供求不确定下零部件供应商横向协同研究

考虑了由2个供应商与1个制造商组成的按订单装配的供应链模型。在供应商的零部件供应不确定、制造商的客户需求不确定的环境下,从多供应商的视角来研究如何通过供应商之间形成零部件横向协同,向制造商齐套供应零部件,从而降低制造商的期望总库存成本。首先,建立了单周期和多周期的理论模型,并对形成协同前后的期望总库存成本进行了比较;然后,通过模拟仿真的方法,对模型进行验证和比较,并分析了不同的缺货成本对最优订单量、最优订至点和最小期望总库存成本的影响。结果表明,多供应商之间的零部件横向协同降低了制造商的期望总库存成本,提高了对客户需求的响应。     

基于Supply-Hub运作模式的供应商协同补货策略研究

Supply-Hub作为整合管理不同供应商零件库存的供应链节点,同时也承担了供应物流协同运作管理平台的功能.本文考虑加工-装配系统中存在的因一种零件缺货而造成其它配套使用的零件滞存的问题.研究了一种基于Supply-Hub运作模式,在供应商之间可以共享补货及库存信息的条件下,供应商协同补货策略,并与供应商分散补货模式下的基本补货模型进行比较分析.通过算例验证了该补货策略能有效降低供应链系统成本以及供应商成本.     

需求预测信息共享对供应商入侵策略的影响

考虑由一个供应商和一个风险规避的零售商组成的二级供应链． 在零售商拥有私有需求信息和供应商具有开通直销渠道能力情形下,得到了不同策略下供应链成员的最优决策及期望效用,探讨了需求预测精确度及风险规避程度的影响,分析了信息(不) 共享下供应商入侵对供应链成员效用的影响,进一步得到了零售商和供应商之间的均衡策略及其条件． 研究发现: 预测精确度的提升(或零售商风险规避程度的降低) 能够增加供应链成员的效用; 供应商入侵会产生“输 － 赢”、“输 － 输”、“赢 － 输”、“赢 － 赢”四种可能结果; 零售商的最优信息共享策略与基本需求、自身销售优势以及风险规避程度密切相关; 当且仅当基本需求不太高且零售商具有较强的销售成本优势时,零售商才会主动共享信息以诱使供应商开通直销渠道,并且风险规避程度越高,零售商越有可能共享需求信息; 当入侵成本很高时,供应商仍有可能战略性地开通直销渠道．最后,数值分析表明,只有当零售商的销售成本不是太高时,他才有可能共享需求信息．     

信息不对称条件下可控提前期供应链协调机制研究

探讨了信息不对称条件下提前期可以通过额外的赶工成本来加以控制的两级供应链协调问题。分别建立了分散决策和集中决策情形下的可控提前期供应链库存优化模型,并在充分考虑各参与方个体理性的基础上,探讨了分销商库存信息不对称情形下的供应链协调机制。最后通过数值分析证明该协调机制既能诱使分销商申报真实的库存持有成本信息,又能够在供应链合作双方成本均有改进的基础上,达到供应链系统的最优。     

基于可控提前期的随机寄售库存模型

本文通过假定需求提前期为随机且可控的,将寄售库存（Consignment Stock,CS）模型拓展到随机情形。本文首先将库存成本分为与财务相关的成本和与储存相关的成本两部分,得出CS方式下买卖双方的联合期望总成本公式,然后将订货量、订货点、提前期、运送次数作为决策变量,求得系统的最优参数设置及最小总成本。文章最后提出一个算法,并通过仿真的形式表明无论在确定还是随机环境中,CS方式的总成本都可能优于集成化库存方式。     

