Mühendislik Fakültesi

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Citation Count: Küçükoğlu, Afşin; Baykal, Yahya. "Genişbant Erişim Telekomünikasyon Sistemlerinin Kullanım Kriterleri", pp. 158-160.
Genişbant Erişim Telekomünikasyon Sistemlerinin Kullanım Kriterleri
(1) Küçükoğlu, Afşin; Baykal, Yahya; 7812
Hızla artan bilgisayar ağı ihtiyacını gidermek ve yüksek hızı son kullanıcı noktalarına ulaştırabilmek amacıyla geliştirilmiş olan genişbant erişim sistemlerinin (access systems) teknolojik son durumu incelendi. Herhangi bir erişim uygulamasında kullanılması gereken tercih nedenleri karşılaştırıldı. Bu karşılaştırmayı sistematik olarak yapan internet tabanlı bir yazılım geliştirildi. Yazılımda, sistem kullanıcısının ihtiyacı ve mevcut altyapı faktörleri doğrultusunda hangi erişim sisteminin kullanıcı tarafından tercih edilmesi gerektiği kararına optimum olarak varılabilmesi hedeflendi. Çalışmamız, xDSL (x Digital Subscriber Line) ile Fiber Optic erişimlerini kapsayan kablolu ve LMDS (Local Multipoint Distribution Services) ile FSO (Free Space Optics) erişimlerini kapsayan kablosuz sistemleri içermektedir. Yazılım tarafından istenilen sorular ihtiyaç doğrultusunda cevaplandırıldığında, tüm sistemler bir ana karşılaştırma tablosunda toplanmakta, sistem maliyetleri de göz önüne alınarak bir karşılaştırma yapılmakta, sonuçta ise teknik ve ekonomik olarak uygulanabilir çözümler ve optimum çözüm önerilmektedir.
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: Erden, Z; Erkmen, AM; Erden, A, "A Petri Net-based inference network for design automation under nondeterminism applied to mechatronic systems", 6th UK Mechatronics Forum International Conference, pp. 17-22, (1998).
A Petri Net-based inference network for design automation under nondeterminism applied to mechatronic systems
(1998) Erden, Z.; Erkemn, A. M.; Erden, A.
This paper introduces the completed part of an ongoing research, in which a Petri Net-based design inference network is developed for the representation and analysis of the functions and their interrelationships through information flow for the conceptual design stage of mechatronic systems in order to facilitate design automation. The theoretical framework behind the network is based on transition of Hybrid Automata into Petri Nets and application of this framework is introduced by a mechatronic design example.
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: Güvenç, Ziya B.; Güvenç, Dilek; Jellinek, Julius (1999). "Structural forms and energies of Nin, n = 12-14, clusters", Mathematical and Computational Applications, Vol. 4, No. 1, pp. 75-81.
Structural forms and energies of Nin, n = 12-14, clusters
(1999) Güvenç, Ziya B.; Güvenç, Dilek; Jellinek, Julius
Equilibrium structural forms of the Nin, n = 12-14, clusters, as defined by an embedded-atom potential, are obtained using molecular dynamics and thermal quenching simulations. The isomers (locally stable geometric forms) are distinguished from those stationary structures that correspond to saddle points of the potential energy surface. Isomer statistics are obtained using a large number of initial quenching configurations generated along high-energy trajectories (the energies are high enough to `melt' the clusters). Probabilities of sampling the basins of attraction of the different isomers are computed and the spectra of their energies are analyzed.
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: Güvenç, Ziya B.; Sha, XW.; Jackson B., "Eley-Rideal and hot atom reactions between hydrogen atoms on Ni(100): electronic structure and quasiclassical studies" Journal of Chemical Physics, Vol.115, No.19, pp.9018-9027, (2001).
Eley-Rideal and hot atom reactions between hydrogen atoms on Ni(100): electronic structure and quasiclassical studies
(Amer Inst Physics, 2001) Güvenç, Ziya B.; Sha, Xianwei; Jackson, Bret
The reactions of gas-phase H (or D) atoms with D (or H) atoms adsorbed onto a Ni(100) surface are studied. Electronic structure calculations based on density functional theory are used to examine the interaction of H atoms with the Ni(100) surface, as well as the interactions between two H atoms near the metal surface. A model potential-energy surface based on ideas from effective medium theory is fit to the results of these electronic structure calculations. Quasiclassical trajectory methods are used to simulate the interaction of low energy H and D atom beams with H and D-covered Ni(100) surfaces. It is found that hot-atom processes dominate the formation of molecular hydrogen. The distribution of energy in the product molecules is examined with regard to the various pathways available for reaction. The initial adsorbate coverage is varied and is shown to control the relative amounts of reflection, reaction, sticking, and subsurface penetration. Our results are compared with those from similar studies on Cu(111) and available experimental data for Ni(100). (C) 2001 American Institute of Physics.
