• Journal of the Semiconductor & Display Technology
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• v.19 no.4
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• pp.99-104
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• 2020

In this paper, efficiency and loss characteristics of GaN FET were reported by applying it into the QR flyback converter. In particular, for the comparison of efficiency characteristics, QR flyback converter experimental circuits with Si FET and with GaN FET were separately produced in 12W class. As a result of the experiment, the experimental circuit of the QR flyback converter using GaN FET reached a high efficiency of 90% or more when the load power was 2W or more, and the maximum efficiency was observed to be about 92%, and the maximum loss power was about 1.1W. Meanwhile, the efficiency of the experimental circuit with Si FET increased as the input voltage increased, and the maximum efficiency was observed to be about 82% when the load power was 9W or higher, and the maximum loss power was about 2.8W. From the results, it is estimated that that in the case of the experimental circuit applying the GaN FET switch, the power conversion efficiency was improved as the switching loss and conduction loss due to on-resistance were reduced, and the internal loss due to the synchronous rectifier was minimized. Consequently, it is concluded that the GaN FET is suitable for under 20W class power supply unit as a high efficiency power switch.

• Korea Trade Review
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• v.47 no.6
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• pp.135-171
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• 2022

This study is to find out how psychological characteristics and management capabilities of small manufacturers influence business performance through parameters including self-efficiency, network, and collaboration strategies. The survey was implemented between December 26, 2017 and January 15, 2018. The final 439 valid questionnaires were collected and used for analysis. The results were followed. First, the relationship between psychological characteristics and self-efficiency, and the path coefficient for psychological characteristics and network were significant. Second, management capabilities was related to self-efficiency, and the path factor for managing capability and network relationships was significant. Lastly, the path coefficients for self-efficiency and collaboration strategies were not significant, and the path coefficients for network and collaboration strategies were significant.

• Journal of Information Display
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• v.9 no.3
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• pp.28-32
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• 2008

Low sustained voltage $(V_s)$ and high luminous efficiency (lumen/Watts) are required for the enhanced performance of an AC PDP. Both are not realized in the same condition, however, because luminous efficiency decreases when the sustained voltage is lowered in most cases. In this study, the three design factors in the front panel of a PDP, i.e., the thickness and position of the bus electrode and the thickness of the dielectric layer, were chosen to investigate how they affect the sustained voltage and the luminous efficiency, and to find a way to optimize them. Two values were given to each of the three design factors, and experiments were done via full factorial design, i.e., with a total of eight conditions, using a 3-in.diagonal test panel. The changes in the sustained voltage and the luminous characteristics were explained in connection with the discharge characteristics of the PDP cells.

• International journal of advanced smart convergence
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• v.9 no.3
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• pp.9-16
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• 2020

In this paper, we designed a soft switched synchronous boost converter, which can perform discharging the battery, is simulated, and experimented designed. The converter operates synchronous operation to increase efficiency of the converter. The converter has very small switching losses because of its soft switching characteristics. In this paper, battery discharger with a switching frequency of 100 kHz have been designed. The designed converter also simulated and experimented to prove the converter's characteristics during synchronous operation. The simulated and experimental results have confirmed that the battery discharger had soft switching characteristics. In addition, the experimental results confirm that the converter has high efficiency characteristics. The efficiency of the circuit exceeds 97%, the efficiency of soft switched synchronous boost converter is at least 6% higher than that of conventional PWM boost converter.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.3
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• pp.398-404
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• 1999

The EGR is needed for one of various strategies to reduce NOx emission. But to get the proper EGR rate the intake and exhaust system become complicated. That is a reason why we consider using the built0in EGR system. The built-in EGR is a system which reduces Nox by controling the residual gas fraction in cylinder by changing valve timing and valve lift of intake and exhaust. In this paper characteristics of volumetric efficiency and residual gas fraction in cylinder were investigated for various engine speeds by changing valve timing and valve lift of intake and exhaust. In this paper characteristics of volumetric efficiency and residual gas fraction in cylinder were investigated for various engine speeds by changing valve timing and valve lift of intake and exhaust in the 4 stroke-cycle diesel engine. Volumetric efficiency and residual gas fraction were calculated by the method of characteristics. As the results the possibility of suing the built-in EGR system was confirmed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.8
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• pp.671-675
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• 2002

