G. Miranda

Universidade Federal de Ouro Preto · Department of Production Engineering (ICEA)

This paper introduces a multimodal hub network design problem with flexible routes. Routes are flexible in the sense that they may contain a mix of hub and non-hub nodes. Nonetheless, commodity transfers can only occur at hubs, while transportation costs are flow-dependent, i.e., scale economies stem from the transport technology chosen to operate...

This work presents a computational study for two variants of a dynamic or multi-period two-level uncapacitated facility location problem. In this problem, first-level plants serve different demand patterns of scattered clients over a planning horizon via second-level facilities. In the first variant, second-level facilities can be supplied by only...

This study aims at locating and sizing medical centers and allocating equipment to meet the community secondary care needs, since the specialized care on public Brazilian national health system is critical and chronically underfunded. Therefore, we develop a two-step optimization system and Web-based interface to provide scientific-based results to...

This paper studies two-level uncapacitated facility location problems, a class of discrete location problems that consider different hierarchies of facilities and their interactions. Benders reformulations for both single and multiple assignment variants and while several separation procedures for three classes of Benders cuts are presented: standa...

We introduce the Gateway Hub Location Problem (GHLP) to design global air transportation systems. Relying on a three-level hub network structure and on having nodes located in different geographic regions, the GHLP consists of locating international gateways and domestic hubs, activating arcs to induce a connected gateway and hub network, and routi...

[This corrects the article DOI: 10.1371/journal.pone.0194050.].

Multiechelon supply chains are complex logistics systems that require flexibility and coordination at a tactical level to cope with environmental uncertainties in an efficient and effective manner. To cope with these challenges, mathematical programming models are developed to evaluate supply chain flexibility. However, under uncertainty, supply ch...

A non-linear lifting procedure is proposed to generate high density Benders cuts. The new denser cuts cover more master problem variables than traditional Benders cuts, shortening the required number of iterations to reach optimality, and speeding up the Benders decomposition algorithm. To lessen the intricacy stemmed from the non-linearity, a simp...

The incomplete hub location problem with and without hop-constraints is modeled using a Leontief substitution system approach. The Leontief formalism provides a set of important theoretical properties and delivers formulations with tight linear bounds that can explicitly incorporate hop constraints for each origin-destination pair of demands. Furth...

A non-linear lifting procedure is proposed to generate high density Benders cuts. The new denser cuts cover more master problem variables than traditional Benders cuts, shortening the required number of iterations to reach optimality, and speeding up the Benders decomposition algorithm. To lessen the intricacy stemmed from the non-linearity, a simp...

The incomplete hub location problem with and without hop-constraints is modeled using a Leontief substitution system approach. The Leontief formalism provides a set of important theoretical properties and delivers formulations with tight linear bounds that can explicitly incorporate hop constraints for each origin-destination pair of demands. Furth...

This paper presents the hub line location problem in which the location of a set of hub facilities connected by means of a path (or line) is considered. Potential applications arise in the design of public transportation and rapid transit systems, where network design costs greatly dominate routing costs and thus full interconnection of hub facilit...

Transportation hub networks are important for many large-scale logistics and supply chain systems. Basic hub location models rely on some key assumptions about the transportation cost that limits their practicality We present a new model for hub location and network design that uses fixed and variable transportation costs on all arcs, fixed costs f...

This work addresses the hub location problem with price-sensitive demands. The article analyzes sensitivity of demand to quality of service in such systems, and enables the solution of large-scale instances. Two distinct working formulations are provided, and an improved Benders decomposition algorithm is deployed. Simulation of consumer choice bet...

This article formulates a model to analyze the role of fixed costs in the design of optimal transportation hub networks. The primary purpose of this article is to better model costs in hub networks, an issue that has attracted considerable attention. This article allows particular versions of hub networks to emerge from the cost structure, rather t...

An important problem of the freight industry is the parcel delivery network design, where several facilities are responsible for assembling flows from several origins, re-routing them to other facilities where the flows are disassembled and the packages delivered to their final destinations. In order to provide this service, local tours are establi...

The tree of hubs location problem is a particularly hard variant of the so called hub location problems. When solving this problem by a Benders decomposition approach, it is necessary to deal with both optimality and feasibility cuts. While modern implementations of the Benders decomposition method rely on Pareto-optimal optimality cuts or on rende...

When considering hub-and-spoke networks with single allocation, the absence of alternative routes makes this kind of systems specially vulnerable to congestion effects. In order to improve the design of such networks, congestion costs must be addressed. This article deploys two different techniques for addressing congestion on single allocation hub...

When considering hub-and-spoke networks with single allocation, the absence of alternative routes makes this kind of systems specially vulnerable to congestion effects. In order to improve the design of such networks, congestion costs must be addressed. This article deploys two different techniques for addressing congestion on single allocation hub...

The single allocation hub location problem under congestion is addressed in this article. This mixed integer non-linear programming problem is referential in discrete location research having many real applications. Two different network design perspectives are proposed: the network owner and the network user. These perspectives can be translated i...

