生产过程标准差估计值的评价和选取—数理分析与模拟验证

一、问题的提出 在工业产品质量的统计控制中,通常用字母σ表示生产过程的标准差;用距加工中心正负三个生产过程的标准差(即6σ)来描述工序能力,表示产品质量特性值约有99.73%集中在此范围内;而产品的技术要求同工序能力之比则称为工序能力指数.当产品质量特性值分布中心规范界     

面向单小批量产品设计的质量屋模型改进研究

为了使单小批量产品设计能够充分满足顾客需求,提高顾客满意度和忠诚度,帮助企业获得市场竞争优势。本文结合单小批量产品生产自身的特点,在系统的研究和总结传统的质量屋理论与方法及最新进展的基础上,对质量屋模型进行改进,利用设计规则间的影响系数和客户需求与设计规则之间的关系矩阵求出价值矩阵后,借助0—1整数规划技术求解改进的质量屋模型,从而使单小批量产品的设计规则可以按照顾客需求重新排列优先次序,最后通过S公司某单小批量产品的设计过程对模型进行验证。本文的研究意义在于使单小批量产品设计能够完全满足顾客的个性化需求,从而保证了企业最终生产出符合顾客和市场需求的单小批量产品。     

基于质量损失的过程网络及其关键质量链分析

针对传统的过程能力分析仅以生产线中某一单一的生产工序(过程)为对象这一问题,将影响产品质量的所有生产过程视为一个过程网络,根据Taguchi田口方法,阐述了过程能力指数与质量损失的关系,给出了生产制造过程网络过程能力指数的计算方法.进一步应用PERT/CPM的基本思想,建立了生产制造过程网络关键质量链的规划模型,将质量损失最大的路径视为关键质量链.通过实例分析表明,以上方法改进了传统的统计质量控制和分析方法,能够有效地实现过程网络的质量管理.     

基于时间序列的挖掘算法在流程工业产品质量控制模型中的应用

针对目前流程工业产品质量控制采用人工检查和统计质量控制方法,缺乏产品质量预先预报以及时时调整生产过程的工艺参数存在一定困难.利用生产过程采集到的实际数据,采用基于时间序列的动态数据挖掘技术和BP神经元网络,预测产品质量和分析产品生产过程的工艺,最大限度减少不合格产品的产出,提高生产效率.根据上述理论建立流程工业数据动态质量控制平台,以中厚钢板生产过程为例,应用表明了这种方法在实际应用中的正确性和有效性.     

基于非对称损失函数的过程均值与标准差优化设计

质量特性的过程均值与过程标准差的选定是一个重要的命题,它们是影响质量成本的重要因素.由顾客定义的特性目标均值以及初始标准差往往并不一定能使得总体的质量损失最小化。针对此问题,本文首先讨论了非对称的质量损失函数,并在此基础上构造出质量特性目标均值与标准差的优选模型,进而得到最优目标过程均值与标准差。在模型的应用中表明:其他情况不变的情况下,质量特性最优均值与最优标准差对质量损失系数具有一定的稳健性。     

考虑质量控制和损失规避的供应链网络均衡研究

研究质量控制和损失规避背景下供应链网络均衡问题,通过变分不等式原理描述供应链内部成员的最优行为,构建供应链网络均衡模型,证实均衡解的存在性和唯一性,并运用拟牛顿算法进行求解。最后通过算例对损失规避程度、产品合格率和补偿金等参数进行灵敏度分析,展现质量控制和损失规避等要素对供应链均衡解以及成员利益的作用。研究表明:制造商可以通过提高产品合格率来减少损失规避给其带来的损失;损失规避行为会降低因产品合格率提高给零售商带来的效用的增量;零售商可以通过收取补偿金的方式激励制造商生产高质量的产品。     

基于电商产品的使用质量控制

我国电子商务日益发达,但电商产品质量问题一直未得到很好地解决。本文首先研究了电商产品使用过程的质量控制问题,接着以淘宝网上热销的某款产品为例,收集了2013年自6月24日到8月12日之间的所有消费者评价,先通过文本分析和处理获取定量数据,再使用统计控制图来进行过程质量控制。本文的研究说明了产品使用的质量控制具有必要性和可行性。     

产品设计与质量控制的动态因素模型(下)

(续上期)5·5产品动态质量损失和产品技术损失田口的质量损失函数L(y)已被人们所熟知,它不考虑跟时间的关系,其自变量为产品的特性y,其函数形式为L(y)=K(y-y0)2,其中K为常数。质量损失函数的期望值E[L(y)}=K·E(y-y0)2称之为产品质量损失,它表示在统计意义下单位产品的平均质量     

