Person: YUMAK YAHŞİ, AYŞE
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YUMAK YAHŞİ
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AYŞE
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Publication Open Access Dielectronic recombination data for dynamic finite-density plasmas - VI. The boron isoelectronic sequence(EDP SCIENCES S A, 2004-06) YUMAK YAHŞİ, AYŞE; Altun, Z; Yumak, A; Badnell, NR; Colgan, J; Pindzola, MSWe have calculated dielectronic recombination rate coefficients for 22 ions of the boron isoelectronic sequence, between C+ and Xe49+, within the generalized collisional-radiative framework, as outlined by Badnell et al. (2003). Calculations have been performed from both ground and metastable initial states, in both LS- and intermediate-coupling, allowing for Deltan = 0 and Deltan = 1 core-excitations. Results are presented and discussed for a selection of ions from the sequence. Results which are not presented here can be accessed from the Atomic Data and Analysis Structure (ADAS) database (Summers 2003) or from the Oak Ridge Controlled Fusion Atomic Data Center (http://www-cfadc.phy.ornl.gov). Comparison is made with the results of other existing theoretical calculations.Publication Metadata only Relaxation time of polypropylene glycol and polypropylene glycol dimethylether-like polymers in terms of fluid-phase temperature and pressure dependent hole fraction(PERGAMON-ELSEVIER SCIENCE LTD, 2015) YUMAK YAHŞİ, AYŞE; Yahsi, Ugur; Coskun, Bilgehan; Yumak, Ayse; Boubaker, Karem; Tav, CumaliWe present a model explaining relaxation time of PPG (polypropylene glycol) and PPGM (polypropylene glycol dimethylether) as representative compounds, with different molecular weights, PPG2 (M-w = 2 kg mol(-1)), PPG3 (M-w = 3 kg mol(-1)), PPGM1 (M-w = 1 kg mol(-1)), and PPGM2 (M-w = 2 kg mol(-1)), as a function of hole fraction at various fluid phase temperatures and high pressures. Proposed model based on the structural relaxation behavior of chain molecules given by thermo-occupancy function in terms of temperature and tempetature-pressure dependent hole fraction is discussed and compared with the free volume model. The former is the most universal behavior than the latter in terms of temperature and pressure. We discuss activation energy parameter and transmission coefficient for the species in terms of chain length and end groups such as dimethylether. Scaling relaxation time parameter in the proposed model has similar trend with relaxation time parameter of Adam-Gibbs theory. (C) 2015 Elsevier Ltd. All rights reserved.Publication Metadata only Electron-impact ionization of atomic ions in the Na isoelectronic sequence(IOP PUBLISHING LTD, 2008) YUMAK YAHŞİ, AYŞE; Altun, Z.; Yumak, A.; Golcek, U.; Loch, S. D.; Pindzola, M. S.; Griffin, D. C.Electron-impact ionization cross-sections and rate coefficients for the Na-like ions Mg+, Ar7+, Kr25+, Sn39+, Xe43+ and W63+ are presented. The direct ionization cross-sections of 2s, 2p and 3s subshells are calculated within a configuration-average distorted-wave (CADW) method. In addition, excitation-autoionization contributions originating from the inner-shell excitations of the type 2s22p63s -> 2s22p53snl (n = 3-6) and 2s22p63s -> 2s2p63snl (n = 3-6) are calculated using both CADW and level-resolved distorted-wave (LLDW) methods. We include the branching ratios for the radiation damping of the autoionizing configurations and levels. The excitation-autoionization contributions are found to be quite large for the lighter ions. For the heavier ions the radiation damping of the excitation-autoionization contribution is found to be significant. We find that the distorted-wave results are in good agreement with available experimental measurements, which only exist for Mg+, Ar7+ and Xe43+. We also find that the computationally simple configuration-average calculations are in reasonable agreement with the computationally demanding level-resolved calculations for the excitation-autoionization contributions for all the Na-like ions studied. In addition, Maxwellian rate coefficients are produced from our cross-sections and are archived in a format useful for plasma modelers.Publication Metadata only Level-resolved distorted-wave cross-sections of electron impact ionization of Ar5+(Institute of Physics Publishing, 2009-11-01) YUMAK YAHŞİ, AYŞE; Yumak A., Yavuz I., Altun Z.Electron impact ionization cross sections of Ar5+ were calculated using configuration-average (CADW) and level-resolved (LRDW) distorted-wave methods. Direct ionization cross-sections of 2s, 2p, 3s and 3p subshells were calculated within a CADW approximation. The contributions from the excitation autoionization channels were evaluated assuming single excitations from the 2s, 2p, and 3s subshells and in both CADW and LRDW methods. The radiative stabilization of the excitation autoionization channels were found to reduce the excitation autoionization by a small amount. © 2009 IOP Publishing Ltd.Publication Metadata only Stability and morphology-dependence of Sc3+ ions incorporation and substitution kinetics within ZnO host lattice(ELSEVIER SCI LTD, 2015) YUMAK YAHŞİ, AYŞE; Yumak, Aye; Turgut, Guven; Kamoun, Olfa; Ozisik, Haci; Deligoz, Engin; Petkova, Petya; Mimouni, Refka; Boubaker, Karem; Amlouk, Mosbah; Goumri-Said, SourayaIn this study, sol-gel spin coating route was carried out to prepare Scandium doped ZnO thin films with different controlled percentage (1-7%). Particularly, it has been demonstrated, through original conjoint morphological-structural and optical investigations, that some interesting physical properties were induced. Indeed, X-ray diffraction (XRD) analysis shows that (002) preferential crystalline plane for Sc doped ZnO films was kept along with ZnO