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About

About

Elsa Silva is a researcher at INESC TEC's Industrial Engineering and Management Center and an invited Assistant Professor at the University of Minho's Production and Systems Department.  

She has a PhD in Industrial and Systems Engineering since 2012 from the University of Minho. Her main research interests include the ability to solve hard and large-scale combinatorial optimization problems that arise in various fields, such as cutting and packing problems and retail operations, using hybrid linear and meta-heuristic programming approaches.   

Elsa Silva's main research contributions have been in cutting and packing (C&P) problems. Pioneering algorithms have been developed combining mathematical models, decomposition methods and heuristics to solve practical applications that so far have not been studied realistically. This was an important contribution to the advancement of C&P knowledge.   

The practical applications addressed were Shelf Space Allocation problem, Strip Packing Problem in textile industry, Container Loading Problem with stability, weight limit, load balance and multi-drop constraints. Another important contribution in C&P area was the problem generator for every type of 2D and 3D rectangular C&P problems. 

Interest
Topics
Details

Details

  • Name

    Elsa Marília Silva
  • Role

    External Research Collaborator
  • Since

    01st February 2012
006
Publications

2025

A GRASP-based multi-objective approach for the tuna purse seine fishing fleet routing problem

Authors
Granado, I; Silva, E; Carravilla, MA; Oliveira, JF; Hernando, L; Fernandes-Salvador, JA;

Publication
COMPUTERS & OPERATIONS RESEARCH

Abstract
Nowadays, the world's fishing fleet uses 20% more fuel to catch the same amount offish compared to 30 years ago. Addressing this negative environmental and economic performance is crucial due to stricter emission regulations, rising fuel costs, and predicted declines in fish biomass and body sizes due to climate change. Investment in more efficient engines, larger ships and better fuel has been the main response, but this is only feasible in the long term at high infrastructure cost. An alternative is to optimize operations such as the routing of a fleet, which is an extremely complex problem due to its dynamic (time-dependent) moving target characteristics. To date, no other scientific work has approached this problem in its full complexity, i.e., as a dynamic vehicle routing problem with multiple time windows and moving targets. In this paper, two bi-objective mixed linear integer programming (MIP) models are presented, one for the static variant and another for the time-dependent variant. The bi-objective approaches allow to trade off the economic (e.g., probability of high catches) and environmental (e.g., fuel consumption) objectives. To overcome the limitations of exact solutions of the MIP models, a greedy randomized adaptive search procedure for the multi-objective problem (MO-GRASP) is proposed. The computational experiments demonstrate the good performance of the MO-GRASP algorithm with clearly different results when the importance of each objective is varied. In addition, computational experiments conducted on historical data prove the feasibility of applying the MO-GRASP algorithm in a real context and explore the benefits of joint planning (collaborative approach) compared to a non-collaborative strategy. Collaborative approaches enable the definition of better routes that may select slightly worse fishing and planting areas (2.9%), but in exchange fora significant reduction in fuel consumption (17.3%) and time at sea (10.1%) compared to non-collaborative strategies. The final experiment examines the importance of the collaborative approach when the number of available drifting fishing aggregation devices (dFADs) per vessel is reduced.

2025

Anew effective heuristic for the Prisoner Transportation Problem

Authors
Ferreira, L; Maciel, MVM; de Carvalho, JV; Silva, E; Alvelos, FP;

Publication
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH

Abstract
The Prisoner Transportation Problem is an NP-hard combinatorial problem and a complex variant of the Dial-a- Ride Problem. Given a set of requests for pick-up and delivery and a homogeneous fleet, it consists of assigning requests to vehicles to serve all requests, respecting the problem constraints such as route duration, capacity, ride time, time windows, multi-compartment assignment of conflicting prisoners and simultaneous services in order to optimize a given objective function. In this paper, we present anew solution framework to address this problem that leads to an efficient heuristic. A comparison with computational results from previous papers shows that the heuristic is very competitive for some classes of benchmark instances from the literature and clearly superior in the remaining cases. Finally, suggestions for future studies are presented.

