The components of high-performance systems continue to become more complex on the road to exascale. This complexity is exposed at the level of: multi/many-core CPUs, accelerators (GPUs), interconnects (horizontal communication), and memory hierarchies (vertical communication). A crucial task is designing an algorithm and a programming model that scale to the same order of the HPC system size at multiple levels. This trend in HPC architecture more critically affects memory-intensive appli- cations than compute-bound applications. Accomplishing this task involves adopting less synchronous forms of the mathematical algorithm, reducing synchronization in the computational implementation, introducing more SIMT-style concurrency at the finest level of system hierarchy, and increasing arithmetic intensity as the bottleneck shifts from number of floating-point operations to number of memory accesses. This dissertation addresses these challenges in scientific simulation focusing in the dominant kernels of a memory-bound application: sparse solvers in implicit model- ing, and I/O in explicit reverse time migration in seismic imaging. We introduce asynchronous task-based parallelism into iterative algebraic preconditioners. We also introduce a task-based framework that hides the latency of I/O with computation. This dissertation targets two main applications in the oil and gas industry: reservoir simulation and seismic imaging simulation. It presents results on multi- and many- core systems and GPUs on four Top500 supercomputers: Summit, TSUBAME 3.0, Shaheen II, and Makman-2. We introduce an asynchronous implementation of four major memory-bound kernels: Algebraic multigrid (MPI+OmpSs), tridiagonal solve (MPI+OpenMP), Additive Schwarz Preconditioned Inexact Newton (MPI+MPI), and Reverse Time Migration (StarPU/StarPU+MPI and CUDA).

Resin transfer molding (RTM) is an infusion-based closed-mold manufacturing process where resin is injected into a preform of dry reinforcement to create a net shape part. Often, when a preform is draped over a mold with complex geometry, such as the double curvature of a dome, a reorientation of the fibers takes place in the form of in-plane shear. This deformation of the reinforcement structure has the potential to adversely affect the resin flow and the filling of the mold during RTM if the manufacturer fails to properly account for the shear effects. Various process simulation tools are being developed and used to simulate infusions in a virtual environment and assist manufacturers in optimizing tooling features and process parameters before needing to invest in tooling or prototypes. Such simulation requires material characterization of the resin viscosity and reinforcement permeability. The latter is a function of the reinforcement architecture and is highly sensitive to perturbations such as shear. Permeability measurement is well represented in the literature, but for ideal fabric arrangements without the deformations caused by complex mold geometries typical to industrial parts. The purpose of this study is to develop the first method for measuring the three-dimensional (3D) permeability tensor of a sheared fiber reinforcement in a single test and empirical models to show the effect shear has on permeability. The method and models are intended to enhance the accuracy of infusion simulation and further advance the development of liquid composite molding processes. Building off the work of previous researchers who have used trellis tools to induce uniform shear on fabric samples and 3D point-infusion tools for radial flow tests, these two methods were combined to measure the sheared permeability of a carbon fiber non-crimp fabric (NCF) in the x, y, and z directions. To mitigate the amount of spring-back that occurs when transferring the sheared preform from the trellis tool to the permeability tool, a method of incorporating an adhesive binder into the preform is presented. Lastly, the permeability data obtained from testing samples sheared at 0, 10, 20, 30, and 40 degrees is documented. Mathematical models are provided based on the data gathered in this work that show the permeability of a NCF in the x, y, and z directions as a function of shear angle. The resulting models indicate an inverse correlation between permeability and shear due to the reorientation of the fibers and closure of preferential flow channels in the preform. These models can be used to predict the permeability for shear angles less than 40 degrees. To validate these results, theoretical shear permeability models are included for comparison. Recommendations for future studies involving the measurement of 3D sheared permeability are discussed.

