Hindawi Publishing Corporation Abstract and Applied Analysis Volume 2013, Article ID 134691, 9 pages http://dx.doi.org/10.1155/2013/134691 Research Article Existence Result for Impulsive Differential Equations with Integral Boundary Conditions Peipei Ning, Qian Huan, and Wei Ding Department of Mathematics, Shanghai Normal University, Shanghai 200234, China Correspondence should be addressed to Wei Ding; dingwei@shnu.edu.cn Received 5 December 2012; Accepted 5 January 2013 Academic Editor: Yonghui Xia Copyright © 2013 Peipei Ning 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 investigate the following differential equations: −(π¦[1] (π₯))σΈ + π(π₯)π¦(π₯) = ππ(π₯, π¦(π₯)), with impulsive and integral boundary π π conditions −Δ(π¦[1] (π₯π )) = πΌπ (π¦(π₯π )), π = 1, 2, . . . , π, π¦(0) − ππ¦[1] (0) = ∫0 π0 (π )π¦(π )ππ , π¦(π) − ππ¦[1] (π) = ∫0 π1 (π )π¦(π )ππ , where π¦[1] (π₯) = π(π₯)π¦σΈ (π₯). The expression of Green’s function and the existence of positive solution for the system are obtained. Upper and lower bounds for positive solutions are also given. When π(π‘), πΌ(⋅), π0 (π ), and π1 (π ) take different values, the system can be simplified to some forms which has been studied in the works by Guo and LakshmiKantham (1988), Guo et al. (1995), Boucherif (2009), He et al. (2011), and Atici and Guseinov (2001). Our discussion is based on the fixed point index theory in cones. 1. Introduction The theory of impulsive differential equations in abstract spaces has become a new important branch and has developed rapidly (see [1–4]). As an important aspect, impulsive differential equations with boundary value problems have gained more attention. In recent years, experiments in a variety of different areas (especially in applied mathematics and physics) show that integral boundary conditions can represent the model more accurately. And researchers have obtained many good results in this field. In this paper, we study the existence of positive solutions for the following system: σΈ −(π¦[1] (π₯)) + π (π₯) π¦ (π₯) = ππ (π₯, π¦ (π₯)) , −Δ (π¦[1] (π₯π )) = πΌπ (π¦ (π₯π )) , π₯ =ΜΈ π₯π , π₯ ∈ π½− , π = 1, 2, . . . , π, π π¦ (0) − ππ¦[1] (0) = ∫ π0 (π ) π¦ (π ) ππ , π 0 ∫ 0 π π¦ (π) − ππ¦[1] (π) = ∫ π1 (π ) π¦ (π ) ππ , 0 where π¦[1] (π₯) = π(π₯)π¦σΈ (π₯), π½− = π½ \ {π₯1 , π₯2 , . . . , π₯π }, π½ = [0, π], 0 < π₯1 < π₯2 < ⋅ ⋅ ⋅ < π₯π < π, π ∈ πΆ(π½ × π + , π + ). π¦(π₯), π¦[1] (π₯) are left continuous at π₯ = π₯π , Δ(π¦[1] (π₯π )) = π¦[1] (π₯π+ ) − π¦[1] (π₯π− ). πΌπ ∈ πΆ(π + , π + ). And π > 0, π < 0, π0 , π1 : [0, 1] → [0, ∞) are continuous and positive functions. When π(π‘), πΌ(⋅), π0 (π ), and π1 (π ) take different values, the system can be simplified to some forms which have been studied. For example, [5–10] discussed the existence of positive solution in case π(π‘) = 1. Let π(π‘) = 1, π0 , π1 = 0, [11, 12] investigated the system with only one impulse. Reference [13] studied the system when πΌ(⋅) = 0, π0 , π1 = 0. Readers can read the papers in [13] for details. Throughout the rest of the paper, we assume π is a fixed positive number, and π is a parameter. π(π₯), π(π₯) are realvalued measurable functions defined on π½, and they satisfy the following condition: (H1) π(π₯) > 0, π(π₯) ≥ 0, π(π₯) ≡ΜΈ 0 almost everywhere, and (1) 1 ππ₯ < ∞, π (π₯) π ∫ π (π₯) ππ₯ < ∞. 