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Articoli di riviste sul tema "Waves topology"

Autore: Grafiati

Pubblicato: 14 settembre 2024

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1

BUĞDAYCI, NECMI. "SCALAR WAVES IN A WORMHOLE TOPOLOGY". International Journal of Modern Physics D 15, n. 05 (maggio 2006): 669–93. http://dx.doi.org/10.1142/s0218271806008395.

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Global monochromatic solutions of the scalar wave equation are obtained in flat wormholes of dimensions (2+1) and (3+1). The solutions are in the form of infinite series involving cylindrical and spherical wave functions, and they are elucidated by the multiple scattering method. Explicit solutions for some limiting cases are illustrated as well. The results presented in this work constitute instances of solutions of the scalar wave equation in a space–time admitting closed time-like curves.

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Bokhari, Ahmad H., Abbas Mousavi, Bin Niu e Eddie Wadbro. "Topology optimization of an acoustic diode?" Structural and Multidisciplinary Optimization 63, n. 6 (7 febbraio 2021): 2739–49. http://dx.doi.org/10.1007/s00158-020-02832-9.

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AbstractBy using topology optimization, we consider the problem of designing a passive acoustic device that allows for one-way flow of sound waves; such a device is often colloquially referred to as an acoustic diode. The Helmholtz equation is used to model the time harmonic linear wave propagation together with a Dirichlet-to-Neumann (DtN) type boundary condition, and the finite element method is used for discretization. The objective of this study is to maximize the wave propagation in one direction (from left to right) and minimize the wave propagation in the reverse direction (from right to left) for planar incoming waves. The method of moving asymptotes (MMA) solves the optimization problem, and a continuation approach is used for the penalizing intermediate design variables. The results for the optimized waveguide show that more than 99.8% of the power of planar incoming waves get transmitted from left to right while less than 0.3% gets transmitted in the reverse direction for planar incoming waves in the specified frequency range. Since a true diode is a non-reciprocal device and here we used a linear acoustic wave model, which is basically reciprocal, we discuss details about how it appears to be possible to obtain a one-way waveguiding effect using this linear model.

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Hua, Yifei, Chao Qian, Hongsheng Chen e Huaping Wang. "Experimental topology-optimized cloak for water waves". Materials Today Physics 27 (ottobre 2022): 100754. http://dx.doi.org/10.1016/j.mtphys.2022.100754.

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4

Hasan, S. S., O. Steiner e A. van Ballegooijen. "Inferring the chromospheric magnetic topology through waves". Proceedings of the International Astronomical Union 3, S247 (settembre 2007): 78–81. http://dx.doi.org/10.1017/s1743921308014695.

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AbstractThe aim of this work is to examine the hypothesis that the wave propagation time in the solar atmosphere can be used to infer the magnetic topography in the chromosphere as suggested by Finsterle et al. (2004). We do this by using an extension of our earlier 2-D MHD work on the interaction of acoustic waves with a flux sheet. It is well known that these waves undergo mode transformation due to the presence of a magnetic field which is particularly effective at the surface of equipartition between the magnetic and thermal energy density, the β = 1 surface. This transformation depends sensitively on the angle between the wave vector and the local field direction. At the β = 1 interface, the wave that enters the flux sheet, (essentially the fast mode) has a higher phase speed than the incident acoustic wave. A time correlation between wave motions in the non-magnetic and magnetic regions could therefore provide a powerful diagnostic for mapping the magnetic field in the chromospheric network.

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5

Shabana, A. A., e W. H. Gau. "Propagation of Impact-Induced Longitudinal Waves in Mechanical Systems With Variable Kinematic Structure". Journal of Vibration and Acoustics 115, n. 1 (1 gennaio 1993): 1–8. http://dx.doi.org/10.1115/1.2930309.

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In previous publications by the authors of this paper it was shown that elastic media become dispersive as the result of the coupling between the finite rotation and the elastic deformation. Impact-induced harmonic waves no longer travel, in a rotating rod, with the same phase velocity and consequently the group velocity becomes dependent on the wave number. In this investigation, the propagation of impact-induced longitudinal waves in mechanical systems with variable kinematic structure is examined. The configuration of the mechanical system is identified using two different sets of modes. The first set describes the system configuration before the change in the system topology, while the second set describes the configuration of the system after the topology changes. In the analysis presented in this investigation, it is assumed that collision between the system components occurs first, followed by a change in the system topology. Both events are assumed to occur in a very short-lived interval of time such that the system configuration does not appreciably change. By using the first set of modes, the jump discontinuity in the system velocities is predicted using the algebraic generalized impulse momentum equations. The propagation of the impact-induced wave motion after the change in the system topology is described using the Fourier method. The series solution obtained is used to examine the effect of the topology change on the propagation of longitudinal elastic waves in constrained mechanical systems. It is shown that, while, for a nonrotating rod, mass capture or mass release has no effect on the phase and group velocities, in rotating rods the phase and group velocities depend on the change in the system topology. In particular the phase velocities of low harmonic longitudinal waves are more affected by the change in the system topology as compared to high frequency harmonic waves.

