• 한국관개배수논문집
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• 제19권1호
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• pp.87-96
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• 2012

Information of local solar radiation is essential for many field, including water resources management, crop yield estimation, crop growth model, solar energy systems and irrigation and drainage design. Unfortunately, solar radiation measurements are not easily available due to the cost and maintenance and calibration requirements of the measuring equipment and station. Therefore, it is important to elaborate methods to estimate the solar radiation based on readily available meteorological data. In this study, two empirical equations are employed to estimate daily solar radiation using Cheongju Regional Meteorological Office data. Two scenarios are considered: (a) sunshine duration data are available for a given location, or (b) only daily cloudiness index records exist. Simple linear regression with daily sunshine duration and cloudiness index as the dependent variable accounted for 91% and 80%, respectively of the variation of solar radiation(H) at 2011. Daily global solar radiation is highly correlated with sunshine duration. In order to indicate the performance of the models, the statistical test methods of the mean bias error(MBE), root mean square error(RMSE) and correlation coefficient(r) are used. Sunshine duration and cloudiness index can be easily and reliably measured and data are widely available.

• Korean Journal of Radiology
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• 제19권6호
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• pp.1077-1088
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• 2018

Objective: To correlate CT parameters on detector-based dual-energy CT enterography (DECTE) with Crohn's disease activity index (CDAI) and externally validate quantitative CT parameters. Materials and Methods: Thirty-nine patients with CD were retrospectively enrolled. Two radiologists reviewed DECTE images by consensus for qualitative and quantitative CT features. CT attenuation and iodine concentration for the diseased bowel were also measured. Univariate statistical tests were used to evaluate whether there was a significant difference in CTE features between remission and active groups, on the basis of the CDAI score. Pearson's correlation test and multiple linear regression analyses were used to assess the correlation between quantitative CT parameters and CDAI. For external validation, an additional 33 consecutive patients were recruited. The correlation and concordance rate were calculated between real and estimated CDAI. Results: There were significant differences between remission and active groups in the bowel enhancement pattern, subjective degree of enhancement, mesenteric fat infiltration, comb sign, and obstruction (p < 0.05). Significant correlations were found between CDAI and quantitative CT parameters, including number of lesions (correlation coefficient, r = 0.573), bowel wall thickness (r = 0.477), iodine concentration (r = 0.744), and relative degree of enhancement (r = 0.541; p < 0.05). Iodine concentration remained the sole independent variable associated with CDAI in multivariate analysis (p = 0.001). The linear regression equation for CDAI (y) and iodine concentration (x) was y = 53.549x + 55.111. For validation patients, a significant correlation (r = 0.925; p < 0.001) and high concordance rate (87.9%, 29/33) were observed between real and estimated CDAIs. Conclusion: Iodine concentration, measured on detector-based DECTE, represents a convenient and reproducible biomarker to monitor disease activity in CD.

• 한국간호교육학회지
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• 제22권1호
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• pp.14-24
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• 2016

Purpose: The purpose of this study was to identify the impact of academic stress on depression suffered by college nursing students and the moderating effects of academic resilience. Methods: For this survey, 257 students (1st and 2nd year) participated, and it was performed over two weeks in September 2014. In this study, statistical analysis was conducted using SPSS 18.0 for Windows and as a t-test, ANOVA, Pearson correlation, and multiple regression analysis. Results: The students' academic stress had a significant impact on their depression (${\beta}=.279$). The moderating effects of academic resilience did not have a significant impact, which is presumably as a result of there being more complex, nonlinear effects, rather than a simple, linear relationship between academic stress and resilience. Conclusion: It may be incorrect to assume that academic resilience is a moderating variable that lessens academic stress. It is implied that academic resilience can have a significant impact when internal and external support conditions are met, and that the effects can be reinforced when family support, a learning environment, and improved adaptability to life at school are also provided.