0 (2) This paper aims to obtain the positive solution for (1). In Section 2, we introduce some lemmas and notations. In 2 Abstract and Applied Analysis particular, the expression and some properties of Green’s functions are investigated. After the preparatory work, we draw the main results in Section 3. Consider the following boundary value problem with integral boundary conditions: σΈ −(π¦[1] (π₯)) + π (π₯) π¦ (π₯) = β (π₯) , 2. Preliminaries π π¦ (0) − ππ¦[1] (0) = ∫ π0 (π ) π0 (π ) ππ , Theorem 1 (Krasnoselskii’s fixed point theorem). Let πΈ be a Banach space and πΆ ∈ πΈ. Assume Ω1 , Ω2 are open sets in πΈ with 0 ∈ Ω1 ⊂ Ω1 ⊂ Ω2 , and π : πΆ β(Ω2 \ Ω1 ) → πΆ be a completely continuous operator such that either (i) βπ (π¦)β ≤ βπ¦β, π¦ ∈ πΆ ∩ πΩ1 , and βπ (π¦)β ≥ βπ¦β, π¦ ∈ πΆ ∩ πΩ2 ; or 0 Then π has a fixed point in πΆ β(Ω2 \ Ω1 ). Definition 2. For two differential functions π¦ and π§, we defined their Wronskian by ππ₯ (π¦, π§) = π¦ (π₯) π§[1] (π₯) − π¦[1] (π₯) π§ (π₯) = π (π₯) [π¦ (π₯) π§σΈ (π₯) − π¦σΈ (π₯) π§ (π₯)] . (3) Consider the linear nonhomogeneous problem of the form σΈ −(π¦[1] (π₯)) + π (π₯) π¦ (π₯) = β (π₯) , π₯ ∈ π½. (4) Its corresponding homogeneous equation is σΈ −(π¦[1] (π₯)) + π (π₯) π¦ (π₯) = 0, π₯ ∈ π½. (5) Lemma 3. Suppose that π¦1 and π¦2 form a fundamental set of solutions for the homogeneous problem (5). Then the general solution of the nonhomogeneous problem (4) is given by π 0 Denote by π’(π₯) and π£(π₯) the solutions of the homogenous equation (5) satisfying the initial conditions 0 π’ (0) = π, π£ (π) = −π, π¦1 (π₯) π¦2 (π ) − π¦1 (π ) π¦2 (π₯) β (π ) ππ , π€π (π¦1 , π¦2 ) π (π₯, π ) = π’ (π₯) π£ (π₯) π (π ) + π (π ) π’ (π) − ππ’[1] (π) 1 π£ (0) − ππ£[1] (0) 0 (13) satisfies 0 ≤ π(π₯, π ) < 1/π. For convenience, we denote π := min{π(π₯, π ); π₯, π ∈ π½}, π := max{π(π₯, π ); π₯, π ∈ π½}. Lemma 4. Let πΎ(π₯, π ) be a nonnegative continuous function defined for −∞ < π₯1 ≤ π₯, π ≤ π₯2 < ∞ and π(π₯) a nonnegative integrable function on [π₯1 , π₯2 ]. Then for arbitrary nonnegative continuous function π(π₯) defined on [π₯1 , π₯2 ], the Volterra integral equation π₯ π¦ (π₯) = π (π₯) + ∫ πΎ (π₯, π ) π (π ) π¦ (π ) ππ , π₯1 π¦ (π₯) ≥ π (π₯) , 0 π₯ 0 π¦1 (π₯) π¦2 (π ) − π¦1 (π ) π¦2 (π₯) β (π ) ππ π€π (π¦1 , π¦2 ) π¦1σΈ (π₯) π¦2 (π ) − π¦1 (π ) π¦2σΈ (π₯) β (π ) ππ , π€π (π¦1 , π¦2 ) σΈ [π (π₯) π§σΈ (π₯)] = −β (π₯) + π (π₯) π§ (π₯) . (7) Thus, π§(π₯) satisfies (4). [1] π§ π₯1 ≤ π₯ ≤ π₯2 . π₯ π¦π = ∫ πΎ (π₯, π ) π (π ) π¦π−1 (π ) ππ , π₯1 (8) (9) Besides, from (7) and (8), we have π§ (0) = 0, (14) (15) π¦0 (π₯) = π (π₯) , is a particular solution of (4). From (7), we have for π₯ ∈ [0, π], π§σΈ (π₯) = ∫ π₯1 ≤ π₯ ≤ π₯2 Proof. We solve (14) by the method of successive approximations setting Proof. We just need to show that the function π§ (π₯) = ∫ (12) π£[1] (π) = −1. (H2) Let π₯, π ∈ π½, denote a function (6) where π1 and π2 are arbitrary constants. π₯ π’[1] (0) = 1, has a unique solution π¦(π₯). Moreover, this solution