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排序方式: 共有198条查询结果,搜索用时 875 毫秒
41.
Xigang Du Yao Lu Ling Li Jinben Wang Zhengyu Yang 《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,290(1-3):132-137
Seven new dialkyldibenzene disulfonate gemini surfactants have been synthesised. The physico-chemical properties such as their surface tensions, krafft temperatures and melting temperatures have been measured. It was found that the anionic gemini surfactants showed some aberrant properties. The results determined by drop-volume method indicated that surfactants Id, Ie at 25 °C and IIb at 50 °C showed no cmc and lowered surface tension of water hardly despite their seemingly favorable amphiphilic components. However, the three surfactants showed a sharp cmc and good surface activity with the increment of temperature. Surfactant Ie with two longer chains had a higher cmc than that for shorter chain surfactant Id. Furthermore, for this class of anionic gemini surfactants, the spacer carbon number had more important effects than the alkyl chain carbon number on their krafft temperatures and melting temperatures. 相似文献
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Zhou Z Zhou X Fu H Tian L 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(9):2061-2067
The vibrational spectra study of electron transfer of Cl- + CH3Cl --> ClCH3 + Cl- reaction has been examined by density function theory (DFT) calculations at 6-311 + +G** level in this paper. This reaction includes old bond rupture, new bond formation and electronic transfer in the intermolecular. The vibrational frequencies and vibrational modes of reactant, precursor complex, transition state, successor complex and product are analyzed. The relationship and the change among them can confirm the rupture of bond, the formation of bond and the process of electron transfer. 相似文献
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Zhang Zhengyu 《Annals of Differential Equations》2005,21(4):629-638
Reversible system following Hamiltonian system turns out to be another type of equation which has aroused wide interest in recent years. One open problem is whether the celebrated KAM theory and Nekhoroshev method can be extended to reversible system. As showed in [5], there exist KAM tori in reversible system. In this paper, we give a preliminary discussion on whether there is Nekhoroshev type result in reversible system. In particular, we try to apply this method to the reducibility of a type of common reversible system. 相似文献
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非定常IV型激波-激波干扰数值模拟研究 总被引:2,自引:1,他引:2
对IV型激波-激波干扰非定常流动进行了数值模拟,采用有限体积法,结合空间半隐的二阶OC-TVD格式与时间二阶显式Runge-Kutta法求解三维全N-S方程,并且使用了Baldwin-Lomax代数湍流模型.得到了周期性流场变化结果,其中包括周期变化的双涡结构.壁面压强峰值的大小和位置均呈周期性振动,壁面压力系数和Stanton数的时均分布与定常实验结果符合得较好.并从一周期内流场结构的扰动传播出发,分析了结构变化的相位,说明了IV型激波一激波干扰内在的非定常性机理与影响因素。 相似文献
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Chuangang HuYanxia Cao Lin Yang Zhengyu BaiYuming Guo Kui WangPengle Xu Jianguo zhou 《Applied Surface Science》2011,257(18):7968-7974
To maximize the utilization of catalysts and thereby reduce the high price, a new strategy was developed to prepare highly dispersed Pt-SnOx nanoparticles supported on 8-Hydroxyquinoline (HQ) functionalized multi-walled carbon nanotubes (MWCNTs). HQ functionalized MWCNTs (HQ-MWCNTs) provide an ideal support for improving the utilization of platinum-based catalysts, and the introduction of SnOx to the catalyst prevents the CO poisoning effectively. The as-prepared catalysts are characterized by Transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. It is found that the HQ functionalization process preserves the integrity and electronic structure of MWCNTs, and the resulting Pt-SnOx particles are well dispersed on the HQ-MWCNTs with an average diameter of ca. 2.2 nm. Based on the electrochemical properties characterized by cyclic voltammetry and chronoamperometry, the Pt-SnOx/HQ-MWCNTs catalyst displays better electrocatalytic activity and stability for the methanol oxidation. It is worth mentioning that the forward peak current density of Pt-SnOx/HQ-MWCNTs catalyst is ca. 1.9 times of that of JM commercial 20% Pt/C catalyst, which makes it the preferable catalyst for direct methanol fuel cells. 相似文献
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