Investigation of the Dynamic Behavior of Railway Ballast Using Molecular Dynamics Simulations

2001 ◽  
Author(s):  
Holger Kruse ◽  
Karl Popp
Keyword(s):  
Molecular Dynamics ◽  
Initial Conditions ◽  
Contact Forces ◽  
Contact Network ◽  
Railway Ballast ◽  
Particle Layer ◽  
Dynamics Simulations ◽  
Long Term Behavior ◽  
Overlap Area

Abstract The molecular dynamics method (MD method) is a powerful tool for the investigation of granular materials like the railway ballast. The characteristics of this method are explained in detail. In contrast to a continuum description, each single stone of the ballast is taken into account. Since the ballast settlement is strongly influenced by the shape of the stones, in the two-dimensional model polygonal particles are used. These particles are surrounded by fixed boundary walls. At the top of the ballast particle layer, a single sleeper is positioned which is loaded by forces occurring at the real track. The contact forces are calculated from the overlap area of the particle geometries. The paper includes information about the sensitivity of the model behavior on initial conditions and contact law parameters. Furthermore, the contact network, the quasi-static stiffness of the ballast layer and its long-term behavior are addressed. Particular emphasis is put on the description of current difficulties and challenges in applying the MD method.

Visualising the invisible: performing chaos theory

Leonardo ◽  
2020 ◽  
pp. 1-8
Author(s):  
Emma Weitkamp
Keyword(s):  
Complex Systems ◽  
Chaos Theory ◽  
Initial Conditions ◽  
Starting Point ◽  
Weather And Climate ◽  
Butterfly Effect ◽  
Long Term Behavior ◽  
The Invisible

Edward Lorenz, the pioneering figure in the field of chaos theory coined the phrase “butterfly effect” and posed the famous question “Does the flap of a butterfly's wings in Brazil set off a tornado in Texas?” In posing the question, Lorenz sought to highlight the intrinsic difficulty of predicting the long term behavior of complex systems that are sensitive to initial conditions, like, for example, the weather and climate; these systems are often referred to as chaotic. Taking Lorenz' butterfly as a starting point, Chaos Cabaret sought to explore the nuances of chaos theory through performance and music.

Clusters of Discrete Breathers in Carbon and Hydrocarbon Nanostructures

2016 ◽  
Vol 845 ◽  
pp. 255-258
Author(s):  
Julia Baimova ◽  
Ivan P. Lobzenko ◽  
Sergey V. Dmitriev
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Energy Exchange ◽  
Initial Conditions ◽  
Initial Amplitude ◽  
Discrete Breathers ◽  
Dynamics Simulations

Clusters of discrete breathers in graphene and graphane are studied by means of molecular dynamics simulations. For both structures, two-breather and three-breather clusters are considered. Energy exchange between discrete breathers in clusters is strongly dependent on the initial conditions such as initial amplitude and phase. Even small changes in these initial parameters can lead to the considerable changes in the behavior or breather clusters.

Long-term behavior of positive solutions of an exponentially self-regulating system of difference equations

2017 ◽  
Vol 10 (03) ◽  
pp. 1750045 ◽  
Author(s):  
N. Psarros ◽  
G. Papaschinopoulos ◽  
K. B. Papadopoulos
Keyword(s):  
Asymptotic Behavior ◽  
Positive Solutions ◽  
Difference Equations ◽  
Initial Conditions ◽  
System Of Difference Equations ◽  
Long Term Behavior

In this paper, we study the asymptotic behavior of the positive solutions of a system of the following difference equations: [Formula: see text] where [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] are positive constants and the initial conditions [Formula: see text] and [Formula: see text] are positive numbers.

Evaluation of Long-term behavior of bentonite buffer based on Molecular Dynamics and Homogenization Analysis

2004 ◽  
Vol 2004.9 (0) ◽  
pp. 477-480
Author(s):  
Kenichi NAKAOKA ◽  
Hideki KAWAMURA ◽  
Yasuaki ICHIKAWA ◽  
Katsuuki KAWAMURA ◽  
Noriyuki SAITO
Keyword(s):  
Molecular Dynamics ◽  
Bentonite Buffer ◽  
Long Term Behavior

scholarly journals Further Analysis of Lorenz’s Maximum Simplification Equations

2006 ◽  
Vol 63 (11) ◽  
pp. 2673-2699 ◽  
Author(s):  
S. Lakshmivarahan ◽  
Michael E. Baldwin ◽  
Tao Zheng
Keyword(s):  
Initial Conditions ◽  
Complete Picture ◽  
Long Term Behavior

Abstract The goal of this paper is to provide a complete picture of the long-term behavior of Lorenz’s maximum simplification equations along with the corresponding meteorological interpretation for all initial conditions and all values of the parameter.

