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van Zwieten, G.J. (author)A vital component in the management of seismic hazard is the study of past seismic events. Classically, this has been the domain of seismology, which studies the dynamic manifestations of the event to infer properties such as epicenter and moment magnitude. More recently it has become possible to perform similar analyses on the basis of the...doctoral thesis 2023
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Kekkonen, H.N. (author), Lassas, Matti (author), Saksman, Eero (author), Siltanen, Samuli (author)We propose alternatives to Bayesian prior distributions that are frequently used in the study of inverse problems. Our aim is to construct priors that have similar good edge-preserving properties as total variation or Mumford-Shah priors but correspond to well-defined infinite-dimensional random variables, and can be approximated by finite...journal article 2023
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Flaschel, Moritz (author), Kumar, Siddhant (author), De Lorenzis, Laura (author)We extend the scope of our recently developed approach for unsupervised automated discovery of material laws (denoted as EUCLID) to the general case of a material belonging to an unknown class of constitutive behavior. To this end, we leverage the theory of generalized standard materials, which encompasses a plethora of important constitutive...journal article 2023
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Hunter, William (author)Atrial fibrillation is a common cardiovascular disease, affecting the regular beating of the heart through chaotic contraction of the heart's upper chambers. On its own, the condition—increasingly prevalent among the elderly—is not life threatening, but it leads to an increased risk of stroke and heart failure. As of yet, there is no consensus...master thesis 2022
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Ansuinelli, P. (author)The importance of inverse problems is paramount in science and physics because their solution provides information about parameters that cannot be directly observed. This thesis discusses and details the application of a few inverse methods in optical imaging, metrology and inspection of lithographic targets, particularly patterned structures on...doctoral thesis 2022
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Kekkonen, H.N. (author)We consider the statistical non-linear inverse problem of recovering the absorption term f > 0 in the heat equation {∂tu-12Δu+fu=0onO×(0,T)u=gon∂ O×(0,T)u(·,0)=u0onO, where O ϵ ℝd is a bounded domain, T < ∞ is a fixed time, and g, u 0 are given sufficiently smooth functions describing boundary and initial values respectively. The data...journal article 2022
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van Zwieten, GJ (author), van Brummelen, E. Harald (author), Hanssen, R.F. (author)Earthquakes cause lasting changes in static equilibrium, resulting in global deformation fields that can be observed. Consequently, deformation measurements such as those provided by satellite based InSAR monitoring can be used to infer an earthquake's faulting mechanism. This inverse problem requires a numerical forward model that is both...journal article 2022
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van der Jagt, Thomas (author)For modelling microstructures of materials the Voronoi diagram is one of the most commonly used models. In this thesis we study a generalization of Voronoi diagrams known as the Laguerre-Voronoi diagram. In particular, we consider the stereological problem of estimating the 3D cell volume distribution of such a diagram from one of its 2D planar...master thesis 2021
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Abdi, Bahareh (author)Atrial fibrillation (AF) is a common age-related cardiac arrhythmia. AF is characterized by rapid and irregular electrical activity of the heart leading to a higher risk of stroke and heart failure. During AF, the upper chambers of the heart, called atria, experience chaotic electrical wave propagation. However, despite the various mechanisms...doctoral thesis 2021
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Flaschel, Moritz (author), Kumar, Siddhant (author), De Lorenzis, Laura (author)We propose a new approach for data-driven automated discovery of isotropic hyperelastic constitutive laws. The approach is unsupervised, i.e., it requires no stress data but only displacement and global force data, which are realistically available through mechanical testing and digital image correlation techniques; it delivers interpretable...journal article 2021
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Fuchs, P.S. (author)Electrical properties, the conductivity and permittivity of tissue, are quantities that describe the interaction of an object and electromagnetic fields. These properties influence electromagnetic fields and are influenced themselves by physiological phe- nomena such as lesions or a stroke. Therefore, they are important in identifying or...doctoral thesis 2020
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van Rooij, J. (author)Optical imaging is the imaging of objects with visible light. It is a tool often used for diagnostic purposes, such as in biomedical and material sciences. Digital holography is an optical imaging technique that captures and images the amplitude as well as the phase (the complex amplitude) of the lightwave. An advantage is that the complex...doctoral thesis 2020
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Jongbloed, G. (author), Mc Garrity, K.S. (author), Sietsma, J. (author)Kernel estimators are proposed for estimating the cumulative distribution functions and the probability density functions of several quantities of interest in a stereological oriented cylinder model. This oriented cylinder model was developed to represent anisotropic microstructural features in materials. The asymptotic properties of these...journal article 2020
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Shachor, Benny (author)Understanding the permeability of the subsurface is a crucial step to simulate fluid flow in the subsurface. A parameter estimation problem for the flow equations can be solved to find the permeability. The robust identification of material parameters remains a significant challenge. In classical approaches, the non-linear least-squares problem...master thesis 2019
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van den Brink, Robbert-Jan (author)Mines and improvised explosive devices are the cause of many mortalities of vehicle occupants. Both experimental and numerical research in this field aims to improve the safety of military vehicles. TNO has advanced Finite Element (FE) models to simulate such events. The numerical research is done to better understand mine blasts. Another aim is...master thesis 2019
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Nickl, Richard (author), Söhl, J. (author)We study nonparametric Bayesian statistical inference for the parameters governing a pure jump process of the form (Formula Presented) where N(t) is a standard Poisson process of intensity λ, and Z <sub>k</sub> are drawn i.i.d. from jump measure μ. A high-dimensional wavelet series prior for the Lévy measure ν = λμ is devised and the...journal article 2019
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Sun, S. (author), Kooij, B.J. (author), Yarovoy, Alexander (author)In this paper, the generalized multiple measurement vectors (GMMV) linear inversion method is applied to the reconstruction of the 3-D Fresnel data, provided by the Institue Fresnel (Marseille, France). The results show that the GMMV-based method can obtain good resolution along the x- and y- axes, while poor resolution along the z-axis,...conference paper 2019
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Abdi, Bahareh (author), Hendriks, R.C. (author), van der Veen, A.J. (author), de Groot, Natasja M.S. (author)Finding the hidden parameters of the cardiac electrophysiological model would help to gain more insight on the mechanisms underlying atrial fibrillation, and subsequently, facilitate the diagnosis and treatment of the disease in later stages. In this work, we aim to estimate tissue conductivity from recorded electrograms as an indication of...journal article 2019
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Naghibzadeh, S. (author)Fundamental scientific questions such as how the first stars were formed or how the universe came into existence and evolved to its present state drive us to observe weak radio signals impinging on the earth from the early days of the universe. During the last century, radio astronomy has been vastly advancing. Important discoveries on the...doctoral thesis 2018
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Thota Radhakrishnan, A.K. (author), van Lier, J.B. (author), Clemens, F.H.L.R. (author)Information on the rheology of domestic slurries is essential in designing pipeline transportation in novel sanitation systems. As concentrated slurries in their original collected state have wide particle size distribution, with particles up to 2 mm, a wide gap rheometer is used to acquire the rheograms. Rheograms obtained from a wide gap...journal article 2018