基于预防维修的可变抽样区间泊松EWMA控制图经济设计

现代质量控制的核心技术和方法始终围绕着如何提高监控效率和降低控制成本问题而展开。统计过程控制是一种常用的质量控制方法，其重要的工具——控制图对过程中的质量特性值进行统计并描点达到监控过程质量状态的目的。控制图的设计方法将会对产品过程的监控效率和控制成本产生较大影响。针对只考虑传统控制图参数固定以及控制图统计设计的情形，传统的缺陷数c控制图基于泊松分布建立以监控制造过程中产品的缺陷数。为了降低控制过程成本并提高缺陷数c控制图的监控效率，研究预防维修策略下可变抽样区间(VSI) EWMA图的经济设计问题。首先，建立泊松分布下VSI EWMA控制图的经济模型。其次，令单位时间的损失成本函数最小得到经济模型的最优解。以化工建材行业为例，说明如何根据预防维修策略下所构建的控制图经济模型得到最优参数。然后，为得到设计参数与模型参数的影响关系，对经济模型灵敏度分析。最后，对经济模型进行最优性分析验证其优越性。     

非对称需求扰动信息下的供应链显示机制设计

研究由一个供应商和一个零售商组成的供应链在非对称的需求扰动信息下的显示机制设计问题。假定市场需求为指数函数形式和常数柔性需求函数形式,给出了非对称的需求扰动信息下的供应链最优契约,并且分析了非对称扰动信息对于供应链性能的影响。研究表明,当市场需求为指数函数形式和常数柔性函数形式时,仍然可以设计有效的契约菜单来改善供应链的运作性能;当需求扰动满足一定条件时,初始的生产计划仍然是最优的;非对称需求扰动信息并不必然会给供应链带来利润损失,并且显式地给出了非对称的需求扰动信息不会给供应链带来利润损失的条件。     

Quality and pricing decisions in production/inventory systems

In this article, we consider the impact of finite production capacity on the optimal quality and pricing decisions of a make-to-stock manufacturer. Products are differentiated along a quality index; depending on the price and quality levels of the products offered, customers decide to either buy a given product, or not to buy at all. We show that, assuming fixed exogenous lead times and normally distributed product demands, the optimal solution has a simple structure (this is referred to as the load-independent system). Using numerical experiments, we show that with limited production capacity (which implies load-dependent lead times) the manufacturer may have an incentive to limit the quality offered to customers, and to decrease market coverage, especially in settings where higher product quality leads to higher congestion in production. Our findings reveal that the simple solution assuming load-independent lead times is suboptimal, resulting in a profit loss; yet, this profit loss can be mitigated by constraining the system utilization when deciding on quality and price levels. Our results highlight the importance of the relationship between marketing decisions and load-dependent production lead times.     

Improved bid prices for choice-based network revenue management

One of the latest developments in network revenue management (RM) is the incorporation of customer purchase behavior via discrete choice models. Many authors presented control policies for the booking process that are expressed in terms of which combination of products to offer at a given point in time and given resource inventories. However, in many implemented RM systems—most notably in the hotel industry—bid price control is being used, and this entails the problem that the recommended combination of products as identified by these policies might not be representable through bid price control. If demand were independent from available product alternatives, an optimal choice of bid prices is to use the marginal value of capacity for each resource in the network. But under dependent demand, this is not necessarily the case. In fact, it seems that these bid prices are typically not restrictive enough and result in buy-down effects.We propose (1) a simple and fast heuristic that iteratively improves on an initial guess for the bid price vector; this first guess could be, for example, dynamic estimates of the marginal value of capacity. Moreover, (2) we demonstrate that using these dynamic marginal capacity values directly as bid prices can lead to significant revenue loss as compared to using our heuristic to improve them. Finally, (3) we investigate numerically how much revenue performance is lost due to the confinement to product combinations that can be represented by a bid price.The heuristic is not restricted to a particular choice model and can be combined with any method that provides us with estimates of the marginal values of capacity. In our numerical experiments, we test the heuristic on some popular networks examples taken from peer literature. We use a multinomial logit choice model which allows customers from different segments to have products in common that they consider to purchase. In most problem instances, our heuristic policy results in significant revenue gains over some currently available alternatives at low computational cost.     

Dynamic modelling of die melt temperature profile in polymer extrusion: Effects of process settings,screw geometry and material

Extrusion is one of the major methods for processing polymeric materials and the thermal homogeneity of the process output is a major concern for manufacture of high quality extruded products. Therefore, accurate process thermal monitoring and control are important for product quality control. However, most industrial extruders use single point thermocouples for the temperature monitoring/control although their measurements are highly affected by the barrel metal wall temperature. Currently, no industrially established thermal profile measurement technique is available. Furthermore, it has been shown that the melt temperature changes considerably with the die radial position and hence point/bulk measurements are not sufficient for monitoring and control of the temperature across the melt flow. The majority of process thermal control methods are based on linear models which are not capable of dealing with process nonlinearities. In this work, the die melt temperature profile of a single screw extruder was monitored by a thermocouple mesh technique. The data obtained was used to develop a novel approach of modelling the extruder die melt temperature profile under dynamic conditions (i.e. for predicting the die melt temperature profile in real-time). These newly proposed models were in good agreement with the measured unseen data. They were then used to explore the effects of process settings, material and screw geometry on the die melt temperature profile. The results showed that the process thermal homogeneity was affected in a complex manner by changing the process settings, screw geometry and material.     