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6

Rak, Gašper, Marko Hočevar e Franci Steinman. "Water surface topology of supercritical junction flow". Journal of Hydrology and Hydromechanics 67, n. 2 (1 giugno 2019): 163–70. http://dx.doi.org/10.2478/johh-2018-0042.

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Abstract The complexity of flow conditions at junctions amplifies significantly with supercritical flow. It is a pronounced three-dimensional two-phased flow phenomenon, where standing waves with non-stationary water surface are formed. To analyse the hydrodynamic conditions at an asymmetric right-angled junction with incoming supercritical flows at Froude numbers between 2 and 12, an experimental approach was used. For a phenomenological determination of the relations between the integral parameters of incoming flows and the characteristics of standing waves at the junction area, water surface topographies for 168 scenarios at the junction were measured using non-intrusive measurement techniques. The new, phenomenologically derived equations allow for determination of location, height and extent of the main standing waves at the junction. Research results give important information on the processes and their magnitude for engineering applications.

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7

Lin, Mengnan, Zhongwei Tian, Siyuan Chang, Kai Cui e Shulan Dai. "Three-Dimensional Shock Topology Detection Method via Tomographic Reconstruction". Aerospace 10, n. 3 (11 marzo 2023): 275. http://dx.doi.org/10.3390/aerospace10030275.

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Shock waves and shock-shock interaction are typical phenomena in supersonic or hypersonic flows that have significant impacts on aerodynamic performance. To obtain a comprehensive understanding of the mechanism of shock wave interaction, shock wave detection (SWD) methods are required. However, it is often challenging for most current SWD methods to identify the relationship between shock waves (also known as shock topology). To address this issue, this paper proposes a novel three-dimensional shock topology detection method based on the tomographic reconstruction strategy. This method involves extracting parallel slices from the flow field, then utilizing a two-dimensional shock topology recognition algorithm to obtain shock lines. Shock bands are obtained by connecting shock lines for every two adjacent slices, and shock surfaces are generated by assembling shock bands. Interaction lines are also formed by connecting interaction points. The detected shock wave is a structure composed of “point-line-band-surface”, and the topology relationship with other shock waves is obvious. Numerical results show that the shock waves detected by the proposed method can be categorized into families. Moreover, the shock surfaces generated by this method are free of gaps, holes, and un-physical fragments, which is an improvement over existing SWD methods.

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8

Mirev, Andrei, Anton Andonov e Yovko Rakanov. "Photovoltaic’s inverter directly connected to the grid". Science, Engineering and Education 1, n. 1 (28 novembre 2016): 32–35. http://dx.doi.org/10.59957/see.v1.i1.2016.5.

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The paper describes a modification of the topology of a photovoltaic’s inverter with a flying inductor connected to a single phase grid in absence of any transformer. The topology advanced provides the application of buck-, boost- and buck-boost modes of transforming at both half-waves of the grid voltage. It works as a three level inverter reducing high frequency disturbances. The symmetric work in both half-waves facilitates the control required.

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9

Ables, S. T., B. J. Fraser, C. L. Waters, D. A. Neudegg e R. J. Morris. "Monitoring cusp/cleft topology using Pc5 ULF waves". Geophysical Research Letters 25, n. 9 (1 maggio 1998): 1507–10. http://dx.doi.org/10.1029/98gl00848.

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10

Liu, Ze, Hao-Wen Dong e Gui-Lan Yu. "Topology optimization of periodic barriers for surface waves". Structural and Multidisciplinary Optimization 63, n. 1 (26 agosto 2020): 463–78. http://dx.doi.org/10.1007/s00158-020-02703-3.

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11

Zieske, Katja, Jakob Schweizer e Petra Schwille. "Surface topology assisted alignment of Min protein waves". FEBS Letters 588, n. 15 (14 giugno 2014): 2545–49. http://dx.doi.org/10.1016/j.febslet.2014.06.026.

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12

Wang, Hai-Xiao, Guang-Yu Guo e Jian-Hua Jiang. "Band topology in classical waves: Wilson-loop approach to topological numbers and fragile topology". New Journal of Physics 21, n. 9 (16 settembre 2019): 093029. http://dx.doi.org/10.1088/1367-2630/ab3f71.

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13

Han, Sihao, Qiang Han e Chunlei Li. "Deep-learning-based inverse design of phononic crystals for anticipated wave attenuation". Journal of Applied Physics 132, n. 15 (21 ottobre 2022): 154901. http://dx.doi.org/10.1063/5.0111182.

