Non INESC TEC publications

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    3D active surfaces for liver segmentation in multisequence MRI images
    ( 2016) Bereciartua,A ; Picon,A ; Adrian Galdran ; Iriondo,P
    Biopsies for diagnosis can sometimes be replaced by non-invasive techniques such as CT and MRI. Surgeons require accurate and efficient methods that allow proper segmentation of the organs in order to ensure the most reliable intervention planning. Automated liver segmentation is a difficult and open problem where CT has been more widely explored than MRI. MRI liver segmentation represents a challenge due to the presence of characteristic artifacts, such as partial volumes, noise and low contrast. In this paper, we present a novel method for multichannel MRI automatic liver segmentation. The proposed method consists of the minimization of a 3D active surface by means of the dual approach to the variational formulation of the underlying problem. This active surface evolves over a probability map that is based on a new compact descriptor comprising spatial and multisequence information which is further modeled by means of a liver statistical model. This proposed 3D active surface approach naturally integrates volumetric regularization in the statistical model. The advantages of the compact visual descriptor together with the proposed approach result in a fast and accurate 3D segmentation method. The method was tested on 18 healthy liver studies and results were compared to a gold standard made by expert radiologists. Comparisons with other state-of-the-art approaches are provided by means of nine well established quality metrics. The obtained results improve these methodologies, achieving a Dice Similarity Coefficient of 98.59. © 2016 Elsevier Ireland Ltd.
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    3D tendon strain estimation on high-frequency 3D ultrasound images a simulation and phantom study
    ( 2016) Catarina Brito Carvalho ; Bogaerts,S ; Scheys,L ; D'hooge,J ; Peers,K ; Suetens,P
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    3D Tendon Strain Estimation Using High-frequency Volumetric Ultrasound Images: A Feasibility Study
    ( 2017) Catarina Brito Carvalho ; Slagmolen,P ; Bogaerts,S ; Scheys,L ; D’hooge,J ; Peers,K ; Maes,F ; Suetens,P
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    Activity Mapping of Children in Play Using Multivariate Analysis of Movement Events
    ( 2020) Joana Maria Rocha ; Barnes,CM ; Rees,P ; Clark,CT ; Stratton,G ; Summers,HD ; 7800
    Purpose (i) To develop an automated measurement technique for the assessment of both the form and intensity of physical activity undertaken by children during play. (ii) To profile the varying activity across a cohort of children using a multivariate analysis of their movement patterns. Methods Ankle-worn accelerometers were used to record 40 min of activity during a school recess, for 24 children over five consecutive days. Activity events of 1.1 s duration were identified within the acceleration time trace and compared with a reference motif, consisting of a single walking stride acceleration trace, obtained on a treadmill operating at a speed of 4 km h(-1). Dynamic time warping of motif and activity events provided metrics of comparative movement duration and intensity, which formed the data set for multivariate mapping of the cohort activity using a principal component analysis (PCA). Results The two-dimensional PCA plot provided clear differentiation of children displaying diverse activity profiles and clustering of those with similar movement patterns. The first component of the PCA correlated to the integrated intensity of movement over the 40-min period, whereas the second component informed on the temporal phasing of activity. Conclusions By defining movement events and then quantifying them by reference to a motion-standard, meaningful assessment of highly varied activity within free play can be obtained. This allows detailed profiling of individual children's activity and provides an insight on social aspects of play through identification of matched activity time profiles for children participating in conjoined play.
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    Adoption of auditability as a proposal to identify false information on social networks [Adoção da auditabilidade como proposta para identificar informações falsas em redes sociais]
    ( 2016) Alexandre Hostand Souza ; Cappelli,C ; MacIel,C
    The lack of mechanisms made to check reliability of information on social networks is evidenced by the spread of misinformation and rumors in this kind of system. Given this scenario, the provision of tools to assist users with information auditability on social networks needs an emergencial approach. This article describes a catalog, followed by a guide of features that provide auditability on social networks. The guide contains guidelines for development of funcionalities in order to promote the adoption of auditability and enable users to identify false information and validate content on social networks. © 2016 for this paper by its authors.
