Monte Carlo simulation of sequential structure control of AN-MA-IA aqueous copolymerization by different operation modes

The regulation of polyacrylonitrile(PAN)copolymer composition and sequence structure is the precondition for producing high-quality carbon fiber high quality.In this work,the sequential structure control of acrylonitrile(AN),methyl acrylate(MA)and itaconic acid(IA)aqueous copolymerization was investigated by Monte Carlo(MC)simulation.The parameters used in Monte Carlo were optimized via machine learning(ML)and genetic algorithms(GA)using the experimental data from batch copolymerization.The results reveal that it is difficult to control the aqueous copolymerization to obtain PAN copolymer with uniform sequence structure by batch polymerization with one-time feeding.By contrary,it is found that the PAN copolymer with uniform composition and sequence structure can be obtained by adjusting IA feeding quantity in each reactor of a train of five CSTRs.Hopefully,the results obtained in this work can provide valuable information for the understanding and optimization of AN copolymerization process to obtain high-quality PAN copolymer precursor.

Monte Carlo simulations of biaxial structure in thin hybrid nematic film based upon spatially anisotropic pair potential

Hybrid nematic films have been studied by Monte Carlo simulations using a lattice spin model, in which the pair potential is spatially anisotropic and dependent on elastic constants of liquid crystals. We confirm in the thin hybrid nematic film the existence of a biaxially nonbent structure and the structure transition from the biaxial to the bent-director structure, which is similar to the result obtained using the Lebwoh-Lasher model. However, the step-like director＇s profile, characteristic for the biaxial structure, is spatially asymmetric in the film because the pair potential leads to K1 ≠ K3. We estimate the upper cell thickness to be 69 spin layers, in which the biaxial structure can be found.

COMPUTER SIMULATION OF STRUCTURE OF MOLTEN DyF_3－BaF_2－LiF SYSTEM BY MONTE CARLO METHOD

ＣＯＭＰＵＴＥＲＳＩＭＵＬＡＴＩＯＮＯＦＳＴＲＵＣＴＵＲＥＯＦＭＯＬＴＥＮＤｙＦ_３－ＢａＦ_２－ＬｉＦＳＹＳＴＥＭＢＹＭＯＮＴＥＣＡＲＬＯＭＥＴＨＯＤ￥ＸｕＣｈｉ；ＳｕＨａｎｇ；ＣｈｅｎＮｉａｎｙｉ（ＳｈａｎｇｈａｉＩｎｓｔｉｔｕｔｅｏｆＭｅｔａｌｌ...

Noninvasive in vivo study of NADH fluorescence and its real-time intrinsic dynamical changes: Experiments and seven-layered skin model Monte Carlo simulations

Reduced nicotinamide adenine dinucleotide(NADH)plays a crucial role in many biochemical reactions in human metabolism.In this work,a flow-mediated skin fluorescence(FMSF)-postocclusion reactive hyperaemia(PORH)system was developed for noninvasive and in vivo measurement of NADH fluorescence and its real-time dynamical changes in human skin tissue.The real-time dynamical changes of NADH fluorescence were analyzed with the changes of skin blood flow measured by laser speckle contrast imaging(LSCI)experiments simultaneously with FMSFPORH measurements,which suggests that the dynamical changes of NADH fluorescence would be mainly correlated with the intrinsic changes of NADH level in the skin tissue.In addition,Monte Carlo simulations were applied to understand the impact of optical property changes on the dynamical changes of NADH fluorescence during the PORH process,which further supports that the dynamical changes of NADH fluorescence measured in our system would be intrinsic changes of NADH level in the skin tissue.

Comparison Between Three-Valley Model and Full Band Model in Monte Carlo Simulation of Bulk Wurtzite GaN

The Monte Carlo simulators with the three valley model and the full band Monte Carlo model are used to explore electron transport in bulk wurtzite gallium nitride (GaN).Comparison of the results based on the two models is made.The results based on both models are basically the same at the lower field region,but exhibit some differences at the higher field region.The electron average energy exhibits obvious difference at the high field region between the two models.This difference further causes several other differences of GaN properties,such as the drift velocity versus field characteristics,the repopulation.Because of the complicated energy band structures at the high energy region for wurtzite GaN,the analytical band structures in the three valley model can not cover all properties of the band structures of wurtzite GaN,so the results based on the full band Monte Carlo model should be more exact.

