scholarly journals A Mass- and Energy-Conserving Numerical Model for a Fractional Gross–Pitaevskii System in Multiple Dimensions

Mathematics ◽  
2021 ◽  
Vol 9 (15) ◽  
pp. 1765
Author(s):  
Adán J. Serna-Reyes ◽  
Jorge E. Macías-Díaz
Keyword(s):  
Initial Conditions ◽  
Type System ◽  
Continuous System ◽  
Mass Conservation ◽  
Continuous Model ◽  
Manuscript Studies ◽  
Multiple Dimensions ◽  
Negative Constant ◽  
Energy Conserving ◽  
Finite Difference Discretization

This manuscript studies a double fractional extended p-dimensional coupled Gross–Pitaevskii-type system. This system consists of two parabolic partial differential equations with equal interaction constants, coupling terms, and spatial derivatives of the Riesz type. Associated with the mathematical model, there are energy and non-negative mass functions which are conserved throughout time. Motivated by this fact, we propose a finite-difference discretization of the double fractional Gross–Pitaevskii system which inherits the energy and mass conservation properties. As the continuous model, the mass is a non-negative constant and the solutions are bounded under suitable numerical parameter assumptions. We prove rigorously the existence of solutions for any set of initial conditions. As in the continuous system, the discretization has a discrete Hamiltonian associated. The method is implicit, multi-consistent, stable and quadratically convergent. Finally, we implemented the scheme computationally to confirm the validity of the mass and energy conservation properties, obtaining satisfactory results.

Dynamics of a Continuous System With Clearance and Motion Limiting Stops

1999 ◽  
Author(s):  
P. Metallidis ◽  
S. Natsiavas
Keyword(s):  
Piecewise Linear ◽  
Research Work ◽  
Continuous System ◽  
Continuous Model ◽  
Equation Of Motion ◽  
Model System ◽  
Periodic Motions ◽  
System Parameters ◽  
Rigid Rods ◽  
The Stability

Abstract The present study generalises previous research work on the dynamics of discrete oscillators with piecewise linear characteristics and investigates the response of a continuous model system with clearance and motion-limiting constraints. More specifically, in the first part of this work, an analysis is presented for determining exact periodic response of a periodically excited deformable rod, whose motion is constrained by a flexible obstacle. This methodology is based on the exact solution form obtained within response intervals where the system parameters remain constant and its behavior is governed by a linear equation of motion. The unknowns of the problem are subsequently determined by imposing an appropriate set of periodicity and matching conditions. The analytical part is complemented by a suitable method for determining the stability properties of the located periodic motions. In the second part of the study, the analysis is applied to several cases in order to investigate the effect of the system parameters on its dynamics. Special emphasis is placed on comparing these results with results obtained for similar but rigid rods. Finally, direct integration of the equation of motion in selected areas reveals the existence of motions, which are more complicated than the periodic motions determined analytically.

Approximate Analytic Method of Piping Systems With Elasto-Plastic Damper

2002 ◽  
Author(s):  
Shigeru Aoki ◽  
Takeshi Watanabe
Keyword(s):  
Simple Procedure ◽  
Continuous System ◽  
Approximate Solutions ◽  
Continuous Model ◽  
Equation Of Motion ◽  
Forced Response ◽  
Mode Shapes ◽  
Piping System ◽  
Restoring Force ◽  
Approximate Methods

An elasto-plastic damper is one of the vibration absorbers in which energy is absorbed by elasto-plastic deformation of the hysteretic type damper. It is used for the piping system. The piping system is continuous system. Since it is difficult to find the analytical solution of the equation of motion for the system with elasto-plastic damper, the equation of motion is treated by various approximate methods in which the system is usually considered as a single- or a multiple-degree-of-freedom system, but not as a continuous system. In order to analyze the response of a nonlinear continuous system, however, it is necessary to consider the system as a continuous system. In this paper, the nonlinear steady-state response of the piping system with elasto-plastic damper is undertaken by approximate solutions, which are easily obtained by a simple procedure and are more practical than the exact solutions. As a continuous model of the piping system, a beam simply supported or clamped at one end, with elasto-plastic damper at the other end is used. The restoring force is modeled as hysteresis loop characteristics in order to consider the energy loss in the damper. In the analysis, the restoring force is expanded into the Fourier series, and only fundamental terms are considered. The resonance curves and mode shapes of the beam are obtained from the approximate solution. And effect of elasto-plastic damper on the forced response of continuous system is examined.

