Elektronik ve Haberleşme Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/260
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Article Citation - WoS: 5Citation - Scopus: 9Strategy Creation, Decomposition and Distribution in Particle Navigation(Elsevier Science inc, 2007) Leblebicioglu, Kemal; Beldek, UlasStrategy planning is crucial to control a group to achieve a number of tasks in a closed area full of obstacles. In this study, genetic programming has been used to evolve rule-based hierarchical structures to move the particles in a grid region to accomplish navigation tasks. Communications operations such as receiving and sending commands between particles are also provided to develop improved strategies. In order to produce more capable strategies, a task decomposition procedure is proposed. In addition, a conflict module is constructed to handle the challenging situations and conflicts such as blockage of a particle's pathway to destination by other particles. (C) 2006 Elsevier Inc. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 3Dissociative Chemisorption of an H2 (V,j) Molecule on Rigid Ni (100) Surface: Dependence on Surface Topologies and Initial Rovibrational States of the Molecules(Iop Publishing Ltd, 2005) Evecen, M; Böyükata, M; Çivi, M; Güvenç, ZBThe H-2(v,j)+Ni(100) collision system has been studied to understand the effects of the surface sites and initial rovibrational states of the molecule on molecule-surface interactions, by a quasiclassical molecular dynamic simulation method. Dissociative adsorption of an H-2 molecule on the rigid Ni(100) surface is investigated at topologically different three sites of the surface. Interaction between the molecule and Ni surface was described by a London-Eyring Polani-Sato (LEPS) potential. Dissociative chemisorption probabilities of the H-2(v, j) molecule on various sites of the surface are presented as a function of the translation energies between 0.001-1.0eV. The probabilities obtained at each collision site have unique behaviour. At lower collision energies, indirect processes enhance the reactivity, effects of the rotational excitations and impact sites on the reactivity are more pronounced. The results are compared with the available studies, The physical mechanisms underlying the results and quantum effects are discussed.Article Hydrogen hosting of nanoscale boron cluster(Editura Academiei Romane, 2008) Böyükata, Mustafa; Özdoğan, C.; Güvenç, Ziya B.; Bäoyäukata, M.; ÄozdoGan, C.; Gäuvenc, Z.B.In this paper the Density Functional Results of hydrogen bonded boron micro clusters with B3LYP/6-311++G(d,p) level of computations will be presented. Energetics and structural stability with their possible stable geometries of various selected micro complexes of B(m)H(n) (for m and n <= 11 )boron hydrides have been analysed, and their binding energies with HOMO-LUMO energy gaps have been determined. Mainly, erects of the number of hydrogen atoms on the structures of the boranes are assessed. Moreover, for the cage configurations their distortions have been investigated for the neutral, anionic and cationic cases. It has been observed that there have been two opposing factors for the cage configurations. One of which is the "peeling" of the cage structures by the hydrogen atoms, and the other one is reforming a smaller cage form simultaneously with there remaining boron atoms inside. This is observed mostly for the odd values of m. From our studies it has been also observed that with the bare boronclusters alone, it is difficult to increase the capacity of the hydrogen storage. Therefore, further studies are necessary with the boron complexesArticle Citation - WoS: 15Citation - Scopus: 15A Density Functional Study of Small Li-B and Li-B Clusters(Pergamon-elsevier Science Ltd, 2009) Yildirim, E. K.; Guvenc, Z. B.In this work we present the results of a detailed theoretical research for the small LinBm clusters and their hydrogen storage properties by means of density functional theory. All calculations were performed by using Gaussian03 program. For the optimization of the clusters 6-311++G(d,p) basis set was employed. We have chosen global minimum of B-6 cluster as the starting point and replaced the boron atoms one at a time, in a stepwise manner, with Li atoms. For these new structures we have searched for the stable configurations, and calculated their energies, HOMO-LUMO energy gaps, Raman and infrared data, average boron, and lithium charge distribution, and vibrational frequencies. Our results show that as the number of Li atoms increases, stability of the clusters decreases and they become more reactive. In addition to that, there are significant charge transfers from boron atoms to lithium atoms on average. The hydrogen storage capabilities of the most stable isomers of LinBm and B-6 clusters have also been investigated by the same methods, and the results are compared. The Li3B3 has the highest hydrogen storage capacity among the clusters investigated in this study. Furthermore, formation of hydrogen molecules is observed in the vicinity of the clusters, some of which are attached to the Li atoms. In addition, as the number of hydrogen atoms increases, the boron atoms are separated from the other boron atoms, and they form satellite BHx (x = 3,4) clusters around the center. These are attached to the system by a bridging bond of a hydrogen or a Li atom. