Computational steering in Monte Carlo simulations of thin film polystyrene

2005 ◽  
Vol 363 (1833) ◽  
pp. 1961-1974 ◽  
Author(s):  
Daniel R Mason ◽  
Adrian P Sutton
Keyword(s):  
Thin Film ◽  
Monte Carlo ◽  
Relaxation Times ◽  
Polymer System ◽  
Atomic Scale ◽  
Computational Steering ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Current State ◽  
Mc Simulation

High molecular weight polymer systems show very long relaxation times, of the order of milliseconds or more. This time-scale proves practically inaccessible for atomic-scale dynamical simulation such as molecular dynamics. Even with a Monte Carlo (MC) simulation, the generation of statistically independent configurations is non-trivial. Many moves have been proposed to enhance the efficiency of MC simulation of polymers. Each is described by a proposal density ( x ′; x ): the probability of selecting the trial state x ′ given that the system is in the current state x . This proposal density must be parametrized for a particular chain length, chemistry and temperature. Choosing the correct set of parameters can greatly increase the rate at which the system explores its configuration space. Computational steering (CS) provides a new methodology for a systematic search to optimize the proposal densities for individual moves, and to combine groups of moves to greatly improve the equilibration of a model polymer system. We show that monitoring the correlation time of the system is an ideal single parameter for characterizing the efficiency of a proposal density function, and that this is best evaluated by a distributed network of replicas of the system, with the operator making decisions based on the averages generated over these replicas. We have developed an MC code for simulating an anisotropic atomistic bead model which implements the CS paradigm. We report simulations of thin film polystyrene.

Shear Studies on Polymer Flooding Systems with High Concentrations

2012 ◽  
Vol 535-537 ◽  
pp. 1189-1192 ◽  
Author(s):  
Ji Gang Wang ◽  
Peng Wu ◽  
Quan Qing Du ◽  
Hui Hui Cao ◽  
Meng Sun
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Oil Recovery ◽  
Polymer System ◽  
Polymer Flooding ◽  
Displacement Efficiency ◽  
High Concentration ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
High Concentrations

Abstract: When the dose level of polymer is settled, the change of injection volume and concentration do not increase oil recovery obviously, while the result of lab research shows that the increasing of oil recovery of high concentration and high molecular weight polymer flooding can reach or over that of ASP flooding. The aim of this paper is to study the shear characteristic in high concentration and high molecular weight polymer flooding, and analyzed the suitable parameter of it.They can provide the theory of high concentration Polymer flooding. In the process of polymer flooding, it was because increasing the water phase viscosit and the retention effect of polymer molecules in porous media that making oil flow degrees than improved ,the sweep volume expand, and improve the oil recovery. Study confirmed [1-3], polymer solution with sticky elastic can effectively improve the oil displacement efficiency, reduce residual oil saturation [4-5]. So, the study on the shear properties of the polymer system in high concentration (>1000mg/L) can provide experimental base for a high concentration of polymer flooding, it also has important significance on theory of polymer flooding development and application research.

Electro-Thermal Analysis and Monte Carlo Simulation for Thermal Issue in Si Devices

2009 ◽  
Author(s):  
Tomoyuki Hatakeyama ◽  
Kazuyoshi Fushinobu ◽  
Ken Okazaki ◽  
Masaru Ishizuka
Keyword(s):  
Thermal Analysis ◽  
Monte Carlo ◽  
Relaxation Time ◽  
Energy Conservation ◽  
Heat Generation ◽  
Relaxation Times ◽  
Conservation Equation ◽  
Energy Conservation Equation ◽  
Precise Prediction ◽  
Mc Simulation

Nowadays, precise prediction of the heat generation in semiconductor devices is significant. Electro-thermal analysis is one of the attractive methods to predict the heat generation in devices. However, in electro-thermal analysis, the relaxation time approximation is applied to calculate the scattering term in momentum and energy conservation equation. And the assumption of the constant relaxation time for the scattering term of energy conservation equation and the momentum relaxation time derived from the empirical carrier mobility are conventionally applied. For precise prediction of the relaxation times, Monte Carlo (MC) simulation can be applied. In this research, we consider the importance of these relaxation times for heat generation in semiconductor devices. We compare the results with conventional relaxation times and those with the relaxation time from MC simulation in electro-thermal analysis. The calculation results show the electro-thermal analysis with the conventional relaxation time model will overestimate the heat generation density in lower electric field of devices and in higher clock frequency devices.

