• ETRI Journal
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• v.38 no.5
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• pp.1008-1018
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• 2016

This paper presents a control scheme for the leader-following formation of multiple robots. The control scheme combines the sliding mode control (SMC) method with the nonlinear disturbance observer (NDOB) technique. The formation dynamics suffer from uncertainties because the individual robots are uncertain. Concerning such formation uncertainties, the leader-following formation dynamics are modeled. Assuming that the formation uncertainties have an unknown boundary, an NDOB-based observer was designed to estimate the formation uncertainties. A sliding surface containing the observer outputs has been defined. Regarding the sliding surface, an SMC-based controller was investigated to form uncertain robots. A sufficient condition in the sense of the Lyapunov theory was proven such that the formation system is asymptotically stable. Herein, some comparison results between the sole SMC method and the second-order SMC method are presented to demonstrate the effectiveness and feasibility of the control scheme for multiple robots in the presence of uncertainties.

• Communications for Statistical Applications and Methods
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• v.30 no.1
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• pp.1-19
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• 2023

Observational data with missing or incomplete data are common in biomedical research. Multiple imputation is an effective approach to handle missing data with the ability to decrease bias while increasing statistical power and efficiency. In recent years propensity score (PS) matching has been increasingly used in observational studies to estimate treatment effect as it can reduce confounding due to measured baseline covariates. In this paper, we describe in detail approaches to competing risk analysis in the setting of incomplete observational data when using PS matching. First, we used multiple imputation to impute several missing variables simultaneously, then conducted propensity-score matching to match statin-exposed patients with those unexposed. Afterwards, we assessed the effect of statin exposure on the risk of heart failure-related hospitalizations or emergency visits by estimating both relative and absolute effects. Collectively, we provided a general methodological framework to assess treatment effect in incomplete observational data. In addition, we presented a practical approach to produce overall cumulative incidence function (CIF) based on estimates from multiple imputed and PS-matched samples.

• ETRI Journal
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• v.46 no.1
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• pp.35-47
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• 2024

This study introduces CR-M-SpanBERT, a coreference resolution (CR) model that utilizes multiple embedding-based span bidirectional encoder representations from transformers, for antecedent recognition in natural language (NL) text. Information extraction studies aimed to extract knowledge from NL text autonomously and cost-effectively. However, the extracted information may not represent knowledge accurately owing to the presence of ambiguous entities. Therefore, we propose a CR model that identifies mentions referring to the same entity in NL text. In the case of CR, it is necessary to understand both the syntax and semantics of the NL text simultaneously. Therefore, multiple embeddings are generated for CR, which can include syntactic and semantic information for each word. We evaluate the effectiveness of CR-M-SpanBERT by comparing it to a model that uses SpanBERT as the language model in CR studies. The results demonstrate that our proposed deep neural network model achieves high-recognition accuracy for extracting antecedents from NL text. Additionally, it requires fewer epochs to achieve an average F1 accuracy greater than 75% compared with the conventional SpanBERT approach.

• Journal of The Korean Association of Information Education
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• v.16 no.1
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• pp.51-60
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• 2012

The purpose of this study was to investigate how task value, twitter self-efficacy, and social presence affect learning satisfaction on twitter discussion. In addition, this study examined the mediating effects of social presence. Participants were 46 undergraduate students in A university in Seoul, Korea. They responded the following surveys: task value, twitter self-efficacy, social presence, and learning satisfaction. Baron & Kenny (1986)'s mediation analysis approach with correlation and multiple regression analyses were applied to this study. Findings showed the significant effects of task value, twitter self-efficacy, and social presence on satisfaction on twitter discussion. In addition, social presence mediated task value, twitter self-efficacy, and satisfaction. These results suggest that the twitter discussion should be designed to accommodate different learners characteristics such as task value and twitter self-efficacy and promote greater social presence between learners.

• Journal of Digital Convergence
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• v.17 no.12
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• pp.1-11
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• 2019

The purpose of this study is to investigate factors influencing educational performance and mediating effects of learning presence in the university flipped learning classroom. For achieving this purpose, self-regulation, learning presence, and collaborative preference were selected as learner variables, and perceived academic achievement and learning engagement were selected as variables for educational performance. To investigate causal relationships among the variables, 39 university students who took 16 week course flipped-learning class participated self-reported survey. Collected data were analyzed by multiple regression and mediation analyses. The results were as follows: first, learning presence and self-regulation affected learning engagement, and moreover, the learning presence mediated between self-regulation and learning engagement. Second, only learning presence affected perceived academic achievement. Therefore, various strategies for effective flipped learning should be considered, and well-designed classroom activities that can promote learners self-regulation, learning presence, and learning engagement are needed to successful flipped learning.

