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21.
使用叠栅层析技术测量超音速风洞中的非对称复杂密度场 总被引:1,自引:1,他引:0
使用叠栅层析技术解决超音速风洞中复杂密度场的测量难题。应用高灵敏度叠栅偏折仪和间隔角度旋转模型的方法获取超音速风洞中流场的多方向叠栅条纹图。层析计算中使用一种新的偏折角修正迭代的叠栅层析算法,该方法可以实现对有限角采样和包含遮挡物的非完全数据重建,迭代过程中结合内边界平滑滤波提高重建精度。实验中获取了马赫数为2.52的超音速风洞中9幅不同采样角的条纹图,经过50次迭代计算后重建出膨胀波区非对称密度场的截面分布,并对测量结果和误差进行了分析和讨论。使用计算流体力学技术对该密度场进行建模和计算,验证了叠栅层析重建结果的正确性,证实了该技术在测量复杂流场领域的重要价值。 相似文献
22.
Shilong Chen Dejun Zhang Shengyun Chen Tao Xia Qingbo Gao Yizhong Duan Faqi Zhang 《Chromatographia》2008,68(3-4):299-302
The Rhodiola L. genus (Crassulaceae) is one of the most important medicinal plant products used by Tibetans in Chinese phytotherapy. Fourteen species were examined for their content of salidroside. A considerable quantitative variation was observed using high-performance liquid chromatography and this depended on species and regional factors. It was found that all samples contained salidroside at concentrations ranging between 0.02 mg g?1 (R. sinuate) and 15.95 mg g?1 (R. sacra), respectively. The content of salidroside in R. sacra was significantly higher than in other popular medicinal plants of this genus. This finding indicated that there may be more Rhodiola species present in the Qinghai–Tibet Plateau which may be used as a potential source of salidroside. 相似文献
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Yude Li Yunguang Zhang Yizhong Kuang Weiming Liu Xiouyun Zhang Yi Qiu Yonggen Xu Mei Chen Jinglum Liu 《Optics Communications》2010,283(12):2575-2579
First, the kinetic investigation of UF6 + HCl reaction and the isotopic selectivity under CO laser irradiation is performed. On this investigation, the kinetics of UF6 + HCl reaction by using an intracativity CO laser and CO2 laser irradiation system, and the isotopic selectivity for this process are studied theoretically. It is found that under the resonant CO laser and CO2 laser irradiations, the laser-catalyzed reaction rate can increase, and a good selectivity can be achieved. The uranium isotope separation factors β calculated are about 2.44 ∼ 4.05 at laser intensity 50 ∼ 100 W cm−2 and temperature 235 K. 相似文献
25.
Star-g-poly (acrylic acid)/organo-zeolite 4A (S-g-PAA/OZ) superabsorbent composite was prepared by grafting partially neutralized acrylic acid onto starch in the presence of organo-zeolite 4A (OZ) as an inorganic component. The morphology was characterized with scanning electron microscopy (SEM). Energy dispersive spectrometer (EDS) analysis revealed the fine distribution of OZ in superabsorbent composite. The swelling kinetics of the composites were characterized by means of a Schott's second-order model. The effect of OZ concentration in the composite on the water absorbency and swelling behavior were tested. The swelling properties of the composites were evaluated in various environments; pH, salinity, temperature, urea solution, and solvent-water mixtures. The activation energy (ΔE) for water during the swelling process was also determined through Arrhenius plots. The results showed that the proper amount of OZ was beneficial for improvement of the water absorbent capacity and the initial swelling rate in distilled water. The optimum prepared composite with 10 wt % OZ, possessed the maximum water absorption (511g/g) in distilled water and (521 g/g) in 0.1 wt % urea solution. The results inferred that S-g-PAA/OZ superabsorbent composite can be exploited for agriculture and medical applications. 相似文献
26.
A mild, photoactivated 1,3-dipolar cycloaddition procedure was successfully developed for the synthesis of polysubstituted pyrazolines. This procedure involved the in situ generation of the reactive nitrile imine dipoles using a hand-held UV lamp at 302 nm, followed by spontaneous cycloaddition with a broad range of 1,3-dipolarophiles with excellent solvent compatibility, functional group tolerance, regioselectivity, and yield. 相似文献
27.
Hong Zhang Xiaogang Li Cuiwei Du Huibin Qi Yizhong Huang 《Journal of Raman spectroscopy : JRS》2009,40(6):656-660
The corrosion products formed on hot‐dip galvanized steel sheets for the automobile application with adhesion of alkaline mud containing different Cl− ion contents are investigated by means of Raman and infrared (IR) spectroscopy. Results show that the Cl− ion content in alkaline mud has great influence on the corrosion behavior of the galvanized steel. The Cl− ions are responsible for the formation of the Zn5Cl2(OH)8· H2O layer on the surface of the steel at the early stage of corrosion. The rest of the Cl− ions then penetrate and interrupt corrosion product layer resulting in pitting corrosion. Subsequently, the red corrosion product of α‐FeOOH (shaped as needle‐like structure) is formed, which then transforms into black rust of Fe3O4 (having a shape of slim needle). It is interesting to find out that pitting depth is inversely proportional to the Cl− ion content. However, corrosion rate decreases with the increase of the Cl− ions in mud. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
28.
1 INTRODUCTIONItwasoftenencounteredthationizationofambient gasshouldoccurredwhena plasmawasproducedwithlaserablatingatarget .Manya 相似文献
29.
Zeng Y Zhang W Xu C Xiao N Huang Y Yu DY Hng HH Yan Q 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(13):4026-4030
Single-crystalline TiOF(2) nanotubes were prepared by a one-step solvothermal method. The nanotubes are rectangular in shape with a length of 2-3?μm, width of 200-300?nm, and wall thickness of 40-60?nm. The formation of TiOF(2) nanotubes is directly driven by the interaction between TiF(4) and oleic acid in octadecane to form the 1D nanorods, and this is followed by a mass diffusion process to form the hollow structures. The synthesis approach can be extended to grow TiOF(2) nanoparticles and nanorods. Compared with TiO(2), which is the more commonly considered anode material in lithium-ion batteries, TiOF(2) has the advantages of a lower Li-intercalation voltage (e.g., to help increase the total voltage of the battery cell) and higher specific capacities. The TiOF(2) nanotubes showed good Li-storage properties with high specific capacities, stable cyclabilities, and good rate capabilities. 相似文献
30.
Sub-nanometre sized metal clusters, with dimensions between metal atoms and nanoparticles, have attracted more and more attention due to their unique electronic structures and the subsequent unusual physical and chemical properties. However, the tiny size of the metal clusters brings the difficulty of their synthesis compared to the easier preparation of large nanoparticles. Up to now various synthetic techniques and routes have been successfully applied to the preparation of sub-nanometre clusters. Among the metals, gold clusters, especially the alkanethiolate monolayer protected clusters (MPCs), have been extensively investigated during the past decades. In recent years, silver and copper nanoclusters have also attracted enormous interest mainly due to their excellent photoluminescent properties. Meanwhile, more structural characteristics, particular optical, catalytic, electronic and magnetic properties and the related technical applications of the metal nanoclusters have been discovered in recent years. In this critical review, recent advances in sub-nanometre sized metal clusters (Au, Ag, Cu, etc.) including the synthetic techniques, structural characterizations, novel physical, chemical and optical properties and their potential applications are discussed in detail. We finally give a brief outlook on the future development of metal nanoclusters from the viewpoint of controlled synthesis and their potential applications. 相似文献