• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.191-195
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• 2003

충격음 저감재의 동탄성계수와 감쇠계수는 차단성능을 평가하는데 있어 중요한 물성치가 된다. 저감재의 동탄성계수는 뜬바닥구조의 고유진동수를 결정짓게 되며, 저감재의 동탄성계수가 높을수록, 즉 고유진동수가 높아짐에 따라 실험실 경량충격음레벨 저감량은 지수함수적으로 감소됨을 실험을 통해 알 수 있다. 또한, 저감재를 포함한 뜬바닥구조를 1자유도 진동계로 가정한 이론값과 실험실 경량충격음레벨 저감량의 결과가 비교적 잘 일치하는 것으로 나타났으며, 이 때 감쇠계수의 영향은 반드시 고려되어야 한다.

• Communications for Statistical Applications and Methods
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• v.3 no.3
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• pp.103-111
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• 1996

정상조건에서는 수명이 상당히 긴 두 개의 부품으로 구성된 병렬형 시스템의 수명검사를 수행하기 위해 고정충격 수명검사의 최적 검사계획에 관하여 고찰하였 다. 시스템을 구성하고 있는 부품의 수명이 서로 독립인 지수분포를 따르는 것으로 가정하여 각 가속조건에서의 부품들의 고장률의 최우추정량을 구하였다. 또한 각 가속조건에서의 부품들의 고장률에 관한 최우추정량의 점근분산의 합을 구하여 이를 최소가 되게 하는 최적 표본 할당비율을 결정하는 방법을 제안하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.3
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• pp.311-319
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• 2003

This paper aims at investigating the exact dynamic response of the system undergoing a exponential impact force from the viewpoints of conservations of momentum and energy. The midpoint method applied in the Newmark's family algorithm is found to be identical to the case of the application of the trapezoidal method which provides conservations of momentum and energy. For the linear impact force the mid point, the trapezoidal and the (n+1) point method exactly meet the conservation characteristics independent of the size of integration interval. On the other hand, constants for the dynamic motion resulting from the nonlinear impact are underestimated or overestimated by these method mentioned above. To overcome this indispensible error, the Simpson 1/3 method as one of multi step methods whose advantages is to use longer time interval with the same number of evaluation functions is adopted for the exact conservations of momentum and energy. Moreover, the suggested method is expected to expand the similar algorithm for the general dynamic motion including finite rotations.

• Journal of Service Research and Studies
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• v.6 no.1
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• pp.83-95
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• 2016

We examine the information transmission between the Service Industrial Production Index and the Service Industrial Wholesale and Retail Index, based on the returns data offered by the Korea Bank. The data includes daily return data from January 2000 to September 2015. Utilizing a dynamic analytical tool-the VAR model, Granger Causality test, Impulse Response Function and Variance Decomposition have been implemented. The results of the analysis are as follows. Firstly, results of Granger Causality test suggests the existence of mutual causality the Service Industrial Production Index precede and have explanatory power the Service Industrial Wholesale and Retail Index However the results also identified a greater causality and explanatory power of the Service Industrial Wholesale and Retail Index over the Service Industrial Production Index. Secondly, the results of impulse response function suggest that the Service Industrial Production Index show immediate response to the Service Industrial Wholesale and Retail Index and are influenced by till time 5 From time 2, the impact gradually disappears. Also the Service Industrial Wholesale and Retail Index show immediate response to the Service Industrial Production Index and are influenced by till time 2.5, the impact gradually disappears. Lastly, the variance decomposition analysis shows that the changes of return of Service Industrial Production Index are dependent on those of the Service Industrial Wholesale and Retail Index. This implies that returns on the Service Industrial Production Index have a significant influence over returns on the Service Industrial Wholesale and Retail Index. It contributes to the understanding of market price formation function through analysis of detached the Service Industrial Production Index and Service Industrial Wholesale and Retail Index. Finally, our results can be used as a guide by the Korea Bank and Republic of Korea and as well as Statistics Korea.

• Composites Research
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• v.16 no.1
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• pp.50-57
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• 2003

Usually many researchers have used the modified Hertzian contact law or experimental static indentation law to analyze impact response of composite laminates subjected to the low-velocity impact. In this study, physical meaning of the method using the laws was investigated and the difference between the analytical results obtained using the laws was also investigated. Furthermore parametric study on contact constant and exponent in the contact law was performed. Finally it was shown that a linearized contact law can be well applied to low-velocity impact response analysis of composite laminates. If this concept is used, commercial finite element software can be used to solve impact problem without making any auxiliary code.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.02a
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• pp.304-310
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• 2002

배 포장용 골판지 상자의 자유낙하 실험을 통하여 완충재로써의 골판지 상자에 대한 충격력을 분석하기 위한 시스템을 구성하고 계측 및 분석용 컴퓨터 프로그램을 작성하여 자유낙하에 의한 배 골판지 포장상자의 충격력을 분석하였으며, 배 골판지 포장상자의 낙하높이에 따른 배의 손상정도는 낙하높이가 높아짐에 따라 손상이 심하고 낙하높이가 낮은 25cm에서도 진동에 의한 손상지수보다는 훨씬 큼을 알 수가 있었다. 이것은 자유낙하에 의한 골판지의 충격력이 배에 전달되어 멍이 발생하는 것으로, 진동에 의한 변위 증폭 및 압상에 의한 손상보다 낙하 충격력에 의한 손상이 더 큰 것을 알 수가 있었으며, 배 골판지 포장상자의 적재 및 하역 작업시에는 낮은 낙하높이에서도 포장상자를 떨어뜨리지 않도록 주의를 하여야 할 것이다.

