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On the periodic solutions of a type of differential-iterative equations

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Chinese Science Bulletin 1998年第3期43卷 204-206页

作者： GE Weigao 1, LIU Zhengrong 2.and YU Yuanhong 3 1. Department of applied Mathematics, beijing Institute of {2., beijing 100081, china 2. Department of Mathematics, Yunnan university, Kunming 650091, china 3. Institute of applied Mathematics, C Department of applied Mathematics Beijing Institute of Technology Beijing China Department of Mathematics Yunnan University Kunming China Institute of applied Mathematics Chinese Academy of Sciences Beijing China

Sufficient conditions for the existence of periodic solutions to a type of nonautonomous differential_iterative equations are given.

关键词： differential_iterative equation periodic solution fixed point.

Strengthening of the boreal winter Hadley circulation and its connection with ENSO

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Progress in Natural Science:Materials International 2007年第11期17卷 1327-1333页

作者： Ma Jie1,2.and Li Jianping2.1. college of Atmospheric sciences, Lanzhou {2., Lanzhou 730000, china 2. LASG, Institute of Atmospheric Physics, Chinese Academy of sciences, beijing 10002., china) college of Atmospheric sciences Lanzhou University Lanzhou 730000 China LASG Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

Empirical orthogonal function (EOF) analysis is carried out for the year-to-year variability of the boreal winter (DJF) mass stream function of the mean meridional circulation (MMC) during the period 1948—2.05. The results demonstrate that it is dominated by the equatorially asymmetric and symmetric modes. Further analysis shows that the former mode is linked with the boreal winter Hadley cell mainly on the decadal time-scale, and the latter on the interannual time-scale. The asymmetric mode index (AMI) with a clear upward trend contributes to the decadal strengthening of the boreal Hadley circulation, and is closely correlated with the tropical SST warming, especially in the region of Indo-west Pacific warm pool (INWP). Furthermore, the AMI also contributes to the abrupt change of the correlation coefficient between the boreal Hadley circulation and ENSO after 1976. The symmetric mode index (SMI) with robust and stable linkage with ENSO shows a significant interannual variability, suggesting that the variability of the Hadley circulation is mainly associated with ENSO on the interannual time-scale.

关键词： the Hadley circulation interannual time-scale decadal time-scale

Nonlinear interactions between gravity waves and background winds

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Progress in Natural Science:Materials International 2007年第6期17卷 639-644页

作者： Liu Xiao1,2.and Xu Jiyao1(1. State Key Laboratory for Space Weather, Center for Space Science and applied Research, Chinese Academy of sciences, {2. 100080, china 2. Graduate university of Chinese Academy of sciences, {2. 100039, china) [a]State Key Laboratory for Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing China [b]Graduate university of Chinese Academy of sciences Beijing China

Using the nonlinear propagating gravity waves (GW) model in the two-dimensional compressible atmosphere and the linear GW theory, the process of GW propagation in different background winds, e.g. the direction of the background wind is opposite to (dead wind) or the same as (tail wind) the direction of the horizontal phase velocity of GW, is studied. The results show that the dead wind prolongs the vertical wavelength and accelerates GW propagation. Therefore, GW propagates up to a higher height becomes instable in a short time and eventually induces an inverse jet flow. Then, the vertical wavelength is becoming short due to the nonlinear interactions between GW and the inverse jet flow. The vertical wavelength and group velocity decrease after GW propagates into the tail wind. The initial instable time is delayed. Although most of GW is trapped in the instable region, some of GW propagates above the instable region. Compared with GW propagation in the tail wind, the nonlinear interactions between GW and the dead wind are also strong. In contrast, the linear GW theory predicts that GW can propagate freely in the dead wind. The vertical wavelength simulated by the nonlinear numerical model is different from that predicted by the linear theory greatly after GW propagates into the dead wind.

关键词： gravity waves background winds vertical group velocity vertical wavelength nonlinear interactions.

On the stability of diffusion processes with state-dependent switching

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Science china Mathematics 2006年第9期49卷 1258-1274页

作者： XI Fubao & ZHAO Liqin Department of Mathematics, beijing Institute of technology, beijing 100081, china School of Mathematical sciences, beijing Normal university, beijing 100875, china Department of Mathematics Beijing Institute of Technology Beijing 100081 China School of Mathematical sciences Beijing Normal University Beijing 100875 China

In this paper we consider the stability for diffusion processes with state-dependent switching. We first prove their Feller continuity by the coupling methods. Furthermore, we also prove their strong Feller continuity and their exponential ergodicity under some reasonable conditions. Finally, we append a very brief discussion about the regularity of these processes.

关键词： Feller continuity, coupling, strong Feller continuity, exponential ergodicity,state-dependent switching.

