The Periodic System of Chemical Elements. An Essay Review

J. W. van Spronsen, The Periodic System of Chemical Elements. A History of the First Hundred Years , Amsterdam (Elsevier), 1969, pp. XV + 368, Dfl. 50.     

非线性挤压油膜阻尼器柔性转子系统中的周期分叉特性

利用轴心轨迹、Ｐｏｉｎｃａｒｅ映射及分叉图等方法，详细地研究了支承在非线性挤压油膜阻尼器上的柔性转子系统中的周期分叉特性。     

具有自消化引擎的库存模型初探

具有自消化引擎的库存模型是与传统库存完全不同的库存模型.自消化引擎库存是指库存系统具有内循环需求引擎、库存物资具有自修复能力以及寿命递减等生命库存的特征,库存的保有量与物资的用途、使用方法、技术定义、管理模式以及外部变化或扰动等密切相关.本文提出自消化引擎这一概念来描述这类库存的模型特征,并对这类库存模型的相关特征进行了讨论和初步研究.     

面向柔性制造环境的智能集成诊断系统

介绍了一个面向柔性制造环境的智能集成诊断系统的结构与功能，并研究了相关的诊断信息集成，诊断模型和诊断推理等关键技术，最后给出了研究的结论。     

Two Periodic Review inventory Models with Backorders and Stuttering Poisson Demands

Two periodic review inventory models, (R, T) and (nQ, r, T), are analyzed for the situation where demands are characterized by either a Poisson or stuttering Poisson process. In each model, backorders are allowed and the procurement lead time is considered to be a constant. Average annual cost equations are developed for each model and solution techniques presented, so that minimum average annual costs can be determined. A numerical example is also presented. It is shown for large times between reviews that the (R, T) and (nQ, r, T) models are essentially equivalent.     

Continuous Review Perishable Inventory Systems: Models and Heuristics

We consider continuous review perishable inventory models with renewal batch demands. Assuming zero lead time, we construct an embedded Markov chain. With a probabilistic approach, we derive a closed-form long run average cost function under the (s, S) replenishment policy. Numerical analysis is then used to identify the properties of the cost function and to demonstrate the impacts of changing batch sizes and other system parameters. Based on these results, a heuristic approach to handle problems with positive lead times is proposed. The performance of the heuristics against simulation results demonstrates its effectiveness and accuracy     

An Algorithm for the Computer Control of a Flexible Manufacturing System

The problem of production management for an automated manufacturing system is described. The system consists of machines that can perform a variety of tasks on a family of parts. The machines are unreliable, and the main difficulty the control system faces is to meet production requirements while the machines fail and are repaired at random times. A multilevel hierarchical control algorithm is proposed which involves a stochastic optimal control problem at the first level. Optimal production policies are characterized, and a computational scheme is described.     

Scheduling in a Multistage Production System with Set-up and Inventory Costs

This paper considers a multistage production system with constant known demand rate across an infinite horizon. A unit of product passes through the stages sequentially, so each stage draws from the in-process inventory of the previous stage. Each stage of the process is assumed to produce at a fixed, known, finite rate greater than the demand rate, so that it must be shut down and restarted periodically. Different stages may produce at different rates. This paper describes a procedure to find the start-up and shut-down schedule of each production stage which minimizes the sum of inventory costs and set-up costs for the system. This problem is solved using dynamic programming.     

具有有效期易变质品的最优补货策略研究

易变质物品库存管理策略一直是实务界与学术界高度关注的问题,其中具有有效期易变质物品的最优补货策略是研究中的难点。本文研究了有限销售时域内具有有效期易变质物品的库存补货策略,在物品的需求率依赖于物品的库存水平,且物品有效期已知的假设下,本文建立了一个确定易变质物品最优补货策略的优化模型,并给出了具体的求解算法。文章最后给出了数值算例,并对模型中的相关参数作了敏感性分析。     

An Application of Multi-echelon Inventory System Theory to Management of Equipment Maintenance

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有碰撞存在的多体振动系统的周期运动和稳定条件

有碰撞存在的多体振动系统在工程中应用甚广,但由于运动过于复杂,过去一般限于研究和利用个别特殊系统.本文考虑任意多个串联质体在多个正弦力的激励下振动,并和多个自由体碰撞(弹性或塑性碰撞)的一般情况,提出振动和稳定的统一解法.首先按工程需要选择周期运动的界点(碰撞点与脱离点),以避免解非线性方程.然后采用矩阵迭代方法求得周期运动的简便条件及其若干推论(如界点的最多个数、周期运动的存在唯一条件等).再用差分方程和矩阵迭代确定周期运动的稳定条件.文末讨论了多体系统的多种功能,如参数稳定区域大、优化程度高、自动消振和隔振等,可以充分加以利用.     

