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Journal articles on the topic 'Sinusoidal Wave Method'
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1
Noviantri, Viska, and Ro’fah Nur Rachmawati. "Bragg Resonance around the Coast of Hardwall." ComTech: Computer, Mathematics and Engineering Applications 7, no. 4 (2016): 275. http://dx.doi.org/10.21512/comtech.v7i4.2547.
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Basically, when waves pass an uneven basis, then this wave will be split into transmission and reflection waves. First of all, it will be shown that a sinusoidal seabed can lead to the phenomenon of Bragg resonance. Bragg resonance occurs when the wave-length comes at twice the wave-length of a sinusoidal basis. The method used to obtain approximation solution is a multi-scale asymptotic expansion method. A research on the effect of Bragg resonance on sinusoidal basis had been studied. Sinusoidal basis can reduce the amplitude of the incoming wave so that the amplitude of the wave transmission is quite small. In these researcher, the coast is assumed ideal and can absorb all the energy of the wave transmission. If the beach can reflect waves, this indicates that the existence of sinusoidal basis is more harmful to the coast. This mechanism relies on the distance between the base sinusoidal and beaches. The present research will examined the influence of the base, when there was a beach of hard-wall on the right, which was perfectly capable of reflecting waves. Having regard to the phase difference, from super positioned waves when they hit the beach, so it can determine the safert and the most dangerous distance.
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Ghassemizadeh, Seyyed-Mahmood, and Mohammad Javad Ketabdari. "Modeling of Solitary Wave Interaction with Curved Face Seawalls Using Numerical Method." Advances in Civil Engineering 2022 (June 6, 2022): 1–12. http://dx.doi.org/10.1155/2022/5649637.
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This paper considers the solitary wave interaction with seawalls of different curved geometries and sloped faces using numerical modeling. This interaction was simulated using the Finite Volume Method-Volume of Fraction (FVM-VOF) approach. To model the turbulent free-surface flow, coupled VOF and k-ε-RNG methods were used. To validate the model, the numerical results for a conventional sloping seawall were compared with the available experimental data. Then the interaction of solitary waves and seawalls with different sinusoidal, logarithmic, and parabolic functions front faces and linear slope was modeled. The results showed that for these seawalls in general by increasing the solitary wavelength, the wave reflection coefficient (Cr) increases. However, the wave run-up on seawalls demonstrates an oscillatory decrease. Furthermore, for parabolic walls in comparison to conventional linear sloping seawalls, the wave run-up and wave reflection increased by 4.1% and 4.7%. For sinusoidal walls, the wave run-up and wave reflection increased by 5% and 1.8%. For logarithmic walls, the wave run-up and wave reflection increased by 6.3% and decreased by 1.1%, respectively. This means that wave run-up on logarithmic walls is more than that of the sinusoidal, parabolic, and sloped walls. The simulation results revealed that normalized maximum run-up increases with an increase in normalized incident wave height for all types of curved walls.
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Matalata, Hendi, and Rozlinda Dewi. "Desain Rangkaian Gate Driver Analog untuk Dual Mosfet Drivers." Jurnal Ilmiah Universitas Batanghari Jambi 21, no. 2 (2021): 714. http://dx.doi.org/10.33087/jiubj.v21i2.1534.
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Switching techniques have been continued to develop, including sinusoidal PWM, space vector PWM, current tracking PWM, harmonic elimination PWM and others. Each method has advantages and disadvantages, but the most commonly used methods are sinusoidal PWM and space vector PWM. PWM that is generated using a microcontroller or analog IC component generally has a maximum voltage value of 5V. To strengthen the PWM wave, a gate-driver circuit is needed, so that the PWM control wave is able to move the IGBT / MOSFET. On this paper, the design of gate driver circuit use An analog IC, which starts from the generation of two waves, namely a sinusoidal wave and a DC source to be compared (Comparator) so that it can produce a PWM wave. Then this PWM wave is isolated using an optocoupler and MOSFET driver IC to limit interference in the switching process on high power supplies. Based on the results, it can be cancluded PWM control wave output from the gate-driver circuit is isolated from the system intended for designing a power converter and other applications.
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Effendi, Effendi, Ira Devi Sara, and Rakhmad Syafutra Lubis. "Disain SPWM Multilevel Inverter Satu Fasa Lima Belas Level." Jurnal Rekayasa Elektrika 12, no. 2 (2016): 60. http://dx.doi.org/10.17529/jre.v12i2.3966.
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Fifteen level single phase multilevel inverter is constructed using power circuit consist of 7 MOSFETs, seven independents DC sources, seven diodes, and an H-Bridge circuit. Switching method used in this MLI is sinusoidal pulse width modulation (SPWM) multicarrier where the reference wave in the form of a sinusoidal wave. Multicarrier SPWM circuit is designed using electronic components such as Op-Amp that used as a comparator and some logic gates such as AND, OR and NOT gate to trigger S1, S2, S3, S4, S5, S6, S7, and H-Bridge circuit. Carrier waves used in this MLI modified from the triangle wave that having a frequency into carrier waves without frequency (DC sources) where THD that generated into 5.502%. While methods that use frequency such as Phase Disposition PWM (PD PWM), Phase Shift PWM (PS-PWM), and Carrier Overlapping PWM (CO PWM) that produces THD greater than the proposed method, this system was simulated using PSIM software.
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Yuan, Zhen Zhong, Bhupendra Singh Chauhan, and Hee Chang Lim. "Study of a Wave Absorber in Various Distance Placed in a Sinusoidal Propagate Wave." Applied Mechanics and Materials 302 (February 2013): 326–31. http://dx.doi.org/10.4028/www.scientific.net/amm.302.326.
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Since there has been a rapid progress to understand the dynamics of an offshore floating body under an ocean environment, we undertake to generate the ocean waves in a lab-scale wind-wave flume. The study is aiming to observe and optimize the similar ocean environmental condition as input wave and to reduce the wall reflective wave. Several absorption methods are suggested to optimize the propagate wave by measuring the maximum and minimum of the standing wave envelope. There has been no optimized absorption method, as they highly depend on the wave period and the wave length. One of the methods - two fixed wave gauges measuring two wave heights and one wave phase - is applied in this study. In the present paper various approaches were used to analyze the results using the flume, by position of probes, with absorber and without absorber, different position, condition and angle of the wave absorber, This paper also focuses on the analysis of fundamental equations which describe the separating method of the incident and reflective wave, and finally we confirm that the wave absorber is highly efficient considering all the permutation and combination.From the study it is clear that there is a change in the wave amplitude at the receiving end then the generated end; wave absorber is a strong source to control the energy of the coming wave. With the changing the period of the wave, the reflectance is increasing when the period becomes larger.
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Li, Zhuang, Liangyu Chen, Yan Zhong, and Lei Wang. "Study on Sinusoidal Post-Buckling Deformation of Coiled Tubing in Horizontal Wells Based on the Separation Constant Method." Machines 11, no. 5 (2023): 563. http://dx.doi.org/10.3390/machines11050563.
