Bibliographies thématiques / FFT solveurs

Littérature scientifique sur le sujet « FFT solveurs »

Auteur : Grafiati
Publié le 23 février 2024

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Articles de revues sur le sujet "FFT solveurs"

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Fortunato, Daniel, et Alex Townsend. « Fast Poisson solvers for spectral methods ». IMA Journal of Numerical Analysis 40, no 3 (29 novembre 2019) : 1994–2018. http://dx.doi.org/10.1093/imanum/drz034.

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Abstract Poisson’s equation is the canonical elliptic partial differential equation. While there exist fast Poisson solvers for finite difference (FD) and finite element methods, fast Poisson solvers for spectral methods have remained elusive. Here we derive spectral methods for solving Poisson’s equation on a square, cylinder, solid sphere and cube that have optimal complexity (up to polylogarithmic terms) in terms of the degrees of freedom used to represent the solution. Whereas FFT-based fast Poisson solvers exploit structured eigenvectors of FD matrices, our solver exploits a separated spectra property that holds for our carefully designed spectral discretizations. Without parallelization we can solve Poisson’s equation on a square with 100 million degrees of freedom in under 2 min on a standard laptop.
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Hosseinzadegan, Samar, Andreas Fhager, Mikael Persson et Paul Meaney. « A Discrete Dipole Approximation Solver Based on the COCG-FFT Algorithm and Its Application to Microwave Breast Imaging ». International Journal of Antennas and Propagation 2019 (17 juillet 2019) : 1–12. http://dx.doi.org/10.1155/2019/9014969.

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We introduce the discrete dipole approximation (DDA) for efficiently calculating the two-dimensional electric field distribution for our microwave tomographic breast imaging system. For iterative inverse problems such as microwave tomography, the forward field computation is the time limiting step. In this paper, the two-dimensional algorithm is derived and formulated such that the iterative conjugate orthogonal conjugate gradient (COCG) method can be used for efficiently solving the forward problem. We have also optimized the matrix-vector multiplication step by formulating the problem such that the nondiagonal portion of the matrix used to compute the dipole moments is block-Toeplitz. The computation costs for multiplying the block matrices times a vector can be dramatically accelerated by expanding each Toeplitz matrix to a circulant matrix for which the convolution theorem is applied for fast computation utilizing the fast Fourier transform (FFT). The results demonstrate that this formulation is accurate and efficient. In this work, the computation times for the direct solvers, the iterative solver (COCG), and the iterative solver using the fast Fourier transform (COCG-FFT) are compared with the best performance achieved using the iterative solver (COCG-FFT) in C++. Utilizing this formulation provides a computationally efficient building block for developing a low cost and fast breast imaging system to serve under-resourced populations.
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Morin, Léo, Renald Brenner, Katell Derrien et Khaoula Dorhmi. « Periodic smoothing splines for FFT-based solvers ». Computer Methods in Applied Mechanics and Engineering 373 (janvier 2021) : 113549. http://dx.doi.org/10.1016/j.cma.2020.113549.

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Fang, Jiannong. « A Fast Hybrid Pressure-Correction Algorithm for Simulating Incompressible Flows by Projection Methods ». Algorithms 16, no 6 (2 juin 2023) : 287. http://dx.doi.org/10.3390/a16060287.

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To enforce the conservation of mass principle, a pressure Poisson equation arises in the numerical solution of incompressible fluid flow using the pressure-based segregated algorithms such as projection methods. For unsteady flows, the pressure Poisson equation is solved at each time step usually in physical space using iterative solvers, and the resulting pressure gradient is then applied to make the velocity field divergence-free. It is generally accepted that this pressure-correction stage is the most time-consuming part of the flow solver and any meaningful acceleration would contribute significantly to the overall computational efficiency. The objective of the present work was to develop a fast hybrid pressure-correction algorithm for numerical simulation of incompressible flows around obstacles in the context of projection methods. The key idea is to adopt different numerical methods/discretisations in the sub-steps of projection methods. Here, a classical second-order time-marching projection method, which consists of two sub-steps, was chosen for the purposes of demonstration. In the first sub-step, the momentum equations were discretised on unstructured grids and solved by conventional numerical methods, here a meshless method. In the second sub-step (pressure-correction), the proposed algorithm adopts a double-discretisation system and combines the weighted least-squares approximation with the essence of immersed boundary methods. Such a design allowed us to develop an FFT-based solver to speed up the solution of the pressure Poisson equation for flow cases with obstacles, while keeping the implementation of the boundary conditions for the momentum equations as easy as conventional numerical methods do with unstructured grids. The numerical experiments of five test cases were performed to verify and validate the proposed hybrid algorithm and evaluate its computational performance. The results showed that the new FFT-based hybrid algorithm works and is robust, and it was significantly faster than the multigrid-based reference method. The hybrid algorithm opens an avenue for the development of next-generation high-performance parallel computational fluid dynamics solvers for incompressible flows.
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de Geus, T. W. J., J. Vondřejc, J. Zeman, R. H. J. Peerlings et M. G. D. Geers. « Finite strain FFT-based non-linear solvers made simple ». Computer Methods in Applied Mechanics and Engineering 318 (mai 2017) : 412–30. http://dx.doi.org/10.1016/j.cma.2016.12.032.

