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121.
The oxidation behavior of a Cu60Hf25Ti15 bulk metallic glass was studied over the temperature range of 375–520 °C in dry air. The oxidation kinetics of the amorphous
alloy generally followed the parabolic law at all temperatures, with an oxidation rate increasing with temperature. The oxidation
rates of the amorphous alloy were much higher than those of polycrystalline pure-Cu, implying that the additions of Hf and
Ti accelerated the oxidation reaction. The composition of the scales formed on the amorphous alloy was strongly temperature-dependent,
since they consisted mostly of Cu4O3 and CuO with minor amounts of HfO2 at T ≤ 450 °C, while mostly CuO with minor amounts of HfO2 and Cu2TiO3 were detected at higher temperatures. In addition, nanocrystalline Cu51Hf14 and Cu3Ti2 phases were detected on the substrate after oxidation at T ≥ 450 °C, indicating the occurrence of phase transformation. 相似文献
122.
The kinetics of disproportionation of methylamine to dimethylamine and ammonia in the presence of hydrogen have been investigated over a silica-supported palladium catalyst. At a fixed partial pressure of methylamine, the reaction rate generally increases with decreasing hydrogen partial pressure, approaching a limiting or maximum value at sufficiently low pressures of hydrogen. The existence of a maximum is supported by the observation that the presence of some hydrogen appears to be necessary for the reaction to proceed at a conveniently measurable rate. At a fixed hydrogen partial pressure, the reaction rate increases with increasing methylamine partial pressure. When the methylamine partial pressure is sufficiently low or the hydrogen partial pressure is sufficiently high, the reaction order with respect to methylamine can be somewhat higher than one. At such conditions, a mechanism involving a bimolecular reaction between two partially dehydrogenated methylamine molecules on the surface appears to make a significant contribution to the overall catalytic reaction. 相似文献
123.
用EGS4分析9MeV行波直线加速器屏蔽系统 总被引:1,自引:0,他引:1
采用了国际上广泛使用的MonteCarlo模拟计算程序EGS4对海关集装箱检测系统用加速器屏蔽系统进行了辐射模拟分析,与实际测试数据进行分析、比较,解释了特殊剂量分布的原因,提出了系统改进的参考方案。 相似文献
124.
本文研究了SiH4—O2体系LPCVDSiO2的工艺及设备。为了得到厚度均匀性好的薄膜,改进了反应气体的进气方式和装片舟的结构,获得了每炉100片、直径为100mm的硅片的膜厚不均匀性≤士5%的结果。 相似文献
125.
先进音频编码(AdvancedAudioCoding,AAC)以其多声道、多采样率、高压缩比、音质好等特点被广泛使用。文中首先介绍了MPEG-2/4AAC音频编码技术;接着基于MPEG-2/4AAC音频编码原理,开发了时钟复位、寄存器配置和音频数据收发的BFM模型,搭建了音频编码模块的RTL级虚拟验证平台,同时归纳了验证项;最后基于此验证平台和验证项,对设计进行了全面的仿真验证。实践证明该验证方法效率高、收敛快、覆盖率高,取得了较好的效果,为后续的FPGA平台验证和芯片应用提供了有力的保证。 相似文献
126.
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128.
针对视觉检测设备在复杂的生产环境下存在图像处理参数设置问题,设计了一套B/S架构的通用的专家在线平台,通过在原有的视觉检测平台上增加一个普通的USB摄像头及相应的应用软件,并通过网络将出现的新问题的图像实时传输给生产厂家或外部专家,由专家通过浏览器设置合理的图像处理参数,平台综合了数据协同、远程培训等功能,达到了远程解决问题的目的。 相似文献
129.
A microsecond-resolution pulse heating technique was used for the measurement of the heat of fusion of titanium and a titanium alloy (90Ti-6Al-4V). The method is based on rapid (50- to 100-s) resistive self-heating of the specimen by a high-current pulse from a capacitor discharge system and measuring, as functions of time, current through the specimen, voltage across the specimen, and radiance of the specimen. Melting of the specimen is manifested by a plateau in the measured radiance. The time integral of the net power absorbed by the specimen during melting yields the heat of fusion. The values obtained for heat of fusion were 272 J · g–1 (13.0 kJ · mol–1) for titanium and 286 J · g–1 for the alloy 90Ti-6Al-4V, with an estimated maximum uncertainty of ±6% in each value.Paper presented at the Second Workshop on Subsecond Thermophysics, September 20–21, 1990, Torino, Italy. 相似文献
130.
Examined the 10 most cited articles published in the Psychological Bulletin over the past 4 decades. Seven of the 10 articles were methodologically oriented. A survey of the authors revealed that highly cited articles have an important message that goes beyond momentary fads, are broad in topic and intended audience, accessible, and well written. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献