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Publication Metadata only A multi-window fractional evolutionary spectral analysis(Institute of Electrical and Electronics Engineers Inc., 2003) Cekic, Yalcin; Akan, Aydin I.; Cekic, Yalcin, Department of Electrical Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey; Akan, Aydin I., Department of Electrical Engineering, Istanbul Üniversitesi, Istanbul, TurkeyIn this work, we present a multiple window Evolutionary Spectral analysis on a non-rectangular time-frequency lattice based on a discrete fractional Gabor expansion. The traditional Gabor expansion uses a fixed, and rectangular time-frequency plane tiling. Many of the practical signals such as speech, music, etc., require a more flexible, non-rectangular time-frequency lattice for a compact representation. The proposed method uses a set of basis functions that are related to the fractional Fourier basis and generate a parallelogram-shaped tiling. Simulation results are given to illustrate the performance of our algorithm. © 2022 Elsevier B.V., All rights reserved.Publication Metadata only High capacity image watermarking in the joint spatio-frequency domain(2009) Ozturk, Mahmut; Akan, Aydin I.; Yalçin Çekiç; Ozturk, Mahmut, Department of Electrical and Electronics Engineering, Istanbul Üniversitesi, Istanbul, Turkey; Akan, Aydin I., Department of Electrical and Electronics Engineering, Istanbul Üniversitesi, Istanbul, Turkey; Yalçin Çekiç, null, Department of Electrical and Electronic Engineering, Bahçeşehir Üniversitesi, Istanbul, TurkeyWatermarking techniques are proposed as a solution to copyright protection of digital media files. Watermarking algorithms are mainly concentrated on spatial or spectral domains. In this work, a robust and high capacity watermarking method that is based on spatio-frequency (SF) representations is presented. We use the Discrete Evolutionary Transform (DET) to represent an image in the SF domain. A watermark is embedded onto selected coefficients in the joint SF domain. Hence by combining the advantages of spatial and spectral domain watermarking methods, a robust, invisible, secure and high capacity watermarking method is presented. Simulations results yield that the proposed algorithm is robust to many signal processing attacks and outperforms several previous watermarking techniques. © 2010 Elsevier B.V., All rights reserved.Publication Metadata only Denoising embolic Doppler ultrasound signals using Dual Tree Complex Discrete Wavelet Transform(2010) Serbes, Görkem; Aydın, Nizamettin; Serbes, Görkem, Department of Electrical Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey; Aydın, Nizamettin, Department of Computer Engineering, Yıldız Teknik Üniversitesi, Istanbul, TurkeyEarly and accurate detection of asymptomatic emboli is important for monitoring of preventive therapy in stroke-prone patients. One of the problems in detection of emboli is the identification of an embolic signal caused by very small emboli. The amplitude of the embolic signal may be so small that advanced processing methods are required to distinguish these signals from Doppler signals arising from red blood cells. In this study instead of conventional discrete wavelet transform, the Dual Tree Complex Discrete Wavelet Transform was used for denoising embolic signals. Performances of both approaches were compared. Unlike the conventional discrete wavelet transform discrete complex wavelet transform is a shift invariant transform with limited redundancy. Results demonstrate that the Dual Tree Complex Discrete Wavelet Transform based denoising outperforms conventional discrete wavelet denoising. Approximately 8 dB improvement is obtained by using the Dual Tree Complex Discrete Wavelet Transform compared to the improvement provided by the conventional Discrete Wavelet Transform (less than 5 dB). © 2010 IEEE. © 2011 Elsevier B.V., All rights reserved.Publication Metadata only Multipose face detection using Zernike moment invariants, Zernike moment deǧi̇şmezleri̇ i̇le pozdan baǧimsiz yüz tespi̇ti̇(2012) Karaali, Ali; Erdem, Cigdem Eroglu; Ulukaya, Sezer; Karaali, Ali, Bahçeşehir Üniversitesi, Istanbul, Turkey; Erdem, Cigdem Eroglu, Bahçeşehir Üniversitesi, Istanbul, Turkey; Ulukaya, Sezer, Bahçeşehir Üniversitesi, Istanbul, TurkeyWe propose a new efficient technique for localization of faces in arbitrary images. The technique is based on segmentation of images into skin colored blobs, which is followed by computation of scale, translation and rotation invariant moment-based features to learn a statistical model of faces and non-face regions. The superiority of the method to the state-of-the-art face detection methods is its ability to detect non-frontal faces in a person independent way. Experimental results on