排序方式: 共有167条查询结果,搜索用时 15 毫秒
1.
白洋淀内水体的流动特征研究 总被引:2,自引:0,他引:2
研究了风对白洋淀内水体循环流动的影响,研究指出:(1)风应力可看作是水体循环
的主要驱动力. (2)在风应力的作用下,水体表层的流动主方向与风的方向一致,下层水体
的流动方向与表层方向相逆或近似相逆. (3)表层以下水体流动复杂,次表层水平流动有明
显的双涡结构. (4)淀底地形对水体垂向流动影响很大,垂向速度变化复杂,垂向上有双涡
流动现象. 从动力学角度研究了淀内水体流动的情况. 相似文献
2.
LIU ChengHui WANG Zhe WANG XiaoKe & LI ZhengPing Key Laboratory of Medicinal Chemistry Molecular Diagnosis Ministry of Education College of Chemistry Environmental Science Hebei University Baoding China 《中国科学B辑(英文版)》2011,(8)
β-NaYF4:Yb,Er upconversion nanophosphor (UCNP) is known as one of the most efficient NIR-to-visible upconversion materials, which shows great potential in bioanalytical chemistry and bioimaging. However, its applications are greatly limited due to its low water dispersibility and thus poor biocompatibility. In this paper, poly(acrylic acid) (PAA)-based ligand exchange strategies are carried out to modify oleic acid-capped hydrophobic β-NaYF4:Yb,Er UCNPs into hydrophilic ones. After efficient surface modific... 相似文献
3.
FAN CuiLing LEI JianGuo & SHAN XiuLing School of Sciences Nantong University Nantong China College of Mathematics Information Science Hebei Normal University Shijiazhuang 《中国科学 数学(英文版)》2011,(1)
Difference systems of sets (DSSs) are combinatorial configurations which were introduced in 1971 by Levenstein for the construction of codes for synchronization. In this paper, we present two kinds of constructions of difference systems of sets by using disjoint difference families and a special type of difference sets, respectively. As a consequence, new infinite classes of optimal DSSs are obtained. 相似文献
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一种基于结构性改变的光子晶体光纤光栅理论研究 总被引:2,自引:0,他引:2
对一种新型基于结构性改变的光子晶体光纤光栅原理进行了研究.采用多极法分析了结构性改变对折射率的影响,得到有效折射率与包层气孔塌缩之间的关系,建立了结构性改变光子晶体光纤光栅模型.利用耦合模理论对所成光栅性能进行了分析,重点研究了包层空气孔层数、空气孔占空比、气孔塌缩程度对光栅谐振波长、带宽的影响.研究结果表明,光子晶体... 相似文献
6.
LI Pan-lai WANG Zhi-jun YANG Zhi-ping GUO Qing-lin College of Physics Science & Technology Hebei University Baoding P. R. China 《高等学校化学研究》2009,25(5):610-613
LiSrBO3:Tb3+ green phosphor was synthesized by means of a solid state reaction and its spectral characteristics were studied. The emission spectrum of LiSrBO3:Tb3+ consists of four major bands at 486, 544, 595 and 620 nm under the excitation of near ultraviolet irradiation, which are originated from the 5D4→7F6, 5D4→7F5, 5D4→7F4 and 5D4→7F3 characteristic transitions of Tb3+, respectively. Monitored at 544 nm, the excitation spectrum of the phosphor extends from 220 nm to 390 nm, with the excitation peaks c... 相似文献
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LI Cun-man XIAO Yuan-sheng XUE Xing-ya FENG Jia-tao ZHANG Xiu-li LIANG Xin-miao . Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian P. R. China . Hebei Research Centre of Analysis Testing Hebei University of Science Technology Shijiazhuang 《高等学校化学研究》2011,(3):392-396
An efficient preparative method was successfully developed for isolation and purification of unstable components from medicinal plant extracts, using a combined method of preparative high performance liquid chro-matography(HPLC) and solid-phase extraction(SPE). The aim of this study was to obtain an effective method with high preparative efficiency and importantly to avoid the transformation of unstable compounds. The preparative HPLC system was based on an LC/MS controlled four-channel autopurification sys... 相似文献
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Bartlett分解与多元正态总体均值的广义推断 总被引:2,自引:0,他引:2
对多个正态总体均值的统计推断是一个古老而令人感兴趣的问题.本文利用样本协方差矩阵的Bartlett分解和广义p-值的概念给出一些关于均值的精确检验.模拟显示这些检验比已有的检验有更高的功效.同时,还根据协方差矩阵的Bartlett分解和样本均值向量,得到一个分布和未知参数无关的统计量,用它可以对多个正态总体共同均值做精确检验.模拟显示,这些检验犯第一错误的概率小于显著性水平,而且有更高的检验功效. 相似文献
10.
This paper constructs a class of Harish-Chandra modules with multiplicity ≤1 of the two parameter deformation of Virasoro algebra and proves a classification theorem. 相似文献