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Estimating Primary Demand for a Heterogeneous-Groups Product Category under Hierarchical Consumer Choice Model 层次消费者选择模型下异质群体产品类别的初级需求估计
Pub Date : 2016-06-02 DOI: 10.1080/0740817X.2015.1078524
Haengju Lee, Y. Eun
Abstract This paper discusses the estimation of primary demand (i.e., the true demand before the stockout-based substitution effect occurs) for a heterogeneous-groups product category that is sold in the department store setting, based on historical sales data, product availability, and market share information. For such products, a hierarchical consumer choice model can better represent purchasing behavior. This means that choice occurs on multiple levels: A consumer might choose a particular product group on the first level and purchase a product within that chosen group on the second level. Hence, in the present study, we used the nested multinomial logit (NMNL) choice model for the hierarchical choice and combined it with non-homogeneous Poisson arrivals over multiple periods. The expectation-maximization (EM) algorithm was applied to estimate the primary demand while treating the observed sales data as an incomplete observation of that demand. We considered the estimation problem as an optimization problem in terms of the inter-product-group heterogeneity, and this approach relieves the revenue management system of the computational burden of using a nonlinear optimization package. We subsequently tested the procedure with simulated data sets. The results confirmed that our algorithm estimates the demand parameters effectively for data sets with a high level of inter-product-group heterogeneity.
摘要本文基于历史销售数据、产品可用性和市场份额信息,讨论了在百货商店环境中销售的异质群体产品类别的初级需求估计(即基于缺货的替代效应发生之前的真实需求)。对于这类产品,分层消费者选择模型可以更好地表示购买行为。这意味着选择发生在多个层次上:消费者可能在第一级选择特定的产品组,并在第二级购买所选组中的产品。因此,在本研究中,我们使用嵌套多项式logit (NMNL)选择模型进行分层选择,并将其与多个时期的非齐次泊松到达相结合。期望最大化(EM)算法用于估计主要需求,同时将观察到的销售数据视为对该需求的不完全观察。我们将估计问题视为产品组间异质性的优化问题,这种方法减轻了使用非线性优化包的收益管理系统的计算负担。我们随后用模拟数据集测试了该程序。结果证实,我们的算法有效地估计了具有高水平的产品组间异质性的数据集的需求参数。
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引用次数: 5
Reliability estimation of a system subject to condition monitoring with two dependent failure modes 具有两种相关失效模式的状态监测系统的可靠性估计
Pub Date : 2016-05-26 DOI: 10.1080/0740817X.2016.1189632
A. Khaleghei, V. Makis
ABSTRACT A new competing risk model is proposed to calculate the Conditional Mean Residual Life (CMRL) and Conditional Reliability Function (CRF) of a system subject to two dependent failure modes, namely, degradation failure and catastrophic failure. The degradation process can be represented by a three-state continuous-time stochastic process having a healthy state, a warning state, and a failure state. The system is subject to condition monitoring at regular sampling times that provides partial information about the system is working state and only the failure state is observable. To model the dependency between two failure modes, it is assumed that the joint distribution of the time to catastrophic failure and sojourn time in the healthy state follow Marshal–Olkin bivariate exponential distributions. The Expectation–Maximization algorithm is developed to estimate the model's parameters and the explicit formulas for the CRF and CMRL are derived in terms of the posterior probability that the system is in the warning state. A comparison with a previously published model is provided to illustrate the effectiveness of the proposed model using real data.