CVL database show that the proposed algorithm gives higher true positive rates as compared to the well-known Viola-Jones face detector. © 2012 IEEE. © 2012 Elsevier B.V., All rights reserved.Publication Metadata only Region growing on frangi vesselness values in 3-D CTA data, 3-BOYUTLU bt anjiyografi verilerinde frangi damarlik yöntemi üzerine bölge büyütme yaklasimi(2013) Oksuz, Ilkay; Ünay, Devrim; Kadipaşaoǧlu, Kâmuran A.; Oksuz, Ilkay, Bahçeşehir Üniversitesi, Istanbul, Turkey; Ünay, Devrim, Bahçeşehir Üniversitesi, Istanbul, Turkey; Kadipaşaoǧlu, Kâmuran A., Bahçeşehir Üniversitesi, Istanbul, TurkeyIn cardiac related diagnostic methods, the shape and curvature of coronary arteries is essential. Consequently, one of the most important requirements for Computer Aided Diagnosis (CAD) Systems is automated segmentation of vasculature. In this paper, we propose a new hybrid algorithm, which segment the coronary arterial tree in CTA images by merging methodologies-, namely, Region Growing and Frangi Approach. The algorithm first runs a region growing on Frangi vesselness values and subsequently optimizes the results with several threshold values. Comparison of the present results with optimal results of existing segmentation algorithms reveals that the proposed approach outperforms its predecessors. The diagnostic accuracy of the algorithm will next be validated on the segmentation of coronary arteries from real CT data. © 2013 IEEE. © 2013 Elsevier B.V., All rights reserved.Publication Metadata only Internal calibration of a camera and an inertial measurement unit, Kamera ve ataletsel ölçüm birimi iç kalibrasyonu(2013) Erdem, Tanju Tanju; Ercan, Ali Özer; Aydin, Tarkan; Erdem, Tanju Tanju, Özyeğin Üniversitesi, Istanbul, Turkey; Ercan, Ali Özer, Özyeğin Üniversitesi, Istanbul, Turkey; Aydin, Tarkan, Bahçeşehir Üniversitesi, Istanbul, TurkeyIn this paper, we address the problem of internal calibration of a camera and an inertial measurement unit (IMU). The internal calibration of a camera and an IMU requires the determination of the relative orientation and displacement between the camera and the IMU. Although the problem of orientation estimation is well studied, and there exists simple algorithms for it, current displacement estimation techniques require very special data collection setups or particular sensor movements. We propose a novel method for estimating the displacement between the camera and an IMU. Our method has a very simple data collection step and involves the solution of linear equations only. Experimental results with real data show the effectiveness of our proposed algorithm. © 2013 IEEE. © 2013 Elsevier B.V., All rights reserved.Publication Metadata only A watershed and active contours based method for dendritic spine segmentation in 2-photon microscopy images, 2-Foton mikroskopi görüntülerindeki dendritik dikenlerin bölütlenmesi için watershed ve etkin çevritlere dayali bir yöntem(2013) Erdil, Ertunç; Argunşah, Ali Özgür; Ünay, Devrim; Çetin, Müjdat; Erdil, Ertunç, Mühendislik ve Doǧa Bilimleri Fakültesi, Sabancı Üniversitesi, Tuzla, Turkey; Argunşah, Ali Özgür, Champalimaud Neuroscience Programme, Champalimaud Centre for the Unknown, Lisbon, Portugal; Ünay, Devrim, Bahçeşehir Üniversitesi, Istanbul, Turkey; Çetin, Müjdat, Mühendislik ve Doǧa Bilimleri Fakültesi, Sabancı Üniversitesi, Tuzla, TurkeyAnalysing morphological and volumetric properties of dendritic spines from 2-photon microscopy images has been of interest to neuroscientists in recent years. Developing robust and reliable tools for automatic analysis depends on the segmentation quality. In this paper, we propose a new segmentation algorithm for dendritic spine segmentation based on watershed and active contour methods. First, our proposed method coarsely segments the dendritic spine area using the watershed algorithm. Then, these results are further refined using a region-based active contour approach. We compare our results and the results of existing methods in the literature to manual delineations of a domain expert. Experimental results demonstrate that our proposed method produces more accurate results than the existing algorithms proposed for dendritic spine segmentation. © 2013 IEEE. © 2013 Elsevier B.V., All rights reserved.Publication Metadata only Directional dual-tree complex wavelet packet transform(2013) Serbes, Görkem; Aydın, Nizamettin; Gülçür, Halil Ö.; Serbes, Görkem, Department of Biomedical Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey, Institute of Biomedical Engineering, Boğaziçi Üniversitesi, Bebek, Turkey; Aydın, Nizamettin, Department of Computer Engineering, Yıldız Teknik Üniversitesi, Istanbul, Turkey; Gülçür, Halil Ö., Institute of Biomedical Engineering, Boğaziçi Üniversitesi, Bebek, TurkeyDoppler ultrasound