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1
Kchaou, Mouna. "Modeling and solving a distribution network design problem with multiple operational constraints : Application to a case-study in the automotive industry". Phd thesis, Ecole Centrale Paris, 2013. http://tel.archives-ouvertes.fr/tel-00978486.
Abstract (sommario):
L'objet de notre projet de recherche est le développement d'un modèle de conception d'un réseau de distribution composé de trois niveaux : les usines, les centres de distribution (CD) et les clients. Nous supposons que le nombre et la localisation des usines ainsi que le nombre et la localisation des clients sont connus. Etant donné la demande des clients et une liste de CD potentiels, l'objectif est de déterminer la localisation des CD à ouvrir et d'y affecter les clients de manière à minimiser le coût total. En termes de modélisation, nous considérons divers aspects opérationnels qui sont inspirés d'une étude de cas dans l'industrie automobile. Ces aspect ont été pris en compte séparément dans la littérature mais jamais combinés dans un même modèle. Plus particulièrement, nous introduisons un " clustering " en prétraitement afin de modéliser les tournées de camions. Nous intégrons également des contraintes de volume minimum sur les axes de transport, des contraintes de volume minimum et de capacité maximale sur les centres de distribution, des contraintes de distance de couverture maximale et des contraintes d'uni-affectation. Par ailleurs, nous étudions une extension multi-périodes du problème en utilisant un " clustering " dynamique pour modéliser des tournées de camions multi-périodes. En termes de résolution, comme le problème étudié est NP-difficile au sens fort, nous proposons différentes méthodes heuristiques performantes basées sur la relaxation linéaire. A travers les tests effectués, nous montrons que ces méthodes fournissent des solutions proches de l'optimale en moins de temps de calcul que l'application directe d'un solveur linéaire. Nous analysons également la structure des réseaux de distribution obtenus et nous comparons les résultats issus de plusieurs versions du modèle afin de montrer la valeur ajoutée du " clustering " ainsi que de l'approche multi-périodes.
2
Rajagopalan, Sreekanth. "Design and Maintenance Planning Problems in Commodity Distribution and Chemical Site Networks". Research Showcase @ CMU, 2018. http://repository.cmu.edu/dissertations/1141.
Abstract (sommario):
In this dissertation, we consider two specific types of problems over networks. In the first problem, we explore systematic methods to address some of the challenges in largescale maintenance planning in integrated chemical sites. In the second problem, we investigate different optimization model formulations for the design of flow distribution networks where the flow is potential-driven and nonlinearly related to the potential loss. Maintenance turnaround in the processing industry is a complex asset renewal project that includes huge capital expenditures and downtime losses. The option of deferring or rescheduling a turnaround project typically provides immediate financial relief from capital expenditure. However, the risk of running into site-wide disruptions in the form of unplanned events, yield, and reliability losses is not straightforward to assess. We propose mathematical optimization models to evaluate the risk of loss from turnaround deferrals in integrated sites and provide alternatives to reliably operate the site in a medium-term horizon. In the first chapter, we introduce the turnaround planning problem and the challenges it poses in integrated sites. We also introduce the background for the network design problem. In the second chapter, we study the financial impact of rescheduling turnarounds and the associated risk under unplanned outages. We compare the risk profiles presented by different production planning strategies. We propose a stochastic programming model for production planning that optimally builds up inventory ahead of time to hedge against production losses during unplanned outages. In the third chapter, we extend the stochastic optimization to handle a large set of scenarios and propose a Lagrangean decomposition method that improves a myopic production plan. The fourth chapter proposes a mixed-integer linear programming model that prescribes turnaround schedules when the underlying assets undergo yield loses and selectivity degradation. Here, we also study the impact of deferrals over a long-term horizon. The penultimate chapter addresses the nonlinear network design problem.The closing chapter summarizes the work and provides a few future directions. In the spirit of advancing manufacturing paradigms, the thesis supports investment in modeling efforts that address enterprise-wide planning problems.
3
Subramanian, Shivaram. "Optimization Models and Analysis of Routing, Location, Distribution, and Design Problems on Networks". Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/27224.
Abstract (sommario):
A variety of practical network optimization problems arising in the context of public supply and commercial transportation, emergency response and risk management, engineering design, and industrial planning are addressed in this study. The decisions to be made in these problems include the location of supply centers, the routing, allocation and scheduling of flow between supply and demand locations, and the design of links in the network. This study is concerned with the development of optimization models and the analysis of five such problems, and the subsequent design and testing of exact and heuristic algorithms for solving these various network optimization problems.
The first problem addressed is the time-dependent shortest pair of disjoint paths problem. We examine computational complexity issues, models, and algorithms for the problem of finding a shortest pair of disjoint paths between two nodes of a network such that the total travel delay is minimized, given that the individual arc delays are time-dependent. It is shown that this problem, and many variations of it, are nP-Hard and a 0-1 linear programming model that can be used to solve this problem is developed. This model can accommodate various degrees of disjointedness of the pair of paths, from complete to partial with respect to specific arcs.
Next, we examine a minimum-risk routing problem and pursue the development, analysis, and testing of a mathematical model for determining a route that attempts to reduce the risk of low probability-high consequence accidents related with the transportation of hazardous materials (hazmat). More specifically, the problem addressed in this study involves finding a path that minimizes the conditional expectation of a consequence, given that an accident occurs, subject to the expected value of the consequence being lesser than or equal to a specified level n, and the probability of an accident on the path being also constrained to be no more than some value h. Various insights into related modeling issues are also provided. The values n and h are user-prescribed and could be prompted by the solution of shortest path problems that minimize the respective corresponding linear risk functions. The proposed model is a discrete, fractional programming problem that is solved using a specialized branch-and-bound approach. The model is also tested using realistic data associated with a case concerned with routing hazmat through the roadways of Bethlehem, Pennsylvania.
The third problem deals with the development of a resource allocation strategy for emergency and risk management. An important and novel issue addressed in modeling this problem is the effect of loss in coverage due to the non-availability of emergency response vehicles that are currently serving certain primary incidents. This is accommodated within the model by including in the objective function a term that reflects the opportunity cost for serving an additional incident that might occur probabilistically on the network. A mixed-integer programming model is formulated for the multiple incident - multiple response problem, and we show how its solution capability can be significantly enhanced by injecting a particular structure into the constraints that results in an equivalent alternative model representation. Furthermore, for certain special cases of the MIMR problem, efficient polynomial-time solution approaches are prescribed. An algorithmic module composed of these procedures, and used in concert with a computationally efficient LP-based heuristic scheme that is developed, has been incorporated into an area-wide incident management decision support system (WAIMSS) at the Center for Transportation Research, Virginia Tech.
The fourth problem addressed in this study deals with the development of global optimization algorithms for designing a water distribution network, or expanding an already existing one, that satisfies specified flow demands at stated pressure head requirements. The nonlinear, nonconvex network problem is transformed into the space of certain design variables. By relaxing the nonlinear constraints in the transformed space via suitable polyhedral outer approximations and applying the Reformulation-Linearization Technique (RLT), a tight linear lower bounding problem is derived. This problem provides an enhancement and a more precise representation of previous lower bounding relaxations that use similar approximations. Computational experience on three standard test problems from the literature is provided. For all these problems, a proven global optimal solution within a tolerance of 10 -4 % and/or within 1$ of optimality is obtained. For the two larger instances dealing with the Hanoi and New York test networks that have been open for nearly three decades, the solutions derived represent significant improvements, and the global optimality has been verified at the stated level of accuracy for these problems for the very first time in the literature. A new real network design test problem based on the Town of Blacksburg Water Distribution System is also offered to be included in the available library of test cases, and related computational results on deriving global optimal solutions are presented.
The final problem addressed in this study is concerned with a global optimization approach for solving capacitated Euclidean distance multifacility location-allocation problems, as well as the development of a new algorithm for solving the generalized lp distance location-allocation problem. There exists no global optimization algorithm that has been developed and tested for this class of problems, aside from a total enumeration approach. Beginning with the Euclidean distance problem, we design depth-first and best-first branch-and-bound algorithms based on a partitioning of the allocation space that finitely converges to a global optimum for this nonconvex problem. For deriving lower bounds at node subproblems in these partial enumeration schemes, we employ two types of procedures. The first approach computes a lower bound via a simple projected location space lower bounding (PLSB) subproblem. The second approach derives a significantly enhanced lower bound by using a Reformulation-Linearization Technique (RLT) to transform an equivalent representation of the original nonconvex problem into a higher dimensional linear programming relaxation. In addition, certain cut-set inequalities generated in the allocation space, objective function based cuts derived in the location space, and tangential linear supporting hyperplanes for the distance function are added to further tighten the lower bounding relaxation. The RLT procedure is then extended to the.general lp distance problem for 1 < p < 2. Various issues related to the selection of branching variables, the design of heuristics via special selective backtracking mechanisms, and the study of the sensitivity of the proposed algorithm to the value of p in the lp - norm, are computationally investigated. Computational experience is also provided on a set of test problems to investigate both the PLSB and the RLT-lower bounding schemes. The results indicate that the proposed global optimization approach using the RLT-based scheme offers a promising viable solution procedure. In fact, among the problems solved, for the only two test instances previously available in the literature for the Euclidean distance case that were posed in 1979, we report proven global optimal solutions within a tolerance of 0.1% for the first time.
It is hoped that the modeling, analysis, insights, and concepts provided for these various network based problems that arise in diverse routing, location, distribution, and design contexts, will provide guidelines for studying many other problems that arise in related situations.Ph. D.
4
Kchaou-Boujelben, Mouna. "Modeling and solving a distribution network design problem with multiple operational constraints. Application to a case-study in the automotive industry". Phd thesis, Ecole Centrale Paris, 2013. http://tel.archives-ouvertes.fr/tel-00946890.