After the launch of NASA's SeaWinds scatterometer in 1999, a radiometer function was implemented in the Science Ground Data Processing Systems to allow the measurement of the earth's microwave brightness temperature. This dissertation presents results of a comprehensive validation to assess the quality of QRad brightness temperature measurements using near-simultaneous ocean Tb comparisons between the SeaWinds on QuikSCAT (QRad) and WindSat polarimetric radiometer on Coriolis. WindSat was selected because it is a well calibrated radiometer that has many suitable collocations with QuikSCAT; and it has a 10.7 GHz channel, which is close to QRad frequency of 13.4 GHz. Brightness temperature normalizations were made for WindSat before comparison to account for expected differences in Tb with QRad because of incidence angle and channel frequency differences. Brightness temperatures for nine months during 2005 and 2006 were spatially collocated for rain-free homogeneous ocean scenes (match-ups) within 1° latitude x longitude boxes and within a ± 60 minute window. To ensure high quality comparison, these collocations were quality controlled and edited to remove non-homogenous ocean scenes and/or transient environmental conditions, including rain contamination. WindSat and QRad Tb's were averaged within 1° boxes and these were used for the radiometric inter-calibration analysis on a monthly basis. Results show that QRad calibrations are stable in the mean within ± 2K over the yearly seasonal cycle.

Composite flow simulation tools for LCM processing can be expensive and time-consuming but necessary to design a mold system with proper placement of resin inlets and vacuum outlets. Composites manufacturing engineers would benefit from data regarding the impact of mold curvature radius on resin flow. This could help determine whether or not a particular part and mold would require expensive simulation software designed to handle complex flow paths through curved fabric architectures exhibiting variable permeability over the curvature, or if simple flow modeling would provide accurate enough simulations for sound tooling setup decision making. Four molds, with double curvature having equal radii, were fabricated with radii ranging from 3.2 to 25.4 mm to characterize the permeability of two different fiber reinforcements 1) a carbon biaxial NCF and 2) a fiberglass CSM over the mold curvatures. Three infusions of each material type were conducted on each of the 4 molds for a total of 24 test infusions. Flow front position vs. time data was captured during each experimental infusion. The permeability in the bend regions, KB, was first estimated by the integrated form of Darcy's Law to evaluate the permeability for average flow across the entire bend region. This was done for both the convex and concave regions using a geometric estimate for the increased compaction in the bend regions. The permeability increases as the tool radius increases, and the rate of increase diminishes as the tool radius increases and the permeability approaches the flat region permeability. An estimate of KB for VI was then made by applying a ratio calculated from the resulting permeability from the rigid- and VI-based models in the flat regions. Generic power law fits are reported that could be used in LCM process simulation, to give a model to estimate the permeability for any bend in the reinforcement part geometry. The results suggest that any curve with a radius higher than 25 mm requires no adjustment to the flat permeability.

Les réseaux de transport se sont amplifiés par l’accroissement du nombre des véhicules et des stations ainsi que l’apparition de nouvelles notions essentiellement la multimodalité et l’intermodalité. Ainsi, la tâche de gestion des réseaux de transport collectif est devenue très complexe et difficile pour les régulateurs. Pour faire face à ces difficultés, on note le développement des systèmes d’aide à la décision comme solution efficace de régulation de la circulation. Ils permettent de transmettre en temps réel les informations concernant le trafic sur les réseaux de transport.Notre travail se base sur la conception d’un système de régulation des réseaux de transport multimodal. Il peut se révéler comme un outil primordial pour apporter des solutions efficaces et en temps réel à la problématique de la congestion routière. Il peut communiquer l’information nécessaire à l’usager afin de prendre sa décision de déplacement avec ou sans sa voiture. Le système proposé est une approche hybride entre une modélisation par graphes du réseau et un système multi-agents. Ceci sera appuyé par une approche évolutionniste pour la génération d’une solution de régulation optimale. Ce choix est justifié par le caractère ouvert, distribué et complexe des réseaux de transport multimodal / Transport networks have been amplified by the increasing number of vehicles and stations and the emergence of new concepts essentially multimodal and intermodal. Thus, the task of managing public transport systems has become very complex and difficult for regulators.To cope with these difficulties, there is the development of systems decision support as an effective solution to traffic control. They can transmit real-time traffic information on transport networks. Our work is based on designing a control system of multimodal transport networks. It may be as an essential tool for effective solutions and real-time to the problem of traffic congestion. It can provide the necessary information to the user in making its decision to move with or without his car. The proposed system is a hybrid between a graph modeling the network and a multi-agent system. This will be supported by an evolutionary approach for generating an optimal control solution. This is justified by the open, distributed and complex network of multimodal transport

No description available.

