• 한국전자파학회논문지
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• 제21권6호
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• pp.651-659
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• 2010

본 논문에서는 software defined radio(SDR) 기반의 고속의 다중 모드, 다중 대역을 위한 새로운 six-port 직접변환 수신기를 제안한다. 설계한 수신기는 2개의 CMOS four-port BPSK 수신기와 직교 LO 신호 발생을 위한 이중 대역 1단 polyphase 필터로 구성되어 있다. 0.18 ${\mu}m$ CMOS 공정을 이용하여 마이크로파 대역에서 처음으로 개발한 four-port 수신기는 두 개의 능동 결합기, 능동 발룬, 두 개의 전력 검출기 및 아날로그 디코더로 구현되어 있다. 제안한 polyphase 필터는 type-I 구조를 선택하였으며, LO 신호의 전력 손실을 줄이기 위하여 1단으로 구현 하였고, 커패시터를 사용하는 것 대신하여 LC 공진구조를 적용하여 이중 대역 동작을 구현하였다. 제안한 sixport 수신기의 RF 가용범위를 확장하기 위하여, six-port junction과 전력 검출기에 I/Q 위상 및 크기를 보정하는 회로를 추가하였다. 제안한 회로에서 위상과 크기 부정합의 보정 범위는 각각 8도와 14 dB이다. 제작한 six-port 수신기는 이중 대역인 900 MHz와 2.4 GHz 대역에서 M-QAM, M-PSK의 40 Msps의 변조 신호를 성공적으로 복조하였다.

• Journal of Applied Biological Chemistry
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• 제54권1호
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• pp.47-50
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• 2011

본 연구에서는 천연 미백소재 탐색을 위하여 쪽(P. tinctoria) 꽃 추출물의 tyrosinase 저해활성을 검증하였으며, 쪽 꽃 추출물은 $70.8{\pm}2.2{\mu}g/mL$의 $IC_{50}$ 값을 나타내었다. LH-20 chromatography와 HPLC분석을 통해 쪽으로부터 두 개의 활성물질을 정제하였고, 이 물질들의 구조 분석은 LC-MS와 NMR 데이터 해석을 바탕으로 진행하여 두 가지 화합물은 각각 quercetin-3-Orhamnoside (Q3R), myricetin-3-O-rhamnoside (M3R)로 밝혀졌다. Q3R과 M3R은 순서대로 $47.0{\pm}0.1$, $150.5{\pm}1.6{\mu}g/mL$의 $IC_{50}$ 값을 나타내었다. 이로 미루어 보아, 쪽 꽃 추출물과 두 활성물질의 멜라닌 생합성 저해활성을 확인할 수 있었으며, 쪽 꽃추출물의 미백소재로서의 적용 가능성을 확인할 수 있었다.

• 조명전기설비학회논문지
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• 제21권6호
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• pp.117-125
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• 2007

연료전지 발전시스템에서는 DC-DC 승압용 컨버터와 DC-AC 인버터가 필요하다. 그러므로 본 논문에서는 연료전지의 전압을 380[VDC]로 승압하기 위한 절연형 DC-DC 컨버터와 단상 220[VAC]로 변환하기 위한 LC필터를 가진 PWM 인버터로 구성된 전력변환장치를 제안하였다. 특히 제안한 연료전지 시스템용 고효율 DC-DC 컨버터는 위상천이 PWM 제어법을 이용하여 부분 공진에 의한 ZVS를 실현하였으며, 일정 스위칭 주파수화 및 스위치의 스위칭 손실, 피크 전압과 전류를 저감시켰다. 그리고, 정류회로에 2개의 인덕터를 첨가하여 리플성분이 저감된 직류전압과 전류를 부하측에 안정하게 공급할 수 있었다. 또한, 넓은 출력 전압 조정에도 효율을 92[%]정도 얻을 수 있다. 이상과 같이 결과는 시뮬레이션과 실험을 통하여 그 타당성을 확인하였다.

