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Öğe Construction of a quadratic model for predicted and measured global solar radiation in Chile(Iop Publishing Ltd, 2007) Yilmaz, Ercan; Cancino, Beatriz; Lopez, EdmundoGlobal solar radiation data for sites in Chile are analysed and presented in a form suitable for their use in engineering. A new model for monthly average data is developed to predict monthly average global radiation with acceptable accuracy by using actinographic data due to scarcing of pyranometer data. Use of the new quadratic model is proposed because of its relatively wider spectrum of values for Angstrom coefficients a(0), a(1), and a(2).Öğe Photoelectron, Compton and characteristic x-ray escape from an HPGe Detector in the range 8-52 keV(John Wiley and Sons Ltd, 2004) Yilmaz, Ercan; Can, CüneytEscape of photoelectrons, Compton-scattered photons and Ge x-rays from an HPGe detector was studied as a function of energy in the range 8-52 keV. A variable-energy source producing Cu, Rb, Mo, Ag, Ba, and Tb x-rays was used. All three mechanisms for energy loss were observed in the same experiment for Ba and Tb, while only x-ray and photoelectron escapes were evident in the spectra for Ag, Mo, Rb, and Cu. Spectral features and possible mechanisms for partial energy deposition were investigated. A Monte Carlo program was used to simulate the relevant interactions, and to estimate the escape probabilities. Copyright © 2004 John Wiley & Sons, Ltd.Öğe Poly(o-anisidine) on brass(Korean Inst Chem Engineers, 2008) Ozyilmaz, Ali Tuncay; Ozyilmaz, Gul; Yilmaz, Ercan; Colak, NureddinThe electrochemical synthesis of poly(o-anisidine) (POA) was achieved on brass (CuZn) electrode by applying two scan rates (50 and 20 mVs(-1)). The synthesized polymer films were strongly adherent and homogeneous in both cases. Their corrosion performance was investigated by AC impedance spectroscopy (EIS) technique, anodic polarization plots and open circuit potential-time curves, in 3.5% NaCl solution. It was clearly seen that poly(o-anisidine) films provided a significant physical protection for longer exposure time. It was shown that polymer film coated at high scan rate (CuZn/POA-H) exhibited better barrier property against the attack of corrosive agents when compared with polymer film obtained at low scan rate (CuZn/POA-L). It was found out that poly(o-anisidine) film synthesized at high scan rate caused a significant increase in corrosion resistance by its catalytic behavior on formation of protective oxide layers on the surface in longer time.Öğe A systematic study on MOS type radiation sensors(Elsevier, 2007) Yilmaz, Ercan; Kaleli, Buket; Turan, RasitRadiation sensors based on metal oxide semiconductor (MOS) structure are useful because of their superior sensitivity as well as excellent compatibility with the existing microelectronic technology. In this paper, a systematic study of MOS capacitors built on p- and n-type Si substrates with different SiO2 thicknesses (10 nm, 50 nm, 100 nm and 240 nm) is presented. MOS device response to gamma radiation up to 256 Gray have been studied from the sensor application point of view. Variation of the radiation induced device response with oxide thickness, substrate type, applied bias and post annealing have been measured and discussed. Radiation induced charge in MOS devices is shown to be a strong function of the oxide thickness as expected. Application of a positive bias to the gate is found to enhance the device sensitivity for both n- and p-type devices. This is explained in terms of the involvement of the interface states in the sensing process. Devices have also been studied after repeated cycles of irradiation and annealing treatment under hydrogen atmosphere. Each cycle consists of gamma irradiation with 60 Gray dose and an anneal at 200 degrees C for 30 min. The charging-discharging mechanism during these cycles is discussed. (c) 2007 Elsevier B.V. All rights reserved.Öğe Temperature cycling of MOS-based radiation sensors(Elsevier Science Sa, 2008) Yilmaz, Ercan; Turan, RasitWe have studied dosimetric characteristics, linearity and performance of MOS structures as radiation sensors. This was performed by analyzing the correlation between irradiation dose and the shift in flat band voltage of MOS capacitors which were tested against gamma and beta radiations. Devices have been studied after repeated cycles of irradiation and annealing treatment under hydrogen and nitrogen ambient. Each cycle consists of gamma irradiation with 60 Gray-dose and an anneal at 200 degrees C for 30 min. Results obtained by high frequency C-V methods show that irradiation-annealing cycle correlates with the recovery of the measured signal. The charging-discharging mechanism during the cyclic treatment is discussed. The variation of the interface state density during the irradiation-annealing cycle was studied with a model based on conductance-voltage measurements. (c) 2007 Elsevier B.V. All rights reserved.