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In this paper, a set of partial differential equations considering the dynamic effects of the coiled tubing (CT) is established based on the bending theory of slender beams considering the axial loads. The analytical solution of sinusoidal deformation with the time term is obtained. The critical load of coiled tubing during sinusoidal buckling and the change of half-wave number during sinusoidal post-buckling are studied through the introduction of the necessary conditions, solution and the separation constant. The contact force of coiled tubing with sinusoidal post-buckling on the horizontal well wall is analyzed. The results show that the critical load for sinusoidal buckling of fixed-size CT is related to the section angular acceleration coefficient. The half-wave number produced by the sinusoidal post-buckling bending of the CT gradually decreases during compression. The contact force of the deformed CT to the borehole wall is related to the compression speed of the CT. By introducing the dynamic term and the separation constant, this research model can provide a theoretical basis for studying the transformation of the CT from sinusoidal buckling to helical buckling.
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Takita, Nobuhiro, and Kyyoul Yun. "Study on Control Method of Magnetic Flux Density Waveform in AC Magnetic Measurement." Materials Science Forum 1034 (June 15, 2021): 135–40. http://dx.doi.org/10.4028/www.scientific.net/msf.1034.135.
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To estimate the magnetic properties of the magnetic material, magnetic flux density waveform (B waveform) must be sinusoidal wave. However, it is necessary to control the exciting waveform in consideration of the distortion, because voltage waveform induced by B-coil is distorted due to the magnetic properties. As a result, the IBCM can make B waveform sinusoidal wave with the least number of feedbacks than any control method. Because the IBCM performs noise cancelling for measured waveform and make accurate exciting waveform from measured waveform.
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Gallyamov, A. G., L. P. Goldobina, O. V. Minyaeva, R. G. Valeev, and N. A. Gallyamova. "The comprehensive effect of sinusoidal modulated currents and decimeter-wave therapy for neurological manifestations of lumbar osteochondrosis." Russian Journal of Physiotherapy, Balneology and Rehabilitation 17, no. 5 (2020): 241–45. http://dx.doi.org/10.17816/1681-3456-2018-17-5-241-245.
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Background. Comprehensive therapeutic techniques are becoming increasingly common in treatment of various diseases.
 Aim: to study the comprehensive effect of decimeter-wave therapy, sinusoidal modulated current therapy for lumbar osteochondrosis with neurological manifestations.
 Methods. The comprehensive effect of physiotherapeutic treatment in 69 patients with lumbar osteochondrosis and concomitant neurological manifestations was studied. All patients were divided into 2 groups depending on the leading neurological symptoms with reflex and radicular syndrome. Both groups received similar comprehensive physiotherapeutic treatment with sinusoidal modulated currents and decimeter waves.
 Results. A comprehensive assessment of the therapeutic efficiency of treatment, taking into account clinical and paraclinical data, enabled to substantiate the positive results of treatment in 79.5% of patients with reflex syndromes and 69% with radicular syndromes.
 Conclusion. The comprehensive application of sinusoidal modulated currents and decimeter wave therapy can be considered as a method of pathogenetic physiotherapy of patients with lumbar osteochondrosis with various neurological manifestations.
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Gallyamov, A. G., L. P. Goldobina, O. V. Minyaeva, R. G. Valeev, and N. A. Gallyamova. "The comprehensive effect of sinusoidal modulated currents and decimeter-wave therapy for neurological manifestations of lumbar osteochondrosis." Russian Journal of Physiotherapy, Balneology and Rehabilitation 17, no. 5 (2020): 241–45. http://dx.doi.org/10.18821/1681-3456-2018-17-5-241-245.
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Background. Comprehensive therapeutic techniques are becoming increasingly common in treatment of various diseases.
 Aim: to study the comprehensive effect of decimeter-wave therapy, sinusoidal modulated current therapy for lumbar osteochondrosis with neurological manifestations.
 Methods. The comprehensive effect of physiotherapeutic treatment in 69 patients with lumbar osteochondrosis and concomitant neurological manifestations was studied. All patients were divided into 2 groups depending on the leading neurological symptoms with reflex and radicular syndrome. Both groups received similar comprehensive physiotherapeutic treatment with sinusoidal modulated currents and decimeter waves.
 Results. A comprehensive assessment of the therapeutic efficiency of treatment, taking into account clinical and paraclinical data, enabled to substantiate the positive results of treatment in 79.5% of patients with reflex syndromes and 69% with radicular syndromes.
 Conclusion. The comprehensive application of sinusoidal modulated currents and decimeter wave therapy can be considered as a method of pathogenetic physiotherapy of patients with lumbar osteochondrosis with various neurological manifestations.
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Segawa, Yuhiro, Kenji Yamazaki, Jun Yamasaki, and Kazutoshi Gohara. "Quasi-static 3D structure of graphene ripple measured using aberration-corrected TEM." Nanoscale 13, no. 11 (2021): 5847–56. http://dx.doi.org/10.1039/d1nr00237f.
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Our new method of measuring monolayer graphene revealed experimentally that the ripple structure was represented as a superposition of sinusoidal waves, with their wave vectors coinciding with the specific direction of the six-membered ring.
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HE KAI-FEN and HU GANG. "A PERTURBATION METHOD FOR THE NONLINEAR DRIFT WAVES DRIVEN BY A SINUSOIDAL WAVE." Acta Physica Sinica 40, no. 12 (1991): 1948. http://dx.doi.org/10.7498/aps.40.1948.
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Miyara, Akio. "Flow Dynamics and Heat Transfer of Wavy Condensate Film." Journal of Heat Transfer 123, no. 3 (2000): 492–500. http://dx.doi.org/10.1115/1.1370522.
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Wave evolution and heat transfer behavior of a wavy condensate film down a vertical wall have been investigated by a finite difference method, in which the algorithm is based on the HSMAC method, and a staggered grid fixed on a physical space is employed. For the moving interface, newly proposed methods are used. A random perturbation of the film thickness is generated near the leading edge. The perturbation quickly diminishes once and small-amplitude long waves are propagated downstream. Then the amplitude of the wave increases rapidly at a certain position, and the wave shape changes from a sinusoidal wave to a pulse-like solitary wave which is composed of a large-amplitude wave and capillary waves. A circulation flow occurs in the large wave and it affects the temperature field. The heat transfer is enhanced by space-time film thickness variation and convection effects.
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Ramaswamy, B., S. Chippada, and S. W. Joo. "A full-scale numerical study of interfacial instabilities in thin-film flows." Journal of Fluid Mechanics 325 (October 25, 1996): 163–94. http://dx.doi.org/10.1017/s0022112096008075.
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Surface wave instabilities in a two-dimensional thin draining film are studied by a direct numerical simulation of the full nonlinear system. A finite element method is used with an arbitrary Lagrangian–Eulerian formulation to handle the moving boundary problem. Both temporal and spatial stability analysis of the finite-amplitude nonlinear wave regimes are done. As the wavenumber is decreased below the linear cut-off wavenumber, supercritical sinusoidal waves occur as reported earlier from weakly nonlinear analysis and experiments. Further reduction in wavenumber makes the Fourier spectrum broad-banded resulting in solitary humps. This transition from nearly sinusoidal permanent waveforms to solitary humps is found to go through a quasi-periodic regime. The phase boundaries for this quasi-periodic regime have been determined through extensive numerical parametric search. Complex wave interaction processes such as wave merging and wave splitting are discussed. In the exhaustive numerical simulations performed in this paper, no wave-breaking tendency was observed, and it is speculated that the complex wave-interaction processes such as wave merging and wave splitting curb the tendency of the film to break.
