Modified Decomposition Method for Solving Nonlinear Fredholm-Volterra Integral Equations 1 1,2,3 F. S. Zulkarnain, 2Z.K. Eshkuvatov,3N. M. A. Nik Long Department of Mathematics, Faculty of Science, Universiti Putra Malaysia (UPM), Malaysia 2,3 Institute for Mathematical Research (INSPEM),UPM, Malaysia Abstract. In this note, an approximate solution of nonlinear Volterra-Fredholm integral equation is obtained by using modified decomposition method. General cases of nonlinear terms in the equation are considered. Finally some numerical examples are presented to validate the accuracy and efficiency of the method. Keywords: Volterra-Fredholm integral, decomposition method, numerical method. PACS: 02.30.Rz, 02.60.Lj u x, t f x, t INTRODUCTION Recently, Adomian decomposition method [1,2] has been focus on many stochastic and deterministic problems in physics, biology and chemical reactions. In mathematical problems, this method has been applied for solving a large class of linear and nonlinear equations including differential and integral equations, integro-differential equations, and so on. The Volterra-Fredholm integral equation arises from parabolic boundary value problems, the mathematical modeling of the spatio-temporal development of an epidemic and biological problems. The essential features of these models are of wide applicability. Detailed descriptions and formulation of these models can be found in [3,4] and references therein. Particularly, Bildik and Inc (2007) have solved the following nonlinear Volterra-Fredholm integral equation by using modified decomposition method. u x f x 1 K1 x, t u t dt a x p 2 K 2 x, t u t dt b (1) q t 0 F x, t , , , u , d d , (2) x, t 0, T and ux, t is an unknown function, f x, t and F x, t , , , u , are analytic where functions on D 0, T , where is a closed n subset of R , n 1,2,3. Wazwaz (2002) has treated Eq. (2) using modified decomposition method. In this paper, we applied the modified decomposition method (MDM) to obtain approximate solution of nonlinear Fredholm-Volterra integral Equation(9) for any p, q 1 . Moreover, we have shown 4 Examples to validate the method proposed. 2. MODIFIED DECOMPOSITION METHOD (MDM) 2.1 General Scheme for Operator Equation a where p is a positive, q 1 , f x is the given function K1 x, t and K 2 x, t are square integrable kernels, 1 , 2 , a and b are constants. Yalçinbaş (2002) have obtained an approximation solution of Eq. (1) by using Kanwal and Liu method. Maleknejad and Hadizadeh (1999) have presented the solution for following nonlinear mixed Volterra-Fredholm integral equation by using the standard decomposition method Let us consider the operator equation of the form Lu Ru Nu g x, (3) where L is the operator of highest order derivative which is assumed to be invertible, R is the remaining linear operator collecting the lower order derivatives, Nu represents the nonlinear terms and g is a source term. Multiplying inverse function of Eq. (3) we get L1 to both sides u f x L1 Ru L1 Nu , (4) where f x L1 g x .In standard decomposition method, the unknown function u x is searched as a series of the form 2.2 Application of Modified Decomposition Method (MDM) for Nonlinear Fredholm-Volterra Integral Equations We consider nonlinear Fredholm-Volterra equation u x f x 1 K1 x, t F1 u t dt b u x u n x , (5) a n 0 2 K 2 x, t F2 u t dt , (9) x a the components u0 , u1 , u2 , are usually determined where f (x ) is the given function, K1 ( x, t ) and recursively by K 2 ( x, t ) are square integrable kernels of the equation, u0 x f x , u n1 x L1 Ru n x L1 Nun x , (6) n 0. It is note that the decomposition method suggest that the initial component u0 x as the function f x . To apply modified decomposition method, the function f x on the right side of the Eq. (2) is divided into two parts f x f1 x f 2 x. (7) 1 and 2 are parameters while F1 (u(t )) and F2 (u(t )) are nonlinear terms and u (x) is unknown function to be determined. The nonlinear term F1 (u(t )) and F2 (u(t )) are represented by the Adomian polynomial series. Wazwaz (2002) introduced the procedure to calculate the Adomian polynomials F1 u t An t , n 0 (10) F2 u t Bn t . n 0 Based on the expression above, Wazwaz (1999) propose a slight variation only on the components u0 x and u1 x . He proposed that f1 ( x) contain the zeroth component u 0 while f 2 ( x) is the remainder terms. Thus, the following recursive relations for the modified decomposition method are formulated as u0 x f1 x , C0 F u0 , C1 u1 F u0 , 1 2 u1 F u0 , 2! C3 u3 F u0 u1u2 F u0 C2 u 2 F u0 u1 x f 2 x L1 Ru 0 x L1 Nu0 x (8) u n1 x L1 Ru n x L1 Nun x , n 1 We can conclude that the zeroth component of standard decomposition method in (4) is