ON THE MONTE CARLO SIMULATION OF NORMAL GRAIN GROWTH

The microstructures and their kinetics of normal grain growth are simulated using different Monte Carlo （MC） algorithms. Compared with the relative figures and the theoretical normal grain growth exponents of n =0.5, the effects of some factors of MC algorithm, i.e. the lattice types, the methods of selecting lattice sites, and the neighbors selection for energy calculations, on the simulation results of grain growth are studied. Two methods of regression were compared, and the three-parameter nonlinear regression is much more suitable for fitting the grain growth kinetics. A better model with appropriate factors included triangular lattice, the attempted site randomly selected, and the first and second nearest neighbors for energy calculations is obtained.

Monte-Carlo Simulation of Surface Crack Growth Rate for Offshore Structural Steel E36-Z35

The Monte- Carlo method is used to simulate the surface fatigue crack growth rate for offshore structural steel E36-Z35, and to determine the distributions and relevance of the parameters in the Paris equation. By this method, the time and cost of fatigue crack propagation testing can be reduced. The application of the method is demonstrated by use of four sets of fatigue crack propagation data for offshore structural steel E36-Z35. A comparison of the test data with the theoretical prediction for surface crack growth rate shows the application of the simulation method to the fatigue crack propagation tests is successful.

Kinetic Monte Carlo simulation of growth of BaTiO_3 thin film via pulsed laser deposition

Considering the characteristics of perovskite structure, a kinetic Monte Carlo(KMC) model, in which Born-Mayer- Huggins(BMH) potential was introduced to calculate the interatomic interactions and the bonding ratio was defined to reflect the crystallinity, was developed to simulate the growth of BaTiO3 thin film via pulsed laser deposition(PLD). Not only the atoms deposition and adatoms diffusion, but also the bonding of adatoms were considered distinguishing with the traditional algorithm. The effects of substrate temperature, laser pulse repetition rate and incident kinetic energy on BaTiO3 thin film growth were investigated at submonolayer regime. The results show that the island density decreases and the bonding ratio increases with the increase of substrate temperature from 700 to 850 K. With the laser pulse repetition rate increasing, the island density decreases while the bonding ratio increases. With the incident kinetic energy increasing, the island density decreases except 6.2 eV<Ek<9.6 eV, and the bonding ratio increases at Ek<9.6 eV. The simulation results were discussed compared with the previous experimental results.

大规模非线性系统随机振动显式迭代Monte Carlo模拟法

探讨了非平稳随机激励下大规模非线性系统随机振动Monte Carlo模拟法。引入等效激励的概念,把非线性系统动力方程写成状态方程的形式,并采用精细积分法对状态方程进行数值求解,导出非线性系统振动分析的显式迭代法。基于所导出的显式迭代公式,可以有效提高单次确定性非线性振动分析的计算效率,从而可以通过Monte Carlo模拟获得非平稳随机激励下非线性系统随机响应的统计信息,同时还可以获取非线性系统随机响应的演化概率密度函数。数值算例表明,所提出的方法迭代收敛速度快,计算精度高,适用于求解大规模非线性系统随机振动问题。

Cu(111)与Cu(110)上水煤气变换反应的微观动力学分析及MonteCarlo模拟

通过对Ｃｕ（１１１）与Ｃｕ（１１０）晶面上水煤气变换反应中基元步骤动力学参数的计算及表面氧化还原机理的ＭｏｎｔｅＣａｒｌｏ模拟，发现该反应为结构敏感反应，其表观活化能强烈地依赖于催化剂的表面结构，从而在一定程度上从分子水平阐明了催化剂表面结构对反应活性的影响．

不同金属催化水煤气变换反应活性的Monte Carlo模拟研究

运用BOC一MP方法对Cu(110),Cu(111),Pd(111)Au(111)等过渡金属催化的WGS反应的可能微观动力学步骤进行了详尽的能学数据计算,并结合Monte Carlo方法对WGS反应的表面氧化还原机理进行了计算机模拟.结果表明,Cu的催化活性优于Pd,Au的催化活性,并获得了相应金属上WGS反应的表观活化能及动力学指前因子(相对值);在此基础上,对该反应的结构敏感性进行了研究,发现该反应为一结构敏感反应,与实验结果相符.

