Documents published in Scipedia

• Embedded multilevel Monte Carlo for uncertainty quantification in random domains

  S. Badia, J. Hampton, J. Principe

  (2019). Under review

  
  

  Abstract

  The multilevel Monte Carlo (MLMC) method has proven to be an effective variance-reduction statistical method for Uncertainty quantification in PDE models. It combines approximations at different levels of accuracy using a hierarchy of meshes in a similar way as multigrid. The generation of body-fitted mesh hierarchies is only possible for simple geometries. On top of that, MLMC for random domains involves the generation of a mesh for every sample. Instead, here we consider the use of embedded methods which make use of simple background meshes of an artificial domain (a bounding-box) for which it is easy to define a mesh hierarchy, thus eliminating the need of body-fitted unstructured meshes, but can produce ill-conditioned discrete problems. To avoid this complication, we consider the recent aggregated finite element method (AgFEM). In particular, we design an embedded MLMC framework for (geometrically and topologically) random domains implicitly defined through a random level-set function, which makes use of a set of hierarchical background meshes and the AgFEM. Performance predictions from existing theory are verified statistically in three numerical experiments, namely the solution of the Poisson equation on a circular domain of random radius, the solution of the Poisson equation on a topologically identical but more complex domain, and the solution of a heat-transfer problem in a domain that has geometric and topological uncertainties. Finally, the use of AgFE is statistically demonstrated to be crucial for complex and uncertain geometries in terms of robustness and computational cost. Date: November 28, 2019.

  Abstract
  The multilevel Monte Carlo (MLMC) method has proven to be an effective variance-reduction statistical method for Uncertainty quantification in PDE models. It combines approximations [...]

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• A modified Finite Element formulation for the imposition of the slip boundary condition over embedded volumeless geometries

  R. Zorrilla, A. Larese, R. Rossi

  Comput. Methods Appl. Mech. Engrg., (2019). (Preprint) Vol. 353, pp. 123-157

  
  

  Abstract

  This work describes a novel formulation for the simulation of Navier-Stokes problems including embedded objects. The new proposal is based on the use of a modified finite element space, which replaces the standard one within the elements intersected by the immersed geometry. The modified space is able to exactly reproduce the jumps happening at the embedded boundary while preserving the conformity across the faces intersected by the embedded object. The paper focuses particularly on the imposition of a slip boundary condition on the surface of the embedded geometry, proposing a new technique for the application of such constraint. The new proposal is carefully benchmarked using the results of a body fitted technique and of an alternative embedded approach. Potential applications of interest are also presented.

  Abstract
  This work describes a novel formulation for the simulation of Navier-Stokes problems including embedded objects. The new proposal is based on the use of a modified finite [...]

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• Computational modeling of the fluid flow in type B aortic dissection using a modified finite element embedded formulation

  R. Zorrilla, E. Soudah, R. Rossi

  Biomechanics and Modeling in Mechanobiology (2020). (Preprint)

  
  

  Abstract

  This work explores the use of an embedded computational fluid dynamics method to study the type B aortic dissection. The use of the proposed technique makes it possible to easily test different intimal flap configurations without any need of remeshing. To validate the presented methodology, we take as reference test case an in vitro experiment present in the literature. This experiment, which considers several intimal flap tear configurations (number, size and location), mimics the blood flow in a real type B aortic dissection. We prove the correctness and suitability of the presented approach by comparing the pressure values and waveform. The obtained results exhibit a remarkable similarity with the experimental reference data. Complementary, we present a feasible surgical application of the presented computer method. The aim is to help the clinicians in the decision making before the type B aortic dissection surgical fenestration. The capabilities of the proposed technique are exploited to efficiently create artificial reentry tear configurations. We highlight that only the radius and center of the reentry tear need to be specified by the clinicians, without any need to modify neither the model geometry nor the mesh. The obtained computational surgical fenestration results are in line with the medical observations in similar clinical studies.

  Abstract
  This work explores the use of an embedded computational fluid dynamics method to study the type B aortic dissection. The use of the proposed technique makes it possible to [...]

