Ambiguities and Deviations in Qualitative Circuit Analysis

Lee M.H., Bell J. and Coghill G.M., Ambiguities and Deviations in Qualitative Circuit Analysis, in Proc. QR?2001, 15th Int. Workshop on Qualitative Reasoning, San Antonio, Texas, May 2001, pp51-58.

Efficient modeling of novel uniplanar left-handed metamaterials

This paper presents an efficient. modeling technique for the derivation of the dispersion characteristics of novel uniplanar metallodielectric periodic structures. The analysis is based on the method of moments and an interpolation scheme, which significantly accelerates the computations. Triangular basis functions are used that allow for modeling of arbitrary shaped metallic elements. Based on this method, novel uniplanar left-handed (LH) metamaterials are proposed. Variations of the split rectangular-loop element printed on grounded dielectric substrate are demonstrated to possess LH propagation properties. Full-wave dispersion curves are presented. Based on the dual transmission-line concept, we study the distribution of the modal fields And the variation of series capacitance and shunt inductance for all the proposed elements. A verification of the left-handedness is presented by means of full-wave simulation of finite uniplanar arrays using commercial software (HFSS). The cell dimensions are a small fraction of the wavelength (approximately lambda/24) so that the structures can he considered as a homogeneous effective medium. The structures are simple, readily scalable to higher frequencies, and compatible with low-cost fabrication techniques.

Sub-Wavelength Profile 2-D Leaky-Wave Antennas With Two Periodic Layers

A fast and accurate analysis and synthesis technique for high-gain sub-wavelength 2-D Fabry-Perot leaky-wave antennas (LWA) consisting of two periodic metallodielectric arrays over a ground plane is presented. Full-wave method of moments (MoM) together with reciprocity is employed for the estimation of the near fields upon plane wave illumination and the extraction of the radiation patterns of the LWA. This yields a fast and rigorous tool for the characterisation of this type of antennas. A thorough convergence study for different antenna designs is presented and the operation principles of these antennas as well as the radiation characteristics are discussed. Moreover, design guidelines to tailor the antenna profile, the dimensions of the arrays as well as the antenna directivity and bandwidth are provided. A study on the radiation efficiency for antennas with different profiles is also presented and the trade off between directivity and radiation bandwidth is discussed. Numerical examples are given throughout to demonstrate the technique. A finite size antenna model is simulated using commercial software (CST Microstripes 2009) which validates the technique.

Sustainable non-automotive vehicles: The simulation challenges

Simulation is a well-established and effective approach to the development of fuel-efficient and low-emissions vehicles in both on-highway and off-highway applications.

The simulation of on-highway automotive vehicles is widely reported in literature, whereas research relating to non-automotive and off-highway vehicles is relatively sparse. This review paper focuses on the challenges of simulating such vehicles and discusses the differences in the approach to drive cycle testing and experimental validation of vehicle simulations. In particular, an inner-city diesel-electric hybrid bus and an ICE (Internal Combustion Engine) powered forklift truck will be used as case studies.

Computer prediction of fuel consumption and emissions of automotive vehicles on standardised drive cycles is well-established and commercial software packages such as AVL CRUISE have been specifically developed for this purpose. The vehicles considered in this review paper present new challenges from both the simulation and drive-cycle testing perspectives. For example, in the case of the forklift truck, the drive cycles involve reversing elements, variable mass, lifting operations, and do not specify a precise velocity-time profile. In particular, the difficulties associated with the prediction of productivity, i.e. the maximum rate of completing a series of defined operations, are discussed. In the case of the hybrid bus, the standardised drive cycles are unrepresentative of real-life use and alternative approaches are required in the development of efficient and low-emission vehicles.

Two simulation approaches are reviewed: the adaptation of a standard automotive vehicle simulation package, and the development of bespoke models using packages such as MATLAB/Simulink.

