2019
Autores
Ndawula M.B.; De Paola A.; Hernando-Gil I.;
Publicação
2019 IEEE Milan PowerTech, PowerTech 2019
Abstract
The valuation of whether network operators meet users' expectations in ensuring a continuous supply to their premises is important in determining their willingness-to-pay (WTP) for electricity. Distributed resources such as photovoltaic (PV) systems will dominate future networks, and thus customers' WTP will vary dynamically, both spatially and temporally. Whereas system-wide indices are typically used to assess network performance, there is a requirement to complement these with customer-based indices to accurately quantify the risk of outages to affected and worst-served customers. This paper presents an enhanced Monte Carlo simulation technique, which performs reliability assessment of a typical MV/LV urban distribution network. Two smart grid scenarios considering controllability of PV and energy storage (ES) are designed to improve network performance. Customerbased reliability indices, measuring the frequency and duration of interruptions, and energy not supplied are thoroughly assessed. Results demonstrate the potential of hybrid PV-ES in reducing power supply risk for worst-served customers.
2019
Autores
Rodrigues, C; Correia, M; Abrantes, J; Nadal, J; Benedetti, M;
Publicação
WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING 2018, VOL 2
Abstract
This study presents and applies 3D spherical angular analysis in relation with 2D polar coordinates to assess anatomic pelvic movement on modified gait, namely stiff knee (SKG) gait and slow running (SR) comparing with normal gait (NG). Subject specific analysis was performed of an adult healthy male based on inverse kinematics from in vivo and noninvasive capture at human movement lab of reflective markers position from pelvis anatomical selected points with Qualisys camera system during a complete stride of NG, SKG and SR. Radial distance (R), pitch (psi) and azimuth (lambda) angular phases were computed from pelvic angle-angle diagrams (theta(T), theta(C), theta(S)) at transverse (T), coronal (C) and sagittal (S) planes, and angular phase (phi) and planar radial distance (r) polar coordinates computed from pelvic angle-angle diagrams projections at cartesian planes (theta(T), theta(C)), (theta(T), theta(S)), (theta(C), theta(S)). Average radial distances and phase standard deviation were assessed on spherical and polar coordinates.
2019
Autores
Santos, P; Petrescu, AM; Pedrosa, JP; Orlowska, M; Komini, V; Voigt, JU; D'Hooge, J;
Publicação
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Abstract
Left ventricular myocardial stiffness could offer superior quantification of cardiac systolic and diastolic function when compared to the current diagnostic tools. Shear wave elastography in combination with acoustic radiation force has been widely proposed to noninvasively assess tissue stiffness. Interestingly, shear waves can also result from intrinsic cardiac mechanical events (e.g., closure of valves) without the need for external excitation. However, it remains unknown whether these natural shear waves always occur, how reproducible they can be detected and what the normal range of shear wave propagation speed is. The present study, therefore, aimed at establishing the feasibility of detecting shear waves created after mitral valve closure (MVC) and aortic valve closure (AVC), the variability of the measurements, and at reporting the normal values of propagation velocity. Hereto, a group of 30 healthy volunteers was scanned with high-frame rate imaging (>1000 Hz) using an experimental ultrasound system transmitting a diverging wave sequence. Tissue Doppler velocity and acceleration were used to create septal color M-modes, on which the shear waves were tracked and their velocities measured. Overall, the methodology was capable of detecting the transient vibrations that spread throughout the intraventricular septum in response to the closure of the cardiac valves in 92% of the recordings. Reference velocities of 3.2±0.6 m/s at MVC and 3.5±0.6 m/s at AVC were obtained. Moreover, in order to show the diagnostic potential of this approach, two patients (one with cardiac amyloidosis and one undergoing a dobutamine stress echocardiography) were scanned with the same protocol and showed markedly higher propagation speeds: the former presented velocities of 6.6 and 5.6 m/s; the latter revealed normal propagation velocities at baseline, and largely increased during the dobutamine infusion (>15 m/s). Both cases showed values consistent with the expected changes in stiffness and cardiac loading conditions. © 1986-2012 IEEE.
