SIMULATION OF NEMATIC FREE SURFACES

1999 ◽  
Vol 10 (02n03) ◽  
pp. 431-443 ◽  
Author(s):  
ENRIQUE DE MIGUEL ◽  
ELVIRA MARTÍN DEL RÍO
Keyword(s):  
Molecular Dynamics ◽  
Monte Carlo ◽  
Free Surface ◽  
Monte Carlo Methods ◽  
Hard Core ◽  
Free Surfaces ◽  
Model Liquid ◽  
Theoretical Predictions ◽  
Homeotropic Orientation ◽  
Simulation Results

Molecular dynamics and Monte Carlo methods are applied to study the liquid free surfaces in model liquid crystals. The simulation results suggest that the attractive interactions promote parallel alignment of the molecules at the nematic free surface in the Gay–Berne model, in agreement with theoretical predictions. A change in the orientation from planar to homeotropic is observed and explained in terms of a competing effect between attractive and repulsive interactions. Finally, the simulation results give clear evidence that the hard-core repulsions favor homeotropic orientation at the nematic free surface, in agreement with most theories.

scholarly journals Impact of background effects on the inclusive Vcb determination

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Thomas Mannel ◽  
Muslem Rahimi ◽  
K. Keri Vos
Keyword(s):  
Monte Carlo ◽  
Heavy Quark ◽  
High Precision ◽  
Monte Carlo Methods ◽  
Monte Carlo Data ◽  
Theoretical Predictions ◽  
Experimental Side ◽  
Belle Ii

Abstract The determination of the CKM element Vcb from inclusive semileptonic b → cℓ$$ \overline{\nu} $$ ν ¯ decays has reached a high precision thanks to a combination of theoretical and experimental efforts. Aiming towards even higher precision, we discuss two processes that contaminate the inclusive Vcb determination; the b → u background and the contribution of the tauonic mode: b → c(τ → μν$$ \overline{\nu} $$ ν ¯ )$$ \overline{\nu} $$ ν ¯ . Both of these contributions are dealt with at the experimental side, using Monte-Carlo methods and momentum cuts. However, these contributions can be calculated with high precision within the Heavy-Quark Expansion. In this note, we calculate the theoretical predictions for these two processes. We compare our b → u results qualitatively with generator-level Monte-Carlo data used at Belle and Belle II. Finally, we suggest to change the strategy for the extraction of Vcb by comparing the data on B → Xℓ directly with the theoretical expressions, to which our paper facilitates.

scholarly journals A Comparison of Bootstrap and Monte Carlo Approaches to Testing for Symmetry in the Granger and Lee Error Correction Model

2013 ◽  
Vol 5 (5) ◽  
pp. 240-244
Author(s):  
Henry de-Graft Acquah
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Methods ◽  
Large Error ◽  
Small Error ◽  
Small Samples ◽  
Monte Carlo Techniques ◽  
Large Samples ◽  
Monte Carlo Algorithms ◽  
Power Of The Test ◽  
Simulation Results

In this paper, I investigate the power of the Granger and Lee model of asymmetry via bootstrap and Monte Carlo techniques. The simulation results indicate that sample size, level of asymmetry and the amount of noise in the data generating process are important determinants of the power of the test for asymmetry based on bootstrap and Monte Carlo techniques. Additionally, the simulation results suggest that both bootstrap and Monte Carlo methods are successful in rejecting the false null hypothesis of symmetric adjustment in large samples with small error size and strong levels of asymmetry. In large samples, with small error size and strong levels of asymmetry, the results suggest that asymmetry test based on Monte Carlo methods achieve greater power gains when compared with the test for asymmetry based on bootstrap. However, in small samples, with large error size and subtle levels of asymmetry, the results suggest that asymmetry test based on bootstrap is more powerful than those based on the Monte Carlo methods. I conclude that both bootstrap and Monte Carlo algorithms provide valuable tools for investigating the power of the test of asymmetry.

scholarly journals SIMULATION AND CHARACTERIZATION OF RANDOM SYSTEMS OF HARD PARTICLES

2011 ◽  
Vol 21 (4) ◽  
pp. 41 ◽  
Author(s):  
Dietrich Stoyan
Keyword(s):  
Molecular Dynamics ◽  
Monte Carlo ◽  
Monte Carlo Methods ◽  
Random Systems ◽  
Statistical Characteristics ◽  
Topological Descriptors ◽  
Hard Particles

This paper surveys methods for the simulation of random systems of hard particles, namely sedimentation and collective rearrangement algorithms, molecular dynamics, and Monte Carlo methods such as the Metropolis­ Hastings algorithm. Furthermore, some set-theoretic statistical characteristics are discussed: the covariance and topological descriptors such as specific connectivity numbers and Meck.e's morphological functions.

