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: 8Electroinitiated polymerization of 2-allylphenol(Springer-verlag, 2000) Cihaner, Atilla; 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.Conference Object Citation Count: 9Effect of lithium doping on the properties of Tl-based superconductors(Iop Publishing Ltd, 2001) Kayed, Tarek Said; Özkan, Hakan; 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: 19Crystal data, photoconductivity and carrier scattering mechanisms in CuIn5S8 single crystals(Wiley-v C H verlag Gmbh, 2001) Qasrawı, Atef Fayez Hasan; 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 Citation Count: 38Synthesis and characterization of fluorine-substituted polyanilines(Pergamon-elsevier Science Ltd, 2001) Cihaner, Atilla; 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) Qasrawı, Atef Fayez Hasan; 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.Article Citation Count: 20Characterization of p-In2Se3 thin films(Kluwer Academic Publ, 2001) Qasrawı, Atef Fayez Hasan; 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: 5Electrochemical polymerization of 4-allylanisole(Pergamon-elsevier Science Ltd, 2001) Cihaner, Atilla; 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 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 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: 65Doubly warped products(Elsevier Science Bv, 2001) Ünal, Bernis; 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: 1Sets of random variables with a given uncorrelation structure(Elsevier Science Bv, 2001) Ostrovska, Sofiya; 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: 57A curvature condition for a twisted product to be a warped product(Springer-verlag, 2001) Ünal, Bernis; 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.Master Thesis Siegfried Sassoon: More thanjust a war poet(2002) Airey, Ian; Vale, Marcia142 ÖZET Bu tezin giriş bölümünde, ilkönce Sassoon'un ailesiyle ilgili detayi vermeyi, daha sonra 1914 I. Dünya Savaşı'nın başlamasıyla birlikte Sassoon'un şiirsel gelişimini incelemeyi amaçlıyorum. Bunu yaparken, hem şiir akımlarının hem de yakın çevresinin ona olan etkilerini inceleyeceğim. Bunu takiben, Savaş Yılları bölümünde Batı Cephesi olaylarının Sassoon üzerindeki kişisel etkilerini ve şiirlerindeki tarz ve içerik yönündeki etkileri de inceleyeceğim. Savaş şiirini incelerken eksiksiz bir inceleme yapabilmek için günlükleri, hatıraları ve otobiyografileri de dikkate alacağım. Ayrıca Sassoon'un şiirlerinin zamanın eleştirmenleri tarafından nasıl değerlendirildiğine dair bir bölümü de olacaktır. Sadece yazarın savaş yıllarında başından geçenler değil buna ek olarak bu olaylara yolaçan gelişmeleri ve Sassoon'un 'A Soldier's Declaration' (Bir Askerin Beyanatı)'nın Wilfred Owen üzerindeki etkilerini içerecek şekilde inceleyeceğim. Sherston üçlemesini incelerken Sassoon'un düzyazı tarzının ve içeriğinin, şiirlerin anlaşılması için fikir vermesi açısından, oynadığı rolünü de inceleyeceğim. Bundan sonra Sassoon'un kendi anılarında tanımladığı asıl kişiliğinin tasvirinin tamamlanması açısından öz hayat hikayesini inceleyeceğim. Son olarak da özellikle düzyazı eserlerini yazarken içinde bulunduğu ruh halinin yansıması olarak 1918'den sonra yazdığı şiirlerinde görülen, hayatının son dönemindeki gelişmeleri göstermesi açısından inceleyeceğim.143 Yukarıdaki araştırmaları yapmaktaki amacım, Sassoon'un yirminci yüzyıl edebiyatına yapmış olduğu bütün katkıların değerlendirmesini yapmak; O 'nun ününün sadece bir avuç epigramatik savaş şiirlerine bağlı olup olmadığı veya tamamen bir insanın bütün çalışmaları; şiiri, düzyazısı ve anıları bütünleşmiş olarak yirminci yüzyılın diğer bölümlerinin toplamından daha büyük olan yirminci yüzyılın ilk yansını anlamamıza sağlayabilir mi sorusuna cevap vermektir.Article Citation Count: 7Photoelectronic and electrical properties of InS crystals(Iop Publishing Ltd, 2002) Qasrawı, Atef Fayez Hasan; 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.Article Citation Count: 1The local Mobius equation and decomposition theorems in Riemannian geometry(Canadian Mathematical Soc, 2002) Fernández-López, M; García-Río, E; Kupeli, DNA partial differential equation, the local Mobius equation, is introduced in Riemannian geometry which completely characterizes the local twisted