高能球磨合成纳米WC-Co复合粉末的特性

采用变转速多次循环高能球磨工艺在32min制备出了平均晶粒尺寸约为25nm的纳米WC-10CO-0．8VC-0．2Cr3C2(重量分数)复合粉末，并用化学元素分析、XRD，TEM，DTA对纳米WC—Co复合粉末的特性进行了表征和分析。结果表明，变转速多次循环高能球磨工艺制备的纳米WC—CO复合粉末，化学成分合格，杂质含量低，球磨效率高；球磨过程是一个晶粒逐渐细化的过程，同时也是一个晶格畸变逐渐增加、粉末体系能量逐渐增大的过程；球磨得到的WC-Co纳米复合粉末颗粒形貌基本为球形，粒径分布较宽，颗粒中存在着一些团聚体，平均颗粒尺寸约为50nm；纳米WC-10Co-0．8VC-0．2Cr3C2(wt％)复合粉末的共晶点约为1280℃。纳米复合粉末中W，Co，V，Cr元素分布均匀弥散。     

湿式球磨机润滑系统的改进

针对湿式球磨机的工况条件，介绍了其集中润滑的改进特点及应用效果。     

Results of the NIST National Ball Plate Round Robin

This report examines the results of the ball plate round robin administered by NIST. The round robin was part of an effort to assess the current state of industry practices for measurements made using coordinate measuring machines. Measurements of a two-dimensional ball plate (240 mm by 240 mm) on 41 coordinate measuring machines were collected and analyzed. Typically, the deviations of the reported X and Y coordinates from the calibrated values were within ± 5 μm, with some coordinate deviations exceeding 20.0 μm. One of the most significant observations from these data was that over 75 % of the participants failed to correctly estimate their measurement error on one or more of the ball plate spheres.     

纳米铁粉的稳定性及超细铁粉的生物利用率

分析了用高能球磨法，以食品添加剂为助磨剂制备出的纳米级铁粉在空气和其它不同条件下的稳定性。并分析了超细铁粉在果汁中的溶解度和稳定性。     

后路皮磨磨辊技术特性的试验

本文通过实验,摸索出较为合适的后路皮磨磨辊技术特性,经生产实践证明效果较好,取得了较好的经济效益.     

对密珠式检测芯轴的进一步探讨

通过对密珠式检测芯轴的进一步探讨 ,克服了圆柱式检测芯轴的许多缺点。经过实践证明 ,合理设计芯轴的制造关键部分———密珠套 ,可以大大地提高测量精度     

龙门移动式镗铣床的同步进给控制

针对龙门移动式高速镗铣床中两个龙门柱的同步进给问题，提出一个自适应控制方案。通过自适应律的设计来实现同步进给。仿真结果表明，该控制方案具有鲁棒性强、同步误差小的优点。     

航空铝合金7050-T7451铣削力模型的实验研究

采用多因素回归正交实验法进行铣削实验，在给出四因素、四水平实验模型中常系数和指数数学推导公式的基础上，建立了特种材料7050-T7451的铣削力模型，为进一步研究航空铝合金数控加工变形提供了可靠的边界条件。     

Plastic ball grid array (PBGA) overview

As integrated circuit functionality and clock speed continue to rise, innovative packaging approaches are in great demand. Recently, the plastic ball grid array (PBGA) technology has been gaining industry-wide interest and commitment as the potentially lowest-cost package for high-I/O devices and even for some lower-pincount applications. Drivers include the density advantages of an area array, quickly achieving six-sigma assembly yields with existing assembly equipment, the potential for excellent electrical and thermal performance, along with the traditional low cost of plastic packages. Because some perceived weaknesses are being eradicated, worldwide evaluation of the PBGA has accelerated. Although various aspects of this technology are discussed frequently, an overall assessment is still under development. In this paper, a systematic and comprehensive evaluation of PBGA technology will be described to identify (1) its technical advantages and limitations, (2) unique application areas where PBGA is the package of choice, and (3) current major hurdles for acceptance of PBGA and possible approaches to overcome these problems. The PBGA will be compared with PQFP, CQFP and CBGA in terms of package characteristics and their impact on system assembly. The characteristics include package attributes (i.e., package size, I/O counts and lead pitch), performance (i.e., electrical, thermal) and reliability (moisture). At the system level, solder joint fatigue, board routing, solder assembly yield, solder reparability and board delay are key metrics. The cost implication of various package families will be discussed. By analogy with SMT, the infrastructure for PBGA will take time to develop. The key elements and the current status of this infrastructure will be discussed.     

正交车铣工件侧母线的研究

简要地描述了正交车铣的运动形式，通过数学方法详细分析了正交车铣工件的侧母线的形状，并由此得出了偏心量和刀具半径对侧母线的影响。