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51.
Scientific techniques for inventory management typically are applied to systems containing many items. Such techniques require an estimation of the demand variance (and mean) of each item from historical data. This research demonstrates a significant potential for improvement in system cost performance from using least-squares regression fits of a variance-to-mean functional relation instead of the standard statistical variance estimate. Even when there is a moderate degree of heterogeneity among items and when the form of the variance-to-mean relation is misspecified, substantial cost savings may be realized. The cost of statistical uncertainty may be reduced by half. The research also provides evidence that system cost is fairly insensitive to the number of items used to fit the regression. This paper provides the underlying reason why a regression-derived variance estimator yields lower cost: it is less variable than the usual individual item variance estimator. 相似文献
52.
In a recent paper, Pinto and Mabert [5] presented a lot-sizing rule and an improvement procedure for the joint lot-sizing problem with zero setup costs. We show that this procedure often yields infeasible schedules. We also present and discuss two interesting properties of the joint lot-sizing problem with zero setup costs. A numerical example to illustrate the second property is provided. 相似文献
53.
The advent of the wide variety of new, highly integrated, advanced manufacturing technologies available for acquisition by a firm's managers has brought to light an accompanying set of unexpected issues. These issues include expectations for the benefits and costs of these technologies, determining the appropriate order of implementation and finding a way to justify acquisition when many of the benefits are a function of the technology's learning and synergistic effects on other operations and technologies. We present here a model that captures the interaction effects of these highly integrated technologies and discuss the data requirements for application of the construct. We then illustrate the model's workings with a number of multitechnology examples and show the danger of ignoring the synergistic and learning effects of these technologies when considering their acquisition. 相似文献
54.
Wealth Holdings and Portfolio Allocation of the Elderly: The Role of Marital History 总被引:1,自引:1,他引:0
Aydogan Ulker 《Journal of Family and Economic Issues》2009,30(1):90-108
This paper investigates the role of marital history in terms of explaining differences in wealth holdings and portfolio allocation
of older individuals by studying data from the first wave of Health and Retirement Study which was conducted in 1992. The
results generally suggest that both men and women suffer from the negative shocks of past marital dissolutions in terms of
household wealth accumulation. The significance level, however, differs across currently married couples, single males, and single females. The examination of the asset components of net worth also indicates that
both the probability of owning a particular asset and the fraction of wealth allocated to that asset might vary depending
on the elderly individuals’ marital history.
相似文献
Aydogan UlkerEmail: |
55.
Stephen E. Bechtold 《决策科学》1988,19(2):353-372
This paper presents a tractable set of integer programming models for the days-off scheduling of a mix of full- and part-time employees working α to β days/week (cycle) in a multiple-objective, multiple-location environment. Previous models were formulated to specifically schedule part-time employees working either two or three days per week. These models were intractable because they required complete employee schedule information. The new models are deemed implicit optimal since they are required to supply only essential information. While the number of variables in previous models is an exponential increasing function of β-α, the size of three of the new models is independent of α and β. The first three models developed here (as in [18]) deal with the trade-offs between idle time, the number of employees required to work at multiple “locations,” and the size of the total labor pool. The inherent flexibility of the implicit modeling approach is illustrated by the presentation of various modifications of the basic models. These modifications permit the use of preference weights on the number of employee work days/week (cycle) or the minimization of payroll costs where differential pay rates exist. These latter models may also be formulated such that idle time is ignored, constrained or minimized. The execution time for the implicit models (on a CDC CYBER 730 computer with commercially available software) averaged well under five seconds on 1200 trial problems for the type of application considered in [18]. A solution was obtained in less than 46 seconds of CPU time for a trial problem which would have required over 1.4 million integer variables with previous models. The availability of optimal solutions was invaluable in the development of two heuristics designed to deal with the trade-offs of [16]. In an experimental analysis a previous heuristic produced results which averaged from 74 to 508 percent above optimum across six experimental conditions. The comparable new heuristic produced results which averaged from 3 to 8 percent above optimum for the same experimental conditions. The paper concludes by developing a framework to integrate the results of this research with the tour scheduling problem and by identifying several other areas for related research. 相似文献
56.
An integer linear programming model is presented for the scheduling of n products on m identical machines. The particular problem studied is one that occurs frequently in the fiberglass and textile industries. The model incorporates setup costs, lost production costs, and overtime costs. Due to the structure of the model, integer solutions can be obtained by explicitly restricting only a small number of the integer variables. This allows those responsible for scheduling to solve realistically sized problems in an efficient manner. Computational results are provided for a set of generated test problems. 相似文献
57.
Diversification gains in mean-variance efficiency derived from including real estate in financial asset portfolios are examined. Optimal financial and mixed-asset portfolios were generated by selecting from an investment universe including several distinct financial and real estate media. Deficiencies of previous studies were overcome by employing data with improved representativeness and comparability. The efficient mixed-asset portfolios dominated the efficient financial asset portfolios implying that purely financial asset diversification is inefficient. The optimal mixed-asset portfolio prescribed that approximately two-thirds of the investment wealth be allocated to real estate and one-third to the financial media. 相似文献
58.
Roger J. Gagnon 《决策科学》1988,19(2):453-471
Teaching an operations design course has major pedagogical challenges. (1) The design topics—output, process, facility, and work design—are necessarily taught sequentially, yet the decisions are integrative. (2) Instruction must be generic to service or product producers. (3) Discussing output design is difficult since students typically have had no exposure to the “product language” of engineering graphics. (4) No text is available which examines in sufficient depth all the operations design decisions. (5) Cases necessarily depict historical situations—process technologies and economic data—while operations managers must plan future directions for their productive systems. (6) While the commercial world contains fresh information and data, students are inexperienced in obtaining knowledge from the real world. (7) While the course presents an operations management perspective, students must recognize the information, data, and cooperation necessary from the other functional areas to successfully complete the operations design. To help overcome these seven pedagogical challenges, the students in the undergraduate and graduate operation design courses complete a comprehensive feasibility study for a new product or service and the entire productive system. 相似文献
59.
This paper addresses the problem of open order rescheduling in a job shop. Results are reported of experiments conducted in a simulation model of an 8-machine job shop. Four different order updating policies are examined. The due-date process is modeled to include several realistic features about the pattern of due-date variability. These features are parameterized and tested at several levels. Tardiness results indicate that open order rescheduling is beneficial only when allowances are loosely set. The results indicate that inventory performance is improved by order rescheduling, particularly in cases when due dates are revised to earlier times than originally forecast. 相似文献
60.
This paper analyses the importance of evaluating the various components of the programmes or actions carried out by education organisations. It highlights the need to assess the impact of the intervention on the organisation and consider how changes are consolidated over time in interaction with the context. We propose an impact evaluation model and as an example have chosen the implementation of Quality Management Systems in schools. The paper analyses the results obtained in 40 schools in three regions (Spanish Autonomous Communities) with varying levels of implementation. The results show overall impact on these education centres as the teachers and management teams of the centres perceive it. This impact is more evident in some of the dimensions considered in the study than in others. The results also confirm the differences between regional contexts. 相似文献