hexagonal wurtzite structure, although Sc doping seemed to cause a decrease in crystallinity. Except for 1 at% Sc doping ratio, optical band gap changes reversely with Urbach energy with a decrease in optical gap and a broadening of the absorption tail. Ab-initio calculations of lattice dynamical properties outlined additional strong hybridization between Sc and O atoms and show the stability of Scandium doped ZnO. (C) 2015 Elsevier Ltd. All rights reserved.Publication Metadata only An attempt to give exact solitary and periodic wave polynomial solutions to the nonlinear Klein-Gordon-Schrodinger equations(PERGAMON-ELSEVIER SCIENCE LTD, 2015) YUMAK YAHŞİ, AYŞE; Yumak, A.; Boubaker, K.; Petkova, P.This study proposes exact solitary and periodic wave polynomial solutions to the nonlinear Klein-Gordon-Schrodinger equation in nonlinearly dispersive Schrodinger equation in a particular geometry. These solutions include integer coefficient polynomial function type and are found as such for the first time for the particular case of an electron which is confined inside a spherical finite quantum dot. The results were compared to recently published records so far. (C) 2015 Elsevier Ltd. All rights reserved.Publication Metadata only FİZİK, Fen ve Mühendislik için Teknoloji Güncellemeli, Serway, Jewett,, CİLT 2, Elektrik ve Manyetizma, Optik(Palme Yayın Dağıtım, 2022-07-01) KESKİN, SIDDIK SİNAN; DUMLUDAĞ, FATİH; TAV, CUMALİ; YUMAK YAHŞİ, AYŞE; YAHŞİ, UĞUR; Yahşi U., Saçlı Ö. A., Keskin S. S., Tav C., Dumludağ F., Altındal A., Yumak Yahşi A., Avgın İ., Atav Ü., Ulutaş D., et al.Publication Metadata only Europium doping-induced stability and quantum confinement effect in ZnO quantum well wires QWW: Electronic structure calculation and material structural investigation in terms of band-gap shift(ELSEVIER SCIENCE BV, 2016) YUMAK YAHŞİ, AYŞE; Yumak, A.; Yahsi, U.; Petkova, P.; Boubaker, K.ZnO quantum well wires QWW have been grown on glass substrates by an inexpensive, simplified and enhanced spray pyrolysis technique, at 460 degrees C and using Zn(CH3COO)(2)center dot 2H(2)O as main precursor. Consecutively, the as-grown wires have been gradually doped by Europium within hexa-hydrated chlorinated Europium EuCl3 center dot 6H(2)O (ACROS, 99.0% purity) with different europium-doping levels (0, 0.5 and 1.0 at%). The effects of Eu-doping on the structural and optical properties of the QWW were investigated. Results reflect that accuracy of control can be achieved on functional performance by adjusting doping extent. Two-dimensional self-consistent calculations of the electronic structure within the Brillouin zone, along with Lattice Compatibility Theory analyses results show excellent agreement with the experimental results. (C) 2015 Elsevier B.V. All rights reserved.Publication Metadata only Pure and zirconium-doped manganese(II,III) oxide: Investigations on structural and conduction-related properties within the Lattice Compatibility Theory scope(ELSEVIER SCI LTD, 2015) YUMAK YAHŞİ, AYŞE; Ben Said, L.; Larbi, T.; Yumak, A.; Boubaker, K.; Amlouk, M.Manganese(II,III) oxide Mn3O4 thin films have been deposited on glass substrates using a simple spray pyrolysis method. Zirconium doping protocol was applied in order to verify some recently claimed enhancements of hausmannite physical properties. Gradual doping was achieved with ratio [Zr]/[Mn] = 1%, 2% and 3% in addition to pure Mn3O4. Beyond classical characterization techniques, effects of Zr-doping were studied in reference to the expected use in rechargeable batteries and sensing devices. Moreover, additional opto-thermal investigation and analyses of the Lattice Compatibility Theory led to a founded understanding to the dynamics of Zirconium ion incorporation inside Mn3O4 host matrices. (C) 2015 Elsevier Ltd. All rights reserved.Publication Metadata only Impedance spectroscopy and sensors under ethanol vapors application of sprayed vanadium-doped ZnO compounds(ELSEVIER SCIENCE SA, 2015) YUMAK YAHŞİ, AYŞE; Mhamdi, A.; Labidi, A.; Souissi, B.; Kahlaoui, M.; Yumak, A.; Boubaker, K.; Amlouk, A.; Amlouk, M.Thin films of vanadium-doped zinc oxide with different vanadium-doping levels (0, 1, 2 and 3 at%) were deposited on glass substrates by employing an inexpensive, simplified spray technique using at relatively low substrate temperature (460 degrees C). The effect of V doping on the structural, morphological and optical properties of the films was investigated by Mhamdi et al. (2013). The X-ray diffraction analysis shows that the films were well crystallized in wurtzite phase with the crystallites preferentially oriented toward (002) direction parallel c-axis. As also that the average particle size along the surface of the films decreases with increasing of concentration of vanadium. In this work we study the AC and DC conductivity and gas sensor application on ZnO:V thin films. The dielectric properties of ZnO:V thin films were studied by means of complex impedance spectroscopy and frequency dependence of conductivity measured from the impedance data at a range of frequency intervals between 10 Hz and 13 MHz with a temperature between 355 and 445 degrees C. The frequency dependence of the dielectric constant epsilon', dielectric loss epsilon '', loss tangent (tan delta) and AC electrical conductivity (sigma(AC)) of the layers was subsequently investigated. In literature, we have shown in previous papers that structural and surface morphology of ZnO thin films, prepared by spray, plays an important role in the gas detection mechanism. In this article, we have studied the response evolution of ZnO:V sensors ethanol versus time and working temperature, relative doping and the concentration of the ethanol vapor. (C) 2015 Elsevier B.V. All rights reserved.