• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.789-795
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• 1999

In this study, carbon fiber reinforced cement composites(CFRCs) reinforced with short noncircular type carbon fibers were fabricated and properties(drying shrinkage, resistance to freezing and thawing, and fracture toughness) were compared with those of the CFRCs reinforced with circular type carbon fibers. It was found that these properties greatly depended on the shape and length of carbon fibers. The drying shrinkage of CFRCs reinforced with C-type carbon fiber was superior to other CFRCs. This effect was increased with a high aspect ratio of fiber. The resistance to freezing and thawing was increased with the fiber length and fiber volume percent, but there was on remarkable effect to fiber shape. Fracture toughness and resistance to crack propagation of CFRCs reinforced with C-CFs were improved compared with other CFRCs. It was believed that the more absorption of fracture energy into the larger interface caused an increase in fracture toughness and resistance to crack propagation.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.2
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• pp.160-165
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• 1991

Growth performance of dry seeded paddy rice was studied at four N levels (10, 15, 20, and 25 kg/l0a) in tillage and no-tillage systems. Althougth the number of seedlings and maximum tillers tended to be higher and heading date was delayed by 2 days in tillage compared with those in no-tillage system, grainyield, yield components, lodging related characteristics, and N uptake were similar between two tillage ,systems. As N level increased, grain yield increased due to increased panicle number althougth the number of spikelets per panicle and percent ripended grains were similar and I, 000 grain weight decreased slightly. {Lodging index increased with increased N level due to higher plant height and decreased breaking strength and (culm base weigth, but lodging was not occurred in the field. Cellulose, hemicellulose, and lignin contents of culm base were similar among N levels. Concentration and uptake of N increased as N level increased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.5
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• pp.289-296
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• 2016

The availability of NMP, a solvent used in the manufacturing process of cathode material for lithium ion battery, depends on importation, and the price remains high because of the monopoly of BASF and ISP. For these reasons, most Lithium ion battery manufacturers reuse NMP after recovering it from the exhaust air in the drying process. In Korea, absorption method is mainly used for recovering NMP from the absorption tower using the hydrophilicity of NMP. However, this system has a few disadvantages, such as low purity (80％) of the recovered NMP and 100％ emission due to high water content of the treated gas. In this study, we develop a hybrid NMP recovery system by combining cooling condensation method with concentration method, by which it is possible to obtain an NMP recovery rate of 99.6％, and a high purity (96.1％) of the recovered NMP.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.397.1-397.1
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• 2014

최근 방사선 진단 영역에 이용되고 있는 증감지는 입사된 방사선의 감도를 증가시키기 위해 형광체를 사용하고 있으며, 외부의 에너지를 흡수하여 빛으로 방출하는 역할을 한다. 이는 방사선 검출기, 디스플레이, 의료기기 등 다양한 분야에 활용되고 있다. 필름에 X선을 노출 할 경우 형광체의 사용 유무에 따라 방사선 흡수 효율에 영향을 미치며, 이는 발광 효율 및 감도에 주요한 인자로 작용한다. 현재 상용화되어 있는 형광체는 낮은 발광 효율로 인한 한계를 가지므로, 발광 효율 향상을 위하여 제작 구조에 대한 연구가 진행되고 있다. 이 중 반사막을 활용하는 연구가 활발히 진행되고 있다. 일반적으로 형광체의 제조를 위하여 보편적으로 이용하고 있는 스크린프린팅 방법에서 건조 공정을 수행 시 균일도가 감소하는 현상이 발생한다. 이러한 현상은 반사막의 증착을 불균일하게 만드는 원인으로 작용하고 빛의 산란을 초래하는 현상을 초래한다. 이에 본 연구에서는 증착 시 투명도 저하에 따라 반사율이 증가되는 반사막 성질을 가지며, 방수성 및 절연성과 같은 보호층 특성을 지닌 유기성 투명 박막 페를린에 대하여 연구하고자 한다. 본 연구에서는 화학적 증기 증착법(Chemical Vapor Deposition, CVD)을 이용하여 투명 필름의 상단에 페를린을 코팅한 시편과 코팅하지 않은 시편으로 구분하여 제작하였고, 상단에 스크핀프린팅 방법을 활용하여 형광체를 도포 하였다. 시편 제작 후 실험은 시편을 필름 상단에 위치시키고, 일반진단에너지 대역(Model-SF 80)의 X선을 조사하였다. 이 후 현상기(model-pro14)를 통해 현상된 필름에 나타난 광학적 농도(Optical Density, O.D)를 농도계(Fluke Biomedical Nuclear Associates Densitometer)로 측정하였는데, 불확실성을 줄이기 위하여 총 5회를 측정하여 그 중 2번째로 높은 값을 도출하였다. 측정 결과, 페를린을 코팅한 형광체에서는 1.71의 O.D 값이 측정되었고, 페를린을 코팅하지 않은 형광체에서는 1.43의 O.D 값이 측정되었다. 이를 이용하여 투명도를 산출한 결과 상대적으로 약 1.76% 차이가 나타났다. 이러한 결과는 페를린 활용 시 환자의 피폭 선량 저감화 및 해상력 개선을 도모할 수 있을 것으로 사료된다.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.5
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• pp.405-412
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• 1992