A Study of Particle Settling in Non-Newtonian Fluids—Part II: Rheological Characterization of Polymer Solutions

1994 ◽  
Vol 116 (1) ◽  
pp. 16-21 ◽  
Author(s):  
L. Jin ◽  
M. E. Chenevert
Keyword(s):  
Relaxation Times ◽  
Maxwell Model ◽  
Cellulose Derivatives ◽  
Rheological Characterization ◽  
Frequency Pattern ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Shear Thinning Fluids ◽  
Viscous Shear ◽  
Frequency Sweeps

Aqueous solutions of different concentrations of three polymers: a synthetic high molecular weight polymer, partially hydrolyzed polyacrylamide (PHPA), a xanthantype biopolymer (Xanvis), and a cellulose-type polymer (HEC) were investigated in this study. It was found that the steric arrangement of molecules or interactions between molecules can be detected by a systematically designed strain and frequency sweep measurement, and is reflected by the different relaxation times of the solutions. The degree of elasticity can be quantified by G′/|G*| in linear viscoelastic range. The responses of the fluids to frequency sweeps are displayed in a normalized moduli versus normalized frequency pattern derived from the Maxwell model. Results show that within the tested concentration ranges, PHPA solutions are highly elastic with moderate relaxation times that are strain and concentration insensitive. Xanvis solutions are also highly elastic, but with high relaxation times that are both strain and concentration sensitive, indicating a different mechanism of elasticity compared to PHPA solutions. HEC (cellulose derivatives) are mostly viscous shear thinning fluids with weak elasticity and short relaxation times that are insensitive to strain, but sensitive to concentration.

Monte Carlo Simulation Model for Magnetron Sputtering Deposition

2015 ◽  
Vol 1105 ◽  
pp. 69-73 ◽  
Author(s):  
M.A. Hassan ◽  
M.B. Elfiky ◽  
Y. Nukman ◽  
Reza Mahmoodian
Keyword(s):  
Thin Film ◽  
Monte Carlo ◽  
Magnetron Sputtering ◽  
Simulation Model ◽  
Deposition Rate ◽  
Operating Conditions ◽  
Optimum Operating ◽  
Plastic Substrate ◽  
Deposition Parameters ◽  
Mc Simulation

Thin Film layers of metal are often prepared by magnetron sputtering technique for electronic, optical and micro/nanoelectromechanical systems. Usually, experimental work is a common way to find out the optimum deposition conditions and correlate between the thin film properties and the deposition parameters. However, experimental methods are very exhaustive, time and cost-consuming. A good simulation model which can provide the optimum operating conditions to avoid exhaustive experiments and reduce time and cost is highly recommended. Therefore, the present paper is focusing on the development of a computer simulation model of the deposition process in the magnetron sputtering system since such type of models is not well established yet. Monte Carlo (MC) simulation model has been developed to study the effects of deposition parameters on the deposition rate and thin film thickness uniformity. Titanium (Ti) samples were used as the target whereas argon (Ar) was the ambient inert gas. MC simulation has successfully predicted the optimum deposition rate and thickness of Ti thin films on the plastic substrate. The model also depicted the performance of magnetron deposition due to change of processing parameters. Comparison between the simulation and experimental results proved the validity of the proposed model.

Determination of Stoichiometry of GaAs Component in (Gaas)Ge Epitaxially Grown Thin Films by Electron Microprobe X-Ray Analysis

1990 ◽  
Vol 48 (2) ◽  
pp. 264-265
Author(s):  
D. R. Liu ◽  
S. S. Shinozaki ◽  
R. J. Baird
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Compound Semiconductors ◽  
Energy Dispersive Analysis ◽  
X Ray ◽  
Metastable Alloys ◽  
Lower Voltage

The epitaxially grown (GaAs)Ge thin film has been arousing much interest because it is one of metastable alloys of III-V compound semiconductors with germanium and a possible candidate in optoelectronic applications. It is important to be able to accurately determine the composition of the film, particularly whether or not the GaAs component is in stoichiometry, but x-ray energy dispersive analysis (EDS) cannot meet this need. The thickness of the film is usually about 0.5-1.5 μm. If Kα peaks are used for quantification, the accelerating voltage must be more than 10 kV in order for these peaks to be excited. Under this voltage, the generation depth of x-ray photons approaches 1 μm, as evidenced by a Monte Carlo simulation and actual x-ray intensity measurement as discussed below. If a lower voltage is used to reduce the generation depth, their L peaks have to be used. But these L peaks actually are merged as one big hump simply because the atomic numbers of these three elements are relatively small and close together, and the EDS energy resolution is limited.

