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Publications

Publications by LIAAD

2016

Lagrangian relaxation bounds for a production-inventory-routing problem

Authors
Agra, A; Cerveira, A; Requejo, C;

Publication
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Abstract
We consider a single item Production-Inventory-Routing problem with a single producer/supplier and multiple retailers. Inventory management constraints are considered both at the producer and at the retailers, following a vendor managed inventory approach, where the supplier monitors the inventory at retailers and decides on the replenishment policy for each retailer. We assume a constant production capacity. Based on the mathematical formulation we discuss a classical Lagrangian relaxation which allows to decompose the problem into four subproblems, and a new Lagrangian decomposition which decomposes the problem into just a production-inventory subproblem and a routing subproblem. The new decomposition is enhanced with valid inequalities. A computational study is reported to compare the bounds from the two approaches. © Springer International Publishing AG 2016.

2016

Lexicon Expansion System for Domain and Time Oriented Sentiment Analysis

Authors
Guimaraes, N; Torgo, L; Figueira, A;

Publication
KDIR: PROCEEDINGS OF THE 8TH INTERNATIONAL JOINT CONFERENCE ON KNOWLEDGE DISCOVERY, KNOWLEDGE ENGINEERING AND KNOWLEDGE MANAGEMENT - VOL. 1

Abstract
In sentiment analysis the polarity of a text is often assessed recurring to sentiment lexicons, which usually consist of verbs and adjectives with an associated positive or negative value. However, in short informal texts like tweets or web comments, the absence of such words does not necessarily indicates that the text lacks opinion. Tweets like "First Paris, now Brussels... What can we do?" imply opinion in spite of not using words present in sentiment lexicons, but rather due to the general sentiment or public opinion associated with terms in a specific time and domain. In order to complement general sentiment dictionaries with those domain and time specific terms, we propose a novel system for lexicon expansion that automatically extracts the more relevant and up to date terms on several different domains and then assesses their sentiment through Twitter. Experimental results on our system show an 82% accuracy on extracting domain and time specific terms and 80% on correct polarity assessment. The achieved results provide evidence that our lexicon expansion system can extract and determined the sentiment of terms for domain and time specific corpora in a fully automatic form.

2016

Computer-supported Techniques to Increase Students Engagement in Programming

Authors
Tavares, PC; Henriques, PR; Gomes, EF;

Publication
PROCEEDINGS OF THE 8TH INTERNATIONAL CONFERENCE ON COMPUTER SUPPORTED EDUCATION, VOL 2 (CSEDU)

Abstract
One of the main reasons that justify the student's failure in (introductory) programming courses is the lack of motivation that impacts on the knowledge acquisition process, affecting learning results. As soon as students face the difficulties concerning the development of algorithms or the coding in a programming language, they give up and do not try harder to solve other problems; they think it is a demanding activity and feel frustrated. In this paper we describe in detail an experiment conducted to verify the effectiveness, in terms of the increase in motivation and in knowledge acquisition, of combining program Animation tools with the immediate feedback provided by Automatic Evaluations Systems.

2016

Bankruptcy problems with two references: an impartial compromise

Authors
Giménez Gómez, JM; Osório, A; Peris, JE;

Publication
TOP

Abstract
Pulido et al. (Annals Oper Res 158:133–141, 2008) present an extension of the classical bankruptcy problem (O’Neill in Math Social Sci 2:345–371, 1982) where the involved agents have, apart from the claims vector, an additional reference vector. To analyze this extended problem, they propose the extreme and the diagonal approaches, both of them restricted to the case in which the reference vector is lower than the claims vector. We note that if the claims and the reference vectors are interchanged, the allocation proposed by the extreme approach varies. Therefore, by introducing the idea of impartiality, in the current approach, we propose an extension of their model in which no relation is assumed between the claims and reference vectors. © 2015, Sociedad de Estadística e Investigación Operativa.

2016

Spatiotemporal Control of Forkhead Binding to DNA Regulates the Meiotic Gene Expression Program

Authors
Alves Rodrigues, I; Ferreira, PG; Moldon, A; Vivancos, AP; Hidalgo, E; Guigo, R; Ayte, J;

Publication
CELL REPORTS

Abstract
Meiosis is a differentiated program of the cell cycle that is characterized by high levels of recombination followed by two nuclear divisions. In fission yeast, the genetic program during meiosis is regulated at multiple levels, including transcription, mRNA stabilization, and splicing. Mei4 is a forkhead transcription factor that controls the expression of mid-meiotic genes. Here, we describe that Fkh2, another forkhead transcription factor that is essential for mitotic cell-cycle progression, also plays a pivotal role in the control of meiosis. Fkh2 binding preexists in most Mei4-dependent genes, inhibiting their expression. During meiosis, Fkh2 is phosphorylated in a CDK/Cig2-dependent manner, decreasing its affinity for DNA, which creates a window of opportunity for Mei4 binding to its target genes. We propose that Fkh2 serves as a placeholder until the later appearance of Mei4 with a higher affinity for DNA that induces the expression of a subset of meiotic genes.

2016

Sequence variation between 462 human individuals fine-tunes functional sites of RNA processing

Authors
Ferreira, PG; Oti, M; Barann, M; Wieland, T; Ezquina, S; Friedländer, MR; Rivas, MA; Esteve-Codina, A; Estivill, X; Guigó, R; Dermitzakis, E; Antonarakis, S; Meitinger, T; Strom, TM; Palotie, A; François Deleuze, J; Sudbrak, R; Lerach, H; Gut, I; Syvänen, A; Gyllensten, U; Schreiber, S; Rosenstiel, P; Brunner, H; Veltman, J; Hoen, PA; Jan van Ommen, G; Carracedo, A; Brazma, A; Flicek, P; Cambon-Thomsen, A; Mangion, J; Bentley, D; Hamosh, A; Rosenstiel, P; Strom, TM; Lappalainen, T; Guigó, R; Sammeth, M;

Publication
SCIENTIFIC REPORTS

Abstract
Recent advances in the cost-efficiency of sequencing technologies enabled the combined DNA-and RNA-sequencing of human individuals at the population-scale, making genome-wide investigations of the inter-individual genetic impact on gene expression viable. Employing mRNA-sequencing data from the Geuvadis Project and genome sequencing data from the 1000 Genomes Project we show that the computational analysis of DNA sequences around splice sites and poly-A signals is able to explain several observations in the phenotype data. In contrast to widespread assessments of statistically significant associations between DNA polymorphisms and quantitative traits, we developed a computational tool to pinpoint the molecular mechanisms by which genetic markers drive variation in RNA-processing, cataloguing and classifying alleles that change the affinity of core RNA elements to their recognizing factors. The in silico models we employ further suggest RNA editing can moonlight as a splicing-modulator, albeit less frequently than genomic sequence diversity. Beyond existing annotations, we demonstrate that the ultra-high resolution of RNA-Seq combined from 462 individuals also provides evidence for thousands of bona fide novel elements of RNA processing-alternative splice sites, introns, and cleavage sites-which are often rare and lowly expressed but in other characteristics similar to their annotated counterparts.

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