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Lagrangian Bonnet Problems in Complex Space Forms

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Acta Mathematica Sinica,English Series 2019年第8期35卷 1357-1366页

作者： Hui Xia HE Hui MA er Xiao WANG School of Mathematics and Systems Science Beihang University LIMB of the Ministry of Education Beijing 100083 P. R. China Department of Mathematical Sciences Tsinghua University Beijing 100084 P. R. China Department of Mathematics Hong Kong Univ of Sci. and Tech. Clear Water Bay Kowloon Hong Kong P. R. China

In this note we consider Lagrangian Bonnet problem for Lagrangian surfaces in complex space forms. We first give a Bonnet type theorem for conformal Lagrangian surfaces in complex space forms, then we show that any compact Lagrangian surface in the complex space form admits at most one other global isometric Lagrangian surface with the same mean curvature form, unless the Maslov form is conformal. These two Lagrangian surfaces are then called Lagrangian Bonnet pairs. We also studied Lagrangian Bonnet surfaces in complex space forms, and obtain some characterizations of such surfaces.

关键词： Lagrangian submanifolds complex space forms. Bonnet pairs

The Approximate Solutions of FPK Equations in High Dimensions for Some Nonlinear Stochastic Dynamic Systems

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Communications in Computational Physics 2011年第10期10卷 1241-1256页

作者： Guo-Kang er Vai Pan Iu Faculty of Science and Technology University of MacaoMacao SARP.R.China

The probabilistic solutions of the nonlinear stochastic dynamic(NSD)systems with polynomial type of nonlinearity are investigated with the subspace-EPC *** space of the state variables of large-scale nonlinear stochastic dynamic system excited by white noises is separated into two *** sides of the Fokker-Planck-Kolmogorov(FPK)equation corresponding to the NSD system is then integrated over one of the *** FPK equation for the joint probability density function of the state variables in another subspace is ***,the FPK equation in low dimensions is obtained from the original FPK equation in high dimensions and it makes the problem of obtaining the probabilistic solutions of largescale NSD systems solvable with the exponential polynomial closure *** about the NSD systems with polynomial type of nonlinearity are given to show the effectiveness of the subspace-EPC method in these cases.

关键词： Nonlinear stochastic dynamic systems large-scale systems probability density function Fokker-Planck-Kolmogorov equation subspace

Nowhere-zero 15-Flow in 3-Edge-connected Bidirected Graphs

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维普期刊数据库

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Acta Mathematica Sinica,English Series 2014年第4期30卷 649-660页

作者： er Ling WEI Wen Liang TANG Dong YE Department of Mathematics Renmin University of China Department of Mathematics West Virginia University Department of Mathematical Sciences Middle Tennessee State University

It was conjectured by Bouchet that every bidirected graph which admits a nowhere-zero κ flow will admit a nowhere-zero 6-flow. He proved that the conjecture is true when 6 is replaced by 216. Zyka improved the result with 6 replaced by 30. Xu and Zhang showed that the conjecture is true for 6-edge-connected graphs. And for 4-edge-connected graphs, Raspaud and Zhu proved it is true with 6 replaced by 4. In this paper, we show that Bouchet＇s conjecture is true with 6 replaced by 15 for 3-edge-connected graphs.

关键词： Bidirected graph integer flow signed graph

A Study of the Large Scale Flooding over Eastern China in 1755

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Advances in Climate Change Research 2012年第3期3卷 128-137页

作者： ZHANG De-er National Climate Center China Meteorological Administration Beijing 100081 China

Following disastrous flooding in several river valleys over eastern China in 1755, serious flooding occurred in the middle and lower reaches of the Yellow River in 1756 and 1757, a rarely seen precipitation pattern of north-flood and south-drought in China for two successive years. This is a serious meteorological disaster and extreme climatic event taking place under the climatic background of a warm phase of the Little Ice Age. In this paper, by means of historical literature records, the rainy and flooding situation and the weather characteristics of these years are reconstructed and the maps depicting areas of prolonged rain, flood and concomitant famine, insect pest, and pestilence are made. The results show that, in 1755, the middle and lower reaches of the Yellow River and the Yangtze River, and the Huaihe River Basin experienced a prolonged rainy season with multiple torrential rain events. The continuous rainy period exceeded 40 days in the Huang-Huai Region. An early Meiyu occurred, and the duration of the Meiyu period in the lower Yangtze River Basin was 43 days, the longest in the 18th century. Particularly in Nanjing the annual rainfall of 1755 was 1,378 mm, the highest record of the 18th century. The year of 1755 is characterized by lower temperature in summer, early frost in autumn, and heavy snowfall and freezing rain in winter. These characteristics are extremely similar to those of 1823 and 1954, two typical years of extreme rainfall. And all these three years with extreme precipitation axe corresponding to the minimum phase of the solar activity cycle.

关键词： extreme climatic event flood meteorological disaster 1755 historical climate

Effect of Different Surface Treatment Methods on the Friction and Wear Behavior of AISI 4140 Steel

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Journal of Materials Science & Technology 2010年第3期26卷 251-257页

作者： Mustafa Ulutan Osman N.Celik Hakan Gasan Umit er University of Eskisehir Osmangazi Faculty of EngineeringDepartment of Mechanical Engineering University of Eskisehir Osmangazi Institute of Metallurgy

In this study,the effects of various surface treatments on the friction and wear behavior of AISI 4140 steel have been *** surfaces of AISI 4140 steel were treated by quenching,carburizing,boronizing and plasma transferred arc （PTA） *** microstructural characteristics of surface treated steel samples were examined by optical microscopy and scanning electron microscopy （SEM）.The mechanical properties of the samples including the surface roughness,microhardness,and abrasive and adhesive wear characteristics were also *** tests were applied by using a block-on-disc configuration under dry sliding *** wear behavior and friction characteristics of the samples were determined as a function of sliding *** sample group was compared with the other sample groups,and it was observed that the carburized samples demonstrated the lowest weight losses;however,PTA-treated samples demonstrated the lowest coefficient of friction in comparison to the other sample groups at the same sliding distance.

