钛合金的扩散焊连接技术

本文介绍了扩散焊的原理、特点和主要扩散焊方法,对其在钛合金材料中的应用研究现状进行了综述,并对钛合金扩散连接的应用前景进行了展望。     

LaO_x(OH)_y supported platinum catalysts for CO oxidation:Deactivation by formation of lanthanum carbonate

Platinum catalyst for CO oxidation has been studied for decades,due to its high activity and good stability.In this work,we prepared three different lantha num oxide or hydroxide supports(LaO_x(OH)_y),and deposited platinum(Pt) with 0.5 at% via an impregnation approach to synthesize Pt/LaO_x(OH)_y catalysts.However,we find that these catalysts perform a poor stability for the CO oxidation reaction.The fresh and used samples were comprehensively characterized by multiple techniques including power X-ray diffraction(XRD),X-ray absorption fine structure(XAFS),transmission electron microscopy(TEM),temperature-programmed reduction by carbon monoxide(CO-TPR) and thermogravimetric analysis(TGA),to demonstrate that the oxidized platinum atoms or clusters,without any component of Pt-Pt metallic bond,are highly dispersed on the surface of LaO_x(OH)_y.Furthermore,the as-formed lanthanum carbonate(La₂O₂CO₃) during the exposure to ambient circumstances or in the reaction atmosphere of CO+O₂,severely impair the reactivity of Pt/LaO_x(OH)_y.On the basis of the obtained experimental results,we have drawn a conclusion that the oxidized P_tO_x atoms or PtxOy clusters are the active species for CO oxidation,while the formation of lanthanum carbonate is the origin of deactivation on reactivity.     

数据与知识驱动的零件特征工艺决策方法

在零件的工艺设计阶段, 加工工艺方案的生成强依赖于设计人员选择和应用的工艺知识. 而由于实际的生产环境与设计人员选择工艺知识存在着诸多偏差, 加工方案与实际的工艺过程不匹配成为当前零件制造领域关注的难题. 为解决上述问题, 本文提出了一种数据与知识双驱动的零件特征工艺决策方法. 本方法使用基于注意力机制的MLP深度学习算法, 从结构化工艺数据中挖掘工艺知识, 关联零件特征与特征工艺标签. 将其经过数据加工后, 用于训练神经网络模型. 经过验证, 该方法能够以零件特征的工艺数据为输入, 输出其对应的特征工艺标签的概率分布, 为零件工艺方案的选择提供决策支持.     

Electrode Evaporation Effects on Air Arc Behavior

A numerical study of the effects of copper and silver vapours on the air arc behavior is performed. The commercial software FLUENT is adapted and modified to develop a twodimensional magneto-hydrodynamic （MHD） models of arc with the thermodynamic properties and transport coefficients, net emission coefficient for the radiation model of 99% ai-1% Cu, 99% air-1% Ag, and pure air, respectively. The simulation result demonstrates that vaporization of the electrode material may cool the arc center region and reduce the arc velocity. The effects of Ag vapour are stronger compared to those of Cu vapour.     

The E3 Ligase GmPUB21 Negatively Regulates Drought and Salinity Stress Response in Soybean

E3-ubiquitin ligases are known to confer abiotic stress responses in plants. In the present study, GmPUB21, a novel U-box E3-ubiquitin ligase-encoding gene, was isolated from soybean and functionally characterized. The expression of GmPUB21, which possesses E3-ubiquitin ligase activity, was found to be significantly up-regulated by drought, salinity, and ABA treatments. The fusion protein GmPUB21-GFP was localized in the cytoplasm, nucleus, and plasma membrane. Transgenic lines of the Nicotiana benthamiana over-expressing GmPUB21 showed more sensitive to osmotic, salinity stress and ABA in seed germination and inhibited mannitol/NaCl-mediated stomatal closure. Moreover, higher reactive oxygen species accumulation was observed in GmPUB21 overexpressing plants after drought and salinity treatment than in wild-type (WT) plants. Contrarily, silencing of GmPUB21 in soybean plants significantly enhanced the tolerance to drought and salinity stresses. Collectively, our results revealed that GmPUB21 negatively regulates the drought and salinity tolerance by increasing the stomatal density and aperture via the ABA signaling pathway. These findings improved our understanding of the role of GmPUB21 under drought and salinity stresses in soybean.     

微流控光脉冲调制器

为了解决常见光调制器偏振依赖或结构复杂的问题,本文基于微流控光学提出一种可控光脉冲调制器。利用基于T形结产生的离散液滴和全反射原理的微流控光开关,将连续光变换成数字脉冲信号,并通过调节液滴的长度和生成速率调制光脉冲的宽度和频率。所提微流控光脉冲调制器具有结构简单、插入损耗低、消光比高、易集成的优点。微流控光脉冲调制器的流场与光场特性被分析,结构被优化。研究结果显示：该光脉冲调制器的消光比为17.74 dB,插入损耗为0.49 dB。     

基于SQL Server数据库的安全性策略研究

从数据库系统的安全模型入手,讨论分析了SQL Server数据库使用中的安全问题,针对可能存在的安全问题,提出了一些具体的解决方法和建议,以提高用户对数据库安全的认识.     

燃煤含硫量对高参数机组锅炉选型的影响

针对燃煤特性(主要是含硫量)对锅炉参数选择可能带来的影响,以美国B&W公司对各种钢材的年腐蚀量试验数据为依据,对高参数机组所能适用的燃煤含硫量进行了分析,指出对国内电厂燃煤含硫量超过2%以上机组不适宜采用超(超)临界机组。     

模糊模型在机车车轮故障诊断中的应用

提出了一种改进的能面向高阶T-S模糊推理模型.并将改进型IRBFN的神经模糊模型学习算法应用于车轮的故障诊断当中,提出了一套新的简单、高效的车轮故障诊断方法.仿真结果表明,该方法是有效的.