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Publicações

Publicações por Elsa Marília Silva

2021

Analysis of the Impact of Physical Internet on the Container Loading Problem

Autores
Ferreira, AR; Ramos, AG; Silva, E;

Publicação
COMPUTATIONAL LOGISTICS (ICCL 2021)

Abstract
In the Physical Internet supply chain paradigm, modular boxes are one of the main drivers. The dimension of the modular boxes has already been subject to some studies. However, the usage of a modular approach on the container loading problem has not been accessed. In thiswork, we aim to assess the impact of modular boxes in the context of the Physical Internet on the optimization of loading solutions. A mathematical model for the CLP problem is used, and extensive computational experimentswere performed in a set of problem instances generated considering the Physical Internet concept. From this study, it was possible to conclude for the used instances that modular boxes contribute to a higher volume usage and lower computational times.

2021

Adaptive Sequence-Based Heuristic for Two-Dimensional Non-guillotine Packing Problems

Autores
Oliveira, Ó; Gamboa, D; Silva, E;

Publicação
Springer Proceedings in Mathematics and Statistics

Abstract
We present heuristics for two related two-dimensional non-guillotine packing problems. The first problem aims to pack a set of items into the minimum number of larger identical bins, while the second aims to pack the items that generates most value into one bin. Our approach successively creates sequences of items that defines a packing order considering knowledge obtained from sequences previously generated. Computational experiments demonstrated that the proposed heuristics are very effective in terms of solution quality with small computing times. © 2021, Springer Nature Switzerland AG.

2022

CrossLog: Automatic Mixed-Palletizing for Cross-Docking Logistics Centers

Autores
Rocha, P; Ramos, AG; Silva, E;

Publicação
COMPUTATIONAL LOGISTICS (ICCL 2022)

Abstract
The CrossLog project aims to investigate, study, develop and implement an automated and collaborative cross-docking system (aligned with Industry 4.0) capable of moving and managing the flow of products within the warehouse in the fastest and safest way. In CrossLog, the ability to generate intelligent three-dimensional packing patterns is essential to ensure the flexibility and productivity of the cross-docking system while ensuring the stability of the palletised load. In this work, a heuristic solution approach is proposed to generate efficient pallet packing patterns that simultaneously minimise the total number of pallets required and address the balance of weight and volume between pallets. Computational experiments with data from a real company demonstrate the quality of the proposed solution approach.

2025

A 3D printing nesting algorithm with dynamic collision constraints

Autores
Rocha, P; Ramos, AG; Silva, E;

Publicação
INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH

Abstract
Additive Layer Manufacturing, particularly Fused Deposition Modelling, faces significant batch loss risks during production. The traditional Concurrent Printing Mode produces all parts simultaneously (layer-by-layer, bottom-to-top), efficiently using printing space but risking complete batch failure if problems occur. In contrast, Sequential Printing Mode produces one part at a time, reducing the risk of total batch loss but utilising printing space less efficiently. In this work, we propose an algorithm that, given a set of parts, performs the nesting of the parts for Concurrent Printing Mode, and for the first time, for the Sequential Printing Mode. A no-fit polygon based approach is used to handle geometry between pairs of parts by using multiple horizontal 2D layer projections of 3D parts, to ensure non-overlapping constraints and prevent machine-part collisions. A Greedy Randomized Adaptive Search Procedure is proposed, tested and benchmarked against a commercial software, using a new set of real-world instances. The approach shows the ability to find high-quality solutions. The approach significantly reduces the number of batches, minimises waste, reduces manufacturing time, and promotes parts quality.

2025

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

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

Publicação
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.

2025

Anew effective heuristic for the Prisoner Transportation Problem

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

Publicação
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.

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