is continuous and satisfied the inequality π¦ (π₯) = π1 π¦1 (π₯) + π2 π¦2 (π₯) π₯ (11) π¦ (π) − ππ¦[1] (π) = ∫ π1 (π ) π1 (π ) ππ . (ii) βπ (π¦)β ≥ βπ¦β, π¦ ∈ πΆ ∩ πΩ1 , and βπ (π¦)β ≤ βπ¦β, π¦ ∈ πΆ ∩ πΩ2 . +∫ π₯ ∈ π½, π = 1, 2, . . . . (16) If the series ∑∞ π=0 π¦π (π₯) converges uniformly with respect to π₯ ∈ [π₯1 , π₯2 ], then its sum will be, obviously, a continuous solution of (14). To prove the uniform convergence of this series, we put max π (π₯) = π, π₯1 β©½π₯β©½π₯2 max πΎ (π₯, π ) = π1 . π₯1 β©½π₯,π β©½π₯2 (17) Then it is easy to get from (16) that (0) = 0. (10) 0 β©½ π¦π (π₯) β©½ π π π1π π₯ [∫ π (π ) ππ ] , π! π₯1 π = 0, 1, 2, . . . . (18) Abstract and Applied Analysis 3 Hence it follows that (14) has a continuous solution Similarly from the second boundary condition of (11), we can find ∞ π¦ (π₯) = ∑ π¦π (π₯) (19) π=0 and because π¦0 = π(π₯), π¦π ≥ 0, π = 1, 2, . . ., for this solution the inequality (15) holds. Uniqueness of the solution of (14) can be proved in a usual way. The proof is complete. Remark 5. Evidently, the statement of Lemma 4 is also valid for the Volterra equation of the form π₯2 π¦ (π₯) = π (π₯) + ∫ πΎ (π₯, π ) π (π ) π¦ (π ) ππ , π₯ π₯1 ≤ π₯ ≤ π₯2 . (20) Lemma 6. For the solution π¦(π₯) of the BVP (11), the formula π π¦ (π₯) = π€ (π₯) + ∫ πΊ (π₯, π ) β (π ) ππ , 0 π₯∈π½ (21) π1 = π 1 ∫ π1 (π ) π1 (π ) ππ [1] π’ (π) − ππ’ (π) 0 π π£ (π ) −∫ β (π ) ππ . 0 ππ (π’, π£) (27) Putting these values of π1 and π2 in (23), we get the formula (21), (22). Lemma 7. Let condition (H1) hold. Then for the Wronskian of solution π’(π₯) and π£(π₯), the inequality ππ₯ (π’, π£) < 0, π₯ ∈ π½ holds. Proof. Using the initial conditions (12), we can deduce from (5) for π’(π₯) and π£(π₯) the following equations: π₯ π’[1] (π₯) = 1 + ∫ π (π ) π’ (π ) ππ , 0 holds, where π’ (π₯) = π + ∫ π π’ (π₯) π (π ) π1 (π ) ππ π€ (π₯) = ∫ π’ (π) − ππ’[1] (π) 0 1 π π£ (π₯) π (π ) π0 (π ) ππ , + ∫ π£ (0) − ππ£[1] (0) 0 0 πΊ (π₯, π ) = − 0 [1] π£ Proof. By Lemma 3, the general solutions of the nonhomogeneous problem (4) has the form 0 (23) where π1 and π2 are arbitrary constants. Now we try to choose the constants π1 and π2 so that the function π¦(π₯) satisfies the boundary conditions of (11). From (23), we have π¦[1] (π₯) = π1 π’[1] (π₯) + π2 π£[1] (π₯) +∫ π₯ 0 π’ [1] (π₯) π£ (π ) − π’ (π ) π£ ππ (π’, π£) (π₯) β (π ) ππ . (24) 0 π ππ‘ ] π (π ) π’ (π ) ππ , π (π‘) (28) (π₯) = −1 − ∫ π (π ) π£ (π ) ππ , π₯ π£ (π₯) = −π + ∫ π 1 ππ‘ π (π‘) π₯ π π π₯ π₯ ππ‘ ] π (π ) π£ (π ) ππ . π (π‘) From (28), by condition (H1) and Lemma 4, it follows that π’ (π₯) ≥ π + ∫ π₯ 0 π ππ‘ > 0, π (π‘) ππ‘ > 0, π£ (π₯) ≥ −π + ∫ π (π‘) π₯ π’[1] (π₯) ≥ 1 > 0, (29) [1] π£ (π₯) ≤ −1 < 0. Now from (3), we get ππ₯ (π’, π£) < 0, π₯ ∈ π½. The proof is complete. From (21), (22), and Lemma 7, the following lemma follows. Consequently, π¦ (0) = π1 π + π2 π£ (0) , π¦[1] (0) = π1 + π2 π£[1] (0) . (25) [1] Substituting these values of π¦(0) and π¦ (0) into the first boundary condition of (11), we find π2 = π₯ + ∫ [∫ π’ (π₯) π£ (π ) − π’ (π ) π£ (π₯) β (π ) ππ , ππ (π’, π£) [1] π₯ π π¦ (π₯) = π1 π’ (π₯) + π2 π£ (π₯) π₯ 1 ππ‘ π (π‘) + ∫ [∫ (22) π’ (π ) π£ (π₯) , 0 ≤ π ≤ π₯ ≤ π, 1 { π€π (π’, π£) π’ (π₯) π£ (π ) , 0 ≤ π₯ ≤ π ≤ π. +∫ π₯ π 1 ∫ π0 (π ) π0 (π ) ππ . [1] π£ (0) − ππ£ (0) 0 (26) Lemma 8. Under condition (H1) the Green’s function πΊ(π₯, π ) of the BVP (11) is positive. That is, πΊ(π₯, π ) > 0 for π₯, π ∈ π½. Let πΆ(π½) denote the Banach of all continuous functions π¦ : πΌ → R equipped with the form βπ¦β = max{|π¦(π₯)|; π₯ ∈ π½}, for any π¦ ∈ πΆ(π½). Denote π = {π¦ ∈ πΆ(π½); π¦(π₯) β©Ύ 0, π¦ ∈ π½}, then π is a positive cone in πΆ(π½). Let us set π΄ = max0β©½π₯,π β©½π πΊ(π₯, π ), π΅ = min0β©½π₯,π β©½π πΊ(π₯, π ), and by Lemma 8, obviously, π΄ > π΅ > 0, π₯, π ∈ π½. 4 Abstract and Applied Analysis Define a mapping Φ in Banach space πΆ(π½) by π (Φπ¦) (π₯) = π€ (π₯) + π ∫ πΊ (π₯, π ) π (π , π¦ (π )) ππ × πΌπ (π¦ (π₯π )) 0 (30) π + ∑πΊ (π₯, π₯π ) πΌπ (π¦ (π₯π )) , = −πΌπ (π¦ (π₯π )) , π₯ ∈ π½, π=0 σΈ σΈ (π (π₯) (Φπ¦) (π₯)) = [π (π₯) π€σΈ (π₯) where π€ (π₯) = π’ (π₯π ) π£σΈ (π₯π ) π’σΈ (π₯π ) π£ (π₯π ) + ] ππ₯π (π’, π£) ππ‘π (π’, π£) = π (π₯π ) [− π π’ (π₯) π (π ) π¦ (π ) ππ ∫ π’ (π) − ππ’[1] (π) 0 1 π π£ (π₯) π (π ) π¦ (π ) ππ . + ∫ π£ (0) − ππ£[1] (0) 0 0 π + π ∫ π (π₯) 0 (31) π=0 σΈ π 0 π × ∫ πΊ (π₯, π ) π (π , π¦ (π )) ππ 0 ππΊ π (π , π¦ (π )) ππ ππ₯ π ππΊ (π₯, π₯π ) πΌπ (π¦ (π₯π )) , +∑ ππ₯ π=0 ππΊ (π₯, π₯π ) πΌπ (π¦ (π₯π ))] ππ₯ = π (π₯) π€ (π₯) + ππ (π₯) Proof. Clearly, Φπ¦ is continuous in π₯ for π₯ ∈ π½. For π₯ =ΜΈ π₯π , (Φπ¦) (π₯) = π€σΈ (π₯) + π ∫ σΈ π + ∑π (π₯) Lemma 9. The fixed point of the mapping Φ is a solution of (1). ππΊ π (π , π¦ (π )) ππ ππ₯ − ππ (π₯, π¦ (π₯)) + π (π₯) (32) π × ∑πΊ (π₯, π₯π ) πΌπ (π¦ (π₯π )) π=0 = π (π₯) (Φπ¦) (π₯) − ππ (π₯, π¦ (π₯)) , where π π’σΈ (π₯) π€ (π₯) = π (π ) π¦ (π ) ππ ∫ π’ (π) − ππ’[1] (π) 0 1 (36) σΈ + π π£σΈ (π₯) π (π ) π¦ (π ) ππ . ∫ π£ (0) − ππ£[1] (0) 0 0 (33) Lemma 10. Let π0 := {π¦ ∈ π; minπ₯∈π½ π¦(π₯) ≥ ((1 − ππ)π΅/(1 − ππ)π΄)βπ¦β}, then π0 is a cone. We have [1] (Φπ¦) [1] (π₯) = π€ Proof. (i) For for all π¦1 , π¦2 ∈ π0 and for all πΌ ≥ 0, π½ ≥ 0, we have π ππΊ π (π , π¦ (π )) ππ (π₯) + π ∫ π (π₯) ππ₯ 0 π ππΊ (π₯, π₯π ) πΌπ (π¦ (π₯π )) , + ∑π (π₯) ππ₯ π=0 which implies that the fixed poind of Φ is a solution of (1). The proof is complete. (34) min (πΌπ¦1 ) β©Ύ πΌ ⋅ (1 − ππ) π΅ σ΅©σ΅© σ΅©σ΅© min (π½π¦2 ) β©Ύ π½ ⋅ σ΅©π¦ σ΅© . (1 − ππ) π΄ σ΅© 2 σ΅© where π€[1] (π₯) = π π’[1] (π₯) π (π ) π¦ (π ) ππ ∫ π’ (π) − ππ’[1] (π) 0 1 + π π£[1] (π₯) ∫ π0 (π ) π¦ (π ) ππ . [1] π£ (0) − ππ£ (0) 0 [1] [1] (Φπ¦) (π) − π(Φπ¦) [1] Δ(Φπ¦) π (0) = ∫ π0 (π ) π¦ (π ) ππ , 0 π (π) = ∫ π1 (π ) π¦ (π ) ππ , (35) min (πΌπ¦1 + π½π¦2 ) β©Ύ (1 − ππ) π΅ σ΅©σ΅© σ΅©σ΅© σ΅© σ΅© (πΌ σ΅©π¦ σ΅© + π½ σ΅©σ΅©σ΅©π¦2 σ΅©σ΅©σ΅©) (1 − ππ) π΄ σ΅© 1 σ΅© (1 − ππ) π΅ σ΅©σ΅© σ΅© β©Ύ σ΅©πΌπ¦ + π½π¦2 σ΅©σ΅©σ΅© . (1 − ππ) π΄ σ΅© 1 Thus πΌπ¦1 + π½π¦2 ∈ π0 . (ii) If π¦ ∈ π0 and −π¦ ∈ π0 , we have (1 − ππ) π΅ σ΅©σ΅© σ΅©σ΅© min (π¦ (π₯)) β©Ύ σ΅©π¦σ΅© , π₯∈π½ (1 − ππ) π΄ σ΅© σ΅© 0 σΈ (π₯π ) = π (π₯π+ ) (Φπ¦) (π₯π+ ) σΈ − π (π₯π− ) (Φπ¦) (π₯π− ) (37) Moreover We can easy get that (Φπ¦) (0) − π(Φπ¦) (1 − ππ) π΅ σ΅©σ΅© σ΅©σ΅© σ΅©π¦ σ΅© , (1 − ππ) π΄ σ΅© 1 σ΅© min (−π¦ (π₯)) β©Ύ π₯∈π½ (1 − ππ) π΅ σ΅©σ΅© σ΅©σ΅© σ΅©π¦σ΅© . (1 − ππ) π΄ σ΅© σ΅© It implies that π¦ = 0. Hence π0 is a cone. (38) (39) Abstract and Applied Analysis 5 Defined a linear operator π΄ : πΆ(π½) → πΆ(π½) by where the resolvent kernel π (π₯, π ) is given by ∞ π (π΄π¦) (π₯) = ∫ π (π₯, π ) π¦ (π ) ππ . 