New Approach for Predicting the Long-Term Behavior of Bentonite: The Unified Method of Molecular Dynamics and Homogenization Analysis

1997 ◽  
Vol 506 ◽  
Author(s):  
K. Kawamura ◽  
Y. Ichikawa ◽  
M. Nakano ◽  
K. Kitayama ◽  
H. Kawamura
Keyword(s):  
Molecular Dynamics ◽  
Molecular Model ◽  
New Approach ◽  
Method Of Molecular Dynamics ◽  
Bulk Scale ◽  
Long Term Behavior ◽  
The Unified Method ◽  
Dynamics Method ◽  
Unified Method

ABSTRACTFor predicting the long-term behavior of bentonite, we present a new and unified simulation procedure of Molecular Dynamics Method (MD) and Homogenization Analysis (HA). The MD is applied to establish molecular-scale bentonite properties and the HA is introduced to extrapolate the molecular model to the bulk-scale continuum model.

Study on the Effect of Different Factors of Displacement Cascades in Alpha-Fe by Molecular Dynamics Simulations

2020 ◽  
Author(s):  
Pandong Lin ◽  
Junfeng Nie ◽  
Meidan Liu
Keyword(s):  
Molecular Dynamics ◽  
Tensile Strain ◽  
Vacancy Concentration ◽  
Irradiation Damage ◽  
Effect Of Temperature ◽  
Displacement Cascade ◽  
Rpv Steel ◽  
Dynamics Simulations ◽  
Dynamics Method

Abstract As the key component of RPV steel, α-Fe is under neutron irradiation during its long-term service, and lattice atoms of α-Fe are knocked by neutrons, which leads to irradiation damage. In this paper, molecular dynamics method is conducted to investigate the effect of temperature, vacancy concentration and tensile strain on irradiation-induced damage by displacement cascade simulations in α-Fe. The simulations are performed with primary knock-on atom energies ranging from 0.1 to 5 keV, temperature ranging from 100 to 500K, vacancy concentration ranging from 0% to 1% and applied tensile strain ranging from 0 to 5%. The time evolution of defects produced during displacement cascade can be obtained where the surviving number of Frenkel pairs increases rapidly at first, then decrease and comes to stability finally. The influence of these factors on defect production can be concluded as following: The increase of PKA energy, vacancy concentration and applied tensile strain can lead to the increase of defect numbers. In contrast, the increase of temperature decreases the defect numbers. Vacancies and interstitials cluster size distributions are varied in different case. The results are meaningful to describe some microcosmic mechanisms of RPV steels in nuclear system.

Molecular Simulations of Pore Diffusion in Zeolites

1998 ◽  
Vol 527 ◽  
Author(s):  
P.I. Pohl ◽  
D.K. Fisler ◽  
T.M. Nenoff
Keyword(s):  
Molecular Dynamics ◽  
Energy Surface ◽  
Diffusion Rate ◽  
Pore Diffusion ◽  
High Permeability ◽  
Ionic Size ◽  
Gas Molecules ◽  
Dynamics Simulations ◽  
High Degree

ABSTRACTA combination of molecular dynamics and energy barrier mapping has been used to study diffusion of xylene gas molecules in silica zeolites. Rigid ion models were created for silicalite phases and the energy barriers to xylene permeation by pore diffusion were mapped using constrained steps and energy minimization. Zeolite ZSM-5 proved to exhibit the desirable properties of a high degree of selectivity while retaining a high permeability to p-xylene. The model zeolite was then minimized with various cation dopants using a shell model to mimic ionic polarization, and changes in cell size and energy surface were examined. Long term molecular dynamics simulations showed an increased diffusion rate for the structures doped with cations of larger ionic size.

Structural impact analysis of missense SNPs present in the uroguanylin gene by long-term molecular dynamics simulations

2016 ◽  
Vol 410 ◽  
pp. 9-17 ◽  
Author(s):  
Antonio C.S. Marcolino ◽  
William F. Porto ◽  
Állan S. Pires ◽  
Octavio L. Franco ◽  
Sérgio A. Alencar
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Impact Analysis ◽  
Structural Impact ◽  
Dynamics Simulations
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