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Sun, M. (author)Atrial fibrillation (AF) is a frequently encountered cardiac arrhythmia characterized by rapid and irregular atrial activity, which increases the risk of strokes, heart failure and other heart-related complications. The mechanisms of AF are complicated. Although various mechanisms were proposed in previous research, the precise mechanisms of AF...doctoral thesis 2022
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Altiparmaki, O. (author), Kleinherenbrink, M. (author), Naeije, M.C. (author), Slobbe, D.C. (author), Visser, P.N.A.M. (author)This article shows the first spectral analysis of fully-focused Synthetic Aperture Radar (FFSAR) altimetry data with the objective of studying backscatter modulations caused by swells. Swell waves distort the backscatter in altimetry radargrams by means of velocity and range bunching. These swell signatures are visible in the tail of the...journal article 2022
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Sun, M. (author), Isufi, E. (author), de Groot, N.M.S. (author), Hendriks, R.C. (author)Atrial fibrillation is a clinical arrhythmia with multifactorial mechanisms still unresolved. Time-frequency analysis of epicardial electrograms has been investigated to study atrial fibrillation. However, deeper understanding can be achieved by incorporating the spatial dimension. Unfortunately, the physical models describing the spatial...journal article 2020
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Cheng, L. (author), Xin, H. (author), Groves, R.M. (author), Veljkovic, M. (author)S460 steel is increasingly used in civil engineering, especially in a harsh environment such as offshore structures [1]. Material damage is inevitable for structures subjected to static and dynamic loads during their technical life time. Thus, monitoring material damage is important for providing information regarding critical damage of in...abstract 2020
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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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Qian, Cheng (author), Fan, Jiajie (author), Fan, Xuejun (author), Zhang, Kouchi (author)The spectral power distribution (SPD) is considered as the figureprint of a light emitting diode (LED). Based on the analysis on its SPD, a method to predict both lumen depreciation and color shift for the phosphor converted white LEDs (pc-LEDs) is proposed in this paper. First, the entire SPD of a pc-LED is predicted by superimposing two...journal article 2017
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Bni Lam, N.H.N. (author), Al-Khoury, Rafid (author)This paper introduces a semi-analytical model for the simulation of transient heat transfer with friction heat gain in a single U-tube geothermal borehole heat exchanger subjected to an arbitrary heat flux signal. The friction effect appears as a nonhomogeneous term in the governing equations, which constitutes a set of coupled partial...journal article 2016
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Al-Khoury, Rafid (author), Focaccia, S. (author)This paper introduces a semi-analytical model based on the spectral analysis method for the simulation of transient conductive-convective heat flow in an axisymmetric shallow geothermal system consisting of a double U-tube borehole heat exchanger embedded in a soil mass. The proposed model combines the exactness of the analytical methods with...journal article 2016
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Van Hoek, Mattijn (author), Jia, Li (author), Zhou, J. (author), Zheng, Chaolei (author), Menenti, M. (author)The time lag between anomalies in precipitation and vegetation activity plays a critical role in early drought detection as agricultural droughts are caused by precipitation shortages. The aim of this study is to explore a new approach to estimate the time lag between a forcing (precipitation) and a response (NDVI) signal in the frequency...journal article 2016
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Minato, S. (author), Ghose, R. (author)Using the scattered elastic wavefield, a method to derive the power spectral density (PSD) of the heterogeneous compliance distribution, along the plane of a single fracture, is formulated. The method involves estimation of the stress field at the fracture depth from the scattered wavefield followed by least-squares optimization of the PSD of...journal article 2014
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Broersen, P.M.T. (author)The use of time series models for irregular data requires resampling of the data on an equidistant grid. Slotted resampling transforms an irregular randomly sampled process into an equidistant signal where data are missing. An approximate maximum-likelihood time series estimator has been developed to estimate the power spectral density and the...journal article 2009
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Broersen, P.M.T. (author)Spectra with narrow valleys can accurately be described with moving-average (MA) models by using only a small number of parameters. Durbin's MA method uses the estimated parameters of a long autoregressive (AR) model to calculate the MA parameters. Probably all the pejorative remarks on the quality of Durbin's method in the literature are based...journal article 2009
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- Sydney, A. (author), Schumm, P. (author), Scoglio, C. (author), Kooij, R.E. (author) conference paper 2008
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Groenevelt, W. (author)Big q-Jacobi functions are eigenfunctions of a second-order q-difference operator L. We study L as an unbounded self-adjoint operator on an L-2-space of functions on R with a discrete measure. We describe explicitly the spectral decomposition of L using an integral transform F with two different big q-Jacobi functions as a kernel, and we...journal article 2008
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- Verdoold, J. (author), Van Reeuwijk, M. (author), Tummers, M.J. (author), Jonker, H.J. (author), Hanjalic, K. (author) journal article 2008
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Tang, J.M. (author), Vuik, C. (author)Simulating bubbly flows is a very popular topic in CFD. These bubbly flows are governed by the Navier-Stokes equations. In many popular operator splitting formulations for these equations, solving the linear system coming from the discontinuous diffusion equation takes the most computational time, despite of its elliptic origins. Sometimes these...conference paper 2006
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Tang, J.M. (author), Vuik, C. (author)Simulating bubbly flows is a very popular topic in CFD. These bubbly flows are governed by the Navier-Stokes equations. In many popular operator splitting formulations for these equations, solving the linear system coming from the discontinuous diffusion equation takes the most computational time, despite of its elliptic origins. Sometimes these...conference paper 2006
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Hasnaoui, M. (author)The influence of Coriolis forces is studied under realistic conditions on a jet in atmospheric medium. Under the Boussinesq approximation, the relative thickness of the jet defines a small parameter in the flow. This parameter governs the asymptotic expansion of the analysis. Using a linear spectral approach, two-point closure correlation...conference paper 2006
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Kavelin, K.G. (author)This work is carried out within a university project, which is focused on the life cycle efficiency of products. This project is conducted because of the growing interest towards environmental protection, which requires a sustainable development of the industrial progress. A Dutch-EVO concept car was taken as a vehicle for the research within...doctoral thesis 2005
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Tang, J.M., (author), Vuik, C. (author)In this report we give new insights into the properties of invertible and singular deflated and preconditioned linear systems where the coefficient matrices are also symmetric and positive (semi-) definite. First we prove that the invertible de ated matrix has always a more favorable effeective condition number compared to the original matrix....report 2005
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