H.Z. Alisoy

Investigation of the characteristics of dielectric barrier discharge in transition region

In the paper, we study the dielectric barrier discharge (DBD) occurring in a metal?insulator?gas?insulator?metal system. We encounter these kinds of discharges in ozonator-type reactors used in gas electrochemistry. The experiments are done in air medium when the gap width value is 580??m and the pressure is in the interval of 1?100?mbar. The schematic diagram of the experimental mechanism and the drawing methods of the characteristics are given, and it is determined that the barrier discharge has an impulse character. Experimentally, we determine that the voltage?current (v?i) and voltage?charge (v?q) characteristics of the discharge are linear for the case of (pl) (pl)cr, and these cases are explained theoretically. Furthermore, the determination method of the ratio of the fading voltage depending on the width of the steps of the experimental v?i characteristic to the inception voltage is given in this paper.

Calculation of electrical field of spherical and cylindrical gas voids in dielectrics by taking surface conductivity into consideration

Purpose – To determine the electrical field E1(t) in spherical and cylindrical gas voids existing in an insulator by considering surface conductivity of gas voids having an electrical permittivity of e1 and conductivity of γ1 for DC and AC situations.Design/methodology/approach – Analytical expressions satisfying Laplace equation for inside and outside of the cylindrical and spherical gas voids in an insulator located in an external electrical field having a definite time dependent character, have been derived by considering the surface conductivity of the gas void. The coefficients included by these analytical expressions have been determined by utilizing the continuity equation of the current on the surface of the voids.Findings – It has been demonstrated that the electrical field remains uniform in spherical and cylindrical gas voids when the surface conductivity of gas void has been considered. It has been determined that the contact charging process of different shaped particles has an exponential ch...

An analysis of corona field charging kinetics for polydisperse aerosol particles by considering concentration and mobility

In this paper, the kinetics of the charging process of polydisperse aerosol particles in a unipolar corona field is analysed and the effects of the particle concentration and particle mobility on the charging kinetics are investigated theoretically. An equation for time constant is derived to evaluate charging time of the particles.

Sigmoid based PID controller implementation for rotor control

This paper presents a sigmoid based variable coefficient PID (SBVC-PID) controller design for Twin Rotor MIMO System (TRMS). The proposed SBVC-PID controller dynamically changes controller coefficients according to a modified sigmoid function of the error signal. The modified sigmoid function is used to limit variability of PID controller coefficients in a predefined range. In the proposed method, each parameters of PID, namely pk, kt and kd, alter between predefined upper and lower bounds. A modified sigmoid function adjusted by a transition coefficient is used to alter each of the PID parameters between these bound limits. The variable coefficients of SBVC-PID maintain a hypercube in kp, kt and kd parameter space satisfying robust stability of the system. Well-known Kharitonov polynomials are used to ensure that the SBVC-PID coefficient alteration takes place in the robust stability intervals. Due to dynamically change of PID coefficients depending on magnitude of error signal, the control performance can be improved compared to conventional PID control. Performance of SBVC-PID controller is demonstrated via theoretical examples and TRMS rotor control simulations.

A space charge motion simulation with FDTD method and application in negative corona electrostatic field analysis

Abstract 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.

An Investigation of Ionic Flows in a Sphere-Plate Electrode Gap

This paper presents analyses of ion flow characteristics and ion discharge pulses in a sphere-ground plate electrode system. As a result of variation in electric field intensity in the electrode gap, the ion flows towards electrodes generate non-uniform discharging pulses. Inspection of these pulses provides useful information on ionic stream kinetics, the effective thickness of ion cover around electrodes, and the timing of ion clouds discharge pulse sequences. A finite difference time domain (FDTD) based space-charge motion simulation is used for the numerical analysis of the spatio-temporal development of ionic flows following the first Townsend avalanche, and the simulation results demonstrate expansion of the positive ion flow and compression of the negative ion flow, which results in non-uniform discharge pulse characteristics.

Effect of plasma deposited thin carbon layer on dielectric characteristics of Au-PI-Au structures

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°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.

Space charge formation in non-cristalline polymers and GaSe by DBD In SF 6 medium

In this study, we investigate the formation mechanism of space charges in PI - polyimide, PTFE - polytetrafluoroethylene, PET - polyethylene terephtalate and GaSe(Sn)-GaSe doped with (0.05 at%) Sn which are exposed to dielectric barrier discharge (DBD) in SF6 medium. The expressions for the concentration of trapped electrons in materials, electrical field strength and total charge are derived by solving total current equation at stationary state. Space charges are determined experimentally by using thermally stimulated depolarization current (TSDC) method, and TSDC spectrums are illustrated for investigated materials.

Yün ve Yün Karışımlı Elyafta Makine Hızına ve Harmana Bağlı Statik Elektriklenme Miktarının İncelenmesi

100% yun ve yun karisimli elyafin iplik uretimi esnasinda hazirlama hattinda meydan gelen lif-lif ve lif-metal surtunmesi lifler uzerinde statik elektriklenmeye neden olmaktadir. Bu calismada, elyaf cekme makinesi uzerinde hareket halinde iken elyaf uzerinde biriken statik elektriklenmenin makine hizina ve harman karisimina bagli olarak degisimi incelenmistir.%100 yun, %45/55 Yun/polyester, %90/10 Yun/naylon harmanlarin cekim makinesi uzerinde 3 farkli hizda harman yagi verilerek dinamik rejimde elyaf yuzeyine temas eden silindir elektrot ile akim degerleri olculerek yuzey yuk yogunlugu olcum metoduna gore statik elektriklenme artisi tespit edilmistir. Iplik uretim asamasinda silindirlere sarma kaynakli telef oraninin artmasina sebep olan elyaf partilerinde statik elektriklenme miktarinin daha fazla oldugu ve statik elektriklenme artisi ile iplik kalitesinin olumsuz etkilendigi calisma sonucunda gorulmustur.

Modeling and analysis of dielectric materials by using gradient-descent optimization method

This study presents a numerical method based on parallel RC equivalent circuit model fitting methodology for analysis and modeling of dielectric materials. The proposed method employs gradient-descent optimization method (GDOM) to estimate parallel RC equivalent circuit model from current waveforms by minimizing sum of squared difference (SSD) error. Estimation of parallel RC equivalent circuit parameters from measured current waveforms provides a useful tool for identification, simulation and analysis of dielectric materials. Moreover, applications of the proposed method for time and frequency analyses of dielectric materials are demonstrated numerically. Numerical simulations were presented to discuss efficiency of the proposed method for modeling, analysis and monitoring of insulator materials.