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Existence and Non-Existence of Periodic Solutions of Generalized Lineard Equations with Damping of No Lower Bound

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Acta Mathematica Sinica,English Series 1996年第4期12卷 361-371页

作者： Jiang Jifa department of Mathematics university of science and technology of china {2., 2.002. china department of Mathematics University of Science and Technology of China Hefei China

This paper establishes criteria for the existence and non-existence of nonzero periodic solutions of the generalized lienard equation （?）+f（x,（?））（?）+g（x）=*** main goal is to study to what extent the damping f can be small so as to guarantee the existence of nonzero periodic solutions of such a system. With some standard edditional assumptions we prove that if for a small |x|, ∫±∞|f（x,y）|-1dy=±∞, then the system has at least one nonzero periodic solution, otherwise, the system has no nonzero periodic solution. Many classical and well-known results can be proved as corollaries to ours.

关键词： Generalized lienard equation Limit cycle

D^p Spaces on Bounded Symmetric Domains of C^n

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Acta Mathematica Sinica,English Series 1994年第1期10卷 11-18页

作者： Shi Jihuai department of Mathematics university of {2. technology of china hefei,2.002. china 1. department of Mathematics University of Science Technology of China 230027 Hefei China

In this paper,the space D^p(Ω)of functions holomorphic on bounded symmetric domain of C^n is *** prove that H^P(Ω) D^P(Ω)if 02.and D^P(Ω) H^P(Ω)if p≥2.and both the inclusions axe ***,we find that some theore... 详细信息

关键词： Th Hp D~p Spaces on Bounded Symmetric Domains of C~n

Relation between Starlight and Nebular Emission Lines of Star-Forming Galaxies

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Research in Astronomy and Astrophysics 2005年第3期5卷 221-228页

作者： Hong-Lin Lu, Hong-Yan Zhou, Ting-Gui Wang, Zhen-Quan Zhuang, xiao-Bo Dong, Jun-Xian Wang and Cheng Li department for Electronics of {2. & technology, university of science and technology of china, hefei 2.002. Center for Astrophysics, university of science and technology of china, hefei 2.002. Center for Astrophysics University of Science and Technology of China Hefei 230026

We present an exercise that intends to establish a relationship between the strength of nebular emission lines and optical stellar features in the spectrum of a galaxy. After accurately subtracting the stellar continuum and the underlying stellar absorption, we made reliable measurements of the emission lines of all the galaxies in the Sloan Digital Sky Survey Data Release 2.(SDSS DR2.. More than 4000 star-forming galaxies with high S/N ratio of both the stellar spectrum and the emission lines are selected. These galaxy spectra are fitted with the 10 PCs of Yip et al., after all the emission line regions have been filtered out. We find that the flux of hydrogen Balmer emission lines, Ha and Hβcan be well recovered from the PCs, while the metal lines are not well reproduced. The fluxes of Ha and Hβmeasured from the PC-reconstructed spectra and from the observed spectra agree well with an rms scatter of only - 0.1 dex. This result suggests that, with moderate spectral resolution and S/N ratio, the optica

关键词： galaxies: fundamental parameters - galaxies: starburst - radiation: lines continuum

Non-isothermal Melt Crystallization Kinetics of Anhydrite-Filled Polypropylene Composites

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Journal of Wuhan university of technology(Materials {2.) 2010年第1期25卷 12-19页

作者：王少会 department of Chemistry and Chemical engineering East China JiaoTong University

The non-isothermal crystallization kinetics of polypropylene （PP）, PP/anhydrite composites were investigated by differential scanning calorimetry （DSC） with various cooling rates. The Avrami analysis modified by Jeziorny and a method developed by Mo were employed to describe the non-isothermal crystallization process of these samples. The difference in the exponent n between PP and PP/anhydrite composites indicated that non-isothermal kinetic crystallization corresponded to tri-dimensional growth with heterogeneous nucleation. The values of half-time, Zc and F（T） showed that the crystallization rate increased with the increasing of cooling rates for PP and PP/anhydrite composites, but the crystallization rate of PP/anhydrite composites was faster than that of PP at a given cooling rate. The method developed by Ozawa did not describe the non-isothermal crystallization process of PP very well. Moreover, the method proposed by Kissinger was used to evaluate the activation energy of the mentioned samples. The result showed that the activation energy of PP/anhydrite was greatly larger than that of PP.