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LAURITSCH, G., et P. G. REINHARD. « AN FFT SOLVER FOR THE COULOMB PROBLEM ». International Journal of Modern Physics C 05, no 01 (février 1994) : 65–75. http://dx.doi.org/10.1142/s0129183194000064.

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A solution of the Coulomb problem in Fourier representation is given. The problems with the long-range parts of the Coulomb potential are circumvented by a separate handling of them. This allows the Fourier representation to develop its typical efficiency and robusteness.
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Sharma, L., R. H. J. Peerlings, M. G. D. Geers et F. Roters. « Integral nonlocal approach to model interface decohesion in FFT solvers ». Engineering Fracture Mechanics 243 (février 2021) : 107516. http://dx.doi.org/10.1016/j.engfracmech.2020.107516.

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Heymann, Dieter, et Franco Cataldo. « UNSTABLE PRODUCTS FROM THE OZONATION OF C60IN SOLVENTS ». Fullerene Science and Technology 9, no 1 (26 février 2001) : 71–76. http://dx.doi.org/10.1081/fst-100000166.

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Murthy, C. N., et K. E. Geckeler. « SOLUBILITY CORRELATION OF [60]FULLERENE IN DIFFERENT SOLVENTS ». Fullerene Science and Technology 9, no 4 (31 août 2001) : 477–86. http://dx.doi.org/10.1081/fst-100107150.

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Nath, S., H. Pal, A. V. Sapre, V. P. Bubnov, Y. I. Estrin, T. A. Parnyuk et V. K. Koltover. « Aggregation of Endometallofullerene Y@C82 in Polar Solvents ». Fullerenes, Nanotubes and Carbon Nanostructures 12, no 1-2 (2 janvier 2005) : 53–57. http://dx.doi.org/10.1081/fst-120027133.

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Thèses sur le sujet "FFT solveurs"

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Kallala, Haithem. « Massively parallel algorithms for realistic PIC simulations of ultra high intensity laser-plasma interaction, application to attosecond pulses separation of Doppler harmonics ». Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS052.