Abstract (sommario):
A cause de leur aspect strat égique et des divers challenges qu'ils repr ésentent en termes de mod élisation et de r ésolution, les probl èmes de localisation et de conception de r éseaux ont été largement étudi es par les sp écialistes en recherche opérationnelle. Par ailleurs, bien que les études de cas dans ce domaine soient rares dans la litt érature, plusieurs travaux r écents ont int égr é certains aspects op érationnels afi n de rendre ces probl èmes d'optimisation plus r éalistes. L'objet de notre projet de recherche est le d éveloppement d'un mod èle de conception d'un r éseau de distribution prenant en compte plusieurs aspects op érationnels inspir és d'une étude de cas dans le domaine de l'automobile. Bien que nos choix de mod élisation soient motiv és par cette étude de cas, ils restent applicables dans d'autres secteurs industriels. Le r éseau de distribution consid ér é se compose de trois niveaux : les usines au premier niveau, les centres de distribution (CD) au deuxi ème niveau et les clients au dernier niveau. Nous supposons que le nombre et la localisation des usines ainsi que le nombre et la localisation des clients sont connus. Etant donn é la demande des clients et une liste de CD potentiels, l'objectif est de d éterminer la localisation des CD a ouvrir et d'y a ffecter les clients de mani ère a minimiser le coût total. Nos contributions par rapport aux travaux existants concernent la mod élisation et la r ésolution du probl ème ainsi que les tests num ériques eff ectu és. En termes de mod élisation, nous consid érons divers aspects op érationnels qui ont été pris en compte s épar ément dans la litt érature mais jamais combin és dans un même mod èle. Plus particuli èrement, nous introduisons un "clustering" en pr étraitement afi n de mod éliser les tourn ées de camions. Nous int égrons également des contraintes de volume minimum sur les axes de transport pour assurer l'utilisation de camions pleins, des contraintes de volume minimum et de capacit é maximale sur les centres de distribution, des contraintes de distance de couverture maximale et des contraintes d'uni-aff ectation. Par ailleurs, nous étudions une extension multi-p ériodes du probl ème en utilisant un "clustering" dynamique pour mod éliser des tourn ées de camions multi-p ériodes. En termes de r ésolution, comme le probl ème étudi é est NP-di ffcile au sens fort, nous proposons di fférentes m éthodes heuristiques performantes bas ées sur la relaxation lin éaire. A travers les tests eff ectu és, nous montrons que ces m éthodes fournissent des solutions proches de l'optimale en moins de temps de calcul que l'application directe d'un solveur lin éaire. Nous analysons également la structure des r éseaux de distribution obtenus et nous comparons les r ésultats issus de plusieurs versions du mod èle afi n de montrer la valeur ajout ée du "clustering" ainsi que de l'approche multi-p ériodes.
5
Ben, Mohamed Imen. "Designing Two-Echelon Distribution Networks under Uncertainty". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0073.
Abstract (sommario):
Avec la forte croissance du e-commerce et l'augmentation continue de la population des villes impliquant des niveaux de congestion plus élevés, les réseaux de distribution doivent déployer des échelons supplémentaires pour offrir un ajustement dynamique aux besoins des entreprises au cours du temps et faire face aux aléas affectant l’activité de distribution. Dans ce contexte, les praticiens s'intéressent aux réseaux de distribution à deux échelons. Dans cette thèse, nous commençons par présenter une revue complète des problèmes de design des réseaux de distribution et souligner des caractéristiques essentielles de modélisation. Ces aspects impliquent la structure à deux échelons, l’aspect multi-période, l’incertitude et les méthodes de résolution. Notre objectif est donc, d’élaborer un cadre complet pour le design d’un réseau de distribution efficace à deux échelons, sous incertitude et multi-périodicité, dans lequel les produits sont acheminés depuis les plateformes de stockage (WP) vers les plateformes de distribution (DP) avant d'être transportés vers les clients. Ce cadre est caractérisé par une hiérarchie temporelle entre le niveau de design impliquant des décisions relatives à la localisation des plateformes et à la capacité allouée aux DPs sur une échelle de temps annuelle, et le niveau opérationnel concernant des décisions journalières de transport. % sur une base journalière.Dans une première étude, nous introduisons le cadre complet pour le problème de design de réseaux de distribution à deux échelons avec une demande incertaine, une demande et un coût variables dans le temps. Le problème est formulé comme un programme stochastique à plusieurs étapes. Il implique au niveau stratégique des décisions de localisation des DPs ainsi que des décisions d'affectation des capacités aux DPs sur plusieurs périodes de design, et au niveau opérationnel des décisions de transport sous forme d'arcs origine-destination. Ensuite, nous proposons deux modèles alternatifs basés sur la programmation stochastique à deux étapes avec recours, et les résolvons par une approche de décomposition de Benders intégrée à une technique d’approximation moyenne d’échantillon (SAA). Par la suite, nous nous intéressons à la livraison du dernier kilomètre dans un contexte urbain où les décisions de transport dans le deuxième échelon sont caractérisées par des tournées de véhicules. Un problème multi-période stochastique de localisation-routage à deux échelons avec capacité (2E-SM-CLRP) est défini, dans lequel les décisions de localisation concernent les WPs et les DPs. Le modèle est un programme stochastique à deux étapes avec recours en nombre entier. Nous développons un algorithme de décomposition de Benders. Les décisions de localisation et de capacité sont déterminées par la solution du problème maître de Benders. Le sous-problème résultant est un problème multi-dépôt de tournées de véhicule avec des dépôts et véhicules capacitaires qui est résolu par un algorithme de branch-cut-and-price.Enfin, nous étudions le cadre à plusieurs étapes proposé pour le problème stochastique multi-période de design de réseaux de distribution à deux échelons et évaluons sa tractabilité. Pour ceci, nous développons une heuristique à horizon glissant qui permet d’obtenir des bornes de bonne qualité et des solutions de design pour le modèle à plusieurs étapesWith the high growth of e-commerce and the continuous increase in cities population contrasted with the rising levels of congestion, distribution schemes need to deploy additional echelons to offer more dynamic adjustment to the requirement of the business over time and to cope with all the random factors. In this context, a two-echelon distribution network is nowadays investigated by the practitioners.In this thesis, we first present a global survey on distribution network design problems and point out many critical modeling features, namely the two-echelon structure, the multi-period setting, the uncertainty and solution approaches. The aim, here, is to propose a comprehensive framework for the design of an efficient two-echelon distribution network under multi-period and stochastic settings in which products are directed from warehouse platforms (WPs) to distribution platforms (DPs) before being transported to customers. A temporal hierarchy characterizes the design level dealing with facility-location and capacity decisions over a set of design periods, while the operational level involves transportation decisions on a daily basis.Then, we introduce the comprehensive framework for the two-echelon distribution network design problem under uncertain demand, and time-varying demand and cost, formulated as a multi-stage stochastic program. This work looks at a generic case for the deployment of a retailer's distribution network. Thus, the problem involves, at the strategic level, decisions on the number and location of DPs along the set of design periods as well as decisions on the capacity assignment to calibrate DP throughput capacity. The operational decisions related to transportation are modeled as origin-destination arcs. Subsequently, we propose alternative modeling approaches based on two-stage stochastic programming with recourse, and solve the resulting models using a Benders decomposition approach integrated with a sample average approximation (SAA) technique.Next, we are interested in the last-mile delivery in an urban context where transportation decisions involved in the second echelon are addressed through multi-drop routes. A two-echelon stochastic multi-period capacitated location-routing problem (2E-SM-CLRP) is defined in which facility-location decisions concern both WPs and DPs. We model the problem using a two-stage stochastic program with integer recourse. To solve the 2E-SM-CLRP, we develop a Benders decomposition algorithm. The location and capacity decisions are fixed from the solution of the Benders master problem. The resulting subproblem is a capacitated vehicle-routing problem with capacitated multi-depot (CVRP-CMD) and is solved using a branch-cut-and-price algorithm.Finally, we focus on the multi-stage framework proposed for the stochastic multi-period two-echelon distribution network design problem and evaluate its tractability. A scenario tree is built to handle the set of scenarios representing demand uncertainty. We present a compact formulation and develop a rolling horizon heuristic to produce design solutions for the multi-stage model. It provides good quality bounds in a reasonable computational times
6
Mrabti, Nassim. "Contribution à l'optimisation de la distribution collaborative avec partage de gains sous critères de durabilité". Electronic Thesis or Diss., Amiens, 2021. http://www.theses.fr/2021AMIE0072.
Abstract (sommario):
Les préoccupations liées au développement durable influencent de plus en plus le comportement des clients ainsi que les stratégies des entreprises. Ainsi, l'optimisation des réseaux de distribution par la collaboration horizontale devient une nécessité. Après une analyse exhaustive de la littérature, nous avons constaté que la plupart des travaux proposant des approches quantitatives abordent le niveau de décision opérationnelle par le biais de l'optimisation de la planification du transport. Par conséquent, nous traitons dans cette thèse les deux niveaux de décision : stratégique et tactique. Le premier niveau est étudié à travers le problème de conception des réseaux de distribution collaboratifs, tandis que le deuxième niveau s'intéresse au problème de répartition des coûts et des émissions de CO2. En outre, nous pensons que réduire tous les aspects de la durabilité en un seul objectif n'est pas recommandé. Dans ce contexte, nous abordons les deux problèmes en tenant compte de la durabilité économique, environnementale et sociale. Nous proposons des modèles mathématiques pour concevoir des réseaux de distribution à deux et à trois échelons. Par ailleurs, l'implication des indicateurs de durabilité lors du partage des bénéfices permet de récompenser les partenaires qui participent au mieux à la durabilité. Dans ce contexte, nous avons développé deux approches qui utilisent les niveaux de durabilité et de flexibilité de chaque partenaire dans le but de répartir d'une manière équitable les bénéfices de la collaboration. D'autre part, plusieurs scénarios sont comparés sur la base des indicateurs proposés. Au niveau de la résolution des modèles mathématiques, l'optimisation mono-objectif est effectuée d'une façon exacte et en utilisant l'algorithme génétique et le recuit simulé, tandis que l'optimisation multi-objectif est réalisée par la méthode ε-contrainte et le NSGA-II. Les résultats et les analyses obtenus montrent que la collaboration offre toujours une meilleure performance par rapport à la non-collaboration sur tous les niveaux de durabilité. Plusieurs décisions managériales sont présentées pour appliquer correctement la collaboration horizontale et améliorer davantage sa performance en termes de durabilitéSustainability issues are increasingly influencing customer behavior and corporate strategy. Consequently, the optimization of distribution networks through horizontal collaboration is becoming a necessity. After a comprehensive review of the literature, we found that most studies proposing quantitative approaches address the operational decision level through the optimization of transport planning. Therefore, in this thesis we deal with both strategic and tactical decision levels. The first level is studied by the collaborative distribution network design problem, while the second level is studied by the cost and CO2 emission allocation problem. Furthermore, we believe that reducing all sustainability dimensions to a single objective is not desirable. In this context, we address both problems by taking into account economic, environmental and social sustainability. We have developed mathematical models to design two- and three-echelon distribution networks. In addition, the inclusion of sustainability indicators in the profit-sharing process makes it possible to reward partners who best contribute to sustainability. In this context, we have developed two approaches that use the levels of sustainability and flexibility of each partner in order to distribute the benefits of the collaboration in a fair way. Furthermore, several scenarios are compared on the basis of the proposed indicators. Regarding the resolution of the mathematical models, the single-objective optimization is carried out in an exact way and by using the genetic algorithm and the simulated annealing, while the multi-objective optimization is carried out by the ε-constraint method and the NSGA-II. The results and analyses obtained show that collaboration always provides better performance compared to non-collaboration on all sustainability levels. Several managerial decisions are presented to properly apply horizontal collaboration and further improve its sustainability performance
7
Balakrishnan, Anantaram, Thomas L. Magnanti e Prakash Mirchandani. "The Multi-Network Design Problem". Massachusetts Institute of Technology, Operations Research Center, 1991. http://hdl.handle.net/1721.1/5200.
