Reducing simulation models for scheduling manufacturing facilities

Within the framework of the application of their industrial management system, companies compile a Master Production Schedule (MPS). However, once the MPS is released, daily events may require it to be brought into question. The use of reduced models within the framework of flow dynamic simulation enables quick decision-making while maximizing the use of resources and minimizing risk. The article shows the advantage of model reduction and how we arrive at it. Afterwards we develop an analysis of the influence of the model factors by highlighting the differences between the simulation results and MPS. Finally we show the circumstances in which the flow dynamic simulation with reduced models is relevant.     

应用驱动的企业信息系统动态数据更新策略研究

大数据时代下,外界数据源的快速变化为保证企业信息系统中动态数据的及时性带来巨大挑战。以企业资源计划(Enterprise Resource Planning, ERP)系统中动态的采购数据为研究对象,从数据应用角度研究如何以及何时更新ERP系统中的采购数据,从而使系统更新成本与数据过时成本最优的问题。将ERP系统中采购数据动态更新过程刻画为马尔科夫决策过程,设计了求解数据最优更新策略的动态规划算法。通过数值分析的对比结果发现,相对于传统的基于固定周期的数据更新策略而言,应用驱动的非固定周期动态数据更新策略不仅能有效保证动态数据的及时性,还能够有效降低企业的数据更新成本。     

Pre-constructed dynamic geometry materials in the classroom – how do they facilitate the learning of ‘Similar Triangles’?

The use of dynamic geometry software (DGS) is becoming increasingly familiar among teachers, but letting students conduct inquiries using computers is still not a welcome idea. In addition to logistics and discipline concerns, many teachers believe that mathematics at the lower secondary level can be learned efficiently through practice alone. Thus, the application of DGS remains limited to demonstration and explanation. This article discusses how a set of pre-constructed dynamic geometry (DG) materials was designed to teach the ‘similar triangles’ concept. The reactions and behaviour of students with relatively low levels of mathematic achievement are also analysed. Finally, the potential value of pre-constructed DG materials, with lab sheets and teacher intervention, in inquiry activities for junior-level students is discussed.     

Fluid dynamics models and their applications in transportation and pricing

Fluid dynamics models provide a powerful deterministic technique to approximate stochasticity in a variety of application areas. In this paper, we study two classes of fluid models, investigate their relationship as well as some of their applications. This analysis allows us to provide analytical models of travel times as they arise in dynamically evolving environments, such as transportation networks as well as supply chains. In particular, using the laws of hydrodynamic theory, we first propose and examine a general second-order fluid model. We consider a first-order approximation of this model and show how it is helpful in analyzing the dynamic traffic equilibrium problem. Furthermore, we present an alternate class of fluid models that are traditionally used in the context of dynamic traffic assignment. By interpreting travel times as price/inventory–sojourn-time relationships, we are also able to connect this approach with a tractable fluid model in the context of dynamic pricing and inventory management.     

Performance evaluation of scheduling control of queueing networks: Fluid model heuristics

Motivated by dynamic scheduling control for queueing networks, Chen and Yao [8] developed a systematic method to generate dynamic scheduling control policies for a fluid network, a simple and highly aggregated model that approximates the queueing network. This study addresses the question of how good these fluid policies are as heuristic scheduling policies for queueing networks. Using simulation on some examples these heuristic policies are compared with traditional simple scheduling rules. The results show that the heuristic policies perform at least comparably to classical priority rules, regardless of the assumptions made about the traffic intensities and the arrival and service time distributions. However, they are certainly not always the best and, even when they are, the improvement is seldom dramatic. The comparative advantage of these policies may lie in their application to nonstationary situations such as might occur with unreliable machines or nonstationary demand patterns.     

Regular variation on measure chains

In this paper we show how the recently introduced concept of regular variation on time scales (or measure chains) is related to a Karamata type definition. We also present characterization theorems and an embedding theorem for regularly varying functions defined on suitable subsets of reals. We demonstrate that for a “reasonable” theory of regular variation on time scales, certain additional condition on a graininess is needed, which cannot be omitted. We establish a number of elementary properties of regularly varying functions. As an application, we study the asymptotic properties of solution to second order dynamic equations.     

