• Nuclear Engineering and Technology
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• 제40권3호
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• pp.225-232
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• 2008

To understand the effect of the cyclic strain rate on the environmentally assisted cracking behaviors of SA508 Gr.1a low alloy steel in deoxygenated water at $310^{\circ}C$, the fatigue surface and a sectioned area of specimens were observed after low cycle fatigue tests. On the fatigue surface of the specimen tested at a strain rate of 0.008 %/s, unclear ductile striations and a blunt crack tip were observed. Therefore, metal dissolution could be the main cracking mechanism of the material at this strain rate. On the other hand, on the fatigue surfaces of the specimens tested at strain rates of 0.04 and 0.4 %/s, brittle cracks and flat facets, which are evidences of the hydrogen induced cracking, were observed. In addition, a tendency of linkage between the main crack and the micro-cracks was observed on the sectioned area. Therefore, at higher strain rates, the main cracking mechanism could be hydrogen induced cracking. Additionally, evidence of the dissolved MnS inclusions was observed on the fatigue surface from energy dispersive x-ray spectrometer analyses. Thus, despite the low sulfur content of the test material, the sulfides seem to contribute to environmentally assisted cracking of SA508 Gr.1a low alloy steel in deoxygenated water at $310^{\circ}C$.

• 미생물학회지
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• 제32권4호
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• pp.252-257
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• 1994

황화수소 산화세균인 Thiobacillus sp.를 전남 화순의 폐탄광수에서 분리하였다. 분리된 균주는 그람음성의 운동성이 있고, 포자를 형성하는 간균이었으며, 환원된 무기 황화합물을 산화하여 에너지원으로 사용하는 호기성 통성 화학합성 영양균이었다. 분리균주는 thiosulfate를 첨가한 기본배지에서 유기물을 동화하며 성장하였고, 에너지원으로 사용된 thiosulfate는 32mM 이상의 농도에서는 오히려 기질억제 인자로 작용하여 균의 성장을 억제하였다. 최적 thiosulfate 농도는 32mM이었다. DNA의 G+C 함량은 65.0mol%이고, 세포내 주요 지방산중 비순산화 지방산은 16:1+7$_{cyc}$, 16:0과 수산화 지방산은 3-OH 12:0을 가지며, $C_{18}$의 미동정 가지형의 지방산도 포함하고 있었다. Ubiquinone system은 Q-9을 가지고 있었다. 위와 같은 생리생화학적 특성 결과로부터, 본 분리균주는 Thiobacillus sp. iw.의 새로운 종으로 판단하였다.

• 한국미생물·생명공학회지
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• 제32권2호
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• pp.123-127
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• 2004

토양으로부터 oleic acid 를 탄소원으로 이용하여 MCL-PHA의 생산능이 우수한 균주를 분리하여 Pseudomonas sp. MBEL21이라 명명하였다. Pseudomonas sp. MBEL21의 PHA함량을 증가시키기 위하여 여러 가지 필수 영양분의 제한 조건에서 배양한 결과, 인산이 제한된 조건에서 가장 높은 함량의 PHA를 축적하였다. 고농도의 MCL-PHA생산을 위한 Pseudomonas sp. MBEL21의 유가식 배양 전략을 개발하여 28.1 wt％의 함량으로 23 g/L. MCL-PHA를 생산하였다. 또한, 분리된 Pseudomonas sp. MBEL21을 olive oil을 탄소원으로 이용하여 배양한 결과 9.3 wt％의 PHA가 축적되어졌으며, MCL-hydroxyalkanoate와 함께 3-hyoxy-butyrate 의 단량체들로 이루어진 PHA가 확인되어졌다. 이러한 결과들은 분리된 신규 Pseudomonas sp. MBEL21이 저가의 olive oil로부터 생분해성 탄성체의 응용분야를 갖는 MCL-PHA를 효율적으로 생산할 수 있다는 것을 보여준다.

