第3期 王峰,等:叠合度的计算及其对非线性Picard边值问题的应用 25 3 应用 考虑非线性Picard边值问题 (£)+f(t,z(£),z (£))一0, £∈T, (7) Iz(0)一z(7c)一0, 这里T一[0,7c],f:T×R×R—R非负连续. 令X一{z∈C [0,7c]l z(0)一z(7c)一0},Z—CET,R3,dom L—C IT,R]n X.定义算子L:dom L— Z s N:x—Z为 (Lx)(£)一一 (£), (Nx)(£)一f(t,z(£),z (£)), 则Ker L一{0},Im L—Z,故L是零指标的Fredholm算子,并且L一:Z—X的表达式为 (L-l y)( )==——— 一(J' s(rc-t) (s)ds—卜J' (兀——s) (s)ds). 由Arzela—Ascoli定理易知L一:Z—X是线性全连续算子.由于N:X—Z是连续有界算子,因此N是L 紧的.在X和Z中分别取锥为 K 一{z(£)l z E X,z(£)≥0,z(£)为T上的凹函数}, K一{z(£)l z E Z,z(£)≥0}. 据上述讨论,问题(7)的解等价于方程Lz(£)一Nx(£)在dom LNK 的解.由厂(t,z, )非负,N(X)c K,并且L (K)CK .用ll・ 表示空间L P[T,R]的范数. 定理4假设关于tE T,一致地有 li m < 1, (8) I +1 I一+oo l z l十l l lirainf>1, (9) I I+ +I—oyl l z l十l l 则问题(7)至少有一解z (£),且有z (£)>0,tE(0,7c). 证 注意到问题(8),(9)等价于抽象算子方程Lz Nx.由(9)式,存在r>0,使当l zI+l I≤r时, f(t,z, )≥l z l+l l≥l z 1.取T,为X中半径为r,中心在0点的开球,则当zE dom L N aT,N K 时, 有l z(£)l+l z (£)l≤I zl 一r,从而 f(t,z,z (£))≥z(£),t E T. 上式两边同乘sin t,并且在T上积分,利用分部积分公式,得到 I sin£厂(£,z,z (£))d£≥I sin£z(t)dt—I sin t(- (£))dt, 即I sin t Nx(t)dt≥I sin t Lx(t)dt.不妨假设当z E dom L N OT,N K 时,Lx≠Nx.故 I sin t Nx(£)dt>I sin t Lx(£)dt. (10) 设Bx(£)一I sin tx(£)dt,则B是映K 入K 一[0,+oo)的有界正线性算子.下面证明对于V E dom L N OT,N K ,有BNx BLx成立.事实上,若存在z E dom L N OT,N K ,满足BNx ≤ BLx .这与(10)式矛盾、根据定理1,有 D[(L,N),dora L N T,N K1]一0. 由常规证法知结论成立 ]. 本课题由导师孙经先教授于2006年5月向第一作者建议,作者谨致谢意! 参考文献: [1]王峰,邹玉梅.拓扑度的计算及其对超线性奇异四阶微分方程的应用I-J].徐州师范大学学报:自然科学版,2006,24 (4):31. 维普资讯 http://www.cqvip.com 26 徐州师范大学学报(自然科学版) 第25卷 E2]郭大钧,孙经先,刘兆理.非线性常微分方程泛函方法[M].济南:山东科技出版社,1994:105—107,167—168. [3]Gaines R E,Mawhin J1 .Coincidence degree and nonlinear differential equations[M].Berlin:Springer—Verlag,1977 [43张福保.叠合度的缺方向性与边值共振问题的非平凡解[J].数学研究与评论,1999,19(4):693. Computation for Coincidence Degree and Applications tO Nonlinear Picard Boun dary Value Problems of Second—order Differential Equations WANG Feng ,ZHANGFang ,WANG Xin (1.Department of Information Science,Jiangsu Polytechnic University,Changzhou,Jiangsu,213164,China; 2.School of Mathematical Science,Xuzhou Normal University,Xuzhou,Jiangsu,221116,China) Abstract:In this paper,a new method of computation of coincidence degree is given by using the theory of cones and applied to investigation on the existence of solutions for nonlinear Picard boundary value problems of second order differential equatioms. Key words:coincidence degree;Fredholm operator;cone;boundary value problem (上接第22页) 参考文献: [1] ze E,Gonzfilez—Olivares E.Dynamics of a predator—prey model[J].SIAM J Appl Math,1999,59:1867. [2]Peng Rui,Wang Mingxin.Global stability of the equilibrium of a diffusive Holling—Tanner prey—predator model[J]. Appl Math Letters,2007,20(6):664. [33刘勇,林支桂.具有扩敞的二种群捕食一被捕食模型中的共存解[J].徐州师范大学学报:自然科学版,2005,23(1): 16. [43吴强,高静.一类具有Michaelis—Menten响应函数的三种群捕食模型的定性分析[J].徐州师范大学学报:自然科学 版,2006,24(4):27. [5]Wang Mingxin.Non—constant positive steady states of the Sel’kov model[J].J Differential Equations,2003,190(2): 600. [63 Hsu S B,Huang T W.Global stability for a class of predator—prey systems[J].SIAM J Appl Math,1995,35:763. Large Qualitative Analysis for a Ratio—dependent Holling—Tanner Predator-Prey Model JIANG Le .WU Qiang .LUXiao—guang (1.Huaihai Institute of Technology,Lianyungang,Jiangsu,222005,China; 2.School of Mathematical Science,Xuzhou Normal University,Xuzhou,Jiangsu,221116,China) Abstract:In this paper,a ratio—dependent Holling—Tanner predator—prey model is studied.The dis— sipation,persistence and global stability of the positive constant solution are given out.The diffusion system is discussed by using the e—Young and Poincar6 inequalities.and the non—existence of non—con— stant positive solution is deduced when the diffusion parameters are large enough. Key words:functional response;dissipation;persistence;global stability
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