Made available in DSpace on 2014-12-17T14:56:09Z (GMT). No. of bitstreams: 1 DesnesANR_DISSERT.pdf: 3501359 bytes, checksum: 5155a508018af1e52dae20205b8f726b (MD5) Previous issue date: 2012-12-21 / The seismic method is of extreme importance in geophysics. Mainly associated with oil exploration, this line of research focuses most of all investment in this area. The acquisition, processing and interpretation of seismic data are the parts that instantiate a seismic study. Seismic processing in particular is focused on the imaging that represents the geological structures in subsurface. Seismic processing has evolved significantly in recent decades due to the demands of the oil industry, and also due to the technological advances of hardware that achieved higher storage and digital information processing capabilities, which enabled the development of more sophisticated processing algorithms such as the ones that use of parallel architectures. One of the most important steps in seismic processing is imaging. Migration of seismic data is one of the techniques used for imaging, with the goal of obtaining a seismic section image that represents the geological structures the most accurately and faithfully as possible. The result of migration is a 2D or 3D image which it is possible to identify faults and salt domes among other structures of interest, such as potential hydrocarbon reservoirs. However, a migration fulfilled with quality and accuracy may be a long time consuming process, due to the mathematical algorithm heuristics and the extensive amount of data inputs and outputs involved in this process, which may take days, weeks and even months of uninterrupted execution on the supercomputers, representing large computational and financial costs, that could derail the implementation of these methods. Aiming at performance improvement, this work conducted the core parallelization of a Reverse Time Migration (RTM) algorithm, using the parallel programming model Open Multi-Processing (OpenMP), due to the large computational effort required by this migration technique. Furthermore, analyzes such as speedup, efficiency were performed, and ultimately, the identification of the algorithmic scalability degree with respect to the technological advancement expected by future processors / A s?smica ? uma ?rea de extrema import?ncia na geof?sica. Associada principalmente ? explora??o de petr?leo, essa linha de pesquisa concentra boa parte de todo o investimento realizado nesta grande ?rea. A aquisi??o, o processamento e a interpreta??o dos dados s?smicos s?o as partes que comp?em um estudo s?smico. O processamento s?smico em especial tem como objetivo ? obten??o de uma imagem que represente as estruturas geol?gicas em subsuperf?cie. O processamento s?smico evoluiu significativamente nas ?ltimas d?cadas devido ?s demandas da ind?stria petrol?fera, e aos avan?os tecnol?gicos de hardware que proporcionaram maiores capacidades de armazenamento e processamento de informa??es digitais, que por sua vez possibilitaram o desenvolvimento de algoritmos de processamento mais sofisticados, tais como os que utilizam arquiteturas paralelas de processamento. Uma das etapas importantes contidas no processamento s?smico ? o imageamento. A migra??o ? uma das t?cnicas usadas para no imageamento com o objetivo de obter uma se??o s?smica que represente de forma mais precisa e fiel as estruturas geol?gicas. O resultado da migra??o ? uma imagem 2D ou 3D na qual ? poss?vel a identifica??o de falhas e domos salinos dentre outras estruturas de interesse, poss?veis reservat?rios de hidrocarbonetos. Entretanto, uma migra??o rica em qualidade e precis?o pode ser um processo demasiadamente longo, devido ?s heur?sticas matem?ticas do algoritmo e ? quantidade extensa de entradas e sa?das de dados envolvida neste processo, podendo levar dias, semanas e at? meses de execu??o ininterrupta em supercomputadores, o que representa grande