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Swart, Céline (author)The transverse flute can be studied on many aspects. In this thesis the sound waves that can be generated inside the flute are studied on their shape and frequencies. To achieve this, two mathematical models of the sound waves inside a flute are developed. To develop these models, solutions to the second dimensional wave equation are calculated...bachelor thesis 2022
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van Ooijen, Cas (author)This thesis is about the wave equation. The wave equation describes waves that propagate through a certain medium. The solution of the wave equation is a mathematical description of what that wave looks like. There are many fields of study where the wave equation is used to model processes that behave like travelling waves. For instance, a...bachelor thesis 2022
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Steinbach, Olaf (author), Urzúa-Torres, Carolina (author)We present a new approach for boundary integral equations for the wave equation with zero initial conditions. Unlike previous attempts, our mathematical formulation allows us to prove that the associated boundary integral operators are continuous and satisfy inf-sup conditions in trace spaces of the same regularity, which are closely related...journal article 2022
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Mulder, W.A. (author)When solving the wave equation with finite elements, mass lumping allows for explicit time stepping, avoiding the cost of a lower-upper decomposition of the large sparse mass matrix. Mass lumping on the reference element amounts to numerical quadrature. The weights should be positive for stable time stepping and preserve numerical accuracy....journal article 2022
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Marynets, Vasyl (author), Marynets, K. (author), Kohutych, Oksana (author)We study a boundary value problem for nonlinear partial differential equations of the hyperbolic type on the plain in a domain with a complex boundary. To find the missing data for the given boundary constraints, we solve a supplementary nonlinear problem. For the approximation of solutions, one constructive method is built.journal article 2021
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Wapenaar, C.P.A. (author), Brackenhoff, J.A. (author), Dukalski, Marcin (author), Meles, G.A. (author), Slob, E.C. (author), Staring, M. (author), Thorbecke, J.W. (author), van der Neut, J.R. (author), Zhang, L. (author), Reinicke Urruticoechea, C. (author)With the Marchenko method it is possible to retrieve Green's functions between virtual sources in the subsurface and receivers at the surface from reflection data at the surface and focusing functions. A macro model of the subsurface is needed to estimate the first arrival; the internal multiples are retrieved entirely from the reflection data....journal article 2021
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Missula, Sharanya (author)Vibrations or oscillations can be caused in overhead cable lines or bridge cables due to strong rain and winds, making the structure unstable.These vibrations can be mathematically described as a string like initial boundary value problem with non-classical boundary conditions. In this thesis, we consider a nonlinear attachment at the boundary...master thesis 2020
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Waasdorp, Britt (author)In this thesis the nonlinear spring system is considered. This system contains a semi-infinite string that is modelled by the wave equation with a pair of inititial conditions and a nonlinear boundary condition. The goal of this thesis is to find a good approximation of this system. Furthermore, the behaviour of the string is studied by plotting...bachelor thesis 2020
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Csobo, E. (author)This dissertation addresses the local-well posedness, singularity formation, and orbital stability of standing waves to inhomogeneous nonlinear dispersive equations. Inhomogeneous equations are equations with space-dependent coe <br/>cients, which account for the impurities of the propagating media or the presence of an outer potential. Despite...doctoral thesis 2019
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Eppenga, Eric (author)The multi-pole PML (MPML) is tested on models that simulate seismic waves traveling through the subsurface. Using a recursive integration technique a stretching function consisting of the sum of multiple stretching functions is implemented in the velocity-stress finite difference time domain wave equations. The MPML is implemented in both the...master thesis 2019
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Geevers, S. (author), Mulder, W.A. (author), van der Vegt, J (author)We present a new accuracy condition for constructing mass-lumped elements. This condition is less restrictive than the one previously used and enabled us to construct new mass-lumped tetrahedral elements for 3D wave propagation modelling. The new degree-2 and degree-3 elements require significantly fewer nodes than previous versions and mass...abstract 2019
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Baumann, M.M. (author), van Gijzen, M.B. (author)We consider wave propagation problems that are modeled in the frequency-domain, and that need to be solved simultaneously for multiple frequencies within a fixed range. For this, a single shift-and-invert preconditioner at a so-called seed frequency is applied. The choice of the seed is crucial for the performance of preconditioned multi...journal article 2019
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Geevers, S. (author), Mulder, W.A. (author), van der Vegt, J.J.W. (author)We present new and efficient quadrature rules for computing the stiffness matrices of mass-lumped tetrahedral elements for wave propagation modeling. These quadrature rules allow for a more efficient implementation of the mass-lumped finite element method and can handle materials that are heterogeneous within the element without loss of the...journal article 2019
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Geevers, S. (author), Mulder, W.A. (author), van der Vegt, J. J.W. (author)We analyse the dispersion properties of two types of explicit finite element methods for modelling acoustic and elastic wave propagation on tetrahedral meshes, namely mass-lumped finite element methods and symmetric interior penalty discontinuous Galerkin methods, both combined with a suitable Lax–Wendroff time integration scheme. The...journal article 2018
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Ergin, Mert (author)The thesis project is aimed at designing an unobtrusive method to find the obstruction location and severity for patients who are not diagnosed with Obstructive sleep apnea, during their non-sedated sleep using simple recording devices within uncontrolled environment. Similar to speech generation, which is enabled by opening and closing of the...master thesis 2018
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Godefrooij, Roos (author)Agragrians in the Dutch Wadden sea region struggles with salinizing farmlands. Acacia Water's project Spaarwater enabled agrarians to measure salt concentrations in the ditches of their land using their mobile phone. All these measurements would ideally be used to evaluate the effects of salinization mitigation measures and to predict water...master thesis 2018
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Baumann, M.M. (author)Seismic Full-Waveform Inversion is an imaging technique to better understand the earth's subsurface. Therefore, the reflection intensity of sound waves is measured in a field experiment and is matched with the results from a computer simulation in a least-squares sense. From a computational point-of-view, but also from an economic view point,...doctoral thesis 2018
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Baumann, M.M. (author), van Gijzen, M.B. (author)In this paper we present a comparison study of three different frameworks of iterative Krylov methods that we have recently developed for the simultaneous numerical solution of frequency-domain wave propagation problems when multiple wave frequencies are present. The three approaches have in common that they require the application of a...journal article 2018
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Baumann, M.M. (author), Astudillo Rengifo, R.A. (author), Qiu, Y. (author), Ang, Y.M.E. (author), van Gijzen, M.B. (author), Plessix, R.E. (author)In this work, we present a new numerical framework for the efficient solution of the time-harmonic elastic wave equation at multiple frequencies. We show that multiple frequencies (and multiple right-hand sides) can be incorporated when the discretized problem is written as a matrix equation. This matrix equation can be solved efficiently...journal article 2018
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Rozendaal, J. (author), Veraar, M.C. (author)We study growth rates for strongly continuous semigroups. We prove that a growth rate for the resolvent on imaginary lines implies a corresponding growth rate for the semigroup if either the underlying space is a Hilbert space, or the semigroup is asymptotically analytic, or if the semigroup is positive and the underlying space is an (Formula...journal article 2018