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ON THE EXISTENCE OF NONTRIVIAL PERIODIC SOLUTIONS OF DIFFERENTIAL DIFFERENCE EQUATIONS

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Chinese Annals of Mathematics,Series B 1990年第4期11卷 438-444页

作者：王克 Department of Mathematics Northeast Normal UniversityChangchunJilinChina.

This paper cosiders the existence of nontrivial periodic solutions of the differentialdifference equationsx′(t)=-f(x(t-1)),x′(t)=-(f(x(t-1)+f(x(t-2))),and(x′(t)=f(x(t),y(t),x(t-1),y(t-1)),y′(t)=g(x(t),y(t),x(t-1),... 详细信息

关键词： nontrivial proof unbounded ordinary 云一必华 Fixed 耐公 belongs 七气

The Juancheng chondrite──A new meteorite falling recently in China

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Chinese Science Bulletin 1998年第21期43卷 1834-1837页

作者： CHEN Yongheng 1,2, WANG Daode+2 and WANG Ruitian+31. Department of Chemistry, Guangzhou Normal University, Guangzhou 510400, China 2. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China 3. Heze Bureau of Seismolo Department of Chemistry Guangzhou Normal University Guangzhou China Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou China Heze Bureau of Seismology Shandong Province Heze China

The Juancheng chondrite, a new meteorite falling recently in Juancheng County, Shandong Province, China, is classified as an H5 (S2) chondrite based on the compositions of olivine (Fa= 19.2, σ Fa=0.46) and low-Ca pyroxene (Fs=16.9, σ Fa=0.4). The plagioclase in the Juancheng chondrite is rich in CaO, indicating a relatively high metamorphic temperature the parent body underwent.

关键词： Juancheng ordinary chondrite new meteorite.

Zhong Zhaohui:An Extraordinary General Surgeon

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China Today 2022年第7期71卷 58-61页

作者： LI YUAN 不详

Zhong Zhaohui,a general surgeon at the Baitasi branch of Peking University People’s Hospital,is both a witness and promoter to the development of Chinese surgical medicine.THERE is a building featuring distinctive Victorian architecture style on the bustling Fuchengmennei Street,in downtown Beijing.It was the first comprehensive Western medicine hospital financed and operated by Chinese nationals,originally named Cen-tral Hospital.Today,the 104-year-old building is used as the main building of the Baitasi branch of Peking University People’s Hospital.Zhong Zhaohui,a general surgeon at the branch,has worked in this ancient building for 22years,and witnessed the development of Chinese surgical medicine.

关键词： branch ordinary finance

Lost in the Northeast

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China Weekly 2023年第7期 48-50页

作者： Yi Ziyi 不详

The highest-rated Chinese TV show in the last five years,suspense drama The Long Season strikes a provocative balance between realism and aesthetic through its portrayals of ordinary people struggling through tremendo... 详细信息

关键词： Northeast change. ordinary

Ringel duals of extension algebras of posets

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Chinese Science Bulletin 1999年第2期44卷 129-132页

作者： ZHANG YuehuiDepartment of Mathematics and Physics, Hainan University, Haikou 570228, China Department of Mathematics and physics Hainan University Haikou China

The Ringel dual of the dual extension algebra of a poset having a largest element is

关键词： dual extension algebra ordinary quiver Ringel dual.

Simultaneous approximation of a function and its derivatives by Sobolev polynomials: Applications in satellite geodesy and precise orbit determination for LEO CubeSats

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Geodesy and Geodynamics 2020年第5期11卷 376-390页

作者： M.Kiani Graduated from Department of Geodesy School of Surveying and Geospatial Data EngineeringUniversity of TehranTehranIran