• Journal of Microbiology and Biotechnology
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• 제18권10호
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• pp.1659-1662
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• 2008

Pseudomonas chlororaphis O6 exhibits induced systemic resistance (ISR) against P. syringae pv. tabaci in tobacco. To identify one of the ISR metabolites, O6 cultures were extracted with organic solvents, and the organic extracts were subjected to column chromatography followed by spectroscopy analyses. The ISR bioassay-guided fractionation was carried out for isolation of the metabolite. High-resolution mass spectrometric analysis of the metabolite found $C_{9}H_{9}O_{3}N$ with an exact mass of 179.0582. LC/MS analysis in positive mode showed an $(M+H)^{+}$ peak at m/z 180. Nuclear magnetic resonance ($^{1}H,\;^{13}C$) analyses identified all protons and carbons of the metabolite. Based on the spectroscopy data, the metabolite was identified as 4-(aminocarbonyl) phenylacetate (4-ACPA). 4-ACPA applied at 68.0 mM exhibited ISR activity at a level similar to 1.0 mM salicylic acid. This is the first report to identify an ISR metabolite produced by P. chlororaphis O6 against the wildfire pathogen P. syringae pv. tabaci in tobacco.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.139.2-139.2
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• 2015

In this study, We applied the magnetic field that has CW frequency and AM frequency to heating magnetic nano powder. For this experiment, We set up the devices flat-type magnetic field generator with CW frequency and AM frequency. We supplied the current to encircling coil by adjusting the power of generating of magnetic field device for AC voltage through Slidacs and using way of LC resonance circuit and SMPS(Switching Mode Power Supply). Above the encircling coil, We covered the circular flat insulator like glass. And we located the well plate containing the magnetic nano powder liquor above the circular flat insulator and exposed the magnetic field to this well plate. Using the flat-type magnetic field generator with CW and AM frequency and the magnetic field measurement sensor(Magnetic pick up coil or Hall sensor), We measured the strength of the magnetic field of circular flat insulator's surface in each position. The temperature of the magnetic nano powder in the well plate was quantitatively measured by the magnetic field strength through the Fluoroptic thermometer.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.66.1-66.1
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• 2015

Plasma medicine is an upcoming research area that has attracted the scientists to explore more deeply the utility of plasma. So, apart from the treating biomaterials and tissues with plasma, we have studied the effect of plasma with different feeding gases on modification of biomolecules. Additionally, we have checked the action of nanosecond pulsed plasma on the biomolecules. We have checked the plasma action on proteins ((Hemoglobin (Hb) Myoglobin (Mb) and lysoenzyme), calf thymus DNA and amino acids. The structural changes or structural modification of proteins and DNA have been studied using circular dichroism (CD), dynamic light scattering (DLS), gel electrophoresis, protein oxidation test, UV-vis spectroscopy and 1D NMR, while Liquid Chromatograph/Capillary Electrophoresis-Mass Spectrometer(LC/CE-MS) based qualitative bio-analysis have been used to study the modification of amino acids. We have also shown the effect of NaCl and ionic liquid on the formation of OH radicals using electron spin resonance and fluorescence techinques.

• 대한의용생체공학회:의공학회지
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• 제37권5호
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• pp.168-177
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• 2016

In this paper we present an implantable pressure sensor to measure real-time blood pressure by monitoring mechanical movement of artery. Sensor is composed of inductors (L) and capacitors (C) which are formed by microfabrication and direct bonding on two biocompatible substrates (quartz). When electrical potential is applied to the sensor, the inductors and capacitors generates a LC resonance circuit and produce characteristic resonant frequencies. Real-time variation of the resonant frequency is monitored by an external measurement system using inductive coupling. Structural and electrical simulation was performed by Computer Aided Engineering (CAE) programs, ANSYS and HFSS, to optimize geometry of sensor. Ultrafast laser (femto-second) cutting and MEMS process were executed as sensor fabrication methods with consideration of brittleness of the substrate and small radial artery size. After whole fabrication processes, we got sensors of $3mm{\times}15mm{\times}0.5mm$. Resonant frequency of the sensor was around 90 MHz at atmosphere (760 mmHg), and the sensor has good linearity without any hysteresis. Longterm (5 years) stability of the sensor was verified by thermal acceleration testing with Arrhenius model. Moreover, in-vitro cytotoxicity test was done to show biocompatiblity of the sensor and validation of real-time blood pressure measurement was verified with animal test by implant of the sensor. By integration with development of external interrogation system, the proposed sensor system will be a promising method to measure real-time blood pressure.