Growth characters of dry seeded paddy rice was studied at different levels of nitrogen(N) split application (basal : immediately after irrigation : 2 weeks after irrigation: 25 days before heading: heading stage with 10 : 20 : 30 : 20 : 20%, 20 : 30 : 20 : 20 : 10%, 30 : 40 : 0 : 20 : 10%, and 100% basal of slow release urea) in tillage and no-tillage systems. On May 17 in 1990, 6kg /10a of dry seeds of a breeding line of Milyang 95 was broadcasted and covered with a power tiller. Between tillage and no-tillage systems yield and its components, lodging related characteristics, and contents of cellulose, hemicellulose and lignin of culm base were similar. Leaf area index at heading stage was higher in tillage, but lodging index was lower compared with those in no-tillage plot. Culm length, effective tiller ratio, culm base weight, 1000-grain weight, harvest index in slow release N applied plot were higher compared with those in other N treatments. Grain yield of rice among levels of N split applications was similar in tillage, but it was higher in slow release N applied plot in no-tillage if 1kg /10a of additional N was applied as urea at panicle formation stage. At early growth stage N concentration and N uptake were lower in the slow release N applied plot, but higher after heading stage compared with other N treatments. The number of tillers was lowest in slow release N applied plot during the tillering stage, but the number of panicles per hill was similar to other N treatments.

• Analytical Science and Technology
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• v.16 no.2
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• pp.102-109
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• 2003

Microwave digestion and solid-state extraction were studied for determination of trace aluminum{Al(III)} in human urine samples. A mixed acid of nitric acid and hydrogen peroxide was added to urine samples, organic materials were destructed in a home microwave oven and dried in a drying oven. The dried residues were dissolved in a sulfuric acid solution. The solution was eluted through a XAD-4 resin column adsorbed with 8-hydroxyquinoline(Oxine, HQ). Al(III)-8-hydroxyquinolinate complex was formed in the column and eluted with 0.5 M nitric acid solution. The Al(III) eluted was determined by graphite atomic absorption spectrophotometry. Various experimental conditions of followings were investigated for the optimization : the type of acid to dissolve the residues, the amount of HQ adsorbed on the resin, the pH of sample solutions, the type and concentration of acid to elute the complex from column and so on. The contents of Al(III) in real samples were determinated by a calibration curve method. The recovery in standard spiked samples was 94~101% and the detection limit of this procedure was 0.05 ng/mL.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.126-126
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• 2017