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Ge, Hongli, Bingchen Liang, Libang Zhang, Zhenlu Wang, and Zihan Li. "Global field performance of monopile-supported offshore wind turbines with sinusoidal layouts using innovative combined grating conditions." Physics of Fluids 34, no. 9 (2022): 096608. http://dx.doi.org/10.1063/5.0116129.
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For the global performance of monopile wind farms, the desired wave field distribution using traditional layout methods is hard to obtain. In this study, the investigation aims to efficiently explore the potential wave response reduction of the multiple layer design of wind farm layouts using novel grating conditions. It is very important and necessary to optimize the layouts of monopile-supported OWTs (offshore wind turbines) by analyzing the wave field performance, especially considering scour protection and avoiding the proximity of the wave frequency to natural frequency of OWTs. This paper presents a layout and a design method of monopile-supported OWTs using combined grating theorems, which can take space modulation into account to deal with various issues in existing layouts. The results show that the present method can modulate the wave field responses more evenly than the conventional cases. More specifically, total wave field distribution sensitivities were discussed under different wavelengths, amplitudes, layouts, pile-radius, and the angles of incident waves. It can be illustrated that the monopile-supported OTWs with sinusoidal configurations can have more modulation effects on wave fields in an appropriate wavelength band. As indicated, this method not only provides wave space modulation control but also sheds light on the wave field reduction mechanisms.
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Chen, Binqiang, Qixin Lan, Yang Li, Shiqiang Zhuang, and Xincheng Cao. "Enhancement of Fault Feature Extraction from Displacement Signals by Suppressing Severe End Distortions via Sinusoidal Wave Reduction." Energies 12, no. 18 (2019): 3536. http://dx.doi.org/10.3390/en12183536.
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Displacement signals, acquired by eddy current sensors, are extensively used in condition monitoring and health prognosis of electromechanical equipment. Owing to its sensitivity to low frequency components, the displacement signal often contains sinusoidal waves of high amplitudes. If the digitization of the sinusoidal wave does not satisfy the condition of full period sampling, an effect of severe end distortion (SED), in the form of impulsive features, is likely to occur because of boundary extensions in discrete wavelet decompositions. The SED effect will complicate the extraction of weak fault features if it is left untreated. In this paper, we investigate the mechanism of the SED effect using theories based on Fourier analysis and wavelet analysis. To enhance feature extraction performance from displacement signals in the presence of strong sinusoidal waves, a novel method, based on the Fourier basis and a compound wavelet dictionary, is proposed. In the procedure, ratio-based spectrum correction methods, using the rectangle window as well as the Hanning window, are employed to obtain an optimized reduction of strong sinusoidal waves. The residual signal is further decomposed by the compound wavelet dictionary which consists of dyadic wavelet packets and implicit wavelet packets. It was verified through numerical simulations that the reconstructed signal in each wavelet subspace can avoid severe end distortions. The proposed method was applied to case studies of an experimental test with rub impact fault and an engineering test with blade crack fault. The analysis results demonstrate the proposed method can effectively suppress the SED effect in displacement signal analysis, and therefore enhance the performance of wavelet analysis in extracting weak fault features.
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Wang, Xiuwang, Jalil Manafian, Wayan Eka Mahendra, Azher M. Abed, Mustafa Z. Mahmoud, and Guizhen Liang. "Combined Damped Sinusoidal Oscillation Solutions to the (3 + 1)-D Variable-Coefficient Generalized NLW Equation in Liquid with Gas Bubbles." Advances in Mathematical Physics 2022 (May 18, 2022): 1–20. http://dx.doi.org/10.1155/2022/8144911.
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This paper investigates the combined damped sinusoidal oscillation solutions to the 3 + 1 -D variable-coefficient (VC) generalized nonlinear wave equation. The bilinear form is considered in terms of Hirota derivatives. Accordingly, we utilize a binary Bell polynomial transformation for reducing the Cole-Hopf algorithm to get the exact solutions of the VC generalized NLW equation. The damped sinusoidal oscillations for two cases of the nonlinear wave ordinary differential equation will be studied. Using suitable mathematical assumptions, the novel kinds of solitary, periodic, and singular soliton solutions are derived and established in view of the trigonometric and rational functions of the governing equation. To achieve this, the illustrative example of the VC generalized nonlinear wave equation is provided to demonstrate the feasibility and reliability of the procedure used in this study. The trajectory solutions of the traveling waves are shown explicitly and graphically. The effect of the free parameters on the behavior of acquired figures of a few obtained solutions for two nonlinear rational exact cases was also discussed. By comparing the proposed method with the other existing methods, the results show that the execution of this method is concise, simple, and straightforward.
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Lei, Dan, Kazutaka Mitsuishi, Masayuki Shimojo, and Masaki Takeguchi. "Reconstruction Method for Phase-Shifting Electron Holography Fitted with Fresnel Diffraction Affected Fringes." Materials Science Forum 833 (November 2015): 215–21. http://dx.doi.org/10.4028/www.scientific.net/msf.833.215.
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Phase shifting electron holography is a transmission electron microscope technique that a number of holograms with different initial phases are acquired by changing the angle of the incident electron beam, and the intensity variation at a certain point on the holograms is fitted by sinusoidal curve to retrieve the object wave passing through a specimen. In reality, however, Fresnel fringes caused by the electrostatic biprism modulates the electron wave, limits the fitting accuracy and results in phase errors in phase reconstruction. In this study, we suggest a modified phase reconstruction method for phase shifting electron holography. The intensity variations at a certain point on each hologram are fitted not by sinusoidal curve, but by Fresnel diffraction affected curve to retrieve the object wave. This would provide better fitting accuracy, and has a potential to improve the precision of phase shifting electron holography. Simulations demonstrated the improvements of this method comparing with conventional phase shifting holography method.
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SAKUSABE, Takashi, Takehiro TAKAHASHI, and Noboru SCHIBUYA. "Development of New Characteristic Impedance Measurement Method Using Sinusoidal Wave TDR." Journal of Japan Institute of Electronics Packaging 6, no. 6 (2003): 516–19. http://dx.doi.org/10.5104/jiep.6.516.
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Li, Di, Jin-Hua Zhou, Xin-Yao Hu, et al. "In situ calibrating optical tweezers with sinusoidal-wave drag force method." Chinese Physics B 24, no. 11 (2015): 118703. http://dx.doi.org/10.1088/1674-1056/24/11/118703.
