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극 저탄소강의 Intercritical coarse grained HAZ에서의 M-A상과 인장특성 간의 상관관계
이윤기,문준오,김상훈,이창희,Lee, Yoon-Ki,Moon, Joon-Oh,Kim, Sang-Hoon,Lee, Chang-Hee 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.3
It is well known that martensite-austenite (M-A) constituents are formed in the intercritically reheated coarse grained heat affected zone (ICCGHAZ) of a multipass weld and they act on the local brittle zone (LBZ) in the welded structures. To investigate the effect of M-A constituents on the tensile properties of ICCGHAZ, specimens with M-A constituents of different volume fraction and size were prepared through the multipass welding cycles simulated by a Gleeble simulator and then tensile test was carried out. The results indicated that finely distributed M-A constituents contributed to decrease the yield ratio, which is mainly due to the increased tensile strength.
임상연구 : 외래 사시 수술의 Monitored Anesthetic Care에서 Fentanyl과 Ketamine 병용사용의 효과
이윤기 ( Yoon Ki Lee ),장혜원 ( Hae Wone Chang ),심재용 ( Jae Yong Shim ) 대한마취과학회 2006 Korean Journal of Anesthesiology Vol.50 No.4
Background: Monitored anesthetic care can provide patient safety and optimal surgical conditions. However, propofol and fentanyl decrease the hypoxic ventilatory response and heart rate. Ketamine has less respiratory depression and blocks bradycardia. Furthermore, ketamine can reduce the amount of opioid use but it delays discharge in the outpatient anesthesia. Therefore, this study retrospectively examined the effects of combined fentanyl and ketamine administered during monitored anesthetic care on the use of opioids, cardiorespiratory side effects, and patient discharge. Methods: The anesthetic room, the recovery room and day surgery center records of ambulatory strabismus surgery with monitored anesthetic care was reviewed by anesthesiologists from Oct. 2004 to July 2005. The patients were classified as those receiving either fentanyl (F group: n = 32) or fentanyl and ketamine (FK group: n = 19) with a propofol infusion. The fentanyl dose used, the need for airway support, anticholinergics and naloxone were compared. The stay in the recovery room and the day surgery center was also examined. Results: The FK group used significantly less fentanyl than the F group (P < 0.05). Although airway support was needed, there was less anticholinergics and naloxone used in the FK group, but this difference was not significant. The stay in recovery room and the day surgery center were similar. Conclusions: Co-administered ketamine reduces the amount of fentanyl-needed, but it does not reduce the need for airway support and anticholinergics. In addition, co-administered ketamine does not affect the number of days in the recovery room and day surgery center. (Korean J Anesthesiol 2006; 50: 434~8)
이윤기(Yoon Ki Lee),명광재(Kwang Jae Myong) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.2
최근, 승용차는 물론 대형차에서도 하이브리드시스템 등의 전기동력방식을 도입하려는 연구개발이 활발하다. 기존의 내연기관을 대체하는 전기구동모터를 이용하여 차량을 구동하는 전기동력방식을 채용하는 것이 한층 더 효율적이며 가속성능, 승차감 등의 면에서도 유리한 점이 많다. 그러나 모터는 엔진과 전혀 다른 특징을 갖기 때문에 동력성능과 에너지효율에 관한 적합한 평가수법을 검토할 필요가 있다. 본 논문에서는 전기구동버스에 대한 구동모터 시스템을 다이나모미터 상에서 운전하여, 노선버스의 운행패턴을 반영한 모의운전을 실시, 가속성능 및 에너지변환효율, 회생효과의 평가방법 등을 고찰하였다. 그 결과 실 주행 패턴운전에 대한 모터일률, 전력량 등의 계측으로부터 모터 변환효율은 90% 전후, 회생전력량은 요구전력량의 40% 이상으로 평가되었다. Recently, research and development of a hybrid system for passenger cars as well as for heavy-duty vehicles has become more intensive. An electric powertrain system using an electric motor can replace conventional gasoline and diesel engines. The electric motor has a higher efficiency, better acceleration performance, and is more comfortable than conventional powertrain systems; however, new methods for assessing power performance and energy convergence efficiency have to be investigated because the characteristics of an electric motor are entirely different from those of an internal combustion engine (ICE). In this study, an experiment was carried out on a motor (PMSM: Permanent Magnet Synchronous Motor) test bench. One simple driving mode and four other driving modes identified from real-world driving data of a city bus were selected to perform the experiment on the motor test bench. Then, methods for assessing the acceleration performance, energy convergence efficiency, regenerative effect, etc., were investigated. It was found that the energy efficiency of PMSM was about 90% and that 40% of demand energy was regenerated.
이윤기 ( Yoon Ki Lee ),윤지현 ( Ji Hyun Yoon ),정형수 ( Hyungsoo Jung ),염헌영 ( Heon Young Yeom ),양영규 ( Young Kyu Yang ),황순욱 ( Soon Wook Hwang ) 한국정보처리학회 2007 한국정보처리학회 학술대회논문집 Vol.14 No.2
키워드 유사성 검색은 입력받은 키워드에 관련된 의미 있는 데이터를 검색하는 것을 말한다. 데이터 들은 매우 다양한 형태로 표현 될 수 있고, 각각의 형태에 대한 키워드 유사성 검색에 대한 많은 연구 가 이루어졌다. 이 논문에서는 다양한 키워드 유사성 검색에 대한 연구들의 개관을 살펴보고 그것들을 비교해 볼 것이다. 이 연구들을 비교·분석하는 것은 키워드 유사성 검색을 일반화 하는데 도움이 될 것으로 기대한다.