中国商品期货隔夜信息对日间交易的预测能力

鉴于供应管理对装配系统的重要意义,本文以VMI管理策略和成本共担机制为背景,研究了信息封闭和信息共享两种环境中多供应商对单制造商的库存博弈问题,以及供应商决策对于零部件库存量和供应链利润分配的影响。此外,通过对比集中模式,给出了提高分散模式绩效的两种途径。研究结果表明:在信息封闭时,供应商对较小库存者的不合理预期会导致决策失误,从而同时损害到制造商和供应商的收益。在保证各参与方期望利润不减和博弈均衡解存在的前提下,信息共享和成本共担比例的调节可以提高分散模式的绩效。如果分散决策能够协同为集中决策,那么在延误成本较高时,集中模式应该采取等量的零部件库存策略,而在延误成本较低时,非等量库存策略会更优,这一结论细分了分散模式向集中模式的改进方向。     

可控提前期下基于交易信用契约的供应链协调模型

提前期压缩是企业在激烈竞争环境中赢得与保持竞争优势的一种有效方式。本文制定了一个交易信用(即零售商向供应商提前付款)契约,讨论了可控提前期下非一体化供应链中的库存协作问题,得到了供应商与零售商的最优策略组合。研究表明,当提前期压缩成本系数足够小时,供应商采用所设计的交易信用契约,能够在满足零售商个体理性约束的前提下,赚取可观的成本节约金额,而且比纯粹延期付款协调零售商订货行为时所获得的成本节约更多;并且通过对该成本节约的合理分配,实现了供应商与零售商成本境况的帕累托改进乃至整条供应链的协调。最后的数值分析考察了安全库存系数、提前期需求波动、或者供应商的资金投资收益率对供应链最优策略与成本节约幅度的影响。     

绿色供应链中不对称需求预测下的信息共享研究

研究了由一个制造商和一个零售商组成的绿色供应链和他们的需求预测信息共享问题。考虑了两种方案：订货型生产方案和库存型生产方案，两种方案下分别考虑了无信息共享和信息共享两种情况。分析了预测信息对两种方案下制造商利润、零售商利润和信息共享价值的影响，同时研究了绿色成本系数对信息共享的影响。研究表明，两种方案中制造商始终能从信息共享中获利，而零售商只有在制造商绿色成本系数较低时才会自愿共享预测信息。当绿色成本系数较高时，制造商可以通过一个讨价还价合同，促进零售商进行信息共享。当绿色成本系数很高时，供应链成员之间不存在信息共享。此外，库存型生产方案中信息共享带来的总收益增量要高于订货型生产方案，因此，库存型生产方案中参与者信息共享的可能性要高于订货型生产方案。     

供应链提前期供需联合优化库存模型研究

本文研究由生产商和客户组成的二级供应链库存联合优化问题, 假设提前期服从均匀分布, 提前期订货受生产商的生产行为和客户的订货行为的制约, 建立了以库存成本为目标函数的供应链提前期供需库存模型, 提出了联合优化解决方案, 证明了目标函数在最优订货量和最优订货次数处存在最小目标值。在此基础上, 分析了提前期对供应链库存联合优化决策的影响。数据分析表明, 联合优化决策方法的库存成本曲线始终在分散决策优化方法的成本曲线的下方, 因此联合决策方法是非常有效的。     

考虑可控提前期和缺货损失的供应链费用分担策略研究

假定在一个由一个供应商与一个零售商组成的供应链中,供应商向零售商提供单一产品且其补货提前期可以通过增加费用进行压缩,零售商的外部需求不确定和部分缺货可以补充,本文建立了供应链分散决策和集中情形下的库存模型,得出了包含最优提前期、订货批量、安全库存因子和生产批量等决策变量的最优解,并提出了买卖双方分担压缩提前期投入费用的策略。算例分析表明,单项费用分担策略虽然能够使提前期压缩到与供应链集中决策时的情形一致,并实现供应链帕累托优化,但无法实现供应链整体最优化。     

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.     

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.     

