Combining an alternative multi-delivery policy into economic production lot size problem with partial rework

This paper combines an alternative multi-delivery policy into an imperfect economic production quantity (EPQ) model with partial rework, with the purpose of reducing supplier’s stock holding cost. We extend the problem examined by Chiu et al. [Chiu, Y.-S. P, Chiu, S. W., Li, C.-Y., & Ting, C.-K. (2009). Incorporating multi-delivery policy and quality assurance into economic production lot size problem. Journal of Scientific and Industrial Research, 68(6), 505-512] by considering an n + 1 delivery policy in lieu of n multi-delivery plan for the specific EPQ model with partial rework. Under such a policy, an initial delivery of perfect (finished) items is distributed to customer for satisfying product demand during manufacturer’s regular production time and rework time. At the end of rework, fixed quantity n installments of the finished products are delivered to customer at a fixed interval of time. As a result, a closed-form optimal replenishment batch size solution to the problem is obtained. A numerical example with analysis and comparison is provided to show practical usage of the proposed model and demonstrate its significant savings in stock holding cost.     

基于工作流管理的连续补货系统的设计与实现

VMI是供应链管理中一种先进的库存管理策略，连续补货系统则是VMI的主要支撑技术之一。介绍了一个连续补货系统的具体设计与实现，并且介绍了其中利用到的主要技术——工作流管理。     

器材动态存贮模型研究

器材随机库存管理控制策略及其有关因素包括:订货费用、存贮费用、单位时间内备件的平均费用、不缺备件概率及决策模型.在保证随机性需求并满足一定器材保障率的条件下,以系统所需费用最小为目标,建立其动态存贮模型.同时假设备件消耗量服从泊松分布、定货延迟时间为常数、并考虑单一品种的存贮模型等.仿真表明,该模型可实现优化管理,降低费用.     

A heuristic to manage perishable inventory with batch ordering,positive lead-times,and time-varying demand

So far the literature on inventory control for perishable products has mainly focused on (near-) optimal replenishment policies for a stylized environment, assuming no lead-time, no lot-sizing, stationary demand, a first in first out withdrawal policy and/or product life time equal to two periods. This literature has given fundamental insight in the behavior and the complexity of inventory systems for perishable products. In practice, many grocery retailers have recently automated the inventory replenishment for non-perishable products. They recognize they may need a different replenishment logic for perishable products, which takes into account e.g. the age of the inventory in the system. Due to new information technologies like RFID, it now also becomes more economically feasible to register this type of information. This paper suggests a replenishment policy for perishable products which takes into account the age of inventories and which requires only very simple calculations. It will be shown that in an environment, which contains important features of the real-life retail environment, this new policy leads to substantial cost reductions compared with a base policy that does not take into account the age of inventories.     

A replenishment decision involving partial postponement

This paper was motivated by a practical situation in the fast food industry. We consider the choice of the order quantities for a group of end items, each facing random demand in a period of interest. There is the additional option of having a limited number of units of unfinished stock that can be customized to produce any of the end items once demands materialize. Solution procedures are developed, the results of a large set of examples are presented, and a number of managerial insights are provided.This complete issue was revised and published online in November 2004. The previous version contained a false date. Correspondence to: Stefan MinnerThe authors wish to thank Y. Segal, D. Borotsik and J. Bermudez who worked on the original student project. Thanks are also extended to two anonymous referees for their constructive comments. The research leading to this paper was supported by the Natural Sciences and Engineering Research Council of Canada under Grant A1485 and by the Carma Chair at the University of Calgary. The research was carried out while the second author was a postdoctoral assistant at the University of Calgary and part of the work was completed while the first author was on sabbatical leave in the Department of Mathematics at the Swiss Federal Institute of Technology in Lausanne.     

A simulation approach for production-distribution planning with consideration given to replenishment policies

One of the key issues in the current research area of supply-chain networks is a production-distribution plan taking into account a multi-facility, multi-product, and multi-period problem. The purpose of this study is to determine the optimal production-distribution plan in a network with a bill of material (BOM). First, we present a mathematical model to determine the capacities of facilities including the manufacturing plant and distribution center (DC). Next, with consideration given to the uncertainty and complexity of solving such a network, we apply a simulation approach. The simulation model is developed to analyze a production-distribution plan that satisfies customer demands for higher customer satisfaction and lower total relevant costs, while taking replenishment policies into consideration . The computational results for a simple example of the network represent the developed mathematical and simulation model and show the prospects of using this approach. The multi-factor analysis of variance (ANOVA) test results clearly indicate that all three factors have a significant effect on the grouping output.     

