المؤلفون: Stender, Merten, Ohlsen, Jakob, Geisler, Hendrik, Chabchoub, Amin, Hoffmann, Norbert, Schlaefer, Alexander

المصدر: Computational Mechanics 71 (2023), Nr. 6 ; Computational Mechanics

مصطلحات موضوعية: Machine learning, Partial differential equations, Representation learning, Sensor data fusion, Time integration, Wave propagation, ddc:530, ddc:004

الوصف: In the age of big data availability, data-driven techniques have been proposed recently to compute the time evolution of spatio-temporal dynamics. Depending on the required a priori knowledge about the underlying processes, a spectrum of black-box end-to-end learning approaches, physics-informed neural networks, and data-informed discrepancy modeling approaches can be identified. In this work, we propose a purely data-driven approach that uses fully convolutional neural networks to learn spatio-temporal dynamics directly from parameterized datasets of linear spatio-temporal processes. The parameterization allows for data fusion of field quantities, domain shapes, and boundary conditions in the proposed Up-Net architecture. Multi-domain Up-Net models, therefore, can generalize to different scenes, initial conditions, domain shapes, and domain sizes without requiring re-training or physical priors. Numerical experiments conducted on a universal and two-dimensional wave equation and the transient heat equation for validation purposes show that the proposed Up-Net outperforms classical U-Net and conventional encoder–decoder architectures of the same complexity. Owing to the scene parameterization, the Up-Net models learn to predict refraction and reflections arising from domain inhomogeneities and boundaries. Generalization properties of the model outside the physical training parameter distributions and for unseen domain shapes are analyzed. The deep learning flow map models are employed for long-term predictions in a recursive time-stepping scheme, indicating the potential for data-driven forecasting tasks. This work is accompanied by an open-sourced code.

العلاقة: ESSN:1432-0924; http://dx.doi.org/10.15488/14757Test; https://www.repo.uni-hannover.de/handle/123456789/14876Test

الإتاحة: https://doi.org/10.15488/14757Test
https://doi.org/10.1007/s00466-023-02295-xTest
https://www.repo.uni-hannover.de/handle/123456789/14876Test

المؤلفون: Sandmann, Sergei, Garbe, Heyno

المصدر: Advances in Radio Science 17 (2019)

مصطلحات موضوعية: Electric utilities, Electromagnetic waves, Omnidirectional antennas, Wave propagation, Wind power, Wind turbines, Antenna characteristics, Large buildings, Navigation aids, Navigation service, Omni-directional radios, Operation range, Scattering objects, ddc:620

الوصف: Radio navigation aids, like the Doppler Very High Frequency Omnidirectional Radio Range (DVOR), provide their navigation service by specific radiation of electromagnetic waves depending on the direction in space and according to their specific antenna characteristics. Therefore, these navigation aids are reliant on undisturbed wave propagation in their operation range. Certainly, a propagation disturbance can be implicated by the presence of scattering objects like large buildings or wind turbines (WT) in the surrounding area of the DVOR, which potentially leads to deviations of the transmitted navigation content. In order to comply with the specified flight safety limits, especially respecting WTs, there is a necessity to predict the prospective bearing error due to installations not only of individual WTs but also of additional ones in a present wind farm or repowering projects. Accordingly, this paper is aimed at ascertaining the bearing deviations' dependency on the quantity of WTs in a realistic wind farm close to a DVOR, calculated in space areas of practical relevance.

العلاقة: http://dx.doi.org/10.15488/8800Test; https://www.repo.uni-hannover.de/handle/123456789/8853Test

الإتاحة: https://doi.org/10.15488/8800Test
https://doi.org/10.5194/ars-17-11-2019Test
https://www.repo.uni-hannover.de/handle/123456789/8853Test

المؤلفون: Kunitski, Maksim, Eicke, Nicolas, Huber, Pia, Köhler, Jonas, Zeller, S., Voigtsberger, J., Schlott, Nikolai, Henrichs, Kevin, Sann, H., Trinter, F., Schmidt, L., Kalinin, Anton, Schöffler, M., Jahnke, T., Lein, Manfred, Dörner, R.

المصدر: Nature Communications 10 (2019), Nr. 1

مصطلحات موضوعية: Quantum decoherence, Ion, Electron, Molecular biology, Interference (wave propagation), Atomic physics, Ionization, Field desorption, Laser, Neon, Biology, ddc:500

الوصف: Wave-particle duality is an inherent peculiarity of the quantum world. The double-slit experiment has been frequently used for understanding different aspects of this fundamental concept. The occurrence of interference rests on the lack of which-way information and on the absence of decoherence mechanisms, which could scramble the wave fronts. Here, we report on the observation of two-center interference in the molecular-frame photoelectron momentum distribution upon ionization of the neon dimer by a strong laser field. Postselection of ions, which are measured in coincidence with electrons, allows choosing the symmetry of the residual ion, leading to observation of both, gerade and ungerade, types of interference.