Modeling Impacts Between a Continuous System and a Rigid Obstacle Using Coefficient of Restitution

2009 ◽  
Vol 77 (2) ◽  
Author(s):  
Chandrika P. Vyasarayani ◽  
John McPhee ◽  
Stephen Birkett
Keyword(s):  
Initial Conditions ◽  
Equations Of Motion ◽  
Continuous System ◽  
Coefficient Of Restitution ◽  
Continuous Systems ◽  
Rigid Obstacle ◽  
Unit Impulse ◽  
Before And After ◽  
System Equations ◽  
The Impact

In this work, we discuss the limitations of the existing collocation-based coefficient of restitution method for simulating impacts in continuous systems. We propose a new method for modeling the impact dynamics of continuous systems based on the unit impulse response. The developed method allows one to relate modal velocity initial conditions before and after impact without requiring the integration of the system equations of motion during impact. The proposed method has been used to model the impact of a pinned-pinned beam with a rigid obstacle. Numerical simulations are presented to illustrate the inability of the collocation-based coefficient of restitution method to predict an accurate and energy-consistent response. We also compare the results obtained by unit impulse-based coefficient of restitution method with a penalty approach.

The Evolution of a Self-Sustained Oscillation in a Nonlinear Continuous System

1973 ◽  
Vol 40 (1) ◽  
pp. 53-60 ◽  
Author(s):  
M. P. Mortell ◽  
B. R. Seymour
Keyword(s):  
Difference Equation ◽  
Initial Conditions ◽  
Initial Perturbation ◽  
Continuous System ◽  
Periodic Oscillation ◽  
Sustained Oscillation ◽  
Nonlinear Difference Equation ◽  
Simple Waves ◽  
Periodic State ◽  
Dissipative Mechanism

We consider a gas-filled tube into which there is an input of energy due to a pressure sensitive heat source. The system is linearly unstable to perturbations about the initial equilibrium state. Within nonlinear theory a disturbance grows until a shock forms. The shock can then act as a dissipative mechanism so that ultimately a time periodic oscillation may result. The small amplitude disturbance in the pipe is represented as the superposition of two simple waves traveling in opposite directions, and without interaction. Thereby, the problem is reduced to solving a nonlinear difference equation subject to given initial conditions. Then not only is the final periodic state described but also its evolution from the prescribed initial perturbation. The concept of critical points of a nonlinear difference equation is introduced which allows the direct computation of the periodic state. The effects of dissipation and of a retarded heater response are also treated.

scholarly journals Simulation of Discrete Predator-Prey Model

2020 ◽  
Vol 55 (1) ◽  
Author(s):  
Adel A. Abed Al Wahab ◽  
Nihad Mahmoud Nasir ◽  
Adil I. Khalil
Keyword(s):  
Discrete Model ◽  
Initial Conditions ◽  
Current Model ◽  
Continuous Model ◽  
Predator Prey ◽  
Predator Prey Model ◽  
Prey Model ◽  
Computerized Simulation ◽  
Theoretical Results ◽  
Over Time

It is well known that dynamical systems deal with situations in which the system transforms over time. In fact, undertaking a manual simulation of such systems is a difficult task due to the complexity of the computations. Therefore, a computerized simulation is frequently required for accurate results and fast execution time. Nowadays, computer programs have become an important tool to confirm the theoretical results obtained from the study of models. This paper aims to employ new MATLAB codes to examine a discrete predator–prey model using a difference equations system. The paper discusses the existences and stabilities of each possible fixed point appearing in the current model. Furthermore, numerical simulations fixed by a certain parameter to plot the diagrams are presented. Our results confirm that the systems sensitive to initial conditions are chaotic. Furthermore, the theoretical results as well as numerical examples illustrated that the discrete model exhibits complex behavior compared to a continuous model. The conclusion drawn is that the numerical simulation is an important tool to confirm theoretical results.

scholarly journals Finite Volume approximation of a two-phase two fluxes degenerate Cahn-Hilliard model

2021 ◽  
Author(s):  
Clément Cancès ◽  
Flore Nabet
Keyword(s):  
Finite Volume ◽  
Mass Conservation ◽  
Continuous Model ◽  
Finite Volume Scheme ◽  
Two Phase ◽  
Existence Of A Solution ◽  
Entropy Dissipation ◽  
Continuous Problems ◽  
Volume Approximation ◽  
Compactness Arguments

We study a time implicit Finite Volume scheme for degenerate Cahn-Hilliard model proposed in [W. E and P. Palffy-Muhoray. Phys. Rev. E , 55:R3844–R3846, 1997] and studied mathematically by the authors in [C. Canc\`es, D. Matthes, and F. Nabet. Arch. Ration. Mech. Anal. , 233(2):837-866, 2019]. The scheme is shown to preserve the key properties of the continuous model, namely mass conservation, positivity of the concentrations, the decay of the energy and the control of the entropy dissipation rate. This allows to establish the existence of a solution to the nonlinear algebraic system corresponding to the scheme. Further, we show thanks to compactness arguments that the approximate solution converges towards a weak solution of the continuous problems as the discretization parameters tend to 0. Numerical results illustrate the behavior of the numerical model.

