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Ankara, Turkey

Bilkent University, or Bilkent, is the first private university of Turkey, located in Ankara, with the fundamental aim of creating a center of excellence in higher education and research. The name "Bilkent" exemplifies this aim, since it is an acronym of "bilim kenti": Turkish for "city of science".Bilkent University is among the 226th to 250th best universities in the world and 1st in Turkey according to Times Higher Education World University Rankings of the world's top universities for 2012. Bilkent is ranked as the 32nd best university in the world for 2012 in the category "100 best universities under the age of 50" by Times Higher Education, making it one of the best educational institutions in Eurasia. It is also the only university in Turkey that is ranked in top 100 in a subject list, being ranked 98th in the World in Engineering and Technology in 2014. Wikipedia.

Temizer I.,Bilkent University
Computer Methods in Applied Mechanics and Engineering | Year: 2013

A classical three-field mixed variational formulation of frictionless contact is extended to the frictional regime. The construction of the variational framework with respect to a curvilinear coordinate system naturally induces projected mortar counterparts of tangential kinetic and kinematic quantities while automatically satisfying incremental objectivity of the associated discrete penalty-regularized mortar constraints. Mixed contact variables that contribute to the boundary value problem are then obtained through unconstrained, lumped or constrained recovery approaches, complemented by Uzawa augmentations. Patch tests and surface locking studies are presented together with local and global quality monitors of the contact interactions in two- and three-dimensional settings at the infinitesimal and finite deformation regimes. © 2012 Elsevier B.V. Source

Salzner U.,Bilkent University
Journal of Chemical Theory and Computation | Year: 2013

The ultraviolet-visible light (UV-vis) absorption spectrum of ferrocene is modeled with time-dependent density functional theory employing LSDA, BLYP, B3LYP, and CAM-B3LYP functionals in combination with 6-31G*, 6-31+G*, CC-PVTZ, and aug-CC-PVTZ basis sets. With the exception of LSDA, all functionals predict a reasonable Fe-CP distance of ∼1.67 Å. Diffuse functions are essential for the strongly allowed states at high energy but of lesser consequence for the visible range of the spectrum. Dipole forbidden states are examined with vibrationally excited structures, obtained from the normal modes of the infrared (IR) spectrum. Despite earlier claims, TDB3LYP predicts the UV-vis spectrum of ferrocene quantitatively correct. TDBLYP predicts a large number of spurious charge-transfer states, TDCAM-B3LYP and TDwB97XD are correct in the low-energy region but overestimate the energy of strongest peak of the spectrum by 0.8 eV. The amount of charge transfer involved in "d-d transitions" is equal to that in "charge-transfer states". © 2013 American Chemical Society. Source

Tuncel D.,Bilkent University
Nanoscale | Year: 2011

Carbon nanotubes (CNTs) are interest to many different disciplines including chemistry, physics, biology, material science and engineering because of their unique properties and potential applications in various areas spanning from optoelectronics to biotechnology. However, one of the drawbacks associated with these materials is their insolubility which limits their wide accessibility for many applications. Various approaches have been adopted to circumvent this problem including modification of carbon nanotube surfaces by non-covalent and covalent attachments of solubilizing groups. Covalent approach modification may alter the intrinsic properties of carbon nanotubes and, in turn make them undesirable for many applications. On the other hand, a non-covalent approach helps to improve the solubility of CNTs while preserving their intrinsic properties. Among many non-covalent modifiers of CNTs, conjugated polymers are receiving increasing attention and highly appealing because of a number of reasons. To this end, the aim of this feature article is to review the recent results on the conjugated polymer-based non-covalent functionalization of CNTs with an emphasis on the effect of conjugated polymers in the dispersibility/solubility, optical, thermal and mechanical properties of carbon nanotubes as well as their usage in the purification and isolation of a specific single-walled nanotube from the mixture of the various tubes. © The Royal Society of Chemistry 2011. Source

Onural L.,Bilkent University
IEEE Signal Processing Magazine | Year: 2010

Frequently, the most important sporting events are used as platforms to showcase and sometimes launch the latest communication technologies. Over the years, we have enjoyed watching the Olympic Games or the World Cup soccer games with new technologies such as satellite broadcasting, color TV, and high-definition TV. The 2010 World Cup continues this tradition by broadcasting the games in three-dimensional (3D) TV (3DTV) [1]. This article presents an introduction to the technological issues facing a broad deployment of 3DTV systems and discusses some of the signal processing techniques that are used or need to be developed in this area. © 2010 IEEE. Source

Salzner U.,Bilkent University
Journal of Chemical Theory and Computation | Year: 2014

The impact of donor-acceptor substitution on optical and electronic properties of conducting polymers was investigated with time-dependent density functional theory (TDDFT). A series of donor-acceptor systems with thiophene, 3,4-ethylenedioxythiophene, and pyrrole as donors and 3,4-difluorothiophene, diketopyrrolopyrrole, 2,1,3-benzothiadiazole, 4-dicyanomethylene-4H-cyclopenta[2,1-b;3,4-b']dithiophene, and indeno[1-2b]-fluorene-6,12-dimalonitrile as acceptors as examples of donor-acceptor systems with increasing donor-acceptor character was studied. Spectral properties were analyzed in terms of differences in ionization potentials and electron affinities of donors and acceptors, charge separations between donors and acceptors in ground and excited states, and electron distribution in the acceptor units. A shift in electron density away from the backbone caused by some of the acceptors correlates with localization of the conduction band on the acceptor. Localization does not correlate with energy level differences between donor and acceptor. Localization results in shift of oscillator strength from the HOMO-LUMO peak to a higher energy feature where the first delocalized orbital acts as the acceptor. The 'camel back' absorption with two equally strong peaks that gives rise to green polymers is the intermediate case associated with partial localization of the conduction band. Stronger localization causes the HOMO-LUMO band to almost vanish. © 2014 American Chemical Society. Source

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