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• Parallel unstructured mesh adaptation using iterative remeshing and repartitioning

  L. Cirrattola, A. Froehly

  (2019). RR-9307, INRIA Bordeaux, équipe CARDAMOM

  
  

  Abstract

  Mesh adaptation has proven to be a powerful tool for increasing the accuracy ofnumerical simulations whenever the solution exhibits strong non-uniform features over the com-putational domain. Sequential remeshing currently represents a bottleneck for parallel solvers. Tothis aim, we present a parallel remeshing algorithm that enables the reuse of existing sequential remeshing libraries, a non-intrusive linkage with third-party solvers, and an efficient exploitationof distributed parallel environments. The numerical procedure is implemented in the open sourceParMmg software package.

  Abstract
  Mesh adaptation has proven to be a powerful tool for increasing the accuracy ofnumerical simulations whenever the solution exhibits strong non-uniform features over the com-putational [...]

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• Balancing domain decomposition by constraints associated with subobjects

  S. Badia, A. Martín, H. Nguyen

  Applied Mathematics Letters (2019). (preprint) Vol. 87, pp. 93-100

  
  

  Abstract

  A simple variant of the BDDC preconditioner in which constraints are imposed on a selected set of subobjects (subdomain subedges, subfaces and vertices between pairs of subedges) is presented. We are able to show that the condition number of the preconditioner is bounded by C 1 + log(L/h)2, where C is a constant, and h and L are the characteristic sizes of the mesh and the subobjects, respectively. As L can be chosen almost freely, the condition number can theoretically be as small as O(1). We will discuss the pros and cons of the preconditioner and its application to heterogeneous problems. Numerical results on supercomputers are provided.

  Abstract
  A simple variant of the BDDC preconditioner in which constraints are imposed on a selected set of subobjects (subdomain subedges, subfaces and vertices between pairs of subedges) [...]

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• Distributed-memory parallelization of the aggregated unfitted finite element method

  F. Verdugo, A. Martín, S. Badia

  Comput. Methods Appl. Mech. Engrg., (2019). (Preprint) Vol. 357, pp. 112583

  
  

  Abstract

  The aggregated unfitted finite element method (AgFEM) is a methodology recently introduced in order to address conditioning and stability problems associated with embedded, unfitted, or extended finite element methods. The method is based on removal of basis functions associated with badly cut cells by introducing carefully designed constraints, which results in well-posed systems of linear algebraic equations, while preserving the optimal approximation order of the underlying finite element spaces. The specific goal of this work is to present the implementation and performance of the method on distributed-memory platforms aiming at the efficient solution of large-scale problems. In particular, we show that, by considering AgFEM, the resulting systems of linear algebraic equations can be effectively solved using standard algebraic multigrid preconditioners. This is in contrast with previous works that consider highly customized preconditioners in order to allow one the usage of iterative solvers in combination with unfitted techniques. Another novelty with respect to the methods available in the literature is the problem sizes that can be handled with the proposed approach. While most of previous references discussing linear solvers for unfitted methods are based on serial non-scalable algorithms, we propose a parallel distributed-memory method able to efficiently solve problems at large scales. This is demonstrated by means of a weak scaling test defined on complex 3D domains up to 300M degrees of freedom and one billion cells on 16K CPU cores in the Marenostrum-IV platform. The parallel implementation of the AgFEM method is available in the large-scale finite element package FEMPAR.

  Abstract
  The aggregated unfitted finite element method (AgFEM) is a methodology recently introduced in order to address conditioning and stability problems associated with embedded, [...]

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• The surrogate matrix methodology: A reference implementation for low-cost assembly in isogeometric analysis

  D. Drzisga, B. Keith, B. Wohlmuth

  (2019). Under review

  
  

  Abstract

  A reference implementation of a new method in isogeometric analysis (IGA) is presented. It delivers lowcost variable-scale approximations (surrogates) of the matrices which IGA conventionally requires to be computed by element-scale quadrature. To generate surrogate matrices, quadrature must only be performed on a fraction of the elements in the computational domain. In this way, quadrature determines only a subset of the entries in the final matrix. The remaining matrix entries are computed by a simple B-spline interpolation procedure. We present the modifications and extensions required for a reference implementation in the open-source IGA software library GeoPDEs. The exposition is fashioned to help facilitate similar modifications in other contemporary software libraries. Method name: Surrogate matrix method for isogeometric analysis

  Abstract
  A reference implementation of a new method in isogeometric analysis (IGA) is presented. It delivers lowcost variable-scale approximations (surrogates) of the matrices which [...]

