range of demographic and psychological variables. Models were applied to men and women separately, which showed there to be different predictors of the likelihood of suffering distress (measured by the General Health Questionnaire, GHQ) in terms of the officer's gender and operational role. Overall the model for women officers was better at predicting psychological distress than that for men. These findings are related to aspects of the police occupational culture. Further discussion is offered that conceptualizes police operational stressors as traumatic, routine and vicarious. Finally, some implications are drawn for the provision of stress intervention in the light of this differentiation.     

Criteria for selecting a production control philosophy

Logistic objectives constitute a compromise between having short leadtimes and a low volume of work in progress on the one hand and a high resource loading and due date obligation on the other. Miscellaneous production planning approaches offered today provide different combinations of logistic objectives for satisfying a manufacturing strategy. To combine the strength of the various approaches into a unified system, a new approach based on a dynamic and distributed production planning methodology is proposed. To customize the approach, various analyses and specifications have to be made and for that reason some important characteristics and criteria for analysing production control philosophies will be given.     

The social construction of the meaning of acute stressors: a qualitative study of the personal accounts of police officers using a stress counselling service

The police profession is one in which acute stressors are encountered more frequently than in other occupations. Using the personal accounts of 35 police officers attending an in-house stress counselling clinic, the aim of the present study was to provide a qualitative examination of how the institutional context of policing influenced the ways in which acute stressors signified to individual police officers experiencing felt distress. Using the framework of Rational Emotive Behaviour Therapy as an analytical tool, it is argued that beliefs contributing to the experience of felt distress are related to the way in which policing as both an identity and an activity is constructed through the police organizational culture. Not only do these constructions influence the ways in which officers perceive themselves and their environments, but they also operate at the collective level to 'normalize' some emotional responses and to 'pathologize' others which, it is argued, could impact upon the outcomes of interventions such as stress counselling.     

The moderating role of social support in Karasek's job strain model

This paper examines whether social support is a boundary-determining criterion in the job strain model of Karasek (1979). The particular focus is the extent to which different sources of social support, work overload and task control influence job satisfaction, depersonalization and supervisor assessments of work performance. Hypotheses are tested using prospective survey data from 80 clerical staff in a university setting. Results revealed 3-way interactions among levels of support (supervisor, co-worker, non-work), perceived task control and work overload on levels of work performance and employee adjustment (self-report). After controlling for levels of negative affect in all analyses, there was evidence that high levels of supervisor support mitigated against the negative effects of high strain jobs on levels of job satisfaction and reduced reported levels of depersonalization. Moreover, high levels of non-work support and co-worker support also mitigated against the negative effects of high strain jobs on levels of work performance. The results are discussed in terms of the importance of social support networks both at, and beyond, the work context.     

Job insecurity, coping resources and personality dispositions in occupational strain

This paper presents research on the relationships between the work-related stressor of perceived job insecurity and various indicators of occupational strain, taking into account employees' personality dispositions (trait negative and positive affectivity) and coping resources. Respondents were 222 Australian public servants surveyed during organizational restructuring that involved downsizing and threat to job certainty. The research was formulated within an adaptation of Osipow, Doty, and Spokane's (1985) framework of stress-strain-coping that included the possible direct as well as moderating effects of personality dispositions in reporting occupational strain (Parkes, 1990). Findings from hierarchical regression analyses indicate consistent significant independent effects of personality dispositions, coping resources and perceived job insecurity on various indicators of strain. There was also support for the moderating roles of negative affectivity and self-care in the relation between perceived job insecurity and physical strain. Implications for the role of dispositional factors, especially negative affectivity, and the utility of various coping resources in accounting for occupational strain in times of threatened job security are discussed.     

Job stress, job strain, and psychological withdrawal among Dutch university staff: towards a dualprocess model for the effects of occupational stress

This study examined the antecedents of job strain (emotional exhaustion, health complaints) and withdrawal behaviour (e.g. lowered organizational commitment) among a cross-sectional sample of 131 academic staff members of the law department of a large Dutch university. Conservation of resources theory (Hobfoll, 1989) provided the theoretical background for this study. Strains and withdrawal behaviours were expected to be most prominent among those who reported having few resources and/or who reported high job demands. Structural equation modelling revealed that this was indeed the case. As predicted, differential patterns of effects emerged for job demands and job resources. Analysis of the effects of four job-specific stressors revealed that especially the structural aspects of a staff member's teaching task (e.g. the number of students in their classes) contributed strongly to perceived job demands. Theoretical and practical implications of the study are discussed.     