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Bandgaps of phononic crystals dominating the propagation of evanescent waves have received significant attention recently, which can be determined and tuned by the topology of a unit cell. Predicting a band structure and designing topological structures with desirable characteristics have become a research hotspot. In this study, a data-driven deep learning framework is applied to arrive at the prediction of the band structure and the inverse design of topology. A convolutional neural network is trained to predict band structures of phononic crystals. After training a generative adversarial network, the generator is concatenated with the convolutional neural network for inverse design. Meanwhile, a complex band structure of phononic crystals is computed by the periodic spectral finite element method to present the spatial decay of evanescent waves. The topology with the greater spatial attenuation is screened from the ground truth topology and the inversely designed topology. Finally, an optimized topological phononic crystal with an anticipated bandgap is obtained, which has the potential for better acoustic insulation and vibration isolation.

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14

Ivanov, S. T., K. M. Ivanova e E. G. Alexov. "Rayleigh surface waves along the boundary between a plasma and a metallic screen". Journal of Plasma Physics 49, n. 2 (aprile 1993): 227–35. http://dx.doi.org/10.1017/s0022377800016949.

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Electromagnetic wave propagation along the interface between a magnetoactive plasma and a metallic screen is investigated analytically and numerically. It is shown that the waves have a Rayleigh character: they are superpositions of two partial waves. It is concluded that electromagnetic waves propagate only at frequencies lower than min (ωp, ωc), where ωpis the plasma frequency and ωcis the cyclotron frequency. The field topology is found, and the physical character of the waves is discussed.

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15

He, Jingjie, e Zhan Kang. "Achieving directional propagation of elastic waves via topology optimization". Ultrasonics 82 (gennaio 2018): 1–10. http://dx.doi.org/10.1016/j.ultras.2017.07.006.

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16

Kiritsis, Elias, e Costas Kounnas. "Dynamical topology change, compactification and waves in string cosmology". Nuclear Physics B - Proceedings Supplements 41, n. 1-3 (aprile 1995): 311–30. http://dx.doi.org/10.1016/0920-5632(95)00440-k.

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17

Zhang, W. Z., H. S. Fu, J. B. Cao, Z. Wang e Y. Y. Liu. "Properties of the Turbulence and Topology in a Turbulent Magnetic Reconnection". Astrophysical Journal 953, n. 1 (28 luglio 2023): 23. http://dx.doi.org/10.3847/1538-4357/acdacf.

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Abstract Magnetic reconnection is a crucial process responsible for energy conversion and particle acceleration in space, astrophysical, and laboratory plasmas. Turbulence and magnetic reconnection can be mutually driven, but the underlying nature of energy dissipation, intrinsic turbulence waves, and magnetic field topologies in turbulent magnetic reconnection is still poorly understood. Here, using advanced multi-spacecraft mission and innovative methods, we provide a few new perspectives to investigate the properties of the turbulence and topology in a turbulent magnetic reconnection in the magnetotail. Our results reveal that in turbulent magnetic reconnection: (1) cyclotron resonance, an important mechanism of energy dissipation, is more effective in the core region of the reconnection than in the outflow regions; (2) energy is deposited in the form of kinetic Alfvén waves (KAWs) and fast/slow waves, with KAWs corresponding to low-frequency (ion cyclotron scale) and fast/slow waves corresponding to high-frequency (low-hybrid scale); and (3) the number of spiral nulls (O-lines) were about 3.6 times more than radial ones (X-lines), and three-dimensional structures were about 8 times more prevalent than two-dimensional ones. These findings should help us better unravel the dynamics of turbulent magnetic reconnection.

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18

Deng, Yongbo, e Jan G. Korvink. "Topology optimization for three-dimensional electromagnetic waves using an edge element-based finite-element method". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, n. 2189 (maggio 2016): 20150835. http://dx.doi.org/10.1098/rspa.2015.0835.

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This paper develops a topology optimization procedure for three-dimensional electromagnetic waves with an edge element-based finite-element method. In contrast to the two-dimensional case, three-dimensional electromagnetic waves must include an additional divergence-free condition for the field variables. The edge element-based finite-element method is used to both discretize the wave equations and enforce the divergence-free condition. For wave propagation described in terms of the magnetic field in the widely used class of non-magnetic materials, the divergence-free condition is imposed on the magnetic field. This naturally leads to a nodal topology optimization method. When wave propagation is described using the electric field, the divergence-free condition must be imposed on the electric displacement. In this case, the material in the design domain is assumed to be piecewise homogeneous to impose the divergence-free condition on the electric field. This results in an element-wise topology optimization algorithm. The topology optimization problems are regularized using a Helmholtz filter and a threshold projection method and are analysed using a continuous adjoint method. In order to ensure the applicability of the filter in the element-wise topology optimization version, a regularization method is presented to project the nodal into an element-wise physical density variable.

