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머신러닝 CatBoost 다중 분류 알고리즘을 이용한 조류 발생 예측 모형 성능 평가 연구
김준오,박정수 한국물환경학회 2023 한국물환경학회지 Vol.39 No.1
Monitoring and prediction of water quality are essential for effective river pollution prevention and water quality management. In this study, a multi-classification model was developed to predict chlorophyll-a (Chl-a) level in rivers. A model was developed using CatBoost, a novel ensemble machine learning algorithm. The model was developed using hourly field monitoring data collected from January 1 to December 31, 2015. For model development, chl-a was classified into class 1 (Chl-a≤10 ㎍/L), class 2 (10<Chl-a≤50 ㎍/L), and class 3 (Chl-a>50 ㎍/L), where the number of data used for the model training were 27,192, 11,031, and 511, respectively. The macro averages of precision, recall, and F1-score for the three classes were 0.58, 0.58, and 0.58, respectively, while the weighted averages were 0.89, 0.90, and 0.89, for precision, recall, and F1-score, respectively. The model showed relatively poor performance for class 3 where the number of observations was much smaller compared to the other two classes. The imbalance of data distribution among the three classes was resolved by using the synthetic minority over-sampling technique (SMOTE) algorithm, where the number of data used for model training was evenly distributed as 26,868 for each class. The model performance was improved with the macro averages of precision, rcall, and F1-score of the three classes as 0.58, 0.70, and 0.59, respectively, while the weighted averages were 0.88, 0.84, and 0.86 after SMOTE application.
김준오,천득염,Kim, Jun-O,Cheon, Deuk-Youm 한국건축역사학회 2011 건축역사연구 Vol.20 No.4
Stupa in India divides into two: stupa in flatland temple with a character of tomb, and devotional stupa made for offering. The difference of such character is made by whether there is any Sari, and main center for worship is flatland stupa where Sari is settled. Stupa in flatland temple is targeted to that with Sari, whose character is applied into Relief-stupa. The characteristics of Relief-stupa can be divided into two: a relief with similar type of flatland stupa in the form, and a devotional relief in which drum and upper part of tower are developed. The Relief-stupa of flatland temple could be confirmed at tower gate of Sanchi tower, decoration of handrail, and the wall attached to Amaravati and Nagarjunakonda stupa. To the contrary, drum and upper wheel part in the Relief-stupa are developed in the votive stupa. Such characteristics had different features according to usage: The example of former is that there is an expression of landscape of stupa built at that time, and the example of latter is those which had similar type of stone cave temple or offering tower near stupa. Thus, the meaning is subject to the existing of Sari. Stupa building developed along with the development of Buddhist structural activity with the existing popular tradition. And its influence was expanded along with various cultures locally. And, the structure and tower reflected various types and thoughts. Stupa reflected its building site and method according to types, and was created in a new form by its usage.