- About this Journal
- Abstracting and Indexing
- Aims and Scope
- Annual Issues
- Article Processing Charges
- Articles in Press
- Author Guidelines
- Bibliographic Information
- Citations to this Journal
- Contact Information
- Editorial Board
- Editorial Workflow
- Free eTOC Alerts
- Publication Ethics
- Reviewers Acknowledgment
- Submit a Manuscript
- Subscription Information
- Table of Contents
Abstract and Applied Analysis
Volume 2013 (2013), Article ID 931643, 3 pages
A Note on the Semi-Inverse Method and a Variational Principle for the Generalized KdV-mKdV Equation
1Department of Mathematics, Kunming University, 2 Puxin Road, Kunming, Yunnan 650214, China
2Institute of Nonlinear Analysis, Kunming University, 2 Puxin Road, Kunming, Yunnan 650214, China
Received 1 January 2013; Revised 5 January 2013; Accepted 27 January 2013
Copyright © 2013 Li Yao 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.
Ji-Huan He systematically studied the inverse problem of calculus of variations. This note reveals that the semi-inverse method also works for a generalized KdV-mKdV equation with nonlinear terms of any orders.
In , the semi-inverse method is systematically studied and many examples are given to show how to establish a variational formulation for a nonlinear equation. From the given examples, we found that it is difficult to find a variational principle for nonlinear evolution equations with nonlinear terms of any orders.
For example, consider the following generalized KdV-mKdV equation: where , , , and are constant coefficients, while is a positive number. Equation (1) is an important model in plasma physics and solid state physics.
2. Variational Principle by He’s Semi-Inverse Method
For (1), we introduce a potential function defined as ; we have the following equation: In order to use the semi-inverse method [1–4] to establish a Lagrangian for (2), we first check some simple cases: We can easily obtain a variational principle for (2) for , which is Now, according to the semi-inverse method [1–4], we construct a trial functional for (2): where is an unknown function of and/or its derivatives.
Making the trial-functional, (5), stationary with respect to results in the following Euler-Lagrange equation: where is called variational differential with respect to , defined as We rewrite (6) in the form Comparison of (8) and (2) leads to the following results: from which we identify the unknown and as follows: We, therefore, obtain the following needed variational principle:
This note shows that the semi-inverse method in  works also for the present problem, and it is concluded that the semi-inverse method is a powerful mathematical tool to the construction of a variational formulation for a nonlinear equation; illustrating examples are available in [5–10].
This work was supported by the Chinese Natural Science Foundation Grant no. 10961029 and Kunming University Research Fund (2010SX01).
- J.-H. He, “Asymptotic methods for solitary solutions and compactons,” Abstract and Applied Analysis, vol. 2012, Article ID 916793, 130 pages, 2012.
- J.-H. He, “An elementary introduction to recently developed asymptotic methods and nanomechanics in textile engineering,” International Journal of Modern Physics B, vol. 22, pp. 3487–3578, 2008.
- J.-H. He, “Some asymptotic methods for strongly nonlinear equations,” International Journal of Modern Physics B, vol. 20, no. 10, pp. 1141–1199, 2006.
- J.-H. He, “Variational principles for some nonlinear partial differential equations with variable coefficients,” Chaos, Solitons & Fractals, vol. 19, no. 4, pp. 847–851, 2004.
- L. Yao, “How to discover a variational principle for a damped vibration problem,” International Journal of Nonlinear Sciences and Numerical Simulation, vol. 11, pp. 171–173, 2010.
- G.-C. Wu, “Laplace transform overcoming principle drawbacks in application of the variational iteration method to fractional heat equations,” Thermal Science, vol. 16, no. 4, pp. 1257–1261, 2012.
- X.-W. Zhou and L. Wang, “A variational principle for coupled nonlinear Schrödinger equations with variable coefficients and high nonlinearity,” Computers & Mathematics with Applications, vol. 61, no. 8, pp. 2035–2038, 2011.
- Z.-L. Tao, “Variational approach to the Benjamin Ono equation,” Nonlinear Analysis. Real World Applications, vol. 10, no. 3, pp. 1939–1941, 2009.
- Z.-L. Tao, “Solitary solutions of the Boiti-Leon-Manna-Pempinelli equation using He's variational method,” Zeitschrift fur Natuforschung A, vol. 63, no. 10-11, pp. 634–636, 2008.
- L. Xu, “Variational approach to solitons of nonlinear dispersive K(m, n) equations,” Chaos, Solitons and Fractals, vol. 37, no. 1, pp. 137–143, 2008.
- D. Baleanu and S. I. Muslih, “Lagrangian formulation of classical fields within Riemann-Liouville fractional derivatives,” Physica Scripta, vol. 72, no. 2-3, pp. 119–121, 2005.
- D. Baleanu, K. Diethelm, E. Scalas, and J. J. Trujillo, Fractional Calculus Models and Numerical Methods, vol. 3, World Scientific, 2012.
- G.-C. Wu and D. Baleanu, “Variational iteration method for the Burgers’ flow with fractional derivatives—new Lagrange Mutipliers,” Applied Mathematical Modelling, vol. 37, no. 9, pp. 6183–6190, 2013.
- G.-C. Wu, “New trends in variational iteration method,” Communications in Fractional Calculus, vol. 2, no. 2, pp. 59–75, 2011.