A Pareto-metaheuristic for a bi-objective winner determination problem in a combinatorial reverse auction

The bi-objective winner determination problem (2WDP-SC) of a combinatorial procurement auction for transport contracts comes up to a multi-criteria set covering problem. We are given a set B of bundle bids. A bundle bid b in B consists of a bidding carrier c_b, a bid price p_b, and a set tau_b of transport contracts which is a subset of the set T of tendered transport contracts. Additionally, the transport quality q_t,c_b is given which is expected to be realized when a transport contract t is executed by a carrier c_b. The task of the auctioneer is to find a set X of winning bids (X is subset of B), such that each transport contract is part of at least one winning bid, the total procurement costs are minimized, and the total transport quality is maximized. This article presents a metaheuristic approach for the 2WDP-SC which integrates the greedy randomized adaptive search procedure, large neighborhood search, and self-adaptive parameter setting in order to find a competitive set of non-dominated solutions. The procedure outperforms existing heuristics. Computational experiments performed on a set of benchmark instances show that, for small instances, the presented procedure is the sole approach that succeeds to find all Pareto-optimal solutions. For each of the large benchmark instances, according to common multi-criteria quality indicators of the literature, it attains new best-known solution sets.Pareto optimization; multi-criteria winner determination; combinatorial auction; GRASP; LNS

Multi-objective optimisation model under multiplex weighted drivers’ collaboration network : Risk, time and profit management perspectives

This study aims to devise a multi-objective optimisation model through the use of drivers’ information diffusion capacity in transportation service procurement [TSP]. In this model, in addition to the profit optimisation of transportation companies, the allocation of freights to the most suitable drivers in the shortest possible time is considered. First, driver-to-driver interactions are modelled on a weighted drivers’ collaboration network and an overlapping community detection algorithm is used to identify the communities’ leaders and their drivers. Also, an objective function is developed to optimise the speed of order allocation to drivers in communities. To reduce the risk of losing customers, the VIKOR method is developed for ranking and allocating shipping orders to the most qualified drivers. This optimisation model enables us to simultaneously manage the three factors of time, cost, and suitability of drivers in allocating shipping orders to drivers. By solving this model, the results show novice companies tend to allocate orders to drivers in the shortest time, but well-known companies are willing to assign the orders with the lowest cost. Therefore, the results reflect the real behaviour of the TSP system, and companies can adopt policies corresponding to their risk level in allocating orders to drivers.publishedVersionPeer reviewe

Opérationnalisation des stratégies de sélection des prestataires logistiques

Ce mémoire traite un problème de sélection des transporteurs à un niveau opérationnel de la hiérarchie de décision, d'un système de trafic constitué de trois flottes de transporteurs (interne, externe et spot), plusieurs entrepôts, plusieurs centres de distributions et plusieurs produits. Les demandes de produits sont considérées aléatoires et les transporteurs des flottes, interne et externe, sont sujets à des périodes de non-disponibilités. Pour permettre de suivre l'évolution du système dans le temps, la politique de sélection devrait inclure une stratégie d'affectation des quantités transférées en fonction de l'état du système. Les transporteurs externes proviennent d'un processus de sélection au niveau stratégique. Les transporteurs spots sont appelés du marché au comptant. Dans la première partie de ce mémoire, un cadre conceptuel est proposé permettant de raccorder les décisions de sélection prises au niveau stratégique et opérationnel. La sélection stratégique utilise un mécanisme d'enchères combinatoires dans lequel les transporteurs se mettent en concurrence en soumettant des mises en paquet sur les offres proposées par les expéditeurs. Un modèle mathématique mixte en nombres entiers est exposé pour déterminer les transporteurs gagnants de l'enchère avec lesquels l'expéditeur va s'engager sur une longue période. Les transporteurs gagnants de cette phase seront regroupés dans une seule flotte, appelée flotte externe. Dans la deuxième partie du projet, le problème de sélection des transporteurs, qui traite le cas d'une chaîne logistique simple, constituée d'un seul entrepôt, un seul centre de distribution, un seul produit et les trois flottes des transporteurs, est abordé. De ce fait, une formulation en programmation dynamique stochastique du problème est développée. Une résolution numérique est menée par la suite pour résoudre les équations d'optimalité obtenues. Pour illustrer l'utilité pratique et le comportement robuste de la politique développée, plusieurs analyses de sensibilité sont effectuées. Cette politique combine les deux aspects : la sélection des transporteurs et le contrôle des inventaires dans les centres de distribution. Par la suite, une approche expérimentale basée sur la simulation et des techniques d'optimisation statistiques est adoptée, en vue de valider, quantifier et optimiser la structure de la politique obtenue par modélisation mathématique. Une comparaison statistique est par la suite menée permettant de montrer la supériorité de la politique paramétrée développée par rapport à une autre politique basée principalement sur les coûts du transport comme critères de sélection. Finalement, une politique générale est proposée permettant de résoudre le problème de sélection des transporteurs à la phase opérationnelle de la hiérarchie. Cette politique est basée sur la structure globale de la politique développée du cas simple dans la deuxième partie du projet. Elle est appliquée dans un cadre plus représentatif de la réalité. Une comparaison statistique est par la suite menée montrant les gains que la politique générale proposée occasionnent par rapport à une autre politique générale visant un minimum de stock dans les centres de distribution et un coût de transport réduit. Plusieurs interprétations ont été dégagées à travers cette étude

