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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 Yayın Harmonic resonance phenomena on nonlinear SH waves(Işık University Press, 2023-04) Ahmetolan, Semra; Özdemir, Neşe; Peker Dobie, Ayşe; Demirci, AliThe interaction of shear horizontal (SH) waves in a two layered elastic medium and its mth harmonic component is studied. The dispersion relation is analysed to obtain the wave number-phase velocity pairs where the third and fifth harmonic resonance phenomena emerge. By employing an asymptotic perturbation method it is shown that the balance between the weak nonlinearity and dispersion yields a coupled nonlinear Schrödinger (CNLS) equation for the slowly varying amplitudes of the fundamental wave and its fifth harmonic component. The nonlinearity effects of the materials and the ratio of layers’ thicknesses on the linear instabilities of solutions and the existence of solitary waves are examined.Yayın Computational and asymptotic methods in aeroacoustics with applications(Işık University Press, 2011) Delale, Can Fuat; Zafer, Baha; Aslan, Alim RüstemIn this article the computational and asymptotic methods used in aeroacoustics are reviewed. In particular, two different aeroacoustic applications are demonstrated.In the first problem we investigate the first and second order asymptotic predictions of the thickness and loading noise of a subsonic B-bladed helicopter rotor in the far field and compare the SPL noise results with those of full numerical computations. The results of the second order asymptotic formula seem to be in better agreement with full numerical computations than the first order asymptotic formula. In the second problem, the effect of acoustic wave propagation in transonic nozzle flow is investigated by solving the unsteady quasi-one-dimensional transonic nozzle equations in conservative form using high order computational aeroacoustic schemes, where a novel non-reflecting boundary condition is implemented in addition to the standard non-reflecting boundary condition using characteristics. Excellent agreement with the exact solution is obtained in each case.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 Harmonic mappings related to starlike function of complex order ?(Işık University Press, 2014) Aydoğan, Seher MelikeLet SH be the class of harmonic mappings defined by SH = { f = h(z) + g(z) | h(z) = z + ?? n=2 anz?, g(z) = ?? n=1 bnz?} The purpose of this talk is to present some results about harmonic mappings which was introduced by R. M. Robinson [8].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.Yayın Some results on a subclass of harmonic mappings of order alpha(Işık University Press, 2014) Varol, Dürdane; Aydoğan, Seher Melike; Owa, ShigeyoshiLet S-H be the class of harmonic mappings defined by S-H - {f - h(z) + <(g(z))over bar> vertical bar h(z) - z + Sigma(infinity)(n=2)a(n)z(n) , g(z) - b(1)z + Sigma(infinity)(n=2) b(n)z(n), b(1) < 1} where h(z) and g(z) are analytic. Additionally f(z) is an element of S-H(alpha) double left right arrow vertical bar zh'(z) - <(zg'(z))over bar>/h(z) + <(g(z))over bar> - 1-(b(1)) over bar /1+(b(1)) over bar vertical bar < vertical bar 1 - <(b(1))over bar>/1 + (b(1)) over bar vertical bar - alpha, z is an element of u, 0 <= alpha < 1 - <(b(1))over bar>/1 + (b(1)) over bar In the present work, by considering the analyticity of the functions defined by R. M. Robinson [7], we discuss the applications to the harmonic mappings.Yayın An application of modified reductive perturbation method to symmetric regularized-long-wave(Işık University Press, 2011-03-24) Demiray, HilmiIn this work, we extended the application of "the modified reductive perturbation method" to symmetrical regularized long waves with quadratic nonlinearity and obtained various form of KdV equations as the governing equations. Seeking a localized travelling wave solutions to these evolution equations we determined the scale parameters g(1) and g(2) so as to remove the possible secularities that might occur. To indicate the power and elegance of the present method, we compared our result with the exact travelling wave solution of the symmetric regularized long-wave equation with quadratic nonlinearity. These results show that for weakly nonlinear case the solutions for both approaches coincide with each other. The present method is seen to be fairly simple as compared to the renormalization method of Kodama and Taniuti [4] and the multiple scale expansion method of Kraenkel et al [6].Yayın Contribution of higher order terms to the nonlinear shallow water waves(Işık University Press, 2012-05-12) Demiray, HilmiIn this work, by utilizing the scaled multiple-space expansion method, we studied the propagation of weakly nonlinear waves in shallow water and obtained the governing evolution equations of various order terms in the perturbation expansion. Seeking a progressive wave solution to these evolution equations we obtained the speed correction terms so as to remove some possible secularities. The result obtained here is exactly the same with that of obtained by the modified reductive perturbation method [12]. We also proposed a method for the evolution equation governing the n th order term in the perturbation expansion. By defining a single time parameter we showed the connection of the modified reductive perturbation method to the scaled multiple-space expansion method.
