钢板混凝土组合剪力墙抗震性能试验研究及有限元分析

为研究带约束拉杆钢板混凝土组合剪力墙的抗震性能及螺栓连接的可靠性,对3片高宽比为1.5的螺栓连接带约束拉杆钢板混凝土组合剪力墙进行了水平方向低周反复加载试验及有限元静力弹塑性分析.研究了试件的破坏形态及变形能力,得到了试件滞回曲线、承载力及骨架曲线.分析了约束拉杆间距对试件抗震性能的影响.建立有限元模型,对试件进行静力弹塑性分析并针对轴压比、约束拉杆间距进行了参数分析.结果表明,钢板之间采用螺栓连接可行,带约束拉杆钢板混凝土组合剪力墙具有较好的抗震性能,密布约束拉杆可有效提高其抗震性能,轴压比越高提高试件受力性能的效果越显著.     

基于内点法考虑风电穿透率的区域间可用输电能力研究

根据鼠笼异步风力发电机（SCIM）无功功率对机端电压和有功功率的表达式,修正了原-对偶内点法中的雅可比矩阵和海森矩阵,协调了算法的计算精度与迭代效率。采用连续潮流法计算了不同节点的穿透功率极限,得到SCIM和恒功率因数控制的双馈感应风力发电机（DFIG）不同穿透率下的可用输电能力（ATC）值。仿真结果表明,联络区域节点接入风电场大幅提升送电区与受电区间的ATC,而对于送电区的风电接入情况结论相反;DFIG的功率因数对ATC有较大的影响;通过合理的补偿措施可解决某些并网方式下算法收敛于局部最优解的问题,多节点电压越限为陷入局部最优的主因。     

具有二次曲面型端面的光纤连接问题

本文应用于Ｊｏｎｅｓ矩阵和光学设计方法，导出光纤活动连接中二次曲在型端面的插入损耗，反射损耗的解析表达式，对分析和改进端面结构以及设计二次曲面型端面光纤连接器，光纤器件提供依据，并给出了对称二次曲面型端面的曲率半径与透射，反射以及插入损耗，反射损耗的计算曲线。     

电子和光子封装无铅钎料的研究和应用进展

对目前国内外电子和光子封装用无铅钎料研究和应用的新进展和发展趋势进行了回顾、评述和展望,重点评述了无铅钎料的种类和钎焊接头的力学性能、封装结构的可靠性和耐久性,以及目前出现的影响电子封装可靠性的一些新问题(如电迁移和锡须问题).对光子封装钎料和相关钎焊工艺也进行了简要评述.最后,探讨了电子和光子封装无铅钎料及其可靠性和耐久性研究的发展趋势.     

热丝TIG焊在管道焊接中的应用

为了提高钨极气体保护焊的的焊接效率,扩大应用范围,介绍了热丝TIG焊的特点和分类,重点阐述了单丝热丝TIG焊、窄间隙热丝TIG焊和热丝TIG复合焊在石油化工、核电以及海洋工程等管道应用行业的现状,提出了热丝TIG焊存在的主要问题。分析认为,热丝TIG焊虽然具有优质、高效和节能等系列优点,但在焊接效率、磁偏吹等方面仍需进行改进。最后,指出了热丝TIG焊的发展趋势及未来的应用领域。     

Effect of Internal Current Flow During the Sintering of Zirconium Diboride by Field Assisted Sintering Technology

Effect of electric current on sintering behavior and microstructure evolution of zirconium diboride (ZrB₂) was investigated using three different configurations of Field Assisted Sintering Technology/Spark Plasma Sintering. The current flow through the ZrB₂ compact was controlled by modifying the interface between the graphite punches and the electrical conductive powder. Boron nitride discs, graphite foils or direct contact with the graphite punches were the three different interfaces used in order to deflect, conduct or promote, respectively, the current during the sintering process of the electrically conductive ZrB₂ ceramics. The current flow during the sintering process triggered the elimination/reduction in B₂O₃, leading to faster diffusion rates at high temperatures and limiting the formation of B₄C secondary phase. This allows to control the final density, grain size (from 19.6 to 43.2 μm) and secondary phase formation (from 5.95 to 11.61 vol%) as well as the electrical resistivity (from 7.7 to 9.4 μΩ·cm) of the specimens.     

基于内点法考虑风电穿透率的区域间可用输电能力研究

根据鼠笼异步风力发电机（SCIM）无功功率对机端电压和有功功率的表达式,修正了原-对偶内点法中的雅可比矩阵和海森矩阵,协调了算法的计算精度与迭代效率。采用连续潮流法计算了不同节点的穿透功率极限,得到SCIM和恒功率因数控制的双馈感应风力发电机（DFIG）不同穿透率下的可用输电能力（ATC）值。仿真结果表明,联络区域节点接入风电场大幅提升送电区与受电区间的ATC,而对于送电区的风电接入情况结论相反;DFIG的功率因数对ATC有较大的影响;通过合理的补偿措施可解决某些并网方式下算法收敛于局部最优解的问题,多节点电压越限为陷入局部最优的主因。     

煤粉锅炉后屏过热器水塞爆管分析与预防

某电厂4号锅炉发生后屏过热器爆管事故,分析认为主要原因是锅炉紧急停炉后在未能及时排出冷凝水的情况下再次点火,导致屏式过热器发生水塞,受热面局部短时过热引发爆管。对比该炉最近发生的多次水塞爆管事故,制定相应的预防措施,对同类锅炉的水塞爆管问题具有一定参考意义。     

不同体积无铅微尺度焊点的蠕变力学性能

采用基于动态力学分析仪的精密蠕变试验方法,对比研究了5.34×107 μm3与7.07×106 μm3两种体积相差近一个数量级的无铅Sn-3.0Ag-0.5Cu微尺度焊点的高温蠕变力学行为与蠕变性能.结果表明,所有微尺度焊点的蠕变曲线均呈现初始蠕变、稳态蠕变和加速蠕变阶段.虽然微尺度焊点的体积存在较大差异,但是它们的蠕变激活能与蠕变应力指数均非常接近.此外,在相同的试验温度与拉伸应力作用下,大体积微尺度焊点的稳态蠕变速率相对小体积焊点更大,而蠕变寿命则呈现完全相反的趋势.     

Effect of Sm2O3 content on microstructure and thermal conductivity of Spark Plasma Sintered AlN ceramics

Dense aluminum nitride ceramics were prepared by Spark Plasma Sintering at a lower sintering temperature of 1700 °C with Sm₂O₃ as sintering additives. The effect of Sm₂O₃ content on the density, phase composition, microstructure and thermal conductivity of AlN ceramics was investigated. The results showed that Spark Plasma Sintering could fabricate dense AlN ceramics with superior thermal properties in a very short time. Sm₂O₃ not only facilitated the densification via the liquid-phase sintering mechanism but also improved thermal conductivity by decreasing oxygen impurity. Thermal conductivity decreased with increasing amount of Sm₂O₃ and the highest thermal conductivity was obtained for the AlN ceramics with 2 wt.% Sm₂O₃ content. During Spark Plasma Sintering process, only 2–3 wt.% sintering additives was enough to fabricate dense AlN ceramics, and the microstructures played a key role in controlling the thermal conductivity of AlN ceramics.