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153 results on '"Filippone S"'

1. Foreword

Author

Morris, K, Yelick, KA, Zheng, Y, Filippone, S, Bradford, L, and Long, B

Published
2017

2. Spectroscopic Signatures of Photogenerated Radical Anions in Polymer-[C70]Fullerene Bulk Heterojunctions

Author

Liedtke, M., Sperlich, A., Kraus, H., Deibel, C., Dyakonov, V., Filippone, S., Delgado, J. L., Martin, N., and Poluektov, O. G.

Subjects
Condensed Matter - Materials Science
Abstract

Light induced polarons in solid films of polymer-fullerene blends were studied by applying photoluminescence (PL), photo induced absorption (PIA) techniques as well as electron spin resonance (ESR). The materials used were poly(3-hexylthiophene) (P3HT) and poly-[2-methoxy, 5-(2'-ethyl-hexyloxy) phenylene vinylene] (MEH-PPV) as donors. As acceptors we used [6,6]-phenyl-C61-butyric acid methyl ester ([C60]PCBM) and various soluble C70-derivates: [C70]PCBM, diphenylmethano[70]fullerene oligoether (C70-DPM-OE), C70-DPM-OE2, and two fullerene dimers, C70-C70 and C60-C70 (all shown in figure 1). In all blends containing C70 we found typical signatures which were absent if [C60]PCBM was used as acceptor. Light-induced ESR revealed signals at g>=2.005, which we previously assigned to an electron localized on the C70 cage, the PIA measurements showed a new sub-bandgap absorption band at 0.92 eV, which we correspondingly ascribe to C70 radical anions formed in the course of photoinduced electron transfer from donor to acceptor., Comment: 4 pages, 5 figures

Published
2010
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5. Preconditioning Richards Equations: spectral analysis and parallel solution at very large scale

Author

D'Ambra P, Durastante F, and Filippone S

Subjects
AMG preconditioners, Parallel scalability, Richards equation, spectral analysis
Abstract

We consider here a cell-centered finite difference approximation of the Richards equation in three dimensions, averaging for interface values the hydraulic conductivity K=K(p), a highly nonlinear function, by arithmetic, upstream, and harmonic means. The nonlinearities in the equation can lead to changes in soil conductivity over several orders of magnitude and discretizations with respect to space variables often produce stiff systems of differential equations. Fully implicit time discretization is provided by backward Euler one-step formula; the resulting nonlinear algebraic system is solved by an inexact Newton Armijo-Goldstein algorithm, requiring the solution of a sequence of linear systems involving Jacobian matrices. We prove some new results concerning the distribution of the Jacobians eigenvalues and the explicit expression of their entries. Moreover, we explore some connections between the saturation of the soil and the ill-conditioning of the Jacobians. The information on eigenvalues justifies the effectiveness of some preconditioner approaches which are widely used in the solution of the Richards equation. We propose a new software framework to experiment with scalable and robust preconditioners suitable for efficient parallel simulations at very large scales. Performance results on a literature test case show that our framework is very promising in the advance towards realistic simulations at extreme scale.

Published
2021

6. Scalable AMG Preconditioners for Computational Science at Extreme Scale

Author

D'Ambra P, Durastante F, and Filippone S

Subjects
Numerical Linear Algebra, Parallel Scalability
Abstract

The challenge of exascale requires rethinking numerical algorithms and mathematical software for efficient exploitation of heterogeneous massively parallel supercomputers. In this talk, we present some activities aimed at developing highly scalable and robust sparse linear solvers for solving scientific and engineering applications with a huge number of degrees of freedom (dof)[1]. We discuss algorithmic advances and implementation aspects in the design of Algebraic MultiGrid (AMG) preconditioners based on aggregation, to be used in conjunction with Krylov-subspace projection methods, suitable to exploit high levels of parallelism of current petascale supercomputers. These activities are carried on within two ongoing European Projects, the Energy-oriented Center of Excellence (EoCoE-II) and the EuroHPC TEXTAROSSA project, having the final aim to provide methods and tools for preparing scientific applications in facing and successfully grasping the near future exascale challenge. Beyond possible advances in base software technology to make available programming environments that tend to hide the details of the hardware, we still need to rethink and redesign numerical methods and applications, especially for irregular computations and memory-bound kernels, like sparse solvers.