• 대한전자공학회논문지SP
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• 제49권4호
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• pp.105-110
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• 2012

정준상관분석 (canonical correlation analysis, CCA)은 두 변수집단 사이의 선형 관계를 측정하는 확률적 분석 기법으로 이를 이용하여 다수의 신호가 혼재되어 수신된 신호로부터 각각의 신호원을 분리하는 것이 가능하다. 기존에 CCA와 자기회귀(auto regressive) 기법을 이용하여 혼재된 신호를 분리하는 기법이 제안되었으나 신호원 분리를 효과적으로 수행하기 위해서는 높은 신호 대 잡음비 (signal-to-noise ratio)가 요구되는 문제가 있다. 본 논문에서는 자기회귀 기법의 파라미터 계산시 잡음성분이 포함되어있는 자기공분산 행렬의 주대각 원소를 제거하여 잡음의 영향을 최소화하고 이를 통하여 신호원 분리 성능을 개선하는 방안을 제안한다. 제안하는 기법은 기존에 제안된 CCA와 자기회귀을 이용한 신호 분리 기법에 비하여 더 우수한 신호 분리 성능을 보일 뿐 만 아니라 신호원 분리 과정에서 요구되는 계산량을 줄일 수 있다.

• 한국초지조사료학회지
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• 제36권3호
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• pp.223-236
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• 2016

The objective of this study was to construct Italian ryegrass (IRG) dry matter yield (DMY) estimation models in South Korea based on climatic data by locations. Obviously, the climatic environment of Jeju Island has great differences with Korean Peninsula. Meanwhile, many data points were from Jeju Island in the prepared data set. Statistically significant differences in both DMY values and climatic variables were observed between south areas of Korean Peninsula and Jeju Island. Therefore, the estimation models were constructed separately for south areas of Korean Peninsula and Jeju Island separately. For south areas of Korean Peninsula, a data set with a sample size of 933 during 26 years was used. Four optimal climatic variables were selected through a stepwise approach of multiple regression analysis with DMY as the response variable. Subsequently, via general linear model, the final model including the selected four climatic variables and cultivated locations as dummy variables was constructed. The model could explain 37.7% of the variations in DMY of IRG in south areas of Korean Peninsula. For Jeju Island, a data set containing 130 data points during 17 years were used in the modeling construction via the stepwise approach of multiple regression analysis. The model constructed in this research could explain 51.0% of the variations in DMY of IRG. For the two models, homoscedasticity and the assumption that the mean of the residuals were equal to zero were satisfied. Meanwhile, the fitness of both models was good based on most scatters of predicted DMY values fell within the 95% confidence interval.

• 대한산업공학회지
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• 제40권1호
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• pp.8-17
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• 2014

In this research, we employed various data mining techniques to build predictive models for win-loss prediction in Korean professional baseball games. The historical data containing information about players and teams was obtained from the official materials that are provided by the KBO website. Using the collected raw data, we additionally prepared two more types of dataset, which are in ratio and binary format respectively. Dividing away-team's records by the records of the corresponding home-team generated the ratio dataset, while the binary dataset was obtained by comparing the record values. We applied seven classification techniques to three (raw, ratio, and binary) datasets. The employed data mining techniques are decision tree, random forest, logistic regression, neural network, support vector machine, linear discriminant analysis, and quadratic discriminant analysis. Among 21(= 3 datasets${\times}$7 techniques) prediction scenarios, the most accurate model was obtained from the random forest technique based on the binary dataset, which prediction accuracy was 84.14%. It was also observed that using the ratio and the binary dataset helped to build better prediction models than using the raw data. From the capability of variable selection in decision tree, random forest, and stepwise logistic regression, we found that annual salary, earned run, strikeout, pitcher's winning percentage, and four balls are important winning factors of a game. This research is distinct from existing studies in that we used three different types of data and various data mining techniques for win-loss prediction in Korean professional baseball games.

• 대한치과교정학회지
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• 제51권3호
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• pp.166-178
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• 2021

Objective: To investigate dimensional changes in regional pharyngeal airway spaces after premolar extraction in bimaxillary skeletal protrusion (BSP) patients according to vertical skeletal pattern, and to further identify dentoskeletal risk factors to predict posttreatment pharyngeal changes. Methods: Fifty-five adults showing BSP treated with microimplant anchorage after four premolar extractions were included in this retrospective study. The subjects were divided into two groups according to the mandibular plane steepness: hyperdivergent (Frankfort horizontal plane to mandibular plane [FH-MP] ≥ 30) and nonhyperdivergent groups (FH-MP < 30). The control group consisted of 20 untreated adults with skeletal Class I normodivergent pattern and favorable profile. Treatment changes in cephalometric variables were evaluated and compared. The association between posttreatment changes in the dentoskeletal and upper airway variables were analyzed using linear regression analysis. Results: The BSP patients showed no significant decrease in the pharyngeal dimensions to the lower level in comparison with controls, except for middle airway space (MAS, p < 0.01). The upper airway variable representing greater decrease in the hyperdivergent group than in the nonhyperdivergent group was the MAS (p < 0.01). Posttreatment changes in FH-MP had negative correlation with changes in MAS (β = -0.42, p < 0.01) and inferior airway space (β = -0.52, p < 0.01) as a result of multivariable regression analysis adjusted for sagittal skeletal relationship. Conclusions: Decreased pharyngeal dimensions after treatment in BSP patients showed no significant difference from the normal range of pharyngeal dimensions. However, the glossopharyngeal airway space may be susceptible to treatment when vertical dimension increased in hyperdivergent BSP patients.

