Thin film limits for Ginzburg--Landau with strong applied magnetic fields

In this work, we study thin-film limits of the full three-dimensional Ginzburg-Landau model for a superconductor in an applied magnetic field oriented obliquely to the film surface. We obtain Gamma-convergence results in several regimes, determined by the asymptotic ratio between the magnitude of the parallel applied magnetic field and the thickness of the film. Depending on the regime, we show that there may be a decrease in the density of Cooper pairs. We also show that in the case of variable thickness of the film, its geometry will affect the effective applied magnetic field, thus influencing the position of vortices

Higher-order phase transitions with line-tension effect

The behavior of energy minimizers at the boundary of the domain is of great importance in the Van de Waals-Cahn-Hilliard theory for fluid-fluid phase transitions, since it describes the effect of the container walls on the configuration of the liquid. This problem, also known as the liquid-drop problem, was studied by Modica in [Ann. Inst. Henri Poincaré, Anal. non linéaire 4 (1987) 487–512], and in a different form by Alberti et al. in [Arch. Rational Mech. Anal. 144 (1998) 1–46] for a first-order perturbation model. This work shows that using a second-order perturbation Cahn-Hilliard-type model, the boundary layer is intrinsically connected with the transition layer in the interior of the domain. Precisely, considering the energies \[ {\cal F}_{\varepsilon}(u) := \varepsilon^{3} \int_{\Omega} |D^{2}u|^{2} + \frac{1}{\varepsilon} \int_{\Omega} W (u) + \lambda_{\varepsilon} \int_{\partial \Omega} V(Tu), \] where u is a scalar density function and W and V are double-well potentials, the exact scaling law is identified in the critical regime, when $\varepsilon\lambda_{\varepsilon}^{\frac{2}{3}} \sim 1$

Information system to manage the evaluation of employees' performance in a preschool: a prototype in development

In education, teachers are one of the most important components in achieving success. More than that, teachers are first of all people and, like any person, they have their own strengths and weaknesses. A performance evaluation process is intended to capture their flaws, and use that information to consistently improve the quality of the service provided by these professionals. In an attempt to achieve a positive progress, we worked with a Portuguese preschool to implement a performance evaluation process to all its employees. The end goal of this dissertation is to support the implementation of this process with the proposal and development of an Information System (IS) model that can assist the preschool’s management in understanding what is going well and what needs to be adjusted, in order to provide a better service to the children. In order to achieve this goal, the system was modelled and developed into a prototype that was then tested by the end-users using real data. These tests allowed for adjustments and improvements of the IS, especially since the universe of users are not accustomed to working with computers. For this reason, another important goal of the dissertation is to develop a system with the most simple and organized interface possible so that all end-users can easily take advantage of it.Na educação, os professores são um dos componentes mais importantes para o sucesso. Mais do que isso, os professores são antes de mais pessoas, e como quaisquer pessoas, têm os seus pontos fortes e pontos fracos. Um processo de avaliação de desempenho pretende capturar as falhas e usar essa informação para melhorar, consistentemente, a qualidade do serviço prestado pelos profissionais. Numa tentativa de alcançar um progresso positivo, trabalhámos com um jardim-de-infância português para informatizar um processo de avaliação de desempenho para todos os seus profissionais. O grande objectivo desta dissertação é assim suportar a implementação deste processo, com a proposta e desenvolvimento de um modelo de Sistema de Informação (SI) que possa auxiliar os órgãos de gestão do jardim-de-infância a compreender o que se passa, e o que precisa de ser ajustado, de modo a fornecer um melhor serviço às crianças. Para atingir este objectivo, foi feita a modelação do sistema e desenvolvido um protótipo do SI, posteriormente testado com os utilizadores finais, utilizando dados reais. Estes testes permitiram o ajuste e melhoramento do SI, especialmente devido ao facto de o universo de utilizadores deste SI não estar acostumado a utilizar computadores. Por esta mesma razão, outro objectivo fulcral para esta dissertação é o desenvolvimento de um sistema com uma interface o mais simples e organizada possível, de modo a que todos os utilizadores finais o possam utilizar sem dificuldade

Direct comparasion of an engine working under Otto, Miller end Diesel cycles : thermodynamic analysis and real engine performance

One of the ways to improve thermodynamic efficiency of Spark Ignition engines is by the optimisation of valve timing and lift and compression ratio. The throttleless engine and the Miller cycle engine are proven concepts for efficiency improvements of such engines. This paper reports on an engine with variable valve timing (VVT) and variable compression ratio (VCR) in order to fulfill such an enhancement of efficiency. Engine load is controlled by the valve opening period (enabling throttleless operation and Miller cycle), while the variable compression ratio keeps the efficiency high throughout all speed and load conditions. A computer model is used to simulate such an engine and evaluate its improvement potential, while a single cylinder engine demonstrates these results. The same base engine was run on the test bench under the Diesel cycle, Otto cycle and Miller cycle conditions, enabling direct thermodynamic comparisons under a wide variety of conditions of speed and load. The results show a significant improvement of the Miller cycle over the Otto cycle engine. Comparisons of the Miller engine with the Diesel engine shown that it is possible to have a SI engine with better efficiency than a similar Diesel engine for most of the working conditions.Fundação para a Ciência e a Tecnologia (FCT) e Fundo Social Europeu (FSE) - SFRH/BD/11194/2002, FCT/FEDER POCI/ENR/59168/2004, POCI/EME/59186/200

Miller cycle analysis using EGM

The Entropy Generation Minimization (EGM) method is based on the analysis by three sciences (thermodynamics, fluid flow and heat transfer) of the different processes that may occur in a system or in an equipment. Herein the EGM method is applied to internal combustion engines to determine the entropy generation caused by different processes. A model incorporating entropy generation calculations is used to assess various engines configurations. Otto cycle was tested and Variable Valve Timing (VVT) and Variable Compression Ratio (VCR) were applied so thermodynamic benefits could be tested and evaluated. With the referred model, the Miller cycle variables are analyzed in order to establish the best working conditions of an engine under a certain load. The intake and exhaust valve timing, combustion start, compression ratio adjustment and heat transfer are the variables for which a best working condition is determined based on the minimization of the entropy generation of the several engine processes.Fundação para a Ciência e a Tecnologia (FCT)Fundo Social Europeu (FSE