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491.
The corrosionbehaviors of X52, 3Cr low-alloy steel, and 13Cr stainless steel were investigated inanO2–H2O–CO2 environment at varioustemperaturesand O2–CO2partial-pressure ratios. The results showed thatthe corrosion rates of X52, 3Cr, and 13Cr steels in-creased with increasing temperature. The corrosion ratesslowly increased at temperaturesless than100℃ and increased sharply when the temperature exceeded100℃. In the absence of O2, X52, 3Cr, and 13Cr exhibited uniform corrosion morphology and FeCO3 was the main corrosion product. When O2 was introduced into the system, various forms of Fe2O3 appeared on the surface of the samples. The Cr content strongly influenced the corrosion resistance. The 3Cr steel with a low Cr content was more sensitive to pitting than the X52 or 13Cr steel. Thus, pitting occurred on the surface of 3Cr when 1.25 MPa of O2 was added; this phenomenon is related to the non-uniform distribution of Cr in 3Cr. 相似文献
492.
Hai-xia Qin Yong Li Li-xiong Bai Meng-long Long Wen-dong Xue Jun-hong Chen 《矿物冶金与材料学报》2017,24(3):324-331
In this work, Fe3Si-Si3N4-Al2O3 composites were prepared at 1300℃ in an N2 atmosphere using fused corundum and tabular alumina particles, Al2O3 fine powder, and ferrosilicon nitride (Fe3Si-Si3N4) as raw materials and thermosetting phenolic resin as a binder. The effect of ferrosilicon nitride with different concentrations (0wt%, 5wt%, 10wt%, 15wt%, 20wt%, and 25wt%) on the properties of Fe3Si-Si3N4-Al2O3 composites was investigated. The results show that the apparent porosity varies between 10.3% and 17.3%, the bulk density varies from 2.94 g/cm3 and 3.30 g/cm3, and the cold crushing strength ranges from 67 MPa to 93 MPa. Under the experimental conditions, ferrosilicon nitride, whose content decreases substantially, is unstable; part of the ferrosilicon nitride is converted into Fe2C, whereas the remainder is retained, eventually forming the ferrosilicon alloy. Thermodynamic assessment of the Si5AlON7 indicated that the ferrosilicon alloy accelerated the reactions between Si3N4 and α-Al2O3 fine powder and that Si in the ferrosilicon alloy was nitrided directly, forming β-SiAlON simultaneously. In addition, fused corundum did not react directly with Si3N4 because of its low reactivity. 相似文献
493.
494.
The GaInP/GaAs/Ge triple-junction tandem cells with a conversion efficiency of 27.1% were fabricated using metalorganic chemical vapor deposition (MOCVD) technique. Temperature dependence of the spectral response measurements of the GaInP/GaAs/Ge tandem cell was performed by a quantum effi-ciency system at temperatures ranging from 25℃ to 160℃. The red-shift phenomena of the absorption limit for all subcells were observed with increasing temperature, which is dued to the energy gap nar-rowing with temperature. The short-circuit current densities (Jsc)of GaInP, GaAs and Ge subcells at room temperature calculated based on the spectral response data were 12.9, 13.7 and 17 mA/cm2, re-spectively. The temperature coefficient of Jsc for the tandem cell was determined to be 8.9 mA/(cm2·℃), and the corresponding temperature coefficient of the open-circuit voltage deduced from the se-ries-connected model was -6.27 mV/℃. 相似文献
495.
基于Gabor小波和颜色模型的阴影检测算法 总被引:2,自引:0,他引:2
在视频处理中,阴影的存在会严重影响对目标的跟踪和识别.为了有效地检测视频序列中的阴影,文中提出了一种基于Gabor小波和颜色模型的阴影检测算法.首先,建立背景的混合高斯分布模型和阴影颜色模型,通过差分法提取前景区域并结合Gabor小波纹理特征分析找出潜在的阴影点;然后通过阴影颜色模型对这些潜在的阴影点进行颜色分析;最后通过后续处理,找出真正的阴影区域.实验结果表明,文中算法具有较好的阴影检测效果. 相似文献
496.
497.
水泥与外加剂的适应性是影响混凝土质量的重要因素,适应性要求外加剂适应水泥,同时也要求水泥适应外加剂.文章论述了影响外加剂与水泥适应性的几方面因素. 相似文献
498.
499.
文章从如何提取工程量及正确套用定额两方面,详述了编制桥梁工程预算造价的方法,并论述了施工组织设计对预算造价的影响.为广大预算人员合理确定桥梁造价提供参考. 相似文献
500.
通过分析大跨径连续梁桥施工控制的方法、对箱行截面的温度场进行观测,并用观测结果剔除温度对施工控制的影响,提出大跨径预应力混凝土桥梁施工应力监测的一些具体概念及在监测中应注意的一些相关问题。 相似文献