The objectives of this paper are twofold:(1) to present a new method of approximation such that the function and some of its derivatives are simultaneously approximated;and(2) to investigate the potential applications of this new method in the field of satellite geodesy by deriving a numerical solver of ordinary differential equations. To fulfill both the objectives, Sobolev polynomials are used. Explicit formulas for these polynomials are presented. A quadrature rule is derived based on the explicit forms of these polynomials. Solution of first order ordinary differential equations is presented based on the numerical integration method by the new quadrature rule. To present the applications of the results, three problems are investigated in the field of satellite geodesy. In the first application, orbit propagated by the numerical solution of orbital equations is compared with the Keplerian motion. It is shown that the new method for solving ordinary differential equations can be used alongside any other method, including the adaptive Runge-Kutta and Adams-Bashforth-Moulton integration methods. The comparison of this new method with the adaptive Runge-Kutta, Adams-Bashforth-Moulton, and the powerful and newly established adaptive Gaussian numerical integration methods reveals that it is at least 580, 666667, and72 times more accurate than the mentioned methods, respectively, in any given absolute tolerance and time increment. The method is fast, stable, consistent, and capable of handling high accuracy, even with large time increment and low absolute tolerance, which is shown in this application. In the second application, the Gravity Recovery and Climate Experiment(GRACE) satellites’ orbits are propagated using both the Ensemble Kalman Filter(EnKF) with stochastic updates and smoothing for the position and the Sobolev numerical integration. The orbits are then compared with the observed positions of the satellites. It is shown that the Sobolev polynomials work better in this problem, being more than 2 times mor

关键词： numerical approximation ordinary

On Existence and Nonexistence of Some Harmonic Maps

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Acta Mathematica Sinica,English Series 1990年第1期6卷 1-9页

作者：洪家兴刘嘉荃 institute of Mathematics Fudan University Shanghai People’s Republic of China Institute of Systems Science Academia Sinica Beijing People’s Republic of China International Centre for Theoretical Physics Trieste Italy

Let Sdenote the submanifold of Lorentz space Rwhich is Composed of all points lwith l~2=1 and let T=R/Z×Z. In this paper we study the existence of nontrivial harmonic mapsfrom Tto Sand H~2. and construct a harmonic m... 详细信息

关键词： nontrivial Lorentz harmonic semilinear infinitely estimates ordinary constants Lagrangian proof

The Dynamic Mechanism of the Formation of the Low Level Jet

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Advances in Atmospheric Sciences 1990年第4期7卷 383-394页

作者：杨大升简茂球 Department of Geophysics Peking University Beijing 100871 Department of Geophysics Peking University Beijing 100871he ordinary multidimensional reductive perturbation method is generalized so as to apply to the general case including the dissipative factor. With this the corresponding Cubic-Schrbdinger equation is deduced and by the preliminary study of its solution it shows that it is more admissible to consider atmospheric meso-scale systems as the nonlinear Cubic-Schrbdinger waves.With suitable boundary and initial conditions the Cubic-Schrodinger equation is numerically integrated so as to investigate the possible dynamic mechanism as well as the impacts of the nonlinear action turbulent friction and topogrphy to the formation of the LLJ. The results indicate that the downward transfer of the momentum and the effect of the surface friction are responsible for the concentration of the momentum in the layer between 850 and 700 hPa. The location of the horizontal concentration of momentum depends on the propagation of momentum in the process the inertia-gravity internal wave is very important whereas turbulent friction is unfavourable for or delays the formation of the low level jet.

The ordinary multidimensional reductive perturbation method is generalized so as to apply to the general case including the dissipative factor. With this the corresponding Cubic-Schrbdinger equation is deduced, and by the preliminary study of its solution, it shows that it is more admissible to consider atmospheric meso-scale systems as the nonlinear Cubic-Schrbdinger waves.With suitable boundary and initial conditions, the Cubic-Schrodinger equation is numerically integrated so as to investigate the possible dynamic mechanism as well as the impacts of the nonlinear action, turbulent friction and topogrphy to the formation of the LLJ. The results indicate that the downward transfer of the momentum and the effect of the surface friction are responsible for the concentration of the momentum in the layer between 850 and 700 hPa. The location of the horizontal concentration of momentum depends on the propagation of momentum, in the process the inertia-gravity internal wave is very important, whereas turbulent friction is unfavourable for or delays the formation of the low level jet.

关键词： momentum turbulent perturbation inertia ordinary admissible dissipative deduced gravity downward

Influencer's University Comments Spark Major Debate on Majors

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China Weekly 2023年第8期 12-13页

Netizen Comments:"Zhang Xuefeng is providing valuableinfomation to ordinary families,specilly those in impoverished areas.He is doing meaningful work"There are two sets of rules in China:one seems idealistic,touted by mainstream media and highly eulogized at school.The otheris crullyutlitarian and often left unspoken,but keeps society running.Zhang is saying what goes unsaid.His words may cut like sharp knives,but heisspeaking the truth".

关键词： Spark meaningful ordinary