Hindawi Publishing Corporation Journal of Applied Mathematics Volume 2013, Article ID 679316, 12 pages http://dx.doi.org/10.1155/2013/679316 Research Article Multiple Positive Solutions to Multipoint Boundary Value Problem for a System of Second-Order Nonlinear Semipositone Differential Equations on Time Scales Gang Wu,1,2 Longsuo Li,1 Xinrong Cong,1 and Xiufeng Miao1 1 2 Department of Mathematics, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China Basic Science, Harbin University of Commerce, Harbin, Heilongjiang 150076, China Correspondence should be addressed to Longsuo Li; lilongsuo6982@126.com Received 13 November 2012; Revised 31 January 2013; Accepted 31 January 2013 Academic Editor: Naseer Shahzad Copyright © 2013 Gang Wu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We study a system of second-order dynamic equations on time scales (π1 π’1∇ )Δ (π‘) − π1 (π‘)π’1 (π‘) + ππ1 (π‘, π’1 (π‘), π’2 (π‘)) = 0, π‘ ∈ (π‘1 , π‘π ), (π2 π’2∇ )Δ (π‘) − π2 (π‘)π’2 (π‘) + ππ2 (π‘, π’1 (π‘), π’2 (π‘)) = 0, satisfying four kinds of different multipoint boundary value conditions, ππ is continuous and semipositone. We derive an interval of π such that any π lying in this interval, the semipositone coupled boundary value problem has multiple positive solutions. The arguments are based upon fixed-point theorems in a cone. π−2 1. Introduction πΌ1 π’1 (π‘1 ) − π½1 π1 (π‘1 ) π’1∇ (π‘1 ) = ∑ ππ π’1 (π‘π ) , In this paper, we consider the following dynamic equations on time scales: π=2 πΎ1 π’1 (π‘π ) + πΏ1 π1 (π‘π ) π’1∇ (π‘π ) = 0, Δ (π1 π’1∇ ) (π‘) − π1 (π‘) π’1 (π‘) + ππ1 (π‘, π’1 (π‘) , π’2 (π‘)) = 0, π‘ ∈ (π‘1 , π‘π ) , π > 0, π−2 πΌ2 π’2 (π‘1 ) − π½2 π2 (π‘1 ) π’2∇ (π‘1 ) = ∑ ππ π’2 (π‘π ) , πΎ2 π’2 (π‘π ) + πΏ2 π1 (π‘π ) π’2∇ (π‘π ) = 0, Δ πΌ1 π’1 (π‘1 ) − π½1 π1 (π‘1 ) π’1∇ (π‘1 ) = 0, satisfying one of the boundary value conditions π−2 πΎ1 π’1 (π‘π ) + πΏ1 π1 (π‘π ) π’1∇ (π‘π ) = ∑ ππ π’1 (π‘π ) , πΌ1 π’1 (π‘1 ) − π½1 π1 (π‘1 ) π’1∇ (π‘1 ) = 0, πΎ1 π’1 (π‘π ) + π=2 (1) (π2 π’2∇ ) (π‘) − π2 (π‘) π’2 (π‘) + ππ2 (π‘, π’1 (π‘) , π’2 (π‘)) = 0, πΏ1 π1 (π‘π ) π’1∇ π=2 π−2 (π‘π ) = ∑ ππ π’1 (π‘π ) , π=2 πΌ2 π’2 (π‘1 ) − π½2 π2 (π‘1 ) π’2∇ (π‘1 ) = 0, π−2 πΎ2 π’2 (π‘π ) + πΏ2 π1 (π‘π ) π’2∇ (π‘π ) = ∑ ππ π’2 (π‘π ) , π=2 (3) πΌ2 π’2 (π‘1 ) − (2) π½2 π2 (π‘1 ) π’2∇ π−2 (π‘1 ) = ∑ ππ π’2 (π‘π ) , π=2 πΎ2 π’2 (π‘π ) + πΏ2 π1 (π‘π ) π’2∇ (π‘π ) = 0, π−2 πΌ1 π’1 (π‘1 ) − π½1 π1 (π‘1 ) π’1∇ (π‘1 ) = ∑ ππ π’1 (π‘π ) , π=2 (4) 2 Journal of Applied Mathematics πΎ1 π’1 (π‘π ) + πΏ1 π1 (π‘π ) π’1∇ (π‘π ) = 0, existence of multiple positive solutions for the boundary value problem on time scales. In 2009, Topal and Yantir [3] studied the second-order nonlinear π-point boundary value problems πΌ2 π’2 (π‘1 ) − π½2 π2 (π‘1 ) π’2∇ (π‘1 ) = 0, π−2 πΎ2 π’2 (π‘π ) + πΏ2 π1 (π‘π ) π’2∇ (π‘π ) = ∑ ππ π’2 (π‘π ) , π=2 (5) π’Δ∇ (π‘) + π (π‘) π’Δ (π‘) + π (π‘) π’ (π‘) + ππ (π‘) π (π‘, π’ (π‘)) = 0, where ππ , ππ : [π‘1 , π‘π ] σ³¨→ (0, +∞) Δ with ππ ∈ πΆ [π‘1 , π‘π ) , π’ (π (0)) = 0, ππ ∈ πΆ [π‘1 , π‘π ] for π = 1, 2; πΌπ , π½π , πΎπ , πΏπ ∈ [0, +∞) with πΌπ πΎπ +πΌπ πΏπ +π½π πΎπ > 0 π’ (π (1)) = ∑ πΌπ π’ (ππ ) , (6) and ππ is continuously and nonegative functionsquad, ππ , ππ ∈ [0, +∞) for π ∈ {1, 2, . . . , π}; the points π‘π ∈ Tπ π for π ∈ {1, 2, . . . , π} with π‘1 < π‘2 < ⋅ ⋅ ⋅ < π‘π . In the past few years, the boundary value problems of dynamic equations on time scales have been studied by many authors (see [1–19] and references). Recently, multipoint boundary value problems on time scale have been studied, for instance, see [1–12]. In 2006, Anderson and Ma [1] studied the second-order multiple time-scale eigenvalue problem: Δ (ππ¦∇ ) (π‘) − π (π‘) π¦ (π‘) + πβ (π‘) π (π¦) = 0, π‘ ∈ (π‘1 , π‘π ) , π > 0, π−2 (9) π−2 π=1 for π = 1, 2, πΌπ¦ (π‘1 ) − π½π (π‘1 ) π¦∇ (π‘1 ) = ∑ ππ π¦ (π‘π ) , π‘ ∈ (0, 1)T , (7) π=2 where πΌπ ≥ 0, 0 < ππ < ππ+1 < 1; for all π = 1, 2, . . . , π − 2; π ∈ πΆ([0, 1], [0, +∞)), π ∈ πΆ([0, 1], (−∞, 0]), π, π are continuously and nonegative functions. The authors deal with determining the value of π, and