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采用沉淀法制备前驱体,通过不同温度合成了上转换发光材料Y2O2S∶Er3+,Yb3+,运用XRD,SEM和上转换发射光谱对其进行表征。结果表明,所合成的Y2O2S∶Er3+Yb3+属于六方晶系晶体,随着合成温度的升高,产物的粒径不断增大,上转换发射光强度逐渐增加。研究Y2O2S∶Er3+Yb3+的上转换发光过程,红光发射和绿光发射分别源于Er3+离子的4F9/2→4I15/2以及2H11/2→4I15/2,4S3/2→4I15/2能级跃迁。利用群论计算了晶场中Er3+离子的能级分裂数目。 相似文献
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本文主要研究如下含非线性梯度项的非强制拟线性椭圆方程\begin{equation*}\left \{\begin{array}{rl}-\text{div}(\frac{|\nabla u|^{p-2}\nabla u}{(1+|u|)^{\theta(p-1)}})+\frac{|u|^{p-2}u|\nabla u|^{p}}{(1+|u|)^{\theta p}}=\mu,~&x\in\Omega,\\ u=0,~&x\in\partial\Omega,\end{array}\right.\end{equation*} 弱解的存在性和不存在性, 其中$\Omega\subseteq\mathbb{R}^N(N\geq3)$ 是有界光滑区域, $1
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Ye Wang Jian-Qing Gao Feng Li Sang-Hon RI Wen-Quan Liang 《Colloid and polymer science》2006,285(2):233-238
In many cases, initial release of drugs from microparticles is undesirable. In the present study, Pluronic®F127, which shows thermosensitive characteristic, was used for controlling both the initial release and the sustained release of insulin from microspheres. Calcium-alginate insulin microspheres were prepared by emulsion technology and dispersed in a thermosensitive semisolid gel, the PF127. In vitro study demonstrated that PF127 could protect the activity of insulin in some extent and control the initial release and sustained release of insulin well. The results of in vivo hypoglycemic experiment carried out on diabetic rats also displayed a well correlation with in vitro release patterns. The results suggested that PF127 could sustain insulin release through a subcutaneous injection, and this material was available to deliver insulin aiming for prolonged and smooth hypoglycemic function. 相似文献
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P. JÓVÁRI 《Molecular physics》2013,111(11):1149-1156
The structure factor of liquid CS2 has been measured at ambient temperature by the 7C2 diffractometer at the Laboratoire Leon Brillouin?, Saclay, France. The result has been modelled by the reverse Monte Carlo (RMC) method. The only reported neutron diffraction measurement on liquid CSe2 has also been investigated in detail. In both cases initial configurations for the RMC runs have been obtained by molecular dynamics simulation using a simple soft sphere potential. It has been found that the main features of experimental results have been reproduced even by this choice suggesting that the structure of these systems is almost entirely described by the excluded volume. Examination of model size dependence of results has also been carried out revealing the importance of using large simulation boxes. 相似文献
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李光云 《浙江大学学报(理学版)》2010,37(4)
基于Bézier曲线升阶的思想,构造了带多个形状参数的Bézier曲线,它具有与Bézier曲线相同的性质.在控制顶点不变的情况下,可通过改变多个形状参数的取值调整曲线的形状.n次Bézier曲线是n次带多个形状参数的Bézier曲线的一个特例,多个形状参数可使曲线变化更灵活. 相似文献
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The lower trophic linkages in lake plankton food webs are generally described as relatively simple, even accounting for the additional complexity of potential 'microbial looping'. Crustacean zooplankton are frequently amalgamated into one trophic functional group as grazers of autotrophic production. The carbon stable isotope ratios for separated zooplankton species, particulate organic matter (POM) and phytoplankton from a number of lakes in Finland and the UK were analysed. These revealed greater complexity in trophic interactions than would otherwise be observed if the zooplankton had been represented by a mixed sample. Grazing zooplankton were usually depleted in (13)C relative to the bulk POM on which they might feed, with (13)C deviating by up to 17 per thousand There were no consistent differences between (13)C values for copepods and cladocerans. Predatory cladocerans were generally enriched by greater than 1 per thousand compared to their putative prey. We suggest that care in separating the zooplankton species for stable isotope analysis may expose otherwise undetected sources of carbon and facilitate unravelling trophic links further up the food web. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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Let(X, d, μ) be a metric measure space satisfying both the upper doubling and the geometrically doubling conditions in the sense of Hyt?nen. In this paper, the authors obtain the boundedness of the commutators of θ-type Calderón-Zygmund operators with RBMO functions from L~∞(μ) into RBMO(μ) and from H_(at)~(1,∞)(μ) into L~1(μ), respectively.As a consequence of these results, they establish the L~p(μ) boundedness of the commutators on the non-homogeneous metric spaces. 相似文献
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