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21.
利用Leggett-Williams不动点定理研究了一类具有P-Laplacian算子的边值问题,得到了三个正解存在性的一组充分条件. 相似文献
22.
In this article, we investigate the tail probability of the product of finitely many non-negative dependent random variables. They follow distributions from max-domains of attraction of extreme value distributions and their dependence is modeled via a multivariate Farlie–Gumbel–Morgenstern distribution. For each of the Fréchet, Gumbel and Weibull cases, we obtain an explicit asymptotic formula for the tail probability of the product. Our study extends a few known results in the literature. 相似文献
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讨论了一类非线性分数阶微分方程三点边值问题解的存在性.微分算子是Riemann-Liouville导算子并且非线性项依赖于低阶分数阶导数.通过将所考虑的问题转化为等价的Fredholm型积分方程,利用Schauder不动点定理获得该三点边值问题至少存在一个解. 相似文献
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R. N. Nurmukhametov A. V. Shapovalov A. M. Sergeev A. I. Kovalev N. S. Kushakova I. A. Khotina 《Journal of Applied Spectroscopy》2011,78(3):344-351
Absorption spectra and fluorescence parameters (spectra, quantum yields, and lifetimes) were obtained for a number of branched
oligophenylenes (OPh) with long-wavelength chromophores such as p-quaterphenyl (OPh4-2), p-pentaphenyl (OPh5), and p-hexaphenyl (OPh6) and for oligofluorenylphenylenes (OFl) in solutions and films. It is demonstrated that the absorption spectrum
of OPh4-2 is a superposition of p-quaterphenyl, p-terphenyl, and diphenyl absorption bands taken in a ∼3:2:2 ratio. The obtained OPh5 and OPh6 absorption and fluorescence
spectra are shown to be determined mainly by the longest-wavelength chromophores, p-pentaphenyl and p-hexaphenyl, respectively. It is demonstrated that the obtained compounds contain traces of impurities with fluorescence at
longer wavelengths than that of the base material. The branched oligomers exhibit high fluorescence quantum yields in solutions,
those for OPh5 and OPh6 reaching 1. Transparent fluorescent films were produced from all of the synthesized oligomers. 相似文献
27.
用溶胶-凝胶(so-lgel)法制备了多铁Bi1-xLaxMnO3(BLMO,0.1≤x≤0.4)系列样品.样品的结构表征(X-射线衍射,扫描电子显微镜)及差热-热重(TG-DTA)分析测量显示,形成稳定的BLMO钙钛矿相的烧结温度位于900~950℃.La掺杂对BLMO样品(950℃烧结)的结构和磁性能的影响也被仔细研究.结果显示,随着La掺杂减少,样品中BLMO钙钛矿相减弱,铁磁转变温度(TC)由53K降至41K,而饱和磁化强度经历了先降低再升高的变化.这可归因于La含量较少的样品中Bi空位浓度的增加诱导了Mn-O-Mn键角的减小和局域Mn4+离子的增多,使得Mn3+和Mn4+离子的铁磁超交换增强和Mn3+离子的dz2轨道有序受到局域破坏. 相似文献
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Jianguo Lv Kai Huang Xuemei Chen Jianbo Zhu Lijun Wang Xueping Song Zhaoqi Sun 《Superlattices and Microstructures》2011
The chemical composition, crystalline structure, surface morphology and photoluminescence spectra of Na-doped ZnO thin films with different heat treatment process were investigated by X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy and a fluorescence spectrometer. The results show that preferred orientation, residual stress, average crystal size and surface morphology of the thin films are strongly determined by the preheating temperature. The effects of preheating temperature on microstructure and surface morphology have been discussed in detail. The photoluminescence spectra show that there are strong violet & UV emission, blue emission and green emission bands. The violet & UV emission is ascribed to the electron transition from the localized level below the conduction band to the valence band. The blue emission is attributed to the electron transition from the shallow donor level of oxygen vacancies to the valence band, and the electron transition from the shallow donor level of interstitial zinc to the valence band. The green emission is assigned to the electron transition from the level of ionized oxygen vacancies to the valence band. 相似文献
30.
A scheme is proposed for generating maximally entangled Dicke states among four modes. The scheme only uses Kerr medium and homodyne measurements on coherent light fields, which can be efficiently made in quantum optical laboratories. The scheme can be generalized to produce maximally entangled 2k-qubit states. 相似文献