Optimal tree structure with loyal users and batch updates

We study the probabilistic model in the key tree management problem. Users have different behaviors. Normal users have probability p to issue join/leave request while the loyal users have probability zero. Given the numbers of such users, our objective is to construct a key tree with minimum expected updating cost. We observe that a single LUN (Loyal User Node) is enough to represent all loyal users. When 1−p≤0.57 we prove that the optimal tree that minimizes the cost is a star. When 1−p>0.57, we try to bound the size of the subtree rooted at every non-root node. Based on the size bound, we construct the optimal tree using dynamic programming algorithm in O(n⋅K+K ⁴) time where K=min {4(log (1−p)⁻¹)⁻¹,n} and n is the number of normal users.     

An improved algorithm for tree edit distance with applications for RNA secondary structure comparison

An ordered labeled tree is a tree in which the nodes are labeled and the left-to-right order among siblings is relevant. The edit distance between two ordered labeled trees is the minimum cost of transforming one tree into the other through a sequence of edit operations. We present techniques for speeding up the tree edit distance computation which are applicable to a family of algorithms based on closely related recursion strategies. These techniques aim to reduce repetitious steps in the original algorithms by exploring certain structural features in the tree. When these features exist in a large portion of the tree, the speedup due to our techniques would be significant. Viable examples for application include RNA secondary structure comparison and structured text comparison.     

Optimal price,warranty length and production rate for free replacement policy in the static demand market

In the present paper, a decision model is developed for producers in the static demand market to determine the optimal price, warranty length and production rate of a product to maximize profit based on the pre-determined life cycle. The free renewal warranty policy is considered under which failed products are renewed before the end of warranty length at no cost to consumers. The expected number of renewals based on warranty length is derived for Weibull life distributed products. The objective function includes both demand and cost functions, where production cost, warranty cost and inventory cost are involved. A solution approach using the maximum principle is described, and is applied to two specific cases of markets. The first case of market considers positive discount rate, and the second case of market considers zero discount rate. The economic sensitivity analysis is conducted to evaluate the effect of model parameters on the optimal solution. Some conclusions are drawn based on the sensitivity analysis.     

Deterministic models for premature and postponed replacement

We examine the possibilities of premature and postponed replacement in a deterministic infinite horizon model when there is technological progress. Both revenue and operating cost deteriorate with age, but at different rates. The optimal deterministic replacement time is an implicit solution from the timing boundary obtained for the equivalent real option model using a dynamic programming framework, and then by setting the underlying volatilities equal to zero. A step change improvement characterizing technological progress in the initial operating cost level for the successor occurring during the economic lifetime of the incumbent justifies premature replacement, compared to the traditional present value approach. This finding can be extended to step change improvements in the initial revenue level for the successor and for the re-investment cost. In contrast, if the technological progress can be characterized by a constant declining rate for the initial operating cost level for the successor, then the replacement is postponed for certain parameter values. This finding can be extended to different assumed improvement rates in the initial revenue level for the successor and for the re-investment cost.     

Medial Axis and Optimal Locations for Min-Max Sphere Packing

We study the following min-max sphere packing problem originated from radiosurgical treatment planning using gamma knife (Bourland and Wu, 1996; Wu, 1996). Given an input (R, V), where R is a 3-dimensional (3D) bounded region and V a positive integer, find a packing of R using the minimum number of spheres (spheres may not be identical) such that the covered volume is at least V, and the number of points on the boundary of R touched by spheres is maximized. Bourland and Wu (1996) and Wu (1996), devised a greedy algorithm to solve the problem based on medial axis analysis. In particular, the algorithm places the center of each sphere on the medial axis of each subsequent region starting from R. While this approach has met with certain success, we show that medial axis does not always provide optimal locations for min-max sphere packing.     

炼钢连铸计划调度优化系统

钢铁企业的炼钢连铸计划调度问题一直是学术界和企业界研究的热门课题.炼钢连铸生产计划调度系统是钢铁企业制造执行系统的重要组成部分,在企业的生产管理中起着承上启下的作用.本文首先简述了炼钢连铸计划调度理论的发展历程和生产工艺流程,并进一步描述了炼钢连铸计划编制的流程.针对炼钢连铸计划调度的现场要求,架构了炼钢连铸计划调度优化系统的功能模块,并较详细地说明了各功能模块的功能特点.该系统不仅能对静态调度计划应用多种优化方法进行编制,而且对复杂生产环境的各类响应事件可以做到快速响应,满足动态调度的要求,保证生产的稳定顺行.     