结构随机分析的Monte Carlo加权残值法

本文提出一种结构随机分析的Monte Carlo加权残值法。文中建立了这种方法的基本列式,并通过静力挠度、固有频率和屈曲荷载等算例,表明本文方法理论简捷,计算工程量少,精度较高,是随机结构数值分析的有效方法。

Monte Carlo模拟纤锌矿GaN材料中粒子最终态的确定

介绍了M on te C arlo方法模拟半导体材料和器件特性使用的三种模型,重点介绍用全带M on te C arlo方法模拟纤锌矿相G aN材料所用的两项关键技术即散射几率计算和能带结构数据库应用问题。提出了确定散射后最终态能量和波矢量的计算方法。根据散射机理和粒子能量的不同,确定最终态的方法有4种。对各向异性的极性光学声子散射,采用分析带模型与全带模型相结合,对不同的能量,非抛物面系数取不同的值的方法,提高了确定最终态的准确性,提高了计算速度。

非高斯荷载作用下结构首次失效时间分析的Monte Carlo模拟方法

利用结构反应的头四阶矩,基于Winterstein变换,模拟非高斯荷载作用下结构的反应过程,并由结构反应过程的样本函数,建立了结构首次失效时间分析的模拟方法。二次力函数激励下线性SDOF系统的首次失效时间分析,说明了该方法的使用过程,并揭示了系统阻尼对首次失效的影响。

小功率LED光源封装光学结构的Monte Carlo模拟及实验分析

采用 Monte Carlo方法对不同光学封装结构的 L ED进行模拟 ,建立了小功率 L ED的仿真模型 ,应用空间二次曲面方程描述 L ED的封装结构 ,对其光强分布进行模拟和统计 .通过测量实际样品 ,并与模拟结果进行比较和分析 ,表明计算机模拟值与实验测量值比较吻合 .

ReverseMonteCarlo计算机模拟

介绍了ＲｅｖｅｒｓｅＭｏｎｔｅＣａｒｌｏ计算机模拟原理，及其在应用时应注意的问题。

嵌段共聚高分子链构象的Monte Carlo模拟

采用非格子Monte Carlo模拟方法对嵌段共聚高分子链构象的演化过程进行模拟研究,具体地考察了结构单元的序列结构以及单元间的相互作用对高分子链的聚集态结构的影响.结果表明,在合适的条件下,嵌段高分子链可以发生线团-螺旋转变以及线团-链滴转变,相应结果可为理解生物大分子的结构提供可能的线索.

二维Ising模型的Monte Carlo模拟

利用Monte Carlo方法对二维Ising模型的相变行为进行了计算机模拟,发现当温度变化时该模型会发生相变行为,该结果与前人的理论计算结果和实验结果一致。

地震数据反演中的Monte－Carlo算法、模拟退火算法（SA）及遗传算法（GA）

Ｍｏｎｔｅ－Ｃａｒｌｏ反演方法不是从方程出发直接求反问题，而是在可行解空间中随机产生一系列搜索点，通过检验各搜索点得到反问题的解，该方法具有很强的抗噪音能力，不需对问题作任何线性近似．模拟退火技术是把最优化问题与统计力学中热平衡问题进行类比得来的，它是一种最优化技术，把我们要找极值的函数看成是整个系统的能量函数，任一时制的系统状态则看成是模型空间的一个点．其优点是可避免陷入局部极小值，缺点是计算量很大。遗传算法（ＧＡ）这种新的“全局优化”算法的出现早于模拟退火十多年。ＧＡ的实质是应用于一个模型群体的一组运算，使我们得到一个新的群体，它比上一代成员有更大的期望平均拟合度。上述三种用于反演问题求解的算法已广泛地应用在地球物理求解中，已成为求解非线性反问题的有力数学工具。

从fcc到sc结构相变的MonteCarlo研究

提出了一个改进的Ｐｏｔｔｓ模型并用它描述从面心立方（ｆｃｃ）到简立方（ｓｃ）的有序无序转变．用ＭｏｎｔｅＣａｒｌｏ的方法对它进行了模拟，结果表明，相变温度为Ｔｃ≈（０．７７±０．０２）２ＪｃｏｓθｋＢ．