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Parameters optimization of grounded dynamic vibration absorber with pendulum connected via the lever mechanism

Noise and Vibration Worldwide 2023年第6期54卷 297-306页

作者： Baduidana, Marcial Kenfack-Jiotsa, Aurelien Laboratory of Mechanics Materials and Structures Department of Physics Faculty of Science University of Yaounde Yaounde Cameroon Nonlinear and Complex Systems Physics Group Departement of Physics The Higher Teacher Training College University of Yaounde Yaounde Cameroon Department of Physics Higher Teacher Training College University of Yaounde Yaounde Cameroon

This paper investigates the control performance of grounded dynamic vibration absorber (DVA) with pendulum connected via the lever mechanism. These optimal parameters are found based on the extended fixed point theory. However, in the optimal equivalent stiffness derivation process, it was found that the amplified mass ratio could only take limited values to guarantee the stability condition of the coupled system and make positive equivalent stiffness. As a result, the best working range of the amplified mass ratio was established. The results analysis of the influence of system parameters on the primary system response shown that the amplified mass ratio has greatly vibration reduction effect, which push the peak resonant vibration of the primary system smaller than its static response without control. To better understand the control performance of the proposed DVA, three other dynamic vibration absorbers with or without negative stiffness are considered. The control performance comparison show that under harmonic excitation or even random excitation of the primary system, the proposed DVA model has a significant vibration reduction effect compared to the considered its DVA counterparts. The interest of these relevant results can be used in the field of vibration control engineering. © The Author(s) 2023.

关键词： Pendulums

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Localized nonlinear waves in a myelinated nerve fiber with self-excitable membrane

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Chinese physics B 2023年第2期32卷 150-162页

作者： Nkeh Oma Nfor Patrick Guemkam Ghomsi Francois Marie Moukam Kakmeni Department of Physics HTTC BambiliUniversity of BamendaP.P.Box 39 BambiliCameroon Complex Systems and Theoretical Biology Group Laboratory of Research on Advanced Materials and Nonlinear Science(LaRAMaNS)Department of PhysicsFaculty of ScienceUniversity of BueaP.O.Box 63 BueaCameroon

We systematically study the evolution of modulated nerve impulses in a myelinated nerve fiber, where both the ionic current and membrane capacitance provide the necessary nonlinear feedbacks. This is achieved by using a perturbation technique, in which the Liénard form of the modified discrete Fitzhugh–Nagumo equation is reduced to the complex Ginzburg–Landau amplitude equation. Three distinct values of the capacitive feedback parameter are considered. At the critical value of the capacitive feedback parameter, it is shown that the dynamics of the system is governed by the dissipative nonlinear Schr?dinger equation. Linear stability analysis of the system depicts the instability of plane waves,which is manifested as burst of modulated nerve impulses that fulfills the Benjamin–Feir criteria. Variations of the capacitive feedback parameter generally influences the plane wave stability and hence the type of wave profile identified in the neural network. Results of numerical simulations mainly confirm the propagation, collision, and annihilation of nerve impulses in the myelinated axon.

关键词： myelinated nerve Fitzhugh–Nagumo capacitive feedback parameter Ginzburg–Landau collision annihilation

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PT-symmetric electronic dimer without gain material

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Communications in Theoretical physics 2023年第11期75卷 56-65页

作者： Senghor Tagouegni Fernande Fotsa-Ngaffo Aurélien Kenfack-Jiotsa Laboratory of Mechanics Materials and StructuresDepartment of PhysicsFaculty of ScienceUniversity of Yaounde IPO Box 812YaoundeCameroon Nonlinear Physics and Complex Systems Group Department of PhysicsThe Higher Teacher’s Training CollegeUniversity of Yaounde IPO Box 47 YaoundeCameroon Institute of Wood Technologies University of Yaounde IPO Box 306MbalmayoCameroon

In this paper,a way of building an electronic Parity Time(PT)-symmetric dimer without gain material is *** is achieved by capacitively coupling a pair of LZC circuits,each combining an inductance L,an imaginary resistance Z and a positive/negative capacitance *** derive the effective Hamiltonian of the system,which commutes with the joint PT *** eigenspectrum displays spontaneous breaking points,where the system undergoes a transition from real to complex *** transition points are imposed by the range value of the coupling thanks to the use of a negative *** charge solutions and energy propagation are also analytically and numerically investigated,and the results are *** the exact phase,these quantities oscillate,whereas in the broken phase,oscillations disappear,giving place to *** results pave the way to innovative PT-symmetric *** could include,among others,optics,metamaterials,photonics and sensitive detection.