the existences of multiple positive solutions of the equation are obtained. In 2010, Yuan and Liu [4] also study the second-order π-point boundary value problems; Yuan and Liu shows the existence of multiple positive solutions if π is semipositone and superlinear. Motivated by the above results mentioned, we study the second-order nonlinear π-point boundary value problem (1) with boundary condition (π), and nonlinear term may be singularity and semipositone. In this paper, the nonlinear term ππ of (1) is suit to and semipositone and the superlinear case, we shall prove our two existence results for the problem (1) with (π) by using a nonlinear alternative of Leray-Schauder type and Krasnosel’skii fixed-point theorem. This paper is organized as follows. In Section 2, we start with some preliminary lemmas. In Section 3, we give the main result which state the sufficient conditions for (1) with π-point boundary value (π) to have existence of positive solutions (π = 2, . . . , 5). π−2 πΎπ¦ (π‘π ) + πΏπ (π‘π ) π¦∇ (π‘π ) = ∑ ππ π¦ (π‘π ) , 2. Preliminaries π=2 where the functions π : [0, +∞) → [0, +∞) and β : [π‘1 , π‘π ] → [0, +∞) are continuous. The authors discuss conditions for the existence of at least one positive solution to the second-order Sturm-Liouville-type multiple eigenvalue problem on time scales. In 2009, Feng et al. [2] studied Δ (ππ¦∇ ) (π‘) − π (π‘) π¦ (π‘) = π (π‘, π¦) , π‘ ∈ (π‘1 , π‘π ) , ∇ π−2 πΌπ¦ (π‘1 ) − π½π (π‘1 ) π¦ (π‘1 ) = ∑ ππ π¦ (π‘π ) , In this section, we state the preliminary information that we need to prove the main results. In this paper, for our constructions, we shall consider the Banach space πΈ = πΆ[π(π‘1 ), π‘π ] equipped with standard norm βπ₯β = maxπ(π‘1 )≤π‘≤π‘π |π₯(π‘)|, π₯ ∈ πΈ; for each (π₯, π¦) ∈ πΈ × πΈ, we write ||(π₯, π¦)||1 = ||π₯||+||π¦||. Clearly, (πΈ×πΈ, ||⋅||1 ) is a Banach space. Denote by ππ1 and ππ2 (π = 1, 2), the solutions of the equation Δ (8) (ππ π’π∇ ) (π‘) − ππ (π‘) π’π (π‘) = 0, π‘ ∈ [π‘1 , π‘π ) , (10) π=2 ∇ π−2 under the initial conditions πΎπ¦ (π‘π ) + πΏπ (π‘π ) π¦ (π‘π ) = ∑ ππ π¦ (π‘π ) , π=2 ∑ππ=1 ππ (π‘)π¦Vπ , ππ where the functions π(π‘, π¦) = ∈ πΆ([π‘1 , π‘π ], [0, ∞)), Vπ ∈ [0, ∞), π = 1, 2, . . . , π. This paper shows the π’π (π‘1 ) = π½π , ππ (π‘1 ) π’π∇ (π‘1 ) = πΌπ , π’π (π‘π ) = πΏπ , ππ (π‘π ) π’π∇ (π‘π ) = −πΎπ , (11) Journal of Applied Mathematics 3 respectively. So that ππ1 and ππ2 (π = 1, 2) satisfy ∇ Δ (ππ ππ1 ) π»14 (π‘, π ) = πΊ1 (π‘, π ) + (π‘) − ππ (π‘) ππ1 (π‘) = 0, π‘ ∈ [π‘1 , π‘π ) , ππ1 (π‘1 ) = π½π , ∇ ππ (π‘1 ) ππ1 (π‘1 ) = πΌπ , (12) Δ 1 π−1 1 π−1 ∑ ππ πΊ1 (π‘π , π ) π11 (π‘) π1 − ∑π−1 π=2 ππ π11 (π‘π ) π=2 π»24 (π‘, π ) = πΊ2 (π‘, π ) + ππ2 (π‘π ) = πΏπ , ∑ ππ πΊ2 (π‘π , π ) π22 (π‘) π2 − ∑π−1 π=2 ππ π22 (π‘π ) π=2 = π»23 (π‘, π ) , ∇ ππ (π‘π ) ππ2 (π‘π ) = −πΎπ , π»15 (π‘, π ) ∇ respectively. For π = 1, 2, set ππ = πΌπ ππ2 (π‘1 ) − π½π ππ (π‘1 )ππ2 (π‘1 ) = ∇ πΎπ ππ1 (π‘π ) + πΏπ ππ (π‘π )ππ1 (π‘π ), the Green’s function of the corresponding homogeneous boundary value problem is defined by = πΊ1 (π‘, π ) + π1 − ∑π−1 π=2 ππ π12 ∑ ππ πΊ1 (π‘π , π ) π12 (π‘) (π‘π ) π=2 = π»13 (π‘, π ) , π»25 (π‘, π ) πΊπ (π‘, π ) = π−1 = π»12 (π‘, π ) , ∇ (ππ ππ2 ) (π‘) − ππ (π‘) ππ2 (π‘) = 0, π‘ ∈ [π‘1 , π‘π ) , 1 1 ππ2 (π‘) ππ1 (π ) , { ππ ππ1 (π‘) ππ2 (π ) , π (π‘1 ) ≤ π ≤ π‘ ≤ π‘π , π (π‘1 ) ≤ π‘ ≤ π ≤ π‘π , for π = 1, 2. (13) = πΊ2 (π‘, π ) + 1 π−1 ∑ ππ πΊ2 (π‘π , π ) π21 (π‘) π2 − ∑π−1 π=2 ππ π21 (π‘π ) π=2 = π»22 (π‘, π ) . (16) From Lemmas 3.1 and 3.3 in [1], we have the following lemma. Lemma 1. If ππ =ΜΈ 0, (π’1 , π’2 ) is a solution of (1) with boundary value condition (π) if only and if π‘π π’1 (π‘) = π ∫ π»1π (π‘, π ) π1 (π , π’1 (π ) , π’2 (π )) Δπ , π‘1 (14) For the rest of the paper, we need the following assumption: π−1 π−1 π=2 π=2 0 < ∑ ππ ππ1 (π‘π ) , ∑ ππ ππ2 (π‘π ) < ππ , for π = 1, 2. (C) π‘ ∈ [π (π‘1 ) , π‘π ] , π‘π π’2 (π‘) = π ∫ π»2π (π‘, π ) π2 (π , π’1 (π ) , π’2 (π )) Δπ , π‘1 (15) From ππ1 is nondecreasing on [π(π‘1 ), π‘π ], ππ2 is nonincreasing on [π(π‘1 ), π‘π ] (see [2, Proposition 2.3]), it