Das Monte Carlo-studium der copolymerisation der ester der benzylidencyanessigsäure mit styrol

The Monte Carlo study of copolymerization of styrene with four esters of benzylidenecyanoacetic acid has pointed out that (a) for methyl and hexyl esters one cannot decide among the ultimate and penultimate effect (using copolymer composition and Fischer statistic), and (b) cyclohexyl and benzyl esters copolymerize following the kinetics of penultimate effect. Finally, the most probable sequence distribution in the studied copolymers is presented.     

Monte Carlo Study of Binary Copolymerizations. 1. Ultimate and Penultimate Effect,Applications

The Monte Carlo models of binary irreversible copolymeriza-tion with ultimate and penultimate effect are applied to the copolymerization of acrylic acid and methyl acrylate, and styrene and benzylidene malononitrile, respectively. The agreement with available experimental data is quite good. A comparative study between the formal kinetics model and the Monte Carlo model reveals that statements concerning the copolymer composition are robust, but statements concerning the sequence distribution are not always robust.     

Das Monte Carlo-studium der verteilung der sequenzen in den copolymeren des methylmethacrylats mit chloropren und des 2-hydroxyäthyl-methacrylats mit alkylacrylaten

Using our Monte Carlo model of binary copolymerization, one studies the sequence distribution in methyl methacrylate/chloroprene and 2-hydroxyethyl methacrylate/alkyl acrylate copolymers. Our study points out incontestably that the copolymerization of methyl methacrylate is explainable through ultimate group effect (Ebdon has stated a penultimate group effect). In the case of 2-hydroxyethyl methacrylate/alkyl acrylate copolymers the agreement between computed and experimental data is satisfactory.     

Monte Carlo-studium der reversiblen copolymerisation. I. Theorie,memøry-6 programm,anwendungen

The binary reversible copolymerization, taking into account the length of the terminal sequence, are studied by the Monte Carlo method. We discuss the theoretical model, the algorithm, and a FR?RAN program. Finally, the α-methylstyrene-methyl methacrylate copolymerization is studied by means of the proposed Monte Carlo model, and the results obtained are compared with those obtained using the Markov chain model and Wittmer's equations.     

Win X-ray: a new Monte Carlo program that computes X-ray spectra obtained with a scanning electron microscope.

A new Monte Carlo program, Win X-ray, is presented that predicts X-ray spectra measured with an energy dispersive spectrometer (EDS) attached to a scanning electron microscope (SEM) operating between 10 and 40 keV. All the underlying equations of the Monte Carlo simulation model are included. By simulating X-ray spectra, it is possible to establish the optimum conditions to perform a specific analysis as well as establish detection limits or explore possible peak overlaps. Examples of simulations are also presented to demonstrate the utility of this new program. Although this article concentrates on the simulation of spectra obtained from what are considered conventional thick samples routinely explored by conventional microanalysis techniques, its real power will be in future refinements to address the analysis of sample classifications that include rough surfaces, fine structures, thin films, and inclined surfaces because many of these can be best characterized by Monte Carlo methods. The first step, however, is to develop, refine, and validate a viable Monte Carlo program for simulating spectra from conventional samples.     

基于自适应蒙特卡洛法评定测量不确定度程序开发与应用

进行了基于自适应蒙特卡洛法评定测量不确定度的程序开发与应用。基于Python语言,设计开发自适应蒙特卡洛法评定测量不确定度程序,包含评定过程框架、自定义变量名称模块、过程参数关联计算模块以及蒙特卡洛法采样计算模块。程序界面简洁,操作简单,计算准确,适用于任意多个独立变量、任意多个过程参数及单一被测量的数学模型,为利用自适应蒙特卡洛法评定测量不确定度提供了方便。     

Monte Carlo-studium der ireversiblen terpolymerisation: Das modell und anwendungen

The Monte Carlo model of the ternary irreversible copolymerization is presented. The computer program MEMøRY-4, which implements the described model, is used to study the methyl methacrylate/methyl acrylate/maleic anhydride, butadiene/styrene/2-methyl-5-vinylpyridine, and styrene/methacrylonitrile/α-methyl styrene terpolymers. One discusses the problem of transferability of reactivity ratios determined for binary copolymerizations to the ternary ones. It can be concluded that the transferability is not assured, but using only composition data it is difficult to achieve a safe conclusion (Fisher statistics).     

