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Physical Review E 2020年第4期102卷 042217-042217页

作者： Géraud R. Goune Chengui Kengne Jacques Paul Woafo Yanne K. Chembo Laboratories d'Automatique et Informatique Appliquée (UR-AIA) Department of Electrical Engineering IUT-FV Bandjoun P.O. Box 134 Bandjoun Cameroon Laboratory of Modelling and Simulation in Engineering Biomimetics and Prototypes Department of Physics Faculty of Science P.O. Box 812 Yaoundé Cameroon University of Maryland A. James Clark School of Engineering Department of Electrical and Computer Engineering and Institute for Research in Electronics and Applied Physics (IREAP) 8279 Paint Branch Drive College Park Maryland 20742 USA

We investigate the nonlinear dynamics of a recent architecture of an optoelectronic oscillator, where the emitting laser and the receiving diode are connected in a head-to-tail configuration via an optical fiber delay line. The resulting nonlinear transfer function is a piecewise linear profile, and its interplay with the delay leads to many complex behaviors such as relaxation oscillations and deterministic chaos. This system belongs to a recent class of optoelectronic oscillators where the nonlinearity does not originate from the sinusoidal transfer function of an imbalanced interferometer, and, in particular, it is a simple optoelectronic oscillator configuration that is capable of displaying a chaotic behavior. The results of the analytic study are confirmed by numerical simulations and experimental measurements.

关键词： Control & applications of chaos Chaotic systems

Modeling of Hygro-Mechanical Behaviour through Raffia vinifera Fiber during the Water Diffusion Phenomenon

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Mathematical Problems in engineering 2021年第1期2021卷

作者： Takoudjou, Harrond Nimjieu Sikame Tagne, Nicodème R. Nwagoum Tuwa, Peguy R. Fogue, Médard Njeugna, Ebenezer IUT/FV Bandjoun-University of Dschang P.O. Box. 134 Dschang Bandjoun Cameroon Faculty of Science-University of Dschang Dschang Cameroon ENSET-University of Douala P.O. Box. 1872 Douala Douala Cameroon ENSET-University of Douala P.O. Box. 1872 Douala Douala Cameroon Lab. on Modelling and Simulation in Engineering Biomimetics and Prototypes and Twas Research Unit Faculty of Science University of Yaounde I P.O. Box. 812 Yaounde Yaounde Cameroon

In an industrial context where the use of friendly materials is encouraged, natural fibers of vegetable origin become more solicited for the reinforcement of composite materials. This work deals with the modeling of the hygro-mechanical behavior through raffia vinifera fiber during the diffusion phenomenon. The modeling of water diffusion through the raffia vinifera fiber is described by Fick's second law and taking into account the swelling phenomenon of the fiber. The equation obtained is solved numerically by the finite difference method, and the evolution of the fiber radius as a function of time is obtained. By applying the Leibniz integration rule, a mathematical expression to predict the evolution of this radius as a function of time is proposed. It is observed numerically and analytically an increase of the dimensionless fiber radius with time up to a critical value after what one observes the saturation. This model allowed us to propose a mathematical model describing the absorption kinetics of the raffia vinifera fiber through its absorption ratio. By comparing the results of this model with the experimental results from the literature, one observes a good agreement. Moreover, the induced stresses in the fiber during the water diffusion can also be estimated with the proposed mathematical model expression of fiber. These stresses increase with time and can reach between 5 and 7 GPa. The results of this work can be used to predict the behavior of the raffia vinifera fiber inside a composite material during its development. © 2021 Harrond Nimjieu Takoudjou et al.

关键词： Finite difference method

Chaotic dynamics of piezoelectric MEMS based on maximal Lyapunov exponent and Smaller Alignment Index computations

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arXiv 2019年

作者： Tchakui, M.V. Woafo, P. Skokos, Ch. Laboratory of Modelling and Simulation in Engineering Biomimetics and Prototypes Department of Physics Faculty of Science University of Yaounde i BOX 812 Yaounde Cameroon Nonlinear Dynamics and Chaos Group Department of Mathematics and Applied Mathematics University of Cape Town Rondebosch7701 South Africa