关键词： negative capacitance parity-time(PT)symmetry imaginary resistance

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Modeling the Seasonal Temperature from Hourly Data: Seasonal Divisions

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Atmospheric and Climate Sciences 2024年第4期14卷 474-483页

作者： Nicodeme Djiedeu Esther C. Modi-Mbog Laurent Nana CEPAMOQ Faculty of Science University of Douala Douala Cameroon Pure Physics Laboratory Group of Nonlinear Physics and Complex Systems Department of Physics Faculty of Science University of Douala Douala Cameroon Department of National Meteorology Ministry of Transport Yaounde Cameroon

In this work, we present a general theoretical study leading to analytical expression of the seasonal temperature at the near surface that is expected to evaluate any area seasonal temperature of the world using the least square method to fit the hourly data to the theoretical curve of the temperature. It is shown that the temperature is globally the result of two contributions: the contribution of the revolution movement of the terrestrial globe on its elliptical orbit around the sun, the contribution of the spin-orbit coupling for the rotation movement of the terrestrial globe around its polar axis and its revolution movement. The orbital behavior of the temperature is used to find the seasonal divisions of the climate for the local area considered. The whole expression of the temperature is very useful for the meteorological needs. The contribution of the human activities and natural instabilities are the results of discrepancies which increase errors (standard deviations).

关键词： Seasonal Temperature Orbital Temperature Spin-Orbit Temperature Hourly Data Seasonal Divisions

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Annealing approach to root finding

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Physical Review E 2024年第2期110卷 025305-025305页

作者： Junghyo Jo Alexandre Wagemakers Vipul Periwal Department of Physics Education Center for Theoretical Physics and Artificial Intelligence Institute School of Computational Sciences Nonlinear Dynamics Chaos and Complex Systems Group Departamento de Física Laboratory of Biological Modeling National Institute of Diabetes and Digestive and Kidney Diseases

The Newton-Raphson method is a fundamental root-finding technique with numerous applications in physics. In this study, we propose a parameterized variant of the Newton-Raphson method, inspired by principles from physics. Through analytical and empirical validation, we demonstrate that this approach offers increased robustness and faster convergence during root-finding iterations. Furthermore, we establish connections to the Adomian series method and provide a natural interpretation within a series framework. Remarkably, the introduced parameter, akin to a temperature variable, enables an annealing approach. This advancement sets the stage for a fresh exploration of numerical iterative root-finding methodologies.

关键词： Numerical techniques Simulated annealing

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Single Mode Periodic Wave Trains in Self-Gravitating Dusty Plasma

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Journal of Applied Mathematics and physics 2023年第11期11卷 3585-3609页

作者： Francis Formusang Ngwabe François Marie Moukam Kakmeni Complex Systems and Theoretical Biology Group Laboratory of Research on Advanced Materials and Nonlinear Science (LaRAMaNS) Department of Physics Faculty of Science University of Buea Buea Cameroon

In this paper, we consider the dynamics of modulated waves in an unmagnetized, non-isothermal self-gravitating dusty plasma model. The varying charge on the moving dust, as it moves in and out of regions of differing electron and ion densities (due to changes in the electrostatic potential), will be out of phase with the equilibrium charge. The effect of the dust is to increase the phase velocity of the ion-acoustic (IA) waves i.e. decrease the Landau damping. In the low-amplitude limit and weak damping, we apply the reductive perturbation method on the model that resulted to the complex cubic Ginzburg-Landau (CCGL) equation. From these results, it is observed that, the plasma parameters strongly influence the properties of the solitary wave solution namely, the amplitude and the width. The effects of non-isothermal electrons, gravity, dust charge fluctuations and drifting motion on the ion-acoustic solitary waves are discussed with application in astrophysical contexts. It is also observed that the number of charges residing on the dust grains increases the modulational stability of the plane waves in the plasma, thus, enhancing the generation of modulated waves.

关键词： Ginzburg-Landau Equation Weierstrass Function Modulated Waves Self-Gravitating Dusty Plasma

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Influence of the discrete lattice spacing on the formation of intrinsic localized structures in the Salerno model

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Optik 2024年 299卷

作者： Djoufack, Z.I. Nguenang, J.P. Kenfack-Jiotsa, A. Fotso Victor University Institute of Technology University of Dschang P.O. Box 134 Bandjoun Cameroon Pure physics laboratory: Group of Nonlinear physics and Complex systems Department of Physics University of Douala P.O. Box 24157 Douala Cameroon 6 Melrose Road Muizenberg Cape Town7945 South Africa Nonlinear physics and Complex systems Department of Physics The Higher Teachers’ Training College University of Yaounde I P.O. Box 47 Yaounde Cameroon

We report in this paper the influence of the discrete lattice spacing on the formation of intrinsic localized structures in the Salerno model. Through the linear stability analysis, appearance criterions of the modulation instability (MI) are derived. We show via the growth rate that, the discrete lattice spacing and the nonlinearity term can affect significantly the formation of instability zones. We find that for large values of the discrete lattice spacing, the MI is developed to increase the number instability zones whereas for very low values of this parameter, the MI growth rate is arisen up to enlarge the bandwidth. The theoretical findings have been numerically tested via the discrete spatial Fourier transform method and the direct simulations, and have been found to be in full agreement with the analytical prediction. Moreover, it has been revealed that a higher modulation index can dramatically modify the shape and the amplitude of the modulated waves. © 2024 Elsevier GmbH