2025

A new effective heuristic for the Prisoner Transportation Problem

Authors
Ferreira, L; Milan Maciel, MV; de Carvalho, JMV; Silva, E; Alvelos, FP;

Publication
Eur. J. Oper. Res.

Abstract
The Prisoner Transportation Problem is an NP-hard combinatorial problem and a complex variant of the Dial-a-Ride Problem. Given a set of requests for pick-up and delivery and a homogeneous fleet, it consists of assigning requests to vehicles to serve all requests, respecting the problem constraints such as route duration, capacity, ride time, time windows, multi-compartment assignment of conflicting prisoners and simultaneous services in order to optimize a given objective function. In this paper, we present a new solution framework to address this problem that leads to an efficient heuristic. A comparison with computational results from previous papers shows that the heuristic is very competitive for some classes of benchmark instances from the literature and clearly superior in the remaining cases. Finally, suggestions for future studies are presented.

2025

Improving warehouse operations: leveraging simulation for efficient layout design and process improvement in a picking by line operation

Authors
de Carvalho Paula, M; Carvalho, MS; Silva, E;

Publication
Procedia Computer Science

Abstract
This study focuses on improving the picking processes within a Picking-by-Line (PBL) warehouse through the development of a simulation model to assess different layouts and new operational rules. Utilizing a combination of Discrete Event Simulation (DES) and Agent-Based Modeling (ABS) in AnyLogic, the simulation model was validated against real-world Key Performance Indicators (KPIs) to ensure accuracy. The study identified three primary improvement opportunities. To address these opportunities, four scenarios were tested. The results showed varying impacts on productivity, with three of the four scenarios yielding improvements in picking productivity. Pilot testing confirmed the simulation model's predictions. The findings indicate that balancing travel distance reduction with congestion management is key to increasing picking productivity. This study reaffirms the value of simulation modeling in warehouse management, providing a robust framework for free-risk testing. © 2025 Elsevier B.V., All rights reserved.

2024

Pallets delivery: Two matheuristics for combined loading and routing

Authors
Silva, E; Ramos, AG; Moura, A;

Publication
EXPERT SYSTEMS WITH APPLICATIONS

Abstract
The implementation of novel regulatory and technical requirements for the distribution of vehicle axle weights in road freight transport introduces a new set of constraints on vehicle routing. Until now, axle weight distribution in determining the load plan for freight transport units has been overlooked in the vehicle routing process. Compliance with these axle weight constraints has become paramount for road freight transport companies, since noncompliance with the axle weight distribution legislation translates into heavy fines. This work aims to provide a tool capable of generating cargo loading plans and routing sequences for a palletised cargo distribution problem. The problem addressed integrates the capacitated vehicle routing problem with time window and the two-dimensional loading problem with load balance constraints. Two integrative solution approaches are proposed, one giving greater importance to the routing and the other prioritising the loading. In addition, a novel MILP model is proposed for the 2D pallet loading problem with load-balance constraints that take advantage of the standard dimension of the pallets. Extensive computational experiments were performed with a set of well-known literature benchmark instances, extended to incorporate additional features. The computational results show the effectiveness of the proposed approaches.

Supervised
thesis

2021

Otimização do problema integrado de carregamento e roteamento de veículos de frota heterogénea

Author
Gerardo Guedes Saraiva de Menezes

Institution

2020

OTIMIZAÇÃO DA ENTREGA DE ENCOMENDAS POR DRONES

Author
JOÃO PEDRO MOUTINHO ALVES BARBOSA

Institution
INESCTEC

2019

Efficient Heuristics for Two-Dimensional Cutting and Packing Problems

Author
Óscar António Maia de Oliveira

Institution
INESCTEC

2019

Conceção e desenvolvimento de um sistema de apoio à decisão para gestão de inventários no retalho

Author
Edgar Filipe dos Anjos Couto

Institution
INESCTEC

The Two-Dimensional Rectangular Strip Packing Problem

Author
Alvaro Luiz Neuenfeldt Junior

Institution
FCT