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    Advanced fiber-optic acoustic sensors
    ( 2014) Teixeira,JGV ; Leite,IT ; Susana Oliveira Silva ; Orlando Frazão
    Acoustic sensing is nowadays a very demanding field which plays an important role in modern society, with applications spanning from structural health monitoring to medical imaging. Fiber-optics can bring many advantages to this field, and fiber-optic acoustic sensors show already performance levels capable of competing with the standard sensors based on piezoelectric transducers. This review presents the recent advances in the field of fiber-optic dynamic strain sensing, particularly for acoustic detection. Three dominant technologies are identified - fiber Bragg gratings, interferometric Mach-Zehnder, and Fabry-Pérot configurations - and their recent developments are summarized. © 2014 The Author(s).
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    Aggregated dynamic model of active distribution networks for large voltage disturbances
    (Elsevier - Electrical Power System Research Volume 178, 2020-01) Fulgêncio, Nuno ; Moreira, Carlos ; Carvalho, Leonel ; Peças Lopes, João
    This paper proposes a “grey-box” aggregated dynamic model for active distribution networks, taking into account a heterogeneous fleet of generation technologies alongside their expected behavior when taking into account the latest European grid codes requirements in terms of voltage support services. The main goal of the proposed model and underlying methodology for its identification is to represent the transient behavior of the active distribution system following large voltage disturbances occurring at the transmission side. The proposed aggregated model is composed by three main components: an equivalent power converter for generation and battery energy storage systems portfolio representation; an equivalent synchronous generation unit; and an equivalent composite load model. The model’s parameters are estimated by an evolutionary particle swarm optimization algorithm, by comparing a fully-detailed model of a distribution network with the aggregated model’s frequency domain’s responses of active and reactive power flows, at the boundary of transmission-distribution interface substation.
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    Algoritmos Meméticos Aplicados à Identificação de Sistemas e Sintonização de Controladores PID
    ( 2018) Sousa,AL ; Vidal,JF ; Silva,OF ; Victor Silva Freitas ; 7194
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    Allocation of PEVs' Parking Lots in Renewable-Based Distribution System
    ( 2014) Nilufar Neyestani ; Damavandi,MY ; Shafie Khah,M ; João Catalão ; Contreras,J
    Emerging trends in electric vehicles both in science and industry, as well as increasing popularity of these devices among end-users have laid serious issues in front of a system operator or planner. Higher deployment of available resources in the system will lead to higher flexibility for system operator in its interactions, besides to higher level of user satisfaction. In this study, various states of a 13 bus radial distribution network have been considered for allocation of Plug-in Electric Vehicles' (PEVs') parking lots. As Renewable Energy Resources (RERs) are becoming a main element of power systems, it is investigated how the future distribution network planning has to be organized by employing both RERs and PEV parking lots. Also, it is investigated how the allocation of parking lots varies in the system where these resources exist. Moreover, the costs and revenues obtained by the system operator in such systems are also studied.
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    Allocation of Plug-In Vehicles' Parking Lots in Distribution Systems Considering Network-Constrained Objectives
    ( 2015) Nilufar Neyestani ; Damavandi,MY ; Shafie Khah,M ; Contreras,J ; João Catalão
    A recent solution to tackle environmental issues is the electrification of transportation. Effective integration of plug-in electric vehicles (PEVs) into the grid is important in the process of achieving sustainable development. One of the key solutions regarding the need for charging stations is the installation of PEV parking lots (PLs). However, contrary to common parkings, PLs are constrained by various organizations such as municipalities, urban traffic regulators, and electrical distribution systems. Therefore, this paper aims to allocate PLs in distribution systems with the objective of minimizing system costs including power loss, network reliability, and voltage deviation as possible objectives. A two-stage model has been designed for this purpose. PLs' behavior considering market interactions is optimized at the first stage to provide profit to the PL owner. At the second stage, the PL allocation problem is solved considering various network constraints. Conclusions are duly drawn with a realistic example.