is easy to verify the following inequalities: where π = 2, . . . , 5, and ππ πΊπ (π‘, π ) ≤ ππ1 (π‘) ππ2 (π‘) , π»π2 (π‘, π ) = πΊπ (π‘, π ) + ππ πΊπ (π‘, π ) ≤ ππ1 (π ) ππ2 (π ) , 1 ππ − ∑π−1 π=2 ππ ππ1 π−1 ∑ ππ πΊπ (π‘π , π ) ππ1 (π‘) , (π‘π ) π=2 (π = 1, 2) , π»π3 (π‘, π ) = πΊπ (π‘, π ) + 1 π−1 ∑ ππ πΊπ (π‘π , π ) ππ2 (π‘) , ππ − ∑π−1 π=2 ππ ππ2 (π‘π ) π=2 (π = 1, 2) , (17) 1 ππ πΊπ (π‘, π ) ≥ σ΅©σ΅© σ΅©σ΅© σ΅©σ΅© σ΅©σ΅© ππ1 (π‘) ππ2 (π‘) ππ1 (π ) ππ2 (π ) . σ΅©σ΅©ππ1 σ΅©σ΅© σ΅©σ΅©ππ2 σ΅©σ΅© Lemma 2. The Green’s function πΊπ (π‘, π ) has properties πΊπ (π‘, π ) ≤ πΊπ (π‘, π‘) , ππ σ΅©σ΅© σ΅©σ΅© σ΅©σ΅© σ΅©σ΅© πΊπ (π‘, π‘) πΊπ (π , π ) ≤ πΊπ (π‘, π ) ≤ πΊπ (π , π ) . σ΅©σ΅©ππ1 σ΅©σ΅© σ΅©σ΅©ππ2 σ΅©σ΅© (18) 4 Journal of Applied Mathematics Lemma 3. For π»ππ (π‘, π ), π = 2, . . . , 5 and π = 1, 2, one has the conclusions π»ππ (π‘, π ) ≤ πΆ∗ πΊπ (π , π ) and π∗ ππ1 (π‘) πΊπ (π , π ) ≤ π»π2 (π‘, π ) ≤ πΆ∗ ππ1 (π‘) , (π = 1, 2) , π∗ ππ2 (π‘) πΊπ (π , π ) ≤ π»π3 (π‘, π ) ≤ πΆ∗ ππ2 (π‘) , (π = 1, 2) , ∗ π∗ πππ (π‘) πΊ1 (π , π ) ≤ π»π4 (π‘, π ) ≤ πΆ πππ (π‘) , π−1 1 ππ − ≤ ∑π−1 π=2 ππ ππ2 ∑ ππ πΊπ (π‘π , π ) ππ2 (π‘) (π‘π ) π=2 π−1 1 σ΅© σ΅© ∑ ππ πΊπ (π , π ) σ΅©σ΅©σ΅©ππ2 σ΅©σ΅©σ΅© , ππ − ∑π−1 π π (π‘ ) π=2 π π2 π π=2 (21) (π = 1, 2) , (19) π∗ π12 (π‘) πΊ1 (π , π ) ≤ π»15 (π‘, π ) ≤ πΆ∗ π12 (π‘) , we have π∗ π21 (π‘) πΊ1 (π , π ) ≤ π»25 (π‘, π ) ≤ πΆ∗ π21 (π‘) , π»ππ (π‘, π ) ≤ πΆ1 πΊπ (π , π ) ≤ πΆ∗ πΊπ (π , π ) . ∗ where πΆ = πΆ1 + πΆ2 and For π = 2 or 3, we have σ΅©σ΅© σ΅©σ΅© π−1 { σ΅©σ΅©ππ1 σ΅©σ΅© πΆ1 = max {1 + ∑ ππ π−1 π=1,2 ππ − ∑π=2 ππ ππ1 (π‘π ) π=1 { + σ΅© σ΅©σ΅© σ΅©π (π‘)σ΅©σ΅© 1 π»π2 (π‘, π ) ≤ σ΅© π2 σ΅© ππ1 (π‘) + π−1 ππ ππ − ∑π=2 ππ ππ1 (π‘π ) σ΅©σ΅© σ΅©σ΅© π−1 } σ΅©σ΅©ππ2 σ΅©σ΅© ∑ ππ } , ππ − ∑π−1 π=2 ππ ππ2 (π‘π ) π=2 } π−1 × ∑ ππ πΊπ (π‘π , π‘π ) ππ1 (π‘) π=2 { σ΅©σ΅©σ΅©π σ΅©σ΅©σ΅© + σ΅©σ΅©σ΅©π σ΅©σ΅©σ΅© 1 πΆ2 = max { σ΅© π1 σ΅© σ΅© π2 σ΅© + π−1 π=1,2 ππ ππ − ∑π=2 ππ ππ1 (π‘π ) { π−1 × ∑ ππ πΊπ (π‘π , π‘π ) + π=2 ≤ πΆ∗ ππ1 (π‘) , σ΅© σ΅©σ΅© σ΅©π (π‘)σ΅©σ΅© 1 π»π3 (π‘, π ) ≤ σ΅© π1 σ΅© ππ2 (π‘) + π−1 ππ ππ − ∑π=2 ππ ππ2 (π‘π ) 1 ππ − ∑π−1 π=2 ππ ππ2 (π‘π ) π−1 } × ∑ ππ πΊ2 (π‘π , π‘π )} , π=2 } { π 1 π∗ = min { σ΅©σ΅© σ΅©σ΅© σ΅©σ΅©π σ΅©σ΅© σ΅©σ΅©ππ1 σ΅©σ΅© σ΅©σ΅©ππ2 σ΅©σ΅© ππ − ∑π−1 π=2 ππ ππ1 (π‘π ) { π−1 × ∑ ππ πΊπ (π‘π , π‘π ) ππ2 (π‘) π=2 (20) ≤ πΆ∗ ππ2 (π‘) , π»π2 (π‘, π ) ≥ π=2 π=2 ≥ 1 ππ − ≤ ∑π−1 π=2 ππ ππ1 1 ππ − ∑π−1 π=2 ππ ππ1 (π‘π ) π−1 π × ∑ ππ σ΅©σ΅© σ΅©σ΅© σ΅©σ΅©π σ΅©σ΅© πΊπ (π‘π , π‘π ) πΊπ (π , π ) ππ1 (π‘) σ΅©π1 σ΅©σ΅© σ΅©σ΅©π2 σ΅©σ΅© π=2 σ΅© π−1 Proof. From Lemma 2 and (π‘π ) × ∑ ππ πΊπ (π‘π , π ) ππ1 (π‘) × ∑ ππ πΊπ (π‘π , π‘π ) , } × ∑ ππ πΊπ (π‘π , π‘π ) ; π = 1, 2} . π=2 } ππ − π−1 π−1 ππ 1 σ΅©σ΅© σ΅©σ΅© σ΅©σ΅© σ΅©σ΅© σ΅©σ΅©ππ1 σ΅©σ΅© σ΅©σ΅©ππ2 σ΅©σ΅© ππ − ∑π−1 π=2 ππ ππ2 (π‘π ) 1 ∑π−1 π=2 ππ ππ1 ≥ π∗ ππ1 (π‘) πΊπ (π , π ) , π»π3 (π‘, π ) ≥ π−1 1 ππ − ∑π−1 π=2 ππ ππ2 (π‘π ) π−1 ∑ ππ πΊπ (π‘π , π ) ππ1 (π‘) × ∑ ππ πΊπ (π‘π , π ) ππ2 (π‘) (π‘π ) π=2 π=2 π−1 1 σ΅© σ΅© ∑ ππ πΊπ (π , π ) σ΅©σ΅©σ΅©ππ1 σ΅©σ΅©σ΅© , ππ − ∑π−1 π π (π‘ ) π=2 π π1 π π=2 ≥ 1 ππ − ∑π−1 π=2 ππ ππ1 (π‘π ) (22) Journal of Applied Mathematics 5 π−1 π × ∑ ππ σ΅©σ΅© σ΅©σ΅© σ΅©σ΅©π σ΅©σ΅© πΊπ (π‘π , π‘π ) πΊπ (π , π ) ππ2 (π‘) π σ΅© σ΅© σ΅©π2 σ΅©σ΅© π=2 σ΅© 1 σ΅© σ΅© ⊂ (π‘1 , π‘π ) such that (H3 ) There exists [π1 , π2 ] limπ’1 +π’2 ↑+∞ minπ‘∈[π1 ,π2 ] (ππ (π‘, π’1 , π’2 )/(π’1 + π’2 )) = +∞ (π = 1, 2). ≥ π∗ ππ2 (π‘) πΊπ (π , π ) . (23) So, we have π∗ ππ1 (π‘) πΊπ (π , π ) ≤ π»π2 (π‘, π ) ≤ πΆ∗ ππ1 (π‘) , (π = 1, 2) , π∗ ππ2 (π‘) πΊπ (π , π ) ≤ π»π3 (π‘, π ) ≤ πΆ∗ ππ2 (π‘) , (π = 1, 2) . (24) Since π»14 (π‘, π ) = π»12 (π‘, π ), π»24 (π‘, π ) = π»23 (π‘, π ), π»15 (π‘, π ) = π»13 (π‘, π ), π»25 (π‘, π ) = π»22 (π‘, π ), then we also have π‘ π‘ (H4 ) ∫π‘ π πΊπ (π , π )π(π )∇π < +∞ and ∫π‘ π πΊπ (π , π )ππ (π , π§1 , 1 1 π§2 )∇π < +∞ for any π§π ∈ [0, π], π > 0 is any constant (π = 1, 2). In fact, we only consider the system Δ ∗ (π1 π₯1∇ ) (π‘) − π1 (π‘) π₯1 (π‘) + π (π1 (π‘, [π₯1 (π‘) − V1π (π‘)] , π∗ π11 (π‘) πΊ1 (π , π ) ≤ π»14 (π‘, π ) = π»12 (π‘, π ) ≤ πΆ∗ π11 (π‘) , π∗ π22 (π‘) πΊ1 (π , π ) ≤ π»24 (π‘, π ) = π»23 (π‘, π ) ≤ πΆ∗ π22 (π‘) , π∗ π12 (π‘) πΊ1 (π , π ) ≤ π»15 (π‘, π ) = π»13 (π‘, π ) ≤ πΆ∗ π12 (π‘) , ∗ [π₯2 (π‘) − V2π (π‘)] ) (25) +π (π‘) ) = 0, π∗ π21 (π‘) πΊ1 (π , π ) ≤ π»25 (π‘, π ) = π»22 (π‘, π ) ≤ πΆ∗ π21 (π‘) . The proof is complete. π > 0, Δ The following theorems will play a major role in our next analysis. ∗ (π2 π₯2∇ ) (π‘) − π2 (π‘) π₯2 (π‘) + π (π2 (π‘, [π₯1 (π‘) − V1π (π‘)] , ∗ [π₯2 (π‘) − V2π (π‘)] ) Theorem 4 (see [20]). Let π be a Banach space, and Ω ⊂ π closed and convex. Assume π is a relatively open subset of Ω with 0 ∈ π, and let π : π → Ω be a compact, continuous map. Then either +π (π‘) ) = 0, π > 0, (1) π has a fixed point in π, or (26) (2) there exists π’ ∈ ππ and ] ∈ (0, 1), with π’ = ]ππ’. Theorem 5 (see [21]). Let π be a Banach space, and let π ⊂ π be a cone in π. Let Ω1 , Ω2 be bounded open subsets of π with 0 ∈ Ω1 ⊂ Ω1 ⊂ Ω2 , and let π : π → π be a completely continuous operator such that, either (1) βππ€β ≤ βπ€β, π€ ∈ π ∩ πΩ1 , βππ€β ≥ βπ€β, π€ ∈ π ∩ πΩ2 , or (2) βππ€β ≥ βπ€β, π€ ∈ π ∩ πΩ1 , βππ€β ≤ βπ€β, π€ ∈ π ∩ πΩ2 . Then π has a fixed point in π ∩ Ω2 \ Ω1 . πΌ1 π₯1 (π‘1 ) − π½1 π1 (π‘1 ) π₯1∇ (π‘1 ) = 0, π−2 πΎ1 π₯1 (π‘π ) + πΏ1 π1 (π‘π ) π₯1∇ (π‘π ) = ∑ ππ π₯1 (ππ ) , π=2 πΌ2 π₯2 (π‘1 ) − π½2 π2 (π‘1 ) π₯2∇ (π‘1 ) = 0, π−2 πΎ2 π₯2 (π‘π ) + πΏ2 π1 (π‘π ) π₯2∇ (π‘π ) = ∑ ππ π₯2 (ππ ) , 3. Main Results π=2 π−2 We make the following assumptions: (H1 ) ππ (π‘, π’1 , π’2 ) ∈ πΆ([π‘1 , π‘π ] × [0, +∞)2 , (−∞, +∞)), moreover there exists a function π(π‘) ∈ πΏ1 ([π‘1 , π‘π ], (0, +∞)) such that ππ (π‘, π’1 , π’2 ) ≥ −π(π‘), for any π‘ ∈ (π‘1 , π‘π ), π’π ∈ [0, +∞), π = 1, 2. (H∗1 ) with one of the boundary value conditions 2 ππ (π‘, π’1 , π’2 ) ∈ πΆ((π‘1 , π‘π ) × [0, +∞) , (−∞, +∞)) may be singular at π‘ = π‘1 , π‘π ; moreover, there exists a function π(π‘) ∈ πΏ1 ((π‘1 , π‘π ), (0, +∞)) such that ππ (π‘, π’1 , π’2 ) ≥ −π(π‘), for any π‘ ∈ (π‘1 , π‘π ), π’π ∈ [0, +∞). (H2 ) ππ (π‘, 0, 0) > 0, for π‘ ∈ [π‘1 , π‘π ] (π = 1, 2). πΌ1 π₯1 (π‘1 ) − π½1 π1 (π‘1 ) π₯1∇ (π‘1 ) = ∑ ππ π₯1 (ππ ) , π=2 πΎ1 π₯1 (π‘π ) + πΏ1 π1 (π‘π ) π₯1∇ (π‘π ) = 0, π−2 πΌ2 π₯2 (π‘1 ) − π½2 π2 (π‘1 ) π₯2∇ (π‘1 ) = ∑ ππ π₯2 (ππ ) , π=2 πΎ2 π₯2 (π‘π ) + πΏ2 π1 (π‘π ) π₯2∇ (π‘π ) = 0, πΌ1 π₯1 (π‘1 )−π½1 π1 (π‘1 ) π₯1∇ (π‘1 ) = 0, 6 Journal of Applied Mathematics π−2 π−2 πΎ1 π₯1 (π‘π ) + πΏ1 π1 (π‘π ) π₯1∇ (π‘π ) = ∑ ππ π₯1 (ππ ) , πΌ1 V1 (π‘1 ) − π½1 π1 (π‘1 ) V1∇ (π‘1 ) = ∑ ππ V1 (ππ ) , π=2 π=2 πΎ1 V1 (π‘π ) + πΏ1 π1 (π‘π ) V1∇ (π‘π ) = 0, π−2 πΌ2 π₯2 (π‘1 ) − π½2 π2 (π‘1 ) π₯2∇ (π‘1 ) = ∑ ππ π₯2 (ππ ) , π=2 π−2 πΌ2 V2 (π‘1 ) − π½2 π2 (π‘1 ) V2∇ (π‘1 ) = ∑ ππ V2 (ππ ) , πΎ2 π₯2 (π‘π ) + πΏ2 π1 (π‘π ) π₯2∇ (π‘π ) = 0, π=2 π−2 πΎ2 V2 (π‘π ) + πΏ2 π1 (π‘π ) V2∇ (π‘π ) = 0, π=2 πΌ1 V1 (π‘1 ) − π½1 π1 (π‘1 ) V1∇ (π‘1 ) = 0, πΌ1 π₯1 (π‘1 ) − π½1 π1 (π‘1 ) π₯1∇ (π‘1 ) = ∑ ππ π₯1 (ππ ) , πΎ1 π₯1 (π‘π ) + πΏ1 π1 (π‘π ) π₯1∇ (π‘π ) = 0, πΌ2 π₯2 (π‘1 ) − π½2 π2 (π‘1 ) π₯2∇ π−2 πΎ1 V1 (π‘π ) + πΏ1 π1 (π‘π ) V1∇ (π‘π ) = ∑ ππ V1 (ππ ) , (π‘1 ) = 0, π=2 π−2 π−2 πΎ2 π₯2 (π‘π ) + πΏ2 π1 (π‘π ) π₯2∇ (π‘π ) = ∑ ππ π₯2 (ππ ) , πΌ2 V2 (π‘1 ) − π½2 π2 (π‘1 ) V2∇ (π‘1 ) = ∑ ππ V2 (ππ ) , π=2 π=2 (27) πΎ2 V2 (π‘π ) + πΏ2 π1 (π‘π ) V2∇ (π‘π ) = 0, π−2 πΌ1 V1 (π‘1 ) − π½1 π1 (π‘1 ) π₯1∇ (π‘1 ) = ∑ ππ V1 (ππ ) , where π=2 πΎ1 V1 (π‘π ) + πΏ1 π1 (π‘π ) π₯1∇ (π‘π ) = 0, π¦ (π‘) , π¦ (π‘) ≥ 0, π¦(π‘)∗ = { 0, π¦ (π‘) < 0, πΌ2 V2 (π‘1 ) − π½2 π2 (π‘1 ) π₯2∇ (π‘1 ) = 0, (28) π−2 πΎ2 V2 (π‘π ) + πΏ2 π1 (π‘π ) π₯2∇ (π‘π ) = ∑ ππ V2 (ππ ) . π=2 π‘ and Vππ (π‘) = π ∫π‘ π π»ππ (π‘, π )π(π )Δπ . For π = 2, . . . , 5, from 1 Lemma 1, (V1π (π‘), V2π (π‘)) is the solution of the equation Δ (π1 V1∇ ) (π‘) − π1 (π‘) V1 (π‘) + ππ (π‘) = 0, π > 0, π‘1 < π‘ < π‘π , Δ (π2 V2∇ ) (π‘) − π2 (π‘) V2 (π‘) + ππ (π‘) = 0, (29) π > 0, (30) We will show that there exists a solution (π₯1π , π₯2π ) to the boundary value problem (π) of the system (26) with π₯ππ (π‘) ≥ Vππ (π‘), π‘ ∈ [π(π‘1 ), π‘π ]. If this is true, then π’ππ (π‘) = π₯ππ (π‘) − Vππ (π‘) is a nonnegative solution (positive on (π(π‘1 ), π‘π )) of the system (1) with the boundary value problem (π), (where π = 1, 2; π = 2, . . . , 5, π = π + 11). Since for any π‘ ∈ (π‘1 , π‘π ), from Δ ∇ ∇ ) (π‘) − ππ (π‘) π₯ππ (ππ π₯ππ (π‘) ∇ Δ ∇ = (ππ (π’ππ + Vππ ) ) (π‘) − ππ (π‘) (π’ππ + Vππ ) (π‘) respectively, satisfying the following boundary value conditions: ∗ ∗ = −π (ππ (π‘, [π₯1π (π‘)−V1π (π‘)] , [π₯2π (π‘)−V2π (π‘)] )+π (π‘)) = −π (ππ (π‘, π’1π (π‘) , π’2π (π‘)) + π (π‘)) , (31) πΌ1 V1 (π‘1 ) − π½1 π1 (π‘1 ) V1∇ (π‘1 ) = 0, π−2 πΎ1 V1 (π‘π ) + πΏ1 π1 (π‘π ) V1∇ (π‘π ) = ∑ ππ V1 (ππ ) , π=2 πΌ2 V2 (π‘1 ) − π½2 π2 (π‘1 ) V2∇ (π‘1 ) = 0, π−2 πΎ2 V2 (π‘π ) + πΏ2 π1 (π‘π ) V2∇ (π‘π ) = ∑ ππ V2 (ππ ) , π=2 we have Δ ∇ ) (π‘) − ππ (π‘) π’ππ (π‘) = −πππ (π‘, π’1π (π‘) , π’2π (π‘)) . (32) (ππ π’ππ As a result, we will concentrate our study on (26) with the boundary value problem (π). Journal of Applied Mathematics 7 Employing Lemma 1, we note that (π₯1π (π‘), π₯2π (π‘)) is a solution of the system (26) with boundary value (π) if and only if π‘π For π = 2, . . . , 5, from (35) and Lemma 3, we have ππ (π₯1π , π₯2π )(π‘) ≥ 0 on [0, 1], for (π₯1π , π₯2π ) ∈ πππ × πππ , we have πππ (π₯1π , π₯2π ) (π‘) ∗ π₯1π (π‘) = π ∫ π»1π (π‘, π ) (π1 (π , [π₯1π (π ) − V1π (π )] , π‘π π‘1 ∗ = π ∫ π»ππ (π‘, π ) (ππ (π , [π₯1π (π ) − V1π (π )] , π‘1 ∗ [π₯2π (π ) − V2π (π )] ) ∗ [π₯2π (π ) − V2π (π )] ) +π (π ) ) Δπ , (37) +π (π )) Δπ π‘ ∈ [π (π‘1 ) , π‘π ] , (33) π‘π ≤ πΆ∗ π ∗ π₯2π (π‘) = π ∫ π»2π (π‘, π ) (π2 (π , [π₯1π (π ) − V1π (π )] , ×∫ π‘1 π(π‘π ) π(π‘1 ) ∗ [π₯2π (π ) − V2π (π )] ) πΊπ (π , π ) (ππ (π , [π₯ (π )−V (π )]∗ ) + π (π )) Δπ , π(π‘ ) then βπππ (π₯1π , π₯2π )β ≤ πΆ∗ π ∫π(π‘ π) πΊπ (π , π )(π(π‘, [π₯(π‘) − V(π‘)]∗ ) + 1 π(π‘))Δπ . On the other hand, when π = 2, we have +π (π ) ) Δπ . We define a cone πππ (π, π = 1, 2) by ππ2 (π₯1π , π₯2π ) (π‘) πππ = {π₯ ∈ πΈ | π₯ (π‘) ≥ π∗ π (π‘) βπ₯β , π‘ ∈ [π (π‘1 ) , π‘π ]} . πΆ∗ ππ (34) π‘π ∗ = π ∫ π»π2 (π‘, π ) (ππ (π , [π₯1π (π ) − V1π (π )] , π‘1 ∗ [π₯2π (π ) − V2π (π )] ) + π (π )) Δπ It is clearly that πππ × πππ is a cone of πΈ × πΈ, (π, π, π, π = 1, 2). Define the integral operator π2 : π11 × π21 → πΈ × πΈ, π3 : π12 × π22 → πΈ × πΈ, π4 : π12 × π21 → πΈ × πΈ, π5 : π21 × π12 → πΈ × πΈ, by ππ (π₯1π , π₯2π ) = (π1π (π₯1π , π₯2π ) , π2π (π₯1π , π₯2π )) , (π = 2, . . . , 5) , π‘π π‘1 ∗ [π₯2π (π ) − V2π (π )] ) +π (π )) Δπ (35) ≥ π∗ π (π‘) π πΆ∗ π1 ×∫ π(π‘π ) π(π‘1 ) where operators πππ are defined by ≥ π‘π ∗ ≥ π ∫ π∗ ππ1 (π‘) πΊπ (π , π ) (ππ (π , [π₯1π (π )−V1π (π )] , ∗ πΆ∗ πΊπ (π , π ) (ππ (π , [π₯ (π )−V (π )]∗ )+π (π )) Δπ π∗ σ΅© σ΅© π (π‘) σ΅©σ΅©π (π₯ , π₯ )σ΅©σ΅© . πΆ∗ π1 σ΅© π2 1π 2π σ΅© (38) πππ (π₯1π , π₯2π ) (π‘) = π ∫ π»ππ (π‘, π ) (ππ (π , [π₯1π (π ) − V1π (π )] , π‘1 ∗ [π₯2π (π ) − V2π (π )] ) Thus, ππ2 (π11 × π21 ) ⊂ ππ1 . Hence π2 (π11 × π21 ) ⊂ π11 × π21 . When π = 3, we have +π (π ) ) Δπ , ππ3 (π₯1π , π₯2π ) (π‘) π‘ ∈ [π (π‘1 ) , π‘π ] , (36) π‘π ∗ = π ∫ π»π3 (π‘, π ) (ππ (π , [π₯1π (π ) − V1π (π )] , π‘1 where π = 1, 2. Clearly, if (π₯1π , π₯2π ) is a fixed point of ππ , then (π₯1π , π₯2π ) is a solution of system (26) with (π) (π = 2, . . . , 5, π = π + 11). ∗ [π₯2π (π ) − V2π (π )] ) +π (π ) ) Δπ 8 Journal of Applied Mathematics π‘π claim that β(π₯1π , π₯2π )β1 =ΜΈ π 0 . In fact for (π₯1π , π₯2π ) ∈ πππ and β(π₯1π , π₯2π )β1 = π 0 , we have ∗ ≥ π ∫ π∗ ππ2 (π‘) πΊπ (π , π ) (ππ (π , [π₯1π (π )−V1π (π )] , π‘1 ∗ π₯ππ = ]πππ (π₯1π , π₯2π ) [π₯2π (π ) − V2π (π )] ) π‘π +π (π )) Δπ ≥ π(π‘π ) π(π‘1 ) ≥ π‘1 π∗ π (π‘) π πΆ∗ π2 ×∫ ∗ ≤ π ∫ π»ππ (π‘, π ) (ππ (π , [π₯1π (π ) − V1π (π )] , ∗ [π₯2π (π ) − V2π (π )] ) + π (π )) Δπ πΆ∗ πΊπ (π , π ) (ππ (π , [π₯ (π )−V (π )]∗ )+π (π )) Δπ π‘π π‘1 π∗ σ΅© σ΅© π (π‘) σ΅©σ΅©π (π₯ , π₯ )σ΅©σ΅© . πΆ∗ π2 σ΅© π3 1π 2π σ΅© ∗ [π₯2π (π ) − V2π (π )] ) + π (π )) Δπ (39) Thus, ππ3 (π12 × π22 ) ⊂ ππ2 . Hence π3 (π12 × π22 ) ⊂ π12 × π22 . Similarly discussion, we also have π4 (π12 ×π21 ) ⊂ π12 ×π21 , π5 (π21 × π12 ) ⊂ π21 × π12 . In addition, standard arguments show that ππ is a completely continuous operator. For simplicity, we adopt the notation: π14 = π25 := π12 and π24 = π15 := π21 , then, we can write ππ (π1(π−1) × π2(π−1) ) ⊂ π1(π−1) × π2(π−1) , that is, πππ (π1(π−1) × π2(π−1) ) ⊂ ππ(π−1) , (π = 1, 2, π = 2, . . . , 5). Theorem 6. Suppose that (H1 )-(H2 ) hold. Then there exists a constant π > 0 such that, for any 0 < π ≤ π, (1) with boundary value condition (π) has at least one positive solution (π = 2, . . . , 5). Proof. Fix πΏ ∈ (0, 1) and π (π = 2, . . . , 5). From (H2 ) let 0 < π < 1 be such that ππ (π‘, π§1 , π§2 ) ≥ πΏππ (π‘, 0, 0) , for π‘1 ≤ π‘ ≤ π‘π , 0 ≤ π§π ≤ π, π = 1, 2. (40) Let π(π) = maxπ‘1 ≤π‘≤π‘π ,0≤π§1 ,π§2 ≤π {maxπ=1,2 {ππ (π‘, π§1 , π§2 )} + π‘π ≤ π ∫ πΆ∗ πΊπ (π , π ) π (π 0 ) Δπ π‘1 ≤ πππ (π 0 ) . (44) It follows that 1 (41) π (π 0 ) π (π 0 ) 1 1 ≥ , > = π 0 2ππ 4ππ π 0 (46) which implies that β(π₯1π , π₯2π )β1 =ΜΈ π 0 . By the nonlinear alternative of Leray-Schauder type, ππ has a fixed point (π₯π1 , π₯π2 ) ∈ ππ . Moreover combining (40) and the fact that π 0 < π, we obtain π‘π ∗ π₯ππ = π ∫ π»ππ (π‘, π ) (ππ (π‘, [π₯1π (π‘) − V1π (π‘)] , π‘1 ∗ [π₯2π (π‘) − V2π (π‘)] ) + π (π‘)) Δπ ≥ π ∫ π»ππ (π‘, π ) (πΏπ (π , 0, 0) + π (π‘)) Δπ π‘1 π‘π ≥ π ∫ π»ππ (π‘, π ) π (π‘) Δπ π‘1 = Vππ (π‘) for π‘ ∈ (π (π‘1 ) , π‘π ) . (47) lim (42) π (π) 1 < , π 4ππ Then there exists a π 0 ∈ (0, π] such that π (π 0 ) 1 = . π 0 4ππ (45) π‘π Set π = π/4ππ(π), since for any 0 < π ≤ π, fix the π ∈ (0, π], we always have π (π§) = +∞, π§↓0 π§ σ΅© σ΅© π 0 = σ΅©σ΅©σ΅©(π₯1π , π₯2π )σ΅©σ΅©σ΅©1 ≤ 2πππ (π 0 ) , that is, π‘ π(π‘)}, and π = ∫π‘ π πΆ∗ πΊπ (π , π )Δπ . We have π (π§) lim = +∞. π§↓0 π§ ∗ ≤ π ∫ πΆ∗ πΊπ (π , π ) (ππ (π , [π₯1π (π ) − V1π (π )] , (43) Let ππ = {(π₯1π , π₯2π ) ∈ π1(π−1) × π2(π−1) : β(π₯1π , π₯2π )β1 < π 0 }, (π₯1π , π₯2π ) ∈ πππ and ] ∈ (0, 1) be such that (π₯1π , π₯2π ) = ]ππ (π₯1π , π₯2π ), that is, π₯ππ = ]πππ (π₯1π , π₯2π ) (π = 1, 2). We Then ππ has a positive fixed point (π₯π1 , π₯π2 ) and β(π₯π1 , π₯π2 )β1 ≤ π 0 < 1; that is, (π₯π1 , π₯π2 ) is a positive solution of the boundary value problem (26) with π₯ππ > Vππ (π‘) for π‘ ∈ (π‘1 , π‘π ). Let π’ππ (π‘) = π₯ππ (π‘)−Vππ (π‘) ≥ 0 (π = 1, 2), then (π’1π , π’2π ) is a nonnegative solution (positive on (π(π‘1 ), π‘π )) of the boundary value problem (1). Theorem 7. Suppose that (H∗1 ) and (H3 )-(H4 ) hold. Then there exists a constant π∗ > 0 such that, for any 0 < π ≤ π∗ , (1) with boundary value condition (π) has at least one positive solution (π = 2, . . . , 5). Journal of Applied Mathematics 9 Proof. We fix π (π = 2, . . . , 5). Let Ω1 = {(π₯1π , π₯2π ) ∈ πΈ × πΈ : βπ₯ππ β < π 1 , π = 1, 2}, where π 1 = max{1, π} and π = π‘ 2 (πΆ∗ /π∗ ) ∫π‘ π π(π )Δπ . Choose (π1(π−1) × π2(π−1) ) ∩ πΩ2 , we have βπ₯1π β = π 2 or βπ₯2π β = π 2 . Without loss of generality let βπ₯1π β = π 2 , so we have 1 π π π = min {1, 1 (π + 1)−1 , 1 } , 2 2π ∗ π‘π (48) π₯1π (π‘) − V1π (π‘) = π₯1π (π‘) − π ∫ π»1π (π‘, π ) π (π ) Δπ π‘1 ≥ π₯1π (π‘) − π ∫ π‘ where π = ∫π‘ π πΆ∗ πΊπ (π , π )(max0≤π§1 ,π§2 ≤π 1 ππ (π , π§1 , π§2 ) + π(π ))Δπ 1 and π ≥ 0. Then for any (π₯1π , π₯2π ) ∈ (π1(π−1) × π2(π−1) ) ∩ πΩ1 , π₯ππ (π ) − Vππ (π ) ≤ π₯ππ (π ) ≤ βπ₯ππ β ≤ π 1 (π = 1, 2) and for 0 < π ≤ π∗ , we have π‘1 2 π₯1π (π‘) σ΅©σ΅© σ΅©σ΅© π (π ) Δπ σ΅©σ΅©π₯1π σ΅©σ΅© π₯ (π‘) ≥ π₯1π (π‘) − σ΅©σ΅©1π σ΅©σ΅© ππ σ΅©σ΅©π₯1π σ΅©σ΅© ∗ ≥ π₯1π (π‘) − ∗ ≥ (1 − ≤ π ∫ πΆ∗ πΊπ (π , π ) (ππ (π , [π₯1π (π ) − V1π (π )] , π‘1 [π₯2π (π ) − V2π (π )] ) + π (π )) Δπ π‘π ≤ π ∫ πΆ∗ πΊπ (π , π ) ( max ππ (π , π§1 , π§2 ) + π (π )) Δπ ≥ 0≤π§1 ,π§2 ≤π 1 π‘1 πΆ∗ π∗ π₯ (π‘) π‘π πΆ∗ 2 = π₯1π (π‘) − π σ΅©σ΅©1π σ΅©σ΅© ∫ π (π ) Δπ σ΅©σ΅©π₯1π σ΅©σ΅© π‘1 π∗ σ΅© σ΅©σ΅© σ΅©σ΅©πππ (π₯1π , π₯2π ) (π‘)σ΅©σ΅©σ΅© π‘π π‘π (53) π₯1π (π‘) ππ π 2 ππ ) π₯1π (π‘) π 2 1 π₯ (π‘) ≥ 0, 2 1π π‘ ∈ [π (π‘1 ) , π‘π ] . ≤ ππ ≤ Thus π 1 . 2 (49) ∗ ∗ min {[π₯1π (π‘) − V1π (π‘)] + [π₯2π (π‘) − V2π (π‘)] } π1 ≤π‘≤π2 This implies σ΅© σ΅© σ΅© σ΅©σ΅© σ΅©σ΅©ππ (π₯1π , π₯2π )σ΅©σ΅©σ΅©1 ≤ π 1 ≤ σ΅©σ΅©σ΅©(π₯1π , π₯2π )σ΅©σ΅©σ΅©1 , (π₯1π , π₯2π ) ∈ (π1(π−1) × π2(π−1) ) ∩ πΩ1 . 