본 연구는 가축분뇨를 퇴비화 하는 과정에서 흔히 사용되는 수분조절제인 톱밥, 왕겨 등의 가격적 부담으로 인해 좀 더 가격이 저렴한 수분조절제들의 성분을 비교 분석하여 어떤 차이가 있는지 확인하기 위하여 실시되었다. 이를 위해 6가지 수분조절제를 토대로 유도결합플라즈마분광계 장비를 이용하여 화학적 분석, 인장시험기를 이용하여 물리적 분석을 하였다. 화학적 분석을 통해 수분조절제 내 함유되어 있는 성분들을 분석하였으며 물리적 분석을 통해 중량, 함수율, 흡수율, 인장강도 등을 측정하였다. 화학적으로 분석을 했을 시 K, Cd, Pb, Ni, Zn, Cu, Cr, As 등을 측정을 하였으며 앞서 분석했던 각각의 성분들은 농촌진흥청에 명시되어 있는 유해성분의 최대량보다 대부분 적게 측정이 되었다. 물리적으로 분석을 했을 시, 각 수분조절제의 함수율은 최소 10.29%에서 최대 16.07%까지 측정이 되었다. 전단강도는 기존 상태가 가장 높게 측정이 되었으며 다음으로 건조상태 흡수상태로 측정이 되었다. 일반적으로 사용하기에는 흡수율이 가장 높은 우드 브리켓-1이 가장 적합한 것으로 판단된다.

• Journal of the Korean Geotechnical Society
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• v.38 no.8
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• pp.39-52
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• 2022

Multilayer perceptron neural network was trained to determine the factor of safety and slip surface of the slope. Slope geometry is a simple slope based on Korean design standards, and the case of dry and existing groundwater levels are both considered, and the properties of the soil composing the slope are considered to be sandy soil including fine particles. When curating the data required for model training, slope stability analysis was performed in 42,000 cases using the limit equilibrium method. Steady-state seepage analysis of groundwater was also performed, and the results generated were applied to slope stability analysis. Results show that the multilayer perceptron model can predict the factor of safety and failure arc with high performance when the slope's physical properties data are input. A method for quantitative validation of the model performance is presented.

• Journal of Sericultural and Entomological Science
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• v.35 no.1
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• pp.21-27
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• 1993

Yongchonppong is liable to withering of leaf and it is lowering leaf value for the feed. In this respect, covering of the vinylon gauze over the feed has been carried out in the branch rearing system to sustain leaf value as itself. The covering of the vintlon gauze over Yongchonppong marks 7% and 9% increment of cocoon yield in dry season, spring rearing season, as compared to the non-covering of the vinylon gauze over Kaeryangppong and Yongchonppong, respectively. There was no significant differences in cocoon shell percentages of them. In more humid environment than average relative humidity in Korea the rearing results of "Yongchonppong" was improved by covering with vinylon gauze after feeding compared with the non-covered rearing. However, the vinylon guage covering was not effective for improving the rearing results of "Kaeryangppong". No effect of the vinylon gauze covering was seen in the area where it frequently rains and raining season lasts. In case of the non-covering of the vinylon gauze, Yongchonppong reduces repidly in the first three hours of exposure to the air, as compared to Kaeryangppong. The water content reductions rate of Yongchonppong in 6 hours of exposure to the air marks 7% to so when the dry vinylon gauze cover and 17 to 26% when the wet vinylon gauze covers, as compared to 58.8% of it for the noncovering of the vinylon gauze.f the vinylon gauze.

• Korean Journal of Environmental Agriculture
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• v.16 no.2
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• pp.181-186
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• 1997

Since volcanic ash soils in Cheju island have high capacities of adsorption and immobilization of phosphate, a relatively high rate of P application has been recommended in citrus orchards for many years and such a large amount of P application could be problematic both in agricultural and environmental point of view. The objective of this study was to test whether arbuscular-mycorrhizae can be used to improve P availability in Cheju citrus orchard soils. Soil, root and leaf samples were taken from 14 citrus orchards of different location and soil texture. Mycorrhizal spore distribution in the soils, mycorrhizal infection ratio on the citrus roots, and mineral nutrients in leaf samples were determined. Numbers of mycorrhizal spore were in the range of $9,000{\sim}40,000/100g$ soil. The population level was not correlated with any of the soil characteristics examined. Mycorrhizae were found in all of the examined orchards and root infection ratio varied between $14{\sim}60%$. The mycorrhizae infection ratio differed substantially in different soils. Although root infection was high at soils with low extractable P level, it was not significantly correlated with other soil factors measured. Since a positive correlation was observed between leaf P concentration and root infection, enhancement of P uptake seemed to be associated with mycorrhizal infection. These results indicate that mycorrhizae could be a useful method to reduce P applications in Cheju citrus orchards.