Dynamic graph models

Research in graph theory has focused on studying the structure of graphs with the assumption that they are static. However, in many applications, the graphs that arise change with time, i.e., they are dynamic in nature. This is especially true of applications involving graph models in computer science. We present an expository study of dynamic graphs with the main driving force being practical applications. We first develop a formal classification of dynamic graphs. This taxonomy in the form of generalizations and extensions will in turn suggest new areas of application. Next, we discuss areas where dynamic graphs arise in computer science such as compilers, databases, fault-tolerance, artificial intelligence, and computer networks. Finally, we propose approaches that can be used for studying dynamic graphs. The main objective in any study of dynamic graphs should be to

• 1.(i) extend results developed for static graph theory to dynamic graphs,
• 2.(ii) study the properties that describe how a dynamic graph changes,
• 3.(iii) investigate problems and issues in dynamic graph theory that are raised by practical applications of dynamic graphs in computer science.

     

Three-dimensional discrete-time Lotka–Volterra models with an application to industrial clusters

We consider a three-dimensional discrete dynamical system that describes an application to economics of a generalization of the Lotka–Volterra prey–predator model. The dynamic model proposed is used to describe the interactions among industrial clusters (or districts), following a suggestion given by [23]. After studying some local and global properties and bifurcations in bidimensional Lotka–Volterra maps, by numerical explorations we show how some of them can be extended to their three-dimensional counterparts, even if their analytic and geometric characterization becomes much more difficult and challenging. We also show a global bifurcation of the three-dimensional system that has no two-dimensional analogue. Besides the particular economic application considered, the study of the discrete version of Lotka–Volterra dynamical systems turns out to be a quite rich and interesting topic by itself, i.e. from a purely mathematical point of view.     

核心人力资源对企业动态能力影响分析

企业动态能力是企业获取和发展可持续竞争优势的主要来源.面对当今激烈的市场竞争和不断变化的外部环境,如何培育企业的动态能力,已成为国内外学者所关注的热点问题.大量的研究表明,构建企业动态能力的关键要素在于企业的核心人力资源.因此,主要侧重于从核心入力资源管理的角度分析企业动态能力与核心人力资源的关系,包括核心人力资源如何影响动态能力的形成,以及在动态的环境下,核心人力资源应该怎样配合企业的总体战略提升企业竞争力提高企业的绩效.     

The inverse maximum dynamic flow problem

We consider the inverse maximum dynamic flow (IMDF) problem. IMDF problem can be described as: how to change the capacity vector of a dynamic network as little as possible so that a given feasible dynamic flow becomes a maximum dynamic flow. After discussing some characteristics of this problem, it is converted to a constrained minimum dynamic cut problem. Then an efficient algorithm which uses two maximum dynamic flow algorithms is proposed to solve the problem.     

Projection formulation of the cavitation problem in elastohydrodynamic lubrication contact

This contribution presents an alternative numerical method on how to find the cavitation region in elastohydrodynamic (EHD) lubrication using an augmented Lagrangian approach. A theoretical framework for the use of a projection formulation instead of a Linear Complementarity Problem (LCP) is given and the application to multibody systems with EHD contacts is shown. With this new formulation the cavitation condition can be covered by an additional algebraic equation. The projection formulation is applied to the steady-state as well as to the dynamic, mass conservative treatment of the cavitation problem. A numerical verification is given for a rigid rotor with unbalance in an elastic bearing. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Web page importance ranking

An approach is proposed that uses a set of interesting Web pages as starting point for a minimum walk algorithm to provide recommendations of additionally important Web information within a m-clicks-ahead situation. A discussion of known page importance ranking techniques as well as examples of the application of the new algorithm show that Web link structure dependent approaches should be enriched by considerations as to how the analysis of additional data and the use of suited support tools can be incorporated. These considerations include aspects as, e.g., personalization, query dependence and topic sensitivity of the underlying pages, the dynamic nature of the Web, as well as the possibility to perform calculations online.     

