Cookies Policy
The website need some cookies and similar means to function. If you permit us, we will use those means to collect data on your visits for aggregated statistics to improve our service. Find out More
Accept Reject
  • Menu
Publications

2014

Influence of cable losses on the economic analysis of efficient and sustainable electrical equipment

Authors
Lobao, JA; Devezas, T; Catalao, JPS;

Publication
ENERGY

Abstract
Increasing energy needs are accompanied by environmental responsibilities, since nowadays electricity companies operate in a competitive and sustainable energy framework. In this context, any proposal for action on energy efficiency becomes important for consumers to minimize operational costs. In electrical installations, electricity consumption can be decreased by reducing losses in the cables, associated with the overall efficiency of the equipment, allowing a better use of the installed power. The losses must be analysed in conjunction with all loads that contribute to the currents in the sections of an electrical installation. When replacing equipment in output distribution boxes with more efficient ones, the current in those sections is reduced in association with the decrease in power losses. This decrease, often forgotten, is taken into account in this work for the economic analysis of efficiency and sustainable electrical equipment. This paper presents a new software application that compares and chooses the best investment in the acquisition of electrical equipment. Simulation results obtained with the new software application are provided and are then validated with experimental results from a real electrical installation.

2014

Setting the Criteria for theTool - Qualitative and Quantitative Aspects for Wearable Fall Prediction

Authors
Espinoza, MS; Correia, MV;

Publication
BIOSIGNALS

Abstract
For the first time in history, the world shows a clear trend towards aging. This poses an intrinsic hazard for the ever growing population, which becomes more vulnerable to common age-related illnesses and conditions. One of the most serious risks elders face is falling, as it is responsible for countless admissions to geriatric care institutions and thousands of deaths each year. In an effort to improve elders' safety and quality of life many groups have address the fall prevention issue, coming to several different results as of what variables are the most important to consider in a fall prediction tool. These variables range from qualitative aspects (history of falls, dementia, use of medication, etc.) to quantitative ones (total walked distance per day, walking cadence, center of mass, etc.), but none of them per se seems to deliver a definite and complete answer to the problem at hand. The paper herein aims to present a new hybrid approach, which combines both the highest co-related qualitative and quantitative biovariables in a single tool: the MATHOV + QAVS, which is proposed as a new fall assessment screening tool and eventually as baseline criteria for a complete elder fall prediction system. Copyright © 2014 SCITEPRESS - Science and Technology Publications. All rights reserved.

2014

Computer-based Modelling and Optimization in Transportation

Authors
de Sousa J.; Rossi R.;

Publication
Advances in Intelligent Systems and Computing

Abstract

2014

Can hydrogen or natural gas be alternatives for aviation? - A life cycle assessment

Authors
Pereira, SR; Fontes, T; Coelho, MC;

Publication
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY

Abstract
Between 1989 and 2011 the aviation traffic has been growing 4.6% per year. The increase on aviation traffic had consequences in terms of greenhouse gases (GHGs) and local pollutant emissions (e.g. carbon monoxide - CO, hydrocarbons - HC, nitrogen oxides - NOx). In order to minimize this problem, the evaluation of sustainable alternatives to current fuel (jet fuel A) has been discussed but their impact on emissions is still unclear. The main research goals of this paper are: (i) to evaluate if the well-to-wake energy consumption in aviation can be reduced with alternative fuels as liquid natural gas (LNG) and/or liquid hydrogen (LH2) and (ii) to assess if alternative fuels can be used in aviation to minimize carbon dioxide emissions and local pollutants. In this analysis two types of flights were evaluated: short flights (<5000 km) and long flights (>5000 km) for six typical aircrafts. We verified that LH2 from SMR can provide between 13% and 21% less environmental and social impacts than jet fuel A, in the same aircraft. Copyright

2014

Comparing Data Distribution Using Fading Histograms

Authors
Sebastiao, R; Gama, J; Mendonça, T;

Publication
21ST EUROPEAN CONFERENCE ON ARTIFICIAL INTELLIGENCE (ECAI 2014)

Abstract
The emergence of real temporal applications under non-stationary scenarios has drastically altered the ability to generate and gather information. Nowadays, under dynamic scenarios, potentially unbounded and massive amounts of information are generated at high-speed rate, known as data streams. Dealing with evolving data streams imposes the online monitoring of data in order to detect changes. The contribution of this paper is to present the advantage of using fading histograms to compare data distribution for change detection purposes. In an windowing scheme, data distributions provided by the fading histograms are compared using the Kullback-Leibler divergence. The experimental results support that the detection delay time is smaller when using fading histograms to represent data instead of standard histograms.

2014

HarmoSim: A tool for harmonic distortion simulation and assessment of nonlinear loads

Authors
Baptista, J; Morais, R; Valente, A; Soares, S; Candeias, M; Reis, MJCS;

Publication
COMPUTER APPLICATIONS IN ENGINEERING EDUCATION

Abstract
Electrical power quality (PQ) is a crucial competitive and developing factor to all economic activities. The economic impact resulting from a bad PQ would be drastic on all consumers. Computers, uninterruptible and switched power supplies (UPS), and fluorescent lamps/tubes are examples of nonlinear loads that have the consumption of a nonsinusoidal current, which cause disturbances in the power supply system (that may be severe or not). This study discusses residential generic power circuitry analysis and simulation, under nonlinear loads, in connection with undergraduate electrical engineering education. It briefly reviews some of the basic techniques, and presents a software tool that has been found to be very useful in the context. The tool has an easy-to-use, friendly interface, and can be used to teach design techniques or as a laboratory support to study the applicability of known methods to real situations. The students can perform simulations with their own data on Microsoft (TM) Windows (R)-based platforms. (c) 2011 Wiley Periodicals, Inc. Comput Appl Eng Educ 22:340-348, 2014; View this article online at ; DOI

  • 2940
  • 4538