• 전력전자학회논문지
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• 제23권1호
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• pp.9-15
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• 2018

This study investigates a bidirectional quasi-Z-source inverter (Bq-ZSI) system with bidirectional power transfer capability and a modified space vector modulation scheme for reducing the ripple of the inductor current. By replacing the diode in the impedance network with an active switch, the power flow can be bidirectional. The average inductor current of the Bq-ZSI network is negative in the regenerative braking mode, thereby regenerating the power. In addition, modified space vector modulation scheme is applied to the Bq-ZSI to control shoot-through time effectively. A 5 kW prototype is built and tested to implement the proposed system. Experimental results show that the Bq-ZSI system is capable of regenerative braking of the induction motor and that the modified space vector modulation method is efficient.

• Journal of Plant Biotechnology
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• 제45권2호
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• pp.140-145
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• 2018

Inducing genetic and morphological variation through conventional method is very difficult. Therefore, mutation induction through in vitro technology brings numerous advantages over the conventional breeding. Thus, the individual shoots (1 ~ 2 cm) were irradiated with gamma rays (10 ~ 70 Gy). The result revealed that the explants treated with higher doses (40, 50, 60, and 70 Gy) showed deleterious effects of ionizing radiation. The highest survival rate among ${\gamma}$ treated explants recorded was 71% in 10 Gy treatments while the lowest survivality was 15% in 70 Gy. Lethal dose 50% ($LD_{50}$) dose was found to be 33 Gy. In the in vitro condition, rooting reponse showed that increase in gamma irradiation dose resulted in the inhibition of root growth. Meanwhile, non-treated explants had the best rooting ability with the maximum number of root per explant (20) within a short period of time (6 days), with the highest root length of (15.1 cm). The longer period in rooting (12 days) and lowest number of root per explant (8) with shortest root length (10.1 cm) were recorded at 30 Gy treatment. The highest shoot length (13.6 cm) was observed at control treatment and the shortest shoot length (10.4 cm) was observed at 30 Gy. In the nursery, lowest leaf number (5) was observed at 30 Gy compared with other treatments. The highest chlorophyll content (49.8) was recorded at 10 Gy treated seedling. Irradiated explants with 10 Gy found to be superior over the control treatment and had positive effects in main growth parameters such as chlorophyll content.

• 전기학회논문지
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• 제62권3호
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• pp.355-364
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• 2013

Respect to the input AC voltage and output DC voltage, conventional three-phase PWM rectifier is classified as the voltage type rectifier with boost capability and the current type rectifier voltage with buck capability. Conventional PWM rectifier can not at the same time the boost and buck capability and its bridge is weak in the shoot- through state. These problems can be solved by Z-source PWM rectifier which has all characteristic of voltage and current type PWM rectifier. By shoot-through duty ratio control, the Z-source PWM rectifier can buck and boost at the same time, also, there is no need to consider the dead time. This paper proposes the input AC voltage sensorless control method of a three-phase Z-source PWM rectifier in order to accomplish the unity input power factor and output DC voltage control. The proposed method is estimated the input AC voltage by using input AC current and output DC voltage, hence, the sensor for the input AC voltage detection is no needed. comparison of the estimated and detected input AC voltage, estimated phase angle of the input voltage, the output DC voltage response for reference value, unity power factor, FFT(Fast Fourier Transform) of the estimated voltage and efficiency are verified by PSIM simulation.

• 대한전기학회논문지
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• 제39권3호
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• pp.273-280
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• 1990

To prevent the shoot-through phenomena in a PWM inverter, a short dead time is usually provided between a pair of switching transistors in the same leg of the inverter. In this approach, the amount of the dead time is designed to meet the worst case condition of the inverter transistors and the base drive elements. So, in normal cases, relatively large portion of the dead time is unnecessary and it results in an undesirablecurrent waveform distortion and generates ripple torque on the motor shaft. In this paper, a new base drive method to remove the undesirable portion of the dead time is described. The method senses the transistor on/off states to interlock the other transistor of the leg without the external dead time. Also, for the transistors of large current rating, the Darlington drive circuit is combined to the proposed method and is tested to verify the effectiveness. The experimental results of the proposed method are described and compared with those of the conventional dead time method.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권9호
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• pp.618-625
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• 2000

Recently PWM inverters are widely utilized for many industrial applications e.g. high performance motor drive and PWM techniques are newly developed for an accurate output voltage. Among them space voltage vector PWM(SVPWM) inverter has high voltage ratio and low harmonics compared to the conventional sinusoidal PWM inverter. However output voltage of PWM inverter is distorted and has error duet o the conducting voltage drop of switching devices and the dead time that is inevitable to prevent the shoot-through phenomenon. This paper investigates 3-phase SVPWM inverter which has a new compensation method against dead time and voltage drop. Proposed algorithm calculates gate pulse periods which directly compensates the dead time and nonlinear voltage drop without modification of reference voltages. Direct compensation of gate pulse periods produces exact output voltage and does not need additional circuits. The propose algorithm is verified through the simulation and experiments.

