Bilgisayar Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/253

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Citation Count: M. Saran; U. Güleç, "Contribution of Intelligent Repeat Engine in Mobile Learning for Enhancing Students’ Learning in Industrial Engineering Education".
Contribution of Intelligent Repeat Engine in Mobile Learning for Enhancing Students’ Learning in Industrial Engineering Education
(1) Saran, Murat; Güleç, Ulaş; 17753
Citation Count: Avcı, Halil...et al (1999). "Fragmentation of a Non-Rotating Ni19 Cluster: A Molecular Dynamics Study", Mathematical and Computational Applications, Vol. 4, No. 2, pp. 99-106.
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.
Citation Count: Böyükata, Mustafa...at all (1999). "D2 +Nin(T), n=7 and 9, Collision System", Mathematical and Computational Applications, Vol. 4, No. 1, pp. 61-67.
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.
Citation Count: Durmus, P...et al., "Reactions of small Ni clusters with a diatomic molecule: MD simulation of D(2)+Ni(n) (n=7-10) systems", 18th European Conference on Surface Science (ECOSS 18), Vol. 454, pp. 310-315, (2000).
Reactions of small Ni clusters with a diatomic molecule: MD simulation of D(2)+Ni(n) (n=7-10) systems
(2000) Durmuş, Perihan; Böyükata, Mustafa; Özçelik, Süleyman; Güvenç, Ziya B.; Jellinek, Julius
The kinetics of the reactions of nickel clusters with a deuterium molecule are studied, Dissociative chemisorption probabilities of the D(2) molecule on the small Ni(n) (n=7-10) clusters are computed by a quasi-classical molecular dynamics computer simulation technique. Structures of the clusters are obtained by an embedded-atom potential, and the interaction between the D(2) and Ni(n) is modelled by an LEPS (London-Eyring-Polanyi-Sato) function (energy surface). This analysis includes the chemisorption probabilities as functions of the impact parameter and of the relative translational energy of the D(2). The corresponding reactive cross-sections for the ground state of the molecule are calculated as functions of the collision energy and the size of the cluster. The role of the size of the clusters is examined. An indirect mechanism to the reaction, which involves formation of molecular adsorption as precursors to dissociative adsorption in the low collision energy region (less than 0.1eV), is observed. Results are discussed by comparing with the other similar theoretical and experimental studies. (C) 2000 Elsevier Science B.V. All rights reserved.
Citation Count: Guvenc, ZB; Hundur, Y; Hippler, R, "Sputtering yield and dynamical analysis of Ni(100) surface: A comparison of four different Ar-surface interaction potentials", 18th International Conference on Atomic Collisions in Solids (ICACS-18), Vol. 164, pp. 854-860, (2000).
Sputtering yield and dynamical analysis of Ni(100) surface: A comparison of four different Ar-surface interaction potentials
(2000) Güvenç, Ziya B.; Hundur, Yakup; Hippler, Rainer
The sputtering process of the Ar + Ni(100) collision system is investigated by means of constant energy molecular dynamics simulations. The Ni(100) is mimicked by an embedded-atom potential, and the interaction between the projectile and the surface is modelled by using four different screened Coulomb type potentials. The Ni atom emission from the lattice is analysed over the range of 10-40 eV collision energy. The maximum penetration depths of Ar, probability distributions of kinetic energy of the reflected Ar, and energy of the Ar and sputtered Ni atoms in the same collision events are evaluated as functions of the impact energy and sputtering time. Further, angular distributions of the scattered Ar are obtained. The calculated sputtering yields are compared with the available theoretical and experimental data. (C) 2000 Elsevier Science B.V. All rights reserved.
Citation Count: Kondakci, S, "Efficiency evaluation of the averaging noise reduction system", 23rd Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society, Vol. 23, pp. 1958-1961, (2001).
