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Publicações

2019

Tackling perishability in multi-level process industries

Autores
Wei, WC; Amorim, P; Guimaraes, L; Almada Lobo, B;

Publicação
International Journal of Production Research

Abstract
The classical multi-level lot-sizing and scheduling problem formulations for process industries rarely address perishability issues, such as limited shelf lives of intermediate products. In some industries, ignoring this specificity may result in severe losses. In this paper, we start by extending a classical multi-level lot-sizing and scheduling problem formulation (MLGLSP) to incorporate perishability issues. We further demonstrate that with the objective of minimising the total costs (purchasing, inventory and setup), the production plans generated by classical models are often infeasible under a setting with perishable products. The model distinguishes different perishability characteristics of raw materials, intermediates and end products according to various industries. Finally, we provide quantitative insights on the importance of considering perishability for different production settings when solving integrated production planning and scheduling problems. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.

2019

Analysis of Switch Automation Based on Active Reconfiguration Considering Reliability, Energy Storage Systems, and Variable Renewables

Autores
Santos, SF; Fitiwi, DZ; Cruz, MRM; Santos, C; Catalao, JPS;

Publicação
IEEE Transactions on Industry Applications

Abstract

2019

Spherical angular analysis for pelvis coordination assessment on modified gait

Autores
Rodrigues, C; Correia, M; Abrantes, J; Nadal, J; Benedetti, M;

Publicação
IFMBE Proceedings

Abstract
This study presents and applies 3D spherical angular analysis in relation with 2D polar coordinates to assess anatomic pelvic movement on modified gait, namely stiff knee (SKG) gait and slow running (SR) comparing with normal gait (NG). Subject specific analysis was performed of an adult healthy male based on inverse kinematics from in vivo and noninvasive capture at human movement lab of reflective markers position from pelvis anatomical selected points with Qualisys camera system during a complete stride of NG, SKG and SR. Radial distance (R), pitch (?) and azimuth (?) angular phases were computed from pelvic angle-angle diagrams (?T, ?C, ?S) at transverse (T), coronal (C) and sagittal (S) planes, and angular phase (?) and planar radial distance (r) polar coordinates computed from pelvic angle-angle diagrams projections at cartesian planes (?T, ?C), (?T, ?S), (?C, ?S). Average radial distances and phase standard deviation were assessed on spherical and polar coordinates. © Springer Nature Singapore Pte Ltd. 2019.

2019

Clustering of interval time series

Autores
Maharaj, EA; Teles, P; Brito, P;

Publicação
Statistics and Computing

Abstract
Interval time series occur when real intervals of some variable of interest are registered as an ordered sequence along time. We address the problem of clustering interval time series (ITS), for which different approaches are proposed. First, clustering is performed based on point-to-point comparisons. Time-domain and wavelet features also serve as clustering variables in alternative approaches. Furthermore, autocorrelation matrix functions, gathering the autocorrelation and cross-correlation functions of the ITS upper and lower bounds, may be compared using adequate distances (e.g. the Frobenius distance) and used for clustering ITS. An improved procedure to determine the autocorrelation function of ITS is proposed, which also serves as a basis for clustering. The different alternative approaches are explored and their performances compared for ITS simulated under different setups. An application to sea level daily ranges, observed at different locations in Australia, illustrates the proposed methods. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

2019

Computer aided detection of deep inferior epigastric perforators in computed tomography angiography scans

Autores
Araujo, RJ; Garrido, V; Baracas, CA; Vasconcelos, MA; Mavioso, C; Anacleto, JC; Cardoso, MJ; Oliveira, HP;

Publicação
Computerized Medical Imaging and Graphics

Abstract
The deep inferior epigastric artery perforator (DIEAP) flap is the most common free flap used for breast reconstruction after a mastectomy. It makes use of the skin and fat of the lower abdomen to build a new breast mound either at the same time of the mastectomy or in a second surgery. This operation requires preoperative imaging studies to evaluate the branches – the perforators – that irrigate the tissue that will be used to reconstruct the breast mound. These branches will support tissue viability after the microsurgical ligation of the inferior epigastric vessels to the receptor vessels in the thorax. Usually through a computed tomography angiography (CTA), each perforator is manually identified and characterized by the imaging team, who will subsequently draw a map for the identification of the best vascular support for the reconstruction. In the current work we propose a semi-automatic methodology that aims at reducing the time and subjectivity inherent to the manual annotation. In 21 CTAs from patients proposed for breast reconstruction with DIEAP flaps, the subcutaneous region of each perforator was extracted, by means of a tracking procedure, whereas the intramuscular portion was detected through a minimum cost approach. Both were subsequently compared with the radiologist manual annotation. Results showed that the semi-automatic procedure was able to correctly detect the course of the DIEAPs with a minimum error (average error of 0.64 and 0.50 mm regarding the extraction of subcutaneous and intramuscular paths, respectively), taking little time to do so. The objective methodology is a promising tool in the automatic detection of perforators in CTA and can contribute to spare human resources and reduce subjectivity in the aforementioned task. © 2019 Elsevier Ltd

2019

Joint production and transportation scheduling in flexible manufacturing systems

Autores
Fontes, DBMM; Homayouni, SM;

Publicação
Journal of Global Optimization

Abstract
This work proposes an integrated formulation for the joint production and transportation scheduling problem in flexible manufacturing environments. In this type of systems, parts (jobs) need to be moved around as the production operations required involve different machines. The transportation of the parts is typically done by a limited number of Automatic Guided Vehicles (AGVs). Therefore, machine scheduling and AGV scheduling are two interrelated problems that need to be addressed simultaneously. The joint production and transportation scheduling problem is formulated as a novel mixed integer linear programming model. The modeling approach proposed makes use of two sets of chained decisions, one for the machine and another for the AGVs, which are inter-connected through the completion time constraints both for machine operations and transportation tasks. The computational experiments on benchmark problem instances using a commercial software (Gurobi) show the efficiency of the modeling approach in finding optimal solutions. © 2018 Springer Science+Business Media, LLC, part of Springer Nature

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