Calculating soil moisture by remote sensing and analyzing hydrologic cycle process in the Yellow River basin

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Science china(Technological sciences) 2004年第z1期47卷 1-13页

作者： YANG Shengtian1 & LIU Changming1, 2.1. School of Environmental sciences, beijing Normal {2., beijing 100875, china 2. Institute of Geographic Science and Natural Resources Research, beijing 100101, china beijing Normal Univ Sch Environm Sci Beijing 100875 Peoples R China Inst Geog Sci & Nat Resources Beijing 100101 Peoples R China

Based on the AVHRR pathfinder remote sensing data, soil moisture, precipitation and evaporation during the period of 1982.1998, soil moisture of all layers of soil-profile (0—1 m) in the Yellow River basin over the 17 years are calculated by the remote sensing model of calculating soil water. The Yellow River basin is divided into seven subcatchments as control sections at the location of six hydrologic stations (Lanzhou, Toudaoguai, Longmen, Sanmenxia, Huayuankou and Lijin). After calculating soil moisture and obtaining runoff data and precipitation data, the dynamical features of hydrological cycle in the Yellow River basin are analyzed for the period from 1982.to 1988 using water balance method. The conclusions are as follows: It is feasible to calculate the soil water on the macro-scale, in the soil profile with temporal continuity by means of remote sensing and survey in land. Some values of the key water cycle factors in the Yellow River are obtained, which include the annual precipitation of 4000 km3, the evapotranspiration of 3000-3500 km3, and the soil moisture transformation of ?500- 500 km3. Consequently, we analyzed the process of the water cycle in the Yellow River over the 17 years, and the results show that the segment upstream of Lanzhou city is a relatively humid region, and the area of internal waters and the reaches of Shanshan is the most desiccated region. Therefore, the runoff in the depth process is intensive and the runoff-generating process is weak in more arid regions.

关键词： the Yellow River, soil moisture, remote sensing, hydrologic cycle.

Time-variation of the near 5-month period of sunspot numbers

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Chinese Science Bulletin 2002年第23期47卷 1969-1973页

作者： HAN Yanben1 & HAN Yonggang1,2.. National Astronomical Observatories, Chinese Academy of sciences, beijing 100012.{2. 2. Department of applied Mathematics, beijing Polytechnic university, beijing 10002.,{2. National Astronomical Observatories Chinese Academy of Sciences Beijing China Department of applied Mathematics Beijing Polytechnic University Beijing China

The variation of the near 5-month period of sunspot numbers is discussed on the basis of the wavelet transform of the daily sunspot number series in the 14th-2.nd solar cycles. The result shows that the period exists in every cycle and its energy density (amplitude) is comparatively large in the peak section of the cycle. In the distinct cycle, the length and intensity of the period is different, which means that the period varies with time. The near 2.-day period is also analyzed and it is found to be time-variable and even not very stable in the peak section of the cycle. The variations of the two periods show that the near 5-month period should not be simply regarded as the multiples of the near 2.-day period.

关键词： solar activity sunspot time-variation wavelet.

Convergence of Hermite interpolatory operators

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Science china Mathematics 2010年第8期53卷 2115-2126页

作者： LIU YouMing & ZHAO JunJian Department of applied Mathematics,beijing {2. of technology,beijing 10012.,china 1. Department of applied Mathematics Beijing University of Technology Beijing 100124 China

Divergence-free wavelets play important roles in both partial differential equations and fluid *** constructions of those wavelets depend usually on Hermite *** study several types of convergence of the related Hermite interpolatory operators in this *** precisely,the uniform convergence is firstly discussed in the second part;then,the third section provides the convergence in the Donoho's *** on these results,the last two parts are devoted to show the convergence in some Besov spaces,which concludes the completeness of Bittner and Urban's expansions.

关键词： Besov spaces Hermite splines convergence completeness

Statistical Characteristics of Metastable Pitting of 316 Stainless Steel

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Journal of Materials Science & technology 2000年第3期16卷 286-290页

作者： Yu ZUO, Haiou DU and Jinping XIONG (Dept. of applied Chemistry, beijing {2. of Chemical technology, beijing 10002., china) Dept. of applied Chemistry Beijing University of Chemical Technology Beijing 100029 China

The statistical characteristics of the current fluctuations during metastable pitting of 316L stainless steel in NaCI solution were studied using potentiostatic method. The growth rates and peak currents of metastable pits followed log-normal distributions. As potential and chloride concentration increased, both growth rate and peak current of metastable pits increased. The lifetime of metastable pits also followed log-normal distribution, and was almost not affected by potential. Higher growth rates did not definitely result in larger metastable pits. A certain propagation rate range was found beneficial for the micropit to remain growth. At constant potential, the maximum peak currents in different time intervals during a potentiostatic test followed extreme distribution. The statistical characteristics of metastable pitting may be used to predict the tendency of pitting corrosion.

关键词： Statistical Characteristics of Metastable Pitting of 316 Stainless Steel

Prediction of Enthalpies of Fusion for Divalent Rare Earth Halides Based on Modeling by Artificial Neural Networks and Pattern Recognition

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International Journal of Minerals,Metallurgy and Materials 1999年第1期13卷 24-26页

作者： Yimin Sun Zhiyu Qiao Minghong He(applied Science School, university of Science & {2. beijing, beijing 100083, china)(National Natural Science Foundation of china, beijing 100083, china) applied Science School University of Science and Technology Beijing Beijing 100083 China National Natural Science Foundation of china Beijing 100083 China

The artificial neural network (ANN) and the pattern recognition were applied to study the correlation of enthalpies of fusion for divalent rare earth halides with their microstructural parameters,such as ionic radius and electronegativity. The model,represented by a back-propagation netal network, was trained with a 12.set of published data for divalent rare earth halides and then was used to predict the unknown ones. Also the criterion equations were ptesented to determine the enthalpies of fuSion for divalent rare earth halides using pattern recognition in mis work. The results from the model in ANN and criterion equations are in very good agreement with reference data.

关键词： BP neural network pattern recognition enthalpy of fusion divalent rare earth halides microstructural parameters