• Journal of Microbiology and Biotechnology
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• 제14권3호
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• pp.503-508
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• 2004

The antimicrobial substance produced by Lactobacillus bulgaricus was inactivated by protease. It showed inhibitory activity against Staphylococcus aureus ATCC6538, Streptococcus agalactiae ATCC14364, some Gram-positive and Gram-negative bacteria, and characteristics of a bacteriocin. The optimal temperature and culture time for the production of bacteriocin were $30^{\circ}C$ and 10 h, respectively, in the culture of L. bulgaricus. The bacteriocin production started in the exponential phase and reached a maximum at the early stationary phase. Using Staph. aureus ATCC6538 and Strep. agalactiae ATCC14364, known as common bovine mastitis pathogens, as indicator strains for determination of the bacteriocin activity, the antimicrobial activity of the bacteriocin was found to be stable in acidic and neutral pH's (2- 7) even at lOOT, whereas it was lost at high pH (10- 11) and $100^{\circ}C$. The mode of action for the antimicrobial activity was bacteriocidal, and the molecular weight determined by SDS-PAGE and overlay method was 14 kDa.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권3호
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• pp.178-184
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• 2002

High-throughput screening has become a popular method used to identify new “leads”for potentially therapeutic compounds. Further screening of these lead compounds is typically done with secondary assays which may utilize living, functioning cells as screening tools. A problem (or benefit) with these cell-based assays is that living cells are very sensitive to their environment. We have been interested in the process of stem cell migration and how it relates to the cellular therapy of bone marrow transplantation. In this study we describe a secondary, cell-based assay for screening the effects of various in-vitro conditions on Immature Hematopoietic Cell (IHC) migration. Our results have revealed many subtle factors, such as the cell's adhesive characteristics, or the effect of a culture's growth phase, that need to be accounted for in a screening protocol. Finally, we show that exponentially glowing KG1a cells (a human IHC cell line) were 10 times more motile than those in the lag or stationary phases. These data strongly suggest that KG1a cells secrete a chemokinetic factor during the exponential growth phase of a culture.

• Journal of Power Electronics
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• 제14권1호
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• pp.115-124
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• 2014

This paper presents the implementation of two-arm modulation (TAM) technique for the independent control of a two-induction motor drive fed by a five-leg inverter (FLI). A carrier-based space vector pulse width modulation technique for TAM is proposed to generate switching signals for FLI. Two independent three-phase space vector modulators are utilized to control two motors. The motor drive system applies two separate indirect field-oriented control methods. The stationary voltage outputs from the vector control are synthesized in the three-phase space vector modulator to generate switching signals for FLI. The performance of the independent control of the motors and the voltage utilization factor are likewise analyzed. Simulation and experimental results verify the effectiveness of the proposed method for the independent control of the two-motor drive system. The proposed technique is successfully validated by dSPACE DS1103 experimental work.

• 대한화학회지
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• 제31권2호
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• pp.123-132
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• 1987

반경험적 분자궤도함수법인 MNDO방법을 사용하여 $SH^-,\;CN^-$ 그리고 $OH^-$와 메틸티오시아네이트(MTC)의 친핵성치환반응을 연구하였다. 각 친핵체에 대해 MTC세반응중심의 계산된 포텐샬에너지곡면(Intrinsic term)과 전이상태에서의 친핵체의 음전하크기(Solvent term)을 고려하여 가스상과 용액상에 대한 선택성을 논의하였다. 결과로써$SH^-$에 대해서는 선택성의 두 성분 모두 4-methylbenzylthiocyanate (4-MBTC)에 대해 얻어진 실험결과와 일치한반면 $CN^-$의 경우에는 고유항(Intrinsic term)의 선택성만이 일치하였고 $OH^-$의 경우에는 두 항중 어느것도 실험결과로 얻은 선택성과 일치하지 않았다. 정류점에서 모든 종에 대한 MNDO최적화된 구조들을 밝혔다.

• Journal of Positioning, Navigation, and Timing
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• 제7권4호
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• pp.235-243
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• 2018

Conventional Real Time Kinematics (RTK) collect measurements in stationary state for several minutes to resolve the integer ambiguity in the carrier phase measurement or resolve the integer ambiguity on the move assuming low maneuvering movement. In this paper, an On The Move-RTK (OTM-RTK) technique that resolves the integer ambiguity on the move for fast and precise positioning of ground vehicles such as high maneuvering vehicles was proposed. The OTM-RTK estimates the precise amount of movement between epochs using the carrier phase measurements acquired on the move, and by using this, resolves the integer ambiguity within a short period of time by evaluating the integer ambiguity candidates for each epoch. This study analyzed the integer ambiguity resolution performance using field driving experiment data in order to verify the performance of the proposed method. The results of the experiment showed that the precise trajectory including the initial position bias can be obtained prior to resolving the integer ambiguity, and after resolving the integer ambiguity on the move, it was possible to obtain the bias-corrected precise position solution. It was confirmed that the integer ambiguity can be resolved by collecting measurements of about 10 epochs from the moving vehicle using a dual frequency receiver.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 전력전자학술대회
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• pp.207-209
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• 2019

