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81.
The reduction of selenious acid solution with hydrazine hydrate in the presence of poly(vinylpyrrolidone) (PVP) can produce a stable dispersion of uniform and amorphous selenium particles capped with PVP with a size of 100 nm. Further addition of a solvent with low polarity such as n-butyl alcohol into this aqueous solution and mild stirring result in the transportation of amorphous selenium particles onto a liquid-liquid interface between water and n-butyl alcohol. Subsequent crystallization and shape evolution on this interface occurred and finally resulted in the formation of single crystalline selenium nanorods. The results demonstrated that the enrichment of nanoparticles with amphiphilic property at a liquid-liquid interface between a polar solvent and another solvent of low polarity can result in crystallization and phase transformation for the formation of nanostructures. 相似文献
82.
载体酸性对铜基交联黏土催化剂上C3H6选择性催化还原NO反应的影响 总被引:2,自引:0,他引:2
采用聚合羟基复合阳离子合成交联蒙脱土Al-Ce-PILC, 并分别用NH4NO3和(NH4)2SO4处理后, 将其作为载体, 采用浸渍法制备了应用于C3H6选择性催化还原NO反应的铜基交联黏土催化剂Cu/Al-Ce-PILC. 用Py-IR, IR和DSC等表征技术研究了不同处理方式对Al-Ce-PILC的结构、 酸性和催化剂活性的影响. 结果表明, 未经处理的Al-Ce-PILC中同时存在L酸和B酸, 以L酸为主, Cu/Al-Ce-PILC上NO的最大转化率仅为18。5%; 用NH4NO3处理提高了L酸量, NO转化率降低; 而用(NH4)2SO4处理改变了Al-Ce-PILC的酸性结构, 增大了B酸量, 并形成了超强酸中心, 催化剂上NO转化率显著提高, 在350 ℃时达最大值50.2%. B酸对于Cu/Al-Ce-PILC上NO的还原是必要的, 它有利于C3H6吸附并适度氧化为活性中间物种, 其酸量和酸强度的增加是催化剂活性改善的主要原因. 相似文献
83.
The equilibrium electron transport of 1,4-diaminobenzene sandwiched between two Au electrodes is simulated by using a first principles analysis. The results show that equilibrium conductance increases with the molecule- electrode distance decreasing, and a platform occurs at the distance varying from 1.4 A to 1.9 A, implying the insensitiveness of 1,4-diaminobenzene equilibrium conductance to molecule-electrode distance. This is helpful to understand the improved reliability and reproducibility of conductance measurements using amines. 相似文献
84.
利用密度泛函和含时密度泛函理论研究了氧(O)和硫(S)原子掺杂的石墨相氮化碳(g-C_3N_4)_6量子点的几何、电子结构和紫外-可见光吸收性质.结果表明:掺杂后(g-C_3N_4)_6量子点杂质原子周围的C-N键长发生了一定的改变,最高电子占据分子轨道-最低电子未占据分子轨道(HOMO-LUMO)能隙显著减小.形成能的计算表明O原子取代掺杂的(g-C_3N_4)_6量子点体系更稳定,且O原子更易取代N3位点,而S原子更易取代N8位点.模拟的紫外-可见电子吸收光谱表明,O和S原子的掺杂改善了(g-C_3N_4)_6量子点的光吸收,使其吸收范围覆盖了整个可见光区域,甚至扩展到了红外区.而且适当的杂质浓度使(g-C_3N_4)_6量子点光吸收在强度和范围上都得到明显改善.通过O和S掺杂的比较,发现二者在可见光区对(g-C_3N_4)_6量子点的光吸收有相似的影响,然而在长波长区域二者的影响有明显差异.总体而言,O掺杂要优于S掺杂对(g-C_3N_4)_6量子点光吸收的影响. 相似文献
85.
86.
Ji-Ming Guo 《Discrete Mathematics》2008,308(23):5702-5711
In this paper, we completely solve a conjecture on the minimum algebraic connectivity of connected graphs with fixed girth (see [S. Fallat, S. Kirkland, Extremizing algebraic connectivity subject to graph theoretic constraints, Electron. J. Linear Algebra 3 (1998) 48-74]). 相似文献
87.
Orientation effects on the bandgap and dispersion behavior of 0.91Pb(Zn<sub>1/3</sub>Nb<sub>2/3</sub>)O<sub>3</sub>-0.09PbTiO<sub>3</sub> single crystals 下载免费PDF全文
0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO 3(PZN-9%PT) single crystals with different orientations are investigated by using a spectroscopic ellipsometer,and the refractive indices and the extinction coefficients are obtained.The Sellmeier dispersion equations for the refractive indices are obtained by the least square fitting,which can be used to calculate the refractive indices in a low absorption wavelength range.Average Sellmeier oscillator parameters E o,λ o,S o,and E d are calculated by fitting with the single-term oscillator equation,which are related directly to the electronic energy band structure.The optical energy bandgaps are obtained from the absorption coefficient spectra.Our results show that the optical properties of [001] and [111] poled crystals are very similar,but quite different from those of the [011] poled crystal. 相似文献
88.
The variational inequality problem (VIP) can be reformulated as an unconstrained minimization problem through the D-gap function.
It is proved that the D-gap function has bounded level sets for the strongly monotone VIP. A hybrid Newton-type method is
proposed for minimizing the D-gap function. Under some conditions, it is shown that the algorithm is globally convergent and
locally quadratically convergent.
Received May 6, 1997 / Revised version received October 30, 1998?Published online June 11, 1999 相似文献
89.
In this paper we investigate the effect on the multiplicity of Laplacian eigenvalues of two disjoint connected graphs when
adding an edge between them. As an application of the result, the multiplicity of 1 as a Laplacian eigenvalue of trees is
also considered. 相似文献
90.