Araştırma Çıktıları / Research Outputs
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video.listelement.badge Veritabanlarına Uzaktan Erişmek için Proxy ayarlarından; OpenAthens Sistemine Geçiş(0202-11-21) Kemaloğlu, Öznur SelenArticle Citation Count: 6Optimum dragline selection for strip coal mines(inst Mining Metallurgy, 1998) Erdem, B; Çelebi, N; Pasamehmetoglu, AG; Department of Civil EngineeringA model is presented by means of which the optimal dragline selection may be made. An outline is given of the methodology that was adopted in developing a series of generic algorithms to first define and then formularize the need to extend the working bench under a nat-lying topography and coal seam. Rehandle percentages were calculated for four generalized extended bench geometries, in each of which the percentage rehandle varied according to the relative positions of the extended bench and pit. A set of geometric and simulative equations was developed on which a model for the optimal selection of a dragline was based. Finally, a typical application was tested through the use of data associated with a hypothetical strip-mining operation.Article Citation Count: 0Unit cost analysis model for stripping of open-pit lignite mines(inst Mining Metallurgy, 1998) Çelebi, N; Pasamehmetoglu, AG; Karpuz, C; Department of Civil Engineering[No Abstract Available]Conference Object Citation Count: 0Complexity engineering, evolution and optimality of structures(Morgan Kaufmann Pub inc, 1999) Kundu, SComplexity Engineering deals with harnessing the power of Cellular Automata (CA) like simple models to solve real life difficult and complex engineering problems, dealing with systems that have very simple components that collectively exhibit complex behaviors. The state transition rules are generally fixed in a CA, but evolution of the rules, is considered here. To evolve the local rules, we use the Genetic Algorithm (GA) model. The example application described here will serve to demonstrate that the GAs can discover CA rules that give rise to emergent computational strategies by self-organization and exhibit globally coordinated tasks for optimization, with simple local interactions only.Article Citation Count: 8Electroinitiated polymerization of 2-allylphenol(Springer-verlag, 2000) Cihaner, A; Önal, AM; Chemical EngineeringRedox behaviour of 2-allylphenol (2APhOH) was studied by using cyclic voltammetry (CV) and electroinitiated polymerization was conducted at the measured peak potentials. Constant potential electrolysis (CPE) of the monomer was carried out in acetonitrile-sodium perchlorate, solvent-electrolyte couple, at room temperature. Polymerization of the monomer yielded insoluble polymer films on the surface of the electrode together with the low molecular weight polymers in the bulk of the solution. The structural analysis of the polymers were carried by H-1-NMR and FTIR spectroscopy. Molecular weight of the soluble polymer was determined by GPC. Thermal properties of the polymer film and soluble polymer were studied by DSC. The course of electroinitiated polymerization was monitored by in-situ UV-VIS spectroscopy.Publication Citation Count: 1Kavramsal tasarım otomasyonunda Petri Net ve Melez Otomat sentezi(2001) Erden, Zühal; Erkmen, Aydan M.; Erden, Abdülkadir; Mechatronics Engineering; Department of Mechatronics EngineeringBu çalışmada, mühendislik tasarımındaki kavramsal tasarım aşamasının otomasyonu için Petri Net ve Melez Otomat (Hybrid Automata) sentezine dayanan PNDN adlı bir tasarım ağı modeli geliştirilmiştir. PNDN, tasarımı yapılacak ürünün mantıksal davranışını ürünün alt işlevleri arasındaki kesin ve belirsizlik içeren bilgi akışı ile iki tarzda modellemektedir. Bilgi akışındaki belirsizliklerin modellenmesinde Sezgisel Bulanık Önermeler yaklaşımı kullanılmıştır. Genel amaçlı ve işlevsel düzeyde geliştirilen model, tümleşik bir tasarım felsefesi olan mekatronik tasarımda uygulanmıştır. Bu makalede tasarım ağının yapısı ve kesin bilgi akışı modeli anlatılmaktadır.Conference Object Citation Count: 9Effect of lithium doping on the properties of Tl-based superconductors(Iop Publishing Ltd, 2001) Kayed, TS; Özkan, H; Gasanly, NM; Department of Electrical & Electronics EngineeringThe effects of lithium doping on the formation and properties of the T1-based superconductors have been studied. Lithium atoms up to around 3 mol.