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Publications

Publications by LIAAD

2022

Graph Multi-Head Convolution for Spatio-Temporal Attention in Origin Destination Tensor Prediction

Authors
Bhanu, M; Kumar, R; Roy, S; Mendes-Moreira, J; Chandra, J;

Publication
ADVANCES IN KNOWLEDGE DISCOVERY AND DATA MINING, PAKDD 2022, PT I

Abstract
Capturing complex spatio-temporal features of thousands of correlated taxi-demand time-series in the city makes the traffic flow prediction problem a challenging task. Hence, several Deep Neural Network (DNN) models have been developed to mimic the latent spatio-temporal behaviour of taxi-demand time-series in a city to improve the prediction results. Despite, good performance of recent DNN based traffic prediction techniques, such models can only identify either adjacent or connected regions with direct or transitive connection; hence they fail to capture spatio-temporal correlation among regions that exhibit implicit or latent connection. Additionally, the dependency of the recent DNN models on recursive components facilitates error propagation during feature aggregation without any counter strategy for it. In view of these existing glitches, we introduce a novel DNN model, graph Multi-Head Convolution for patio-Temporal Aggregation (gMHC-STA) which supports capturing spatio-temporal correlation among regions with explicit and implicit connection both. Moreover, gMHC-STA aggregates both spatial and temporal characteristics using multi-head attention; thus overriding recursive RNN or its variant approach to prevent noise propagation. The experimental results of gMHC-STA on two real-world city taxi-demand datasets report minimum of 6.5-10% improvement over the best state-of-the-art on standard benchmark metric in varying experimental conditions.

2022

Tracking Data Visual Representations for Sports Broadcasting Enrichment

Authors
Couceiro, M; Lima, IR; Ulisses, A; Neves, TM; Moreira, JM;

Publication
Proceedings of the 10th International Conference on Sport Sciences Research and Technology Support, icSPORTS 2022, Valletta, Malta, October 27-28, 2022.

Abstract
The broadcast of audio-video sports content is a field with increasingly larger audiences demanding higher quality content and involvement. This growth creates the necessity to develop more content to engage the users and keep this trend. Otherwise, it may stall or even diminish. Therefore, enhancing the user experience, engagement, and involvement during live sports event broadcasts is of utmost importance. This paper proposes a solution to extract event’s information from video, resorting to Computer Vision techniques and Deep Learning algorithms. More specifically, the project encompassed the definition and implementation of field registration, object detection and tracking tasks. Focusing on football sports events, a novel dataset combining several video sources was created and used for analysis and metadata extraction. In particular, the proposed solution can detect and track players with acceptable precision using state-of-the-art methods, like YOLOv5 and DeepSORT. Furthermore, resorting to unsupervised learning techniques, the system provides team segmentation based on the colour of the players’ kits. A series of visual representations regarding the players’ movements on the field enables broadcast enrichment and increased user experience. The presented solution is framed in the H2020 DataCloud project and will be deployed in a cloud environment simplifying its access and utilisation. Copyright © 2022 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved.

2022

ST-A(G)P: Spatio-Temporal aggregator predictor model for multi-step taxi-demand prediction in cities

Authors
Bhanu, M; Priya, S; Moreira, JM; Chandra, J;

