需求信息滞后下的零售商决策与牛鞭效应分析

牛鞭效应是一种在企业经营中广泛存在的普遍现象,对企业的生产经营产生了极大的负面影响。本文考虑一个供应商和一个零售商组成的简单两级供应链系统。在这个系统中,首先建立在需求信息滞后情况下的零售商库存决策和混合决策(库存决策和定价决策)模型;然后进行决策对牛鞭效应的影响分析。结果显示:在需求信息存在滞后的情况下,零售商最优决策的定价和订货点的期望值是确定的,与需求信息滞后期的长度无关;零售商的库存决策能产生牛鞭效应,且牛鞭效应会随需求滞后期增加而逐渐减少;零售商的混合决策能否产生牛鞭效应,取决于需求自相关系数的变化,而与需求滞后期无关,但随着需求滞后期会改变期变化程度。此外,库存决策还是混合决策,在需求不具有滞后时较具有滞后时牛鞭效应表现得较为为减弱;零售商的混合决策与库存决策相比,只有在需求的自相关系数取较小值时,才表现得更为强烈,否则会减弱。因而对于零售商而言,适当的需求信息滞后以及供应商对零售商的定价柔性能减少牛鞭效应。     

基于短生命周期产品的供应链订货策略的博弈研究

本文针对短生命周期产品的特点,利用短生命周期产品订货的特殊性,分析了简单的两级供应链的订货机制.构建了当供应商以履行订单时间为决策变量和零售商以是否提前订货和自身促销努力水平为决策变量时,供应链上下游之间的博弈模型.通过分析双方之间的利益关系,供应商修正初始决策从而得到均衡解,并以契约方式提出了有效的激励措施使零售商增大促销努力水平从而加大了订货量,实现了供应链中双方利益最大化.     

决策者过度自信视角下考虑质量控制的供应链库存策略

研究了由单个供应商和零售商组成的供应链中,零售商进行质量控制的条件下,供应链成员对市场需求的过度自信如何影响其库存管理决策和供应商的质量投资。分析了零售商管理库存、供应商管理库存和集中决策三种供应链库存管理模式下供应链成员库存和质量投资决策的博弈均衡,并通过与完全理性下均衡结果的比较探讨了过度自信对供应链成员库存决策、质量投资和利润等的冲击。研究表明,在零售商管理库存模式下,过度自信的决策者对库存量的决策受其心理预期市场需求的正向影响,而在供应商管理库存和集中决策模式下则相反。     

时变供需下基于商业信用的零售商最优订货策略

论文在时变供需环境下,即市场需求为斜坡式时间函数及补货率依赖于市场需求情境下,探讨了基于商业信用的供应链中零售商最优订货策略。首先,根据商业信用期和零售商补货周期的关系,分两种情形构建了零售商库存模型;其次,根据零售商的库存模型,证明了其最优解的存在,并给出相关的命题和算法来求解零售商的最优库存策略;最后,通过数值算例和灵敏度分析来论证文中的有关结论。研究发现:当供应商给予零售商的商业信用期较短时,此时市场需求仍处于增长期,随着市场需求稳定时间点的增大,零售商的最优订货周期逐渐减小,最优订货量和年费用也逐渐减小;当供应商给予零售商的商业信用期较长时,此时市场需求已趋于稳定期,随着市场需求稳定时间点的增大,零售商的最优订货周期逐渐增大,最优订货量和年费用也逐渐增大;当供应商生产与市场需求依赖性逐渐增大时,零售商的最优订货周期逐渐增大,最优订货量及年费用也逐渐增大。     

供应突发事件下基于CVaR的供应链订货决策及协调

供应突发事件下,引入条件风险值(conditional value at risk-CVa R)刻画了零售商的运营目标,构建了收益共享契约下的供应链订货模型,着重研究了CVa R下的供应链协调及零售商最优订货量对供应商可靠性及对其自身的风险规避系数的敏感性。研究表明:收益共享契约具有一定的鲁棒性,能协调突发事件风险下的供应链;风险规避型零售商的最优订货量总是不小于风险中性情况,且风险规避程度越高,订货量越大;最优订货量对供应商可靠性均值的敏感性不依赖于零售商的风险规避程度,且均值越小,最优订货量越大,这与风险中性情况是类似的;最优订货量对供应商可靠性标准差的敏感性则依赖于零售商的风险规避程度,当零售商的风险规避程度较高时,供应可靠性标准差越大,最优订货量越大,这与风险中性情况是相反的。     

