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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

ANNarchy: a code generation approach to neural simulations on parallel hardware

Vitay, Julien, Dinkelbach, Helge Ülo, Hamker, Fred Henrik 07 October 2015 (has links)
Many modern neural simulators focus on the simulation of networks of spiking neurons on parallel hardware. Another important framework in computational neuroscience, rate-coded neural networks, is mostly difficult or impossible to implement using these simulators. We present here the ANNarchy (Artificial Neural Networks architect) neural simulator, which allows to easily define and simulate rate-coded and spiking networks, as well as combinations of both. The interface in Python has been designed to be close to the PyNN interface, while the definition of neuron and synapse models can be specified using an equation-oriented mathematical description similar to the Brian neural simulator. This information is used to generate C++ code that will efficiently perform the simulation on the chosen parallel hardware (multi-core system or graphical processing unit). Several numerical methods are available to transform ordinary differential equations into an efficient C++code. We compare the parallel performance of the simulator to existing solutions.
162

En jämförelse av Eigenface- och Fisherface-metoden tillämpade i en Raspberry Pi 2 / A comparison between Eigenfaces and Fisherfaces implemented on a Raspberry Pi 2

Dahl, Dag, Gustaf, Sterne January 2016 (has links)
Syftet med rapporten är att visa möjligheten att använda Raspberry Pi 2 i ett ansiktsigenkänningssystem. Studien redogör för prestandaskillnader mellan Eigenface och Fisherfacemetoden. Studieförfattarna har genomfört en experimentell studie enligt en kvantitativ metod där tester utgör empirin. Resultatet från testerna kommer presenteras genom diagram och påvisa möjligheten att använda Raspberry Pi 2 som hårdvara i ett ansiktsigenkänningssystem. Genom samma testutförande kommer skillnader mellan igenkänningsmetoderna att påvisas. Studien visar att Raspberry Pi 2 är en lämplig kandidat att använda för mindre ansiktsigenkänningssystem. Vidare framgår det att Fisherface-metoden är det lämpligaste valet att använda vid implementation av systemet. / The purpose with this report is to demonstrate the possibility to use Raspberry Pi 2 as hardware in a face recognition system. The study will show performance differences regarding the Eigenface- and Fisherface-method. To demonstrate the possibility the authors have done tests using an experimental study and quantitative method. To review the tests and to understand the result a qualitative literature review was taken. The tests will be presented as graphs to show the possibility to use Raspberry Pi 2 as hardware in a face recognition system. The same goes for the comparison of the chosen algorithms. The work indicates that Raspberry Pi 2 is a possible candidate to use for smaller face recognition systems. There is also an indication that the Fisherface method is the better choice for face recognition.
163

Desenvolvimento de ferramentas computacionais para análise de perfis de difração de raios X / Development of computational tools for analysis of X-ray diffraction profiles

Silva, André Santos Barros da 23 April 2018 (has links)
Neste trabalho foi desenvolvido um conjunto de ferramentas computacionais, em linguagem de programação Python, para a análise de perfis de difração de raios X, tanto para o estudo quanto para obtenção dos valores microestruturais como tamanhos médios de cristalitos e microdeformações, através de dos métodos de: Scherrer, Single-Line, Williamson-Hall e Warren-Averbach. Para aplicar os métodos de análise de perfis, foram também implementados métodos de remoção da contribuição instrumental pelo método de Stokes e ajuste de funções, remoção de ruídos pelo método de Savitzky-Golay, correção da radiação de fundo pelo método de ajuste linear, correção do fator de Lorentz-Polarização e correção do dubleto Kalfa2 . / In this work, a set of computational tools was developed, in the Python programming language, for the analysis of X-ray diffraction profiles, both for the study and for obtaining the microstructural values, as well as the mean values of crystallites and microdeformations, using Scherrer, Single-Line, Williamson-Hall and Warren-Averbach. To apply the methods of profile analysis, methods were also implemented for the removal of instrumental contributions by the Stokes method and adjustment of functions, removal by the Savitzky-Golay method, correction of the background radiation by the linear adjustment method, correction of the factor of Lorentz-Polarization and correction of dubleto Kalfa2 .
164

