A heuristic algorithm for capacity sensitive requirements planning

Available lot sizing rules for use in MRP (Material Requirements Planning) systems ignore capacity limitations at various work centers when sizing future orders. Planned order releases are instead determined by the tradeoff only between the item's set up and inventory holding costs. This limitation can cause unanticipated overloads and underloads at the various work centers, along with higher inventories, poorer customer service, and excessive overtime.This research explores one way to make MRP systems more sensitive to capacity limitations at the time of each regeneration run. A relatively simple heuristic algorithm is designed for this purpose. The procedure is applied to those planned order releases that standard MRP logic identifies as mature for release. The lot sizes for a small percentage of these items are increased or decreased so as to have the greatest impact in smoothing capacity requirements at the various work centers in the system. This algorithm for better integrating material requirements plans and capacity requirements plans is tested with a large scale simulator in a variety of manufacturing environments. This simulator has subsequently undergone extensive tests, including its successful validation with actual data at a large plant of major corporations.Simulation results show that the algorithm's modest extension to MRP logic significantly helps overall performance, particularly with customer service. For a wide range of test environments, past due orders were reduced by more than 30% when the algorithm was used. Inventory levels and capacity problems also improved. Not surprisingly, the algorithm helps the most (compared to not using it at all as an MRP enhancement) in environments in which short-term bottlenecks are most severe. Large lot sizes and tight shop capacities are characteristic of these environments. The algorithm works the best when forecast errors are not excessive and the master schedule is not too “nervous.”This proposed procedure is but one step toward making MRP more capacity sensitive. The widely heralded concept of “closed-loop” MRP means that inventory analysts must change or “fix up” parts of the computer generated material requirements plan. What has been missing is a tool for identifying the unrealistic parts of the plan. Our algorithm helps formalize this identification process and singles out a few planned order releases each week. This information comes to the analyst's attention as part of the usual action notices. These pointers to capacity problems go well beyond capacity requirements planning (CRP) and would be impossible without computer assistance.Our study produced two other findings. First, short-term bottlenecks occur even when the master production schedule is leveled. The culprits are the lot sizing choices for items at lower levels in the bills of material. “Rough-cut” capacity planning, such as resource requirements planning, therefore is not a sufficient tool for leveling capacity requirements. It must be supplemented by a way to smooth bottlenecks otherwise caused by shop orders for intermediate items. Second, the disruptive effect of large lot sizes is apparent, both in terms of higher inventories and worse customer service. Large lot sizes not only inflate inventories, but paradoxically hurt customer service because they create more capacity bottlenecks. The only reason why management should prefer large lot sizes is if set-up times are substantial and cannot be efficiently reduced. This finding is very much in step with the current interest in just-in-time (JIT) systems.     

A reformulation of the aggregate planning problem

This article proposes a reformulation of the aggregate planning problem which more closely agrees with situations frequently encountered in practice. The proposed reformulation assumes that a firm's production planners want to determine the expected service and inventory levels for a given production profile in the face of uncertain seasonal demand. By using several different production profiles that are each consistent with the firm's staffing, subcontracting, and overtime policies, it is possible to pick the profile that best meets the firm's preferences for service level and inventory turns. Actually, the trade-offs between inventory and service levels are examined so that an informed choice can be made by all of those concerned.One of the advantages of the proposed model is that communications can be established among production, marketing, and finance managers who often have conflicting goals. Also, levels for inventory turns, service, and production can be set that are consistent with each other. Furthermore, several alternative production profiles can be examined in a relatively short time through the use of the simulation model proposed.An application of the model to the Wagner Spray Tech Company, a producer of painting equipment, is presented. In this particular case, where forecasting errors are quite high, some of the potential uses of the model are presented. Also, reasons are given why this particular reformulation of the aggregate planning problem was found to be useful.     

基于供应链规划的生产安排仿真决策

以某电缆生产企业D公司为例,研究其基于供应链整体规划的理念,根据对现实生产中存在的相关生产因素不确定的情况进行数学描述,编写出仿真算法,并用EXCEL构建其数学仿真模型,进而在分析仿真数据的基础上得到合理的仿真结果,并阐述该模型的实用价值和推广意义,为生产安排决策提供参考依据。     

Towards right-shoring: a framework for off-and re-shoring decision making

Location decisions are crucial for manufacturing plants. While current research mainly stresses the cost considerations of location decisions, this research focusses on a more comprehensive decision-making process. Based on analyzing the motivations for off-and re-shoring, we present a decision-making framework which will help companies to ‘right-shore’. Through a multiple case study approach in the aeronautics industry, an industry known for its technical complexity and innovative nature, we will validate and broaden our initial decision-making framework based on literature. While analyzing this framework, it became apparent that the main motivation for offshoring in the aeronautic industry is far from being restricted to cost-cutting considerations. More specific, companies in this industry are willing to develop sustainable commercial partnerships in emerging countries to benefit from new capacities and resources. In the same vein, re-shoring decisions are grounded on long-term perspectives and are carefully balanced. While providing a comprehensive framework for offshoring and re-shoring decisions, our framework enables companies to make better informed decisions for choosing the right location for their plants.     