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La complexité des mécanismes physiques mis en jeu lors de l'interaction laser-plasma à ultra-haute intensité nécessite de recourir à des simulations PIC particulièrement lourdes. Au cœur de ces codes de calcul, les solveurs de Maxwell pseudo-spectraux d'ordre élevé présentent de nombreux avantages en termes de précision numérique. Néanmoins, ces solveurs ont un coût élevé en termes de ressources nécessaires. En effet, les techniques de parallélisation existantes pour ces solveurs sont peu performantes au-delà de quelques milliers de coeurs, ou induisent un important usage mémoire, ce qui limite leur scalabilité à large échelle. Dans cette thèse, nous avons développé une toute nouvelle approche de parallélisation qui combine les avantages des méthodes existantes. Cette méthode a été testée à très large échelle et montre un scaling significativement meilleur que les précédentes techniques, tout en garantissant un usage mémoire réduit.En capitalisant sur ce travail numérique, nous avons réalisé une étude numérique/théorique approfondie dans le cadre de la génération d'harmoniques d'ordres élevés sur cible solide. Lorsqu'une impulsion laser ultra-intense (I>10¹⁶W.cm⁻² ) et ultra-courte (de quelques dizaines de femtosecondes) est focalisée sur une cible solide, elle génère un plasma sur-dense, appelé miroir plasma, qui réfléchit non-linéairement le laser incident. La réflexion de l'impulsion laser est accompagnée par l'émission cohérente d'harmoniques d'ordres élevées, sous forme d'impulsions X-UV attosecondes (1 attosecond = 10⁻¹⁸s). Pour des intensités laser relativistes (I>10¹⁹ W.cm⁻²), la surface du plasma est incurvée sous l'effet de la pression de radiation du laser. De ce fait, les harmoniques rayonnées par la surface du plasma sont focalisées. Dans cette thèse, j'ai étudié la possibilité de produire des impulsions attosecondes isolées en régime relativiste sur miroir plasma, grâce au mécanisme de phare attoseconde. Celui-ci consiste à introduire une rotation des fronts d'onde du laser incident de façon à séparer angulairement les différentes impulsions attosecondes produites à chaque cycle optique. En régime relativiste, la courbure du miroir plasma augmente considérablement la divergence du faisceau harmonique, ce qui rend le mécanisme phare attoseconde inefficace. Pour y remédier, j'ai développé deux techniques de réduction de divergence harmonique afin de mitiger l'effet de focalisation induit par la courbure du miroir plasma et permettre de générer des impulsions attosecondes isolées à partir d’harmoniques Doppler. Ces deux techniques sont basées sur la mise en forme en amplitude et en phase du faisceau laser. Par ailleurs, j'ai développé un modèle théorique pour déterminer les régimes optimaux d'interaction afin de maximiser la séparation angulaire des impulsions attosecondes. Ce modèle a été validé par des simulations numériques PIC en géométries 2D et 3D et sur une large gamme de paramètres laser et plasma. Finalement, on montre qu'en ajustant des paramètres laser et plasma réalistes, il est possible de séparer efficacement les impulsions attosecondes en régime relativiste
The complexity of the physical mechanisms involved in ultra-high intensity laser-plasma interaction requires the use of particularly heavy PIC simulations. At the heart of these computational codes, high-order pseudo-spectral Maxwell solvers have many advantages in terms of numerical accuracy. This numerical approach comes however with an expensive computational cost. Indeed, existing parallelization methods for pseudo-spectral solvers are only scalable to few tens of thousands of cores, or induce an important memory footprint, which also hinders the scaling of the method at large scales. In this thesis, we developed a novel, arbitrarily scalable, parallelization strategy for pseudo-spectral Maxwell's equations solvers which combines the advantages of existing parallelization techniques. This method proved to be more scalable than previously proposed approaches, while ensuring a significant drop in the total memory use.By capitalizing on this computational work, we conducted an extensive numerical and theoretical study in the field of high order harmonics generation on solid targets. In this context, when an ultra-intense (I>10¹⁶W.cm⁻²) ultra-short (few tens of femtoseconds) laser pulse irradiates a solid target, a reflective overdense plasma mirror is formed at the target-vacuum interface. The subsequent laser pulse non linear reflection is accompanied with the emission of coherent high order laser harmonics, in the form of attosecond X-UV light pulses (1 attosecond = 10⁻¹⁸s). For relativistic laser intensities (I>10¹⁹ W.cm⁻²), the plasma surface is curved under the laser radiation pressure. And the plasma mirror acts as a focusing optics for the radiated harmonic beam. In this thesis, we investigated feasible ways for producing isolated attosecond light pulses from relativistic plasma-mirror harmonics, with the so called attosecond lighthouse effect. This effect relies introducing a wavefront rotation on the driving laser pulse in order to send attosecond pulses emitted during different laser optical cycles along different directions. In the case of high order harmonics generated in the relativistic regime, the plasma mirror curvature significantly increases the attosecond pulses divergence and prevents their separation with the attosecond lighthouse scheme. For this matter, we developed two harmonic divergence reduction techniques, based on tailoring the laser pulse phase or amplitude profiles in order to significantly inhibit the plasma mirror focusing effect and allow for a clear separation of attosecond light pulses by reducing the harmonic beam divergence. Furthermore, we developed an analytical model to predict optimal interaction conditions favoring attosecond pulses separation. This model was fully validated with 2D and 3D PIC simulations over a broad range of laser and plasma parameters. In the end, we show that under realistic laser and plasma conditions, it is possible to produce isolated attosecond pulses from Doppler harmonics
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Marano, Aldo. « Simulation numérique de la localisation intra granulaire de la déformation au sein de polycristaux irradiés ». Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEM041.

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Les polycristaux irradiés sont connus pour être le siège d’une intense localisation de la déformation plastique à l’échelle du grain, causant une diminution de leur ductilité ainsi qu’une sensibilité accrue à la corrosion sous contrainte. Cette thèse met à profit les performances offertes par le développement des solveurs FFT massivement parallèles pour améliorer la modélisation de ce phénomène crucial. Nous avons mis au point des méthodes de traitement permettant l’analyse systématique de la nature des bandes de localisation, ainsi que leur caractérisation quantitative, à partir des champs issus de la simulation haute résolution de cellules polycristallines. Elles ont permis de mettre en évidence les limites fondamentales de la plasticité cristalline classique, fondement des modèles de métaux irradiés actuels, quant à la prédiction des modes de localisation intra granulaire du glissement plastique. Pour y remédier, nous avons étudié en détail les prévisions analytiques et numériques d’un modèle de plasticité à gradient, en étendant l’implémentation du solveur AMITEX_FFTP à la résolution de problèmes non locaux. Nous avons pu montrer qu’il constitue un cadre prometteur pour une modélisation physiquement fidèle des modes de localisation intra-granulaires dans les polycristaux adoucissants, donc a fortiori pour les métaux irradiés. Par ailleurs, nous avons également abordé ce problème par la modélisation explicite des bandes de glissement. Nous avons amélioré ses performances grâce au développement de modèles de voxels composites génériques, et montré que cette approche constitue une alternative efficace pour simuler les conséquences de la localisation de la déformation, comme la modification de la distribution de contraintes aux joints de grains, ou l’augmentation de l’écrouissage cinématique
Irradiated polycrystals are known to exhibit an intense localization of plastic deformation at the grain scale, responsible for a severe loss of ductility and increased sensitivity to intergranular stress corrosion cracking. This thesis takes advantage of the performances offered by the recent progresses of highly parallel FFT-based solvers, to improve the modeling of this crucial phenomenon. We developed field processing methods to produce a systematic analysis of the nature and quantitative characterization of localization bands, from high resolution polycrystalline simulation results. They allowed to evidence a fundamental shortcoming of classical crystal plasticity, cornerstone of all irradiated metals models, in the prediction of intragranular localization modes. To overcome this issue, we extended the scope of our FFT solver, AMITEX_FFTP, to nonlocal mechanics. We used it to extensively study the analytical and numerical predictions of a strain gradient plasticity model, showing that it is a promising way to achieve an accurate modeling of plastic slip localization modes in softening polycrystals, and a fortiori for irradiated metals. Additionally, we explored the explicit modeling of slip bands with FFT-based solvers. We developed generic composite voxel models allowing to strongly reduce its computational cost. We show that this approach provides an efficient way to simulate the consequences of strain localization, such as the evolution of the grain boundary stress distribution or the increased kinematic hardening
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Vernier, Patricia. « Homogenization of composite materials with fractional viscoelastic constituents ». Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS552.