提出了一种新的竞争风险模型,用于计算退化失效和灾难性失效两种依赖失效模式下系统的条件平均剩余寿命(CMRL)和条件可靠性函数(CRF)。退化过程可以表示为具有健康状态、警告状态和失效状态的三状态连续时间随机过程。系统在定期采样时间进行状态监测,提供有关系统工作状态的部分信息,只有故障状态是可观察到的。为了模拟两种失效模式之间的相关性,假设在健康状态下,灾难性失效时间和逗留时间的联合分布遵循marshall - olkin二元指数分布。提出了期望最大化算法来估计模型的参数,并根据系统处于预警状态的后验概率推导出了CRF和CMRL的显式公式。通过与先前发表的模型的比较,用实际数据说明了该模型的有效性。
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引用次数: 27
A novel strategy for redundant components in reliability--redundancy allocation problems 可靠性冗余组件的一种新策略——冗余分配问题
Pub Date : 2016-05-26 DOI: 10.1080/0740817X.2016.1189631
Mostafa Abouei Ardakan, M. Sima, Ali Zeinal Hamadani, D. Coit
ABSTRACT This article presents a new interpretation and formulation of the Reliability–Redundancy Allocation Problem (RRAP) and demonstrates that solutions to this new problem provide distinct advantages compared with traditional approaches. Using redundant components is a common method to increase the reliability of a system. In order to add the redundant components to a system or a subsystem, there are two traditional types of strategies called active and standby redundancy. Recently a new redundancy strategy, called the “mixed” strategy, has been introduced. It has been proved that in the Redundancy Allocation Problem (RAP), this new strategy has a better performance compared with active and standby strategies alone. In this article, the recently introduced mixed strategy is implemented in the RRAP, which is more complicated than the RAP, and the results of using the mixed strategy are compared with the active and standby strategies. To analyze the performance of the new approach, some benchmark problems on the RRAP are selected and the mixed strategy is used to optimize the system reliability in these situations. Finally, the reliability of benchmark problems with the mixed strategy is compared with the best results of the systems when active or standby strategies are considered. The final results show that the mixed strategy results in an improvement in the reliability of all the benchmark problems and the new strategy outperforms the active and standby strategies in RRAP.
本文提出了可靠性冗余分配问题(RRAP)的一种新的解释和表述,并论证了该问题的解决方案与传统方法相比具有明显的优势。使用冗余组件是提高系统可靠性的常用方法。为了将冗余组件添加到系统或子系统中,有两种传统类型的策略,称为活动冗余和备用冗余。最近引入了一种新的冗余策略,称为“混合”策略。实验证明,在冗余分配问题(RAP)中,该策略比单独的主备策略具有更好的性能。本文将新引入的混合策略应用于比RAP更复杂的RRAP中,并将混合策略的使用结果与主备策略进行了比较。为了分析新方法的性能,选择了RRAP上的一些基准问题,并采用混合策略对这些情况下的系统可靠性进行了优化。最后,将混合策略下基准问题的可靠性与考虑主动或备用策略时系统的最佳结果进行了比较。最后的结果表明,混合策略提高了所有基准问题的可靠性,并且新策略优于RRAP中的主备策略。
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引用次数: 69
The value of demand forecast updates in managing component procurement for assembly systems 需求预测更新在装配系统部件采购管理中的价值
Pub Date : 2016-05-26 DOI: 10.1080/0740817X.2016.1189630
James Cao, K. C. So
ABSTRACT This article examines the value of demand forecast updates in an assembly system where a single assembler must order components from independent suppliers with different lead times. By staggering each ordering time, the assembler can utilize the latest market information, as it is developed, to form a better forecast over time. The updated forecast can subsequently be used to decide the following procurement decision. The objective of this research is to understand the specific operating environment under which demand forecast updates are most beneficial. Using a uniform demand adjustment model, we are able to derive analytical results that allow us to quantify the impact of demand forecast updates. We show that forecast updates can drastically improve profitability by reducing the mismatch cost caused by demand uncertainty.
本文研究了在装配系统中需求预测更新的价值,其中单个装配商必须从具有不同交货时间的独立供应商处订购组件。通过错开每次订货时间,装配商可以利用最新的市场信息,随着时间的推移,形成一个更好的预测。更新后的预测随后可用于决定以下采购决策。本研究的目的是了解需求预测更新最有益的具体运营环境。使用统一的需求调整模型,我们能够得出分析结果,使我们能够量化需求预测更新的影响。我们表明,预测更新可以通过减少由需求不确定性引起的不匹配成本来大幅提高盈利能力。
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引用次数: 3
Production planning with price-dependent supply capacity 供应能力与价格相关的生产计划
Pub Date : 2016-05-21 DOI: 10.1080/0740817X.2016.1189628
Z. M. Teksan, J. Geunes
ABSTRACT We consider a production planning problem in which a producer procures an input component for production by offering a price to suppliers. The available supply quantity for the production input depends on the price the producer offers, and this supply level constrains production output. The producer seeks to meet a set of demands over a finite horizon at a minimum cost, including component procurement costs. We model the problem as a discrete-time production and component supply–pricing planning problem with nonstationary costs, demands, and component supply levels. This leads to a two-level lot-sizing problem with an objective function that is neither concave nor convex. Although the most general version of the problem is -hard, we provide polynomial-time algorithms for two special cases of the model under particular assumptions on the cost structure. We then apply the resulting algorithms heuristically to the more general problem version and provide computational results that demonstrate the high performance quality of the resulting heuristic solution methods.