关键词： AISI 4140 steel Quenching Boronizing Plasma transferred arc (PTA) Carburizing Sliding wear

Valence Bond Study of Dissociation Behavior and Spectroscopic Constants for the Ground States of LiF and NaF

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Chemical Research in Chinese Universities 1998年第3期14卷 75-81页

作者： CAO Ze-xing WU Wei ZHANG Qian-er Department of Chemistry State Key Laboratory for Physical Chemistry of the Surface Scienceand Institute of Physical ChemistryXiamen UniversityXiamen361005

Ab initio VB calculations were used to determine the accurate spectroscopic parameters of the ground states of LiF and NaF. A set of potential energy curves corresponding to the ground states including ionic and covalent interactions, pure ionic interaction and covalent interaction were generated using the VBSCF method. Curve crossing in the dissociation processes of LiF and NaF was discussed. The optimized VB wave functions suggest that LiF and NaF are of high ionicity, and their ionic weights are 86 2% and 94 6%, respectively. NaF has a higher ionicity. The main difference between atom F and ion F - and the effect of the proper description of this difference on dissociation energies were investigated.

关键词： VBSCF Spectroscopic constant Curve crossing

Hot Deformation Behavior of Low Carbon Steel during Compression at Elevated Temperature

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Journal of Wuhan University of Technology(Materials Science) 2014年第3期29卷 601-605页

作者：刘和平 LIU Bin LI Dazhao SUN Hu'er SUN Feng'er JIN Xuejun ZHANG Yongtao School of Materials Science and Engineering North University of China School of Materials Science and Engineering Shanghai Jiao Tong University School of Machinery Shanghai DianJi University

Hot compression tests of low carbon steel were carried out on Gleeble-3500 system in the temperature range from 750 to 900 ℃ and in the strain rate range from 0.001 to 1.0 s^-1, and the associated microstructural evolution was studied by observations with a metallographic microscope. The results show that the stress-strain curves exhibit a peak stress at critical strain, after which the flow stresses *** monotonically until reaching high strains, showing a dynamic flow softening. The peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by the Zener-Hollomon parameter Z in the hyperbolic sine equation. The flow stress increases with increasing strain rate and decreasing deforming temperature. The flow stress can be described by constitutive equation in hyperbolic sine function and can also be described by a Zener-Hollomon parameter Z. With increasing deformation temperature and deereasing strain rate, the grain size as well as the volume fraction of the reerystaUized grains increase. The safe region for hot working of the alloy has been determined according to the processing map and microstructure at the true strain of 0.5, which is the deformation temperature of 840-940 ℃ and the strain rate of 0.001-1.0 s^-1.

关键词： hot deformation dynamic recrystallization constitutive equation processing map

Investigation of Load Prediction on the Mexico Rotor Using the Technique of Determination of the Angle of Attack

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Chinese Journal of Mechanical Engineering 2012年第3期25卷 506-514页

作者： YANG Hua SHEN Wenzhong SORENSEN Jens Nork er ZHU Weijun College of Power and Energy Engineering Yangzhou UniversityYangzhou 225009China Department of Mechanical Engineering Technical University of Denmark2800 LyngbyDenmark

Blade element moment（BEM） is a widely used technique for prediction of wind turbine aerodynamics performance,the reliability of airfoil data is an important factor to improve the prediction accuracy of aerodynamic loads and power using a BEM *** method of determination of angle of attack on rotor blades developed by SHEN,et al is successfully used to extract airfoil data from experimental characteristics on the MEXICO（Model experiments in controlled conditions） *** surface pressure and particle image velocimetry（PIV） flow fields at different rotor azimuth positions are examined to determine the sectional airfoil *** present technique uses simultaneously both PIV data and blade pressure data that include the actual flow conditions（for example,tunnel effects）,therefore it is more advantageous than other techniques which only use the blade loading（pressure data）.The extracted airfoil data are put into a BEM code,and the calculated axial and tangential forces are compared to both computations using BEM with Glauert＇s and SHEN＇s tip loss correction models and experimental *** comparisons show that the present method of determination of angle of attack is correct,and the re-calculated forces have good agreements with the experiment.

关键词： wind turbine rotor aerodynamics airfoil data

First-principles Study of Adsorption and Dissociation of Methanol on the Pt（lO0） Surface

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Chinese Journal of Chemical Physics 2012年第2期25卷 199-203,I0004页

作者： Zhuo Wang er-jun Kan Jin-long Yang Hefei National Laboratory for Physical Sciences at the Microscale University of Science and Technology of ChinaHefei 230025China Department of Applied Physics Nanjing University of Science and TechnologyNanjing 210037China

Using first-principles calculations, we studied the interaction of methanol with the Pt（100） surface based on generalized gradient approximation. We found that top sites of Pt（100） surface are the favored adsorptive positions in energy, and methanol molecule interacts with the Pt surface through oxygen atoms. Moreover, we also explored the possible dissociation pathways of methanol on the Pt surface, and suggested that the products of dissociation can be controlled by the external manipulation.

关键词： Methanol Pt(100) surface Adsorption Dissociation