Job strain and psychotropic drug use among white-collar workers

The main objective of this study was to measure the association between simultaneous exposure to high psychological demand and low decision latitude at work and the use of psychotropic drugs among white-collar workers. A second objective was to determine whether social support at work modified this association. A cross-sectional study was performed that included 2786 workers from the public sector in the Greater Quebec City area. A self-administered questionnaire was used in order to evaluate psychological demand, decision latitude and social support at work. Psychotropic drug use was measured over a period of 2 days. The prevalence of psychotropic drug use among the participants was found to be 3.9%, even though 20.5% were exposed to job strain. The association between job strain and psychotropic drug use, after adjustment for social support at work, age, gender, education, family income, employment status, occupation, stressful life events, cigarette smoking, alcohol consumption and physical activity, was statistically significant (odds ratio: 4.5, 95% CI 1.7?12.2). Social support did not appear to modify this association. The results of this study suggest that job strain might be a determinant of psychotropic drug use among white collar workers. Social support at work does not appear, however, to modify this association.     

Role clarity, work overload and organizational support: multilevel evidence of the importance of support

The present study extended the demands-control-support model used in occupational stress research in two ways. First, it hypothesized that role clarity (i.e. role ambiguity), like control, would moderate the relationship between demands and psychological strain. Second, the study assessed support (from leaders) as a macro characteristic of the work-group environment. Data were drawn from a large study of US army soldiers, the study sample consisting of 1786 lower enlisted male soldiers. The inclusion of support as a work-group characteristic lead to a multilevel test of the model. A three-way multilevel interaction among work demands, role clarity and support was observed. As predicted, the relationship between demands and psychological strain was moderated by role clarity; however, this moderating relationship was found only when work-group support was high.     

Leadership, levels of analysis, and déjà vu: Modest proposals for taxonomy and cladistics coupled with replication and visualization

In the inaugural issue of LQ's Yearly Review of Leadership, Hunt and Dodge (2000, p. 442) note that, “Within the last two decades, one of the crucial developments in organizational research in general, and in leadership research specifically, is the articulation of specific levels of analysis and their implications for theory building, measurement, and observation.” Their original observations are updated by extending the inferential logic of Yammarino, Dionne, Chun and Dansereau (2005) to determine if any increase in the utilization of a level of analysis perspective has occurred in the last five years. The possible evolution of leadership theory and analysis is discussed, especially with reference to Relational Leadership Theory, Leader–Member Exchange, and Individualized Dyadic Theory. Proposals incorporating taxonomic and visualization tools as a means to help bridge the stakeholder gap are also offered.     

Information Frictions in Trade

It is costly to learn about market conditions elsewhere, especially in developing countries. This paper examines how such information frictions affect trade. Using data on regional agricultural trade in the Philippines, I first document a number of observed patterns in trade flows and prices that suggest the presence of information frictions. I then incorporate information frictions into a perfect competition trade model by embedding a process whereby heterogeneous producers engage in a costly sequential search process to determine where to sell their produce. I show that introducing information frictions reconciles the theory with the observed patterns in the data. Structural estimation of the model finds that information frictions are quantitatively important: roughly half the observed regional price dispersion is due to information frictions. Furthermore, incorporating information frictions improves the out‐of‐sample predictive power of the model.     

The Economics of Density: Evidence From the Berlin Wall

This paper develops a quantitative model of internal city structure that features agglomeration and dispersion forces and an arbitrary number of heterogeneous city blocks. The model remains tractable and amenable to empirical analysis because of stochastic shocks to commuting decisions, which yield a gravity equation for commuting flows. To structurally estimate agglomeration and dispersion forces, we use data on thousands of city blocks in Berlin for 1936, 1986, and 2006 and exogenous variation from the city's division and reunification. We estimate substantial and highly localized production and residential externalities. We show that the model with the estimated agglomeration parameters can account both qualitatively and quantitatively for the observed changes in city structure. We show how our quantitative framework can be used to undertake counterfactuals for changes in the organization of economic activity within cities in response, for example, to changes in the transport network.     

Modelling end-of-life product recovery chains - a case study

European Union legislation, and existing national legislation of many European countries, mandates that manufacturers take back and recover their electronic and electrical equipment. If manufacturers are to comply with legislation, models need to be developed for these activities. Whilst infrastructural and technological deficits exist and must be addressed, so too must the organization of recovery, from a business perspective. In this paper, models of resource recovery are presented and a case study described.