Searched for: subject%3A%22Spherical%255C+harmonics%22
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Subramani, Surya Natarajan (author)
Radiation pattern measurements is a critical step in characterizing antennas before they are used in any system for a specific application. To identify any defects or to acquire the true radiation characteristics of the antenna under test, densely sampled measurements are desired. However, this results in a time and cost expensive measurement...
master thesis 2023
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Ditmar, P.G. (author)
A novel technique has been developed to assess noise levels in GRACE-based mass anomaly time-series when the true signal is not known. The technique is based on computing an optimal combination of analyzed time-series in the presence of a regularization. To find the optimal weights associated with individual time-series, variance component...
journal article 2022
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Fleuren, Jules (author)
Vector spherical harmonics are a set of basis functions for vector fields derived from the spherical harmonic functions. They are commonly used in spectral methods in certain areas of applied mathematics. In most of the existing literature they are defined in a way that is heavily dependent on the used coördinate system. In this thesis we define...
bachelor thesis 2021
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Zuo, Y. (author)
Alkali-activated materials (AAMs) show promising potentials for use as building materials. Before the utilization, AAMs must satisfy the properties required from the construction sector, such as good durability and long-term service life. These properties mainly depend on the chemical and physical properties of the microstructure of AAMs. In the...
doctoral thesis 2019
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Wervers, Jurgen (author), van Nifterik, Bob (author)
This document describes the design process the prototype of a measurement light bulb which is able to project spherical harmonics of orders 0-1-2. Photographs of these projections can be combined to represent many light distributions. The measurement light bulb can be used in the field of research focused on the computation of the illumination...
bachelor thesis 2019
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van der Werf, Ids (author), Jordan, Sebastian (author)
This document describes the design process the prototype of a measurement light bulb which is able to project spherical harmonics of orders 0-1-2. Photographs of these projections can be combined to represent many light distributions. The measurement light bulb can be used in the field of research focused on the computation of the illumination...
bachelor thesis 2019
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Damsteegt, Rob (author), van Dunné, Jippe (author)
This document describes the design process the prototype of a measurement light bulb which is able to project spherical harmonics of orders 0-1-2. Photographs of these projections can be combined to represent many light distributions. The measurement light bulb can be used in the field of research focused on the computation of the illumination...
bachelor thesis 2019
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Ragunathan, CS (author)
A study has been conducted on the application of Spherical Harmonics based Statistical Shape Modelling for Image Segmentation. This study is focused on the segmentation of Wrist bones using the above mentioned technique.
master thesis 2019
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van Oosterom, Simon (author)
In this thesis we consider the reconstruction of albedo maps of exoplanets. This is done with a new variant of spin-orbit tomography that has been described in [Cowan and Agol, 2008] and more in depth in [Fujii and Kawahara, 2012]. This method reconstructs the albedo map from the reflected-light curve, the total intensity of the light that...
bachelor thesis 2019
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Dirkx, D. (author), Mooij, E. (author), Root, B.C. (author)
Next-generation planetary tracking methods, such as interplanetary laser ranging (ILR) and same-beam interferometry (SBI) promise an orders-of-magnitude increase in the accuracy of measurements of solar system dynamics. This requires a reconsideration of modelling strategies for the translational and rotational dynamics of natural bodies, to...
journal article 2019
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Pail, R. (author), Bamber, J. (author), Biancale, R. (author), Bingham, R. (author), Braitenberg, C. (author), Flechtner, F. (author), Gruber, T. (author), Güntner, A. (author), Savenije, Hubert (author)
As changes in gravity are directly related to mass variability, satellite missions observing the Earth's time varying gravity field are a unique tool for observing mass transport processes in the Earth system, such as the water cycle, rapid changes in the cryosphere, oceans, and solid Earth processes, on a global scale. The observation of...
journal article 2019
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Ditmar, P.G. (author)
Time-varying Stokes coefficients estimated from GRACE satellite data are routinely converted into mass anomalies at the Earth’s surface with the expression proposed for that purpose by Wahr et al. (J Geophys Res 103(B12):30,205–30,229, 1998). However, the results obtained with it represent mass transport at the spherical surface of 6378 km...
journal article 2018
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Nardi, Alex (author)
This research aims at modeling the trajectory followed by the Galileo spacecraft during a variety of flybys about the Galilean moons. The chosen flybys have good Earth’s elevation angles and either low or high closest-approach altitudes, so that the comparison of the two can give relevant insight into the accuracy of the corresponding...
master thesis 2017
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Root, B.C. (author), Novak, P. (author), Dirkx, D. (author), Kaban, M. (author), van der Wal, W. (author), Vermeersen, L.L.A. (author)
This article reviews a spectral forward gravity field modelling method that was initially designed for topographic/isostatic mass reduction of gravity data. The method transforms 3D spherical density models into gravitational potential fields using a spherical harmonic representation. The binomial series approximation in the approach, which...
journal article 2016
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Feng, J. (author), Noomen, R. (author), Visser, P.N.A.M. (author), Yuan, J. (author)
The existence and characteristics of periodic orbits (POs) in the vicinity of a contact binary asteroid are investigated with an averaged spherical harmonics model. A contact binary asteroid consists of two components connected to each other, resulting in a highly bifurcated shape. Here, it is represented by a combination of an ellipsoid and a...
journal article 2015
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Caratelli, D. (author), Gielis, J. (author), Tavkhelidze, I. (author), Ricci, P.E. (author)
The Robin problem for the Helmholtz equation in normal-polar shells is addressed by using a suitable spherical har-monic expansion technique. Attention is in particular focused on the wide class of domains whose boundaries are de-fined by a generalized version of the so-called “superformula” introduced by Gielis. A dedicated numerical procedure...
journal article 2013
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Dilsiz, G. (author)
The shape of aggregates has significant effect on the concrete properties. To predict these properties with computational models the mathematically characterized shape has to be known. In the past, scientists assumed simple shapes like spheres and ellipsoids. To make models more realistic, aggregate shapes has to be also more realistic. X-ray...
bachelor thesis 2011
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Tenzer, R. (author), Novak, P. (author), Vajda, P. (author)
We derive expressions for computing the gravitational field (potential and its radial derivative) generated by an arbitrary homogeneous or laterally varying density contrast layer with a variable depth and thickness based on methods for a spherical harmonic analysis and synthesis of gravity field. The newly derived expressions are utilised in...
journal article 2011
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Han, S.C. (author), Ditmar, P. (author)
A spatiospectral localization method is discussed for processing the global geopotential coefficients from satellite mission data to investigate time-variable gravity. The time-variable mass variation signal usually appears associated with a particular geographical area yielding inherently regional structure, while the dependence of the...
journal article 2007
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Schrama, E.J.O. (author), Wouters, B. (author), Lavallée, D.A. (author)
The Gravity Recovery and Climate Experiment (GRACE) product used for this study consists of 43 monthly potential coefficient sets released by the GRACE science team which are used to generate surface mass thickness grids expressed as equivalent water heights (EQWHs). We optimized both the smoothing radius and the level of approximation by...
journal article 2007
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