Atomic-scale computer simulation for early precipitation process of Ni75AlxV25-x alloy with intermediate Al composition

The microscopic phase-field approach is applied to model the early precipitation process of Ni75AlxV25-x alloy. Without any prior assumptions, this model can be used to simulate the temporal evolution of arbitrary morphologies and microstructures on atomic scale. By simulating the atomic pictures, and calculating the order parameters and volume fraction of the θ (Ni3V) and γ'(Ni3Al) ordered phases, we study Ni75AlxV25-x alloys with Al composition of 0.05, 0. 053 and 0. 055 (atom fraction). Our calculated results show that,for these alloys, θ and γ' phases precipitate at the same time; with the increase of Al content, the amount of γ' phase increases and that of θ phase decreases; the precipitation characteristic of γ' phase transforms from Non-Classical Nucleation and Growth (NCNG) to Congruent Ordering Spinodal Decomposition (CO SD) gradually; otherwise, the precipitation characteristic of θ phase transforms from Congruent Ordering Spinodal Decomposition (CO SD) to Non-Classical Nucleation and Growth (NCNG) mechanism gradually. Both θ and γ' phases have undergone the transition process of mixture precipitation mechanism characterized by both NCNG and CO SD mechanisms. No incontinuous transition of precipitation mechanism has been found.     

A template of rat brain based on fMRI T*2 imaging

The development of functional magnetic resonance imaging (fMRI) technology has made it possible to carry out functional brain imaging experiments in small animals. Usually, group data is required to form the assessment of population, which can not only increase the sensitivity of the overall experiment, but also allow the generalization of the conclusion to the whole population. In order to average the signals of functional brain images from different subjects, it is necessary to put all the mapping images into the same standard space (template image). However, up to now, most animal brain templates remain unavailable and it must be done by ourselves. In this study, a template image based on the brains of eight male Wistar rats is obtained, and it is successfully used in our present Alzheimer disease (AD)-like rat model studies as template for spatially normalizing images to the same stereotaxical space. The fMRI results processed with statistical parametric mapping (SPM99) software are in agreement with the results from immunohistochemical experiment, which proves that this method is universally applicable to the pathologic models of other small animals and to human brain lesion studies.     

Computational fluid dynamics for dense gas-solid fluidized beds

Many computational fluid dynamics (CFD) models for describing the hydrodynamics of dense gas-solid flows in fluidized beds have been put forward in the past few decades. These models treat the solid phase as continuum or discrete particles, which leads to Eulerian-Eulerian or Eulerian-Lagrangian formulations, respectively. Different governing equations and closure relations essentially result from an insufficient understanding of the complex gas?particle and particle?particle interactions for gas?solid flows. The current status of these models is discussed briefly in this paper. All the approaches in the literature modify only the solid phase momentum balance equation introducing various forms of the solid phase stress tensor and the solid phase pressure drop in the Eulerian-Eulerian models. Taking them into consideration, a new model for predicting the fluid behavior of dense gas?solid flows in fluidized beds has been developed, which contains new terms in both the particle and gas phase momentum balance equations and requires only the use of an experimental drag force correlation. Several results are shown to verify the model’s reliability, which include the homogeneous fluidization of Geldart type A particles, the bubbling and jetting fluidization of Geldart type B particles in rectangular beds, and fluid dynamics in a complicated geometry for a bubbling?bed of a fast internally circulating fluidized?bed biomass gasifier.     

环境素养评价体系与模型的构建及实证分析

结合国内外环境素养的研究成果 ,指出环境素养的概念应主要包括环境知识、环境行为和环境意识 3方面 ,并具有 3个特征·以此为基础 ,注意相关性、简洁性、可操作性等原则 ,构建出 3级 4层的环境素养评价指标体系和对应的数学评价模型 ,并进行了实证分析·该文有助于人们重视环境素养及其现代研究方法的构建与应用 ,增进交流 ,促进环境素养的提高·     

基于竞争神经网络的ABS路面辨识

在传统的防抱死系统中,由于没有额外的传感器测试更多的参数,以及路面的不平度、信号的干扰等原因,至使路面辨识非常困难·针对以上问题,通过对整车制动模型和ABS制动模型的研究,建立了基于竞争神经网络的ABS路面辨识模型,此路面辨识模型是通过对标准信号进行反复学习记忆,用非线性映射方法进行特征抽取并存储于网络的各节点上·工作时,当输入信号存在变形或噪声时,该模型通过联想记忆对输入信号进行聚类分析,得出正确的判断·实验表明,该辨识过程是一种高层次的认知过程且便于批量生产、升级、更新和维护·     

基于模型库的冷连轧过程控制仿真支撑系统

结合当前实际应用对改善仿真建模过程的需求,以简化专业领域仿真过程、提高仿真建模效率为目的,提出了以模型重用技术为基础,基于领域模型库的仿真支撑系统的思想,给出了仿真支撑系统总体结构设计方案,并针对带钢冷连轧过程优化控制系统,就标准仿真流程框架的提取、层次化领域模型库的构建及支撑系统运行机制的实现等关键问题进行了探讨·应用实例说明本文提出的仿真支撑系统总体框架及运行机制是可行的·     

基于MES的动态成本控制系统设计及其应用

以某钢铁公司选矿厂为背景,提出了在网络、数据库等信息技术支持下的基于ERP/MES/PCS三层框架结构的生产过程动态成本控制系统结构,设计并实施了选矿厂动态成本控制系统·系统以选矿生产过程为对象,按确定的成本中心采集各工序的成本数据,监测成本指标,完成成本的动态核算·并采用模型对成本进行分解、预测和分析,实现了成本的动态在线控制以及信息流、物流、资金流的集成,取得了良好的应用成效·     

中厚板控制冷却数学模型

介绍了中厚板控制冷却过程中所用的数学模型,包括差分模型、空冷和水冷换热系数模型、比热和热传导率模型,并采用有限差分法模拟计算了钢板在冷却过程中厚度、宽度方向上的温度场分布,以及间歇冷却对控制冷却的影响·从模拟结果可以看出,返红时间、厚度上温度梯度随钢板厚度增加而增加;间歇冷却时钢板内部温度呈均匀下降,表面不断冷却与返红过程·在线应用证明该套数学模型计算精度较高,可以满足现场实际生产的要求·     

基于移动互联网的材料加工工程搜索系统

确定了服务器端为基于Windows2000Server平台的WAPSEEKER无线搜索集成系统·给出无线数据与互联网的通信原理,使用ActiveServerPage3.0、VbScript、WMLScript等嵌入式编程语言和面向对象的数据库技术,完成了搜索文档的目标表示、结果信息的分段浏览、文档信息的自动查询、用户信息收发等功能模块·使用GPRS、WAP手机等移动设备访问互联网上材料加工工程领域信息成为现实·     

集成电路噪声模型算法及其矩阵表达

给出了集成电路噪声模型算法及其矩阵表达．噪声模型算法是利用功率谱密度叠加原理推证得出的，根据噪声叠加原理，多级集成电路的功率谱密度为单级集成电路功率谱密度的叠加之和，而单级集成电路的功率谱密度同样也基于叠加原理求得；并借助电路噪声等效理论，以反相输入运算放大器为例，探讨了运放噪声模型的矩阵算式，其方法和步骤同样适用于同相输入运算放大器；给出的程序设计方法为噪声模型算法的应用提供了思路，使系统参数的计算变得更精确．