• 대한토목학회논문집
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• 제29권3C호
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• pp.97-104
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• 2009

본 연구에서는 하천제방의 현장투수계수를 예측하기 위하여 낙동강과 금호강 유역에 위치한 12개소 제방의 지반물성치, 표준관입실험 그리고 현장투수실험 자료를 이용하여 인공신경망해석을 실시하였다. 총 108개의 자료 중 82%인 89개 자료를 학습단계에 그리고, 나머지 19개 자료는 예측단계에 사용하였다. 또한 그 적용성 평가를 위하여 현재 널리 사용되고 있는 경험식들에 의한 결과와 비교하였다. 그 결과 경험식을 통한 현장투수계수는 모두 실측치와의 상관계수가 0.3 이하로 나와 실측치와는 큰 차이가 있으나, 그에 비하여 신경망에 의한 예측결과는 모든 Case에서 실측치와의 상관계수가 모두 0.8이상으로 기존 경험식들에 비하여 정확한 현장투수계수를 예측을 하였다.

• 한국도로학회논문집
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• 제11권4호
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• pp.17-23
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• 2009

노상토의 변형특성은 포장설계에 있어서 매우 중요한 기본적인 입력물성치다. 노상토의 탄성계수를 실험적으로 결정하기 위해서는 많은 노력이 필요하다. 포장 단면이 간단하거나 중요도가 낮은 도로 설계의 경우 시험적인 탄성계수 결정이 과다한 비용을 요구하게 된다. 보다 간편한 대체시험 또는 기초물성치로부터 탄성계수를 결정하는 다양한 경험모형이 제안되어 있다. 본 연구에서는 7종의 국내 노상토에 대한 시험을 수행하였다. 국내 노상토의 경우 강도특성과 변형특성의 밀접한 상관성을 확인 하였으며, 경험적 상관모형을 제안하였다. 점착력과 낮은 구속응력단계에서의 탄성계수는 매우 큰 상관관계가 있었다($r^2=0.93$). 제안된 상관모형을 적용하여 강도특성으로부터 추정된 탄성계수와 시험을 통하여 측정된 탄성계수의 비교에서 결정계수($r^2$)는 0.75로 나타났다.

• 설비공학논문집
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• 제15권9호
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• pp.744-750
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• 2003

The performance of adiabatic capillary tubes are measured to provide the database for a generalized correlation. Test conditions and capillary tube geometries are selected to cover a wide range typically observed in air-conditioning and heat pump applications. Based on extensive experimental data for R22, R290, and R407C measured in this study, a generalized correlation for refrigerant flow rate in adiabatic capillary tubes is developed by implementing dimensionless parameters for tube inlet conditions, capillary tube geometry, and refrigerant properties. The correlation yields good agreement with the present data for R22, R290, and R407C with average and standard deviations of 0.9% and 5.0%, respectively. In addition, approximately 97% of the data for Rl2, R134a, R152a, R410A, and R600a obtained in the open literature are correlated within a relative deviation of $\pm$ 15%.

• 설비공학논문집
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• 제23권4호
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• pp.251-258
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• 2011

The objective of this study is to propose two empirical correlations to predict the mass flow rate through an automotive block type thermostatic expansion valve and then to evaluate the correlations. The first correlation is deduced by modifying the basic equation of the orifice meter for the mass flow rate and the second correlation is deduced by using the Buckingham's ${\pi}$ theorem. The first correlation showed very good agreement on the measured data for R134a, given by Monforte. Average relative deviation and standard deviation of it are 2.5% and 1.6%, respectively. The second correlation agreed on the same measured data with a little greater deviations. The two correlations may apply to common expansion valves which have different geometrical sizes of the same shape.

• 응용통계연구
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• 제30권4호
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• pp.579-590
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• 2017

다변량 자료의 분포함수를 알고 있거나 추정할 수 있으면 다변량 경험분포함수를 정의할 수 있다. 이변량인 경우에는 계단그림과 분위그림을 사용하여 경험분포함수를 시각화할 수 있는데, 본 연구에서는 다변량인 경우에 경험분포함수를 정사각형에 표현할 수 있는 다변량 경험분포그림을 제안하였다. 여러 종류의 다변량 정규분포와 특정한 분포에 대하여 경험분포그림을 작성하고 특징을 살펴보니, 다양한 분산공분산행렬을 포함된 분포함수에 따라 경험분포그림이 민감하게 반응하는 것을 탐색하였다. 이를 바탕으로 경험분포함수를 구할 때 가정한 다변량 분포함수의 적합도 검정방법을 제안하였다. 대표적인 다섯 종류의 적합도 검정방법을 사용하고, 다양한 분포함수들에 대하여 각각의 검정통계량 기각역을 구하였다. 본 연구에서 얻은 기각역은 문헌에서 구할 수 있는 기각역과 큰 차이가 없음을 발견하였다. 그러므로 본 연구에서 제안한 적합도 검정방법을 문헌에서 제시한 기각역으로 쉽게 사용할 수 있는 장점이 있다.

