Learning Parallel Computations with ParaLab

In this paper, we present the ParaLab teachware system, which can be used for learning the parallel computation methods. ParaLab provides the tools for simulating the multiprocessor computational systems with various network topologies, for carrying out the computational experiments in the simulation mode, and for evaluating the efficiency of the parallel computation methods. The visual presentation of the parallel computations taking place in the computational experiments is the key feature of the system. ParaLab can be used for the laboratory training within various teaching courses in the field of parallel, distributed, and supercomputer computations

Industrial scale large eddy simulations (LES) with adaptive octree meshes using immersogeometric analysis

We present a variant of the immersed boundary method integrated with octree meshes for highly efficient and accurate Large-Eddy Simulations (LES) of flows around complex geometries. We demonstrate the scalability of the proposed method up to $\mathcal{O}(32K)$ processors. This is achieved by (a) rapid in-out tests; (b) adaptive quadrature for an accurate evaluation of forces; (c) tensorized evaluation during matrix assembly. We showcase this method on two non-trivial applications: accurately computing the drag coefficient of a sphere across Reynolds numbers $1-10^6$ encompassing the drag crisis regime; simulating flow features across a semi-truck for investigating the effect of platooning on efficiency.Comment: Accepted for publication at Computer and Mathematics with Application

Oligomerização de olefinas leves na presença de catalisadores ácidos inorgânicos porosos

With the global growth in fuel demand for transportation and increasing environmental concerns, the oligomerization of light olefins obtainable from fossil or renewable sources and refinery streams, represents a promising route for producing clean synthetic fuels with low aromatics and sulphur contents, and other added-value chemicals. This thesis deals with the oligomerization of 1-butene to produce diesel range products, under high pressure and continuous operation, in the presence of heterogeneous acid catalysts. The oligomerization of light olefins is a complex reaction system. The yields and characteristics of the products are governed by the properties of the catalytic materials and the operating conditions. These aspects were investigated with the practical goal of producing clean diesel range products, using porous inorganic acid catalysts based on silicon and aluminium oxides. The materials were prepared via different methodologies and characterized by complementary techniques, with special attention given to morphological, textural and acid properties. The catalytic performances were evaluated in terms of activity, selectivity to clean diesel type products and stability, based on experimental studies and multivariate statistical tools. The characteristics of the catalytic reaction products were studied based on comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-ToFMS) and nuclear magnetic resonance (NMR) spectroscopy. In the search for promising catalysts, the research work evolved from eco-friendly mesoporous aluminosilicate of the type TUD-1 prepared via one-pot or stepwise approaches, and a composite material comprising BEA nanocrystallites embedded in a TUD-1 siliceous matrix, to micro/mesoporous zeotypes possessing different topologies (BEA, MFI) prepared via bottom-up or top-down approaches. The catalysts were benchmarked with commercially available zeolites and a catalyst based on the MFI topology which was developed for commercial oligomerization processes, namely COD-9. The micro/mesoporous zeotypes outperformed the commercial zeolites (Beta, ZSM-5, COD-9), leading to conversions of butenes of up to 86 % and selectivity to diesel ranged products of up to 71 wt.%, at 200 ºC, 30 bar and 2.2 g gcat-1 h-1. Based on principal component analysis (PCA), structure-activity relationships were established that pointed to the importance of good compromises between textural and acid properties for maximizing the yields of clean diesel range products - intermediate concentrations of acid sites and enhanced mesoporosity resulted in superior catalytic performances. One of the best-performing catalysts was MZS-0.4-Cl prepared via top-down approach from commercial ZSM-5. Optimization studies were carried out for 1-butene oligomerization over this type of catalyst. The optimization was based on a Box-Behnken design of experiments (DoE) and response surface methodology (RSM), contemplating the yields of the diesel range products, as well as the product quality (reduced aromatics content). These studies indicated that the favourable operating conditions were in the ranges 220-250 ºC of reaction temperature, 30-40 bar and 2.5-3.5 g1C4 gcat-1 h-1 weight hourly space velocity. Finally, PCA studies were conducted for all materials studied in this thesis, to show the complex interplay of material properties influencing the catalytic performances.Com o aumento global do consumo de combustíveis para o setor dos transportes e as crescentes preocupações ambientais, a oligomerização de alcenos leves provenientes de fontes fósseis ou renováveis, ou de efluentes de refinarias, representa uma via de valorização promissora para produzir combustíveis limpos com reduzidos teores de compostos aromáticos e enxofre, e outros produtos químicos de valor acrescentado. Esta tese incide na oligomerização do 1-buteno em produtos do tipo diesel sintético, em reator contínuo, a alta pressão, usando catalisadores heterogéneos ácidos. A oligomerização de alcenos leves envolve mecanismos reacionais complexos. Os rendimentos e as características dos produtos dependem das propriedades dos materiais catalíticos e das condições de operação. Estes aspetos foram investigados com o objetivo prático de produzir diesel limpo, usando catalisadores ácidos inorgânicos porosos à base de óxidos de silício e alumínio. Os materiais foram preparados por diversas metodologias e caracterizados por técnicas complementares, com especial atenção dada às propriedades morfológicas, texturais e ácidas. Os desempenhos catalíticos foram avaliados em termos de atividade, seletividade para produtos do tipo diesel e estabilidade, com base em estudos experimentais e o recurso a ferramentas estatísticas de análise multivariada. As misturas de produtos reacionais foram caracterizadas com base em cromatografia de gás bidimensional abrangente acoplada a espectrometria de massa com analisador por tempo de voo (GC×GC-ToFMS) e espectroscopia por ressonância magnética nuclear (RMN). À descoberta de catalisadores promissores, o trabalho de investigação evoluiu de aluminossilicatos mesoporosos do tipo TUD-1 sintetizados por metodologias relativamente limpas (sem agentes tensoativos) e um compósito de nanocristais de zeólito Beta dispersos numa matriz do tipo TUD-1, até zeótipos micro- e mesoporosos possuindo diferentes topologias (BEA, MFI) e preparados por estratégias bottom-up (não destrutivas) ou top-down. Os desempenhos dos catalisadores preparados foram comparados com zeólitos comerciais e um catalisador que foi desenvolvido para processos comerciais de oligomerização, nomeadamente o COD-9 (baseado na topologia MFI). Os zeótipos micro/mesoporosos apresentaram melhores desempenhos do que os zeólitos comerciais (Beta, ZSM-5, COD-9), obtendo-se conversões de butenos até 86 % e seletividades para produtos do tipo diesel até 71 % (m/m), a 200 ºC, 30 bar e 2.2 g gcat-1 h-1. Com base em análise estatística de componentes principais (PCA) foram estabelecidas relações de atividade-estrutura que apontaram para a necessidade de haver compromissos entre as propriedades texturais e ácidas para maximizar os rendimentos em diesel limpo – concentrações intermédias de centros ácidos e elevada mesoporosidade resultaram em melhores desempenhos catalíticos. Um dos catalisadores mais promissores foi o MZS-0.4-Cl preparado pela abordagem top-down a partir do zeólito comercial ZSM-5. Foram realizados estudos de otimização para a oligomerização do 1-buteno usando este tipo de catalisador. A otimização baseou-se no desenho fatorial de experiências (DoE, com uma matriz Box-Behnken) e a metodologia da superfície de resposta (RSM), contemplando os rendimentos em produtos do tipo diesel, assim como aspetos da qualidade dos produtos (teor de compostos aromáticos). Estes estudos indicaram as seguintes gamas de condições de operação mais favoráveis: 220-250 ºC de temperatura de reação, 30-40 bar de pressão e 2.5-3.5 g1C4 gcat-1 h-1 de velocidade espacial por unidade de massa de catalisador. Por fim, estudos de PCA com todos os materiais estudados nesta tese mostraram que a influência das propriedades dos materiais nos desempenhos não é trivial.Programa Doutoral em Engenharia Químic

