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。     

震后应急物资配送的模糊动态定位—路径问题

进行震后应急物资配送系统优化是提高其配送绩效的重要手段.从系统集成优化的角度,研究应急物资配送中心定位与配送车辆路径安排的联合决策问题.综合考虑应急物资需求的模糊性、动态性和限制期,震后受损路网的动态恢复状况,不同类型有容量限制的配送车辆,以及物资需求分割配送等特点,以各物资需求点的应急物资运达时间之和最小为目标,采用机会约束规划方法建立了一个模糊动态定位—路径问题优化模型,并设计了一种两阶段启发式算法予以求解.最后,通过算例验证了该模型和算法的可行性及有效性.     

突发公共事件应急系统中的模糊多目标定位-路径问题研究

本文从应急系统集成优化的角度出发,以应急系统中各资源需求点的应急救援时间满意度之和最大及系统总成本最小为目标,建立了一个应急资源需求和应急救援时间范围均模糊的多目标定位-路径问题(LRP)模型,并提出了一种混合多目标遗传算法。算例分析结果表明,所提模型和算法可以有效解决应急系统优化中的模糊多目标LRP。     

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。     

模糊信息下多种类应急物资多周期分配优化模型

考虑灾害的突发性、信息获取的不完全性以及应急救援的紧迫性，引入区间数描述应急物资供给与需求的模糊不确定性，引入三角模糊数刻画路网容量受限情况下每周期的最大物资运输总量，综合考虑灾害、灾区、灾民以及物资等多重因素，引入延迟系数，以应急物资分配的总延迟时间最小化和总系统损失最小化为目标，构建模糊信息条件下考虑多需求点、多配送中心、多物资、多周期、多目标的应急物资动态分配优化决策模型，分析了区间目标函数、区间模糊与三角模糊约束条件的清晰化方法，采用基于二维欧式距离客观赋权模糊算法求解模型，并以青海玉树地震为例对所提出模型的有效性和可行性进行验证。结果表明：所提出的模型能够最大程度地权衡延迟时间与系统损失，形成多周期最优的物资分配方案；现实多周期应急物资分配，时间并不是唯一考虑的因素，需要综合考虑不同应急周期的灾情、灾区、灾民和物资等多种因素对系统总损失造成的影响；重视时间偏好系数，可能使系统总损失增大，表明单一考虑时间偏好系数和损失偏好系数均具有片面性，应该把握选择"度"，发挥二者结合的相互促进作用；物资分配方案基于决策者偏好，并考虑每周期不同需求点的易损性、重要性、需求紧急性以及各类应急物资的重要性与时效性差异参数，有利于提高多周期决策的柔性和现实适用性。     

模糊供求条件下应急物资动态调度决策研究

围绕大规模突发事件应急的特点,在供应点、集配中心到需求点的三级供应网络的基础上,研究了模糊供求条件下的多模式联合调运的应急物资动态调度问题。首先建立了在需求满足率最大化的基础上,以总运输时间和应急成本为目标的带序关系的多目标非线性规划模型。考虑供大于求和供不应求两种供求关系,对于供不应求的物资,下一周期将优先配给。另外,采用最可能值法确定模糊数的权重和置信水平,采用平均权重法将三角模糊数转化为确定值,给出了去模糊化的策略和具体算法。通过决策者对运输时间和应急成本的动态赋权,提高了模型的柔性。最后以汶川地震为背景,设计仿真实例,验证了模型和算法的有效性。     

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。     

灾后模糊需求情境下考虑救援公平性的应急物资调度问题模型与算法研究

在重大灾害发生初期,由于受灾地区对应急物资的需求激增,合理的应急物资分配有助于提高救援效率。本文考虑受灾点应急物资需求具有模糊属性,将需求物资用三角模糊数表示,以受灾群众损失最小、体现救援公平性的受灾点应急物资满意度方差最小及应急救援成本最小为目标,构建了灾后初期应急物资调度的多目标模糊优化模型,并采用改进的粒子群算法对模型进行求解。该算法在粒子群算法的基础上采取天牛寻找食物的策略,将单一粒子分为左、中、右三个粒子,并结合单纯形算子和模拟退火策略,使算法不易陷入局部收敛。本文通过算例进行模拟实验表明,所提出的模型和算法可以有效解决重大灾害事件下应急物资的合理分配问题,且改进算法的性能更优。     

