ESTGV - DMAT - Capítulo em obra internacional, como autor
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- Brugada Syndrome Diagnosis - Three Approaches to Combining Diagnostic MarkersPublication . Henriques, Carla; Matos, Ana; Santos, LuisBrugada Syndrome (BS) is an inherited cardiopathy that predisposes individuals without structural heart disease to sudden cardiac death. The diagnosis is performed by detecting a typical pattern in the electrocardiogram (ECG), called Type 1 Brugada pattern, but this is not always visible, so the diagnosis is not straight- forward. In this study, we investigated other ECG markers, independent of the typ- ical pattern, which exhibited a good ability to differentiate the carriers and the non-carriers of the genetic mutation responsible for this disease. The combination of these markers through linear models has led to enhancing the ability of each marker to discriminate between the two groups. We found linear combinations of these markers for which the area under the ROC curve (AUC) was greater than 0.9, which suggests an excellent ability to discriminate between the two groups. This study points towards good alternatives for diagnosing BS which may prevent searching for the Type 1 Brugada pattern in an ECG, but these alternatives should be investigated with a larger database in order to produce a good effective predictive model.
- An Experimental Study of the Ant Colony System for the Period Vehicle Routing ProblemPublication . Matos, Ana Cristina; Oliveira, Rui CarvalhoIn this paper, a new Ant System approach to the Period Vehicle Routing Problem (PVRP) is presented. In PVRP, visit days have to be assigned to customers in order to find efficient routes over the period. We suggest a new technique for defining the initial solution and a novel strategy to update the pheromone trails that is especially suited for solving large scale problems. An illustrative example for a waste collection system involving 202 localities in the municipality of Viseu, Portugal, demonstrates the effectiveness of the model.
- Computational Science and Its Applications – ICCSA 2014, Lecture Notes in Computer Science, Predictive Models for Mutation Carriers in Brugada Syndrome ScreeningPublication . Henriques, Carla; Matos, Ana; Santos, LuisIn this study we consider logistic regression models to predict mutation carriers in family members affected by Brugada Syndrome. This Syndrome is an inherited cardiopathy that predisposes individuals without structural heart disease to sudden cardiac death. We focused on five electrocardiographic markers, which have been explored as good discriminators between carriers and non-carriers of the genetic mutation responsible for this disease. Logistic regression models which combine some of the five markers were investigated. Our objective was to assess the predictive ability of these models through internal validation procedures. We also applied shrinkage methods to improve calibration of the models and future predictive accuracy. Validation of these models, using bootstrapping, point to some superiority of two models, for which fairly good measures of predictive accuracy were obtained. This study provides confidence in these models, which offer greater sensitivity than the usual screening by detecting a characteristic pattern in an electrocardiogram.
- Accurate Spectral Estimation of Non-periodic Signals Based on Compressive SensingPublication . Duarte, Isabel M. P.; Vieira, José M. N.; Ferreira, Paulo J S G; Albuquerque, DanielIn this work we propose a method based on compressive sensing (CS) for estimating the spectrum of a signal written as a linear combination of a small number of sinusoids. In practice one deals with signals with finite-length and so the Fourier coefficients are not exactly sparse. Due to the leakage effect in the case where the frequency is not a multiple of the fundamental frequency of the DFT, the success of the traditional CS algorithms is limited. To overcome this problem our algorithm transform the DFT basis into a frame with a larger number of vectors, by inserting a small number of columns between some of the initial ones. The algorithm takes advantage of the compactness of the interpolation function that results from the ‘1 norm minimization of the Basis Pursuit (BP) and is based on the compressive sensing theory that allows us to acquire and represent sparse and compressible signals, using a much lower sampling rate than the Nyquist rate. Our method allow us to estimate the sinusoids amplitude, phase and frequency.
- A Stochastic Model for Managing Tasks of R&D ProjectsPublication . Fialho, Joana; Godinho, Pedro; Costa, João PauloIn this paper, we propose a model for managing tasks of R&D projects. We assume that di®erent amounts of resources may be allocated to a task, leading to different costs, and di®erent average execution speeds. The advancement of the task will be stochastic, and the manager may change the allocated amount of resources according to the way the task is progressing. The revenues will depend on the time to the completion of the task, and their expected value will follow a stochastic process. We consider that a strategy for completing the task will consist on a set of rules that de¯ne the level of resources to be chosen at each moment, according to the values of several state variables. We discuss the evaluation for completing the task, and we brie°y address the problem of finding the optimal strategy
- A tool to manage tasks of R&D projectsPublication . Fialho, Joana; Godinho, Pedro; Costa, João PauloWe propose a tool for managing tasks of Research and Development (R&D) projects. We define an R&D project as a network of tasks and we assume that different amounts of resources may be allocated to a task, leading to different costs and different average execution times. The advancement of a task is stochastic, and the management may reallocate resources while the task is being performed,according to its progress. The operational cash flows depend on the task completion time, and their expected values follow a stochastic process. We consider that a strategy for completing a task is a set of rules that define the level of resources to be allocated to the task at each moment. We discuss the evaluation of strategies for completing a task, and we address the problem of finding the optimal strategy
- A Level-Based Approach to Prioritize Telecommunications R&DPublication . Fialho, Joana; Godinho, Pedro; Costa, João Paulo; Afonso, Ricardo; Regalado, José GonçaloIn this paper, an approach to evaluate R&D projects in telecommunications is presented. These projects have particular features that cannot be properly incorporated by classical valuation methods. This approach incorporates different criteria, both quantitative and qualitative, and also management flexibility and uncertainty. Thus, it is an approach that can be applied to real data of R&D projects in a telecommunications company.
- Some issues about the application of the analytic hierarchy process to R&D project selectionPublication . Godinho, Pedro; Costa, João Paulo; Fialho, Joana; Afonso, RicardoThe analytic hierarchy process (AHP) has been used in the process of selecting research and development (R&D) projects. Such a selection process usually possesses some particular features that require adjustments in the application of the AHP method, such as the existence of a large number of very different alternatives or the integration of qualitative and quantitative criteria. In this paper, we discuss the application of AHP to the selection of a portfolio of R&D projects, and we propose some methods for handling the issues that arise from such an application
- Study of the Electrocardiographic Fluctuations on Brugada Syndrome ScreeningPublication . Matos, Ana Cristina; Henriques, Carla; Santos, Luís Ferreira dos