• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.761-764
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• 2003

Islanding phenomenon of a grid-connected photovoltaic (PV) power conditioning system (PCS) is said to occur if the PCS continues to power a section of the utility system after that section has been disconnected from the utility source. Since islanding creates hazards for personnel and equipment, PCSs are required to detect and prevent Et. In this paper, several islanding detection methods (IDMs) and reactive power variation method are described. Islanding test results for 9kW PCS are presented for verification.

• Economic and Environmental Geology
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• v.27 no.5
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• pp.423-440
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• 1994

The Samhwa iron ore deposit, which is of typical magnetite skarn type, is located in the Samhwadong area of Donghae city, Kangwon-do, Korea. Skarn minerals are mainly composed of garnet, clinopyroxene, vesuvianite, wollastonite and small amounts of epidote and quartz. The garnets are isotropic $(Ad_{92.82{\sim}98.37})$ or anisotropic andradite $(Ad_{45.30{\sim}75.85})$ and grossular $(Gr_{86.26{\sim}24.47})$, the clinopyroxenes are ferrosalite and salite, Homogenization temperature of gas rich two phase inclusions in garnet are $368{\sim}593^{\circ}C$, and salnities of polyphase inclusions in garnet have 33.9~68.4 equ. NaCl wt. %. Garnet grain often shows composional variation from its core to rim. In other words, Fe and Al contents in garnet vary inversely, which suggest that the variation depends upon $f_{o2}$ during skarn formation.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1998.10a
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• pp.150-160
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• 1998

Measuring temperature with ultrasonic wave apparatus is desirable in the case of both below 300$0^{\circ}C$ and ideal gas because of the fact that the temperature of gas is the function of only sound velocity. In this study, being used a heatable wind channel and a blower, the variation of temperature is observed in accordance with diverse flow rate(air velocity). The frequency modulation method is used to measure the temperature which is varying in hot air flow till 10$0^{\circ}C$. The length changed in the position of ultrasonic sensors is considered. Also, the effects of air velocity at the same temperature and various facing angles of ultrasonic sensors are considered. As a result of this study, it has been found that the temperature in gas flow is correctly measured regardless of both the distance of ultrasonic sensors and the variation of air velocity, and that there is just a little influence of facing angles.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1995.11a
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• pp.110-114
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• 1995

This paper is dealing with speed control of Darrieus Wind Turbine, which can be figured out from torque equation. The operating point of Darrieus Wind Turbine can be found from speed-torque curve, which is either stable or instable. The transfer of operating point due to variation of wind speed and generating power is shown in this paper.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.4
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• pp.47-55
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• 1998

A new ignition system concept was developed to improve ignition performance, accuracy of control and the reliability of the ignition system. The new ignition system has ho호 frequency discharge characteristics with 1.5-2.0 ms discharge duration, in place of the usual solitary longer duration event. We applied the system to a commercial engine to study its influence on the maximum combustion pressure attained during the cycle, when this peak pressure occurred, imep, variation rate of the engine speed and the flammability limit of a lean mixture. In this study, we clarified that the new ignition system had a beneficial effect of the lean mixture flammability limit. Also for a given mixture strength we found that the mew ignition system gave a higher peak cylinder pressure than in the case of the conventional ignition system.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.395-398
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• 2005

A novel full-bridge converter with a new energy-recovery driver implemented a regenerative transformer is proposed to improve the efficiency for wide input voltage range and load variation. The main switches achieve ZVS independent of the load current condition. During the free wheeling period, conduction loss is minimized by recovering the circulating energy to the source. The principle of operation, design consideration and experimental result, including efficiency, are presented in the case of large variation of the input voltage or load. A proposed 1kW converter prototype is compared with a PS-FB converter.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.19-20
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• 2018

As energy related problems continue to arise, Korea's thermal insulation market for the zero energy homes is also demanding major changes, but there are no realistic countermeasures. Also, interest in inorganic insulation is growing as damage from multifamily housing fire using flammable insulation materials is increasing. On the other hand, many studies have been conducted on lightweight foam concrete, which implies a sufficient possibility as an insulation material by generating a large amount of air bubbles. However, studies of existion bubble concrete are not quantified by the experimental difficulty of using bubbles when compared. Therefore, in this study, the change in strength due to air pressure using a bubble foam, one of the types of air bubbles for the development of light foam concrete.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.6 no.1
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• pp.29-35
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• 2010

Long-term temperature monitoring has been performed for ground heat exchanger at the Earthquake Research Center (ERC) building in Korea Institute of Geoscience and Mineral Resources (KIGAM). For the 3 years of monitoring, overall temperature increases are observed at various depths within a borehole heat exchanger. But monitoring of ground temperature variation at the monitoring well beforehand showed that geothermal utilization is not the only source for the temperature increase, Because various kinds of sources can cause the ground temperature change, more thorough investigation should be followed.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1994.11a
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• pp.135-140
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• 1994

An improved steam generator model has been developed for the DSNP simulation of normal operational transient behavior of CANDU nuclear power plant. For more realistic prediction of steam generator behavior during transient, tube bundle region is divided into two separate control volumes, subcooled region and saturated region, and the variation of thermal hydraulic properties in the control volume is accounted for more realistic estimates of outlet enthalpy of each control volume. Test results for typical CANDU operational transient case show reasonable transient behavior of steam generator with overall CANDU operation and improved operational characteristics of steam generator with power variation.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.799-809
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• 2020

In this study, the supercavitating flow of a high-velocity moving body near air-water surface is calculated and analyzed based on a commercial CFD software ANSYS Fluent. The effect of regular wave parameters including both wave height and wavelength on the cavitating flow and force characteristics of a body at different velocities is investigated. It is found that the cavity shape, lift coefficient and drag coefficient of the body vary periodically with wave fluctuation, and the variation period is basically consistent with wave period. When the wavelength is much greater than the cavity length, the effect of wave on supercavitation is the alternating effect of axial compression and radial compression. However, when the wavelength varies around the cavity length, the cavity often crosses two adjacent troughs and is compressed periodically by the two wave troughs. With the variation of wavelength, the average area of cavity shows a different trend with the change of wave height.