주행거리를 이용한 연료소비량 산정방법: 몬테카를로 기법 중심으로

박천건,소진영,이영섭 한국데이터정보과학회 2012 한국데이터정보과학회지 Vol.23 No.2

최근 온실가스 배출량에 대한 국제적 이슈가 지속적으로 대두되어 왔다. 본 연구는 이동 배출원 중에서 도로교통부분에 대한 배출량을 산출하는데 필요한 연료소비량 산정에 관한 통계적인 기법들을 비교한 것이다. 지금까지 연료소비량을 산정하는데 단순히 연료공급량 또는 주행거리에 의한 방법으로 초점을 두어왔다. 그러나 연료공급량을 토대로 산출된 배출량은 다양한 차량 및 연식을 반영하지 못한다. 본 연구는 통계적 관점에서 주행거리와 연비를 조합한 각 차량의 연료소비량 및 모든 차량의 소비한 총연료소비량의 추정에 적용되는 방법들을 나열하고 비교한다. 또한 향후 연구로 제시된 일부 방법들에 대해서 차량 및 연식을 고려한 연료소비량의 추정에 관한 현실적인 적용방법을 제시한다. Recently, estimation of greenhouse gas (GHG) emission has continuously emerged as an important global issue. This study compares various statistical methods for estimation of fuel consumption, which is necessary for calculation of GHG emission in road transportation sector. Existing methods have focused on using merely transportation fuel supply or distance traveled for calculation of fuel consumption. Estimates of GHG emission based on fuel supply, however, cannot reflect various vehicle types or model year. This study suggests and compares, from statistical point of view, several methods,which can be applied to estimate fuel consumption of each vehicle, by combining distance traveled and fuel efficiency (mileage), and total fuel consumption of all vehicles. It also suggests practical measures that can reflect vehicle types and model year to suggested methods for future research.

단순회귀모형에서 선형성 검정통계량

박천건,이경은,Park, Chun Gun,Lee, Kyeong Eun 한국데이터정보과학회 2014 한국데이터정보과학회지 Vol.25 No.2

전통적으로 단순선형회귀모형에서 설명변수와 반응변수의 선형성 평가는 산점도로 쉽게 파악되었다. 보통 반복수가 존재하는 자료에서 적합결여검정은 선형성을 평가하는데 사용되었다. 하지만 반복수가 오직 하나인 경우에 선형성 검정이 수월하지 않다. 본 연구에서는 반복수가 오직 하나인 단순선형회귀모형의 선형성을 검정하는 통계량을 제안하고 모의실험 및 실증연구를 통하여 신뢰성을 파악한다. In a simple linear regression, a linear relationship between an explanatory variable and a response variable can be easily recognized in the scatter plot of them. The lack of fit test for the replicated data is commonly used for testing the linearity but it is not easy to test the linearity when the explanatory variable is not replicated. In this paper, we propose three new test statistics for testing the linearity regardless of replication using the principle of average slope and validate them through several simulations and empirical studies.

Estimation of error variance in nonparametric regression under a finite sample using ridge regression

박천건 한국데이터정보과학회 2011 한국데이터정보과학회지 Vol.22 No.6

Tong and Wang's estimator (2005) is a new approach to estimate the error variance using least squares method such that a simple linear regression is asymptotically derived from Rice's lag- estimator (1984). Their estimator highly depends on the setting of a regressor and weights in small sample sizes. In this article, we propose a new approach via a local quadratic approximation to set regressors in a small sample case. We estimate the error variance as the intercept using a ridge regression because the regressors have the problem of multicollinearity. From the small simulation study, the performance of our approach with some existing methods is better in small sample cases and comparable in large cases. More research is required on unequally spaced points.

On statistical properties of some difference-based error variance estimators in nonparametric regression with a finite sample

박천건 한국데이터정보과학회 2011 한국데이터정보과학회지 Vol.22 No.3

We investigate some statistical properties of several difference-based error variance estimators in nonparametric regression model. Most of existing difference-based methods are developed under asymptotical properties. Our focus is on the exact form of mean and variance for the lag-k dierence-based estimator and the second-order dierence-based estimator in a nite sample size. Our approach can be extended to Tong's estimator (2005) and be helpful to obtain optimal k.

이상치가 존재하는 단순회귀모형에서 Rice 추정량에 관해서

박천건,Park, Chun Gun 한국통계학회 2013 응용통계연구 Vol.26 No.3

이상치가 존재하는 회귀모형에서 이상치를 탐색하거나 로버스트 추정량에 대한 연구는 매우 중요하다. 이러한 연구는 leave-one-out를 이용하여 회귀계수를 추정하고 잔차를 이용하여 오차 분산을 추정하여 이상치를 탐색하는데 있다. 본 연구는 회귀모형에서 회귀계수를 추정하지 않고 오차 분산을 추정할 수 있는 Rice 추정량의 적용을 소개한 것이다. 특히, 단순회귀모형에서 이상치의 유무에 따라 Rice 추정량의 통계적 성질을 비교하고 이상치 탐색에 있어 어떤 장점이 있는지를 탐색한 연구이다. Detection outliers and robust estimators are crucial in regression models with outliers. In such studies the focus is on detecting outliers and estimating the coefficients using leave-one-out. Our study introduces Rice estimator which is an error variance estimator without estimating the coefficients. In particular, we study a comparison of the statistical properties for Rice estimator with and without outliers in simple regression models.