Abstract (sommario):
This paper studies a new multi-facility network synthesis problem, called the Multi-level Network Design (MLND) problem, that arises in the topological design of hierarchical communication, transportation, and electric power distribution networks whose nodes have varying levels of importance:the more critical or higher level nodes require higher grade interconnections. Given an undirected network with L possible facility types for each edge, and a partition of the nodes into L levels, the MLND problem seeks a connected design that minimizes total fixed cost while spanning all the nodes, and connecting nodes at each level via facilities of the corresponding or higher type. This problem generalizes the well-known Steiner network problem and the hierarchical network design problem. In this paper, we describe alternative model formulations for this problem and analyze the worst-case performance for heuristics based upon Steiner and spanning tree computations. For one model that we consider, the heuristic worst-case bounds on the performance ratio are either 4/3 or the worst-case performance ratio p of the embedded Steiner tree heuristic. A companion paper develops and tests a dual ascent procedure that generates tight upper and lower bounds on the optimal value of the problem. Keywords: Network design, integer programming, valid inequalities, worstcase analysis of heuristics.
8
Melovic, Dejan. "Optimal distribution network design policy". Thesis, University of Manchester, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.557289.
9
Akkas, Izzet Saygin. "Reliability Based Water Distribution Network Design". Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607830/index.pdf.
Abstract (sommario):
The need of water and the limited sources, force the researchers to find the most economical and feasible solution in the design of a water distribution network. In this study, reliability and optimization of a water distribution network are taken into account together in the design stage of the network. The relationship between reliability of a water distribution network and its cost is examined during the design of a water distribution network. A methodology for deciding the reliability level of the selected design is proposed by examining the reliability-cost relationship. The design alternatives for the case study area are obtained by the aid of a commercially available software WADISO employing partial enumeration optimization technique. The reliability value for each of the design alternative is calculated according to Misirdali (2003)&rsquos adaptation based on the methodology proposed by Bao and Mays (1990) by the aid of a hydraulic network solver program HapMam prepared by Nohutç
u (2002). For purposes of illustration, the skeletonized form of Ankara Water Distribution Network subpressure zone (N8-1) is taken as the case study area. The methodology in this study, covering the relation between the reliability and the cost of a water distribution network and the proposed reliability level can be used in the design of new systems.
10
Keles, Gultekin. "Water Distribution Network Design By Partial Enumeration". Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606816/index.pdf.
Abstract (sommario):
Water distribution networks are being designed by traditional methods based on rules-of-thumb and personal experience of the designer. However, since there is no unique solution to any network design, namely there are various combinations of
pipes, pumps, tanks all of which satisfy the same pressure and velocity restrictions, it is most probable that the design performed by traditional techniques is not the optimum one.
This study deals how an optimization technique can be a useful tool for a designer during the design to find a solution. The method used within the study is the partial enumeration technique developed by Gessler. The technique is applied by a
commercially available software, i.e. WADISO SA. The study is focused on discrepancies between a network designed by traditional techniques and the same network designed by partial enumeration method. Attention is given to steps of enumeration, which are basically grouping of pipes, candidate pipe size and price function assignments, to demonstrate that the designers can control all the phases of optimization process. In this respect, special attention is given to price functions to show the effect of them on the result. The study also revealed that the cost of fitting materials cannot be included in the price function although it may have significant
effect in a system composed of closely located junctions.
The results obtained from this study are useful to show that although optimization methods do not provide a definite solutionpartial enumeration method can assist designers to select the optimum system combination.
11
Luan, Hao. "Peer-to-peer content distribution network design /". View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?ECED%202007%20LUAN.
12
Fréchette, Alexandre. "Hub routing for the robust network design problem". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114431.
Abstract (sommario):
Robust network design (RND) applies the concept of robustness from optimization with uncertainty to the area of network design. Primary motivations stem from applications in telecommunication networks. The main presupposition is that demands across the networks are variable or unpredictable. They originate from a predefined demand set, called a demand universe. Moreover, practical impediments of network design enforce the routing of the demands to be oblivious, or fixed in advance, and to not depend on a particular instantiation from the demand universe. Additional restrictions, referred to as a routing model, are often enforced on the routing's structure. Shortest paths (SP) and hub (HUB) routing models have received particular attention, both on the theoretical and practical level. In this work, we introduce a new routing model, called the hierarchical hub routing model (HH), as a generalization to HUB. We study the theoretical properties of RND restricted to HH (RNDHH). Namely, we show its APX-hardness and provide a O(log n)-approximation algorithm. We then show how RNDHH is tractable when the problem is constrained to a particular demand universe based on demands routable on a tree. We also compare the costs of optimal solutions to RND using HH and other important oblivious routing models. Finally, we leverage HH in a practical study of a new demand universe called the capped hose model, which is a blend of the hose and the pipe model, two widely used demand universes. We use the capped hose model to shed light on which demand universes favour more a SP-like as opposed to a HH-like routing. To do so, we develop a heuristic algorithm for RNDHH, and benchmark our approach against SP using representative carrier networks and a variety of capped hose demands, parametrized by their similitude to a hose or pipe model. This study reveals conditions under which multi-hub routings, that is HH, gives improvements over single-hub and shortest path routings.Le design de réseaux robustes (RND) est celui qui applique le concept de robustesse, issu de l'optimisation avec incertitude, au domaine de la conception de réseaux. Les principales motivations derrière cette application découlent de demandes provenant des réseaux de télécommunication. La prémisse principale est que les demandes à travers les réseaux sont variables ou imprévisibles. Toutefois, nous savons que ces demandes proviennent d'un ensemble prédéfini appelé univers de demandes. De plus, des contraintes pratiques du design de réseaux requiert que le routage des demandes soit inconscient, ou fixé d'avance, et qu'il ne dépende pas d'une instanciation particulière de l'univers de demandes. Des contraintes additionnelles, connues sous le nom de modèle de routage, s'appliquent souvent à la structure du routage. Les routages par chemins les plus courts (SP) et par moyeu unique (HUB) ont reçu une attention importante, tant au niveau théorique que pratique. Dans cette thèse, nous introduisons un nouveau modèle de routage appelé routage hiérarchique par moyeux (HH), qui est une généralisation de HUB. Nous étudions les propriétés théoriques de RND restreint à HH (RNDHH). Plus particulièrement, nous démontrons son caractère APX-difficile et fournissons un algorithme O(log n)-approché. Par la suite, nous montrons comment RNDHH devient facilement soluble lorsque restreint à un univers de demandes particulier, basé sur des demandes qui peuvent être routées sur un arbre donné. Nous comparons également le coût des solutions optimales lorsque RND utilise HH ainsi que d'autres modèles de routage inconscients importants. Finalement, nous exploitons HH dans une étude pratique sur un nouvel univers de demandes, appelé modèle par tuyaux restreints, qui est un mélange de deux univers de demandes largement utilisés soit le modèle par tuyaux et le modèle par conduits. Nous utilisons le modèle par tuyaux restreints pour caractériser quel univers de demandes favorise un routage similaire à SP contrairement à un routage HH. Pour ce faire, nous développons un algorithme heuristique pour RNDHH et évaluons notre approche par rapport à SP à l'aide de réseaux d'opérateur ainsi que plusieurs types de demandes du modèle par tuyaux restreints, ceux-ci ayant été paramétrés par leur similitude à un modèle par tuyaux ou un modèle par conduits. Cette étude révèle les conditions à travers lesquelles le routage par multiples moyeux, c'est-à-dire HH, surpasse celui par HUB et SP.
13
Zorgani, Nagib Youssef. "The Design of FTTH Network". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-221007.
Abstract (sommario):
The aim of this thesis is to explain the problems of optical access networks with wavelength division multiplexers, main purpose is to demonstrate the difference between theoretical and real measurement. The work is divided into several thematic areas. The introduction outlines the basic of telecommunications, fiber optics lasers, single mode, multimode, lasers fibers cables & cores, splitters division multiplexing system, there are known solutions discussed fundamental wavelength multiplexes and their possible combinations. The following chapter deals with the active elements such as AON, PON, which are essential part xWDM systems such as optical lasers, detectors and amplifiers. Another chapter focuses on passive elements, which form a key part of the wavelength multiplex. Methods of measurement of WDM/PON networks are discussed in the following part. The next section describes the topology used active and passive optical networks. The penultimate part of the work consists of architecture & technology of xWDM such as GPON and WDM-PON networks and comparing their transmission parameters. The final part of the paper presents the results of practical experimental measurements of optical access networks with wavelengths division multiplex while these results are compared with the theoretical output & methods of Optical lost test, OTDR & LSPM, with advantage & disadvantage of every methods. The second part of practical is the draft to the connection resident housing units of 30 houses, boarding-house (10 rooms) and 2 shops, 20 km distant from exchange. With comparing the possibilities of two options- passive and active optical network- PON system – WDM- Wave multiplex. Suggest the possibility of measuring and monitoring the created network.
14
Peixoto, Alan Bessa Gomes. "The Inspections problem in the network distribution of electricity: an evolutionary approach". Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15835.
Abstract (sommario):
nÃo hÃThe planning of preventive maintenance is key role in the performance and quality of service of a power utility. The control of vegetation in the process of the electricity distribution network maintenance is of great importance to and continuous improvement of quality indicators of electricity supply, accompanied by the National Electric Energy Agency (ANEEL). The degree of criticality of pruning and productivity of teams are critical in this process. To resolve this issue it proposed a routing algorithm, in order to meet all the anomalies detected in previews, ensuring priority execution of critical cases within the period of maturity of the anomalies and before the occurrence of the failure. A genetic algorithm was developed and applied in solving this problem. The proposed technique has been adapted to a practical case of an electric utility and contributed a good economy and gains in productivity compared the current situation.