2019
Autores
Maharaj, EA; Teles, P; Brito, P;
Publicação
STATISTICS AND COMPUTING
Abstract
Interval time series occur when real intervals of some variable of interest are registered as an ordered sequence along time. We address the problem of clustering interval time series (ITS), for which different approaches are proposed. First, clustering is performed based on point-to-point comparisons. Time-domain and wavelet features also serve as clustering variables in alternative approaches. Furthermore, autocorrelation matrix functions, gathering the autocorrelation and cross-correlation functions of the ITS upper and lower bounds, may be compared using adequate distances (e.g. the Frobenius distance) and used for clustering ITS. An improved procedure to determine the autocorrelation function of ITS is proposed, which also serves as a basis for clustering. The different alternative approaches are explored and their performances compared for ITS simulated under different setups. An application to sea level daily ranges, observed at different locations in Australia, illustrates the proposed methods.
2019
Autores
Araujo, RJ; Garrido, V; Baracas, CA; Vasconcelos, MA; Mavioso, C; Anacleto, JC; Cardoso, MJ; Oliveira, HP;
Publicação
COMPUTERIZED MEDICAL IMAGING AND GRAPHICS
Abstract
The deep inferior epigastric artery perforator (DIEAP) flap is the most common free flap used for breast reconstruction after a mastectomy. It makes use of the skin and fat of the lower abdomen to build a new breast mound either at the same time of the mastectomy or in a second surgery. This operation requires preoperative imaging studies to evaluate the branches - the perforators - that irrigate the tissue that will be used to reconstruct the breast mound. These branches will support tissue viability after the microsurgical ligation of the inferior epigastric vessels to the receptor vessels in the thorax. Usually through a computed tomography angiography (CTA), each perforator is manually identified and characterized by the imaging team, who will subsequently draw a map for the identification of the best vascular support for the reconstruction. In the current work we propose a semi-automatic methodology that aims at reducing the time and subjectivity inherent to the manual annotation. In 21 CTAs from patients proposed for breast reconstruction with DIEAP flaps, the subcutaneous region of each perforator was extracted, by means of a tracking procedure, whereas the intramuscular portion was detected through a minimum cost approach. Both were subsequently compared with the radiologist manual annotation. Results showed that the semi-automatic procedure was able to correctly detect the course of the DIEAPs with a minimum error (average error of 0.64 and 0.50 mm regarding the extraction of subcutaneous and intramuscular paths, respectively), taking little time to do so. The objective methodology is a promising tool in the automatic detection of perforators in CTA and can contribute to spare human resources and reduce subjectivity in the aforementioned task.
2019
Autores
Gomes, AD; Ferreira, MS; Bierlich, J; Kobelke, J; Rothhardt, M; Bartelt, H; Frazao, O;
Publicação
SENSORS
Abstract
The optical Vernier effect magnifies the sensing capabilities of an interferometer, allowing for unprecedented sensitivities and resolutions to be achieved. Just like a caliper uses two different scales to achieve higher resolution measurements, the optical Vernier effect is based on the overlap in the responses of two interferometers with slightly detuned interference signals. Here, we present a novel approach in detail, which introduces optical harmonics to the Vernier effect through Fabry-Perot interferometers, where the two interferometers can have very different frequencies in the interferometric pattern. We demonstrate not only a considerable enhancement compared to current methods, but also better control of the sensitivity magnification factor, which scales up with the order of the harmonics, allowing us to surpass the limits of the conventional Vernier effect as used today. In addition, this novel concept opens also new ways of dimensioning the sensing structures, together with improved fabrication tolerances.
The access to the final selection minute is only available to applicants.
Please check the confirmation e-mail of your application to obtain the access code.