Published
2021

7. AMG preconditioners for Linear Solvers towards Extreme Scale

Author

D'Ambra P., Durastante F., and Filippone S.

Subjects
preconditioners, Algebraic Multigrid, parallel scalability
Abstract

Linear solvers for large and sparse systems are a key element of scientific applications, and their efficient implementation is necessary to harness the computational power of current computers. Algebraic Multigrid (AMG) Preconditioners are a popular ingredient of such linear solvers; this is the motivation for the present work where we examine some recent developments in a package of AMG preconditioners to improve efficiency, scalability, and robustness on extreme-scale problems. The main novelty is the design and implementation of a new parallel coarsening algorithm based on aggregation of unknowns employing weighted graph matching techniques; this is a completely automated procedure, requiring no information from the user, and applicable to general symmetric positive definite (s.p.d.) matrices. The new coarsening algorithm improves in terms of numerical scalability at low operator complexity over decoupled aggregation algorithms available in previous releases of the package. The preconditioners package is built on the parallel software framework PSBLAS, which has also been updated to progress towards exascale. We present weak scalability results on two of the most powerful supercomputers in Europe, for linear systems with sizes up to O(10^10) unknowns.

Published
2020

8. On the Quality of Matching-based Aggregates for Algebraic Coarsening of SPD Matrices in AMG

Author

D'Ambra P., Durastante F., and Filippone S.

Subjects
compatible relaxation, graph matching, AMG, aggregation
Abstract

In this paper, we discuss a quality measure for an aggregation-based coarsening algorithm, named coarsening based on compatible weighted matching, which relies on the interplay between the principle of compatible relaxation and the maximum product matching in weighted graphs. The measure we use is based on a recent general convergence analysis theory applied to the class of multigrid methods employing unsmoothed aggregation. The analysis, as well as the coarsening procedure, is purely algebraic and allows an a posteriori evaluation of the quality of the aggregates analogously to what was previously obtained for similar methods. The connection between the choice of the aggregates and the compatible relaxation principle is also highlighted, confirming the consistency between available theories for designing effective coarsening procedure in purely algebraic multigrid methods and the effectiveness of the coarsening based on compatible weighted matching. We discuss general methods to obtain aggregates for which good convergence properties are achieved, as well as their application to various test cases.

Published
2020

9. Site-selective Synthesis of β-[70]PCBM-like Fullerenes: Efficient Application in Perovskite Solar Cells

Author

Vidal S., Izquierdo M., Filippone S., Fernández I., Akin S., Seo J.-Y., Zakeeruddin S.M., Grätzel M., Martín N. and 'N.M.L. acknowledges support from the European Research Council (ERC-320441-Chirallcarbon), the MINECO of Spain (projects CTQ2017-83531-R and CTQ2016-81911-REDT) and the Comunidad de Madrid (PHOTOCARBON project S2013/MIT-2841), IMDEA Nanociencia thanks support from the 'Severo Ochoa' Programme for Centers of Excellence in R&D (MINECO, Grant SEV-2016-0686)',' I.F. thanks the Spanish MINECO-FEDER (Grants CTQ2016-78205-P and CTQ2016-81797-REDC)',' M.I. thanks the MINECO of Spain (JC IJCI-2014–19320). S.A. would like to thank TUBITAK-2214-A International Doctoral Research Fellowship Programme, for supporting his research at EPFL. S.M.Z. and M.G. thank the King Abdulaziz City for Science and Technology (KACST) for financial support.'

Published
2019

10. Chiral Molecular Carbon Nanostructures

Author

Fernández-Garciá J.M., Evans P.J., Filippone S., Herranz M.Á., Martín N. and Nazario Mart?? has research interests spanning a range of targets, with emphasis on the molecular and supramolecular chemistry of carbon nanostructures and their applications in energy and nano-science. He is a fellow of the Royal Society of Chemistry and a member of the Academia Europaea and belongs to the Editorial Advisory Board of Accounts of Chemical Research. He is a recipient of an Advanced Grant from the European Research Council.