% have been added to the oxides of nominal composition Tl1.8Ba2Ca2.2Cu3Ox, and the usual solid-state reaction method has been applied. Lithium additions in the range 0.23-0.29 mol.% increase the fraction of the Tl-2223 phase and significantly improve the critical temperature of the samples. Higher amounts of lithium additions diminish the Tl-2223 phase, reduce the fraction of the Tl-2212 phase, and cause separate non-superconducting phases to be formed.Article Citation Count: 38Synthesis and characterization of fluorine-substituted polyanilines(Pergamon-elsevier Science Ltd, 2001) Cihaner, A; Önal, AM; Chemical EngineeringPoly(2-fluoroaniline), P2FAN, poly(3-fluoroaniline). P3FAN. and poly(4-fluoroaniline), P4FAN, have been synthesized from fluorine substituted aniline monomers in aqueous acidic medium using potassium dichromate as oxidizing agent. Characterization of polymer products has been carried out using FTIR, and NMR spectroscopic techniques. Thermal analysis of polyfluoroaniline powders was also investigated using differential scanning calorimetry and thermogravimetric analysis. To compare the structural properties of the polymers, polyfluoroanilines were also synthesized using ammonium peroxydisulfate as oxidizing agent. Polyfluoroanilines synthesized by chemical oxidation were doped by using iodine and the change in the paramagnetic behavior was monitored by electron spin resonance spectroscopy. (C) 2001 Elsevier Science Ltd. All rights reserved.Article Citation Count: 25Crystal data, electrical resistivity, and Hall mobility of n-type AgIn5S8 single crystals(Wiley-v C H verlag Gmbh, 2001) Qasrawi, AF; Gasanly, NM; Department of Electrical & Electronics EngineeringThe X-ray diffraction has revealed that AgIn5S8 is a single phase crystal of cubic spinel structure. The value of the unit cell parameter for this crystal is 1.08286 nm. The electrical resistivity and Hall effect of n-type AgIn5S8 crystals are measured in the temperature range of 50-400 K. A carrier effective mass of 0.20 m(0), an acceptor to donor concentration ratio of 0.8 and an acoustic phonons deformation potential of 20 eV are identified from the Hall effect measurement. The Hall mobility data art: analyzed assuming the carrier scattering by acoustic and polar optical phonons, and ionized impurities.Conference Object Citation Count: 1The generalized divergence theorem and its application to harmonic maps(Pergamon-elsevier Science Ltd, 2001) García-Río, E; Kupeli, DNA survey of divergence theorems in semi-Riemannian geometry is made. The generalization of a divergence theorem to vector fields along a map is given in semi-Riemannian geometry and an application of it is made in Riemannian geometry to obtain some sufficient conditions for a map to be harmonic.Conference Object Citation Count: 25Blockage/shadowing and polarization measurements at 2.45GHz for interference evaluation between Bluetooth and IEEE 802.11 WLAN(2001) Kara,A.; Bertoni,H.L.; Department of Electrical & Electronics EngineeringWe present measurement results at 2.45 GHz to evaluate blockage shadowing and fading effects due to furniture and people next to terminals for short range indoor communication systems. The followings are the results: people crossing the link near to a terminal can cause fading up to 20dB which is more than furniture blockage measured of about 5-13dB depending on objects over the links, polarization coupling was also measured by using dual polarized antenna at receiving end, and coupling is higher for obstructed links, which suggests polarization diversity.Article Citation Count: 20Characterization of p-In2Se3 thin films(Kluwer Academic Publ, 2001) Qasrawi, AF; Parlak, M; Erçelebi, Ç; Günal, I; Department of Electrical & Electronics EngineeringIndium selenide thin films were deposited