0 π (π₯, π ) = ∑ ππ (π₯, π ) . (40) π=1 (45) π Here ππ (π₯, π ) = ∫0 π(π₯, π)ππ−1 (π, π )ππ , π = 2, . . . and π1 (π₯, π ) = π(π₯, π ). The series on the right in (45) is convergent because |π(π₯, π )| β©½ π < 1/π. It can be easily verified that π (π₯, π ) ≤ π/(1 − ππ). So we can get Then we have the following lemma. Lemma 11. If (H2) is satisfied, then (i) π΄ is a bounded linear operator, π΄(π) ⊂ π; (ii) (πΌ − π΄) is invertible; π (iii) β(πΌ − π΄)−1 β ≤ 1/(1 − ππ). (πΌ − π΄)−1 π§ (π₯) = π§ (π₯) + ∫ π (π₯, π ) π§ (π ) ππ . 0 Proof. (i) (46) Therefore π π΄ (πΌπ¦1 (π₯) + π½π¦2 (π₯)) = ∫ π (π₯, π ) [πΌπ¦1 (π ) + π½π¦2 (π )] ππ π π ∫ π§ (π ) ππ 1 − ππ 0 (πΌ − π΄)−1 π§ (π₯) ≤ π§ (π₯) + 0 ππ 1 ≤ βπ§β (1 + )= βπ§β . 1 − ππ 1 − ππ = πΌ (π΄π¦1 ) (π₯) + π½ (π΄π¦2 ) (π₯) , (41) So for all πΌ, π½ ∈ R, π¦1 , π¦2 ∈ πΆ(π½). Using π(π₯, π ) ≤ π, it is easy to see that |(π΄π¦)(π‘)| ≤ ππβπ¦β. Let π¦ ∈ π. Then π¦(π ) ≥ 0 for all π ∈ π½. Since π(π‘, π ) ≥ π ≥ 0, it follows that (π΄π¦)(π₯) ≥ 0 for each π₯ ∈ π½. So π΄(π) ⊂ π. (ii) We want to show that (πΌ − π΄) is invertible, or equivalently 1 is not an eigenvalue of π΄. Since π < 1/π, it follows from condition (H2) that βπ΄π¦β ≤ ππβπ¦β < βπ¦β. So σ΅©σ΅© σ΅©σ΅© σ΅©π΄π¦σ΅© βπ΄β = sup σ΅©σ΅©σ΅© σ΅©σ΅©σ΅© β©½ ππ < 1. π¦ =ΜΈ 0 σ΅© σ΅©π¦σ΅©σ΅© (42) On the other hand, we suppose 1 is an eigenvalue of π΄, then there exists a π¦ ∈ πΆ(π½) such that π΄π¦ = π¦. Moreover, we can obtain that βπ΄π¦β/βπ¦β = 1. So βπ΄β β©Ύ 1. Thus this assumption is false. Conversely, 1 is not an eigenvalue of π΄. Equivalently, (πΌ − π΄) is invertible. (iii) We use the theory of Fredholm integral equations to find the expression for (πΌ − π΄)−1 . Obviously, for each π₯ ∈ π½, π¦(π₯) = (πΌ−π΄)−1 π§(π₯) ⇔ π¦(π₯) = π§(π₯) + (π΄π¦)(π₯). By (40), we can get π π¦ (π₯) = π§ (π₯) + ∫ π (π₯, π ) π¦ (π ) ππ . 0 (43) π 0 (48) Thus β(πΌ − π΄)−1 β ≤ 1/(1 − ππ). This completes the proof of the lemma. Remark 12. Since π(π₯, π ) ≥ π for each (π₯, π ) ∈ π½, it is easy to prove that π (π₯, π ) ≥ π/(1 − ππ). 3. Main Results Consider the following boundary value problem (BVP) with impulses: σΈ − (π¦[1] (π₯)) + π (π₯) π¦ (π₯) = ππ (π₯, π¦ (π₯)) , π₯ =ΜΈ π₯π , π₯ ∈ π½, −Δ (π¦[1] (π₯π )) = πΌπ (π¦ (π₯π )) , π = 1, 2, . . . , π, π (49) π¦ (0) − ππ¦[1] (0) = ∫ π0 (π ) π¦ (π ) ππ , 0 π π¦ (π) − ππ¦[1] (π) = ∫ π1 (π ) π¦ (π ) ππ . 0 Denote a nonlinear operator π : ππΆ(π½) → ππΆ(π½) by π (ππ¦) (π₯) = π ∫ πΊ (π₯, π ) π (π , π¦ (π )) ππ 0 The condition π < 1/π implies that 1 is not an eigenvalue of the kernel π(π₯, π ). So (43) has a unique continuous solution π¦ for every continuous function π§. By successive substitutions in (43), we obtain π¦ (π₯) = π§ (π₯) + ∫ π (π₯, π ) π§ (π ) ππ , σ΅©σ΅© σ΅© σ΅©σ΅©(πΌ − π΄)−1 π§σ΅©σ΅©σ΅© 1 σ΅© σ΅©≤ . 