The Effects of Multitasking on Operations Scheduling

This study considers a typical scheduling environment that is influenced by the behavioral phenomenon of multitasking. Under multitasking, the processing of a selected job suffers from interruption by other jobs that are available but unfinished. This situation arises in a wide variety of applications; for example, administration, manufacturing, and process and project management. Several classical solution methods for scheduling problems no longer apply in the presence of multitasking. The solvability of any scheduling problem under multitasking is no easier than that of the corresponding classical problem. We develop optimal algorithms for some fundamental and practical single machine scheduling problems with multitasking. For other problems, we show that they are computationally intractable, even though in some cases the corresponding problem in classical scheduling is efficiently solvable. We also study the cost increase and value gained due to multitasking. This analysis informs companies about how much it would be worthwhile to invest in measures to reduce or encourage multitasking.     

Keep Your Friends Close? Supply Chain Design and Disruption Risk

In this article, we evaluate the relationship between supply chain design decisions and supply chain disruption risk. We explore two supply chain design strategies: (i) the dispersion of supply chain partners to reduce supply chain disruption risk versus (ii) the co‐location of supply chain partners to reduce supply chain disruption risk. In addition, we assess supply chain disruption risk from three perspectives: the inbound material flow from the supplier (supply side), the internal production processes (internal), and the outbound material flow to the customer (customer side) as a disruption can occur at any of these locations. We measure disruption risk in terms of stoppages in flows, reductions in flow, close calls (disruptions that were prevented at the last minute), disruption duration (time until normal operation flow was restored), and the spread of disruptions all the way through the supply chain. We use seemingly unrelated regression (SUR) to analyze our data, finding that lead times, especially supply side lead times, are significantly associated with higher levels of supply chain disruption risk. We find co‐location with suppliers appears to have beneficial effects to the reduction of disruption duration, and, overall supply side factors have a higher impact when it comes to supply chain disruption risk than comparable customer side factors.     

新冠肺炎疫情突发期政策制定的特征分析与效果评价 ——基于江苏省疾病预防控制中心的田野观察

文章聚焦政策本身,采用在江苏省疾病预防控制中心进行田野观察的研究方法,收集新型冠状病毒肺炎（简称新冠肺炎）疫情突发期的政策并进行文本分析,主要讨论政策文本发布时间的分布态势、发布单位、发布形式和政策内容4个方面。研究发现,在新冠肺炎疫情突发期（2020年1月15日至1月31日）国家级和省级指导性文件数量锐增。以江苏省为例,省级政策发文单位单一、文本类型多为通知类,起到了应对突发公共卫生事件时的及时反馈、迅速应急以及布置指导的作用。政策发布主体联防联控的及时应对性以及对政策文本的长效性考虑上尚有欠缺。总结政策制定的规律、原则以及经验,提出公共卫生事件突发期的政策观念应从单一权威主义走向多元协作,政策导向应从“战”时应急转向“平战结合”,政策价值应从“短期”应急转向“常态化”指导。     

我国劳动合同期限制度的缺失与重构——兼评《劳动合同法》相关规定

劳动合同期限制度具有明显不同于私法之特色.其正当性基础在于,宏观上维护劳动关系乃至社会的和谐稳定,微观上避免解雇保护制度形同虚设.在我国当前劳动力供大于求且不可替代性差、劳动合同短期化问题严重之现状下,此正当性尤为明显.我国原有现行立法功能错位、难堪其用,而新颁布的《劳动合同法》对此的改进仍极为有限.我国立法应当建立劳动合同期限制度,且应正面直接限制固定期限劳动合同,同时注意避免该制度的僵化.     

A SIMULATION ANALYSIS OF THE JAPANESE JUST-IN-TIME TECHNIQUE (WITH KANBANS) FOR A MULTILINE,MULTISTAGE PRODUCTION SYSTEM

The Japanese “just-in-time with kanban” technique reduces in-process inventory to absolute minimal levels, in concert with the Japanese belief that inventory is an unnecessary evil. Due to the success of Japanese firms that employ this type of system, American firms would like to import this technique and emulate Japanese successes. But this Japanese success may be attributable not only to the just-in-time with kanban technique but also to the production environment in which the technique is employed. This paper simulates the just-in-time with kanban technique for a multiline, multistage production system in order to determine its adaptability to an American production environment that might include such characteristics as variable processing times, variable master production scheduling, and imbalances between production stages. The results have practical implications for those firms considering adoption of the Japanese technique.     

On Bartlett correction of empirical likelihood for regularly spaced spatial data

Bartlett correction constitutes one of the attractive features of empirical likelihood because it enables the construction of confidence regions for parameters with improved coverage probabilities. We study the Bartlett correction of spatial frequency domain empirical likelihood (SFDEL) based on general spectral estimating functions for regularly spaced spatial data. This general formulation can be applied to testing and estimation problems in spatial analysis, for example testing covariance isotropy, testing covariance separability as well as estimating the parameters of spatial covariance models. We show that the SFDEL is Bartlett correctable. In particular, the improvement in coverage accuracies of the Bartlett‐corrected confidence regions depends on the underlying spatial structures. The Canadian Journal of Statistics 47: 455–472; 2019 © 2019 Statistical Society of Canada     

Cox regression of clustered event times with covariates missing not at random

Motivated by a recent tuberculosis (TB) study, this paper is concerned with covariates missing not at random (MNAR) and models the potential intracluster correlation by a frailty. We consider the regression analysis of right‐censored event times from clustered subjects under a Cox proportional hazards frailty model and present the semiparametric maximum likelihood estimator (SPMLE) of the model parameters. An easy‐to‐implement pseudo‐SPMLE is then proposed to accommodate more realistic situations using readily available supplementary information on the missing covariates. Algorithms are provided to compute the estimators and their consistent variance estimators. We demonstrate that both the SPMLE and the pseudo‐SPMLE are consistent and asymptotically normal by the arguments based on the theory of modern empirical processes. The proposed approach is examined numerically via simulation and illustrated with an analysis of the motivating TB study data.     

Business Collaboration within the Nazi War Machine: Corporations and the State in the Austrian Semiperiphery

The military strength of German National Socialism was based on the collaboration of large corporations with the Nazi state. Business provided capital, loans, taxes, managerial expertise and production for war industries. I elaborate four ideal‐typical modes of business collaboration. Each mode is illustrated by a case study of a German corporation that acquires an Austrian firm: Krupp (traditional mode); the Reichswerke state conglomerate (coercive); Deutsche Bank (managerial nationalist); and IG Farben (competitive investment mode). The first and the last modes occurred when the state was highly dependent on large businesses for the economic requisites of war. The acquired firms in the Austrian semiperiphery contributed to Nazi war mobilization, as they exploited labor and resources from the peripheral regions of southeastern Europe. Patterns of the state's resource dependency on business led to bargaining interactions between state and business, over time shaping the mix between state and private ownership of war industry.