Bilgisayar Mühendisliği Bölümü Yayın Koleksiyonu

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  • Article
    Citation - WoS: 43
    Citation - Scopus: 50
    Detection of Hip Osteoarthritis by Using Plain Pelvic Radiographs With Deep Learning Methods
    (Springer, 2020) Ureten, Kemal; Arslan, Tayfun; Gultekin, Korcan Emre; Demir, Ayse Nur Demirgoz; Ozer, Hafsa Feyza; Bilgili, Yasemin
    Objective The incidence of osteoarthritis is gradually increasing in public due to aging and increase in obesity. Various imaging methods are used in the diagnosis of hip osteoarthritis, and plain pelvic radiography is the first preferred imaging method in the diagnosis of hip osteoarthritis. In this study, we aimed to develop a computer-aided diagnosis method that will help physicians for the diagnosis of hip osteoarthritis by interpreting plain pelvic radiographs. Materials and methods In this retrospective study, convolutional neural networks were used and transfer learning was applied with the pre-trained VGG-16 network. Our dataset consisted of 221 normal hip radiographs and 213 hip radiographs with osteoarthritis. In this study, the training of the network was performed using a total of 426 hip osteoarthritis images and a total of 442 normal pelvic images obtained by flipping the raw data set. Results Training results were evaluated with performance metrics such as accuracy, sensitivity, specificity, and precision calculated by using the confusion matrix. We achieved accuracy, sensitivity, specificity and precision results at 90.2%, 97.6%, 83.0%, and 84.7% respectively. Conclusion We achieved promising results with this computer-aided diagnosis method that we tried to develop using convolutional neural networks based on transfer learning. This method can help clinicians for the diagnosis of hip osteoarthritis while interpreting plain pelvic radiographs, also provides assistance for a second objective interpretation. It may also reduce the need for advanced imaging methods in the diagnosis of hip osteoarthritis.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Binary Background Model With Geometric Mean for Author-Independent Authorship Verification
    (Sage Publications Ltd, 2023) Sezer, Ebru A.; Sever, Hayri; Canbay, Pelin
    Authorship verification (AV) is one of the main problems of authorship analysis and digital text forensics. The classical AV problem is to decide whether or not a particular author wrote the document in question. However, if there is one and relatively short document as the author's known document, the verification problem becomes more difficult than the classical AV and needs a generalised solution. Regarding to decide AV of the given two unlabeled documents (2D-AV), we proposed a system that provides an author-independent solution with the help of a Binary Background Model (BBM). The BBM is a supervised model that provides an informative background to distinguish document pairs written by the same or different authors. To evaluate the document pairs in one representation, we also proposed a new, simple and efficient document combination method based on the geometric mean of the stylometric features. We tested the performance of the proposed system for both author-dependent and author-independent AV cases. In addition, we introduced a new, well-defined, manually labelled Turkish blog corpus to be used in subsequent studies about authorship analysis. Using a publicly available English blog corpus for generating the BBM, the proposed system demonstrated an accuracy of over 90% from both trained and unseen authors' test sets. Furthermore, the proposed combination method and the system using the BBM with the English blog corpus were also evaluated with other genres, which were used in the international PAN AV competitions, and achieved promising results.
  • Article
    D2 +Nin(T), n=7 and 9, Collision System
    (1999) Böyükata, Mustafa; Durmuş, Perihan; Özçelik, Süleyman; Güvenç, Ziya Burhanettin; Jellinek, Julius
    In this study the kinetics of reactions of Nin n=7 and 9, clusters with a deuterium D2 molecule are studied via quasiclassical molecular dynamics. Dissociative chemisorption probabilities as functions of impact parameters, collision energies, and a rovibrational state of a molecule are calculated. And the corresponding reactive cross sections are evaluated. Resonance formation in the low collision energy region is discussed.
  • Article
    Fragmentation of a Non-Rotating Ni19 Cluster: A Molecular Dynamics Study
    (1999) Avcı, Halil; Çivi, Mehmet; Güvenç, Ziya Burhanettin; Jellinek, Julius
    Collisionless fragmentation of a non-rotating Ni19 cluster is studied using constant-energy molecular dynamics computer simulations. The cluster is modelled by an embedded atom model (EAM) energy surface. Distribution of the channel-specific fragmentation probabilities, and global rate constants are computed and analyzed as functions of the internal energy of the cluster. The results are compared with those obtained using the RRK statistical approach, and also compared with the other multi-channel fragmentation work.
  • Article
    Structural stability and energetics of single-walled carbon nanotubes under uniaxial strain
    (2003) Dereli, G.; Özdoğan, Cem
    A (10x10) single-walled carbon nanotube consisting of 400 atoms with 20 layers is simulated under tensile loading using our developed O(N) parallel tight-binding molecular-dynamics algorithms. It is observed that the simulated carbon nanotube is able to carry the strain up to 122% of the relaxed tube length in elongation and up to 93% for compression. Young's modulus, tensile strength, and the Poisson ratio are calculated and the values found are 0.311 TPa, 4.92 GPa, and 0.287, respectively. The stress-strain curve is obtained. The elastic limit is observed at a strain rate of 0.09 while the breaking point is at 0.23. The frequency of vibration for the pristine (10x10) carbon nanotube in the radial direction is 4.71x10(3) GHz and it is sensitive to the strain rate.