• 한국사회정책
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• 제20권2호
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• pp.9-34
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• 2013

본 연구는 자활사업 참여자들의 정서적 자활과 조직헌신의 관계를 분석하고 동시에 이들이 경험하는 경제적 스트레스의 조절효과를 검증하여 향후 국내 자활사업에 대한 실천적 함의를 제시하는 것을 목적으로 한다. 이를 위해 본 연구에서는 2012년 11월 대구광역시 자활근로사업 참여자를 대상으로 실시한 설문조사자료를 활용하였으며 698명이 최종 분석에 사용되었다. 변수간의 인과관계 및 조절효과 검증을 위해 다중선형회귀분석방법(Multiple Linear Regression Analysis)을 적용하였다. 주요 연구결과를 살펴보면 자활사업단에 소속된 자활참여자의 조직헌신 정도가 높을수록 정서적 자활 역시 증가하는 것으로 나타났다. 또한 조직헌신과 정서적 자활간의 관계에서 참여자들이 인식하는 경제적 스트레스 정도가 조절변수(moderating variable)로 기능하는 것으로 나타났다. 이러한 연구결과에 비춰본다면 향후 국내 자활사업 참여자들의 정서적 자활 향상을 위해서는 공동체의식교육 이외에 경제적 스트레스를 감소시킬 수 있는 다양한 정책적 노력이 필요함을 시사한다. 본 연구는 자활사업 참여자들의 정서적 자활에 대한 조직헌신과 경제적 스트레스 효과를 검증함으로써 향후 자활사업의 효과성 제고를 위한 실천적 개입의 기초자료를 제공해준다는 점에서 그 의의를 찾을 수 있다.

• 한국환경보건학회지
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• 제44권4호
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• pp.348-359
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• 2018

Objectives: The purpose of this study was to investigate the relationship between frequency of alcohol drinking and blood mercury concentration in Korea. Methods: This was a cross-sectional study that used data from the Korean National Health and Nutrition Examination Survey. Among them, 3,174 persons were selected for the final study. Results: The concentration of mercury in the blood increased as the frequency of drinking soju or beer increased. Similarly, in the multiple-linear regression analysis model, the frequency of soju drinking was identified as an independent variable showing a statistically significant positive linearity (p<0.001). After controlling for confounding factors, comparing those drinking 'more than twice a week' with those who almost do not drink alcohol, the adjusted ORs for exposure to high concentrations of mercury were 3.24 (95% CI, 2.10-4.99) for drinking soju and 2.07 (95% CI, 1.33-3.22) for drinking beer. The interaction effect between 'soju drinking' and 'spicy pollack and seafood stew' was not statistically significant (p=0.098) for evaluating the interaction effect between the two variables. Conclusions: The concentration of mercury in the blood increased as the frequency of drinking of soju or beer increased. The higher the frequency of alcohol drinking, the more likely is the blood mercury to be included in the high-concentration group. The results of this study can be used as important scientific evidence for the field of environmental health related to alcohol drinking and blood heavy metal exposure in Korea.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.571-572
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• 2009

초고강도 콘크리트의 개발에 따라 철근 압축이음에 대한 연구 필요성이 높아지고 있다. 현행 설계 기준에서 콘크리트강도와 횡보강근의 영향을 고려하지 않기 때문에 압축이음길이가 인장이음길이보다 길어지는 기현상(奇現象)이 발생한다. 본 연구에서는 51개 실험체의 결과를 바탕으로 40MPa부터 70MPa까지 콘크리트에 대한 압축이음길이 설계식을 제안하였다. 본 연구에서 제안된 압축이음길이 설계식을 이용하여 고강도 콘크리트에서 압축이음길이가 인장이음길이보다 길어지는 이상 현상을 해소할 수 있다. 더불어 제안된 압축이음길이 설계식은 통계적 기법에 기반을 두어 재료강도와 동일한 수준의 신뢰성을 확보할 수 있다.