Optimal temperature control for quality of perishable foods

An optimal control model on temperature control for quality of perishable foods is presented in this paper, in which the quality deteriorates according to the first-order reaction and the temperature is defined as a control variable. The objective functional includes the loss induced by quality deterioration and the cost of temperature control. To minimise the total cost, the optimal temperature is obtained by solving the optimal control problem with Pontryagin's maximum principle. It is strictly proved that the isotherm condition of storage is optimal, which can be implemented conveniently in practice and improve the economic benefits of enterprises. A numerical example is given to illustrate the effectiveness of the proposed method.     

多品种联合补充库存策略综述

为了系统总结多品种物品环境下联合补充问题的研究历史和现状,在相关资料的基础上,对联合补充问题中确定型策略和随机型策略的模型和算法等问题进行了综述,分析了这些研究的特点与不足。对该领域的发展历史进行了简述。分别针对确定型策略的间接分组策略和随机型联合补充策略进行综述。讨论了策略形式间的比较问题,提出了联合补充库存理论研究的方向和重点。     

炼油厂综合库存管理优化问题研究

针对需求不确定条件下的炼油厂各级库存的综合优化问题,以在线连续调和技术为背景,建立了一个系统视角下的全厂库存管理的过程模型。求解时先进行多种产品需求的预测,根据预测值,采用实数编码的遗传算法,在局部优化控制器中以成品油非线性调和属性方程和混炼原油的线性调和属性方程为约束,计算出所需原油和各侧线产出率允许范围内的组分油流速及相应各级库存的优化值。最后,用广义预测控制算法,以局部优化结果为预先设定目标,考虑仿真模型实际运行过程中产生的模型失配、时变和干扰等不确定因素的影响,及时修改模型数据,在线滚动计算全厂库存仿真周期内的综合优化值。     

一类库存控制系统的稳定性分析

为了克服供应链系统存在的供货提前期、供货数量、价格等不确定以及市场环境多变的困难,保证供应链系统的库存稳定,建立了在一类改进的最大库存策略下一级库存控制系统的状态空间模型,针对不同的提前期,根据离散控制系统原理结合非线性系统的分析方法,给出了使系统稳定的订货策略参数的取值范围,并对之进行了仿真试验。结果表明,在最大库存策略下,系统的结构稳定性主要由订货决策的参数决定,与外部需求无关,而决策参数选取不当会使系统行为出现混沌等复杂现象。仿真显示,这些现象可使系统有较大的库存偏差,从而导致库存及相关费用的增加,表明稳定性对降低供应链系统的费用、提高其性能有重要意义。     

A replenishment policy for perishable products with non-linear holding cost under stochastic supply lead time

The development and application of inventory models for deteriorating items is one of the main concerns of subject matter experts. The inventory models developed in this field have focused mainly on supply chains under the assumption of constant lead time. In this study, we develop an inventory model for a main class of deteriorating items, namely perishable products, under stochastic lead time assumption. The inventory system is modeled as a continuous review system (r, Q). Demand rate per unit time is assumed to be constant over an infinite planning horizon and the shortages could be backordered completely. For modeling the deterioration process, a non-linear holding cost is considered. Taking into account the stochastic lead time as well as a non-linear holding cost makes the mathematical model more complicated. We customize the proposed model for a uniform distribution function that could be tractable to solve optimally by means of an exact approach. We then solve an example taken from the literature to demonstrate the applicability and effectiveness of the proposed model. Finally, by doing several sensitivity analyses for the key parameters of the model, some managerial insights are proposed.     

Adaptive inventory control models for supply chain management

Uncertainties inherent in customer demands make it difficult for supply chains to achieve just-in-time inventory replenishment, resulting in loosing sales opportunities or keeping excessive chain-wide inventories. In this paper, we propose two adaptive inventory-control models for a supply chain consisting of one supplier and multiple retailers. The one is a centralized model and the other is a decentralized model. The objective of the two models is to satisfy a target service level predefined for each retailer. The inventory-control parameters of the supplier and retailers are safety lead time and safety stocks, respectively. Unlike most extant inventory-control approaches, modelling the uncertainty of customer demand as a statistical distribution is not a prerequisite in the two models. Instead, using a reinforcement learning technique called action-value method, the control parameters are designed to adaptively change as customer-demand patterns changes. A simulation-based experiment was performed to compare the performance of the two inventory-control models.     

