374 research outputs found
Estudo do comportamento vibratório de uma embarcação em escala reduzida
No full textTCC (graduação) - Universidade Federal de Santa Catarina, Campus Joinville, Engenharia NavalVibração em embarcações é um tema de alta complexidade, pois podem ser induzidas por diferentes fontes como, por exemplo, máquinas, equipamentos, ondas, ventos e efeitos hidrodinâmicos. Esse trabalho visa o entendimento do comportamento vibratório de uma embarcação em escala reduzida e aborda a excitação dada pelo motor da embarcação e o campo de pressão gerado pelo hélice propulsor. Durante o projeto de novas embarcações recomenda-se calcular suas propriedades dinâmicas, tais como frequências naturais e modos de vibração da viga-navio. Tal estudo dos modos de vibração tem por objetivo facilitar a conclusão, através de métodos analíticos, ainda nas fases preliminares de estudo de modo a obter embarcações menos suscetíveis ao fenômeno da ressonância. Em caso de ressonância, além de ser indesejável por provocar desconforto aos usuários e movimentação das cargas, a vibração excessiva compromete a estrutura do casco, das subestruturas do navio e dos componentes mecânicos e eletrônicos. Para tanto, foi realizada a análise experimental e uma análise analítica de uma embarcação em escala reduzida. Os modelos analíticos que representam a análise modal tanto na condição livre-livre quanto na condição molhada, sendo estas a viga de Euller-Bernoulli e o modelo da viga-navio, respectivamente, apresentaram erro máximo de 10,65%, essa diferença ocorre por motivos de simplificações e falta do completo domínio das propriedades mecânicas da embarcação. Em um segundo momento, será avaliada a condição de operação da embarcação, através da ODS, tal procedimento permite concluir que a frequência natural da embarcação é excitada durante o funcionamento, dada a frequência de rotação do motor, frequência passagem das pás e a combinação destas.Vibration on vessels is a high complexity theme, they can be induced by different sources as, for example, machinery, equipment, waves, winds and hydrodynamic effects. This project focuses on the vibration behavior of a scaled vessel and discusses the excitation forces by the main engine and the generated pressure field generated by its propeller. While a new vessel is being projected it is recommended to estimate its dynamic properties, such as natural frequencies and mode shape of the ship hull beam. Such study aims to make easier the conclusion, by analytical methods, still in the early design stages to obtain vessel less susceptible to the phenomena of resonance. The reason an engineer is trying to avoid the resonance on his project is because, besides being uncomfortable for the crew and the possibility of cargo movement, the excessive vibration commits the ship’s hull structure, the substructures of the ship, mechanical and electronic components. Thinking of that, was performed an experimental analysis and analytical one on a reduced scale vessel. The analytical models that represents the modal analysis in the free condition and in the wet condition are the Euller-Bernoulli and the hull ship beam, respectively, show a maximum error of 10,65%, this difference occurs for simplification and missing of complete domination of the mechanical properties of the vessel purposes. In a second moment, this project will evaluate the vessel operation condition, trough ODS, such procedure allows finding out which vessel’s natural frequency is excited during the operation of the ship, given the engine rotation rate, the frequency of the propeller blades and a combination of those
A Facility for the Analysis of Reflection Properties of Surfaces
No full textA new innovative photometric laboratory starts its activity at the University of Padova in the field characterization of optical materials, like retroreflectors, road signs, road markings and asphalt. The system is composed by a light source, a detector to measure the luminance and the color of the light reflected by the sample and a goniometer to reproduce different geometrical alignments among the sample, the light source and the detector. The system and the measurement procedure are described in this paper. A CCD camera operates as luminance meter. Its use as detector and relative measurements procedure improve the result accuracies and overcome inconveniences due to the techniques commonly used in these type of measurements
Calibration and Characterisation of a CCD detector fo light engineering
