二元合金多晶粒的枝晶生长的等温相场模型

基于Ginzburg-Landau理论和单晶粒的枝晶生长模型，发展了一个单相场控制的多个晶粒的枝晶生长模型. 采用相场和溶质场耦合的方法，以Al-2%Cu合金为例模拟了二元合金等温凝固过程中多个晶粒的生长过程. 结果表明，这个模型的计算结果展现了多个晶粒枝晶的竞争生长，能较真实的再现凝固过程中的枝晶的生长过程.     

基于VB数据库的单片机主从式串口通讯

介绍一种基于Ｖｉｓｕａｌ Ｂａｓｉｃ６．０数据库的ＭＣＳ５１单片机与ＰＣ机的串行通信方法，详细说明了在ＶＢ环境下进行串口通讯时数据库应用技术，并给出了串行通信的软件编程技巧。     

Tripwire在入侵检测系统中的运用

绝大多数计算机系统的核心是文件系统。文件系统包括用户数据、可执行程序、配置和认证信息以及操作系统本身的基本可执行程序。Tripwire是基于UNIX系统的用来检查文件系统完整性的程序。它所具备的监测系统中是否发生了对系统文件的非授权或意外改动的功能给系统管理员提供了维护系统安全的宝贵数据,同时对发生入侵事件后系统灾难的评估与恢复起着重要的作用。     

FPGA芯片的节能设计技术

本文的侧重点在于讨论那些用于减少功耗的设计技术，这些设计经验及设计规则包括了设计周期中不同的几个方面，包括在系统级、寄存器传输级（RTL）及低层等几个方面的技术。     

尼龙66-盐与碳纤维复合-固态缩聚的研究

本工作借助偏光显微镜,扫描电子显微镜和热分析方法(DSC,TGA)研究了尼龙66盐与碳纤维复合-固态缩聚反应历程及纤维-树脂之间的界面效应。发现对尼龙66盐的“原位固态缩聚”存有如碳纤维表面的成核结晶和催化效应之类的界面效应。讨论了碳纤维的界面效应对尼龙66基体的外延结晶和熔融行为及其热氧化稳定作用的影响。     

多柔体系统动力学符号演算的研究

多柔体系统动力学涉及繁杂的数学运算,对系统动力学方程和系数矩阵进行手工推导是低效而不可靠的．采用数值化方法进行系统动力学分析将包括许多虚运算和重复计算,使得计算效率和精度受到了影响．同时对约束和外力的变化适应性较差．本文在通用计算机符号演算软件ＭＡＴＨＥＭＡＴＩＣＡ环境下,研究了多柔体系统动力学的计算机符号演算方法,提出将多柔体系统动力学建模和数值分析的问题在ＭＡＴＨＥＭＡＴＩＣＡ环境中一体化解决,并通过实践说明这一方法是可行的和有效的．     

La和Nd在其氯化物熔体中的电化学腐蚀

稀土金属在其氯化物熔盐中的自腐蚀是导致电解制备稀土金属时电流效率降低的一个重要原因。但由于实验技术上的困难,有关这方面的研究报道不多。本文将在水溶液体系中常用的电化学弱极化测量腐蚀速度及电化学参数的方法用之于La、Nd在其氯化物熔盐体系中的腐蚀,表明同样适用。     

Multi-phase field simulation of competitive grain growth for directional solidification

The multi-phase field model of grain competitive growth during directional solidification of alloy is established. Solving multi-phase field models for thin interface layer thickness conditions, the grain boundary evolution and grain elimination during the competitive growth of SCN-0.24-wt% camphor model alloy bi-crystals are investigated. The effects of different crystal orientations and pulling velocities on grain boundary microstructure evolution are quantitatively analyzed. The obtained results are shown below. In the competitive growth of convergent bi-crystals, when favorably oriented dendrites are in the same direction as the heat flow and the pulling speed is too large, the orientation angle of the bi-crystal from small to large size is the normal elimination phenomenon of the favorably oriented dendrite, blocking the unfavorably oriented dendrite, and the grain boundary is along the growth direction of the favorably oriented dendrite. When the pulling speed becomes small, the grain boundary shows the anomalous elimination phenomenon of the unfavorably oriented dendrite, eliminating the favorably oriented dendrite. In the process of competitive growth of divergent bi-crystal, when the growth direction of favorably oriented dendrites is the same as the heat flow direction and the orientation angle of unfavorably oriented grains is small, the frequency of new spindles of favorably oriented grains is significantly higher than that of unfavorably oriented grains, and as the orientation angle of unfavorably oriented dendrites becomes larger, the unfavorably oriented grains are more likely to have stable secondary dendritic arms, which in turn develop new primary dendritic arms to occupy the liquid phase grain boundary space, but the grain boundary direction is still parallel to favorably oriented dendrites. In addition, the tertiary dendritic arms on the developed secondary dendritic arms may also be blocked by the surrounding lateral branches from further developing into nascent main axes, this blocking of the tertiary dendritic arms has a random nature, which can have aninfluence on the generation of nascent primary main axes in the grain boundaries.     

温补晶体振荡器的频率温度稳定度

大部分晶体振荡器生产厂家的数据手册不会兼顾所有使用者的需要,特别是温补晶体振荡器的频率温度稳定度指标,多数情况下,数据手册所列指标往往只适应于某一类典型的应用场合或只符合生产厂家与其某几个主要用户的验收规则,所以只有充分理解频率温度稳定度的不同定义方法、与频率温度稳定度相关的其他频率温度特性指标、不同的环境温度测试方法,才能正确制定符合自己使用要求的频率温度稳定度指标,不加分析地简单套用频率温度