Radiolänk med GNU Radio

Nordin Hellström, Kristopher, Williams, Kenny January 2008 (has links)
<p>At the Department of Technology and Built environment at the University of Gävle there was an interest to study GNU Radio, which is an "open source radio project. The project is based on that most of the radio signal processing is made in an ordinary PC. The idea behind this degree project was that in a laptop there are several radio transmitters/receivers that takes space, generates heat and transmit in varied frequency band etcetera.</p><p> </p><p>All these radio transmitters/receivers could be replaced with a Software Defined Radio system. It means that one common, general radio hardware is used to different communications such as: WLAN, Bluetooth, GPRS, 3G etcetera. The waveform is generated in the software, which makes the system very flexible. To transmit and receive radio signals a USB-based hardware is required, for example from Ettus Research LLC.</p><p> </p><p>During this degree project two PC:s was used for the signal processing and the signal transferring. The operating system that was used on the computers, were the Linux based Ubuntu 8.04. To generate the signals, to modulate/demodulate the signals and to get the communication on the sound cards in/out-port working, the different packages in the GNU Radio software was used and for programming the high level language, Python, was used.</p><p> </p><p>In this degree project a lot of experiments where made, for example a sine wave was generated in computer 1 and the signal was amplitude modulated and transferred to computer 2, through the sound card. In computer 2 the signal was demodulated and filtrated, before it was saved to the hard drive. When the signal was saved on computer 2, it could be sent out on the sound card and be studied on an oscilloscope. This transfer between the computers was made with a stereo cable, but also with a radio link equipment on the University of Gävle.</p><p> </p><p>The result of this degree project was satisfying, because the signal was possible to modulate, transfer, demodulate and save. In the wire transfer a lot of noise was generated on to the signal, mostly because of the sound cards. When the wireless transfer was made it appeared more noise, because of the quality of the receiver, the transmitter and the antennas.</p><p> </p><p>This work can be developed to more advanced systems.</p> / <p>Vid Högskolan i Gävle på institutionen för Teknik och Byggd miljö (ITB) fanns ett intresse att undersöka GNU Radio, som är ett open source radio-projekt. Projektet bygger på att den största delen av radiosignalbehandlingen sker i en vanlig PC. Idén som låg till grund för detta examensarbete var att det i en laptop finns ett stort antal radiosändar- och mottagarkretsar som tar plats, genererar värme och sänder på olika frekvensband med mera.</p><p> </p><p>Alla dessa radiosändar- och mottagarkretsar skulle kunna ersättas med ett Software Defined Radio-system. Vilket innebär att en gemensam, generell radiohårdvara används för olika kommunikationer som: WLAN, Bluetooth, GPRS, 3G med flera. Vågformerna genereras i mjukvaran, vilket gör systemet mycket flexibelt. För att kunna ta emot och sända radiosignaler behövs en hårdvara. Denna hårdvara har bland annat Ettus Research LLC tagit fram, med USB-anslutning.</p><p> </p><p>Under examensarbetet har två stycken PC använts för behandling av signaler, samt överföring mellan dessa. Operativsystemet som användes på datorerna var det Linuxbaserade Ubuntu 8.04. För att generera signaler, modulation/demodulation av dessa signaler samt för att få kommunikation med ljudkortets in-/utgång att fungera, användes de olika paketen i mjukvaran GNU Radio och för programmering användes högnivåspråket Python.</p><p> </p><p>I detta examensarbete utfördes ett flertal experiment, bland annat genererades en sinussignal i dator 1 och signalen amplitudmodulerades och överfördes till dator 2 via ljudkortet. På dator 2 demodulerades denna signal och filtrerades, innan den sparades på hårddisken. Signalen kunde sedan skickas ut på ljudkortet och studeras med ett oscilloskop. Överföringen mellan datorerna gjordes med en stereokabel, men också med en radiolänkutrustning som fanns på Högskolan i Gävle.</p><p> </p><p>Resultatet var tillfredställande då signalen kunde moduleras, överföras samt demoduleras och sparas. I den trådbundna överföringen uppstod mycket brus i signalen, till största delen berodde detta på ljudkorten. När den trådlösa överföringen gjordes uppstod mera brus, vilket berodde på kvalitén hos mottagare, sändare och antennerna.</p><p> </p><p>Detta arbete kan utvecklas till mer avancerade system.</p>
165

