Integrated scheduling and inventory management of an oil products distribution system

The oil supply chain is facing new challenges due to emerging issues such as new alternative energy sources, oil sources scarcity, and price variability with high impact on demand and production and profit margins reduction. Additionally, the existence of large, complex and world wide spread businesses implies a complex system to be managed where distribution can be seen as one of the key areas that needs to be efficiently and effectively managed. Different types of distribution modes characterize the oil supply chain where the pipeline mode is one of the most complex to operate when having multiproduct characteristics. This paper addresses the planning of a generic oil derivatives transportation system characterized by a multiproduct pipeline that connects a single refinery to a storage tank farm. Two alternative mixed integer linear programming models (MILP) that aim to attain a set of planning objectives such as fulfilling costumers’ demands (which is mandatory) while minimizing the medium flow rate are developed. Additionally, final inventory levels are avoided to be excessively low. A real world scenario of a Portuguese company is used to validate and compare the two alternative MILP models developed in this paper.     

Integrated supply,production and distribution scheduling under disruption risks

This paper presents a bi-objective stochastic mixed integer programming approach for a joint selection of suppliers and scheduling of production and distribution in a multi-echelon supply chain subject to local and regional disruption risks. Two conflicting problem objectives are minimization of cost and maximization of service level. The three shipping methods are considered for distribution of products: batch shipping with a single shipment of different customer orders, batch shipping with multiple shipments of different customer orders and individual shipping of each customer order immediately after its completion. The stochastic combinatorial optimization problem is formulated as a time-indexed mixed integer program with the weighted-sum aggregation of the two objective functions. The supply portfolio is determined by binary selection and fractional allocation variables while time-indexed assignment variables determine the production and distribution schedules. The problem formulation incorporates supply–production, production–distribution and supply–distribution coordinating constraints to efficiently coordinate supply, production and distribution schedules. Numerical examples modelled after an electronics supply chain and computational results are presented and some managerial insights are reported. The findings indicate that for all shipping methods, the service-oriented supply portfolio is more diversified than the cost-oriented portfolio and the more cost-oriented decision-making, the more delayed the expected supply, production and distribution schedules.     

Optimal production,replenishment, delivery,routing and inventory management policies for products with perishable inventory

This paper presents a generalized production-inventory-routing model with perishable inventory. We analyze the optimal integrated decisions of when and how much to deliver and sell products with varying manufacturing periods. We discuss main inventory management policies to demonstrate the applicability of the model in real-world applications for production routing problems (PRPs) with perishable inventory. Furthermore, an exact branch-and-cut algorithm is developed and discussed. We introduce new families of logical, strengthened lot-sizing and lifted Miller–Tucker–Zemlin subtour elimination constraints for the PRP with perishable inventory. Finally, we test the performance of the algorithm. We also implement and compare 8 suboptimal delivery and selling priority policies with an optimized policy to develop managerial implications.     

A hybrid inventory management system responding to regular demand and surge demand

This paper proposes a hybrid policy for a stochastic inventory system facing regular demand and surge demand. The combination of two different demand patterns can be observed in many areas, such as healthcare inventory and humanitarian supply chain management. The surge demand has a lower arrival rate but higher demand volume per arrival. The solution approach proposed in this paper incorporates the level crossing method and mixed integer programming technique to optimize the hybrid inventory policy with both regular orders and emergency orders. The level crossing method is applied to obtain the equilibrium distributions of inventory levels under a given policy. The model is further transformed into a mixed integer program to identify an optimal hybrid policy. A sensitivity analysis is conducted to investigate the impact of parameters on the optimal inventory policy and minimum cost. Numerical results clearly show the benefit of using the proposed hybrid inventory model. The model and solution approach could help healthcare providers or humanitarian logistics providers in managing their emergency supplies in responding to surge demands.     

同步物流系统下准时化生产与配送调度问题研究

对于"加工-装配"行业而言,物流管理水平的高低直接决定了供应链绩效的好坏。本文以Supply Hub运作模式为背景,研究同步物流下装配系统中各节点的生产与配送调度问题。建立供应链各参与方的生产与配送模型,并通过规划求解得到供应商和制造商的最优生产周期、零部件的最优配送间隔以及零售商的最佳采购周期。最后,结合数值实验,对同步物流模式和传统物流模式下的供应链绩效进行了对比分析。研究结果表明:较之传统物流模式,基于同步化物流方式的装配系统总成本更低,这主要得益于库存成本的下降;由于采取拉动式的生产模式,因此同步物流系统下供应链中的生产和配送活动更加频繁;生产调整成本的增加提高了制造商的平均总成本,由此可见在同步物流系统下,供应商、制造商和零售商之间更需要相互协商和收益共享,从而实现多赢。     

Materials receiving capacity and inventory management

This paper analyses the optimal level of materials receiving capacity for a manufacturer that receives deliveries from many suppliers. Inventory levels and inventory carrying costs depend on the frequency of deliveries and thus, on the materials receiving capacity. An analytic model that captures the tradeoff between inventory costs and materials receiving costs is presented and discussed. The receiving cost is modeled as increasing in discrete jumps of varying sizes whenever materials receiving resources are added. Practical issues in implementing the model are highlighted and methods to reduce the marginal materials receiving cost are discussed. The paper also discusses connections to the JIT approach for production environments where materials receiving is heavily automated.     

