• Korean Journal of Soil Science and Fertilizer
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• v.17 no.2
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• pp.82-89
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• 1984

These studies were carried out to investigate the effects of rice straw on microflora in relation to nitrogen metabolism in submerged soil. Rice plants were cultured in submerged soil to which rice straw was applied. In the submerged soil applied with rice straw the value of Eh lowered. pH was higher in the upper layer than in the lower. The content of iron(II) in submerged soil increased, while that of ammonium nitrogen decreased when rice straw was applied and nitrate-nitrogen was hardly detected during the rice cultivation period Under application of rice straw the number of denitrifying bacteria observed to increase at the early growing stage of rice plant and to decrease thereafter, and that of nitrate reducing bacteria increased at the late growing stage. The number of ammonium oxidizing bacteria and that of nitrite oxidizing bacteria decreased continually but the latter were rather sharply decreased.

• Microbiology and Biotechnology Letters
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• v.20 no.1
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• pp.102-109
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• 1992

The microfloral changes of lactic acid bacteria during Kimchi fermentation at 5, 20 and $30^{\circ}C$ were compared by using various selective media, and the lactic acid bacterial strains were isolated and identified. The patterns of microfloral changes in each lactic acid bacterial group, leuconostoc, lactobacilli, streptococci and pediococci, were similar at different fermentation temperature, and the changes were accelerated by increased temperature. Among them, leuconostoc and lactobacilli showed high population, and at low temperature the number of leuconostoc were higher than at high temperature. Leuconostoc and streptococci were increased in number from the beginning, but they rapidly decreased after the optimum ripening period. Pediococci increased their number after streptococci, but they were rapidly decreased later. Lactobacilli were highly distributed throughout the whole fermentation period. However, they were slightly declined as the acidity increased. Those strains of leuconostoc, streptococci, pediococci and lactobacilli were identified as Luuconostoc mesenteroida subsp. musenteroides, Streptococcus fuecalzs, S, faeciurn, Pediococcus pentosaceus, Lactobacillus plarttarum, L. sake and L. brevis. Among lactobacilli, Id. sake and L. brmk, and L. plantarum were isolated mainly at the beginning and around the overripening period of fermentation, respectively.

• Magazine of the Korea Concrete Institute
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• v.5 no.1
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• pp.165-173
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• 1993

본 연구는 고강도 콘크리트 실용화의 일환으로 국내에서 시판되고 있는 고성능 감수제의 품질성능을 평가하기 위한 것이다. 이러한 연구를 위하여 8종류의 고성능 감수제를 대상으로 첨가량에 따른 특성을 비교하였다. 또한 경시변화에 따른 특성을 비교, 분석하기 위하여 슬럼프, 공기량 그리고 압축강도비를 측정하였다. 이 때 고성능 감수제의 품질성능 평가 규준는 JASS 5T-402 규준에 따라 실시하였다. 실험결과 국내에서 시판되는 고성능 감수제는 공기량, 앞축강도비에 대해서는 모두 만족하였지만 슬럼프 경시 저하량은 DA를 제외한 모든 고성능 감수제가 규준치를 초과하였다. 따라서 현장에서 고강도콘크리트를 생산할 경우 배합방법이나 첨가방법을 개선하여 시공성을 확보하는 방안이 필요할 것이다.

• Journal of the Korean Wood Science and Technology
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• v.36 no.1
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• pp.30-35
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• 2008

Degradation of mechanical properties of fire-killed Korean red pine has been investigated after death in 5 years period. Impact bending absorbed energy was the most sensitive property by elapsed time after forest fire. It is an indication of incipient decay of the wood and can be useful indicator to monitor any change of mechanical property of fire-killed tree after death. Degradation of mechanical properties was more pronounced in sapwood than heartwood. Impact bending absorbed energy was more reduced than any other properties in both sapwood and heartwood, while compressive strength was least impacted by elapsed time after forest fire. It is recommended that the fire-killed Korean red pine can be harvested in one year after the fire for industrial uses by considering decay and consequent changes of mechanical properties.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.136.2-136.2
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• 2011

한국천문올림피아드(KAO)는 경시대회에 의한 입시 과열 및 사교육 조장 논란으로 촉발된 정부 정책의 변화로 2010년 1차 선발 방식을 지필고사에서 서류전형으로 바꾸는 등 대대적인 개편을 겪었다. 그 결과로 지원자 수의 급감 등 양적 변화 외에 지원자의 성향에 있어서도 상당한 변화가 예상되고 있다. 이에 따라 2011년도 KAO 2차 선발 심층면접 참가 학생 96명을 대상으로 실시한 설문조사를 토대로 KAO 참가 동기, 참가준비방법, 타 올림피아드 중복 참가 여부, 그리고 천문올림피아드 자체교육(온라인 강좌, 인터넷과제, 주말교육) 및 서류심사, 심층면접에 대한 평가 의견을 전체 및 소속 학교별, 성별, 지역별로 분류하여 분석하였다. 또한 위의 결과를 2010년도에 시범적으로 실시한 설문조사 결과와 비교 분석하여 시간적 변화 추이에 대해서도 살펴보았다. 이로부터 도출된 결론을 바탕으로 단기적 관점에서 KAO의 선발 방식 및 선발학생의 교육을 어떤 방식으로 개선해나가야 할지, 그리고 장기적 관점에서 천문학에 관심 있는 과학영재를 어떻게 발굴하고 육성해나갈지에 대해 논의했다.