Optimal replenishment policies for deteriorating control wafers inventory

This paper considers a control wafers replenishment problem with inventory deterioration. In the process, control wafers begin to deteriorate after the pre-disposition. The objective of this research is to minimize the total cost of control wafers, where the cost includes ordering cost, holding cost and purchase cost. We first formulate the control wafers inventory problem as a dynamic programming model. We then transform the control wafers’ inventory problem into the mixed 0–1 linear programming model. An illustrative example with four cases is used to illustrate the practicality of these models, and sensitivity analysis is applied to understand the impact of parameters to these models. The results demonstrate that the proposed mixed 0–1 linear programming model is an effective tool for determining the replenishment of control wafers for multi-periods.     

Joint optimization of spare parts inventory and maintenance policies using genetic algorithms

In general, the maintenance and spare parts inventory policies are treated either separately or sequentially in industry. However, since the stock level of spare parts is often dependent on the maintenance policies, it is a better practice to deal with these problems simultaneously. In this study, a simulation optimization approach using genetic algorithms (GAs) has been proposed for the joint optimization of preventive maintenance (PM) and spare provisioning policies of a manufacturing system operating in the automotive sector. A factorial experiment was carried out to identify the best values for the GA parameters, including the probabilities of crossover and mutation, the population size, and the number of generations. The computational experiments showed that the parameter settings given by the proposed approach achieves a significant cost reduction while increasing the throughput of the manufacturing system.     

石化装置备件储备对通用机械的要求

主要介绍了相同装置事故件储备采取的几种形式，指出了它们的优缺点。并阐述随着信息系统的发展和大型石化装备国产化率的提高，实施供应商管理库存是可行的。     

多资源概率约束下多品种变质产品库存优化

为降低多产品多资源概率约束下易腐产品库存系统的长期平均成本,首先得出了多品种多资源概率约束下易腐产品库存系统的几个有用的性质和定理;然后基于这些定理,给出了一种搜索多品种多资源概率约束下库存系统最优订货策略的多项式算法,在算法中运用系统动力学仿真方法代替传统算法的复杂过程,并证明了多品种多资源概率约束库存系统优化问题等价于一个单资源多品种概率约束库存系统优化问题;最后给出了一个计算实例,表明多资源约束下概率约束对线性约束的优越性和新算法的可行性.     

A service level model for the control wafers safety inventory problem

This paper considers the control wafers safety inventory problem (CWSIP) in the wafer fabrication photolithography area. The objective is to minimize the total cost of control wafers, where the cost includes new wafers cost, re-entrant cost and holding cost while maintaining the same level of production throughput. For the problem under pulling control production environment, a nonlinear programming model is presented to set safety inventory levels so as to minimize total cost of control wafers. A numerical example is given to illustrate the practicality of the model. The results demonstrate that the proposed model is an effective tool for determining the service level of safety inventory of control wafers for each grade.     

可拆分ATO系统的最优、渐进最优和次优库存控制策略

求解面向订单装配(ATO)系统最优库存控制策略是库存控制领域内的重要问题,因为结构的复杂性,目前只在一些很特殊的情形下有明确的结论.针对一类范围广泛的ATO系统,求解其在不同条件下的最优和渐进最优库存控制策略,并将思路推广到具有一般物料清单结构的ATO系统中.以在ATO系统库存控制研究中比较常用的W型和M型系统为例进行...     