onto glass substrates kept at 150 degreesC by thermal evaporation of alpha -In2Se3. Some of the films were annealed at 150 degreesC and 200 degreesC and they all were found to exhibit p-type conductivity without intentional doping. Scanning electron microscopy (SEM) established that the films have an atomic content of In51Se49. X-ray diffraction (XRD) indicated that the as-grown films were amorphous in nature and became polycrystalline \beta-In2Se3 films after annealing. The analysis of conductivity temperature-dependence measurements in the range 320-100 K revealed that thermal excitation and thermionic emission of the carriers are the predominant conduction mechanisms above 200 K in the amorphous and polycrystalline samples, respectively. The carrier transport below 200 K is due to variable range hopping in all the samples. Hall measurements revealed that the mobility of the polycrystalline films is limited by the scattering of the charged carriers through the grain boundaries above 200 K. (C) 2001 Kluwer Academic Publishers.Article Citation Count: 57A curvature condition for a twisted product to be a warped product(Springer-verlag, 2001) Fernández-López, M; García-Río, E; Kupeli, DN; Ünal, B; Department of Modern LanguagesIt is shown that a mixed Ricci-flat twisted product semi-Riemannian manifold can be expressed as a warped product semi-Riemannian manifold. Asa consequence, any Einstein twisted product semi-Riemannian manifold is in fact, a warped product serni-Riemannian manifold.Article ÖĞRETİMDE BİLGİSAYAR KULLANIMINA İLİŞKİN ÖĞRETMEN GÖRÜŞLERİ(2001) Çağıltay, Kürşat; Çakıroğlu, Jale; Çağıltay, Nergiz; Çakıroğlu, ErdinçBu çalışmanın amacı Türkiye'deki ögretmenlerin bilgisayarları nasıl kullandıklarını ve ögretirnde bilgisayar kullanımını nasıl algıladıklarını onaya koymaktır. Araştırma için veriler, çeşitli konularda 95 soru içeren bir anket aracılIgı ile toplanmıştır. Araştırmaya Türkiye'nin üç şehrinden rasgele seçilen 27 okulda çalışan 202 ögretmen katılmıştır. Araştırma sonucunda elde edilen bulgulara göre ögretmenlerin büyük çogunlugu bilgisayarların ögrenme ve ögretim sürecini olumlu etkileyecegini belinirken çok azı bu konuda kaygı taşımaktadır.Article Citation Count: 19Crystal data, photoconductivity and carrier scattering mechanisms in CuIn5S8 single crystals(Wiley-v C H verlag Gmbh, 2001) Qasrawi, AF; Gasanly, NM; Department of Electrical & Electronics EngineeringThe X-ray diffraction has revealed that CuIn5S8 is a single phase crystal of cubic spinet structure. The value of the unit cell parameter for this crystal is 1.06736 nm. The crystal is assigned to the conventional space group Fd3m. The photocurrent is found to have the characteristic of monomolecular and bimolecular recombination at low and high illumination intensities, respectively. The electrical resistivity and Hall effect of CuIn5S8 crystals are measured in the temperature range of 50-400 K. The crystals are found to be intrinsic and extrinsic above and below 300 K, respectively. An energy band gap of similar to1.35 eV at 0 K, a carrier effective mass of 0.2 m(0), an acceptor to donor concentration ratio of 0.9, an acoustic phonon deformation potential of 10 eV and a nonpolar optical phonon deformation potential of 15 eV are identified from the resistivity and Hall measurements. The Hall mobility data are analyzed assuming the carrier scattering by polar optical phonons, acoustic combined with nonpolar optical phonons, and ionized impurities.Article BİR ELEKTRONİK KÜTÜPHANE PROJESİNE BAŞLARKEN(2001) Çağıltay, Nergiz; Software EngineeringBu çalışmanın temel amacı, İndiana Üniversitesi elektronik (sayılsal) kütüphane programında halen yürütülmekta olan çalışmalrı incelemektir. Ayrıca, sunulan bilgiler ışığında bu kapsamda ne tür projeler gerçekleştirildiğini irdeleyerek bir elektronik kütüphane projesine nasıl başlanılması gerektiği ve proje aşamalarında nelere dikkat edilmesi gerektiği gibi konularda bir değerlendirme yapmaktır. Bu çalışmanın, ülkemizde bu konuda yapılmakta olan ve yapılması planlanan benzeri projelere ışık tutması amaçlanmıştır.Article