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Yayın Nonlinear wave modulation in a prestressed thin elastic tube filled with an inviscid fluid(Wit Press, 2002) Bakırtaş, İlkay; Demiray, HilmiIn the present work, employing the nonlinear equations of an incompressible, isotropic and elastic thin tube and the approximate equations of an incompressible inviscid fluid and then utilizing the reductive perturbation technique, the amplitude modulation of weakly nonlinear waves is examined. It is shown that, the amplitude modulation of these waves is governed by a nonlinear Schrödinger (NLS) equation. The result is compared with some previous works on the same subject. The modulational instability of the monochromatic wave solution is discussed for some elastic materials and initial deformations. It is shown that the amplitude modulation of weakly nonlinear waves near the marginal state is governed by the Generalized Nonlinear Schrödinger equation (GNLS).Yayın Weakly non-linear waves in a tapered elastic tube filled with an inviscid fluid(Pergamon-Elsevier Science Ltd, 2005-07) Bakırtaş, İlkay; Demiray, HilmiIn the present work, treating the artery as a tapered, thin walled, long and circularly conical prestressed elastic tube and using the longwave approximation, we have studied the propagation of weakly non-linear waves in such a fluid-filled elastic tube by employing the reductive perturbation method. By considering the blood as an incompressible inviscid fluid, the evolution equation is obtained as the Korteweg-de Vries equation with a variable coefficient. It is shown that this type of equation admits a solitary wave-type solution with variable wave speed. It is observed that, the wave speed decreases with distance for positive tapering while it increases for negative tapering. It is further observed that, the progressive wave profile for expanding tubes (a > 0) becomes more steepened whereas for narrowing tubes (a < 0) it becomes more flattened.Yayın A novel fast algorithm for speech and audio coding(IEEE, 2007) Güz, Ümit; Gürkan, Hakan; Yarman, Bekir Sıddık BinboğaIn this work a new mathematical modeling approach is proposed for the representation of the speech and audio signals. This approach is based on the generation of the so called Predefined Signature Sequence (PSS) and Predefined Envelope Sequence (PES) Sets. After the generation process of the PSS and PES sets, they are clustered by effective k-means clustering algorithm and the PSS and PES are redefined by using these centroids. By using this approach, the drawbacks by means of the size of the sets, speed of the reconstruction process (computational complexity) which arise in the proposed methods previously are highly eliminated. In spite of these improvements, the initial results proved that, the quality of the reconstructed signals remains within the limitations of the acceptable hearing quality.Yayın A novel method to represent the speech signals by using language and speaker independent predefined functions sets(IEEE, 2004) Güz, Ümit; Gürkan, Hakan; Yarman, Bekir Sıddık BinboğaIn this paper a new modeling method of speech signals is introduced. The proposed method is based on the generation of the so-called Predefined Signature S={s(R)(t)} and Envelope Function E = {e(K)(t)} Sets (PSEFS). These function sets are independent of any speaker and any language. Once the speech signals are divided into frames with selected lengths, then each frame signal piece X-i(t) is synthesized by means of the mathematical form of x(i)(t)=C(i)e(K)(t)s(R)(t). In this representation, C-i is called the frame coefficient, s(R)(t) and e(K)(t) are properly assigned from the PSEFS respectively. It is shown that the proposed method provides fast reconstruction and substantial compression with acceptable hearing quality.Yayın Real frequency design of multiband matching networks with mixed lumped-distributed elements and foster resonance sections(IEEE, 2018) Yıldız, Serkan; Aksen, Ahmet; Yarman, Bekir Sıddık BinboğaIn this study, a multiband matching network design technique is presented. Mixed lumped and distributed elements are used to form Transducer Power Gain (TPG) of the matching network. Finite frequency transmission zeros are included in final design to create multiband TPG characteristic. Foster resonance sections are used to realize finite transmission zeros. Approximate distributed model of Foster resonance section is incorporated in design. An illustrative dual band matching network design for a PIFA antenna is presented. It has been shown that using distributed equivalent models of Foster resonance sections in mixed matching network design provides satisfactory TPG levels at intended frequency bands.Yayın Gerçel ve karmaşık süzgeç öbeklerinin eşdalgacıklı tasarımı(IEEE, 2006-07-31) Ateş, Hasan Fehmi; Orchard, Michael T.; Kanberoğlu, BerkayBu bildiride, eşdalgacıklı tam geri çatma süzgeç öbekleri tasarlamak için, Parks-McClellan algoritması gibi tekniklerle üretilen enküçük-enbüyük optimal eşdalgacıklı kısıtsız süzgeçleri eşlemlemede kullanılan basit bir yöntem sunulmaktadır. Bu yöntem, hem standart alçak- ve yüksek geçiren süzgeçlerin tam geri çatması sağlayacak şekilde tasarımlarına hem de kritik örneklenmiş karmaşık süzgeçlerin tasarımlarına uygulanmıştır. Gerçel süzgeç öbeği tasarımı için, yöntemimiz, tam geri çatma kısıtlarını karşılayan ve aynı zamanda standart enküçük-enbüyük süzgeç tasarımı ölçütlerini eniyileyen eşdalgacıklı alçak ve yüksek geçiren süzgeçleri üretmektedir. Karmaşık süzgeç öbeği tasarımı için, yöntemimiz, tam geri çatmaya izin verirken aynı zamanda rezone eden sinyaller için kritik örneklenmiş bir zarf/faz gösterimi oluşturmaktadır. Karmaşık süzgecin genlik tepkisi, ideal pozitif bir frekans geçirme kuşağının eşdalgacıklı yaklaşımıdır. Faz tepkisi ise salt doğrusal fazın eşdalgacıklı yaklaşımıdır.Yayın Genetik algoritma ile kesirli dereceli sistemler için frekans tabanlı yaklaşımların karşılaştırılması(Institute of Electrical and Electronics Engineers Inc., 2025-08-15) Astekin, Dorukhan; Değirmenci, Ali Murat; İstefanopulos, YorgoKesirli dereceli sistemler tam sayı yerine kesirli tümlevsel veya türevsel terimlerin yer aldığı sistemlerdir ve yapısı gereği hesaplama zorluğunu da beraberinde getirmektedir. Bu nedenle birçok çalışmada kesirli dereceli sistemler için bazı yaklaşım yöntemleri araştırmacılar tarafından önerilmektedir. Bu çalışma kapsamında kesirli dereceli sistemler için frekans tabanlı yaklaşım yöntemlerinin karşılaştırılmalı çalışması ve eniyileme yöntemlerinden biri olan genetik algoritma ile tasarlanan kesirli dereceli PID denetleyici ile kesirli dereceli sistemin ve yaklaşımlarının karşılaştırılması sunulmaktadır. Karşılaştırılan yöntemler MATLAB/Simulink ortamında modellenerek benzetim sonuçları verilmektedir.