Citation Count: Boyukata, M...et al. "Dynamics of the D(2)+Ni(100) collision system: Analysis of the reactive and inelastic channels" 3rd European Conference on Computational Chemistry, Vol.84, No.1, pp.48-57, (2001).
Dynamics of the D(2)+Ni(100) collision system: Analysis of the reactive and inelastic channels
(Wiley-Blackwell, 2001) Böyükata, Mustafa; Güvenç, Büşra; Jackson, Bret; Jellinek, Johanna
The reactive and scattering channels of the D(2)(v, j) + Ni(100) collision system are studied using quasiclassical molecular dynamics simulations. The interaction between the D(2) and the atoms of the surface is modeled by a LEPS (London-Eyring-Polani-Sato) potential energy function. The molecule is aimed at three different impact sites (atop, bridge, and center) of a rigid Ni(100) surface along the normal direction with various collision energies less than or equal to1.0 eV. Dissociative chemisorption probabilities are computed for different rotational states of the molecule. Probability distributions of the final rovibrational states of the ground-state Dp molecule scattered from those impact sites are also computed as a function of the collision energy. Higher collision energy results in excitation of higher rotational and/or vibrational states of the scattered molecule. At collision energies below 0.1 eV an indirect dissociation mechanism (through molecular adsorption) dominates the reaction. (C) 2001 John Wiley & Sons, Inc.
Citation Count: Güvenç, Ziya B...et al. "Structure and reactivity of Ni(n) (n=7-14, 19) clusters" International Journal Of Quantum Chemistry, Vol.84, No.2, pp.208-215, (2001).
Structure and reactivity of Ni(n) (n=7-14, 19) clusters
(Wiley-Blackwell, 2001) Böyükata, Mustafa; Güvenç, Ziya B.; Özçelik, Süleyman; Durmuş, Perihan; Jellinek, Julius
Results of a computer simulation study of Ni(n) (n = 7-14, 19) clusters, their structures, energetics, and reactivity with a D(2) molecule are presented. The clusters are described by an embedded atom potential, whereas the interaction between the molecule and the clusters is modeled by an LEPS (London-Eyring-Polanyi-Sato) potential energy function. The focus is on structures of the dusters and their reactive channels. The total numbers of stable isomers of the clusters are obtained by sampling their phase space, and the isomers' energy spectra are determined. On the reactive side, dissociative chemisorptions cross sections and decay-rate constants are calculated. (C) 2001 John Wiley & Sons, Inc.
Citation Count: Güvenç, Ziya B.; Sha, XW; Jackson B., "The effects of lattice motion on Eley-Rideal and hot atom reactions: Quasiclassical studies of hydrogen recombination on Ni(100)" Journal of Physical Chemistry B, Vol.106, No.33, pp.8342-8348, (2002).
The effects of lattice motion on Eley-Rideal and hot atom reactions: Quasiclassical studies of hydrogen recombination on Ni(100)
(Amer Chemical Soc, 2002) Güvenç, Ziya B.; Sha, Xianwei; Jackson, Bret
Quasiclassical methods are used to simulate the interactions of H or D atom beams with D- or H-covered Ni(100) surfaces. The Ni substrate is treated as a multilayer slab, and the Ni atoms are allowed to move. The model potential energy surface is fit to the results of detailed total-energy calculations based on density functional theory. Most of the incident atoms trap to form hot atoms, which can eventually react with an adsorbate, or dissipate their energy and stick. The incident atom is found to lose several tenths of an eV of energy into the metal, upon initially colliding with the surface. This limits reflection to a few percent, at all coverages, and secondary reactions between adsorbates are significantly lowered. Long time hot atom reactions are also found to be damped out by the inclusion of lattice motion, leading to increased sticking, even at high coverages where dissipation into the adsorbates should be the primary energy loss mechanism. Overall, the inclusion of lattice motion is found to improve agreement with experiment.
