Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
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Research Project Bağımsız bileşen analizinin iletişim, imge işleme ve jeofizikteki uygulamaları(TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2006) Sankur, Bülent; Gençağa, Deniz; Kalkan, Olcay; Altınkaya, Mustafa AzizBu projede literatürde kaynak ayrıştırma olarak bilinen istatistiksel işaret işleme yöntemleri hem kuramsal açıdan, hem de uygulamaları açısından ele alınmıştır. Kuramsal çalışmalarda, kaynakların uzamda ve zamanda birbirlerinden bağımsız olmadıkları düşüncesiyle parçacık süzgeçleri yöntemi ele alınmıştır. Bu yaklaşımda süreç hakkında elimizde varolan önsel bilgilerin algoritmaya ağdırılması mümkün olmuştur. Ayrıca durağan olmayan süreçlerin de ayrıştırılma problemi ele alınmış, farklı yeniden örnekleme ve önem fonksiyonları seçerek literatürdeki teknikleri aşan sonuçlar bulunmuştur. Uygulamaya dönük çalışmalarda ise, jeofizik işaret işlemede klimatolojik verilere bakılmış ve gerek Kuzey Atlantik Salınımı diye adlandırılan olgu irdelenmiştir. Ancak topografık etkiler istenen sonuca ulaşılmasına engel olmuştur. Öte yandan sıcaklık verileri faktör analizi ile incelenmiş ve volkanik hareketlerin etkisi ortaya çıkarılmaya çalışılmıştır. Beyin-işaretleri konusunda özellikle prefrontal korteks bölgesinden bilişsel süreçlerle ilgili araştırmalar yapılmıştır. Deneklerin biliş esnasında beyindeki kan dengesinin, oksi- ve deoksi hemoglobinin değişimleri yakalanmaya çalışılmıştır. Bağımsız bileşen analizinin bu türlü dalga biçimlerini ortaya çıkarmakta çok etkili bir araç olduğu gösterilmiştir. Biyometri alanında, bağımsız bileşenler analizi hem yüz imgelerine hem de el imgelerine uygulanmıştır. Bağımsız-bileşenlerin deneklerin kimlik bilgilerini taşıyan ve bozucu etkilere karşı en dayanıklı öznitelikler olduğu görülmüştür. Nihayet bağımsız bileşen analizi CDMA: kod bölüşümlü çoklu erişim işaretlerine uygulanmış ve sönümlü kanallardaki alıcının performansını iyileştirici tasarımlar irdelenmiştir.Conference Object Citation - Scopus: 5Adaptive Visual Servo Regulation Control for Camera-In Configuration With a Fixed Camera Extension(Institute of Electrical and Electronics Engineers Inc., 2007) Tatlıcıoğlu, Enver; Dawson, Darren M.; Xian, B.In this paper, image-based regulation control of a robot manipulator with an uncalibrated vision system is discussed. To compensate for the unknown camera calibration parameters, a novel prediction error formulation is presented. To achieve the control objectives, a Lyapunov-based adaptive control strategy is employed. The control development for the camera-in-hand problem is presented in detail and a fixed-camera problem is included as an extension.Conference Object All-Optical Switching Based on Grating Written Photorefractive Slab/Fiber Waveguide Coupler(Institute of Electrical and Electronics Engineers Inc., 2002) Dinleyici, Mehmet SalihSince all optical switching is a key element for all kinds of optical networks, great amount of works have been dedicated either for material researches or various waveguide structures. Generally speaking the switching time of devices based on photorefractive effect are rather slow for today's high capacity optical fiber networks. In the field of waveguide architecture various geometries have been proposed and investigated for grating assisted or guided optical coupling for the purpose of designing all-optical switch, adddrop multiplexers, filters etc.Conference Object Citation - Scopus: 1Kod Bölüşümlü Çoklu Erişim (cdma) İletişiminde Gauss Olmayan Sönümlü Kanal Kestirimi için Pearson Sistemi'ne Dayalı Gözü Kapalı Kaynak Ayrıştırma Yöntemi(Institute of Electrical and Electronics Engineers Inc., 2004) Kalkan, Olcay; Altınkaya, Mustafa AzizIn this work, a Pearson System based-blind source separation method is used for detecting the signal coming to a mobile user which is subject to multiple access interference in a CDMA downlink communication. Considering some fading channel measurements showing that the fading channel coefficients may have an impulsive nature, these coefficients are modeled with an a-stable distribution whose shape parameter a takes values between 1.8 and 1.9. These a values show that the distribution resembles a Gaussian distribution but has a more impulsive nature. Simulation studies show that the conventional MMSE receiver fails in this impulsive fading scenario. Both the independent component analysis (ICA) method using the conventional hyperbolic tangent score function and the Pearson System-based ICA are successful in estimating the channel coefficients and the proposed Pearson System-based ICA method performs faster.Conference Object Citation - WoS: 3Citation - Scopus: 4Düşük Maliyetli Serbest-uzay Optik İletişim Sistemi Tasarımı(Institute of Electrical and Electronics Engineers Inc., 2004) Karatay, Okan; Dinleyici, Mehmet Salihhi recent years commercial and military interest in free-space optical communication (FSO) is growing due to the high bandwidths, portability and high security. Although the numerous advantages, atmospheric events such as attenuation and scintillation severely effects the link quality. Novel methods of mitigating atmospheric events were applied. Usage of large aperture lenses and high transmitted power according to decrease scintillation effects increases the system cost. Fresnel lenses, as an alternative to the classical optic system for mitigating scintillation effects would be a low-cost solution. As a result of the technological improvements on the output power and divergence angles of VSCEL (Vertical Cavity Surface Emitting Laser) enables high-speed cost effective FSO communication system design. In this research current applied FSO systems are analysed