• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.314-317
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• 1991

The waveforms of high voltage and current pulse were measured using laser measuring systems. Existing potential transformer and current transformer have low measuring precision because of resonance phenomena and waveform distortion due to the magnetic saturation. But using laser measurement, it is possible to obtain clear waveforms which have no effect of distortion and harmonic resonances. And electromagnetic interferences (EMI) in the measuring of high voltage and current pulse, but the optical measuring systems are not subjet to the influence of EMI. Using laser measuring systems based upon Pockels effect and Faraday effect is not free from any errors yet, but it could replace existing measuring systems by routine experiments and error corrections. And it needs that more research and development of optical crystals and equipments would be taken.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.162-162
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• 2015

본 연구는 환경 및 인체에 유해한 포르말린을 사용하지 않은 무전해 동 도금액을 개발한 후 도금액을 전자파 차폐 섬유도금에 적용하기 위해 도금 조건에 따른 특성을 파악하였다. 본 연구에서는 무전해 동 도금액의 온도, pH, Bath loading, 도금시간을 변화시켜 도금액의 도금속도 및 도금피막의 형상을 관찰하였으며, 전자파 차폐를 위한 섬유에 개발된 도금액을 적용하고자 현재 상용 전처리 공정을 통해 도금실험을 수행하였다. 여러 도금조건을 변화하여 실험한 결과 $50^{\circ}C$의 도금액 온도, 12.8~13.5의 pH 조건에서 현재 사용 중인 포르말린 도금액과 유사하거나 더 우수한 도금속도를 나타내었으며 현재 사용중인 도금액의 대체가 가능할 것으로 판단되었다.

• Journal of Power Electronics
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• v.11 no.3
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• pp.256-263
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• 2011

This paper utilizes free oscillation and energy injection principles to generate and control the high frequency current in the primary track of a contactless power transfer system. Here the primary power inverter maintains natural resonance while ensuring near constant current magnitude in the primary track as required for multiple independent loads. Such energy injection controllers exhibit low switching frequency and achieve ZCS (Zero Current Switching) by detecting the high frequency current, thus the switching stress, power losses and EMI of the inverter are low. An example full bridge topology is investigated for a contactless power transfer system with multiple pickups. Theoretical analysis, simulation and experimental results show that the proposed system has a fast and smooth start-up transient response. The output track current is fully controllable with a sufficiently good waveform for contactless power transfer applications.

• Journal of Power Electronics
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• v.17 no.3
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• pp.590-600
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• 2017

This paper presents a ripple-free input current modified interleaved boost converter for high step-up applications. By integrating dual coupled inductors and voltage multiplier techniques, the proposed converter can reach a high step-up gain without an extremely high turn-ON period. In addition, a very small auxiliary inductor employed in series to the input dc source makes the input current ripple theoretically decreased to zero, which simplifies the design of the electromagnetic interference (EMI) filter. In addition, the voltage stresses on the semiconductor devices of the proposed converter are efficiently reduced, which makes high performance MOSFETs with low voltage rated and low resistance $r_{DS}$(ON) available to reduce the cost and conduction loss. The operating principles and steady-state analyses of the proposed converter are introduced in detail. Finally, a prototype circuit rated at 400W with a 42-50V input voltage and a 400V output voltage is built and tested to verify the effectiveness of theoretical analysis. Experimental results show that an efficiency of 95.3% can be achieved.

• Mycobiology
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• v.47 no.2
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• pp.217-229
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• 2019

Two manganese peroxidases (MnPs), MnP1 and MnP2, and a laccase, Lac1, were purified from Trametes polyzona KU-RNW027. Both MnPs showed high stability in organic solvents which triggered their activities. Metal ions activated both MnPs at certain concentrations. The two MnPs and Lac1, played important roles in dye degradation and pharmaceutical products deactivation in a redox mediator-free system. They completely degraded Remazol brilliant blue (25 mg/L) in 10-30 min and showed high degradation activities to Remazol navy blue and Remazol brilliant yellow, while Lac1 could remove 75% of Remazol red. These three purified enzymes effectively deactivated tetracycline, doxycycline, amoxicillin, and ciprofloxacin. Optimal reaction conditions were $50^{\circ}C$ and pH 4.5. The two MnPs were activated by organic solvents and metal ions, indicating the efficacy of using T. polyzona KU-RNW027 for bioremediation of aromatic compounds in environments polluted with organic solvents and metal ions with no need for redox mediator supplements.