Bestämning av vattendelare i urban miljö : Metod för avgränsning av avrinningsområden i ArcGIS utgående från dagvattensystemet / Watershed delineation in urban catchment areas : Method for delineating catchment areas in ArcMap based on storm-water drains

Calestam, Karl-Martin January 2013 (has links)
Växande städer leder till att naturmark omvandlas till stadsmiljöer. Det skapar mer hårdgjorda ytor och därmed ökade volymer dagvatten som behöver hanteras. Modellering av dagvattennätet används ofta för att bedöma kapaciteten och risk för översvämningar. Avrinningsområdets storlek är en avgörande parameter för att bedöma hur mycket vatten som kommer till en viss ledning. Traditionellt har automatisk bestämning av avrinningsområden gjorts enbart utifrån topografin. I områden med dagvattennät styr däremot ledningarnas sträckning i första hand hur vattnet rinner, och de följer inte nödvändigtvis terrängen. ArcHydro Tools, som är ett tilläggsprogram till ArcMap, har utvecklats för att beräkna topografiska avrinningsområden. Genom att programmera en tilläggsfunktion i Python har processen i ArcHydro Tools anpassats för att kunna ta hänsyn till dagvattennätet. Dagvattennätet approximerades som vattendrag. Tryckledningar och tunnlar tillåter inte något inflöde av vatten. Därför beskrevs dessa som ändpunkter i ledningsnätet, varifrån vattnet inte rann vidare. Funktionen som skapades i det här examensarbetet tillät att vattnet stannade i dessa punkter, till skillnad från i den ursprungliga metoden. Den utgick istället från att vattnet rann till kanten av det undersökta området, vilket i de här fallen skulle ha resulterat i felaktigt avgränsade avrinningsområden. Tilläggsfunktionen anpassades för att användas som övriga funktioner i ArcMap och testades på data över Lidingö stad. Resultatet visade att det var möjligt att utnyttja topografiskt baserade metoder för bestämning av avrinningsområden så att avgränsningen istället skedde med utgångspunkt i dagvattennätet. Det är ett steg mot att effektivisera processen för bestämning av avrinningsområden för användning vid hydrologisk modellering av dagvattennätet. Behovet av manuell bearbetning minskas. Ett försök att i ArcMap implementera en funktion för efterbehandling av avrinningsområden gjordes också. Funktionen letar upp avrinningsområden som bedöms som för små och lägger ihop dem med ett närliggande område. Avrinningsområden som beräknats med den modifierade metoden har senare använts vid modellering av dagvattennätet i Molkom, Värmland. / Growing populations result in expanding cities. An increase in the amount of impervious surfaces in the area will follow and thereby generate more storm water. The capacity of the drainage system can be evaluated using hydraulic modelling. The model highly depends on the catchment areas, which will determine the water volume each pipe section receive. Watershed delineation is usually done based on the topography. However, if a storm water drainage system is present, it may route the water in a different direction than the slope indicates. ArcHydro Tools is an extension to ArcMap and is commonly used to delineate catchment areas. The method heavily relies on topography during this process. A function has been developed during the course of this project to allow for the drainage system to be the primary source of information for watershed delineation. This function made sure that outlets in the model were to be evaluated as such, even if they happen to be located in the middle of the area of interest. The water is therefore not necessarily routed to the edge of the elevation model, but can be allowed to stay at the appropriate position. In order to do this, the drainage system was represented as a stream network. The new method was applied to test data supplied by Lidingö city, Stockholm, Sweden, and included elevation data and information about the drainage system. The result implies that it is indeed possible to use the drainage system as a base for delineation of catchment areas. A more efficient method of calculating catchment areas will reduce the required amount of manual processing, thereby saving time and resources. Another function, for finishing up the resulting catchment areas, is proposed but not fully implemented. The whole process was used to delineate catchment areas for Molkom, County of Värmland, Sweden. The resulting watersheds were later successfully used for modelling the storm water drains in the area.
166