Algoritmos evolutivos para alguns problemas em telecomunicações

Orientadores: Flavio Keidi Miyazawa, Mauricio Guilherme de Carvalho ResendeTese (doutorado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: Nos últimos anos, as redes de telecomunicação tem experienciado um grande aumento no fluxo de dados. Desde a utilização massiva de vídeo sob demanda até o incontável número de dispositivos móveis trocando texto e vídeo, o tráfego alcançou uma escala capaz de superar a capacidade das redes atuais. Portanto, as companhias de telecomunicação ao redor do mundo tem sido forçadas a aumentar a capacidade de suas redes para servir esta crescente demanda. Como o custo de instalar uma infraestrutura de rede é geralmente muito grande, o projeto de redes usa fortemente ferramentas de otimização para manter os custos tão baixos quanto possível. Nesta tese, nós analisamos vários aspectos do projeto e implementação de redes de telecomunicação. Primeiramente, nós apresentamos um novo problema de projeto de redes usado para servir demandas sem fio de dispositivos móveis e rotear tal tráfego para a rede principal. Tais redes de acesso são baseadas em tecnologias sem fio modernos como Wi-Fi, LTE e HSPA. Este problema consideramos várias restrições reais e é difícil de ser resolvido. Nós estudamos casos reais nas vizinhanças de uma grande cidade nos Estados Unidos. Em seguida, nós apresentamos uma variação do problema de localização de hubs usado para modelar as redes principais (backbones ou laços centrais). Este problema também pode ser utilizado para modelar redes de transporte de cargas e passageiros. Nós também estudamos o problema de clusterização correlacionada com sobreposições usado para modelar o comportamento dos usuários quando utilizam seus equipamentos móveis. Neste problema, nós podemos rotular um objeto usando múltiplos rótulos e analisar a conexão entre eles. Este problema é adequado para análise de mobilidade de equipamentos que pode ser usada para estimar o tráfego em uma dada região. E finalmente, nós analisamos o licenciamento de espectro sobre uma perspectiva governamental. Nestes casos, uma agência do governo deseja vender licenças para companhias de telecomunicação para que operem em uma dada faixa de espectro. Este processo usualmente é conduzido usando leilões combinatoriais. Para todos problemas, nós propomos algoritmos genéticos de chaves aleatórias viciadas e modelos de programação linear inteira mista para resolvê-los (exceto para o problema de clusterização correlacionada com sobreposição, devido sua natureza não-linear). Os algoritmos que propusemos foram capazes de superar algoritmos do estado da arte para todos problemasAbstract: Cutting and packing problems are common problems that occur in many industry and business process. Their optimized resolution leads to great profits in several sectors. A common problem, that occur in textil and paper industries, is to cut a strip of some material to obtain several small items, using the minimum length of material. This problem, known by Two Dimensional Strip Packing Problem (2SP), is a hard combinatorial optimization problem. In this work, we present an exact algorithm to 2SP, restricted to two staged cuts (known by Two Dimensional Level Strip Packing, 2LSP). The algorithm uses the branch-and-price technique, and heuristics based on approximation algorithms to obtain upper bounds. The algorithm obtained optimal or almost optimal for small and moderate sized instancesAbstract: In last twenty years, telecommunication networks have experienced a huge increase in data utilization. From massive on-demand video to uncountable mobile devices exchanging text and video, traffic reached scales that overcame the network capacities. Therefore, telecommunication companies around the world have been forced to increase their capacity to serve this increasing demand. As the cost to deploy network infrastructure is usually very large, the design of a network heavily uses optimization tools to keep costs as low as possible. In this thesis, we analyze several aspects of the design and deployment of communication networks. First, we present a new network design problem used to serve wireless demands from mobile devices and route the traffic to the core network. Such access networks are based on modern wireless access technologies such as Wi-Fi, LTE, and HSPA. This problem has several real world constraints and it is hard to solve. We study real cases of the vicinity of a large city in the United States. Following, we present a variation of the hub-location problem used to model these core networks. Such problem is also suitable to model transportation networks. We also study the overlapping correlation clustering problem used to model the user's behavior when using their mobile devices. In such problem, one can label an object with multiple labels and analyzes the connections between them. Although this problem is very generic, it is suitable to analyze device mobility which can be used to estimate traffic in geographical regions. Finally, we analyze spectrum licensing from a governmental perspective. In these cases, a governmental agency wants to sell rights for telecommunication companies to operate over a given spectrum range. This process usually is conducted using combinatorial auctions. For all problems we propose biased random-key genetic algorithms and mixed integer linear programming models (except in the case of the overlapping correlation clustering problem due its non-linear nature). Our algorithms were able to overcome the state of the art algorithms for all problemsDoutoradoCiência da ComputaçãoDoutor em Ciência da Computaçã