Recent Developments on Nonstationary Parametric Responses of Rectangular Plates

1993 ◽  
Author(s):  
Germain L. Ostlguy ◽  
Patrice Lavigne
Keyword(s):  
Initial Conditions ◽  
Lateral Displacement ◽  
Asymptotic Series ◽  
Excitation Frequency ◽  
Continuous System ◽  
Equation Of Motion ◽  
Multiple Time Scales ◽  
Multiple Time ◽  
Rectangular Plates ◽  
Stationary Response

Abstract The non-stationary parametric response of a rectangular plate during a logarithmic sweep of the excitation frequency through a system resonance is studied using five different techniques of solution. Considering only the case of principal parametric resonance, the continuous system is spatially discretized by means of a single-term modal approximation for the lateral displacement. The general form of the resulting nonlinear temporal equation of motion for the damped parametric vibrations in any spatial mode is analyzed using the multiple time scales method and the method of asymptotic series expansion developed by Mitropolsky, in the first and second approximation. The non-stationary response of the plate during transition through parametric resonances is also evaluated by direct integration of the temporal equation of motion and the results obtained by the different techniques are compared. The non-stationary response displays several phenomena depending on the conditions of in-plane loading, the amount of damping, the initial conditions, and the rate as well as the direction of the sweep. The validity of these results is ascertained experimentally.

scholarly journals COHESION, CONSENSUS AND EXTREME INFORMATION IN OPINION DYNAMICS

2013 ◽  
Vol 16 (06) ◽  
pp. 1350035 ◽  
Author(s):  
ALINA SÎRBU ◽  
VITTORIO LORETO ◽  
VITO D. P. SERVEDIO ◽  
FRANCESCA TRIA
Keyword(s):  
Initial Conditions ◽  
Opinion Dynamics ◽  
External Source ◽  
Continuous Model ◽  
External Input ◽  
External Information ◽  
Sources Of Information ◽  
Opinion Formation ◽  
Multiple Sources ◽  
External Sources

Opinion formation is an important element of social dynamics. It has been widely studied in the last years with tools from physics, mathematics and computer science. Here, a continuous model of opinion dynamics for multiple possible choices is analyzed. Its main features are the inclusion of disagreement and possibility of modulating external information/media effects, both from one and multiple sources. The interest is in identifying the effect of the initial cohesion of the population, the interplay between cohesion and media extremism, and the effect of using multiple external sources of information that can influence the system. Final consensus, especially with the external message, depends highly on these factors, as numerical simulations show. When no external input is present, consensus or segregation is determined by the initial cohesion of the population. Interestingly, when only one external source of information is present, consensus can be obtained, in general, only when this is extremely neutral, i.e., there is not a single opinion strongly promoted, or in the special case of a large initial cohesion and low exposure to the external message. On the contrary, when multiple external sources are allowed, consensus can emerge with one of them even when this is not extremely neutral, i.e., it carries a strong message, for a large range of initial conditions.

scholarly journals Eventually Periodic Solutions of a Max-Type System of Difference Equations of Higher Order

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Guangwang Su ◽  
Taixiang Sun ◽  
Bin Qin
Keyword(s):  
Periodic Solutions ◽  
Difference Equations ◽  
Initial Conditions ◽  
Type System ◽  
Higher Order ◽  
System Of Difference Equations

We study in this paper the following max-type system of difference equations of higher order: xn=max{A,yn-k/xn-1} and yn=max{B,xn-k/yn-1}, n∈{0,1,2,…}, where A≥B>0, k≥1, and the initial conditions x-k,y-k,x-k+1,y-k+1,…,x-1,y-1∈(0,+∞). We show that (1) if AB>1, then every solution of the above system is periodic with period 2 eventually. (2) If AB=1>B, then every solution of the above system is periodic with period 2k or 2 eventually. (3) If A=B=1 or AB<1, then the above system has a solution which is not periodic eventually.

Accuracy of Discrete Models for the Solution of the Inverse Dynamics Problem for Flexible Arms, Feasible Trajectories

1997 ◽  
Vol 119 (3) ◽  
pp. 396-404 ◽  
Author(s):  
H. C. Moulin ◽  
E. Bayo
Keyword(s):  
High Frequency ◽  
Inverse Dynamics ◽  
Numerical Procedure ◽  
Continuous System ◽  
Continuous Model ◽  
Discrete Models ◽  
Frequency Range ◽  
Model Order ◽  
Inverse Dynamics Problem ◽  
Tip Mass

The inverse dynamics problem for a single link flexible arm is considered. The tracking order of consistent and lumped finite element models is derived and compared with the tracking order of the continuous model when there is no tip-mass. These comparisons show that discrete models fail to identify the tracking order of a modelled continuous system. A frequency domain analysis shows that an increase in the model order extends the well-modelled low-frequency range and, at the same time, increases the inadequacy in the high-frequency range. As a result, inverse dynamics solutions computed with discrete models do not converge to the continuous solution as the model order increases. The use of high-frequency filters allows us to construct a convergent numerical procedure. A conjecture about the tracking order is presented when there is a tip mass. It is shown that the same results are obtained if superposition of modes rather than finite elements is used.

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