Importância do pré-tratamento químico e o seu impacto na qualidade do revestimento de substratos de alumínio

O pré-tratamento químico é fundamental no processo de revestimento de alumínio, apresentando três principais funções, a limpeza da peça, a ampliação da resistência corrosiva do alumínio, e o aumento da aderência das peliculas poliméricas de tinta. Estas três funções representam fatores determinantes na obtenção de um revestimento que cumpra as especificações de qualidade. Posto isto, a presente dissertação focou-se na análise do impacto do processo de pré-tratamento na qualidade do revestimento aplicado a componentes de alumínio. Assim, foram definidas como potenciais causas para os problemas de qualidade do revestimento os parâmetros controlados no pré-tratamento, tendo sido nomeados de X1 a X32. Estes parâmetros foram sujeitos a uma análise de capacidade, com base no histórico de dados recolhido, afim de verificar se se encontram a produzir dentro de especificação, tendo-se comprovado que apenas os parâmetros X1, X2, X16, X17, X18, X19, X20, X21, X23, X28, X30, X31 e X33 apresentam uma boa probabilidade de serem capazes de produzir dentro de especificação. De seguida procedeu-se à análise de tabelas comparativas, que relacionam os valores referentes aos parâmetros do pré-tratamento e os resultados obtidos para os ensaios de caracterização da qualidade do revestimento, sendo possível concluir que a combinação de um valor de ± 52 °C para X2, com um valor de ± 50 μS/cm para X16 e um valor de ± 23 ppm para X22 poderia potencialmente resultar em falha no ensaio de Aderência. Afim de comprovar as suspeitas sobre a potencial influência desta combinação na qualidade da Aderência, efetuaram-se tanto testes simulando processos de pré-tratamento por imersão (com a combinação mencionada) como o processo de produção normal por aspersão, com posterior pintura eletrostática das peças. Os resultados obtidos não se demonstraram muito conclusivos, o que pode dever-se a duas hipóteses explicativas, sendo elas: A diferença do teor de Alumínio Dissolvido do estágio Silanos verificada entre os testes e a produção normal; A aplicação do pré-tratamento, visto que uma aplicação por imersão, contrariamente à por aspersão, trata a peça interna e externamente, o que aliado ao formato da peça poderá ter exercido influência sobre o potencial eletrostático da peça, causando impacto no processo de pintura

Modelação numérica de um concentrador solar do tipo central de torre com configuração beam-down

Este trabalho consiste na modelação de um sistema de concentração do tipo torre com uma nova configuração beam-down (ST-BD), com o objetivo de estudar o seu desempenho ótico e térmico. A performance ótica dos sistemas de torre (SPT) e (ST-BD) são analisadas para duas localizações distintas utilizando os softwares Tonatiuh e Matlab, sendo demonstrado que o sistema ST-BD, que tem um maior número de estágios que o sistema SPT, apresenta uma menor eficiência ótica. Na performance térmica é considerado um sistema de armazenamento com o recetor integrado, considerando ar como fluido de transferência de calor e gabro para armazenar calor sensível e absorver energia. É desenvolvido um modelo transiente unidimensional no software MATLAB para estudar a performance e avaliar diferentes casos de funcionamento do sistema. Os resultados obtidos são otimistas, sendo demonstrando que a tecnologia poderá evoluir para um patamar comercial; Numerical modeling of a central tower type solar concentrator with beam-down configuration Abstract: This work consists of the modeling of a tower type concentration system with a new beam-down configuration (ST-BD), in order to study its optic and thermal performance. The optical performance of the tower (SPT) and ST-BD systems are analysed for two different locations using the software Tonatiuh and Matlab, being demonstrated that the ST-BD system, which has a higher number of optical stages that SPT system, presents lower optical efficiency. In thermal performance is considered a storage system with an integrated receiver, considering air has a heat transfer fluid and gabbro for sensible heat storage and absorber of energy. A one-dimensional transient model is developed using software MATLAB to study the performance and evaluate different cases of system operation. The results obtained are optimistic, being demonstrated that technology may be developed to a commercial level

Processamento automático de uma rede GPS permanente

Tese mestr., Ciências e Engenharia da Terra, Universidade de Lisboa, 200

Etendue-Matched Solar Tower Beam-Down System for High-Temperature Industrial Processes

