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Öğe Analyses of Elliptical Coplanar Coupled Waveguides and Coplanar Coupled Waveguides With Finite Ground Width(IEEE-İnst Electrical Electronics Engineers Inc, 2006) Duyar, Mehmet; Akan, Volkan; Yazgan, Erdem; Bayrak, MehmetIn this paper, the quasi-TEM characteristic parameters of elliptical coplanar coupled waveguides and coupled coplanar waveguide with a finite ground width configuration are presented and analyzed. Computer-aided design (CAD)-oriented fast, simple, and accurate analytic formulas are derived by using conformal mapping techniques, which provide satisfactory accuracy at microwave frequencies and lead to closed-form analytical solutions suitable for CAD software packages. The results for the odd- and even-mode characteristic impedance, effective dielectric constant, and coupling coefficient have been computed by these formulas. Good agreement between the present results and published results [1] is observed. For the planar case, simulations have also been undertaken with Sonnet electromagnetic-circuit solver software. The computed results agree well with those of the simulation ones.Öğe Analytical attenuation calculation of asymmetrical coplanar waveguide with finite-extent ground planes for coplanar waveguide mode(JOHN WILEY & SONS INC, 2007) Duyar, Mehmet; Akan, Volkan; Yazgan, Erdem; Bayrak, MehmetIn this study, fast and new analytical formulations have been presented for correct loss calculations in asymmetrical coplanar waveguides (CPW) with finite-extent ground planes for CPW mode. To generalize loss analysis for CPW mode, not only gaps but also finite ground planes are assumed as asymmetric. Moreover, dielectric thickness and ground plane widths are considered as finite for this transmission line. Another important concept presented in this article is that the proposed expressions are easily applicable for CAD platforms. Through the analyses, conformal mapping techniques (CMT) have been employed. The obtained results in this work have been compared with the results of other similar studies (spectral domain method, mode matching, etc.) available in the literature. These comparisons indicate that the expressions developed in this study are found to he more suitable for accurate calculations of loss as well as the characterization of asymmetrical CPW with finite-extent ground planes. (C) 2007 Wiley Periodicals, Inc.Öğe Assessment of exercise stress testing with artificial neural network in determining coronary artery disease and predicting lesion localization(PERGAMON-ELSEVIER SCIENCE LTD, 2009) Babaoglu, Ismail; Baykan, Omer Kaan; Aygul, Nazif; Ozdemir, Kurtulus; Bayrak, MehmetThe aim of this study is to show the artificial neural network (ANN) on determination of coronary artery disease existence and localization of lesion based upon exercise stress testing (EST) data. EST and coronary angiography were performed on 330 patients. The data studied acquiring 27 verifying features was normalized employing z-score method. To select training and test data, 10-fold cross-validation methods were involved and multi-layered perceptron neural network was employed for the classification. The interpretation of EST using ANN proved 91%, 73% and 65% diagnostic accuracy for the left main coronary (LMCA), left anterior descending and left circum-flex coronary arteries, respectively. Besides, 69% for the right coronary artery is also predicted. For the LMCA, a 94% negative predictive value (NPV) was obtained. This high percentage of NPV encourages the elimination of LMCA lesions. Some knowledge call also be obtained about lesion localization, besides diagnosing of coronary artery disease by the assessment of EST via ANN. (C) 2007 Elsevier Ltd. All rights reserved.Öğe Color Image Watermarking Scheme Based on Efficient Preprocessing and Support Vector Machines(SPRINGER-VERLAG BERLIN, 2008) Findik, Oguz; Bayrak, Mehmet; Babaoglu, Ismail; Comak, EmreThis paper suggests a new block based watermarking technique utilizing preprocessing and support vector machine (PPSVMW) to protect color image's intellectual property rights. Binary test set is employed here to train support vector machine (SVM). Before adding binary data into the original image, blocks have been separated into two parts to train SVM for better accuracy. Watermark's I valued bits were randomly added into the first block part and 0 into the second block part. Watermark is embedded by modifying the blue channel pixel value in the middle of each block so that watermarked image could be composed. SVM was trained with set-bits and three other features which are averages of the differences of pixels in three distinct shapes extracted from each block, and hence without the need of original image, it could be extracted. The results of PPSVMW technique proposed in this study were compared with those of the Tsai's technique. Our technique was proved to be more efficient.