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19

Kolobov, D. Y., e N. I. Kobanov. "Two modes of propagating waves in sunspots". Proceedings of the International Astronomical Union 3, S247 (settembre 2007): 105–9. http://dx.doi.org/10.1017/s1743921308014749.

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AbstractThe observations of sunspot chromosphere are presented. The authors suggest the existence of two modes of propagating waves at the chromospheric level. The connection between these modes and magnetic field topology can be inferred from the analysis of mode propagation velocity and spatial localization. Two hypotheses are tested to explain the phenomenon: “Visual pattern” and “Trans-sunspot wave”.

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Asgari-Targhi, M., A. Asgari-Targhi e S. R. Habbal. "Magnetic Topology and the Structure of the Slow Solar Wind". Journal of Physics: Conference Series 2544, n. 1 (1 luglio 2023): 012003. http://dx.doi.org/10.1088/1742-6596/2544/1/012003.

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Abstract We present a 3D reduced magnetohydrodynamic (RMHD) model of reflection driven Alfvén wave turbulence in an open magnetic field positioned near the solar equator. The non-linear interactions between outward and inward propagating waves generate turbulence. The RMHD equations describing the turbulence include the effects of solar wind outflow velocity on the dissipation of waves. For Alfvén wave turbulence to be a viable mechanism for heating the corona and accelerating the slow solar wind, there must be sufficient counter-propagating waves to generate the turbulence. In our previous study of the fast wind, we showed that the Alfvén wave turbulence model creates the energy needed for accelerating the fast solar wind, when observed density fluctuations are included in the model. Here, we will explore whether the conditions of the equatorial corona, a source of slow solar wind, are capable of generating sufficient Alfvén wave turbulence to account for the acceleration of the slow wind. We show that for a specific sets of model parameters, the energy from the Alfvén wave turbulence model is smaller by an order of magnitude than the energy needed to heat and accelerate the slow solar wind.

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Zhuo, Rui, Jiansen He, Die Duan, Xingyu Zhu e Chuanpeng Hou. "Oblique Compressible Waves in the Reconnection Exhaust Region Embedded in the Inner Heliospheric Current Sheet Observed by Parker Solar Probe". Astrophysical Journal 969, n. 1 (28 giugno 2024): 47. http://dx.doi.org/10.3847/1538-4357/ad4bd9.

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Abstract Magnetic reconnection is an important physical process of energy conversion in the heliosphere. Parker Solar Probe (PSP) passes through current sheets of the inner heliosphere and is likely to encounter magnetic reconnection events there. PSP traversed a magnetic reconnection exhaust region that occurred in the coronal streamer during its perihelion Encounter 8. We report an observation of the counterstream of strahl electrons and compressible waves in the exhaust region on the antisunward side of the reconnection site. We analyze the wave characteristics using electromagnetic singular value decomposition techniques and find that the propagation direction of the compressible waves is quasi-perpendicular to the local magnetic field. Combining with the topology of the magnetic field, we infer that the compressible waves converge from the edge to the center of the exhaust region, and then propagate away from it. Further, we select 12 magnetic reconnection events during Encounter 5–8 for statistics and find that the oblique compressible waves are commonly detected throughout the inner heliospheric current sheet. In addition, we discuss the possible nature of wave branches for these compressible waves. Our work shows that magnetic reconnection in the heliosphere not only changes the topology of the large-scale magnetic field in the heliosphere, but also affects the transport characteristics of solar wind plasma and suprathermal particles, and regulates the states of waves and turbulence in the heliosphere.

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Deng, Yongbo, e Jan G. Korvink. "Self-consistent adjoint analysis for topology optimization of electromagnetic waves". Journal of Computational Physics 361 (maggio 2018): 353–76. http://dx.doi.org/10.1016/j.jcp.2018.01.045.

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Jensen, Jakob S. "Topology optimization problems for reflection and dissipation of elastic waves". Journal of Sound and Vibration 301, n. 1-2 (marzo 2007): 319–40. http://dx.doi.org/10.1016/j.jsv.2006.10.004.

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Egedal, J., e H. Bindslev. "Topology of relativistic refractive index surfaces for electron cyclotron waves". Plasma Physics and Controlled Fusion 36, n. 3 (1 marzo 1994): 543–59. http://dx.doi.org/10.1088/0741-3335/36/3/011.

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KAYANUMA, Tetsurou, e Garuda FUJII. "Controlling thermal waves of conduction and convection via topology optimization". Proceedings of OPTIS 2022.14 (2022): U00024. http://dx.doi.org/10.1299/jsmeoptis.2022.14.u00024.

