Switching-Mode BJT Driver for Self-Oscillated Push-Pull Inverters

Borekci, Selim,Oncu, Selim The Korean Institute of Power Electronics 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.2

Self oscillating current fed push pull resonant inverters can be controlled without using special drivers. Dc current flows through the choke coil and the power switches, although the driving signals of the power switches are sinusoidal. When the base current is near zero, the transistors cannot be operated in switching mode. Hence higher switching power losses and instantaneous peak power during off transitions are observed. In this study, an alternative design has been proposed to overcome this problem. A prototype circuit has been built which provides dc bias current to the base of the transistors. Experimental results are compared with theoretical calculations to demonstrate the validity of the design. The proposed design decreases the peak and average power losses by about 8 times, when compared to conventional designs.

Fragility analysis of R/C frame buildings based on different types of hysteretic model

Borekci, Muzaffer,Kircil, Murat S. Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.6

Estimation of damage probability of buildings under a future earthquake is an essential issue to ensure the seismic reliability. Fragility curves are useful tools for showing the probability of structural damage due to earthquakes as a function of ground motion indices. The purpose of this study is to compare the damage probability of R/C buildings with low and high level of strength and ductility through fragility analysis. Two different types of sample buildings have been considered which represent the building types mentioned above. The first one was designed according to TEC-2007 and the latter was designed according to TEC-1975. The pushover curves of sample buildings were obtained via pushover analyses. Using 60 ground motion records, nonlinear time-history analyses of equivalent single degree of freedom systems were performed using bilinear hysteretic model and peak-oriented hysteretic model with stiffness - strength deterioration for each scaled elastic spectral displacement. The damage measure is maximum inter-story drift ratio and each performance level considered in this study has an assumed limit value of damage measure. Discrete damage probabilities were calculated using statistical methods for each considered performance level and elastic spectral displacement. Consequently, continuous fragility curves have been constructed based on the lognormal distribution assumption. Furthermore, the effect of hysteresis model parameters on the damage probability is investigated.

STRATEGIC INSIGHTS FOR THE GLOBAL COMPANIES: A STUDY ON CONSUMER ATTITUDES TOWARDS COUNTERFEITS OF LUXURY FASHION GOODS

Elif Borekci,Selime Sezgin,Gulberk Gultekin Salman,Nimet Uray 글로벌지식마케팅경영학회 2015 Global Fashion Management Conference Vol.2015 No.06

The purpose of this study is to investigate which of the main social and personality factors affect the attitudes of consumers towards counterfeit products and their purchase intentions in one of largest counterfeit product market as much as the attractive one for the Global Luxury goods ,namely Turkey.

Fragility analysis of R/C frame buildings based on different types of hysteretic model

Muzaffer Borekci,Murat S. Kirçil 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.6

Estimation of damage probability of buildings under a future earthquake is an essential issue to ensure the seismic reliability. Fragility curves are useful tools for showing the probability of structural damage due to earthquakes as a function of ground motion indices. The purpose of this study is to compare the damage probability of R/C buildings with low and high level of strength and ductility through fragility analysis. Two different types of sample buildings have been considered which represent the building types mentioned above. The first one was designed according to TEC-2007 and the latter was designed according to TEC-1975. The pushover curves of sample buildings were obtained via pushover analyses. Using 60 ground motion records, nonlinear time-history analyses of equivalent single degree of freedom systems were performed using bilinear hysteretic model and peak-oriented hysteretic model with stiffness – strength deterioration for each scaled elastic spectral displacement. The damage measure is maximum inter-story drift ratio and each performance level considered in this study has an assumed limit value of damage measure. Discrete damage probabilities were calculated using statistical methods for each considered performance level and elastic spectral displacement. Consequently, continuous fragility curves have been constructed based on the lognormal distribution assumption. Furthermore, the effect of hysteresis model parameters on the damage probability is investigated.

Switching-Mode BJT Driver for Self-Oscillated Push-Pull Inverters

Selim Borekci,Selim Oncu 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.2

Self oscillating current fed push pull resonant inverters can be controlled without using special drivers. Dc current flows through the choke coil and the power switches, although the driving signals of the power switches are sinusoidal. When the base current is near zero, the transistors cannot be operated in switching mode. Hence higher switching power losses and instantaneous peak power during off transitions are observed. In this study, an alternative design has been proposed to overcome this problem. A prototype circuit has been built which provides dc bias current to the base of the transistors. Experimental results are compared with theoretical calculations to demonstrate the validity of the design. The proposed design decreases the peak and average power losses by about 8 times, when compared to conventional designs.

Prenatal MRI Findings of Polycystic Kidney Disease Associated with Holoprosencephaly

Mustafa Koplay,Omer Onbas,Fatih Alper,Bunyamin Borekci 대한영상의학회 2009 Korean Journal of Radiology Vol.10 No.3

Holoprosencephaly (HPE) and polycystic kidney disease (PKD) are genetically heterogeneous anomalies which can make up part of various syndromes or chromosomal anomalies. Due to the rapid lethality prognosis, early and precise prenatal diagnosis would be of great value. This case report describes extensive PKD involvement, already present in utero, in a patient with HPE and subdural effusion visible by MR imaging. The detailed anatomic information obtained by the MR imaging can guide the surgical planning and can aid antenatal counseling.

Is the Neutrophil-Lymphocyte Ratio an Indicator of Progression in Patients with Benign Prostatic Hyperplasia?

Tanik, Serhat,Albayrak, Sebahattin,Zengin, Kursad,Borekci, Hasan,Bakirtas, Hasan,Imamoglu, M. Abdurrahim,Gurdal, Mesut Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.15

Purpose: The aim of this study was to evaluate inflammation parameters and assess the utility of the neutrophil-lymphocyte ratio (NLR) as a simple and readily available predictor for clinical disease activity in patients with nenign prostate hyperplasia BPH. We also aimed to investigate the relationship between inflammatory parameters with ${\alpha}$-blocker therapy response, and evaluate the potential association between NLR and the progression of benign prostatic hyperplasia (BPH). Materials and Methods: We examined 320 consecutive patients (July 2013-December 2013) admitted to our outpatient clinic with symptoms of the lower urinary tract at Bozok University. The mean age was 60 (range, 51-75) years. Complete blood count (CBC), prostate-specific antigen (PSA), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were assessed. Correlations between PSA, CRP, ESR, prostate volume, International Prostate Symptom Score (IPPS), maximum urinary flow rate (Qmax), and NLR were assessed statistically. Patients were divided into two groups: high and low risk of progression. Results: NLR was positively correlated with IPSS (p=0.001, r=0.265), PSA (p=0.001, r=0.194), and negatively correlated with Qmax (p<0.001, r=-0.236). High-risk patients a had a higher NLR compared with low-risk patients, based on IPSS (p<0.001), PSA (p=0.013), and Qmax (p<0.001); however, there were no significant differences between the groups in terms of age (p>0.05), and prostate volume (p>0.05). Conclusions: NLR can predict BPH progression. We propose that increased inflammation is negatively associated with clinical status in BPH patients and suggest that NLR can give information along with LUTS severity which may be used as a readikly accessible marker for patient follow-up.