• Journal of Welding and Joining
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• 제22권5호
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• pp.26-31
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• 2004

In order to propose the optimum welding condition for field application, the effects of welding heat input and cooling rate at PWHT on the mechanical properties were investigated. Submerged arc welding of 1.25Cr-0.5Mo steel for pressure vessel was conducted at welding heat inputs of 15.2kJ/cm, 30.9kJ/cm, and 44.8kJ/cm, and cooling rates of 184$^{\circ}C$/hr, 55$^{\circ}C$/hr, and 2$0^{\circ}C$/hr at PWHT. From the test results, as the welding heat input increase up to 30.9kJ/cm, the changes of microstructure and impact toughness were small. At the heat input of 44.8kJ/cm, however, toughness decreased obviously due to the coarsening of coarse-grained HAZ and formation of ferrite at bainite grainboundary of weld metal. On the other hand, cooling rates at PWHT did not effect on the changes in microstructure and mechanical properties. Even though tensile strength and impact toughness at all welding conditions of this study were above the minimum specification requirement, it was confirmed that heat input of 30.9kJ/cm was the optimum welding condition to improve welding performance by higher heat input.

• 한국결정학회지
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• 제11권1호
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• pp.16-21
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• 2000

(Yb/sub x/Y/sub 1-x/)Ca₄O(BO₃)₃ single crystals where x=0.3,8,15,20% were grown by Czochralski Method. The crystals grown under the optimum conditions were transparent and colorless with good crystal form. Using polarizing microscope, crystal defects such as parasite crystals and bubbles were detected depending on the composition of melts and pulling rates. The optimum growth parameters for high quality of single crystals were 15∼20 rpm of rotation rate and 2mm/h of pulling rate at the flow rate of 2 l/min of Nitrogen gas. The relationship between crystal axes and optical axes was investigated by optical crystallographic method, polarization technique and single crystal X-ray method. From the spectroscopic measurements, it was confirmed that there were strong absorption bands at 900 and 976.4 nm and strong emission band at 976.4 nm in Yb/sup 3+/ ion doped YCa₄O(BO₃)₃ crystal. For the application of second harmonic generation of 1.064 ㎛ laser, non-linear optical devices with θ=32.32° and Ψ=0°, λ/10 of flatness and the size of 6x8x5.73 mm were fabricated from the grown YCa₄O(BO₃)₃ crystal.

• 설비공학논문집
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• 제23권7호
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• pp.513-519
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• 2011

The object of this study is to investigate the performance characteristics of refrigerators using a single-circuit multi cycle and a bypass two-circuit multi cycle. Each refrigeration cycle was tested by varying secondary fluid mass flow rate and temperature. Based on the experimental data, the optimum refrigerant charge was 48 g and the COP at the optimum secondary fluid mass flow rate was 1.53 for the single-circuit multi cycle. For freezer(F)-only mode, both the single-circuit multi cycle and the bypass two-circuit multi cycle were operated at overcharge conditions, resulting in an increase of the secondary fluid mass flow rate. The maximum COPs of the single-circuit multi cycle and the bypass two-circuit multi cycle were 1.22 and 1.35, respectively. The COP increased by 10.7% with the application of the bypass two-circuit multi cycle.

• 한국약용작물학회지
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• 제17권5호
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• pp.363-368
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• 2009

To fulfill the increasing demand for a high quality of flower, we investigated the effects of nitrogen application on plant growth, yield and bioactive compounds of Chrysanthemum indicum L.. C. indicum L. was cultivated in a pot scale, and nitrogen applied with the level of 0 (N0), 50 (N50), 100 (N100), 150 (N150), 200 (N200) and $300\;(N300)\;kg\;ha^{-1}$ to suggest optimum rate of nitrogen fertilization. Phosphate and potassium applied the same amount of $80-80\;kg\;ha^{-1}$ ($P_2O_5-K_2O$) in all treatments. Growth characteristics and yields of C. indicum L. were significantly affected by nitrogen application. Maximum yield achieved in 265 and $295\;kg\;ha^{-1}$ N treatment on the whole plant and the flower parts, respectively. The nitrogen content and uptake of whole plant significantly increased by the increase of nitrogen application. Five major components of essential oil, $\alpha$-pinene, 1,8-cineol, chrysanthenone, germacrene-D, and $\alpha$-curcumene in flowerheads of C. indicum L. occupied approximately 40% of peak area, germacrene-D decreased by the increase of nitrogen application among them. However, cumambrin A contents in the flower parts of C. indicum L. were affected negatively by the increase of nitrogen application, but total yields of cumambrin A in flower part significantly increased. Conclusively, nitrogen fertilization could increase the yield of flowerheads. The optimum application level of nitrogen fertilizer might be on the range of $265-295\;kg\;ha^{-1}$ in a mountainous soil.

