• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.107-109
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• 2007

The recently-developed off-line learning control approaches for the rejection of periodic disturbances utilize the specific property that the learning system tends to oscillate in steady state. Unfortunately, the prior works have not clarified how closely the learning system should approach the steady state to achieve the rejection of periodic disturbances to satisfactory level. In this paper, we address this issue extensively for the class of linear systems. We also attempt to remove the effect of other aperiodic disturbances on the rejection of the periodic disturbances effectively. In fact, the proposed learning control algorithm can provide very fast convergence performance in the presence of aperiodic disturbance. The effectiveness and practicality of our work is demonstrated through mathematical, performance analysis as well as various simulation results.

• Computers and Concrete
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• 제33권4호
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• pp.409-423
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• 2024

Using an extensive database, a sensitivity analysis across fifteen machine learning (ML) classifiers was conducted to evaluate the impact of various data manipulation techniques, evaluation metrics, and explainability tools. The results of this sensitivity analysis reveal that the examined models can achieve an accuracy ranging from 72-93% in predicting the fire-induced spalling of concrete and denote the light gradient boosting machine, extreme gradient boosting, and random forest algorithms as the best-performing models. Among such models, the six key factors influencing spalling were maximum exposure temperature, heating rate, compressive strength of concrete, moisture content, silica fume content, and the quantity of polypropylene fiber. Our analysis also documents some conflicting results observed with the deep learning model. As such, this study highlights the necessity of selecting suitable models and carefully evaluating the presence of possible outcome biases.

• International Journal of Computer Science & Network Security
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• 제21권1호
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• pp.220-225
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• 2021

Human population growth rate is an important parameter for real-world planning. Common approaches rely upon fixed parameters like human population, mortality rate, fertility rate, which is collected historically to determine the region's population growth rate. Literature does not provide a solution for areas with no historical knowledge. In such areas, machine learning can solve the problem, but a multitude of machine learning algorithm makes it difficult to determine the best approach. Further, the missing feature is a common real-world problem. Thus, it is essential to compare and select the machine learning techniques which provide the best and most robust in the presence of missing features. This study compares 17 machine learning techniques (base learners and ensemble learners) performance in predicting the human population growth rate of the country. Among the 17 machine learning techniques, random forest outperformed all the other techniques both in predictive performance and robustness towards missing features. Thus, the study successfully demonstrates and compares machine learning techniques to predict the human population growth rate in settings where historical data and feature information is not available. Further, the study provides the best machine learning algorithm for performing population growth rate prediction.

• 한국교육학연구
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• 제23권1호
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• pp.35-56
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• 2017

이 연구는 가상현실 학습공간에서 동작인식 인터페이스의 적용효과를 검증하기 위한 것이다. 동작인식 인터페이스는 사용자의 동작을 인식해서 작동하는 방식이므로 기존의 인터페이스와는 달리 신체적인 움직임을 자연스럽게 표현한다는 장점을 갖고 있다. 이러한 특징 때문에 동작인식 인터페이스가 가상현실과 같은 실감형 학습환경에서 실제로 긍정적인 효과를 나타내는지 검증하기 위하여 이 연구가 수행되었다. 특히, 동작기반 인터페이스가 가상현실 학습공간의 실감형 디스플레이와 함께 사용될 때 어떤 영향을 미치는지를 검증하였다. 이 연구를 44명의 대학생이 참여했으며 디스플레이의 실감성 수준(착용형 vs. 모니터)과 동작기반 인터페이스의 적용여부(동작기반 vs. 조이스틱)에 따른 적용효과를 검증했다. 연구결과에 따르면 공간구조가 적용되지 않은 학습내용에서는 동작기반 인터페이스가 긍정적인 영향을 미치는 것으로 나타났다. 반면에 공간구조가 적용된 학습내용에서는 조이스틱을 활용하는 것이 더 효과적이었다. 또한 착용형 디스플레이와 같이 실감성이 높은 매체와 함께 동작기반 인터페이스를 함께 활용한다고 하더라도 실감성을 더 높이지 않는 것으로 나타났다. 이 연구에서는 동작기반 인터페이스의 장점과 가상현실 학습공간에서 어떻게 활용될 수 있을 것인지에 대해서 논의하였다.

• Smart Structures and Systems
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• 제31권5호
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• pp.485-500
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• 2023

Machine learning-based structural health monitoring (ML-based SHM) methods are researched extensively in the recent decade due to the availability of advanced information and sensing technology. ML methods are well-known for their pattern recognition capability for complex problems. However, the main obstacle of ML-based SHM is that it often requires pre-collected historical data for model training. In most actual scenarios, damage presence can be detected using the unsupervised learning method through anomaly detection, but to further identify the damage types would require prior knowledge or historical events as references. This creates the cold-start problem, especially for new and unobserved structures. Modal-based methods identify damages based on the changes in the structural global properties but often require dense measurements for accurate results. Therefore, a two-stage hybrid modal-machine learning damage detection scheme is proposed. The first stage detects damage presence using Principal Component Analysis-Frequency Response Function (PCA-FRF) in an unsupervised manner, whereas the second stage further identifies the damage. To solve the cold-start problem, mode shape assessment using the first mode is initiated when no trained model is available yet in the second stage. The damage identified by the modal-based method would be stored for future training. This work highlights the performance of the scheme in alleviating the cold-start issue as it transitions through different phases, starting from zero damage sample available. Results showed that single and multiple damages can be identified at an acceptable accuracy level even when training samples are limited.

