• Title/Summary/Keyword: Ensemble model

검색결과 84건 처리시간 0.107초

Ensemble Model Output Statistics를 이용한 평창지역 다중 모델 앙상블 결합 및 보정 (A Combination and Calibration of Multi-Model Ensemble of PyeongChang Area Using Ensemble Model Output Statistics)

  • 황유선;김찬수
    • 대기
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    • v.28 no.3
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    • pp.247-261
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    • 2018
  • The objective of this paper is to compare probabilistic temperature forecasts from different regional and global ensemble prediction systems over PyeongChang area. A statistical post-processing method is used to take into account combination and calibration of forecasts from different numerical prediction systems, laying greater weight on ensemble model that exhibits the best performance. Observations for temperature were obtained from the 30 stations in PyeongChang and three different ensemble forecasts derived from the European Centre for Medium-Range Weather Forecasts, Ensemble Prediction System for Global and Limited Area Ensemble Prediction System that were obtained between 1 May 2014 and 18 March 2017. Prior to applying to the post-processing methods, reliability analysis was conducted to identify the statistical consistency of ensemble forecasts and corresponding observations. Then, ensemble model output statistics and bias-corrected methods were applied to each raw ensemble model and then proposed weighted combination of ensembles. The results showed that the proposed methods provide improved performances than raw ensemble mean. In particular, multi-model forecast based on ensemble model output statistics was superior to the bias-corrected forecast in terms of deterministic prediction.

사례 선택 기법을 활용한 앙상블 모형의 성능 개선 (Improving an Ensemble Model Using Instance Selection Method)

  • 민성환
    • 산업경영시스템학회지
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    • v.39 no.1
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    • pp.105-115
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    • 2016
  • Ensemble classification involves combining individually trained classifiers to yield more accurate prediction, compared with individual models. Ensemble techniques are very useful for improving the generalization ability of classifiers. The random subspace ensemble technique is a simple but effective method for constructing ensemble classifiers; it involves randomly drawing some of the features from each classifier in the ensemble. The instance selection technique involves selecting critical instances while deleting and removing irrelevant and noisy instances from the original dataset. The instance selection and random subspace methods are both well known in the field of data mining and have proven to be very effective in many applications. However, few studies have focused on integrating the instance selection and random subspace methods. Therefore, this study proposed a new hybrid ensemble model that integrates instance selection and random subspace techniques using genetic algorithms (GAs) to improve the performance of a random subspace ensemble model. GAs are used to select optimal (or near optimal) instances, which are used as input data for the random subspace ensemble model. The proposed model was applied to both Kaggle credit data and corporate credit data, and the results were compared with those of other models to investigate performance in terms of classification accuracy, levels of diversity, and average classification rates of base classifiers in the ensemble. The experimental results demonstrated that the proposed model outperformed other models including the single model, the instance selection model, and the original random subspace ensemble model.

앙상블 모형을 이용한 단기 용수사용량 예측의 적용성 평가 (Evaluation of short-term water demand forecasting using ensemble model)

  • 소병진;권현한;구자용;나봉길;김병섭
    • 상하수도학회지
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    • v.28 no.4
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    • pp.377-389
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    • 2014
  • In recent years, Smart Water Grid (SWG) concept has globally emerged over the last decade and also gained significant recognition in South Korea. Especially, there has been growing interest in water demand forecast and this has led to various studies regarding energy saving and improvement of water supply reliability. In this regard, this study aims to develop a nonlinear ensemble model for hourly water demand forecasting which allow us to estimate uncertainties across different model classes. The concepts was demonstrated through application to observed from water plant (A) in the South Korea. Various statistics (e.g. the efficiency coefficient, the correlation coefficient, the root mean square error, and a maximum error rate) were evaluated to investigate model efficiency. The ensemble based model with an cross-validate prediction procedure showed better predictability for water demand forecasting at different temporal resolutions. In particular, the performance of the ensemble model on hourly water demand data showed promising results against other individual prediction schemes.

