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Kim, Chulgoo,Choi, Jong-Yun,Choi, Byungwoong,Lee, JunSeok,Jeon, Yonglak,Yi, Taewoo National Institute of Ecology 2021 국립생태원회보(PNIE) Vol.2 No.4
We conducted a study to investigate the characteristics of the carbon cycle of two streams (located in Shig a Prefecture, Japan), having similar size, namely, the Adokawa stream (length: 52 km, area: 305 km<sup>2</sup>, watershed population: 8,000) and the Yasukawa stream (length: 62 km, area: 380 km<sup>2</sup>, watershed population: 120,000), but with different degree of human activity. Samples were collected from these two streams at 14 (Adokawa stream) and 23 (Yasukawa stream) stations in the flowing direction. The dissolved inorganic carbon (DIC) concentration and the stable carbon isotope ratio of DIC (δ<sup>13</sup>C-DIC) were measured in addition to the watershed features and the chemical variables of the stream water. The δ<sup>13</sup>C-DIC (-9.50 ± 2.54‰), DIC concentration (249 ± 76 µM), and electric conductivity (52 ± 13 µS/cm) in Adokawa stream showed small variations from upstream to downstream. However, the δ<sup>13</sup>C-DIC (-8.68 ± 2.3‰) upstream of Yasukawa stream was similar to that of Adokawa stream and decreased downstream (-12.13 ± 0.43‰). DIC concentration (upstream: 272 ± 89 µM, downstream: 690 ± 37 µM) and electric conductivity (upstream: 69 ± 17 µS/cm, downstream: 193 ± 37 µS/cm) were higher downstream than upstream of Yasukawa stream. The DIC concentration of Yasukawa stream was significantly correlated with watershed environmental variables, such as, watershed population density (r = 0.8581, p<0.0001, n = 23), and forest area percentage of the watershed (r = -0.9188, p<0.0001, n = 23). δ<sup>13</sup>C-DIC showed significant negative correlation with the DIC concentration (r = -0.7734, p<0.0001, n = 23), electric conductivity (r = -0.5396, p = 0.0079, n = 23), and watershed population density (r = -0.6836, p = 0.0003, n = 23). Our approach using a stable carbon isotope ratio suggests that DIC concentration and δ<sup>13</sup>C-DIC could be used as indicators for monitoring the health of stream ecosystems with different watershed characteristics.
엔진 구동계 크랭크샤프트 피로강도에 대한 축계 진동의 영향성 검증
김민철(Mincheol Kim),조성용(Sungyong Cho),김철구(Chulgoo Kim) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
Driving system which is one of the main system of engine consists of dynamic components and have significant influence on engine performance. Recently emission control has been more and more tightened up and engine makers have prepared for countermeasure to deal with it. Increase of firing pressure in cylinder can be considered as one of the effective alternatives for it, but this has strong influence on the strength and vibration of components of driving system. Crankshaft which delivers power to the transmission and vehicle is the most critical component among them and so must be robustly designed to have sufficient durability and stable vibration characteristics. In this study the influence on crankshaft fatigue strength by vibration due to increase of firing pressure in cylinder and inertia load is predicted by analytical method and validated by real measurement.
디젤 엔진 Gear Box의 Whining noise 저감에 대한 연구
조성용(Sungyong Cho),김철구(Chulgoo Kim),김민철(Mincheol Kim),김상우(Sangwoo Kim) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
Recently, Emission regulation for automobiles has become stricter as people are being more aware of the importance of air-pollution. Therefore, automobile manufacturers are paying close attention towards after-treatment technologies in order to improve efficiency to fulfill these requirements. Due to this factor, high firing pressure in cylinder and optimization of timing system are becoming more relevant these days. The development of this new technology causes a new problem to arise as it produces an increased whining noise in engine gear box. As a result of the importance to cause this problem, this paper presents case study about reduction of whining noise in gear box by experimental and analytical method that include ODS(operational deflection shape) and FEM analysis.
이철구(Chulgoo Lee),김종대(Jongdae Kim),임태순(Taesoon Im),최명식(Myungsik Choi),방승기(Seungki Pang),함흥돈(Heungdon Ham) 한국지열·수열에너지학회 2013 한국지열에너지학회논문집 Vol.9 No.2
It has become very important for unused energy to be used for building air conditioning. Economic evaluation on energy system by using river water as a heat source, which is one of the unused energy, was carried out. The floor area of the building and the distance between heat source equipment and river was assumed 50,000 ㎡ and 200 m. General heat source system using absorption chiller-heater was used for comparing to the energy saving system, and payback period method using initial cost and running cost of two system, was used to perform economic evaluation. According to development of high capacity of water source heat pump which is appropriate for using river water, initial cost for the system has been reduced. Payback period was about 3.2 years, and this period might be shortened if nation’s economic support enact.
이철구(Chulgoo Lee),김종대(Jongdae Kim),임태순(Taesoon Im),방승기(Seungki Pang),함흥돈(Heungdon Ham) 한국지열·수열에너지학회 2011 한국지열에너지학회논문집 Vol.7 No.1
Feasibility study on energy saving system by utilizing exhausted heat from subway, which is one of the unused energy, was carried out. General heat source system using absorption chiller-heater was used for comparing to the energy saving system, and payback period method using initial cost and running cost of two systems, was used to perform economic estimation. Payback period was about ten years, and this period might be shortened if nation's economic support enact.