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RISS 인기검색어
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- 저자 : Mahmoud El‑Ghazaly (검색결과 2 건)
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Mahmoud El Ghazaly 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.1
The induced modifications in the photoluminescence spectra and the optical properties, as well as the correlation between them, of CR-39 polymer-based solid-state nuclear track detectors were investigated after thermal annealing. CR-39 samples were thermally annealed for two hours at different temperatures higher than the glass transition temperature. A linear relationship between the relative mass loss of the CR-39 detector and the annealing temperature was found. The photoluminescence intensity of the pristine CR-39 detector was studied at different excitation wavelengths, where an isosbestic point was observed at 350 nm, which was used as an excitation wavelength. The photoluminescence increased with increasing annealing temperature until temperatures of 200 ℃; thereafter, it decreased at temperatures of 220 and 250 ℃. Moreover, the wavelength of the photoluminescence emission band was subjected to a red shift that increased with increasing annealing temperature. The optical band gaps, direct and indirect band gaps, were obtained from the optical absorption spectra by using a UV-visible spectrophotometer. The direct and indirect band gaps were found to decrease with increasing annealing temperature. A correlation between the photoluminescence peak wavelength and the optical band gaps was found. The spectral peaks red shifted as both of the optical band gaps decreased. We concluded that the reduction in the optical band gaps for both the direct and the indirect band gaps caused the red shift in the photoluminescence peak of the CR-39 detector.
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Mazen Abdel‑Salam,Mohamed Th. El‑Mohandes,Mahmoud El‑Ghazaly 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.1
This paper proposes a newly-formulated Perturb and Observe (P&O) method for Maximum Power Point Tracking (MPPT) in PV systems. The new formulation considers the efect of solar irradiation level on tracking the maximum power point (MPP). The formulated P&O method is tested under standard test condition (STC) to achieve tracking efciency 99.98% against 98.4% for the conventional P&O method, 99.5% for the improved and 99.85 for the adaptive versions of the P&O method irrespective of the location of the initial operating point to the right or left of the MPP. The higher the tracking efciency, the closer is the operation of the PV module to the MPP with a subsequent capture of maximum electric energy available in the incident solar radiation. At constant irradiation level, the tracking efciency reaches 99.98% for the formulated method against 98.4% for the conventional P&O and 83.6–98.5% for the improved and adaptive versions. The amplitude of output power oscillations around the MPP is reduced to 0.05% of its average value for the formulated method against 1.02% for the conventional P&O, 0.5% for the improved and 0.8% for the adaptive versions. Also, the smaller the oscillations’ amplitude, the closer is the operating point to the MPP. The proposed formulation of P&O tracks successfully the MPP under various conditions including the Ropp irradiation profle, step and ramp changes of irradiation level. However, the conventional P&O method fails to track the MPP under Ropp and ramp changes of irradiation level.
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