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Noguchi, Yuki, e Takayuki Yamada. "Level set-based topology optimization for programmable acoustic structures". INTER-NOISE and NOISE-CON Congress and Conference Proceedings 268, n. 7 (30 novembre 2023): 1001–8. http://dx.doi.org/10.3397/in_2023_0155.

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Controlling acoustic waves is essential in noise-reduction applications. Acoustic structures, which can efficiently manipulate acoustic waves based on their structural design, have been used to achieve the desired wave propagation behaviors. To meet various demands on sound propagation, it is crucial to design acoustic structures with multiple functionalities. In this research, we propose a level set-based topology optimization method for acoustic structures with desired acoustic performances that depend on their deformation. Firstly, we introduce a mathematical model that represents acoustic wave propagation based on the Helmholtz equation and the coordinate transformation. Next, we formulate the optimization problem based on the framework of a level set-based topology optimization method. A two-dimensional numerical example is provided to demonstrate the validity of the proposed method. As an example, we optimize a sound reflective structure with the desired acoustic responses that are dependent on the deformation of the optimized structure.

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Altynnikov, Andrey, Roman Platonov, Andrey Tumarkin, Peter K. Petrov e Andrey Kozyrev. "Formation of Millimeter Waves with Electrically Tunable Orbital Angular Momentum". Coatings 11, n. 5 (13 maggio 2021): 569. http://dx.doi.org/10.3390/coatings11050569.

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A method for forming electromagnetic waves with a tunable nonzero orbital angular momentum (OAM) is proposed. The approach is based on transforming an incident plane wave into a helical one using an electrically tunable ferroelectric lens. It uses high-resistive thin/thick film electrodes with a special discrete topology. The correlation between film electrodes topology and the highest order of OAM modes that the lens can form is described. A lens prototype based on Ba0.55Sr0.45TiO3 ferroelectric material and operating at a frequency of 60 GHz was designed, manufactured, and tested. The amplitude and phase distribution of the OAM wave with l = +1 formed by prototype were measured to confirm the effectiveness of the proposed method. The proposed lens has a combination of advantages such as low dimensions, electrical control over the OAM modes, and the possibility to operate in the millimeter wavelength range.

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Kühnel, W., e H. B. Rademacher. "Conformal Geometry of Gravitational Plane Waves". Geometriae Dedicata 109, n. 1 (dicembre 2004): 175–88. http://dx.doi.org/10.1007/s10711-004-2453-4.

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Xu, Jie, Hui Li, You-Ling zhou, Qian Li, Liu-Xun Xue, Chong-Yue Shi e Hou Wang. "Performance analysis of vortex acoustic wave based on uniform circular array". Journal of Physics: Conference Series 2078, n. 1 (1 novembre 2021): 012069. http://dx.doi.org/10.1088/1742-6596/2078/1/012069.

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Abstract As a carrier for information and energy, acoustic waves have been applied in underwater communication widely, however, the narrow band and low transmission speed are the main problems. Whether in the field of optics or electromagnetic waves, the orbital angular momentum (OAM) represents the natural properties of the spiral phase structure. By introducing the OAM into the acoustics field, the transmission capacity and spectrum efficiency of the underwater acoustic communication system can be expanded. Based on the analysis and detection of the vortex acoustic wave generated by the circular array of transducers, we studied the array generation method of the spiral acoustic beam, and gave the characteristics of the vortex acoustic beam when propagating under the water. In the direction of the main axis, the uniform circular array was used to generate different topological acoustic vortex. To determine the relationship between the OAM topology mode and the transducer array, the spiral acoustic waves in different topology modes were generated, and the number of array elements, array radius, transmission frequency, etc. were investigated to give the effects on OAM acoustic vortex.

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MIRANDA, ALEX S., e VILSON T. ZANCHIN. "GRAVITATIONAL PERTURBATIONS AND QUASINORMAL MODES OF BLACK HOLES WITH NON-SPHERICAL TOPOLOGY". International Journal of Modern Physics D 16, n. 02n03 (febbraio 2007): 421–26. http://dx.doi.org/10.1142/s0218271807010201.

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In the present work we investigate the physical interpretation of gravitational perturbations of static asymptotically anti-de Sitter black holes with non-spherical topology. For zero wavenumber modes, the axial perturbations yield only small rotations on the system, while the polar perturbations lead to a change in the mass and may also produce gravitational waves. Additionally, it is verified that perturbations with any nonzero wavenumber are able to produce gravitational waves in these space–times. On the basis of these results, the quasinormal frequencies corresponding to polar perturbation modes with null wavenumber are calculated and briefly analyzed.

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Graf, Gian Michele, Hansueli Jud e Clément Tauber. "Topology in Shallow-Water Waves: A Violation of Bulk-Edge Correspondence". Communications in Mathematical Physics 383, n. 2 (18 marzo 2021): 731–61. http://dx.doi.org/10.1007/s00220-021-03982-7.