O planejamento da manutenÃÃo preventiva à papel fundamental para o bom desempenho e qualidade dos serviÃos prestados de uma concessionÃria de energia. O controle da vegetaÃÃo no processo de manutenÃÃo da rede de distribuiÃÃo de energia elÃtrica à de grande importÃncia para e melhoria contÃnua dos indicadores de qualidade do fornecimento de energia elÃtrica, acompanhado pela AgÃncia Nacional de Energia ElÃtrica (ANEEL). O grau de criticidade da poda e produtividade das equipes sÃo fatores crÃticos neste processo. Para resolver este problema foi proposto um algoritmo de roteirizaÃÃo, com o objetivo de atender todas as anomalias detectadas em inspeÃÃes prÃvias, garantindo a execuÃÃo prioritÃria dos casos mais crÃticos, dentro do prazo do vencimento das anomalias e antes da ocorrÃncia da falha. Um Algoritmo GenÃtico foi desenvolvido e aplicado na resoluÃÃo deste problema. A tÃcnica proposta foi adaptada a um caso prÃtico de uma concessionÃria de energia elÃtrica e contribuiu com uma boa economia e ganhos em produtividade, quando comparada a situaÃÃo atual.
15
Bouras, Ikram. "Fixed charge network design problem with user-optimal flows". Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS136.
Abstract (sommario):
Cette thèse s'adresse à la classe des problèmes de conception de réseaux bi-niveaux. Nous nous sommes intéressés à l'étude des applications des différents domaines et au développement d'algorithmes exacts pour la résolution des problème de réseaux bi-niveau correspondants. En particulier, nous avons étudié le problème de conception de réseau bi-niveau dans lequel le ``leader" sélectionne une partie du réseau à activer, puis, dans le deuxième niveau, la solution doit être optimale pour un problème de flot dans le sous-réseau sélectionné. Dans cette thèse, trois applications de ce problème sont étudiées : le transport de matières dangereuses, les réseaux de télécommunication et les réseaux sociaux. Le problème de deuxième niveau dans la première et la dernière application est un problème de plus court chemin alors qu'un flot de coûts minimum est requis dans la deuxième application.Le premier problème étudié est le problème de conception de réseau avec coût fixe avec contraintes de plus court chemin. Le problème est modélisé comme un programme bi-niveaux qui peut être appliqué dans le transport des matières dangereuses. Pour ce problème, nous proposons deux nouvelles formulations de programmation en nombres entiers (PLNE) inspirées par des inégalités de chemin et de cycle. Nous incorporons ces formulations dans des algorithmes de branch-and-cut et de plans coupants. Des tests numériques sont effectués sur des instances réelles et sur un ensembles d'instances aléatoires qui sont générées avec différents critères pour examiner la difficulté de ces instances. Les résultats montrent que les algorithmes de plan coupants proposés peuvent résoudre jusqu’à 19% d’instances de plus que les formulations compactes.Le deuxième problème étudié concerne la gestion de la consommation d'énergie dans les réseaux de télécommunication en utilisant un protocole de routage multi-chemins pour minimiser la capacité des liens utilisée. Nous proposons un modèle d'optimisation bi-niveaux dans lequel le premier niveau représente la fonction de gestion de l'énergie et le deuxième est un protocole de routage multi-chemins. Ensuite, le problème est reformulé par des formulations PLNE en remplaçant le problème du deuxième niveau par ses conditions d'optimalité. Ces formulations sont utilisées pour résoudre le problème avec les algorithmes classiques de plans coupants et de branch-and-cut. Les expérimentations sont effectuées sur des instances réelles afin de comparer les algorithmes proposés et d'évaluer l'efficacité de notre modèle par rapport aux modèles existants à un seul chemin et de multi-objectifs.Enfin, nous étudions le problème de la maximisation d’influence dans les réseaux sociaux signés. A notre connaissance, c'est la première fois que ce problème est considéré comme un problème de programmation à deux niveaux. Nous reformulons le problème en modèles PLNE à un niveau en utilisant trois différentes conditions d'optimalité du problème de plus court chemin apparaissant dans le deuxième niveau. Ces formulations sont renforcées en ajoutant un ensemble d'inégalités valides. Des tests numériques sont effectués sur des instances aléatoires pour comparer les différentes formulations proposées. Enfin, des solutions optimales en temps polynomial sont proposées pour des cas particuliers des graphesThis thesis addresses a class of bi-level network design problems. We are interested in investigating applications from different domains and in developing exact algorithms to solve the corresponding bi-level network problem. In particular, we study a bi-level network design problem where the leader selects a part of the network to be activated, then, in the second level, the solution must be optimal for a network flow problem in the selected sub-network. In this thesis, three applications of this problem are studied: hazmats transportation, telecommunication, and social networks analysis. The second level problem in the first and the last applications is a shortest path problem while a minimum cost flow is required in the second application.The first studied problem is the fixed charge network design problem with shortest path constraints, which is modeled as a bi-level program and can be applied in hazardous transportation. For this problem, we propose two new binary integer programming (BILP) formulations inspired by path and cycle inequalities. We incorporate these formulations in a branch-and-cut algorithm and another cutting-plane based method. Numerical experiments are performed on real instances, and random data sets generated with different criteria to examine the difficulty of the instances. The results show that the proposed cutting plane algorithms can solve up to 19% more instances than the compact formulations.The second studied problem is the energy-aware traffic engineering while using multi-path routing to minimize link capacity utilization in ISP backbone networks. We propose a bi-level optimization model where the upper level represents the energy management function, and the lower one refers to the deployed multi-path routing protocol. Then, we reformulate it as a one-level MILP replacing the second level problem by different sets of flow optimality conditions. We further use these formulations to solve the problem with classical cutting plane and branch-and-cut algorithms. The computational experiments are performed on real instances to compare the proposed algorithms and to evaluate the efficiency of our model against existing single-path and multi-objective models.Finally, we study the problem of maximization influence in signed social networks. To the best of our knowledge, it is the first time that this problem is modeled as a bi-level programming problem. We reformulate the problem as one-level MILP models using three different optimality conditions of the shortest path problem appearing in the second level. These formulations are strengthened by adding a set of valid inequalities. Computational experiments are performed using random instances to compare the different proposed formulations. Finally, explicit solutions and bounds are proposed for particular cases of instances
16
Guasch, Rodriguez David. "Reducing total fulfillment costs through distribution network design optimization". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/80998.
Abstract (sommario):
Thesis (M.B.A.)--Massachusetts Institute of Technology, Sloan School of Management; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; in conjunction with the Leaders for Global Operations Program at MIT, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 56-57).
Compared to legacy retailers, online retailers have the potential to better accommodate buyer needs by offering more service time and inventory options. One fundamental operational challenge faced by most online businesses is designing a cost effective distribution network. Based on a fixed number of locations with finite resources, companies strive for finding the cost minimizing formula for fulfilling each customer order while meeting rigorous time constraints. In practice this involves allocating specific geographies to each warehouse and defining the logistic routes serving each customer. In an attempt to address this question, a Mixed Integer Linear Programming model has been developed as a decisionmaking tool for determining the optimal carrier-destination combination at each facility. The resulting algorithm is capable of analyzing thousands of potential shipping lanes and selecting those that minimize overall shipping cost. Based on historical data from customer orders, the model consistently finds an optimal network configuration yielding operational savings on the order of 1.5%. Furthermore, the algorithm can be used to identify near-optimal solutions requiring minor tweaks on the current configuration that produce significant economic gains. This simulation tool can be used on a regular basis to adapt the outbound network to demand fluctuations. However, this phenomenon evinces the existence of a fine trade-off between economic gains and operational feasibility. For that reason, a heuristic for selecting the most robust solution is also proposed.
by David Guasch Rodriguez.
S.M.
M.B.A.
17
Snoeck, André Cornelis Joseph. "Strategic last-mile distribution network design under demand uncertainty". Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127326.
Abstract (sommario):
Thesis: Ph. D. in Transportation, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 167-173).
We propose quantitative models to incorporate demand uncertainty and physical distribution flexibility into the strategic design of last-mile distribution networks. Last-mile distribution typically constitutes the most expensive part of any global supply chain, and it is becoming increasingly complex due to the ongoing boom in e-commerce, the associated rise in customer expectations, and the increasing levels of urbanization. Appropriately designing the underlying distribution networks, including facility location, inventory allocation, and eet composition decisions, is paramount for the ecient operation of both traditional and highly responsive last-mile distribution services. In traditional networks, the order collection and delivery periods are segregated by an order cut-o, rendering the operational distribution problem deterministic.
We propose a stochastic programming model to capture the temporal hierarchy of decision making between strategic decisions made under uncertainty and deterministic operational recourse actions. However, for highly responsive networks, the order collection and delivery periods are intertwined, rendering the operational planning problem dynamic and stochastic. The aggregations and approximations required to formulate a tractable stochastic programming model fail to accurately capture the constraining impact of the strategic design on the operational response to dynamically realizing demand. Therefore, we propose a metamodel simulation-based optimization approach to address the design problem for highly responsive last-mile services. In this approach, we integrate a high-level analytical metamodel with an in-depth, disaggregate simulator.
We show that including demand uncertainty in the design process leads to networks that incorporate redundancy and flexibility in the strategic design, resulting in increased cost performance. Based on a study with a fast-moving consumer goods company that operates traditional distribution networks in emerging economies, we show that a stochastic design approach outperforms deterministic approaches, with and without embedding physical distribution flexibility in the network. In addition, we conduct a study with a global fashion company that aims to deploy a one-hour delivery service in Manhattan, NY. We show how congestion in order processing at facilities leads to picking queues that harm performance by an increase in late-delivery and a reduction in consolidation opportunities. Furthermore, we show that incorporating uncertainty allows to accurately incorporate local stock-out inventory effects.
Based on a generalization of the newsvendor model, we analytically show the potential for cost reduction that emerges from leveraging existing brick-and-mortar assets, including inventory positions and retail stores, in highly responsive distribution networks.
by André Cornelis Joseph Snoeck.
Ph. D. in Transportation
Ph.D.inTransportation Massachusetts Institute of Technology, Department of Civil and Environmental Engineering
18
Hodgdon, Tammy Jo. "A Combined Inventory-Location Model for Distribution Network Design". Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/35892.