• 전기학회논문지
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• 제58권12호
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• pp.2474-2479
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• 2009

This paper presents an atmospheric microplasma-jet device for bio~medical application. The microplasma-jet device consists of four components; a thin Ni anode, porous alumina insulator, a stainless steel cathode and an aluminum case. The anode has 8 holes, and hole diameter and depth are $200 {\mu}m$ and $60 {\mu}m$, respectively. The discharge test was performed in atmospheric pressure using nitrogen gas and AC voltage at the optimum gas flow rate of 4 Vmin. The plasma-jet is ejected stably for the input voltage ranging from 5.5 to $9.5 kV_{p-p}$. The plasma becomes dense as the input voltage increases, which was verified by the hydrophilicity change of PMMA surface treated by the plasma. The temperature increasement of the aluminum film exposed to plasma-jet illustrates that the micro plasma-jet device is feasible for bio-medical application.

• 한국도로학회논문집
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• 제20권1호
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• pp.69-76
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• 2018

PURPOSES : This study determined the optimal usage rate of RAP (reclaimed asphalt pavement) using cold central-plant recycling (CCPR) on a road-surface layer. In addition, a mixture-aggregate gradation design and a curing method based on the proposed rate for the surface-layer mix design were proposed. METHODS : First, current research trends were investigated by analyzing the optimum moisture content, mix design, and quality standards for surface layers in Korea and abroad. To analyze the aggregate characteristics of the RAP, its aggregate-size characteristics were analyzed through the combustion asphalt content test and the aggregate sieve analysis test. Moreover, aggregate-segregation experiments were performed to examine the possibility of RAP aggregate segregation from field compaction and vehicle traffic. After confirming the RAP quality standards, coarse aggregate and fine aggregate, aggregate-gradation design and quality tests were conducted for mixtures with 40% and 50% RAP usage. The optimum moisture content of the surface-layer mixture containing RAP was tested, as was the evapotranspiration effect on the surface-layer mixture of the optimum moisture content. RESULTS : After analyzing the RAP recycled aggregate size and extraction aggregate size, 13-8mm aggregate was found to be mostly 8mm aggregate after combustion. After using surface-chipping and mixing methods to examine the possibility of RAP aggregate segregation, it was found that the mixing method contributed very little for 3.32%, and because the surface-chipping method applied compaction energy directly as the maximum assumption the separation ratio was 15.46%. However, the composite aggregate gradation did not change. Using a 40% RAP aggregate rate on the surface-layer mixture for cold central-plant recycling satisfied the Abroad quality standard. The optimum moisture content of the surface-layer mixture was found to be 7.9% using the modified Marshall compaction test. It was found that the mixture was over 90% cured after curing at $60^{\circ}C$ for two days. CONCLUSIONS : To use the cold central-plant recycling mixture on a road-surface layer, a mixture-aggregate gradation design was proposed as the RAP recycled aggregate size without considering aggregate segregation, and the RAP optimal usage rate was 40%. In addition, the modified Marshall compaction test was used to determine the optimum moisture content as a mix-design parameter, and the curing method was adapted using the method recommended by Asphalt Recycling & Reclaiming Association (ARRA).

• 한국자원식물학회지
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• 제15권1호
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• pp.67-71
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• 2002

삼백초의 3요소 시비 적량을 구명하고자 3요소 시비수준을 무비구 등 3요소별 4수준으로 11조합하여 시험을 수행한 결과를 요약하면 다음과 같다. 1. 토양의 이화학적 변화는 pH, 유기물, 마그네슘, CEC 그리고 EC는 시험 전에 비해 시험 후에 높은 경향을 보였으나, 인산, 칼리 그리고 칼슘은 상반된 경향이었다. 2. 건엽중은 무비구 281kg/10a에 비하여 3요소 시비구에서 26~108kg가 많았으며, 건근중은 무비구 610kg/10a에 비하여 3요소 시비구에서 19~157kg가 많았다. 3. 2년생 삼백초의 3요소 시비적량은 질소 7.1, 인산 2.5, 칼리 4.2kg/10a이었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2845-2849
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• 2008

Long Term Asset Management(LTAM) means a plan developed by using LCM(Life Cycle Management) process for optimum life cycle management of significant plant assets at each plant across the fleet. As a part of development of LTAM Strategies on nuclear turbines, a method so as to determine the future failure rates for low pressure turbine facilities at a nuclear plant was studied and developed by using both plant specific and industry-wide performance data. INPO's EPIX data were analyzed and some failure rate evaluation values considering preventive maintenance practices were calculated by using EPRI's PM Basis software. As the result, failure rate functions applicable to a priori and a posteriori replacement of low pressure turbines at a nuclear plant were developed and utilized in an assessment of economics of LCM alternatives on the nuclear turbine facilities in the respects of 40-year and 60-year operation bases.

