John Paul Ward

Cette personne n’est plus à l’EPFL

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Publications associées (30)

On the Unique Identification of Continuous-Time Autoregressive Models From Sampled Data

Michaël Unser, Hagay Kirshner, John Paul Ward

In this work, we investigate the relationship between continuous-time autoregressive (AR) models and their sampled version. We consider uniform sampling and derive criteria for uniquely determining the continuous-time parameters from sampled data; the mode ...

Ieee-Inst Electrical Electronics Engineers Inc2014

Adaptive Image Resizing Based on Continuous-Domain Stochastic Modeling

Michaël Unser, Aurélien Bourquard, Hagay Kirshner, John Paul Ward

We introduce an adaptive continuous-domain modeling approach to texture and natural images. The continuous-domain image is assumed to be a smooth function, and we embed it in a parameterized Sobolev space. We point out a link between Sobolev spaces and sto ...

Ieee-Inst Electrical Electronics Engineers Inc2014

Operator-Like Wavelet Bases of $ L _{ 2 } $ $ (\mathbb{R} ^{ d } $ )

Michaël Unser, Ildar Khalidov, John Paul Ward

The connection between derivative operators and wavelets is well known. Here we generalize the concept by constructing multiresolution approximations and wavelet basis functions that act like Fourier multiplier operators. This construction follows from a s ...

Springer US2013

Identification of Rational Transfer Functions from Sampled Data

Michaël Unser, Hagay Kirshner, John Paul Ward

We consider the task of estimating an operator from sampled data. The operator, which is described by a rational transfer function, is applied to continuous-time white noise and the resulting continuous-time process is sampled uniformly. The main question ...

SampTA2013

Hessian Schatten-Norm Regularization for Linear Inverse Problems

Michaël Unser, Stamatios Lefkimmiatis, John Paul Ward

We introduce a novel family of invariant, convex, and non-quadratic functionals that we employ to derive regularized solutions of ill-posed linear inverse imaging problems. The proposed regularizers involve the Schatten norms of the Hessian matrix, which a ...

Ieee-Inst Electrical Electronics Engineers Inc2013

On the Linearity of Bayesian Interpolators for Non-Gaussian Continuous-Time AR(1) Processes

Philippe Thévenaz, Michaël Unser, Arash Amini, John Paul Ward

Bayesian estimation problems involving Gaussian distributions often result in linear estimation techniques. Nevertheless, there are no general statements as to whether the linearity of the Bayesian estimator is restricted to the Gaussian case. The two comm ...

Ieee-Inst Electrical Electronics Engineers Inc2013

L (p) error estimates for approximation by Sobolev splines and Wendland functions on a"e (d)

John Paul Ward

It is known that a Green's function-type condition may be used to derive rates for approximation by radial basis functions (RBFs). In this paper, we introduce a method for obtaining rates for approximation by functions which can be convolved with a finite ...

Springer US2013

Decay Properties of Riesz Transforms and Steerable Wavelets

Michaël Unser, Kunal Narayan Chaudhury, John Paul Ward

The Riesz transform is a natural multidimensional extension of the Hilbert transform, and it has been the object of study for many years due to its nice mathematical properties. More recently, the Riesz transform and its variants have been used to construc ...

Siam Publications2013

Linear Interpolation Of Biomedical Images Using A Data-Adaptive Kernel

Michaël Unser, Aurélien Bourquard, Hagay Kirshner, John Paul Ward

In this work, we propose a continuous-domain stochastic model that can be applied to image data. This model is autoregressive, and accounts for Gaussian-type as well as for non-Gaussian-type innovations. In order to estimate the corresponding parameters fr ...

IEEE2013

Is Uniqueness Lost for Under-Sampled Continuous-Time Auto-Regressive Processes?

Michaël Unser, Hagay Kirshner, John Paul Ward

We consider the problem of sampling continuous-time auto-regressive processes on a uniform grid. We investigate whether a given sampled process originates from a single continuous-time model, and address this uniqueness problem by introducing an alternativ ...

IEEE Institute of Electrical and Electronics Engineers2012

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