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101.
陈化温度和Fe/Zr配比对SO42-/Fe2O3-ZrO2固体超强酸结构与性能的影响 总被引:6,自引:0,他引:6
用低温陈化法制备了SO42 -/Fe2 O3 ZrO2 (简称SFZ)固体超强酸催化剂 ,用红外光谱 (IR)和X光衍射(XRD)对其结构进行了表征 ,并考察了它对合成癸二酸二正丁酯的催化性能 .IR谱显示 ,低温陈化的SFZ样品在10 70cm-1处吸收峰远强于常温陈化样品 .XRD分析则显示 ,在焙烧温度为 6 5 0℃、Fe/Zr为 2∶1时 ,低温陈化的样品出现了亚稳态的ZrO2 四方晶相 .该样品在催化酯化反应中使产率达 90 %以上 ,高于常温陈化样品的 30 % .研究结果表明 :在其他条件不变时 ,低温陈化所出现的亚稳态的ZrO2 四方晶相是表面酸性和催化活性增加的微观原因 相似文献
102.
In this article a new technique was developed to fabricate scaffolds with a unique microstructure by solid–liquid separation in combination with particulate-leaching. Firstly, the effects of polymer concentration, quenching temperature on the porous morphology and the mechanical property of obtained scaffolds during solid–liquid separation have been investigated. Then, salt granules as porogen were introduced into the solid–liquid phase separation to produce the unique pore structure of the scaffold. The pore diameter of the scaffold could be controlled with the particulate size and the wall of pores possessed special microstructure, which enhanced the pore interconnectivity. The cell culture results confirmed that a good interconnectivity of the scaffold prepared by the improved solid–liquid separation was useful for nutrition transportation and cell proliferation. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
103.
Chongyi Wan Shiming Liu Rongqing Tan Jin Wu Jinwen Zhou Yan Lv Yanning Yu Hua Yang 《Optics & Laser Technology》2004,36(8):2389-649
A high average power, high-repetition-rate TEA CO2 laser employing printed-circuit-board preionizer is described. The power scaling of this preionization configuration has been demonstrated. The average output power reaches 3.6 kW at pulse repetition rate of 180 pps. Furthermore, the scaling-up ability of the rotating spark gap as high-voltage switch for high-average-power gas laser has been validated. 相似文献
104.
Spirals generated from the excitable media within the Barkley model is investigated under the gradient electric fields by a numerical simulation. The spiral drift and spiral break up are observed when the amplitude of the electric fields is modulated by a constant signal or a chaotic signal. It is also verified that, even in the presence of the white noise, the whole system can reach homogeneous states after the spiral breakup, by using an adaptive strategy. 相似文献
105.
Lanthanide Complexes for Oligomerization of Phenyl Isocyanate 总被引:1,自引:0,他引:1
IntroductionThestudyonthereactivitiesoflanthanidecomplexesto wardisocyanateshasattractedmuchattention .Ithasbeenre portedthatlanthanidealkoxides,1anddivalentdiaza pentadi enyllanthanidecomplexes2 canbeusedasthesinglecompo nentinitiatorsforisocyanatespolymerization .Recentlyourre searchgrouphasalsofoundthatlanthanoceneamide ,3diva lentaryloxideofsamarium4 ,5anddivalentsamarocene6 areallactivefortheoligomerizationofphenylisocyanate,andtheactivespeciesforthesethreesystemswereallsuccessfullyisolat… 相似文献
106.
Wenping Deng Gang Xu Lei Wan Anwen Liu Bo Gao Junhe Du Shuiming Hu Yang Chen 《Acta Physico》2008,24(8):1329-1334
Apparatus integrating a Fourier transform-infrared (FT-IR) spectrometer and a mid-infrared difference frequency generation (DFG) laser spectrometer was built for the study of the matrix isolation spectrum in solid molecular hydrogen. A 3-cm-long molecular hydrogen crystal was grown in a liquid-helium Dewar, and its infrared absorption spectrum in the 1-5 μm region was recorded to test the system. The W0(0) (ν=0←0, J=6←0) line around 2410 cm−1 of solid hydrogen was investigated with the DFG laser spectroscopy. High-resolution matrix isolation spectrum of CO2 co-deposited with hydrogen on a BaF2 cold plate at liquid-helium temperature was studied. 相似文献
107.
Retractable structures which alter their geometries according to practical requirements are widely used in roof structures of stadiums for their versatility. A retractable structure based on threefold-symmetric Bricard linkages and rotating rings of tetrahedra is proposed and developed in this paper. By replacing each link of a threefold-symmetric Bricard linkage with a tetrahedron, a retractable structure is obtained which can repeatedly open and close by rotating the tetrahedra. The geometric relationship between the retractable structure and the threefold-symmetric Bricard linkage is derived and ranges of main geometric parameters are determined to ensure a continuous and smooth movement in the deployment of the structure. Then the relative displacement of the support and the open rate of the structure, two main parameters concerned in practical applications, are investigated. Preferred ranges of main geometric parameters are proposed and a physical model is manufactured to verify them. A discussion on some possible improvements and modifications of the structure is also presented. 相似文献
108.
109.
110.
中国莲的定量染色体图 总被引:4,自引:0,他引:4
利用MetaMorph软件定量分析了中国莲(Nelumbo mucifera Gaertn.)每条前中期染色体上(从短臂到长臂)二脒基苯基吲哚(DAPI)荧光强度的变化,结合染色体的相对长度和臂比作为辅助参数,构建了中国莲前中期染色体的定量染色体图.该定量染色体图是实际的前中期染色体的一种直观模式,可识别中国莲基因组中每条染色体以及分析染色体上的异染色质分布,为莲的细胞遗传学研究提供了一种新的方法. 相似文献