Strength and ductility of RC jacketed columns: a simplified analytical method

Reinforced concrete (RC) jacketing is a common method for retrofitting existing columns with poor structural performance. It can be applied in two different ways: if the continuity of the jacket is ensured, the axial load of the column can be transferred to the jacket, which will be directly loaded; conversely, if no continuity is provided, the jacket will induce only confinement action. In both cases the strength and ductility evaluation is rather complex, due to the different physical phenomena included, such as confinement, core-jacket composite action, preload and buckling of longitudinal bars.
Although different theoretical studies have been carried out to calculate the confinement effects, a practical approach to evaluate the flexural capacity and ductility is still missing. The calculation of these quantities is often related to the use of commercial software, taking advantage of numerical methods such as fibre method or finite element method.
This paper presents a simplified approach to calculate the flexural strength and ductility of square RC jacketed sections subjected to axial load and bending moment. In particular the proposed approach is based on the calibration of the stress-block parameters including the confinement effect. Equilibrium equations are determined and buckling of longitudinal bars is modelled with a suitable stress-strain law. Moment-curvature curves are derived with simple calculations. Finally, comparisons are made with numerical analyses carried out with the code OpenSees and with experimental data available in the literature, showing good agreement.

Optimization models for a short sea fuel oil distribution problem

O transporte marítimo e o principal meio de transporte de mercadorias em todo o mundo. Combustíveis e produtos petrolíferos representam grande parte das mercadorias transportadas por via marítima. Sendo Cabo Verde um arquipelago o transporte por mar desempenha um papel de grande relevância na economia do país. Consideramos o problema da distribuicao de combustíveis em Cabo Verde, onde uma companhia e responsavel por coordenar a distribuicao de produtos petrolíferos com a gestão dos respetivos níveis armazenados em cada porto, de modo a satisfazer a procura dos varios produtos. O objetivo consiste em determinar políticas de distribuicão de combustíveis que minimizam o custo total de distribuiçao (transporte e operacões) enquanto os n íveis de armazenamento sao mantidos nos n íveis desejados. Por conveniencia, de acordo com o planeamento temporal, o prob¬lema e divido em dois sub-problemas interligados. Um de curto prazo e outro de medio prazo. Para o problema de curto prazo sao discutidos modelos matemáticos de programacao inteira mista, que consideram simultaneamente uma medicao temporal cont ínua e uma discreta de modo a modelar multiplas janelas temporais e taxas de consumo que variam diariamente. Os modelos sao fortalecidos com a inclusão de desigualdades validas. O problema e então resolvido usando um "software" comercial. Para o problema de medio prazo sao inicialmente discutidos e comparados varios modelos de programacao inteira mista para um horizonte temporal curto assumindo agora uma taxa de consumo constante, e sao introduzidas novas desigualdades validas. Com base no modelo escolhido sao compara¬das estrategias heurísticas que combinam três heur ísticas bem conhecidas: "Rolling Horizon", "Feasibility Pump" e "Local Branching", de modo a gerar boas soluçoes admissíveis para planeamentos com horizontes temporais de varios meses. Finalmente, de modo a lidar com situaçoes imprevistas, mas impor¬tantes no transporte marítimo, como as mas condicões meteorológicas e congestionamento dos portos, apresentamos um modelo estocastico para um problema de curto prazo, onde os tempos de viagens e os tempos de espera nos portos sao aleatórios. O problema e formulado como um modelo em duas etapas, onde na primeira etapa sao tomadas as decisões relativas as rotas do navio e quantidades a carregar e descarregar e na segunda etapa (designada por sub-problema) sao consideradas as decisoes (com recurso) relativas ao escalonamento das operacões. O problema e resolvido por um metodo de decomposto que usa um algoritmo eficiente para separar as desigualdades violadas no sub-problema.

Numerical tools for isogeometric analysis in the nonlinear regime

The present work deals with the development of robust numerical tools for Isogeometric Analysis suitable for problems of solid mechanics in the nonlinear regime. To that end, a new solid-shell element, based on the Assumed Natural Strain method, is proposed for the analysis of thin shell-like structures. The formulation is extensively validated using a set of well-known benchmark problems available in the literature, in both linear and nonlinear (geometric and material) regimes. It is also proposed an alternative formulation which is focused on the alleviation of the volumetric locking pathology in linear elastic problems. In addition, an introductory study in the field of contact mechanics, in the context of Isogeometric Analysis, is also presented, with special focus on the implementation of a the Point-to-Segment algorithm. All the methodologies presented in the current work were implemented in a in-house code, together with several pre- and post-processing tools. In addition, user subroutines for the commercial software Abaqus were also implemented.