and fresnel lens optical system of alternative low-cost system designed.Conference Object Paralel Model Kombinasyonu ve Yerel Öznitelikler Kullanarak Gürbüz Konuşmacı Onaylama(Institute of Electrical and Electronics Engineers Inc., 2004) Tüfekçi, ZekeriyaInterfering noise severely degrades the performance of a speaker verification system. The Parallel Model Combination (PMC) technique is one of the most efficient techniques for dealing with such noise. Another method is to use features local in the frequency domain. Recently, we proposed Mel-Frequency Discrete Wavelet Coefficients (MFDWCs) [1] as speech features local in frequency domain. In this paper, we discuss using PMC along with MFDWC features to take advantage of both noise compensation and local features (MFDWCs) to decrease the effect of noise on verification performance. We evaluate the performance of MFDWCs for various noise types and noise levels. We also compare the performance of these versus MFCCs and both using PMC for dealing with additive noise. The experimental results show significant performance improvements for MFDWCs versus MFCCs after compensating the HMMs using the PMC technique. For example the MFDWCs gave 6.29 points performance improvement on average over MFCCs for 12 dB. This corresponds to 38.33% error reduction.Conference Object Citation - WoS: 2Citation - Scopus: 4Tek Kamera ve Aynalar Kullanan Bir Görsel Denetleme Sistemi(Institute of Electrical and Electronics Engineers Inc., 2004) Gümüştekin, ŞevketIn this paper the geometrical properties of an imaging system are investigated. This system uses mirrors to simulate additional cameras. The geometry developed here helps us to capture the images of an object from meaningful viewpoint locations. The imaging system with the desired geometry is realized by adjusting the positions and orientations of mirrors. A special calibration pattern is used for the process of camera calibration which finds the unknown camera parameters and gives feedback about the degree of compliance with the desired geometry. The calibrated camera and its mirror images are used to create a 2D image of an object surface with a uniform geometry. After a pre-defined inner or outer surface of a test object is imaged from different view angles using mirrors, these images are warped and blended in a single image which is used for visual inspection. Hence, the vaguely defined process of inspecting 3D objects and their surface textures is converted to an efficient and well defined process of inspecting 2D images.Conference Object Citation - Scopus: 1Özilinti Matrisinin Oluşturulma Yönteminin Modele Dayalı Sinüzoidal Parametre Kestirimindeki Etkileri(Institute of Electrical and Electronics Engineers Inc., 2004) Altınkaya, Mustafa AzizAlthough the maximum likelihood method gives the optimum solutions for the parameter estimation problem of the sinusoids embedded in noise, it is computationally difficult since it generally requires to solve nonlinear optimization problems. So some model-based parameter estimators with high frequency resolution property are preferred quite often. In order to find these estimates the first step is usually forming the autocorrelation (AC) matrix. In this work the effects of the method utilized in the generation of the AC matrix on the performances of sinusoidal parameter estimators are investigated. One way of forming the AC matrix is to use a Toeplitz structure with either the biased or the unbiased AC lag estimates as the matrix elements. Another way is to use the socalled "covariance method" in the AC matrix generation. In this method the matrix formed is no longer Toeplitz; but it is still symmetric. We can think of that the Toeplitz AC matrix is a perturbed version of the non-Toeplitz AC matrix. The differences in the performances of the MUSIC spectral estimator with Toeplitz; and non-Toeplitz AC matrix usage is related to the perturbation in the AC matrix estimate. For this purpose the 3 x 3 AC matrix is is utilized in the estimation of the frequency of a single sinusoid using the MUSIC frequency estimator. The accuracy of the perturbation analysis is checked with the simulation results. Additionally, the fact that the performance of an estimator with data windowing and Toeplitz AC matrix generation becomes near to the performance of the same estimator with non-Toeplitz AC matrix is shown with simulation studies.Conference Object Citation - Scopus: 13-D Switching Fabric Node Design(ACTA Press, 2004) Dinleyici, Mehmet Salih; Akın, OsmanIn this work we investigate an all-optical switching node that can be controlled by means of a transient grating, which is formed by interference of two Gaussian beams. This design considers 3-D architecture of switching fabrics.. real profile of Gaussian beams and fast switching time requirements. Four Wave Mixing (FWM) technique is applied in the evanescent field region of waveguide, showing chi((3)) nonlinearity. The formed grating is analysed by standart methods to obtain reflection coefficient and then coupling coefficient for power exchange between waveguides.Conference Object Citation - Scopus: 1Hava Fotoğraflarından Deniz Kıyılarının Belirlenmesi(Institute of Electrical and Electronics Engineers Inc., 2006) Kahraman, Metin; Gümüştekin, ŞevketThe unique structures of different coastline segments provide distinctive image features for several applications such as oceanography, georeferencing, cartography and autonomous navigation. In this paper, a procedure involving automatic multiresolution coastline extraction is described. Using this method, sea and land textures are segmented utilizing cooccurrence and histogram features of wavelet image representation. The coastlines are identified as the boundaries of the sea regions.