systems, which are widely used in cardiovascular disorders detection, have quadrature format outputs. Various types of algorithms were described in literature to process quadrature Doppler signals (QDS), such as phasing filter technique (PFT), fast Fourier transform method, frequency domain Hilbert transform method and complex continuous wavelet transform. However for the discrete wavelet transform (DWT) case, which becomes a common method for processing QDSs, there was not a direct method to recover flow direction from quadrature signals. Traditionally, to process QDSs with DWT, firstly directional signals have to be extracted and later two DWTs must be applied. Although there exists a complex DWT algorithm called dual tree complex discrete wavelet transform (DTCWT), it does not provide directional signal decoding during analysis because of the unwanted energy leaks into its negative frequency bands. Modified DTCWT, which is a combination of PFT and DTCWT, has the capability of extracting directional information while decomposing QDSs into different frequency bands, but it uses an additional Hilbert transform filter and it increases the computational complexity of whole transform. Discrete wavelet packet transform (DWPT), which is a generalization of the ordinary DWT allowing subband analysis without the constraint of dyadic decomposition, can perform an adaptive decomposition of the frequency axis. In this study, a novel complex DWPT, which maps directional information while processing QDSs, is proposed. The success of proposed method will be measured by using simulated quadrature signals. © 2013 IEEE. © 2013 Elsevier B.V., All rights reserved.Publication Metadata only Particle velocity gradient based acoustic mode beamforming for short linear vector sensor arrays(Acoustical Society of America [email protected], 2014) Gür, M. Berke; Gür, M. Berke, Department of Mechanical Engineering, Bahçeşehir Üniversitesi, Istanbul, TurkeyIn this paper, a subtractive beamforming algorithm for short linear arrays of two-dimensional particle velocity sensors is described. The proposed method extracts the highly directional acoustic modes from the spatial gradients of the particle velocity field measured at closely spaced sensors along the array. The number of sensors in the array limits the highest order of modes that can be extracted. Theoretical analysis and numerical simulations indicate that the acoustic mode beamformer achieves directivity comparable to the maximum directivity that can be obtained with differential microphone arrays of equivalent aperture. When compared to conventional delay-and-sum beamformers for pressure sensor arrays, the proposed method achieves comparable directivity with 70%-85% shorter apertures. Moreover, the proposed method has additional capabilities such as high front-back (port-starboard) discrimination, frequency and steer direction independent response, and robustness to correlated ambient noise. Small inter-sensor spacing that results in very compact apertures makes the proposed beamformer suitable for space constrained applications such as hearing aids and short towed arrays for autonomous underwater platforms. © 2014 Acoustical Society of America. © 2014 Elsevier B.V., All rights reserved.Publication Metadata only Object tracking by combining tracking-by-detection and marginal particle filter, Tespit-ile-Takip ve Marjinal Parçacik Süzgecinin Birleştirilmesiyle Nesne Takibi(Institute of Electrical and Electronics Engineers Inc., 2016) Maraş, Bahri; Arica, Nafiz; Ertüzün, Ayşin Baytan; Maraş, Bahri, Boğaziçi Üniversitesi, Bebek, Turkey; Arica, Nafiz, Bilgisayar Mühendisliǧi Bölümü, Bahçeşehir Üniversitesi, Istanbul, Turkey; Ertüzün, Ayşin Baytan, Boğaziçi Üniversitesi, Bebek, TurkeyIn this paper, we propose a new algorithm based on tracking-by-detection approach for tracking of the objects having non-linear dynamic motion. For this purpose, the tracking-by-detection method depending on the Gauss kernel using the circulant matrix theory and the Fourier transform is employed together with the marginal particle filter method. Marginal particle filter uses the scores derived from the Gauss kernel at the measurement update phase of the filter to weight the particles propagated around the target that has been tracked. While updating the state variables by marginal particle filter, the object coordinates, the correction values belonging to these coordinates and the dimensions of the image window surrounding the object is estimated. The proposed method is tested on the video sequences which include the object having a high non-linear motion, and it was observed that marginal particle filter enhanced the performance of the track-by-detection method in an important scale. © 2017 Elsevier B.V., All rights reserved.