This paper proposes a grid-tied photovoltaic (PV) system, consisting of Voltage-fed dual-active-bridge (DAB) dc-dc converter with single phase inverter. The proposed converter allows a small dc-link capacitor, so that system reliability can be improved by replacing electrolytic capacitors with film capacitors. The double line frequency free maximum power point tracking (MPPT) is also realized in the proposed converter by using Ripple Correlation method. First of all, to eliminate the double line frequency ripple which influence the reduction of DC source capacitance, control is developed. Then, a designing of Current control in DQ frame is analyzed and to fulfill the international harmonics standards such as IEEE 519 and P1547, $3^{rd}$ harmonic in the grid is directly compensated by the feedforward terms generated by the PR controller with the grid current in stationary frame to achieve desire Total Harmonic Distortion (THD). 5-kW PV converter and inverter module with a small dc-link film capacitor was built in the laboratory with the proposed control and MPPT algorithm. Experimental results are given to validate the converter performance.

• KSBB Journal
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• 제19권4호
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• pp.263-268
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• 2004

최근 생체 내에서 다른 약리활성을 보이는 키랄물질의 고순도 제조에 관심이 증가되고 있다. 현재 널리 사용되고 있는 것은 키랄고정상을 이용한 기존 분리방법에 비해서, 제조 후 안정성과 환경적인 측면을 고려한 초임계유체를 이용한 분리방을 시도하였다. 본 연구에서는 키랄물질인 ibuprofen의 최적의 분리 조건을 구하기 위해서 온도와 압력, 첨가되는 IPA의 양에 따른 체류인자와 분리도의 영향을 고찰하였다. 온도가 감소하고 압력이 증가할수록 체류인자는 감소하였다. IPA의 양에 따라 더 큰 영향을 받아서 IPA의 양이 많을수록 분리도는 감소하는 경향을 보였다. 실험으로부터 정한 최적의 분리조건은 130 bar, 311.15 K, 4% IPA (vol.)일 때이었다. 동일한 주입량에서 액체 크로마토그래피에서는 비선형의 용출곡선을 보였지만, 초임계유체 크로마토그래피에서는 선형의 용출곡선을 얻었다.

• 대한화학회지
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• 제42권1호
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• pp.51-56
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• 1998

남조류 독성물질인 Microcystins은 자연계에 매우 미량 존재하기 때문에 이를 분리 및 정제하기가 쉽지 않다. 본 연구에서는 자연계에 존재하는 남조류 동결건조시료로부터 Microcystin RR과 LR을 분리 및 정제하는 새로운 방법을 개발하였다. 약 7.5g의 실리카겔을 정지상으로 사용하고 혼합용액인 ethyl acetate: iso-propanol:water(30: 45: 25)을 이동상으로 사용하는 open column system으로 시료를 전개한후 용액을 3mL간격으로 받아냈다. 받아낸 용액중의 Microcystin RR과 LR은 TLC와 HPLC(high performance Liquid Chromatography)를 이용하여 확인한 후 농축, 정제하였다.

• 전기전자학회논문지
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• 제4권2호
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• pp.225-232
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• 2000

전압원 인버터의 PWM 신호에 삽입되는 데드 타임은 인버터 출력 파형을 왜곡시키고, 토크 리플을 발생시켜 유도 전동기의 제어 성능을 떨어뜨린다. 본 논문에서 벡터 제어 유도 전동기의 데드 타임 보상 방법이 제안된다. 제안된 방법은 2상 정지 좌표계에서 인버터 출력 기준전압에 보상 전압을 더하는 전향 보상에 근거한다. 제안된 방법은 부가적인 하드웨어 없이 소프트웨어적으로 실현 가능하다. 실험 결과를 통하여 제안된 방법의 타당성과 유용성을 확인한다.

• Archives of Pharmacal Research
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• 제23권2호
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• pp.178-181
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• 2000

In order to study the simultaneous determination of (+)- and (-)-cetirizine in human urine we have developed a chiral separation method by HPLC. A chiral stationary phase of $\alpha$$_1$-acidglycoprotein, the AGP-CSP was used to separate the enantiomers. The pH of the phosphate buffer, as well as the content of the organic modifier in the mobile phase, markedly affected the chromatographic separation of (+)- and (-)-cetirizine. A mobile phase of 10 m㏖/1 phosphate buffer (pH 7.0)-acetonitrile (95 : 5, v/v) was used for the urine assays. Ultraviolet absorption was monitored at 230nm and roxatidine was employed as the internal standard for quantification. (+)-Cetirizine, (-)-cetirizine and the internal standard were eluted at retention times of 12, 16, and 32 mins, respectively. The detection limit for cetirizine enantiomers was 400 ng/$m\ell$ of urine. A pharmacokinetic study was conducted with the help of 5 healthy female volunteers who were administered with a single oral dose of racemic cetirizine (20 mg). The peak area ratios provided by the cetirizine enantiomers were linear(r>0.997) over a concentration range of 2.5-200 ${\mu}g/ml$. The peak of the excreted cetirizine enantiomers appeared in the urine sample during the period of 1-2 hrs following the administration of the oral dose. The excreted level of (+)-cetirizine was slightly higher than (-)-cetirizine but the difference was not statistically significant. However, this method appears to have applications for enantioselective pharmacokinetic studies of racemic drugs.