العلاقة: http://dx.doi.org/10.15488/5174Test; https://www.repo.uni-hannover.de/handle/123456789/5221Test

الإتاحة: https://doi.org/10.15488/5174Test
https://doi.org/10.1038/s41467-018-07882-8Test
https://www.repo.uni-hannover.de/handle/123456789/5221Test

المؤلفون: Pham, Hoang Duc, Ploennigs, Soeren, Mathis, Wolfgang

المصدر: Advances in Radio Science 16 (2018)

مصطلحات موضوعية: Computation theory, Electromagnetic wave propagation, Electromagnetic waves, Maxwell equations, Numerical methods, Optical waveguides, Analytic solution, Coupled mode theory, General theory, Model and simulation, Propagation constant, Propagation of electromagnetic waves, Transmission medium, Transverse field, Circular waveguides, ddc:530

الوصف: This paper deals with the propagation of electromagnetic waves in cylindrical waveguides with irregularly deformed cross-sections. The general theory of electromagnetic waves is of high interest because of its practical use as a transmission medium. But only in a few special cases, an analytic solution of Maxwell's equations and the appropriate boundary conditions can be found (Spencer 1951). The coupled-mode theory, also known as Schelkunoff's method, is a semi-numerical method for computing electromagnetic waves in hollow and cylindrical waveguides bounded by perfect electric walls (Saad 1985). It allows to calculate the transverse field pattern and the propagation constant. The aim of this paper is to derive the so-called generalized telegraphist's equations for irregular deformed waveguides. Subsequently, the method's application will be used on a circular waveguide as an illustrating example.

العلاقة: http://dx.doi.org/10.15488/4263Test; https://www.repo.uni-hannover.de/handle/123456789/4297Test

الإتاحة: https://doi.org/10.15488/4263Test
https://doi.org/10.5194/ars-16-35-2018Test
https://www.repo.uni-hannover.de/handle/123456789/4297Test

المؤلفون: David, C. Gabriel, Roeber, Volker, Goseberg, Nils, Schlurmann, Torsten

المصدر: Coastal Engineering 127 (2017)

مصطلحات موضوعية: Coastal engineering, Ships, Wave propagation, Boussinesq-type equations, Boussinesq-type models, Depth-averaged equations, Irregular bathymetries, Kelvin wedge, Ship waves, Surrounding environment, Waterway infrastructure, Water waves, Vessel wake, Waterway and port engineering, ddc:720, ddc:620

الوصف: Ship-borne waves are of significant interest for the design of port and waterway infrastructure and the maintenance of its surrounding environment. Computation of these nonlinear and dispersive waves has mainly been focusing on their near-field generation as a fluid-body interaction problem. This study presents an approach for the computation of ship waves generated by a moving pressure disturbance with phase-resolving and depth-averaged equations. To support a wide range of applicability, the paper deals with the evolution of the vessel wedge compared to an analytical solution for sub-to supercritical speeds and the assessment of wave patterns from a broad range of pressure term dimensions, including cross-references to findings in other studies. The conducted numerical experiments showcase the typical response of a Boussinesq-type model to a simplified moving pressure disturbance and identify the main factors and criteria for ship-wave propagation in the far-field of a vessel. Finally, a unique field dataset underlines the capability of an extended Boussinesq-type model to compute the propagation of vessel waves over an irregular bathymetry. ; Hamburg Port Authority (HPA) ; Japanese Society for the Promotion of Sciences (JSPS) ; EC/FP7/Marie Curie International Outgoing Fellowship

العلاقة: http://dx.doi.org/10.15488/1793Test; http://www.repo.uni-hannover.de/handle/123456789/1818Test

الإتاحة: https://doi.org/10.15488/1793Test
https://doi.org/10.1016/j.coastaleng.2017.07.001Test
http://www.repo.uni-hannover.de/handle/123456789/1818Test

المؤلفون: Lokesha, Kerpen, Nils B., Sannasiraj, S.A., Sundar, V., Schlurmann, Torsten

المصدر: Procedia Engineering 116 (2015), Nr. 1

مصطلحات موضوعية: Relative depth of submergence of breakwater, Transmission, Coastal engineering, Energy dissipation, Floating breakwaters, Shore protection, Transmissions, Water waves, Wave energy conversion, Wave propagation, Wave transmission, Breakwater height, Coastal protection, Experimental investigations, Incident wave energy, Relative breakwater width, Submerged breakwater, Two-dimensional waves, Wave energy dissipation, Breakwaters, ddc:570, Konferenzschrift

