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Publications

2021

Open source platform for big data exploration and analysis

Authors
Almeida, FL; Kovalevski, P; Sakalauskas, D;

Publication
Int. J. Bus. Inf. Syst.

Abstract
Despite the enormous potential of big data, it is a relatively new issue for many companies, particularly for those of smaller size that looks at this as a challenge, is unattainable and only possible for companies with high financial capacity. However, open source software presents itself as an excellent alternative for these companies, which will allow them to exploit the high volume of data they have at their disposal. In this sense, this study presents a proposal for an architecture based exclusively on open source software that includes the entire value chain of big data, from data collection to data analysis. This architecture was tested considering three emerging scenarios in which big data become very relevant and challenging, namely for mobile analytics, network analytics, and mobile analytics. Copyright © 2021 Inderscience Enterprises Ltd.

2021

Closed loop predictive control of adaptive optics systems with convolutional neural networks

Authors
Swanson, R; Lamb, M; Correia, CM; Sivanandam, S; Kutulakos, K;

Publication
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Abstract
Predictive wavefront control is an important and rapidly developing field of adaptive optics (AO). Through the prediction of future wavefront effects, the inherent AO system servo-lag caused by the measurement, computation, and application of the wavefront correction can be significantly mitigated. This lag can impact the final delivered science image, including reduced strehl and contrast, and inhibits our ability to reliably use faint guide stars. We summarize here a novel method for training deep neural networks for predictive control based on an adversarial prior. Unlike previous methods in the literature, which have shown results based on previously generated data or for open-loop systems, we demonstrate our network's performance simulated in closed loop. Our models are able to both reduce effects induced by servo-lag and push the faint end of reliable control with natural guide stars, improving K-band Strehl performance compared to classical methods by over 55 per cent for 16th magnitude guide stars on an 8-m telescope. We further show that LSTM based approaches may be better suited in high-contrast scenarios where servo-lag error is most pronounced, while traditional feed forward models are better suited for high noise scenarios. Finally, we discuss future strategies for implementing our system in real-time and on astronomical telescope systems.

2021

Cross-Domain Co-Author Recommendation Based on Knowledge Graph Clustering

Authors
Munna, TA; Delhibabu, R;

Publication
INTELLIGENT INFORMATION AND DATABASE SYSTEMS, ACIIDS 2021

Abstract
Nowadays, due to the growing demand for interdisciplinary research and innovation, different scientific communities pay substantial attention to cross-domain collaboration. However, having only information retrieval technologies in hands might be not enough to find prospective collaborators due to the large volume of stored bibliographic records in scholarly databases and unawareness about emerging cross-disciplinary trends. To address this issue, the endorsement of the cross-disciplinary scientific alliances have been introduced as a new tool for scientific research and technological modernization. In this paper, we use a state-of-art knowledge representation technique named Knowledge Graphs (KGs) and demonstrate how clustering of learned KGs embeddings helps to build a cross-disciplinary co-author recommendation system. © 2021, Springer Nature Switzerland AG.

2021

A Hybrid Recommender System for Improving Automatic Playlist Continuation

Authors
Gatzioura, A; Vinagre, J; Jorge, AM; Sànchez Marrè, M;

Publication
IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING

Abstract
Although widely used, the majority of current music recommender systems still focus on recommendations' accuracy, user preferences and isolated item characteristics, without evaluating other important factors, like the joint item selections and the recommendation moment. However, when it comes to playlist recommendations, additional dimensions, as well as the notion of user experience and perception, should be taken into account to improve recommendations' quality. In this work, HybA, a hybrid recommender system for automatic playlist continuation, that combines Latent Dirichlet Allocation and Case-Based Reasoning, is proposed. This system aims to address "similar concepts" rather than similar users. More than generating a playlist based on user requirements, like automatic playlist generation methods, HybA identifies the semantic characteristics of a started playlist and reuses the most similar past ones, to recommend relevant playlist continuations. In addition, support to beyond accuracy dimensions, like increased coherence or diverse items' discovery, is provided. To overcome the semantic gap between music descriptions and user preferences, identify playlist structures and capture songs' similarity, a graph model is used. Experiments on real datasets have shown that the proposed algorithm is able to outperform other state of the art techniques, in terms of accuracy, while balancing between diversity and coherence.

2021

A comparison between simultaneous and hierarchical approaches to solve a multi-objective location-routing problem

Authors
Teymourifar, A; Rodrigues, AM; Ferreira, JS;

Publication
AIRO Springer Series

Abstract
This paper deals with a multi-objective location-routing problem (MO-LRP) and follows the idea of sectorization to simplify the solution approaches. The MO-LRP consists of sectorization, sub-sectorization, and routing sub-problems. In the sectorization sub-problem, a subset of potential distribution centres (DCs) is opened and a subset of customers is assigned to each of them. Each DC and the customers assigned to it form a sector. Afterward, in the sub-sectorization stage customers of each DC are divided into different sub-sector. Then, in the routing sub-problem, a route is determined and a vehicle is assigned to meet demands. To solve the problem, we design two approaches, which adapt the sectorization, sub-sectorization and routing sub-problems with the non-dominated sorting genetic algorithm (NSGA-II) in two different manners. In the first approach, NSGA-II is used to find non-dominated solutions for all sub-problems, simultaneously. The second one is similar to the first one but it has a hierarchical structure, such that the routing sub-problem is solved with a solver for binary integer programming in MATLAB optimization toolbox after solving sectorization and sub-sectorization sub-problem with NSGA-II. Four benchmarks are used and based on a comparison between the obtained results it is shown that the first approach finds more non-dominated solutions. Therefore, it is concluded that the simultaneous approach is more effective than the hierarchical approach for the defined problem in terms of finding more non-dominated solutions. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021.

2021

CAUSAL DISCOVERY IN MACHINE LEARNING: THEORIES AND APPLICATIONS

Authors
Nogueira, AR; Gama, J; Ferreira, CA;

Publication
JOURNAL OF DYNAMICS AND GAMES

Abstract
Determining the cause of a particular event has been a case of study for several researchers over the years. Finding out why an event happens (its cause) means that, for example, if we remove the cause from the equation, we can stop the effect from happening or if we replicate it, we can create the subsequent effect. Causality can be seen as a mean of predicting the future, based on information about past events, and with that, prevent or alter future outcomes. This temporal notion of past and future is often one of the critical points in discovering the causes of a given event. The purpose of this survey is to present a cross-sectional view of causal discovery domain, with an emphasis in the machine learning/data mining area.

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