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Marchesin, Dan, e C. Frederico B. Palmeira. "Topology of elementary waves for mixed-type systems of conservation laws". Journal of Dynamics and Differential Equations 6, n. 3 (luglio 1994): 427–46. http://dx.doi.org/10.1007/bf02218857.

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Ahn, Byungseong, Hyuk Lee, Joong Seok Lee e Yoon Young Kim. "Topology optimization of metasurfaces for anomalous reflection of longitudinal elastic waves". Computer Methods in Applied Mechanics and Engineering 357 (dicembre 2019): 112582. http://dx.doi.org/10.1016/j.cma.2019.112582.

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FOURNIER, J. D., e S. GALTIER. "Meromorphy and topology of localized solutions in the Thomas–MHD model". Journal of Plasma Physics 65, n. 5 (giugno 2001): 365–406. http://dx.doi.org/10.1017/s002237780100887x.

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The one-dimensional MHD system first introduced by J.H. Thomas [Phys. Fluids 11, 1245 (1968)] as a model of the dynamo effect is thoroughly studied in the limit of large magnetic Prandtl number. The focus is on two types of localized solutions involving shocks (antishocks) and hollow (bump) waves. Numerical simulations suggest phenomenological rules concerning their generation, stability and basin of attraction. Their topology, amplitude and thickness are compared favourably with those of the meromorphic travelling waves, which are obtained exactly, and respectively those of asymptotic descriptions involving rational or degenerate elliptic functions. The meromorphy bars the existence of certain configurations, while others are explained by assuming imaginary residues. These explanations are tested using the numerical amplitude and phase of the Fourier transforms as probes of the analyticity properties. Theoretically, the proof of the partial integrability backs up the role ascribed to meromorphy. Practically, predictions are derived for MHD plasmas.

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Noguchi, Y., T. Yamada, M. Otomori, K. Izui e S. Nishiwaki. "An acoustic metasurface design for wave motion conversion of longitudinal waves to transverse waves using topology optimization". Applied Physics Letters 107, n. 22 (30 novembre 2015): 221909. http://dx.doi.org/10.1063/1.4936997.

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Prosovetsky, Dmitry. "Coronal waves in coronal loops during non-flare stage". Proceedings of the International Astronomical Union 4, S257 (settembre 2008): 245–49. http://dx.doi.org/10.1017/s1743921309029354.

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AbstractUsing SOHO/EIT Fe XII λ195 Å observations the new type of oscillations in coronal loops was detected. The oscillation corresponds to wave propagated to outer area of atmosphere of active area. As opposed to most kind of oscillations associated with coronal loops the waves are observed at non-flare stage of active areas evolution. Velocities of the wave propagation were 8-20 km s−1 and had quasi-perpendicular direction with magnetic field. Such waves were detected in active areas located on solar disk and loops structures outside solar limb. Investigation of EIT data shows the waves are not result of changes of topology of a magnetic field and loops configuration. The nature and probable sources of waves are discussed.

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MYONG, R. S., e P. L. ROE. "Shock waves and rarefaction waves in magnetohydrodynamics. Part 1. A model system". Journal of Plasma Physics 58, n. 3 (ottobre 1997): 485–519. http://dx.doi.org/10.1017/s002237789700593x.

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The present study consists of two parts. Here in Part 1, a model set of conservation laws exactly preserving the MHD hyperbolic singularities is investigated to develop the general theory of the nonlinear evolution of MHD shock waves. Great emphasis is placed on shock admissibility conditions. By developing the viscosity admissibility condition, it is shown that the intermediate shocks are necessary to ensure that the planar Riemann problem is well-posed. In contrast, it turns out that the evolutionary condition is inappropriate for determining physically relevant MHD shocks. In the general non-planar case, by studying canonical cases, we show that the solution of the Riemann problem is not necessarily unique – in particular, that it depends not only on reference states but also on the associated internal structure. Finally, the stability of intermediate shocks is discussed, and a theory of their nonlinear evolution is proposed. In Part 2, the theory of nonlinear waves developed for the model is applied to the MHD problem. It is shown that the topology of the MHD Hugoniot and wave curves is identical to that of the model problem.

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38

Doss, M. Arun Noyal, K. Mohanraj, Sayantan Bhattacharjee, Maulik Tiwari e Devashish Vashishtha. "Photovoltaic fed multilevel inverter using reverse voltage topology for standalone systems". International Journal of Power Electronics and Drive Systems (IJPEDS) 10, n. 3 (1 settembre 2019): 1347. http://dx.doi.org/10.11591/ijpeds.v10.i3.pp1347-1354.