Abstract (sommario):
Two important areas of decision-making in distribution system design involve facility loca-
tion and inventory policy determination. Facility location analyzes questions such as how
many facilities should be opened, where they should be located, and which customers should
be assigned to which DCs. Inventory policy determination involves more tactical decisions
such as the order quantities and frequencies at each level or echelon in the network. It is
believed that these two decisions can influence each other significantly. Including a multi-
echelon inventory policy decision in a location analysis allows a user to capitalize on the
strengths that each DC has to offer (e.g., lower labor rates, land costs, etc.). Likewise, when
the locations of two facilities are known, a multi-echelon inventory policy can be designed
better to incorporate the exact lead times and fixed costs between the facilities at each
level of the system. Despite this, the two problems are typically solved independently. This
research addresses these problems together and investigates different heuristic methods for
solving a combined inventory-location model. We begin by presenting the background and
formulation for each problem. These formulations are then combined to show how the two
problems can be mathematically formulated together. Rather than solve the problem ex-
actly, two heuristic methods using different philosophies are tested. We apply these heuristic
methods to the combined inventory-location problem to determine how much we can im-
prove distribution network design solutions and what type of heuristic methodology is most
effective in gaining these improvements. Our results show that the combined inventory-
location model is capable of improving on the solutions obtained by a location model with
a fixed inventory policy. The improvement based on the data sets tested in this research
was approximately $60,000. However, in cases where the inventory costs are a larger portion
of the total cost, the improvement made by the inventory-location model increased to over
$1,000,000. We also found that our second heuristic method tested provided statistically
significant improved results over our first heuristic method. Moreover, the second heuristic
method typically ran 67% faster. The improved results, although small in a relative sense
(the average improvement was 0.18%), would still represent a large absolute improvement in
supply chain costs. As much as $174,000 was saved in the data sets tested for this research.Master of Science
19
Dahan, Mathieu. "Network security and min-cost max-flow problem". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104555.
Abstract (sommario):
Thesis: S.M., Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 92-93).
Network optimization has widely been studied in the literature for a variety of design and operational problems. This has resulted in the development of computational algorithms for the study of classical operations research problems such as the maximum flow problem, the shortest path problem, and the network interdiction problem. However, in environments where network components are subject to adversarial failures, the network operator needs to strategically allocate at least some of her resources (e.g., link capacities, network flows, etc.) while accounting for the presence of a strategic adversary. This motivates the study of network security games. This thesis considers a class of network security games on flow networks, and focuses on utilizing well-known results in network optimization toward the characterization of Nash equilibria of this class of games. Specifically, we consider a 2-player strategic game for network routing under link disruptions. Player 1 (defender) routes flow through a network to maximize her value of effective flow while facing transportation costs. Player 2 (attacker) simultaneously disrupts one or more links to maximize her value of lost flow but also faces cost of disrupting links. Linear programming duality and the Max-Flow Min-Cut Theorem are applied to obtain properties that are satisfied in any Nash equilibrium. Using graph theoretic arguments, we give a characterization of the support of the equilibrium strategies. Finally, we study the conditions under which these results extend to a revised version of the game where both players face budget constraints. Thus, our contribution can be viewed as a generalization of the classical minimum cost maximum flow problem and the minimum cut problem to adversarial environments.
by Mathieu Dahan.
S.M.
20
De, Schaetzen Werner. "Optimal calibration and sampling design for hydraulic network models". Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322278.
21
Ceylan, Halim. "A genetic algorithm approach to the equilibrium network design problem". Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391956.
22
ALOISE, DANIEL. "HEURISTICS FOR THE NETWORK DESIGN PROBLEM WITH DISCRETE COST FUNCTIONS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2005. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=6665@1.
Abstract (sommario):
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORProblemas de multifluxos surgem como modelos básicos no contexto de várias aplicações de fluxos em redes, tais como redes de telecomunicações, redes de transporte e logística. Em tais aplicações, os fluxos que atravessam a rede compartilham simultaneamente os mesmos recursos disponíveis e são definidos por suas próprias restrições. A cada uma das arestas ligando os pontos da rede está associado um custo, fixo ou proporcional à sua utilização. Este trabalho trata problemas de projeto de redes multifluxos, em que os custos estão associados às capacidades instaladas nas arestas. Particularmente, será estudado o caso em que a função de custo nas arestas possui o comportamento de uma função escada crescente e descontínua, para o qual métodos exatos de resolução são ineficientes. Métodos heurísticos são propostos para a resolução aproximada do problema e sintetizados em um algoritmo de multi-partida com memória adaptativa. Um mecanismo de intensificação, conhecido na literatura como construção de vocabulário, é também explorado e aplicado. Finalmente, experimentos computacionais são realizados e o método de resolução proposto é analisado quanto aos seus resultados e os resultados obtidos pelo método de resolução proposto são analisados. O método obtém as melhores soluções conhecidas para algumas instâncias da literatura.
Multicommodity flow problems arise widely as basic models in the context of network flows applications such as telecommunication networks, transportation problems, and logistic. In these applicatons, the flows that cross the networks share the same avaiable resources simultaneously and are defined by their own constraints. Each edge connecting two nodes in the network has an associated cost that is either fixed or proportional to its use. This work focuses on a network design problem in which the cost are associated with the capacities installed in the edges. Particularly, the network design problem studied has discrete and step increasing cost functions on the edges, for which exact methods are inefficient. Heuristics are proposed for the approximate memory algorithm. An intensification mechanism, known in the literature as vocabulary building, is also explored and applied. Finally, computational experiments are performed and the results obtained with the proposed solution method are evaluated. The method obtains the best known solutions for some instances in the literature.
23
Fiambolis, Panagiotis Prokopakis Georgios. "A network design architecture for distribution of generic scene graphs /". Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA371846.
Abstract (sommario):
Thesis (M.S. in Computer Science) Naval Postgraduate School, September 1999."September 1999". Thesis advisor(s): Michael J. Zyda, Michael V. Capps, John S. Falby. Includes bibliographical references (p. 141-144). Also available online.
24
Fiambolis, Panagiotis, e Georgios Prokopakis. "A network design architecture for distribution of generic scene graphs". Thesis, Monterey, California. Naval Postgraduate School, 1999. http://hdl.handle.net/10945/8730.
Abstract (sommario):
Sharing a common view while collaborating in networked virtual environments is complex. The SOFT project examines a new approach: using generic scene graphs as a bus, for graphics distribution. This thesis (as part of the SOFT project) examines network architecture for distribution of generic scene graphs. We design and implement the network architecture with a centralized Java server. This server provides scalability, persistence, reliability, and latecomer support. The server provides interoperability and can support any SSGs on any platform. The extraction of information from the network layer is implemented in two ways. In the first, we use Java's inherent serialization mechanisms; in the second, we use the Dial a Behavior (DaBP) protocol. We empirically test the server's overhead with both network mechanisms. We have concluded that using DaBP significantly reduces the server's overhead by a factor of six but only for less than 50,000 packets. Moreover, the use of DaBP provides implementation flexibility because data format can change dynamically without requiring recompilation. Finally, DaBP, while promising, must mature and be shown to reduce overhead for large number of packets before it is ready to be incorporated into the final architecture solution for SOFT
25
SANTO, DANIEL PRADO DO ESPÍRITO. "THE INFLUENCE OF TAX PLANNING IN THE DISTRIBUTION NETWORK DESIGN AND LOCATION OF DISTRIBUTION CENTERS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=26871@1.
Abstract (sommario):
A inclusão da gestão tributária no planejamento da cadeia de distribuição é fator diferenciador, especialmente no Brasil, onde os Estados têm políticas tributárias díspares e uma postura agressiva para atrair empresas. A inclusão das preocupações tributárias quando da definição de redes de distribuição, nomeadamente na escolha de localização de infraestruturas, é, no entanto, ainda feito de forma empírica. Para avaliar o impacto dos incentivos fiscais no desenho da rede de distribuição, foi proposto um modelo de programação linear inteira mista (PLIM), incluindo como parâmetros e restrições as oportunidades criadas pela política tributária. O objetivo é definir o número e o local de centros de distribuição, bem como a alocação de clientes a cada centro, tal que o custo logístico seja minimizado (custo de frete, custo de construção, operação e manutenção dos centros de distribuição e custos tributários divididos entre mudanças de alíquotas de produtos e de fretes ao realizar cada transferência de localização). O modelo é aplicado a uma empresa brasileira que comercializa produtos químicos e foi instalada em um local distante do ponto de entrega final dos produtos, devido à inserção em um programa de incentivos fiscais, sem a adoção de nenhum modelo de localização para avaliação desta estratégia. A solução gerada pelo modelo obteve menores custos totais para o novo desenho de rede em comparação com a rede atual.Including tax management in supply chain planning is a profitable differentiating factor, especially in Brazil, where each State exhibits its own tax policy. Some studies have been conducted taking into account the tax issues in the logistics network design, however this thesis takes into account the tax incentives offered by some Brazilian states to attract business. To assess the impact of tax incentives in the distribution network design, it proposed a model for locating distribution centers based on Mixed Integer Linear Programming (MILP) that includes parameters and factors related to the restrictions and opportunities created by Brazilian tax policies. The model is applied to a Brazilian company that sells chemical products. This company is installed in a location away from the end point of delivery of the products due to insertion into a tax incentive program, without adopting any location model for evaluating the strategy. The goal is to determine the actual advantages of a reduction in tax rates offset an increase in logistics transportation costs. The solution determined whether the construction of a new distribution center is beneficial, if the results generated by the model had lower total costs for the new network design compared to the current network.
26
Parkinson, J. S. "Control system design for low pressure gas distribution networks". Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378367.
27
Mascarino, Esteban Ezequiel. "Last-mile network design for urban commodity distribution in Latin America". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/120647.
Abstract (sommario):
Thesis: S.M. in Transportation, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2018.Cataloged from PDF version of thesis. Vita.
Includes bibliographical references (pages 76-81).
Transportation, as the carrier of freight and passengers, is undeniably one of the fundamental components required for both economic growth and development. In an urban environment, freight movements support most city-based activities, while detrimentally impacting the quality of life through negative externalities (e.g., congestion, noise and air pollution, etc.). Specifically, last-mile delivery is regarded as an important yet highly expensive section within every supply chain. This is partially caused by inherent inefficiencies such as prolonged delays in traffic and unproductive idle periods at customers locations, among others. Consequently, there is a need for methodologies addressing the design of improved last-mile delivery networks. In this context, the optimal design of distribution systems requires an integrated view of strategic, tactical, and operational decisions. This work contributes with a mathematical framework that provides such an integrated view while leveraging both customer-generated waiting time inefficiencies and existing network infrastructure to serve additional clients. It also provides computationally feasible algorithms to obtain solutions for realistic situations. First, we formulate a single-echelon, multi-depot, capacitated routing problem. Employing a brownfield approach, this model optimizes the fleet composition as well as the delivery schedule and allocation to distribution facilities of medium- and high-dropsize clients, hereafter 'big-box' customers. This Routing Problem (RP) is modeled as a special case of a Bin Packing Problem (BPP) combined with a customer clustering approach. However, given its high combinatorial complexity, two alternative methodologies, a two-step approach and Benders Decomposition (BD), are tested to reduce computational times. Second, we develop a two-echelon extension, which builds on the previous model, to evaluate the economic impact of including a large number of low-dropsize customers, also known as 'nanostores', into the original distribution footprint. Those newly added customers will be served through the second echelon using a subset of the original big-box customer locations as transshipment points. To solve this Location-Routing Problem (LRP), a three-step iterative optimization approach is developed and tested. Both models are applied to a real-world consumer goods distribution case study in Latin America. Results suggest that a systematic and properly framed optimization approach, which makes efficient use of available resources, can significantly reduce the total distribution cost. Further, we show that the case study company, leveraging its existing assets and addressing inherent network inefficiencies, can efficiently expand its distribution footprint towards nanostores.
by Esteban Ezequiel Mascarino.
