• Journal of Korean Society of Rural Planning
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• v.23 no.3
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• pp.13-20
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• 2017

본 연구는 가나의 비료 보조금 정책(Fertilizer subsidy program: FSP)의 농업 생산성에 대한 영향을 분석하였다. 가나의 군(district) 지역 수준의 농업 생산량 및 투입요소에 대한 자료를 사용하여, FSP 도입 이전과 FSP 도입 이후의 농업 생산성을 계측하였다. 지역적으로 상이한 수준의 농업 생산성을 반영하기 위한 지리적가중회귀(GWR)모형을 사용하여 계측의 오류를 줄이고 공간이질성을 고려하였다. 추정 결과를 바탕으로 ArcMap을 이용하여 생산성을 지도로 시각화 한 자료를 살펴보면, FSP 도입 이후 농업 생산성이 전반적으로 개선되었으며 그 중에서도 생산성이 크게 향상된 지역을 특정할 수 있다. 이러한 공간적 변화는 FSP의 지역적 할당의 효율성 증진을 위한 의사결정 자료로 이용 가능하며, 국내 ODA 추진기관에서 농업 지도 및 지원을 위해 유용한 정보로 사용할 수 있다.

• Journal of the Korean Data and Information Science Society
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• v.28 no.1
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• pp.11-20
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• 2017

In this paper, we introduced linear spatial time series (space-time autoregressive and moving average model) and nonlinear spatial time series (space-time bilinear model). Also we estimated the parameters by Kalman Filter method and made comparative studies of power of forecast in the final model. We proposed several weight matrices such as equal proportion allocation, reciprocal proportion between distances, and proportion of population sizes. For applications, we collected Mumps data at Korea Center for Disease Control and Prevention from January 2001 until August 2008. We compared three approaches of weight matrices using the Mumps data. Finally, we also decided the most effective model based on sum of square forecast error.

• Journal of Advanced Navigation Technology
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• v.27 no.1
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• pp.111-118
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• 2023

For the implementation of a smart factory, it is necessary to collect data by connecting various sensors and devices in the manufacturing environment and to diagnose or predict failures in production facilities through data analysis. In this paper, to predict the residual useful lifetime of milling insert used for machining products in CNC machine, weight k-NN algorithm, Decision Tree, SVR, XGBoost, Random forest, 1D-CNN, and frequency spectrum based on vibration signal are investigated. As the results of the paper, the frequency spectrum does not provide a reliable criterion for an accurate prediction of the residual useful lifetime of an insert. And the weighted k-nearest neighbor algorithm performed best with an MAE of 0.0013, MSE of 0.004, and RMSE of 0.0192. This is an error of 0.001 seconds of the remaining useful lifetime of the insert predicted by the weighted-nearest neighbor algorithm, and it is considered to be a level that can be applied to actual industrial sites.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.2088-2092
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• 2009

비점오염원은 면으로 분포하는 오염원으로 강우시 지표유출에 의해 유출되기 때문에 발생지점 및 발생량 추정이 어려우며, 이에 대한 처리가 어려운 실정이다. 현재 점오염원의 처리는 어는 정도 도달한 선진국에서는 비점오염원이 가장 중요한 오염원으로 대두되고 있는 실정이다. 따라서, 본 연구에서는 소양호 상류유역의 지류하천인 내린천, 인북천, 북천을 대상으로 부영영화를 일으키는 수질인자 BOD, COD, SS, T-N, T-P를 대상으로 강우량에 따른 수질농도가 변화하는 양상을 고찰하였다. 연구결과, 강우시 기간이 6월 ${\sim}$ 8월에 오염물질의 유출이 크게 발생하는 것을 알 수 있었으며, 연구지점 모두 비강우시에는 1급수의 수질상태를 보였으나, 강우시에는 3급수 이하의 수질로 악화되는 것을 알 수 있었다. 또한, 각 지류하천으로부터 유입되는 부하량을 추정하여 유역면적대비 유출량 - 오염부하량의 회귀식을 작성하였다. 끝으로, 유출량비를 이용하여 각 지류 하천의 유역면적대비 연간 총 오염유출량을 산정하였다.