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    Ammonia sensing system based on wavelength modulation spectroscopy
    ( 2015) Carlos Duarte Viveiros ; João Ferreira ; Susana Oliveira Silva ; Ribeiro,J ; Flores,D ; José Luís Santos ; Orlando Frazão ; José Manuel Baptista
    A sensing system in the near infrared region has been developed for ammonia sensing based on the wavelength modulation spectroscopy (WMS) principle. The WMS is a rather sensitive technique for detecting atomic/molecular species, presenting the advantage that it can be used in the near-infrared region by using the optical telecommunications technology. In this technique, the laser wavelength and intensity were modulated by applying a sine wave signal through the injection current, which allowed the shift of the detection bandwidth to higher frequencies where laser intensity noise was typically lower. Two multi-pass cells based on free space light propagation with 160 cm and 16 cm of optical path length were used, allowing the redundancy operation and technology validation. This system used a diode laser with an emission wavelength at 1512.21 nm, where NH3 has a strong absorption line. The control of the NH3 gas sensing system, as well as acquisition, processing and data presentation was performed. © 2015, The Author(s).
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    Analysing Traffic Flows Through Sampling: A Comparative Study
    ( 2015) João Marco ; Carvalho,P ; Lima,SR
    Understanding network workload through the characterization of network flows, being essential for assisting network management tasks, can benefit largely from traffic sampling as long as an accurate snapshot of network behavior is captured. This paper is devoted to evaluate the real applicability of using sampling to support flow analysis. Considering both classical and emerging sampling techniques, a comparative performance study is carried out to assess the accuracy of estimating flow parameters through sampling. After identifying the main building blocks of sampled-based measurements, a sampling framework has been implemented to provide a versatile and fair platform for carrying out the testing and comparison process. Through an encompassing coverage of representative sampling techniques, the present study aims to provide useful insights regarding the use of sampling in traffic flow analysis.
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    Analysis of a Plasmonic Based Optical Fiber Optrode With Phase Interrogation
    ( 2016) Hamed Moayyed ; Leite,IT ; Luís Carlos Coelho ; José Luís Santos ; Diana Viegas
    Optical fiber optrodes are attractive sensing devices due to their ability to perform point measurement in remote locations. Mostly, they are oriented to biochemical sensing, quite often supported by fluorescent and spectroscopic techniques, but with the refractometric approach considered as well when the objective is of high measurement performance, particularly when the focus is on enhancing the measurand resolution. In this work, we address this subject, proposing and analyzing the characteristics of a fiber optic optrode relying on plasmonic interaction. A linearly tapered optical fiber tip is covered by a double overlay: the inner one - a silver thin film and over it a dielectric layer, with this combination allowing to achieve, at a specific wavelength range, surface plasmonic resonance (SPR) interaction sensitive to the refractive index of the surrounding medium. Typically, the interrogation of the SPR sensing structures is performed, considering spectroscopic techniques, but in principle, a far better performance can be obtained, considering the reading of the phase of the light at a specific wavelength located within the spectral plasmonic resonance. This is the approach which is studied here in the context of the proposed optical fiber optrode configuration. The analysis performed shows the combination of a silver inner layer with a dielectric titanium oxide layer with tuned thicknesses enables sensitive phase reading and allows the operation of the fiber optic optrode sensor in the third telecommunication wavelength window.
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    Analysis of Signal Saturation in a Fiber Ring Resonator integrating an Intensity Sensor
    ( 2017) Magalhaes,R ; Susana Oliveira Silva ; Orlando Frazão
    The proposed technique consists in an optical fiber resonator interrogated for sensor characterization, implementing an alternative technique for dynamic range improvement. Such technique relies on the analysis of an added-signal caused by signal saturation, which occurs due to the broadening of the laser pulse. A wide study for different pulse widths is presented in this work, namely for 100 ns, 5 mu s and 20 mu s, being the last one related to the emergence of an added-signal for the proposed configuration. The behavior of the waveform in the presence of an intensity sensor is also characterized.
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    Analysis of the Brazilian Energy Efficiency Program for Electricity Distribution Systems
    ( 2017) de Souza e Silva,RDDE ; Rosana Cavalcante Oliveira ; de Lima Tostes,MED
    In this paper, a methodology was developed to analyze the results of energy efficiency programs used in the electricity distribution sector in Brazil. Analyzing the gains obtained through the investments made, and classifying which actions resulted in the best performance, contributed to decision making on the best allocation of investments to obtain the greatest energy savings. The Brazilian Energy Efficiency program was analyzed with a developed non-parametric model, using the data envelopment analysis method, and the categories of projects with better performance were determined. A database of the results from 1704 projects, from 2008 to 2016 in the Energy Efficiency program in Brazil's electricity distribution sector, was used. The results obtained show that the best performance was achieved by projects in the industrial and cogeneration categories; however, in Brazil these constitute only 4.24% of the projects presented and 5.28% of the total investments in the last eight years, indicating a need to review the regulatory strategies for energy efficiency in this country.