The standard Concentrating Solar Thermal (CST) mono-tower technology, which uses one receiver placed on top of a tower to which all heliostats in the heliostat field aim to, is regarded as one of the best and most promising technologies for various CST-driven applications, namely CST power plants, solar metallurgical processes, thermochemical production of solar fuels and waste materials recycling. However, the technology has some technical challenges concerning optical performance/tolerances, system dimensions, operation and maintenance issues, etc. An alternative to this standard CST mono-tower technology is the so-called beam-down technology, where a special mirror is placed on the top of the tower, instead of a receiver, to redirect the incident radiation from the heliostat field onto a receiver/reactor placed closer to the ground and potentially delivering higher concentrations at the receiver than the standard CST mono-tower technology. This paper presents a new approach to improve the optics of beam-down systems, applies it to the optical design of a specific system, and shows the optical behavior of this design at two locations: Évora (Portugal) and Hurghada (Egypt). The approach uses etendue-matching between all the optical stages to minimize the optical losses between them. To analyze the optical behavior of the system designed, as an example, using the etendue-matching approach, raytracing simulations were carried out and are presented also in the paper.Projecto H2020 INSHIP - Grant No. 731287

Renewing terraces and drystone walls of Algarvian Barrocal. Cultural and touristic values

This paper aims to enhance the functions of terraces and drystone walls as structural elements and distinctive factors of the traditional rural zone known as the barrocal of the Algarve, south of Portugal. In fact, such elements define the character of the landscape that forms the background of a traditional touristic region along the coast. The core of this paper will be the knowledge of construc-tion processes, spatial distribution, and hydrological, ecological, economic and social functions, once it is quite necessary for the Algarve region. Some projects and studies have been developed in the Mediterranean context, but there is not enough research on this subject in the south of Portugal. Secondly, the social meaning, or acknowledgement of the landscape characterized by drystone wall structures, will be the key for finding real possibilities of renewing the terraces. Therefore, the landscape will be assumed as a common good. In this subject, we take into account the potential role and sensibility of tourists and resident popu-lation. Beyond static patrimonial statutes, we can design some practical possibil-ities to enhance plastic features and new uses leading to an acknowledgement of the Algarvian drystone wall structure, referred as a part of Mediterranean coastal landscapes. Some examples that can add cultural and touristic value could be: recreation areas for urbanites, new cooperative forms of agriculture, hobby farm-ing, workshops about harvesting traditional products, circuits and pedestrian paths, and interchange with similar Mediterranean regions defining broader cir-cuits.info:eu-repo/semantics/publishedVersio

Estruturas mediterrânicas tradicionais. A utopia da paisagem urbano-turística do Algarve

Uma das características marcantes das paisagens mediterrânicas é a armação dos terrenos montanhosos em socalcos suportados por muros de pedra seca. Além do carácter identitário que imprimem na paisagem, as construções milenares em pedra seca estabelecem uma rede de compartimentação com várias funções ou utilidades, como suporte de terras, drenagem, armazenamento de águas, divisão de propriedade, limitação de caminhos e veredas. Para além destas funções, focar-nos-emos de forma especial nos valores sociais e éticos capazes de gerar alternativas de evolução da paisagem. No Algarve, se bem que os valores atribuídos pelas populações locais sejam determinantes nessa evolução, o papel dos turistas e população residente estrangeira pode, no entanto, ser fundamental para gerar novos contextos cénicos. O nosso argumento gira em torno do futuro da estrutura dos muros de pedra seca, a prospetar dentro da diversidade de possíveis soluções sobre o desenvolvimento da paisagem envolvente do sistema urbano, enquanto parte viva de uma unidade que inclui as áreas mais densamente urbanizadas. Designamos essa unidade região urbanoturística do Algarve, inspirada em duas referências utópicas: a de ‘região urbana’ e a de ‘agropólia’, em que a paisagem é assumida como bem comum e instrumento de conhecimento e reconhecimento –governança democrática– de espaços regionais.info:eu-repo/semantics/publishedVersio

Search for the standard model Higgs boson produced in association with top quarks and decaying into a bbˉb\bar{b} pair in pppp collisions at s\sqrt{s} = 13 TeV with the ATLAS detector