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Effendi and Makandibengkel. "Studi Analisis Perbandingan Pwm Carrier Untuk Multilevel Inverter Tiga Fasa Lima Belas Level Dengan Sumber Input Simetris Terpisah." Jurnal JEETech 3, no. 1 (2022): 10–18. http://dx.doi.org/10.48056/jeetech.v3i1.185.
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Inverters are used to convert direct current or DC (Direct Current) sources into alternating current sources or AC (Alternating Current). A method is needed to make the output waveform close to a sinusoidal waveform. The Multi Level Inverter (MLI) method has a large number of levels and is closer to a sinusoidal wave. The three-phase MLI design with a separate symmetrical input source in this study is able to produce a three-phase output wave, where the resulting Total Harmonic Distortion (THD) value is smaller, namely 5.65% when using the Modified PWM method where the carrier signal has no frequency
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Wei, Yiwen, Lixin Guo, and Xiao Meng. "The Fast Simulation of Scattering Characteristics from a Simplified Time Varying Sea Surface." International Journal of Antennas and Propagation 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/815913.
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This paper aims at applying a simplified sea surface model into the physical optics (PO) method to accelerate the scattering calculation from 1D time varying sea surface. To reduce the number of the segments and make further improvement on the efficiency of PO method, a simplified sea surface is proposed. In this simplified sea surface, the geometry of long waves is locally approximated by tilted facets that are much longer than the electromagnetic wavelength. The capillary waves are considered to be sinusoidal line superimposing on the long waves. The wavenumber of the sinusoidal waves is supposed to satisfy the resonant condition of Bragg waves which is dominant in all the scattered short wave components. Since the capillary wave is periodical within one facet, an analytical integration of the PO term can be performed. The backscattering coefficient obtained from a simplified sea surface model agrees well with that obtained from a realistic sea surface. The Doppler shifts and width also agree well with the realistic model since the capillary waves are taken into consideration. The good agreements indicate that the simplified model is reasonable and valid in predicting both the scattering coefficients and the Doppler spectra.
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Sethu Meenakshi, M. V., S. Athisayanathan, V. Chinnathambi, and S. Rajasekar. "Effect of Fractional Damping in Double-Well Duffing–Vander Pol Oscillator Driven by Different Sinusoidal Forces." International Journal of Nonlinear Sciences and Numerical Simulation 20, no. 2 (2019): 115–24. http://dx.doi.org/10.1515/ijnsns-2016-0165.
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AbstractThe effect of nonlinear damping including fractional damping on the onset of horseshoe chaos is studied both analytically and numerically in the double-well Duffing–Vander Pol (DVP) oscillator driven by various sinusoidal forces. The sinusoidal type periodic forces of our interest are sine wave, rectified sine wave, and modulus of sine wave. Using the Melnikov analytical method, the threshold condition for the onset of horseshoe chaos is obtained for each sinusoidal force. Melnikov threshold curves are drawn in (f,\;ω) parameters space for each force. When the damping component (p) increases from a small value, the Melnikov threshold value $(f_{M})$ is decreased for each force. Suppression of horseshoe chaos is predicted due to the effect of weak periodic perturbation and nonlinear fractional damping. Analytical predictions are demonstrated through direct numerical simulations.
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Tuboi, Kazuo, Tatsuhiko Yamamoto, and Sadayoshi Hibino. "The running performance calculation using a quasi-sinusoidal wave method for a sinusoidal PWM inverter fed induction motor." IEEJ Transactions on Industry Applications 107, no. 10 (1987): 1213–20. http://dx.doi.org/10.1541/ieejias.107.1213.
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Zhao, Hui-Hui, Hong Du, Yujie Cai, Chao Liu, Zeyu Xie, and Kevin C. Chen. "Time-resolved quantification of the dynamic extracellular space in the brain: study of cortical spreading depression." Journal of Neurophysiology 121, no. 5 (2019): 1735–47. http://dx.doi.org/10.1152/jn.00348.2018.
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Extracellular diffusion in the brain is customarily characterized by two parameters, the extracellular space (ECS) volume fraction α and the diffusion tortuosity λ. How these two parameters are temporarily modified and correlated in a physiological/pathological event remains unclear to date. Using tetramethylammonium (TMA+) as an ECS ion tracer in a newly updated iontophoretic sinusoidal method, we studied in this work the dynamic α( t) and λ( t) in rat somatosensory cortex during spreading depression (SD). Temporal variations of α( t) and λ( t), as evoked by SD, were obtained through analyses of the extracellular TMA+ diffusion waveform resulting from a sinusoidally modulated point source. Most of the time, cortical SD induced coordinated α( t) decreases and λ( t) increases. In rare occasions, SD induced sole decreases of α( t) with no changes in λ( t). The independent modulation of α( t) and λ( t) was neither associated with cortical anatomy nor with the specific shape of the SD field potential wave. Changes of α( t) and λ( t) often took place acutely at the onset of SD, followed by a more transient modulation. Compared with the prior iontophoretic methods of TMA+, the sinusoidal method provides time-resolved quantification of α( t) and λ( t) in relative terms but also raises a higher property requirement on the TMA+-selective microelectrode. The sinusoidal method could become a valuable tool in the studies of the dynamic ECS response in various brain events. NEW & NOTEWORTHY An iontophoretic sinusoidal method was applied to study the dynamic changes of two extracellular space parameters, the extracellular volume fraction α( t) and tortuosity λ( t), in the brain during cortical spreading depression. Both parameters showed coordinated (most often) and independent (rarely) modulations in spreading depression. The sinusoidal method is equally applicable to other acute pathological events and a valuable tool to study the functional role of extracellular space in brain events.
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Del Giudice, Silvio, and Giancarlo Bernasconi. "Acoustic Response of a Sinusoidally Perturbed Hard-Walled Duct." Mathematical Problems in Engineering 2013 (2013): 1–6. http://dx.doi.org/10.1155/2013/267291.
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Acoustic wave propagation in hard-walled ducts is of interest in many fields including vehicle design, musical instruments acoustics, and architectural and environmental noise-control. For the case of small sinusoidal perturbation of the cross-section, it is possible to derive simple though approximate analytical formulas of its plane wave acoustic reflection and transmission spectral response that resembles the optical situation of uniform Bragg gratings. The proof is given here, starting from the “horn equation” and then exploiting the coupled-modes theory. Examples of the results obtained with these analytical formulas are shown for some sinusoidally perturbed ducts and compared to results obtained through a numerical method, revealing a very good agreement.
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Sang, Yong, Jianlong Zhao, Yu Zhu, and Lilai Shao. "A Novel Method of Improving Non-Sinusoidal Periodic Waveform in Force Excitation Control System." International Journal of Automation Technology 10, no. 3 (2016): 420–28. http://dx.doi.org/10.20965/ijat.2016.p0420.
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A non-sinusoidal periodic waveform, such as a triangle wave, is often used as the testing input signal in force excitation control systems. Limited by the bandwidth of the system, the output waveform is often distorted, and the dynamic tracking accuracy is reduced. As an alternative to a hardware upgrade, a novel method of improving the tracking precision of the non-sinusoidal periodic waveform in the force excitation control system is presented. A key technique of the method is the adjustment of the spectrum of the non-sinusoidal periodic waveform in advance according to the frequency response characteristic of the control system. The working principle of the frequency-box regulator, the formula derivation, and the operation steps are explained. Simulations and tests are conducted to confirm the effectiveness of the method. The results show that the novel method (frequency-box regulation) works well in the force excitation control system.