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Cette thèse porte sur la prédiction des propriétés mécaniques effectives de matériaux hétérogènes composés de constituants viscoélastiques fractional, au moyen d'une approche incrémentale variationnelle. Nous appliquons la méthode Effective Internal Variable (EIV) développée par Lahellec and Suquet (2007), particulièrement attrayante pour le traitement de comportements viscoélastiques (Tressou et al., 2016). Contrairement aux méthodes d'homogénéisation communément utilisées qui reposent sur le principe de correspondance et pour lesquelles les fluctuations des champs ne sont pas accessibles, cette approche incrémentale permet de calculer les propriétés effectives dans le domaine direct au moyen des méthodes variationalles de Ponte Castañeda (1991 et 2002) qui prennent en compte les seconds-moments des champs mécaniques. La méthode EIV s'inscrit dans le cadre des Matériaux Standards Généralisés (MSG), dans lequel le comportement des matériaux dissipatifs est décrit par deux potentiels thermodynamiques convexes. Nous considérons des constituants viscoélastiques fractionnaires, dont la loi constitutive est décrite par des équations différentielles linéaires avec des dérivées fractionnaires. En accord avec des observations expérimentales, ce formalisme prend en compte des effets de mémoire longue à travers la superposition de plusieurs temps caractéristiques (Caputo et Mainardi, 1971). La distribution de ces derniers est donnée explicitement par l'expression du spectre en loi puissance. Les potentiels thermodynamiques des matériaux viscoélastiques fractionnaires sont définis en cohérence avec le cadre des MSG. Cette cohérence s'appuie sur l'interprétation rhéologique de l'élément fractionnaire comme un Maxwell généralisé (Lion, 1997). Ainsi, nous tirons parti de l'extension de la méthode EIV à plusieurs variables internes développée par Tressou et al. (2023) afin d'homogénéiser des matériaux composites contenant des constituants viscoélastiques fractionnaires. De plus, les temps caractéristiques sont adéquatement choisis à partir de la discrétisation du spectre. Cette discrétisation est réalisée avec la procédure de Papoulia et al. (2010), basée sur une méthode des trapèzes améliorée. Plus précisément, nous appliquons cette méthode à la fonction de Mittag-Leffler impliquée dans la définition des spectres de relaxation. Nous abordons deux problèmes hétérogènes différents au moyen de la méthode EIV. Nous considérons d'abord un composite de type matrice-inclusions sous chargement harmonique, pour lequel nous rencontrons des difficultés numériques. Nous évaluons ensuite la méthode EIV sur un polycristal de glace soumis à un essai de fluage
This PhD thesis deals with the prediction of the mechanical effective properties of composite materials with linear fractional viscoelastic constituents by means of an incremental variational approach. We make use of the Effective Internal Variable (EIV) method developed by Lahellec and Suquet (2007), which is particularly attractive for viscoelasticity (Tressou et al., 2016). Contrary to the common homogenization methods that rely on the correspondence principle and where the fluctuations are not accessible, this incremental method evaluates the effective properties into the direct domain through the variational methods of Ponte Castañeda (1991 and 2002) that take into account the second-moments of the fields. The EIV method is based on the Generalized Standard Materials framework, in which the dissipative materials are described by means of two convex thermodynamic potentials. We consider local fractional viscoelastic constituents, of which the constitutive behaviours follow linear differential equations with fractional derivative operators. In accordance with experimental observations, this formalism takes into account long-memory effects through the superposition of several characteristic times (Caputo and Mainardi, 1971). Their distribution is provided by the explicit expression of the spectrum as a power law. The potentials of fractional viscoelastic constituents are consistently defined in the GSM framework through the rheological interpretation of the fractional damping element as a generalized Maxwell model (Lion, 1997). Therefore, we take advantage of the extension of the EIV method to several internal variables, developed by Tressou et al. (2023) for the homogenization of composites with local fractional viscoelastic behaviours. Besides, the characteristic times are appropriately chosen by discretizing the spectrum. This is done using the midpoint-based procedure developed by Papoulia et al. (2010). More specifically, we apply their method to the Mittag-Leffler function involved in the definition of the relaxation spectrum. We use the EIV method to tackle two different heterogeneous problems. We consider a matrix-inclusion composite under harmonic loading, for which we come accros numerical issues. We then evaluate the EIV method for a polycrystal subject to a monotonous creep loading
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Rattermann, Dale N. « A Fast Poisson Solver with Periodic Boundary Conditions for GPU Clusters in Various Configurations ». University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1397233840.