1 ≥ min {π₯1π (π‘) − V1π (π‘)} ≥ min { π₯1π (π‘)} π1 ≤π‘≤π2 π1 ≤π‘≤π2 2 (50) π1 ≤π‘≤π2 = Choose a constant π > 1 such that πππΎ π2 π∗ πΊ (π , π ) ππ1 (π ) ππ2 (π ) Δπ ≥ 1, (51) ∫ σ΅© σ΅© σ΅© σ΅© 2 (σ΅©σ΅©σ΅©ππ1 σ΅©σ΅©σ΅© + σ΅©σ΅©σ΅©ππ2 σ΅©σ΅©σ΅©) π1 π where πΎ = minπ minπ1 ≤π‘≤π2 {π1π (π‘), π2π (π‘)}. By assumption (H3 ) and (H4 ), there exists a constant π΅ > π 1 such that ππ (π‘, π§1 , π§2 ) > π, π§1 + π§2 ≥ min { π∗ σ΅© σ΅© π σ΅© σ΅© π (π‘) σ΅©σ΅©π₯ σ΅©σ΅© , ∗ π (π‘) σ΅©σ΅©π₯ σ΅©σ΅©} 2πΆ∗ 1π σ΅© 1π σ΅© 2πΆ∗ 2π σ΅© 1π σ΅© π∗ π min {π (π‘) , π2π (π‘)} ≥ π΅ + 1 > π΅. 2πΆ∗ 2 π1 ≤π‘≤π2 1π Now since π΅ > π 1 , it follows that πππ (π₯1π , π₯2π ) (π‘) π‘π ∗ = π ∫ π»ππ (π‘, π ) (ππ (π , [π₯1π (π ) − V1π (π )] , π‘1 ∗ that is, ππ (π‘, π§1 , π§2 ) > π (π§1 + π§2 ) , [π₯2π (π ) − V2π (π )] ) + π (π )) Δπ π2 for π‘ ∈ [π1 , π2 ] , π§1 + π§2 > π΅ (π = 1, 2) . ∗ ≥ π ∫ π»ππ (π‘, π ) (ππ (π , [π₯1π (π ) − V1π (π )] , (52) π1 ∗ Choose π 2 = max{π 1 + 1, 2ππ, 2πΆ∗ (π΅ + 1)/π∗ πΎ} and let Ω2 = {(π₯1π , π₯2π ) ∈ πΈ × πΈ : βπ₯ππ β < π 2 , π = 1, 2}. We note that π₯(π‘) ≥ (π∗ /πΆ∗ )πππ (π‘)βπ₯β for all π₯ ∈ πππ , by Lemma 3, we 2 have π»ππ (π‘, π ) ≤ (πΆ∗ /π∗ )(π₯(π‘)/βπ₯β). Then for any (π₯1π , π₯2π ) ∈ [π₯2π (π ) − V2π (π )] ) + π (π )) Δπ π2 ∗ ≥ π ∫ π»ππ (π‘, π ) ππ (π , [π₯1π (π ) − V1π (π )] , π1 ∗ [π₯2π (π ) − V2π (π )] ) Δπ (54) 10 Journal of Applied Mathematics π2 ≥ π ∫ π»ππ (π‘, π ) π ([π₯1π (π ) − V1π (π )] Theorem 8. Suppose that (H1 )–(H3 ) hold. Then (1) with boundary value condition (π) has at least two positive solutions for π > 0 sufficiently small (π = 2, . . . , 5). ∗ π1 ∗ + [π₯2π (π ) − V2π (π )] ) Δπ In fact with 0 < π < min{π, π∗ } then (1) with boundary value condition (π) has at least two positive solutions. π2 ≥ π ∫ π»ππ (π‘, s) π (π₯1π (π ) − V1π (π )) Δπ π1 π2 ≥ π ∫ π∗ min {π1π (π‘) , π2π (π‘)} πΊπ (π , π ) π (π₯1π (π ) − V1π (π )) Δπ π1 ≤π‘≤π2 π1 π2 ≥ π ∫ π∗ min {π1π (π‘) , π2π (π‘)} πΊπ (π , π ) π1 ≤π‘≤π2 π1 π π₯ (π ) ππ 2 1π Remark 9. In Theorems 6–8, we use the assumption condition 16. If we have not the condition 16, that is, ππ = ππ = 0, then the system (1) and boundary condition (π) are Δ (π1 π’1∇ ) (π‘)−π1 (π‘) π’1 (π‘)+ππ1 (π‘, π’1 (π‘) , π’2 (π‘)) = 0, ≥ π min {π1π (π‘) , π2π (π‘)} π‘ ∈ (π‘1 , π‘π ) , π > 0, π1 ≤π‘≤π2 π2 × ∫ π∗ πΊπ (π , π ) π1 Δ (π2 π’2∇ ) (π‘)−π2 (π‘) π’2 (π‘)+ππ2 (π‘, π’1 (π‘) , π’2 (π‘)) = 0, π∗ π σ΅© σ΅© σ΅© σ΅© σ΅© σ΅© π (π ) ππ2 (π ) σ΅©σ΅©σ΅©π₯1π σ΅©σ΅©σ΅© Δπ 2 (σ΅©σ΅©σ΅©ππ1 σ΅©σ΅©σ΅© + σ΅©σ΅©σ΅©ππ2 σ΅©σ΅©σ΅©) π1 πΌ1 π’1 (π‘1 ) − π½1 π1 (π‘1 ) π’1∇ (π‘1 ) = 0, π2 π ≥ πππΎ σ΅©σ΅© σ΅©σ΅© ∗ σ΅©σ΅© σ΅©σ΅© ∫ πΊπ (π , π ) ππ1 (π ) ππ2 (π ) Δπ π 2 2 (σ΅©σ΅©ππ1 σ΅©σ΅© + σ΅©σ΅©ππ2 σ΅©σ΅©) π1 ≥ π 2 , πΎ1 π’1 (π‘π ) + πΏ1 π1 (π‘π ) π’1∇ (π‘π ) = 0, π‘ ∈ [π1 , π2 ] . (55) This implies σ΅©σ΅© σ΅© σ΅© σ΅© σ΅©σ΅©ππ (π₯1π , π₯2π )σ΅©σ΅©σ΅©1 ≥ σ΅©σ΅©σ΅©(π₯1π , π₯2π )σ΅©σ΅©σ΅©1 , (π₯1π , π₯2π ) ∈ (π1(π−1) × π2(π−1) ) ∩ πΩ2 . (56) For the Krasnosel’skii’s fixed point theorem, one deduces that ππ has a fixed point (π₯1π , π₯2π ) with π 1 < β(π₯1π , π₯2π )β < π 2 ⇔ π 1 < βπ₯1π β + βπ₯2π β < π 2 . Since π ≤ π 1 < βπ₯ππ β < π 2 (π = 1, 2), then π‘π π₯ππ (π‘) − Vππ (π‘) = π₯ππ (π‘) − π ∫ π»ππ (π‘, π ) π (π ) Δπ π‘1 π‘π ≥ π₯ππ (π‘) − π ∫ π‘1 ∗2 πΆ π∗ πΌ2 π’2 (π‘1 ) − π½2 π2 (π‘1 ) π’2∇ (π‘1 ) = 0, πΎ2 π’2 (π‘π ) + πΏ2 π1 (π‘π ) π’2∇ (π‘π ) = 0. From Lemma 2, an argument similar to those in Theorems 6–8 yields the following theorems. Theorem 10. Suppose that (H1 ) and (H2 ) hold. Then there exists a constant π > 0 such that, for any 0 < π ≤ π, the boundary value problem (58) has at least one positive solution. Theorem 11. Suppose that (H∗1 ) and (H3 )-(H4 ) hold. Then there exists a constant π∗ > 0 such that, for any 0 < π ≤ π∗ , the boundary value problem (58) has at least one positive solution. Theorem 12. Suppose that (H1 )–(H4 ) hold. Then the boundary value problem (58) has at least two positive solutions for π > 0 sufficiently small. π₯ππ (π‘) σ΅©σ΅© σ΅©σ΅© π (π ) Δπ σ΅©σ΅©π₯ππ σ΅©σ΅© π₯ (π‘) = π₯ππ (π‘) − π σ΅©σ΅©ππ σ΅©σ΅© π σ΅©σ΅©π₯ππ σ΅©σ΅© (58) 4. Example (57) ≥ π₯ππ (π‘) − ππ₯ππ (π‘) To illustrate the usefulness of the results, we give some examples. = (1 − π) π₯ππ (π‘) Example 13. Consider the boundary value problem ≥ (1 − π) > 0, π∗ ππ1 (π‘) ππ2 (π‘) σ΅©σ΅© σ΅©σ΅© σ΅©π₯ σ΅© πΆ∗ σ΅©σ΅©σ΅©σ΅©ππ1 σ΅©σ΅©σ΅©σ΅© + σ΅©σ΅©σ΅©σ΅©ππ2 σ΅©σ΅©σ΅©σ΅© σ΅© ππ σ΅© π’σΈ σΈ − π’ = − π ((π’ + V)π + 1 π‘ ∈ (π (π‘1 ) , π‘π ) . Thus (π₯1π , π₯2π ) is a positive solution of the boundary value problem (26) with π₯ππ (π‘) > Vππ (π‘) (π = 1, 2) for π‘ ∈ (π(π‘1 ), π‘π ). Let π’ππ (π‘) = π₯ππ (π‘)−Vππ (π‘) ≥ 0 (π = 1, 2), then (π’1π , π’2π ) is a nonnegative solution (positive on (π(π‘1 ), π‘π )) of the boundary value problem (1). Since condition (H1 ) implies conditions (H∗1 ) and (H4 ) then from the proof of Theorems 6 and 7, we immediately have the following theorem. 