造船企业与供应商产品质量演化博弈分析

船舶作为大型复杂系统产品,其上游供应商所提供的零部件质量会对最终产品的质量产生重要影响。在考虑造船企业和供应商质量策略和收益的基础上,本文构建了双方的演化博弈模型,对其策略的稳定性开展分析;进一步地,引入了造船企业的动态惩罚措施研究如何对双方的策略产生影响。研究结果表明:(1)造船企业对配套供应商采取产品质量提升措施的奖励和惩罚力度、供应商采取相应措施的收益与成本会直接影响博弈的相关结果;(2)造船企业和配套供应商在三种条件下存在各自的演化稳定策略,同时在一定条件下系统的演化过程呈现周期性质的特征;(3)当造船企业采取动态惩罚措施时,此博弈模型存在稳定的Nash均衡点。研究结果可以为造船企业督促供应商改善供货质量提供决策支持。     

Local design vs. global design: A strategic business choice

The market for a particular product consists of many customers having different needs and wants. A local design strategy attempts to increase market share and sales revenue by designing many variants of the product to exploit these differences. Such a strategy involves increased requirements for design, manufacturing, and marketing resources. A global design strategy offers a single product concept to all customers. Thus, the choice between a local design strategy and a global design strategy poses a fundamental tradeoff to the managers in many markets. Making such a decision is a complex process as it involves many design, manufacturing and marketing factors. We present a model based on optimal control theory representing major tradeoffs that exist between a local design strategy and a global design strategy. We demonstrate, through extensive computational experiments, how the model helps to gain strategic insight into the complex tradeoffs that exist between global design strategy and local design strategy alternatives under various scenarios over the life of a product.     

非正态总体控制图和预防维修策略耦合优化的研究

主要探讨非正态有偏总体的过程监控和预防维修耦合优化问题。假定设备故障率随时间递增,设备发生异常前在正常状态的停留时间服从威布尔分布,一旦发生异常将导致过程均值漂移。采用赋权方差法构造X控制图,将过程监控和预防维修策略联系起来,结合生产不合格品损失、抽样成本及维修成本等,构建综合损失模型,提出动态抽样方案、控制图参数和预防维修间隔的确定方法。最后对模型进行了灵敏度分析。     

On a multicommodity stochastic-flow network with unreliable nodes subject to budget constraint

From the quality management and decision making view point, reliability and unreliability are important indices to measure the quality level for a stochastic-flow network. In a multicommodity stochastic-flow network with unreliable nodes, the branches and nodes all have several possible capacities and may fail. Different types of the commodity, which are transmitted through the same network simultaneously, compete the capacities of branches and nodes. In this paper we first define the system capacity as a vector for a multicommodity stochastic-flow network with unreliable nodes. Then we design a performance index which is the probability that the upper bound of the system capacity is a given pattern subject to the budget constraint. It can be applied to evaluate the quality level for such a network. A simple approach based on minimal cuts is thus presented to evaluate the performance index.     

Variables sampling plans with PPM fraction of defectives and process loss consideration

Acceptance sampling plans provide the vendor and the buyer decision rules for lot sentencing to meet their product quality needs. A problem the quality practitioners have to deal with is the determination of the critical acceptance values and inspection sample sizes that provide the desired levels of protection to both vendors and buyers. As today's modern quality improvement philosophy, reduction of variation from the target value is the guiding principle as well as reducing the fraction of defectives. The C_pm index adopts the concept of product loss, which distinguishes the product quality by setting increased penalty to products deviating from the target. In this paper, a variables sampling plan based on C_pm index is proposed to handle processes requiring very low parts per million (PPM) fraction of defectives with process loss consideration. We develop an effective method for obtaining the required sample sizes n and the critical acceptance value C₀ by solving simultaneously two nonlinear equations. Based on the designed sampling plan, the practitioners can determine the number of production items to be sampled for inspection and the corresponding critical acceptance value for lot sentencing.     

基于非对称损失的过程均值设计研究

在损失非对称的情况下，使工序加工出的产品均值等于目标值，并不会使期望损失最小，优化过程均值，使其接近目标值，尤为重要。本研究了三种典型的非对称损失的过程均值设计问题，探讨了非对称比率与质量损失率之间的关系，提出了有效偏移的概念，给出了具体的调整措施，最后给出一个实例。