앙상블 딥러닝을 이용한 초음파 영상의 간병변증 분류 알고리즘 (Classification Algorithm for Liver Lesions of Ultrasound Images using Ensemble Deep Learning)

  • 조영복
    • 한국인터넷방송통신학회논문지
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    • v.20 no.4
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    • pp.101-106
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    • 2020
  • 현재 의료 현장에서 초음파 진단은 과거 청진기와 같다고 할 수 있다. 그러나 초음파의 특성상 검사자의 숙련도에 따라 결과 예측이 불확실하다는 단점을 가진다. 따라서 본 논문에서는 이런 문제를 해결하기 위해 딥러닝 기술을 기반으로 초음파 검사 중 간병변 탐지의 정확도를 높이고자 한다. 제안 논문에서는 CNN 모델과 앙상블 모델을 이용해 병변 분류의 정확도 비교 실험하였다. 실험결과 CNN 모델에서 분류 정확도는 평균 82.33%에서 앙상블모델의 경우 평균 89.9%로 약 7% 높은 것을 확인하였다. 또한 앙상블 모델이 평균 ROC커브에서도 0.97로 CNN모델보다 약 0.4정도 높은 것을 확인하였다.

헬리콥터 주로터 블레이드 동적밸런싱 시험을 위한 조절변수 최적화 연구 (A Study on Adjustment Optimization for Dynamic Balancing Test of Helicopter Main Rotor Blade)

  • 송근웅;최종수
    • 한국소음진동공학회논문집
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    • v.26 no.6_spc
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    • pp.736-743
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    • 2016
  • This study describes optimization methods for adjustment of helicopter main rotor tracking and balancing (RTB). RTB is a essential process for helicopter operation and maintenance. Linear and non-linear models were developed with past RTB test results for estimation of RTB adjustment. Then global and sequential optimization methods were applied to the each of models. Utilization of the individual optimization method with each model is hard to fulfill the RTB requirements because of different characteristics of each blade. Therefore an ensemble model was used to integrate every estimated adjustment result, and an adaptive method was also applied to adjustment values of the linear model to update for next estimations. The goal of this developed RTB adjustment optimization program is to achieve the requirements within 2 run. Additional tests for comparison of weight factor of the ensemble model are however necessary.

랜덤화 배깅을 이용한 재무 부실화 예측 (Randomized Bagging for Bankruptcy Prediction)

  • 민성환
    • 한국IT서비스학회지
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    • v.15 no.1
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    • pp.153-166
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    • 2016
  • Ensemble classification is an approach that combines individually trained classifiers in order to improve prediction accuracy over individual classifiers. Ensemble techniques have been shown to be very effective in improving the generalization ability of the classifier. But base classifiers need to be as accurate and diverse as possible in order to enhance the generalization abilities of an ensemble model. Bagging is one of the most popular ensemble methods. In bagging, the different training data subsets are randomly drawn with replacement from the original training dataset. Base classifiers are trained on the different bootstrap samples. In this study we proposed a new bagging variant ensemble model, Randomized Bagging (RBagging) for improving the standard bagging ensemble model. The proposed model was applied to the bankruptcy prediction problem using a real data set and the results were compared with those of the other models. The experimental results showed that the proposed model outperformed the standard bagging model.

유전자 알고리즘 기반 통합 앙상블 모형 (Genetic Algorithm based Hybrid Ensemble Model)

  • 민성환
    • Journal of Information Technology Applications and Management
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    • v.23 no.1
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    • pp.45-59
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    • 2016
  • An ensemble classifier is a method that combines output of multiple classifiers. It has been widely accepted that ensemble classifiers can improve the prediction accuracy. Recently, ensemble techniques have been successfully applied to the bankruptcy prediction. Bagging and random subspace are the most popular ensemble techniques. Bagging and random subspace have proved to be very effective in improving the generalization ability respectively. However, there are few studies which have focused on the integration of bagging and random subspace. In this study, we proposed a new hybrid ensemble model to integrate bagging and random subspace method using genetic algorithm for improving the performance of the model. The proposed model is applied to the bankruptcy prediction for Korean companies and compared with other models in this study. The experimental results showed that the proposed model performs better than the other models such as the single classifier, the original ensemble model and the simple hybrid model.