• Journal of Microbiology and Biotechnology
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• 제19권6호
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• pp.542-546
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• 2009

Leaves are the major biomass-producing organs in herbaceous plants and mainly develop during vegetative stage by activities of shoot apical meristem. There is a strong correlation between leaf number and bolting, a characteristic phenotype during the transition to reproductive phase in Arabidopsis thaliana. In order to study interactions between leaf number and bolting, we isolated a Landsberg erecta-derived mutant named multifolial (mfo1) that produces increased number of leaves and bolts at the same time as the wild type. Through positional cloning and allelism test, mfo1 was found to be an allele of a previously reported mutant, altered meristem program1-1 (amp1-1) that is defective in a glutamate carboxypeptidase and bolts earlier than its wild type, Columbia ecotype, with the increased number of leaves. The bolting time differences between mfo1 and amp1, despite the same phenotype of many leaves, suggest the existence of genetic factor(s) differently function in each ecotype in the presence of mfo1/amp1 mutation.

• Ecology and Resilient Infrastructure
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• 제9권4호
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• pp.259-268
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• 2022

본 연구는 장기간 중금속 오염에 노출된 폐 석탄매립지에 생육하고 있는 참김의털 (Festuca ovina var. coreana) 종자를 채집하고 발아한 유식물을 가지고 온실 재배 실험을 통해 생육특성과 중금속축적능을 평가하고 식물정화법 (phytoremediation) 적용 가능성을 위해 수행하였다. 참김의털을 온실에서 인공적으로 오염된 토양에서 12 주 동안 재배하였다. 비소처리 인공토양의 농도구배는 각각 25, 62.5, 125, 250 mg/kg, 납 농도는 200, 500, 1000, 2000 mg/kg 및 카드뮴의 농도는 각각 15, 30, 60, 100 mg/kg로 처리하여 실험하였다. 비소, 납 및 카드뮴 처리구에서 참김의털의 엽수는 납 처리구 (200, 500, 1000 mg/kg)를 제외하고 대조구보다 모두 감소하였고, 지상부의 길이 성장은 비소 처리구 모두에서 대조구보다 증가하였으나 지하부는 모두 감소하였고, 1000 및 2000 mg/kg 납 처리구에서는 대조구보다 증가하였으나 나머지 처리구에서는 대조구보다 모두 감소하였고, 카드뮴 처리구의 경우, 지상부는 대조구보다 모두 증가하였고, 지하부는 모두 감소하였다. 비소 처리구의 경우, 생체량은 모든 부위와 모든 농도에서 대조구보다 감소하였고, 200, 500, 1000 mg/kg 납 처리구는 지상부와 지하부 모두에서 대조구보다 생체량이 증가하였고, 카드뮴 처리구에서는 지상부와 지하부의 생체량이 대조군보다 모두 감소하였다. 중금속의 처리구 농도가 높아질수록 엽수와 식물부위별 생체량은 모두 감소하는 경향을 보였고, 중금속의 처리구 농도가 높아질수록 지상부의 길이 성장은 소폭 증가하는 경향이 있으나 지하부는 다소 감소하는 경향이 있었다. 62.5 mg/kg 비소 처리구의 지상부, 지하부의 비소축적농도는 9.4 mg/kg와 253.3 mg/kg로 지하부가 26.9배로 축적율이 높았으며 250 mg/kg 비소 처리구의 지상부는 고사한 반면 지하부의 비소축적농도는 859.1 mg/kg로 분석되었고, 2,000 mg/kg 납 처리구에서 지상부와 지하부는 10,308.1 및 11,012.0 mg/kg로 지상부가 지하부의 1.1배 높게 축적되었고, 100 mg/kg 카드뮴 처리구에서 지상부와 지하부는 176.0 및 287.2 mg/kg로 지하부가 지상부의 1.6배 높게 축적되었다. 참김의털의 내성평가 결과, 비소, 납, 카드뮴의 모든 처리구에서 고사하지 않고 생장을 유지하여 3종의 중금속에 다재내성이 확인되었다. 참김의털의 납 오염토양에 대한 식물추출 (phytoextraction)은 납 오염농도 2,000 mg/kg까지 적용할 수 있는 식물종으로 검증되었다.