• The Korean Journal of Financial Management
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• v.14 no.2
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• pp.1-19
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• 1997

본 연구는 주가지수옵션의 도입이 주식시장의 주가변동성 및 정보적 시장효율성에 미치는 영향에 대해 실증적으로 분석하였다. 주가지수옵션의 도입이 주식시장의 변동성에 어떠한 영향을 미치는 가를 보기위해 각국별로 동일한 가중치를 둔(equally weighted) 국제 포트폴리오를 구성함으로써 주가지수옵션 도입이라는 요인외의 다른 요인들을 통제하였다. 이 포트폴리오를 이용한 분석결과에 의하면, 주가지수옵션의 거래는 단기간에 걸쳐서는 주식시장의 주가변동성에 별 영향을 주지 않았으나 다소 긴 기간인 1년 정도의 기간에서는 주가변동성을 증가시켰다. 또한 본 연구는 GARCH 형태의 모델을 이용하여 주가지수옵션시장의 개설이후로 주식시장의 시간에 따라 변하는 주가변동성(time-varying volatility)에 어떤 구조적 변화가 있었느냐를 분석함으로써, 주가지수옵션의 거래가 정보적 시장효율성(informational market efficiency)에 어떠한 영향을 미치는가를 알아보았다. 우리의 실증분석 결과는 지수옵션 도입 이후로 정보의 이산적 패킷(discrete packets)인 여러 변동성 충격(volatility shock)이 주식시장에 더욱 더 빨리 흡수된다는 것을 보여주었다. 이는 주가지수옵션의 도입은 주식시장의 효율성 증대에 도움을 준다는 것을 의미한다.

• Aerospace Engineering and Technology
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• v.2 no.1
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• pp.213-222
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• 2003

Some analytical methods to analyze low-velocity impact force history of composite laminated structures used in aerospace vehicles are reviewed. A classical method used at initial research of low-velocity impact problem in 1980s was reviewed on its physical meaning, and the approximate method assuming the shape of impact force history as a sinusoidal wave was reviewed. A parametric study on contact constant and exponent in contact law was performed in order to analyze an effect on impact force history, and finally its was understood that impact force history could be analyzed accurately even though the linearized contact law was used. Also, in this paper it was shown that impact problem could be analyzed simply and easily using a commercial finite element code.

• The Korean Journal of Applied Statistics
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• v.23 no.3
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• pp.443-456
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• 2010

This study is an empirical research of the stock markets to prove the synchronization phenomenon of the world economy. For this research I analyzed Korea's KOSPI, USA's DOW & NASDAQ reflecting stock markets in North America, Japan's NIKKEI in Asia, and Germany's DAX in Europe. Because the raw series are not stationary, they are to be transformed to returns series. The results of the study are follows: First of all, there are significant causalities between KOSPI's returns and those of other indices. Second, feedback effects are found between the market returns with several time lags. Third, there are 4 cointegrating equations which embody the relation of the five returns series. And forth, KOSPI reacts more sensitively to impacts from the foreign indices compared to the other indices do when they got impacts from each other except KOSPI. On conclusion, there exists a clear evidence for the synchronization phenomenon in returns of the stock indices, and we can expect Korea market may get similar changes depending on the economic changes of North America, Europe, or Asia. Therefore more closing researches should be conducted about the world economy synchronization in various fields as soon as possible.

• Journal of Korea Port Economic Association
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• v.27 no.1
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• pp.263-280
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• 2011

The global financial crisis, triggered by the subprime mortgage crisis in 2007, has put the world economy into the recession with financial market turmoil. I tested whether variables were cointegrated or whether there was an equilibrium relationship. Also, Generalized impulse-response function (GIRF) and accumulation impulse-response function (AIRF) may be used to understand and characterize the time series dynamics inherent in economical systems comprised of variables that may be highly interdependent. Moreover, the IRFs enables us to simulate the response in freight to a shock in the USD/JPY exchange rate, Dow Jones industrial average index, Dow Jones volatility, Chinese Import volatility. The result on the cointegration test show that the hypothesis of no cointergrating vector could be rejected at the 5 percent level. Also, the empirical analysis of cointegrating vector reveals that the increases of USD/JPY exchange rate have negative relations with freight. The result on the impulse-response analysis indicate that freight respond negatively to volatility, and then decay very quickly. Consequently, the results highlight the potential usefulness of the multivariate time series techniques accounting to behavior of Freight.