Hindawi Publishing Corporation Journal of Applied Mathematics Volume 2013, Article ID 481729, 10 pages http://dx.doi.org/10.1155/2013/481729 Research Article A New Fractional Subequation Method and Its Applications for Space-Time Fractional Partial Differential Equations Fanwei Meng1 and Qinghua Feng2 1 2 School of Mathematical Sciences, Qufu Normal University, Qufu, Shandong 273165, China School of Science, Shandong University of Technology, Zibo, Shandong 255049, China Correspondence should be addressed to Qinghua Feng; fqhua@sina.com Received 22 February 2013; Accepted 1 July 2013 Academic Editor: Magdy A. Ezzat Copyright © 2013 F. Meng and Q. Feng. 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. A new fractional subequation method is proposed for finding exact solutions for fractional partial differential equations (FPDEs). The fractional derivative is defined in the sense of modified Riemann-Liouville derivative. As applications, abundant exact solutions including solitary wave solutions as well as periodic wave solutions for the space-time fractional generalized Hirota-Satsuma coupled KdV equations are obtained by using this method. 1. Introduction Fractional differential equations are generalizations of classical differential equations of integer order. Recently, fractional differential equations have been the focus of many studies due to their frequent appearance in various applications in physics, biology, engineering, signal processing, systems identification, control theory, finance, and fractional dynamics. Among the investigations for fractional differential equations, research for seeking exact solutions and approximate solutions of fractional differential equations is a hot topic. New exact solutions for fractional differential equations may help to understand better corresponding nonlinear wave phenomena they describe. Some powerful methods have been proposed so far (e.g., see [1–12]). Using these methods, a variety of fractional differential equations have been investigated. In this paper, we propose a new fractional subequation method to establish exact solutions for fractional partial differential equations (FPDEs), which is based on the following fractional ordinary differential equation: π·π2πΌ πΊ (π) + ππ·ππΌ πΊ (π) + ππΊ (π) = 0, 0 < πΌ ≤ 1, (1) where π·ππΌ πΊ(π) denotes the modified Riemann-Liouville derivative of order πΌ for πΊ(π) with respect to π. The definition and some important properties for Jumarie’s modified Riemann-Liouville derivative of order πΌ are listed as follows (see [13–16]): π·π‘πΌ π (π‘) π π‘ 1 { { ∫ (π‘ − π)−πΌ (π (π) − π (0)) ππ, { { Γ (1 − πΌ) ππ‘ 0 ={ 0 < πΌ < 1, { { (πΌ−π) { (π) , π ≤ πΌ < π + 1, π ≥ 1, { (π (π‘)) (2) π·π‘πΌ π‘π = Γ (1 + π) π−πΌ π‘ , Γ (1 + π − πΌ) (3) π·π‘πΌ (π (π‘) π (π‘)) = π (π‘) π·π‘πΌ π (π‘) + π (π‘) π·π‘πΌ π (π‘) , (4) πΌ π·π‘πΌ π [π (π‘)] = ππσΈ [π (π‘)] π·π‘πΌ π (π‘) = π·ππΌ π [π (π‘)] (πσΈ (π‘)) . (5) We organize this paper as follows. In Section 2, we derive the expression for π·ππΌ πΊ(π)/πΊ(π) related to (1). In Section 3, we give the description of the fractional subequation method for solving FPDEs. Then in Section 4 we apply this method to establish exact solutions for the space-time fractional generalized Hirota-Satsuma coupled KdV equations. Some conclusions are presented at the end of the paper. 