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 4General Formulation of the Edge-Diffracted Paraxial Waves(Elsevier Sci Ltd, 2009) Umul, Yusuf Z.A general formula for edge-diffracted paraxial waves is derived in terms of the Fourier integral transform. It is observed that the scattered paraxial wave can be divided into components of the geometrical optics and diffracted fields in the spectral domain. An edge-diffracted Gaussian beam is examined numerically as an application of the formula. (C) 2008 Elsevier Ltd. All rights reserved.Article Citation - WoS: 11Citation - Scopus: 11Uniform Theory of the Boundary Diffraction Wave(Elsevier Sci Ltd, 2009) Umul, Yusuf Z.A uniform version of the potential function of the Maggi-Rubinowicz boundary diffraction wave theory is obtained by using the large argument expansion of the Fresnel integral. The derived function is obtained for the problem of diffraction of plane waves by a circular edge. The results are plotted numerically. (c) 2008 Elsevier Ltd. All rights reserved.Article Citation - WoS: 2Citation - Scopus: 3Dynamical Analysis of Sputtering at Threshold Energy Range: Modelling of Ar+ni(100) Collision System(Iop Publishing Ltd, 2008) Hundur, Yakup; Guvenc, Ziya B.; Hippler, RainerThe sputtering process of Ar+Ni(100) collision systems is investigated by means of constant energy molecular dynamics simulations. The Ni(100) slab is mimicked by an embedded-atom potential, and the interaction between the projectile and the surface is modelled by using the reparametrized ZBL potential. Ni atom emission from the lattice is analysed over the range of 20-50 eV collision energy. Sputtering yield, angular and energy distributions of the scattered Ar and of the sputtered Ni atoms are calculated, and compared to the available theoretical and experimental data.Article Citation - WoS: 33Citation - Scopus: 36Mtpo Based Potential Function of the Boundary Diffraction Wave Theory(Elsevier Sci Ltd, 2008) Umul, Yusuf Z.A novel potential function is introduced by using the modified theory of physical optics integrals for a perfectly conducting half-plane. The function is valid for arbitrary aspects of observation. The line integration of these functions gives the total scattered fields. The method is applied to the problem of diffraction of plane waves by an opaque half-plane for oblique incidence. (c) 2008 Elsevier Ltd. All rights reserved.Article Citation - WoS: 76Citation - Scopus: 81Propagation and Coherence Properties of Higher Order Partially Coherent Dark Hollow Beams in Turbulence(Elsevier Sci Ltd, 2008) Eyyuboglu, Haill TanyerWe formulate and evaluate in terms of graphical outputs, source and receiver plane expressions, the complex degree of coherence, beam size variation and power in bucket performance for higher order partially coherent dark hollow beams propagating in turbulent atmosphere. Our formulation is able to cover square, rectangular, circular, elliptical geometries for dark hollow and flat-topped beams in one single expression. From the graphical outputs of the receiver plane, it is observed that higher order partially coherent dark hollow beams will initially develop an outer ring around a central lobe, but will eventually evolve towards a Gaussian shape as the propagation distance is extended. It is further observed that stronger turbulence levels and greater partial coherence have similar effects on beam profile. During propagation, modulus of complex degree of coherence of partially coherent dark hollow beams appears to rise above that of the source plane values, reaching as high as near unity. Beam size analysis shows that, among the types examined, (nearly) flat-topped beam experiences the least beam expansion. Power in bucket analysis indicates that lowest order square fully coherent dark beam offers the best power capturing. (c) 2007 Published by Elsevier Ltd.Article Citation - WoS: 2Citation - Scopus: 4A New Quadrature Routine for Improper and Oscillatory Integrals(Elsevier Science inc, 2007) Eyyuboglu, H. T.; Sermutlu, E.In MATLAB environment, a new quadrature routine based on Gaussian quadrature rule has been developed. Its performance is evaluated for improper integrals, rapidly oscillating functions and other types of functions requiring a. large number of evaluations. This performance is compared against the other quadrature routines written for MATLAB in terms of capability, accuracy and computation time. It is found that our routine rates quite favourably. (c) 2006 Elsevier Inc. All rights reserved.