Combining decision tree and MAUT for selecting a country for a global manufacturing facility

The paper presents a multi-phase approach for selecting a country in which to locate a global manufacturing facility. An influence diagram is used to frame the decision. A decision tree then analyzes uncertainties regarding cost and generates a risk profile. The risk profile becomes one of the measures in an MAUT model that incorporate a wide range of factors. This sequential approach of using the output from a decision tree as input to MAUT is demonstrated with an example involving an auto supplier locating a new plant in one of five countries. Three decision makers were interviewed to determine the weights and the shape of the individual utility curves. The paper identifies, clearly defines, and incorporates a variety of measures for which national data are readily available. This list is broader and less subjective when compared to other examples reported in the literature.     

Complexity of domination,hamiltonicity and treewidth for tree convex bipartite graphs

In this paper, we first give the definition of randomized time-varying knapsack problems (\(\textit{RTVKP}\)) and its mathematic model, and analyze the character about the various forms of \(\textit{RTVKP}\). Next, we propose three algorithms for \(\textit{RTVKP}\): (1) an exact algorithm with pseudo-polynomial time based on dynamic programming; (2) a 2-approximation algorithm for \(\textit{RTVKP}\) based on greedy algorithm; (3) a heuristic algorithm by using elitists model based on genetic algorithms. Finally, we advance an evaluation criterion for the algorithm which is used for solving dynamic combinational optimization problems, and analyze the virtue and shortage of three algorithms above by using the criterion. For the given three instances of \(\textit{RTVKP}\), the simulation computation results coincide with the theory analysis.     

An unexpected meeting of four seemingly unrelated problems: graph testing, DNA complex screening, superimposed codes and secure key distribution

This paper discusses the relation among four problems: graph testing, DNA complex screening, superimposed codes and secure key distribution. We prove a surprising equivalence relation among these four problems, and use this equivalence to improve current results on graph testing. In the rest of this paper, we give a lower bound for the minimum number of tests on DNA complex screening model. The first and second author would like to dedicate this paper to professor Frank K. Hwang on the occasion of his 65th birthday. This research is partially supported by Republic of China, National Science Council grant NSC 92-2115-M-009-014.     

Optimal and Heuristic Decision Strategies for Integrated Production and Marketing Planning

In this study we examine the effects of integrating production and marketing decisions for a short- to medium-range planning horizon in a profit maximizing firm. We formulate two models for determining price, marketing expenditure, demand or production volume, and lot size for a single product with stable demand when economies of scale are present. The full integration (FI) model simultaneously determines all the decisions involved, while the partial integration (PI) model separates the lot sizing decision from the others, as happens frequently in practice. Geometric programming (GP) techniques and marginal analysis are used to compare FI and PI, and obtain important managerial implications regarding the two models.     

Optimal ordering and pricing decisions for a target oriented newsvendor

This paper is the first to study pricing and target oriented decision making together in the newsvendor model. Specifically, this paper studies a newsvendor who decides on order quantity and selling price to maximize the probability of achieving both profit and revenue targets simultaneously. First, it is shown that the probability of a newsvendor achieving both targets depends critically on the relative magnitudes of the profit margin and the ratio between the profit target and the revenue target. Second, the closed-form expressions of the optimal order quantity, the optimal selling price, and the maximal profit and revenue probability are obtained. It is shown that if the product has greater price elasticity, the best strategy is always to price lower and order more.     

Darwinism,organizational evolution and survival: key challenges for future research

How do social organizations evolve? How do they adapt to environmental pressures? What resources and capabilities determine their survival within dynamic competition? Charles Darwin’s seminal work The Origin of Species (1859) has provided a significant impact on the development of the management and organization theory literatures on organizational evolution. This article introduces the JMG Special Issue focused on Darwinism, organizational evolution and survival. We discuss key themes in the organizational evolution research that have emerged in recent years. These include the increasing adoption of the co-evolutionary approach, with a particular focus on the definition of appropriate units of analysis, such as routines, and related challenges associated with exploring the relationship between co-evolution, re-use of knowledge, adaptation, and exaptation processes. We then introduce the three articles that we have finally accepted in this Special Issue after an extensive, multi-round, triple blind-review process. We briefly outline how each of these articles contributes to understanding among scholars, practitioners and policy makers of the continuous evolutionary processes within and among social organizations and systems.     

Improved formulations and branch-and-cut algorithms for the angular constrained minimum spanning tree problem

Journal of Combinatorial Optimization - The Angular Constrained Minimum Spanning Tree Problem ( $$\alpha $$ -MSTP) is defined in terms of a complete undirected graph $$G=(V,E)$$ and an angle...     