We characterize the dynamical states of a piezoelectric microelectromechanical system (MEMS) using several numerical quantifiers including the maximal Lyapunov exponent, the Poincaré Surface of Section and a chaos detection method called the Smaller Alignment Index (SALI). The analysis makes use of the MEMS Hamiltonian. We start our study by considering the case of a conservative piezoelectric MEMS model and describe the behavior of some representative phase space orbits of the system. We show that the dynamics of the piezoelectric MEMS becomes considerably more complex as the natural frequency of the system's mechanical part *** refers to the reduction of the stiffness of the piezoelectric transducer. Then, taking into account the effects of damping and time dependent forces on the piezoelectric MEMS, we derive the corresponding non-autonomous Hamiltonian and investigate its dynamical behavior. We find that the non-conservative system exhibits a rich dynamics, which is strongly inuenced by the values of the parameters that govern the piezoelectric MEMS energy gain and loss. Our results provide further evidences of the ability of the SALI to efficiently characterize the chaoticity of dynamical *** Codes 74H65, 74H60 Copyright © 2019, The Authors. All rights reserved.

关键词： Hamiltonians

Corrigendum to "Modeling, simulation and optimization of solid fuel bread ovens commonly used in developing countries" [Heliyon 7(2), (February 2021) Article e06184]

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Heliyon 2021年第3期7卷 e06585页

作者： C F Kouemou Hatou G Tchuen P Woafo LaMSEBP: Laboratory of Modelling and Simulation in Engineering Biomimetic and Prototypes Department of Physic University of Yaoundé 1 Po Box 812 Yaoundé Cameroon. LISIE: Laboratory of Engineering Industrials and Environmental Systems University Institute of Technology - FOTSO VICTOR Badjoun (I.U.T- FV) University of DSCHANG Cameroon Po Box 134 Bandjoun Cameroon.

[This corrects the article DOI: 10.1016/***.2021.e06184.].

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Distant entanglement enhanced in PT-symmetric optomechanics

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Physical Review A 2017年第3期96卷 033856-033856页

作者： C. Tchodimou P. Djorwe S. G. Nana Engo Laboratory of Photonics Department of Physics Faculty of Science University of Ngaoundere P.O. Box 454 Ngaoundere Cameroon Laboratory of Modelling and Simulation in Engineering Biomimetics and Prototypes Department of Physics Faculty of Science University of Yaounde I P.O. Box 812 Yaounde Cameroon

We study steady-state continuous-variable entanglement in a three-mode optomechanical system consisting of an active optical cavity (gain) coupled to a passive optical cavity (loss) supporting a mechanical mode. For a driving laser which is blue-detuned, we show that coupling between optical and mechanical modes is enhanced in the unbroken-PT-symmetry regime. We analyze the stability and this shows that steady-state solutions are more stable in the gain and loss systems. We use these stable solutions to generate distant entanglement between the mechanical mode and the optical field inside the gain cavity. It results in a giant enhancement of entanglement compared to what is generated in the single lossy cavity. This work offers the prospect of exploring quantum state engineering and quantum information in such systems. Furthermore, such entanglement opens up an interesting possibility to study spatially separated quantum objects.

关键词： Optomechanics

Effect of tendon structural control on the appearance of horseshoes chaos on a cantilever beam due to seismic action

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arXiv 2017年

作者： Nbendjo, B.R. Nana Dorka, U. Laboratory of Modelling and Simulation in Engineering and Biomimetics and Prototypes University of Yaoundé i P. O. Box 812 Yaoundé Cameroon Steel and Composite Structures Kassel University Kurt-Woltersstrasse 3 Kassel34125 Germany

This paper deals with the problem of improving the seismic strength of mechanical structures by using a tendon system as actuation device. It consists of a pair of tension cables transmitting a control torque to the structure at the moment arm position. The purpose of the paper is to, establish the analytical framework consisting of mathematical modelling of cantilever beam under active tendon structural control, analyze the stability and, determine the physical characteristics of tendon system leading to the suppression of horseshoes chaos. The control efficiency is found by analyzing the behavior of the controlled system through the Melnikov methods. We also provide the critical control gain parameters leading to the efficiency of the control process. Copyright © 2017, The Authors. All rights reserved.

关键词： Cantilever beams

Amplitude stochastic response of Rayleigh beams to randomly moving loads

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arXiv 2017年

作者： Anague Tabejieu, L.M. Nana Nbendjo, B.R. Filatrella, G. Woafo, P. Laboratory of Modelling and Simulation in Engineering Biomimetics and Prototypes Faculty of Science University of Yaounde I P.O. Box 812 Yaounde Cameroon Department of Science and Technologies University of Sannio Via Port’ Arsa 11 BeneventoI-82100 Italy

We consider the problem of the nonlinear response of a Rayleigh beam to the passage of a train of forces moving with stochastic velocity. The Fourier transform and the theory of residues is used to estimate the mean-square amplitude of the beam, while the stochastic averaging method gives the stationary probability density function of the oscillations amplitude. The analysis shows that the effect of the load random velocities is highly nonlinear, leading to a non-monotonic behavior of the mean amplitude versus the intensity of the stochastic term and of the load weight. The analytic approach is also checked with numerical simulations. The effect of loads number on the system response is numerically investigated. Copyright © 2017, The Authors. All rights reserved.

