Trend of extreme precipitation events over China in last 40 years

Using the daily precipitation data of 740 stations in China from 1960 to 2000, the analysis on the variations and distributions of the frequency and the percentage of extreme precipitation to the annual rainfall have been performed in this paper. Results indicate that the percentage of heavy rains （above 25mm/day） in the annual rainfall has increased, while on average the day number of heavy rains has slightly reduced during the past 40 years. In the end of 1970s and the beginning of 1980s, both the number of days with extreme precipitation and the percentage of extreme precipitation abruptly changed over China, especially in the northern China. By moving t test, the abrupt change year of extreme precipitation for each station and its spatial distribution over the whole country are also obtained. The abrupt change years concentrated in 1978-1982 for most regions of northern China while occurred at various stations in southern China in greatly different/diverse years. Besides the abrupt change years of extreme precipitation at part stations of Northwest China happened about 5 years later in comparison with that of the country＇s average.     

Quantum entanglement in the mode-mode competition system

Considering a two-level atom interacting with the competing two-mode field, this paper investigates the entanglement between the two-level atom and the two-mode field by using the quantum reduced entropy, and that between the two-mode field by using the quantum relative entropy of entanglement. It shows that the two kinds of entanglement are dependent on the relative coupling strength of atom-field and the atomic distribution, and exhibit the periodical evolution. The maximal atom-field entanglement state can be prepared via the appropriate selection of system parameters and interaction time.     

The structure dependence of exchange bias in ferromagnetic/antiferromagnetic bilayers

The structure dependence of exchange bias in ferromagnetic/antiferromagnetic （FM/AF） bilayers has been investigated in detail by extending Slonczewski＇s ＇proximity magnetism＇ idea. Here three important parameters are discussed for FM/AF bilayers, i.e. interracial bilinear exchange coupling J1, interracial biquadratic （spin-flop） exchange coupling J2 and antiferromagnetic layer thickness tAF. The results show that both the occurrence and the variety of the exchange bias strongly depend on the above parameters. More importantly, the small spin-flop exchange coupling may result in an exchange bias without the interracial bilinear exchange coupling. However, in general, the spin-flop exchange coupling cannot result in the exchange bias. The corresponding critical parameters in which the exchange bias will occur or approach saturation are also presented.     

The asymptotic distributions of sums of record values for distributions with lognormal-type tails

Let X1,X2,... be a sequence of i.i.d. random variables and let X(1),X(2),... be the associatedrecord value sequence. We focus on the asymptotic distributions of sums of records, Tn=∑nk=1X(k), forX1 ∈ LN(γ). In this case, we find that 2 is a strange point for parameter γ. When γ＞ 2, Tn is asymptoticallynormal, while for 2 ＞γ＞ 1, we prove that Tn cannot converge in distribution to any non-degenerate lawthrough common centralizing and normalizing and log Tn is asymptotically normal.     

硅基稀土热扩散法初探

稀土元素在我国有丰富的贮量．近年来,稀土元素在各种新科技领域中得到不断的开发和利用．各类稀土功能材料在发光和光通信领域中正展现巨大的应用潜力［１］．稀土磁光薄膜材料是优良的记录介质;稀土Ｅｒ由于其特殊的电子结构,已用来制造掺铒光纤激光器和光纤放大器［２］;掺铒硅还可制造发光谱线单一的发光器件［３］,这为实现人们所期待的硅基光电集成提供了有益途径．此外,基于对掺铒硅荧光发射衰减时间的分析,可用于制造温度传感器［４］．因此,稀土在共价半导体材料如Ｓｉ、ＧａＡｓ中的行为研究日益受到重视．但这些工作主要…     

黑胸大蠊浓核病毒基因组末端序列测定与分析

利用构建的黑胸大蠊浓核病毒(PfDNV)全基因组重组质粒(PfDNV-pUC119)以及一系列完整缺失克隆,通过全自动测序方法完成了PfDNV两末端各728 bp 和730 bp 核苷酸序列的测定. 通过计算机软件分析发现,PfDNV 末端201nt为倒置重复序列,其中最末端122nt为回文序列,能形成典型的发夹结构. 并与同科其它病毒末端序列进行了核苷酸序列同源性比较.     

高临界温度氧化物超导体的临界电流

本文从高T氧化物超导体的基本物理、化学性质出发,深入分析了提高其临界电流密度的关键所在。评述了当前薄膜、体材料、线材和带材料发展的工艺状态和性能。指出了今后的发展趋向和应用前景。     

Spectral Flow and Manifold Decomposition

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