ESTG - Comunicações em conferências e congressos internacionais
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Browsing ESTG - Comunicações em conferências e congressos internacionais by Field of Science and Technology (FOS) "Ciências Naturais::Ciências da Computação e da Informação"
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- 802.21-MPA-IMS ArchitecturePublication . Rodrigues, Carlos Miguel de Jesus; Rabadão, Carlos; Pereira, AntónioMobility has become a keyword nowadays with the evolution of mobile devices market and proliferation of realtime services. IP Multimedia Subsystem (IMS) is a single, standardized service framework that supports voice, video, data and messaging services, but does not provide seamless mobility for packet based sessions. This paper purposes an IMS architecture with IEEE 802.21 and media-independent pre-authentication (MPA) integrated. IEEE 802.21 can enable this seamless mobility in IMS and, additionally, MPA provides a secure handover optimization scheme, reducing, as a consequence, handover latency. The main goal of this architecture is to provide seamless and secure handovers between different access technologies in an IMS-based environment.
- An adaptive strategy for improving the performance of genetic programming-based approaches to evolutionary testingPublication . Ribeiro, José; Zenha-Rela, Mário Alberto; Vega, Francisco Fernández deThis paper proposes an adaptive strategy for enhancing Genetic Programming-based approaches to automatic test case generation. The main contribution of this study is that of proposing an adaptive Evolutionary Testing methodology for promoting the introduction of relevant instructions into the generated test cases by means of mutation; the instructions from which the algorithm can choose are ranked, with their rankings being updated every generation in accordance to the feedback obtained from the individuals evaluated in the preceding generation. The experimental studies developed show that the adaptive strategy proposed improves the algorithm's efficiency considerably, while introducing a negligible computational overhead.
- An Artificial Immune System for Temporal Anomaly Detection Using Cell Activation Thresholds and Clonal Size Regulation with HomeostasisPublication . Antunes, Mário; Correia, Manuel E.This paper presents an Artificial Immune System (AIS) based on Grossman's Tunable Activation Threshold (TAT) for anomaly detection. We describe the immunological metaphor and the algorithm adopted for T-cells, emphasizing two important features: the temporal dynamic adjustment of T-cells clonal size and its associated homeostasis mechanism. We present some promising results obtained with artificially generated data sets, aiming to test the appropriateness of using TAT in dynamic changing environments, to distinguish new unseen patterns as part of what should be detected as normal or as anomalous.
- Assessing the influence of uncertainty in land cover mapping and digital elevation models on flood risk mappingPublication . Gonçalves, Luísa M.S.; Fonte, Cidália C.; Gomes, RicardoThis paper proposes an approach to assess the influence of the uncertainty present in the parameters dependent on the land cover and elevation data over the peak flow values and the subsequent delineation of flooded areas. The proposed approach was applied to produce vulnerability and risk maps that integrate uncertainty for the urban area of Leiria, Portugal. A SPOT-4 satellite image and DEMs of the region were used. The peak flow was computed using the Soil Conservation Service method and HECHMS, HEC-RAS, Matlab and ArcGIS software programs were used. The analysis of the results obtained for the presented case study enables the identification of the order of magnitude of uncertainty associated to the watershed peak flow value and the identification of the areas which are more susceptible to flood risk to be identified.
- Classification-based early termination for coding tree structure decision in HEVCPublication . Correa, Guilherme; Assunção, Pedro; Cruz, Luis A. da Silva; Agostini, LucianoThe High Efficiency Video Coding (HEVC) standard provides improved compression rates in comparison to its predecessors at the cost of large increases in computational complexity. An important share of such increases is due to the introduction of flexible Coding Tree structures, which best configuration is decided through exhaustive tests in a Rate-Distortion Optimization (RDO) scheme. In this work, an early termination method for the decision of such structures was designed using classification trees obtained through Data Mining techniques. The classification trees were trained using intermediate encoding results from a training set of video sequences and implemented in the encoder to skip the full RDO-based decision. An average reduction of 37% in the HEVC encoder computational complexity was achieved when using the designed classification trees, with a negligible cost of only 0.28% in terms of Bjontegaard Delta-rate increase.
- Closed loop knowledge discovery for decision support in intensive care medicinePublication . Gago, Pedro; Santos, Manuel FilipeClinical Decision Support Systems (CDSS) are becoming commonplace. They are used to alert doctors about drug interactions, to suggest possible diagnostics and in several other clinical situations. One of the approaches to building CDSS is by using techniques from the Knowledge Discovery from Databases (KDD) area. However using KDD for the construction of the knowledge base used in such systems, while reducing the maintenance work still demands repeated human intervention. In this work we present a KDD based architecture for CDSS for intensive care medicine. By resorting to automated data acquisition our architecture allows for the evaluation of the predictions made and subsequent action aiming at improving the predictive performance thus closing the KDD loop.
- Complexity Estimation for Load Balancing of 360-Degree Intra Versatile Video CodingPublication . Filipe, Jose N.; Monteiro Carreira, João Filipe; Tavora, Luis M. N.; Faria, Sergio; Navarro, Antonio; Assuncao, Pedro A. A.The ever increasing demand for image and video content poses new requirements to support higher resolutions and richer representation formats, creating new challenges in coding algorithms. The forthcoming Versatile Video Coding (VVC) standard aims to increase the coding efficiency of existing algorithms and it is particularly suitable for Ultra-High Definition (UHD) resolutions and 360° video. However, since coding efficiency gains are obtained at the cost of increased complexity, fast computational approaches are needed to cope with realtime requirements, such as parallel processing. Thus, this work presents a contribution towards efficient parallel encoding of 360° video, based on coding complexity estimation and nonuniform data-level splitting (slice-based) for load balancing across multiple processors. A machine learning approach is proposed to estimate the complexity of intra coding VVC, using uncorrelated features, obtained through Principal Component Analysis (PCA) and Extremely Randomised Trees (ERT). Then, a complexity-balanced slice partition is devised, taking advantage of the clustered complexity inherent to Equirectangular Projection (ERP). It is shown that coding complexity is estimated with an accuracy of 92.25%, and the encoding time is reduced by 8.50%, when compared to the case where the 360° frames are evenly split.
- Cooperative and decomposable approaches on royal road functionsPublication . Reis, Gustavo; Fernandéz, Francisco; Olague, Gustavo
- Database marketing process supported by ontologies: System architecture proposalPublication . Pinto, Filipe Mota; Marques, Alzira; Santos, Manuel FilipeThis work proposes an ontology based system architecture which works as developer guide to a database marketing practitioner. Actually marketing departments handles daily with a great volume of data which are normally task or marketing activity dependent. This sometimes requires specific knowledge background and framework. This article aims to introduce an unexplored research at Database Marketing: the ontological approach to the Database Marketing process. Here we propose a generic framework supported by ontologies and knowledge extraction from databases techniques. Therefore this paper has two purposes: to integrate ontological approach in Database Marketing and to create domain ontology with a knowledge base that will enhance the entire process at both levels: marketing and knowledge extraction techniques. Our work is based in the Action Research methodology. At the end of this research we present some experiments in order to illustrate how knowledge base works and how can it be useful to user.
- Elder Care Modular SolutionPublication . Marcelino, Isabel; Pereira, António Manuel de JesusThe Elder Care solution has two primary goals: monitoring vital signs, sending alerts to family and specialized help and provide a social network in order to wrap all older population to avoid social isolation [1][2]. In this paper we will show the methodology used to obtain Elder Care's architecture and point some guidelines to our present work: Elder Care's implementation.
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