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Ding, Jian. « Fast Boundary Element Method Solutions For Three Dimensional Large Scale Problems ». Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6830.

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Efficiency is one of the key issues in numerical simulation of large-scale problems with complex 3-D geometry. Traditional domain based methods, such as finite element methods, may not be suitable for these problems due to, for example, the complexity of mesh generation. The Boundary Element Method (BEM), based on boundary integral formulations (BIE), offers one possible solution to this issue by discretizing only the surface of the domain. However, to date, successful applications of the BEM are mostly limited to linear and continuum problems. The challenges in the extension of the BEM to nonlinear problems or problems with non-continuum boundary conditions (BC) include, but are not limited to, the lack of appropriate BIE and the difficulties in the treatment of the volume integrals that result from the nonlinear terms. In this thesis work, new approaches and techniques based on the BEM have been developed for 3-D nonlinear problems and Stokes problems with slip BC. For nonlinear problems, a major difficulty in applying the BEM is the treatment of the volume integrals in the BIE. An efficient approach, based on the precorrected-FFT technique, is developed to evaluate the volume integrals. In this approach, the 3-D uniform grid constructed initially to accelerate surface integration is used as the baseline mesh to evaluate volume integrals. The cubes enclosing part of the boundary are partitioned using surface panels. No volume discretization of the interior cubes is necessary. This grid is also used to accelerate volume integration. Based on this approach, accelerated BEM solvers for non-homogeneous and nonlinear problems are developed and tested. Good agreement is achieved between simulation results and analytical results. Qualitative comparison is made with current approaches. Stokes problems with slip BC are of particular importance in micro gas flows such as those encountered in MEMS devices. An efficient approach based on the BEM combined with the precorrected-FFT technique has been proposed and various techniques have been developed to solve these problems. As the applications of the developed method, drag forces on oscillating objects immersed in an unbounded slip flow are calculated and validated with either analytic solutions or experimental results.
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Shah, Prateek Pinakin. « Thermodynamics of apolar solvation in mixed aqueous solvents ». Access to citation, abstract and download form provided by ProQuest Information and Learning Company ; downloadable PDF file, 227 p, 2008. http://proquest.umi.com/pqdweb?did=1601517501&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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Givens, Steven Romel. « The effect of solvent properties on electrospun polymer fibers and applications in biomaterials ». Access to citation, abstract and download form provided by ProQuest Information and Learning Company ; downloadable PDF file, 163 p, 2008. http://proquest.umi.com/pqdweb?did=1597616611&sid=9&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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Cui, Honggang. « Thermodynamic and kinetic control of charged, amphiphilic triblock copolymer assembly via interaction with organic counterions in solvent mixtures ». Access to citation, abstract and download form provided by ProQuest Information and Learning Company ; downloadable PDF file, 195 p, 2007. http://proquest.umi.com/pqdweb?did=1362540841&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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Price, Daniel Kenneth. « Development of an accelerated finite-difference time-domain solver using modern graphics processors ». Access to citation, abstract and download form provided by ProQuest Information and Learning Company ; downloadable PDF file, 111 p, 2009. http://proquest.umi.com/pqdweb?did=1654487621&sid=4&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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Spagnoli, Kyle Edward. « An electromagnetic scattering solver utilizing shooting and bouncing rays implemented on modern graphics cards ». Access to citation, abstract and download form provided by ProQuest Information and Learning Company ; downloadable PDF file, 75 p, 2008. http://proquest.umi.com/pqdweb?did=1601517961&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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Livres sur le sujet "FFT solveurs"

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Does This Church Make Me Look Fat ? : A Mennonite Finds Faith, Meets Mr. Right, and Solves Her Lady Problems. Grand Central Publishing, 2012.

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Janzen, Rhoda. Does This Church Make Me Look Fat ? : A Mennonite Finds Faith, Meets Mr. Right, and Solves Her Lady Problems. Grand Central Publishing, 2012.

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Lord, Errol. Achievements and Intelligibility. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198815099.003.0006.

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The type of view defended about correctly responding to normative reasons doesn’t fit nicely into the landscape of views in the philosophy of mind and action about reacting for reasons. This is because it doesn’t account for cases where we react for reasons that are not normative reasons—i.e., cases where we merely react for motivating reasons. This chapter defends a view about what it is to react for motivating reasons. According to this view, what it is for A to X for a consideration r is for A to X in virtue of the fact that A conceives of r as a normative reason to X. It is argued that this account solves the classic deviant causal chain problems for causal theories of reacting for reasons. Finally, disjunctivism about reacting-for-reasons is defended: the view that reacting for motivating reasons is different in kind from reacting for normative reasons.
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Chapitres de livres sur le sujet "FFT solveurs"

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Koshigoe, Hideyuki. « Direct Solver Based on FFT and SEL for Diffraction Problems with Distribution ». Dans Computational Science - ICCS 2004, 105–12. Berlin, Heidelberg : Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-540-24687-9_14.

