JAEM 2018, Vol 8, No 2
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Yayın Compressive spectral renormalization method(Işık University Press, 2018-09-09) Bayındır, CihanIn this paper a novel numerical scheme for finding the sparse self-localized states of a nonlinear system of equations with missing spectral data is introduced. As in the Petviashivili's and the spectral renormalization method, the governing equation is transformed into Fourier domain, but the iterations are performed for far fewer number of spectral components (M) than classical versions of the these methods with higher number of spectral components (N). After the converge criteria is achieved for M components, N component signal is reconstructed from M components by using the l(1) minimization technique of the compressive sampling. This method can be named as compressive spectral renormalization (CSRM) method. The main advantage of the CSRM is that, it is capable of finding the sparse self-localized states of the evolution equation(s) with many spectral data missing.Yayın Head-on collision of the solitary waves in fluid-filled elastic tubes(Işık University Press, 2018-04-12) Özden, Ali Erinç; Demiray, HilmiIn the present work, by employing the field equations given in [15] and the extended PLK method derived in [9], we have studied the head-on collision of solitary waves in arteries. Introducing a set of stretched coordinates which include some unknown functions characterizing the higher order dispersive effects and the trajectory functions to be determined from the removal of possible secularities that might occur in the solution. Expanding these unknown functions and the field variables into power series of the smallness parameter epsilon and introducing the resulting expansions into the field equations we obtained the sets of partial differential equations. By solving these differential equations and imposing the requirements for the removal of possible secularities we obtained the speed correction terms and the trajectory functions. The results of our calculation show that both the evolution equations and the phase shifts resulting from the head-on collision of solitary waves are quite different from those of Xue [15], who employed the incorrect formulation of Su and Mirie [4]. As opposed to the result of previous works on the same subject, in the present work the phase shifts depend on the amplitudes of both colliding waves.Yayın Higher order perturbation expansion for ion-acoustic solitary waves with q-nonextensive nonthermal velocity distribution(Işık University Press, 2018-09-11) Demiray, HilmiThe basic nonlinear equations describing the dynamics of a two component plasma consisting of cold positive ions and electrons obeying hybrid q-nonextensive nonthermal velocity distribution are examined through the use of modified PLK formalism and the reductive perturbation method and obtained the KdV equation for the lowest order term in the perturbation expansion. The method is further extended to include the contribution of higher order terms in the expansion; the evolution equation for the second order term is found to be the degenerate(linearized) KdV equation with non-homogeneous term. Seekink the localized travelling wave solution (solitons) to these evolution equations we obtained the speed correction terms and the wave profiles. Numerical results for the set of suitable parameters( Williams et. al. [23]) are shown inb the form of some graphs. The combined effect of nonextensive parameter (q) and the nonthermal parameter (alpha) on the soliton dynamics has also been studied.