Available technologies to replenish soil fertility in East Africa

Low inherent soil fertility in the highly weathered and leached soils largely accounts for low and unsustained crop yields in most African countries. But in particular, the major nutrients, nitrogen (N) and phosphorus (P), are commonly deficient in these soils. This scenario of nutrient depletion is reflected in food deficits and hence the food aid received continuously, specifically in sub-Saharan Africa. Undoubtedly, substantial efforts have been made in the continent to replenish the fertility of degraded soils in attempts to raise crop yields, towards self-sufficiency and export. Such efforts consist of applications of both organic and inorganic resources to improve the nutrient status of soils and enhanced nutrient uptake by crops, provided that soil moisture is adequate. Overall, positive crop responses to these materials have been obtained. Thus in the East African region, maize (staple) yields have been raised in one growing season from below 0.5 t/ha without nutrient inputs, to 3–5 t/ha from various nutrient amendments at the smallhold farm level. However, in spite of the positive crop responses to nutrient inputs, farmers are generally slow to adopt the soil fertility management technologies. In this paper we review the impact of some technologies, focussing the use of nutrient resources of different characteristics (qualities) in relation to improved crop yields, with an overall goal to enhance technology adoption. Thus, inorganic resources or fertilizers often give immediate crop responses, but their use or adoption is rather restricted to large-scale farmers who can afford to buy these materials. Organic resources, which include crop residues, water hyacinth and agroforestry shrubs and trees, are widely distributed, but they are generally of low quality, reflecting the need to apply large quantities to meet crop nutrient demands. Moreover, most organics will add N mainly to soils. On the other hand, phosphate rocks of varying reactivity are found widely in Africa and are refined elsewhere to supply soluble P sources. The recently developed soil fertility management options in East Africa have targeted the efficient use of N and P by crops and the integrated nutrient management approach. Some people have also felt that the repackaging of inputs in small, affordable quantities, such as the PREP-PAC described in this paper, may be an avenue to attract smallhold farmers to use nutrient inputs. Nonetheless, crop responses to nutrient inputs vary widely within and across agroecozones (AEZs), suggesting specificity in recommendations. We highlight this observation in a case study whereby eight soil fertility management options, developed independently, are being tested side-by-side at on-farm level. Farmers will be empowered to identify technologies from their own choices that are agronomically effective and economically friendly. This approach of technology testing and subsequent adoption is recommended for technology development in future.     

Mathematical modeling for solving manufacturing run time problem with defective rate and random machine breakdown

This paper employs mathematical modeling for solving manufacturing run time problem with random defective rate and stochastic machine breakdown. In real life manufacturing systems, generation of nonconforming items and unexpected breakdown of production equipment are inevitable. For the purpose of addressing these practical issues, this paper studies a system that may produce defective items randomly and it is also subject to a random equipment failure. A no resumption inventory control policy is adopted when breakdown occurs. Under such a policy, the interrupted lot is aborted and malfunction machine is immediately under repair. A new lot will be started only when all on-hand inventory are depleted. Modeling and numerical analyses are used to establish the solution procedure for such a problem. As a result, the optimal manufacturing run time that minimizes the long-run average production–inventory cost is derived. A numerical example is provided to show how the solution procedure works as well as the usages of research results.     

Determination of replenishment dates for restricted-storage,static demand,cyclic replenishment schedule

This study focuses on scheduling replenishment lots of multiple products in a warehouse with restricted storage space where the replenishment cycle time of each product is given and is an integer multiple of some basic period. Assuming that the warehouse replenishes at the beginning of some basic period, this study proposes a new heuristic that utilizes two simple procedures to generate a replenishment schedule that minimizes the maximum warehouse-space requirement. By including a re-optimization mechanism and a Boltzmann function, the proposed heuristic obtains solutions very close to the global optimum within a reasonable run time. Using randomly generated instances, this study shows that the proposed heuristic significantly outperforms a previously published heuristic.     

Alternative approach for solving replenishment lot size problem with discontinuous issuing policy and rework

Conventional approach for solving the replenishment lot size problem is by using differential calculus on the long-run average production cost function with the need to prove optimality first. Recent studies proposed an algebraic approach to the solution of classic economic order quantity (EOQ) and the economic production quantity (EPQ) models without reference to the use of derivatives. This paper extends it to the solution of a specific EPQ model as was examined by Chiu et al. [Chiu, S. W, Chen, K. -K, Lin, H. -D. Numerical method for determination of the optimal lot size for amanufacturing system with discontinuous issuing policy and rework. International Journal forNumerical Methods in Biomedical Engineering. doi: 10.1002/cnm.1369. (in Press; Published online March-10-2010).]. As a result, optimal replenishment lot size and a simplified optimal production-inventory cost formula for such a particular EPQ model can be derived without derivatives. This alternative approach may enable practitioners who with little knowledge of calculus to understand the realistic production systems with ease.