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<span lang="EN-US">Multilevel Inverters are generally utilized for medium voltage and high power applications. Invented in 1975, MLIs have brought huge change in the field of Electrical and Electronics. It contains distinctive topologies. This paper proposes a photovoltaic aided multilevel inverter with Reverse Voltage topology with diminished number of switches. In comparison to other existing topologies this topology utilizes minimum number of switches and less number of carrier signals which in turns diminishes the complexity of the system as well as cost. The proposed framework contains five MOSFETs, five diodes to create eleven levels. In this topology the SPWM strategy has been utilized. This topology utilizes one sine wave and five triangular waves, which is half in comparison to the existing topologies. As sustainable power sources can be utilized for multilevel inverter, photovoltaic cell has been utilized. The MATLAB recreation for both solar powered module and Multilevel inverter has been appeared alongside the equipment approach.</span>

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39

Cheng, Xianming. "Injection signal coding based topology identification method and system for low voltage substation". Journal of Physics: Conference Series 2378, n. 1 (1 dicembre 2022): 012067. http://dx.doi.org/10.1088/1742-6596/2378/1/012067.

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Abstract In view of the low efficiency and low reliability of the traditional topology identification method of distribution station area, this paper proposes a low-voltage station area topology identification method based on injection signal coding. The signal transceiver terminal sends the topology identification signal, which is composed of preamble, equipment ID number and characteristic code composed of multiple groups of characteristic waves. The rest of the signal transceiver terminals judge whether it is on the same branch and the hierarchical relationship through the characteristic code, The intelligent fusion terminal finally realizes the topological relationship of the whole station area by statistics and analysis of the connection relationship and hierarchical relationship between all the branch master tables. A low-voltage distribution station area is selected to verify the topology identification method proposed in this paper. The test results show that the results obtained by this method are consistent with the real household transformer relationship, and the identification accuracy is high, which has certain engineering application value.

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40

Ghodake, Pravinkumar R. "Design optimization of metamaterials to control waves in cylindrical rods". Journal of the Acoustical Society of America 151, n. 4 (aprile 2022): A56. http://dx.doi.org/10.1121/10.0010642.

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Metamaterials can control different modes of waves by tuning their bandgap structures. Various design strategies are implemented to obtain desired responses of metamaterials by solving multiple forward problems using parametric sweeps, topology, and shape optimization problems. This study focuses on the design of cylindrical metamaterials to control wave propagation in a cylindrical rod using a shape optimization approach. Topology optimization requires relatively more computational resources and time as well as it also gives relatively complex structures in comparison with shape optimization. Optimal widths of layered elastic materials arranged periodically along an axis, on subsurface, and an outer surface of cylindrical surface are obtained by solving multiple time-dependent shape optimization problems. Optimization problems are solved using the finite element method and non-gradient optimization algorithm. Single and multi-objective functions are defined to reduce only axial and both axial as well as radial displacements integrated over the end surface, and monochromatic Gaussian input pulse is considered in this study. Every design solution obtained during each design iteration can be easily manufactured as a weak constraint is applied to the total length of the metamaterial. Prior knowledge of possible bandgaps helps to set an effective optimization problem, but it is not a necessary condition.

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41

Liu, Chen-Xu, e Gui-Lan Yu. "Deep learning-based topology design of periodic barrier for full-mode waves". Construction and Building Materials 314 (gennaio 2022): 125579. http://dx.doi.org/10.1016/j.conbuildmat.2021.125579.

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42

Deymier, Pierre, e Keith Runge. "One-Dimensional Mass-Spring Chains Supporting Elastic Waves with Non-Conventional Topology". Crystals 6, n. 4 (16 aprile 2016): 44. http://dx.doi.org/10.3390/cryst6040044.

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43

Delplace, Pierre, e Antoine Venaille. "From the geometry of Foucault pendulum to the topology of planetary waves". Comptes Rendus. Physique 21, n. 2 (3 novembre 2020): 165–75. http://dx.doi.org/10.5802/crphys.28.

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44

Mesleh, Michael F., Sangwon Lee, Gianluigi Veglia, David S. Thiriot, Francesca M. Marassi e Stanley J. Opella. "Dipolar Waves Map the Structure and Topology of Helices in Membrane Proteins". Journal of the American Chemical Society 125, n. 29 (luglio 2003): 8928–35. http://dx.doi.org/10.1021/ja034211q.

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45

Chen, Yafeng, Xiaodong Huang, Guangyong Sun, Xiaolei Yan e Guangyao Li. "Maximizing spatial decay of evanescent waves in phononic crystals by topology optimization". Computers & Structures 182 (aprile 2017): 430–47. http://dx.doi.org/10.1016/j.compstruc.2017.01.001.

