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Publicações

2019

Energy performance of buildings with on-site energy generation and storage - An integrated assessment using dynamic simulation

Autores
Bot, K; Ramos, NMM; Almeida, RMSF; Pereira, PF; Monteiro, C;

Publicação
JOURNAL OF BUILDING ENGINEERING

Abstract
The European Union aims to achieve a nearly zero energy balance in buildings by 2020. The present study takes into consideration the passive systems of the building, energy demand, and energy generated by the on-site photovoltaic and storage system, and how they interact in different scenarios. The study also considers the energy demand from the grid and the surplus of renewable energy. The software EnergyPlus was used and the parametric sensitivity simulation method was applied, taking into account blinds operation, ventilation strategies, HVAC operation schemes and battery storage capacity, in 96 scenarios. The results highlight that there is great variability between the considered scenarios, highlighting the importance of sizing methodologies for the passive systems and the use of optimized home management algorithms. It was found that the use of batteries with higher storage capacity increases the demand-supply from the on-site PV energy but decreases the amount of energy injected into the grid. The design of the PV and battery system based on yearly integrated simulations allows for an optimized solution. This study also emphasizes the importance of knowing the expected occupancy during the design phase, as a significant input to the sizing methodologies of the storage capacity and on-site generation.

2019

Electricity consumption forecasting in office buildings: An artificial intelligence approach

Autores
Jozi, A; Pinto, T; Marreiros, G; Vale, Z;

Publicação
2019 IEEE Milan PowerTech, PowerTech 2019

Abstract
The rising needs for increased energy efficiency and better use of renewable energy sources bring out the necessity for improved energy management and forecasting models. Electricity consumption, in particular, is subject to large variations due to the effect of multiple variables, such as the temperature, luminosity or humidity, and of course, consumers' habits. Current forecasting models are not able to deal adequately with the influence and correlation between the multiple involved variables. Hence, novel, adaptive forecasting models are needed. This paper presents a novel approach based on multiple artificial intelligence-based forecasting algorithms. The considered algorithms are artificial neural networks, support vector machines hybrid fuzzy inference systems, Wang and Mendel's fuzzy rule learning method and a genetic fuzzy system for fuzzy rule learning based on the MOGUL methodology. These algorithms are used to forecast the electricity consumption of a real office building, using multiple input variables and consumption disaggregation. © 2019 IEEE.

2019

Spherical Angular Analysis for Pelvis Coordination Assessment on Modified Gait

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

Natural Shear Wave Imaging in the Human Heart: Normal Values, Feasibility, and Reproducibility

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

Clustering of interval time series

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

Computer aided detection of deep inferior epigastric perforators in computed tomography angiography scans

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.

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