S.M. in Transportation
28
Atkinson, Stuart. "A futures approach to water distribution and sewer network (re)design". Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/10730.
Abstract (sommario):
When designing urban water systems (i.e. water distribution and sewer systems) it is imperative that uncertainty is taken into consideration. However, this is a challenging problem due to the inherent uncertainty associated with both system loading requirements and the potential for physical components failure. It is therefore desirable to improve the reliability of each system in order to account for these uncertainties. Although it is possible to directly evaluate the reliability of a water distribution systems (WDS) (using reliability measures), the calculation processes involved are computationally intensive and therefore unsuitable for some state-of-the-art, iterative design approaches (such as optimisation). Consequently, interest has recently grown in the use of reliability indicators, which are simpler and faster to evaluate than conventional direct reliability methods. In this thesis, a novel measure (the RUF) is developed to quantify reliability in urban water systems with a view to enhance their robustness under a range of future scenarios (Policy Reform, Market Forces, Fortress World and New-Sustainability Paradigm). The considered four future scenarios were synthesized in the EPSRC supported multidisciplinary 4 year project: Urban Futures. Each investigated urban future scenario is characterised by a distinct household water demand and local demand distribution (emerging due to different urban forms evolving in future scenarios). In order to assess the impact of urban futures, RUF has been incorporated into Urban Water System (UWS) dynamic simulations for both WDSs and Foul Sewer Systems (FSSs) using open source codes of EPANET and SWMM. Additionally, in order to overcome extensive computational effort, resulting from the use of traditional reliability measures, a new holistic reliability indicator, the hydraulic power entropy (IHPE) has been developed and compared to existing reliability indicators. Additionally, the relationship between the new reliability indicator and the above mentioned RUF reliability measure is investigated. Results suggest that the magnitude of the IHPE in network solutions provides a holistic indication of the hydraulic performance and reliability for a WDS. However, the performance of optimal solutions under some Urban Futures indicates that additional design interventions are required in order to achieve desired future operation. This thesis also proposes a new holistic foul sewer system (FSS) reliability indicator (the IFSR). The IFSR represents sewer performance as a function of excess pipe capacity (in terms of available increase and also decrease in inflow). The indicator has been tested for two case studies (i.e. different sewer network layouts). Results suggest that the magnitude of IFSR has positive correlations with a number of identified key performance indicators (i.e. relating to capacity, velocity, blockages). Finally, an Integrated Design Approach (IDA) has been developed in order to assess the implications of applying design interventions on both a WDS and downstream FSS. The approach holistically considers present and future operation of each interconnected system. The approach was subsequently demonstrated using two proposed design interventions. Results suggest that, for the considered design interventions, there is trade-off between the simultaneous improvement of both WDS and FSS operation and reliability.
29
Hultman, Gustav. "DISTRIBUTION NETWORK DESIGN : Optimization & simulation of an international supply chain". Thesis, Umeå universitet, Institutionen för matematik och matematisk statistik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-171754.
Abstract (sommario):
Höganäs AB's current distribution network for iron powder in the Asia Pacific (APAC) region is subject to high costs incurred by large inventories and high cost of capital. As a result of increasing demand and service level requirements from customers, inventories have steadily increased. Keeping a high inventory level has enabled high service levels irrespective of supply disruptions or changes in demand. It is important that the distribution network incorporates a balance between robustness and cost efficiency and not only focuses on one of these aspects. The purpose of this project is to provide Höganäs AB with scientific data on how the distribution network can be improved in terms of lowering the total cost of warehousing and distribution while maintaining or improving customer service. There are several goals for this project. The first goal is to optimize the flow of material in the distribution network given empirical data of customer demand. The intended model is a linear program. The linear program will solve a multi echelon, period, product, location and transportation mode instance of the distribution network design problem. The second goal is to test the robustness of the optimal solutions resulting from the linear program by stochastic simulation. The simulations utilize the optimal network designs generated by the linear program and is done for a set of possible scenarios where key parameters are changed. By adjusting key parameters and measuring the effect on cost and service level, the goal is to evaluate the robustness of each configuration. By keeping the existing nodes of the distribution network and changing the flow of material and distribution strategy, lower inventories can be maintained and service level kept high regardless of demand growth and supply disruption. The optimal distribution network design is one from the linear program, configured with a 14 day inventory level and 10 day reorder point for warehouses. The optimal design shows that distribution is made more robust and efficient by allowing for distribution between warehouses or supplying customers normally affiliated with other warehouses. It also suggests that a central redistribution warehouse is a possible improvement to the current network design.Höganäs AB's nuvarande distributionsnätverket for järnpulver i Asien-Stillahavsregionen (APAC) är kostsamt till följd av höga lagernivåer och kapitalkostnader. Ökande efterfrågan och krav på hög servicenivå har inneburit en stadig ökning av lagernivåerna, vilket möjliggjort för företaget att upprätthålla servicenivån oberoende av störningar i leveranskedjan eller förändringar i efterfrågan. Det är viktigt att distributionsnätverket är balanserat avseende stabilitet och kostnadseffektivitet och inte endast optimeras avseende en av faktorerna. Syftet med projektet är förse Höganäs AB vetenskapligt understödd information om hur den totala kostnaden för distributionsnätverket kan sänkas samtidigt som kundservicen upprätthålls eller förbättras. Det finns flera mål för projektet. Det första målet är att optimera materialflödet i distributionsnätverket givet empiriska data över efterfrågan. Den avsedda modellen är ett linjärprogram som löser en instans av distributionsnätverkverksdesign-problemet med multipla lager, perioder, produkter, lokaliseringar och transportsätt. Det andra målet är att utvärdera stabiliteten hos de optimala lösningar som härrör från linjärprogrammet genom stokastisk simulering. Simuleringarna använder de optimala nätverksdesigner som genereras av det linjärprogrammet och genomförs för en uppsättning möjliga scenarier där nyckelparametrar ändras. Genom att justera nyckelparametrar och mäta effekten på kostnad och servicenivå är målet att utvärdera stabiliteten för varje konfiguration. Genom att behålla de befintliga noderna i distributionsnätverket och ändra materialflödet samt distributionsstrategin kan lägre lagernivåer uppnås och servicenivån hålls hög oavsett förändrad efterfrågan och störningar i leveranskedjan. Den optimala distributionsnätverkverksdesignen är en lösning från linjärprogrammet konfigurerat med 14 dagars lagernivå och 10 dagars beställningspunkt. Den optimala designen visar att distributionen görs mer stabil och effektiv genom att tillåta leveranser mellan lagerpunkterna eller att försörja kunder från andra lagerpunkter än de normalt försörjs från. Resultatet påvisar också att en strategiskt placerad omlastningscentral kan förbättra det nuvarande distributionsnätverket.
30
Bullene, Rachel. "A Case Study of Network Design for Middle East Water Distribution". VCU Scholars Compass, 2010. http://scholarscompass.vcu.edu/etd/2260.
Abstract (sommario):
The Middle Eastern region encompassing Israel, Jordan, and the Palestinian Territories (West Bank and Gaza) is an arid region with fast growing populations. Adequate and equitable access to water for all the people of the region is crucial to the future of Middle East peace. However, the current water distribution system not only fails to provide an adequate and equitable allocation of water, but also results adverse impacts on the environment. This project involves building a mathematical model to aid decision-makers in designing an optimal water distribution network. A new method for incorporating uncertainty in optimization that is based on Bayesian simulation of posterior predictive distributions is used to represent uncertainty in demands and costs. The output of the model is a most-probable least-cost modication to the existing water distribution infrastructure. Additionally, the model output includes the probability that a network component (new desalination plant, new pipe, new canal) is part of a least-cost installation.
31
Schittekatte, Tim. "Distribution network tariff design and active consumers : a regulatory impact analysis". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS054/document.
Abstract (sommario):
La diffusion des panneaux solaires photovoltaïques à prix abordables nous amène à repenser à la manière avec laquelle les coûts des réseaux de distribution sont récupérés auprès des consommateurs. Historiquement, les consommateurs étaient facturés pour l'utilisation du réseau de distribution principalement sur la base de leur volume (net) d'électricité consommé. Avec tel type de tarif de réseau, les consommateurs qui installent des panneaux photovoltaïques contribuent beaucoup moins à la récupération du coût d’investissement réseau. Cependant, ces consommateurs (prosummeurs) dépendent autant du réseau qu’avant. La question examinée dans cette thèse est de savoir comment définir le tarif du réseau de distribution dans ce contexte changeant. Des différents modèles de théorie des jeux sont développés pour faire cette analyse. Dans ces modèles, en plus des investissements dans l’énergie solaire photovoltaïque, des investissements dans les batteries du côté des consommateurs sont aussi considérés. Ce rapport de thèse consiste en un bref aperçu suivi de quatre chapitres indépendants et d'une conclusionThe uptake of affordable solar PV panels challenges the way in which costs of distribution networks are recuperated from consumers. Historically, consumers were charged for the use of the distribution network mainly according to their (net) volume of electricity consumed over a period of time. With such volumetric network charges, consumers installing PV panels contribute a lot less towards the recuperation of network costs. However, these consumers (prosumers) still rely on the network as much as they did before. The question investigated in this thesis is how to re-design the distribution network tariff in this changing context. Different game-theoretical models are developed to conduct this analysis. In the models, not only investments in solar PV but also investments in batteries at the consumer-side are considered. The thesis consists of a brief overview followed by four standalone chapters and a conclusion
32
Wu, Yanghui. "Problem dependent metaheuristic performance in Bayesian network structure learning". Thesis, Robert Gordon University, 2012. http://hdl.handle.net/10059/790.