Efficiency evaluation of the averaging noise reduction system
(IEEE, 2001) Kondakçı, Süleyman; 102350
This paper presents the development of a method for estimation of denoising performance performed by an averaging algorithm presented in an earlier work Ill. The method was designed to evaluate statistical results when the noise reduction algorithm was applied to Gaussian-distributed noisy responses from a measurement system. Iterative noise reconstruction algorithm is efficient when number of iterations is kept at a higher level. However, the reduction in noise tends to converge slowly after a certain number of recursions were achieved[l]. Determination of the slow convergence point is important in order to find an optimum system configuration. Otherwise, improper usage will cause reduced system bandwidth, thus making the system useless for real-time measurements.
Citation Count: Erkoç, S.; Kokten, Hande; Güvenç, Ziya B., "Fragmentation of water clusters: molecular-dynamics simulation study" European Physical Journal D, Vol.13, No.2, pp.361-365, (2001).
Fragmentation of water clusters: molecular-dynamics simulation study
(Springer Verlag, 2001) Erkoç, S.; Kökten, Hande; Güvenç, Ziya B.
The fragmentation of water clusters, [(H2O)(n): n = 2-8], have been investigated by using molecular-dynamics simulation method. In the simulations a polarizable-dissociable potential energy function for water has been used. Particular attention has been paid to investigate the effect of structural properties and cluster size of the fragmentation.
Citation Count: Demirtürk, Semra...et al (2001)."Finite size scaling by using scaling functions in two-dimensional q = 2 and 7 state Potts models", International Journal of Modern Physics C, vol. 12, No. 3, pp. 403-412.
Finite size scaling by using scaling functions in two-dimensional q = 2 and 7 state Potts models
(2001) Demirtürk, Semra; Seferoğlu, Nurgül; Aydın, Meral; Gündüç, Yiğit
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.
Citation Count: Kondakci, S, "An approach to noise reduction in human skin admittance measurements", 23rd Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society, Vol. 23, pp. 2028-2031, (2001).
An approach to noise reduction in human skin admittance measurements
(IEEE, 2001) Kondakçı, Süleyman; 102350
This paper presents the development of a signal averaging algorithm for recovering excitation responses contaminated by overwhelming amount of various types of interference in skin admittance measurements. The algorithm is designed to eliminate Gaussian-distributed noise by use of a recursive approach. The process of recovering low magnitude voltage responses from highly noise-contaminated waveforms is a CPU-intensive task. In real-time measurements, iterative reconstruction algorithm is inefficient and time consuming when slow varying input waveforms are present. To increase the quality of the reconstruction a considerably large number of recursions is required. Increasing the number of recursions is appropriate for batch processing of measurement data. However, the algorithm considers measurements in real-time, whereas required quality of signal reconstruction should be kept independent from the number of recursions.
Citation Count: Hassanpour, Reza; Atalay, Volkan. "Head Modeling with Camera Auto-calibration and Deformation", 2002.
Head Modeling with Camera Auto-calibration and Deformation
(2002) Hassanpour, Reza; Atalay, Volkan
A 3D head modeling method from a sequence of 2D images is described. The views from which the input images are acquired are not calibrated. Therefore, an auto-calibration method for a sequence of images with small rotations and translation is developed. For this purpose, we have modified an already existing auto-calibration algorithm to incorporate known aspect ratio and skew values to make it applicable for small rotation around a single axis. We apply this auto-calibration technique to head (face) modeling. Three dimensional positions of known facial features computed from two dimensional images are used to deform a generic head model by using a spring based energy minimization method.
Citation Count: Hassanpour, Reza; Atalay, Mehmet Volkan (2002). "Head Modeling with Camera Autocalibration and Deformation", Proceedings of the Vision, Modeling, and Visualization Conference 2002 (VMV 2002), Erlangen, Germany, November 20-22, 2002.
Head Modeling with Camera Autocalibration and Deformation.
(2002) Hassanpour, Reza; Atalay, Mehmet Volkan
Citation Count: Dereli, G.; Özdoğan, Cem (2003). "Structural stability and energetics of single-walled carbon nanotubes under uniaxial strain", PHYSICAL REVIEW B, Vol. 67, No. 3.
Structural stability and energetics of single-walled carbon nanotubes under uniaxial strain
(2003) Dereli, G.; Özdoğan, Cem; 40569
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.