Öğe A Comparison of Artificial Intelligence Methods on Determining Coronary Artery Disease(Springer-Verlag Berlin, 2010) Babaoğlu, İsmail; Baykan, Ömer Kaan; Aygül, Nazif; Özdemir, Kurtuluş; Bayrak, MehmetThe aim of this study is to show a comparison of multi-layered perceptron neural network (MLPNN) and support vector machine (SVM) on determination of coronary artery disease existence upon exercise stress testing (EST) data. EST and coronary angiography were performed on 480 patients with acquiring 23 verifying features from each. The robustness of the proposed methods is examined using classification accuracy, k-fold cross-validation method and Cohen's kappa coefficient. The obtained classification accuracies are approximately 78% and 79% for MLPNN and SVM respectively. Both MLPNN and SVM methods are rather satisfactory than human-based method looking to Cohen's kappa coefficients. Besides, SVM is slightly better than MLPNN when looking to the diagnostic accuracy, average of sensitivity and specificity, and also Cohen's kappa coefficient.Öğe Conductor loss calculation of elliptical, cylindrical coplanar waveguides and coplanar waveguides with finite conductor thickness(IOS PRESS, 2009) Duyar, Mehmet; Akan, Volkan; Yazgan, Erdem; Bayrak, MehmetIn this paper, new and fast analytical formulations have been presented for conductor loss calculations of elliptical (ECPW) and cylindrical coplanar waveguide (CCPW) with finite conductor thickness. These expressions are derived using conformal mapping techniques (CMT) and the validity of them is established by comparing the numerical results in the literature. These comparisons indicate that for the same conductor thickness the conductor losses of elliptical and cylindrical coplanar waveguide are higher than the conductor losses of coplanar waveguide presented in [1]. Calculation method developed in this study is an extension of the approximate technique proposed by Ghione [1].Öğe A Different Method Determining Dielectric Constant of Soil and Its FDTD Simulation(2003) Yaldiz, Ercan; Bayrak, MehmetIn this study, a different method determining the dielectric constant of soil via probes is presented. The method is based on the principle of measuring pulse delay in a given matter. The experimental study, which was carried out basically using an HP8753A vector network analyser, was repeated for various soil mixtures having different values of wetness. The results obtained from the measurements have clearly shown that the dielectric constant of the soil was increasing almost proportionally with that of the moisture content in the soil. The suitability of the measuring method was also checked with a number of simulation results obtained directly using the finite difference time domain method (FDTD).Öğe Effects of Principle Component Analysis on Assessment of Coronary Artery Diseases Using Support Vector Machine(Pergamon-Elsevier Science Ltd, 2010) Babaoğlu, İsmail; Fındık, Oğuz; Bayrak, MehmetArtificial intelligence techniques are being effectively used in medical diagnostic support tools to increase the diagnostic accuracy and to provide additional knowledge to medical stuff. Effects of principle component analysis on the assessment of exercise stress test with support vector machine in determination of coronary artery disease are studied in this work. Study dataset consist of 480 patients with 23 features for each patient. By reducing study dataset with principle component analysis method, optimum support vector machine model is found for each reduced dimension. According to the obtained results, optimum support vector machine model in which the dataset is reduced to 18 features with principle component analysis is more accurate than optimum support vector machine model which uses the whole 23 featured dataset. Besides, principle component analysis implementation decreases the training error and the sum of the training and test times.Öğe Error performance of super-orthogonal space-time trellis codes with transmit antenna selection(2006) Özdemir, Özgür; Altunbaş, İbrahim; Bayrak, MehmetA space-time coding scheme with transmit antenna selection that employs conventional super-orthogonal space-time trellis and improved super-orthogonal space-time trellis codes is considered. Transmit antenna selection criterion is given and the error performance of the proposed structure is tested by computer simulations for systems that have two active transmit antennas and single receive antenna in quasi-static flat Rayleigh fading channels. It has been shown that proposed scheme outperforms the previous space-time trellis coding structures with transmit antenna selection given in the literature.Öğe Genel amaçlı web tabanlı mobil robot: SUNAR(2006) Yılmaz, Nihat; Sağıroğlu, Şeref; Bayrak, MehmetBu çalışmada, mühendislik eğitimi ve bilimsel çalışmalarda kullanılmak üzere web tabanlı bir mobil robot platformu geliştirilmiş ve farklı uygulamalarda başarıyla kullanılabileceği gösterilmiştir. Web üzerinden izlenebilen, kontrol edilebilen, yeniden programlanabilen ve kablosuz olarak haberleşebilen bu robot platform, gerçek zamanlı uygulamalarda kullanılmak üzere tasarlanmıştır. Farklı uygulamaları gerçekleştirmek için, mobil robot üzerinde gerçek zamanlı destek verebilen bir kütüphane geliştirilmiştir. Yarı otonom ve tam otonom çalışmalarda kullanılabilen bu robot ile yapılan testlerde, mobil robotun çok amaçlı olarak kullanılabileceği ve özellikle mühendislik eğitiminde bazı derslerine web tabanlı uygulama desteği verebileceği tespit edilmiştir.