• 자원리싸이클링
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• 제14권5호
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• pp.54-61
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• 2005

국내 경제성장과 더불어 발전소 에너지원으로 이용되고 있는 석탄은 매년 증가하여 2006년에는 전체 에너지 구성의 30%인 16,000MW에 이를 것으로 예측되고 있다. 이러한 석탄은 다른 화석연료에 비해 매장량이 풍부하고 경제성은 높지만, 사용이 불편하고 석탄회, 아황산가스 등 많은 공해물질을 배출하고 있다. 따라서 본 연구에서는 마찰하전형정전선별법을 이용하여 석탄과 회분구성 광물의 선별기술을 확립, 청정석탄을 생산하고자 한다. 본 연구에서는 bench-scale의 마찰하전형정전선별 장치를 제작하였으며, 선별에 영향을 미치는 인자들을 선정하고 분리실험을 수행하여 최적조건을 확립하였다. 연구결과 최적조건에서 석탄 회수율과 회분 및 유황분 제거율이 각각 68.10%. 31.23% 그리고 28.33%인 정제석탄을 얻을 수 있었다.

• 한국약용작물학회지
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• 제23권2호
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• pp.125-131
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• 2015

In this study, we determined the ingredient analysis of harvested garlic bulb and soil analysis of four garlic-cultivated regions in Jeju, being one of the major areas of Namdo garlic production. Soil pH and electric conductivity were 7.02 and 1.03 dS/m, respectively. Soil organic matter was 4.31%. The mineral elements (potassium, calcium, magnesium, sodium, iron, manganese, copper and zinc) of Namdo garlic cultivated soil were analyzed by ICP, and calcium was the most highly contained mineral with $14.67cmol_+/kg$ and in the decreasing order of magnesium ($2.25cmol_+/kg$), potassium ($1.51cmol_+/kg$). Soluble solid and total acidity were 7.60 oBrix and 0.49%, respectively. The mineral contents of garlic bulb were in order of potassium (12,728 ppm) > sulfur (7,778 ppm) > phosphorus (4,916 ppm) > magnesium (691 ppm) > calcium (359 ppm). The content of total phenolic, total flavonoid and reducing sugar were 71.14 mg GAE/100 g, 17.64 mg QE/100 g and 26.53 mg GE/g, respectively. Alliin and allicin were 8.78 mg/g and 2.10 mg/g, respectively. The Pearson's correlation coefficients between mineral contents of soil and garlic bulb are analyzed. Macronutrients of soil is correlated with macronutrients of garlic (positive) and micronutrients of garlic (negative) contents.

• Tribology and Lubricants
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• 제32권3호
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• pp.82-87
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• 2016

We performed an experimental research on lubricant oil in dual fuel medium-speed engines. It is important to select the appropriate lubricant oil because it could significantly affect engine lifetime and performance. We generally recommend the selection of the lubricant oil according to the fuel grades as contents in the project guide. However, it is a considerable challenge for shipyards to implement this concept because of the lack of space to install the complicated lubricating oil system for dual fuel engines. Therefore, we determine the adaptability of one-common lubricant oil for HiMSEN dual fuel engine through this experimental research. To check abnormality in gas mode operation and durability of engine components when a lubricating oil with high BN (base number) is used, overhaul inspections and lubricant oil analysis are carried out two times, and four times, respectively, during an operation of approximately 300 h. We investigated the variations in kinematic viscosity, base number, element quantity, pentane insoluble and sulfated ash in lubricant oil analysis. Moreover, we also investigated whether the deposit formation or wear occurred in various bearings, injectors, exhaust valves, intake valves, piston rings and so on through the overhaul inspections. There are no problems in the lubricant analysis and the overhaul inspections. Through the experimental research, we confirm that one-common lubricant oil should be selected according to the higher sulfur content of fuel oil in dual fuel engines.

• 미생물학회지
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• 제53권4호
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• pp.320-322
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• 2017

그람 음성이며 긴 막대 모양의 betaproteobacteria에 속하는 GR16-43을 한강 발원지 검룡소에서 분리하였다. GR16-43 균주에 대한 유전체분석을 실시하였으며, G + C 비율이 67.12%인 4,806,848 bp 크기의 염기서열을 얻었다. 유전체 특징은 황산화와 관련된 다량의 유전자를 보유하고 있어 균주의 잠재적 중요성을 보여준다. 이러한 결과는 GR16-43 균주가 빈영양 담수 환경에서의 적응 연구를 위한 유전체 정보를 제공한다.

