• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.12
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• pp.670-677
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• 2004

The Conventional approach for estimating the locations of transmission line shunt faults has been to measure the apparent impedance to the fault from a line terminal and to convert the reactive component of the impedance to line length. But, these methods do not adequately address the problems associated with the fault location on distribution systems. This thesis presents a technique that estimates the location of shunt fault on a radial distribution system that has several single and multiphase laterals. Tapped loads and non-homogenity of the distribution system are take into account. The developed technique, which can handle shunt faults was tested to evaluate its suitability. Results from computer simulation of faults on a model of a 25KV distribution lines like real system are presented. The results approved that the proposed technique works well for estimating the locations of the distribution line shunt faults.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.431-432
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• 2006

In this study, the effect of the temperature of magnesium slurry was investigated by mechanical stirring method. The evaluations of rheological behavior of AM50A magnesium alloy were measuring of viscosity and microstructures in the semisolid state. The apparent viscosity was investigated at continuous cooling rate using a concentric cylinder viscometer. Measurement of viscosity measures torque that act to stirrer rotating in slurry doing continuous cooling using torque-meter and expressed by POWER-LAW. Microstructures were observed after mechanical stirring that enforce time at steady state temperature of solid fraction.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.70-73
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• 2002

Using a simple compression test, the viscosity measurement experiment is carried out with the grain-refined Al-Si alloy(A356). The measured rheological data are expressed with power-law(Ostwald-de Waele) model and using commercial package, MAGMAsoft, coefficients of Ostwald-de Waele model and Carreau-Yasuda model are calculated. To verify the viscosity data, the die is designed to be applicable to the semi-solid die casting of automotive component and filling test is carried out. The filling test and the simulation result are compared and in good agreement. Hereafter, these data are considered to be usefully allied other product in the semi-solid die casting.

• Journal of Biosystems Engineering
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• v.17 no.1
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• pp.5-17
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• 1992

To develop an analytic method of combustion characteristics in a small sized and single cylinder type diesel engine for a power tiller, 1) the theoritical analysis of combustion gas in engine cylinder was performed based on thermoscience and 2) the computer program which could be used to calculate those values of the apparent burning rate, the heat loss, the gas temperature and the fuel-air equivalence ratio with the experimental cylinder pressure data, was developed. This method would provide the practical and quantative data for the diesel combustion process. Through the use of this method, following details would be obtained: 1) the application in the modeling of combustion process without detail knowledeg of combustion process, 2) the basis for the complete modeling of diesel engine, and 3) the basic information for the design of combustion chamber by the prediction of engine performance.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.349-356
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• 1997

The purpose of this study is to evaluate the effect of curing conditions on adhesion in tension of polymer-modified mortar to cement mortar substrate in comparision with ordinary cement mortar. The polymer-modifies mortars using two polymer dispersions and a redispersible polymer power are prepared with various polymer-cement ratios, and tested for the adhesion in tension of the specimens subjected to five curing conditions. From the test results, the adhesion in tension of polymer-modified mortars tends to increase with increasing polymer-cement ratio irrespective of the polymer types and curing conditions. It is apparent that adhesion in tension of polymer-modified mortars is considerably influenced by curing conditions.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.1
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• pp.1-5
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• 2000

Physicochemical properties and gelatinization patterns of purple-fleshed sweet potato starch were studied. Shape of starch granule was round and polygonal, X-ray diffraction pattern was Ca-type. Amylose content was 14.4% which was lower than that of other sweet potato starch. Water binding capacity was 82.54%, swelling power and solubility at 8$0^{\circ}C$ were 27.94% and 15.35%, respectively. Initial temperature of gelatinization was 72$^{\circ}C$ using Brabender/Visco/Amylograph, consistency and setback were lower than those of other sweet potato starch. The peak temperature and enthalpy determined by DSC were 68.1$^{\circ}C$, 1.24cal/g, respectively. The transmittance of starch dispersions in alkaline solutions increased with NaOH concentration up to 0.17N, and then changed slowly at 0.19N or above. The apparent viscosities were similar to the transmittance of starch dispersions in alkaline solutions, but drastically increased above 0.21N.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.281-284
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• 2003

Multi-code CDMA is an appropriate scheme for transmitting high rate data. However, dynamic range of the signal is large, and power amplifier with good linearity is required. Code select CDMA (CS/CDMA) is a variation of multi-code CDMA scheme that ensures constant amplitude transmission. In CS/CDMA input data selects multiple orthogonal codes, and sum of these selected codes are MPSK modulated to convert multi-level symbol into different carrier phases. CS/CDMA system employs level clipping to limit the number of levels at the output symbol to avoid hish density of signal constellation. In our previous work we showed that by encoding input data of CS/CDMA amplitude of the output symbol can be made constant. With this coding scheme, level clipping is not necessary and the output signal can be BPSK modulated for transmission. In this paper we show that the constant amplitude coded(CA-) CS/CDMA transmitter can be implemented using only logic gates, and the hardware complexity is very low. In the proposed transmitter architecture there is no apparent redundant encoder block which plays a major role in the constant amplitude coded CS/CDMA.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.7
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• pp.1050-1060
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• 1994

This paper is a study on the computer simulation of the characteristics of the superconducting fault current limiter. Input variable parameters are apparent power, load resistance value, line resistance value and so on. Initial fault current 2 times larger than the trigger current is required to reduce the switching time of SFCL. The propagation velocity increases abruptly, the transport current is several times larger than the ciritical current. In this paper, the switching time is calculated to be 323$\mu$ sec, and the initial fault current is 19 times larger than the critical current. Because the trigger coils are bifilar winding, they have little impedance in superconducting state. After fault occurred, the limiting coil acts as a superconducting reactor and the trigger coils quench at a critical current. Without the SFCL in the circuit, fault current after the load impedence is shorted might be increased to 1100A. The fault current is, therefore, successfully limited by the superconducting limiting coil to 100A determined by the coil inductance.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.377-386
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• 2000

Hybrid mass dampers consist of passive tuned mass dampers and active mass dampers. They have the advantage that passive tuned mass dampers are still operated even when active mass dampers are stopped by excessive disturbances or power failure. This paper begins first with the comparative analysis of tuned mass dampers, hybrid mass dampers, and active mass dampers. Next more detailed study is carried out on the hybrid mass dampers: cascade hybrid mass dampers (CHMD) and active tuned mass dampers (ATMD). CHMD is regarded as more reasonable device because of its lighter active mass than ATMD's. However CHMD can not neglect stroke saturation problem caused by the length limitation of active damper mass. We compensate the saturation problem with nonlinear restoring force. The restoring force is calculated based on the states and phases of active mass dampers and added to the control force. It is shown that the presented compensation method prevents CHMD from saturation behavior without apparent changes of control force and responses compared to those in case of not considering the saturation problem.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.05a
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• pp.15-20
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• 1999

In this study, the effects of the maximum grit depth of cut on the grinding characteristics were investigated. And AE signals produced during grinding processes have been studied to find out the appropriate AE parameters for assessing grinding processes. S45C steel has been ground under the conditions yielding removal rate of workpiece, 100, 200, 300 and 400rnm$^3$/min which was achived by altering workpiece velocity($\upsilon$) and apparent depth of cut(Z). According to the experimental results, the value of surface roughness increases but grinding power, energy rate of AE signal(AErms$^2$) and specific grinding energy consumed decrease with increase of the maximum grit depth of cut.