2 Journal of Applied Mathematics 2. The General Expression for π·ππΌ πΊ(π)/πΊ(π) equality in (5), (1) can be turned into the following second ordinary differential equation: In order to obtain the general solutions for (1), we suppose πΊ(π) = π»(π) and a nonlinear fractional complex transformation π = ππΌ /Γ(1 + πΌ). Then, by (3) and the first π»σΈ σΈ (π) + ππ»σΈ (π) + ππ» (π) = 0. By the general solutions of (6), we have 2 πΆ1 sinh (√π2 − 4π/2) π + πΆ2 cosh (√π2 − 4π/2) π { { π √π − 4π { { ( ), { {− 2 + { 2 { πΆ1 cosh (√π2 − 4π/2) π + πΆ2 sinh (√π2 − 4π/2) π { { { { { { π»σΈ (π) { = { π √4π − π2 −πΆ1 sin (√4π − π2 /2) π + πΆ2 cos (√4π − π2 /2) π {− + π» (π) { ), ( { { 2 2 { { πΆ1 cos (√4π − π2 /2) π + πΆ2 sin (√4π − π2 /2) π { { { { { { πΆ2 { {− π + , { 2 πΆ1 + πΆ2 π π2 − 4π > 0, π2 − 4π < 0, (7) π2 − 4π = 0, Since π·ππΌ πΊ(π) = π·ππΌ π»(π) = π»σΈ (π)π·ππΌ π = π»σΈ (π), we obtain where πΆ1 and πΆ2 are arbitrary constants. πΌ πΌ { √π2 − 4π πΆ1 sinh (√π2 − 4π/2Γ (1 + πΌ)) π + πΆ2 cosh (√π2 − 4π/2Γ (1 + πΌ)) π { π { { ( − + ) , π2 − 4π > 0, { { 2 2 { 2 πΌ 2 πΌ { πΆ1 cosh (√π − 4π/2Γ (1 + πΌ)) π + πΆ2 sinh (√π − 4π/2Γ (1 + πΌ)) π { { { { { { { πΌ πΌ 2 2 { π·ππΌ πΊ (π) { { π √4π − π2 −πΆ1 sin (√4π − π /2Γ (1 + πΌ)) π + πΆ2 cos (√4π − π /2Γ (1 + πΌ)) π ) , π2 − 4π < 0, ( = {− + 2 2 { πΊ (π) 2 πΌ 2 πΌ { √ √ πΆ1 cos ( 4π − π /2Γ (1 + πΌ)) π + πΆ2 sin ( 4π − π /2Γ (1 + πΌ)) π { { { { { { πΆ2 Γ (1 + πΌ) π { { { , π2 − 4π = 0. − + { πΌ { 2 πΆ Γ + πΌ) + πΆ π (1 { 1 2 { { { { 3. Description of the Fractional Subequation Method (8) Step 1. Suppose that In this section, we give the main steps of the fractional subequation method for finding exact solutions for FPDEs. Suppose that an FPDE, say in the independent variables π‘, π₯1 , π₯2 , . . . , π₯π , is given by π (π’1 , . . . , π’π , π·π‘πΌ π’1 , . . . , π·π‘πΌ π’π , π·π₯πΌ1 π’1 , . . . , π·π₯πΌ1 π’π , . . . , π·π₯πΌπ π’1 , . . . , π·π₯πΌπ π’π , π·π‘2πΌ π’1 , . . . , (6) (9) π·π‘2πΌ π’π , π·π₯2πΌ1 π’1 , . . .) = 0, where π’π = π’π (π‘, π₯1 , π₯2 , . . . , π₯π ), π = 1, . . . , π, are unknown functions and π is a polynomial in π’π and their various partial derivatives including fractional derivatives. π’π (π‘, π₯1 , π₯2 , . . . , π₯π ) = ππ (π) , π = ππ‘ + π1 π₯1 + π2 π₯2 + ⋅ ⋅ ⋅ + ππ π₯π + π0 . (10) Then, by the second equality in (5), (9) can be turned into the following fractional ordinary differential equation with respect to the variable π: πΜ (π1 , . . . , ππ , ππΌ π·ππΌ π1 , . . . , ππΌ π·ππΌ ππ , π1πΌ π·ππΌ π1 , . . . , π1πΌ π·ππΌ ππ , . . . , πππΌ π·ππΌ π1 , . . . , πππΌ π·ππΌ ππ , π2πΌ π·π2πΌ π1 , . . . , π2πΌ π·π2πΌ ππ , π12πΌ π·π2πΌ π1 , . . .) = 0. (11) Journal of Applied Mathematics 