• 대한기계학회논문집A
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• 제34권8호
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• pp.1067-1074
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• 2010

본 논문에서는, 운전조건에서의 저압최종단 블레이드에 대하여 약결합 유체-구조 연계해석기법을 이용한 해석이 수행되었다. 저압터빈 최종단에 대한 해석이전에 경계조건에 대한 검증을 위하여 15도 후퇴익과 NASA Rotor 37을 대상으로 예비해석이 수행되었다. 각각의 해석결과들을 기존 문헌들과 비교하였다. 15도 후퇴익에 대한 안정상태와 불안정상태에서 동적 FSI해석이 수행되었다. 해석결과 변위가 일정한 안정상태에 비하여 고속에서는 0.05 초 만에 발산하는 결과를 산출하였다. NASA Rotor 37의 정상상태 해석결과를 바탕으로 정적 동적 FSI 해석을 수행하여 뒷전의 변형크기에 대하여 정적 FSI 결과와 동적 FSI간의 차이가 있음을 확인하였다. 저압 최종단 블레이드의 형상측정 및 동특성시험을 바탕으로 해석모델을 생성하였다. 이를 바탕으로, 운전조건에서 저압최종단 블레이드에 대한 정적 유체-구조 연계해석을 성공적으로 수행하였다.

• 산경연구논집
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• 제9권7호
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• pp.53-59
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• 2018

Purpose - This study examines the effect of control-ownership wedge on stock crash risk. In Korea, controlling shareholders have exclusive control rights compared to their cash flow rights. With increasing disparity, controlling shareholders abuse their power and extract private benefits at the expense of the minority shareholders. Managers who are controlling shareholders of the companies tend not to disclose critical information that would prevent them from pursuing private interests. They accumulate negative information in the firm. When the accumulated bad news crosses a tipping point, it will be suddenly released to the market at once, resulting in an abrupt decline in stock prices. We predict that stock price crash likelihood due to information opaqueness increases as the wedge increases. Research design, data, and methodology - 831 KOSPI-listed firm-year observations are from KisValue database from 2005 to 2011. Control-ownership wedge is measured as the ratio (UCO -UCF)/UCO where UCF(UCO) is the ultimate cash-flow(control) rights of the largest controlling shareholder. Dependent variable CRASH is a dummy variable that equals one if the firm has at least 1 crash week during a year, and zero otherwise. Logistic regression is used to examine the relationship between control-ownership wedge and stock price crash risk. Results - Using a sample of KOSPI-listed firms in KisValue database for the period 2005-2011, we find that stock price crash risk increases as the disparity increases. Specifically, we find that the coefficient of WEDGE is significantly positive, supporting our prediction. The result implies that as controlling shareholders' ownership increases, controlling shareholders tend to withhold bad news. Conclusions - Our results show that agency problems arising from the divergence between control rights and cash flow rights increase the opaqueness of accounting information. Eventually, the accumulated bad news is released all at once, leading to stock price crashes. It could be seen that companies with high control-ownership wedge are likely to experience future stock price crashes. Our study is related to a broader literature that examined the effect of the control-ownership wedge on stock markets. Our findings suggest that the disparity is a meaningful predictor for future stock price crash risk. The results are expected to provide useful implications for firms, regulators, and investors.