• 한국정보교육학회:학술대회논문집
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• 한국정보교육학회 2021년도 학술논문집
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• pp.361-368
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• 2021

코로나19(COVID-19)로 인해 사회·경제·문화 등 일상생활이 근본적으로 변화되고 있으며 인공지능, 데이터, 클라우드 등 정보기술(IT)을 기반으로 하는 디지털 전환(digital transformation)이 가속화되고 있다. 본 연구에서는 가상세계(virtual world)와 현실세계(real world)의 상호작용을 기반으로 하는 메타버스(Metaverse)에 주목하고 메타버스 기반 플랫폼을 교육적으로 활용할 수 있는 가능성을 탐색하였다. 메타버스 기반 플랫폼을 온라인 교육 생태계 관점에서 접근했으며 이는 단순히 온라인 교수·학습 활동 뿐만 아니라 메타버스 내에서 학습, 소통, 공감 등의 전인적 교육 활동이 함께 이루어짐을 의미한다. 이러한 메타버스 플랫폼에서 학습자는 학습 현존감(presence)을 느낄 수 있고, 학습 동기와 몰입이 촉진될 수 있다. 또한 공간 이동의 자율성을 기반으로 자기주도적인 학습을 경험할 수 있다. 메타버스 플랫폼을 적용하기 위해 기술적, 윤리적 한계점도 있으나 높은 기대 수준을 가지는 것 보다는 메타버스 세계의 학습자들의 교육적 상호작용에 초점을 맞추는 것이 바람직할 것이다.

• 산업경영시스템학회지
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• 제47권1호
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• pp.9-19
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• 2024

Deep learning-based computer vision anomaly detection algorithms are widely utilized in various fields. Especially in the manufacturing industry, the difficulty in collecting abnormal data compared to normal data, and the challenge of defining all potential abnormalities in advance, have led to an increasing demand for unsupervised learning methods that rely on normal data. In this study, we conducted a comparative analysis of deep learning-based unsupervised learning algorithms that define and detect abnormalities that can occur when transparent contact lenses are immersed in liquid solution. We validated and applied the unsupervised learning algorithms used in this study to the existing anomaly detection benchmark dataset, MvTecAD. The existing anomaly detection benchmark dataset primarily consists of solid objects, whereas in our study, we compared unsupervised learning-based algorithms in experiments judging the shape and presence of lenses submerged in liquid. Among the algorithms analyzed, EfficientAD showed an AUROC and F1-score of 0.97 in image-level tests. However, the F1-score decreased to 0.18 in pixel-level tests, making it challenging to determine the locations where abnormalities occurred. Despite this, EfficientAD demonstrated excellent performance in image-level tests classifying normal and abnormal instances, suggesting that with the collection and training of large-scale data in real industrial settings, it is expected to exhibit even better performance.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.836-841
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• 1993

For a class of discrete-time nonlinear systems, an iterative learning control method is proposed and a sufficient condition is derived for the convergence of the output error. The proposed method is shown to be less sensitive to modelling errors and the uniform boundedness of the output error is guaranteed even in the presence of initial state errors. It is illustrated by simulations that the actual output converges to a desired output within the tolerance bound and convergence performance is improved by the presented method.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1993년도 Fifth International Fuzzy Systems Association World Congress 93
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• pp.761-764
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• 1993

In this paper we consider techniques for reducing the generated number of rules in learning fuzzy controllers of the state-space action-reinforcement type that can be simply implemented and that behave well in the presence of process noise. Fewer rules lead to better performance, less contradiction in controller action estimation, smaller required execution-time and make it easier for a human to comprehend the generated rules and possibly intervene.

• 문화기술의 융합
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• 제8권6호
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• pp.207-213
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• 2022

MBTI(Myer Briggs Type Indicator)는 사람들의 성향을 직관적으로 파악하고 분류하는데 효과적인 성격유형검사이다. 이에 따라 학습 영역에 MBTI를 적용하려는 시도가 활발히 이뤄지고 있으나, MBTI를 활용하여 새로운 학습유형을 만드는 연구는 부족한 실정이다. 따라서 본 논문은 학습에 영향을 미치는 요인들을 살펴보고, 이를 특성으로 하는 머신러닝 알고리즘에 적용하여 새로운 학습 유형 MY, STI(MY, Study Type Indicator)를 구현했다. 데이터는 일반인 144명에게 구글폼으로 제작한 학습유형 검사를 실시하여 수집하였고, 머신러닝 중 지도 학습을 사용하여 학습시켰다. 그 결과 MY, STI의 정확도는 학습 방법, 학습 동기, 외부 자극 유무, 학습 시간 기준별 각각 0.933, 0.866, 0.844, 0.733으로 나타났다.