3 Step 2. Suppose that the solution of (11) can be expressed by a polynomial in (π·ππΌ πΊ/πΊ) as follows: constants with π, π =ΜΈ 0. Then, by usinge the second equality in (4), we obtain πΌ π·π₯πΌ π’ = π·π₯πΌ π (π) = (π·ππΌ π) (ππ₯σΈ ) = ππΌ π·ππΌ π, ππ (π) ππ = ππ,0 + ∑ [ππ,π ( π·ππΌ πΊ π=1 + ππ,π ( πΊ ) π·ππΌ πΊ πΊ and similarly we have π−1 ) (14) πΌ π·π‘πΌ π’ = π·π‘πΌ π (π) = (π·ππΌ π) (ππ‘σΈ ) = ππΌ π·ππΌ π, π π·ππΌ πΊ 2 ] √ π (1 + 1 ( ) )] , π πΊ ] π = 1, 2, . . . , π, (12) where πΊ = πΊ(π) satisfies (1), π is a constant, and ππ,π , π = 0, 1, . . . , π, π = 1, 2, . . . , π, are constants to be determined later. The positive integer π can be determined by considering the homogeneous balance between the highest-order derivatives and nonlinear terms appearing in (11). Step 3. Substituting (12) into (11), using (1), and collecting all terms with the same order of (π·ππΌ πΊ/ πΊ)√π(1 + (1/π)(π·ππΌ πΊ/πΊ)2 ) together, the left-hand side of (11) is converted into another polynomial in (π·ππΌ πΊ/πΊ). Equating each coefficient of this polynomial to zero yields a set of algebraic equations for ππ0 , ππ,π , ππ,π , π = 1, . . . , π, π = 1, 2, . . . , π. Step 4. Solving the equations in Step 3 and using (8), we can construct a variety of exact solutions for (9). 4. Application of the Method to Space-Time Fractional Generalized Hirota-Satsuma Coupled KdV Equations π·π₯πΌ V = ππΌ π·ππΌ π, π·π‘πΌ V = ππΌ π·ππΌ π, π·π₯πΌ π€ = ππΌ π·ππΌ π, π·π‘πΌ π€ = ππΌ π·ππΌ π; then (11) can be turned into the following fractional ordinary differential equations with respect to the variable π: 1 ππΌ π·ππΌ π − π3πΌ π·π3πΌ π + 3ππΌ ππ·ππΌ π − 3ππΌ π·ππΌ (ππ) = 0, 2 ππΌ π·ππΌ π + π3πΌ π·π3πΌ π − 3ππΌ ππ·ππΌ π = 0, Suppose that the solutions of (16) can be expressed by π1 π (π) = π0 + ∑ [ππ ( π·ππΌ πΊ πΊ π=1 + ππ ( π2 π (π) = π0 + ∑ [ππ ( πΊ π·ππΌ πΊ πΊ π=1 π3 π (π) = π0 + ∑ [ππ ( (13) π·π‘πΌ π€ + π·π₯3πΌ π€ − 3π’π·π₯πΌ π€ = 0, 0 < πΌ ≤ 1. Equations (13) can be used to describe the interaction of two long waves with different dispersion relations [17]. In [15], the authors solved equations (13) by a proposed fractional subequation method based on the fractional Riccati equation, while in [16], (13) are solved by the known (πΊσΈ /πΊ)-expansion method. Now we apply the described method in Section 3 to solve (13). To begin with, suppose that π’(π₯, π‘) = π(π), V(π₯, π‘) = π(π), π€(π₯, π‘) = π(π), where π = ππ₯ + ππ‘ + π0 , π, π, π0 are all π ) π·ππΌ πΊ ) πΊ πΊ + ππ ( ) 2 πΌ π· πΊ √ π (1 + 1 ( π ) )] ], π πΊ ] π π·ππΌ πΊ π=1 π−1 π·ππΌ πΊ π−1 ) 2 π·πΌ πΊ √ π (1 + 1 ( π ) )] ], π πΊ ] π ) π·ππΌ πΊ πΊ 1 π·π‘πΌ π’ − π·π₯3πΌ π’ + 3π’π·π₯πΌ π’ − 3π·π₯πΌ (Vπ€) = 0, 2 π·π‘πΌ V + π·π₯3πΌ V − 3π’π·π₯πΌ V = 0, (16) ππΌ π·ππΌ π + π3πΌ π·π3πΌ π − 3ππΌ ππ·ππΌ π = 0. + ππ ( In this section, we will apply the described method in Section 3 to solve the space-time fractional generalized Hirota-Satsuma coupled KdV equations [15, 16]: (15) π−1 ) 2 π·πΌ πΊ √ π (1 + 1 ( π ) )] ]. π πΊ ] (17) Balancing the order of