为了揭示低温退火温度对硅晶圆内V-O2对介观演变的影响,基于所建相场模型及其应用程序,对2个不同温度下退火的硅晶圆中V-O2对演变过程进行了仿真.结果表明:当低温退火温度降低时,V-O2对变化速率减慢、数量减少,这与相应的空位相对浓度演变及其均匀化过程有关.

为了揭示自间隙硅原子相对浓度和间隙氧原子相对浓度的初始分布状态对低温退火期间硅晶圆内V-O2对介观演变的影响,应用原有相场仿真模型及其改进模型,仿真了两个不同的点缺陷相对浓度初始分布状态下退火的硅晶圆内V-O2对演变过程.结果表明:在文章的仿真条件下,均匀分布的硅原子相对浓度未影响V-O2对演变,这与不考虑硅原子存在的情况相同;与均匀分布状态相比,初始的氧原子相对浓度随机均匀分布状态使得V-O2对生成速度减慢.

为了揭示初始空位浓度对低温退火的硅晶圆内V-O2对演变的影响,基于所建相场模型及其应用程序,对随机均匀分布的3个初始空位浓度条件下硅晶圆内V-O2对演变进行了模拟研究.结果表明:随着初始空位浓度平均值的减小,V-O2对数量相应减少且变化速率减慢,这与相应的空位浓度演变及其均匀化过程有关;初始空位浓度平均值过低时,V-O2对不能产生.

为了开展低温退火过程硅单晶圆片中V-O2对演变的仿真研究,基于相场理论创建了仿真模型,首次完成了介观的V-O2对存在状态及其数量演变的模拟.结果表明:随着退火时间延长,V-O2对数量增加直至饱和且点缺陷相对浓度分布由非平衡态转变为平衡态;这两个演变规律符合实际且产生机理清晰,证实了该模型的合理性及其使用价值.

为了模拟粒子激发形核对于动态再结晶行为的影响,将粒子的激发形核、钉扎晶界效应和非均匀位错密度增量模型引入传统的动态再结晶元胞自动机模型,以HPS485wf钢为研究对象,在设定的3种大尺寸析出粒子体积分数状态下,模拟了动态再结晶过程,并通过同样变形条件下热压缩模拟实验进行了验证.结果表明:这一改进模型不仅模拟了孕育—形核—长大、多轮次、形核有序的动态再结晶组织演变特征,而且真实模拟了粒子激发形核效应及其对于动态再结晶的影响.

为了解决传统的动态再结晶元胞自动机模型不能模拟实际存在的形核和长大的有序性,基于相关理论和模型,提出了一个考虑晶粒尺寸和晶界综合影响的位错密度增量非均匀分布模型,分别采用含有该模型的元胞自动机模型和传统的元胞自动机模型对同一模拟条件下的 H PS485w f钢动态再结晶过程进行了仿真,并与热模拟实验结果进行了比较.结果表明:这一模型具有可靠的物理基础,所模拟的动态再结晶组织演变特征与传统的动态再结晶元胞自动机模拟结果相同;与传统的元胞自动机模型相比,含有该模型的元胞自动机模型所模拟的动态再结晶形核和长大表现出更加接近实际现象的有序特征,真应力-真应变曲线更加接近实验结果;动态再结晶速率在变形初期较快、在变形中后期较慢.

为了进一步改善瞬态形核率动态再结晶CA模型的动态回复阶段模拟精度,提出了采用应力差闭环控制-黄金搜索法取代唯象的位错密度增量模型来搜索、优化动态回复位错密度增量的方法,通过HPS485wf钢动态再结晶过程仿真和热模拟实验检验了该方法的合理性和应用效果.结果表明,这一方法合理、可行,能优化位错密度增量以提高动态回复阶段和动态再结晶全程的模拟精度和稳定性,较比传统的恒形核率动态再结晶CA模型的动态回复阶段和动态再结晶全程的模拟精度分别提高了98.91％和91.71％,较比瞬态形核率动态再结晶CA模型的动态回复阶段和动态再结晶全程的模拟精度分别提高了95.16％和49.47％.

In order to investigate the effect of annealing temperature on oxygen clusters’ evolution in silicon wafer during low temperature annealing, a phase-field model and it’s algorithm were established, and the changes of the oxygen clusters’ structure, amount (concentration) and sizes were simulated at different annealing temperature. The results show that when the temperature varies from 923 to 1023K, the oxygen clusters with reasonable amount and average size can be gained; when the temperature is too higher or lower, the suitable oxygen clusters cannot be found; it is verified that the established model and its algorithm have credible thermodynamics and experimental basis.

