Browsing by resource type "conference proceedings"
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- Adjustment parameters of an internal combustion engine working with methanePublication . Dimitrov, R.; Bogdanov, K.; Wrobel, R.; Mihaylov, V.; Serrano, Luis; Institute of Physics PublishingThe paper presents a study of the variation of ignition advance when the engine works with methane and a comparison with values when the engine runs on gasoline. It is known that methane has a lower burning velocity than gasoline, and therefore, to obtain a maximal efficiency from the working process (the maximum value of cylinder pressure pz should be 7-15 degrees after TDC), ignition advance should be increased, as for different operating regimes this angle should be increased with different values. A gasoline engine has been studied and were measured and analysed the ignition advance at work with gasoline and methane, with optimal air-fuel ratio (α) for both fuels. Three-dimensional graphics of ignition advance variation across the rpm and load range were made. In conclusion, on the basis of the experiments, a table is produced, which presents the values of coefficients for change of base parameters of ignition advance for all engine operating modes, in dependence on rpm and load of the engine.
- Analysis of the initial delamination size on the mode I interlaminar fracture of carbon/epoxy compositesPublication . Reis, P.N.B.; Ferreira, J.A.M.; Antunes, F.V.; Costa, J.D.M.; Capela, C.; Capela, Carlos;This paper describes an experimental study of the initial delamination length effects on the mode I fracture toughness using DCB tests. Delamination failure was also predicted using exponential cohesive model and a quite good agreement with experimental results was obtained. Numerical predictions showed a significant influence of initial delamination length on the force-displacement curves.
- A dual-band single-layer frequency selective surface for Wi-Fi applicationsPublication . Ferreira, David; Cuinas, Inigo; Caldeirinha, Rafael; Fernandes, Telmo, Telmo Rui Carvalhinho Cunha, Telmo R.This paper proposes a frequency selective surface (FSS) design to be used in Wi-Fi applications as either a reject or pass band single-layer filter. This design consists of a combination of canonical elements, i.e. ring loops/slots, and is tuned for both 2.4 and 5.2 GHz Wi-Fi frequency bands. It has a stable frequency response in the aforementioned Wi-Fi bands for incidence angles ranging from 0° to 45°. Both reject and pass band designs are presented, along with their respective unit cell dimensions and simulated frequency response. Active variants are also proposed and briefly evaluated which should allow for an on-off switching at the 2.4 and 5.2 GHz Wi-Fi bands. © 2015 EurAAP.
- Flow characteristics of gas injectorsPublication . Ivanov, Zdravko; Stoyanov, Stoyan; Mihaylov, Veselin; Santos, HelderThe operation of Internal Combustion Engine (ICE) with gaseous fuels is characterized by the specificity of the fuelling process. Nowadays the most common system is the one in which after lowering its pressure the gas fuel is delivered to the engine intake manifold by means of gas injectors. This leads to a difference in the laws of fuel supply relative to the original gasoline injection system that dispenses fuel in liquid phase. Theoretical research has been done and gas leakage has been found to be critical under engine normal operating conditions, that is, it depends on fuel pressure and not on the environment in which the fuel leaks (intake manifold). An experimental test stand was set-up and multiparametric characteristics of a common construction bottom feed gas injectors were determined experimentally under conditions very close to the real working ones
- Indoor environment and energy efficiency in school buildings - part 1: Indoor Air QualityPublication . Dias, Maria João; Bernardo, H.; Ramos, João; Manzano, Moisés EgidoThis paper is the first one in a series of two papers presenting the main results obtained in a School Building, which are analyzed in view of the actual Indoor Air Quality (IAQ) Portuguese national regulation. Measurements were carried out in one building, ventilated by mechanical system to evaluate IAQ and thermal comfort parameters. Direct measurements were made with portable monitoring data loggers and in some longterm measurements. The students assessed through questionnaires the IEQ parameters felt in the classrooms a few moments before the end of the class. The IAQ and thermal comfort conditions in higher/university schools buildings has been found to be poor because of the high density of students in class rooms. In particular, the IAQ is a significant issue for these buildings in order to be healthy and comfortable for learning performance of students.
