• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.3
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• pp.363-368
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• 2004

In this paper, the robustness property of 2nd-order iterative learning control(ILC) method for a class of linear and nonlinear discrete-time dynamic systems is studied. 2nd-order ILC method has the PD-type learning algorithm based on both time-domain performance and iteration-domain performance. It is proved that the 2nd-order ILC method has robustness in the presence of state disturbances, measurement noise and initial state error. In the absence of state disturbances, measurement noise and initialization error, the convergence of the 2nd-order ILC algorithm is guaranteed. A numerical example is given to show the robustness and convergence property according to the learning parameters.

• Transactions of the Society of Information Storage Systems
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• v.3 no.4
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• pp.167-172
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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.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.8
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• pp.2732-2748
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• 2021

In post-COVID-19 pandemic era, students' learning effects and experience may sharply decrease when teaching is transferred from offline to online. Several tools suitable for online teaching have been developed to guarantee and promote students' learning effects. However, they cannot fully consider teacher-student interaction in online teaching. To figure out this issue, this paper proposes integrated media platform-based virtual office hours implementation for online teaching. Specifically, an integrated media platform (IMP) is first constructed. Then, virtual office hours (VOH) is implemented based on the IMP, aiming at increasing student-teacher interactions. For evaluating the effectiveness of this scheme, 140 undergraduate students using IMP are divided into one control group and three experimental groups that respectively contain text, voice and video modes. The experiment results indicate that applying VOH in the IMP can improve students' online presence and test scores. Furthermore, students' participating modes during VOH implementation can largely affect their degree of presence, which can be well classified by using principal component analysis. The implication of this work is that IMP-based VOH is an effective and sustainable tool to be continuously implemented even when the COVID-19 pandemic period ends.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.2
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• pp.137-144
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• 2016

The purpose of this study is to investigate the structural relationships among goal orientation, teaching presence, approaches to leaning, satisfaction and academic achievement. For this study, the web survey was administered to 235 learners who participated in distance lifelong education centers of A, B, and C university in South Korea. Structural equation modeling (SEM) analysis was conducted in order to examine the causal relationships among the variables. The results indicated that first, mastery-approach goal and teaching presence had positive effects on deep approach. Second, mastery-approach goal showed negative effects on surface approach, while teaching presence did not. Third, deep approach had positive effects on satisfaction, Fourth, surface approach had negative effects on satisfaction. Fifth, deep approach showed positive effects. Last, surface approach showed negative effects on academic achievement. Based on the result of the research, the study propose the constructive foundation for providing strategies raising the satisfaction and academic achievement in distance life-long education.

• International Journal of Computer Science & Network Security
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• v.21 no.12spc
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• pp.483-490
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• 2021

The COVID-19 pandemic has posed significant community challenges towards higher education around the world. The urgent and unexpected request for full-time university courses to switch over to online teaching was a particular challenge. Online learning and learning imply a certain pedagogical knowledge content (PKC), mainly related to the design and organization for better learning and the creation of unique learning environments using digital technologies. With the help of the present academic paper, we provide some expert opinion on the PKC connected with online learning with the aim of helping non-university professionals (that is, those with lack of online learning experience) navigate these challenging times. Our findings point to the planning of learning activities with certain features, a combination of three types of presence (social, cognitive and facilitative) and the need to adapt the assessment system to new learning requirements. We will conclude by contemplating on how responding to a crisis can improve teaching and learning practices in the post-digital era.

• Proceedings of the Korean Society of Computer Information Conference
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• 2021.01a
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• pp.303-304
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• 2021

본 연구에서는 비대면 환경에서 실재감이 학습성과에 미치는 영향을 분석하였다. 전문대학의 프로그래밍 수업을 수강하는 427명의 학생을 대상으로 교수실재감, 인지적 실재감, 감성적 실재감과 만족도, 학습지속의 향의 관계를 분석하였다. 연구 결과, 만족도에는 교수실재감과 인지적 실재감이, 학습지속의향에는 교수실재감, 인지적 실재감, 감성적 실재감이 영향을 미치는 것으로 나타났다. 연구결과에 기초하여 비대면 환경의 프로그래밍 수업에 대한 설계 및 운영전략을 시사하였다.