Projecto suspensão formula student

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Mecânica

TRFS: desenvolvimento de um protótipo para simulação microscópica de tráfego

Dissertação para obtenção do grau de Mestre em Engenharia Civil na Área de Especialização de Vias de Comunicação e Transportes

Dimensionamento de ligações aço-betão segundo a prEN1992-4:2013

O presente relatório documenta o estágio desenvolvido na empresa SE2P – Sociedade de Engenharia, Projeto e Planeamento Lda. no âmbito da unidade curricular de DIPRE (Dissertação/Projeto/ Estágio) do Mestrado em Engenharia Civil – Ramo de Estruturas do Instituto Superior de Engenharia do Porto. A frequência no estágio curricular teve como objetivo principal o desenvolvimento de uma ferramenta de cálculo que permitisse o dimensionamento de ligações aço-betão segundo a prEN1992-4:2013. O desenvolvimento desta ferramenta resulta da necessidade do dimensionamento de soluções leves, económicas e esteticamente agradáveis tendo em conta a uniformização da legislação existente em toda a União Europeia. Atualmente, os projetistas têm utilizado programas de cálculo automático desenvolvidos por fabricantes de sistemas de ancoragens, como é o caso do Profis Anchor da Hilti. Esses programas de cálculo têm como base de dados as Diretrizes de Aprovação Técnica Europeia, a ETAG001- anexo C para dimensionamento de ancoragens mecânicas em betão e o relatório técnico EOTA TR029 para o dimensionamento de ancoragens químicas, apresentando até métodos de cálculo simplificados para uma rápida resposta ao cliente. A publicação da prEN1992-4:2013 é um marco importante, pois há já algum tempo que a construção metálica e mista está regulamentada apresentando algumas falhas no que diz respeito às ligações aço-betão. Esta norma é o culminar de anos de pesquisas, estudos e testes efetuados aos diferentes tipos de ligação tendo em conta além dos modos de rotura possíveis, os princípios de transferência de esforços.

REFLECT : logiciel de restitution des réflectances au sol pour l’amélioration de la qualité de l'information extraite des images satellitales à haute résolution spatiale

