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41.
Studies on the structure and catalytic performance of Cu-Zn-Al catalyst prepared by liquid-phase preparation technology under different heat treatment atmosphere 下载免费PDF全文
Cu-Zn-Al slurry catalysts were prepared using a complete liquid-phase preparation technology under different heat treatment atmospheres. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscope, and N2 adsorption-desorption. Their application in the single-step synthesis of dimethyl ether from syngas was also investigated. The results indicate that the type of heat treatment atmosphere has an influence on the Cu species and the Cu0/Cu+ ratio on the catalyst surface. Moreover, the final Cu/Zn ratio on the catalyst surface is mainly dependent on the composition and reaction environment of the catalyst and little on the type of heat treatment atmosphere. The prepared catalysts can suppress sintering of active sites at high temperatures, and the type of heat treatment atmosphere mainly affects the capability of the catalyst for methanol synthesis. The catalysts perform best using N2 as the heat treatment atmosphere. 相似文献
42.
Propagation properties of partially coherent Laguerre-Gaussian beams in turbulent atmosphere 总被引:2,自引:0,他引:2
Yanli Zhong 《Optics & Laser Technology》2011,43(4):741-747
To study the propagation properties of partially coherent Laguerre-Gaussian (PLG) beams through turbulent atmosphere, the analytical formulas are derived for the angular width and the beam-propagation factor (M2-factor) of PLG beams by using the extended Huygens-Fresnel principle and the second-order moments of the Wigner distribution function (WDF). The corresponding numerical results are also calculated. When propagation distance increases, the angular width is found to spread faster for PLG beams with higher beam order, smaller correlation length and bigger structure constant The angular width of PLG beams decreases with increase in waist width (w0).The M2-factor of PLG beams with higher beam order and smaller correlation length is less affected by turbulence with increase in propagation distance. The propagation properties of the M2-factor for PLG beams with the smaller structure constant are better than that with bigger structure constant . The M2-factor of PLG beams decreases with increase in the wavelength λ, and it is also less affected by turbulence for beams with higher order and smaller correlation length. Furthermore, for the PLG beams with the same beam order, the angular width and the M2-factor keep invariable in free space. 相似文献
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Shijing WangBoping Zhang Cuihua ZhaoSongjie Li Meixia ZhangLiping Yan 《Applied Surface Science》2011,257(8):3358-3362
The cobalt oxide (CoO and Co3O4) thin films were successfully prepared using a spin-coating technique by a chemical solution method with CH3OCH2CH2OH and Co(NO3)2·6H2O as starting materials. The grayish cobalt oxide films had uniform crystalline grains with less than 50 nm in diameter. The phase structure is able to tailor by controlling the annealing atmosphere and temperature, in which Co3O4 thin film was obtained by annealing in air at 300-600, and N2 at 300, and transferred to CoO thin film by raising annealing temperature in N2. The fitted X-ray photoelectron spectroscopy (XPS) spectra of the Co2p electrons are distinguishable from different valence states of cobalt oxide especially for their satellite structure. The valence control of cobalt oxide thin films by annealing atmosphere contributes to the tailored optical absorption property. 相似文献
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减压氩气环境下激光显微光谱分析再现性和灵敏度的研究 总被引:2,自引:0,他引:2
以金属合金光谱分析标样为样品,采用激光显微发射光谱分析系统在减压氩气环境下,实验研究了光谱分析再现性和灵敏度。以原子线作为分析线的RSD减压氩气环境好于常压空气环境,以离子线作为分析线的RSD基本相同,样品的组成和元素的浓度对分析线的RSD有较大的影响。测定的铝合金样品Cu,Zn,Mg浓度曲线斜率是空气环境下的1.5-2倍,表明分析灵敏度得到明显改善,有利于激光显微光谱分析范围的扩展。 相似文献
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利用钠荧光散射激光雷达对中层顶(75~105km)高度的钠原子层进行探测,以钠原子作为示踪物,通过反演得到了该区域大气密度起伏随高度分布和随时间变化关系.结果表明,中层顶附近大气密度起伏远大于平流层和对流层,在2h内,密度起伏可达5%,3日平均Richordson数为0.46. 相似文献
48.
The present study investigated the modification of mesoscale inhomogeneous distribu-tion of soil wetness, resulting from mesoscale irrigation over arid or semiarid lands in mid-latitude in the later summer or early autumn, on mesoscale climate under conditions withand without synoptic flow influence, using an interactive model between soil and atmo-sphere. The simulations indicated that after a mesoscale irrgation, a wet soil breeze circu-lation was thermally forced, which was, in many features, similar to that of the sea breezecirculation. The influence of synoptic flows on the structure of thermally--induced wet soilbreeze circulation was also discussed. 相似文献
49.
A parameter study is performed for the case of two-dimensional sound propagation from a (source) city canyon to a nearby, identical (receiver) city canyon. Focus was on sound pressure levels, relative to the free field, in the shielded canyon. An accurate and efficient coupled FDTD-PE model was applied, exploiting symmetry of the source and receiver canyon. With the proposed calculation method, simulations were necessary in only half the sound propagation domain. The shielding in the receiver canyon in case of a coherent line source was compared to the shielding by an incoherent line source, by means of sound propagation calculations in a number of 2D cross-sections through source and receiver. It was found that the shielding is rather insensitive to the width-height ratio of the canyons. The presence of diffusely reflecting façades and balconies lead to an important increase in shielding compared to flat façades. Rigid façades yield significantly lower shielding compared to partly reflecting façades. Effects of a moving atmosphere were modeled in detail. Shielding decreases significantly in case of downwind sound propagation when comparing to sound propagation in a non-moving atmosphere. Refraction is the most important effect in the latter. In case of upwind sound propagation, turbulent scattering plays an important role and the shielding is similar to the one of a non-moving atmosphere for the parameters used in this paper. The combination of effects, as is shown by some examples, is in general not a simple addition of the separate effects. 相似文献
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