新鲜产品跨季销售中的动态库存管理策略研究

新鲜产品在跨季销售过程中不可避免地发生变质，给分销商带来较大的风险。本文基于一个两阶段决策模型来帮助分销商动态管理库存，在考虑产品质量随机变化的情形下更好地匹配供给与需求。具体来说，在采摘季节确定采购的总数量；在销售季节结合产品新鲜度的演变以及剩余库存水平的变化动态地决策每周期的销售量，以实现期望利润的最大化。我们采用动态规划模型分析销售期的库存管理决策，刻画了利润函数和最优决策的结构性质，并考察了库存量、新鲜度水平和价格等参数对最优库存决策的影响。数值实验结果表明，当产品变质风险大、需求不确定性低时，动态库存管理策略相比静态策略的利润改进效果更为显著。     

一种考虑原材料库存成本的变质物品EPQ模型

在库存管理研究中,单独实现产成品或原材料库存成本最小,往往无法获得整个库存系统的最优控制策略.本文提出了一种同时考虑产成品和原材料库存成本的变质物品EPQ集成模型.运用迭代寻优法得到模型最优解,得出计划期内最优原材料订购次数,原材料订购周期内的最优生产次数和最优服务水平,并对主要参数进行了灵敏度分析,为生产制造企业的库存管理提供了决策依据.     

VMI环境下库存竞争性产品的补货策略及最优货架空间的确定

本文在文献[1]的研究基础上,通过深入剖析FKO模型,运用动态规划方法,探讨了呈现特殊需求性质的库存竞争性产品在VMI环境下的多期动态补货策略,以及传统库存管理中不加考虑的库存空间优化问题。本文一方面是对FKO模型的补充与扩展,同时也证实了对于在特定的VMI补货环境下采用多期库存盘查模式的供应商来说,封顶式的补货策略是最优的,并且其关于最优补货水平的多期决策都是无远见的。因此收益分享合同下的单期最优库存水平可以作为设定最优货架展示空间的依据。     

一类制造商与零售商纵向集成供应链的最优生产与库存策略

对供应链内部库存系统进行优化控制是提高供应链协调性的一种重要手段.而竞争的不断激化加剧了需求的波动,此时作为消化需求波动缓冲库的库存系统对提高供应链的协调性起着重要的作用.本文综合考虑顾客退货、库存自然损失等随机因素对供应链生产和库存策略的影响,构造出一类制造商与零售商纵向集成的供应链的最优生产与库存模型,并借助于动态规划的最优性原理给出了最优生产库存策略的表达式.本文从协调生产与销售的角度探索了提高供应链协调性的方法,不仅对供应链协调性的理论研究而且对实际应用中如何供应链协调性都作了一个崭新的尝试.     

网上拍卖销售与逆向拍卖采购下的库存管理

以电子商务为背景研究网上拍卖销售与逆向拍卖采购下的库存管理。在该问题中,零售商一方面利用网上拍卖销售产品,另一方面利用逆向拍卖进行采购。对于单阶段情形,证明网上拍卖下零售商的期望收益函数是采购量的严格递增的凹函数,从而得到零售商的最优采购策略和供应商的最优投标策略。对于多阶段情形,利用马尔可夫决策过程理论建立该问题的最优控制模型,得到零售商的最优采购策略和供应商的贝叶斯-纳什均衡投标策略均与基本库存策略相类似。     

基于产品时间价值的闭环供应链库存策略研究

许多被回收产品的价值会随着时间推移迅速减少,因此如何尽可能地利用库存策略减少此类产品价值的损失就成为了非常值得研究的问题.本文将EOQ模型拓展到闭环供应链中,基于产品的时间价值推导出了允许缺货和不允许缺货两种情况下回收品和成品库存的最优策略,并讨论了产品价值的流失对库存策略的影响.     

生产管理中动态规划模型的应用

在实际生活中,特别是生产管理中,经常需要进行多个阶段的决策。本文通过生产-库存问题介绍了解决多阶段决策的方法——动态规划法,并建立了生产-库存问题的模型,得到了最优的决策序列。     

采购价格柔性策略与供应链利润风险分析

面对原材料市场价格的大幅波动,供应链节点企业需要采用相应策略来规避价格波动带来的风险。本文通过设计价格柔性合同,分析供应链企业通过采购价格柔性策略来缓解采购价格波动给企业利润带来的风险。采用Stackelberg主从博弈模型研究得出了制造商的最优采购数量和供应商的最优价格柔性系数,并分别分析了各最优结果随采购价格柔性合同参数的变化趋势。利用供应链各主体的利润方差度量各自承担的利润风险,分析了供应商和制造商的利润风险随采购价格柔性合同参数的变化规律。     

需求依赖于库存的易变质品在线采购问题研究

根据现实生活中常见的库存量越大越吸引消费者购买兴趣的现象，本文建立了需求依赖于库存的易变质品采购模型。在不假设价格服从任何分布的条件下，提出了采购价格不确定背景下的易变质品在线采购策略。本文采用在线问题及其竞争分析的方法来进行建模分析，设计出有效的在线竞争采购价格驱动的(s,S)策略，与离线最优策略进行比较，得出理论竞争比和最优经济采购数量和采购时间间隔。最后，通过数值算例说明该策略在现实中具有较好的实际竞争性能比，且在多个价格序列下都表现良好，从而说明了该策略是鲁棒的，可以为企业提供有价值的决策建议。     

基于VMI理论的南水北调水资源供应链的库存协调

节点湖泊水资源库存的协调控制是南水北调工程运行管理中的重要研究内容之一.通过引入供应链的产品库存控制理论,以由长江抽水口和单个节点湖泊共同组成的简单南水北调水资源供应链为研究对象,分别建立了水资源库存集中决策、双方独立决策和VMI决策等情况下的湖泊水资源最优订货量模型和双方利润模型.在此基础上,提出了VMI策略下的水资源库存管理的转移支付协调策略,并给出了该协调策略的有效性,最后利用仿真算例对相关结论进行了验证和分析.     

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.