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Abate, Alessandro, Mirco Giacobbe et Diptarko Roy. « Learning Probabilistic Termination Proofs ». Dans Computer Aided Verification, 3–26. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-81688-9_1.

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AbstractWe present the first machine learning approach to the termination analysis of probabilistic programs. Ranking supermartingales (RSMs) prove that probabilistic programs halt, in expectation, within a finite number of steps. While previously RSMs were directly synthesised from source code, our method learns them from sampled execution traces. We introduce the neural ranking supermartingale: we let a neural network fit an RSM over execution traces and then we verify it over the source code using satisfiability modulo theories (SMT); if the latter step produces a counterexample, we generate from it new sample traces and repeat learning in a counterexample-guided inductive synthesis loop, until the SMT solver confirms the validity of the RSM. The result is thus a sound witness of probabilistic termination. Our learning strategy is agnostic to the source code and its verification counterpart supports the widest range of probabilistic single-loop programs that any existing tool can handle to date. We demonstrate the efficacy of our method over a range of benchmarks that include linear and polynomial programs with discrete, continuous, state-dependent, multi-variate, hierarchical distributions, and distributions with undefined moments.
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Stam, Jos. « A Simple Fluid Solver Based on the FFT ». Dans Graphics Tools---The jgt Editors' Choice, 155–64. A K Peters/CRC Press, 2005. http://dx.doi.org/10.1201/b10628-20.

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Ko, John H. « Poly(N-vinyl carbazole) ». Dans Polymer Data Handbook, 1142–44. Oxford University PressNew York, NY, 2009. http://dx.doi.org/10.1093/oso/9780195181012.003.0197.

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Abstract Major Applications Incorporated in ABS (≥80%). Appliances, housewares, packing materials, automotive features, industrial applications, medical devices, and custom molding products. Properties of Special Interest Rigidity, resistance to heat and chemicals (acids, alkalis, fat, grease, oil, gasoline, alcohol, and some solvents), and high optical clarity.
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Wang, Shuhong. « Styrene-acrylonitrile polymers ». Dans Polymer Data Handbook, 1204–6. Oxford University PressNew York, NY, 2009. http://dx.doi.org/10.1093/oso/9780195181012.003.0212.

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Abstract Major Applications Incorporated in ABS (≥80%). Appliances, housewares, packing materials, automotive features, industrial applications, medical devices, and custom molding products. Properties of Special Interest Rigidity, resistance to heat and chemicals (acids, alkalis, fat, grease, oil, gasoline, alcohol, and some solvents), and high optical clarity.
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Nelson, William M. « Green Solvents for Academic Chemistry ». Dans Green Solvents for Chemistry, 133–97. Oxford University PressNew York, NY, 2003. http://dx.doi.org/10.1093/oso/9780195157369.003.0006.

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Abstract Environmental chemistry is generating considerable interest. Hardly a week goes by without some chemical aspect of the environment making it into the news within the academic community; environmental chemistry is a hot topic. But environmental issues and the standard chemistry curriculum do not correlate exactly. Many environmental subjects require understanding chemical principles that are not taught until fairly advanced courses. Teaching both environmental issues and basic chemistry to nonscience students requires making choices in emphasis: to teach mainly environmental topics with chemical “facts” introduced when necessary, to teach mainly basic chemistry with environmental “points” interjected when possible, or to integrate the two subjects so that both are taught simultaneously. Reciprocally, education provides the initial vantage from which chemistry is critically evaluated. The process of communicating green chemistry is more complex and less direct than it appears. The meaning of the ideas and concepts yields an interpretation that is heavily dependent on the structure of language, on where information is situated relative to other information. Context is critical. It allows us to make sense out of information by selecting among competing interpretations. The need for connection pertains not only to the lectures, but also to the laboratories and problem sets as well. Students arrive at their understanding of a subject by actively constructing it using the material at hand. When that material is not integrated, when the linkages between the different parts of the course are not explicit, students are forced to spend much of their energy simply figuring out how the different parts of the course fit together (Swan and Spiro, 1995).
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Lukman, Salihu, Isaiah Adesola Oke et Afolabi M. Asani. « A Comprehensive Update and Performance Evaluation of Friction Factor Formulae ». Dans Encyclopedia of Information Science and Technology, Fifth Edition, 1231–53. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-3479-3.ch085.

