• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.271-275
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• 2001

In this paper, proposes a novel AC-DC converter of high power factor and high efficiency by partial resonant method. The input current waveform in proposed circuit is got to be a discontinuous sinusoidal form in proportion to magnitude of ac input voltage under the constant duty cycle switching. Thereupon, the input power factor is nearly unity and the control circuit is simple. Also the switching devices in a proposed circuit are operated with soft switching by the partial resonant method. The result is that the switching loss is very low and the efficiency of system is high. The partial resonant circuit makes use of a inductor using step up and $L^2SC$ (Loss-Less Snubber Condenser). The switching control technique of the converter is simplified for switches to drive in constant duty cycle. Some simulative results and experimental results are included to confirm the validity of the analytical results.

• Korean Journal of Exercise Nutrition
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• v.24 no.3
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• pp.19-24
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• 2020

[Purpose] Although physical activity is required to prevent or ameliorate osteoporosis, medicine prescription should precede it, since it may be limited in severe osteoporosis patients. Furthermore, osteoporosis has a great effect on physical activity disorders that accompany fractures and pain, and therefore, research on treatment or prevention to decrease the number of patients is required. The purpose of this study was to discover candidate substances from natural products with an effective pharmacological action and to prepare basic data to help patients. [Methods] To prepare the osteoporosis model, ovariectomy (OVX) was performed using surgical methods. The prepared prescription [Shinkiwhan (SKH), a Korean medicine] was administered orally at a dose of 210 mg/kg/day for 8 weeks. After completion of the animal experiment, the bone mineral density (BMD) was analyzed using double-energy X-ray absorptiometry. The analysis of the effect of drugs on bones was performed using histological analysis and immunostaining. [Results] SKH increased the BMD in the OVX rats. Furthermore, SKH significantly increased the expression of osteoprotegerin and downregulated receptor activator of nuclear factor kappa B ligand and phosphorylation of c-jun N-terminal kinases in the bones of the OVX model. [Conclusion] Our findings suggest a protective effect of SKH against BMD loss in the OVX model.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1353-1355
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• 2003

Total six units of 3kW photovoltaic (PV) system and data acquisition system (DAS) are constructed for analyzing performance of PV system at field demonstration test center of Gwang-Ju in Korea. As climatic and irradiation conditions are varied, operation characteristics of the PV system are collected and analyzed in data-acquisition system. Furthermore, not only performance test of each PV system component such as PV module and power conditioning system, but also performance of total PV system e.g. system efficiency, electric power and loss factor at the site are reviewed.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2003.11a
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• pp.365-367
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• 2003

Total six units of 3㎾ photovoltaic system and data acquisition system (DAS) are constructed for analyzing performance of PV system at field demonstration test center of Gwang-Ju in Korea. As climatic and irradiation conditions are varied. operation characteristics of the PV system are collected and analyzed in data-acquisition system furthermore, not only performance test of each PV system component such as PV module and power conditioning system but also performance of total PV system e.g. system efficiency power and loss factor at the site are reviewed.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.10
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• pp.741-747
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• 1987

The high-power Nd:glass system with five-stage amplifier was designed and its amplification characteristics was studied for developing high-power Nd:glass laser system as an energy driver of inertial confinement fusion(ICF). In order to study the amplification characteristics of remporal and spacial Gaussian laser beam, the dependence of them on pumping efficiency and rod loss were studied and discussed. The output energy of this system using phosphate Nd glass rod(LHG-7,LHG-8) and silicate Nd glass rod(LSG-91H), respectively, was calculated by the computer simulation using Avizonis-Grotbeck and Frantz Nodvik equations. As results of this simulation, it was found that the shorter the risetime of laser pulse, the larger the amplification factor and that the larger peak value of laser pulse, the lower the amplification factor. The output inergies of 179J, 344J, and 7J were obtained by the designed five-stage amplified high-power Nd:glass laser system using glass rods of LHG-7,LHG-8, and LSG-91H, respectively. From the results it was found that the laser system using the LHG-8 glass rod was the most excellent one among the systems and the cross section for stimulated emission of the gain coefficient was essentially important parameter for the amplification characteristics.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.569-575
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• 2014