• The Korean Journal of Applied Statistics
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• v.21 no.3
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• pp.413-427
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• 2008

In sample design, it is usually planned by purpose and the range of the announcing statistics from the survey. After survey, getting a proper and decent statistics, applying the proper weights on the results of survey is very important and necessary. Therefore in this study, three estimation methods which are raking, BLS and general linear regression method are compared with MSE, Coverage, CV, LE and NC.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.8
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• pp.557-565
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• 2012

In this research, it was analyzed that the effect of the non-point source pollution that occurs in the lower reaches of the livestock area. The analysis on the hydro- and polluto-graphs showed that the concentration of pollution gradually increased as the flow rate increased and, after reaching the peak flow rate, the flow rate dropped drastically. For Event Mean Concentration (EMC), in the lower reaches of livestock area, TSS EMC was 146.80~424.95 mg/L, COD EMC 11.64~55.66 mg/L, BOD EMC 6.66~49.88 mg/L, T-N EMC 7.650~43.825 mg/L and T-P EMC 0.711~3.855 mg/L. According to the results of the analysis on the correlations between pollutants, TSS and BOD, COD, T-N and T-P had correlations at a 0.53~0.95 confidence level. In addition, according to the result of the analysis on the correlations between EMC (mg/L) and storm runoff ($m^3$), the correlation was well explained by a Cubic regression. In addition, among the determination coefficients, TSS and T-N were relatively high, at 0.767~0.835 and 0.773~0.901 respectively, which indicates that EMC goes up as the storm runoff increases. Therefore, it is expected that EMC can be forecasted according to the amount of runoff ($m^3$). The results of this research will be a practical information for the assessment of the non-point source pollution that occurs in the lower reaches of the livestock area.

• Korean Journal of Agricultural and Forest Meteorology
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• v.2 no.4
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• pp.175-182
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• 2000

Spatial interpolation of daily temperature forecasts and observations issued by public weather services is frequently required to make them applicable to agricultural activities and modeling tasks. In contrast to the long term averages like monthly normals, terrain effects are not considered in most spatial interpolations for short term temperatures. This may cause erroneous results in mountainous regions where the observation network hardly covers full features of the complicated terrain. We developed a spatial interpolation model for daily minimum temperature which combines inverse distance squared weighting and elevation difference correction. This model uses a time dependent function for 'mountain slope lapse rate', which can be derived from regression analyses of the station observations with respect to the geographical and topographical features of the surroundings including the station elevation. We applied this model to interpolation of daily minimum temperature over the mountainous Korean Peninsula using 63 standard weather station data. For the first step, a primitive temperature surface was interpolated by inverse distance squared weighting of the 63 point data. Next, a virtual elevation surface was reconstructed by spatially interpolating the 63 station elevation data and subtracted from the elevation surface of a digital elevation model with 1 km grid spacing to obtain the elevation difference at each grid cell. Final estimates of daily minimum temperature at all the grid cells were obtained by applying the calculated daily lapse rate to the elevation difference and adjusting the inverse distance weighted estimates. Independent, measured data sets from 267 automated weather station locations were used to calculate the estimation errors on 12 dates, randomly selected one for each month in 1999. Analysis of 3 terms of estimation errors (mean error, mean absolute error, and root mean squared error) indicates a substantial improvement over the inverse distance squared weighting.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.19 no.2
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• pp.18-35
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• 2020

Many human, roadway, and vehicle factors affect vehicle-pedestrian crashes. Especially, the roadway factors are easily defined and suitable for suggesting countermeasures. The characteristics of the road network are one of the roadway factors. The road network significantly influences behaviors and conflicts of drivers and pedestrians. A metropolitan city such as Seoul contains various types of road networks, and crash prevention strategy considering characteristics of the road network is required. In this study, we analyze the effects of road networks on vehicle-pedestrian crashes. In the study, high order road ratio, intersection ratio, high-low intersection ratio are considered as road network variables. Using Geographically Weighted Poisson Regression, crash frequencies in Dongs of Seoul are analyzed based on the road network variable as well as socioeconomic variables. As a result, Dongs are grouped by coefficient signs, and each group is suggested about improvement directions considering conflict situations.