- Obstacle Detection using Stereo Imaging to Assist the Navigation of Visually Impaired PeoplePublication . Costa, Paulo; Fernandes, Hugo; Martins, Paulo; Barroso, João; Hadjileontiadis, Leontios J.Assistive technology enables people to achieve independence when performing daily tasks and it enhances their overall quality of life. Visual information is the basis for most navigational tasks, so visually impaired individuals are at disadvantage due to the lack of sufficient information about their surrounding environment. With recent advances in inclusive technology it is possible to extend the support given to people with visual disabilities in terms of their mobility. In this context we propose and describe the Blavigator project, whose global objective is to assist visually impaired people in their navigation on indoor and outdoor environments. This paper is focused mainly on the Computer Vision module of the Blavigator prototype. We propose an object collision detection algorithm based on disparity images. The proposed algorithm uses a 2D Ensemble Empirical Mode Decomposition image optimization algorithm and a two layer disparity image segmentation to detect nearby objects.
- Optimized Reference Picture Selection for Light Field Image CodingPublication . Monteiro, J. S. Ricardo; Nunes, J. L. Paulo; M. M. Rodrigues, Nuno; Faria, SergioThis paper proposes a new reference picture selection method for light field image coding using the pseudovideo sequence (PVS) format. State-of-the-art solutions to encode light field images using the PVS format rely on video coding standards to exploit the inter-view redundancy between each sub-aperture image (SAI) that composes the light field. However, the PVS scanning order is not usually considered by the video codec. The proposed solution signals the PVS scanning order to the decoder, enabling implicit optimized reference picture selection for each specific scanning order. With the proposed method each reference picture is selected by minimizing the Euclidean distance to the current SAI being encoded. Experimental results show that, for the same PVS scanning order, the proposed optimized reference picture selection codec outperforms HEVC video coding standard for light field image coding, up to 50% in terms of bitrate savings
- Use of parabolic trough solar collectors for building air conditioning and domestic hot water production - case studyPublication . Quintal, E. S.; Bernardo, H.; Amaral, P. G.; Pires Neves, LuísThe aim of this study is the evaluation of the economic and technical viability for the installation of a solar air conditioning system based on parabolic solar concentrators and adsorption technology, in an existent building. As case study was selected a university canteen located in the centre region of Portugal. Besides air conditioning, this system is also used for domestic hot water production. This solution enables the system use throughout the year in order to maximize the investment. Results show that the implementation of these systems is feasible for the portuguese reality and the return of the investment can be achieved in 8 years without governmental financial support.
- Video game interaction and reward mechanisms applied to business applications: A comparative reviewPublication . Diogo Lopes; Esteves, Micaela; Carlos MesquitaUpon entering in a new institution, an employee has a learning curve to absorb new tools, this learning curve brings extra costs to the employing institution. Besides this, in 2008, a study from the National Institute of Statistics concluded that various Portuguese institutions have a low index of productivity. These two facts may make institutions feel more discouraged to make new hires. In this study we show that there is an unexplored potential in the adaptation of some of the gaming industry interaction and reward mechanisms to the corporate world, in order to improve the intuitiveness of business applications, by not only reducing learning and adjustment time for new users, but also to use the reward and fidelization mechanisms, as a means to motivate and increase overall productivity and employee involvement.
- WINSYS 2009 - International Conference on Wireless Information Networks and Systems, Proceedings: ForewordPublication . Caldeirinha, Rafael; Obaidat, Mohammad S.We warmly welcome you to WINSYS 2009 - the International Conference on Wireless Information Networks and Systems, which is held, this year in Milan, Italy. This conference reflects a continuing effort to increase the dissemination of recent research among professionals who work on the field of Wireless Information Systems. WINSYS is integrated as one of the modules of the ICETE joint conference.