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Publicações

Publicações por SYSTEM

2015

Measures in Sectorization Problems

Autores
Rodrigues, AM; Ferreira, JS;

Publicação
Studies in Big Data

Abstract
Sectorization means dividing a whole into parts (sectors), a procedure that occurs in many contexts and applications, usually to achieve some goal or to facilitate an activity. The objective may be a better organization or simplification of a large problem into smaller sub-problems. Examples of applications are political districting and sales territory division. When designing/comparing sectors some characteristics such as contiguity, equilibrium and compactness are usually considered. This paper presents and describes new generic measures and proposes a new measure, desirability, connected with the idea of preference. © 2015, Springer International Publishing Switzerland.

2015

Setorização aplicada à definição de rotas

Autores
Rodrigues, Ana Maria; Soeiro Ferreira, José;

Publicação
IO 2015 - XVII Congresso da Associação Portuguesa de Investigação Operacional

Abstract
A Setorização entendida como a divisão de um território em regiões mais pequenas pode apresentar vantagens em problemas de rotas com capacidades. Decidir, a priori, que região atribuir a que veículos, reduz substancialmente a dimensão das instâncias e conduz a resultados que, para além de serem obtidos de forma mais rápida podem expressar o interesse do agente decisor. A introdução de sectores em rotas de veículos permite igualmente lidar com situações de planeamento/calendário e outras restrições. Uma situação real será apresentada onde uma abordagem integrada sectores-rotas foi aplicada.

2015

Sectorization: measures and an electromagnetism based approach

Autores
Rodrigues, Ana Maria; Soeiro Ferreira, José;

Publicação
28th Conference of the European Chapter on Combinatorial Optimization

Abstract
Sectorization means dividing a set of basic units into sectors or parts, a procedure that occurs in several contexts, such as political, health and school districting, social networks and sales territory or airspace assignment, to achieve some goal or to facilitate an activity. This presentation will focus on three main issues: Measures, a new approach to sectorization problems and an application in waste collection. When designing or comparing sectors different characteristics are usually taken into account. Some are commonly used, and they are related to the concepts of contiguity, equilibrium and compactness. These fundamental characteristics will be addressed, by defining new generic measures and by proposing a new measure, desirability, connected with the idea of preference. A new approach to sectorization inspired in Coulomb’s Law, which establishes a relation of force between electrically charged points, will be proposed. A charged point represents a small region with specific characteristics/values creating relations of attraction/repulsion with the others (two by two), proportional to the charges and inversely proportional to their distance. Finally, a real case about sectorization and vehicle routing in solid waste collection will be mentioned.

2015

Dynamic stability metrics for the container loading problem

Autores
Galrao Ramos, AG; Oliveira, JF; Goncalves, JF; Lopes, MP;

Publicação
TRANSPORTATION RESEARCH PART C-EMERGING TECHNOLOGIES

Abstract
The Container Loading Problem (CLP) literature has traditionally evaluated the dynamic stability of cargo by applying two metrics to box arrangements: the mean number of boxes supporting the items excluding those placed directly on the floor (M1) and the percentage of boxes with insufficient lateral support (M2). However, these metrics, that aim to be proxies for cargo stability during transportation, fail to translate real-world cargo conditions of dynamic stability. In this paper two new performance indicators are proposed to evaluate the dynamic stability of cargo arrangements: the number of fallen boxes (NFB) and the number of boxes within the Damage Boundary Curve fragility test (NB_DBC). Using 1500 solutions for well-known problem instances found in the literature, these new performance indicators are evaluated using a physics simulation tool (StableCargo), replacing the real-world transportation by a truck with a simulation of the dynamic behaviour of container loading arrangements. Two new dynamic stability metrics that can be integrated within any container loading algorithm are also proposed. The metrics are analytical models of the proposed stability performance indicators, computed by multiple linear regression. Pearson's r correlation coefficient was used as an evaluation parameter for the performance of the models. The extensive computational results show that the proposed metrics are better proxies for dynamic stability in the CLP than the previous widely used metrics.

2015

Integrated cutting and production planning: A case study in a home textile manufacturing company

Autores
Silva, E; Viães, C; Oliveira, JF; Carravilla, MA;

Publicação
Operations Research and Big Data: IO2015-XVII Congress of Portuguese Association of Operational Research (APDIO)

Abstract
In this paper we consider the problem of minimizing the waste of textile material in a Portuguese home textile manufacturing company. The company has a vertical structure covering the different production stages of the home textile, from weaving until the finished products. Production planning comprises different decisions: the definition of the widths and lengths of the fabric rolls to be produced, the number of fabric rolls to be used from stock or purchased and the definition of the cutting patterns to be applied to each width of the fabric roll, so that the waste is minimized. We propose a MIP model, solved by a column generation method, to tackle the problem.

2015

Pricing for Internet Sales Channels in Car Rentals

Autores
Oliveira, BB; Carravilla, MA; Oliveira, JF; Raicar, P; Acácio, D; Ferreira, J; Araújo, P;

Publicação
Studies in Big Data

Abstract
Internet sales channels, especially e-brokers that compare prices in the market, have a major impact on car rentals. As costs are heavily correlated with unoccupied fleet, occupation considerations should be integrated with swift responses to the market prices. This work was developed alongside Guerin, a Portuguese car rental, to build a tool that quickly updates prices on e-brokers websites to increase total value. This paper describes the specificities of the problem and their implication on the solution, and presents an adaptative heuristic to update prices and the system’s architecture. © 2015, Springer International Publishing Switzerland.

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