• Journal of Plant Biotechnology
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• 제5권4호
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• pp.239-244
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• 2003

A protocol has been developed for rapid large scale clonal propagation of an aromatic endangered medicinal plant, Hemidesmus indicus R. Br. with the elimination of the problems such as premature leaf fall and callus formation during caulogenesis and rhizogenesis. Multiple shoots were induced from shoot tip and nodal explants on Murashige and Skoog (MS) medium supplemented with 1 mg/L Benzylaminopurine (BAP) and 0.5 mg/L Napthaleneaceticacid (NAA). Addition of 15 mg/L adenine sulphate to the above medium checked leaf abscission completely, reduced the time required for caulogenesis and restored morphogenetic potential after several subcultures. The in vitro grown propagules were rooted in 1/2 MS medium supplemented with 2 mg/L Indolebutyric acid (IBA) +1 mg/L NAA and sucrose 0.7% (w/v). Addition of charcoal at 100 mg/L to the rooting medium quickened root initiation with a complete check on callus formation. The effect of sucrose concentration on both caulogenesis and rhizogenesis was also studied. The resultant plantlets were acclimatized and grown in fields where ninety eight percent of the rooted shoots survived and grew normally. The estimation of the secondary metabolite content in the shoots of the regenerated plant and the mother plant indicated that the concentration of the three secondary metabolites lupeol, vanillin and rutin was similar.

• 식물조직배양학회지
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• 제27권6호
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• pp.491-496
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• 2000

더덕의 효과적인 재분화조건 (약 90%의 재분화율)을 바탕으로 개화시기 조절유전자인 RAG25 Codonopsis lanceolata유전자의 도입을 시도하였다. 더덕의 잎 절편을Agrobacterium과 3일 동안 공조배양 하였으며 NAA 2 mg/L, BA 2 mg/L (N2B2)와 NAA 2 mg/L, BA 4 mg/L (N2B4)가 첨가된 shoot inducing media (Km 20mg/L와 Cf 250 mg/L가 첨가됨)에서 배양하였을 때 형질전환 신초가 형성되었다. 획득된 신초에서 genomic DNA를 추출하고 npt II와 RAG25 primer를 이용한 PCR을 수행하여 각각 0.7 kb와 0.6 kb의 band를 확인하였다. RAG25 유전자에 대한 PCR산물을 이용하여 Southern hybridization을 수행한 결과 PCR과 동일한 위치에서 band 가 검출되어져 이 유전자의 도입을 재확인하였다.

• 한국해양학회지:바다
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• 제14권1호
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• pp.41-47
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• 2009

최근 훼손된 잘피서식지의 복원이 다양한 이식방법을 통하여 시도되고 있다. 이식된 잘피는 이식시기와 이식방법에 따라 생존율과 착생기간 등이 차이를 보인다. Staple method는 잘피를 직접 식재하는 방법으로 잘피 이식에서 가장 일반적으로 이용되고 있는 방법이며, 다양한 퇴적물 환경에서 높은 생존율을 보이는 방법이다. 본 연구에서는 staple method로 이식된 잘피의 정착과정을 파악하기 위하여 초겨울에 잘피를 이식한 후, 이식된 잘피의 밀도, 형태적 특성, 생산성의 변화와 이식 장소의 환경요인을 2004년 12월부터 약 1년 동안 월별 조사하였다. 조사된 이식잘피의 생리생태학적 특성을 이식 장소 인근에 자생하고 있는 잘피 개체군과 비교하였다. 이식된 잘피는 초기 밀도 감소가 발생하지 않았으나, 잎의 폭, 엽초의 길이 등이 이식초기에 감소하여 이식개체들이 이식충격을 받은 것으로 보였다. 개체별 잎의 생산성도 이식 초기에는 자생개체들보다 현저히 낮은 값을 보이다가 약 4개월 후 이식개체와 자생개체의 생산성이 유사한 경향을 보였다. 이식된 잘피는 자생하는 잘피와 마찬가지로 봄에 급격히 성장하였으며, 자생개체보다 낮은 밀도로 이식되었으나, 약 1년 후에는 자생잘피 개체군의 밀도와 유사해졌다. 이식된 잘피들이 이식초기에 이식충격을 받았지만, 비교적 짧은 기간 내에 새로운 이식 장소에 잘 적응하는 것으로 나타났다.