A framework for strategic decision making and performance among Chinese managers

This study develops an integrative model that explains the relationship between Chinese culture, managers' strategic decision making (SDM) processes, and organizational performance. For the study 1200 participants were randomly selected from a business club's company register, resulting in 204 valid respondents. The results highlighted two significant SDM paths used by managers: (1) the cognitive-speed path, which suggested that Overseas Chinese managers (the Chinese who live outside of Mainland China) focus on the big picture, draw analogies from past experiences, and use extensive networks to reduce the duration of the decision process; and (2) the social-political path which shows that Overseas Chinese managers focus on collective interests, strive to maintain harmony, and to save face while using a collaborative style to handle conflict; this approach reduces dysfunctional political behavior, while reinforcing the decision team's focus on common goals. From these results we concluded that a speedier decision making process (based on intuition, experience, and networks) accompanied by the appropriate use of political behavior (that created harmony, through a hierarchical structure, during conflict management) in the Overseas Chinese managers' strategic decision making process could positively influence organizational performance.     

PDF versus LP: An empirical aggregate planning comparison

Production Decision Framework (PDF) is a recently introduced heuristic method for solving the aggregate planning problem. The algorithm was developed and tested over a wide range of deterministic demand patterns and cost parameters. The decision by Wayn-Tex Inc., to adopt the methodology provided a real world opportunity to evaluate the performance of PDF under uncertainty over a one year's operating period.This paper concentrated on a study of (1) the effectiveness of the model in selecting a suitable rolling planning horizon, and (2) the performance of PDF as compared to a linear program solution using the same length horizon. The monthly sales forecast used in the study, developed by the sales department, took into consideration trend, seasonality, and known market conditions. The results were gratifying. Management has indicated their desire to continue using PDF as a guide in the production planning process through the use of the computerized program available.     

A heuristic method for parameter selection in LS-SVM: Application to time series prediction

Least Squares Support Vector Machines (LS-SVM) are the state of the art in kernel methods for regression. These models have been successfully applied for time series modelling and prediction. A critical issue for the performance of these models is the choice of the kernel parameters and the hyperparameters which define the function to be minimized. In this paper a heuristic method for setting both the σ parameter of the Gaussian kernel and the regularization hyperparameter based on information extracted from the time series to be modelled is presented and evaluated.     

An aggregate quantity framework for measuring and decomposing productivity change

Total factor productivity (TFP) can be defined as the ratio of an aggregate output to an aggregate input. This definition naturally leads to TFP indexes that can be expressed as the ratio of an output quantity index to an input quantity index. If the aggregator functions satisfy certain regularity properties then these TFP indexes are said to be multiplicatively complete. This paper formally defines what is meant by completeness and reveals that (1) the class of multiplicatively complete TFP indexes includes Laspeyres, Paasche, Fisher, T?rnqvist and Hicks-Moorsteen indexes, (2) the popular Malmquist TFP index of Caves et al. (Econometrica 50(6):1393?C1414, 1982a) is incomplete, implying it cannot always be interpreted as a measure of productivity change, (3) all multiplicatively complete TFP indexes can be exhaustively decomposed into measures of technical change and efficiency change, and (4) the efficiency change component can be further decomposed into measures of technical, mix and scale efficiency change. Artificial data are used to illustrate the decomposition of Hicks-Moorsteen and Fisher TFP indexes.     

采用价值工程方法优选城市交通规划方案

本文介绍了温哥华市的城市交通规划方案的评价决策实例,揭示其中存在的问题,并运用价值工程方法对该市的城市交通规划备选方案进行优劣排序。事实证明,价值工程方法是进行方案选优的简便有效的方法之一。     

采用价值工程方法优选城市交通规划方案

本文介绍了温哥华市的城市交通规划方案的评价决策实例,揭示其中存在的问题,并运用价值工程方法对该市的城市交通规划备选方案进行优劣排序.事实证明,价值工程方法是进行方案选优的简便有效的方法之一.     

