Yazar "Alisoy, Hafiz Z." seçeneğine göre listele

Listeleniyor 1 - 4 / 4
  • Küçük Resim Yok
    Öğe
    An approach for unipolar corona discharge in N2/O2 gas mixture by considering townsend conditions
    (Elsevier Science Bv, 2011) Alisoy, Hafiz Z.; Yesil, Ali; Koseoglu, Murat; Unal, Ibrahim
    In this study (alpha/p)=f(E/p) functional relation is derived for the gas mixture of N-2/O-2 by considering Townsend approach, and formation mechanism of corona discharge is investigated for the coaxial electrode system located in this gas medium. The electron energy distribution function (EEDF) which is required for estimation of ionization coefficient, is determined by considering probability distribution function of inelastic electron collisions versus energy. An algorithm for determining ionization coefficient for binary gas mixture is presented. The development and motion of the electron avalanche in inter-electrode gap are studied by considering the effect of positive space charges. It is determined by considering the derived mathematical expressions that the formation of corona discharge is related with the variation of the current characteristics in inter-electrode gaps depending on the change of potential of central electrode. (C) 2011 Elsevier B.V. All rights reserved.
  • Küçük Resim Yok
    Öğe
    The Changes in Electrical and Interfacial Properties of Polyimide Exposed to Dielectric Barrier Discharge in SF6 Medium
    (Hindawi Publishing Corp, 2013) Alisoy, Hafiz Z.; Koseoglu, Murat
    The formation mechanism of space charges in polyimide (PI) which was exposed to dielectric barrier discharge (DBD) in SF6 medium and the effects of the space charges on interfacial and electrical properties of PI were investigated. The variation of normalized surface charge density on PI sample was calculated and illustrated for different DBD exposure times. The surface potential was measured to determine the effect of the space charges on the sample. Then, the contact angle values were measured to obtain the relation between the surface energy and the surface charge density. The expressions for the total charge and the concentration of trapped electrons were derived by using Poisson and continuity equations at stationary state. The space charges were determined experimentally by using thermally stimulated depolarization current (TSDC) method. Also, SEM image and FTIR spectrum of virgin and treated samples were presented to observe the structural variations. It was seen that the approach for the formation mechanism of the space charges agreed with the experimental data. However, it was concluded particularly for the short-time DBD treatments that the space charges accumulated in the sample should be considered besides the effects of surface functionalization in the determination of the surface energy.
  • Küçük Resim Yok
    Öğe
    Effect of Plasma Deposited Thin Carbon Layer on Dielectric Characteristics of Au-PI-Au Structures
    (Ieee-Inst Electrical Electronics Engineers Inc, 2012) Koseoglu, Murat; Alisoy, Hafiz Z.
    In this study, dielectric properties of a virgin polyimide (PI) sample and tailored PI sample are investigated in a metal-insulator-metal (MIM) structure comparatively. In order to modify the dielectric properties of the tailored sample, plasma enhanced chemical vapor deposition (PECVD) method was used, and a thin a-C:H layer was deposited on the sample surface. Then dielectric permittivity, dielectric loss and ac conductivity characteristics, which were calculated according to the measured capacitance, loss factor and conductance values, were plotted versus frequency (0.1-100 kHz) and temperature (20-300 degrees C). Also, SEM images and FTIR spectrum of the samples were presented and evaluated. Consequently, a-C:H layer and accompanying plasma polymer interactions during PECVD led to decrease the permittivity of the sample, and increase the thermal stability of the tailored sample relatively.
  • Küçük Resim Yok
    Öğe
    A space charge motion simulation with FDTD method and application in negative corona electrostatic field analysis
    (Elsevier Science Inc, 2012) Alagoz, Baris Baykant; Alisoy, Hafiz Z.; Alagoz, Serkan; Hansu, Fevzi
    In this paper, a finite difference time domain based simulation method is presented for the spatio-temporal analysis of space charge motion and the proposed method is applied to negative corona electrostatic field analysis. Drifting and diffusion motion equations of space charges are numerically solved and used in the simulation of corona discharges considering effects of impact ionization, electron attachment, ion-ion recombination and ion-electron recombination. The results obtained from the simulation are discussed. (C) 2012 Elsevier Inc. All rights reserved.