Radiolänk med GNU Radio

Nordin Hellström, Kristopher, Williams, Kenny January 2008 (has links)
At the Department of Technology and Built environment at the University of Gävle there was an interest to study GNU Radio, which is an "open source radio project. The project is based on that most of the radio signal processing is made in an ordinary PC. The idea behind this degree project was that in a laptop there are several radio transmitters/receivers that takes space, generates heat and transmit in varied frequency band etcetera.   All these radio transmitters/receivers could be replaced with a Software Defined Radio system. It means that one common, general radio hardware is used to different communications such as: WLAN, Bluetooth, GPRS, 3G etcetera. The waveform is generated in the software, which makes the system very flexible. To transmit and receive radio signals a USB-based hardware is required, for example from Ettus Research LLC.   During this degree project two PC:s was used for the signal processing and the signal transferring. The operating system that was used on the computers, were the Linux based Ubuntu 8.04. To generate the signals, to modulate/demodulate the signals and to get the communication on the sound cards in/out-port working, the different packages in the GNU Radio software was used and for programming the high level language, Python, was used.   In this degree project a lot of experiments where made, for example a sine wave was generated in computer 1 and the signal was amplitude modulated and transferred to computer 2, through the sound card. In computer 2 the signal was demodulated and filtrated, before it was saved to the hard drive. When the signal was saved on computer 2, it could be sent out on the sound card and be studied on an oscilloscope. This transfer between the computers was made with a stereo cable, but also with a radio link equipment on the University of Gävle.   The result of this degree project was satisfying, because the signal was possible to modulate, transfer, demodulate and save. In the wire transfer a lot of noise was generated on to the signal, mostly because of the sound cards. When the wireless transfer was made it appeared more noise, because of the quality of the receiver, the transmitter and the antennas.   This work can be developed to more advanced systems. / Vid Högskolan i Gävle på institutionen för Teknik och Byggd miljö (ITB) fanns ett intresse att undersöka GNU Radio, som är ett open source radio-projekt. Projektet bygger på att den största delen av radiosignalbehandlingen sker i en vanlig PC. Idén som låg till grund för detta examensarbete var att det i en laptop finns ett stort antal radiosändar- och mottagarkretsar som tar plats, genererar värme och sänder på olika frekvensband med mera.   Alla dessa radiosändar- och mottagarkretsar skulle kunna ersättas med ett Software Defined Radio-system. Vilket innebär att en gemensam, generell radiohårdvara används för olika kommunikationer som: WLAN, Bluetooth, GPRS, 3G med flera. Vågformerna genereras i mjukvaran, vilket gör systemet mycket flexibelt. För att kunna ta emot och sända radiosignaler behövs en hårdvara. Denna hårdvara har bland annat Ettus Research LLC tagit fram, med USB-anslutning.   Under examensarbetet har två stycken PC använts för behandling av signaler, samt överföring mellan dessa. Operativsystemet som användes på datorerna var det Linuxbaserade Ubuntu 8.04. För att generera signaler, modulation/demodulation av dessa signaler samt för att få kommunikation med ljudkortets in-/utgång att fungera, användes de olika paketen i mjukvaran GNU Radio och för programmering användes högnivåspråket Python.   I detta examensarbete utfördes ett flertal experiment, bland annat genererades en sinussignal i dator 1 och signalen amplitudmodulerades och överfördes till dator 2 via ljudkortet. På dator 2 demodulerades denna signal och filtrerades, innan den sparades på hårddisken. Signalen kunde sedan skickas ut på ljudkortet och studeras med ett oscilloskop. Överföringen mellan datorerna gjordes med en stereokabel, men också med en radiolänkutrustning som fanns på Högskolan i Gävle.   Resultatet var tillfredställande då signalen kunde moduleras, överföras samt demoduleras och sparas. I den trådbundna överföringen uppstod mycket brus i signalen, till största delen berodde detta på ljudkorten. När den trådlösa överföringen gjordes uppstod mera brus, vilket berodde på kvalitén hos mottagare, sändare och antennerna.   Detta arbete kan utvecklas till mer avancerade system.
167