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46

Deymier, Pierre A., Keith Runge, Nick Swinteck e Krishna Muralidharan. "Torsional topology and fermion-like behavior of elastic waves in phononic structures". Comptes Rendus Mécanique 343, n. 12 (dicembre 2015): 700–711. http://dx.doi.org/10.1016/j.crme.2015.07.003.

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47

Canzani, Yaiza, e Peter Sarnak. "Topology and Nesting of the Zero Set Components of Monochromatic Random Waves". Communications on Pure and Applied Mathematics 72, n. 2 (15 ottobre 2018): 343–74. http://dx.doi.org/10.1002/cpa.21795.

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48

HADZHIEV, BORISLAV, KATJA WINDT, WERNER BERGHOLZ e MARC-THORSTEN HÜTT. "A MODEL OF GRAPH COLORING DYNAMICS WITH ATTENTION WAVES AND STRATEGIC WAITING". Advances in Complex Systems 12, n. 06 (dicembre 2009): 549–64. http://dx.doi.org/10.1142/s0219525909002386.

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Recently, Kearns et al. [Kearns, M., Suri, S. and Montfort, N., An experimental study of the coloring problem on human subject networks, Science313 (2006) 824–827] studied the topology dependence of graph coloring dynamics. In their empirical study, the authors analyze, how a network of human subjects acting as autonomous agents performs in solving a conflict-avoidance task (the graph coloring problem) for different network architectures. A surprising result was that the run-time of the empirical dynamics decreases with the number of shortcuts in a Watts–Strogatz small-world graph. In a simulation of the dynamics based on randomly selecting color conflicts for update, they observe a strong increase of the run-time with the number of shortcuts. Here, we propose classes of strategies, which are capable of explaining the decrease in run-time with an increasing number of shortcuts. We show that the agent's strategy, the graph topology, and the complexity of the problem (essentially given by the graph's chromatic number) interact nontrivially yielding unexpected insights into the problem-solving capacity of organizational structures.

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49

Ball, L. T. "Non-relativistic thermal effects on parallel-propagating ion cyclotron waves". Journal of Plasma Physics 38, n. 1 (agosto 1987): 117–38. http://dx.doi.org/10.1017/s0022377800012447.

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We investigate strictly non-relativistic thermal effects on the dispersion of lefthanded (LH) ion cyclotron waves (ICW's) with real frequency and complex wave vector, propagating parallel to a uniform ambient magnetic field. Changes to the topology of the cold-plasma dispersion relations in the vicinity of the ion gyrofrequencies are studied in plasmas consisting predominantly of protons with a small admixture of a heavy ion. The two branches of the LH mode reconnect near the heavy-ion gyrofrequency as the heavy-ion temperature is increased or its relative density is reduced. The reconnection results in one mode in which waves can propagate at all frequencies below the proton gyrofrequency and another which allows propagation only in a narrow frequency range extending upwards from the cut-off frequency to a regime where strong damping occurs. The topology of the reconnected dispersion curves is quite different from that seen in the real wave vector – complex frequency case. This work is relevant to theories of ion heating and acceleration in multi-ion plasmas as are found in the solar wind, in solar and stellar flares, and in the Earth's magnetosphere. In particular, strongly species-dependent heating and acceleration can arise from wave–particle interactions between the various ionic species, and ICW's at frequencies near the respective ion gyrofrequencies. These interactions depend critically on the wave dispersion.

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50

Rao, S. Nagaraja, D. V. Ashok Kumar e Ch Sai Babu. "Implementation of Cascaded based Reversing Voltage Multilevel Inverter using Multi Carrier Modulation Strategies". International Journal of Power Electronics and Drive Systems (IJPEDS) 9, n. 1 (1 marzo 2018): 220. http://dx.doi.org/10.11591/ijpeds.v9.i1.pp220-230.

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In this paper, a cascaded based reversing voltage (CBRV) multilevel inverter structure is proposed inorder to compensate the major drawbacks in the conventional multilevel inverters. The proposed topology requires less number of components, less carrier signals and gate drives when compared to existing multilevel inverters particularly at higher levels. Therefore, the complexity and overall cost are greatly reduced particularly for higher output voltage levels. This paper also presents the most relevant control and modulation methods by a triangular based multi carrier pulse width modulation (PWM) scheme for the proposed CBRV inverter topology. This paper presents a comparison between different modulation strategies for CBRV inverter topology based on sinusoidal and space vector references with multi triangular carrier waves. The work strive hard to present the scrutiny that has been made between various PWM control techniques for 1–Ф seven level CBRV inverter structure. The comparison is made in terms of Total Harmonic Distortion (THD) and fundamental RMS voltage. Finally, the simulation results are included to verify the effectiveness of the proposed CBRV inverter topology and validate the proposed theory. A hardware set up was developed for a 1–Ф seven level CBRV inverter topology using FPGA based pulse generation.

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