• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.8
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• pp.1571-1577
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• 1994

This paper is designed and implemented mixer of 12GHz/14GHz as up-conversion. Observation that harmonics and intermodulation power level varied by two signal power level and bias obtained operation points of mixer. Finally, optimum operation points shows that $P_{RF}$(radio signal frequency power level). $P_{LO}$(local oscillation power level) is below -30[dBm], -2[dBm] respectively. Simultaneously $V_{DS}$ is 2.7[V]and $V_{GS}$ is -0.2[V].

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1207-1208
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• 2006

Recently, a fuel cell with low voltage and high current output characteristics is remarkable for new generation system. It needs both a DC-DC step-up converter and DC-AC inverter to be used in fuel cell generation system. Therefor, this paper, consists of an isolated DC-DC converter to boost the fuel cell voltage 380[VDC] and a PWM inverter with LC filter to convent the DC voltage to single-phase 220[VAC]. Expressly, a tapped inductor filter with freewheeling diode is newly implemented in the output filter of the proposed high frequency isolated ZVZCS PWM DC-DC converter to suppress circulating current under the wide output voltage regulation range, thus to eliminate the switching and transformer turn-on/off over-short voltage or transient phenomena. Besides the efficiency of 93-97[%] is obtained over the wide output voltage regulation ranges and load variations.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1148-1150
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• 2003

Power conversion system must be increased switching frequency in order to achieve a small size, a light weight and a low noise. However, the switches of converter are subjected to high switching power losses and switching stresses. As a result of those, the power system brings on a low efficiency. To improved these, a large number of soft switching topologies included a resonant circuit has been prosed. But these circuits increase number of switch in circuit and complicate sequence of switching operation. In this paper, the authors propose a high power factor and high efficiency DC-DC converter using single-pulse soft switching by partial resonant switching node. The switching devices in a prosed circuit are operated with soft switching by the partial resonant method, that is, Partial Resonant Switch Mode Power Converter. The partial resonant circuit makes use of a inductor using step up and a condenser of loss-less snubber. The result is that the switching loss is very low and the efficiency of system is high. Also the proposed converter is deemed the most suitable for high power applications where the power switching devices are used. Some simulative results on computer results are included to confirm the validity of the analytical results.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.05a
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• pp.336-339
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• 2009

In this paper, such as battery power or solar energy and fuel cells generated from Renewable energy sources, high voltage to low voltage DC-DC Converter for converting the design of the study. System consists of low voltage ($24{\sim}28$ [VDC]) and Boosts the voltage (270 [VDC]) for a 3 [kW] DC-DC converter and control circuit is configured as, Power switch the ST Tomson's Automotive low voltage high current MOSFET switches STE250NS10S (temperature 250A) was applied to the two parallel. Also, Controller's processor used ATMEGA128, and Gate Drive applies and composed Photo Coupler TLP250. development. Input voltage (24V) and output voltage (270V) for Conversion in the H-bridge converter topology of the circuit output side power and voltage to control the implementation of the Phase shift angle control applied. And, 3kW of power to pass appropriate specification of the secondary side as interpreted by the high frequency transformer, and the experimental production and analysis of the experiment

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.8
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• pp.54-61
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• 1999

This paper proposes a new optic link structure applicable to broad-band wireless access microcellularsystem servicing in the millimeter wave frequency band. The proposed structure utilizes photonic mixing by exploiting the nonlinear property of EOMs, which leads to the frequency up-conversion at the CS and thus, electrical mixing at a BS is not required. Moreover, via transmitting an additional optical millimeter wave carrier into the Bs, the dispenses with an active optic source, which miniaturizes the BS. We analyze CNR, IM3/C in the downlink and SFDR in the uplink. Through simulation using the typical parameter values we also show the feasibility of the proposed system based on the requirements in the current microcellular system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.2
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• pp.54-63
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• 2007

Recently, a fuel cell with low voltage and high current output characteristics is remarkable for new generation system. It needs both a DC-DC step-up converter and DC-AC inverter to be used in fuel cell generation system. Therefor, this paper, consists of an isolated DC-DC converter to boost the fuel cell voltage $380[V_{DC}]$ and a PWM inverter with LC filter to convent the DC voltage to single-phase $220[V_{AC}]$. Expressly, a tapped inductor filter with freewheeling diode is newly implemented in the output filter of the proposed high frequency isolated ZVZCS PWM DC-DC converter to suppress circulating current under the wide output voltage regulation range, thus to eliminate the switching and transformer turn-on/off over-short voltage or transient phenomena. Besides the efficiency of 93-97[%]is obtained over the wide output voltage regulation ranges and load variations.