Measuring supply chain carbon efficiency : a carbon label framework

Thesis (Ph. D.)--Massachusetts Institute of Technology, Engineering Systems Division, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 273-293).In the near term, efficiency improvements represent a key option for reducing the impacts of climate change. The growing awareness of climate change has increased the attention regarding the carbon emissions "embedded" in the products we consume. This increased attention creates a need to measure and improve the carbon efficiency of the supply chains that produce those goods. In this thesis we present a method for measuring the carbon efficiency of a supply chain that recognizes the decentralized nature of supply chains. First, drawing from concepts in supply chain performance measurement and eco-efficiency we propose a definition of supply chain carbon efficiency that is consistent with the idea of a product's carbon footprint. We present Life Cycle Assessment (LCA), a method for quantifying the environmental impact of a product or service, as the appropriate method of measuring a product's carbon footprint and demonstrate the use of LCA through a case study involving the supply chain of bananas. Next, we characterize the difficulty and uncertainty in performing an LCA of a supply chain through an analysis of our case study of bananas. We present a framework to reduce the uncertainty though the concept of a carbon label. The carbon label provides a system where firms can measure the carbon footprint of their activities and share this information with their supply chain partners. We identify the role of third parties in facilitating information sharing and define the characteristics that describe the carbon label. Finally, we demonstrate how the carbon label works in the context of the supply chain. Through an analysis of the mode and carrier assignment steps in an integrated supply chain we develop new metrics that show how sharing information can increase the accuracy of the measured carbon footprint and improve decision-making. We provide incentive for firms to share information through the development of a vertical differentiation model of product carbon labels. Our model shows how consumer demand for lower carbon products drives reductions in the carbon footprint throughout the supply chain and induces firms to voluntarily disclose their carbon footprint.by Anthony J. Craig.Ph.D