Abstract (sommario):
Bayesian network (BN) structure learning from data has been an active research area in the machine learning field in recent decades. Much of the research has considered BN structure learning as an optimization problem. However, the finding of optimal BN from data is NP-hard. This fact has driven the use of heuristic algorithms for solving this kind of problem. Amajor recent focus in BN structure learning is on search and score algorithms. In these algorithms, a scoring function is introduced and a heuristic search algorithm is used to evaluate each network with respect to the training data. The optimal network is produced according to the best score evaluated. This thesis investigates a range of search and score algorithms to understand the relationship between technique performance and structure features of the problems. The main contributions of this thesis include (a) Two novel Ant Colony Optimization based search and score algorithms for BN structure learning; (b) Node juxtaposition distribution for studying the relationship between the best node ordering and the optimal BN structure; (c) Fitness landscape analysis for investigating the di erent performances of both chain score function and the CH score function; (d) A classifier method is constructed by utilizing receiver operating characteristic curve with the results on fitness landscape analysis; and finally (e) a selective o -line hyperheuristic algorithm is built for unseen BN structure learning with search and score algorithms. In this thesis, we also construct a new algorithm for producing BN benchmark structures and apply our novel approaches to a range of benchmark problems and real world problem.
33
Say, Fatih. "Minimum Concave Cost Multicommodity Network Design". Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606432/index.pdf.
Abstract (sommario):
Minimum Concave Cost Multicommodity Network Design Problem arises in many application areas, such as transportation planning, distributed energy system and especially both circuit and packet switching backbone network design. Exact concave optimization algorithms have been developed, but these methods are applicable if the network size is small. Therefore, these problems are usually solved by non-exact iterative methods.
In this thesis work, methods proposed for circuit switching and packet switching network design are evaluated in detail. After a comprehensive literate survey, Yaged&rsquos Linearization, Minoux greedy and Minoux accelerated greedy methods are found to be applicable to circuit switching network design when both solution quality and computational time is considered. Previously, it has been found that Minoux greedy methods may create routings with cycles and in order to eliminate these cycles a modification has been proposed. In this work, this modification is extended and evaluated in detail. Similarly, Gerla and Kleinrock&rsquo
s Concave Branch Elimination, Gersht&rsquo
s greedy and Stacey&rsquo
s Concave Link Elimination methods are investigated within the context of packet switching network design. All of these methods consider aggregate flows on each link simultaneously re-routing more than one commodity in one step. This thesis work also considers an alternative disaggregate approach, where only one commodity is handled at a time. Finally, algorithms proposed for circuit switching network design problem are adapted to the packet switching case and an extensive comparative computational study is performed to point out the best method with respect to time and solution quality for a number of networks and cost structure. Computational results have shown that modification on Minoux greedy to eliminate cycles leads to considerable improvements and the disaggregate approach gives the best result in some networks and cost structure.
34
Galymov, Birzhan. "Distribution Network Reconfiguration For Loss Reduction By Multi-branch Exchange Method". Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614663/index.pdf.
Abstract (sommario):
As structure and size of electric power distribution systems are getting more complex, distribution automation schemes become more attractive. One of the features that is desirable in an automated system is feeder reconfiguration for loss reduction. Loss reduction can make considerable savings for a utility and results in released system capacity. There is also improved voltage regulation in the system as a result of reduced feeder voltage drop.
In this thesis, multi branch exchange algorithm is introduced to solve the network reconfiguration for loss reduction problem. The proposed technique is based on heuristic techniques applied to constraint satisfaction optimization problems. A critical review of earlier methods related with feeder reconfiguration is presented. A computer program was developed using Matlab to simulate this algorithm and results of simulations demonstrate its advantages over single branch exchange method. Moreover, the results show that the final configuration is independent of the initial configuration and give assurance that any solution offered will have a radial configuration with all loads connected.
35
Kao, Yu-Chun, e 高于珺. "Physical distribution network design problem for multi-echelons supply chain". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/60994419218247068623.
Abstract (sommario):
碩士國立高雄第一科技大學
運籌管理研究所
99
This study addresses the design of physical distribution network in multi-echelons supply chain, where the system includes manufacturers, distribution centers and retailers/customers. The problem is formulated as a mixed integer program. The proposed model determines the locations of distribution centers, the transport paths of commodity, and the volumes on the transport paths. An illustrative example and a case study based on a real distribution network were used to test the proposed model. Sensitive analysis was performed to identify some critical factors for the system. The results show that the model is practical and able to provide a promising solution.
36
Liou, Jyh-Yeuan, e 劉志遠. "The Freight Transportation Network Design Problem for Time Definite Cargo Distribution Carriers". Thesis, 1997. http://ndltd.ncl.edu.tw/handle/03760831760914516418.
Abstract (sommario):
碩士國立成功大學
交通管理(科學)學系
85
Time definite cargo distribution carriers pickup, consolidate and deliver partial loads.The strategy for a successful carrier is to provide services with competitive prices,design a freight transportation network, and implement an efficient operating plan tomaximize its profits. The freight transportation network consists of two sub-networks,line-haul operations and service operations. A proper line-haul operations network canprovide ample opportunities to consolidate partial loads therefore, reducestractor-trailer runs. On the other hand, a proper service network will providenot only convenient facilities but also a high quality services for customers. The hub-and-spoke network is a most commonly used and proven to be an efficientnetwork structure for freight shipments. However, the network structure oftime definite carriers in Taiwan mainly consists of operating spokes(centers).The consolidation function of partial loads is performed in some designated large centerswhich is integrated but often conflicted with pickup and delivery operations.Additionally, the lack of mechanical consolidation facilities, due to insufficient volumes,results in a high sorting cost. In order to avoid high sorting costs, carriers adopt stopover operation. 83% of the feeder runs perform loadingand unloading operations at centers on their routes.Unfortunately, the stopover operation substantially reduces the usable trailer capacitywhich results an ineffective feeder operation. In the near future, the external environments for carriers will be undergo a substantial change.The demand will increase which may exceed carriers'' current capacities.The desire of the Central Government in Taiwan to join WTO may result in aderegulation of the cargo industry to allow the entrance of international carriersfor domestic cargo. The government will also implement a stimulate package tocombat the economic depression. The economic package includes release ofnon-productive farm lands and a construction of 12 additional inter-city expressways.Thus, some of the carriers size this opportunity to totally reconstruct their freighttransportation networks. The network under consideration is based on a hub- and-spokeconfiguration. The whole island of Taiwan will need three major hubs and a high density ofsmall scale centers. The purpose of this research is to study the transportation network design problem for carriers.We investigate the current time definite cargo market to understand the service characteristics. We also survey carriers to gain the insight of the their operational characteristics.With the information of operational restrictions and candidate facility locations,we construct a network design mathematical model for carriers anddevelop a local improvement heuristic algorithm to solve such a NP hard integeprogramming problem. We use one of the three carriers in Taiwan as the numerical examples.
37
Lu, Min-Xian, e 呂旻憲. "Physical Distribution Network Design Problem for Multi-echelons and Product Supply Chain - A Case Study of W Company". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/e63e5x.
Abstract (sommario):
碩士國立雲林科技大學
工業工程與管理系
104
This study is a network design supply chain for multi-echelons and product. There are many suppliers, factories, DCs and customers, which are three stages in total. Firstly, the products were transported to plants from suppliers, then were produced by factories and stored in DCs secondly, and were transported to customers from DCs finally. It contains the location of suppliers and also it determines the number, transported routing deliveries and flow. During the research, we realized that the problem of three-staged supply chain was NP-hard, thus we develop Genetic Algorithm to solve it. We can solve the problem by Microsoft Excel solver and find the optimal solution for small problems. The result of Genetic Algorithm will be verified from Microsoft Excel solver. The two methods in experimental design adopt the practical situation, but adopting different stages of cost. Discovering the largest influence of cost in total cost then solving it. It can reduce the difficulties and procedures in total.
38
Sima, Said Athuman. "Integrated stochastic distribution network design: a two-level facility location problem with applications to maize crops transportation in Tanzania". Thesis, 2015. http://hdl.handle.net/10539/18589.
Abstract (sommario):
thesis submitted to the Faculty of Science in fulfilment of the requirements for the degree of Doctor of Philosophy. March 17, 2015.A two-level facility location problem (FLP) arose in the transport network of maize crop in Tanzania has been studied. The three layers, namely, production centers (PCs), distribution centers (DCs) and customer points (CPs) are considered in the two-level FLP. The stochastic e ect on the two-level FLP due to rainfall in the network links, between the DCs and CPs, has been studied. The ow of maize crop from PCs to CPs through DCs is designed at a minimum cost under deterministic and stochastic scenarios. The three decisions made simultaneously are: to determine the locations of DCs (including number of DCs), allocation of CPs to the selected DCs, allocation of selected DCs to PCs, and to determine the amount of maize crop transported from PCs to DCs and then from DCs to CPs. We have modelled the problem and generate results by optimizing the model with respect to optimal location-allocation strategies. We have considered two networks, the existing network and an extended network. In the existing network there are four PCs, ve DCs and ninety three CPs. In the extended network three additional DCs are considered. For the modelling purpose we have used the rainfall data from 2007 - 2010 in each week for 17 weeks. The optimized results for the existing network have shown improvements in cost saving compared to the manually operated existing network. In the extended network, the results have shown much more e cient and cost saving distribution system compared to the results of the existing network.
39
Ng, Man Wo. "Travel time reliability assessment techniques for large-scale stochastic transportation networks". Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-05-1050.
Abstract (sommario):
Real-life transportation systems are subject to numerous uncertainties in their operation. Researchers have suggested various reliability measures to characterize their network-level performances. One of these measures is given by travel time reliability, defined as the probability that travel times remain below certain (acceptable) levels. Existing reliability assessment (and optimization) techniques tend to be computationally intensive. In this dissertation we develop computationally efficient alternatives. In particular, we make the following three contributions.
In the first contribution, we present a novel reliability assessment methodology when the source of uncertainty is given by road capacities. More specifically, we present a method based on the theory of Fourier transforms to numerically approximate the probability density function of the (system-wide) travel time. The proposed methodology takes advantage of the established computational efficiency of the fast Fourier transform.
In the second contribution, we relax the common assumption that probability distributions of the sources of uncertainties are known explicitly. In reality, this distribution may be unavailable (or inaccurate) as we may have no (or insufficient) data to calibrate the distributions. We present a new method to assess travel time reliability that is distribution-free in the sense that the methodology only requires that the first N moments (where N is any positive integer) of the travel time to be known and that the travel times reside in a set of known and bounded intervals. Instead of deriving exact probabilities on travel times exceeding certain thresholds via computationally intensive methods, we develop analytical probability inequalities to quickly obtain upper bounds on the desired probability.