Discrete Event Simulations in Forest Technology

Jundén, Linus January 2011 (has links)
Development of a tool for discrete event simulations in forest technology, dependent onspatial components, has successfully been initialized in this thesis project. These simulations may be used to optimize the way the forest is used and to evaluate new machine concepts in forestry. The Python library for discrete event simulation, SimPy, was chosen as the foundationfor the tool. The developed tool can handle spatial objects such as moving machines, trees and boulders. Support for continuous linear movements was also added, which has resulted in a model that partially overlaps continuous and discrete event simulations without any additional computational costs. The result is simulations of a forest with machines operating in it. Two pilot simulations,one of a thinning machine and one of a planting machine, were performed with useful results. The new simulation tool shows promising properties. Limitations and improvements arediscussed, with the conclusion that continued development is recommended. / I det här examensarbetet har ett verktyg för diskret event simuleringar inom skogsteknikutvecklats. Sådana simuleringar kan användas för att optimera arbete inom skogsbruk samtför att utvärdera nya maskintekniska koncept. Programmeringsspråket Pythons bibliotek för diskret event simulering, SimPy, valdessom grund för verktyget. Det utvecklade verktyget kan hantera spatiala objekt såsom träd,stenar och stubbar. Stöd för kontinuerliga rörelser har även utvecklats, vilket resulterat i enmodell som delvis överlappar kontinuerliga simuleringar och diskret event simuleringar.Resultatet är kvalitativa simuleringar av skog och skogsmaskiner. Två lyckade simule-ringsstudier har gjorts för Sveriges Lantbruksuniversitet, en simulering av en gallringsmaskinoch en simulering av en planteringsmaskin. Det nya simuleringsverktyget uppvisar lovande egenskaper, även om det har sina be-gränsningar. Fortsatt utveckling av verktyget rekommenderas starkt.
168

Uma perspectiva de extens?o do modelo de aceita??o de tecnologia para explicar o uso de linguagens de desenvolvimento WEB: pesquisa com desenvolvedores Pyton e Java / An extension perspective of the technology acceptance model to explain the use of web development languages: a research on Python and Java developers

Oliveira, Idelm?rcia Dantas de 19 October 2007 (has links)
Made available in DSpace on 2014-12-17T14:52:34Z (GMT). No. of bitstreams: 1 IdelmarciaDO.pdf: 781272 bytes, checksum: fb2e5ba3247ab47eff60bb3c30b07e21 (MD5) Previous issue date: 2007-10-19 / The spread of the Web boosted the dissemination of Information Systems (IS) based on the Web. In order to support the implementation of these systems, several technologies came up or evolved with this purpose, namely the programming languages. The Technology Acceptance Model TAM (Davis, 1986) was conceived aiming to evaluate the acceptance/use of information technologies by their users. A lot of studies and many applications have used the TAM, however, in the literature it was not found a mention of the use of such model related to the use of programming languages. This study aims to investigate which factors influence the use of programming languages on the development of Web systems by their developers, applying an extension of the TAM, proposed in this work. To do so, a research was done with Web developers in two Yahoo groups: java-br and python-brasil, where 26 Java questionnaires and 39 Python questionnaires were fully answered. The questionnaire had general questions and questions which measured intrinsic and extrinsic factors of the programming languages, the perceived usefulness, the perceived ease of use, the attitude toward the using and the programming language use. Most of the respondents were men, graduate, between 20 and 30 years old, working in the southeast and south regions. The research was descriptive in the sense of its objectives. Statistical tools, descriptive statistics, main components and linear regression analysis were used for the data analysis. The foremost research results were: Java and Python have machine independence, extensibility, generality and reliability; Java and Python are more used by corporations and international organizations than supported by the government or educational institutions; there are more Java programmers than Python programmers; the perceived usefulness is influenced by the perceived ease of use; the generality and the extensibility are intrinsic factors of programming languages which influence the perceived ease of use; the perceived ease of use influences the attitude toward the using of the programming language / A difus?o da Web impulsionou a dissemina??o de Sistemas de Informa??o (SI) baseados na Web. Para apoiar a implementa??o desses sistemas, diversas tecnologias surgiram ou evolu?ram com este prop?sito, dentre elas as linguagens de programa??o. O Modelo de Aceita??o de Tecnologia - TAM (Davis, 1986) foi concebido com o intuito de avaliar a aceita??o/uso de tecnologias da informa??o por seus usu?rios. V?rios estudos e aplica??es diversas t?m utilizado o TAM, no entanto, n?o foi encontrada na literatura men??o a utiliza??o de tal modelo com rela??o ao uso de linguagens de programa??o. Este estudo objetiva investigar que fatores influenciam o uso de linguagens de programa??o utilizadas no desenvolvimento de sistemas Web por parte de seus desenvolvedores, utilizando uma extens?o do TAM, proposta neste estudo. Para tanto, foi realizada uma pesquisa com desenvolvedores Web pertencentes a dois grupos do Yahoo: java-br e python-brasil, no qual foram respondidos, na ?ntegra, 26 question?rios Java e 39 Python. O question?rio tinha quest?es de car?ter geral e quest?es que mediam os fatores intr?nsecos e extr?nsecos das linguagens de programa??o, a utilidade percebida, a facilidade de uso percebida, a atitude sobre o uso e o uso da linguagem de programa??o. A maioria dos respondentes eram homens, com n?vel superior, idade entre 20 e 30 anos, atuando nas regi?es sudeste e sul. Do ponto de vista de seus objetivos, a pesquisa foi descritiva. Em rela??o ? forma de abordagem, quantitativa. Para a an?lise de dados foram utilizadas ferramentas estat?sticas, estat?stica descritiva, componentes principais e an?lise de regress?o linear m?ltipla. Os principais resultados da pesquisa foram: Java e Python possuem independ?ncia de m?quina, extensibilidade, generalidade e confian?a; Java e Python s?o mais utilizadas por corpora??es e organiza??es internacionais do que apoiadas pelo governo ou institui??es de ensino; h? mais programadores Java do que Python; a utilidade percebida ? influenciada pela facilidade de uso percebida; a generalidade e a extensibilidade s?o fatores intr?nsecos as linguagens de programa??o que influenciam a facilidade de uso percebida; a facilidade de uso percebida influencia a atitude em rela??o ao uso da linguagem de programa??o
169

