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Limitations to upscaling of groundwater flow models dominated by surface water interaction

Vermeulen, P.T.M. (author), Te Stroet, C.B.M. (author), Heemink, A.W. (author)

Different upscaling methods for groundwater flow models are investigated. A suite of different upscaling methods is applied to several synthetic cases with structured and unstructured porous media. Although each of the methods applies best to one of the synthetic cases, no performance differences are formed if the methods were applied to a real...

journal article 2006

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Model inversion of transient nonlinear groundwater flow models using model reduction

Vermeulen, P.T.M. (author), Te Stroet, C.B.M. (author), Heemink, A.W. (author)

Despite increasing computational resources many high?dimensional applications are impractical for model inversions. In this paper, two methods are presented that are promising for high?dimensional model inversion. The methods draw on proper orthogonal decomposition (POD) and yield reduced models that describe a truncated behavior of the original...

journal article 2006

document

A suite of sharp interface models for solid-state transformations in alloys

Vermolen, F.J. (author), Pinson, P. (author), Vuik, C. (author), Van der Zwaag, S. (author)

The work deals in particular with dissolution and growth of particles in solid-state alloys. Several models are presented and numerical solution procedures are summarized briefly. Further, some analytic solutions are considered shortly, which are useful to validate the numerical solutions. One model, which incorporates surface energy effects is...

conference paper 2006

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Domain decomposition methods and deflated Krylov subspace iterations

Nabben, R. (author), Vuik, C. (author)

The balancing Neumann-Neumann (BNN) and the additive coarse grid correction (BPS) preconditioner are fast and successful preconditioners within domain decomposition methods for solving partial differential equations. For certain elliptic problems these preconditioners lead to condition numbers which are independent of the mesh sizes and are...

conference paper 2006

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A stochastic Datko-Pazy theorem

Haak, B.H. (author), Van Neerven, J.M.A.M. (author), Veraar, M.C. (author)

journal article 2006

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Second class particles and cube root asymptotics for Hammersley’s process

Cator, E.A. (author), Groeneboom, P. (author)

We show that, for a stationary version of Hammersley’s process, with Poisson sources on the positive x-axis and Poisson sinks on the positive y-axis, the variance of the length of a longest weakly North–East path L(t, t) from (0, 0) to (t, t) is equal to 2E(t ? X(t))+, where X(t) is the location of a second class particle at time t . This...

journal article 2006

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Continuity versus nonexistence for a class of linear stochastic Cauchy problems driven by a Brownian motion

Dettweiler, J. (author), Van Neerven, J.M.A.M. (author)

journal article 2006

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Entropy quotients and correct digits in number-theoretic expansions

Bosma, W. (author), Dajani, K. (author), Kraaikamp, C. (author)

Expansions that furnish increasingly good approximations to real numbers are usually related to dynamical systems. Although comparing dynamical systems seems difficult in general, Lochs was able in 1964 to relate the relative speed of approximation of decimal and regular continued fraction expansions (almost everywhere) to the quotient of the...

conference paper 2006

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The behavior of the NPMLE of a decreasing density near the boundaries of the support

Kulikov, V.N. (author), Lopuhaa, H.P. (author)

journal article 2006

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Invariant measures for stochastic cauchy problems with asymptotically unstable drift semigroup

Van Gaans, O. (author), Van Neerven, J. (author)

We investigate existence and permanence properties of invariant measures for abstract stochastic Cauchy problems of the form

journal article 2006

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Invariant measures for the linear stochastic Cauchy problem and R-boundedness of the resolvent

Van Neerven, J.M.A.M. (author), Weis, L. (author)

journal article 2006

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Norm discontinuity and spectral properties of Ornstein-Uhlenbeck semigroups

Van Neerven, J.M.A.M. (author), Priola, E. (author)

journal article 2005

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Asymptotic normality of the Lk-error of the Grenander estimator

Kulikov, V.N. (author), Lopuhaa, H.P. (author)

We investigate the limit behavior of the Lk-distance between a decreasing density f and its nonparametric maximum likelihood estimator ˆ fn for k ? 1. Due to the inconsistency of ˆ fn at zero, the case k = 2.5 turns out to be a kind of transition point.We extend asymptotic normality of the L1-distance to the Lk-distance for 1 ? k < 2.5, and...

journal article 2005

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Inverse modeling of groundwater flow using model reduction

Vermeulen, P.T.M. (author), Heemink, A.W. (author), Valstar, J.R. (author)

Numerical groundwater flow models often have a very high number of model cells (greater than a million). Such models are computationally very demanding, which is disadvantageous for inverse modeling. This paper describes a low?dimensional formulation for groundwater flow that reduces the computational burden necessary for inverse modeling. The...

journal article 2005

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Hammersley's process with sources and inks

Cator, E.A. (author), Groeneboom, P. (author)

We show that, for a stationary version of Hammersley’s process, with Poisson “sources” on the positive x-axis, and Poisson “sinks” on the positive y-axis, an isolated second-class particle, located at the origin at time zero, moves asymptotically, with probability 1, along the characteristic of a conservation equation for Hammersley’s process....

journal article 2005

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Finite-element model for phase-change recording

Brusche, J.H. (author), Segal, A. (author), Urbach, H.P. (author)

The finite-element method is applied to model phase-change recording in a grooved recording stack. A rigorous model for the scattering of a three-dimensional focused spot by a one-dimensional periodic grating is used to determine the absorbed light in a three-dimensional region inside the phase-change layer. The optical model is combined with a...

journal article 2005

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Null controllability and the algebraic Riccati equation in Banach Spaces

Van Neerven, J.M.A.M. (author)

By a recent result of Priola and Zabczyk, a null controllable linear system [y'(t) = Ay(t) + Bu(t)] in a Hilbert space E is null controllable with vanishing energy if and only if it is null controllable and the only positive self-adjoint solution of the associated algebraic Riccati equation [XA + A* X - XBB* X = 0] is the trivial solution X = 0....

journal article 2005

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A Lie-Trotter product formula for Ornstein-Uhlenbeck semigroups in infinite dimensions

Kühnemund, F. (author), Van Neerven, J.M.A.M. (author)

journal article 2004

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Space-time regularity for linear stochastic evolution equations driven by spatially homogeneous noise

Brzezniak, Z. (author), Van Neerven, J. (author)

journal article 2003

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Estimation of a convex function: Characterizations and asymptotic theory

Groeneboom, P. (author), Jongbloed, G. (author), Wellner, J.A. (author)

We study nonparametric estimation of convexregression and density functions by methods of least squares (in the regression and density cases) and maximum likelihood (in the density estimation case).We provide characterizations of these estimators, prove that they are consistent and establish their asymptotic distributions at a fixed point of...

journal article 2001