• 한국토양비료학회지
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• 제15권3호
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• pp.178-187
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• 1982

초지개발이 유망시되는 전국각지의 미개간(未開墾) 산지토양(山地土壤)의 표토(表土)를 채취(採取)하여 다량(多量) 요소(要素)의 음(陰)이온총량(総量) : 양(陽)이온총량(総量)(${\Sigma}$ Anion: ${\Sigma}$ Cation) 적정시비비율(適正施肥比率)과 적정총시비량(適正総施肥量)(${\Sigma}$ion)결정(決定)을 위한 Pot시험(試驗)을 수원(水原)에서 수행(遂行)한 결과(結果)는, 1. 제주등 5개지역(個地域)의 토양(土壤)에 대한 혼파목초재배시(混播牧草栽培市) 각토양(各土壤) 및 초종별(草種別) 다수획(多收獲)을 얻기 위한 당량비기준의 음(陰)과 양(陽)이온 총량간(総量間)의 적정(適正) 시비비율(施肥比率)과 적정총시비량(適正総施肥量)이 계산(計算)되었다(표(表)6,7) 2. 혼파재배(混播栽培)에서 화본과목초(禾本科牧草)는 음(陰)이온총량(総量), 두과목초(荳科牧草)는 양(陽)이온총량(総量) 비율(比率)이 높을수록 이들의 수량(收量)과 식생구성비율(植生構成比率)이 증가(增加)하였다. 적정(適正) 음(陰)과 양(陽)이온총량(総量) 비율(比率)은 화본과목초(禾本科牧草)에서는 음(陰)이온총량(総量)이 두과목초(荳科牧草)에서는 양(陽)이온총량비율(総量比率)이 각각(各各) 타(他)이온총량비율(総量比率)보다 훨씬 높을 때였다. 3. 두과목초(荳科牧草)의 수량제고(收量提高)를 위(爲)한 적정총시비량(適正総施肥量)은 음(陰)과 양(陽)이온총량비율(総量比率)에 따라 달렀다. 양(陽)이온총량비율(総量比率)이 높아질수록 적정총(適正総)이온농도(濃度)(총시비량(総施肥量))는 증가(增加)하였고 이의 역(逆)도 성립(成立)하였다. 4. 화본과목초(禾本科牧草) 및 총수량(総收量)(화본과(禾本科)+두과(荳科))에 미치는 음(陰)과 양(陽)이온총량(総量)의 각(各) 효율(效率)은 이들의 비율(比率)이 낮을때 그리고 총(総)이온농도(濃度)가 낮을때 제일(第一) 높았다. 5. 두과목초수량(荳科牧草收量)에 미치는 음(陰)이온총량효율은 대구토양(大邱土壤)을 제외(除外)하고는 화본과목초(禾本科牧草)와 같은 경향(傾向)이였고, 양(陽)이온총량효율은 총(総)이온농도(濃度)와 토양종류(土壤種類)에 따라 달랐으나 보편적(普遍的)으로 양(陽)이온총량비율(総量比率)이 높아질수록 본효율도 높아졌다. 6. 각(各) 구성초종(構成草種)의 수량(收量), 식생비율(植生比率)은 음(陰)과 양(陽)이온총량비율(総量比率), 총(総)이온농도(濃度)와 이들의 상호작용(相互作用)에 크게 영향(影響)을 받았고, 화본과(禾本科)와 두과목초(荳科牧草)는 서로 상반적영향(相反的影響)을 받았다.

• 한국토양비료학회지
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• 제34권4호
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• pp.265-272
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• 2001

토양비옥도와 토성이 서로 다른 논토양에서 수도 생산성과 환경을 고려한 가축분퇴비의 적정시용기준량을 확립하기 위하여 남계 사양토, 용지 양토, 화동 식양토에서 돈분퇴비를 0, 5, 10, 20 톤 $ha^{-1}$을 시용하고 추청벼를 공시 품종으로 하여 포장시험을 1년간 수행하여 다음과 같은 결과를 얻었다. 토양검정에 의한 화학비료 시용시 돈분퇴비 적정시용량은 사양토 4.0, 양토와 식양토 7.0 톤 $ha^{-1}$ 이었으며, 이때의 정조 수량은 사양토 7.440, 양토 7.000 식양토 6.020 톤 $ha^{-1}$이었다. 사양토와 양토에서 NPK와 함께 돈분퇴비를 15 톤 $ha^{-1}$ 이상 시용시에는 도복에 의한 수량 감소가 발생되었다. 수확기 식물체의 양분흡수량은 돈분 퇴비 시용량이 증가할수록 많아지는 경향이었으며, 시험 후 토양의 인산과 칼리의 함량은 돈분퇴비 시용량의 증가에 따라 높아지는 경향을 보였으며, 그 외의 성분은 처리구간 큰 차이가 없었다.