http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
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.
Surface Modification of Magnetites Using Maltotrionic Acid and Folic Acid for Molecular Imaging
Selim, K.M.Kamruzzaman,Lee, Joo-Hee,Kim, Sun-Jung,Xing, Zhicai,Kang, Inn-Kyu,Chang, Yong-Min,Guo, Haiqing The Polymer Society of Korea 2006 Macromolecular Research Vol.14 No.6
Highly hydrophilic, uniform, superparamagnetic and nontoxic maltotrionic acid (MA)-coated magnetite nano-particles (MAM) were prepared and characterized by TEM, DLS, XRD and VSM. MA was used to improve the biocompatibility, monodispersity and non-specific intracellular uptake of nanoparticles. Folic acid (FA) was subsequently conjugated to the MAM to preferentially target KB cells (cancer cells) that have folate receptors expressed on their surfaces and to facilitate nanoparticles in their transit across the cell membrane. Finally, fluorescence isothiocyanate (FITC) was added to the nanoparticles to visualize the nanoparticle internalization into KB cells. After the cells were cultured in a media containing the MAM and MAM-folate conjugate (FAMAM), the results of fluorescence and confocal microscopy showed that both types of nanoparticles were internalized into the cells. Nevertheless, the amount of FAMAM uptake was higher than that of MAM. This result indicated that nanoparticles modified with MA and FA could be used to facilitate the nanoparticle uptake to specific KB cells (cancer cells) for molecular imaging.
Selim, Mahmoud M.,Althobaiti, Saad,Yahia, I.S.,Mohammed, Ibtisam M.O.,Hussin, Amira M.,Mohamed, Abdel-Baset A. Techno-Press 2022 Advances in nano research Vol.12 No.5
The present work is an attempt to study the vibration analysis of the single-walled carbon nanotubes (SWCNTs) under the effect of the surface irregularity using Donnell's model. The surface irregularity represented by the parabolic form. According to Donnell's model and three-dimensional elasticity theory, a novel governing equations and its solution are derived and matched with the case of no irregularity effects. To understand the reaction of the nanotube to the irregularity effects in terms of natural frequency, the numerical calculations are done. The results obtained could provide a better representation of the vibration behavior of an irregular single-walled carbon nanotube, where the aspect ratio (L/d) and surface irregularity all have a significant impact on the natural frequency of vibrating SWCNTs. Furthermore, the findings of surface irregularity effects on vibration SWCNT can be utilized to forecast and prevent the phenomena of resonance of single-walled carbon nanotubes.
Curing effect on mortar properties produced with styrene-butadiene rubber
Selim Cemalgil,Serkan Etli,Onur Onat 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.21 No.6
This paper presents an experimentally investigation pertinent to the mechanical properties of rubberized mortar (RM) with styrene-butadiene rubber (SBR). The SBR were used with constant water-to-cement ratio of 0.485 and two different volume proportion of SBR particles were utilized as aggregates. One types of SBR particles with fineness modulus of 4.951 were utilized 0%, 10%, and 20% of aggregate volume. Effectiveness of SBR replacement ratio, curing and aging effect on the compressive strength, flexural strengths as well as load-displacement. Compressive and flexural strength of concrete were investigated at the end of 28-days and 56-days age. Obtained results demonstrated that utilization of SBR reduced the flexural strength of SBR mortar at the earlier curing age while SBR increased. Moreover, mechanical properties of mortar mentioned above were significantly affected by the water cure timing with an increasing proportion of the replacement level of SBR.
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.
The effect of carbide particle additives on rheology of shear thickening fluids
Selim Gürgen,Melih Cemal Kuşhan,Weihua Li 한국유변학회 2016 Korea-Australia rheology journal Vol.28 No.2
In this paper, shear thickening fluids (STFs) including silicon carbide particles are presented. We fabricated a kind of STF based on nanosize fumed silica suspended in a liquid medium, polyethylene glycol, at a constant concentration of 20 wt.%. Then, different particle size silicon carbide (SiC) particles were added to the STF with various amounts. Their rheological properties under various temperatures were tested by using a rheometer. The suspension exhibits different systematic variations with respect to the varied parameters.
Selim Kim,Jungil Hong 한국식품영양과학회 2021 한국식품영양과학회 학술대회발표집 Vol.2021 No.10
Riboflavin (Rb) and its biotransformed metabolites including flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) have an isoalloxazine ring as a common photoactive moiety. In this study, photostability and photosensitizing properties of Rb, FMN, and FAD were evaluated under different LEDs (Blue, red, green, white) and a regular fluorescent light. Among the derivatives, FAD was most stable under irradiation of all types of light. Among the lights irradiated, Blue LED induced most rapid degradation of the derivatives; their half-lives of Rb, FMN, and FAD at 50 μg/mL under 50 lx Blue LED were 1.28, 0.40, and 4.99 h, respectively. The derivatives were stable under Red LED up to 24 h (2000 lx). Blue LED induced the strongest photosensitizing activities of all Rb derivatives. Enhancement of DCF fluorescence by FMN was most pronounced under light, indicating that ROS generation due to its photosensitizing activity was most prominent. These results indicate that the Rb derivatives were unstable under various lights showing photosensitizing properties, and these characteristics should be considered when exposed to light.