1/2 (π‘ − π‘2 ) cos (2π (π’ + V))) , − 1 < π‘ < 1, π > 0, VσΈ σΈ − V = −π ((π’ − 1)2 + V2 + π’ (−1) = V (1) = 0, 1 1/2 (π‘ − π‘2 ) π’ (1) = ππ’ (0) , sin (2ππ’)) , V (−1) = πV (0) , (59) where π > 1. Then if π > 0 is sufficiently small, (59) has a positive solution π’ with π’(π‘) > 0 for π‘ ∈ (0, 1). Journal of Applied Mathematics 11 To see this, we will apply Theorem 7 with π1 (π‘, π’, V) = (π’ + V)π + 1 1/4 (π‘2 − π‘4 ) π2 (π‘, π’, V) = (π’ − 1)2 + V2 + π∗ = min {1, cos (2π (π’ + V)) , 1 sin (2ππ’) , 1/4 (π‘2 − π‘4 ) π1 (π‘) = π2 (π‘) = π (π‘) = Also let 1 (π‘2 − 1/4 π‘4 ) (60) lim inf π’+V↑+∞ Example 14. Consider the boundary value problem: . Δ (π1 π’1∇ ) (π‘) − π1 (π‘) π’1 (π‘) = −π (ππ’1 + π’22 + 7 cos (2ππ‘π’1 )) , for π‘ ∈ (0, 1) π = 1, 2, π‘1 < π‘ < π‘π , ππ (π‘, π’, V) = +∞ for all π‘ ∈ [π1 , π2 ] ⊂ (0, 1) . π’+V (61) Now (H∗1 ), (H3 ), and (H4 ) hold. We note that the boundary condition of (59) is in accord with (4), and from [1], we have ππ‘+1 − π−π‘−1 π11 = π21 = , 2 (65) Now, if π < π∗ , Theorem 7 guarantees that (59) has a positive solutions (π’, V) with βπ’β ≥ 1 and βVβ ≥ 1. Clearly for π‘ ∈ (0, 1), ππ (π‘, π’, V) + π (π‘) > 0, −1 π π 1 (π π+2 + π) , 1 } . 2π+2 πΆ∗ π4 1 2π π−π‘+1 − ππ‘−1 π12 = π22 = , 2 π1 = π2 = sinh (2) . (62) π > 0, (66) Δ (π2 π’2∇ ) (π‘) − π2 (π‘) π’2 (π‘) 2 = −π ((π’1 − 1) + π’22 + 5 sin (2ππ‘π’2 )) satisfying one of the boundary value conditions (π), (π = 2, . . . , 5). Then if π > 0 is sufficiently small, (66) has two solutions (π’11 , π’12 ), (π’21 , π’22 ) with π’ππ (π‘) > 0 for π‘ ∈ (0, 1), π, π = 1, 2. To see this, we will apply Theorem 8 with π1 (π‘, π’1 , π’2 ) = ππ’1 + π’22 + 7 cos (2ππ‘π’1 ) , Then 2 π2 (π‘, π’1 , π’2 ) = (π’1 − 1) + π’22 + 5 sin (2ππ‘π’2 ) , πΊ1 (π‘, π ) = πΊ2 (π‘, π ) = 1 π12 (π‘) π11 (π ) , { π1 π11 (π‘) π12 (π ) , π»24 (π‘, π ) = πΊ2 (π‘, π ) + π‘π π1 (π‘) = π2 (π‘) = π (π‘) = 8. π (π‘1 ) ≤ π ≤ π‘ ≤ π‘π , π (π‘1 ) ≤ π‘ ≤ π ≤ π‘π , 1 π»14 (π‘, π ) = πΊ1 (π‘, π ) + ππΊ (0, π ) π11 (π‘) , π1 − ππ11 (0) 1 (63) Clearly, for π‘ ∈ (0, 1), ππ (π‘, π’1 , π’2 ) + π (π‘) ≥ 1 > 0, 1 ππΊ (0, π ) π22 (π‘) . π2 − ππ22 (0) 2 π1 (π‘, 0, 0) = 8 > 0, Note π = ∫π‘ (πΆ /π∗ )π(π )Δπ . Let π 1 = π + 1 and we have 1 lim inf π’+V↑+∞ π‘π π = ∫ πΆ∗ πΊπ (π , π ) ( max ππ (π , π§1 , π§2 ) + π (π )) Δπ 0≤π§1 ,π§2 ≤π 1 π‘π ≤ ∫ πΆ∗ πΊπ (π , π ) [2π+2 π 1π+2 + π‘1 ≤ ∫ −1 = ∫ 0 1/4 (π 2 − π 4 ) πΆ∗ π4 π+2 π+2 2 ] Δπ [2 π 1 + 1/4 2 4 (π − π 4 ) 1 1 2 ∗ 4 πΆ π 2 ] Δπ [2π+2 π 1π+2 + 1/4 2 2 (π − π 4 ) πΆ∗ π4 π+2 π+2 2 ≤ ∫ ] Δπ [2 π 1 + 1/2 2 0 (π − π 2 ) 1 π+1 ≤2 ∗ 4 πΆ π (π 1π+2 + π) . (68) π2 (π‘, 0, 0) = 3 > 0, ∗2 π‘1 (67) ππ (π‘, π’1 , π’2 ) = +∞, π’1 + π’2 π = 1, 2. Now (H1 )–(H4 ) hold. Let πΏ = 1/100, π = 1/8, and we have ππ (π‘, π’1 , π’2 ) ≥ πΏππ (π‘, 0, 0) , ] Δπ (64) for 0 ≤ π‘ ≤ 1, 0 ≤ π’π ≤ π, π = 1, 2. (69) Furthermore let π(π) = max0≤π‘≤1,0≤π’1 ,π’2 ≤π {maxπ=1,2 ππ (π‘, π’1 , π’2 ) + π(π‘)}, and π = π‘ ∫π‘ π πΆ∗ πΊπ (π , π )Δπ . Note 1 π 4ππ (π) ≥ 1 1 > . 32π (π + 8) 352π (70) Let π = 1/352π. Now, if 0 < π < π then 0 < π < π/4ππ(π) and Theorem 6 guarantees that (66) has positive solutions (π’11 , π’12 ) with βπ’1π β ≤ (1/8) (π = 1, 2). 12 Journal of Applied Mathematics 2 Next note π = 8πΆ∗ (π‘π − π‘1 )/π∗ and let π 1 = π + 2 so we have 1 π = ∫ πΆ∗ πΊπ (π , π ) ( max ππ (π , π§1 , π§2 ) + π (π )) Δπ 0≤π§1 ,π§2 ≤π 1 0 1 ≤ ∫ πΆ∗ πΊπ (π , π ) (ππ 1 + 2π 12 + 7 + 8) Δπ 0 (71) 1 ≤ ∫ πΆ∗ πΊπ (π , π ) Δπ (ππ 1 + 2π 12 + 15) 0 ≤ (ππ 1 + 2π 12 + 15) π. 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