• Progress in Superconductivity and Cryogenics
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• v.6 no.2
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• pp.46-51
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• 2004

This paper presents the results of a series of performance and reliability tests for the Stirling cryocooler. Infrared sensor systems incorporating cryocoolers are required to be qualified to the appropriate specification for the performance and reliability. FPFD Stirling cryocooler is currently under development for cooling infrared detector. Manufactured Stirling cryocooler delivers approximately 0.9W cooling at 80K for 30W∼40W of input power. It takes approximately 2 minutes to cool down to 80K at the ambient temperature of 23$^{\circ}C$. Performance characteristics for the vibration, acoustic noise, EMI and leak rate of the Stirling cryocooler are evaluated. We performed low and high temperature keeping test from -32$^{\circ}C$ to +52$^{\circ}C$ and operating test at high and low temperature cyclic range with acceptance tests performed at scheduled intervals. Cooling capacity is determined as a function of the temperatures at the compressor, hot end and cold tip at the expander. Finally, we describe the experimental facility for the MTTF evaluation and some typical results of the Stirling cryocooler.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.4
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• pp.346-352
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• 2002

A novel Zero Current Switching(ZCS) Pulse Width Modulation(PWM) boost converter with dual mode for reducing two rectifiers reverse recovery related losses is proposed. The switches of the proposed converter are operating to work alternatively turn-on and turn-off with soft switching condition In the every cycle and the proposed converter reduces the reverse recovery current, which is related switching losses and EMI problems, of the free-wheeling diode$(D_1, D_2)$ by adding the resonant inductor Lr, in series with the switch $S_1$. The switching components$(S_1, S_2, D, D_1)$ in the proposed boost converter are subjected to minimum voltage and current stresses same as those in their PWM counterparts because there are no additional active switches and resonant elements compared with the conventional ZVT PWM $converters^{[2]}$. The operation of the proposed converter, in this paper, is analyzed and to verify the feasibility of the characteristics is built and tested.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.57-60
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• 2008

Magnesium alloys usage has been increased every year owing to its lightness, damping capacity, and EMI shielding, etc. In case of magnesium, it is mainly produced by diecasting due to high fluidity of melts. But, casting defect occurs many times because of low heat capacity of the magnesium. Therefore, wrought products can be applied for defect-free and mechanical properties. but it is insufficient in market share because of crystalline structure. The domestic market of wrought magnesium products are not revitalized compare to advanced countries. Accordingly we are going to forecast a domestic market of wrought products through searching the present of korean magnesium industry.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.12
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• pp.597-600
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• 2006

When the energy of the nanoseconds high voltage pulse with hundreds picoseconds of the pulse rise time is emitted into the free space via an antenna, an ultra wide band electromagnetic wave is generated. This electromagnetic wave is expected to be used in transmitting vast amount of informations to far distance, high performance radars, post-packaging pasteurization of food, the detection of underground buried objects, searching of underground water veins or caves, the treatment of waste water or polluted gases and so forth. Additionally, this technology can be used in EMI(electromagnetic interference) evaluation of measuring instruments or printed circuit boards.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.2
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• pp.63-68
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• 2007

A number of process problems should be solved in the multi-layered ceramic devices such as EMI filter. In particular, it is essential to control the sintering shrinkage in co-firing of different materials for obtaining defect-free samples such as crack, camber, and delamination which usually occur near the surface and interface. We studied the effect of the powder properties of ferrite on the co-firing behavior of green ceramic layers composed of ferrite and varistor. Three kind of ferrite powder samples as a function of milling time (24, 48, and 72 hr) were prepared. Varistor and ferrite ceramic green sheet were made by means of doctor blade process using slurry (ceramic powder and binder solution). Here, slurry was prepared by mixing 55 wt% powder with 45wt% binder solution. Varistor and ferrite green sheets were laminated at $80 kg/cm^2$, and co-fired at $900^{\circ}C$ and $1000^{\circ}C$ for 3 hr. We obtained the camber-free and co-fired ferrite/varistor layer structure by controlling the milling time and sintering temperature.