我们考虑一个生产计划问题,其中生产商通过向供应商提供价格来采购生产所需的投入部件。生产投入的可用供应量取决于生产者提供的价格,而这种供应水平限制了生产产出。生产商寻求在有限的时间内以最低的成本(包括零部件采购成本)满足一系列需求。我们将该问题建模为具有非平稳成本、需求和组件供应水平的离散时间生产和组件供应定价计划问题。这导致了一个目标函数既非凹也非凸的两级批量问题。虽然这个问题的最一般版本是困难的,但我们在特定的成本结构假设下,为模型的两种特殊情况提供了多项式时间算法。然后,我们将结果算法启发式地应用于更一般的问题版本,并提供计算结果,证明结果启发式解决方法的高性能质量。
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引用次数: 2
Integrated storage space allocation and ship scheduling problem in bulk cargo terminals 散货码头综合存储空间分配与船舶调度问题
Pub Date : 2016-05-03 DOI: 10.1080/0740817X.2015.1063791
Lixin Tang, Defeng Sun, Jiyin Liu
ABSTRACT This study is motivated by the practices of large iron and steel companies that have steady and heavy demands for bulk raw materials, such as iron ore, coal, limestone, etc. These materials are usually transported to a bulk cargo terminal by ships (or to a station by trains). Once unloaded, they are moved to and stored in a bulk material stockyard, waiting for retrieval for use in production. Efficient storage space allocation and ship scheduling are critical to achieving high space utilization, low material loss, and low transportation costs. In this article, we study the integrated storage space allocation and ship scheduling problem in the bulk cargo terminal. Our problem is different from other associated problems due to the special way that the materials are transported and stored. A novel mixed-integer programming model is developed and then solved using a Benders decomposition algorithm, which is enhanced by the use of various valid inequalities, combinatorial Benders cuts, variable reduction tests, and an iterative heuristic procedure. Computational results indicate that the proposed solution method is much more efficient than the standard solution software CPLEX.
本研究的动机是大型钢铁公司的实践,这些公司对铁矿石、煤炭、石灰石等大宗原材料有稳定和大量的需求。这些材料通常由船舶运输到散货码头(或由火车运输到车站)。一旦卸下,它们就被转移到散装物料堆场并储存起来,等待在生产中使用。有效的存储空间分配和船舶调度是实现高空间利用率、低材料损耗和低运输成本的关键。本文主要研究散货码头的仓储空间分配与船舶调度问题。我们的问题不同于其他相关的问题,因为材料的运输和储存方式是特殊的。提出了一种新的混合整数规划模型,并利用Benders分解算法进行求解,该算法通过使用各种有效不等式、组合Benders切割、变量约简检验和迭代启发式过程得到增强。计算结果表明,所提出的求解方法比标准求解软件CPLEX的求解效率高得多。
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引用次数: 21
The effect of buffers and work sharing on makespan improvement of small batches in assembly lines under learning effects 学习效应下缓冲和工作分担对装配线小批量完工时间改进的影响
Pub Date : 2016-05-03 DOI: 10.1080/0740817X.2015.1056392
Y. Bukchin, E. Wexler
Abstract The effect of workers’ learning curves on the production rate in manual assembly lines is significant when producing relatively small batches of different products. This research studies this effect and suggests applying a work-sharing mechanism among the workers to improve the makespan (time to complete the batch). The proposed mechanism suggests that adjacent cross-trained workers will help each other in order to reduce idle times caused by blockage and starvation. The effect of work sharing and buffers on the makespan is studied and compared with a baseline situation, where the line does not contain any buffers and work sharing is not applied. Several linear programming and mixed-integer linear programming formulations for makespan minimization are presented. These formulations provide optimal work allocations to stations and optimal parameters of the work-sharing mechanism. A numerical study is conducted to examine the effect of buffers and work sharing on the makespan reduction in different environment settings. Numerical results are given along with some recommendations regarding the system design and operation.