A search for the standard model Higgs boson produced in association with a top-quark pair, tt¯H, is presented. The analysis uses 36.1  fb-1 of pp collision data at s=13  TeV collected with the ATLAS detector at the Large Hadron Collider in 2015 and 2016. The search targets the H→bb¯ decay mode. The selected events contain either one or two electrons or muons from the top-quark decays, and are then categorized according to the number of jets and how likely these are to contain b-hadrons. Multivariate techniques are used to discriminate between signal and background events, the latter being dominated by tt¯+jets production. For a Higgs boson mass of 125 GeV, the ratio of the measured tt¯H signal cross-section to the standard model expectation is found to be μ=0.84-0.61+0.64. A value of μ greater than 2.0 is excluded at 95% confidence level (C.L.) while the expected upper limit is μ<1.2 in the absence of a tt¯H signal.Peer Reviewe

Performance of the ATLAS Track Reconstruction Algorithms in Dense Environments in LHC Run 2

With the increase in energy of the Large Hadron Collider to a centre-of-mass energy of 13  $\text {TeV}$ for Run 2, events with dense environments, such as in the cores of high-energy jets, became a focus for new physics searches as well as measurements of the Standard Model. These environments are characterized by charged-particle separations of the order of the tracking detectors sensor granularity. Basic track quantities are compared between 3.2 fb$^{-1}$ of data collected by the ATLAS experiment and simulation of proton–proton collisions producing high-transverse-momentum jets at a centre-of-mass energy of 13  $\text {TeV}$ . The impact of charged-particle separations and multiplicities on the track reconstruction performance is discussed. The track reconstruction efficiency in the cores of jets with transverse momenta between 200 and 1600 $\text {GeV}$ is quantified using a novel, data-driven, method. The method uses the energy loss, ${\text { d}}{} \textit{E}/d\textit{x}$ , to identify pixel clusters originating from two charged particles. Of the charged particles creating these clusters, the measured fraction that fail to be reconstructed is $0.061 \pm 0.006\ {\text {(stat.)}} \pm 0.014\ {\text {(syst.)}}$ and $0.093 \pm 0.017\ {\text {(stat.)}}\pm 0.021\ {\text {(syst.)}}$ for jet transverse momenta of 200–400  $\text {GeV}$ and 1400–1600  $\text {GeV}$ , respectively.Peer Reviewe

Measurement of the cross section for isolated-photon plus jet production in pppp collisions at s=13\sqrt s=13 TeV using the ATLAS detector

The dynamics of isolated-photon production in association with a jet in proton–proton collisions at a centre-of-mass energy of 13 TeV are studied with the ATLAS detector at the LHC using a dataset with an integrated luminosity of 3.2 fb −1 . Photons are required to have transverse energies above 125 GeV. Jets are identified using the anti- kt algorithm with radius parameter R=0.4 and required to have transverse momenta above 100 GeV. Measurements of isolated-photon plus jet cross sections are presented as functions of the leading-photon transverse energy, the leading-jet transverse momentum, the azimuthal angular separation between the photon and the jet, the photon–jet invariant mass and the scattering angle in the photon–jet centre-of-mass system. Tree-level plus parton-shower predictions from Sherpa and Pythia as well as next-to-leading-order QCD predictions from Jetphox and Sherpa are compared to the measurements.Peer Reviewe

Measurements of top-quark pair differential cross-sections in the eμe\mu channel in pppp collisions at s=13\sqrt{s} = 13 TeV using the ATLAS detector

This article presents measurements of $t\bar{t}$ differential cross-sections in a fiducial phase-space region, using an integrated luminosity of 3.2 fb$^{-1}$ of proton–proton data at a centre-of-mass energy of $\sqrt{s} = 13$  TeV recorded by the ATLAS experiment at the LHC in 2015. Differential cross-sections are measured as a function of the transverse momentum and absolute rapidity of the top quark, and of the transverse momentum, absolute rapidity and invariant mass of the $t\bar{t}$ system. The $t\bar{t}$ events are selected by requiring one electron and one muon of opposite electric charge, and at least two jets, one of which must be tagged as containing a b-hadron. The measured differential cross-sections are compared to predictions of next-to-leading order generators matched to parton showers and the measurements are found to be consistent with all models within the experimental uncertainties with the exception of the Powheg-Box $+$ Herwig++ predictions, which differ significantly from the data in both the transverse momentum of the top quark and the mass of the $t\bar{t}$ system.Peer Reviewe