π·π3πΌ π and π·ππΌ (ππ), π·π3πΌ π and ππ·ππΌ π, and π·π3πΌ π and ππ·ππΌ π in (16), we have π1 = π2 = π3 = 2. So π (π) = π0 + π1 ( π·ππΌ πΊ πΊ ) + π2 ( π·ππΌ πΊ πΊ 2 ) 2 πΌ 1 π·π πΊ √ + π1 π (1 + ( )) π πΊ + π2 ( π·ππΌ πΊ πΊ 2 ) √ π (1 + πΌ 1 π·π πΊ ( ) ), π πΊ 4 Journal of Applied Mathematics π (π) = π0 + π1 ( π·ππΌ πΊ πΊ ) + π2 ( π·ππΌ πΊ πΊ π·ππΌ πΊ 2 π0 = ) 1 π1 = π2 π−2πΌ π1 , 4 2 1 + π1 √ π (1 + ( )) π πΊ π2 = 0, π·ππΌ πΊ 2 πΌ 1 π·π πΊ + π2 ( ) √ π (1 + ( ) ), πΊ π πΊ π (π) = π0 + π1 ( π·ππΌ πΊ πΊ ) + π2 ( π·ππΌ πΊ πΊ π2 = ) πΊ π= πΌ 1 π·π πΊ ( ) ). π πΊ (1/π)(π·ππΌ πΊ/πΊ)2 ) √π(1 + together, equating each coefficient to zero yields a set of algebraic equations. Solving these equations, with the aid of the mathematical software Maple, yields the following seven groups of values. Case 1. One has π2 = π π2 , 2π2 1 5 π0 = π−πΌ ππΌ + π−2πΌ ππ22 , 3 12 π = 0, 2πΌ π2 = 2π , π1 = 0, π1 = 0, π2 = 2π2πΌ π2 π2 = , π2 π1 = 0, π1 = π1 , π2 = 2π2πΌ , π1 = 0, π2 = 0, π0 = π0 , π1 = π1 , π2 = 0, π1 = 0, π2 = 0, π0 = π1 (π−2πΌ π1 π1 − 2π0 ) 2π1 π2 = 0, , (21) π1 = π1 , π1 = 0, π2 = π2 , π22 4π2 π2 = 0. π0 = π0 , π0 = π0 , π1 = 0, π0 = (19) π = π, π1 = − 1 8 1 π0 = π−2πΌ π12 + π2πΌ π + π−πΌ ππΌ , 48 3 3 π2 = 4π2πΌ , π1 = 0, π2 = 0, π1 = π2 = π2 , π2πΌ π1 , π2 π2 = 0, π2 = 0, (22) π0 π22 (π−4πΌ ππ22 − 4ππΌ π−3πΌ ) 12π12 π2 (−π−2πΌ ππ22 + 4π−πΌ ππΌ ) Case 2. One has π1 = 0, π1 = 0, π1 = π1 , π2 = π2 . 1 π = π−2πΌ π1 , 4 π = 0, 2 1 π0 = π−2πΌ ππ22 + π−πΌ ππΌ , 3 3 π2 = π2πΌ , π1 = 0, , π = π−4πΌ ππ22 , π1 = π1 = π1 , 1 −4πΌ 2 πΌ −3πΌ 3 −4πΌ π π1 + π π − π π1 π1 , 16 4 Case 4. One has −πΌ πΌ −2πΌ 2 1 π2 (16π π π2 + 5π π2 ππ2 − 6π0 π2 ) , π0 = 24 π22 2πΌ π2 = 0. 1 1 π0 = π−2πΌ π12 + π−πΌ ππΌ − π−2πΌ π1 π1 , 8 2 Substituting (18) into (16), using (1), and collecting all the terms with the same power of (π·ππΌ πΊ/πΊ) π1 = 0, π1 = 0, π2πΌ π1 , π2 1 π = π−2πΌ π1 , 2 (18) 1 π = π−4πΌ ππ22 , 4 4π4πΌ , π2 π1 = Case 3. One has 2 ) √ π (1 + π0 = π0 , π1 = 0, (20) 2 π·ππΌ πΊ π2 = π2 , 2 πΌ 1 π·π πΊ + π1 √ π (1 + ( )) π πΊ + π2 ( 1 π (π−4πΌ π12 + 128π + 64ππΌ π−3πΌ − 24π−4πΌ π2 π0 ) , 96 2 12π1 , π22 (π−4πΌ ππ22 − 4ππΌ π−3πΌ ) 12π1 , , π2 = 0, π2 = 0. Case 5. One has π = 4ππΌ π−3πΌ , π1 = 0, π = 0, π2 = π2πΌ , π0 = 3π−πΌ ππΌ , π1 = 0, Journal of Applied Mathematics π2 = ±π πΌ 3πΌ −πΌ √ π π , π0 = 0, π1 = 0, π1 = 0, π2 = 0, π0 = π0 , π π2 = 0, π1 = ± 5 π3πΌ π1 π √ πΌ 3πΌ , 2 π π π1 = π1 , + πΆ2 cosh ( πΌ √−ππ )) Γ (1 + πΌ) × (πΆ1 cosh ( πΌ √−ππ ) Γ (1 + πΌ) −1 2 π2 = 0, + πΆ2 sinh ( π2 = 0. (23) πΌ √−ππ )) ] Γ (1 + πΌ) + π2 √−π [ (πΆ1 sinh ( Case 6. One has π = π, 2 1 π0 = π2πΌ π + π−πΌ ππΌ , 3 3 π = 0, 2πΌ π1 = 0, π2 = 2π , π0 = π0 , π1 = π1 , π2 = 0, π1 = 0, π2 = 0, π1 = 4π0 (−π4πΌ π + ππΌ ππΌ ) 3π12 4 (−π4πΌ π + ππΌ ππΌ ) 3π1 π2 = 0, π1 = 0, πΌ √−ππ )) Γ (1 + πΌ) × (πΆ1 cosh ( π1 = 0, π2 = 0, π0 = − + πΆ2 cosh ( πΌ √−ππ ) Γ (1 + πΌ) + πΆ2 sinh ( (24) πΌ √−ππ ) Γ (1 + πΌ) πΌ { √−ππ ) × (π {1 − [ (πΆ1 sinh ( Γ (1 + πΌ) { , , + πΆ2 cosh ( π2 = 0. πΌ √−ππ )) Γ (1 + πΌ) × (πΆ1 cosh ( Case 