Coordinated scheduling of production and delivery stages with stage-dependent inventory holding costs

This paper considers a problem of integrated decision-making for job scheduling and delivery batching wherein different inventory holding costs between production and delivery stages are allowed. In the problem, jobs are processed on a facility at a production stage and then delivered at the subsequent delivery stage by a capacitated vehicle. The objective is to find the coordinated schedule of production and delivery that minimizes the total cost of the associated WIP inventory, finished product inventory and delivery, where both the inventory costs are characterized in terms of the weighted flow-time and the delivery cost is proportional to the required number of delivery batches. It is proved that the problem is NP-hard in the strong sense. Thereupon, three heuristic algorithms are derived. Some restricted cases are also characterized as being solvable in polynomial time. Numerical experiments are conducted to evaluate the performance of the derived heuristic algorithms.     

Single cycle policies for the one-warehouse N-retailer inventory/distribution system

We address a multi-echelon inventory system with one-warehouse and N  -retailers. The demand at each retailer is assumed to be known and satisfied by the warehouse. Shortages are not allowed and lead times are negligible. Costs at each facility consist of a fixed charge per order and a holding cost. The goal is to determine single-cycle policies which minimize the average cost per unit time, that is, the sum of the average holding and setup costs per unit time at the retailers and at the warehouse. We propose a O(NlogN)$\mathrm{O}(N\log N)$ heuristic procedure to compute efficient single-cycle policies. This heuristic is compared with other approaches proposed by Schwarz, Graves and Schwarz and Muckstadt and Roundy. We carry out a computational study to test the effectiveness of the heuristic and to compare the performance of the different procedures. From the computational results, it is shown that the new heuristic provides, on average, better single-cycle policies than those given by the Muckstadt and Roundy method.     

行为库存管理研究综述及前景展望

库存管理是运作管理学科的研究重点之一.由于其在经济活动中具有重要的地位,库存管理在行为运作管理这一新兴学科中再次成为学术界关注的焦点.本文首先简述了行为运作管理的行为理论基础以及行为经济学的发展,根据行为运作管理的研究目标构建了行为库存管理的整体研究框架,进而在这一框架下对现有的行为库存管理相关研究进行系统综述,并进一...     

短生命周期产品的三种库存模型的比较

讨论短生命周期产品库存模型,考虑无形变质因素,并假定无形变质率与需求率成反比关系.在线性需求和常数生产率的条件下,假设,若需求率为1,则视作产品的市场生命周期结束.并且,在产品生命周期的前期不存在缺货的情况下,给出了短生命周期产品分别在理想状态、允许缺货以及价格折扣导致需求率变化等3种状态下的库存模型,最后在相同参数条件下对这3种模型进行比较,找出了单位时间内平均总成本最小的最优库存模型,厂商可以根据自身的情况选择合适的库存策略.     

A simple approach to an integrated single-vendor single-buyer inventory system with shortage

In this article, a simple approach with two basic inequalities (Cauchy–Schwarz inequality and arithmetic–geometric mean inequality) is used to solve the integrated single-vendor single-buyer inventory problem developed by Wu and Ouyang (Wu, K.-S. and Ouyang, L.-Y., 2003. An integrated single-vendor single-buyer inventory system with shortage derived algebraically. Production Planning & Control, 14 (6), 555–561). Without the method of completing perfect square, the proposed approach yields the global minimum of the integrated total cost per year more easily than the algebraic approach used by Wu and Ouyang (2003 Wu, K-S and Ouyang, L-Y. 2003. An integrated single-vendor single-buyer inventory system with shortage derived algebraically. Production Planning & Control, 14(6): 555–561. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]). In addition, for people without the background of calculus, it is more useful to determine the buyer's economic order quantity and the vendor's optimal number of deliveries.     

Integrated project operations and personnel scheduling with multiple labour classes

The main theme of this paper is improving project schedules by integrating the scheduling of project jobs and labour resources. An ILP model is presented of the integrated project operations and personnel scheduling problem with multiple labour categories. Traditionally, this problem is solved in two steps: first, operations are scheduled by solving the resource-constrained project scheduling problem; then, labour categories are scheduled by solving the personnel days-off scheduling problem. The proposed model combines the two stages into an integrated problem, which is solved in one step. Using 48 test problems, the two methods were compared in terms of total cost, labour cost and scheduling efficiency. The results clearly indicate that the integrated model outperforms the traditional two-step method.     