Production/operations management—A key discipline and area for research

This paper reports the results of a stocktaking and review of research in Production/Operations Management, carried out for the Social Science Research Council. The paper describes the scope and importance of the management of production/operations. Areas of importance for future directions for research are explored and a number of issues concerned with research in the area are examined.     

Optimal and Heuristic Models for Lot Splitting in a Flow Shop

This paper investigates optimal lot-splitting policies in a multiprocess flow shop environment with the objective of minimizing either mean flow time or makespan. Using a quadratic programming approach to the mean flow time problem, we determine the optimal way of splitting a job into smaller sublots under various setup times to run time ratios, number of machines in the flow shop, and number of allowed sublots. Our results come from a deterministic flow shop environment, but also provide insights into the repetitive lots scheme using equal lot splits for job shop scheduling in a stochastic environment. We indicate those conditions in which managers should implement the repetitive lots scheme and where other lot-splitting schemes should work better.     

寡头市场信息产品与服务的最优定价策略

在信息产品与服务竞争性市场中,信息产品及附加服务的定价策略日渐成为信息产品提供商关心的首要问题.而以往的研究多集中于单一信息产品的定价策略,没有统一考虑产品的后续服务,且假设消费者的网络外部性强度相同.分析了异质消费者和双寡头垄断市场,针对基础信息产品和附加服务的定价策略选择问题,建立了双寡头垄断市场中两个企业的捆绑销售和分别销售策略的博弈模型,使得双寡头企业通过4种局势下的策略选择实现收益最大化的定价策略.同时,将差异化网络外部性强度系数引入Hotelling模型,计算企业的需求函数和收益函数,并采用两阶段Bertrand博弈分析两个企业的定价策略和竞争行为.通过模型求解,得到4种局势下两家企业的最优定价解析解.通过数值模拟分析了潜在消费者的构成比例及市场规模对企业定价、市场占有率和最优收益产生的影响,以及不同成本和市场规模组合下企业的最优定价策略.     

Optimal inventory model for items with imperfect quality and shortage backordering

In this study, we develop an optimal inventory model for items with imperfect quality and shortage backordering. Such implicit assumption is reasonable in view of the fact that poor-quality items do exist during production. They are usually picked up during the screening process and are withdrawn from stock instantaneously. It is assumed that all customers are willing to wait for new supply when there is a shortage. The analysis shows that our model is a generalization of the models in current literatures. An algorithm and numerical analysis developed show that our model always results in better performance.     

Optimal Purchase and Transportation Cost Lot Sizing for a Single Item

A review of the literature indicates that the traditional approach for evaluating quantity discount offerings for purchased items has not adequately considered the effect that transportation costs may have on the optimal order quantity; despite the general fact that purchased materials must bear transportation charges. The transportation cost structure for less-than-truckload (LTL) shipments reflects sizable reductions in freight rates when the shipment size exceeds one of the nominal rate breakpoints. However, the shipper must also be aware of the opportunity to reduce total freight costs by artificially inflating the actual shipping weight to the next rate breakpoint, in order that a lower marginal tariff is achieved for the entire shipment. Such over-declared shipments result in an effective freight rate schedule that is characterized by constant fixed charge segments in addition to the nominal marginal rates. Over-declared shipments are economical when the shipment volume is less than the rate breakpoint, but greater than a cost indifference point between the two adjacent marginal rates. This paper presents a simple analytical procedure for finding the order quantity that minimizes total purchase costs which reflect both transportation economies and quantity discounts. After first solving for the series of indifference points that apply to a particular freight rate schedule, a total purchase cost expression is presented that properly accounts for the actual transportation cost structure. The optimal purchase order quantity will be one of the four following possibilities: (1) the valid economic order quantity (EOQ), QC; (2) a purchase price breakpoint in excess of QC; (3) a transportation rate breakpoint in excess of QC; and (4) a modified EOQ which provides an over-declared shipment in excess of QC. Finally, an algorithm which systematically explores these four possibilities is presented and illustrated with a numerical example.     

易变质类季节性商品销售价格及总采购量的确定

产品市场需求不仅受库存水平影响,也与销售价格密切相关.为此,建立了一个连续时间的变质类产品库存模型,以解决公司的变质类季节性产品销售策略,即确定公司最优的销售价格及采购量.最后,用数值算例进行敏感性分析,得到了一些重要的结论.