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A Multiplicity Result of Positive Solutions for a Class of Multi-parameter Ordinary Differential Systems

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Acta Mathematicae Applicatae Sinica 2012年第4期28卷 653-662页

作者： Xi-you CHENG xiao-lin yan School of Mathematics and Statistics Lanzhou University School of Science Tianjin Polytechnic University

In this paper, we establish a result of Leray-Schauder degree on the order interval which is induced by a pair of strict lower and upper solutions for a system of second-order ordinary differential equations. As applications, we prove the global existence of positive solutions for a multi-parameter system of second-order ordinary differential equations with respect to parameters. The discussion is based on the result of Leray- Schauder degree on the order interval and the fixed point index theory in cones.

关键词： positive solution ordinary differential system fixed point index

Hierarchically 1D CdS decorated on 2D perovskite-type La_(2)Ti_(2)O_(7) nanosheet hybrids with enhanced photocatalytic performance

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Rare Metals 2021年第5期40卷 1067-1076页

作者： Liang Mao xiao-yan Cai Ming-Shan Zhu School of Materials Science and Physics China University of Mining and TechnologyXuzhou 221116China Jiangsu Province Engineering Laboratory of High Efficient Energy Storage Technology and Equipment China University of Mining and TechnologyXuzhou 221116China School of Environment Jinan UniversityGuangzhou 511443China

In this paper,a heterojunction of hierarchically one-dimensional(1D)cadmium sulfide(CdS)nanowires decorated on the two-dimensional(2D) La_(2)Ti_(2)O_(7) (LTO)has been fabricated by a simple two-step hydrothermal *** structure,morphology and surface chemical composition of CdS/LTO were studied by a variety of characterizations,in which the X-ray photoelectron spectroscopy(XPS)results showed a strong interaction between CdS and LTO through S-O *** typeⅡband alignment of CdS/LTO for favorable electron transfer from CdS to LTO and hole transfer from LTO to CdS was clarified by ultraviolet-visible(UV-Vis)diffuse reflectance spectroscopy and Mott-Schottky(M-S)plot *** the absence of any co-catalyst,H2 production from water splitting and Rhodamine B(RhB)decomposition in aqueous solution were carried out to evaluate the photocatalytic activities,showing that the photocatalytic performance of CdS/LTO was superior to that of pure LTO and CdS under visible light and simulated *** optimal CdS content in the CdS/LTO system was determined to be 7.5 wt%.The present results show an effective pathway to design a 1D/2D heterojunction photocatalyst in the face of overwhelming problems of energy crisis and environmental pollution.

关键词： Cadmium sulfide Lanthanum titanium oxide Heterojunction H_(2)production Dyes degradation

Hedging Game Contingent Claims with Constrained Portfolios

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Advances in Applied Mathematics and Mechanics 2009年第4期1卷 529-545页

作者： Lei Wang yan xiao College of Science National University of Defense TechnologyChangsha 410073China Changsha Medical College Changsha 410219China

Game option is an American-type option with added feature that the writer can exercise the option at any time before *** this paper,we consider the problem of hedging Game Contingent Claims(GCC)in two *** the case that portfolio is unconstrained,we provide a single arbitrage-free price P_(0).Whereas for the constrained case,the price is replaced by an interval[h_(low),h_(up)]of arbitrage-free *** for the portfolio with some closed constraints,we give the expressions of the upper-hedging price and lower-hedging ***,for a special type of game option,we provide explicit expressions of the price and optimal portfolio for the writer and holder.

关键词： Game option contingent claims hedging optimal stopping free boundary

Multi-mode controller IC for soft-switched flyback converter with high efficiency over the entire load range

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第10期9卷 1411-1419页

作者： Hai CHEN Meng-lian ZHAO xiao-bo WU xiao-lang yan Institute of VLSI Design Zhejiang University Hangzhou 310027 China

This paper presents a multi-mode control scheme for a soft-switched flyback converter to achieve high efficiency and excellent load regulation over the entire load range. At heavy load, critical conduction mode with valley switching (CCMVS) is employed to realize soft switching so as to reduce turn-on loss of power switch as well as conducted electromagnetic interference (EMI). At light load, the converter operates in discontinuous conduction mode (DCM) with valley switching and adaptive off-time control (AOT) to limit the switching frequency range and maintain load regulation. At extremely light load or in standby mode, burst mode operation is adopted to provide low power consumption through reducing both switching frequency and static power dissipation of the controller. The multi-mode control is implemented by an oscillator whose pulse duration is adjusted by output feedback. An accurate valley switching control circuit guarantees the minimum turn-on voltage drop of power switch. The pro-totype of the controller IC was fabricated in a 1.5-μm BiCMOS process and applied to a 310 V/20 V, 90 W flyback DC/DC converter circuitry. Experimental results showed that all expected functions were realized successfully. The flyback converter achieved a high efficiency of over 80% from full load down to 2.5 W, with the maximum reaching 88.8%, while the total power consumption in standby mode was about 300 mW.