Dermal Uptake of 18 Dilute Aqueous Chemicals: In Vivo Disappearance‐Method Measures Greatly Exceed In Vitro‐Based Predictions

Average rates of total dermal uptake (K_up) from short‐term (e.g., bathing) contact with dilute aqueous organic chemicals (DAOCs) are typically estimated from steady‐state in vitro diffusion‐cell measures of chemical permeability (K_p) through skin into receptor solution. Widely used (“PCR‐vitro”) methods estimate K_up by applying diffusion theory to increase K_p predictions made by a physico‐chemical regression (PCR) model that was fit to a large set of K_p measures. Here, K_up predictions for 18 DAOCs made by three PCR‐vitro models (EPA, NIOSH, and MH) were compared to previous in vivo measures obtained by methods unlikely to underestimate K_up. A new PCR model fit to all 18 measures is accurate to within approximately threefold (r = 0.91, p < 10^?5), but the PCR‐vitro predictions (r > 0.63) all tend to underestimate the K_up measures by mean factors (UF, and p value for testing UF = 1) of 10 (EPA, p < 10^?6), 11 (NIOSH, p < 10^?8), and 6.2 (MH, p = 0.018). For all three PCR‐vitro models, log(UF) correlates negatively with molecular weight (r² = 0.31 to 0.84, p = 0.017 to < 10^?6) but not with log(vapor pressure) as an additional predictor (p > 0.05), so vapor pressure appears not to explain the significant in vivo/PCR‐vitro discrepancy. Until this discrepancy is explained, careful in vivo measures of K_up should be obtained for more chemicals, the expanded in vivo database should be compared to in vitro‐based predictions, and in vivo data should be considered in assessing aqueous dermal exposure and its uncertainty.     

Systems Resilience for Multihazard Environments: Definition,Metrics, and Valuation for Decision Making

The United Nations Office for Disaster Risk Reduction reported that the 2011 natural disasters, including the earthquake and tsunami that struck Japan, resulted in $366 billion in direct damages and 29,782 fatalities worldwide. Storms and floods accounted for up to 70% of the 302 natural disasters worldwide in 2011, with earthquakes producing the greatest number of fatalities. Average annual losses in the United States amount to about $55 billion. Enhancing community and system resilience could lead to massive savings through risk reduction and expeditious recovery. The rational management of such reduction and recovery is facilitated by an appropriate definition of resilience and associated metrics. In this article, a resilience definition is provided that meets a set of requirements with clear relationships to the metrics of the relevant abstract notions of reliability and risk. Those metrics also meet logically consistent requirements drawn from measure theory, and provide a sound basis for the development of effective decision‐making tools for multihazard environments. Improving the resiliency of a system to meet target levels requires the examination of system enhancement alternatives in economic terms, within a decision‐making framework. Relevant decision analysis methods would typically require the examination of resilience based on its valuation by society at large. The article provides methods for valuation and benefit‐cost analysis based on concepts from risk analysis and management.     

Employees' perceptions of organizational restructuring: the role of social support

Organizational change and restructuring is often perceived as leading to increased occupational stress, impacting negatively on the psychological well-being of employees. This pragmatic study investigates the role of social support and dispositional affect as moderators of role stress post-restructuring for employees in a public utility company. A total of 176 employees, including 37 managers, 60 graded staff and 78 industrial staff completed a self-report questionnaire, approximately 1 year postrestructuring, retrospectively assessing role conflict, ambiguity, overload and positive and negative feedback pre- and post-restructuring. Results suggested that overall role stress increased for managers/ senior officers and graded staff, but not for industrial staff. Social support was linked with lower role stress, more positive feedback and less negative feedback at post-restructuring. For certain role stressors this impact was moderated by dispositional affect, but the effect was not consistent across occupational groups. Positive affect enhanced the effect of manager support in reducing role conflict for graded staff, and the effect of co-worker support in increasing positive feedback and reducing negative feedback for industrial staff. Findings suggest that managers should pay particular attention to support and feedback for employees during periods of chronic occupational stress following organizational restructuring.