• 한국철도학회논문집
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• 제9권6호
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• pp.761-765
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• 2006

At present, harmonic currents cause serious problems in power conversion system using the semiconductor switching device. Also some of the conversion system provokes harmonic currents against to the main power supply system and causes hindrances for the system. Main power impedance of the traditional LC passive filter method, influences on the filter characteristics and amplifies the harmonics when resonance phenomenon is occurred. And the traditional existing 2 level inverter systems show the limit in capacity of voltage and current in case of occurring sudden load change. So, to solve this problem active filter which uses cascaded H-bridge multi level inverter has been designed and ex-filter system circuits were totally investigated. With multi level active filtering system not only the size of filter but also the size of filter for transformer can be reduced by half and so as to the weight, while the capacity of inverter can be double sized and wave forms can be compensated exactly and precisely. Also by the benefit of the increase in rating capacity, the various currents owing to the load fluctuation can be dealt more steadily. In order to simulate the wave form of harmonics based on the measured data on the AC 25kV high speed Domestic Commercial railway, it was simulated with PSCAD/EMTDC and PSIM. Based on the results of this demonstration, the power supply system and inverter system would be more stable and also promoting its efficiency.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2006년도 추계 학술발표회 발표논문집
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• pp.285-289
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• 2006

In screening of algicidal bacteria, we isolated a marine bacterium which had potent algicidal effects on harmful algal bloom (HAB) species. This organism was identified as a strain very close to Bacillus subtilisby 16S rRNA gene sequencing. This bacterium, Bacillus sp. SY-1, produces very active algicidal compounds against the harmful dinoflagellate Cochlodinium polykrikoides. We isolated three algicidal compounds (MS 1056, 1070, 1084) and identified them by amino acid analyses, fast atom bombardment mass spectrometry (FAB-MS), infrared spectroscopy (IR), $^1H$, $^{13}C$, and extensive two-dimensional nuclear magnetic resonance (2D NMR) techniques including $^1H-^{15}N$ HMBC analysis. One of them, MS 1056, contains a b-amino acid residue with an alkyl side chain of $C_{15}$. MS 1056, 1070, and 1084 showed algicidal activities against C. polykrikoides with an $LC_{50}$ (6 hrs) of 2.3, 0.8, $0.6\;{\mu}g/ml$, respectively. These compounds also showed significant algicidal activities against other harmful dinoflagellates and raphidophytes. In contrast, MS 1084 showed no significant growth inhibition against various organisms coexisting with HAB species in natural environments, including bacteria, eukaryotic microalgae, and cyanobacteria, although it inhibited growth of some fungi and yeasts. These observations imply that algicidal bacterium Bacillus sp. SY-1 and its algicidal compounds could play an important role in regulating the onset and development of HABs in the natural environments.

• 한국전자파학회논문지
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• 제18권2호
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• pp.206-212
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• 2007

본 논문에서는 넓은 영역에서 GBN/SSN 억제 특성을 보이는 이종 셀 EBG 구조를 이용한 새로운 전원면 구조를 제안하였다. 제안된 구조는 -30 dB 이하의 삽입 손실로 정의되는 저지 대역이 GBN의 에너지가 집중적으로 분포하는 수 백 MHz에서 시작하며 약 7.9 GHz의 넓은 대역폭을 갖는다. 본 구조의 특징은 인덕턴스를 강화하는 나선형 연결 선로와 분산적 LC 회로의 주기를 줄이는 이종 셀을 추가한 것이다. 그 결과 -30 dB 저지 대역의 저주파에서의 차단 주파수가 낮아짐은 물론 대역폭이 넓어진 특성을 보였다. 또한, 전원면과 접지면 사이의 구조적 공진 모드가 현격히 억제되었으며 평행판 도파관에 비해 낮은 EMI 특성을 보였다.