在手工装配线中,当生产相对小批量的不同产品时,工人的学习曲线对生产率的影响是显著的。本研究研究了这一效应,并建议在工人之间应用工作共享机制来提高makespan(完成批次的时间)。拟议的机制表明,相邻的交叉训练的工人将相互帮助,以减少堵塞和饥饿造成的闲置时间。研究了工作共享和缓冲区对makespan的影响,并与基线情况进行了比较,在基线情况下,生产线不包含任何缓冲区,也不应用工作共享。给出了最大跨度最小化的几种线性规划和混合整数线性规划公式。这些公式为工位提供了最优的工作分配和工作分担机制的最优参数。通过数值研究,考察了缓冲和工作分担对不同环境下最大完工时间缩减的影响。给出了数值结果,并对系统的设计和运行提出了建议。
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引用次数: 5
A false discovery approach for scanning spatial disease clusters with arbitrary shapes 一种用于扫描任意形状空间疾病簇的错误发现方法
Pub Date : 2016-04-25 DOI: 10.1080/0740817X.2015.1133940
Yanting Li, L. Shu, F. Tsung
ABSTRACT The spatial scan statistic is one of the main tools for testing the presence of clusters in a geographical region. The recently proposed Fast Subset Scan (FSS) method represents an important extension, as it is computationally efficient and enables detection of clusters with arbitrary shapes. Aimed at automatically and simultaneously detecting multiple clusters of any shapes, this article explores the False Discovery (FD) approach originated from multiple hypothesis testing. We show that the FD approach can provide a higher detection power and better identification capability than the standard scan and FSS methods, on average.
空间扫描统计量是检测地理区域内集群是否存在的主要工具之一。最近提出的快速子集扫描(FSS)方法是一种重要的扩展,因为它具有计算效率,并且可以检测任意形状的簇。为了自动同时检测任意形状的多个聚类,本文探讨了基于多假设检验的错误发现(FD)方法。我们表明,平均而言,FD方法可以提供比标准扫描和FSS方法更高的检测功率和更好的识别能力。
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引用次数: 1
Lévy-driven non-Gaussian Ornstein–Uhlenbeck processes for degradation-based reliability analysis 基于退化的可靠性分析的l<s:1>驱动非高斯Ornstein-Uhlenbeck过程
Pub Date : 2016-04-13 DOI: 10.1080/0740817X.2016.1172743
Y. Shu, Q. Feng, E. P. Kao, Hao Liu
ABSTRACT We use Lévy subordinators and non-Gaussian Ornstein–Uhlenbeck processes to model the evolution of degradation with random jumps. The superiority of our models stems from the flexibility of such processes in the modeling of stylized features of degradation data series such as jumps, linearity/nonlinearity, symmetry/asymmetry, and light/heavy tails. Based on corresponding Fokker–Planck equations, we derive explicit results for the reliability function and lifetime moments in terms of Laplace transforms, represented by Lévy measures. Numerical experiments are used to demonstrate that our general models perform well and are applicable for analyzing a large number of degradation phenomena. More important, they provide us with a new methodology to deal with multi-degradation processes under dynamicenvironments.
摘要本文利用lsamvy从属子和非高斯Ornstein-Uhlenbeck过程来模拟随机跳跃退化的演化。我们的模型的优势在于这些过程在建模退化数据系列的风格化特征(如跳跃、线性/非线性、对称/不对称、轻尾/重尾)时的灵活性。基于相应的Fokker-Planck方程,我们得到了可靠度函数和寿命矩的拉普拉斯变换的显式结果,用lsamvy测度表示。数值实验表明,该模型具有良好的性能,适用于分析大量的退化现象。更重要的是,它们为我们提供了一种新的方法来处理动态环境下的多重降解过程。
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引用次数: 18
A new budget allocation framework for selecting top simulated designs 一种新的顶级仿真设计选择预算分配框架
Pub Date : 2016-04-06 DOI: 10.1080/0740817X.2016.1156788
Siyang Gao, Weiwei Chen
ABSTRACT In this article, the problem of selecting an optimal subset from a finite set of simulated designs is considered. Given the total simulation budget constraint, the selection problem aims to maximize the Probability of Correct Selection (PCS) of the top m designs. To simplify the complexity of the PCS, an approximated probability measure is developed and an asymptotically optimal solution of the resulting problem is derived. A subset selection procedure, which is easy to implement in practice, is then designed. More important, we provide some useful insights on characterizing an efficient subset selection rule and how it can be achieved by adjusting the simulation budgets allocated to all of the designs.
摘要本文考虑了从有限的模拟设计集合中选择最优子集的问题。在总仿真预算约束下,选择问题的目标是最大化前m个设计的正确选择概率(PCS)。为了简化PCS的复杂性,提出了一个近似的概率测度,并给出了问题的渐近最优解。然后设计了一个易于实现的子集选择程序。更重要的是,我们提供了一些关于描述有效子集选择规则的有用见解,以及如何通过调整分配给所有设计的仿真预算来实现它。
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引用次数: 33
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