Modulation instability in nonlinear chiral fiber

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Demissie Jobir Gelmecha ◽  
Ram Sewak Singh
Keyword(s):  
Theoretical Model ◽  
Numerical Simulations ◽  
Pulse Propagation ◽  
Modulation Instability ◽  
Constitutive Relations ◽  
Gain Spectrum ◽  
Circularly Polarized ◽  
Left Handed ◽  
Simulation Results ◽  
The Difference

AbstractIn this paper, the rigorous derivations of generalized coupled chiral nonlinear Schrödinger equations (CCNLSEs) and their modulation instability analysis have been explored theoretically and computationally. With the consideration of Maxwell’s equations and Post’s constitutive relations, a generalized CCNLSE has been derived, which describes the evolution of left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) components propagating through single-core nonlinear chiral fiber. The analysis of modulation instability in nonlinear chiral fiber has been investigated starting from CCNLSEs. Based on a theoretical model and numerical simulations, the difference on the modulation instability gain spectrum in LCP and RCP components through chiral fiber has been analyzed by considering loss and chirality into account. The obtained simulation results have shown that the loss distorts the sidebands of the modulation instability gain spectrum, while chirality modulates the gain for LCP and RCP components in a different manner. This suggests that adjusting chirality strength may control the loss, and nonlinearity simultaneously provides stable modulated pulse propagation.

scholarly journals Balanced gain for a square metaloop antenna

2019 ◽  
Vol 6 ◽  
pp. 3
Author(s):  
Hisamatsu Nakano ◽  
Ittoku Yoshino ◽  
Tomoki Abe ◽  
Junji Yamauchi
Keyword(s):  
Frequency Response ◽  
Radiation Pattern ◽  
Free Space ◽  
Loop Antenna ◽  
Circularly Polarized ◽  
Left Handed ◽  
The Difference

A square loop antenna implemented using a metamaterial line, referred to as a metaloop, is discussed. The metaloop radiates a counter circularly polarized (CP) broadside beam when the loop circumference equals one guided wavelength. The frequency response of the gain shows two different maximum values: gain G Lmax for a left-handed CP wave at frequency fGLmax and gain GRmax for a right-handed CP wave at frequency fGRmax, where GLmax is smaller than GRmax. In order to increase GLmax, while not affecting the original GRmax as much as possible (i.e. balance the gain), a parasitic natural conducting loop (paraloop), whose circumference is one free-space wavelength at fGLmax, is placed at height Hpara above the metaloop. It is found that the difference in the gains can be reduced by choosing an appropriate Hpara. The radiation pattern at fGLmax is narrowed by the paraloop, while the VSWR is not remarkably affected.

scholarly journals Solitary waves and modulation instability with the influence of fractional derivative order in nonlinear left-handed transmission line

2021 ◽  
Author(s):  
Djidere Ahmadou ◽  
Alphonse Houwe ◽  
Justin Mibaile ◽  
Gambo Betchewe ◽  
Serge Y. Doka ◽  
...  
Keyword(s):  
Fractional Derivative ◽  
Transmission Line ◽  
Information And Communication Technologies ◽  
Solitary Waves ◽  
Fractional Derivatives ◽  
Modulation Instability ◽  
Gain Spectrum ◽  
Left Handed ◽  
Adomian Decomposition ◽  
Derivative Order

Abstract The resolution of the reduced fractional nonlinear Schrodinger equation obtained from the model describing the wave propagation in the left-handed nonlinear transmission line presented by Djidere et al recently, allowed us in this work through the Adomian decomposition method (ADM) to highlight the behavior and to study the propagation process of the dark and bright soliton solutions with the e ect of the fractional derivative order as well as the Modulation Instability gain spectrum (MI) in the LHNLTL. By inserting fractional derivatives in the sense of Caputo, we used ADM to structure the approximate solitons solutions of the fractional nonlinear Schrodinger equation reduced with fractional derivatives. The pipe is obtained from the bright and dark soliton by the fractional derivatives order (see Figures 2 and 5). By the bias of MI gain spectrum the instability zones occur when the value of the fractional derivative order tends to 1. Furthermore, when the fractional derivative order takes small values, stability zones appear. These results could bring new perspectives in the study of solitary waves in left-handed metamaterials, as the memory e ect could have a better future for the propagation of modulated waves because we also show in this article that the stabilization of zones of the dark and bright solitons could be described by a fractional nonlinear Schrodinger equation with small values of fractional derivatives order. In addition, the obtained signi cant results are new and could nd applications in many research areas such as in the eld of information and communication technologies.

scholarly journals Determination of Absolute Structure of Chiral Crystals Using Three-Wave X-ray Diffraction