• Journal of Sericultural and Entomological Science
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• v.31 no.1
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• pp.1-11
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• 1989

To investigate changes of dry weight, C/N ratio, carbohydrate, ratein and nucleic acids in the barks of the hardwood cutting of mulberry plants, the barks of the hardwood cutting were taken every 10days from the cutting day to 40days after cutting. Results were summarized as follows : Growth of shoot and root in Keomseolppong (Morus bimbycis KoIDZ.) after cutting was better than that in kaeryangppon (Morus alba L.) and Daeryugppong(Morus Lhou(SER.) KoIDZ.). Dry weight in the barks of the hardwood cutting decreased up to 40days after cutting (decrease percentage of dry weight : about 14%) and Keomiseolppong showed the highest decrease precentage of dry weight. Change of C/N ratio decreased in the initiation, whereas that from 10days after cutting increased with the growth of new shoot, C/N ratio was the highest in Keomseolppong and the lowest in Kaeryangppong. Total sugar showed decreasing tendency up to 40 days after cutting the increase from 10 days to 20 days. Reducing sugar increased in the frist 20days, followed gradually decrease up to 40 days after cutting Starch levels decreased up to 40 days. Change in the content of starch closely paralleled to that of dry weight of bark of the hardwood cutting. Content of total sugar and starch in Keomseolppong was the highest, and was consumed more than that in the rest of varieties. Crude protein and soluble protein increased up to 10 days after cutting, followed decrease up to 40 days. Protein content of Keomseolppong was smaller than that in the rest of varieties. RNA content showed the same tendency with that of protein content, but Keomseolppong showed always the highest. Content of DNA did not show any change and difference among three varieties.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.4
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• pp.73-80
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• 2022

This study evaluated changes in fluidity and rheological properties over time for 3D printed composite materials, and evaluated compressive strength and splitting tensile strength properties for laminated and molded specimens. The composite material for 3D printing starts to change rapidly after 30 minutes of extrusion, and the viscosity of the material tends to be maintained up to 90 minutes, but it was confirmed that construction within 60 minutes after mixing is effective. The compressive strength of the laminated test specimen showed equivalent or better performance at all ages compared to the molded test specimen. In the stress-strain curve of the laminated specimen, the initial slope was similar to that of the molded specimen, but the descending slope was on average 1.9 times higher than that of the molded specimen, indicating relatively brittle behavior. The splitting tensile strength of the P-V laminated specimen was about 6% lower than that of the molded specimen. It is judged that this is because the interfacial adhesion force against the vertical load is affected by the pattern direction of the laminated test specimen.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.23 no.1
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• pp.55-59
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• 1978

This study was carried out to investigate the sea sonal changes of the contents of inhibitors in leaves and fruits of Ginseng plant during ripening. Three kinds of inhibitors in leaves and all parts of fruit, i.e., seed, sarcocarp and endocarp were recognized at the Rf 0.1, 0.4-0.6 and 0.8-1.0 zones by the bioassay of lettuce seed germination. Among them, the level of the inhibitor at the Rf 0.4-0.6 zone in leaf and seed increased most significantly in accordance with fruit ripening. The activities of three inhibitors found in endocarp gradually decreased during ripening.

• Electrical & Electronic Materials
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• v.7 no.6
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• pp.543-548
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• 1994

전기화학반응은 일반적으로 반응속도가 전류에, 반응의 구동력이 과전압에 대응하기 때문에 전류 또는 전위의 경시적 변화로 부터 적극 반응기구나 반응의 과정을 해석하는 법이 널리 이용되고 있다. cyclic voltammetry과 chrono-potentiometry을 비롯한 시간영역에서의 해석에 대해, 전극계의 동적인 특성을 주파수 영역에서 해석하는 것도 가능하며 교류임피던스법이 가장 잘 알려진 방법이다. 여기서는 교류임피던스법의 고찰법, 기본적인 측정법, 몇개의 계에 있어서 임피던스 특성 및 그 방법의 새로운 전개에 대해서 설명한다.

• Journal of Korean Society of Forest Science
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• v.86 no.1
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• pp.56-68
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• 1997

This study was carried out to evaluate the capacity of environment purification of forest and to reveal formation processes of stream water quality by evaluating water quality variations in forest hydrological processes. Water quantity, pH, electric conductivity(EC), dissolved oxygen(DO), and dissolved matter concentrations were monitored in open rainfall, throughfall, stemflow, litter flow and short-term stream flow for one unit storm, and also for those were monitored in long-term stream flow in Palgong, Yongsung, and Daedong catchments. The results were summarized as follows; 1. pH and DO values of stream flow were increased as the flux increased but EC values were decreased. 2. pH values of stemflow and throughfall were decreased with the lapse of rainfall time with lower values than open rainfall. Arid EC values were higher in initial rainfall period but lower gradually with the lapse of time than open rainfall. In litter flow, pH values were lower than open rainfall but EC values were higher. In stream flow, pH values of stream flow showed a high level in initial rainfall period and decreased remarkably with the lapse of time, but it recovered after the rainfall stopped. And however, the values of EC showed almost reverse tendency. DO values of litter flow and stream flow were decreased gradually with the lapse of time in litter flow and stream flow but there were no any tendency in open rainfall, stemflow and throughfall. 3. pH values of stemflow and throughfall in Quercus acutissima were higher than in Pinus densiflora, but EC values were lower. Total amount of canons in stemflow was higher in Pinus densiflora than in Quercus acutissima. 4. pH, DO, EC and total amount of cation values in hydrological processes were in the order of; litter flow