• Journal of Advanced Navigation Technology
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• v.28 no.2
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• pp.193-200
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• 2024

This paper describes the design and development of a transmit receiver module(TRM) for mounting on X-band SAR of the NEXTSat-2. The TRM generates the chirp signal with required bandwidth through the DDS in X-band and performs frequency conversion, combination for the signal to transmit and be received and frequency synthesis. Tx path of the TRM produces signals of total 28 bandwidths up to 96.8 MHz and has output signal level of more than + 9.37 dBm. Rx path of the TRM has minimum noise figure of 15.7 dB. The measurement results show that required requirements are satisfied. The TRM is installed on the NEXTSat-2 flight model(FM), launched by KSLV-II(Nuri) on May 23, 2023 and currently operational.

• The Journal of the Acoustical Society of Korea
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• v.37 no.4
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• pp.215-222
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• 2018

This paper reports the development and performance evaluation of a backend system for real-time IVUS (Intravascular Ultrasound) imaging. The developed backend system was designed to minimize the amount of logic and memory usage by means of efficient LUTs (Look-up Tables), and it was implemented in a single FPGA (Field Programmable Gate Array) without using external memory. This makes it possible to implement the backend system that is less expensive, smaller, and lighter. The accuracy of the backend system implemented was evaluated by comparing the output of the FPGA with the result computed using a MATLAB program implemented in the same way as the VHDL (VHSIC Hardware Description Language) code. Based on the result of ex-vivo experiment using rabbit artery, the developed backend system was found to be suitable for real-time intravascular ultrasound imaging.

• Journal of Preventive Medicine and Public Health
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• v.19 no.2 s.20
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• pp.281-292
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• 1986

Infection by hepatitis B virus is one of the major health problems of this nation. HBsAg positive rates of general population and school children were known to be as about 8 percent and 3.9 to 5.9 percent respectively. To study the incidence rate of hepatitis B infection in school children of rural area, author had examined 475 school children of relatively isolated agricultural area for baseline prevalence of hepatitis B virus serologic markers and followed up 415 school children during 10 months to determined the frequency of serologic conversion. The major results are summarized as followings: 1) Among the 278 susceptible children who were followed up, 26 had seroconversion for HBsAg or Anti-HBs. Therefore, the cumulative incidence rate during 10 months is estimated 9.4%. 2) The incidence rate of hepatitis B infection tends to increase with age (6-9yrs: 3.2%, 10-14yrs: 9.5%, 15-17yrs: 18.9%), and the incidence rate in male (13.0%) was higher than in female (5.7%). 3) The incidence rates of hepatitis B virus infection were not different statistically among three economic classes (The rates of lower, middle and higher class were 11.8%, 7.1% and 10.5%.). 4) The incidence rates of hepatitis B virus infection were not different statistically between visitors and non-visitors of clinic or hospital, dental clinic, persons received IV and not received IV, and persons with familial history and without familial history of liver diseases. Therefore all of these factors were not identified as risk factor of hepatitis B virus infection. And the transmissibility within the class of school was not recognized, too. 5) Among the 25 children who were HBsAg positive when enrolled, 15 (60%) were still HBsAg positive, who were identified as chronic carrier 15 of 415 school children were chronic carriers, then chronic carrier rate was estimated 3.6%, and there was no difference between sexes. 6) Of 38 children who had been Anti-HBs positive when enrolled, 5 (13.2%) lost Anti-HBs. Therefore, the loss rate of Anti-HBs per year is estimated to be 15.8%.

• Resources Recycling
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• v.23 no.6
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• pp.40-46
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• 2014

Through the study of the basic characteristics of cow manure and the characteristics of carbonization residue, carbonization degree, conversion rate, kinetic reactions, and activation energy for cow manure were examined. Since the heating value of cow manure was very low, it was converted to carbonization residue as a fuel with heating value of 4,300 kcal/kg by carbonization processes. Conversion rate was increased rapidly up to 10 minutes of the initial reaction stage and was increased with increasing temperature. The carbonization of cow manure could be described by the 1st order reaction. Frequency factor(A) of reaction rate for cow manure was evaluated to be $1.34{\times}10^{-2}min^{-1}$, the activation energy was estimated to be 5,196.4 cal/mol. As carbonization temperature increased from $250^{\circ}C$ to $400^{\circ}C$, the kinetic reaction was increased from $0.2107min^{-1}$ to $0.0679min^{-1}$. From the result of the carbonization for cow manure, it can be determined that the optimal conditions of the carbonization process were 20 minutes in carbonization time and $350^{\circ}C$ for carbonization temperature.