A Hybrid Inventory System with a Time Limit on Backorders

Traditionally, in ( Q , r ) inventory systems, when a shortage occurs, incoming demands are either filled by emergency orders or backordered. However, the backorder costs are usually time-dependent, hence it is costly to backorder early in the lead time. On the other hand, it is obviously expensive to fill the shortages with emergency orders alone. In this paper, we propose a hybrid inventory control system to handle shortages. A cutoff time τis incorporated with the traditional ( Q , r ) systems. Poisson demands and a constant lead time are assumed. Shortages are covered by emergency orders before τand backordered after τ. The traditional backorder and emergency order systems are special cases of the hybrid system with τ= 0 and τ= lead time, respectively. The optimal control variables Q *, r *, and τ* are determined by minimizing the expected annual cost. Numerical examples to illustrate the model are presented together with discussions on the conditions under which the hybrid system provides cost savings over the two traditional systems.     

考虑机器故障的短生命周期产品库存模型

在考虑机器故障、返修费用和担保费用以及短生命周期产品库存成本随着时间呈非线关系的情况下建立短生命周期产品经济制造批量模型,并提供了寻求上述模型唯一最优解的简便方法.举数字实例进行了说明,计算实例验证了该方法的有效性.研究分析了机器故障率、返修费用和担保费用对最优生产批量和单位时间总成本的影响,同时比较了一般产品与短生命周期产品在生产策略上的一些区别,得到了一些有价值的结论.     

柔性制造环境下基于质量控制的状态监控系统

以ＦＭＳ环境下加工单元为对象，建立了通用集成化设备与过程状态监控系统，给出了系统体系结构与硬软件组成，探讨了实际柔性生产过程中实时在线的状态监控系统实现的信息获取，状态描述，开放体系，状态辨识，异常与故障综合决策等关键技术。     

具有分布时滞的广义系统的周期解问题?

周期解问题已成为广义系统领域的一个重要分支,它在许多实际问题中有着更为广泛的应用.本文主要讨论含有离散时滞和分布时滞的广义系统的周期解问题.利用特征方程和傅里叶级数理论给出了广义系统周期解存在的充分必要条件,并给出了二维广义系统周期解存在性的代数判据.利用不动点定理讨论了非线性广义时滞系统周期解的存在唯一性的若干充分条件.最后给出数值算例说明主要结果.     

An Economic Lot Size Model for Perishable Products with Age-Dependent Inventory and Backorder Costs

This paper presents an Economic Lot Size (ELS) model for perishable products where the costs of holding inventory stocks (having backorders) in each period depend on the age of inventories (backorders). We propose a polynomial-time dynamic programming algorithm to solve two structured problems, one with non-decreasing demands and the other with non-decreasing marginal backorder cost with respect to the age of the backorder. Our results generalize a recent study on an ELS model for perishable product but without backorders.     

Weibull分布变质物品库存模型研究

研究了变质物品在考虑资金时间价值时的经济订货批量问题.假定物品的变质率服从两参数的Weibull分布,物品的需求率与库存水平有关,且为库存水平的线性函数,计划时域内进行多次订货,订货时间间隔相等,允许缺货且短缺量完全拖后,以库存系统的总费用最小为目标函数,建立了变质物品在存货依赖性需求下考虑资金时间价值时的最优订货批量模型,分析了模型存在唯一的最优解的必要条件,并且给出了在该条件下求解模型最优解的算法,最后给出了一个计算实例.     

柔性热防护系统的发展与应用

热防护系统是发展航天器必须解决的关键技术,而柔性隔热材料由于具有可重复使用、质量轻、维修时间短等优点被广泛采用。介绍了当前各种热防护系统结构与材料的发展状况,并具体叙述了飞行器减速伞的结构、展开、热流分布以及所用柔性材料,对我国柔性防热材料的发展提出了建议。     

Flexible fixture design and automation: Review,issues and future directions

The cost of designing and fabricating fixtures can amount to 10-20% of the total manufacturing system costs. To reduce manufacturing costs, a fixture system is designed to be competent in fixturing as many workpieces as possible. In mass volume production, this can be achieved by fixturing a large quantity of the same kind of workpieces. In low-to-medium volume production, however, improvement of the flexibility of fixture systems becomes a favourable way to reduce the unit cost of product. This paper summarizes the latest studies in the field of flexible fixture design and automation. First, a brief introduction is given on this research area. Secondly, taxonomy of flexible fixture design activities is presented. Thirdly, the flexibility strategies based on the existing flexible fixture systems are discussed. Fourthly, the contributions on design methodologies and verifications are examined. Fifthly, advances on computer-aided design and see-up systems are summarized. Finally, some prospective research trends are presented.     

A Blood Bank Collection Scheduling and Inventory Control System

This article presents an analytic approach to the blood bank collection scheduling and inventory problem. Based on a specified allowable probability of shortage, the number of units to be collected is determined. A total of six cases are discussed and models for each case are proposed. The six cases arise because of the type of demand forecasts available, and because of the degree of control a blood bank has over its donors. Essentially, any kind of demand/supply situation is covered by the six cases.