An estimator of the mean of the squared functions for a nonparametric regression

박천건 한국데이터정보과학회 2009 한국데이터정보과학회지 Vol.20 No.3

So far in a nonparametric regression model one of the interesting problems is estimating the error variance. In this paper we propose an estimator of the mean of the squared functions which is the numerator of SNR (Signal to Noise Ratio). To estimate SNR, the mean of the squared function should be firstly estimated. Our focus is on estimating the amplitude, that is the mean of the squared functions, in a nonparametric regression using a simple linear regression model with the quadratic form of observations as the dependent variable and the function of a lag as the regressor. Our method can be extended to nonparametric regression models with multivariate functions on unequally spaced design points or clustered designed points.

A Note on A Bayesian Approach to the Choice of Wavelet Basis Functions at Each Resolution Level

박천건 한국데이터정보과학회 2008 한국데이터정보과학회지 Vol.19 No.4

In recent years wavelet methods have been focused on block shrinkage or thresholding approaches to accounting for the sparseness of the wavelet representation for an unknown function. The block shrinkage or thresholding methods have been developed in both of classical methods and Bayesian methods. In this paper, we propose a Bayesian approach to selecting wavelet basis functions at each resolution level without MCMC procedure. Simulation study and an application are shown.

On loss functions for model selection in wavelet based Bayesian method

박천건 한국데이터정보과학회 2009 한국데이터정보과학회지 Vol.20 No.6

Most Bayesian approaches to model selection of wavelet analysis have drawbacks that computational cost is expensive to obtain accuracy for the tted unknown function. To overcome the drawback, this article introduces loss functions which are criteria for level dependent threshold selection in wavelet based Bayesian methods with arbitrary size and regular design points. We demonstrate the utility of these criteria by four test functions and real data.

Determinacy on a maximum resolution in wavelet series

박천건,김영화,양완연 한국데이터정보과학회 2004 한국데이터정보과학회지 Vol.15 No.2

Recently, an approximation of a wavelet series has been developed in the analyses of an unknown function. Most of articles have been studied on thresholding and shrinkage methods for its wavelet coefficients based on (non)parametric and Bayesian methods when the sample size is considered as a maximum resolution in wavelet series. In this paper, regardless of the sample size, we are focusing only on the choice of a maximum resolution in wavelet series. We propose a Bayesian approach to the choice of a maximum resolution based on the linear combination of the wavelet basis functions.

실제증발산 측정 시 연직 풍속 이상치 탐색 및 대체

박천건,임창수,임광섭,채효석,Park, Chun Gun,Rim, Chang-Soo,Lim, Kwang-Suop,Chae, Hyo-Sok 대한토목학회 2014 대한토목학회논문집 Vol.34 No.5

본 연구에서는 2011년 5월, 6월, 7월에 덕유산 덕곡제에서 관측된 플럭스자료를 이용하여 에디공분산방법으로부터 증발산량을 측정하는 경우 발생할 수 있는 연직방향 풍속의 이상치 판별 및 대체에 대한 통계적 분석을 실시하였다. 연직방향 풍속의 이상치를 파악하기 위해 적용된 통계분석방법은 사분위수를 바탕으로 상자그림(boxplot)의 분석결과 중에 이상치를 판별하기 위한 interquartile range (IQR)을 적용하여 이상치를 탐색하였다. 또한 삭제하거나 평균값으로 대체하는 방법을 통하여 보완된 연직방향 풍속자료를 이용하여 증발산량을 측정하였으며, 이를 보완전의 증발산량과 비교분석하였다. 비교분석한 결과에 의하면 이상치를 대체하기 전의 증발산량과 이상치를 대체한 후의 증발산량 사이에 차이를 보였으며, 특히 강우 시에 보다 큰 차이를 보였다. 따라서 증발산량 측정과정에서 발생하는 이상치를 보완하기 위해 이상치를 삭제하거나 대체하여 증발산량을 측정하는 것이 필요하다. In this study, using flux data measured in Deokgokje reservoir watershed near Deokyu mountain in May, June, and July 2011, statistical analysis was conducted for outlier detection and replacement for vertical wind speed in the measurement of evapotranspiration based on eddy covariance method. To statistically analyze the outliers of vertical wind speed, the outlier detection method based on interquartile range (IQR) in boxplot was employed and the detected outliers were deleted or replaced with mean. The comparison was conducted for the measured evapotranspiration before and after the outlier replacement. The study results showed that there is a difference between evapotranspiration before outlier replacement and evapotranspiration after outlier replacement, especially during the rainy day. Therefore, based on the study results, the outliers should be deleted or replaced in the measurement of evapotranspiration.