基于约束满意的供应链应急制造采购策略研究

针对紧急需求与采购成本之间的冲突,研究了模糊时间要求和模糊物资需求下多供应商和单一制造商构成的供应链的应急制造采购问题.建立了供应链应急制造采购的多目标、多约束组合优化模型,提出了一种由约束满意优化模型转换、搜索算法、满意度函数和满意度要求调整方法构成的交互式满意决策方法.运用该方法能够获得体现决策者偏好的满意采购策略,实现以合理成本满足应急需求的目的.通过模拟算例解释了交互式满意决策的过程.     

一个应急条件下港口群物资优化调度模型北大核心

由于海域面积广阔、生存环境恶劣,单一港口供应能力有限,难以满足突发灾害事件时的大量应急物资需求.本文针对港口群应急物资协同调度问题,构建考虑运输成本和任务完成度的双目标规划模型,并设计求解该模型的NSGA-1算法,通过港口群和陆上供应点的协同调度,满足应急物资快速可靠的运送需求.基于南海海区港口数据设计数值实验,对比了受灾顺序随机和受灾顺序确定两种情境下方案的鲁棒性.本文的研究结论对突发灾害事件港口群应急管理具有一定的指导意义.     

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.     

Power,authority and legitimacy

Management, human resources, organization, control, leadership, etc., all seem to be just so many euphemisms for power, and this suggests a discourse of management and organization that calls things by their proper name. This paper on the contrary stresses the need to resolve the concept of ‘power’ itself into more differentiated notions, and proposes that clarification may be derived from distinctions once explicit in the vocabulary of Classical antiquity, but lost in modern European languages. It argues that nothing but confusion in thinking about organizations, management and legitimation can result from the failure to recognize that the phenomena this vocabulary identifies and distinguishes are irreducibly different.     

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.     

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.     

The Danish psychosocial work environment and symptoms of stress: the main, mediating and moderating role of sense of coherence

The aim of this cross-sectional study was to explore the main, mediating and moderating role of sense of coherence (SOC) on stress symptoms and on the association between perceived psychosocial work environment and stress symptoms. The sample includes 2053 Danish employees from 52 workplaces. Hierarchical regression models were applied for each measure of stress. The results strongly supported the presence of a main effect for SOC. People with high levels of SOC experienced fewer stress symptoms. A mediating effect of SOC was also supported. Thus, SOC in part explained the association between work environment and stress symptoms. In addition, some support for a moderating effect of SOC was found, suggesting that people with higher SOC coped more efficiently with work environmental strain that people with lower SOC. Taken together the regression models explained 11-32% of the variance in stress symptoms. The results suggest that measures of individual factors such as SOC should be included in analyses of the effects of work environmental factors on stress and well-being.     

Control at work: a generalized resource factor for the prevention of musculoskeletal symptoms?

During the last two decades two potent groups of predictors for work-related musculoskeletal problems have been identified: physical work load and poor psychosocial working conditions. However, little is known about their combined effects. In this study the buffering effect of control at work with respect to the negative effects of psychological demands and physical work load on musculoskeletal problems is examined. All study variables were sampled from 431 people working in geriatric nursing homes in Germany by means of questionnaires. Main effects and interactions were tested with multiple regression analysis. The results showed that control buffered the effects of high psychological demands, but not of high physical work load; the buffering effect of control was observed only when physical work load was low. The combined effects of demands and physical work load were over-additive. Thus, the power of different predictors for musculoskeletal symptoms depended on the level of other predictors. This suggests that the efficiency of certain strategies for the prevention of musculoskeletal problems is likely to depend on the level of risk factors, with different strategies being appropriate for different levels of risk.     

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.