용접 열영향부 미세조직 및 재질 예측 모델링: V. 저합금강의 초기 오스테나이트 결정립크기 및 냉각 속도의 영향을 고려한 용접 열영향부 상변태 모델
김상훈,문준오,이윤기,정홍철,이창희,Kim, Sang-Hoon,Moon, Joon-Oh,Lee, Yoon-Ki,Jeong, Hong-Chul,Lee, Chang-Hee 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.3
In this study, to predict the microstructure in weld HAZ of low alloyed steel, prediction model for the phase transformation considering the influence of prior austenite grain size and cooling rate was developed. For this study, six low alloyed steels were designed and the effect of alloying elements was also investigated. In order to develop the prediction model for ferrite transformation, isothermal ferrite transformation behaviors were analyzed by dilatometer system and 'Avrami equation' which was modified to consider the effect of prior austenite grain size. After that, model for ferrite phase transformation during continuous cooling was proposed based on the isothermal ferrite transformation model through applying the 'Additivity rule'. Also, start temperatures of ferrite transformation were predicted by $A_{r3}$ considering the cooling rate. CCT diagram was calculated through this model, these results were in good agreement with the experimental results. After ferrite transformation, bainite transformation was predicted using Esaka model which corresponded most closely to the experimental results among various models. The start temperatures of bainite transformation were determined using K. J. Lee model. Phase fraction of martensite was obtained according to phase fractions of ferrite and bainite.
조선용 후판 AH32 강에 대한 SAW 및 Hybrid(CO<sub>2</sub> Laser+MIG) 맞대기 용접부의 열 및 역학적 특성 비교
방한서,오종인,방희선,노찬승,이윤기,봉현수,이정수,Bang, Han-Sur,Oh, Chong-In,Bang, Hee-Seon,Ro, Chan-Seung,Lee, Yoon-Ki,Bong, Hyun-Soo,Lee, Jeong-Soo 대한용접접합학회 2008 대한용접·접합학회지 Vol.26 No.5
In this paper concentrate on the comparison of the thermal and mechanical characteristics in Butt joint of ship structure AH32 steel by using hybrid welding and conventional SAW. For this purpose, fundamental welding phenomena of hybrid process using $CO_2$ Laser and MIG is investigated by the experiments and characteristics of thermal and welding residual stress distribution of welded joint in SAW and hybrid welding are understood from the result of FE numerical simulation and experimental values. From the result of this study, it is understood that Laser-MIG hybrid welding have high potential, make substantial saving of time and manufacturing cost and may proves its self robust in the butt joining of thick AH32 steel ship structural plate in the near future.
임동진 ( Dong Jin Lim ),이윤기 ( Yoon Ki Lee ),윤희석 ( Hi Seak Yoon ),김민호 ( Min Ho Kim ) 한국복합재료학회 2003 Composites research Vol.16 No.3
타이어 벨트충내의 코드간 균열연결 및 층간균열진전을 모사하기 위해 자유단을 갖는 2층 고무/코드 적층시험편에 대한 4~11㎜ 변위제어 실험을 수행하였다. 자유단의 코드간 균열연결시의 폭방향 균열진전량은 45° 경사진 코드들간 길이의 절반에 도달할 때의 측정값으로 하였으며, 이는 탐침법에 의해 측정되었다. 또한, 자유단에서 코드들간 균열연결을 모하기 위해 2차원의 이상화된 모델링 기법을 고안하였다. 이론수명은 테어링에너지(균열파단면의 단위면적당 방출에너지)를 이용하여 코드간 균열연결수명(임계값)과 이후 최종파손까지의 수명으로 구분하였으며, 이들을 각기 실험값과 비교하였다. 임계값까지의 수명예측은 실험과 비교하여 약 20%, 최종파손까지 약 65%의 오차가 발생하였다. 따라서, 전체 이론수명은 실험과 비교하여 약 45%의 오차를 발생하였다. In order to simulate the crack connection between cords and the interply crack growth in the belt-layer of real tire, 2 ply rubberlcord laminate specimens with exposed edges were tested in 4-1 Imm displacement control. Measurement of the crack connection is evaluated when crack reaches the half of the length between 45 aligned cords, and the amount of the crack growth is measured by the steel probe method. 2 dimensional analytic modeling was performed to simulate the crack connection between cords at the exposed edges. Also, the theoretical life of the specimens was calculated from the crack connection life between cords(critica1 value) and from the critical value to the final failure by the use of Tearing energy(T); the strain energy release per unit area of one fracture surface of a crack. Then, theoretical life was compared with those of experiments. The life prediction up to the critical value has about 20% error compared to experimental life, and up to the final failure about 65% error. Therefore, total theoretical life has about 45% error compared to the experimental life, which is conceivable in the case of rubber.