الوصف: Submerged breakwaters are gaining more popularity as a potential coastal protection structure resulting in moderate wave transmission with significant wave energy dissipation. Submerged breakwaters are mainly adopted to prevent erosion and to dissipate the incident wave energy. In addition, the premature wave breaking facilitates the wave surfing activities by proper designing of submerged breakwater. In the present study, the experiments are conducted on submerged breakwaters in a two dimensional wave flume to investigate the influence of stepped and smooth front slope of the submerged breakwater, its height and width in reducing wave energy. A total number of eighteen sets of experiments has been conducted for three different breakwater heights (31cm, 28cm and 26cm) and three different breakwater widths (10cm, 20cm and 30cm) with stepped and smooth front slope of breakwater. The submerged breakwater models are subjected to regular waves of four different wave heights and five different wave periods in a constant water depth of 31cm, to determine wave transmissions characteristics. The influence of relative breakwater width, relative depth of submergence of the breakwater and roughness of breakwater front slope on wave transmission are analyzed and discussed in this paper. ; DAAD

العلاقة: http://dx.doi.org/10.15488/867Test; http://www.repo.uni-hannover.de/handle/123456789/891Test

الإتاحة: https://doi.org/10.15488/867Test
https://doi.org/10.1016/j.proeng.2015.08.356Test
http://www.repo.uni-hannover.de/handle/123456789/891Test

المؤلفون: Sriram, V., Didenkulova, I., Schimmels, Stefan, Sergeeva, A., Goseberg, Nils

المصدر: Proceedings of the Coastal Engineering Conference (2014)

مصطلحات موضوعية: Elongated solitons, Large-scale experimental facility, Long wave dynamics, Numerical simulation, Propagation, Run-up, Coastal engineering, Computer simulation, Nonlinear equations, Numerical models, Wave propagation, Experimental facilities, Fully nonlinear potential flow, KdV equations, Large wave flumes, Long waves, Nearshores, Nonlinear shallow water, Solitons, ddc:500, ddc:550, ddc:510, Konferenzschrift

الوصف: This paper discusses the possibility to study propagation, shoaling and run-up of these waves over a slope in a 300-meter long large wave flume (GWK), Hannover. For this purpose long bell-shaped solitary waves (elongated solitons) of different amplitude and the same period of 30 s are generated. Experimental data of long wave propagation in the flume are compared with numerical simulations performed within the fully nonlinear potential flow theory and KdV equations. Shoaling and run-up of waves on different mild slopes is studied hypothetically using nonlinear shallow water theory. Conclusions about the feasibility of using large scale experimental facility (GWK) to study tsunami wave propagation and run-up are made. ; Alexander von Humboldt foundation ; RFBR/14-02-00983 ; RFBR/14-05-00092

العلاقة: http://dx.doi.org/10.15488/896Test; http://www.repo.uni-hannover.de/handle/123456789/920Test

الإتاحة: https://doi.org/10.15488/896Test
http://www.repo.uni-hannover.de/handle/123456789/920Test

المؤلفون: Sukhodub, G., Hohls, Frank, Haug, Rolf J.

المصدر: Physical Review Letters 93 (2004), Nr. 19

مصطلحات موضوعية: Electric charge, Electric excitation, Electric potential, Electron gas, Frequencies, Heterojunctions, Magnetoplasma, Quantum efficiency, Semiconducting gallium arsenide, Velocity measurement, Edge magnetoplasmon (EMP), Edge structure, Incident voltage pulse, Two-dimensional elecytron gas, Wave propagation, ddc:530

الوصف: The propagation of edge magnetoplasmons (EMP) in a degenerated two-dimensional electron gas was analyzed. Investigations show that an interedge EMP mode attributed to the excitations of boundary between two regions with constant but different charge densities. The splitting of an incident voltage pulse into several EMP modes propagating with different velocities was also observed. The results show that the internal spatial parameters of the edge structure were derived from the analysis of the propagation velocities of each mode.

العلاقة: http://dx.doi.org/10.15488/2890Test; http://www.repo.uni-hannover.de/handle/123456789/2916Test

الإتاحة: https://doi.org/10.15488/2890Test
https://doi.org/10.1103/PhysRevLett.93.196801Test
http://www.repo.uni-hannover.de/handle/123456789/2916Test

المؤلفون: Sabath, F., Garbe, Heyno

المصدر: Advances in Radio Science 1 (2003)

مصطلحات موضوعية: Equipment under tests, Frequency domain estimation, Impulse radiation antennas, Near field effect, Near-field dispersions, Susceptibility tests, Transient radiation, Waveform parameters, Wave propagation, Antennas, ddc:621,3

الوصف: This paper considers the effect of changes of the waveform parameters over the distance. The objective is to show the near field effects on transient radiation and how near the equipment under test can be located to an antenna without significant changes of the width or rise time of the field pulse. It is shown that the well known frequency domain estimation models fail because the dimension of antenna systems and the wave propagation lead to a special kind of dispersion. The importance of this near field dispersion for practical applications is demonstrated by both theoretical considerations and measurements with a half impulse radiation antenna.

العلاقة: http://dx.doi.org/10.15488/1575Test; http://www.repo.uni-hannover.de/handle/123456789/1600Test

الإتاحة: https://doi.org/10.15488/1575Test
https://doi.org/10.5194/ars-1-43-2003Test
http://www.repo.uni-hannover.de/handle/123456789/1600Test