A heuristic for inventory management of slow-moving items

Abstract. The traditional approach in the study of inventory systems is to give more importance to items whose demands are either large or very difficult to forecast, discounting the importance of inventory items with small demand. The objective of this paper is to present a simple and practical heuristic to the slow-moving items problem. First we provide insight into previous work in this area and also give a brief outline of classical models in stochastic inventory theory. Then we present the proposed approach and detail the heuristic. We summarize the paper with an analysis of the simulation results and finish with the conclusions that are drawn from the results.     

Implementing an improved inventory control system in a small company: a case study

The paper presents the implementation of an improved inventory management control system in a small company. The project took place at Trojan Mine, a company involved in mining mineral resources. Firstly, a conceptual framework for the design of an inventory control management system is developed. Secondly, a very effective user-friendly inventory control tool for determining the category A items was developed using EXCEL spreadsheet; a tool that is an asset to the company since it can be used in future. Finally, key performance indicators were also established to give benchmark to operations. The improved inventory control management system developed is found to offer improvement to the performance of the company since capital tied up in overstocking items of high annual usage value is released.     

Analysis of a two-echelon inventory system with returns

Product take-back and recovery activities have grown in recent times as a consequence of stringent government regulations and increased customer awareness of environmental pollution. Inventory management in the context of product returns has drawn the attention of many researchers. However, the inherent complexity of the system with uncertain returns makes the analysis of the system extremely difficult. So far, the literature on this type of system is mostly limited to single echelons. The few papers available in literature on multi-echelon systems with returns base their analyses on simplified assumptions such as non-existence or non-relevance of set-up and holding costs at different levels. In this paper, we relax these assumptions and consider a two-echelon system with returns under more generalized conditions. We develop a deterministic model as well as a stochastic model under continuous review for the system, and provide numerical examples for illustration.     

Optimal regional distribution of petroleum products

An economic model is presented which applies linear programming to determine the most efficient distribution of petroleum products among industries and regions. The model maximizes employment while (1) ensuring a balanced economy via input-output relationships, (2) maintaining at least the minimum production of basic goods and services necessary to prevent abnormally high inflation which could be caused by shortages, (3) ensuring that regional economies do not become severely depressed due to energy unavailability for their industrial base, (4) making sure that the industry capacity in each region is not exceeded, and (5) allowing policy makers control over the balance of payments. The model utilizes an input-output framework at both the national and regional level and makes adjustments for regional differences by incorporating regional multipliers.     

Computer-aided formulation and optimal control of an integrated production system for competitive products

An integrated production, inventory and advertising system has been formulated based on control engineering principles. In this system, the customer's demand is satisfied from stock, which in turn is replenished from production facilities. But sales reflect the advertising effort, present as well as past. The past effort has been considered as a delay with an assumed delay period. The problem is formulated as a state and observation model. Out of this an augmented model of state and parameters is formed. The parameters describing the model are estimated from MAP discrete filter algorithm. It is shown that sales of product 1 or product 2 at (k + l)th period is effected by sales and advertising of product 1 or product 2 at the kth period, and also by sales and advertising of product 2 or product 1 at (k-θ)th period, where 6 is the delay.     

航空公司收入管理价格与舱位控制的统一分析

收入管理对于改善民航企业的经济效益、增强民航企业的竞争能力具有重大意义. 文章 运用随机过程理论和最大凹向包络原理,探讨航空公司客运收入管理研究中动态价格与舱位 控制的统一分析模型,即在任意订票时刻,决定航班的哪些舱位该开放,以什么价格开放,从而 实现单个航班的收入最大化. 文章指出,航空公司可通过三阶段方法来获取最优的动态价格与 舱位控制策略,即确定最优价格集、开放舱位数及最优价格. 最后给出了实例分析.     

局内动态配送车调度管理及其竞争策略

提出了动态物流配送车辆调度优化问题——配送车在一度量空间中进行服务,度量空间中的任何一节点可能在任何时间提出服务请求,要求配送车将该点处的货物运送到另一点,每一个服务请求都有一个服务期限,若在规定的时间内某一服务请求不能被满足则将被取消,在考虑装/卸货所用时间的情况下,决策者如何以局内方式确定调度策略,使配送车完成的服务请求数最多.针对该不确定性条件下的管理决策问题,给出了两种局内管理策略,并利用局内问题及竞争分析理论,给出了不同载重量下(Q=1和Q=∞)的两种策略的竞争比.