RÉSUMÉ - Les images satellitales multispectrales, notamment celles à haute résolution spatiale (plus fine que 30 m au sol), représentent une source d’information inestimable pour la prise de décision dans divers domaines liés à la gestion des ressources naturelles, à la préservation de l’environnement ou à l’aménagement et la gestion des centres urbains. Les échelles d’étude peuvent aller du local (résolutions plus fines que 5 m) à des échelles régionales (résolutions plus grossières que 5 m). Ces images caractérisent la variation de la réflectance des objets dans le spectre qui est l’information clé pour un grand nombre d’applications de ces données. Or, les mesures des capteurs satellitaux sont aussi affectées par des facteurs « parasites » liés aux conditions d’éclairement et d’observation, à l’atmosphère, à la topographie et aux propriétés des capteurs. Deux questions nous ont préoccupé dans cette recherche. Quelle est la meilleure approche pour restituer les réflectances au sol à partir des valeurs numériques enregistrées par les capteurs tenant compte des ces facteurs parasites ? Cette restitution est-elle la condition sine qua non pour extraire une information fiable des images en fonction des problématiques propres aux différents domaines d’application des images (cartographie du territoire, monitoring de l’environnement, suivi des changements du paysage, inventaires des ressources, etc.) ? Les recherches effectuées les 30 dernières années ont abouti à une série de techniques de correction des données des effets des facteurs parasites dont certaines permettent de restituer les réflectances au sol. Plusieurs questions sont cependant encore en suspens et d’autres nécessitent des approfondissements afin, d’une part d’améliorer la précision des résultats et d’autre part, de rendre ces techniques plus versatiles en les adaptant à un plus large éventail de conditions d’acquisition des données. Nous pouvons en mentionner quelques unes : - Comment prendre en compte des caractéristiques atmosphériques (notamment des particules d’aérosol) adaptées à des conditions locales et régionales et ne pas se fier à des modèles par défaut qui indiquent des tendances spatiotemporelles à long terme mais s’ajustent mal à des observations instantanées et restreintes spatialement ? - Comment tenir compte des effets de « contamination » du signal provenant de l’objet visé par le capteur par les signaux provenant des objets environnant (effet d’adjacence) ? ce phénomène devient très important pour des images de résolution plus fine que 5 m; - Quels sont les effets des angles de visée des capteurs hors nadir qui sont de plus en plus présents puisqu’ils offrent une meilleure résolution temporelle et la possibilité d’obtenir des couples d’images stéréoscopiques ? - Comment augmenter l’efficacité des techniques de traitement et d’analyse automatique des images multispectrales à des terrains accidentés et montagneux tenant compte des effets multiples du relief topographique sur le signal capté à distance ? D’autre part, malgré les nombreuses démonstrations par des chercheurs que l’information extraite des images satellitales peut être altérée à cause des tous ces facteurs parasites, force est de constater aujourd’hui que les corrections radiométriques demeurent peu utilisées sur une base routinière tel qu’est le cas pour les corrections géométriques. Pour ces dernières, les logiciels commerciaux de télédétection possèdent des algorithmes versatiles, puissants et à la portée des utilisateurs. Les algorithmes des corrections radiométriques, lorsqu’ils sont proposés, demeurent des boîtes noires peu flexibles nécessitant la plupart de temps des utilisateurs experts en la matière. Les objectifs que nous nous sommes fixés dans cette recherche sont les suivants : 1) Développer un logiciel de restitution des réflectances au sol tenant compte des questions posées ci-haut. Ce logiciel devait être suffisamment modulaire pour pouvoir le bonifier, l’améliorer et l’adapter à diverses problématiques d’application d’images satellitales; et 2) Appliquer ce logiciel dans différents contextes (urbain, agricole, forestier) et analyser les résultats obtenus afin d’évaluer le gain en précision de l’information extraite par des images satellitales transformées en images des réflectances au sol et par conséquent la nécessité d’opérer ainsi peu importe la problématique de l’application. Ainsi, à travers cette recherche, nous avons réalisé un outil de restitution de la réflectance au sol (la nouvelle version du logiciel REFLECT). Ce logiciel est basé sur la formulation (et les routines) du code 6S (Seconde Simulation du Signal Satellitaire dans le Spectre Solaire) et sur la méthode des cibles obscures pour l’estimation de l’épaisseur optique des aérosols (aerosol optical depth, AOD), qui est le facteur le plus difficile à corriger. Des améliorations substantielles ont été apportées aux modèles existants. Ces améliorations concernent essentiellement les propriétés des aérosols (intégration d’un modèle plus récent, amélioration de la recherche des cibles obscures pour l’estimation de l’AOD), la prise en compte de l’effet d’adjacence à l’aide d’un modèle de réflexion spéculaire, la prise en compte de la majorité des capteurs multispectraux à haute résolution (Landsat TM et ETM+, tous les HR de SPOT 1 à 5, EO-1 ALI et ASTER) et à très haute résolution (QuickBird et Ikonos) utilisés actuellement et la correction des effets topographiques l’aide d’un modèle qui sépare les composantes directe et diffuse du rayonnement solaire et qui s’adapte également à la canopée forestière. Les travaux de validation ont montré que la restitution de la réflectance au sol par REFLECT se fait avec une précision de l’ordre de ±0.01 unités de réflectance (pour les bandes spectrales du visible, PIR et MIR), même dans le cas d’une surface à topographie variable. Ce logiciel a permis de montrer, à travers des simulations de réflectances apparentes à quel point les facteurs parasites influant les valeurs numériques des images pouvaient modifier le signal utile qui est la réflectance au sol (erreurs de 10 à plus de 50%). REFLECT a également été utilisé pour voir l’importance de l’utilisation des réflectances au sol plutôt que les valeurs numériques brutes pour diverses applications courantes de la télédétection dans les domaines des classifications, du suivi des changements, de l’agriculture et de la foresterie. Dans la majorité des applications (suivi des changements par images multi-dates, utilisation d’indices de végétation, estimation de paramètres biophysiques, …), la correction des images est une opération cruciale pour obtenir des résultats fiables. D’un point de vue informatique, le logiciel REFLECT se présente comme une série de menus simples d’utilisation correspondant aux différentes étapes de saisie des intrants de la scène, calcul des transmittances gazeuses, estimation de l’AOD par la méthode des cibles obscures et enfin, l’application des corrections radiométriques à l’image, notamment par l’option rapide qui permet de traiter une image de 5000 par 5000 pixels en 15 minutes environ. Cette recherche ouvre une série de pistes pour d’autres améliorations des modèles et méthodes liés au domaine des corrections radiométriques, notamment en ce qui concerne l’intégration de la FDRB (fonction de distribution de la réflectance bidirectionnelle) dans la formulation, la prise en compte des nuages translucides à l’aide de la modélisation de la diffusion non sélective et l’automatisation de la méthode des pentes équivalentes proposée pour les corrections topographiques.

