72 citations · 144 across the 10 of their papers we have counts for
10 papers
On automatic differentiation for the Matérn covariance
Oana Marin, Christopher Geoga, Michel Schanen
To target challenges in differentiable optimization we analyze and propose strategies for derivatives of the Matérn kernel with respect to the smoothness parameter. This problem is…
Fitting Matérn Smoothness Parameters Using Automatic Differentiation
Christopher J. Geoga, Oana Marin, Michel Schanen +1
The Matérn covariance function is ubiquitous in the application of Gaussian processes to spatial statistics and beyond. Perhaps the most important reason for this is that the smoot…
Fourier-Informed Knot Placement Schemes for B-Spline Approximation
David Lenz, Oana Marin, Vijay Mahadevan +2
Fitting B-splines to discrete data is especially challenging when the given data contain noise, jumps, or corners. Here, we describe how periodic data sets with these features can…
Direct Numerical Simulation of Fluid Flow in a 5x5 Square Rod Bundle Using Nek5000
Adam Kraus, Elia Merzari, Thomas Norddine +2
Rod bundle flows are commonplace in nuclear engineering, and are present in light water reactors (LWRs) as well as other more advanced concepts. Inhomogeneities in the bundle cross…
Towards Direct Numerical Simulation of a 5x5 Rod Bundle
Adam Kraus, Elia Merzari, Thomas Norddine +2
Rod bundle flows are prevalent in nuclear engineering for both light water reactors (LWR) and advanced reactor concepts. Unlike canonical channel flow, the flow in rod bundles pres…
Fourier Neural Networks as Function Approximators and Differential Equation Solvers
Marieme Ngom, Oana Marin
We present a Fourier neural network (FNN) that can be mapped directly to the Fourier decomposition. The choice of activation and loss function yields results that replicate a Fouri…
Computing Derivatives for PETSc Adjoint Solvers using Algorithmic Differentiation
J. G. Wallwork, P. Hovland, H. Zhang +1
Most nonlinear partial differential equation (PDE) solvers require the Jacobian matrix associated to the differential operator. In PETSc, this is typically achieved by either an an…
A scalable matrix-free spectral element approach for unsteady PDE constrained optimization using PETSc/TAO
Oana Marin, Emil Constantinescu, Barry Smith
We provide a new approach for the efficient matrix-free application of the transpose of the Jacobian for the spectral element method for the adjoint based solution of partial diffe…
The three-dimensional structure of swirl-switching in bent pipe flow
Lorenz Hufnagel, Jacopo Canton, Ramis Oerlue +3
Swirl-switching is a low-frequency oscillatory phenomenon which affects the Dean vortices in bent pipes and may cause fatigue in piping systems. Despite thirty years worth of resea…
On the Strong Scaling of the Spectral Element Solver Nek5000 on Petascale Systems
Nicolas Offermans, Oana Marin, Michel Schanen +7
The present work is targeted at performing a strong scaling study of the high-order spectral element fluid dynamics solver Nek5000. Prior studies indicated a recommendable metric f…