• International Journal of Industrial Entomology and Biomaterials
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• 제38권2호
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• pp.25-30
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• 2019

Atmospheric-pressure plasma technique is a technology for sterilizing agricultural product. In this study, dielectric barrier discharge plasma was applied to silkworm powder for 1 to 5 h with less than 2 ppm of $O_3$ and $NO_2$. Quantitative compositions including proximate contents, mineral and heavy metal contents, fatty acids, vitamins, and DNJ contents were measured. Proximate contents of silkworm powder were protein (57.2%), fat (9.9%), fiber (4.6%), ash (10.1%), and moisture (5.7%). These compositions were not affected by the treatment of plasma. Silkworm powder has 5 abundant minerals potassium (K), phosphorus (P), sulfur (S), calcium (Ca), and magnesium (Mg). Among these minerals, plasma treatment decreased the contents of P and S sharply from 732.3 to 176.8, and 492.7 to 185.2 mg/100g, respectively. Heavy metal contents including lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) were not detected in the silkworm powder. Five vitamins such as ascorbic acid (13.6 mg/100g), riboflavin (5.4 mg/100g), ${\beta}$-carotene (1.8 mg/100g), niacin (0.6 mg/100g), and thiamine (0.4 mg/100g) were not significantly changed by plasma treatment. Silkworm powder is composed of 30 parts saturated fatty acids and 70 parts unsaturated ones. The fatty acid composition was not significantly changed by plasma treatment. The DNJ content of silkworm powder (3.72 mg/g) was also nearly constant within the experimental condition of plasma treatment.

• 농업과학연구
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• 제45권4호
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• pp.811-821
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• 2018

This study focused on the improvement of blueberry delivery service using pre-cooled ice and $SO_2$ pads to prevent an increase in the fruit temperature as well as decay. To maintain the fruit quality during low temperature storage, the effect of a $SO_2$ pad and modified atmosphere packaging was also examined. Harvested blueberries were precooled at $15^{\circ}C$, sorted, and packaged. And the fruits were placed in a similar environment as that for the parcel service. Part of the fruits were stored at $0^{\circ}C$ for long term storage. The air temperature in the delivery box increased along with an increase in the simulated delivery time regardless of the treatment. However, the rate of temperature increase was lower in the ice pad treatment. No significant difference was not found after 48 h. The oxygen concentration in the box ranged between 10.5 - 14.5% in the ice pad treatment, which was higher than that of the untreated control (7.5 - 11.9%) whereas the $CO_2$ concentration was lower in the ice pad treatment. No differences were found in the occurrence of off-flavor, decay, and sensory quality loss during the 48 hours of the parcel service simulation. The combined treatment of the $SO_2$ pad and modified atmosphere packaging (MAP) using a perforated film increased the shelf-life of the blueberry fruits, the overall quality such as firmness, and the soluble solid content was not different between the treatments except for the decay incidence. No decayed fruit was found in the combined treatment. However, the percentage of decayed fruit in the control was 25% on day 15 of storage and 75% on day 33 of storage, respectively.

• 대한금속재료학회지
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• 제46권10호
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• pp.609-616
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• 2008

Conventional bake-hardenable(BH) steels should be annealed at higher temperatures because of the addition of Ti or/and Nb which forms carbides and raises recrystallization start temperature. In this study, the development of new BH steels without Ti or Nb addition has been reviewed. The new BH steels have nearly same mechanical properties as the conventional BH steels even though it is annealed at lower temperature. The steels also show smaller deviation of the mechanical properties than that of the conventional BH steels because of the conarol of solute carbon content during steel making processes. The deviation of mechanical properties in conventional BH steels is directly dependent on the deviation of solute carbon which is greatly influenced by the amount of the carbide formers in conventional BH steels. Less alloy addition in the newly developed BH steels gives economical benefits. By taking the advantage of sulfur and/or nitrogen which scarenge in Interstitial-Free or conventional BH steels, fine manganese sulfides or nano size copper sulfides were designed to precipitate, and result in refined ferrite grains. Aluminum nitrides used as a precipitation hardening element in the developed steels were also and resull in fine and well dispersed. As a result, the developed steels with less production cost and reduced deviation of mechanical properties are under commercial production. Note that the developed BH steels are registered as a brand name of MAFE(R) and/or MAF-E(R).