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Positive Solutions to m-point Boundary Value Problem of Fractional Differential Equation

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Acta Mathematicae Applicatae Sinica 2013年第3期29卷 661-672页

作者： yuan-sheng TIAN Department of Mathematics Xiangnan University

In this paper, we study the multiplicity of positive solutions to the following m-point boundary value problem of nonlinear fractional differential equations： Dqu（t）＋ f（t, u（t）） = 0, 0 t 1, u（0） = 0, u（1） =sum （μiDpu（t）｜t = ξi ） from i =1 to ∞ m-2, where q ∈R , 1 q ≤2 , 0 ξ1 ξ2 ··· ξm-2 ≤ 1/2 , μi ∈[0 , ＋∞） and p = q-1/2 , Γ（q） sum （μiξi（q-1）/2 Γ（（ q＋1）/2） from i =1 to ∞ m-2,Dq is the standard Riemann-Liouville differentiation, and f ∈C （[0 , 1]×[0 , ＋∞） , [0 , ＋∞））. By using the Leggett-Williams fixed point theorem on a convex cone, some multiplicity results of positive solutions are obtained.

关键词： fractional differential equation m-point boundary value problem fixed-point theorem positive solutions

Rheological model of semisolid Mg_(2)Si/AM60 composites prepared by ultrasonic vibration treatment

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Rare Metals 2022年第8期41卷 2783-2788页

作者： yuan-sheng Rao Hong Yan Jun Wan Department of Materials Processing Engineering School of Mechanical and Electrical EngineeringNanchang UniversityNanchang330031China Key Laboratory of Light Alloy Preparation and Processing in Nanchang City Nanchang330031China

The rheological behavior of semisolid Mg_(2)Si/AM60 composites prepared by ultrasonic vibration treatment was *** effects of primaryα-Mg solid content,the ultrasonic power and the content of reinforcement phase Mg_(2)Si on the apparent viscosity of semisolid composites were *** results show that the apparent viscosity of the semis olid composites increases with the increase in a-Mg solid ***,the apparent viscosity decreases with the increase in ultrasonic power,and the reduction amplitude is higher when the solid content is *** addition,the apparent viscosity increases with the increase in Mg_(2)Si *** on experimental data fitting,the rheological model of semisolid Mg_(2)Si/AM60 composites prepared by ultrasonic vibration was established.

关键词： Semisolid Magnesium matrix composites Ultrasonic vibration Apparent viscosity

Weathering geochemistry and palaeoclimate implication of the Early Permian mudstones from eastern Henan Province, North China

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Journal of Palaeogeography 2017年第4期6卷 370-380页

作者： Jiang-Hai Yang yuan-sheng Du State Key Laboratory of Biogeology and Environmental Geology China University of Geosciences

Terrigenous clastic sediments are generated by the integration of the Earth surface processes and their deep-time counterparts provide a valuable archive for regional/global climatic, geographic and landscape evolution. It is thus important to read and interpret these deep-time sedimentary records, especially for reconstructing continent climate. Previous studies on the Early Permian sequences from the North China document a dominant control of source chemical weathering on mudstone compositions and its linkage with continent climate conditions. Based on the weathering geochemical data of these mudstones, element mobility during weathering can be ordered as Ca 〉 Na ≥ Mg 〉 Sr 〉 K ≥ Ba 〉 Rb. The weathering regime in the source area is inferred to be supply-limited according to the estimated continent physical erosion rate and regional tectonic evolution, sedimentation in North China. Further exploration of palaeoclimate implication is presented in terms of variation of high-to-low latitudinal temperature gradient across the Early Permian glacial to post-glacial climate transition.

关键词： Chemical weathering Weathering geochemistry Mudstones Early Permian North China

Multiplicity of Positive Solutions to M-point Boundary Value Problem of Second Order Impulsive Differential Equations

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Acta Mathematicae Applicatae Sinica 2010年第1期26卷 145-158页

作者： yuan-sheng Tian Chun-gen Liu Department of Mathematics Xiangnan University Chenzhou 423000 China School of Mathematics and LPMC Nankai University Tianjin 300071 China

In this paper, by using Avery-Peterson theorem on a convex cone, we consider the m-point boundary value problems for second order impulsive differential equations with the nonlinear term depending on the first order d... 详细信息

关键词： Boundary value problem impulsive differential equations fixed-point theorem positive solutions

Focusing of Spherical Nonlinear Pulses for Nonlinear Wave Equations

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Acta Mathematicae Applicatae Sinica 2005年第3期21卷 415-428页

作者： Ming-sheng yuan Department of Mathematics Shanghai Jiaotong University Shanghai 200240 China

This paper describes the behavior of spherical pulse solutions of a system of semilinear wave equations in three space variables. Away fi＇om the focal point, we describe solutions with nonlinear geometric optics. We show that the approximation given by nonlinear geometric optics is valid before and after the focal point. We obtain a global asymptotic description including an approximation which is a solution of the linear wave equations near the caustic.