No full textThis paper describes the methodology developed for characterizing a commercial charge-coupled device (CCD) camera as a luminance meter for analyzing lighting systems and especially for measurements in road light plants. Today, several luminance meters based on commercial CCD cameras are on the market. They are very attractive for the lighting engineer: The availability of a high number of closely spaced small detectors (pixels) on a single chip permits analyses almost impossible with a traditional luminance meter. These commercial-industrial CCD cameras are sold at prices lower than scientific grade ones. They are factory equipped with a dedicated filter to reach the correct photopic sensitivity V(A), and they are factory calibrated in luminance SI units. The main counterparts in using these cameras are in the difficulties to define the measurement accuracy and the influence of the environment luminance on the measured values of the framed scene, in the low resolution of their A/D converter (usually 8 or 12 bit), and the higher noise level (usually the CCD chip is not cooled). To reach the measurement accuracy required by lighting norms, it is necessary to characterize metrologically a camera and quantify all the possible external influences which could degrade its performances, in real measurement situations, and which could affect the measurement results. A carefully controlled measurement set up and operating procedure could limit the causes of errors and improve the accuracy of measurements obtained in operating conditions. In this way, the measurement uncertainties might be evaluated completely, and considerations on the results could suggest particular operating practices to limit the causes of error due to measurement setup and environmental conditions.This paper describes the methodology developed for characterizing a commercial charge-coupled device (CCD) camera as a luminance meter for analyzing lighting systems and especially for measurements in road light plants. Today, several luminance meters based on commercial CCD cameras are on the market. They are very attractive for the lighting engineer: The availability of a high number of closely spaced small detectors (pixels) on a single chip permits analyses almost impossible with a traditional luminance meter. These commercial-industrial CCD cameras are sold at prices lower than scientific grade ones. They are factory equipped with a dedicated filter to reach the correct photopic sensitivity V(/spl lambda/), and they are factory calibrated in luminance SI units. The main counterparts in using these cameras are in the difficulties to define the measurement accuracy and the influence of the environment luminance on the measured values of the framed scene, in the low resolution of their A/D converter (usually 8 or 12 bit), and the higher noise level (usually the CCD chip is not cooled). To reach the measurement accuracy required by lighting norms, it is necessary to characterize metrologically a camera and quantify all the possible external influences which could degrade its performances, in real measurement situations, and which could affect the measurement results. A carefully controlled measurement set up and operating procedure could limit the causes of errors and improve the accuracy of measurements obtained in operating conditions. In this way, the measurement uncertainties might be evaluated completely, and considerations on the results could suggest particular operating practices to limit the causes of error due to measurement setup and environmental conditions
Characterization and Calibration of a CCD Detector for Light Engineering
No full textThis paper describes the methodology developed for characterizing a commercial charge-coupled device (CCD) camera as a luminance meter for analyzing lighting systems and especially for measurements in road light plants. Today, several luminance meters based on commercial CCD cameras are on the market. They are very attractive for the lighting engineer: The availability of a high number of closely spaced small detectors (pixels) on a single chip permits analyses almost impossible with a traditional luminance meter. These commercial-industrial CCD cameras are sold at prices lower than scientific grade ones. They are factory equipped with a dedicated filter to reach the correct photopic sensitivity V(λ), and they are factory calibrated in luminance SI units. The main counterparts in using these cameras are in the difficulties to define the measurement accuracy and the influence of the environment luminance on the measured values of the framed scene, in the low resolution of their A/D converter (usually 8 or 12 bit), and the higher noise level (usually the CCD chip is not cooled). To reach the measurement accuracy required by lighting norms, it is necessary to characterize metrologically a camera and quantify all the possible external influences which could degrade its performances, in real measurement situations, and which could affect the measurement results. A carefully controlled measurement set up and operating procedure could limit the causes of errors and improve the accuracy of measurements obtained in operating conditions. In this way, the measurement uncertainties might be evaluated completely, and considerations on the results could suggest particular operating practices to limit the causes of error due to measurement setup and environmental conditions
Representing seesaw neutrino models and their motion in lepton flavour space