Published
2019

11. Reversible stereodivergent cycloaddition of racemic helicenes to [60]fullerene: A chiral resolution strategy

Author

Girón R.M., Ouyang J., Favereau L., Vanthuyne N., Crassous J., Filippone S., Martín N. and N.M. acknowledges financial support by the European Research Council (ERC-320441-Chirallcarbon), the Ministerio de Economiá y Competitividad (MINECO) of Spain (project CTQ2014-52045-R), and the Comunidad Autónoma de Madrid (PHOTOCARBON project S2013/MIT-2841). R.M.G. thanks the Spanish MECD for an FPU grant (FPU13/03677). J.O. thanks the Chinese Scholarship Council for financial support. L.F. and J.C. thank the CNRS and the University of Rennes 1.

Published
2018

12. On the regioselectivity of the Diels-Alder cycloaddition to C60 in high spin states

Author

El Bakouri O., Garcia-Borràs M., Girón R.M., Filippone S., Martín N., Solà M. and We are grateful for financial support from the Spanish Ministerio de Economía y Competitividad (MINECO) for projects CTQ2014-52045-R and CTQ2017-85341-P. N. M. thanks the European Research Council (ERC-320441-Chirallcarbon) and the Comunidad Autónoma de Madrid (FOTOCARBON project S2013/MIT-2841). O. E. B., M. G.-B., and M. S. acknowledge the Catalan DIUE (project 2014SGR931 and XRQTC), and the FEDER fund (UNGI10-4E-801). M. S. is grateful to the Generalitat de Catalunya for the ICREA Academia 2014 Award. M. G.-B. thanks the Spanish MECD for a PhD grant (AP2010-2517) and the Ramón Areces Foundation for a postdoctoral fellowship. O. E. B. is grateful to the Generalitat de Catalunya (grant no. 2014FI_B 00429) and R. M. G. thanks the Spanish MECD for a FPU grant (FPU13/03677). Excellent service from computational centers CSUC and BSC-CNS is acknowledged.

Published
2018

15. Effect of incarcerated HF on the exohedral chemical reactivity of HF@C60

Author

Vidal S., Izquierdo M., Alom S., Garcia-Borràs M., Filippone S., Osuna S., Solà M., Whitby R.J., Martín N. and This work was supported by the European Research Council ERC-320441-Chirallcarbon, MINECO of Spain (project CTQ2014-52045-R) (CTQ2014-54306-P, CTQ2014-59212-P, and RyC contract RYC-2014-16846 to S. O.), the Catalan DIUE (2014-SGR-931, ICREA Academia 2014 Award to M. S. and XRQTC), the FEDER fund (UNGI10-4E-801) and the CAM (FOTOCARBON project S2013/ MIT-2841). R. J. W. and S. A. thank the Engineering and Physical Sciences Research Council (UK) (EP/1029451, M001962, M001970) including core capability (EP/K039466). M. I. thanks to MINECO of Spain (JC IJCI-2014-19320). M. G.-B. thanks the Ramón Areces Foundation and S. O. the European Commission for CIG project (FP7-PEOPLE-2013-CIG-630978), and the ERC (ERC-2015-StG-679001). Excellent service from computational centers CSUC and BSC-CNS is acknowledged. NM thanks to EC FP7 ITN ‘‘MOLESCO’’ Project No. 606728.

Published
2017

18. Synthesis of modified fullerenes for oxygen reduction reactions

Author

María Girón R., Marco-Martínez J., Bellani S., Insuasty A., Comas Rojas H., Tullii G., Antognazza M.R., Filippone S., Martín N. and We acknowledge the financial support of the European Community through the Future and Emerging Technologies (FET) programme under the FP7, collaborative Project contract no. 309223 (PHOCS). NM thanks the European Research Council ERC-2012-ADG-20120216 (Chirallcarbon), MINECO of Spain (CTQ2014-52045-R) and the CAM (FOTOCARBON project S2013/MIT-2841). R. M. G. thanks Ministerio de Educaci?n, Cultura y Deporte for the FPU contract.