关键词： Nonlinear wave equations spherical pulses focusing

Constructions of vector output Boolean functions with high generalized nonlinearity

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The Journal of China Universities of Posts and Telecommunications 2008年第2期15卷 77-81页

作者： KE Pin-hui ZHANG sheng-yuan Key Laboratory of Network Security and Cryptology Fujian Normal UniversityFujian 350007 China

Carlet et al. recently introduced generalized nonlinearity to measure the ability to resist the improved correlation attack of a vector output Boolean function. This article presents a construction of vector output Boolean fimctions with high generalized nonlinearity using the e-biased sample space. The relation between the resilient order and generalized nonlinearity is also discussed.

关键词： Boolean functions correlation attack generalizednonlinearity almost resilient functions

Enhanced Oxidative Coupling of Methane with Oxygen Permeation Membrane

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Chinese Journal of Structural Chemistry 2020年第12期39卷 2115-2122,2054页

作者： yuan sheng-Ze XIE Kui College of Chemistry and Materials Science Fujian Normal UniversityFuzhou 350007China Key Laboratory of Design&Assembly of Functional Nanostructures Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002China

Oxidative coupling of methane to ethylene is of high importance to the future of light olefin ***,the carbon atom efficiency is normally below 50%in gas phase reaction which is limited to the overoxidation of methane to carbon dioxide with *** we present an alternative approach of electrochemical oxidation of methane in an oxygen permeation membrane reactor and show the highest conversion of methane and C2 selectivity of 28%and 40.2%at 1150℃,*** prepare the 100-μm-thick perovskite(La0.8 Sr0.2)1-x Cr0.5 Fe0.5 O3-δ(LSCrF)dense membrane(La0.8 Sr0.2)1-xCr0.5 Fe0.5O3-δ(LSCrF–Fe)(x=0,0.02,0.05 and 0.10)scaffolds while the excess of Fe would be exsolved on porous skeleton to create metal-oxide interfaces toward methane *** metal-oxide interfaces not only facilitate the activation of C–H bond in methane but also enhance the coking resistance.

关键词： oxidative coupling of methane oxygen permeation membrane nanoparticles metal-oxide interfaces

Mechanical behaviour of Al/Al_(2)O_(3) composite in pseudo-semi-solid state during isothermal compression

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Transactions of Nonferrous Metals Society of China 2009年第S2期19卷 368-372页

作者： CHENG yuan-sheng LUO Shou-jing School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China

To gain a better understanding of thixoforging for the Al_(2)O_(3)-37%Al composite,its mechanical behavior in the pseudo-semi-solid state was studied by isothermal compression *** results show that the values of peak stress obviously decrease with increasing temperature and decreasing strain *** compressive true stress-strain curves of the Al_(2)O_(3)-37%Al composite can be divided into four *** are rapidly ascending,decreasing,steady and slowly ***,the main deformation mechanism controlling deformation of the composite in the pseudo-semi-solid state is the sliding or rotary movement between solid particles.

关键词： composite pseudo-semi-solid state mechanical behaviour stress—strain curve

Microstructure Evolution and Growth Orientation of Directionally Solidified Mg–4 wt% Zn Alloy with Different Growth Rates

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Acta Metallurgica Sinica(English Letters) 2017年第12期30卷 1185-1191页

作者： Hong-Min Jia Xiao-Hui Feng yuan-sheng Yang Institute of Metal Research Chinese Academy of SciencesShenyang 110016 China University of Chinese Academy of Sciences Beijing 100039China Shandong Key Laboratory for High Strength Lightweight Metallic Materials Ji'nan 250014 China

The microstructure evolution and growth orientation of directionally solidified Mg-4 wt% Zn alloy in the growth rate range from 20 to 200μm/s were investigated. A typical cellular structure was observed with a growth rate of 20 μm/s, and the cellular spacing was 115 μm. When the growth rate increased to 60 μm/s, cellular structure with some developed perturbations was obtained and the cellular spacing was 145 μm, suggesting that the cell-to-dendrite transition happened at the growth rate lower than 60 μm/s. As the growth rate further increased, the microstructure was dendritic and the primary dendritic arm spacing decreased. The relationship between the primary dendritic arm spacings and the growth rates was in good agreement with Trivedi model during dendritic growth. Besides, X-ray diffraction and transmission electron microscopy analyses showed that the growth direction of directionally solidified Mg-4 wt% Zn alloy was （1120） lay in {0002} crystal plane, and the preferred orientation was explained with the lattice vibration model for one-dimensional monatomic chain.

关键词： Directional solidification Mg-Zn alloy Microstructure evolution Primary dendritic arm spacing Growth orientation