Öğe Görme Tabanlı Mobi?l Robot ile Farklı Renklerde Nesneleri?n Gerçek Zamanlı Taki?bi?(Gazi Univ, Fac Engineering Architecture, 2010) Uzer, Mustafa Serter; Yılmaz, Nihat; Bayrak, MehmetBu çalışmada, görme tabanlı mobil robot ile farklı renklerde nesnelerin gerçek zamanlı takibi uygulaması gerçekleştirilmiştir. Geliştirilen robot; keşif, güvenlik ve gözlem alanlarındaki faaliyetlerde de kullanılabilecek özelliklere sahiptir. Bu görme tabanlı mobil robotun, sadece görüntü işleme ve robotik görme teknikleri kullanılarak otonom bir şekilde hareket ettirilmesi hedeflenmiştir. Farklı renklerde (kırmızı, mavi, yeşil) nesneleri takip edebilen robotun gerçek zamanlı işlemeye uygun olacak şekilde, tepki verme süresi 96 ms ile 106 ms aralığındadır. Geliştirilen iki farklı görüntü işleme algoritması ile mavi ve kırmızı renkli nesneler için % 100, yeşil renkli nesneler için ise % 60' lık bir tanıma başarısı sağladığı deneylerle görülmüştür. Doğrusal ve dairesel yörüngelerde renkli nesne takibi deneylerinde, ortalama 5,7 cm/s hızda maksimum 4,5 cm' lik sapma tespit edilmiştir.Öğe Görme tabanlı mobil robot ile farklı renklerde nesnelerin gerçek zamanlı takibi(2010) Uzer, Mustafa Serter; Yılmaz, Nihat; Bayrak, MehmetBu çalışmada, görme tabanlı mobil robot ile farklı renklerde nesnelerin gerçek zamanlı takibi uygulaması gerçekleştirilmiştir. Geliştirilen robot; keşif, güvenlik ve gözlem alanlarındaki faaliyetlerde de kullanılabilecek özelliklere sahiptir. Bu görme tabanlı mobil robotun, sadece görüntü işleme ve robotik görme teknikleri kullanılarak otonom bir şekilde hareket ettirilmesi hedeflenmiştir. Farklı renklerde (kırmızı, mavi, yeşil) nesneleri takip edebilen robotun gerçek zamanlı işlemeye uygun olacak şekilde, tepki verme süresi 96 ms ile 106 ms aralığındadır. Geliştirilen iki farklı görüntü işleme algoritması ile mavi ve kırmızı renkli nesneler için % 100, yeşil renkli nesneler için ise % 60’ lık bir tanıma başarısı sağladığı deneylerle görülmüştür. Doğrusal ve dairesel yörüngelerde renkli nesne takibi deneylerinde, ortalama 5,7 cm/s hızda maksimum 4,5 cm’ lik sapma tespit edilmiştir.Öğe Landmark detection via ANN for a web based autonomous mobile robot: SUNAR(Selcuk University Research Center of Applied Mathematics, 2006) Yılmaz, Nihat; Sağıroğlu, Şeref; Bayrak, MehmetIn this study, a landmark detection method was developed for finding or position correction of a web based mobile robot designed and implemented for long term and regular scientific purposes. Colored numeric and alphanumeric character sticker in place of other artificial landmarks appropriate for robot is selected to be landmark for understanding of both human and robot. Statistical analysis of captured and segmented image part is used for feature vector extraction. Statistical properties of histogram, projections and image raw data are selectable components of feature vector. The feature vector is tested by previously trained multilayer perceptron feed forward neural network (ANN). For this aim, online programs required for robotic activities, image processing and neural network processes have been developed on web interface of web-robot. In this program, improved software libraries for SUNAR system are employed. Real time results and robot scenes are monitored online on web portal.Öğe Landmark Detection via ANN for a Web Based Autonomous Mobile Robot: Sunar(2006) Yılmaz, Nihat; Sağıroğlu, Şeref; Bayrak, MehmetIn this study, a landmark detection method was developed for finding or position correction of a web based mobile robot designed and implemented for long term and regular scientific purposes. Colored numeric and alphanumeric character sticker in place of other artificial landmarks appropriate for robot is selected to be landmark for understanding of both human and robot. Statistical analysis of captured and segmented image part is used for feature vector extraction. Statistical properties of histogram, projections and image raw data are selectable components of feature vector. The feature vector is tested by previously trained multilayer perceptron feed forward neural network (ANN). For this aim, online programs required for robotic activities, image processing and neural network processes have been developed on web interface of web-robot. In this program, improved software libraries for SUNAR system are employed. Real time results and robot scenes are monitored online on web portal.