关键词： polypropylene anhydrite composites non-isothermal crystallization kinetics

Internal noise stochastic resonance in CO oxidation on nm-sized palladium particles

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science china Chemistry 2005年第5期48卷 395-401页

作者： GONG Yubing1,2. HOU Zhonghuai1 & XIN Houwen1 1. department of Chemical Physics, university of science and technology of china,{2., china 2. department of Physics, Yantai Teachers university, Yantai 2.402., china 1. department of Chemical Physics University of Science and Technology of China 230026 Hefei China 2. department of Physics Yantai Teachers University 264025 Yantai China

Based on a stochastic mesoscopic model, the influence of internal noise on the oscillatory kinetics of the catalytic oxidation of CO on nm-sized palladium particles is studied, using the chemical Langevin equations, Poisson approximation algorithm, and exact stochastic simulation algorithm. The reaction rate oscillations are of stochastic nature due to considerable internal noise in such mesoscopic systems. It is found that the performance of the stochastic oscillations undergoes a maximum with the variation of internal noise level for a given CO partial pressure, which demonstrates the occurrence of internal noise stochastic resonance. This phe-nomenon implies that optimal internal noise would favor the reaction rate oscillation of CO oxi-dation on nm particles. Such a phenomenon is robust to the change of external parameters, such as CO pressures.

关键词： nanometer-sized palladium particles, surface catalytic CO oxidation, internal noise, stochastic resonance, chemical Langevin equation.

Spectra of Composition Operators on Lummer-Hardy Spaces

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Acta Mathematica Sinica,English Series 1994年第2期10卷 209-214页

作者： Yuan Jinyong department of Mathematics university of science and technology of china {2., 2.002. china 1. department of Mathematics University of Science and Technology of China 230027 Heifei China

In this paper, we completely determine the spectrum of a compact composition operator on Lummer-Hardy space.

关键词： LH Spectra of Composition Operators on Lummer-Hardy Spaces

A STUDY OF OSCILLATING FLOWS OVER PROPAGATING RIPPLES:PART Ⅱ. VORTICITY DYNAMICS

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Journal of Hydrodynamics 2000年第1期12卷 8-15页

作者： Lu Xi yun department of Modern Mechanics, university of science and technology of china,{2., P.R.china Univ of science and technology of China Hefei China

Vortex shedding for an oscillating flow over ripples is numerically investigated by solving 2. D time dependent incompressible Navier Stokes equations in curvilinear coordinates. The dynamics of vortex structures generated by flow separation is studied in order to understand some phenomena which take place near the bottom and in particular to get insight into the mechanism through which sediment grains are lifted up and maintained in suspension. Based on our calculated results, some important phenomena, such as vortex shedding, vortices pairing, vortices coalescence, vortex interaction with the free shear layer and so on, can be found. The behaviors of energy dissipation in the flow field and of shear stress along the ripple surface are also discussed for studying the dynamics of sediment grains in suspension and to obtain new information on the suspended load over the ripples.

关键词： oscillating flow ripple vorticity dynamics separation flow

Stochastic resonance in surface catalytic oxidation of carbon monoxide induced by colored noise

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science china Chemistry 2004年第2期47卷 106-112页

The dynamical behavior of surface catalytic oxidation reaction of Pt(110)/CO+O2.modulated by colored noise, under the condition of specific temperature, has been investigated when the partial pressure of CO gas is near the supercritical Hopf bifurcation point. By computer simulation the oscillation and stochastic resonance induced by colored noise are observed. The influences of the intensity and correlation time of colored noise on stochastic resonance are discussed. The range of sensitivity of the system to the environmental fluctuation is analyzed.

关键词： colored noise, stochastic resonance, surface catalytic reaction of Pt(110)/CO+O2. supercritical Hopf bifurcation, signal-to-noise ratio (SNR).

Effect of rare earths on phase transformation in as-cast ZA2. alloy dur-ing compressive creep

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Rare Metals 2003年第4期22卷 259-264页

作者： WEIxiaowei SHENBaoluo DepamnentofAppliedPhysics UniversityofElectronicScienceandTechnologyofChinaChengdu610045China DeparlanentofMetalscience SichuanUniversityChengdu610065China

The effect of the mixed rare earths of Ce on the phase transformation in ascast ZA 2. alloy during compressive was investigated under 37 MPa and at 160 deg C by X-raydiffraction technique and SEM. The results showed that the as cast microstructure of ZA 2.-RE alloyconsisted of a dendritic Al-rich alpha' surrounded by Zn-rich beta' phase, interdendritic epsilonphase and Zn-rich eta phase together with a complex Z phase which was a complex constitute compound,(RE,Cu)Al_5Zn_(16), dispersed in crystal interfaces or branch crystal interfaces and stable duringcompressive creep test at 160 deg C. The phase transformations of ZA 2.-RE alloy, decomposition ofbeta' phase arid four transformation, were delayed by the addition of rare earths, also the lamellarstructure and the spheroidized structure in ZA 2.-RE alloy were finer than in ZA 2. alloy duringcompressive creep test at 160 deg C at the same creep time, and the compressive creep resistance ofZA 2.-RE alloy was higher than that of ZA 2. alloy.

关键词： microstructure change compressive creep rare earths ZA 2. alloy