• Journal of Korean Dental Science
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• v.16 no.1
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• pp.47-62
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• 2023

Purpose: We aimed to investigate the objective cutoff values of unstimulated flow rates (UFR) and stimulated salivary flow rates (SFR) in patients with xerostomia and to present an optimal machine learning model with a classification and regression tree (CART) for all ages. Materials and Methods: A total of 829 patients with oral diseases were enrolled (591 females; mean age, 59.29±16.40 years; 8~95 years old), 199 patients with xerostomia and 630 patients without xerostomia. Salivary and clinical characteristics were collected and analyzed. Result: Patients with xerostomia had significantly lower levels of UFR (0.29±0.22 vs. 0.41±0.24 ml/min) and SFR (1.12±0.55 vs. 1.39±0.94 ml/min) (P<0.001), respectively, compared to those with non-xerostomia. The presence of xerostomia had a significantly negative correlation with UFR (r=-0.603, P=0.002) and SFR (r=-0.301, P=0.017). In the diagnosis of xerostomia based on the CART algorithm, the presence of stomatitis, candidiasis, halitosis, psychiatric disorder, and hyperlipidemia were significant predictors for xerostomia, and the cutoff ranges for xerostomia for UFR and SFR were 0.03~0.18 ml/min and 0.85~1.6 ml/min, respectively. Conclusion: Xerostomia was correlated with decreases in UFR and SFR, and their cutoff values varied depending on the patient's underlying oral and systemic conditions.

• Proceedings of the Korean Society of Computer Information Conference
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• 2022.01a
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• pp.139-140
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• 2022

코로나 팬더믹의 장기화에 따른 비대면 환경에서 대면 수업의 실재감을 제공하는 다양한 교수·학습 방법에 대한 시도가 이루어지고 있다. 실제 수업 현장에서는 대면수업과 다른 환경에서 학습자의 수준과 특성에 맞는 수업 설계의 필요성 또한 대두되고 있다. 본 연구에서는 플립러닝을 기반으로 한 비대면 프로그래밍 수업에서 학업성취도에 따른 학습 참여 수준과 실재감의 차이를 분석하여, 맞춤형 학습역량 강화를 위한 교수 방안을 모색하는 데 그 목적이 있다. 강의 동영상 수업과 상호작용을 포함한 플립러닝 기반 실시간 수업을 혼합하여 수업한 후 설문을 통해 학업성취도에 따른 학습자들의 학습 참여 수준, 교수 실재감과 학습 실재감을 조사한 결과, 학업성취도 가장 높은 학습자일수록 학습 참여도 높고, 다음 수준의 학습자들이 교수 실재감과 학습 실재감은 가장 높은 것으로 조사·분석되었다. 이를 통해 학업성취도에 기반하여 학습자별 맞춤형 교수방안을 제시하였다.

• Korean Journal of Childcare and Education
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• v.20 no.2
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• pp.127-143
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• 2024

Objective: The purpose of this study is to develop a machine learning model to predict the subsequent childbirth intention of married women with one child, aiming to address the low birth rate problem in Korea, This will be achieved by utilizing data from the 2021 Family and Childbirth Survey conducted by the Korea Institute for Health and Social Affairs. Methods: A prediction model was developed using the Random Forest algorithm to predict the subsequent childbirth intention of married women with one child. This algorithm was chosen for its advantages in prediction and generalization, and its performance was evaluated. Results: The significance of variables influencing the Random Forest prediction model was confirmed. With the exception of the presence or absence of leave before and after childbirth, most variables contributed to predicting the intention to have subsequent childbirth. Notably, variables such as the mother's age, number of children planned at the time of marriage, average monthly household income, spouse's share of childcare burden, mother's weekday housework hours, and presence or absence of spouse's maternity leave emerged as relatively important predictors of subsequent childbirth intention.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.2
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• pp.247-252
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• 2004

In this paper are proposed 2nd-order PD-type iterative learning control algorithms for linear continuous-time system and linear discrete-time system. In contrast to conventional methods, the proposed learning algorithms are constructed based on both time-domain performance and iteration-domain performance. The convergence of the proposed learning algorithms is proved. Also, it is shown that the proposed method has robustness in the presence of external disturbances and the convergence accuracy can be improved. A numerical example is provided to show the effectiveness of the proposed algorithms.