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Sun, Jian, Ling Wang, and Dianxuan Gong. "Model for Choosing the Shape Parameter in the Multiquadratic Radial Basis Function Interpolation of an Arbitrary Sine Wave and Its Application." Mathematics 11, no. 8 (2023): 1856. http://dx.doi.org/10.3390/math11081856.
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In multiquadratic radial basis function (MQ-RBF) interpolation, shape parameters have a direct effect on the interpolation accuracy. The paper presents an MQ-RBF interpolation technique with optimized shape parameters for estimating the parameters of sine wave signals. At first, we assessed the impact of basic sinusoidal parameters on the MQ-RBF interpolation outcomes through numerical experiments. The results indicated that the angular frequency of a sine wave is a crucial determinant of the corresponding MQ-RBF interpolation shape parameters. A linear regression method was then used to establish the optimal parameter selection formula for a single-frequency sine wave, based on a large volume of experimental data. For multi-frequency sinusoidal signals, appropriate interpolation shape parameters were selected using the random walk algorithm to create datasets. These datasets were subsequently used to train several regression models, which were then evaluated and compared. Based on its operational cost and prediction accuracy, the random forest algorithm was chosen to establish the shape parameter selection model for multi-frequency sinusoidal signals. The inclusion of the Bayesian optimizer resulted in a highly accurate model. The establishment of this model enabled the adaptive selection of the corresponding shape parameters for any sine wave signal, providing a convenient means of selecting MQ-RBF interpolation shape parameters. Furthermore, the paper proposes an MQ-RBF interpolation subdivision least squares method that significantly improves the estimation accuracy of sine wave parameters. The practicality of the method was validated by successfully applying it in the calibration of the clock delay mismatch of a time-interleaved analog-to-digital converter system.
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Abdolvahab, Vahid. "Investigating the Local Buckling of Rectangular Corrugated Plates." Civil Engineering Journal 2, no. 8 (2016): 389–97. http://dx.doi.org/10.28991/cej-2016-00000043.
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With advances in technology in recent years, the use of orthotropic materials to exclude the mechanical deficiencies of homogeneous plates has increased. Sinusoidal corrugated plates are known as orthotropic plates, as a result of changes in their mechanical properties in two orthogonal directions. Since use of corrugated plates, in particular steel shear walls instead of flat steel plates, has increased, the present study investigated local buckling of sinusoidal corrugated plates under uniform uniaxial loading on the transverse edges of the plate (vertical loading on the sinusoidal wave of corrugated plates), using the Galerkin method. This method is very powerful with regard to solving differential equations, and directly uses these equations in the process of problem-solving. Finally, the results obtained for the critical buckling load of sinusoidal corrugated metal plates and the results relating to the metal homogeneous flat plates were compared using the same supporting conditions and loading.
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Alshammari, Fahad Sameer, Zillur Rahman, Harun-Or Roshid, Mohammad Safi Ullah, Abdullah Aldurayhim, and M. Zulfikar Ali. "Dynamical Structures of Multi-Solitons and Interaction of Solitons to the Higher-Order KdV-5 Equation." Symmetry 15, no. 3 (2023): 626. http://dx.doi.org/10.3390/sym15030626.
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In this study, we build multi-wave solutions of the KdV-5 model through Hirota’s bilinear method. Taking complex conjugate values of the free parameters, various colliding exact solutions in the form of rogue wave, symmetric bell soliton and rogue waves form; breather waves, the interaction of a bell and rogue wave, and two colliding rogue wave solutions are constructed. To explore the characteristics of the breather waves, localized in any direction, the higher-order KdV-5 model, which describes the promulgation of weakly nonlinear elongated waves in a narrow channel, and ion-acoustic, and acoustic emission in harmonic crystals symmetrically is analyzed. With the appropriate parameters that affect and manage phase shifts, transmission routes, as well as energies of waves, a mixed solution relating to hyperbolic and sinusoidal expression are derived and illustrated by figures. All the single and multi-soliton appeared symmetric about an axis of the wave propagation. The analyzed outcomes are functional in achieving an understanding of the nonlinear situations in the mentioned fields.
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Moazam, S., B. Boroomand, S. Naimi, and M. Celikag. "Wave Propagation in Unbounded Domains under a Dirac Delta Function with FPM." Mathematical Problems in Engineering 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/470346.
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Wave propagation in unbounded domains is one of the important engineering problems. There have been many attempts by researchers to solve this problem. This paper intends to shed a light on the finite point method, which is considered as one of the best methods to be used for solving problems of wave propagation in unbounded domains. To ensure the reliability of finite point method, wave propagation in unbounded domain is compared with the sinusoidal unit point stimulation. Results indicate that, in the case of applying stimulation along one direction of a Cartesian coordinate, the results of finite point method parallel to the stimulation have less error in comparison with the results of finite element method along the same direction with the same stimulation.
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LI, Jingang, Ye HE, Shijun YUAN, Dayong QIAO, Deshui YU, and Zhiyuan LI. "Study on sinusoidal estimation deviation of electrostatic actuated MEMS mirror torsion angle." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 41, no. 2 (2023): 338–43. http://dx.doi.org/10.1051/jnwpu/20234120338.
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Electrostatic MEMS micromirrors usually work in resonant state to obtain large amplitude of torsion angle. The real-time prediction of MEMS micromirror torsion angle is calculated according to the measured resonant amplitude and phase under the assumption that the relationship between the torsion angle and time is sinusoidal. However, there are few reports on the deviation of this torsion angle predication based on sinusoidal assumption. In this paper, the real resonant torsion trajectory of C1100 MEMS micromirror under different driving frequencies and voltages is measured by using microscopic laser Doppler method, and the deviation between the real trajectory and the trajectory fitted by sinusoidal curve is compared. The results show that the real trajectory of the MEMS micromirror driven by square wave is not completely consistent with the sinusoidal estimation, and the deviation increases with the increase of the torsional angle amplitude. By obtaining the frequency domain components of the torsion angle signal using FFT method, the main reason of this prediction deviation is due to composition of harmonic signals on base frequency signal. The research results reveal that the sinusoidal assumption method is only suitable for situations when the optical angle accuracy is less than 0.1°.
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Fan, Xinyu, Changkun Wang, Zhibing Zhu, and Hao Meng. "Design and Analysis of a High Power Density Permanent Magnet Linear Generator for Direct-Drive Wave Power Generation." Actuators 11, no. 11 (2022): 327. http://dx.doi.org/10.3390/act11110327.
