万家寨引黄工程北干1号隧洞Ⅳ标155-274型TBM主轴承总成组装概要

文中对万家寨引黄工程北干线1号隧洞Ⅳ标使用的155—274型TBM主轴承总成各部件组装过程及其相应的技术要求进行了概要的描述，目的是进一步熟悉155—274型TBM主轴承总成的各个部件并加深对主轴承工作原理的理解。     

双滑动氧枪的应用

叙述了φO114双焊缝氧枪存在的问题及改型后单焊缝双滑动氧枪的优点及使用效果。     

Ω焊缝自动检测系统定位组件开发

Ω焊缝自动检测系统集超声、涡流和目视检测为一体，专用于核电厂反应堆控制棒驱动机构与反应堆顶盖杯座之间的连接焊缝检测。定位组件是该检测系统的重要组成部分，它由伸缩定位机构和电机驱动保护电路组成，实现了该检测系统的正确、可靠和自动定位。     

用改进的逐次逼近解法计算二维井间电磁场

提出了一种计算积分方程的新方法——改进的逐次逼近解法 (MSAM) ,并用该方法计算了轴对称二维井间电磁场。与传统的逐次逼近解法 (SAM)相比 ,该方法收敛性强 ,应用范围广 ,可适用于高电导率对比地层。由于不必进行直接的大型矩阵求逆运算 ,因此与积分方程的直接解法 (IE)相比 ,该方法计算速度更快 ,所需内存更少。采用矩阵求逆方法计算了成层介质中的二维 Green函数 ,并对含 Green函数的积分进行了简化 ,从而加快了计算速度。数值计算结果显示 ,在地层电导率对比度达到 2个数量级时 MSAM仍收敛 ,且计算结果与直接求解积分方程的结果一致 ,因此 MSAM是一种有效的计算轴对称二维井间电磁场的方法     

地震反射的地层综合效应分析

实践中发现,煤层的反射强度与厚度有直接关系,石油地震勘探中反射层位与钻井地质深度比较往往有较大的误差,本文认为地震反射是一种地层性质的综合效应:同时用过渡层对称层的理论以及超薄层的概念对反射加以分析,得出一致的结论,反射的这种综合效应在煤厚预测、找油地质勘探设计等工作中有一定的应用价值。     

ON THE DISLOCATION SLIP MECHANISM OF THE MARTENSITIC TRANSFORMATION OF STEELS

根据实验证据提出:在钢的马氏体转变过程中,fcc→bcc(或bct)晶格改组时所需的原子相对位置变化是通过畸变fcc奥氏体晶格内的偏位错运动实现的,其方式有两种:一种是偏位错沿(1/m)〈112〉_f/{111}_f中的一个滑移系运动导致的主剪切原子位移;另一种是不同共轭{111}_f滑移面内偏位错同时或先后开动联合造成的M=(1/n)[〈112〉_(f1)/{111}_1+〈112〉_(f2)/{111}_2]复合原子位移。由此出发提出了钢淬火时奥氏体向马氏体转变的偏位错滑移共轭复合原子位移机制,并按此机制对马氏体与奥氏体之间的位向关系,马氏体惯析面及淬火马氏体中的一些特有现象给出了晶体几何学的解释。     

Influences of mullite fibers on mechanical and thermal properties of silica-based ceramic cores

Mullite fibers composite silica-based ceramic cores were successfully prepared by injection molding. The effects of mullite fibers on the mechanical and thermal properties of ceramic cores were investigated. The results indicated that the linear shrinkage was significantly decreased and the porosity was gradually increased with the increase of mullite fibers. In addition, the flexural strength for the room temperature and the simulated casting temperature of 1500°C was increased to a maximum value when the content of mullite fibers was about 1 wt.%, and then decreased with the increase of mullite fibers. The mullite fibers of 1 wt.% presented excellent mechanical properties with a linear shrinkage of .65%, a porosity of 6.96%, and a flexural strength of 17 MPa at room temperature and 34.83 MPa at the simulated casting temperature of 1500°C. Besides, the change in microstructure and properties in various contents of mullite fibers were analyzed.     

Synthesis of exfoliated PP/LDH nanocomposites via melt‐intercalation: Structure,thermal properties,and photo‐oxidative behavior in comparison with PP/MMT nanocomposites

Exfoliated polypropylene (PP)/layered double hydroxide (LDH) nanocomposites have been successfully synthesized via melt‐intercalation. Their structure, thermal properties, and photo‐oxidative behavior have been characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMA), X‐ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectrum. TGA and DMA data show that the PP/LDH nanocomposites have enhanced thermal stability compared with virgin PP and corresponding PP/montmorillonites (MMT) nanocomposites, especially in high temperature range during the thermal decomposition of the samples. XPS and FTIR results give positive evidence that the photo‐oxidation mechanism of PP in the PP/LDH materials is not modified compared with that of virgin PP. However, photo‐oxidation rate of PP/LDH materials is much lower than that of PP and PP/MMT samples, indicating that the PP/LDH nanocomposites have better UV‐stability. POLYM. ENG. SCI. 46:1153–1159, 2006. © 2006 Society of Plastics Engineers