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In this paper, explicit friction factor formulae (Fff), which is a function of Reynolds number (Re) and relative roughness (Rr) were updated and evaluated. Fff were obtained from archive and conduct performance evaluation. Performance evaluation of the Fff were conducted using relative error; model of selection (MSC) and the Akaike Information Criterion (AIC) using Colebrook-White's friction factors as the reference Ff. The study revealed that there are 47 Fff in use. The growth of the Fff can be grouped into four subgroups based on the pattern and into three subgroups based on number of authors and into three subgroups, based on the accuracy. The growth rates were combinations of linear and exponential based on the pattern. The study revealed that Fff provided the lowest relative error of less than 1.00%, the highest MSC of greater than 6.64 and the lowest AIC of less than -34324.17. The study concluded that the recent and third generation Fff are the best and using Microsoft Excel Solver for calculating Ff in the pipe flow systems is a good tool for engineers.
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Gutteridge, John M. C., et Barry Halliwell. « Appendix to Chapter 1 Cholesterol, saturated, and unsaturated fats. What do they do in the body ? » Dans Antioxidants in Nutrition, Health, and Disease, 17–23. Oxford University PressOxford, 1995. http://dx.doi.org/10.1093/oso/9780198549024.003.0004.

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Abstract Membranes encircle all cells and control the exchange of material between the cell and its surroundings. Inside cells, membranes separate the different cell compartments (organelles, such as nucleus and mitochondria) from the fluid cell matrix (the cytosol). The main constituents of membranes are lipid and protein, the amount of protein increasing with the number of functions the membrane performs. ‘ Lipid’ is a general term used to describe any biological compound that is soluble in organic solvents such as chloroform and ether. The term includes both molecules that contain fatty acids, examples being triglycerides and phospholipids, and molecules containing hydrocarbon ring structures, examples being cholesterol, steroid hormones, and some of the fat-soluble vitamins.
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Levin, Harel, Gal Oren, Eyal Shalev et Vladimir Lyakhovsky. « Acceleration of Hydro Poro-Elastic Damage Simulation in a Shared-Memory Environment1 ». Dans Parallel Computing : Technology Trends. IOS Press, 2020. http://dx.doi.org/10.3233/apc200059.

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Hydro-PED [1] is a numerical simulation software which models nucleation and propagation of damage zones and seismicity patterns induced by wellbore fluid injection. While most of the studies in geo-physical simulation acceleration and parallelization usually focus on exascale scenarios which are translated into vast meshes, encouraging a distributed fashion of parallelization, the nature of the current simulations of Hydro-PED dictates amount of data that can conveniently fit on a single compute node – NUMA and accelerator memory alike. Thus shared-memory parallelization (such as OpenMP) can be fully implemented. In order to utilize this insight, Hydro-PED was interfaced with Trilinos [2] linear algebra solvers package, which enabled an evolution to iterative methods such as CG and GMRES. Additionally, several code sectors were parallelized and offloaded to an accelerator using OpenMP in a fine grained manner. The changes implemented in Hydro-PED gained a total speedup of x5-x12, which will enable Hydro-PED to calculate long-term simulation scenarios of hundreds of years in a feasible time – a few weeks rather than a year.
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Ouda, Eman, Andrei Sleptchenko et Mecit Can Emre Simsekler. « Nurse Rostering via Mixed-Integer Programming ». Dans Advances in Transdisciplinary Engineering. IOS Press, 2023. http://dx.doi.org/10.3233/atde230110.

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Nurse scheduling is a topic widely studied due to its overall effect on patient care and hospital performance. This research focuses on formulating a Mixed Integer Programming (MIP) workforce scheduling model as a nurse rostering problem. The model incorporates multiple objectives of individual nurse preference and qualification. This is approached by categorizing nurses into different hierarchical levels based on their qualifications and positions; Head Nurse, Senior Nurse, Nurse, and Assistant Nurse. Moreover, each nurse’s holiday preferences are accounted for in the model. The proposed MIP model is solved to generate a schedule to meet hospital demand and individual nurse preferences. A MIP solver using Python 3 was used to find the optimal solution by cutting planes. The sensitivity analysis and computational results reflect different scenarios and scheduling to fit all hospital environments and demands.
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Actes de conférences sur le sujet "FFT solveurs"

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Francavilla, M. A., F. Vipiana et G. Vecchi. « FFT-based solvers for the EFIE on graphics processors ». Dans 2010 IEEE International Symposium Antennas and Propagation and CNC-USNC/URSI Radio Science Meeting. IEEE, 2010. http://dx.doi.org/10.1109/aps.2010.5561766.

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Polimeridis, Athanasios G., et Jacob K. White. « On the compression of system tensors arising in FFT-VIE solvers ». Dans 2014 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting. IEEE, 2014. http://dx.doi.org/10.1109/aps.2014.6905399.

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Yucel, Abdulkadir C., Luis J. Gomez et Eric Michielssen. « Tucker decomposition for compressing translation operator tensors in FMM-FFT accelerated SIE solvers ». Dans 2015 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium). IEEE, 2015. http://dx.doi.org/10.1109/usnc-ursi.2015.7303425.

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Miranda, Malcolm J., Tayfun Ozdemir et Robert J. Burkholder. « Hardware acceleration of an FMM-FFT solver using consumer-grade GPUs ». Dans 2016 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM). IEEE, 2016. http://dx.doi.org/10.1109/usnc-ursi-nrsm.2016.7436241.