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Wave energy is a new type of clean energy. Aiming at a low wave energy density and small wave height in China’s coastal areas, a tubular permanent magnet linear generator (PMLG) with a short stroke, small volume, and high power density is designed for wave power generation. Firstly, the generator’s electromagnetic parameters are analyzed by the analytical method, and the magnetic circuit topology and basic structure of the generator are analyzed by the equivalent magnetic circuit method (EMCM). Then, the finite element method (FEM) is used to analyze the influence law of the generator’s basic structural parameters on the output electromotive force (EMF) and its sinusoidal characteristics. The multi-factor and multi-level analysis is carried out based on the orthogonal test method to study the size parameters of the above analysis, and the optimal structure parameter combination for the generator is obtained. Finally, the prototype is trial-produced and tested for steady-state and transient performance to confirm the accuracy of the simulation calculations, and the output performance under no-load and load conditions is examined. The results show that both the optimized prototype’s power density and the output EMF’s sinusoidal properties have been improved under the proposed scheme.
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Brühl, Markus, and Matthias Becker. "Analysis of Subaerial Landslide Data Using Nonlinear Fourier Transform Based on Korteweg-deVries Equation (KdV-NLFT)." Journal of Earthquake and Tsunami 12, no. 02 (2018): 1840002. http://dx.doi.org/10.1142/s179343111840002x.
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Subaerial and underwater landslides, rock falls and glacier calvings can generate impulse waves in lakes, fjords and the open sea. Experiments with subaerial landslides have shown that, depending on the slide characteristics, different wave types (Stokes, cnoidal or bore-like waves) are generated. Each of these wave types shows different wave height decay with increasing distance from the impact position. Furthermore, in very shallow water, the first impulse wave shows characteristic properties of a solitary wave. The nonlinear Fourier transform based on the Korteweg–deVries equation (KdV-NLFT) is a frequency-domain analysis method that decomposes shallow-water free-surface data into nonlinear cnoidal waves instead of linear sinusoidal waves. This method explicitly identifies solitons as spectral components within the given data. In this study, we apply the KdV-NLFT for the very first time to available 2D and 3D landslide-test data. The objective of the nonlinear decomposition is to identify the hidden nonlinear spectral structure of the impulse waves, including solitons. Furthermore, we analyze the determined solitons at different downstream positions from the impact point with respect to soliton propagation and modification. Finally, we draw conclusions for the prediction of the expected landslide-generated downstream solitons in the far-field.
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Axilrod, H. D., and J. F. Ferguson. "SH-wave scattering from a sinusoidal grating: An evaluation of four discrete wavenumber methods." Bulletin of the Seismological Society of America 80, no. 3 (1990): 643–55. http://dx.doi.org/10.1785/bssa0800030643.
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Abstract A useful test of discrete wavenumber modeling techniques is to model scattering from a sinusoidal free surface, while varying the maximum slope of the interface. Four discrete wavenumber methods, the Aki-Larner, the Waterman, the Waterman-Fourier, and the Campillo-Bouchon, are evaluated by testing for energy conservation and comparing displacement. Contrary to the claim of some authors (Varadan et al. 1987), the Waterman-Fourier shows no advantage over the Aki-Larner method for steep slopes. With the FFT to calculate the scattering matrix, the Waterman-Fourier method is as fast as Aki-Larner. The Campillo-Bouchon method is superior to the other methods in its ability to handle steep slopes, but it requires more wavenumber samples and is an order of magnitude slower.
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Lehmann, C. I., Y. H. Kim, P. Preusse, H. Y. Chun, M. Ern, and S. Y. Kim. "Consistency between Fourier transform and small-volume few-wave decomposition for spectral and spatial variability of gravity waves above a typhoon." Atmospheric Measurement Techniques Discussions 5, no. 1 (2012): 1763–93. http://dx.doi.org/10.5194/amtd-5-1763-2012.
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Abstract. Convective gravity wave (GW) sources are spatially localized and emit at the same time waves with a wide spectrum of phase speeds. Any wave analysis therefore compromises between spectral and spatial resolution. Future satellite borne limb imagers will for a first time provide real 3d volumes of observations. These volumes will be however limited which will impose further constraints on the analysis technique. In this study a three dimensional few-wave appoach fitting sinusoidal waves to limited 3-D volumes is introduced. The method is applied to simulated GWs above typhoon Ewiniar and GW momentum flux is estimated from temperature fluctuations. Phase speed spectra as well as average profiles of positive, negative and net momentum fluxes are compared to momentum flux estimated by Fourier transform as well as spatial averaging of wind fluctuations. The results agree within 10–20%. The few-wave method can also reveal the spatial orientation of the GWs with respect to the source. The relevance of the results for different types of measurements as well as its applicability to model data is discussed.
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Lehmann, C. I., Y. H. Kim, P. Preusse, H. Y. Chun, M. Ern, and S. Y. Kim. "Consistency between Fourier transform and small-volume few-wave decomposition for spectral and spatial variability of gravity waves above a typhoon." Atmospheric Measurement Techniques 5, no. 7 (2012): 1637–51. http://dx.doi.org/10.5194/amt-5-1637-2012.
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Abstract. Convective gravity wave (GW) sources are spatially localized and emit at the same time waves with a wide spectrum of phase speeds. Any wave analysis therefore compromises between spectral and spatial resolution. Future satellite borne limb imagers will for a first time provide real 3-D volumes of observations. These volumes will be however limited which will impose further constraints on the analysis technique. In this study a three dimensional few-wave approach fitting sinusoidal waves to limited 3-D volumes is introduced. The method is applied to simulated GWs above typhoon Ewiniar and GW momentum flux is estimated from temperature fluctuations. Phase speed spectra as well as average profiles of positive, negative and net momentum fluxes are compared to momentum flux estimated by Fourier transform as well as spatial averaging of wind fluctuations. The results agree within 10–20%. The few-wave method can also reveal the spatial orientation of the GWs with respect to the source. The relevance of the results for different types of measurements as well as its applicability to model data is discussed.
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Benilov, Eugene S. "Dynamics of ideal fluid flows over an uneven bottom." Journal of Fluid Mechanics 185 (December 1987): 551–68. http://dx.doi.org/10.1017/s0022112087003318.
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Two problems of the stability of ideal fluid flows over an uneven bottom are considered. The first is the study of stratified flow with a ‘rigid lid’. We use the method of multiple scales to derive an equation describing the evolution of internal waves corresponding to different modes and wave vectors. For the case of sinusoidal bottom irregularities we have constructed a solution describing the increase in time of the internal wave field - this proves the instability of the basic flow. The phenomenon is interpreted as a result of interaction (mutual generation) of internal waves with energies of opposite signs. Our consideration is based on the Hamiltonian approach which enables us to prove in the most simple way the existence of waves carrying negative energy. The case of random (not sinusoidal) bottom irregularities is also studied. Using the kinetic equation for the amplitudes of internal waves derived in the paper, we have established that the basic flow remains unstable as well. In the second part of the paper we consider the homogeneous flows with a free upper boundary. It is shown that this problem can be reduced to the previous one, with the only difference being that the role of unstable perturbations is now played by the surface (not internal) gravity waves. The Hamiltonian approach is consistently applied and allows us to take into account the nonlinearity of waves.
