Análise teórica e experimental da partida supercrítica de tubos de calor criogênicos

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Mecânica.Tubos de calor criogênicos são dispositivos de controle térmico de satélites que são utilizados principalmente para o controle térmico de superfícies ópticas, sistemas de câmeras infravermelhos, detectores de raios-X, e telescópios em ambiente espacial. Atualmente, pesquisas estão sendo realizadas para incluir outras aplicações de tubos de calor criogênicos, como o resfriamento de dispositivos eletrônicos, particularmente em ambientes de microgravidade. Os mais recentes desenvolvimentos teóricos e experimentais sobre a análise da partida supercritica de tubos de calor criogênicos, efetuada no Núcleo de Controle Térmico de Satélites, da Universidade Federal de Santa Catarina em cooperação com a Universidade de Clemson, são apresentados. Este projeto de pesquisa foi financiado pelo Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq, Fundação CAPES, e Agência Espacial Brasileira, como parte do Programa Uniespaço. O propósito deste trabalho é descrever as técnicas teóricas e experimentais utilizadas para a análise da partida supercritica de tubos de calor criogênicos sob várias condições operacionais. Embora o texto principal desta tese é escrito em inglês, uma sinopse em português é apresentada ao término de cada capítulo

Benchmarking some Portuguese S&T system research units: 2nd Edition

The increasing use of productivity and impact metrics for evaluation and comparison, not only of individual researchers but also of institutions, universities and even countries, has prompted the development of bibliometrics. Currently, metrics are becoming widely accepted as an easy and balanced way to assist the peer review and evaluation of scientists and/or research units, provided they have adequate precision and recall. This paper presents a benchmarking study of a selected list of representative Portuguese research units, based on a fairly complete set of parameters: bibliometric parameters, number of competitive projects and number of PhDs produced. The study aimed at collecting productivity and impact data from the selected research units in comparable conditions i.e., using objective metrics based on public information, retrievable on-line and/or from official sources and thus verifiable and repeatable. The study has thus focused on the activity of the 2003-06 period, where such data was available from the latest official evaluation. The main advantage of our study was the application of automatic tools, achieving relevant results at a reduced cost. Moreover, the results over the selected units suggest that this kind of analyses will be very useful to benchmark scientific productivity and impact, and assist peer review.Comment: 26 pages, 20 figures F. Couto, D. Faria, B. Tavares, P. Gon\c{c}alves, and P. Verissimo, Benchmarking some portuguese S\&T system research units: 2nd edition, DI/FCUL TR 13-03, Department of Informatics, University of Lisbon, February 201

Understanding electronic properties of water: a theoretical approach to the calculation of the adiabatic band gap of liquid water

Tese de doutoramento em Química (Química-Física), apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2008Electronic properties of condensed phase water are not very well understood. They are, however, of fundamental importance for a molecular level understanding of the properties of water as well as the role of water, both as participant and medium where chemical reactions occur. It is generally accepted that bulk water can be described as a lone pair amorphous insulator or a large gap lone-pair amorphous semiconductor and the condensed phase ionization potential de_ned as a vertical quantity. A usually accepted value is 8.7 _ 0.5 eV. However, a de_nition of condensed phase properties such as the condensed phase ionization potential is not straightforward and ultimately dependent our understanding of the elementary mechanisms for ionization/excitation in condensed phase water. A longstanding issue is the concearns the fact that hydrated electrons are produced by photoabsorption at _6.5 eV. It has recently been pointed out that the ability of water to reorganize about charged (and neutral) molecules, as well as the reactive nature of electronically excited water molecules, should be taken into account in explaining observed aqueous anion thermochemical and photochemical properties. Moreover, it has been shown that an adiabatic route for accessing the conduction band of liquid water can be de_ned and that the bottom of the conduction band is characterized by the reorganization of the water molecules around the H3O+ cation and OH radical as well as by the presence of a delocalized or quasi-free electron. A _6.9 eV value was proposed by J.V. Coe [Int. Rev. Phys. Chem. 20, 33, 2001], based on known aqueous anion thermochemical and photochemical properties,The present work presents a theoretical estimate for two key reference quantities required for the quantitative estimate of the adiabatic band gap of pure liquidwater as de_ned by J.V. Coe: the hydration energy of the hydroxyl radical andthe electron a_nity of liquid water. The hydration of the hydroxyl radical wasinvestigated by microsolvation modeling and statistical mechanics Monte Carlosimulation. The electron electronic density of states and a_nity of liquid water wasinvestigated trough a sequential Quantum Mechanical / Monte Carlo methodology.Finally, as the adiabatic approach for a de_nition of a band gap for pure liquidwater is based on macroscopic quantities, a molecular level veri_cation of the adiabatic picture was also undertaken