Citation Count: 5Electrochemical polymerization of 4-allylanisole(Pergamon-elsevier Science Ltd, 2001) Cihaner, A; Testereci, HN; Önal, AM; Chemical EngineeringElectrochemical polymerization of 3-allylanisole (4AA). via constant potential electrolysis, has been investigated in acetonitrile using two different supporting electrolytes. Redox behavior of the monomer was also studied in the same solvent-electrolyte couples at room temperature. Electrochemical polymerization of the monomer yielded insoluble polymer films on the electrode surface, which bears a very low conductivity, together with the low molecular weight polymers in the bulk of the solution. The decrease in the monomer concentration, during the electrochemical polymerization. was monitored by taking the cyclic voltammogram of the electrolysis solution. The effect of temperature on the rate of electrochemical polymerization was: also studied. The polymers were characterized by taking the H-1-NMR and FTIR spectra. Molecular weight of the soluble polymer was determined by vapor pressure osmometry. Thermal analysis of the polymer film and soluble polymer were done by DSC. (C) 2001 Elsevier Science Ltd. All rights reserved.Article Citation Count: 1Sets of random variables with a given uncorrelation structure(Elsevier Science Bv, 2001) Ostrovska, S; MathematicsLet xi (1),...,xi (n) be random variables having finite expectations. Denote i(k) := # {(j(1),...,j(k)): 1 less than or equal to j(1) < ... < j(k) less than or equal to n and E (l=1)pi (k) xi (fi) = (l=1)pi (k) E xi (h)}, k = 2,...,n. The finite sequence (i(2),...,i(n)) is called the uncorrelation structure of xi (1),...,xi (n). It is proved that for any given sequence of nonnegative integers (i(2),...,i(n)) satisfying 0 less than or equal to i(k) less than or equal to ((n)(k))and any given nondegenerate probability distributions P-1,...,P-n there exist random variables eta (1),...,eta (n) with respective distributions P-1,...,P-n such that (i(2),...,i(n)) is their uncorrelation structure. (C) 2001 Elsevier Science B.V. All rights reserved.Article Citation Count: 65Doubly warped products(Elsevier Science Bv, 2001) Ünal, B; Department of Modern LanguagesIn this paper we study geodesic completeness of Riemannian doubly warped products and Lorentzian doubly warped products. We give necessary conditions for generalized Robertson-Walker spacetimes with doubly warped product spacial parts to be globally hyperbolic. We also state some results about killing and conformal vector fields of doubly warped products.Article Citation Count: 7Photoelectronic and electrical properties of InS crystals(Iop Publishing Ltd, 2002) Qasrawi, AF; Gasanly, NM; Department of Electrical & Electronics EngineeringTo identify the localized levels in InS single crystals, the dark electrical conductivity, current-voltage characteristics and photoconductivity measurements were carried out in the temperature range of 10-350 K. Temperature dependence of dark electrical conductivity and the space-charge limited current studies indicate the presence of a single discrete trapping level located at (10 +/- 2) meV below the conduction band with a density of about 4.8 x 10(11) cm(-3). The conductivity data above 110 K reveal an additional two independent donor levels with activation energies of (50 +/- 2) and (164 +/- 4) meV indicating the extrinsic nature of conductivity. The spectral distribution of photocurrent in the photon energy range of 0.8-3.1 eV reveals an indirect band gap of (1.91 +/- 0.04) eV. The photocurrent-illumination intensity dependence follows the law I-ph proportional to F-gamma, with gamma being 1.0 and 0.5 at low and high illumination intensities indicating the domination of monomolecular and bimolecular recombination, respectively. It is observed that the photocurrent increases in the temperature range of 10 K up to T-m = 110 K and decreases or remains constant for 110 K < T < 160 K and increases again above 160 K. The temperature dependence of the photocurrent reveals an additional shallow impurity level with activation energies of 3 meV.