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    Analyzing First-Person Stories Based on Socializing, Eating and Sedentary Patterns
    ( 2017) Herruzo,P ; Portell,L ; Soto,A ; Beatriz Remeseiro López
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    Analyzing the Effect of Various PEV Owner's Charging Tariffs on PEV PL's Market Equilibrium
    ( 2015) Nilufar Neyestani ; Damavandi,MY ; João Catalão
    In this paper, an innovative bi-level model is developed for the interactions of the plug-in electric vehicle (PEV) parking lot (PL) with the upstream markets through an aggregator in the system. The preferences of the PEVs on using the PL are also considered in the study. The PEVs have a choice in participating in grid-to-vehicle or vehicle-to-grid modes with fixed or flexible amount of departed state of charge (SOC). The PL assigns various tariffs for different requirements of the PEVs. In this study, the mutual effect of the variation of PEV tariffs and the PL's behavior in the market is investigated. It is shown that the preferences of PEVs can significantly affect the PL's strategy. The changes of the equilibrium prices for PL and aggregator interaction are thoroughly analyzed in response to changes in PEV tariffs to illustrate their influence on their behavior.
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    Análise da variabilidade da frequência cardíaca em indivíduos saudáveis, doentes com insuficiência cardíaca e doentes transplantados
    ( 2013) Argentina Leite ; Silva,ME ; Rocha,AP
    This study aimed to find parameters to characterize heart rate variability (HRV) and discriminate healthy subjects and patients with heart diseases. The parameters used for discrimination characterize the different components of HRV memory (short and long) and are extracted from HRV recordings using parametric as well as non parametric methods. Thus, the parameters are: spectral components at low frequencies (LH) and high frequencies (HF) which are associated with the short memory of HRV and the long memory parameter (d) obtained from autoregressive fractionally integrated moving average (ARFIMA) models. In the non parametric context, short memory (a1) and long memory (a2) parameters are obtained from detrended fluctuation analysis (DFA). The sample used in this study contains 24-hour Holter HRV recordings of 30 subjects: 10 healthy individuals, 10 patients suffering from congestive heart failure and 10 heart transplanted patients from the Noltisalis database. It was found that short memory parameters present higher values for the healthy individuals whereas long memory parameters present higher values for the diseased individuals. Moreover, there is evidence that ARFIMA modeling allows the discrimination between the 3 groups under study, being advantageous over DFA.
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    Application of Multi-Temporal Interferometric Synthetic Aperture Radar (MT-InSAR) technique to Land Deformation Monitoring in Warri metropolis, Delta State, Nigeria
    ( 2016) Mahmud,MU ; Yakubu,TA ; Oluwafemi,O ; Joaquim João Sousa ; Miguel Ruiz Armenteros,AM ; Arroyo Parras,JG ; Bakon,M ; Lazecky,M ; Perissin,D
    Warri is one of the mega cities in Delta State in the coastal region of Nigeria hosting many industries. One of the three of Nigeria oil refineries is located in Warn. This study reveals the occurence of land deformation in the Warri area which is not only because it was formed in a tectonic setting but because of the high demand of the underground water for indutrial and domestics uses, high population density and oil and gas exploration in the area. Land deformation in this area is currently being accelerated by this indiscriminate withdrawal of underground water from the aquifers and exploration of the oil and gas leading to the compacting sediments. In this study Multi-Temporal Interferometric Synthetic Aperture Radar (MT-InSAR) technique was applied to monitor land deformation in Warri metropolis in the period between 09/02/2006 and 12/08/2010 with Envisat data obtained from European Space Agency (ESA). The processing was done using Stanford Method for Persistent Scatterers/Multi-Temporal InSAR (StaMPS). From the analysis of the results, land deformation is occurring in Warri metropolis at a moderate rates (+/-5 mm/yr). During the preliminary investigations, structures, particularly buildings, were physically observed subsiding while some others with cracks of various types and degrees. (C) 2016 The Authors. Published by Elsevier B.V.