  • Article
    Citation - Scopus: 3
    Oscillation for a Nonlinear Dynamic System on Time Scales
    (2011) Mert, R.; Erbe, L.
    We study the oscillation properties of a system of two first-order nonlinear equations on time scales. This form includes the classical Emden-Fowler differential and difference equations and many of its extensions. We generalize some well-known results of Atkinson, Belohorec, Waltman, Hooker, Patula and others and also describe the relation to solutions of a delay-dynamic system. © 2011 Taylor & Francis.
  • Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Phase Changes in Icosahedral 54-, 55-, 56-Atom Platinum Clusters
    (World Scientific Publ Co Pte Ltd, 2004) Güvenç, ZB; Kökten, H; Sebetci, A
    Using the Voter and Chen version of an embedded-atom model, derived by fitting simultaneously to experimental data both the diatomic molecule and bulk platinum, we have studied the melting behavior of free, icosahedral, 54-, 55- and 56-atom platinum clusters in the molecular dynamics simulation technique. We present an atom-resolved analysis method that includes physical quantities such as the root-mean-square bond-length fluctuation and coordination number for individual atoms as functions of temperature. The effect of a central atom in the icosahedral structure to the melting process is discussed. The results show that the global minimum structures of the 54-, 55- and 56-atom Pt clusters do not melt at a specific temperature, rather, melting processes take place over a finite temperature range. The heat capacity peaks are not delta-functions, but instead remain finite. An ensemble of clusters in the melting region is a mixture of solid-like and liquid-like clusters.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Finite Size Scaling by Using Scaling Functions in Two-Dimensional Q=2 and 7 State Potts Models
    (World Scientific Publ Co Pte Ltd, 2001) Seferoglu, N; Aydin, M; Gündüç, Y; Demirtürk, S
    The scaling behaviors of the percolation cumulant and the surface renormalization are studied on q = 2 and 7 state Potts models. The results show that the scaling functions can be safely used to determine infinite lattice transition points and the thermal and magnetic exponents indicating that these functions have very small correction to scaling contributions.
  • Article
    Citation - WoS: 65
    Citation - Scopus: 74
    Detection of Rheumatoid Arthritis From Hand Radiographs Using a Convolutional Neural Network
    (Springer London Ltd, 2020) Ureten, Kemal; Erbay, Hasan; Maras, Hadi Hakan
    Introduction Plain hand radiographs are the first-line and most commonly used imaging methods for diagnosis or differential diagnosis of rheumatoid arthritis (RA) and for monitoring disease activity. In this study, we used plain hand radiographs and tried to develop an automated diagnostic method using the convolutional neural networks to help physicians while diagnosing rheumatoid arthritis. Methods A convolutional neural network (CNN) is a deep learning method based on a multilayer neural network structure. The network was trained on a dataset containing 135 radiographs of the right hands, of which 61 were normal and 74 RA, and tested it on 45 radiographs, of which 20 were normal and 25 RA. Results The accuracy of the network was 73.33% and the error rate 0.0167. The sensitivity of the network was 0.6818; the specificity was 0.7826 and the precision 0.7500. Conclusion Using only pixel information on hand radiographs, a multi-layer CNN architecture with online data augmentation was designed. The performance metrics such as accuracy, error rate, sensitivity, specificity, and precision state shows that the network is promising in diagnosing rheumatoid arthritis.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 6
    Systematic Investigation of the Effects of Unidirectional Links on the Lifetime of Wireless Sensor Networks
    (Elsevier, 2013) Tavli, Bulent; Dursun, Kayhan; Koyuncu, Murat; Ozyer, Sibel T.
    Link unidirectionality is a commonly encountered phenomenon in wireless sensor networks (WSNs), which is a natural result of various properties of wireless transceivers as well as the environment. Transmission power heterogeneity and random irregularities are important factors that create unidirectional links. Majority of the internode data transfer mechanisms are designed to work on bidirectional links (i.e., due to the lack of a direct reverse path, handshaking cannot be performed between a transmitter and receiver) which render the use of unidirectional links infeasible. Yet, there are some data transfer mechanisms designed specifically to operate on unidirectional links which employ distributed handshaking mechanisms (i.e., instead of using a direct reverse path, a multi-hop reverse path is used for the handshake). In this study, we investigate the impact of both transmission power heterogeneity and random irregularities on the lifetime of WSNs through a novel linear programming (LP) framework both for networks that utilize only bidirectional links and for those that can use bidirectional links as well as unidirectional links. (C) 2013 Elsevier B.V. All rights reserved.