7. One has π = π, π2 = 0, π2 = 0, π0 = − π1 = 0, π1 = π1 , π2 = 0, 2π0 π (π4πΌ π + 2ππΌ ππΌ ) 3ππ12 π1 = 0, π1 (π) = (25) , −πΌ πΌ −2πΌ 2 1 π2 (16π π π2 + 5π π2 ππ2 − 6π0 π2 ) 24 π22 − π2 = 0, 2π (π4πΌ π + 2ππΌ ππΌ ) 3 (ππ1 ) , π2 = 0. From Case 1, we obtain the following exact solutions. When π < 0, × [ (πΆ1 sinh ( πΌ π2πΌ π2 √−ππ ) π [ (πΆ1 sinh ( 2π2 Γ (1 + πΌ) +πΆ2 cosh ( × (πΆ1 cosh ( Substituting the previous results into (18) and combining with (8), we can obtain a series of exact solutions for (13). 1 −πΌ πΌ 5 −2πΌ 2 π π + π ππ2 − 2π2πΌ π 3 12 πΌ √−ππ ) Γ (1 + πΌ) +πΆ2 sinh ( + πΌ √−ππ )) Γ (1 + πΌ) −1 2 πΌ √−ππ )) ] Γ (1 + πΌ) πΌ π22 √−ππ ) √−π [ (πΆ1 sinh ( 4π2 Γ (1 + πΌ) + πΆ2 cosh ( πΌ √−ππ ) Γ (1 + πΌ) , (26) π1 = 0, π0 = π0 , 1/2 −1 πΌ } √−ππ )) ] }) + πΆ2 sinh ( Γ (1 + πΌ) } 5 1 π0 = π2πΌ π + π−πΌ ππΌ , 3 3 π2 = 2π2πΌ , π1 = 0, π1 (π) = πΌ √−ππ ) Γ (1 + πΌ) 2 π = 0, π1 = −1 πΌ √−ππ )) ] Γ (1 + πΌ) × (πΆ1 cosh ( πΌ √−ππ )) Γ (1 + πΌ) πΌ √−ππ ) Γ (1 + πΌ) 6 Journal of Applied Mathematics −1 + πΆ2 sinh ( πΌ √−ππ )) ] Γ (1 + πΌ) When π > 0, 5 1 π2 (π) = π−πΌ ππΌ + π−2πΌ ππ22 + 2π2πΌ π 3 12 πΌ { √−ππ × (π {1 − [ (πΆ1 sinh ( ) Γ (1 + πΌ) { + πΆ2 cosh ( × (πΆ1 cosh ( × [ (−πΆ1 sin ( πΌ √−ππ )) Γ (1 + πΌ) +πΆ2 cos ( πΌ √−ππ ) Γ (1 + πΌ) × (πΆ1 cos ( 1/2 2 −1 πΌ } √−ππ )) ] }) , + πΆ2 sinh ( Γ (1 + πΌ) } (27) −1 2 +πΆ2 cos ( πΌ × (πΆ1 cos ( πΌ √−ππ ) × (πΆ1 cosh ( Γ (1 + πΌ) √−ππ )) ] Γ (1 + πΌ) πΌ πΌ √π ) ππΌ Γ (1 + πΌ) +πΆ2 sin ( π2 (π) = πΌ √−ππ )) Γ (1 + πΌ) + 2 −1 2 π2πΌ π2 √π π [ (−πΆ1 sin ( ) ππΌ 2π2 Γ (1 + πΌ) +πΆ2 cos ( 1/2 −1 πΌ } √−ππ +πΆ2 sinh ( )) ] }) , Γ (1 + πΌ) } (28) × (πΆ1 cos ( √π ) ππΌ ) Γ (1 + πΌ) √π ) ππΌ Γ (1 + πΌ) −1 2 √π +πΆ2 sin ( ) ππΌ ) ] Γ (1 + πΌ) + 1/2 √π ) ππΌ ) ] }) , Γ (1 + πΌ) (29) −πΌ πΌ −2πΌ 2 1 π2 (16π π π2 + 5π π2 ππ2 − 6π0 π2 ) 24 π22 πΌ √−ππ ) Γ (1 + πΌ) where π = ππ₯ + ππ‘ + π0 , π = (1/4)π−4πΌ ππ22 . √π ) ππΌ ) Γ (1 + πΌ) −1 πΌ { √−ππ × (π {1 − [ (πΆ1 sinh ( ) Γ (1 + πΌ) { × (πΆ1 cosh ( −1 √π ) ππΌ ) ] Γ (1 + πΌ) × (πΆ1 cos ( √−ππ )) ] Γ (1 + πΌ) +πΆ2 cosh ( √π ) ππΌ Γ (1 + πΌ) +πΆ2 cos ( πΌ √−ππ ) Γ (1 + πΌ) πΌ √π ) ππΌ ) Γ (1 + πΌ) { √π ) ππΌ × (π {1 + [ (−πΆ1 sin ( Γ (1 + πΌ) { √−ππ )) Γ (1 + πΌ) +πΆ2 sinh ( √π ) ππΌ Γ (1 + πΌ) +πΆ2 sin ( −1 2 πΌ √−ππ + π2 √−π [(πΆ1 sinh ( ) Γ (1 + πΌ) × (πΆ1 cosh ( √π ) ππΌ Γ (1 + πΌ) √π +πΆ2 sin ( ) ππΌ ) ] Γ (1 + πΌ) √−ππ )) + πΆ2 cosh ( Γ (1 + πΌ) +πΆ2 cosh ( √π ) ππΌ ) Γ (1 + πΌ) + π2 √π [ (−πΆ1 sin ( πΌ 2π2πΌ π2 √−ππ π1 (π) = π0 − π [ (πΆ1 sinh ( ) π2 Γ (1 + πΌ) +πΆ2 sinh ( √π ) ππΌ Γ (1 + πΌ) π22 √π ) ππΌ √π [ (−πΆ1 sin ( 4π2 Γ (1 + πΌ) Journal of Applied Mathematics +πΆ2 cos ( × (πΆ1 cos ( 7 √π ) ππΌ ) Γ (1 + πΌ) × (πΆ1 cos ( √π ) ππΌ Γ (1 + πΌ) +πΆ2 sin ( +πΆ2 sin ( × (π {1 + [ (−πΆ1 sin ( +πΆ2 cos ( √π ) ππΌ ) Γ (1 + πΌ) 5 1 π3 (π) = π−πΌ ππΌ + π−2πΌ ππ22 3 12 √π ) ππΌ Γ (1 + πΌ) − 2π2πΌ π[tanh ( 2π2πΌ π2 π π2 × (πΆ1 cos ( −1 2 √π ) ππΌ ) ] Γ (1 + πΌ) +πΆ2 cos ( √π ) ππΌ Γ (1 + πΌ) √π ) ππΌ ) Γ (1 + πΌ) × (πΆ1 cos ( √π ) ππΌ Γ (1 + πΌ) + πΆ2 sin ( −1 √π ) ππΌ ) ] Γ (1 + πΌ) × (π {1 + [ (−πΆ1 sin ( (32) 2 πΌ √−ππ )] }, Γ (1 + πΌ) −πΌ πΌ −2πΌ 2 1 π2 (16π π π2 + 5π π2 ππ2 − 6π0 π2 ) 24 π22 πΌ π2πΌ π2 √−ππ )] π[tanh ( 2π2 Γ (1 + πΌ) 2 (33) πΌ π2 √−ππ )] + 2 √−π [tanh ( 4π2 Γ (1 + πΌ) √π ) ππΌ Γ (1 + πΌ) + π2 √π [ (−πΆ1 sin ( 2 πΌ √−ππ )] Γ (1 + πΌ) × √ π {1 − [tanh ( − √π ) ππΌ ) Γ (1 + πΌ) +πΆ2 sin ( + π2 √−π [tanh ( π3 (π) = √π ) ππΌ Γ (1 + πΌ) πΌ √−ππ )] Γ (1 + πΌ) 1/2 (30) +πΆ2 cos ( , where π = ππ₯ + ππ‘ + π0 and π = (1/4)π−4πΌ ππ22 . In particular, if we let πΆ2 = 0 in (26)–(28), then we obtain the following solitary wave solutions, which are shown in Figures 1, 2, and 3: √π ) ππΌ Γ (1 + πΌ) −1 2 × [ (−πΆ1 sin ( 1/2 (31) √π +πΆ2 sin ( ) ππΌ ) ] }) , Γ (1 + πΌ) π2 (π) = π0 + −1 2 √π ) ππΌ ) ] }) Γ (1 + πΌ) −1 √π ) ππΌ ) ] Γ (1 + πΌ) × (πΆ1 cos ( √π ) ππΌ Γ (1 + πΌ) √π ) ππΌ Γ (1 + πΌ) √π + πΆ2 cos ( ) ππΌ ) Γ (1 + πΌ) × √ π {1 − [tanh ( π3 (π) = π0 − 2 πΌ √−ππ )] }, Γ (1 + πΌ) πΌ 2π2πΌ π2 √−ππ π[tanh ( )] π2 Γ (1 + πΌ) + π2 √−π [tanh ( 2 πΌ √−ππ )] Γ (1 + πΌ) × √ π {1 − [tanh ( (34) 2 πΌ √−ππ )] }. Γ (1 + πΌ) If we let πΆ2 = 0 in (29)–(31), then we obtain the following periodic wave solutions, which are shown in Figures 4, 5, and 6: 1 5 π4 (π) = π−πΌ ππΌ + π−2πΌ ππ22 3 12 + 2π2πΌ π[tan √π ππΌ ] Γ (1 + πΌ) 2 8 Journal of Applied Mathematics 1.15 1.14 2.8 1.13 1.12 1.11 2.7 1.10 1.09 2.6 1.08 1.07 1.06 2.5 0 2 4 6 8 t Figure 1: The solution π3 in (32) with πΎ = 4/5, π = π = π = π2 = 1, π = −1, π0 = 0. − π2 √π [tan √π ππΌ ] Γ (1 + πΌ) × √ π {1 + [tan − (36) 2 4 6 8 7 10 9 8 4 6 5 x 1 3 2 Figure 3: The solution π3 in (34) with πΎ = 4/5, π = π = π = π2 = π2 = 1, π = −1, π0 = 0, π0 = 1. 2 √π ππΌ ] }, Γ (1 + πΌ) √π ππΌ ] Γ (1 + πΌ) × √ π {1 + [tan 8 2.9 t Remark 1. We note that the solutions obtained here are of new forms compared with the solutions obtained in [15, 16] since a fully new method is used here. 2 2π2πΌ π2 √π π[tan ππΌ ] π2 Γ (1 + πΌ) − π2 √π [tan 6 Figure 2: The solution π3 in (33) with πΎ = 4/5, π = π = π = π2 = π2 = 1, π = −1, π0 = 0, π0 = 1. 0 π22 √π ππΌ ] √π [tan 4π2 Γ (1 + πΌ) π4 (π) = π0 + t 2 1 4 3 5 6 8 7 10 9 x 2.8 2 π2πΌ π2 √π π[tan ππΌ ] 2π2 Γ (1 + πΌ) × √ π {1 + [tan 4 3 2 √π ππΌ ] }, Γ (1 + πΌ) −πΌ πΌ −2πΌ 2 1 π2 (16π π π2 + 5π π2 ππ2 − 6π0 π2 ) 24 π22 + 2 3.1 (35) π4 (π) = 0 2 1 4 3 5 6 8 7 x 10 9 (37) 2 √π ππΌ ] }. Γ (1 + πΌ) Similar to the established solutions from Case 1, we can construct corresponding exact solutions to (13) from Cases 2–7, which are omitted here. 5. Conclusions Based on the concept of the modified Riemann-Liouville derivative and a variable transformation π = ππ‘ + π1 π₯1 + π2 π₯2 + ⋅ ⋅ ⋅ + ππ π₯π + π0 , we have proposed a new fractional subequation method for solving fractional partial differential equations (FPDEs). By using this method, the space-time fractional generalized Hirota-Satsuma coupled KdV equations are solved successfully, and, as a result, some exact solutions are established, which may help to understand Journal of Applied Mathematics 9 better the nonlinear wave phenomena. It is supposed that this method can be further applied to solve other FPDEs. 