International greenhouse gas emissions when global warming is a stochastic process

This paper integrates two different but crucial aspects of global warming: free riding and uncertainty. Although certainty equivalence does not hold, an analytical solution is obtained if ‘clean up’ (e.g. reforestation) is possible. Assuming realistically irreversible emissions, numerical methods are necessary to obtain the value function and the implied strategies, which are shown to be unique (for the calibrated parameters). Although uncertainty stresses the importance of conservation, the incentives to free ride are almost the same. Beyond the particular application, the paper shows how to analyze stochastic, dynamic games. Copyright © 2004 John Wiley & Sons, Ltd.     

Creditworthiness dynamics and Hidden Markov Models

A dynamic monitoring of credit risky portfolios is described. In the first section, it is shown how a Markov dependence can be used in modelling the borrower's behaviour: a chain of transition probabilities matrices is built in which the states of the dynamic stochastic system are the number of instalments in arrears. In the second part, such a model is generalized in the framework of the Hidden Markov Models to explain how the credit market conditions could affect the borrower's payment process. Numerical examples complete the note.     

Hybrid synchronization of heterogeneous chaotic systems on dynamic network

For researching the hybrid synchronization of heterogeneous chaotic systems on the complex dynamic network, there are two important issues to be discussed and analyzed. One is how to build a dynamic complex network which the connection between nodes is dynamic. Another is comparing and analyzing the synchronization characteristics of heterogeneous chaotic systems on the dynamic and static complex network. In this paper, the theoretical analysis and numerical simulation are implemented to study the synchronization on different dynamic and static complex networks. The results indicate it is feasible to realize the hybrid synchronization of heterogeneous chaotic systems on the complex dynamic network.     

Finite-state approximations to denumerable-state dynamic programs

We show how to find a sequence of policies for essentially finite-state dynamic programs such that the corresponding vector of optimal returns converges pointwise to that of a denumerable-state dynamic program. The corresponding result for stochastic games is also given.     

An Operations Research Approach to the Problem of the Sugarcane Selection

Selection for superior clones is the most important aspect of sugar cane improvement programs, and is a long and expensive process. While studies have investigated different components of selection independently, there has not been a whole system approach to improve the process. This study observes the problem as an integrated system, where if one parameter changes the state of the whole system changes. A computer based stochastic simulation model that accurately represents the selection was developed. This paper describes the simulation model, showing its accuracy as well as how a combination of dynamic programming and branch and bound can be applied to the model to optimise the selection system, giving a new application of these techniques. The model can be directly applied to any region targeted by sugarcane breeding programs or to other clonally propagated crops.     

Classroom note: Application of the Sumudu transform to discrete dynamic systems

The Sumudu transform is an integral transform introduced to solve differential equations and control engineering problems. The transform possesses many interesting properties that make visualization easier and application has been demonstrated in the solution of partial differential equations, integral equations, integro-differential equations and dynamic/dynamic-differential systems. In this note, application of the method of Sumudu transform to the solution of discrete dynamic systems is described. Derivations find ready application in recurrence relations. Solutions are obtained to certain first degree, second degree and third degree dynamic systems.     

考虑供应链风险和绩效的供应商选择的模糊动态非线性多目标规划模型

基于供应链风险和供应链绩效的模糊性和供应商选择问题的动态性,本文考虑供应链风险和供应链绩效作为模糊变量,讨论如何给生产商一个满意的动态多目标供应商选择方案,确定供应链风险和总成本最小,以及供应链绩效最大。然后对该问题提出了一个动态多目标多产品供应商选择模型,该模型是首次同时考虑供应商选择,订单分配,供应链风险和供应链绩效的一个模糊动态非线性多目标规划模型。为了去模糊化和求解该模型,给出了一个风险和绩效的模糊评估法。最后给出一个数值算例验证了该模型的可行性,为决策者选择供应商提供了理论依据。     

Optimal deployment of logistic units in dynamic combat conditions

One of the problems facing the commander of support units during a combat situation is how to plan the deployment of the units under his command. This paper deals with the tactical problem of how to deploy the support units in order to achieve maximum effectiveness, given the decision of which fighting units will receive support. The problem is formulated as a dynamic decision problem that has some of the characteristics of a dynamic warehouse location problem. A branch and bound technique to reduce the state space of the d.p. formulation is applied in the solution of this model.