• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.12
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• pp.1199-1206
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• 2015

In this study, the exhaust gas of a diesel engine operating on biodiesel(BD) fuel(a mixture of diesel and soybean oil) was investigated for different fuel mixing ratios in the range of BD3 to BD100. The experiments were conducted using injection pressures of 400, 600, 800, 1000, and 1200 bar. The Pearson correlation coefficient and Spearman rank-order correlation coefficient were used to quantify the NOx and Soot emissions based on the fuel mixing ratio and injection pressure. Consequently, the Pearson correlation coefficient obtained for NOx and Soot emissions according to the mixing ratio and injection pressure was -0.811 and the corresponding Spearman rank-order correlation coefficient was -0.884, which indicated that the correlation of the NOx and Soot emissions was linear. Thus, the NOx and Soot have a trade-off relationship. Moreover, at each injection pressure, the Pearson correlation coefficient was a negative number, which indicated an inversely proportional relationship between NOx and Soot.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10b
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• pp.115-117
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• 2001

기존의 인터넷 웹사이트에서는 사용자의 만족을 극대화시키기 위하여 사용자별로 개인화 된 서비스를 제공하는 협력적 필터링 방식을 적용하고 있다. 협력적 필터링 기술은 사용자의 취향에 맞는 아이템을 예측하여 추천하며, 비슷한 선호도를 가진 다른 사용자들과의 상관관계를 구하기 위하여 일반적으로 피어슨 상관계수를 많이 이용한다. 그러나, 피어슨 상관계수를 이용한 방법은 사용자가 평가를 한 아이템이 있을 때에만 상관관계를 구할 수 있다는 단점과 예측의 정확성이 떨어진다는 단점을 가지고 있다. 따라서, 본 논문에서는 피어슨 상관관계 기반 예측 기법을 보완하여 보다 정확한 사용자 유사도를 구하는 방법을 제안한다. 제안된 방법에서는 사용자들을 대상으로 사용자가 평가를 한 아이템의 선호도를 사용해서 엔트로피를 적용하였고, 사용자가 선호도를 표시하지 않은 상품에 대해서는 Default Voting 방법을 이용하여 보다 정확한 헙력적 필터링 방식을 구현하였다.

• Journal of KIISE
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• v.41 no.10
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• pp.799-809
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• 2014

In this paper, we address the problem of computing Pearson correlation coefficients and Spearman's rank correlation coefficients in a secure manner while data providers preserve privacy of their own data in distributed environment. For a data mining or data analysis in the distributed environment, data providers(data owners) need to share their original data with each other. However, the original data may often contain very sensitive information, and thus, data providers do not prefer to disclose their original data for preserving privacy. In this paper, we formally define the secure correlation computation, SCC in short, as the problem of computing correlation coefficients in the distributed computing environment while preserving the data privacy (i.e., not disclosing the sensitive data) of multiple data providers. We then present SCC solutions for Pearson and Spearman's correlation coefficients using secure scalar product. We show the correctness and secure property of the proposed solutions by presenting theorems and proving them formally. We also empirically show that the proposed solutions can be used for practical applications in the performance aspect.

• Korean Journal of Food Science and Technology
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• v.50 no.2
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• pp.244-247
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• 2018

Quantitative analysis for non-host infection bacteriophage was conducted for their enumeration. Flow cytometry and epifluorescence microscopy (EPM) were selected as counting methods. Correlation analysis was performed based on the plaque assay method on the existing host infection and consisted of Pearson correlation statistical analysis, regression analysis, and difference analysis. Analyses of 12 samples with flow cytometry and plaque assay methods showed that there was a correlation of 96.7% with Pearson correlation value r=0.967, $R^2$ 0.9352, and difference value of 1.063. Analyses of 12 samples with EPM and plaque assay methods showed that there was a correlation of 99.0% with Pearson correlation value r=0.990, $R^2$ 0.9811, and difference value of 1.605. Therefore, flow cytometry and epifluorescence microscopy would be effective for enumeration of Weissella cibaria bacteriophage with plaque assay.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.127-127
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• 2016

지난 수년간 4대강 살리기 사업으로 해당 하천은 16개 보로 막혔고 이로 인해 하천수위는 과거 대비 보상류지역은 높아지고 보 하류지역은 낮아졌다. 이에 따라 수문학적 관점에서 기존의 지표수-지하수 연계 특성에 많은 변화가 발생하였다. 이러한 특성 변화 등을 관측하기 위하여 4대강 사업 전, 후로 주요하천 주변 제내지에 지하수 관측정이 설치되었다. 본 연구에서는 4대강 주변 관측정을 대상으로 각 관측정의 지하수위와 지하수위 영향인자들 간의 상관관계를 분석하고, 관측정의 주요영향인자를 판단할 수 있는 지하수 관측정 평가방법을 제시하였다. 각 인자별 상관관계 분석은 피어슨 상관계수를 이용하였으며, 관측정 수위와 주요 영향인자(하천수위, 강우량)의 피어슨 상관계수가 0.7 이상이면 상관성이 높은 것으로 평가하였다. 낙동강 하천 주변 30개소 관측정에 적용한 결과, 10개소는 지하수위와 하천수위와의 상관계수가 0.70~0.93로 상관도가 높은 것으로 평가되었고, 20개소는 지하수와 하천수위와의 상관계수, 지하수와 강우량과의 상관계수 모두 낮은 것으로 분석되었다. 본 연구 결과는 대상 관측정의 모니터링 지속여부 결정, 목적에 맞는 대체 관측정 설치 등 향후 관측정들의 효율적이고 합리적인 관리를 위한 기초자료로 활용할 수 있을 것으로 판단된다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.2
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• pp.129-137
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• 2014

