Browsing by Author "Özdemir, S"

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    Half bridge LLC resonance converter reliability analysis for OLED TV
    (GAZI UNIV, FAC ENGINEERING ARCHITECTURE) Nil, M; Öztürk, Y; Özdemir, S; Sözen, H; Nil, M
    In this study, half-bridge LLC resonant DC-DC converter design was realized for 65 AMOLED TV. The main objective of the design is to achieve the optimum level of reliability and to reach the appropriate life cycle of MTBF (Mean-time between failure). Reliability tests were carried out which cover the thermal, electromagnetic compatibility (EMC) and electrical tests of the designed power board and critical circuit components of this power board. Moreover, in order to analyze the operating characteristics of the circuit at different switching frequencies, simulation analyses were carried out by PSIM Program. As a result of the, all these simulations and empirical studies, a high level of reliability conditions have been achieved with a 120.215 hours MTBF value.
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    HARMONIC ESTIMATION BASED SUPPORT VECTOR MACHINE FOR TYPICAL POWER SYSTEMS
    (ACAD SCIENCES CZECH REPUBLIC, INST COMPUTER SCIENCE) Özdemir, S; Demirtas, M; Aydin, S
    The power quality in electrical energy systems is very important and harmonic is the vital criterion. Traditionally Fast Fourier Transform (FFT) and Discrete Fourier Transform (DFT) have been used for the harmonic distortion analysis and in the literature harmonic estimations have been made using different methods. As an alternative method, this paper suggested using Support Vector Machine (SVM) for harmonic estimation. The real power energy distribution system has been examined and the estimation results have been compared with measured real data. The proposed solution approach was comparatively evaluated with the ANN and LR estimation methods. Comparison results show that THD estimation values that were obtained by the SVM method are close to the THD estimation values obtained from ANN (Artificial Neural Network) and LR (Linear regression) methods. The numerical results clearly showed that the SVM method is valid for THD estimation in the power system.
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    Dietary vitamin E (α-tocopherol acetate) and selenium supplementation from different sources: performance, ascites-related variables and antioxidant status in broilers reared at low and optimum temperatures
    (TAYLOR & FRANCIS LTD) Özkan, S; Malayoglu, HB; Yalçin, S; Karadas, F; Koçtürk, S; Çabuk, M; Oktay, G; Özdemir, S; Özdemir, E; Ergül, M
    1. This study compared the effect of dietary supplementation with organic or inorganic selenium (Se) sources plus control amounts or large amounts of vitamin E (alpha- tocopherol acetate) in broilers raised at control ( 20 to 24 degrees C) or low ( 14 center dot 5 to 16 center dot 8 degrees C) temperatures after 2 weeks of age. 2. The following dietary treatments were used from one day old. Diet 1, the control diet, comprised a commercial diet containing 0 center dot 15 mg/ kg inorganic Se and 50 mg vitamin E/kg feed. Diet 2 was the same as diet 1, supplemented with 0 center dot 15 mg/ kg inorganic Se. Diet 3 was the same as diet 2 but was supplemented with 200 mg/ kg vitamin E. Diet 4 was the same as diet 1, but inorganic Se was replaced with 0 center dot 30 mg/ kg organic Se. Diet 5 was the same as diet 4, supplemented with 200 mg/ kg vitamin E. 3. Low temperature reduced the growth rate of broilers; however, at 6 weeks, there were no differences in the body weights of birds fed on organic Se supplemented diets housed at low or control temperature. The feed conversion ratio was significantly affected by low temperature but not by diet. The heterophil/ lymphocyte ratio was higher in chicks after one week in the cold, indicating mild stress. Blood triiodothyronine levels were significantly higher in birds after 1 and 4 weeks in the cold but thyroxin was not affected. 4. Organic Se supplementation increased relative lung weight at the control temperature, which might lead to greater respiratory capacity. Relative spleen weight significantly decreased in broilers fed diets supplemented with inorganic Se under cold conditions, a possible indication of chronic oxidative stress. 5. At the low temperature, supplementation with organic Se alone, or with inorganic Se and vitamin E increased glutathione peroxidase ( GSHPx) activity and glutathione ( GSH) concentration in the liver of broilers, which may indicate increased activity of birds' antioxidant defence against suboptimal environments.