Simulation of diffusion motion of ionomers using Monte Carlo algorithm

2020 ◽  
Vol 34 (25) ◽  
pp. 2050271
Author(s):  
Kai-Li Xue ◽  
Yun-Feng Hu ◽  
Xu-Chen Yu ◽  
Ji-Xuan Hou
Keyword(s):  
Monte Carlo ◽  
Polymer Chain ◽  
Mean Square Displacement ◽  
Boltzmann Distribution ◽  
Monte Carlo Algorithm ◽  
Theoretical Predictions ◽  
Diffusion Motion ◽  
Simulation Results ◽  
Single Polymer Chain ◽  
Diffusion Function

We present a simple model of ionomers, namely a single polymer chain in a series of fixed attractors. In analogy to ionized bead’s claws of surrounding chains, the set of attractors can affectively slow down the diffusion motion of the target chain. The monomer mean-square displacement of ionomers is studied by using Monte Carlo algorithm, and compared with the prediction of the sticky Rouse model. The diffusion motion properties of ionomers are explored in three aspects, including the chain length of the polymer, the depth of the potential well and the number of ionic groups. The results show that a plateau appears in the monomer diffusion function due to the attraction of the attractors to the claws. However, comparative theoretical predictions and simulation results show that there exists some discrepancy between them. Therefore, the relaxation time distribution of polymer chain motion is explored. The simulation results confirm that the association lifetime is decreasing exponentially, and the expected values of the association lifetime satisfy the Boltzmann distribution as shown by the results. These results perfectly explain the deviation between the simulation data and the theoretical results.

Molecular dynamics simulations of surface reconstruction at the edges of a crack in ruthenium aluminum

1994 ◽  
Vol 9 (3) ◽  
pp. 548-552 ◽  
Author(s):  
C.S. Becquart ◽  
P.C. Clapp ◽  
J.A. Rifkin
Keyword(s):  
Molecular Dynamics ◽  
Free Surface ◽  
Molecular Dynamics Simulations ◽  
Surface Reconstruction ◽  
Computer Simulations ◽  
Interatomic Potentials ◽  
Free Surfaces ◽  
Ductile Behavior ◽  
Dynamics Simulations

Using molecular dynamics computer simulations and interatomic potentials derived partly by Voter and Chen1 and Rifkin et al.,2 we studied the surface reconstruction taking place on free surfaces of arrays of RuAl. Surface reconstruction appears to be very important on {111} and {110} types of planes and almost nonexistent on {100} type of planes. Cracks oriented so that their crack planes were either {111} types or {110} types exhibit on their internal free surface important surface reconstruction. It is believed that this effect may have some contribution in the brittle versus ductile behavior of the crack.

Modeling of Size Effects in Diffusion Driven Processes at Nanoscale - Large Atomic and Mesoscale Methods

2017 ◽  
Vol 12 ◽  
pp. 38-73
Author(s):  
Tomasz Wejrzanowski ◽  
Krzysztof Jan Kurzydlowski
Keyword(s):  
Molecular Dynamics ◽  
Monte Carlo ◽  
Free Surface ◽  
Size Effects ◽  
Experimental Studies ◽  
High Energy ◽  
Intergranular Phase ◽  
Wide Range ◽  
Microstructure Effect

The results of the studies presented here are devoted to understanding of microstructure effect on the processes and properties driven by diffusion. The role of various interfaces (intergranular, phase, free surface), as the high-energy defects, is underlined and investigated with special attention. The methodology relevant to analyses of the microstructural processes is first briefly presented. The capability and limitations of classical molecular dynamics, mesoscale Monte Carlo and cellular automaton techniques are described. Two examples of the diffusion driven processes analyzed at various length and time scale are shown: namely, grain growth in nanometallic materials and melting of thin embedded films. The modeling results are also accompanied with experimental studies. Thanks to application of numerical methods, models of relevant processes were proposed, which enabled to provide quantitative relationships between microstructure and the process kinetics. Such relationships can be later used for design of optimized materials for wide range of applications.

scholarly journals Application of Molecular Dynamics and Monte-Carlo Methods near the Critical Points

2020 ◽  
Vol 15 (2) ◽  
pp. 394-395
Author(s):  
N.K. Balabaev ◽  
V.D. Lakhno
Keyword(s):  
Phase Transition ◽  
Molecular Dynamics ◽  
Monte Carlo ◽  
Critical Points ◽  
Monte Carlo Methods ◽  
Dna Melting

The applicability of molecular dynamics and Monte-Carlo methods near the phase transition is discussed on the example of DNA melting.

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