The gas adsorption efficiency for various surfaces with three different characteristics has been reviewed. The dimethyl disulfide gas has been used to investigate characteristics of gas adsorption for different surface characteristics such as plasma treated, lacquer coated and untreated. Three different surfaces were evaluated in dry conditions initially and tested at wet surface conditions with spraying water to evaluate the gas adsorption efficiency which usually occurred at defrost cycles. The results show that the gas adsorption of the plasma treated sample has better performance than others. The lacquer coated and untreated samples showed the similar result, but the lacquer coated sample showed a slightly better performance.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.7
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• pp.181-186
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• 1999

The objective of present work is to investigate the performance characteristics of three-lobe Roots type supercharger for the applications of low-compression and high-expansion ration gasoline engine. A performance test was conducted to obtain the drive power, volumetric efficiency, adiabatic efficiency and the influence of performance factors of supercharger . In order to analyze the supercharging characteristics, the experiments are made on operating parameters such as the supercharger speed, pressure ration and inlet temperature on the supercharging performance of the Roots type supercharger . Based on experimental results, the drive power and flow rate of supercharger increased with supercharger speed.

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.3
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• pp.53-57
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• 2001

The organic light-emitting devices (OLEDs) based on fluorescence have low efficiency due to the requirement of spin-symmetry conservation. By using the phosphorescent material, internal quantum efficiency can reach 100%, compared with 25% in the case of the fluorescent material. Thus, phosphorescent OLEDs have recently been extensively studied and shown higher internal quantum efficiency than the conventional OLEDs. In this study, we investigated the characteristics of the phosphorescent OLEDs with the green emitting phosphor, $Ir(ppy)_3$ (tris(2-phenylpyridine)iridium). The device with a structure of ITO/TPD$Ir(ppy)_3$ doped in BCP/BCP/$Alq_3$/Li:Al/Al was fabricated, and its electrical and optical characteristics were studied. By changing the doping concentration of $Ir(ppy)_3$, we fabricated several devices and investigated their characteristics.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.132-138
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• 2000

Complex gear shifting and high speed-reduction ratio reduce the transmission efficiency in power driveline of agricultural tractors. According to a field test, the power transmission efficiency of a tractor in transporting operations was estimated about 70%. However, the actual efficiency was found by the experiment to fluctuate in a range of 56 to 87%. Therefore, the constant efficiency model commonly used for a simulation of power drivelines is not likely to simulate its performance more accurately. In order to predict power transmission efficiency more accurately, a new model was proposed and the new concepts of the maximum efficiency and sticking torque were introduced. The error mean between the measured and the predicted efficiencies was about 2.3% in mean. The new model reflecting the transmission characteristics in the power driveline of tractors could be used to analyze and predict the power transmission performance of tractors more accurately.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.5
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• pp.82-88
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• 2001

The EGR is needed fur one of various strategies to reduce NOx emission. But to get the proper EGR rate, the intake and exhaust system become complicated. That is a reason why we consider using the internal EGR system. The internal EGR is a system which reduces NOx by controling the residual gas fraction in cylinder by changing valve timing and valve lift of intake and exhaust. In this paper, characteristics of volumetric efficiency and residual gas fraction in cylinder were investigated for various engine speeds by changing valve timing and valve lift of intake and exhaust in the 4 stroke-cycle diesel engine. Volumetric efficiency and residual gas fraction were calculated by the method of characteristics. As the results, residual gas fraction and volumetric efficiency in cylinder by variable valve timing were visualized.