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Landesa, L., J. M. Taboada, J. L. Rodriguez, F. Obelleiro, J. M. Bertolo, J. C. Mourino et A. Gomez. « Analysis of 0.5 billion unknowns using a parallel FMM-FFT solver ». Dans 2009 IEEE Antennas and Propagation Society International Symposium (APSURSI). IEEE, 2009. http://dx.doi.org/10.1109/aps.2009.5171729.

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J. Hasbestan, Jaber, et Inanc Senocak. « PittPack : Open-Source FFT-Based Poisson’s Equation Solver for Computing With Accelerators ». Dans ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-87697.

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Many environmental flows are simulated in a Cartesian domain using buoyancy-driven incompressible Navier-Stokes equations. A significant cost of the simulation is devoted to the solution of the elliptic pressure equation to enforce the conservation of mass principle. The legacy software, FISHPACK, has been used for this purpose for many years. We present a new software package for the direct solution of the pressure Poisson’s equation on a directionally uniform Cartesian mesh with a second-order accurate finite-difference formulation. We use the separation of variables principle and adopt fast Fourier transforms (FFT) to convert the system to a group of independent tridiagonal systems that can be solved directly. The computational complexity of the present methodology is proportional to N2 (O(NlogN)). However, each stage of the solution algorithm can be performed simultaneously leading to a pleasingly parallel problem that is well suited for massively-threaded accelerators, such as modern graphics processing units (GPU). Theoretically speaking, if an accelerator can sustain N2 resident threads, the computational complexity will drop to O(NlogN). We use OpenACC directives with cuFFT library on a GPU to realize substantial acceleration of the overall solution algorithm and compare its performance relative to an implementation that used the FFTW library on central processing units (CPU). For a problem with 5123 points, the GPU version is about 17 × faster than the CPU version.
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Wu, Jing, et Joseph Jaja. « High Performance FFT Based Poisson Solver on a CPU-GPU Heterogeneous Platform ». Dans 2013 IEEE International Symposium on Parallel & Distributed Processing (IPDPS). IEEE, 2013. http://dx.doi.org/10.1109/ipdps.2013.18.

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van der Bok, Kees, Mottaqiallah Taouil, Panagiotis Afratis et Ioannis Sourdis. « The TU Delft sudoku solver on FPGA ». Dans 2009 International Conference on Field-Programmable Technology (FPT). IEEE, 2009. http://dx.doi.org/10.1109/fpt.2009.5377605.

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Taboada, J. M., L. Landesa, F. Obelleiro, J. L. Rodriguez, J. M. Bertolo, J. C. Mourino et A. Gomez. « Parallel FMM-FFT solver for the analysis of hundreds of millions of unknowns ». Dans 2009 Computational Electromagnetics International Workshop (CEM). IEEE, 2009. http://dx.doi.org/10.1109/cem.2009.5228111.

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Oyarzun, Guillermo, Ricard Borrell, F. Xavier Trias et Assensi Oliva. « Memory Aware Poisson Solver for Peta-Scale Simulations with one FFT Diagonalizable Direction ». Dans 2017 International Conference on High Performance Computing & Simulation (HPCS). IEEE, 2017. http://dx.doi.org/10.1109/hpcs.2017.26.

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Rapports d'organisations sur le sujet "FFT solveurs"

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Zheng, Wanzheng, et Jason Merret. Aerodynamic Survey of Novel eVTOL Configuration Using SU2. Illinois Center for Transportation, août 2022. http://dx.doi.org/10.36501/0197-9191/22-014.

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This report summarizes computational fluid dynamics (CFD) results of electric vertical takeoff and landing (eVTOL) geometries using the SU2 Reynolds-averaged Navier-Stokes (RANS) solver. Geometries were generated based on the Smart Transportation Infrastructure Initiative (STII) Rappor 15th iteration with various rotor-installment solutions. It was found that although open rotors installed on an underwing pylon were superior to shrouded rotors installed in a canoe, the canoe configuration would provide more potential for improvement, and using a canoe door to cover the first rotor opening would reduce the drag experienced by the canoe case below that upon the rod case. Rotor doors were found to be most efficient in reducing drag of the canoe case: Average drag reduction with covering the first rotor and all rotors was 66 and 165 counts, respectively. Changing rotor distributions along the chordwise direction had minimal impact on drag reduction, and placing rotors along the spanwise direction was not advised due to the increase of the projected frontal area. Increasing canoe chord length did not have significant impact on drag reduction; and if rotor doors were implemented, increasing canoe size had negative impact on drag. Rounding rotor edges did not change the aerodynamic performance of the canoe case but promotes vertical air intake when running lifting fans. Drag received by the canoe parabolically correlated to rotor diameter, with 126 counts of drag if the rotor diameter was 0 and 377 counts if the rotor diameter was 2.95 ft. Fuselage and tail added an average 179 counts of drag, and thus the aforementioned differences were still significant in the scale of aerodynamic properties of the full configuration.
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