Publication
APPLIED INTELLIGENCE

Abstract
Taxi demand prediction in a city is a highly demanded smart city research application for better traffic strategies formulation. It is essential for the interest of the commuters and the taxi companies both to have an accurate measure of taxi demands at different regions of a city and at varying time intervals. This reduces the cost of resources, efforts and meets the customers' satisfaction at its best. Modern predictive models have shown the potency of Deep Neural Networks (DNN) in this domain over any traditional, statistical, or Tensor-Based predictive models in terms of accuracy. The recent DNN models using leading technologies like Convolution Neural Networks (CNN), Graph Convolution Networks (GCN), ConvLSTM, etc. are not able to efficiently capture the existing spatio-temporal characteristics in taxi demand time-series. The feature aggregation techniques in these models lack channeling and uniqueness causing less distinctive but overlapping feature space which results in a compromised prediction performance having high error propagation possibility. The present work introduces Spatio-Temporal Aggregator Predictor (ST-A(G)P), a DNN model which aggregates spatio-temporal features into (1) non-redundant and (2) highly distinctive feature space and in turn helps (3) reduce noise propagation for a high performing multi-step predictive model. The proposed model integrates the effective feature engineering techniques of machine learning approach with the non-linear capability of a DNN model. Consequently, the proposed model is able to use only the informative features responsible for the objective task with reduce noise propagation. Unlike, existing DNN models, ST-A(G)P is able to induce these qualities of feature aggregation without the use of Multi-Task Learning (MTL) approach or any additional supervised attention that existing models need for their notable performance. A considerable high-performance gain of 25 - 37% on two real-world city taxi datasets by ST-A(G)P over the state-of-art models on standard benchmark metrics establishes the efficacy of the proposed model over the existing ones.

2022

Valuing Players Over Time

Authors
Neves, TM; Meireles, L; Moreira, JM;

Publication
CoRR

Abstract

2022

Energy-Efficient Scheduling in Job Shop Manufacturing Systems: A Literature Review

Authors
Fernandes, JMRC; Homayouni, SM; Fontes, DBMM;

Publication
SUSTAINABILITY

Abstract
Energy efficiency has become a major concern for manufacturing companies not only due to environmental concerns and stringent regulations, but also due to large and incremental energy costs. Energy-efficient scheduling can be effective at improving energy efficiency and thus reducing energy consumption and associated costs, as well as pollutant emissions. This work reviews recent literature on energy-efficient scheduling in job shop manufacturing systems, with a particular focus on metaheuristics. We review 172 papers published between 2013 and 2022, by analyzing the shop floor type, the energy efficiency strategy, the objective function(s), the newly added problem feature(s), and the solution approach(es). We also report on the existing data sets and make them available to the research community. The paper is concluded by pointing out potential directions for future research, namely developing integrated scheduling approaches for interconnected problems, fast metaheuristic methods to respond to dynamic scheduling problems, and hybrid metaheuristic and big data methods for cyber-physical production systems.

2022

Energy-Efficient Scheduling of Intraterminal Container Transport

Authors
Homayouni, SM; Fontes, DBMM;

Publication
Springer Optimization and Its Applications

Abstract
Maritime transportation has been, historically, a major factor in economic development and prosperity since it enables trade and contacts between nations. The amount of trade through maritime transport has increased drastically; for example, about 90% of the European Union’s external trade and one-third of its internal trade depend on maritime transport. Major ports, typically, incorporate multiple terminals serving containerships, railways, and other forms of hinterland transportation and require interterminal and intraterminal container transport. Many factors influence the productivity and efficiency of ports and hence their economic viability. Moreover, environmental concerns have been leading to stern regulation that requires ports to reduce, for example, greenhouse gas emissions. Therefore, port authorities need to balance economic and ecological objectives in order to ensure sustainable growth and to remain competitive. Once a containership moors at a container terminal, several quay cranes are assigned to the ship to load/unload the containers to/from the ship. Loading activities require the containers to have been previously made available at the quayside, while unloading ones require the containers to be removed from the quayside. The containers are transported between the quayside and the storage yard by a set of vehicles. This chapter addresses the intraterminal container transport scheduling problem by simultaneously scheduling the loading/unloading activities of quay cranes and the transport (between the quayside and the storage yard) activities of vehicles. In addition, the problem includes vehicles with adjustable travelling speed, a characteristic never considered in this context. For this problem, we propose bi-objective mixed-integer linear programming (MILP) models aiming at minimizing the makespan and the total energy consumption simultaneously. Computational experiments are conducted on benchmark instances that we also propose. The computational results show the effectiveness of the MILP models as well as the impact of considering vehicles with adjustable speed, which can reduce the makespan by up to 16.2% and the total energy consumption by up to 2.5%. Finally, we also show that handling unloading and loading activities simultaneously rather than sequentially (the usual practice rule) can improve the makespan by up to 34.5% and the total energy consumption by up to 18.3%. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.

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