product structure of a Riemannian manifold. Also the characterizations of warped product and product structures of Riemannian manifolds are made by the local Mobius equation and an additional partial differential equation.Article Citation Count: 25Classification theorems for general orthogonal polynomials on the unit circle(Academic Press inc Elsevier Science, 2002) Khrushchev, Sergey; MathematicsThe set P of all probability measures a on the unit circle T splits into three disjoint subsets depending on properties of the derived set of {\phi(n)\(2) dsigma}(ngreater than or equal to0), denoted by Lim(sigma). Here {phi(n)}(ngreater than or equal to0) are orthogonal polynomials in L-2(dsigma). The first subset is the set of Rakhmanov measures, i.e., of sigma is an element of P with {m} = Lim(sigma), m being the normalized (m(T) = 1) Lebesgue measure on T. The second subset Mar(T) consists of Markoff measures, i.e., of sigma is an element of P with m is not an element of Lim(sigma), and is in fact the subject of study for the present paper. A measure sigma, belongs to Mar(T) iff there are epsilon > 0 and l > 0 such that sup{\a(n+j)\: 0 less than or equal to j less than or equal to l) > epsilon, n = 0, 1, 2,..., {a(n)} is the Geronimus parameters (= reflection coefficients) of sigma. We use this equivalence to describe the asymptotic behavior of the zeros of the corresponding orthogonal polynomials (see Theorem G). The third subset consists of sigma is an element of P with {m} not subset of or equal toLim(sigma). We show that sigma is ratio asymptotic iff either sigma is a Rakhmanov measure or sigma satisfies the Lopez condition (which implies sigma is an element of Mar(T)). Measures sigma satisfying Lim(sigma) = {v} (i.e., weakly asymptotic measures) are also classified. Either v is the sum of equal point masses placed at the roots of z(n) = lambda, lambda is an element of T, n = 1, 2,..., or v is the equilibrium measure (with respect to the logarithmic kernel) for the inverse image under an m-preserving endomorphism z -->z(n), = 1, 2,..., of a closed arc J (including J = T) with removed open concentric are J(0) (including J(0) = empty set). Next, weakly asymptotic measures are completely described in terms of their Geronimus parameters. Finally, we obtain explicit formulae for the parameters of the equilibrium measures v and show that these measures satisfy {v} = Lim(v). (C) 2002 Elsevier Science (USA).Article Citation Count: 9Carrier scattering mechanisms in GaS0.5Se0.5 layered crystals(Wiley-v C H verlag Gmbh, 2002) Qasrawı, Atef Fayez Hasan; Gasanly, NM; Department of Electrical & Electronics EngineeringSystematic dark electrical resistivity and Hall mobility measurements have been carried out in the temperature range 150-400 K on n-type GaS0.5Se0.5 layered crystals. The analysis of temperature dependent electrical resistivity and carrier concentration reveals the extrinsic type of conduction with a donor impurity level located at 0.44 eV, donor and acceptor concentrations of 3.4x10(17) and 4.1x10(17) cm(-1), respectively, and an electron effective mass of 0.41 m(o). The Hall mobility is limited by the electron-phonon short-range interactions scattering at high temperatures combined with the ionized impurity scattering at low temperatures. The electron-phonon short-range interactions scattering mobility analysis reveals an electron-phonon coupling constant of 0.25 and conduction band deformation potential of 5.57 eV/Angstrom.Article Citation Count: 3LATTICE-ISOMORPHIC GROUPS, AND INFINITE ABELIAN G-COGALOIS FIELD EXTENSIONS(World Scientific Publ Co Pte Ltd, 2002) Albu, Toma; Basarab, SerbanThe aim of this paper is to provide a proof of the following result claimed by Albu (Infinite field extensions with Galois-Cogalois correspondence (II), Revue Roumaine Math. Pures Appl. 47 (2002), to appear): The Kneser group Kne(E/F) of an Abelian G-Cogalois extension E/F and the group of continuous characters Ch(Gal(E/F)) of its Galois group Gal(E/F) are isomorphic (in a noncanonical way). The proof we give in this paper explains why such an isomorphism is expected, being based on a classical result of Baer (Amer. J. Math. 61 (1939), 1-44) devoted to the existence of group isomorphisms arising from lattice isomorphisms of their lattices of subgroups.