Brownian Dynamics, Molecular Dynamics, and Monte Carlo modeling of colloidal systems

This paper serves as an introductory review of Brownian Dynamics (BD), Molecular Dynamics (MD), and Monte Carlo (MC) modeling techniques. These three simulation methods have proven to be exceptional investigative solutions for probing discrete molecular, ionic, and colloidal motions at their basic microscopic levels. The review offers a general study of the classical theories and algorithms that are foundational to Brownian Dynamics, Molecular Dynamics, and Monte Carlo simulations. Important topics of interest include fundamental theories that govern Brownian motion, the Langevin equation, the Verlet algorithm, and the Metropolis method. Brownian Dynamics demonstrates advantages over Molecular Dynamics as pertaining to the issue of time-scale separation. Monte Carlo methods exhibit strengths in terms of ease of implementation. Hybrid techniques that combine these methods and draw from these efficacies are also presented. With their rigorous microscopic approach, Brownian Dynamics, Molecular Dynamics, and Monte Carlo methods prove to be especially viable modeling methods for problems with challenging complexities such as high-level particle concentration and multiple particle interactions. These methods hold promising potential for effective modeling of transport in colloidal systems.     

Monte‐Carlo simulation of secondary electron emission by x‐ray irradiation—an application of x‐ray absorption near‐edge structure (XANES)

A Monte‐Carlo simulation program has been developed for describing x‐ray absorption near‐edge structure (XANES) observed by synchrotron radiation. The Monte‐Carlo simulation was applied for interpreting XANES spectroscopy on a polycrystalline Ag specimen under synchrotron irradiation with photon energy 3340–3390 eV around the absorption edge of the Ag L_α line at 3352 eV. The results clearly indicate that Monte‐Carlo simulation describes the experimental results with considerable success. Dependence of secondary electron yield on the incident angle of synchrotron radiation was also studied. Copyright © 2004 John Wiley & Sons, Ltd.     

Monte Carlo Study of Binary Copolymerizations. 2. The Determination of Reactivity Ratios,Applications

This paper discusses an improved and efficient version of the MEMØRY-7 computer program described in a previous paper. The program, called MEMØRY-7/1, implements a Monte Carlo algorithm to compute reactivity ratios in binary irreversible copolymerizations. For the copolymerization of acrylic acid and methyl acrylate, the computed r₁, r₂ values (r₁ = 1.374, r₂ = 1.038) compare quite well with experimentally determined ones (r₁ = 1.4, r₂ = 1.0; Eldridge and Treloar).     

Zur kopolymerisation: Axiomatische formulierung eines mathematischen modells,das memory 3 programm—anwendungen

This paper presents an axiomatic mathematical model for binary copolymerization reactions. The FØRTRAN program entitled MEMØRY 3 is described. This program implements the Monte Carlo version of the axiomatic model, computing the most probable sequence distribution. Finally, a concrete copolymerization process is studied and good results are presented.     

Monte Carlo simulation of ion transport in non-linear ion mobility spectrometry

A program for Monte Carlo simulation of ion transport in non-linear ion mobility spectrometry, also known as field asymmetric ion mobility spectrometry (FAIMS) or differential mobility spectrometry (DMS), has been developed. Simulations are based on elastic collisions between the ions and the gas particles, and take into account the effects of flow dynamics and asymmetric electric fields. Using this program, the separation and diffusion of the ions moving in a planar DMS filtration gap are demonstrated. Ion focusing in a cylindrical filtration gap is also confirmed. A characteristic compensation voltage is found to provide insight for understanding separation in non-linear ion mobility spectrometry. The simulation program is used to study the characteristics of non-linear ion mobility spectrometry, the effect of the carrier gas flow, and the dependence of the compensation voltage and nonlinear mobility coefficient (α) on the applied asymmetric electric field.     

Interdimensional degeneracies in van der Waals clusters and quantum Monte Carlo computation of rovibrational states

Quantum Monte Carlo estimates of the spectrum of rotationally invariant states of noble gas clusters suggest interdimensional degeneracy in N-1 and N+1 spatial dimensions. We derive this property by mapping the Schrodinger eigenvalue problem onto an eigenvalue equation in which D appears as a continuous variable. We discuss implications for quantum Monte Carlo and dimensional scaling methods.     

Biopolymer structure simulation and optimization via fragment regrowth Monte Carlo

An efficient exploration of the configuration space of a biopolymer is essential for its structure modeling and prediction. In this study, the authors propose a new Monte Carlo method, fragment regrowth via energy-guided sequential sampling (FRESS), which incorporates the idea of multigrid Monte Carlo into the framework of configurational-bias Monte Carlo and is suitable for chain polymer simulations. As a by-product, the authors also found a novel extension of the Metropolis Monte Carlo framework applicable to all Monte Carlo computations. They tested FRESS on hydrophobic-hydrophilic (HP) protein folding models in both two and three dimensions. For the benchmark sequences, FRESS not only found all the minimum energies obtained by previous studies with substantially less computation time but also found new lower energies for all the three-dimensional HP models with sequence length longer than 80 residues.     

