• Management Science and Financial Engineering
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• 제19권2호
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• pp.13-18
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• 2013

In this paper, we analyze the relationship between implementation of information technology and inventory turnover as a measure of operational efficiency. We build a regression model including a dummy variable that indicates whether a firm has been nominated for being good at implementing information technology. By using publicly available data, we have conducted an extensive empirical analysis and found that firms' using information technology is not likely to affect inventory turnover significantly. This result implies that we have to take careful consideration in adapting information technology.

• Journal of the Korean Data and Information Science Society
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• 제26권6호
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• pp.1367-1375
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• 2015

경시적자료의 분석으로 선형성장모형을 고려한다. 시간효과를 고려하는 모형과 임의효과를 추가하는 모형 그리고 가변수가 추가된 모형을 설정한다. 본 연구는 정규분포로 가정한 다양한 자료를 생성하고, 다양한 선형성장모형에 대하여 binormal ROC 곡선과 AUC 통계량을 여러 시점에서 구하여 비교 분석하였다. 공분산의 크기가 증가할수록 그리고 시간이 경과할수록 ROC 곡선은 다른 형태로 나타나며 AUC 값은 서서히 증가한다. 반대로 공분산이 작아질수록 시간이 경과함에 따라 AUC의 증가폭이 커진다. 임의효과모형에서 공분산이 양인 경우에 시간이 경과할수록 임의효과모형의 분산이 증가하며 AUC의 증가량은 시간효과모형의 AUC의 증가량보다 작다. 그리고 시간효과모형의 AUC의 증가량보다 임의효과모형의 증가량이 더 크다는 것을 탐색하였다.

• 대한조선학회논문집
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• 제43권3호
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• pp.294-303
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• 2006

A surface piercing propeller (SPP) in tunnel has been proposed recently as a new propulsion system for a high speed air cavity ship. The purpose of the present study is to investigate the characteristics of the SPP in tunnel through a series of model tests. A model propulsion system is placed on a dummy body made of Acrylics. The tunnel is divided into two regions by a guide vane extending from the inlet to the center of the propeller shaft. Air has been supplied from an air nozzle placed at the bottom of the dummy body and the changes in propeller performances caused by the air flow are investigated. The measurements are done for open water and in-tunnel conditions, both for fully and partially submerged propeller. The influence of the guide vane configurations on the propeller performance is also studied. The experiments are performed at the variable pressure circulation water channel of Inha University

• 응용통계연구
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• 제21권5호
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• pp.727-738
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• 2008

변수들 사이 공적분관계의 존재는 불안정한 시계열의 선형결합이 안정적임을 뜻하지만 이 결합이 표본기간 내 발생한 사건에 영향을 받는다면 공적분검정의 기본 가정에 위배되어 검정력은 약해지고 결과는 현실과 차이가 난다. 이러한 관점에 입각하여 본 연구에서는 전체 표본의 일부를 단계적으로 증가시켜 가며 국내 주식시장 장기균형체계를 추정하여 시간가변성 및 안정성을 검정하였으며, 구조적 변화의 발생이 확인된 구간에 대해서는 가변수를 추가하는 방식으로 전 구간에 걸쳐 공적분 벡터를 안정화시키는 방안을 모색하여 보았다.

• 대한조선학회 특별논문집
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• 대한조선학회 2007년도 특별논문집
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• pp.107-117
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• 2007

A surface piercing propeller (SPP) in tunnel has been proposed recently as a new propulsion system for a high speed air cavity ship. The purpose of the present study is to investigate the characteristics of the SPP in tunnel through a series of model tests. A model propulsion system is placed on a dummy body made of Acrylics. The tunnel is divided into two regions by a guide vane extending from the inlet to the center of the propeller shaft. Air has been supplied from an air nozzle placed at the bottom of the dummy body and the changes in propeller performances caused by the air flow are investigated. The measurements are done for open water and in-tunnel conditions, both for fully and partially submerged propeller. The influence of the guide vane configurations on the propeller performance is also studied. The experiments are performed at the variable pressure circulation water channel of Inha University.

• Communications for Statistical Applications and Methods
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• 제26권4호
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• pp.359-370
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• 2019

Grouping structures in covariates are often ignored in regression models. Recent statistical developments considering grouping structure shows clear advantages; however, reflecting the grouping structure on the quantile regression model has been relatively rare in the literature. Treating the grouping structure is usually conducted by employing a group penalty. In this work, we explore the idea of group penalty to the quantile regression models. The grouping structure is assumed to be known, which is commonly true for some cases. For example, group of dummy variables transformed from one categorical variable can be regarded as one group of covariates. We examine the group quantile regression models via two real data analyses and simulation studies that reveal the beneficial performance of group quantile regression models to the non-group version methods if there exists grouping structures among variables.