암호화폐 가격 예측을 위한 딥러닝 앙상블 모델링 : Deep 4-LSTM Ensemble Model (Development of Deep Learning Ensemble Modeling for Cryptocurrency Price Prediction : Deep 4-LSTM Ensemble Model)

  • 최수빈;신동훈;윤상혁;김희웅
    • 한국IT서비스학회지
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    • v.19 no.6
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    • pp.131-144
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    • 2020
  • As the blockchain technology attracts attention, interest in cryptocurrency that is received as a reward is also increasing. Currently, investments and transactions are continuing with the expectation and increasing value of cryptocurrency. Accordingly, prediction for cryptocurrency price has been attempted through artificial intelligence technology and social sentiment analysis. The purpose of this paper is to develop a deep learning ensemble model for predicting the price fluctuations and one-day lag price of cryptocurrency based on the design science research method. This paper intends to perform predictive modeling on Ethereum among cryptocurrencies to make predictions more efficiently and accurately than existing models. Therefore, it collects data for five years related to Ethereum price and performs pre-processing through customized functions. In the model development stage, four LSTM models, which are efficient for time series data processing, are utilized to build an ensemble model with the optimal combination of hyperparameters found in the experimental process. Then, based on the performance evaluation scale, the superiority of the model is evaluated through comparison with other deep learning models. The results of this paper have a practical contribution that can be used as a model that shows high performance and predictive rate for cryptocurrency price prediction and price fluctuations. Besides, it shows academic contribution in that it improves the quality of research by following scientific design research procedures that solve scientific problems and create and evaluate new and innovative products in the field of information systems.

광역규모 예측인자를 이용한 한반도 계절 강수량의 장기 예측 (Long-term Forecast of Seasonal Precipitation in Korea using the Large-scale Predictors)

  • 김화수;곽종흠;소선섭;서명석;박정규;김맹기
    • 한국지구과학회지
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    • v.23 no.7
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    • pp.587-596
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    • 2002
  • 경험적 직교함수(EOF)분석법과 다중회귀법에 기초하여 지연상관된 광역규모 예측인자로부터 3개월 이전에 계절 강수량을 예측할 수 있는 슈퍼앙상블 모델이 개발되었다. 이 모델의 예측성이 교차검증법에 의해 평가되었다. 관측값과 예측값사이의 상관계수는 봄철에 0.73, 여름철에 0.61, 가을철에 0.69, 겨울철에 0.75로 나타났다. 이러한 값은 유의수준 ${\alpha}$=0.00에서 유의한 값이다. 수퍼 앙상블 방법의 범주형 예측성이 3개 범주로 나누어진 사례에 대해서 평가되었다. 3개 범주는 계절 누적강수량의 상위 33.3%를 과우해, 하위 33.3%를 소우해, 그 나머지를 평년해로 구분하였다. 범주형 예측의 적중률은 계절에 따라 42%에서 74%로 나타났다.

반응표면법과 크리깅의 혼합모델을 이용한 구조설계방법 (A Structural Design Method Using Ensemble Model of RSM and Kriging)

  • 김남희;이권희
    • 한국산학기술학회논문지
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    • v.16 no.3
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    • pp.1630-1638
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    • 2015
  • 많은 산업분야에서 구조설계 시 구조성능을 검토하기 위한 유한요소해석은 필수적인 과정이 되었다. 이와 함께, 컴퓨터의 성능도 급속도로 개선되고 있지만 대형 문제의 경우에는 최적설계기법을 적용하는데 한계가 있다. 이러한 대형 문제의 최적화를 위하여 메타모델을 이용한 근사모델을 이용하고 있다. 근사모델을 생성하는 방법은 곡선맞춤법과 내삽법으로 분류할 수 있는데, 반응표면모델과 크리깅 모델이 대표적인 것이다. 그러나 각 모델은 오버피팅이나 언더피팅이 될 수 있는 단점이 있다. 본 연구에서는 반응표면과 크리깅으로 구성되는 혼합모델에 의한 메타모델을 이용하여 구조설계에 적용하고자 한다. 제안된 방법을 2부재 구조물과 자동차용 아우터타이로드의 구조설계에 적용하였다.