1 − ππ βπ§β (47) (44) (50) π + ∑πΊ (π₯, π₯π ) πΌπ (π¦ (π₯π )) . π=0 It is easy to see that solutions of (49) are solutions of the following equation: π¦ (π₯) = ππ¦ (π₯) + π΄π¦ (π₯) , π₯ ∈ π½−1 . (51) 6 Abstract and Applied Analysis According to Lemma 11, π¦ is a solution of (51) if and only if it is a solution of π¦ (π₯) = (πΌ − π΄)−1 ππ¦ (π₯) . (52) Because from the formula (54), we have π (Φπ¦) (π₯) = (ππ¦) (π₯) + ∫ π (π₯, π ) (ππ¦) (π ) ππ 0 It follows from (46) that π¦ is a solution of (52) if and only if π = π ∫ πΊ (π₯, π ) π (π , π¦ (π )) ππ 0 π π¦ (π₯) = (ππ¦) (π₯) + ∫ π (π₯, π ) (ππ¦) (π ) ππ . 0 (53) π + ∑πΊ (π₯, π₯π ) πΌπ (π¦ (π₯π )) π=0 So, the operator Φ can be written as π π + π ∫ π (π₯, π ) ∫ πΊ (π₯, π) π (π, π¦ (π)) ππ ππ π (Φπ¦) (π₯) = (ππ¦) (π₯) + ∫ π (π₯, π ) (ππ¦) (π ) ππ . 0 0 (54) π π (1 − ππ) π΄2 ∫ πΌ (π ) ππ β©½ (1 − ππ) π΅2 ∫ π½ (π ) ππ , 0 0 (57) π ππ ) ∫ πΊ (π₯, π ) π (π , π¦ (π )) ππ 1 − ππ 0 π π=0 + ππ π ∑πΊ (π₯, π₯π ) πΌπ (π¦ (π₯π )) 1 − ππ π=0 π ππ΄ ∫ π (π , π¦ (π )) ππ 1 − ππ 0 ≤ + (56) Theorem 13. Assume (H1), (H2), (H3), and (H4) are satisfied. And π=0 + ∑πΊ (π₯, π₯π ) πΌπ (π¦ (π₯π )) for all π¦ ∈ (0, πΏ 1 ], π₯ ∈ π½. (H4) There exist πΏ 2 > πΏ 1 and π½(π₯) ∈ π, π1 ∈ R with π π1 β©½ ∑π π=0 πΌπ (π¦(π₯π ))/π ∫0 π½(π )ππ such that for all π¦ ∈ (πΏ 2 , ∞], π₯ ∈ π½. Then, we can get the following theorem. 0 ≤ π (1 + (55) π (π₯, π¦) ≥ π½ (π₯) [π¦ (1 − ππ) − π1 ] π + ∫ π (π₯, π ) ∑πΊ (π₯, π₯π ) πΌπ (π¦ (π₯π )) ππ It satisfies the conditions of Theorem 1 with πΈ = πΆ(π½) and the cone πΆ = π0 . Let us list some marks and conditions for convenience. The nonlinearity π : π½ × [0, ∞) → [0, ∞) is continuous and satisfies the following. (H3) There exist πΏ 1 > 0 and πΌ(π₯) ∈ π, π1 ∈ R with π1 β©Ύ π ∑π π=0 πΌπ (π¦(π₯π ))/π ∫0 πΌ(π )ππ such that π (π₯, π¦) ≤ πΌ (π₯) [π¦ (1 − ππ) − π1 ] 0 π π π΄ ∑πΌπ (π¦ (π₯π )) . 1 − ππ π=0 (60) Hence, inequality (59) is established. This implies that π π ππ΄ π΄ σ΅©σ΅© σ΅©σ΅© ∑πΌπ (π¦ (π₯π )) , ∫ π (π , π¦ (π )) ππ + σ΅©σ΅©Φπ¦σ΅©σ΅© β©½ 1 − ππ 0 1 − ππ π=0 (61) then, if π satisfies (1 − ππ) π΄ π (1 − ππ) π΅2 ∫0 π½ (π ) ππ β©½πβ©½ π 1 π΄ ∫0 πΌ (π ) ππ . or equivalently (58) π ∫ π (π , π¦ (π )) ππ β©Ύ The problem (49) has at least one positive solution. 0 Proof. First of all, we show that operator Φ is defined by (54) maps π0 into itself. Let π¦ ∈ π0 . Then (Φπ¦)(π₯) ≥ 0 for all that π‘ ∈ π½−1 , and (Φπ¦) (π₯) β©½ π ππ΄ ∫ π (π , π¦ (π )) ππ 1 − ππ 0 π π΄ + ∑πΌπ (π¦ (π₯π )) . 1 − ππ π=0 1 − ππ σ΅©σ΅© σ΅©σ΅© 1 π σ΅©Φπ¦σ΅© − ∑πΌ (π¦ (π₯π )) . (62) ππ΄ σ΅© σ΅© π π=0 π On the other hand, it follows that (Φπ¦) (π₯) β©Ύ (59) π ππ΅ ∫ π (π , π¦ (π )) ππ 1 − ππ 0 π π΅ + ∑πΌπ (π¦ (π₯π )) . 1 − ππ π=0 (63) Abstract and Applied Analysis 7 First, let π¦ ∈ π0 with βπ¦β = πΏ 1 . Inequality (59) implies In fact, we have π (Φπ¦) (π₯) ≤ (Φπ¦) (π₯) = π ∫ πΊ (π₯, π ) π (π , π¦ (π )) ππ 0 π ≤ + ∑πΊ (π₯, π₯π ) πΌπ (π¦ (π₯π )) π=0 π π π π π΄ ∑πΌπ (π¦ (π₯π )) 1 − ππ π=0 0 π π = ππ΄ ∫ πΌ (π ) π¦ (π ) ππ − + ∫ π (π₯, π ) ∑πΊ (π₯, π₯π ) πΌπ (π¦ (π₯π )) ππ 0 π ππ΄ ∫ πΌ (π ) [π¦ (π ) (1 − ππ) − π1 ] ππ 1 − ππ 0 + + π ∫ π (π₯, π ) ∫ πΊ (π₯, π) π (π, π¦ (π)) ππ ππ 0 π π π΄ ππ΄ ∑πΌπ (π¦ (π₯π )) ∫ π (π , π¦ (π )) ππ + 1 − ππ 0 1 − ππ π=0 0 π=0 π π ππ ≥ π (1 + ) ∫ πΊ (π₯, π ) π (π , π¦ (π )) ππ 1 − ππ 0 × ∫ πΌ (π ) ππ + 0 = ππ΄ ∫ πΌ (π ) π¦ (π ) ππ + + ∑πΊ (π₯, π₯π ) πΌπ (π¦ (π₯π )) 0 π=0 ππ π + ∑πΊ (π₯, π₯π ) πΌπ (π¦ (π₯π )) 1 − ππ π=0 π π π=0 0 (67) By condition (H3) and (58), we obtain π π π=0 0 ∑πΌπ (π¦ (π₯π )) − ππ1 ∫ πΌ (π ) ππ β©½ 0, It follows from (62) that π 0 So π σ΅© σ΅© σ΅© σ΅© (Φπ¦) (π₯) β©½ ππ΄ ∫ πΌ (π ) ππ σ΅©σ΅©σ΅©π¦σ΅©σ΅©σ΅© β©½ σ΅©σ΅©σ΅©π¦σ΅©σ΅©σ΅© . π π΅ + ∑πΌ (π¦ (π₯π )) 1 − ππ π=0 π = (68) ππ΄ ∫ πΌ (π ) ππ β©½ 1. ππ΅ 1 − ππ σ΅©σ΅© σ΅©σ΅© 1 π (Φπ¦) (π₯) ≥ ⋅[ σ΅©Φπ¦σ΅© − ∑πΌ (π¦ (π₯π ))] 1 − ππ ππ΄ σ΅© σ΅© π π=0 π 0 π΅ (1 − ππ) π΅ σ΅©σ΅© σ΅©σ΅© ∑πΌ (π¦ (π₯π )) σ΅©Φπ¦σ΅© − (1 − ππ) π΄ σ΅© σ΅© 1 − ππ π=0 π π π΅ ∑πΌπ (π¦ (π₯π )) 1 − ππ π=0 (1 − ππ) π΅ σ΅©σ΅© σ΅©σ΅© σ΅©Φπ¦σ΅© . (1 − ππ) π΄ σ΅© σ΅© (69) Consequently, βΦπ¦β β©½ βπ¦β. Let Ω1 := {π¦ ∈ πΆ(π½); βπ¦β < πΏ 1 }. Then, we have βΦπ¦β β©½ βπ¦β for π¦ ∈ π0 ∩ πΩ1 . Next, let πΏΜ2 = max{2πΏ 1 , ((1 − ππ)π΄/(1 − ππ)π΅)πΏ 2 } and set Ω2 := {π¦ ∈ πΆ(π½); βπ¦β < πΏΜ2 }. For π¦ ∈ π0 with βπ¦β = πΏΜ2 , we have π + π΄ 1 − ππ × [∑πΌπ (π¦ (π₯π )) − ππ1 ∫ πΌ (π ) ππ ] . π π ππ΅ π΅ ≥ ∑πΌπ (π¦ (π₯π )) . ∫ π (π , π¦ (π )) ππ + 1 − ππ 0 1 − ππ π=0 (64) = π π΄ ∑πΌπ (π¦ (π₯π )) 1 − ππ π=0 π π ππ΄ π 1 − ππ 1 minπ¦ (π₯) ≥ π₯∈π½ (1 − ππ) π΅ (1 − ππ) π΄ ⋅ πΏ = πΏ 2. ≥ (1 − ππ) π΄ (1 − ππ) π΅ 2 (65) So, we get (1 − ππ) π΅ σ΅©σ΅© σ΅©σ΅© (1 − ππ) π΅ Μ πΏ σ΅©π¦σ΅© = (1 − ππ) π΄ σ΅© σ΅© (1 − ππ) π΄ 2 (70) It follows from (63) that (1 − ππ) π΅ σ΅©σ΅© σ΅©σ΅© (Φπ¦) (π₯) β©Ύ σ΅©Φπ¦σ΅© . (1 − ππ) π΄ σ΅© σ΅© (66) This show that Φπ¦ ∈ π0 . It is easy to see that Φ is the complete continuity. We now proceed with the construction of the open sets Ω1 and Ω2 . (Φπ¦) (π₯) ≥ ≥ π π ππ΅ π΅ ∑πΌπ (π¦ (π₯π )) ∫ π (π , π¦ (π )) ππ + 1 − ππ 0 1 − ππ π=0 π ππ΅ ∫ π½ (π ) [π¦ (π ) (1 − ππ) − π1 ] ππ 1 − ππ 0 + π π΅ ∑πΌπ (π¦ (π₯π )) 1 − ππ π=0 8 Abstract and Applied Analysis π 0 π΅ 1 − ππ π π π=0 0 = ππ΅ ∫ π½ (π ) π¦ (π ) ππ + First, let π¦ ∈ π0 with βπ¦β = πΏ 1 . Inequality (63) implies (Φπ¦) (π₯) ≥ × (∑πΌπ (π¦ (π₯π )) − ππ1 ∫ π½ (π ) ππ ) . (71) ≥ By condition (H4) and (58), we obtain π π π=0 0 ππ΅ β©Ύ (72) π (1 − ππ) π΅ ∫0 π½ (π ) ππ π . 0 (1 − ππ) π΅ ∫0 π½ (π ) ππ ⋅ ∫ π½ (π ) ππ (78) π π π=0 0 ∗ π (π₯, π¦) ≤ π½ (π₯) [π¦ (1 − ππ) − ππ΅ β©Ύ π1∗ ] (75) Theorem 14. Assume (H1), (H2), (H5), and (H6) are satisfied. And π ∗ (1 − ππ) π΄ ∫ π½ (π ) ππ β©½ (1 − ππ) π΅ ∫ πΌ (π ) ππ , (76) 0 0 then, if π satisfies (1 − π ∫0 πΌ∗ (π ) ππ β©½πβ©½ π 1 π΄ ∫0 π½∗ (π ) ππ π (1 − ππ) π΅ ∫0 πΌ∗ (π ) ππ . Hence (Φπ¦) (π₯) β©Ύ (1 − ππ) π΄ π (1 − ππ) π΅ ∫0 πΌ∗ (π ) ππ π ∫ πΌ∗ (π ) π¦ (π ) ππ . 0 (80) Since π¦ ∈ π0 , we have π¦(π₯) β©Ύ ((1 − ππ)π΅/(1 − ππ)π΄)βπ¦β for all π₯ ∈ π½. It follows from the above inequality that (Φπ¦) (π₯) β©Ύ for all π¦ ∈ (πΏ 2 , ∞], π₯ ∈ π½. 2 (79) (1 − ππ) π΄ (74) for all π¦ ∈ (0, πΏ 1 ], π₯ ∈ π½. (H6) There exist π½∗ (π₯) ∈ π, π1∗ ∈ R with π1∗ β©Ύ π π ∑π=0 πΌπ (π¦(π₯π ))/π ∫0 π½∗ (π )ππ such that ππ) π΅2 0 ∑πΌπ (π¦ (π₯π )) − ππ1∗ ∫ πΌ∗ (π ) ππ β©Ύ 0, π (π₯, π¦) ≥ πΌ∗ (π₯) [π¦ (1 − ππ) − π1∗ ] (1 − ππ) π΄ π=0 (73) (1 − ππ) π΅ σ΅©σ΅© σ΅©σ΅© σ΅©σ΅© σ΅©σ΅© σ΅©π¦σ΅© = σ΅©π¦σ΅© . (1 − ππ) π΄ σ΅© σ΅© σ΅© σ΅© ∗ π By condition (H5) and (77), we obtain 0 Next, with πΏ 1 and πΏ 2 as above, we assume that π satisfied the following. (H5) There exist πΌ∗ (π₯) ∈ π, π1∗ ∈ R with π1∗ β©½ π π ∑π=0 πΌπ (π¦(π₯π ))/π ∫0 πΌ∗ (π )ππ such that π π × (∑πΌπ (π¦ (π₯π )) − ππ1∗ ∫ πΌ∗ (π ) ππ ) . Hence βΦπ¦β β©Ύ βπ¦β for π¦ ∈ π0 ∩ πΩ2 . It follows from (i) of Theorem 1 that Φ has a fixed point in π0 ∩ (Ω2 \ Ω1 ), and this fixed point is a solution of (49). This completes the proof. 