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Song, Chao, Tariq Alkhalifah, and Umair Bin Waheed. "A versatile framework to solve the Helmholtz equation using physics-informed neural networks." Geophysical Journal International 228, no. 3 (2021): 1750–62. http://dx.doi.org/10.1093/gji/ggab434.
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SUMMARY Solving the wave equation to obtain wavefield solutions is an essential step in illuminating the subsurface using seismic imaging and waveform inversion methods. Here, we utilize a recently introduced machine-learning based framework called physics-informed neural networks (PINNs) to solve the frequency-domain wave equation, which is also referred to as the Helmholtz equation, for isotropic and anisotropic media. Like functions, PINNs are formed by using a fully connected neural network (NN) to provide the wavefield solution at spatial points in the domain of interest, in which the coordinates of the point form the input to the network. We train such a network by backpropagating the misfit in the wave equation for the output wavefield values and their derivatives for many points in the model space. Generally, a hyperbolic tangent activation is used with PINNs, however, we use an adaptive sinusoidal activation function to optimize the training process. Numerical results show that PINNs with adaptive sinusoidal activation functions are able to generate frequency-domain wavefield solutions that satisfy wave equations. We also show the flexibility and versatility of the proposed method for various media, including anisotropy, and for models with strong irregular topography.
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Ruderman, M. S. "Nonlinear Surface Alfvén Wave Propagation in Solar Atmosphere." Symposium - International Astronomical Union 142 (1990): 237–38. http://dx.doi.org/10.1017/s0074180900087994.
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The paper deals with the surface wave propagation in the solar atmosphere. The plasma motion is supposed to be described by magnetohydrodynamic equations. In the first part of the paper the surface wave propagation on a single magnetic interface in the solar corona is considered. The plasma is assumed to be cold. Using the reductive perturbation method we derive the equation governing the evolution of nonlinear small-amplitude surface waves as follows This equation is written in a coordinate system moving with the phase velocity of linear waves. Dimensionless variables are used. The symbol H denotes the Hilbert transform. The shape of the interface is defined by the equation z = h(t,x) in the Cartesian coordinates x, y, z. The Reynolds number R determines the relative contributions of nonlinearity and viscosity. We take a source radiating a sinusoidal wave. Then the wave evolution is calculated numerically. We get that at large R the wave steepening takes place. This steepening leads to a strong increase of wave damping.
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Verma, Toran. "PWM Strategy with Multiple Carriers for Hybrid Multilevel Inverters Adapted from PV-Based." Journal of Futuristic Sciences and Applications 2, no. 2 (2019): 56–65. http://dx.doi.org/10.51976/jfsa.221908.
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This research makes a design recommendation for a multilayer solar inverter that uses the level shift pulse width modulation technology. Inverters that have numerous layers are able to take advantage of switching at many frequencies, with the fundamental frequency being the frequency with the lowest switching rate. In this particular instance, we make use of not one but two signals: one serves the function of a carrier signal, while the other serves the function of a reference signal. In multilayer level inverters (MLI), the triangle wave is used as a carrier signal, while the sinusoidal wave is employed as a reference signal for the method of pulse width modulation. In addition, the sinusoidal wave is used as a reference signal for the pulse height modulation technique. These two waves are combined to produce what is known as a multilayer level inverter (MLI). This study will conduct an in-depth investigation into how adjusting the level shift of the carrier signals affects hybrid PV-based MLIs and how to count harmonics in multilayer PV-based inverters. Both of these things increase voltage and significantly reduce losses. Both of these things are important for this study. Both of these subjects are going to be discussed at length in this investigation. In order to do an analysis of the voltage and current harmonics, a level shift method simulation is run on a multilayer cascaded hybrid PV-based inverter using Matlab/Simulink. This simulation is utilised to accomplish the task.
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Sharif, Sharifaddin. "Half-Sine Wave Modulation Technique a New Method for Generating Variable Frequency Sinusoidal Current." IEEE Transactions on Power Electronics 34, no. 7 (2019): 6575–82. http://dx.doi.org/10.1109/tpel.2018.2877469.
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Liu, Y., H. Liu, H. Zhang, and G. Miao. "Simulations of oil spread on a water surface." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 214, no. 6 (2000): 889–900. http://dx.doi.org/10.1243/0954406001523876.
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Numerical simulation of an oil slick spreading on still and wavy surfaces is described in this paper. The so-called σ transformation is used to transform the time-varying physical domain into a fixed calculation domain for the water wave motions and, at the same time, the continuity equation is changed into an advection equation of wave elevation. This evolution equation is discretized by the forward time and central space scheme, and the momentum equations by the projection method. A damping zone is set up in front of the outlet boundary coupled with a Sommerfeld-Orlanski condition at that boundary to minimize the wave reflection. The equations for the oil slick are depth-averaged and coupled with the water motions when solving numerically. As examples, sinusoidal and solitary water waves, the oil spread on a smooth plane and on still and wavy water surfaces are calculated to examine the accuracy of simulating water waves by Navier-Stokes equations, the effect of damping zone on wave reflection and the precise structures of oil spread on waves.
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Si, Jikai, Haichao Feng, Peng Su, and Lufeng Zhang. "Design and Analysis of Tubular Permanent Magnet Linear Wave Generator." Scientific World Journal 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/258109.
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Due to the lack of mature design program for the tubular permanent magnet linear wave generator (TPMLWG) and poor sinusoidal characteristics of the air gap flux density for the traditional surface-mounted TPMLWG, a design method and a new secondary structure of TPMLWG are proposed. An equivalent mathematical model of TPMLWG is established to adopt the transformation relationship between the linear velocity of permanent magnet rotary generator and the operating speed of TPMLWG, to determine the structure parameters of the TPMLWG. The new secondary structure of the TPMLWG contains surface-mounted permanent magnets and the interior permanent magnets, which form a series-parallel hybrid magnetic circuit, and their reasonable structure parameters are designed to get the optimum pole-arc coefficient. The electromagnetic field and temperature field of TPMLWG are analyzed using finite element method. It can be included that the sinusoidal characteristics of air gap flux density of the new secondary structure TPMLWG are improved, the cogging force as well as mechanical vibration is reduced in the process of operation, and the stable temperature rise of generator meets the design requirements when adopting the new secondary structure of the TPMLWG.
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Bassi, Hussain M. "A Modulation Scheme for Floating Source Multilevel Inverter Topology with Increased Number of Output Levels." International Journal of Electrical and Computer Engineering (IJECE) 6, no. 5 (2016): 1985. http://dx.doi.org/10.11591/ijece.v6i5.10492.
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<p>This paper presented and studied a new switching scheme for floating source multilevel inverters to produce more levels with the same number of switching devices. In the proposed scheme, the function of the dc sources, except the inner one, is to build up square wave or blocks that is close in the shape to the desired sinusoidal wave. The job of the inner switching devices is to increase the number of the levels to produce smother sinusoidal wave in the inverter output. This job can be done by adding or subtracting the value of the inner dc source to/from the blocks. The topology used in this paper is based on the conventional floating source multi-level inverter using two legs. This topology and modulation technique show substantial reduction in the total harmonics distortion when the modulation technique is the hybrid method. The performance of the proposed switching scheme in generating more levels has been evaluated by PSCAD/EMTDC simulation.</p>
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Bassi, Hussain M. "A Modulation Scheme for Floating Source Multilevel Inverter Topology with Increased Number of Output Levels." International Journal of Electrical and Computer Engineering (IJECE) 6, no. 5 (2016): 1985. http://dx.doi.org/10.11591/ijece.v6i5.pp1985-1993.