荷兰工业区发展中的多准则分析框架

在全面调查分析荷兰工业区发展决策所应用的辅助工具——多准则分析框架的应用背景、技术路线及相关实践的基础上,认为这一框架对我国工业区的可持续发展具有借鉴意义。研究结果表明多准则分析框架通过关注保护生物多样性和提升工业区的经济、社会与环境价值扩展了当前工业区的可持续发展理念,有助于明确工业区土地利用的设计导向与管理措施,且具有结构明晰、导向鲜明、易推广和适用性强的特点。在当前我国土地资源紧缺与工业区可持续发展的严峻形势下,荷兰工业区发展决策中应用的多准则分析框架作为一种土地规划决策的辅助工具应被积极引进并推广。     

Cross-temporal forecast reconciliation: Optimal combination method and heuristic alternatives

Forecast reconciliation is a post-forecasting process aimed to improve the quality of the base forecasts for a system of hierarchical/grouped time series. Cross-sectional and temporal hierarchies have been considered in the literature, but generally, these two features have not been fully considered together. The paper presents two new results by adopting a notation that simultaneously deals with both forecast reconciliation dimensions. (i) The closed-form expression of the optimal (in the least squares sense) point forecasts fulfilling both contemporaneous and temporal constraints. (ii) An iterative procedure that produces cross-temporally reconciled forecasts by alternating forecast reconciliation along one single dimension (either cross-sectional or temporal) at each iteration step. The feasibility of the proposed procedures, along with first evaluations of their performance as compared to the most performing ‘single dimension’ (either cross-sectional or temporal) forecast reconciliation procedures, is studied through a forecasting experiment on the 95 quarterly time series of the Australian Gross Domestic Product from Income and Expenditure sides. For this dataset, the new procedures, in addition to providing fully coherent forecasts in both cross-sectional and temporal dimensions, improve the forecast accuracy of the state-of-the-art point forecast reconciliation techniques.     

A multi-purpose heuristic for communications satellite synthesis

Three satellite system synthesis problems—the satellite location problem, the signal protection problem, and the arc allotment problem—are described and formulated. In each of these problems, satellite administrations are to be allotted some portion of the geostationary orbit for the purpose of deploying their satellites, subject to angle of elevation and electromagnetic interference constraints. A simple heuristic procedure is suggested as a means for solving these three problems. Sufficient conditions for the successful application of the heuristic and solution-value bounds for each problem are presented. The heuristic is applied to each problem for a six-satellite example. Additionally, computational results are presented for an example with 183 satellites worldwide.     

高山峡谷区域景观生态规划模式研究方法

本文结合福贡县的生态系统探索高山峡谷区域景观生态规划的研究方法,以该区域生态系统的社会、经济和生态效益整体优化为目标,将景观生态学中的格局分析和空间模型方法与遥感技术(RS)、地理信息系统(DIS)结合,在景观分析、综合以及评价的基础上,建立区域景观优化利用的空间结构和功能,并提出相应的高山峡谷区域景观生态规划模式的研究方法.     

A multi-criteria decision making method for sustainable development of Naples port city-area

Quality & Quantity - The port of Naples is a city’s important economic resource, and represents a great opportunity for the development of tourism and improvement of businesses. We...     

简易快速的物流中心规划方法

本文提供了一种简易快速的物流中心规划方法.应用该方法,企业不需要太多专业知识,在短时间内即可完成物流中心的初步规划方案.     

达成一致和复杂自适应系统(续)--一种评价协作性规划的框架

五、复杂性科学 在物理学、生物学、数学和计算机科学中出现了一系列关于自组织、复杂系统的适应性本质的观点.这些观点不仅提供了对正在形成的网络社会的理解方法,而且提供了在达成共识中走出这些佯谬的途径.复杂性科学为我们的评价框架提供了灵感,因为它提供了能够同时评价有形和无形结果的方法.复杂性科学提供了概念的工具,使我们关注达成一致过程中的反馈和学习,它帮助我们理解改革和第二、第三位的作用是如何产生的.这些观点暗示达成共识在漫长的过程中的最大贡献将是:在如此频繁变幻的世界上,帮助社区和组织在实施和创造方面提高到新的水准.     

A heuristic rule for routing customers to parallel servers

A practically important problem is the assignment of stochastically arriving service requests to one of several parallel service groups so as to minimize the long-run average sojourn time per service request. An exact solution of this multi-dimensional optimization problem is computationally infeasible. A simple heuristic solution method yielding a good suboptimal rule will be given for the case of server groups with different and generally distributed service times. This solution method is based on a decomposition approach and first principles from Markov decision theory. The main idea of the heuristic method is to apply one step of policy improvement to the best Bernoulli-splitting rule.