A fuzzy reinforcement learning algorithm for inventory control in supply chains

In the real world, applications with very large state and action spaces and unknown state transition probability, classical reinforcement learning algorithms usually show poor performance. One way to address the performance problem is to approximate the policy or value function. Fuzzy rule-based systems are amongst the well-known function approximators. This paper presents a Flexible Fuzzy Reinforcement Learning algorithm, in which value function is approximated by a fuzzy rule-based system. The proposed algorithm has a separate module for tuning the structure of fuzzy rules. Moreover, the parameters of the system are tuned during the learning phase. Next, the proposed algorithm is applied to the problem of inventory control in supply chains. In this problem, a fuzzy agent (supplier) should determine the amount of orders for each retailer based on their utility for supplier, by considering its limited supply capacity. Finally, a simulation is performed to show the capability of the proposed algorithm.     

A service level model for the control wafers safety inventory problem

This paper considers the control wafers safety inventory problem (CWSIP) in the wafer fabrication photolithography area. The objective is to minimize the total cost of control wafers, where the cost includes new wafers cost, re-entrant cost and holding cost while maintaining the same level of production throughput. For the problem under pulling control production environment, a nonlinear programming model is presented to set safety inventory levels so as to minimize total cost of control wafers. A numerical example is given to illustrate the practicality of the model. The results demonstrate that the proposed model is an effective tool for determining the service level of safety inventory of control wafers for each grade.     

A system for quality control of mineral-processing products

In this paper, consideration is given to a quality control system for mineral-processing products that provides a concentrate of optimal quality in a required quantity with minimum acceptable losses of the useful component. Operation of a new type of a specialized teslameter adapted to the conditions of an ore-mining enterprise is considered. Teslameters in an operable state are used in the quality control system for mineral-processing products of dry and liquid magnetic separation at the processing mill of OAO Vanadii and dozens of other enterprises in Russia.     

机加产品库存管理系统开发特点与EXCEL的应用

文章介绍了机加产品库存管理系统开发的功能特点和对一些常用模块的关键技术的处理。系统的开发采用了模块化程序设计，既便于系统功能模块的组合，又便于未参与开发的技术人员的补充、维护，同时结合EXCEL强大的统计、制表功能，使系统的二次应用更加灵活，实用。     

Optimal control of inventory accumulation in selective assembly processes

Assembly is a type of production process in which a number of components are combined to yield a final product. Although the concept of interchangeable parts has long been known as the fundamental principle of assembly processes, randomly picking some bulked components with dimensions varying in predefined tolerances may not be a valid approach to obtain special final products with considerably tighter tolerances. Therefore, each of the components needs to be measured and classified into dimensional groups in advance so that quality products can be obtained by matching components from suitable groups. This assembly scheme is called as “selective assembly.” In this work, we consider an assembly case with a pair of components in which one is manufactured on a given number of parallel processes whose settings can be changed to affect the dimensional distribution of the yield while the other component with a slightly bigger tolerance is manufactured on a single process with constant settings. In order to minimize the number of components which could not have been matched with their counterparts, we develop a nonlinear mathematical model to determine the optimal machine settings corresponding to the nominal mean of the component dimension which follows a normal distribution when it is machined. The solution of the mathematical model not only provides the individual settings for the parallel processes producing the same type of component but also the optimal batch sizes at each trial. We have finally used a simulation model of the whole production system, in order to prove that the solution of the mathematical model is able to provide the machine settings which minimize the number of unmatched parts at each trial.     

以瓶颈资源为基础的生产与库存控制系统的构建

当前较为成熟的生产与库存控制系统中,MRP（Ⅱ）强调生产能力的平衡与利用,而忽视了物流效率;JIT重视物流效率,而以生产能力的闲置为代价。本文依据约束管理的理论,构建以瓶颈资源为基础的生产与库存控制系统,使得在有效利用生产资源的同时,提高物流的效率。     

分销环境下代销库存资源实时控制问题的建模

为了实现对代销库存资源的实时控制,首先对代销业务进行了分析,基于逻辑库存和单据财务确认的观点,建立了代销库存资源的立体模型;然后根据该立体模型设定了表征代销库存资源的三个库存状态量,并根据代销实际设定了代销库存控制的两个原则,进而建立了代销库存实时控制的数学模型;最后给出了该数学模型在代销实例中的应用,并结合某企业分销案例证明了模型的正确性和可行性。