Based on the continuum damage mechanics (CDM) and the cohesive zone model (CZM), a numerical analysis method for the evaluation of damage in composite laminates under low‐velocity impact is proposed. The intraply damage including matrix crack and fiber fracture is represented by the CDM which takes into account the progressive failure behavior in the ply, using the damage variable to describe the intraply damage state. The delamination is characterized by a special contact law including the CZM which takes into account the normal crack and the tangential slip. The effect of the interlaminar toughness on the impact damage is investigated, which is as yet seldom discussed in detail. The results reveal that as the interlaminar fracture toughness enhances, the delamination area and the dissipated energy caused by delamination decrease. The contribution of normal crack and tangential slip to delamination is evaluated numerically, and the later one is the dominant delamination type during the impact process. Meanwhile, the numerical prediction has a good agreement with the experimental results. The study is helpful for the optimal design and application of composite laminates, especially for the design of interlaminar toughness according to certain requirements. POLYM. COMPOS. 37:1085–1092, 2016. © 2014 Society of Plastics Engineers

In order to perform preferential nucleation at triple junction during dynamic recrystallization( DRX ), a method of identifying the cell existed at triple junction and a preferential nucleation model at triple junction were proposed on the basis of the Moore neighbor of cellular automata. The rationality and application of the model were proved by simulating the DRX process of HPS485wf steel. The results showed that the proposed method and model have the ability to simulate the DRX more effectively. Compared with those from the traditional models,the results from the present model don’t only maintain the evolution of multiple rounds, microstructural feature,the“S-type”curve between area fraction and strain,the simulated flow stress with an accuracy of 0. 1% in the process of DRX,and also reveal the preferential nucleation at triple junction,which would provide a more realistic DRX nucleation.

A CZ crystal growth process and voids dynamic in 400 mm diameter silicon with three different pul-ling rate has been simulated by the professional FEM simulation software CGSim.The result show that:(1 ) with different velocities,the voids distribution in the crystal was similar,namely,at first,the voids density in-creased and diameter decreased as crystal radial radius increased,and then,the tendency was weakened as the axial position away from the solid-liquid interface,finally,at the edge of the crystal,voids density and diameter decrease along the radial position,and a non-voids area appeared at last,which range reduce as the axial posi-tion away from the solid-liquid interface;(2)with the pulling rate increasing,voids density and diameter enlar-ges at the center of the crystal,and the area move toward the edge.

为了研究热屏位置对于直拉单晶硅的熔体和固液界面的影响,采用CGSim有限元软件对φ200 mm直拉单晶硅生长过程进行了模拟,结果表明,随着热屏底端位置上升(或径向内移),熔体自由表面及其邻近区域的温度下降;随着热屏底端位置径向内移,位于两个大涡胞之间的较小涡胞强度增大且移向熔体液面深处;热屏位置上升或径向外移均会使固液界面上凸程度增大,这主要归因于晶体热场的相应变化.

为了改善动态再结晶恒形核率模型的模拟精度,基于动态再结晶模拟理论和闭环控制原理,提出了一种采用实验与模拟的流变应力差的闭环控制和黄金搜索法来确定真实瞬态形核率的方法,通过HPS485wf钢动态再结晶过程的元胞自动机仿真研究检验了它的合理性和应用效果.结果表明,这一方法合理、可行,可有效确定瞬态形核率,使得动态再结晶流变应力的模拟精度及其稳定性显著改善,并有益于提高其面积分数的模拟精度.

为了研究硅单晶直拉法生长过程中双空洞的长大动力学以及空洞间的相互作用机理,采用已建立的空洞演化的相场模型及其应用程序,模拟研究了直拉硅单晶生长过程中双空洞演化和相关因素的影响规律.结果表明:所建相场模型能够有效地模拟基体中空位扩散和双空洞长大的过程;双空洞长大趋势随着模拟时间和初始空位浓度的增强而加强;随着空洞初始中心间距的增加和初始空位浓度的减小,双空洞长大由相互融合模式转变为独立长大模式.