Thermodynamic properties of van der Waals fluids from Monte Carlo simulations and perturbative Monte Carlo theory

Computer simulations have been performed for fluids with van der Waals potential, that is, hard spheres with attractive inverse power tails, to determine the equation of state and the excess energy. On the other hand, the first- and second-order perturbative contributions to the energy and the zero- and first-order perturbative contributions to the compressibility factor have been determined too from Monte Carlo simulations performed on the reference hard-sphere system. The aim was to test the reliability of this "exact" perturbation theory. It has been found that the results obtained from the Monte Carlo perturbation theory for these two thermodynamic properties agree well with the direct Monte Carlo simulations. Moreover, it has been found that results from the Barker-Henderson [J. Chem. Phys. 47, 2856 (1967)] perturbation theory are in good agreement with those from the exact perturbation theory.     

Protein structure prediction with the UNRES force-field using Replica-Exchange Monte Carlo-with-Minimization; Comparison with MCM, CSA, and CFMC

Two current methods of global optimization are coupled to produce the Replica-Exchange method together with Monte Carlo-with-Minimization (REMCM). Its performance is compared with each separate component and with other global optimization techniques. REMCM was applied to search the conformational space of coarse grain protein systems described by the UNRES force field. The method consists of several noninteracting copies of Monte Carlo simulation, and minimization was used after every perturbation to enhance the sampling of low-energy conformations. REMCM was applied to five proteins of different topology, and the results were compared to those from other optimization methods, namely Monte Carlo-with-Minimization (MCM), Conformational Space Annealing (CSA), and Conformational Family Monte Carlo (CFMC). REMCM located global minima for four proteins faster and more consistently than either MCM or CFMC, and it converged faster than CSA for three of the five proteins tested. A performance comparison was also carried out between REMCM and the traditional Replica Exchange method (REM) for one protein, with REMCM showing a significant improvement. Moreover, because of its simplicity, REMCM was easy to implement, thereby offering an alternative to other global optimization methods used in protein structure prediction.     

Computational methods in coupled electron-ion Monte Carlo simulations.

In the last few years, we have been developing a Monte Carlo simulation method to cope with systems of many electrons and ions in the Born-Oppenheimer approximation: the coupled electron-ion Monte Carlo method (CEIMC). Electronic properties in CEIMC are computed by quantum Monte Carlo rather than by density functional theory (DFT) based techniques. CEIMC can, in principle, overcome some of the limitations of the present DFT-based ab initio dynamical methods. The new method has recently been applied to high-pressure metallic hydrogen. Herein, we present a new sampling algorithm that we have developed in the framework of the reptation quantum Monte Carlo method chosen to sample the electronic degrees of freedom, thereby improving its efficiency. Moreover, we show herein that, at least for the case of metallic hydrogen, variational estimates of the electronic energies lead to an accurate sampling of the proton degrees of freedom.     

A version of diffusion Monte Carlo method based on random grids of coherent states. II. Six-dimensional simulation of electronic states of H2

We report a new version of the diffusion Monte Carlo (DMC) method, based on coherent-state quantum mechanics. Randomly selected grids of coherent states in phase space are used to obtain numerical imaginary time solutions of the Schrodinger equation, with an iterative refinement technique to improve the quality of the Monte Carlo grid. Accurate results were obtained, for the appropriately symmetrized two lowest states of the hydrogen molecule, by Monte Carlo sampling and six-dimensional propagation in the full phase space.     

STUDY ON THE SEQUENCE STRUCTURE OF SBR BY 13C-NMR METHOD Ⅵ MONTE CARLO SIMULATION OF THE SEQUENCE OF SBR

A program of Monte Carlo simulation of binary copolymerization for E-SBR (emulsion polymn. SB rubber) was made according to the terminal model. The simulation results obtained by this program were in good agreement with those experimental ones. A detail microstructure information of E-SBR molecular chain has been provided.     

An investigation on determination of attenuation coefficients for gamma-rays by Monte Carlo method

The radiation attenuation coefficients ??/?? (cm²?g^?1) for concrete and cement samples that used for experimental studies by other researchers were determined by Monte Carlo calculations at 59.5, 80, 356, 661.6, 1173.2 and 1332.5?keV photon energies. The simulated results of attenuation coefficients were compared with the reported experimental data for the same samples and a good agreement has been observed. The intent of this research was to develop a Monte Carlo program useful for various absorbers and energies. The variation of the attenuation coefficient with photon energy has also been investigated for these samples.