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<p>This paper presented and studied a new switching scheme for floating source multilevel inverters to produce more levels with the same number of switching devices. In the proposed scheme, the function of the dc sources, except the inner one, is to build up square wave or blocks that is close in the shape to the desired sinusoidal wave. The job of the inner switching devices is to increase the number of the levels to produce smother sinusoidal wave in the inverter output. This job can be done by adding or subtracting the value of the inner dc source to/from the blocks. The topology used in this paper is based on the conventional floating source multi-level inverter using two legs. This topology and modulation technique show substantial reduction in the total harmonics distortion when the modulation technique is the hybrid method. The performance of the proposed switching scheme in generating more levels has been evaluated by PSCAD/EMTDC simulation.</p>
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Wang, Hui, Zhengshi Liu, Bin Zhu, and Quanjun Song. "Multiple Harmonics Fitting Algorithms Applied to Periodic Signals Based on Hilbert-Huang Transform." Journal of Sensors 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/580152.
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A new generation of multipurpose measurement equipment is transforming the role of computers in instrumentation. The new features involve mixed devices, such as kinds of sensors, analog-to-digital and digital-to-analog converters, and digital signal processing techniques, that are able to substitute typical discrete instruments like multimeters and analyzers. Signal-processing applications frequently use least-squares (LS) sine-fitting algorithms. Periodic signals may be interpreted as a sum of sine waves with multiple frequencies: the Fourier series. This paper describes a new sine fitting algorithm that is able to fit a multiharmonic acquired periodic signal. By means of a “sinusoidal wave” whose amplitude and phase are both transient, the “triangular wave” can be reconstructed on the basis of Hilbert-Huang transform (HHT). This method can be used to test effective number of bits (ENOBs) of analog-to-digital converter (ADC), avoiding the trouble of selecting initial value of the parameters and working out the nonlinear equations. The simulation results show that the algorithm is precise and efficient. In the case of enough sampling points, even under the circumstances of low-resolution signal with the harmonic distortion existing, the root mean square (RMS) error between the sampling data of original “triangular wave” and the corresponding points of fitting “sinusoidal wave” is marvelously small. That maybe means, under the circumstances of any periodic signal, that ENOBs of high-resolution ADC can be tested accurately.
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Ly, E., and J. Nakamichi. "Time-linearised transonic computations including entropy, vorticity and shock wave motion effects." Aeronautical Journal 107, no. 1077 (2003): 687–95. http://dx.doi.org/10.1017/s0001924000013555.
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Abstract The effect of small perturbations on steady nonlinear transonic small disturbance flowfields, in the context of two-dimensional flows governed by the general-frequency transonic small disturbance equation with nonreflecting far-field boundary conditions, is investigated. This paper presents a time-linearised time-domain solution method that includes effects due to the shock-generated entropy and vorticity and shock wave motions. The solution procedure correctly accounts for the small-amplitude shock wave motion due to small unsteady changes in the aerofoil boundary conditions, and correctly models a flowfield with embedded strong shock waves. Steady and first harmonic pressure distributions for the NACA 0003 aerofoil with a harmonically oscillating flap, and NACA 0012 aerofoil undergoing a sinusoidal pitching oscillation, are predicted and compared with the Euler results.
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Eidsmoen, H. "Optimum Control of a Floating Wave-Energy Converter With Restricted Amplitude." Journal of Offshore Mechanics and Arctic Engineering 118, no. 2 (1996): 96–102. http://dx.doi.org/10.1115/1.2828829.
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In this paper, the use of optimal control techniques for improving the energy absorption by a wave-energy converter (WEC) is investigated. A mathematical model is developed for a floating body, which is exposed to an irregular incident wave, and is moving relative to a fixed reference. This model includes a control force from the power take-off and control machinery, and a friction force which restricts the oscillation amplitude. This force models end-stop devices, which are necessary to protect the machinery. An optimal control strategy is determined, based on variations of a Lagrange functional. This gives a set of adjoint equations in addition to the state equations, as a necessary condition for optimum. An algorithm is given for solving the problem numerically by iteration, based on a gradient method. It is shown that the optimal motion in a sinusoidal wave is not sinusoidal when the excursion is constrained. Instead, the motion should be stopped in certain intervals. In irregular waves the constrained solution is close to the unconstrained solution when the excursion is small. Moreover, the timings of the extrema and of the zero crossings agree fairly well. When the excursion is constrained, the mean output power is reduced compared to the unconstrained case, but the ratio between the output energy and the total energy passing through the machinery is increased. This means that the conversion efficiency of the machinery is less critical.
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Miranda, Martin, Nobuyuki Takei, Yuki Miyazawa, and Mikio Kozuma. "Multi-Harmonic Modulation in a Fiber-Optic Gyroscope." Sensors 23, no. 9 (2023): 4442. http://dx.doi.org/10.3390/s23094442.
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Optimizing the bias modulation of a fiber-optic gyroscope is crucial to improving its precision. In this study, we propose and demonstrate the use of multiple harmonics of sinusoidal modulation as an intermediate alternative to the widely used modulation methods: sinusoidal and square-wave modulation. We show that this alternative integrates the advantages of each modulation method by providing a smooth modulation that produces a clean, spike-free output and a satisfactory signal-to-noise ratio. By using three harmonics of modulation in combination with a high frequency to reduce thermal phase noise, we obtained an angular random walk of 5.2(2)μdeg/h and a bias instability of ∼10μdeg/h. This is the highest performance ever reported for fiber-optic gyroscopes.
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Zhao, Cheng Xi, Ru Hao Hua, Zheng Yin Ye, and Yue Wen Jiang. "Unsteady Aerodynamic Characteristics of the Pitched Supersonic Biplane." Applied Mechanics and Materials 798 (October 2015): 523–30. http://dx.doi.org/10.4028/www.scientific.net/amm.798.523.
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In this work, supersonic biplanes of the Busemann concept have been analysed, focusing on the unsteady aerodynamic characteristic due to flow disturbance using Computational Fluid Dynamics (CFD) codes in viscous flow. Flow disturbance is modelled by sinusoidal pitch motion simulated by mesh morphing using radial basis functions (RBF) method. The results suggest that there are two flow patterns of the Busemann biplane: oblique wave sequences flow (Pattern A) and choke-flow (Pattern B) with higher wave drag. Unsteady aerodynamic disturbance represented by pitch motion may cause flow pattern transformation. We have also obtained that Pattern B is more stable than Pattern A and choke-flow cannot be eliminated even after returning to the initial flight attitude. Moreover, amplitudes and frequencies of sinusoidal pitch motion play important roles in flow pattern transformation and there exist critical amplitudes and frequencies.