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• The surrogate matrix methodology: Low-cost assembly for isogeometric analysis

  D. Drzisga, B. Keith, B. Wohlmuth

  Computer Methods in Applied Mechanics and Engineering (2020). Vol. 361,1, 112776 (preprint)

  
  

  Abstract

  A new methodology in isogeometric analysis (IGA) is presented. This methodology delivers low-cost variable-scale approximations (surrogates) of the matrices which IGA conventionally requires to be computed from element-scale quadrature formulas. To generate surrogate matrices, quadrature must only be performed on certain elements in the computational domain. This, in turn, determines only a subset of the entries in the final matrix.The remaining matrix entries are computed by a simple B-spline interpolation procedure. Poisson’s equation, membrane vibration, plate bending, and Stokes’ flow problems are studied. In these problems, the use of surrogate matrices has a negligible impact on solution accuracy. Because only a small fraction of the original quadrature must be performed, we are able to report beyond a fifty-fold reduction in overall assembly time in the same software. The capacity for even further speed-ups is clearly demonstrated. The implementation used here was achieved by a small number of modifications to the open-source IGA software library GeoPDEs. Similar modifications could be made to other present-day software libraries.

  Abstract
  A new methodology in isogeometric analysis (IGA) is presented. This methodology delivers low-cost variable-scale approximations (surrogates) of the matrices which IGA conventionally [...]

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• The surrogate matrix methodology: a priori error estimation

  D. Drzisga, B. Keith, B. Wohlmuth

  SIAM Journal on Scientific Computing (2019). Vol 41(6), pp. A3806–A3838 (preprint)

  
  

  Abstract

  We give the first mathematically rigorous analysis of an emerging approach to finite element analysis (see, e.g., Bauer et al. [Appl. Numer. Math., 2017]), which we hereby refer to as the surrogate matrix methodology. This methodology is based on the piece-wise smooth approximation of the matrices involved in a standard finite element discretization. In particular, it relies on the projection of smooth so-called stencil functions onto high-order polynomial subspaces. The performance advantage of the surrogate matrix methodology is seen in constructions where each stencil function uniquely determines the values of a significant collection of matrix entries. Such constructions are shown to be widely achievable through the use of locally-structured meshes. Therefore, this methodology can be applied to a wide variety of physically meaningful problems, including nonlinear problems and problems with curvilinear geometries. Rigorous a priori error analysis certifies the convergence of a novel surrogate method for the variable coefficient Poisson equation. The flexibility of the methodology is also demonstrated through the construction of novel methods for linear elasticity and nonlinear diffusion problems. In numerous numerical experiments, we demonstrate the efficacy of these new methods in a matrix-free environment with geometric multigrid solvers. In our experiments, up to a twenty-fold decrease in computation time is witnessed over the classical method with an otherwise identical implementation.

  Abstract
  We give the first mathematically rigorous analysis of an emerging approach to finite element analysis (see, e.g., Bauer et al. [Appl. Numer. Math., 2017]), which we hereby [...]

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• AutoParallel: A Python module for automatic parallelization and distributed execution of affine loop nests

  C. Ramon-Cortes, R. Amela, J. Ejarque, P. Clauss, R. Badia

  (2020). Under review

  
  

  Abstract

  The last improvements in programming languages, programming models, and frameworks have focused on abstracting the users from many programming issues. Among others, recent programming frameworks include simpler syntax, automatic memory management and garbage collection, which simplifies code re-usage through library packages, and easily configurable tools for deployment. For instance, Python has risen to the top of the list of the programming languages due to the simplicity of its syntax, while still achieving a good performance even being an interpreted language. Moreover, the community has helped to develop a large number of libraries and modules, tuning them to obtain great performance. However, there is still room for improvement when preventing users from dealing directly with distributed and parallel computing issues. This paper proposes and evaluates AutoParallel, a Python module to automatically find an appropriate task-based parallelization of affine loop nests to execute them in parallel in a distributed computing infrastructure. This parallelization can also include the building of data blocks to increase task granularity in order to achieve a good execution performance. Moreover, AutoParallel is based on sequential programming and only contains a small annotation in the form of a Python decorator so that anyone with little programming skills can scale up an application to hundreds of cores.