defined by the function f while in modified decomposition method, the zeroth component is defined by selecting some terms f1 x of function f x . The remaining where An (t ) and Bn (t ) are Adomian polynomials defined by part will be added to the next component u1 .Easy calculations and fast solutions in many cases depend on our proper choice of the parts f1 and f 2 of f . (11) 1 3 u1 F u0 , 3! Here Ai Ci if F F1 and Bi Ci if F F2 .The nonlinear terms can be considered in different cases. p For example for the case of F u u x , the first few Adomian polynomials C n are given by C0 u0p , 3. EXAMPLES C1 pu0p 1u1 , Example 1. Consider the nonlinear Fredholm integral equation of the second kind p ( p 1) p 2 2 C2 pu0p 1u2 u0 u1 , 2! C3 pu0p 1u3 p ( p 1)u0p 2u1u2 (12) u x 1 p ( p 1)( p 2) p 3 3 u0 u1 , 3! For the case of F (u ) sin u ( x) , few terms of Adomian polynomials An are defined by C0 sin u 0 , 1 5 x 3xt u 2 t dt , 0 4 (16) Solution: It is clear that f x 1 5 , 1 3, 2 0 4 and K1 x, t xt . Since 2 0 the Adomian Bn 0, n 0,1,... and An for nonlinear term F1 ut u 2 t are given in (12) with p 2 . polynomials A0 u02 , C1 u1 cos u 0 , (13) 1 C 2 u 2 cos u 0 u12 sin u 0 , 2! A1 2u0u1 , A2 2u0u2 u12 , (17) A3 2u0u3 2u1u2 , 1 C3 u3 cos u 0 u1u 2 sin u 0 u13 cos u 0 , 3! For the case of F u e u t , the first few Adomian polynomials Cn are given in the form Now, we divided f x into two parts such as 1 f1 x 1 x and f 2 x x . Using the modified 4 recursive relation (15) we obtain C 0 e uo , 1 1 u1 x x 3xt A0 t dt 0, 0 4 C1 u1e uo , 1 C 2 u 2 u12 e uo , 2 ! 1 C3 u3 u1u 2 u13 e uo , 3! (14) Consequently u k x 0, k 1. Then, the solution is Thus, the components u 0 , u1 , u 2 , of u x substitute into series in Eq (5) and each components are defined by u0 x f1 x , ux 1 x. Example 2. Consider the nonlinear Volterra integral equation of the second kind u x 4x2 u1 x f 2 x 1 K1 x, t A0 t dt b a 2 K 2 x, t B0 t dt , x (15) a x cos 4 x 2 1 2 4 xt sin u t dt , x 0 un 1 x 1 K1 x, t An t dt b Solution: From Eq. (18) we found that a 2 K 2 x, t Bn t dt , x a n 1. (18) f x 4 x 2 x cos 4 x 2 1 , 1 0 , 2 K1 x, t 0 , K 2 x, t xt. u0 x x , 2 4 , u1 x The nonlinear term F2 (u) sin ux are given in Eq. (13). Again we divide f x into two parts by 2 x selecting f1 x 4x and f 2 x cos 4 x 2 1 . 2 Then, it follows that x t t 2 dt et dt , x Consequently u k x 0, u t 0. So that k 1. Its exact solution is Solution: Note that Thus, the solution is Example 3. Consider the nonlinear Fredholm-Volterra integral equation. 5 2 x ex 4 3 (19) x t u t dt e 0 x 0 u t dt (20) u x 2 x . 1 1 1 20 x 12 x 6 , 1 , 2 , 2 4 15 K1 x, t x , K2 x, t x . f x u ( x) 4 x 2 . 2 k 1. 1 20 x 12 x6 15 1 1 1 x x u 2 t dt x u 4 t dt 0 2 4 0 0 1 0 Example 4. Consider the nonlinear Fredholm-Volterra integral equation. 4 xt sin 4t 2 dt , u x 0 ux x. x u1 x cos 4 x 2 1 2 uk ( x) 0, x Then, the solution is Consequently, u1 x is defined by 1 0. u 0 x 4 x 2 , 5 1 x ex 4 3 The Adomian polynomials for F1 t u 2 t are given in (17) and F2 t u 4 t are given in (12) with p 4 . To use the MDM we compare two initial guess: u0 4 999 x and u 0 x. 3 500 Solution: Noted that 5 2 f x x e x , 1 1 , 2 1, 4 3 K1 x t , K 2 1 . The Adomian polynomials for given in (17) while for F1 t u 2 t are F2 t e u t are given in (14). We choose f1 ( x) x as the initial value. Then it follows from Eq. (15) that By using the recursive relation in Eq. (15) we present the numerical results in Table 1. The results in Table 1 are obtained by substituting the 5 terms into the series Eq. (5). Based on Table 1, initial value u 0 x 999 x show 500 that MDM gives more approximate to the exact solution than initial value u 0 x 4 x . 3 Table 1. Numerical results for Example 4. MDM (5 MDM (5 x Exact solution iterations) iterations) with with initial guess initial guess u x u0 x 0 0 0.1 0.2 0.3 0.4 0.5 0.2 0.4 0.6 0.8 1.0 4 x 3 u0 x x Exact solution u x 999 x 500 MDM (5 iterations) with initial guess u0 x 4 x 3 MDM (5 iterations) with initial guess u0 x 999 x 500 0 0 0.6 1.2 1.00712624 1.19805306 0.17106581 0.34210702 0.51290891 0.68263034 0.84902789 0.19970755 0.39941485 0.59911980 0.79881408 0.99847536 0.7 0.8 0.9 1.0 1.4 1.6 1.8 2.0 1.14667287 1.24685921 1.26622664 1.12955769 1.39743720 1.59637529 1.79420977 1.98889004 CONCLUSION In this paper, we have solved general nonlinear Fredholm-Volterra integral equations by using modified decomposition method. From the numerical Examples 1-3 we can see that MDM is identical with the exact solution for the given problems considered. In Example 4 (Table 1) developed MDM is not exact but rate of convergence of MDMcan be accelerated by the choice of initial guess. 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