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Haksoon Kim,Chae Hoon Sohn 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.1
In a liquid rocket engine, acoustic damping induced by gas-liquid scheme injectors is studied experimentally for combustion stability by adopting linear acoustic test. In the previous work, it has been found that gas-liquid scheme injector can playa significant role in acoustic damping or absorption when it is tuned finely. Based on this finding, acoustic-damping characteristics of multi-injectors are intensively investigated. From the experimental data, it is found that acoustic oscillations are almost damped out by multi-injectors when they have the tuning length proposed in the previous study. The length corresponds to a half wavelength of the first longitudinal overtone mode traveling inside the injector with the acoustic frequency intended for damping in the chamber. But, new injector-coupled acoustic modes show up in the chamber with the injectors of the tuning length although the target mode is nearly damped out. And, appreciable frequency shift is always observed except for the case of the worst tuned injector. Accordingly, it is proposed that the tuning length is adjusted to have the shorter length than a half wavelength when these phenomena are considered.
Haksoon Kim,Chae Hoon Sohn 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.6
In a liquid rocket engine, the role of gas-liquid scheme injector as an acoustic resonator or absorber is studied experimentally for combustion stability by adopting linear acoustic test. The acoustic-pressure signals or responses from the chamber are monitored by acoustic amplitude. Acoustic behavior in a rocket combustor with a single injector is investigated and the acoustic-damping effect of the injector is evaluated for cold condition by the quantitative parameter of damping factor as a function of injector length. From the experimental data, it is found that the injector can play a significant role in acoustic damping when it is tuned finely. The optimum tuning-length of the injector to maximize the damping capacity is near half of a full wavelength of the first longitudinal overtone mode traveling in the injector with the acoustic frequency intended for damping in the chamber. When the injector has large diameter, the phenomenon of the mode split is observed near the optimum injector length and thereby, the acoustic-damping effect of the tuned injectors can be degraded.
Corporate Environmental Responsibility and Credit Ratings
( Haksoon Kim ),( Hyung Cheol Kang ),( Hee Sub Byun ) 보험연구원 2021 보험금융연구 Vol.32 No.4
본 연구는 기존 연구가 주목하는 주주의 관점이 아닌, 채권자의 관점에서 기업의 환경적 책임 활동의 편익을 파악한다. 이를 위해, 대표적신흥국가인 한국의 상장기업을 대상으로 환경적 책임 활동이 신용등급에 미치는 효과를 실증적으로 확인한다. 분석결과, 적극적으로 환경적 책임 활동을 이행하는 기업은 높은 신용등급을 부여 받는 것으로 나타났다. 이러한 효과는 환경적 책임 활동을 구성하는 다양한 요인 중 전략과 성과 부문이 개선될 경우 주로 관찰되었다. 한편, 본 연구의 주요 결과는 대리인비용이 높은 기업에서 주로 관찰되었다. 이는 환경적 책임 활동이 사전적으로 경영자의 사적이익 추구 유인의 확대 가능성을 축소시키는 경로로 채권자의 이해를 충족시키고 있음을 시사한다. 이상의 결과들은 신흥국가에서 환경적 책임 활동이 기업의 잠재적 위험을 통제하는 수단으로 간주되어 채권자의 이해에 부합하는 효과를 가짐을 의미한다. While prior literature focuses on the shareholder’s perspective, this study investigates the benefits of corporate environmental responsibility (CER) activities from the debtholder’s perspective. We find a strong positive relationship between CER activities and credit ratings. Specifically, the positive relationship is mainly driven by the strategy and performance factors of CER activities. Also, we find that the positive relationship is more pronounced in firms with higher agency costs. The results indicate that CER activities in emerging countries have the effect of reducing default risk and meet creditors’ interests. Additionally, it suggests that CER activities have the effectiveness of the corporate strategic perspective on corporate financing and disclosure.
김학순,이동호,엄재호,조명찬,이상도,김미경,윤세진,궁성수,김승택,이복희,안치석,이필량 충북대학교 의과대학 충북대학교 의학연구소 1993 忠北醫大學術誌 Vol.3 No.1
임신성 간내 담즙정체증은 비교적 예후가 좋은 담즙정체성 질환으로 대개 임신 후반기(third tri-mester)에 발병하며, 출산후에 후유증없이 회복되지만 다음 임신에서 재발될 수 있다. 주된 임상증상은 황달과 소양감이며, 스칸디나비아와 칠레에서는 전체 임신중 1∼6%로 다른 나라들에 비해 높은 빈도를 보고되고 있다. 한국에서는 아직까지 증례보고나 빈도에 관한 보고가 없는 실정이다. 저자들은 임신 31주째 부터 생긴 황달과 소양감이 있었던 26세 여자 환자가 35주째 생긴 진통으로 본원에서 응급 제왕절개술로 조기분만후 현저한 담즙정체의 호전이 있어 임상적으로 임신성 간내담즙정체증으로 진단된 1례를 경험하였기에 보고하는 바이다. Intrahepatic Cholestasis of Pregnancy(IHCP) is a relatively benign cholestatic disorder that generally commences late in pregnancy, disappears abruptly after delivery, and frequently recurs with subsequent pregnancy. The main clinical manifestations are pruritus and jaundice. There was no case report of this disorder in Korea. We diagnosed IHCP in 26-year old female who had experienced jaundice and pruritus since 31th gestation period. She took emergency cesarian section because of premature labor and breech presentation. The jaundice and pruritus disappeared after delivery.