custo computacional e financeiro, o que pode inviabilizar a aplica??o desses m?todos. Tendo como objetivo a melhoria de desempenho, este trabalho realizou a paraleliza??o do n?cleo de um algoritmo de Migra??o Reversa no Tempo (RTM - do ingl?s: Reverse Time Migration), utilizando o modelo de programa??o paralela OpenMP (do ingl?s: Open Multi-Processing), devido ao alto esfor?o computacional demandado por essa t?cnica de migra??o. Al?m disso, foram realizadas an?lises de desempenho tais como de speedup, efici?ncia, e, por fim, a identifica??o do grau de escalabilidade algor?tmica com rela??o ao avan?o tecnol?gico esperado para futuros processadores

Les pièces situées dans des zones chaudes/tièdes (300-400°C) de l'avion sont actuellement en titane (mât moteur) ou en composite à matrice époxy (plenum). Comment pourrait-on diminuer la masse de ces pièces tout en évitant leur dégradation à hautes températures de fonctionnement ? Le projet TACT (Technologie pour Aérostructures composites Tièdes), porté par Nimitech Innovation® (Groupe LAUAK), propose une solution innovante consistant à mettre en oeuvre par voie RTM des pièces structurales tièdes à base de renfort en fibres de carbone (FC) et de matrice Cyanate ester (CE). Le choix de la matrice thermodurcissable CE est justifié par son caractère thermostable, c'est-à-dire sa capacité d'opérer en continu à de hautes températures de fonctionnement (avec une température de transition vitreuse Tg>300°C). Par ailleurs, elle possède la facilité de mise en oeuvre des époxydes du fait qu'elle s'adapte généralement bien aux paramètres du procédé RTM. Toutefois, l'exothermie élevée de la matrice CE lors de la réticulation implique un gradient de température dans la pièce composite et peut ainsi engendrer des problèmes de surchauffe. Les travaux scientifiques menés dans le cadre de cette thèse se focalisent sur la problématique de surchauffe de la résine pendant le processus de polymérisation très exothermique dans le moule RTM. L'objectif serait ainsi de maîtriser le cycle de cuisson du composite afin d'éviter tout problème d'emballement ou de dégradation pendant la réticulation de la matrice. Dès lors, la thèse s'organise de la manière suivante : dans un premier temps, le comportement thermocinétique de la matrice CE (pure et catalysée) est analysé pendant l'étape de réticulation, et ceci dans l'optique de contribuer à l'optimisation de cycle de cuisson lors de la mise en oeuvre du composite FC/CE par procédé RTM. Ensuite, les propriétés thermiques (capacité calorifique, conductivité, diffusivité) en fonction du degré d'avancement de la résine CE sont menés afin d'évaluer le gradient thermique régi par l'équation de la chaleur permettant de maîtriser la cuisson de la résine dans l'épaisseur. Par ailleurs, la vitrification de la matrice CE est étudiée par le suivi de la température de transition vitreuse Tg en fonction de la température et du taux d'avancement à l'aide de différents techniques de mesure (DSC, DMA, TMA). Enfin, une modélisation de la vitrification à l'aide du modèle Di-Benedetto permettra l'estimation de la température de la transition vitreuse Tg ∞ pour le réseau tridimentionnel entièrement réticulé. / Aeronautical parts which operate in high temperature area (300-400°C) are currently made of titanium (aircraft pylon) or composite materials based on epoxy matrix (plenum). In which extent the weight of these pieces could be reduced as well as avoiding their degradation when operating at these working temperature ranges? TACT project (Technologie pour Aérostructures composites Tièdes), overseen by Nimitech Innovation® (Groupe LAUAK), suggests an innovative solution based on the development of high performance composites parts reinforced by carbon fibers (CF) and cyanate ester matrix (CE) through RTM process. The CE resin belongs to the class of high-performance thermosetting polymers and is mainly chosen in this project due to its thermal