In order to study the growing behavior of NbC precipitated in low‐carbon niobium‐bearing steel ,the growth processes of two NbC particles were simulated ,and the evolution of their morphology and size as well as the effects of the initial interface spacing were also revealed based on a phase‐field model and its software .The results show that :with the extension of the simulation process ,the growth of two parti‐cles is changed from separation to integration and their interface distance decrease continuously to zero , which is resulted from the change of structure order parameter caused by niobium atomic diffusion and lo‐cal free energy density variation;the time taken for merging two particles′interface prolongs with the in‐creases of initial interface spacing until being stable ,w hich has a certain practical significance for analyzing the state of NbC particles existed in the low carbon niobium‐bearing steel .

A set of finite element simulations in Czochralski(Cz) furnace for 200 mm silicon single crystals have been performed to investigate the effect of heat shield position on V / G,grown-in defects and thermal stress field. The result shows that the position of heat shield has little effect on V / G and grown-in defects radial distribution,the axial position of heat shield has much bigger impact on crystal compared with its radial position. That is,as the distance between heat shield and melt increasing,V / G curve moves up and its slop gets bigger along radial direction,the void zone expands and the maximum thermal stress decreases at the same time. Silicon crystal quality could be improved by reasonable control of the axial distance between heat shield and melt.

In order to probe the virtual experiment for studying the dynamic recrystallization behavior of steel,a two dimensions model of dynamic recrystallization was established by cellular automata( CA) method,related theories and thermal simulation experiment. The processes of dynamic recrystallization in the HPS485wf steel hot-compressed at the different conditions were simulated using the model,and the simulated results were compared with the hot-compressed tests and dynamic recrystallization theory. The results show that the dynamic recrystallization behaviors of the steel not only have the same change laws as the experimental results and the dynamic recrystallization theory,but also show the characteristics with the phenomenon of multi-rounds dynamic recrystallization and the single peak type of stress-strain curve. The accuracies of microstructure evolution,recrystallization area fraction,average grain size and stress-strain curve simulated by the model are better.

Background Sm proteins are multimeric RNA-binding factors, found in all three domains of life. Eukaryotic Sm proteins, together with their associated RNAs, form small ribonucleoprotein (RNP) complexes important in multiple aspects of gene regulation. Comprehensive knowledge of the RNA components of Sm RNPs is critical for understanding their functions. Results We developed a multi-targeting RNA-immunoprecipitation sequencing (RIP-seq) strategy to reliably identify Sm-associated RNAs from Drosophila ovaries and cultured human cells. Using this method, we discovered three major categories of Sm-associated transcripts: small nuclear (sn)RNAs, small Cajal body (sca)RNAs and mRNAs. Additional RIP-PCR analysis showed both ubiquitous and tissue-specific interactions. We provide evidence that the mRNA-Sm interactions are mediated by snRNPs, and that one of the mechanisms of interaction is via base pairing. Moreover, the Sm-associated mRNAs are mature, indicating a splicing-independent function for Sm RNPs. Conclusions This study represents the first comprehensive analysis of eukaryotic Sm-containing RNPs, and provides a basis for additional functional analyses of Sm proteins and their associated snRNPs outside of the context of pre-mRNA splicing. Our findings expand the repertoire of eukaryotic Sm-containing RNPs and suggest new functions for snRNPs in mRNA metabolism.

In order to rationally simulate the recrystallization process of the material with secondphase particles,a cellular automata model for recrystallization of single-phase material with tiny second phase particles was created by introducing the Zener force to resist sub-grain growth and the rule of cell orientation transformation of grain boundary pinning,and the recrystallization annealing process of a ferritic steel was simulated. The results show that the model fully consider the combined effects of recovery at variable temperature,non-uniform deforming storage energy,abnormal nucleation and growth of sub-grain,and impeding by fine particles on recrystallization,and the simulated microstructure evolutions and their dynamics analysis reveals the same laws both in theories and in practice,that is,the smaller is particle size and the more is its number,the stronger is the effect of inhibiting recrystallization and the longer are the incubation period and the process of recrystallization.

A modified Voronoi model is established based on the Richard's method to generate 2D non-equiaxed initial microstructure for Monte Carlo simulation. Microstructures produced by the ordinary Voronoi model are isotropic and cannot reflect the effects of the deformed grain shape on the annealing process. The modified Voronoi model based on ellipse set can be used to construct the deformed microstructure. The initial microstructure reflects the mean strain and the grain size distribution follows lognormal distribution.