Rosalie Laure WOULACHE

Propagating discrete breather due to plane wave in electrical transmission lattice with imaginary resistance

Pierre Anselme Simo Motcheyo, Rosalie Laure Woulaché, E. Tchomgo Felenou, A.B. Togueu Motcheyo, Timoléon Crépin Kofané

Physica Scripta

Abstract We examined the discrete nonlinear Schrödinger (DNLS) equation as a voltage on a discrete electrical line in the presence of an imaginary resistance. The continuous approximation of the steady state allows for acquiring a static breather, whose amplitude decreases when the imaginary resistance increases. The linear stability and the full integration lead to seeing that the breather is stable when the centre is in the middle of the lattice, but becomes unstable when it’s near the edge. The analytical amplitude of the static discrete breather matches very well with the numerical supratransmission threshold. A method for propagating discrete breathers is proposed. To achieve this, a static and unstable breather is shaken by periodic excitation of the chain with very small amplitude. By using a method, single and two traveling waves can be generated in the DNLS equation. This is not the case with the classical nonlinear band gap studies.

• #gyrotron and vacuum electronics research
• #nonlinear photonic systems
• #microwave engineering and waveguides
• #breather

Bandpass filter induced by imaginary resistance in the low-pass discrete electrical transmission lattice

Pierre Anselme Simo Motcheyo, Rosalie Laure Woulaché, E. Tchomgo Felenou, Timoléon Crépin Kofané

Physics Letters A

• #terahertz technology and applications
• #mechanical and optical resonators
• #quantum optics and atomic interactions
• #physics

Base pairs opening and bubble transport in damped DNA dynamics with transport memory effects

Joseph Brizar Okaly, Fabien II Ndzana, Rosalie Laure Woulaché, Conrad Bertrand Tabi, Timoléon Crépin Kofané

Chaos An Interdisciplinary Journal of Nonlinear Science

Transport memory effects on nonlinear wave propagation are addressed in a damped Peyrard-Bishop-Dauxois model of DNA dynamics. Under the continuum and overdamped limits, the multiple-scale expansion method is employed to show that an open-state configuration of the DNA molecule is described by a complex nonlinear Schrödinger equation. For the latter, solutions are proposed as bright solitons, which suitably represent the open-state configuration that takes place along the DNA molecule in the form of bubbles. A good agreement between numerical experiments and analytical predictions on the impact of memory effects on the angular frequency, velocity, width, and amplitude of the moving bubble is obtained. It also appears that memory effects can modify qualitatively and quantitatively the nonlinear dynamics of DNA, including the energy brought by enzymes for the initiation of the processes of replication and transcription.

• #spectroscopy and quantum chemical studies
• #nonlinear photonic systems
• #quantum chaos and dynamical systems
• #nonlinear system

Nonlinear dynamics of long-range diatomic chain

Joseph Brizar Okaly, Alain Mvogo, Rosalie Laure Woulaché, Timoléon Crépin Kofané

Physica A Statistical Mechanics and its Applications

• #nonlinear photonic systems
• #advanced fiber laser technologies
• #nonlinear waves and solitons
• #diatomic molecule

Brownian motors in variable-shape medium: Overdamped versus underdamped cases

Maxime Fabrice Kepnang Pebeu, Rosalie Laure Woulaché, Timoléon Crépin Kofané

Physical review. E

In this paper, we investigate the statistical behavior of Brownian particles in a deformable traveling-wave potential in the absence of external load. We model the deformation of the system by the modified Remoissenet-Peyrard on-site potential, which is distinguished by its sine-Gordon shape. We examine numerically the effect of the deformed on-site potential with traveling speeds on the transport properties in overdamped as well as underdamped Brownian particles. Using the Langevin Monte Carlo method, we show that the average velocity of Brownian particles is an increasing function of the shape parameter in the overdamped case, and a decreasing function of the shape parameter in the underdamped case. It is found that, in the overdamped case, the numerical behavior of the average velocity of Brownian particles validates its analytical results. In the presence of the deformable traveling-wave potential, for negative as well as positive values of the shape parameter, the underdamped case favors the transport properties in the medium. The average velocity needed to cross the potential barriers is lowest in the underdamped case. Moreover, the effective diffusion coefficient in both cases exhibits peaks, and the diffusion process enhancement is discussed for some values of the shape parameter. Finally, in the underdamped case, by using the Smoluchowski equation and the finite-element methods, we analyze the distribution of Brownian particles in the deformed system.