关键词： Linear stability analysis

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Chaotic dynamics creates and destroys branched flow

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Physical Review E 2025年第1期111卷 014214-014214页

作者： Alexandre Wagemakers Aleksi Hartikainen Alvar Daza Esa Räsänen Miguel A. F. Sanjuán Nonlinear Dynamics Chaos and Complex Systems Group Departamento de Física Universidad Rey Juan Carlos Tulipán s 28933 Móstoles Madrid Spain Computational Physics Laboratory Tampere University 33720 Tampere Finland Department of Physics Harvard University Cambridge Massachusetts 02138 USA

The phenomenon of branched flow, visualized as a chaotic arborescent pattern of propagating particles, waves, or rays, has been identified in disparate physical systems ranging from electrons to tsunamis, with periodic systems only recently being added to this list. Here, we explore the laws governing the evolution of the branches in periodic potentials. On one hand, we observe that branch formation follows a similar pattern in all nonintegrable potentials, no matter whether the potentials are periodic or completely irregular. Chaotic dynamics ultimately drives the birth of the branches. On the other hand, our results reveal that for periodic potentials the decay of the branches exhibits new characteristics due to the presence of infinitely stable branches known as superwires. Again, the interplay between branched flow and superwires is deeply connected to Hamiltonian chaos. In this work, we explore the relationships between the laws of branched flow and the structures of phase space, providing extensive numerical and theoretical arguments to support our findings.

关键词： Hamiltonians

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Impact of Higher-Order Effects on the Stationary and Pulsating Localized Soliton in a nonlinear and Dissipative Medium

SSRN

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SSRN 2023年

作者： Nana, Laurent Saadeu, Gaétan Kuetche Pure Physics Laboratory Group of Nonlinear phenomena in Complex Systems Department of Physics Faculty of Sciences University of Douala P.O. Box 24157 Douala Cameroon

In this paper, we have investigated by numerical solution of the basic equation as well as by the dynamical model the influence of higher-order effects on the dissipative soliton mapping in the complex cubic-quintic Ginzburg-Landau equation (CCQGLE). We generated stationary and pulsating solutions, localized and delocalized from the equilibrium point. This was done using a mathematical formula developed on the basis of our finite degree of freedom dynamical model. This formula linking all the parameters of disturbance, allowed us to explain certain phenomena. It presented several aspects under the influence of the fourth-order dispersion. It was shown that long-lived pulsed solutions with relatively small fluctuations can be considered as nonlinear solutions. We found that the limit cycle that appeared was faster in the case where the initial frequency was zero and the initial chirp was non-zero. The higher-order effect that moved the trajectory away from the limit cycle was compensated by another effect (the nonlinearity compensated the dispersion). The oscillations were maintained (oscillation of the energy around a fixed value) thanks to the stable limit cycles and we obtained preserved structures over long distances. In the presence of noise, we found that the structure was more robust in the self-frequency shift case compared to the fourth-order dispersion case. The resulting pulsating solutions are distorted and frequency shifted. The self-frequency shift allowed us to modify the initial pulse by changing its amplitude, frequency and bandwidth. Intrapulse Raman scattering allowed us to have a large stability domain. All higher-order effects can influence the dynamics of the initial pulse. A comparison between the results obtained by the basic equation and the dynamical model was presented to verify its applicability. These results allow us to transmit information over long distances. © 2023, The Authors. All rights reserved.

关键词： Solitons

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Investigation of bright and dark solitons in α,β-Fermi Pasta Ulam lattice

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Chinese physics B 2021年第2期30卷 211-219页

作者： Nkeh Oma Nfor Serge Bruno Yamgoué Francois Marie Moukam Kakmeni Department of Physics Higher Teacher Training College BambiliThe University of BamendaP.O.Box 39Bambili-Cameroon Complex Systems and Theoretical Biology Group Laboratory of Research on Advanced Materials and Nonlinear Science(LaRAMaNS)Department of PhysicsFaculty of ScienceUniversity of BueaP.O.Box 63 Buea-Cameroon

We consider the Hamiltonian ofα,β-Fermi Pasta Ulam lattice and explore the Hamilton-Jacobi formalism to obtain the discrete equation of *** using the continuum limit approximations and incorporating some normalized parameters,the extended Korteweg-de Vries equation is obtained,with solutions that elucidate on the Fermi Pasta Ulam *** further derive the nonlinear Schrodinger amplitude equation from the extended Korteweg-de Vries equation,by exploring the reductive perturbative *** dispersion and nonlinear coefficients of this amplitude equation are functions of theαandβparameters,with theβparameter playing a crucial role in the modulational instability analysis of the ***βgreater than or equal to zero,no modulational instability is observed and only dark solitons are identified in the *** forβless than zero,bright solitons are traced in the lattice for some large values of the *** of numerical simulations of both the Korteweg-de Vries and nonlinear Schr¨odinger amplitude equations with periodic boundary conditions clearly show that the bright solitons conserve their amplitude and shape after collisions.

关键词： Fermi Pasta Ulam paradox bright dark

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