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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.
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.
An experimental study on different socket base connections under cyclic loading
Selim Pul,Metin Hüsem,Mehmet Emin Arslan,Sertaç Hamzaçebi 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.13 No.3
This paper presents an experimental study on socket base connections of precast reinforced concrete columns. The main purpose of this study is to determine socket base connection which has the closest behavior to monolithic casted column-base joints. For this purpose, six specimens having different column-socket base connection details were tested under cyclic loading. For each test, strength, stiffness, ductility and drift ratios of the specimens were determined. Test results indicated that a suggested connection type is 10% - 30% stronger than the other type of connections under lateral loading. The welded connection (PC-5) had better lateral load carrying capacity and ductility. On the other hand, performance of standard connection (PC-1) which is commonly used in construction was weaker than other connections. Thus, decision of connection type should be referred not only performance but also applicability.
ON TRIGONOMETRICALLY QUASI-CONVEX FUNCTIONS
( Selim Numan ),( İmdat İşcan ) 호남수학회 2021 호남수학학술지 Vol.43 No.1
In this paper, we introduce and study the concept of trigono-metrically quasi-convex function. We prove Hermite-Hadamard type in- equalities for the newly introduced class of functions and obtain some new Hermite-Hadamard inequalities for functions whose first derivative in absolute value, raised to a certain power which is greater than one, respectively at least one, is trigonometrically quasi-convex convex. We also extend our initial results to functions of several variables. Next, we point out some applications of our results to give estimates for the approximation error of the integral the function in the trapezoidal formula.
Selim Gürgen,Seyid Fehmi Diltemiz,Melih Cemal Kuşhan 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.1
In this study, substrates of 18/10CrNi alloy plates were initially sprayed with a Ni-21Cr-10Al-1Y bond coat and then with an yttria stabilized zirconia top coat by plasma spraying. Subsequently, plasma-sprayed Thermal barrier coatings (TBCs) were treated with two different modification methods, namely, vacuum heat treatment and laser glazing. The effects of modifications on the oxidation and thermal shock behavior of the coatings were evaluated. The effect of coat thickness on the bond strength of the coats was also investigated. Results showed enhancement of the oxidation resistance and thermal shock resistance of TBCs following modifications. Although vacuum heat treatment and laser glazing exhibited comparable results as per oxidation resistance, the former generated the best improvement in the thermal shock resistance of the TBCs. Bond strength also decreased as coat thickness increased.
HAMILTONIAN OF A SECOND ORDER TWO-LAYER EARTH MODEL
Selim, H.H. The Korean Astronomical Society 2007 Journal of The Korean Astronomical Society Vol.40 No.2
This paper deals with the theory for rotational motion of a two-layer Earth model (an inelastic mantle and liquid core) including the dissipation in the mantle-core boundary(CMB) along with tidal effects produced by Moon and Sun. An analytical solution being derived using Hori's perturbation technique at a second order Hamiltonian. Numerical nutation series will be deduced from the theory.
Tuning the Frictional Properties of Carbon Fabrics Using Boron Carbide Particles
Selim Gürgen,Abhijit Majumdar 한국섬유공학회 2019 Fibers and polymers Vol.20 No.4
In recent years, researches have made many efforts to improve the frictional properties of high performance fabricsby using different methods such as applying natural rubber latex, developing metal oxide nano-rods and treating with shearthickening fluids. Even though these methods have provided beneficial results for enhanced frictional behavior, they exhibitsome drawbacks in terms of flexibility, stability and ease of application. For this reason, an attempt has been made in thisresearch to tune the frictional properties of carbon fabric through a simple process such as coating the fabric with boroncarbide particles in polyethylene glycol medium. The surface friction as well as yarn-to-yarn friction were evaluated and itwas found that the presence of only polyethylene glycol (PEG) or the mixture of PEG/boron carbide enhances the surfacefriction and yarn-to-yarn friction in the fabric. In addition, the role of boron carbide concentration used in the treatmentprocess was investigated. It was found that the friction in carbon fabric can be controlled by altering the amount of boroncarbide particles used in the treatment process.