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1389
Author(s):  
Ksenia Kozlovskaya ◽  
Elena Ovchinnikova ◽  
Jun Kokubun ◽  
Andrei Rogalev ◽  
Fabrice Wilhelm ◽  
...  
Keyword(s):  
Bragg Reflection ◽  
Quantitative Description ◽  
X Rays ◽  
Circularly Polarized ◽  
X Ray ◽  
Left Handed ◽  
The Difference ◽  
The Right ◽  
Chiral Crystals ◽  
Absolute Structure

We propose a new method to determine the absolute structure of chiral crystals, which is based on the chiral asymmetry of multiple scattering diffraction. It manifests as a difference in the azimuthal dependence of the forbidden Bragg reflection intensity measured with left and right circularly polarized X-ray beams. Contrary to the existing ones, the suggested method does not use X-ray anomalous dispersion. The difference between the Renninger scans with circularly polarized X-rays has been experimentally demonstrated for the 001 reflection intensities in the right- and left-handed quartz single crystals. A Jmulti-based code on model-independent three-wave-diffraction approach has been developed for quantitative description of our experimental results. The proposed method can be applied to various structures including opaque, organic and monoatomic crystals, even with only light elements. To determine the type of isomer, the Renninger plot of a single forbidden reflection is sufficient.

Nonlinear Pulse Propagation and Modulation Instability in Periodic Media with and without Defects

PIERS Online ◽  
2006 ◽  
Vol 2 (2) ◽  
pp. 177-181
Author(s):  
V. Grimalsky ◽  
Svetlana Koshevaya ◽  
Javier Sanchez-Mondragon ◽  
Margarita Tecpoyotl Torres ◽  
J. Escobedo Alatorre
Keyword(s):  
Pulse Propagation ◽  
Modulation Instability ◽  
Periodic Media ◽  
Nonlinear Pulse Propagation

scholarly journals A Semi-Theoretical Model for Water Condensation: Dew Used in Conservation of Earthen Heritage Sites

Water ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 52
Author(s):  
Xiang He ◽  
Sijia Wang ◽  
Bingjian Zhang
Keyword(s):  
Mass Transfer ◽  
Theoretical Model ◽  
Field Experiments ◽  
Environmental Control ◽  
Mass Transfer Process ◽  
Formation Processes ◽  
Heritage Sites ◽  
Dew Formation ◽  
The Difference ◽  
Two Parameter

Dew is a common but important phenomenon. Though water is previously considered to be a threat to earthen heritage sites, artificial dew is showing potential in relic preservation. A model of dew prediction on earthen sites will be essential for developing preventive protection methods, but studies of dew formation processes on relics are limited. In this study, a two parameter model is proposed. It makes approximations according to the features of earthen heritage sites, assuming that a thin and steady air layer exists close to the air–solid interface. This semi-theoretical model was based on calculations of the mass transfer process in the air layer, and was validated by simulations of laboratory experiments (R > 0.9) as well as field experiments. Additionally, a numerical simulation, performed by the commercial software COMSOL, confirmed that the difference between fitting parameter δ and the thickness of assumed mass transfer field was not significant. This model will be helpful in developing automatic environmental control systems for stabilizing water and soluble salts, thus enhancing preventive protection of earthen heritage sites.

scholarly journals Market Choices Driven by Reference Groups: A Comparison of Analytical and Simulation Results on Random Networks

Entropy ◽  
2021 ◽  
Vol 23 (8) ◽  
pp. 1007
Author(s):  
Michał Ramsza
Keyword(s):  
Theoretical Model ◽  
Reference Group ◽  
Third Party ◽  
Qualitative Behavior ◽  
Reference Groups ◽  
Group Influence ◽  
Simple Theoretical Model ◽  
High Connectivity ◽  
Simulation Results ◽  
Two Equilibria

The present paper reports simulation results for a simple model of reference group influence on market choices, e.g., brand selection. The model was simulated on three types of random graphs, Erdos–Renyi, Barabasi–Albert, and Watts–Strogatz. The estimates of equilibria based on the simulation results were compared to the equilibria of the theoretical model. It was verified that the simulations exhibited the same qualitative behavior as the theoretical model, and for graphs with high connectivity and low clustering, the quantitative predictions offered a viable approximation. These results allowed extending the results from the simple theoretical model to networks. Thus, by increasing the positive response towards the reference group, the third party may create a bistable situation with two equilibria at which respective brands dominate the market. This task is easier for large reference groups.

scholarly journals A modular framework to generate robust biped locomotion: from planning to control

