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보리나무이종군의 날개에 대한 수량형태학적 분석 (동시목: 나무이과)
박희천,이창언,김훈수,Park, Hee-Cheon,Lee, Chang-Eon,Kim, Hoon-Soo The Korean Society of Systematic Zoology 1988 Korean Journal of Systematic Zoology Special Issue Vol.2 No.-
보리나무속식물의 유연종군에 서식하는 큰보리나무이종군의 날개형질을 다변량적 방법으로 분석한 결과는 다음과 같다. 1. 미기재종은 계절형과 성적인 변이형의 개체가 아닌 독립된 종으로 밝혀졌다. 2. 군분석에서 작은보리나무이는 종내 암.수의 형질 pattern이 높은 유사성을 나타내었다. 3. 4종의 군분석 결과는 작은보리나무이의 계절형이 다른 종에 결합하였으며, 큰보리나무이의 지리적변이가 개체군 사이에서 독립된 결합군으로 나타났다. 4. 명보리나무이와 큰보리나무이 및 미기재종의 암컷들은 세 종 모두 같은 그룹에 소속되었다. 5. 판별분석에서는 성별, 계절형 및 지리적 구분에 영향을 받지 않고 4종이 독립된 종군으로 동정되었다. The wing morphometric characters of P.elaeagni complex feeding on the genus Elaeagnus plants was analysed by the multivariate methods using clustering of generalized distance and discriminant analysis. On the clustering of the species, the effect of sexual differences, seasonal variation and geographic population sensitively appeared . However, four species of this group was precicely divided by the discriminant analysis.
계면활성제를 부가하여 전기방사한 PLGA 부직포의 습윤성 개선
박희천,길명섭,김학용,이덕래,최경은,Park, Heui-Chon,Khil,, Myung-Seob,Kim, Hak-Yong,Lee, Douk-Rae,Choi, Kyung-Eun 한국섬유공학회 2005 한국섬유공학회지 Vol.42 No.3
The effects of surfactant on electrospinnability and wettability of electrospun PLGA nonwoven mats were investigated. For PLGA, a mixtured solvent of tetrahydrofuran (THF) and N,N-dimethylformamide (DMF) was used to dissolve the polymer. Sodium dodecyl sulfate(SDS), a surfactant, was added to PLGA solution for electrospinning. The water absorption capacity of resulting fibers increased as the content of surfactant increased.
이종재료 마찰용접에 의한 초내열합금 대형 배기밸브 스핀들 개발
박희천,정호승,조종래,이낙규,오중석,한명섭,Park Hee-Cheon,Jeong Ho-Seung,Cho Jong-Rac,Lee Nak-Kyu,Oh Jung-Seok,Han Mvoung-Seoup 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.8
Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint race, and energy required lot welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy amount of upset. working time, and residual stresses in the joint. Inertia welding was conducted to make the large exhaust valve spindle for low speed marine diesel engine. superalloy Nimonic 80A for valve head of 540mm and high alloy SNCrW for valve stem of 115mm. Due to different material characteristics such as, thermal conductivity and flow stress. on the two sides of the weld interface, modeling is crucial in determining the optimal weld geometry and Parameters. FE simulation was performed by the commercial code DEFORM-2D. A good agreement between the Predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters. especially for welds for which are very expensive materials or large shaft. Many kinds of tests, including macro and microstructure observation, chemical composition tensile , hardness and fatigue test , are conducted to evaluate the qualify of welded joints. Based on the results of the tests it can be concluded that the inertia welding joints of the superalloy exhaust valve spindle are better properties than the material specification of SNCrW.
박희천 ( Hi Chun Park ) 한국환경경제학회·한국자원경제학회(구 한국환경경제학회) 2013 자원·환경경제연구 Vol.22 No.3
상품 및 서비스 소비구조의 변경을 통해 에너지절약이 실현될 수 있기 때문에 가정부문의 간접 및 총 에너지소비를 추정할 필요가 있다. 가정부문의 직간접 에너지소비를 보다 정확히 추정하기 위해 본 연구는 기업과 소비자(가정부문) 간 석유제품 및 전력의 가격을 차별화하였다. 한국의 가정부문은 1995-2010년 기간 중 한국 1차 에너지소비 중 55% 이상을 소비하였다. 가정부문의 에너지소비 중 69% 이상이 간접 에너지소비였다. 따라서 가정부문의 직접뿐만 아니라 간접 에너지소비도 에너지절약의 대상이 되어야 한다. 전력 소비는 2009년 한국의 가정부문의 주 에너지소비가 되었다. 생활수준이 향상됨으로써 가정부문은 전력 원단위가 높은 상품과 서비스를 소비하게 되었다. 한국 가정부문이 소비하는 제품의 에너지 원단위가 낮아짐으로써, 에너지소비의 증가율이 감소하게 되었다. 반면에 한국 가정부문의 상품 및 서비스 소비구조는 에너지 다소비형으로 변경되어 오히려 에너지소비 증가를 가속시키는 결과를 초래함으로써, 구조효과는 악화되었다. 이에 따라 에너지정책은 에너지소비를 감소시키기 위해 소비자로 하여금 에너지 저소비형 재화와 용역을 소비하도록 유도하여야 한다. 에너지 저소비형 소비를 촉진시킬 수 있는 주요 수단인 에너지가격 현실화가 요구된다. As energy conservation can be realized through changes in the composition of goods and services consumed, there is a need to assess indirect and total household energy consumption. The Korean household sector was responsible for more than 55% of Korea`s total energy consumption in the 1995 to 2010 period. More than 69% of household energy consumption was indirect. Thus, not only direct but also indirect household energy consumption should be the target of energy conservation. Electricity consumption became in 2009 the main source of household energy consumption in Korea. Households consume more and more electricity intensive goods and services, a sign of increasing living standards. Decrease in energy intensities of products consumed by Korean households contributed greatly to reduce the increase in the total household energy consumption. However, switching took place towards more energy intensive products, thus the structure effect was negative. It is necessary to direct consumption and production towards much less energy intensive goods and services as to reduce energy consumption or its growth rate. The Korean government should readjust low energy and electricity prices to cost-reflective prices levels as these low prices are one of the main reasons for the consumption of more energy intensive products. This study differentiates prices of oil products and electricity between households and industries, as to allow more accurate estimation.
박희천(Heechun Park),김태환(Taewhan Kim) 대한전자공학회 2015 대한전자공학회 학술대회 Vol.2015 No.11
Existing synchronous-style circuits are faced with the limit of improvement because of the malfunction from clock skew and the necessity of clock margin. To cope with those barriers, asynchronous-style circuit design is arisen again. Although asynchronous circuit is far less effective than synchronous in the past because of limitations in fabrication process, it is becoming competitive under the necessity of faster and more power-saving chips. In this paper, we compared and analyzed two typical asynchronous circuit structures, single-rail and dual rail, in the point of circuit power and area, and suggested directions of future works for designing effective asynchronous circuits.