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Publications

2010

An integrated system for submission, assessment, feedback and publication of online digital portfolios

Authors
Figueira, A; Felix, C; Ferreira, C;

Publication
Proceedings of the 8th IASTED International Conference on Web-Based Education, WBE 2010

Abstract
Digital portfolios have recently assumed an increasing importance in e-learning. In this article we report an integrated system that can be used to publish online projects undertaken by students during their courses. The system was then integrated with the Moodle learning management system featuring the possibility to create, evaluate, publish and maintain digital portfolios assigned and corrected by the institution faculty. This integrated process ensures a high quality level of the projects registered. The system uses information imported from Moodle's database to fill in its own database for users, courses and propagates the existing session between the two systems. It also maintains the projects in specific development phases, thus, allowing asynchronous editing, assessing or commenting on projects by different students or teachers. The creation of a new project is boosted by the use of a set of pre-defined templates which in turn give a standard layout and design quality to the final view of the project.

2010

Hierarchical medical image annotation using SVM-based approaches

Authors
Amaral, IF; Coelho, F; Da Costa, JFP; Cardoso, JS;

Publication
Proceedings of the IEEE/EMBS Region 8 International Conference on Information Technology Applications in Biomedicine, ITAB

Abstract
Automatic image annotation or image classification can be an important step when searching for images from a database. Common approaches to medical image annotation with the Image Retrieval for Medical Applications (IRMA) code make poor or no use of its hierarchical nature, where different dense sampled pixel based information methods outperform global image descriptors. In this work we address the problem of hierarchical medical image annotation by building a Content Based Image Retrieval (CBIR) system aiming to explore the combination of three different methods using Support Vector Machines (SVMs): first we concatenate global image descriptors with an interest points Bag-of-Words (BoW) to build a feature vector; second, we perform an initial annotation of the data using two known methods, disregarding the hierarchy of the IRMA code, and a third that takes the hierarchy into consideration by classifying consecutively its instances; finally, we make use of pairwise majority voting between methods by simply summing strings in order to produce a final annotation. Our results show that although almost all fusion methods result in an improvement over standalone classifications, none clearly outperforms each other. Nevertheless, these are quite competitive when compared with related works using an identical database. © 2010 IEEE.

2010

Multiple machine continuous setup lotsizing with sequence-dependent setups

Authors
Almada Lobo, B; Klabjan, D; Carravilla, MA; Oliveira, JF;

Publication
COMPUTATIONAL OPTIMIZATION AND APPLICATIONS

Abstract
We address the short-term production planning and scheduling problem coming from the glass container industry. A furnace melts the glass that is distributed to a set of parallel molding machines. Both furnace and machine idleness are not allowed. The resulting multi-machine multi-item continuous setup lotsizing problem with a common resource has sequence-dependent setup times and costs. Production losses are penalized in the objective function since we deal with a capital intensive industry. We present two mixed integer programming formulations for this problem, which are reduced to a network flow type problem. The two formulations are improved by adding valid inequalities that lead to good lower bounds. We rely on a Lagrangian decomposition based heuristic for generating good feasible solutions. We report computational experiments for randomly generated instances and for real-life data on the aforementioned problem, as well as on a discrete lotsizing and scheduling version.

2010

g-tries: an efficient data structure for discovering network motifs

Authors
Pinto Ribeiro, PM; Silva, FMA;

Publication
Proceedings of the 2010 ACM Symposium on Applied Computing (SAC), Sierre, Switzerland, March 22-26, 2010

Abstract
In this paper we propose a novel specialized data structure that we call g-trie, designed to deal with collections of subgraphs. The main conceptual idea is akin to a prefix tree in the sense that we take advantage of common topology by constructing a multiway tree where the descendants of a node share a common substructure. We give algorithms to construct a g-trie, to list all stored subgraphs, and to find occurrences on another graph of the subgraphs stored in the g-trie. We evaluate the implementation of this structure and its associated algorithms on a set of representative benchmark biological networks in order to find network motifs. To assess the efficiency of our algorithms we compare their performance with other known network motif algorithms also implemented in the same common platform. Our results show that indeed, g-tries are a feasible, adequate and very efficient data structure for network motifs discovery, clearly outperforming previous algorithms and data structures. © 2010 ACM.

2010

Term Frequency Dynamics in Collaborative Articles

Authors
Nunes, S; Ribeiro, C; David, G;

Publication
DOCENG2010: PROCEEDINGS OF THE 2010 ACM SYMPOSIUM ON DOCUMENT ENGINEERING

Abstract
Documents on the World Wide Web are dynamic entities. Mainstream information retrieval systems and techniques are primarily focused on the latest version a document, generally ignoring its evolution over time. In this work, we study the term frequency dynamics in web documents over their lifespan. We use the Wikipedia as a document collection because it is a broad and public resource and, more important, because it provides access to the complete revision history of each document. We investigate the progression of similarity values over two projection variables, namely revision order and revision date. Based on this investigation we find that term frequency in encyclopedic documents - i.e. comprehensive and focused on a single topic - exhibits a rapid and steady progression towards the document's current version. The content in early versions quickly becomes very similar to the present version of the document.

2010

A Cooperative Communications Platform for Safety Critical Robotics: An Experimental Evaluation

Authors
Cunha, FM; Braga, RAM; Reis, LP;

Publication
ADVANCES IN PRACTICAL APPLICATIONS OF AGENTS AND MULTIAGENT SYSTEMS

Abstract
As the number of handicapped people increases worldwide, Intelligent Wheelchairs (IW) are becoming the solution to enable a higher degree of independence for wheelchair users. In addition, IW Projects relevance is increasing, mainly in the fields of robotics and safety-related systems due to their inherent and still unresolved problems related with environment uncertainty, safe communications and collaboration methodologies. This paper describes the development of new communication system, based on multi-agent systems (MAS) and motivated by Intelligent Wheelchair systems. It uses a message-oriented paradigm as a mean for fault-tolerant communications in open transmission systems as well as a facilitator for entity collaboration. It provides an overview of the related work in the area, the background and the main constraints to system development, contextualized an IW development project. The results achieved enable us to conclude on the effectiveness and adequacy of the proposed communication model to the field of mobile robots, as well as to conclude that it may outperform JADE in several test scenarios.

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