Published
2016

19. Photochemical site-selective synthesis of [70]methanofullerenes

Author

Vidal S., Izquierdo M., Law W.K., Jiang K., Filippone S., Perles J., Yan H., Martín N. and This work was supported by the European Research Council ERC-320441-Chirallcarbon, Ministerio de Economia y Competitividad (MINECO) of Spain (project CTQ2014-52045-R) and the CAM (FOTOCARBON project S2013/MIT-2841). M. I. thanks the Ministerio de Economia y Competitividad (MINECO) of Spain (Juan de la Cierva-Incorporacion IJCI-2014-19320). N. M. thanks the Alexander von Humboldt Foundation.

Published
2016

26. Buckyballs

Author

Delgado J.L., Filippone S., Giacalone F., Herranz M.Á., Illescas B., Pérez, Emilio M., and Martín, Nazario

Published
2014

30. Buckyballs

Author

Delgado J.L., Filippone S., Giacalone F., Herranz M.Á., Illescas B., Pérez E.M., Martín N.

Published
2014

33. Approximate Inverse Preconditioners for Krylov Methods on Heterogeneous Parallel Computers

Author

Bertaccini, D and Filippone, S

Subjects
preconditioners, Settore MAT/08 - Analisi Numerica, Sparse Matrix Computations, Krylov subspace methods, Approximate inversese, preconditioners, Object-oriented programming, Design patterns, Krylov subspace methods, Sparse Matrix Computations, Approximate inversese, Object-oriented programming, Design patterns
Published
2014

34. Parallel Computation of Mesh Motion for CFD of IC Engines

Author

BIANCHI, GIAN MARCO, Schimdt P. D., Toninel S., Filippone S., Bianchi G.M., Schimdt P.D., Toninel S., and Filippone S.

Subjects
ComputingMethodologies_COMPUTERGRAPHICS
Abstract

The burden of creating meshes increases the cost of Computational Fluid Dynamics (CFD) and slows the rate at which new engine geometries can be investigated. Internal Combustion Engines (ICEs) with moving valves and piston present a special challenge, often requiring numerous different target meshes or case–specific codes for adapting the mesh. The goal of the present paper is to facilitate remeshing by calculating vertex motion, in parallel, for hybrid tetrahedral and hexahedral meshes. The calculated vertex motion is intended to maintain good mesh quality and reduce the need for interpolation to a new mesh. The demonstrated approach uses Laplacian–based smoothing for hexahedral cells and optimization–based smoothing for tetrahedral cells. Further, planar and cylindrical surfaces in the engine geometry are automatically recognized. As the engine volume changes shape, vertices may slide along the planar and cylindrical surfaces. Each part of the adaptation process is MPI (Message Passing Interface) parallelized so that the computational performance is maximized. The implementation uses the NEMO library, for efficient deployment on distributed memory architectures.

Published
2008

35. Creation of an ongoing database on food inspections to improve the Food Service effectiveness

Author

Barni, R, Bonazzi, MC, Borroni, G, Del Corno, GG, Filippone, S, Pavan, A., Barni, R, Bonazzi, M, Borroni, G, Del Corno, G, Filippone, S, and Pavan, A

Subjects
Databases as Topic, Italy, Food, Dietary Service, Humans, Nutritional Physiological Phenomena, Food Inspection
Abstract

The purpose of the present study is to create a database for the collection and analysis of data related to the inspection program carried out by a Food and Nutrition Unit, Department of Health Services Milan 1. 1202 reports, stored in the archives of the Unit, were examined. On the basis of the results a computerised reporting form by Microsoft Access was created. The study confirms the necessity of a computerised recording system to point out the most common infractions and to standardise the work of operators. Moreover, on the basis of available data, food inspection activity can be more easily planned focusing on the actual local problems. The described system is a valid tool to store and analyse the information gathered from the inspections. Further implementations could make the database more informative

Published
2003

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