• Journal of the Korean Ceramic Society
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• v.32 no.7
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• pp.817-824
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• 1995

TiB2 was simultaneously synthesized and densified with concurrent self-propagating high-temperature synthesis and direct contact-heating by electrcial power input and pressure. Density of TiB2 synthesized by self-propagating high-temperature synthesis and consolidated simultaneously by direct contact-heating and pressure was maximum 80% of the theoretical density (4.52g/㎤). Temperature profile was analyzed by solving heat balance equation with numerical method (FTCS method). The temperature of the sample was sufficiently raised to that temperature sufficient to be densified. It was ascertained that the density of the SHS synthesized TiB2 is exponentially proportinal to the input thermal energy per mass.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.04a
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• pp.233-240
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• 1997

Seven kinds of hysteric model were used and classified three groups considering the absorbing capacities of strain energy for each model. Four kids of each model. Four kinds of strong motion earthquake record (two of them were recorded in Japan and the others in U.S.A) are used. The yield strength of building was set in the ratio to the maximum input acceleration (Yield Strength / Maximum Acceleration = 0.5~3.0). Natural periods of structures were varied 0.1~3.0 second with an interval of 0.1 second. First group : Elastic-Plastic model, Ramberg-Osgood model Second group : Degrading Tri-liner model, Takeda model Third group : Slip model, Origin model, Max-D model Elastic-plastic response spectra were calculated for response velocities, displacement, energy input, ductility factors, accumulated ductility factors. The equivalent response values of M.D.O.F systems against S.D.O.F system were calculated to compare the relationship of two systems.

• 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.

• Journal of Power Electronics
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• v.14 no.5
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• pp.918-925
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• 2014

This study presents an extended boost single-phase qZ-source DC-AC inverter for a single-phase photovoltaic system. Unlike the previously proposed single-phase qZ-source and semi-qZ-source inverters that achieve the same output voltage as that of the traditional voltage-fed full-bridge inverter, the proposed inverter can obtain higher output than input voltage. The proposed inverter also shares a common ground between DC input voltage and AC output voltage. Thus, possible ground leakage current problem in non-isolated grid-tied inverters can be eliminated with the proposed inverter. A 120 W prototype inverter is built and tested to verify the performance of the proposed inverter.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.4
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• pp.41-46
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• 1983

The current-fed DC-DC converter has only one energy storage reactor in series with the input for any number of outputs and is insensitive to transformer volt-second unbalance. It is considered that these properties of the converter are considerable advantages over other maltiple-output circuits. The steady-state and dynamic characteristic and stability for the current-fed DC-DC con-verter are analyzed in detail. The analysis is carried out by the state-space averaging method for the operation with the duty ratio less than 50% and is confirmed by the experiment. From the evaluation of stability it is identified that the stability of this converter is excellent as compared with that of the conventional buck type converter.

• Structural Engineering and Mechanics
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• v.27 no.2
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• pp.173-197
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• 2007

A wavelet-based procedure to generate artificial accelerograms compatible with a prescribed seismic design spectrum is described. A procedure to perform a baseline correction of the compatible accelerograms is also described. To examine how the frequency content of the modified records evolves with time, they are analyzed in the time and frequency using the wavelet transform. The changes in the strong motion duration and input energy spectrum are also investigated. An alternative way to match the design spectrum, termed the "two-band matching procedure", is proposed with the objective of preserving the non-stationary characteristics of the original record in the modified accelerogram.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.969-970
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• 2007

In this thesis, an algorithm of fault detection and diagnosis during operation for induction motors under the condition of various loads and rates is investigated. For this purpose, the spectrum pattern of input cutterrents was used to monitor the state of induction motors, and by clustering the spectrum pattern of input currents, the newly occurrence of spectrums pattern caused by faults were detected. For diagnosis of the fault detected, the fuzzy fault tree was designed, and the fuzzy relation equation representing the relation between an induction motor fault and each fault type, was solved. The solution of the fuzzy relation equation shows the possibility of each fault's occurring.

• Water Engineering Research
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• v.4 no.1
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• pp.1-17
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• 2003

A mathematical model was developed to simulate the performance of a prototype wind-powered reverse osmosis desalination system. The model consists of two sub-models operated in a series. The first sub-model is the wind-energy conversion sub-model, which has wind energy and feed water as its input and pressurized feed water as its output. The second sub-model is a reverse osmosis (RO) process sub-model, with pressurized feed water as its input and the flow and salinity of the product water or permeate as its output. Model coefficients were determined based on field experiments of a prototype wind powered RO desalination system of the University of Hawaii, from June to December 2001. The mathematical model developed by this study predicts the performance of wind-powered RO desalination systems under different design conditions. The system optimization is achieved using a linear programming approach. Based on the results of system optimization, a design guide is prepared, which can be used by both manufacturer and end-user of the wind-driven reverse osmosis system.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1278-1288
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• 2019

A DC-DC Non-Isolated Three-Port Cuk-Cuk (NI-TPCC) converter for interfacing renewable energy sources (RESs) such as Fuel Cell (FC) and Photovoltaic (PV) energy with a DC load is presented in this paper. It features single-stage power conversion from both of the input ports to the load port. The proposed NI-TPCC converter is designed based on the classical Cuk converter. The operational modes and power flow are analyzed in the continuous conduction mode (CCM), and the relationships among the port voltages are derived. Continuous currents in all three ports with less ripple enhance the performance of a fuel cell and its operating life. Furthermore, the output inductor is shared with both of the input ports, which reduces the number of active and passive components. The effectiveness of the designed NI-TPCC converter has been validated through simulation and experimental results.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.1
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• pp.21-29
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• 2022

Power generated from renewable energy has continuously increased recently. As the distributed generation begins to interconnect in the distribution system, an accurate generation forecasting has become important in efficient distribution planning. This paper explained method and current state of distributed power generation forecasting models. This paper presented selecting input and output variables for the forecasting model. In addition, this paper analyzed input variables and forecasting models that can use as mid-to long-term distributed power generation forecasting.