25000 20000 Acknowledgments 15000 This work is partially supported by the National Natural Science Foundation of China (11171178) and the Program for Scientific Research Innovation Team in Colleges and Universities of Shandong Province. The authors would like to thank the reviewers very much for their valuable suggestions in the paper. 10000 5000 0 0 2 4 t 6 8 8 7 10 9 6 5 4 1 3 2 x Figure 4: The solution π4 in (35) with πΎ = 4/5, π = π = π = π2 = 1, π = 1, π0 = 0. 20000 15000 10000 5000 0 0 2 4 t 6 8 8 10 9 7 6 5 2 4 3 1 x Figure 5: The solution π4 in (36) with πΎ = 4/5, π = π = π = π2 = π2 = 1, π = 1, π0 = 0, π0 = 1. 80000 70000 60000 50000 40000 30000 20000 10000 0 0 2 4 t 6 8 10 9 8 7 6 5 4 3 2 1 x Figure 6: The solution π4 in (37) with πΎ = 4/5, π = π = π = π2 = π2 = 1, π = −1, π0 = 0, π0 = 1. References [1] G. C. Wu, “A fractional variational iteration method for solving fractional nonlinear differential equations,” Computers & Mathematics with Applications, vol. 61, no. 8, pp. 2186–2190, 2011. [2] J. Ji, J. b. Zhang, and Y. J. Dong, “The fractional variational iteration method improved with the Adomian series,” Applied Mathematics Letters, vol. 25, no. 12, pp. 2223–2226, 2012. [3] G. C. Wu and E. W. M. Lee, “Fractional variational iteration method and its application,” Physics Letters A, vol. 374, no. 25, pp. 2506–2509, 2010. [4] S. Guo and L. Mei, “The fractional variational iteration method using He’s polynomials,” Physics Letters A, vol. 375, no. 3, pp. 309–313, 2011. [5] A. M. A. El-Sayed, S. H. Behiry, and W. E. Raslan, “Adomian’s decomposition method for solving an intermediate fractional advection-dispersion equation,” Computers & Mathematics with Applications, vol. 59, no. 5, pp. 1759–1765, 2010. [6] A. M. A. El-Sayed and M. Gaber, “The Adomian decomposition method for solving partial differential equations of fractal order in finite domains,” Physics Letters A, vol. 359, no. 3, pp. 175–182, 2006. [7] S. S. Ray, “A new approach for the application of Adomian decomposition method for the solution of fractional space diffusion equation with insulated ends,” Applied Mathematics and Computation, vol. 202, no. 2, pp. 544–549, 2008. [8] M. Merdan, “A numeric-analytic method for time-fractional Swift-Hohenberg (S-H) equation with modified RiemannLiouville derivative,” Applied Mathematical Modelling, vol. 37, no. 6, pp. 4224–4231, 2013. [9] M. Cui, “Compact finite difference method for the fractional diffusion equation,” Journal of Computational Physics, vol. 228, no. 20, pp. 7792–7804, 2009. [10] K. A. Gepreel, “The homotopy perturbation method applied to the nonlinear fractional Kolmogorov-Petrovskii-Piskunov equations,” Applied Mathematics Letters, vol. 24, no. 8, pp. 1428– 1434, 2011. [11] Q. Huang, G. Huang, and H. Zhan, “A finite element solution for the fractional advection-dispersion equation,” Advances in Water Resources, vol. 31, no. 12, pp. 1578–1589, 2008. [12] B. Lu, “BaΜcklund transformation of fractional Riccati equation and its applications to nonlinear fractional partial differential equations,” Physics Letters A, vol. 376, no. 28-29, pp. 2045–2048, 2012. [13] G. Jumarie, “Modified Riemann-Liouville derivative and fractional Taylor series of nondifferentiable functions further results,” Computers & Mathematics with Applications, vol. 51, no. 9-10, pp. 1367–1376, 2006. 