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A series of Pd/La-Al2O3(PLA) catalysts with La-Al2O3(LA) support calcined at different temperatures(500, 700, 900 and 1050 oC) were prepared using an incipient wetness impregnation method. The activity of the fresh and hydrothermally aged PLA catalysts were tested for total oxidation of CO and C3H8. The activity of the fresh PLA catalysts for CO and C3H8 oxidation increased with increasing calcination temperature of the support, while the activities of the aged catalysts declined and became essentially the same. CO chemisorption results revealed that the suppressed activities of the aged catalysts were mainly due to the decline of palladium dispersion. The turnover frequency(TOF) of CO oxidation increased with increasing reduction ability of the catalysts, with a fresh catalyst calcined at 1050 oC having the highest value(0.048 s–1). However, the TOF of C3H8 total oxidation was affected by not only the redox properties of catalysts but also the size of Pd particle, and large Pd particles possessed higher TOF value of C3H8 oxidation, with the highest value(0.125 s–1) being obtained on an aged catalyst calcined at 500 oC. 相似文献
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随着工业自动化程度和对产品质量要求的逐渐提高,单台电机驱动在某些场合已经不能满足现代化发展的需要,这种需求为多台电机的同步控制提供了发展的空间。目前对多路电机的同步控制主要有非耦合和耦合控制两种。在传统耦合控制中当从电机负载突变时,因主电机没有对从电机运行状态的跟踪,因而造成了主从两台电机间的失步。基于模糊控制器对多电机传统耦合控制方式进行改进。并以模糊控制器为核心,应用Matlab/Simulink进行建模仿真,结果表明改进后的多电机同步控制系统具有良好的同步性和稳定性。 相似文献
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采用固相反应制备了NiO-LaCoO3催化剂,考察了焙烧温度以及Ni含量对催化剂的CO和丙烷氧化活性的影响。用X射线粉末衍射、H2-程序升温还原等技术对催化剂进行了表征。结果表明,在焙烧温度为700~1000℃时,焙烧温度越高,催化剂的丙烷和CO氧化性能越差,其中700℃焙烧后的10NiO-LaCoO3催化剂的效果最好。助剂Ni能有效提高LaCoO3催化剂的丙烷和CO氧化性能,其中Ni含量为7.5%的7.5NiO-LaCoO3催化剂氧化性能最佳。研究发现催化剂的CO和丙烷氧化活性与催化剂中氧活动性具有相关性。 相似文献
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永磁同步平面电机具有直接驱动、出力密度高、低热耗、高精度等特点,在现代精密、超精密加工装备,特别是在极紫外光刻机中具有广阔的应用前景。根据永磁阵列和线圈阵列的结构形式将永磁同步平面电机划分为组合式、半组合式、绕组层叠式和对称式永磁同步平面电机4类,并介绍了各种类型平面电机的特点,总结了永磁同步平面电机关键技术的发展现状,针对目前永磁同步平面电机存在的不足,讨论了未来永磁同步平面电机发展的趋势与方向。 相似文献
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分析花键冷敲精密成形加工工艺以及工件与模具的相对运动关系,运用GUI方式和K文件研究Ansys/Ls-dyna中刚体旋转控制和载荷施加等关键问题.通过建立局部坐标系和重新确定质量中心,解决了利用Ansys/Ls-dyna模拟花键冷敲精密成形中刚体部件偏心旋转和载荷施加等关键技术,并成功应用. 相似文献
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