  Abstract
  The last improvements in programming languages, programming models, and frameworks have focused on abstracting the users from many programming issues. Among others, recent [...]

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Articles (Documents not available in Scipedia)

• Odors and gas emissions during the ceramic sintering of sewage sludge: guidelines for industrial implementation

  LV Cremades Oliver, C Soriano Ortiz, JA Cusidó Fàbregas

  TINOS 2015: 3rd international conference on sustainable solid waste …, 2015

• Incorporation of paper sludge in clay brick formulation: Ten years of industrial experience

  JA Cusidó, LV Cremades, C Soriano, M Devant

  Applied Clay Science 108, 191-198, 2015

• Using solid wastes as raw materials in clay bricks

  LV Cremades Oliver, JA Cusidó Fàbregas, C Soriano, MVF Devant Guille

  Nova Science Publishers, 2014

• Description of extreme longevity in the Balearic Islands: Exploring a potential Blue Zone in Menorca, Spain

  JB Soriano, S Fernández Vázquez, S Carretero, MD Puga González, ...

  Geriatrics & gerontology international 14 (3), 620-627, 2014

• Valorization of pellets from municipal WWTP sludge in lightweight clay ceramics

  JA Cusidó, C Soriano

  Waste management 31 (6), 1372-1380, 2011

• Custom formulation of red ceramics with clay, sewage sludge and forest waste

  M Devant, JA Cusidó, C Soriano

  Applied Clay Science 53 (4), 669-675, 2011

• Identification of the origin of odour episodes through social participation, chemical control and numerical modelling

  E Gallego, C Soriano, FX Roca, JF Perales, M Alarcón, X Guardino

  Atmospheric Environment 42 (35), 8150-8160, 2008

• Pollutant Dispersion in a Heavily Industrialized Region: Comparison of Different Models

  MR Soler, S Ortega, C Soriano, D Pino, M Alarcón

  Air Pollution Modeling and Its Application XVII, 671-673, 2007

• Study of odor episodes using analytical and modeling approaches

  C Soriano, FX Roca, M Alarcón

  Air Pollution Modeling and Its Application XVII, 674-676, 2007

• Objective synoptic classification combined with high resolution meteorological models for wind mesoscale studies

  C Soriano, A Fernández, J Martín-Vide

  Meteorology and Atmospheric Physics 91 (1-4), 165-181, 2006

• Ozone Modeling of the Barcelona Area: Analysis of the Involved Transport Processes

  I Toll, C Soriano, JM Baldasano

  Air Pollution Modeling and Its Application XIV, (Ed: E-E. Gryning and F.A. Schiermieier). Kluwer Academic/Plenum Publishers, NY, pp. 729-730. 2000

• Sobre el uso de los procesos sinópticos objetivos y los modelos meteorológicos a alta resolución para el estudio de los patrones circulatorios a escala regional

  C Soriano Ortiz, AG Fernández, J Martín Vide

  Trópico 2004- CD-Rom con las contribuciones de Trópico 2004. La Habana, CUBA, 2004

• 6.28 PREDICTION OF FOG EPISODES AT THE AIRPORT OF MADRID-BARAJAS USING DIFFERENT MODELING APPROACHES

  C Soriano, D Cano, E Terradellas, B Physick

  9th International Conference on Harmonization within Atmospheric Dispersion …, 2004

• Estudio de la formación de vientos catabáticos en la región de Madrid mediante la simulación con un modelo de mesoescala a alta resolución

  C Soriano, D Cano Espadas, E Terradellas, B Physick

  Agencia Estatal de Meteorología, 2004

• One-way nesting versus two-way nesting: does it really make a difference?

  C Soriano, O Jorba, JM Baldasano

  Air Pollution Modeling and its Application XV, 177-185, 2004

• Environmental impact assessment of emissions from an industrial stack: Gaussian and mesoscale modeling

  C Soriano, R Soler, B Physick, A Luhar, P Hurley

  EGS-AGU-EUG Joint Assembly, 2003

• On wind velocity profiles over urban area

  K Bezpalcova, Z Janour, VMM Prior, C Soriano, M Strizik

  International journal of environment and pollution 20 (1-6), 196-206, 2003

• Modelling different meteorological situations in Catalunya, Spain, with MM5 and TAPM mesoscale models: a comparative study

  C Soriano, RM Soler, D Pino, M Alarcón, B Physick, P Hurley

  International journal of environment and pollution 20 (1-6), 256-268, 2003

• Lidar-aerosol sensing

  F Rocadenbosch

  Encyclopedia of Optical Engineering 1, 1090-102, 2003

• Urban photochemical pollution in the Iberian Peninsula: Lisbon and Barcelona airsheds

  N Barros, C Borrego, I Toll, C Soriano, P Jiménez, JM Baldasano

  Journal of the Air & Waste Management Association 53 (3), 347-359, 2003

• Remote Sensing Of Three-Dimensional Winds With Elastic Lidar: Explanation Of Maximum Cross-Correlation Method

  WT Buttler, C Soriano, JM Baldasano, GH Nickel

  Boundary-Layer Meteorology 103 (1), 173-174, 2002

• Modeling different meteorological situations in Catalunya, Spain, with MM5 and TAPM mesoscale models

  C Soriano, RM Soler, D Pino, M Alarcón, B Physick, P Hurley

  Harmonization within Atmospheric Dispersion Modeling for Regulatory Purposes …, 2002

• The UPC scanning Raman lidar: an engineering overview

  F Rocadenbosch, M Sicard, A Comerón, JM Baldasano, A Rodríguez, ...

  Proceeding of the 21st ILRC 1, 69-70, 2002

• Barcelona atmospheric monitoring with lidar: first measurements with the UPC's scanning portable lidar

  C Soriano, F Rocadenbosch, A Rodríguez, C Munoz, D García-Vizcaíno, ...

  Remote Sensing of Clouds and the Atmosphere V 4168, 170-182, 2001

• Preliminary Numerical Simulation of Winds Fields in Catalonia (NE Spain)

  JM Baldasano, M Millan, C Soriano, R Salvador, P Midgley, M Reuther, ...

  Springer, 2001

• Development of an Upgraded Urban Source Emission Model for Atmospheric Pollutans

  JM Baldasano, C Soriano, S Gassó

  GENEMIS Annual Report, 19-22, 2001

• Simultaneous observations of free tropospheric Saharan dust layers over Europe monitored by a co-ordinated ground-based lidar network in frame of the EARLINET...

  A Papayannis, A Boselli, B Calpini, A Chaikovsky, G Chourdakis, ...

  J. Aerosol Sci 32, 389-390, 2001

• Atlas de Radiació solar a Catalunya

  A Mitjà

  Institut Català d’Energia: Barcelona, Spain, 2001

• 3D scanning portable backscatter lidar platform for atmospheric remote sensing: Performance and architecture overview

  F Rocadenbosch, C Soriano, A Comeron, JM Baldasano, A Rodriguez, ...

  Remote Sensing of Clouds and the Atmosphere V 4168, 158-170, 2001

• Remote sensing of three-dimensional winds with elastic lidar: explanation of maximum cross-correlation method

  WT Buttler, C Soriano, JM Baldasano, GH Nickel

  Boundary-Layer Meteorology 101 (3), 305-327, 2001

• Circulatory patterns of air pollutants within the Barcelona air basin in a summertime situation: lidar and numerical approaches

  C Soriano, JM Baldasano, WT Buttler, KR Moore

  Boundary-Layer Meteorology 98 (1), 33-55, 2001

• Technological assessment of anaerobic digestion and composting-Emission of greenhouse gases from anaerobic digestion processes: Comparison with other muni...

  JM Baldasano, C Soriano

  Water Science and Technology 41 (3), 275-282, 2000

• V. Reports from the principal investigators

  JM Baldasano, C Soriano, I Toll, G Baumbach, K Glaser, U Vogt, A Grauer, ...

  GENEMIS, 17, 2000

• Wind input data for urban dispersion modeling–Activities of working group 1 within COST 715

  MW Rotach, E Batchvarova, R Berkowicz, J Brechler, Z Janour, ...

  3rd Symposium on the Urban Environment, 14-18, 2000

• Wind input data for urban dispersion modelling

  MW Rotach, E Batchvarova, R Berkowicz, J Brechler, Z Janour, ...

  Schatzmann, M., Brechler, J., Fisher, B., Eds, 8-35, 2000

• Vehicle emission model of air pollutants from road traffic: Application to Catalonia (Spain) for 1994

  R Delgado, I Toll, C Soriano, JM Baldasano

  WIT Transactions on Ecology and the Environment 42, 2000

• Emission of greenhouse gases from anaerobic digestion processes: comparison with other municipal solid waste treatments

  JM Baldasano, C Soriano

  Water science and technology 41 (3), 275-282, 2000

• Lidar inversion of atmospheric backscatter and extinction-to-backscatter ratios by use of a Kalman filter

  F Rocadenbosch, C Soriano, A Comerón, JM Baldasano

  Applied optics 38 (15), 3175-3189, 1999

• Emission inventory for greenhouse gases in the City of Barcelona, 1987–1996

  JM Baldasano, C Soriano, L Boada

  Atmospheric Environment 33 (23), 3765-3775, 1999

• Inversion of atmospheric optical parameters from elastic-backscatter lidar returns using a Kalman filter

  F Rocadenbosch, A Comeron, G Vazquez, A Rodriguez-Gomez, ...

  Atmospheric Propagation, Adaptive Systems, and Lidar Techniques for Remote …, 1998

• On the application of meteorological models and lidar techniques for air quality studies at a regional scale

  C Soriano, JM Baldasano, WT Buttler

  Air Pollution Modeling and its Application XII, 591-600, 1998

• Confirmation of a multilayer arrangement of aerosols in the Barcelona air basin using two independent lidar systems

  C Soriano, F Rocadenbosch, C Puente, A Rodriguez-Gomez, ...

  Spectroscopic atmospheric environmental monitoring techniques 3493, 212-223, 1998

• Atlas de Radiació Solar de Catalunya Ed. 1996

  J Baldasano, J Calbo, J Moreno

  Institut Català d'Energia, 1996

• Evaluacion de algoritmos de inversion lidar sin memoria

  D Pineda, F Rocadenbosch Burillo, C Soriano Ortiz, A Comerón Tejero

  X Symposium Nacional de la Unión Científica Internacional de Radio …, 1995

• Performance of a VME-based parallel processing LIDAR data acquisition system (summary)

  K Moore, B Buttler, M Caffrey, C Soriano

  Los Alamos National Lab., NM (United States), 1995

• Comparison of temperature and humidity profiles with elastic-backscatter lidar data

  C Soriano, WT Buttler, JM Baldasano

  Los Alamos National Lab., NM (United States), 1995

• Circulatory of air pollutants over the Barcelona Geographical area in summertime

  JM Baldasano, L Cremades, C Soriano

  Physico Chemical behaviour of Atmospheric Pollutants. Ed. Angletti and …, 1994

• Circulation of air pollutants over the Barcelona geographical area in summer

  J Baldasano, LV Cremades

  EUROPEAN COMMISSION, 1993

• Fonament de l'arc de Sant Martí

  E Jariod, J Llumà, S Cuevas, J Marti, EM Badosa, T Pérez, V Panyella, ...

  Revista de física, 27-31, 1991

• Fonament de l'arc de Sant Martí

  J Martí, T Pérez, S Cuevas, E Martín, V Panyella, E Jariod, J Llumà, ...

  Revista de física, 27-31, 1991

• Study of the land-sea interface in the Barcelona area with lidar data and meteorological models

  C Soriano, JM Baldasano

  WIT Transactions on Ecology and the Environment 25, 1970

Books, book chapters and edited books (Documents not available in Scipedia)

• Assessment of the emissions of greenhouse gases in Barcelona City. Period 1987-1994

  JM Baldasano, C Soriano

  Air Pollution VI, (Ed. Brebbia, C.A., Ratto, C.F. and Power, H.). Computational Mechanics Publications, pp.191-199. 1998. ISBN 1369-5886/1-85312-605-5