In this study, the characteristics of exhaust gas as a function of the biodiesel mixing ratio were investigated. Diesel and waste oil were used for preparing mixed fuel, and the ratios of the mixed fuel were varied in the BD3~BD100 range. The injection pressures(${\Delta}p_{inj}$) was considered as an experimental variable and was set to 400 bar, 600 bar, 800 bar, 1000 bar, and 1200 bar. Furthermore, for quantitatively analyzing the characteristics of exhaust gas(NOx and Soot), the concepts of Pearson correlation coefficient and Spearman rank-order correlation coefficient based on statistics were introduced. Consequently, it was found that the correlation of the emission of NOx and Soot is linear, and the Pearson and Spearman coefficients are -0.732 and -0.724, respectively, under all analysis conditions. Especially, for the injection pressure of 800 bar, a simultaneous reduction in NOx and Soot emission is possible by controlling the biodiesel mixing ratio. This is because the correlation coefficients of NOx and Soot emissions were nearly 0, as the Pearson correlation coefficient was -0.089.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.440-440
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• 2021

본 연구에서는 다양한 수문지수와 생태지수간의 상관성 분석을 통해 하천의 유량이 하천 생태계와 하천 건강성에 어떤 영향을 끼치는지 분석했다. 수문지수는 각 유역의 유량 자료를 이용하여 구하였다. 각 유역의 평균 일일 유량, 평균 월 유량, 일 중앙 유량, 월 중앙 유량, 유량의 왜곡, 유량의 변동계수, 유량 빈도 등을 구하였다. 생태지수는 Benthic Macroinvertebrates Index (BMI)를 이용하였다. 피어슨 상관계수 분석(Pearson's correlation coefficient analysis)을 통해 수문지수와 생태지수 간의 상관성을 분석했다. 또한 Gaussian Process Regression(GPR) Model을 이용하여 수문지수와 유역의 지형적 특성을 이용한 회귀모형을 통해 미래의 BMI를 예측할 수 있었다. 각 수문지수별로 생태지수와 높은 상관성을 보이는 것과 낮은 상관성을 보이는 것을 확인할 수 있었다. GPR 모형을 이용하여 미래의 BMI의 값을 예측해 하천 건강성 평가로 이용될 수 있는 수문지수를 얻을 수 있었다. 본 연구를 통해서 수문학적 지수와 생태지수를 이용해 정량적으로 건강성을 평가할 수 있을 것으로 기대한다. 또한 GPR 모형을 통해 미래 생태지수의 값을 예측해보고 해당 연구 유역의 하천 건강을 위한 하나의 지표를 제안 할 수 있을 것으로 예상된다.

• The Korean Journal of Applied Statistics
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• v.18 no.2
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• pp.371-379
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• 2005

In this paper, we propose a pattern consistency index for detecting heterogeneous time series that deviate from the representative pattern of each cluster in clustering time course gene expression data using the Pearson correlation coefficient. We examine its usefulness by applying this index to serum time course gene expression data from microarrays.

• The Korean Journal of Applied Statistics
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• v.35 no.3
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• pp.421-434
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• 2022

Chatterjee (2021) proposed a new correlation coefficient ξ. Focusing on two questions (1. Is ξ coefficient distinguishable for Anscombe's quartet data set?, 2. How does the ξ coefficient value change according to the number of data for various kinds of scatterplots?), an exploratory data analysis is attempted for ξ coefficient. We can compare three measures (ξ coefficient, Pearson's correlation coefficient and mutual information).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.3
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• pp.384-388
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• 2021

Currently, whether in a domestic or international sphere, many small businesses are suffering due to COVID-19. The grim reality is that several businesses are shutting down. While the national disaster relief grant was used to contain the damages by encouraging consumer spending, it has become difficult to prevent closures of small businesses. As of September 2020, more than 20,000 stores have closed in Seoul due to the COVID-19 pandemic. There has also been an increase in the number of people with depression caused by the COVID-19 blues. This issue is not only confined to Seoul in the Republic of Korea, but is influencing all other areas affected by the pandemic. As the number of COVID-19 patients increase, the number of open stores is decreasing steadily. The analysis of the correlation coefficient of Pearson, Spearman, and Kendall suggests a negative correlation between the number of COVID-19 patients and the number of stores in business.