stability when operating at high temperatures (with a glass transition Tg>300°C), as well as epoxy-like processability. However, the cross-linking reaction exhibits highly exothermic process, resulting in non-linear increase in internal temperature, which may cause a temperature overshoot. The scientific work carried out within this thesis focuses on the problem of overheating of the resin during the highly exothermic polymerization process in the RTM mold. The objective would thus be to control the curing cycle of the composite in order to avoid problems of runaway or degradation during the crosslinking of the matrix. Hence, the thesis is organized as follows: firstly, thermokinetic behavior of CE resin is analyzed during the crosslinking process in order to optimize the curing cycle. Secondly, thermal properties (heat capacity, conductivity, diffusivity) are identified as a function of the conversion degree in order to evaluate the thermal gradient covered by the heat equation making it possible to control the curing along the thickness of the composite. Moreover, the vitrification of the cyanate ester matrix is studied by monitoring the glass transition temperature Tg as a function of the temperature and conversion degree using different methods (DSC, DMA, TMA). Finally, Di-Benedetto model, a vitrification model, is chosen in order to identify the glass transition temperature Tg∞ of a full crosslinked resin.

Um hochsensitive räumliche Auflösung zu erreichen, wurden oberflächenverstärkte Raman-Spektroskopie (SERS) und spitzenverstärkte Raman-Spektroskopie (TERS) weiterentwickelt. Das grundlegende Funktionsprinzip ist jedoch noch nicht vollständig verstanden und auch Experimente dazu fehlen teilweise. In dieser Arbeit habe ich zuerst Gap-mode TERS eingesetzt, bei welcher ein starkes elektromagnetisches Feld es ermöglicht, dünne Schichten von sehr schwach streuenden Molekülen zu untersuchen. Mit der Nanometerauflösung von TERS konnte ein auf der Goldoberfläche spontan phasen-getrennten, gemischtes Thiolsystem räumlich aufgelöst werden, während STM die Nanodomänen nicht über ihre Höhenunterschiede erkennen konnte. Neue Studien deuten auf eine Raman-Verstärkung durch Graphen und Flachgold aufgrund eines chemischen Mechanismus hin. Kupfer Phthalocyanin (CuPc)-Moleküle zwischen Graphen und einer flachen Goldoberfläche erlauben Elektronenübertragungen in beide Richtungen und damit stellt sich die Frage, ob chemische Verstärkungen von SERS zueinander addiert werden können. Die Ergebnisse deuten auf eine Kopplung von den zwei einzelnen Oberflächen hin. Es wurde eine 68-fache Verstärkung von geschichtetem CuPc zwischen Graphen und Gold beobachtet, jeweils bezogen auf CuPc auf Glimmer. Zuletzt wurde mittels TERS diese Schichtstruktur untersucht. Moleküle, die sich auf der Goldoberfläche selbstanordnen und mit Graphen bedeckt worden sind, fungieren als optische Sensoren, bei welchen die Graphenverkapselung die Moleküle beschützt. Außerdem kann eine sehr hohe Raman-Verstärkung mit großer lokaler Auflösung aufgrund der kombinierten Effekte von SERS und TERS herbeigeführt werden. Die Ergebnisse zeigen, dass eine Spitze, die Graphen-verstärkte Raman-Streuung (GERS) zusätzlich um vier Größenordnungen verbessern kann, aber Gap-mode TERS abschirmt. / The quest to achieve ultrahigh sensitivity, surface specificity and high spatial resolution has led to the development of plasmon- and chemically- enhanced Raman spectroscopy, including techniques such as surface-enhanced Raman spectroscopy (SERS) and tip-enhanced Raman spectroscopy (TERS). However, a lack of fundamentally experimental demonstrations still remains. In this thesis, I firstly used gap-mode TERS, which allows studying even molecularly thin layers of very weakly scattering molecules. With the nanoscale spatial resolution provided by TERS, the spontaneous segregation in a mixed thiol system on a gold surface could be resolved, while scanning