Öğe Performance of Super-Orthogonal Space-Time Trellis Codes with Transmit Antenna Selection(Inst Engineering Technology-Iet, 2010) Özdemir, Özgür; Altunbaş, İbrahim; Bayrak, MehmetSuper-orthogonal space-time trellis (SOSTT) codes provide a significant coding gain with respect to the conventional space-time trellis (STT) codes without increasing the decoding complexity at the receiver. Transmit antenna selection (TAS) is an important technique to solve the implementation complexity problems of multiple-antenna systems that arise from employing a separate RF chain for each antenna. This study treats a scheme combining SOSTT coding with TAS in order to exploit performance improvements provided by SOSTT codes while realising the promises made by the TAS technique. In the proposed scheme, transmit antennas that maximise the signal-to-noise ratio at the receiver are chosen and activated out of all available transmit antennas for transmission of the baseline SOSTT code, whereas all other transmit antennas are silent. The error performance of the proposed structure is investigated by deriving moment generating function (MGF)-based upper bound expressions on the pairwise error probability in quasi-static flat Rayleigh fading channels for both perfect and imperfect antenna subset selection. The performance analysis demonstrates that the proposed scheme provides full diversity order as if all transmit antennas were used when antennas are perfectly selected. Moreover, it is shown that this structure provides better error performance almost at the same decoding complexity compared to the previous STT coding structures with TAS in the literature.Öğe Quasi-static solutions of elliptical, cylindrical-coupled parallel coplanar waveguide, and coupled parallel coplanar waveguide with finite ground planes(JOHN WILEY & SONS INC, 2007) Duyar, Mehmet; Akan, Volkan; Yazgan, Erdem; Bayrak, MehmetThis article presents the quasi-static analyses of elliptical-coupled parallel coplanar waveguide (ECP CPW), cylindrical-coupled parallel coplanar waveguide (CCP CPW), and coupled parallel coplanar waveguide (CP CPW) with finite ground planes. Conformal-mappi ng techniques have been used through the analyses. The obtained results show good agreement with IE3D electromagnetic-circuit solver software's simulations for the planar case. In addition, the results have been compared with others available in the literature. (C) 2007 Wiley Periodicals, Inc.Öğe Recording system for Korotkoff sound signals(IEEE, 2006) Altunkaya, Sabri; Bayrak, MehmetThe aim of this study is to help to improve new diagnosis methods for cardiovascular disease by designing a computer program and a hardware which realizes the recording of Korotkoff sounds produced during the measurement of blood pressure and basic analysis process. Korotkoff sounds have been traditionally used to measure blood pressure noninvasively by employing the auscultatory method. The recording system developed in this study can be used to produce a large database by recording some important information such as weight, age, and disease name in addition to Korotkoff sounds. Basic analysis processes like filtering and finding frequency component of recorded data is accomplished by means of the designed software. Thus, the necessity of using different computer programs for analyzing and recording data has been eliminated.Öğe Recording system for Korotkoff sound signals [Korotkoff ses sinyalleri kayit sistemi](2006) Altunkaya, Sabri; Bayrak, MehmetThe aim of this study is to help to improve new diagnosis methods for cardiovascular disease by designing a computer program and a hardware which realizes the recording of Korotkoff sounds produced during the measurement of blood pressure and basic analysis process. Korotkoff sounds have been traditionally used to measure blood pressure noninvasively by employing the auscultatory method. The recording system developed in this study can be used to produce a large database by recording some important information such as weight, age, and disease name in addition to Korotkoff sounds. Basic analysis processes like filtering and finding frequency component of recorded data is accomplished by means of the designed software. Thus, the necessity of using different computer programs for analyzing and recording data has been eliminated. © 2006 IEEE.Öğe Super-orthogonal space-time trellis coding with transmit antenna selection(2005) Özdemir, Özgür; Altunbaş, İbrahim; Bayrak, MehmetIn this paper, combination of transmit antenna selection and super-orthogonal space-time trellis coding technique is proposed, the transmit antenna selection criterion is given and the error performance curves obtained by computer simulations for quasi-static Rayleigh fading channels are presented. It is shown that the proposed scheme provides much better error performance than the conventional spacetime coding schemes with transmit antenna selection. © 2005 IEEE.Öğe Two novel transmission lines with vertical conductors added to ground planes(JOHN WILEY & SONS INC, 2007) Duyar, Mehmet; Akan, Volkan; Yazgan, Erdem; Bayrak, MehmetIn this article, two different novel Coplanar Waveguides (CPW) structures have been proposed and analyzed. The CPW structures proposed provide flexibility for practical applications. For the analyses, conformal mapping techniques were employed. The closed form analytical expressions arc generally suitable for usage in CAD-oriented microwave circuit design. Both the structures have been simulated for quasi-TEM mode in a 3D commercially available software. In addition, the results obtained in this work have been compared with the others available in the literature. Simulations and comparisons give support to the validity of the obtained analytical expressions in this study. (C) 2007 Wiley Periodicals, Inc.