关键词： Integrated circuit Multi-mode controller Soft-switched flyback converter Valley detection

Stress and thickness calculation of a bolted flat cover with double metal sealing rings

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Nuclear Science and Techniques 2018年第8期29卷 210-217页

作者： xiao-yan Wang Shi-Feng Zhu xiao Wang xiao-Chun Zhang Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China

The design of a bolted flat cover is extremely important for the structural integrity of pressure *** present design codes provide the thickness calculation equations for a bolted flat cover with single metal ***,the rules for a bolted flat cover with double metal sealing rings are not developed to *** the study,a new thickness calculation equation for the bolted flat cover with double metal sealing rings is ***,the theoretical stress solution for bolted flat cover with the double metal sealing rings is obtained,based on the theory of simply supported circular plate and then verified using the results from finite element *** results indicate that the influence of double metal sealing ring on the stress of the flat cover is more serious compared to single metal ***,a more accurate and reasonable equation is proposed to calculate the thickness of bolted flat cover with double metal sealing rings based on the derived theoretical equations of maximum ***,the influence of linear load and the spacing between rings on the thickness are ***,a few suggestions are provided to design low-pressure or atmosphere pressure *** study provides a theoretical foundation to develop design codes of pressure vessels in nuclear reactors.

关键词：厚度计算扁平金属封面戒指应力和计算方程压力解

Creep damage characterization of UNS N10003 alloy based on a numerical simulation using the Norton creep law and Kachanov–Rabotnov creep damage model

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Nuclear Science and Techniques 2019年第4期30卷 114-122页

作者： xiao-yan Wang xiao Wang xiao-Chun Zhang Shi-Feng Zhu Shanghai Institute of Applied Physics Chinese Academy of Sciences University of Chinese Academy of Sciences

The calculation of inelastic creep damage is important for the structural integrity evaluation of the elevated temperature structure in a thorium molten salt reactor(TMSR). However, a creep damage theory model and numerical simulation method have not been proposed for the key materials(UNS N10003 alloy) in the TMSR. In this study, creep damage characterization of UNS N10003 alloy is investigated using the Norton creep law and Kachanov–Rabotnov(K–R) creep damage model. First, the creep experimental data of the UNS N10003 alloy at 650 °C were adopted to fit the material constants of the two models. Then, the creep damage behavior of the UNS N10003 alloy was analyzed and discussed under uniaxial and multi-axial stress states. The results indicated that the K–R creep damage model is more suitable for the UNS N10003 alloy than the Norton model. Finally, the numerical simulation method was developed by a user-defined UMAT subroutine and subsequently verified through a finite element analysis(FEA). The FEA results were in agreement with the theoretical solutions. This study provides an effective method for the inelastic creep damage analysis of the elevated temperature structure in the TMSR.

关键词： Thorium molten salt reactor UNS N10003 alloy Creep damage Inelastic analysis Elevated temperature structure

Generalized Gr?tzsch ring function and generalized elliptic integrals

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Applied Mathematics(A Journal of Chinese Universities) 2016年第4期31卷 458-468页

作者： MA xiao-yan QIU Song-liang TU Guo-yan Department of Mathematics Zhejiang Sci-Tech University Hangzhou 310018 China Tongji Zhejiang College Jiaxing 413000 China

Abstract. In this paper, we study the quotient of hypergeometric functions μα （r） in the theory of Ramanujan＇s generalized modular equation for α ∈（0, 1/2]. Several new inequalities are given for this and rela... 详细信息

关键词： Gaussian hypergeometric function generalized GrStzsch ring function generalized elliptic func-tion.

Vanishing of Tate Homology - An Application of Stable Homology for Complexes

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Acta Mathematica Sinica,English Series 2016年第7期32卷 831-844页

作者： yan Ping LIU Zhong Kui LIU xiao yan yanG Department of Mathematics Northwest Normal University Lanzhou 730070 P. R. China

It has been proved that the vanishing of Tare homology is a sufficient condition for the derived depth formula to hold in [J. Pure Appl. Algebra, 219, 464-481 （2015）]. In this paper, we inves- tigate when Tate homology vanishes by studying the stable homology theory for complexes. Properties such as the balancedness and vanishing of stable homology for complexes are studied. Our results show that the vanishing of this homology can detect finiteness of homological dimensions of complexes and regularness of rings.

关键词： Tate homology stable homology complete projective resolution

The Invariance Principle for p-■Chain

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Acta Mathematica Sinica,English Series 2007年第1期23卷 41-56页

作者： Di He HU Zheng yan xiao School of Mathematics and Statistics Wuhan University Wuhan 430072 P. R. China School of Statistics Renmin University of China Beijing 100872 P. R. China

There are two parts in this paper. In the first part we construct the Markov chain in random environment（MCRE）, the skew product Markov chain and p-θ^→ chain from a random transition matrix and a two-dimensional probability distribution, and in the second part we prove that the invarianee principle for p-θ^→ chain, a more complex non-homogeneous Markov chain, is true under some reasonable conditions. This result is more powerful.

关键词： random transition matrix Markov chain in random environment skew product Markov chain p-θ^→ chain invariance principle