2021 ◽  
Vol 3 (9) ◽  
Author(s):  
Mohammadreza Kasaei ◽  
Ali Ahmadi ◽  
Nuno Lau ◽  
Artur Pereira
Keyword(s):  
Numerical Simulations ◽  
Predictive Control ◽  
Biped Locomotion ◽  
Input Output ◽  
Dynamics Model ◽  
Biped Robots ◽  
The Core ◽  
Simulation Results ◽  
Reference Trajectories ◽  
Modular Framework

AbstractBiped robots are inherently unstable because of their complex kinematics as well as dynamics. Despite many research efforts in developing biped locomotion, the performance of biped locomotion is still far from the expectations. This paper proposes a model-based framework to generate stable biped locomotion. The core of this framework is an abstract dynamics model which is composed of three masses to consider the dynamics of stance leg, torso, and swing leg for minimizing the tracking problems. According to this dynamics model, we propose a modular walking reference trajectories planner which takes into account obstacles to plan all the references. Moreover, this dynamics model is used to formulate the controller as a Model Predictive Control (MPC) scheme which can consider some constraints in the states of the system, inputs, outputs, and also mixed input-output. The performance and the robustness of the proposed framework are validated by performing several numerical simulations using MATLAB. Moreover, the framework is deployed on a simulated torque-controlled humanoid to verify its performance and robustness. The simulation results show that the proposed framework is capable of generating biped locomotion robustly.

scholarly journals Spatiotemporal Patterns Formed by a Discrete Nutrient-Phytoplankton Model with Time Delay

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Feifan Zhang ◽  
Wenjiao Zhou ◽  
Lei Yao ◽  
Xuanwen Wu ◽  
Huayong Zhang
Keyword(s):  
Steady State ◽  
Time Delay ◽  
Numerical Simulations ◽  
Functional Response ◽  
Bifurcation Analysis ◽  
Discrete Model ◽  
Continuous Model ◽  
Spatiotemporal Patterns ◽  
Homogeneous Steady State ◽  
Simulation Results

In this research, a continuous nutrient-phytoplankton model with time delay and Michaelis–Menten functional response is discretized to a spatiotemporal discrete model. Around the homogeneous steady state of the discrete model, Neimark–Sacker bifurcation and Turing bifurcation analysis are investigated. Based on the bifurcation analysis, numerical simulations are carried out on the formation of spatiotemporal patterns. Simulation results show that the diffusion of phytoplankton and nutrients can induce the formation of Turing-like patterns, while time delay can also induce the formation of cloud-like pattern by Neimark–Sacker bifurcation. Compared with the results generated by the continuous model, more types of patterns are obtained and are compared with real observed patterns.

Analysis of Center Detonation Characteristics of Water Mist

2014 ◽  
Vol 602-605 ◽  
pp. 3434-3437
Author(s):  
Yu Kun Chen ◽  
Ke Yin Wang ◽  
Hai Ying Huang ◽  
Pai Hang Zhao
Keyword(s):  
Theoretical Model ◽  
Theoretical Calculation ◽  
Water Mist ◽  
Correction Factors ◽  
Simulation Results ◽  
New Formula ◽  
Detonation Characteristics

This paper analyzed the formula for calculating the velocity and scatter radius of water mist droplets after detonation. Through establishing model, calculating by the formula and simulation of theoretical model, the reasons of deviation between calculation and simulation results were found out. In order to make theoretical calculation more accurate and applicable, new formula was created by introducing correction factors.

Dispersion Characteristic of the Symmetric Slab Waveguide with Chiral Negative Refractive Medium

2014 ◽  
Vol 571-572 ◽  
pp. 915-919
Author(s):  
Xiao Xue Xu ◽  
Zhong Yin Xiao ◽  
Quan Wen Ma ◽  
Xiao Long Ma ◽  
De Jun Liu ◽  
...  
Keyword(s):  
Maxwell Equations ◽  
Dispersion Characteristic ◽  
Constitutive Relations ◽  
Great Influence ◽  
Zero Order ◽  
Slab Waveguide ◽  
Order Mode ◽  
The Core ◽  
Left Handed ◽  
Refractive Medium

According to Maxwell equations and constitutive relations in chiral medium, the dispersion characteristic of the symmetric slab waveguide with chiral negative refractive medium is studied. The dispersion equations expressed in the normalized parameter are deduced in the slab waveguide. The numerical results show that the chiral parameter has great influence on the dispersion characteristic of slab waveguide. When the relative chiral parameter is about 0.0477, the zero order mode of left-handed polarized wave disappears. While it is greater than 1, the core becomes chiral negative refractive medium and the zero order mode disappears. In addition, compared with the general chiral waveguide, the tendency of dispersion curves in slab waveguide with chiral negative refractive medium is also analyzed.

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