tunneling microscopy (STM) could not discern the nanodomains via their apparent height difference. Furthermore, since graphene and a flat gold surface both were known to provide some Raman enhancement through mainly a chemical mechanism, sandwiching copper phthalocyanine (CuPc) molecules between graphene and a flat gold surface allowed electrons to be transferred in both directions, and thereby to address the question whether chemical enhancements with different origins in SERS can add to each other. The results suggest that the chemical enhancements were influenced by the two individual surfaces, and a 68-fold enhancement of sandwiched CuPc between graphene and gold was observed, as compared to CuPc on mica. Last, TERS was applied to study this sandwiched structure. Molecules self-assembled on a gold surface and covered by transferred graphene acted as optical probes. Such an arrangement has interesting properties in the sense that molecules are protected and encapsulated by graphene. Also, a possible ultrahigh Raman enhancement together with localized spatial resolution may be achieved due to the combined effects from SERS and TERS. The results showed that a tip can improve graphene-enhanced Raman scattering (GERS) further by 4 orders of magnitude, but graphene exerts some shielding effect to gap-mode TERS.

O uso de nanotubos de carbono (NTC) em compósitos Epóxi (EP)/Fibra de Vidro (FV), produzindo compósitos tri-componente, tem sido recentemente pesquisado, com alguns resultados interessantes relacionados a propriedades mecânicas e eletromagnéticas. Para que haja uma promoção mais significativa nas propriedades mecânicas, deve-se introduzir um teor de NTC maior do que 1% em massa, o que gera graves problemas de dispersão. O grande desafio de trabalhar com um elevado de NTC, é que a viscosidade da resina é significativamente aumentada em relação à resina pura, dificultando a dispersão e o processamento dos compósitos. Foi desenvolvida neste trabalho uma metodologia para dispersão de NTC em tecidos de FV, buscando aumentar os teores de NTC em compósitos tri-componente EP/NTC/FV e produzidos por moldagem por transferência de resina (RTM). Os compósitos tri-componente foram caracterizados por meio de ensaios mecânicos como tração, flexão, impacto Izod, cisalhamento interlaminar (ILSS), dureza Barcol e da análise dinâmico-mecânica (DMA); além da inspeção por ultrassom e avaliação da atenuação da radiação eletromagnética. Os compósitos apresentaram um aumento aproximado de 10% nas propriedades mecânicas, porém mostrando um maior potencial com relação à atenuação eletromagnética, onde alcançaram valores de absorção de ondas de até 95%. / The use of carbon nanotubes (CNT) in Epoxy (EP)/Glass Fiber (GF) composites, producing tri-component composites, has been widely researched, with some interesting results related to mechanical and electromagnetic properties. When the goal is a significant improvement in mechanical properties, CNT content greater than 1%wt. may be necessary, which yields serious dispersion problems. The great challenge when processing a high CNT content resin is that its viscosity is significantly increased in comparison with the neat resin, preventing adequate dispersion and processing of the composite. In this work, a methodology for the dispersion of CNT in GF fabrics was developed aiming to increase the CNT content in EP/CNT/GF tri-component composites produced by resin transfer molding (RTM). The composites were characterized using tensile, flexural, Izod impact, interlaminar shear strength (ILSS), Barcol hardness testing and dynamic mechanical analysis (DMA); ultrasound inspection and attenuation of electromagnetic radiation evaluation were also carried out. The tri-component composites showed an overall maximum increase of only 10% in the mechanical properties, but displayed great potential use for attenuation of electromagnetic radiation, reaching 95% wave absorption.