• 한국산림과학회지
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• 제98권3호
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• pp.284-289
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• 2009

이 논문은 VAR 모형과 계량경제모형으로 섬유판 수요를 추정하고 예측정확성을 비교하였으며, VAR 모형을 이용하여 섬유판 수요의 분산분해와 충격반응을 분석하고, 섬유판 수요를 예측하였다. VAR모형은 소비량, 자체가격, 건설업총생산의 시차변수와 더미변수로 구성되어 있고, 계량경제모형은 자체가격, 비목재가격, 건설업총생산, 더미변수로 구성되어 있다. 더미변수는 1990년대 말에 발생한 구제금융의 영향을 반영하였다. 결과에 의하면 섬유판 수요예측은 VAR모형이 계량경제모형보다 더 효율적이다. VAR모형을 이용하여 섬유판 수요의 분산을 분해한 결과에 의하면 섬유판 최종소비처의 산출수준을 나타내는 건설업총생산의 변화가 약 12개월 후에 섬유판 수요변화의 약 50%를 설명하고, 자체가격의 변화가 약 30%를 설명하는 것으로 나타났다. 즉 건설업총생산이 자체가격보다 섬유판 수요에 더 큰 영향을 미친다. 한편 건설업총생산의 충격에 대한 섬유판 수요의 반응은 12개월 동안 서서히 감소하는 반면에 자체가격의 충격에 대한 반응은 6개월이 지나면 거의 사라진다. 즉 건설업총생산이 자체가격보다 섬유판 수요에 더 오래 영향을 미친다. VAR모형을 이용하여 예측한 섬유판의 수요는 건설투자의 증가로 인하여 연평균 약 1.4%씩 증가하여 2010년에 약 220만$m^3$, 2015년에 약 240만$m^3$가 될 것으로 예상된다.

• 한국병원경영학회지
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• 제11권4호
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• pp.82-103
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• 2006

The purpose of this study is to analyse statistically the relation between medical service quality and managerial performance. And then the way of analysis is the regression analysis that independent variable is service quality, dependent variable is the volume of revenue, the number of patients and the rate of beds utility, and dummy variable is the number of beds, ownership and region. The sample hospitals were the 113 hospitals on general hospitals more than 300beds which were consisted of 20 public hospitals, 41 corporate hospitals and 52 college hospitals, and also distributed 67 hospitals on big city and 46 hospitals other city. The sample hospitals were selected from the Korean Hospital Association and the data of the year 2003 and 2004. The collected data was analyzed using the SPSSWIN 10.0 version, and the study hypothesis was tested using regression analysis. The findings of this study are summarized as follows. First, as a result of analysing hypothesis 1. In the study of the relationship between the service quality and the revenue, it was verified that the more service quality in last year became the more revenue in the year. But the dummy variable, ownership and region, rarely related to hospital revenue. Therefore it means that the more service quality is connected to the more revenue on the large number of beds hospitals. Second, as a result of analysing hypothesis 2 & 3. In the study of the relationship between the service quality and the number of patients, it was verified that the more service quality in last year became the more outpatients in the year. But there was no verified to inpatients. It seems to be the reason why a hospital has operated the fixed number of beds approved by the public office. So there are no free to expand beds according to the number of inpatients as much as inpatients are increasing. Third, as a result of analysing hypothesis 4 & 5. In the study of the relationship between the service quality and the rate of beds utility, it was verified that the more service quality in last year became the shorter of average stay of length in the year. Especially it has influenced much more on a hospital which was the large number of beds, the corporate and the college, but the region. But it was denied that the more service quality became the more the beds turnover. As a result of this study, it shows that the service quality in the last year has importantly influenced on a hospital managerial performance in the year. Estimating the service quality of each hospital, most patients have selected the hospital they want. And the hospital need to keep the number of patients for the proper management. So this result of the study means that a hospital must improve the service quality for keeping efficient management.

• 한국항공우주학회지
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• 제30권8호
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• pp.30-36
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• 2002

풍동시험 모형은 모형 지지부 삽입 등으로 실제 비행체와 다른 형상을 갖게 된다. 이러한 형상의 차이는 비행시험과 다른 힘과 모멘트를 발생시키게 되므로 이에 대한 보정은 필수적이다. 이러한 보정에는 cavity 압력 보정, 모형 지지부 간섭 보정 등이 있다. 본 시험에 사용된 모형은 내장밸런스와 함께 벨리 스팅 지지부를 사용하였으며 보정을 위하여 모형지지부 두께변화 방법과 더미 스팅 방법, wire support 방법의 시험결과를 비교하였다. 모형 지지부 두께 변화 방법은 간섭이 거의 없는 것으로 알려진 wire support 방법과 시험결과가 잘 일치하였다.

• Journal of Korea Trade
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• 제23권7호
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• pp.83-95
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• 2019

Purpose - This study analyzed the effect of the Trump Government's protectionist trade policies on foreign ownership. Specifically, this study empirically analyzes the hypothesis that foreign ownership will decrease after the Trump Government rather than before the Trump Government. Design/methodology - The hypothesis of this study is based on the expectation that US protection trade policy will negatively affect the profitability of Korean companies. The dependent variable in this study is the foreign ownership ratio, and the independent variable is a dummy variable representing before and after the Trump Government. Multiple regression analysis was performed, including the control variables suggested in previous studies related to foreign ownership. Findings - As a result, foreign ownership increased after the Trump Government rather than before the Trump Government. This study further analyzes whether the main variables affecting foreign investor's decision-making are differences before and after Trump Government. The export ratio, profitability and dividends did not differ before and after Trump Government. However, the level of information asymmetry decreased after the Trump Government than before the Trump Government. This suggests that US protection trade policies do not adversely affect the profitability of Korean companies. However, Korean firms are improving their information environment because US protectionist trade policies can lower profitability and negatively impact capital raising. In this regard, the foreign ownership ratio seems to differ before and after the Trump Government. Originality/value - This study contributes in that it presents data that US protectionist policies can affect Korean corporate governance. This study has implications from the short-term analysis of US protection trade policy.