A highly efficient class E power amplifier is demonstrated for application to wireless power transfer system. The amplifier is designed with an L-type matching at the output for harmonic rejection and output matching. The power loss and the effect of each component in the amplifier with the matching circuit are analyzed with the current ratio transmitted to the output load. Inductors with a quality factor of more than 120 are used in a dc feed and the matching circuit to improve transmission efficiency. The single-ended amplifier with 20 V supply voltage shows 7.7 W output power and 90.8% power added efficiency at 6.78 MHz. The wireless power transfer (WPT) system with the amplifier shows 5.4 W transmitted power and 82.3% overall efficiency. The analysis and measurements show that high-Q inductors are required for the amplifier design to realize highly efficient WPT system.

• Nuclear Engineering and Technology
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• v.37 no.4
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• pp.375-384
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• 2005

To investigate the flow-accelerated corrosion (FAC) dependency of carbon steel (A106 Gr. B) and low-alloy steels (1Cr-1/2Mo, 21/4Cr-1Mo) on pH, orifice distance, and material, experiments were carried out. These experiments were performed using a flow velocity of 4 m/sec (partly 9 m/sec) at pH $8.0\~10.0$ in an oxygen-free aqueous solution re-circulated in an Erosion-Corrosion Test Loop at $130^{\circ}\;{\ldots}$ for 500 hours. The weight loss of the carbon steel specimens appeared to be positively dependent on the flow velocity. That of the carbon and low-alloy steel specimens also showed to be distinguishably dependent on the pH. At pH levels of $8.0\~9.5$ it decreased, but increased from 9.5 to 10.0. Utility water chemistry personnel should carefully consider this kind of pH dependency to control the water system pH to mitigate FAC of the piping system material. The weight loss of the specimens located further from the orifice in the distance range of $6.8\~27.2$ mm was shown to be greater, except for 21/4Cr-1Mo, which showed no orifice distance dependency. Low alloy steel specimens exhibited a factor of two times better resistance to FAC than that of the carbon steel. Based on this kind of FAC dependency of the carbon and low-alloy steels on the orifice distance and material, we conclude that it is necessary to alternate the composition of the secondary piping system material of NPPs, using low-alloy steels, such as 21/4Cr-1Mo, particularly when the system piping has to be replaced.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.707-710
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• 2003

3kW grid-connected photovoltaic (PV) system and data acquisition system are constructed for performance analysis of PV system at field demonstration test center of Gwang-Ju in Korea. As climatic and irradiation conditions are varied, operation characteristics of the PV system are collected and analyzed in data acquisition system. From these results, the performances of PV system have simulated and evaluated using simulation tool in comparison with actual value of data acquisition system of field demonstration test center. Furthermore, performance of total PV system e.g. electric power and loss factor at the site are reviewed.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.4
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• pp.307-314
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• 1998

A novel high power factor Dual Half Bridge Series Resonant Inverter (DHB-SRI) for an induction heating appliance with multiple loads is proposed to remove the interferential acoustic noise caused by the difference between operating frequencies of adjacent loads. The circuit enables independent full power range control of two induction heating elements by one inverter circuit and has minimum switching losses due to the zero voltage switching characteristic. According to the mode analysis, I will explain the operation of the proposed circuit. To evaluate the required cooling capacity, loss analysis is performed through deriving some loss equations. In order to obtain the power factor correction capability and to lessen the system size, suitable design guides are given. Using the designed values, the proto-type circuit with 2.8kW power consumption for each induction heating element is built and tested to verify the operation of the proposed circuit.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1376-1382
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• 2009

Railway system is a word that includes rolling stock, railway infrastructure and signalling System in passenger transfer and rail freight. This system get higher competitiveness in energy efficiency part than other transfer system. But it is comprehensive system has latent loss of lives and property by big accident. First of all, to control this comprehensive system and to confirm safety of it, we need human resource management. This research will suggest how to apply efficiency safety verification and certification system to railway system. human resource management systems is defined as three kinds that is recruitment and management, ensure personnel's competencies and fitness, activity of assigning suitable responsible person for work.