No full textAbstract We discuss how seesaw neutrino models can be graphically represented in lepton flavour space. We examine various popular models and show how this representation helps understanding their properties and connection with experimental data showing in particular how certain texture zero models are ruled out. We also introduce a new matrix, the bridging matrix, that brings from the light to the heavy neutrino mass flavour basis, showing how this is related to the orthogonal matrix and how different quantities are easily expressed through it. We then show how one can randomly generate orthogonal and leptonic mixing matrices uniformly covering all flavour space in an unbiased way (Haar-distributed matrices). Using the isomorphism between the group of complex rotations and the Lorentz group, we also introduce the concept of Lorentz boost in flavour space for a seesaw model and how this has an insightful physical interpretation. Finally, as a significant application, we consider N 2-leptogenesis. Using current experimental values of low energy neutrino parameters, we show that the probability that at least one flavoured decay parameter of the lightest right-handed neutrino is smaller than unity is about 49% (to be compared with the tiny probability that the total decay parameter is smaller than unity, P (K I < 1) ∼ 0.1%, confirming the crucial role played by flavour effects). On the other hand when m 1 ≳ 0.1 eV this probability reduces to less than 5%, showing how also N 2-leptogenesis disfavours degenerate light neutrinos
Measurements problems in the electrical characterisation of different type of discarge lamps
No full text
A full analytic solution of SO(10)-inspired leptogenesis
No full textAbstract Recent encouraging experimental results on neutrino mixing parameters prompt further investigation on SO(10)-inspired leptogenesis and on the associated strong thermal solution that has correctly predicted a non-vanishing reactor mixing angle, it further predicts sin δ ≲ 0, now supported by recent results at ∼ 95% C.L., normally ordered neutrino masses and atmospheric mixing angle in the first octant, best fit results in latest global analyses. Extending a recent analytical procedure, we account for the mismatch between the Yukawa basis and the weak basis, that in SO(10)-inspired models is described by a CKM-like unitary transformation V L , obtaining a full analytical solution that provides useful insight and reproduces accurately all numerical results, paving the way for future inclusion of different sources of theoretical uncertainties and for a statistical analysis of the constraints. We show how muon-dominated solutions appear for large values of the lightest neutrino mass in the range (0.01–1) eV but also how they necessarily require a mild fine tuning in the seesaw relation. For the dominant (and untuned) tauon-dominated solutions we show analytically how, turning on V L ≃ V CKM, some of the constraints on the low energy neutrino parameters get significantly relaxed. In particular we show how the upper bound on the atmospheric neutrino mixing angle in the strong thermal solution gets relaxed from θ 23 ≲ 41° to θ 23 ≲ 44°, an important effect in the light of the most recent NOνA, T2K and IceCube results
Supersymmetric SO(10)-inspired leptogenesis and a new N<sub>2</sub>-dominated scenario
No full textWe study the supersymmetric extension of SO(10)-inspired thermal leptogenesis showing the constraints on neutrino parameters and on the reheat temperature TRH that derive from the condition of successful leptogenesis from next-to-lightest right handed (RH) neutrinos (N2) decays and the more stringent ones when independence of the initial conditions (strong thermal leptogenesis) is superimposed. In the latter case, the increase of the lightest right-handed neutrino (N1) decay parameters helps the wash-out of a pre-existing asymmetry and constraints relax compared to the non-supersymmetric case. We find significant changes especially in the case of large tan β values (gsim 15). In particular, for normal ordering, the atmospheric mixing angle can now be also maximal. The lightest left-handed neutrino mass is still constrained within the range 10 lesssim m1/meV lesssim 30 (corresponding to 75lesssim Σi mi/meV lesssim 120). Inverted ordering is still disfavoured, but an allowed region satisfying strong thermal leptogenesis opens up at large tan β values. We also study in detail the lower bound on TRH finding TRH gsim 1 × 1010 GeV independently of the initial N2 abundance. Finally, we propose a new N2-dominated scenario where the N1 mass is lower than the sphaleron freeze-out temperature. In this case there is no N1 wash-out and we find TRH gsim 1× 109 GeV . These results indicate that SO(10)-inspired thermal leptogenesis can be made compatible with the upper bound from the gravitino problem, an important result in light of the role often played by supersymmetry in the quest of a realistic model of fermion masses
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