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: Karabacak, M.; Ozçelik, S.; Güvenç, Ziya B., "Structures and energetics of Pd(n) (n=2-20) clusters using an embedded-atom model potential" Surface Science, Vol.507, pp.636-642
Structures and energetics of Pd(n) (n=2-20) clusters using an embedded-atom model potential
(Elsevier Science BV, 2002) Karabacak, Mehmet; Özçelik, Süleyman; Güvenç, Ziya B.
We have studied the structure and energetics of the stable isomers of Pd(n) (n = 2-20) clusters by using molecular dynamics and slow-quenching techniques. Cohesion of the clusters is modeled by an embedded-atom potential due to Voter and Chen, which contains many-body atomic interactions. The isomers' statistics are obtained from 10000 independent initial configurations, which have been generated along a high-energy trajectory (the chosen energy value is high enough to melt the cluster). The internal kinetic energy of these initial conditions is removed slowly. Because of this slow minimization process the locally stable isomers are separated from those meta-stable ones. Probabilities belonging to sampling the basins of attractions of each isomer are computed, and compared with each other. Furthermore, the spectrum, which is formed by isomers' energies, is analyzed. (C) 2002 Published by Elsevier Science B.V.
Citation Count: Jackson, B.; Sha, XW.; Güvenç, Ziya B., "Kinetic model for Eley-Rideal and hot atom reactions between H atoms on metal surfaces" Journal of Chemical Physics, Vol.116, No.6, pp.2599-2608, (2002).
Kinetic model for Eley-Rideal and hot atom reactions between H atoms on metal surfaces
(Amer Inst Physics, 2002) Jackson, Bret; Sha, Xianwei; Güvenç, Ziya B.
A simple kinetic model is used to describe the interaction of H and D atomic beams with H- and D-covered metal surfaces. The atoms incident from the gas phase can have a direct Eley-Rideal reaction with an adsorbate, reflect, penetrate into the bulk, knock an adsorbate out of its binding site, or trap to form a hot atom. These hot mobile atoms can go on to react with other adsorbates, or eventually relax and stick. A coarse-graining approach, which takes advantage of the large difference between the time scales for the kinetics experiments and the reaction dynamics, allows us to derive relatively simple kinetic equations for reaction rates and coverages. The approach is similar to a kinetic random walk model developed by Kuppers and co-workers [J. Phys. Chem. 109, 4071 (1998)] except that our equations can be used to derive analytical expressions for saturation coverages, rates, and yields. The model is applied to the case of H atom reactions on a Ni(100) surface, and a detailed comparison is made with both experimental and quasiclassical studies. (C) 2002 American Institute of Physics.
Citation Count: Ryyuboğlu, E.Mustafa; Bölükbaşı, Nac,. (2002). "Çayırhan yeraltı işletmesinde kılavuz açma çalışmalarının mekanizasyonu", Madencilik Dergisi, Vol.41, No.1, pp.3-15.
Çayırhan yeraltı işletmesinde kılavuz açma çalışmalarının mekanizasyonu
(2002) Eyyunoğlu, E. Mustafa; Bölükbaşı, Naci; 166981
Mekanize galeri açma yöntemi ile gerçekleştirilebilen yüksek ilerleme hızı bu yöntemin klasik delme-patlatma yöntemine karşı en önemli üstünlüğüdür. Açılacak galerinin toplam uzunluğunun fazla olması mekanize kazının uygulabilmesindeki en önemli önşarttır. Uzunayak oluşturmak için açılan kılavuz uzunluklarının genellikle kısa olması mekanize yöntemlerin uygulanmasını sınırlamaktadır. Ancak madencilik teknolojisindeki gelişmelere parelel olarak artan ayak uzunlukları kılavuzların mekanize açılması gerekliliğini de artırmaktadır. Bu çalışmada, Çayırhan Yeraltı İşletmesinde ayak montaj kılavuzlarının mekanize olarak açılmasına yönelik yapılan çalışmalar, elde edilen sonuçlar ve bu sonuçların klasik yöntemle karşılaştırılması anlatılmaktadır. Sonuçlar, mekanize yöntemin klasik yönteme göre önemli üstünlükler sağladığını göstermektedir.

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