Effect of Rare Earths on Hot Cracking Resistant Property of Mg-Al Alloys

The effect of rare earths （RE） ranging from 0.1% to 1.2%（mass fraction） on hot cracking resistant property of Mg-Al alloys was investigated. The results show that hot cracking resistant property of Mg-Al alloys remarkably declines with an increase of RE addition. The causes of the decline are as follows： First, grain coarsening of Mg-Al alloys caused by RE addition reduces the fracture strain required for hot crack initiation. Second, RE reduces the eutectic microstructure of Mg- Al alloys, and as a result, shortens the time that the feeding channel remains open, making it difficult to feed the alloy. Furthermore, RE elevates the eutectic reaction temperature, which leads to the decrease in the strength of the interdendritic liquid film at the late stage of solidification. Third, when a-Mg dendrites form continuous skeletons, the interdendritic Al11 RE3 phase tends to block the feeding channels and increases the difficulty of feeding. Last, the shrinkage ratio discrepancy between Al11RE3 phases and α-Mg matrix is prone to cause shrinkage stress and promote hot crack initiation.     

Grain Coarsening Behavior of Mg-Al Alloys with Mischmetal Addition

Small addition of mischmetal （MM） into aluminum alloys can lead to grain refinement. However, it is still uncertain whether the same effect applies to Mg-Al alloys. This work indicated that small amount of mischmetal addition ranging from 0.1% to 1.2% （mass fraction） did not cause grain refinement in Mg-Al alloys. On the contrary, they tended to coarsen the grains. When added into Mg-Al alloys, MM reacted preferentially with Al to form Al11 MM3 phase. As Al11 MM3 phase mainly distributed within α-Mg grains than at grain boundaries, it had little effect in restricting grain growth. In addition, MM reacted with Al8（Mn, Fe）5 or ε-AlMn particles to form Al-MM-Mn compounds, thus it reduced the amount of heterogeneous nuclei in the melt and resulted in remarkable grain coarsening.     

MTK手机平台内存使用技术概述

本文简要介绍MTK手机平台的内存构成,说明内存复用技术的原理,最后比较说明MTK内存使用三种情况。     

Mg70Ni15Gd10Ag5块体非晶的制备及晶化行为

采用铜模铸造法制备新型块体非晶合金Mg70Ni15Gd10Ag5(at%),其临界制备尺寸不低于5 mm,是目前Mg-Ni基非晶合金制备尺寸的最大值。采用差示扫描量热（DSC）法研究非晶合金的晶化行为,发现合金的晶化为多级晶化。随着升温速度的提高,玻璃转变温度Tg、晶化开始温度Tx、熔化前4个放热峰温度（Tp1、Tp2、Tp3、Tp4）、熔化开始温度（Tm）和液相线温度（Tl）均向高温区移动,晶化行为具有显著的动力学特征。利用Kissinger法计算特征温度对应的激活能,其值分别为Eg=188.05 kJ/mol、Ex=144.79 kJ/mol、Ep1=138 kJ/mol、Ep2=142.40 kJ/mol、Ep3=119.10 kJ/mol、Ep4=72.86 kJ/mol。     

基于二维模式匹配的镜头检测方法

镜头通常作为分析和检索视频的基本单元.为此,提出了一种基于二维模式匹配的镜头自动检测算法.为克服二值化处理后缺少色彩特征的缺点,进一步采用主色提取的方法,利用色彩信息提高算法准确率.实验结果表明提出的算法可行性好、检测准确率高.     

测氡仪检定报告自动生成系统设计

为实现测氡仪检定数据的自动分析,采用VS2008软件开发平台,研制了基于ACCESS数据库和.NET Framework 3.5的测氡仪检定报告自动生成系统。该系统自动完成数据分析以及待检测氡仪的重复性、体积活度响应、相对固有误差等参数的计算,自动生成检定报告,节省了人力物力,便于历史检定数据和测氡仪检定周期的保存和查询。     

主辅氡箱补氡过程仿真及验证

氧气在主辅氡箱氡室中是一种动态稳定状态,论文首先讨论主辅氡箱中氡活度的积累规律,通过对主辅氡箱同时进行补氡控制过程的仿真及采用实验方法验证主辅氡箱的补氡过程,验证了一个氡源两个箱体氡室氡浓度补氡控制的可行性,并取得了比较好的效果.     

光通信系统中基于伽罗华域乘群的QC-LDPC码的一种新颖构造方法

基于Galois域GF(q)乘群,提出了一种构造简单且编码容易实现的新颖准循环低密度奇偶校验(QC-LDPC)码构造方法,可灵活地调整码长、码率,且编译码复杂度低。用本文方法构造了适用于光通信系统的非规则QC-LDPC(3843,3603)码,仿真表明,与已广泛用于光通信系统中的经典RS(255,239)码相比,用本文方法构造的码具有更好的纠错性能,且其性能优于用SCG方法构造的LDPC码和规则的QC-LDPC(4221,3956)码,适合用于高速长距离光通信系统。     

一种测定氡室漏气率的新方法探讨

氡室是第三代标准氡源,氡室漏气率是影响氡室准确、可靠和安全运行的关键参数。介绍了一种测定漏气率的方法并讨论了氡泄漏对环境的影响,经实验验证该方法是一种既简单又准确的测定漏气率方法,且氡泄漏对环境的影响在安全范围内。     

运用IPA模拟动态装配过程--制造业信息化的解决方案

介绍了一种新兴的、开放的、可交互的软件开发平台——IPA．以及他的应用领域和设计环境；并且结合实例阐述了IPA在制造业中的应用。