关键词： Stochastic systems

Distant entanglement enhanced in PT -symmetric optomechanics

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arXiv 2017年

作者： Tchodimou, C. Djorwe, P. Nana Engo, S.G. Laboratory of Photonics Department of Physics Faculty of Science University of Ngaoundere P.O. Box 454 Ngaoundere Cameroon Laboratory of Modelling and Simulation in Engineering Biomimetics and Prototypes Department of Physics Faculty of Science University of Yaounde I P.O. Box 812 Yaounde Cameroon

We study steady-state continuous variable entanglement in a three-mode optomechanical system consisting of an active optical cavity (gain) coupled to a passive optical cavity (loss) supporting a mechanical mode. For a driving laser which is blue-detuned, we show that coupling between optical and mechanical modes is enhanced in the unbroken-PT -symmetry regime. We analyze the stability and this shows that steady-state solutions are more stable in the gain and loss systems. We use these stable solutions to generate distant entanglement between the mechanical mode and the optical field inside the gain cavity. It results in a giant enhancement of entanglement compared to what is generated in the single lossy cavity. This work offers the prospect of exploring quantum state engineering and quantum information in such systems. Furthermore, such entanglement opens up an interesting possibility to study spatially separated quantum objects. Copyright © 2017, The Authors. All rights reserved.

关键词： Quantum optics

Implementation of a PN junction rectifying diode in a metasurface for efficient electromagnetic energy harvesting

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Implementation of a PN junction rectifying diode in a metasu...

Conference on Lasers and Electro-Optics Europe

作者： G. T. Oumbe Tekam V. Ginis J. Danckaert P. Tassin Applied Physics Research Group Vrije Universiteit Brussel Pleinlaan 2 B-1050 Brussels Belgium Laboratory of Modelling and Simulation in Engineering Biomimetics and Prototypes Department of Physics Faculty of Science University of Yaoundé I P.O. Box 812 Yaoundé Cameroon Department of Physics Chalmers University SE-412 96 Göteborg Sweden

ISBN: (纸本)9781509067374

Recently, it was demonstrated that metamaterials can be used to harvest ambient electromagnetic energy [1]. However, the choice of the rectifying circuit for highly efficient energy conversion of RF electromagnetic power to DC power remains an important challenge [2,3]. Therefore, it is important to design a metasurface integrating a rectifier circuit in combination with a proper matching impedance to optimize the power transfer.

关键词： Finite element method Germanium Metamaterials Microwaves Nonlinear metamaterials Silicon

Existence and switching behavior of bright and dark kerr solitons in whispering-gallery mode resonators with zero group-velocity dispersion

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arXiv 2017年

作者： Talla Mbé, Jimmi H. Milián, Carles Chembo, Yanne K. Laboratory of Electronics Automation and Signal Processing Department of Physics University of Dschang P.O. Box 67 Dschang Cameroon Laboratory of Modelling and Simulation in Engineering Biomimetics and Prototypes Department of Physics University of Yaoundé I P. O. Box 812 Yaoundé Cameroon Polytechnic School of Yaoundé P.O. Box 8390 Yaoundé Cameroon Centre de Physique Théorique CNRS Ecole Polytechnique PalaiseauF-91128 France Optics Department FEMTO-ST Institute CNRS & Univ. Bourgogne-Franche-Comté 15B Avenue des Montboucons Besançon Cedex25030 France Atlanta Mirror Lab School of Electrical and Computer Engineering 777 Atlantic Dr NW AtlantaGA30332-0250 United States

We use the generalized Lugiato-Lefever model to investigate the phenomenon of Kerr optical frequency comb generation when group-velocity dispersion is null. In that case, the first dispersion term that plays a leading role is third-order dispersion. We show that this term is sufficient to allow for the existence of both bright and dark solitons. We identify the areas in the parameter space where both kind of solitons can be excited inside the resonator. We also unveil a phenomenon of hysteretic switching between these two types of solitons when the power of the pump laser is cyclically varied. Copyright © 2017, The Authors. All rights reserved.

关键词： Group velocity dispersion