• The Korean Journal of Financial Studies
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• v.9 no.1
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• pp.245-268
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• 2003

전통적인 방법에 의한 PER는 단순히 그 지표의 일반적인 높고 낮음에 따라 소위 '저평가 종목'이라는 이름으로 투자자들에게 추천되고 있다. 그러나 이런 방법은 개별기업의 구체적 내용을 정확하고 종합적으로 고려하지 못하고 있다. 본 연구는 전통적인 방법으로 사용되는 PER지표의 문제점을 개선코자 배당평가 모형으로부터 도출한 PER지표의 구성요소들을 독립변수로 활용 회귀분석을 했다. 그리고 이를 근거로 이론 지표를 만든 후, 그 이론 지표를 투자의사결정에 적용하였을 때의 유효성을 검증했다. PER지표를 구성하는 독립변수는 Kisor & Whitbeck(1963), Malkiel & Cragg(1970), A. Damodaran(1996)에 의해 연구된 것을 원용, PER지표의 구성요소들로 기업의 배당성향, 이익 성장을, 그리고 위험변수로서의 베타계수를 선정했다. 투자성과는 포트폴리오 투자가 일반적인 현실을 감안해 가치가중수익률을 사용한 포트폴리오의 투자성과를 측정했고, 표본은 국내 거래소 시장에 1991년부터 2001년까지 계속 상장된 금융업종을 제외한 전종목을 대상으로 했다. 실증분석에 사용된 기간은 1997년부터 2001년까지 5년 동안의 자료이며, 투자성과를 검증하기 위한 검증모형으로 위험 프리미엄 모형을 사용했다. 먼저 동 분석기간 중 전통적인 방법에 의한 PER효과는 나타나지 않았고, 아울러 기업규모 효과도 찾을 수 없었다. 그러나 회귀분석을 통해 구해진 이론 지표를 활용할 경우, 이론 지표에 비해 시장 지표가 과소 평가된 그룹이 과대 평가된 그룹과 비교할 때 투자성과가 더 우수한 것으로 나타났다. 또한 이론 지표를 통해 PER수준이 낮아짐에 따라 투자성과가 더 높아지는 PER효과도 발견됐다. 이와 같이 이론 지표에 의해 나타나는 PER효과는 기업규모 효과와는 독립적인 것으로 보인다. 외환위기 이후 우리시장에 나타난 차별화 장세 속에 아직도 PER효과나 기업규모 효과와 같은 시장이례 현상이 존재하는지는 관심의 대상이 됐다고 본다. 본 연구에 의하면 기업규모 효과와는 별개의 PER효과가 여전히 존재하며, 다만 이 PER 효과는 전통적 의미의 일반적으로 낮은 PER종목이 초과수익률을 내는 것이 아니라, 기업규모가 크더라도 그 기업의 개별특성을 고려했을 때 이와 비교해 상대적으로 PER가 낮은 종목에 투자하면 초과수익을 낼 수 있음을 의미한다.

• The Korean Journal of Applied Statistics
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• v.22 no.2
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• pp.375-385
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• 2009

For 2007 Korea presidential election, most polls by telephone surveys indicated Lee Myung-Bak led the second runner-up Jung Dong-Young by certain margin. The margin between two candidates can be estimated accurately by averaging individual poll results, provided there exists no systematic bias in telephone surveys. Most Korean telephone surveys via telephone directory are based on quota samples, with the region, the gender and the age-band as quota variables. Thus the surveys may result in certain systematic bias due to unbalanced factors inherent in quota sampling. The aim of this study is to answer the following questions by the analytic methods adopted in Huh et al. (2004): Question 1. Wasn't there systematic bias in estimates of support rates. Question 2. If yes, what was the source of the bias? To answer the questions, we collected eighteen surveys administered during the election campaign period and applied the iterated proportional weighting (the rim weighting) to the last eleven surveys to obtain the balance in five factors - region, gender, age, occupation and education level. We found that the support rate of Lee Myung-Bak was over-estimated consistently by 1.4%P and that of Jung Dong-Young was underestimated by 0.6%P, resulting in the over-estimation of the margin by 2.0%P. By investigating the Lee Myung-Bak bias with logistic regression models, we conclude that it originated from the under-representation of less educated class and/or the over-representation of house wives in telephone samples.