Citation Count: Dereli, G., Özdoğan, C. "(Formula Presented) Algorithms In Tight-Binding Molecular-Dynamics Simulations of the Electronic Structure of Carbon Nanotubes", Physical Review B - Condensed Matter and Materials Physics, Vol. 67, No 3, pp. 7, (2003).
(Formula Presented) Algorithms In Tight-Binding Molecular-Dynamics Simulations of the Electronic Structure of Carbon Nanotubes
(Physical Review B - Condensed Matter and Materials Physics, 2003) Dereli, Gülay; Özdoğan, Cem; 40569
The (formula presented) and parallelization techniques have been successfully applied in tight-binding molecular-dynamics simulations of single-walled carbon nanotubes (SWNT’s) of various chiralities. The accuracy of the (formula presented) description is found to be enhanced by the use of basis functions of neighboring atoms (buffer). The importance of buffer size in evaluating the simulation time, total energy, and force values together with electronic temperature has been shown. Finally, through the local density of state results, the metallic and semiconducting behavior of (formula presented) armchair and (formula presented) zigzag SWNT’s, respectively, has been demonstrated. © 2003 The American Physical Society.
Citation Count: Musa, Mohamed E.M...et al (2003). "Texture segmentation using the mixtures of principal component analyzers", Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), Vol. 2869, pp. 505-512.
Texture segmentation using the mixtures of principal component analyzers
(2003) Musa, Mohamed E.M.; Duin, Robert P.W.; De Ridder, Dick; Atalay, Volkan
The problem of segmenting an image into several modalities representing different textures can be modelled using Gaussian mixtures. Moreover, texture image patches when translated, rotated or scaled lie in low dimensional subspaces of the high-dimensional space spanned by the grey values. These two aspects make the mixture of local subspace models worth consideration for segmenting this type of images. In recent years a number of mixtures of local PCA models have been proposed. Most of these models require the user to set the number of subspaces and subspace dimensionalities. To make the model autonomous, we propose a greedy EM algorithm to find a suboptimal number of subspaces, besides using a global retained variance ratio to estimate for each subspace the dimensionality that retains the given variability ratio. We provide experimental results for testing the proposed method on texture segmentation.
Citation Count: Hassanpour, R.; Atalay, V. (2003). "Camera auto-calibration using a sequence of 2D images with small rotations and translations", PROCEEDINGS OF THE 17TH INTERNATIONAL SYMPOSIUM ON COMPUTER AND INFORMATION SCIENCES, pp. 215-219.
Camera auto-calibration using a sequence of 2D images with small rotations and translations
(2003) Hassanpour, R.; Atalay, V.
3D model generation needs depth information of the object in the input images. This information can be found using stereo imaging but it needs camera parameters. Camera calibration is not possible without some knowledge about the objects in the scene or assuming fixed or known values for the camera parameters. When using fixed camera parameters, however, small rotation angles or small translation in camera position can degenerate the results. The degeneracy can be omitted by adding new restrictions to the a-priori knowledge about the camera parameters. The calibrated data may be used to reconstruct 3D model of the scene.
Citation Count: Özdoğan, Cem (2003). "Structural stability and energetics of single-walled carbon nanotubes under uniaxial strain", Physical Review B - Condensed Matter and Materials Physics, Vol. 67, No. 3.
O(N) algorithms in tight-binding molecular-dynamics simulations of the electronic structure of carbon nanotubes
(2003) Dereli, G.; Özdoğan, Cem; 40569
A (formula presented) single-walled carbon nanotube consisting of 400 atoms with 20 layers is simulated under tensile loading using our developed (formula presented) 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 (formula presented) carbon nanotube in the radial direction is (formula presented) and it is sensitive to the strain rate.
Citation Count: Sebetçi, Ali; Güvenç, Ziya Burhanettin; Kökten, Hatice (2004). "Phase changes in icosahedral 54-, 55-, 56-atom platinum clusters", International Journal of Modern Physics C, Vol. 15, No. 7, pp. 981-988.