Fuzzy identification and predictive control of the alcoholic fermentation process

In this work a fuzzy identification model for yeast growth applied to the specific case of alcoholic fermentation is presented. Two fuzzy techniques were applied, namely the designated Mamdani modelling and the TSK (Takagi Sugeno Kang) modelling. The results were compared with the ones obtained with a deterministic model proposed by Boulton. A predictive controller is also presented and the results obtained compared with the usual PID controller. The obtained results for the identification models and for the controller showed that both methodologies can be applied to biological processes

GEM – A SOFTWARE FOR STABILITY VERIFICATION OF NON-UNIFORM MEMBERS, Adaptation of the general method procedure to fire design

There is currently no specific rules in Part 1-2 of Eurocode 3 for the stability verification of non-uniform members under fire conditions. For normal temperature, Part 1-1 of the same code provides a General Method to check the stability against lateral and lateral-torsional buckling for these type of members, though it requires some extensive calculations. It is here demonstrated in this paper how both problems can be addressed, by exposing a procedure that accounts for the modifications of the method at elevated temperatures, and by showing its implementation within a computer program. It is also shown how the program can be used to assess the study of the method itself, by applying it to a case of a web-tapered beam-column and comparing it to numerical results

Methods for Evaluation of Measurement Uncertainty

This chapter presents and explains the most used methodologies for the evaluation of measurement uncertainty in metrology with practical examples. The main topics are basic concepts and importance, existing documentation, the harmonized methodology of the Guide to the Expression of Uncertainty in Measurement, types of uncertainty, modeling of measurement systems, use of alternative methods (including the GUM supplement 1 Monte Carlo numerical method), evaluation of uncertainty for calibration curves, correlated uncertainties, uncertainties arising from the calibration of instruments, and the main proposals for the new revised GUM. The chapter also discusses the GUM as a tool for the technical management of measurement processes

Análise de custos em obras de reabilitação de edifícios

A presente comunicação apresenta um estudo em curso sobre a análise de custos em obras de reabilitação de edifícios no Laboratório Nacional de Engenharia Civil (LNEC), no âmbito do projecto ProNIC [1]. Este projecto é constituído por uma aplicação informática onde são definidos trabalhos de construção numa estrutura de capítulos. Cada trabalho é arrumado nessa estrutura e constitui o seu nível inferior. Assim, com base nas descrições dos trabalhos existentes no ProNIC, estão a ser levantados os custos unitários dos trabalhos de reabilitação de edifícios e a respectiva composição de recursos. A quantificação destes custos apresenta dificuldades uma vez que os mesmos se baseiam fortemente na experiência do orçamentista e na consideração global dos trabalhos a efectuar. Contudo, a existência de bases de dados com valores médios em diferentes países da Europa, aliada a alguns preços globais existentes em empresas de construção e entidades promotoras deste tipo de intervenção, podem fornecer indicadores que servem de base para o cálculo das fichas de composição de custo, de que se apresentam exemplos

Projeto e desenvolvimento de radiadores criogênicos passivos para aplicações espaciais /

Dissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico