Inverse problems

P. Chen, U. Villa, and O. Ghattas. Taylor approximation and variance reduction for PDE-constrained optimal control under uncertainty. 2018. [ bib | arXiv ]

B. Kramer, A. N. Marques, B. Peherstorfer, U. Villa, and K. Willcox. Multifidelity probability estimation via fusion of estimators. 2017. [ bib | .pdf ]

P. Chen, U. Villa, and O. Ghattas. Hessian-based adaptive sparse quadrature for infinite-dimensional Bayesian inverse problems. Computer Methods in Applied Mechanics and Engineering, 327:147--172, 2017. [ bib | DOI | arXiv ]

N. Alger, U. Villa, T. Bui-Thanh, and O. Ghattas. A data scalable augmented Lagrangian KKT preconditioner for large scale inverse problems. SIAM Journal on Scientific Computing, 39(5):A2365--A2393, 2017. [ bib | DOI | arXiv ]

Algebraic multigrid and Upscaling

S. Osborn, P. Zulian, T. Benson, U. Villa, R. Krause, and P. Vassilevski. Scalable hierarchical PDE sampler for generating spatially correlated random fields using non-matching meshes. Numerical Linear Algebra with Applications, 25(3):e2146, 2018. [ bib | DOI | arXiv ]

M. Christensen, P. S. Vassilevski, and U. Villa. Nonlinear Multigrid solvers exploiting AMGe coarse spaces with approximation properties. Journal of Computational and Applied Mathematics, available on-line, 2017. [ bib | DOI ]

S. Osborn, P. S. Vassilevski, and U. Villa. A Multilevel Hierarchical Sampling Technique for Spatially Correlated Random Fields. SIAM Journal on Scientific Computing, 39(5):S543--S562, 2017. [ bib | DOI | arXiv ]

M. Christensen, U. Villa, A. Engsig-Karup, and P. S. Vassilevski. Numerical upscaling for incompressible flow in reservoir simulation: an element-based algebraic multigrid (AMGe) approach. SIAM Journal on Scientific Computing, 39(1):B102--B137, 2017. [ bib | DOI ]

M. Neumüller, P. S. Vassilevski, and U. Villa. Space-time constrained First Order Systems Least Squares (CFOSLS) with AMGe upscaling, pages 253--260. Springer, 2017. [ bib | DOI | .pdf ]

D. Kalchev, C. S. Lee, U. Villa, Y. Efendiev, and P. S. Vassilevski. Upscaling of mixed finite element discretization problems by the spectral AMGe method. SIAM Journal on Scientific Computing, 38(5):A2912--A2933, 2016. [ bib | DOI | .pdf ]

M. Christensen, U. Villa, and P. S. Vassilevski. Multilevel techniques lead to accurate numerical upscaling and scalable robust solvers for reservoir simulation. In SPE Reservoir Simulation Symposium. Society of Petroleum Engineers, 2015. 23-25 February, Houston, Texas, USA, SPE-173257-MS. [ bib | http ]

P. S. Vassilevski and U. Villa. A mixed formulation for the Brinkman problem. SIAM Journal on Numerical Analysis, 52(1):258--281, 2014. [ bib | DOI | .pdf ]

P. S. Vassilevski and U. Villa. A block-diagonal algebraic multigrid preconditioner for the Brinkman problem. SIAM Journal on Scientific Computing, 35(5):S3--S17, 2013. [ bib | DOI | .pdf ]

Computational Fluid-Dynamics and Cloud Computing

S. Guzzetti, T. Passerini, J. Slawinski, U. Villa, A. Veneziani, and V. Sunderam. Platform and algorithm effects on computational fluid dynamics applications in life sciences. Future Generation Computer Systems, 67:382 -- 396, 2017. [ bib | DOI | .pdf ]

T. Passerini, J. Slawinski, U. Villa, and V. Sunderam. Experiences with Cost and Utility Trade-offs on IaaS Clouds, Grids, and On-Premise Resources. In Proc. IEEE Intl. Conference on Cloud Engineering (IC2E) - Cloud Analytics Workshop, pages 391--396. IEEE, 2014. [ bib | DOI ]

T. Passerini, A. Quaini, U. Villa, A. Veneziani, and S. Canic. Validation of an open source framework for the simulation of blood flow in rigid and deformable vessels. Int. J. Numerical Methods in Biomedical Engineering, 29(11):1192--1213, 2013. [ bib | DOI | .pdf ]

A. Veneziani and U. Villa. ALADINS: An ALgebraic splitting time ADaptive solver for the Incompressible Navier--Stokes equations. Journal of Computational Physics, 238:359--375, 2013. [ bib | http ]

J. Slawinski, U. Villa, T. Passerini, A. Veneziani, and V. Sunderam. Issues in Communication Heterogeneity for Message-Passing Concurrent Computing. In 27th IEEE Intl. Parallel and Distributed Processing Symposium Workshops & PhD Forum (IPDPSW), pages 93--102. IEEE, 2013. [ bib | DOI ]

J. Slawinski, U. Villa, T. Passerini, A. Veneziani, and V. Sunderam. Experiences with Target-Platform Heterogeneity in Clouds, Grids, and On-Premises Resources. In 26th IEEE Intl. Parallel and Distributed Processing Symposium Workshops & PhD Forum (IPDPSW), pages 41--52. IEEE, 2012. [ bib | DOI | .pdf ]

U. Villa. Scalable Efficient Methods for Incompressible Fluid-dynamics in Engineering Problems. PhD thesis, Emory University, Atlanta, GA, 2012. Advisor: A. Veneziani. [ bib | http ]


U. Villa and A. N. Marques. An UQ-ready finite element solver for a two-dimensional RANS model of free plane jets, 2017. [ bib | arXiv | .pdf ]

D. Salvo, C. Torres, U. Villa, J. A. Rivera, O. L. Sarmiento, R. S. Reis, and M. Pratt. Accelerometer-based physical activity levels among Mexican adults and their relation with sociodemographic characteristics and BMI: a cross-sectional study. Int. J. Behavioral Nutrition and Physical Activity, 12(79):1--11, 2015. [ bib | http ]

K. W. Desmond, U. Villa, M. Newey, and W. Losert. Characterizing the rheology of fluidized granular matter. Physical Review E, 88(3):032202, 2013. [ bib | arXiv | http ]

U. Villa. Finite Element Analysis of the Brake Pad System and Multibody Modeling of Motor Vehicles in Braking-Phase. Master's thesis, Politecnico di Milano, Milan, Italy, 2007. Advisor: A. Veneziani; Committee: L. Trainelli, A. Vigliani. [ bib | .pdf ]

S. Vele and U. Villa. Mathematical modeling and numerical simulation of hemodynamics problems in one dimension. Bachelor's thesis, Politecnico di Milano, Milan, Italy, 2005. Advisor: A. Veneziani. [ bib | .pdf ]