Phase changes in icosahedral 54-, 55-, 56-atom platinum clusters
(2004) Sebetçi, Ali; Güvenç, Ziya Burhanettin; Kökten, Hatice
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.
Citation Count: Salman, N.; Doǧru, A., "Design Effort Estimation Using Complexity Metrics", Journal of Integrated Design and Process Science, Vol. 8, No. 3, pp. 83-88, (2004).
Design Effort Estimation Using Complexity Metrics
(2004) Salman, Nael; Doǧru, A.
Component-oriented software development is a new trend and is becoming very popular these days. In addition to requiring a different development approach, the new orientation also requires a different metrics approach. A set of metrics for Component Oriented Software Engineering was first introduced in previous research. These metrics set were used to measure the quality of component-oriented software designs. The impact of these metrics on design effort is investigated in this paper. A statistical model is developed based on nine projects that carried out component-oriented software development. Design effort is expressed as a junction of a subset of the complexity metrics.
Citation Count: Mousa, A.; Yılmaz, A., "Comparative analysis on wavelet-based detection of finite duration low-amplitude signals related to ventricular late potentials", Physiological Measurement, Vol.25, No.6, (2004).
Comparative analysis on wavelet-based detection of finite duration low-amplitude signals related to ventricular late potentials
(IOP Publishing LTD, 2004) Mousa, A.; Yılmaz, A.
Ventricular late potentials (VLPs) are considered as a noninvasive marker of patients with myocardial infarction, who are prone to the development of ventricular tachycardia. This paper investigates the effects of variations in physical properties of myocardial infarcts in terms of their effects on the parametric variations in VLP analysis. A sufficiently large set of signals underlining the behavior of physical parameters was employed to represent the effect of physical size, position, orientation and type of infarct. The approximated signals are variations from real electrocardiography signals by adding potentials representing late potentials based on duration, frequency, amplitude and position. The aim is not to exactly model VLP but rather to generate an approximate set of signals to examine the performance of the standard methods for different possibilities in infarct dynamics. We investigate some of the detection approaches together with their related assumptions, and try to pinpoint the drawbacks and inaccuracies of these methods and also their assumptions. The three widely accepted criteria-QRS duration, root-mean-square and duration of the signal at the end of QRS for VLP detection-were used in the investigation. Results from the application of these parameters to the set of signals are presented. In addition we investigate the physical nature of an infarct and list a number of possible reasons that might be the cause of a low success rate for the detection of additive potentials. To improve the performance of the common methods, two more wavelet transform parameters are added to those of the standard methods. The method derived from this analysis is presented as an alternative means for the detection of late signals named as delayed potentials, a more general class that includes VLP as a subset.
Citation Count: Hassanpour, R.,; Atalay, V., "Delaunay Triangulation Based 3D Human Face Modeling From Uncalibrated İmages", IEEE Computer Society Conference On Computer Vision and Pattern Recognition Workshops, (2004).
Delaunay Triangulation Based 3D Human Face Modeling From Uncalibrated İmages
(IEEE Computer Society, 2004) Hassanpour, Reza; Atalay, Volkan; 48646
In this paper, we describe an algorithm for generating three dimensional models of human faces from uncalibrated images. Input images are taken by a camera generally with a small rotation around a single axis which may cause degenerate solutions during auto-calibration. We describe a solution to this problem by a priori assumptions on the camera. To generate a specific person's head, a generic human head model is deformed according to the 3D coordinates of points obtained by reconstructing the scene using images calibrated with our algorithm. The deformation process is based on a physical based massless spring model and it requires local re-triangulation in the area with high curvatures. This is achieved by locally applying Delaunay traingulation method. However, there may occur degeneracies in Delaunay triangulation such as encroaching of edges. We describe an algorithm for removing the degeneracies during triangulation by modifying the definition of the Delaunay cavity. This algorithm has also the effect of preserving the curavature in the face area. We have compared the models generated with our algorithm with the models obtained using cyberscanners. The RMS geometric error in these comparisons are less than 1.8 x 10-2.

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