Propagation Patterns of News on Twitter : A Study in How News Propagate Through Twitter Via the Use of Bitly Links. / Spridningsmönster hos nyheter på Twitter : En studie i hur nyheter propagerar på Twitter via Bitly-länkar.

Lundström, Linnea, Ragnarsson, Sebastian January 2018 (has links)
As so called fake news spread widely on the internet it is important to examine how they are spread, and thereby, how much of a problem they are. This thesis investigates how the spread of news articles on Twitter can be represented via a tree structure, as well as whether or not the trees have patterns that correlate to attributes such as the source of the shared news article and how many followers the original tweeter has. As part of the study a tool was built in Python 2.7 that, amongst other things, allows tracking and reconstruction of a news article's propagation on Twitter.It could be concluded that most links that are shared on Twitter propagate over a period of a few days and most retweets are made within the first twelve hours. We observe patterns suggesting that having more followers correlates to getting more retweets. Users who have few followers have to rely on their tweets being retweeted in a longer chain of users for it to reach a larger audience. Tweets that have a substantial spread often spread widely, but not especially deep. Finally, our results suggest that both the news site that created the article and the content of the article has an impact on how much it is retweeted.
170

Solveur parallèle pour l’équation de Poisson sur mailles superposées et hiérarchiques, dans le cadre du langage Python / Parallel solver for the Poisson equation on a hierarchy of superimposed meshes, under a Python framework