Investigations on Structural response of Water Backed Perforated plates

The study envisaged herein contains the numerical investigations on Perforated Plate (PP) as well as numerical and experimental investigations on Perforated Plate with Lining (PPL) which has a variety of applications in underwater engineering especially related to defence applications. Finite element method has been adopted as the tool for analysis of PP and PPL. The commercial software ANSYS has been used for static and free vibration response evaluation, whereas ANSYS LS-DYNA has been used for shock analysis. SHELL63, SHELL93, SOLID45, SOLSH190, BEAM188 and FLUID30 finite elements available in the ANSYS library as well as SHELL193 and SOLID194 available in the ANSYS LS-DYNA library have been made use of. Unit cell of the PP and PPL which is a miniature of the original plate with 16 perforations have been used. Based upon the convergence characteristics, the utility of SHELL63 element for the analysis of PP and PPL, and the required mesh density are brought out. The effect of perforation, geometry and orientation of perforation, boundary conditions and lining plate are investigated for various configurations. Stress concentration and deflection factor are also studied. Based on these investigations, stadium geometry perforation with horizontal orientation is recommended for further analysis.Linear and nonlinear static analysis of PP and PPL subjected to unit normal pressure has been carried out besides the free vibration analysis. Shock analysis has also been carried out on these structural components. The analytical model measures 0.9m x 0.9m with stiffener of 0.3m interval. The influence of finite element, boundary conditions, and lining plate on linear static response has been estimated and presented. Comparison of behavior of PP and PPL in the nonlinear strain regime has been made using geometric nonlinear analysis. Free vibration analysis of the PP and PPL has been carried out ‘in vacuum’ condition and in water backed condition, and the influence of water backed condition and effect of perforation on natural frequency have been investigated.Based upon the studies on the vibration characteristics of NPP, PP and PPL in water backed condition and ‘in vacuum’ condition, the reduction in the natural frequency of the plate in immersed condition has been rightly brought out. The necessity to introduce the effect of water medium in the analysis of water backed underwater structure has been highlighted.Shock analysis of PP and PPL for three explosives viz., PEK, TNT and C4 has been carried out and deflection and stresses on plate as well as free field pressure have been estimated using ANSYS LS-DYNA. The effect of perforations and the effect of lining plate have been predicted. Experimental investigations of the measurement of free field pressure using PPL have been conducted in a shock tank. Free field pressure has been measured and has been validated with finite element analysis results. Besides, an experiment has been carried out on PPL, for the comparison of the static deflection predicted by finite element analysis.The distribution of the free field pressure and the estimation of differential pressure from experimentation and the provision for treating the differential pressure as the resistance, as a part of the design load for PPL, has been brought out.

Transport of Sub-micron Aerosols in Bifurcations

The convective-diffusive transport of sub-micron aerosols in an oscillatory laminar flow within a 2-D single bifurcation is studied, using order-of-magnitude analysis and numerical simulation using a commercial software (FEMLAB®). Based on the similarity between momentum and mass transfer equations, various transient mass transport regimes are classified and scaled according to Strouhal and beta numbers. Results show that the mass transfer rate is highest at the carinal ridge and there is a phase-shift in diffusive transport time if the beta number is greater than one. It is also shown that diffusive mass transfer becomes independent of the oscillating outer flow if the Strouhal number is greater than one.

Learning Resource Coursework - Team Sigma

We have created a slideshow on Open Source, and have created a reference list and poster for it.

El uso de Sistemas de Infomación Geográfica Libre en Costa Rica

The main topic of this article is the use of the free of charge Geographic Information Systems (GIS), in Costa Rica. It begins establishing the advantages associated with the application of this technologies and which benefits can be obtained. Next, a description of the use of commercial software by part of the national institutions is presented and the variety of fields it is used for. In the manner the application that has been developed is shown. The importance of the GIS’s in the management of the territory is explained and how the institutional information is been treated. It also explains the advantages of using free software in the institutions and it's been implemented by them. At the end of this article a series of conclusions about the status of a free GIS and several activities that had been done are explained