Because of the computationally intensive nature of (virtually all) existing reliability assessment techniques, the optimization of the reliability of transportation systems has generally been computationally prohibitive. The third and final contribution of this dissertation is the introduction of a new transportation network design model in which the objective is to minimize the unreliability of travel time. The computational requirements are shown to be much lower due to the assessment techniques developed in this dissertation. Moreover, numerical results suggest that it has the potential to form a computationally efficient proxy for current simulation-based network design models.text
40
"The multi-level network design problem". Sloan School of Management, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/2381.
41
Shu, Jia, Chung Piaw Teo e Zuo-Jun Max Shen. "Stochastic Transportation-Inventory Network Design Problem". 2002. http://hdl.handle.net/1721.1/4018.
Abstract (sommario):
In this paper, we study the stochastic transportation-inventory network design problem involving one supplier and multiple retailers. Each retailer faces some uncertain demand. Due to this uncertainty, some amount of safety stock must be maintained to achieve suitable service levels. However, risk-pooling benefits may be achieved by allowing some retailers to serve as distribution centers (and therefore inventory storage locations) for other retailers. The problem is to determine which retailers should serve as distribution centers and how to allocate the other retailers to the distribution centers. Shen et al. (2000) and Daskin et al. (2001) formulated this problem as a set-covering integer-programming model. The pricing subproblem that arises from the column generation algorithm gives rise to a new class of submodular function minimization problem. They only provided efficient algorithms for two special cases, and assort to ellipsoid method to solve the general pricing problem, which run in O(n⁷ log(n)) time, where n is the number of retailers. In this paper, we show that by exploiting the special structures of the pricing problem, we can solve it in O(n² log n) time. Our approach implicitly utilizes the fact that the set of all lines in 2-D plane has low VC-dimension. Computational results show that moderate size transportation-inventory network design problem can be solved efficiently via this approach.Singapore-MIT Alliance (SMA)
42
Ting, Mu-Jung, e 丁睦容. "Maximum flow problem in the distribution network flow model". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/42267347963163619539.
Abstract (sommario):
碩士國立成功大學
數學系應用數學碩博士班
93
In this paper, we are concerned with the maximum flow problem in the distribution network, a new kind of network recently introduced by Fang and Qi. It differs from the traditional networks by the presence of the D-node through which the commodities are to be distributed proportionally. Adding D-nodes into the network complicates the structure. Particularly, flows in the distribution network are frequently increased through multiple cycles. To this end, we develop a type of depth-first-search algorithm, which counts and finds all unsaturated subgraphs. Those configurations, however, could be invalid either topologically or numerically. The validity are then judged by computing the flow increment with a method we call the multi-labeling method. Finally, we also provide the phase-one procedure for finding an initial flow.
43
Wang, Shih Yuan, e 王詩媛. "Local Network Design for Pharmaceutical Distribution". Thesis, 2019. http://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/login?o=dnclcdr&s=id=%22107CGU05026011%22.&searchmode=basic.
44
Aggarwal, Manica. "Approximation algorithms for the network design problem". Thesis, 1997. http://localhost:8080/iit/handle/2074/2224.
45
Lin, Shiou-Jie, e 林修杰. "A network simplex algorithm for the minimum distribution cost problem". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/29251223326455251674.
Abstract (sommario):
碩士國立成功大學
工業與資訊管理學系碩博士班
94
The minimum cost flow problem seeks an optimal flow assignment over a network satisfying the node flow balance constraints and arc flow bounds constraints. These constraints are too simplified to model some real cases.To model the distillation or decomposition of products in some manufacturing processes, a minimum distribution cost problem (MDCP) on a specialized manufacturing network flow model has been investigated. In an MDCP, a specialized node called D-node is used to model a distillation process which only connects with a single incoming arc and several outgoing arcs. The flows entering a D-node have to be distributedaccording to a pre-specified ratio associated with each of its outgoing arcs. Such a proportional relationship between the arc flows associated with each D-node complicatesthe problem and makes the MDCP harder than conventional min-cost network flow problem. A network simplex algorithm for uncapacitated MDCP has been outlined in literature, but its detailed graphical procedures such as initial basic feasible solution computation, dual variables updates, and flow pivoting operations have not yet been given. In this thesis, we resolve these issues by upper bound techniques as well as graphical operations which decompose each pivoting graph into several components for calculating both the arc flows and the dual variables. Other issues regarding efficient ways to obtain an initial primal basic feasible solution to start with our algorithm and mathematical insights for solving the MDCP on distribution networks will also be investigated and discussed.
46
Zhang, Ben. "Distribution Network Design for Distributed Renewable Energy Sources". Thesis, 2014. http://hdl.handle.net/1828/5171.
Abstract (sommario):
Future electrical power networks should support the integration of distributed renewable energy sources, which may be contributed by individual customers instead of utility companies. Such a demand poses new challenges to power distribution network design, since the energy generation, energy consumption, and power flow all become highly dynamic. An inappropriate network design may not only waste much energy in power distribution but also incur high cost in network construction. In this thesis, we study the optimal network design problem under a dynamic current injection model. We investigate different optimization methods to obtain the optimal network structure that can better adapt to dynamic energy generation/consumption requirements and is more efficient than traditional tree-structured power networks. By predicting users' potential load in the network, network design with our method results in significant energy saving.Graduate
0984
47
Chang, Wen-Hsiang, e 張玟翔. "Power-Distribution-Network Design Methodologies toward Fast Physical-Design Closure". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/699aqd.
Abstract (sommario):
博士國立交通大學
電子研究所
106
As technology node keeps scaling and design complexity keeps increasing, power distribution network (PDN) require more routing resource to meet IR-drop and EM constraints. In this thesis, we first presented a design flow to build a routing-friendly PDN before placement. The design flow considers the impact of the aluminum-pad layer and the impact of PDN layout configurations. Second, we proposed a dynamic programming (DP) approach to further minimize the routing impact of a given uniform PDN by relocating the power stripes after placement. The results based on a 40nm microprocessor demonstrate that the proposed design flow and the proposed DP approach can effectively generate a routing-friendly PDN and in turn speed up the design closure at the physical-design stage. Finally, we propose a design flow to generate a PDN that can result in a near-minimal total wire length of global route (and in turn detailed route as well) after placement. The design flow uses a machine-learning model to quickly predict the total wire length of global route associated with a given PDN configuration. Experiment results based on 28nm industrial block designs demonstrate that the proposed design flow can generate a routing-friendly PDN and in turn speed up the design closure at the physical-design stage.
48
Liu, Ying-Wen, e 劉穎文. "A Logistics Network Design Problem Considering Environmental Concerns". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/34159973019236828949.
Abstract (sommario):
碩士國立交通大學
運輸與物流管理學系
102
It is believed that global warming and extreme weathers is a result of the increasing amount of emissions and greenhouse gases. With the rising environmental concerns in the recent years, it is important to take the related emissions into account when designing the freight transportation network. Policy issues for carbon emissions reduction are widely studied, such as, the evaluation of environmental policies, the strategies and techniques for reducing emissions.How to lower the emissions to meet a mandatory cap is also an issue for freight network design problem. This study proposesa bi-level programming formulation to model the policies of emission reduction for freight transport,whereas the lower-level problem is a transportation network assignment problem modeling the network flows, and the upper-level problem determines the most optimal improvement policies for minimizing the improvement costs. Three improvement policies are considered, including enhancing port capacity, subsidy for using a port, and internalization of external cost. Under the bi-level framework, the leader at the upper-level would consider the reaction function of the follower at the lower-level, and the follower would give its feedback to the leader as well, under the Stackelberg equilibrium. A Branch Sensitivity Analysis-Based (Branch-SAB) algorithm is proposed to solve the upper-level problem, in which the sensitivity of the lower-level equilibrium solution respect to the upper-level decision variables is continuous but non-differentiable at certain points, whereas the lower-level model is a linear programming problem and can be solved by the Simplex Method. Numerical example with a hypothetical network is used to demonstrate the performance of the model, and the results show that the improvement policies can reduce the network emissions, subject to a reduction upper bound. A higher improvement cost is needed for a stricter reduction target, but the corresponding network emissions, environmental cost, as well as transportation cost would be decreased.
49
Chin-ChiaLee e 李晉嘉. "The Network Design Problem of Passenger Railway System". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/04103090902358255750.
Abstract (sommario):
碩士國立成功大學
交通管理科學系
103
Since the railway system plays an important role in transporting passengers around Taiwan, increasing the line capacity is a major issue. For instance, there are many bottlenecks on the Taitung Line, because of 19 single-track sections. The railway line capacity can be increased by upgrading the single-track sections to double-track lines. Increasing transport volumes means that the rail operators should schedule more services. However, services are limited by the railway line capacity and such line capacity is affected by several factors, including train-type heterogeneity, speed and schedule effects. This study has evaluated services for railway line capacity, and has investigated the influence of track design (single-track or double-track) on the number of services and travel times, and has identified the bottlenecks. To solve the problem and find the optimal solution, we have designed Genetic Algorithm by combining the heuristic proposed by Lee and Chen (2009) with regression analysis. When tested with real-world examples from the Taitung Line, the results showed that there are significant differences between single-track and double-track lines. To ensure the quality of the problem solving, we have also used Lee and Chen’s (2009) scheduling timetable algorithm to enumerate the solution. The results prove that our algorithms are able to provide an optimal solution that is both accurate and rapid computationally. This research can provide the Taiwan Railways Administration (TRA) with suggestions for the best locations to upgrade their lines from single-track to double-track under conditions of limited resources.
50
Lin, Hsiao-Ling, e 林筱玲. "The Network Design Problem of Home-Delivery Carriers". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/56280791099912401804.
Abstract (sommario):
碩士南台科技大學
行銷與流通管理系
96
In recent years, with the prosperous development of electronic commerce and the importance of consumers’ demands for product delivery, the home delivery market is developed more rapidly. However, under the environment of keen competitions among home-delivery carriers, it is the subject of this research how the home delivery effectively can reduce its operating costs and promote its customer services, qualities and revenues to maintain its own competitive advantages. According to our initial understanding, the characteristics of this problem includes the service network, the line-haul operation network and the use of vehicles, all of which belong to a extensive problem of pure hub-and-spoke network. And there is not any related document which has ever studied both issues of line-haul operation network and service network. However, the structure of the overall Network for the foundation, this research is only designed to study the location and the quantity of transit centers and operation stations. This research will build the mathematical mode based on the characteristics of problems to get a solution. And then, this research will frame the heuristic mode to solve the problem of original modes and to get a solution for larger-scale problems. The result of solutions shows that the mathematical mode of this research shall be able to process this problem effectively for further research references.