• The Journal of Korean Academic Society of Nursing Education
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• v.27 no.4
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• pp.381-391
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• 2021

Purpose: This study aimed to identify the influence of learning presence and self-directed learning ability on nursing students' learning satisfaction according to the online learning method. Methods: The participants of this study were 167 nursing students attending three universities in different cities. The data were collected from July 16 to July 23, 2021, via an online self-reported questionnaire. Using SPSS WIN 27.0, data were analyzed by descriptive statistics, Pearson's correlation coefficient and a multiple regression analysis. Results: The most effective online learning method experienced by nursing students was asynchronous online learning according to 58.2% of the respondents, while 30.3% of the respondents answered synchronous online learning. The main merit of asynchronous online learning was that it was possible to listen repeatedly (61.7%) to lectures, and the top advantage of synchronous online learning was that the location of the class was free (53.3%). In asynchronous online learning, the factors that significantly affected nursing students' learning satisfaction were cognitive presence (𝛽=.60, p<.001) and emotional presence (𝛽=.25, p<.001). These variables accounted for 56% of their learning satisfaction (F=54.12, p<.001). Similarly, cognitive presence (𝛽=.64, p<.001) and emotional presence (𝛽=.21, p=.001) in synchronous online learning, were the factors cited for significantly affecting learning satisfaction. The explanatory power was 62% (F=69.19, p<.001). Conclusions: In conclusion, it was found that cognitive and social presence from the learning presence factors in both asynchronous and synchronous online learning influence and enhance nursing students' learning satisfaction. Therefore, these results provide important data for future online class design in nursing education.

• Journal of Christian Education in Korea
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• v.72
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• pp.165-182
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• 2022

The purpose of this study is to explore the effect of cognitive Presence on Flow according to the level of interest among the most important factors that have an effect on academic achievement. This study targeted 162 people who took the teaching course of B University. For the study, data were collected through a survey on the level of interest, cognitive Presence, and Flow. In order to verify how cognitive presence affects flow according to the level of interest, multiple regression analysis was performed by dividing the collected data into low and high groups based on the average of the level of interest. As a result, the level of learning management of cognitive presence was .071 in the high level of interest, and the level of learning management was .143 in the low group of interest level. As a result of this, the effect of the level of learning management of cognitive presence on flow according to the level of interest was confirmed. Through the results of this study, a instructional design strategy that can be flow was suggested through supporting cognitive presence according to the level of interest.

• Journal of Gastric Cancer
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• v.10 no.4
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• pp.149-154
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• 2010

Purpose: Replication error is an important mechanism in carcinogenesis. The microsatellite instability (MSI-H) of colorectal cancers is associated with the development of multiple cancers. The influence of MSI-H on the development of multiple gastric cancers in sporadic gastric cancer patients has not been defined. This study was performed to reveal the association between the clinicopathologic features and MSI in sporadic gastric cancers. Materials and Methods: Between July 2004 and March 2009, the clinicopathologic characteristics, including MSI status, were evaluated in 128 consecutive patients with sporadic gastric cancers. None of the patients had hereditary non-polyposis colorectal cancer of familial gastric cancer. The markers that were recommended by the NCI to determine the MSI status for colorectal cancers were used Results: MSI-H cancers were found in 10.9% of the patients (14/128). Synchronous gastric cancers were shown in 4 patients (3.1%). Synchronous cancers were found in 2 of 14 patients with MSI-H gastric cancer (14.3%) and 2 of 114 patients with MSS gastric cancer (1.8%; P=0.059, Fisher's exact test). Among the patients with synchronous cancer 50% (2/4) had MSI-H cancer, but 9.7% of the patients (12/124) without synchronous cancer had MSI-H cancer. MSI-H (RR, 24.7; 95% CI, 1.5~398.9; P=0.024) was related with to synchronous gastric cancer, but age, gender, family history, histologic type, location, gross morphology, size, and stage were not related to synchronous gastric cancer. Conclusions: MSI is associated with the intestinal-type gastric cancer and the presence of multiple gastric cancers in patients with sporadic gastric cancer. Special attention to the presence of synchronous and the development of metachronous multiple cancer in patients with MSI-H gastric cancer is needed.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.19 no.2
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• pp.179-189
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• 2012

Purpose: The purpose of this study was to identify the effects of eating habits, activities of daily living and health behaviors on oral health related-quality of life in elders. Methods: The sample consisted of 246 people 65 years or older. Data were analyzed using frequency, percentage, average standard deviation, t-test, ANOVA, Scheff$\acute{e}$, Pearson Correlation Analysis and Hierarchical Multiple Regression. Results: The control variables such as gender, presence of a spouse, subjective health status, presence of chronic disease and existing number of teeth explained 14% (F=7.76, p<.001) of variance in oral health related-quality of life. The control variables, eating habits, activities of daily living and health behaviors collectively explained 20% of variance in oral health related quality of life. Conclusions: The factors that influence oral health related quality of life were presence of spouse presence factor, existing number of teeth and health behavior. Therefore, oral health related quality of life of elders requires the development of programs to boost the quality of life, and help the elderly people to maintain existing number of teeth by focusing on the variety of characteristics.

• Journal of the Korea Society of Computer and Information
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• v.18 no.11
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• pp.99-106
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• 2013

In Instant message service, the server should process instant messages and request messages which include many presence resources for users. And it also precesses massive notification messages generating from the subscribed presence resources. In this paper a new architecture of instant message service with multiple servers which can distribute loads efficiently as the number of users increases has been suggested. It also provides various functions to users using extended call processing language. The user subscribes presence information and call processing language script which describes user's functions. The server processes instant messages, presence services and call processing language scripts. New extended presence information data structure has been suggested and new call processing language operation tags have been added. Therefore extendability of the system can be increased and various services which combine presence service and call processing can be provided in this system. Furthermore instant message processing module has been integrated in the server to decrease the amount of SIP(Session Initiation Protocol) messages, and it also improves system efficiency, The performance of our proposed system has been analysed by experiments.