• KDI Journal of Economic Policy
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• 제40권1호
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• pp.31-43
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• 2018

There is a large amount of empirical literature reporting that people who regularly attend religious services tend to have better health outcomes. However, it remains an unanswered question as to whether the observed correlation reflects any causality. Exploiting exogenous changes in church attendance driven by law changes in 21 states of the U.S., I find tentative but suggestive evidence that the observed strong correlation between religious participation and health is likely to be driven by endogenous selection.

• The Journal of Asian Finance, Economics and Business
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• 제8권9호
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• pp.143-154
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• 2021

This study aims to explore the dynamic conditional correlation (DCC) between ten Asian stock indexes, the US stock index, and Bitcoin by using the dynamic conditional correlation model. The time span of the daily data is between January 2015 to May 2021, the total observation is 1,116. DCC(1,1)-EGARCH(1,1) with multivariate t and normal distributions for the DCC and EGARCH models, respectively, outperforms other models by the goodness of fit values. Except for Bitcoin, we discovered that the majority of the securities' volatilities have a very high volatility persistence. Furthermore, the negative shocks/news have more impact on the volatilities than positive shocks/news in most of the cases, except the stock index of China and Bitcoin. Most of the correlation pairs exhibit higher correlation during the COVID-19 pandemic compared to the pre-COVID-19, except Hong Kong-The US and Malaysia-Indonesia. Moreover, the correlation between Asian stock indexes during the COVID-19 pandemic is statistically higher than the pre-COVID-19 pandemic. However, there are a few instances where the Hong Kong stock index and a few countries are identical. The result of correlation size shows the connectedness between Asian stock markets, which are well-connected within the region, especially with South Korea, Singapore, and Hong Kong.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1999년도 Proceedings of International Symposium on Remote Sensing
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• pp.154-157
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• 1999

Microwave polarimetric backscattering from a wet soil surface had been measured using a Ku-band polarimetric scatterometer at the incidence angles ranging from 10$^{\circ}$ to 70$^{\circ}$ Since the accurate target parameters as well as the radar parameters are necessary for radar scattering modeling, a complete and accurate set of ground truth data were also collected, from which accurate measurements were made of the rms height, correlation length, and dielectric constant. The measured polarimetric backscattering coefficients (vv-, hh-, vh-, hv-polarizations) were compared with theoretical models and empirical models. A new semi-empirical model for microwave polarimetric radar backscattering from bare soil surfaces was developed using polarimetric radar measurements and the knowledge based on the theoretical and numerical solutions. The model was found to yield very good agreement with the backscattering measurements of this study.

• 한국항해학회지
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• 제18권4호
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• pp.83-118
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• 1994

In this study, the writer embodies factors influencing on ship safety management by an empirical survey. In the empirical survey, the writer used a questionnaire. 1, 271 proper data was obtained from 4, 240 Korean seamen working in 152 domestic and 60 foreign merchant ships. Reliability was tested by Cronbach's Alpha and a conceptual validity by Factor Analysis. Hypotheses established in this study were tested by Correlation and Multiple Regression Analysis. Results of analysis are as follows: Firstly, three levels(i.e. planning, doing, and evaluation) of safety management and satisfaction level of shipboard life correlate significantly with level of ship safety management and between them(P<0.05) Secondly, satisfaction level of shipboard life, evaluation and planning levels of safety management influence significantly on level of ship safety management(P<0.05).

• 국제지역연구
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• 제20권3호
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• pp.123-144
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• 2016

This paper investigates the linkages between returns both in foreign exchange and stock markets, and uncertainties in two markets using daily data for the period of 16 July 2004 to 30 June 2014 in Nepalese economy. Four hypotheses are tested about how uncertainty influences the stock index and exchange rates. From the empirical results, a bivariate EGARCH-M model is the best to explain the volatility in the two markets. There is a negative relationship from the exchange rates return to stock price return. Empirical results do provide strong empirical confirmation that negative effect of stock index uncertainty and positive effect of exchange rates uncertainty on average stock index. GARCH-in-mean variables in AR modeling are significant and shows that there is positive effect of exchange rates uncertainty and negative effect of stock index uncertainty on average exchange rates. Stock index shocks have longer lived effects on uncertainty in the stock market than exchange rates shock have on uncertainly in the foreign exchange market. The effect of the last period's shock, volatility is more sensitive to its own lagged values.