Electron Microscopy Studies of The Chemistry And Microstructure of BaF2 / YBa2Cu3O7-x Thin Films

1994 ◽  
Vol 52 ◽  
pp. 796-797
Author(s):  
J. L. Lee ◽  
C. A. Weiss ◽  
R. A. Buhrman ◽  
J. Silcox
Keyword(s):  
Thin Film ◽  
Electron Microscopy ◽  
Thin Films ◽  
Scanning Transmission Electron Microscope ◽  
Atomic Scale ◽  
Island Growth ◽  
Multilayer Systems ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Mgo Substrate

BaF2 thin films are being investigated as candidates for use in YBa2Cu3O7-x (YBCO) / BaF2 thin film multilayer systems, given the favorable dielectric properties of BaF2. In this study, the microstructural and chemical compatibility of BaF2 thin films with YBCO thin films is examined using transmission electron microscopy and microanalysis. The specimen was prepared by using laser ablation to first deposit an approximately 2500 Å thick (0 0 1) YBCO thin film onto a (0 0 1) MgO substrate. An approximately 7500 Å thick (0 0 1) BaF2 thin film was subsequendy thermally evaporated onto the YBCO film.Images from a VG HB501A UHV scanning transmission electron microscope (STEM) operating at 100 kV show that the thickness of the BaF2 film is rather uniform, with the BaF2/YBCO interface being quite flat. Relatively few intrinsic defects, such as hillocks and depressions, were evident in the BaF2 film. Moreover, the hillocks and depressions appear to be faceted along {111} planes, suggesting that the surface is smooth and well-ordered on an atomic scale and that an island growth mechanism is involved in the evolution of the BaF2 film.

scholarly journals Multiple particle filtering for tracking wireless agents via Monte Carlo likelihood approximation

2019 ◽  
Vol 2019 (1) ◽  
Author(s):  
Stephan Schlupkothen ◽  
Gerd Ascheid
Keyword(s):  
Monte Carlo ◽  
Computational Complexity ◽  
Particle Filtering ◽  
Gaussian Approximation ◽  
State Of The Art ◽  
Approximation Techniques ◽  
Accurate Localization ◽  
Likelihood Approximation ◽  
Current State ◽  
Multiple Particle

Abstract The localization of multiple wireless agents via, for example, distance and/or bearing measurements is challenging, particularly if relying on beacon-to-agent measurements alone is insufficient to guarantee accurate localization. In these cases, agent-to-agent measurements also need to be considered to improve the localization quality. In the context of particle filtering, the computational complexity of tracking many wireless agents is high when relying on conventional schemes. This is because in such schemes, all agents’ states are estimated simultaneously using a single filter. To overcome this problem, the concept of multiple particle filtering (MPF), in which an individual filter is used for each agent, has been proposed in the literature. However, due to the necessity of considering agent-to-agent measurements, additional effort is required to derive information on each individual filter from the available likelihoods. This is necessary because the distance and bearing measurements naturally depend on the states of two agents, which, in MPF, are estimated by two separate filters. Because the required likelihood cannot be analytically derived in general, an approximation is needed. To this end, this work extends current state-of-the-art likelihood approximation techniques based on Gaussian approximation under the assumption that the number of agents to be tracked is fixed and known. Moreover, a novel likelihood approximation method is proposed that enables efficient and accurate tracking. The simulations show that the proposed method achieves up to 22% higher accuracy with the same computational complexity as that of existing methods. Thus, efficient and accurate tracking of wireless agents is achieved.

Multilevel Monte Carlo by using the Halton sequence

2020 ◽  
Vol 26 (3) ◽  
pp. 193-203
Author(s):  
Shady Ahmed Nagy ◽  
Mohamed A. El-Beltagy ◽  
Mohamed Wafa
Keyword(s):  
Monte Carlo ◽  
Differential Equations ◽  
Stochastic Differential Equations ◽  
Computational Cost ◽  
Random Numbers ◽  
Multilevel Monte Carlo ◽  
Halton Sequence ◽  
Random Generator ◽  
Mc Simulation ◽  
Multilevel Monte Carlo Method

AbstractMonte Carlo (MC) simulation depends on pseudo-random numbers. The generation of these numbers is examined in connection with the Brownian motion. We present the low discrepancy sequence known as Halton sequence that generates different stochastic samples in an equally distributed form. This will increase the convergence and accuracy using the generated different samples in the Multilevel Monte Carlo method (MLMC). We compare algorithms by using a pseudo-random generator and a random generator depending on a Halton sequence. The computational cost for different stochastic differential equations increases in a standard MC technique. It will be highly reduced using a Halton sequence, especially in multiplicative stochastic differential equations.

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