10 [14] S. Zhang and H. Q. Zhang, “Fractional sub-equation method and its applications to nonlinear fractional PDEs,” Physics Letters A, vol. 375, no. 7, pp. 1069–1073, 2011. [15] S. M. Guo, L. Q. Mei, Y. Li, and Y. F. Sun, “The improved fractional sub-equation method and its applications to the space-time fractional differential equations in fluid mechanics,” Physics Letters A, vol. 376, no. 4, pp. 407–411, 2012. [16] B. Zheng, “(πΊσΈ /πΊ)-expansion method for solving fractional partial differential equations in the theory of mathematical physics,” Communications in Theoretical Physics, vol. 58, no. 5, pp. 623–630, 2012. [17] R. Abazari and M. Abazari, “Numerical simulation of generalized Hirota-Satsuma coupled KdV equation by RDTM and comparison with DTM,” Communications in Nonlinear Science and Numerical Simulation, vol. 17, no. 2, pp. 619–629, 2012. Journal of Applied Mathematics Advances in Operations Research Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Advances in Decision Sciences Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Mathematical Problems in Engineering Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Journal of Algebra Hindawi Publishing Corporation http://www.hindawi.com Probability and Statistics Volume 2014 The Scientific World Journal Hindawi Publishing Corporation http://www.hindawi.com Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 International Journal of Differential Equations Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Volume 2014 Submit your manuscripts at http://www.hindawi.com International Journal of Advances in Combinatorics Hindawi Publishing Corporation http://www.hindawi.com Mathematical Physics Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Journal of Complex Analysis Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 International Journal of Mathematics and Mathematical Sciences Journal of Hindawi Publishing Corporation http://www.hindawi.com Stochastic Analysis Abstract and Applied Analysis Hindawi Publishing Corporation http://www.hindawi.com Hindawi Publishing Corporation http://www.hindawi.com International Journal of Mathematics Volume 2014 Volume 2014 Discrete Dynamics in Nature and Society Volume 2014 Volume 2014 Journal of Journal of Discrete Mathematics Journal of Volume 2014 Hindawi Publishing Corporation http://www.hindawi.com Applied Mathematics Journal of Function Spaces Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Optimization Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Hindawi Publishing Corporation http://www.hindawi.com Volume 2014