2 π΅ 1 − ππ π (1 − ππ) π΄ π π π΅ ∑πΌπ (π¦ (π₯π )) 1 − ππ π=0 = ππ΅ ∫ πΌ∗ (π ) π¦ (π ) ππ + Since π¦ ∈ π0 we have π¦(π₯) β©Ύ ((1 − ππ)π΅/(1 − ππ)π΄)βπ¦β for all π₯ ∈ π½. It follows from the above inequality that (Φπ¦) (π₯) β©Ύ π ππ΅ ∫ πΌ∗ (π ) [π¦ (π ) (1 − ππ) − π1∗ ] ππ 1 − ππ 0 + ∑πΌπ (π¦ (π₯π )) − ππ1 ∫ π½ (π ) ππ β©Ύ 0, (1 − ππ) π΄ π π ππ΅ π΅ ∑πΌπ (π¦ (π₯π )) ∫ π (π , π¦ (π )) ππ + 1 − ππ 0 1 − ππ π=0 . (1 − ππ) π΄ π (1 − ππ) π΅ ∫0 πΌ∗ (π ) ππ (1 − ππ) π΅ σ΅©σ΅© σ΅©σ΅© σ΅©σ΅© σ΅©σ΅© ⋅ σ΅©π¦σ΅© = σ΅©π¦σ΅© . (1 − ππ) π΄ σ΅© σ΅© σ΅© σ΅© Proof. Let Φ be a completely continuous operator defined by (54). Then Φ maps the cone π0 into itself. 0 (81) Let Ω1 := {π¦ ∈ πΆ(π½); βπ¦β < πΏ 1 }. Then, we have βΦπ¦β β©Ύ βπ¦β for π¦ ∈ π0 ∩ πΩ1 . Next, let πΏΜ2 = max{2πΏ 1 , ((1 − ππ)π΄/(1 − ππ)π΅)πΏ 2 } and set Ω2 := {π¦ ∈ πΆ(π½); βπ¦β < πΏΜ2 }. Then for π¦ ∈ π0 with βπ¦β = πΏΜ2 for all π₯ ∈ π½, we have minπ₯∈π½ π¦(π₯) β©Ύ πΏ 2 . Inequality (59) implies (77) The problem (49) has at least one positive solution. π ∫ πΌ∗ (π ) ππ (Φπ¦) (π₯) ≤ π ππ΄ ∫ π (π , π¦ (π )) ππ 1 − ππ 0 + π π΄ ∑πΌπ (π¦ (π₯π )) 1 − ππ π=0 Abstract and Applied Analysis ≤ 9 π ππ΄ ∫ π½∗ (π ) [π¦ (π ) (1 − ππ) − π1∗ ] ππ 1 − ππ 0 + π π΄ ∑πΌπ (π¦ (π₯π )) 1 − ππ π=0 π = ππ΄ ∫ π½∗ (π ) π¦ (π ) ππ 0 + π π π΄ [∑πΌπ (π¦ (π₯π )) − ππ1∗ ∫ π½∗ (π ) ππ ] . 1 − ππ π=0 0 (82) By condition (H6) and (77), we obtain π π π=0 0 ∑πΌπ (π¦ (π₯π )) − ππ1∗ ∫ π½∗ (π ) ππ β©½ 0, π (83) ππ΄ ∫ π½∗ (π ) ππ β©½ 1. 0 So π σ΅© σ΅© σ΅© σ΅© (Φπ¦) (π₯) β©½ ππ΄ ∫ π½∗ (π ) ππ σ΅©σ΅©σ΅©π¦σ΅©σ΅©σ΅© β©½ σ΅©σ΅©σ΅©π¦σ΅©σ΅©σ΅© β©½ 1. 0 (84) Therefore βΦπ¦β β©½ βπ¦β with βπ¦β = πΏΜ2 . Then, we have βΦπ¦β β©½ βπ¦β for π¦ ∈ π0 ∩ πΩ2 . We see the case (ii) of Theorem 1 is met. It follows that Φ has a fixed point in π0 ∩ (Ω2 \ Ω1 ), and this fixed point is a solution of (49). This completes the proof. Acknowledgments This work was supported by the NNSF of China under Grant no. 11271261, Natural Science Foundation of Shanghai (no. 12ZR1421600), Shanghai Municipal Education Commission (no. 10YZ74), the Slovenian Research Agency, and a Marie Curie International Research Staff Exchange Scheme Fellowship within the 7th European Community Programme (FP7PEOPLE-2012-IRSES-316338). References [1] V. Lakshmikantham, D. D. Bainov, and P. S. Simeonov, Theory of Impulsive Differential Equations, vol. 6, World Scientific Publishing, Singapore, 1989. [2] D. Bainov and P. Simeonov, Impulsive Differential Equations: Periodic Solutions and Applications, vol. 66 of Pitman Monographs and Surveys in Pure and Applied Mathematics, Longman Scientific & Technical, Harlow, UK, 1993. [3] D. J. Guo and V. Lakshmikantham, Nonlinear Problems in Abstract Cones, Academic Press, San Diego, Calif, USA, 1988. [4] D. Guo, J. Sun, and Z. 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