In this work, the single source tree network design problem under convex costs is addressed. This is a referential problem when designing networks for materials, energy or data transportation. The modeling effort yields a large scale mixed-integer nonlinear program which is very hard to solve. In order to overcome the solution difficulties, two dis...

An efficient procedure that concurrently generates Outer-Approximation and Benders cuts is devised to tackle the single allocation hub location problem under congestion, an MINLP. The proposed method is able to optimally solve large instances (up to 200 nodes) in reasonable time. The combination of both cuts is an algorithmic novelty.

We introduce in this paper an optimal method for tree network design avoiding congestion. We see this problem arising in telecommunication and transportation networks as a flow extension of the Steiner problem in directed graphs, thus including as a particular case any alternative approach based on the minimum spanning tree problem. Our multi-commo...

In this work, a mixed integer nonlinear programming model combining direct service links, demand uncertainty and congestion effects is proposed. This model is efficiently solved by Generalized Benders Decomposition, for instances of moderate sizes and reasonable number of scenarios. The deployed algorithms are further used for re-designing the Braz...

In this paper we present a new problem involving assembly lines. It arises when successive variations in the cycle time force line re-configuration. We propose four mixed integer programming formulations for the problem, three of them using a time horizon divided in periods. Such assumption gives the problem a dynamic character. The models try to s...

In this paper we present a new problem involving assembly lines. It arises when successive variations in the cycle time force line re-configuration. We propose four mixed integer programming formulations for the problem, three of them using a time horizon divided in periods. Such assumption gives the problem a dynamic character. The models try to s...

The multiple allocation hub-and-spoke network design under hub congestion problem is addressed in this paper. A non-linear mixed integer programming formulation is proposed, modeling the congestion as a convex cost function. A generalized Benders decomposition algorithm has been deployed and has successfully solved standard data set instances up to...

When considering hub-and-spoke networks with multiple allocation, the classical models of the literature compute solutions with large discount factors for small flows on interhub connections. Addressing the economies of scale issue, a tighter formulation for this problem is presented, bringing forward a special structure. A specialized version of B...

One of the most important challenges for mining engineers is to correctly analyze and generate short-term planning schedules, or simply month mining plan. The objective is to demonstrate how simulation and optimization models were combined, with simultaneous execution, in order to achieve a feasible, reliable and accurate solution for this problem....

This paper presents a Cut-and-Branch algorithm for the Multicommodity Traveling Salesman Problem (MTSP), a useful variant of the Traveling Salesman Problem (TSP). The MTSP presents a more general cost structure, allowing for solutions that consider the quality of service to the customers, delivery priorities and delivery risk, among other possible...

This paper consideres the Multicommodity Traveling Salesman Problem (MTSP), a useful variant of the Traveling Salesman Problem (TSP) which has not been specifically considered in the literature. The MTSP presents a more general cost structure , allowing for solutions that consider the quality of service to the costumers, delivery priorities and del...

In telecommunication and transportation systems, the uncapacitated multiple allocation hub location problem (UMAHLP) arises when we must flow commodities or information between several origin–destination pairs. Instead of establishing a direct node to node connection from an origin to its destination, the flows are concentrated with others at facil...

We are introducing in this article the Multicommodity Traveling Salesman Problem (MTSP), where the objective is to deliver all the demands of different commodities by a tour that minimizes the sum of the fixed and variable costs for the selected arcs. The MTSP yields then a large scale mixed integer linear programming problem. In this article we de...

The minimum latency problem, also known as traveling repairman problem, the Deliveryman problem and the traveling salesman problem with cumulative costs is a variant of the Traveling Salesman Problem in which a repairman is required to visit customers located on each node of a graph in such a way that the overall waiting times of these customers is...

We are introducing in this article the Multicommodity Traveling Salesman Problem (MTSP), where the objective is to deliver all the demands of different commodities by a tour that minimizes the sum of the fixed and variable costs for the selected arcs. The MTSP yields then a large scale mixed integer linear programming problem. In this article we de...

The Minimum Latency Problem, also known as Traveling Repairman Problem, the Deliveryman Problem and the Traveling Salesman Problem with Cumulative Costs is a variant of the Traveling Salesman Problem in which a repairman is required to visit customers located on each node of a graph in such a way that the overall waiting times of these customers is...

In this work, Benders decomposition algorithm is used to deal with a computer motherboard design problem. Amongst all the possible formulations for the component placement problem, the chosen one creates an instance of the extensively studied Quadratic Assignment Problem (QAP). This problem arises as a great challenge for engineers and computer sci...

RESUMO Um dos maiores problemas que os grandes centros urbanos enfrentam atualmente é o congestio-namento no trânsito. Uma alternativa para solucionar esse problema seria uma maior utilização de meios de transporte público como trens, metrô, fura-fila e etc. No entanto, devido ao alto custo para instalar conexões diretas entre todos os pares de pon...