• Transactions of the Korean hydrogen and new energy society
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• v.32 no.6
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• pp.534-541
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• 2021

In this study, a novel microwave-matrix reformer was proposed to convert CH₄, which is a major component, to a high quality hydrogen energy. And to identify this performance, it was investigated for O₂/C ratio, steam feed amount and reformed gas recirculation which are affected for methane conversion and product gas yield. Through the parametric screening studies, optimal operating conditions were that O₂/C ratio, steam feed amount and recirculation rate were 1.1, 10 mL/min and 30 L/min. In this conditions, CH₄ conversion was 68.1%, H₂ selectivity 77.2 and H₂/CO ratio 2.62 which are possible applying SOFC stack for RPG (residential power generator).

• Clean Technology
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• v.8 no.1
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• pp.11-17
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• 2002

Petcokes is the final product obtained from a refinery process. This petcokes includes high percentage of inorganic and sulfur compounds. Currently, the petcokes produced from domestic refinery plants include more than 6% of sulfur. To use petcokes as valuable raw materials, the weight percentage of sulfur must be lower than 2% of sulfur. Solvent extraction, thermal desulfurization, and hydro-desulfurization have been used to remove the sulfur. In this study, we attempted new approach to remove the sulfur introducing microwave energy. Microwave increase the reaction rates by providing the fast heating and disconnecting the bonding structure of the molecules. The experiments of microwave thermal desulfurization and microwave plus hydrogen gas were carried out to remove the sulfur. We obtained 68.3% of sulfur removal rate with the 2 hours of reaction time and 1835 W of microwave powder. In the experiment of microwave with hydrogen gas, we obtained 86.4% of sulfur removal rate with the 1.5 hours of reaction time and 1835 W of microwave power. If we increase reaction time or decrease the particle size of petcokes, we expect more than 90% of sulfur removal.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.360-363
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• 2001

The conventional 60(Hz) power supply for driving magnetron in microwave oven has disadvantages of heavy weight and low efficiency due to 60(Hz) High Voltage Transformer(HVT), capacitor and the phase control of thyristors with open-loop controller. To alleviate these disadvantages, this paper proposes a 20(kHz) phase-shifted(PS) Full-Bridge(FB) Zero- voltage-Switched(ZVS) PWM converter to drive a 600(W) magnetron in an 1(kW) microwave oven and to control the average anode current.

• ETRI Journal
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• v.31 no.3
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• pp.247-253
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• 2009

We propose a Ku-band driver and high-power amplifier monolithic microwave integrated circuits (MMICs) employing a compensating gate bias circuit using a commercial 0.5 ${\mu}m$ GaAs pHEMT technology. The integrated gate bias circuit provides compensation for the threshold voltage and temperature variations as well as independence of the supply voltage variations. A fabricated two-stage Ku-band driver amplifier MMIC exhibits a typical output power of 30.5 dBm and power-added efficiency (PAE) of 37% over a 13.5 GHz to 15.0 GHz frequency band, while a fabricated three-stage Ku-band high-power amplifier MMIC exhibits a maximum saturated output power of 39.25 dBm (8.4 W) and PAE of 22.7% at 14.5 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.7
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• pp.677-684
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• 2004

This paper presents direct T $M_{01}$-T $E_{11}$ small mode converter using circular waveguide with tilted structure for X-band high power system. It is designed to transmit microwave energy from Relativistic Backward-Wave Oscillator(RBWO) source to hem antenna effectively, with optimized geometry a parameter study The simulated and measured results of return loss, fractional power of each mode, impedance bandwidth and mode pattern are provided.d.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03b
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• pp.39-39
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• 2010

낮은 에너지를 이용하여 상대론적 영역에서 동작하는 마이크로파 출력장치를 연구하였다 그에 따른 후진파 발진기는 대전력 마이크로파를 발생시키는 장치로서 연구하였으며 관내에 전자빔을 입사시킴으로서 발진이 일어나 출력을 발생 시킨다.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1318-1319
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• 2008

본 연구는 대출력 마이크로파를 발생하기 위한 장치의 일원인 후진파 발진기에 대하여 연구하였다. 대전력 마이크로파를 발생시키는 다른것과 비교하면 소형이고 구조가 간단하게 할 수 있는 장점이 있어 매우 유용하다. 따라서 본 연구에서는 고주파 영역에서 대전력 발생이 이루어졌으며 실험에 대구경 후진파 발진기를 이용하여 마이크로파출력이 현저히 향상된것을 알았다.

• Korean Journal of Materials Research
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• v.22 no.6
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• pp.321-327
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• 2012

The production of functional activated carbon materials starting from inexpensive natural precursors using environmentally friendly and economically effective processes has attracted much attention in the areas of material science and technology. In particular, the use of plant biomass to produce functional carbonaceous materials has attracted a great deal of attention in various aspects. In this study the preparation of activated carbon has been attempted from rice husks via a chemical activation-assisted microwave system. The rice husks were milled via attrition milling with aluminum balls, and then carbonized under purified $N_2$. The operational parameters including the activation agents, chemical impregnation weight ratio of the calcined rice husk to KOH (1:1, 1:2 and 1:4), microwave power heating within irradiation time (3-5 min), and the second activation process on the adsorption capability were investigated. Experimental results were investigated using XRD, FT-IR, and SEM. It was found that the BET surface area of activated carbons irrespective of the activation agent resulted in surface area. The activated carbons prepared by microwave heating with an activation process have higher surface area and larger average pore size than those prepared by activation without microwave heating when the ratio with KOH solution was the same. The activation time using microwave heating and the chemical impregnation ratio with KOH solution were varied to determine the optimal method for obtaining high surface area activated carbon (1505 $m^2$/g).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.913-917
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• 2003

In the electronic components and devices fabrication, thin film resistors with low TCR(temperature coefficient of resistance) and high precision have been used over 3 GHz microwave in recent years. Ni-Cr alloys thin films resistors is one of the most commonly used resistive materials because it has low TCR and highly stable resistance. In this work, we fabricated thin film resistors using Evanohm alloys target(72Ni-20Cr-3Al-4Mn-Si) of s-type with excellent resistors properties by RF-sputtering. Also we reported best deposited conditions of thin film resistors for microwave to observe microstructure and electronic properties of thin film according to deposited conditions(between target and substrate, power supply)

• Journal of electromagnetic engineering and science
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• v.1 no.1
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• pp.18-23
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• 2001

A fast-sweep broadband FM reflectometer system has been successfully developed and operacted at the DIII-D tokamak, producing reliable density Profiles with excellent spatial (1 $\leq$ cm) and temporal resolution (~100 $\mu$ s). The system uses a solid-state microwave oscillator and an active quadrupler, covering full Q-band frequencies (33~50 GHz) and providing relatively high output power (20~60 mW). The system hardware allows fu11band frequency sweep in 10 $\mu$ s, but due to digitization rate limit on DIII-D, sweep time was limited to 75~100 $\mu$ s. Fast frequency sweep has helped to reduce density fluctuation effects on the reflectometer phase measurements, thus improving reliability for individual sweeps. The fast-sweep system with high spatial and temporal resolution has allowed to measure fast-changing edge density profiles during plasma ELMS and L-H transitions, thus enabling fast-time sca1e physics studies.