基于APIOBPCS模式VMI下牛鞭效应仿真研究

运用系统动力学构建基于APIOBPCS采购模式和供应商管理库存的七成员供应链模型,通过该模型研究8个因素对牛鞭效应的影响.研究表明,平滑指数越小牛鞭效应越弱:库存初始值影响牛鞭效应的具体数值,但不能根本改变牛鞭效应;牛鞭效应受APIOBPCS模式库存调节系数影响巨大,DE-APIOBPCS模式下牛鞭效应相对较弱;在库存调节系数设定为1、某成员的所有下游成员提前期已经确定的前提下,该成员需求的标准方差只与紧邻上游成员的提前期有关,其余成员的提前期对该成员需求标准方差没有影响;库存检查周期越短牛鞭效应越弱;在供应链信息共享以及成员合作的前提下,瓶颈取适当值情况下的牛鞭效应与没有瓶颈情况下的牛鞭效应相比,前者更小;最低采购数量影响牛鞭效应,并且牛鞭效应对此因素表现出比较强的敏感性.     

需求风险和汇率风险在供应链中的传导分析

针对现有文献的缺陷,尝试着利用批发价合同构建了一个包含零售商、制造商与供应商的博弈模型。通过模型均衡,研究了需求风险和汇率风险如何在供应链中传导,并分别讨论了它们对供应链节点企业期望业绩与业绩方差的影响,及供应链节点企业之间的风险分担问题。结果表明,(1)供应链节点企业的期望业绩随市场需求波动和汇率变动程度的增加而增加;(2)供应链节点企业的业绩方差随市场需求波动和汇率变动程度的增加而增加;(3)零售商与制造商之间的相对风险分担(用零售商利润方差与制造商利润方差之比度量)随市场需求函数斜率的增加(零售商(对市场价格变化)的反应灵活性降低)而增加,而供应商与制造商之间的相对风险分担(用供应商利润方差与制造商利润方差之比度量)随供应商边际成本函数斜率的增加(供应商(对制造商的价格变化)的反应灵活性降低)而增加。这些结果从理论上表明,一方面需求风险和汇率风险可以通过节点企业之间的相互作用而在供应链中传导,另一方面供应链中的风险传导受"牛鞭效应"和节点企业利润边际的共同影响。     

基于两单链合作下的集群式供应链牛鞭效应的H∞控制研究

以集群式供应链跨链间库存合作为背景,针对两单链情形,考察零售商的紧急库存补充渠道来自于另一供应链的零售商,建立了集群式供应链跨链间库存合作下的库存模型和牛鞭效应量化方法。并用H_∞控制理论来寻求最优订货系列,以达到降低安全库存水平,提高顾客满意度和减弱牛鞭效应的目的。仿真实验表明,实施H_∞控制和跨链间库存互补策略可以有效抑制牛鞭效应。     

需求信息预测与处理中的牛鞭效应分析与控制

研究了不稳定的市场需求下一个生产商和一个零售商所组成的两层次的简单供应链系统.提出当零售商预测信息的过程中并不存在牛鞭效应现象,而在生产商和零售商利用库存策略处理需求信息的过程中却显著存在牛鞭效应现象.证明了利用信息共享的方式可以控制牛鞭效应,但不能完全消除牛鞭效应.     

基于供应链间品牌竞争的库存管理策略研究

分析两个供应链间竞争的系统,每条供应链由一个供应商和一个零售商组成,供应商通过各自零售商销售具有品牌差异的产品,不同品牌产品之间存在替代度,零售商面临不确定性需求.在此系统上,存在供应商间的竞争、零售商间的竞争,和供应链内上下游之间的竞争,三种竞争交织.每条供应链有两种管理库存的方式,即零售商管理库存和供应商管理库存.通过对比不同库存管理方式下系统成员收益,发现,把不确定性需求风险从零售商转移给供应商,并非能增加零售商收益,或减少供应商收益;同时,通过分析了不同库存管理方式对供应链系统竞争均衡状态的影响,指出,在一定条件下,供应商管理库存方式能加强供应商端的竞争,使得零售商和供应商共同受益.     

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.