Tesser, Federico 11 September 2018 (has links)
Les discrétisations adaptatives sont importantes dans les problèmes de fluxcompressible/incompressible puisqu'il est souvent nécessaire de résoudre desdétails sur plusieurs niveaux, en permettant de modéliser de grandes régionsd'espace en utilisant un nombre réduit de degrés de liberté (et en réduisant letemps de calcul).Il existe une grande variété de méthodes de discrétisation adaptative, maisles grilles cartésiennes sont les plus efficaces, grâce à leurs stencilsnumériques simples et précis et à leurs performances parallèles supérieures.Et telles performance et simplicité sont généralement obtenues en appliquant unschéma de différences finies pour la résolution des problèmes, mais cetteapproche de discrétisation ne présente pas, au contraire, un chemin faciled'adaptation.Dans un schéma de volumes finis, en revanche, nous pouvons incorporer différentstypes de maillages, plus appropriées aux raffinements adaptatifs, en augmentantla complexité sur les stencils et en obtenant une plus grande flexibilité.L'opérateur de Laplace est un élément essentiel des équations de Navier-Stokes,un modèle qui gouverne les écoulements de fluides, mais il se produit égalementdans des équations différentielles qui décrivent de nombreux autres phénomènesphysiques, tels que les potentiels électriques et gravitationnels. Il s'agitdonc d'un opérateur différentiel très important, et toutes les études qui ontété effectuées sur celui-ci, prouvent sa pertinence.Dans ce travail seront présentés des approches de différences finies et devolumes finis 2D pour résoudre l'opérateur laplacien, en appliquant des patchsde grilles superposées où un niveau plus fin est nécessaire, en laissant desmaillages plus grossiers dans le reste du domaine de calcul.Ces grilles superposées auront des formes quadrilatérales génériques.Plus précisément, les sujets abordés seront les suivants:1) introduction à la méthode des différences finies, méthode des volumes finis,partitionnement des domaines, approximation de la solution;2) récapitulatif des différents types de maillages pour représenter de façondiscrète la géométrie impliquée dans un problème, avec un focussur la structure de données octree, présentant PABLO et PABLitO. Le premier estune bibliothèque externe utilisée pour gérer la création de chaque grille,l'équilibrage de charge et les communications internes, tandis que la secondeest l'API Python de cette bibliothèque, écrite ad hoc pour le projet en cours;3) la présentation de l'algorithme utilisé pour communiquer les données entreles maillages (en ignorant chacune l'existence de l'autre) en utilisant lesintercommunicateurs MPI et la clarification de l'approche monolithique appliquéeà la construction finale de la matrice pour résoudre le système, en tenantcompte des blocs diagonaux, de restriction et de prolongement;4) la présentation de certains résultats; conclusions, références.Il est important de souligner que tout est fait sous Python comme framework deprogrammation, en utilisant Cython pour l'écriture de PABLitO, MPI4Py pour lescommunications entre grilles, PETSc4py pour les parties assemblage et résolutiondu système d'inconnues, NumPy pour les objets à mémoire continue.Le choix de ce langage de programmation a été fait car Python, facile àapprendre et à comprendre, est aujourd'hui un concurrent significatif pourl'informatique numérique et l'écosystème HPC, grâce à son style épuré, sespackages, ses compilateurs et pourquoi pas ses versions optimisées pour desarchitectures spécifiques. / Adaptive discretizations are important in compressible/incompressible flow problems since it is often necessary to resolve details on multiple levels,allowing large regions of space to be modeled using a reduced number of degrees of freedom (reducing the computational time).There are a wide variety of methods for adaptively discretizing space, but Cartesian grids have often outperformed them even at high resolutions due totheir simple and accurate numerical stencils and their superior parallel performances.Such performance and simplicity are in general obtained applying afinite-difference scheme for the resolution of the problems involved, but this discretization approach does not present, by contrast, an easy adapting path.In a finite-volume scheme, instead, we can incorporate different types of grids,more suitable for adaptive refinements, increasing the complexity on thestencils and getting a greater flexibility.The Laplace operator is an essential building block of the Navier-Stokes equations, a model that governs fluid flows, but it occurs also in differential equations that describe many other physical phenomena, such as electric and gravitational potentials, and quantum mechanics. So, it is a very importantdifferential operator, and all the studies carried out on it, prove itsrelevance.In this work will be presented 2D finite-difference and finite-volume approaches to solve the Laplacian operator, applying patches of overlapping grids where amore fined level is needed, leaving coarser meshes in the rest of the computational domain.These overlapping grids will have generic quadrilateral shapes.Specifically, the topics covered will be:1) introduction to the finite difference method, finite volume method, domainpartitioning, solution approximation;2) overview of different types of meshes to represent in a discrete way thegeometry involved in a problem, with a focuson the octree data structure, presenting PABLO and PABLitO. The first one is anexternal library used to manage each single grid’s creation, load balancing and internal communications, while the second one is the Python API ofthat library written ad hoc for the current project;3) presentation of the algorithm used to communicate data between meshes (beingall of them unaware of each other’s existence) using MPI inter-communicators and clarification of the monolithic approach applied building the finalmatrix for the system to solve, taking into account diagonal, restriction and prolongation blocks;4) presentation of some results; conclusions, references.It is important to underline that everything is done under Python as programmingframework, using Cython for the writing of PABLitO, MPI4Py for the communications between grids, PETSc4py for the assembling and resolution partsof the system of unknowns, NumPy for contiguous memory buffer objects.The choice of this programming language has been made because Python, easy to learn and understand, is today a significant contender for the numerical computing and HPC ecosystem, thanks to its clean style, its packages, its compilers and, why not, its specific architecture optimized versions.

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