• #stochastic dynamics and bifurcation
• #fractional differential equations solutions
• #diffusion and search dynamics
• #brownian motor

Nonlinear dynamics of damped DNA systems with long-range interactions

Joseph Brizar Okaly, Alain Mvogo, Rosalie Laure Woulaché, Timoléon Crépin Kofané

Communications in Nonlinear Science and Numerical Simulation

• #nonlinear photonic systems
• #spectroscopy and quantum chemical studies
• #hemoglobin structure and function
• #breather

Velocity dependence of sliding friction on a crystalline surface

Christian Apostoli, Giovanni Giusti, Jacopo Ciccoianni, Gabriele Riva, Rosario Capozza, Rosalie Laure Woulaché and 3 more

Beilstein Journal of Nanotechnology

We introduce and study a minimal 1D model for the simulation of dynamic friction and dissipation at the atomic scale. This model consists of a point mass (slider) that moves over and interacts weakly with a linear chain of particles interconnected by springs, representing a crystalline substrate. This interaction converts a part of the kinetic energy of the slider into phonon waves in the substrate. As a result, the slider experiences a friction force. As a function of the slider speed, we observe dissipation peaks at specific values of the slider speed, whose nature we understand by means of a Fourier analysis of the excited phonon modes. By relating the phonon phase velocities with the slider velocity, we obtain an equation whose solutions predict which phonons are being excited by the slider moving at a given speed.

• #force microscopy techniques and applications
• #mechanical and optical resonators
• #adhesion, friction, and surface interactions
• #slider

Dynamics of Brownian motors in deformable medium

Rosalie Laure Woulaché, Fabrice Maxime Kepnang Pebeu, Timoléon Crépin Kofané

Physica A Statistical Mechanics and its Applications

• #stochastic dynamics and bifurcation
• #spectroscopy and quantum chemical studies
• #theoretical and computational physics
• #brownian motor

Influence of substrate potential shape on the dynamics of a sliding lubricant chain

Rosalie Laure Woulaché, Andrea Vanossi, Nicola Manini

Physical Review E

We investigate the frictional sliding of an incommensurate chain of interacting particles confined in between two nonlinear on-site substrate potential profiles in relative motion. We focus here on the class of Remoissenet-Peyrard parametrized potentials V(RP)(x,s), whose shape can be varied continuously as a function of s, recovering the sine-Gordon potential as a particular case. The observed frictional dynamics of the system, crucially dependent on the mutual ratios of the three periodicities in the sandwich geometry, turns out to be significantly influenced also by the shape of the substrate potential. Specifically, variations of the shape parameter s affect significantly and not trivially the existence and robustness of the recently reported velocity quantization phenomena [A. Vanossi et al., Phys. Rev. Lett. 97, 056101 (2006)], where the chain center-of-mass velocity to the externally imposed relative velocity of the sliders stays pinned to exact "plateau" values for wide ranges of the dynamical parameters.

• #force microscopy techniques and applications
• #mechanical and optical resonators
• #adhesion, friction, and surface interactions
• #nonlinear system

The situation of women in physics in Cameroon

Rosalie Laure Woulaché, Guillaume Kom, Beatrice Couonang Siebatcheu, Marthe Boyomo Onana

AIP conference proceedings

The progress of women in science has been widely discussed in recent years. Women have made great progress in the social sciences, but they lag in the field of physics. A survey of the situation of women in physics in Cameroon over the last three years shows some improvement and some areas of stagnation. For example, the statistics show an increase of women teaching physics in secondary school and a slight improvement in the numbers of women studying physics at the university level, but stagnation in the number of women lecturers in physics.

• #energy and environment impacts
• #economic growth and development
• #physics
• #mathematics education

Solitons in Nonlinear Deformable Systems with Impurities

Rosalie Laure Woulaché

• #structural mechanics and materials
• #nonlinear system
• #impurity
• #physics

Threshold field in nucleation process for an inhomogeneous deformable nonlinear Klein-Gordon system

Rosalie Laure Woulaché, David Yemélé, Timoléon Crépin Kofané

The European Physical Journal B

• #nonlinear photonic systems
• #nonlinear dynamics and pattern formation
• #spectroscopy and quantum chemical studies
• #nucleation

Thermal nucleation of kink-antikink pairs in the presence of impurities: The case of a Remoissenet-Peyrard substrate potential

Rosalie Laure Woulaché, David Yemélé, Timoléon Crépin Kofané

Physical Review E

Thermal nucleation of kink-antikink pairs in a nonlinear Klein-Gordon (NKG) model with a Remoissenet-Peyrard (RP) substrate potential in the presence of impurities and coupled to an applied field is analyzed in the limits of moderate temperature and strong damping. Using the Kolmogorov method, the average velocity of particles of the lattice is calculated and its dependence on the intensity of impurities is discussed in connection with the deformability parameter or the shape of the RP substrate potential. Numerical values are carried out by making use of parameters of the hydrogen atom adsorbed in the tungsten and ruthenium substrates. We show that, for large values of the applied field, the presence of impurities in the system makes the nucleation process of kink-antikink pairs more favorable in the high-temperature regime while they contribute to make it less favorable in the low-temperature regime.

• #nonlinear photonic systems
• #strong light-matter interactions
• #nonlinear dynamics and pattern formation
• #nucleation