TECHNART 2017. Non-destructive and microanalytical techniques in art and cultural heritage. Book of abstracts

440 p.TECHNART2017 is the international biannual congress on the application of Analytical Techniques in Art and Cultural Heritage. The aim of this European conference is to provide a scientific forum to present and promote the use of analytical spectroscopic techniques in cultural heritage on a worldwide scale to stimulate contacts and exchange experiences, making a bridge between science and art. This conference builds on the momentum of the previous TECHNART editions of Lisbon, Athens, Berlin, Amsterdam and Catania, offering an outstanding and unique opportunity for exchanging knowledge on leading edge developments. Cultural heritage studies are interpreted in a broad sense, including pigments, stones, metal, glass, ceramics, chemometrics on artwork studies, resins, fibers, forensic applications in art, history, archaeology and conservation science. The meeting is focused in different aspects: - X-ray analysis (XRF, PIXE, XRD, SEM-EDX). - Confocal X-ray microscopy (3D Micro-XRF, 3D Micro-PIXE). - Synchrotron, ion beam and neutron based techniques/instrumentation. - FT-IR and Raman spectroscopy. - UV-Vis and NIR absorption/reflectance and fluorescence. - Laser-based analytical techniques (LIBS, etc.). - Magnetic resonance techniques. - Chromatography (GC, HPLC) and mass spectrometry. - Optical imaging and coherence techniques. - Mobile spectrometry and remote sensing