• Korean Journal of Cognitive Science
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• v.33 no.3
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• pp.155-168
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• 2022

In this paper, we introduce the SNUDM-G, a diffusion model analysis tool with improved computational speed. Although the diffusion model has been applied to explain various cognitive tasks, its use was limited due to computational difficulties. In particular, SNUDM(Koh et al., 2020), one of the diffusion model analysis tools, has a disadvantage in terms of processing speed because it sequentially generates 20,000 data when approximating the diffusion process. To overcome this limitation, we propose to use graphic processing units(GPU) in the process of approximating the diffusion process with a random walk process. Since 20,000 data can be generated in parallel using the graphic processing units, the estimation speed can be increased compared to generating data through sequential processing. As a result of analyzing the data of Experiment 1 by Ratcliff et al. (2004) and recovering the parameters with SNUDM-G using GPU and SNUDM using CPU, SNUDM-G estimated slightly higher values for certain parameters than SNUDM. However, in term of computational speed, SNUDM-G estimated the parameters much faster than SNUDM. This result shows that a more efficient diffusion model analysis for various cognitive tasks is possible using this tool and further suggests that the processing speed of various cognitive models can be improved by using graphic processing units in the future.

• The Journal of the Korea Contents Association
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• v.18 no.2
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• pp.520-532
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• 2018

Based on advanced research, this study examined the relations between savoring belief and gratitude, and identify a model of the mediating mechanisms of positive affect and cognitive emotion regulation in the relation between savoring belief and gratitude. For this purpose, savoring belief, positive affect, cognitive emotion regulation, and gratitude were measured, among 485 adults. Using a structural equation model, hypothesis and the patterns of variables was confirmed. The results showed that savoring belief, gratitude, positive affect, adaptive cognitive emotion regulation have the positive correlation and savoring belief, gratitude, positive affect was negatively correlated with maladaptive cognitive emotion regulation. The dual mediation effect by positive affect and adaptive cognitive emotion regulation was also verified. Implications for clinical practice, limitations of the study and suggestions for future researches are discussed.

• The Journal of Information Systems
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• v.23 no.3
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• pp.1-23
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• 2014

Nowadays, smartphones have become a portable multimedia computer because of a variety of useful applications in our daily lives, which can be downloaded and installed easily in smartphones. Despite of the fact that, however in the IS literature there has been little research on smartphone applications' user interface design. Specifically, there has been little understanding about smartphone users' cognitive functions as a mediating variable in the relationship between the user interface design of smartphone applications and users' work performance with the applications. Thus, the research aims of this study are to examine 1) the effects of the user interface design attributes including simplicity, consistency, and metaphor on the compliance with or the extension of users' mental models representing users' cognitive functions, and 2) the effects of the users' cognitive functions on their work performance with the applications. A survey was conducted and Structural Equation Modeling(SEM) was employed to analyze the data. The results of this study showed that two of the user interface design attributes, simplicity and consistency, strongly affected users' cognitive functions. In addition, users' cognitive functions significantly influenced users' work performance. However, there was no relationship between the metaphors in the user interfaces of smartphone applications and the compliance with users' mental model. This study contributed theoretically not only to explore users' mental models that are rarely investigated in the IS field, but also to add some findings related to users' cognitive functions to the IS literature. This study also can help practitioners to develop more user friendly user interfaces of smartphone applications by suggesting the design attributes, such as simplicity, consistency, and metaphor.

• Health Policy and Management
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• v.30 no.4
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• pp.493-504
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• 2020

Background: There have been many studies on the associations between body mass index (BMI) and cognitive function. However, no study has ever compared the associations across the methods of categorizing BMI. In this study, we aimed to fill the gap in the previous studies and examine whether the obesity paradox is valid in the risk of cognitive function. Methods: Of the 10,254 people aged 45 and older from the Korean Longitudinal Study of Ageing from 2006 to 2016, 8,970 people were finalized as the study population. The dependent variable was whether a person has a normal cognitive function or not, and the independent variables of interest were BMI categorized by the World Health Organization Western Pacific Regional Office (WHO-WPRO) method, the WHO method, and a 10-group method. Covariates included sociodemographic factors, health behavior factors, and health status factors. A generalized linear mixed model analysis with a logit link was used. Results: In the adjusted model with all covariates, first, in the case of BMI categories of the WHO-WPRO method, underweight (odds ratio [OR], 1.16; 95% confidence interval [CI], 1.15-1.17), overweight (OR, 1.36; 95% CI, 1.35-1.36), and obese (OR, 1.34; 95% CI, 1.33-1.34) groups were more likely to have a normal cognitive function than a normal-weight group. Next, in the case of BMI categories of the WHO method, compared to a normal-weight group, underweight (OR, 1.15; 95% CI, 1.14-1.16) and overweight (OR, 1.06; 95% CI, 1.06-1.07) groups were more likely to have a normal cognitive function; however, obese (OR, 0.62; 95% CI, 0.61-0.63) group was less likely to have it. Lastly, in the case of the 10-group method, as BMI increased, the likelihood to have a normal cognitive function changed like a wave, reaching a global top at group-7 (26.5 kg/㎡ ≤ BMI <28.0 kg/㎡). Conclusion: The associations between BMI and cognitive function differed according to how BMI was categorized among people aged 45 and older in Korea, which suggests that cognitive function may be positively associated with BMI in some categories of BMI but negatively in its other categories. Health policies to reduce cognitive impairment need to consider this association between BMI and cognitive function.

• 한국노년학
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• v.40 no.1
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• pp.147-161
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• 2020

The purpose of this research is to investigates 10-year trajectories of cognitive functions among older adults in their 70s to understand changes in cognitive functions as a continuum until very late life. This study also examines differences in trajectories of cognitive functions by gender and by changes in marital status, especially widowhood. Among participants of the Korean Longitudinal Study of Ageing(KLoSA), the sample of this study includes 800 older adults in their 70s during the first study wave (2006) and those who reported their cognitive functions for six consecutive study waves (2006, 2008, 2010, 2012, 2014, and 2016). The analyses were conducted in two steps. First, we conducted Latent Class Growth Analyses(LCGA) to investigated heterogeneous trajectories of cognitive functions in 10 years. Then, we performed multinomial logistic regression. Three heterogeneous trajectories of cognitive functions were identified. One group of 48.7% of older adults showed high cognitive function at baseline and maintained it over 10 years. Second group of 14.7% of older adults reported low cognitive function scores at baseline and showed continuous decline over time. Third group of 36.6% were showed mid-level cognitive functions and maintained their functions over time. We also found significant gender differences but not significant differences in marital status when we consider both in our model; however, the we found significant differences in changes in marital status when we did not consider gender in the model. The results suggest that the importance of considering dynamics of gender and changes in marital status to understand changes in cognitive functions in later life.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.6
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• pp.2709-2734
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• 2020

The growing demand to make wireless data services 5G compatible has necessitated the development of an energy-efficient approach for an effective new wireless environment. In this paper, we first propose a cognitive sensor node (CSN) based game theory for deriving energy via a primary user-transmitted radio frequency signal. Cognitive users' time was segmented into three phases based on a time switching protocol: energy harvest, spectrum sensing and data transmission. The proposed model chooses the optimal energy-harvesting phase as the effected factor. We further propose a distributed energy-harvesting model as a utility function via pricing techniques. The model is a non-cooperative game where players can increase their net benefit in a selfish manner. Here, the price is described as a function pertaining to transmit power, which proves that the proposed energy harvest game includes Nash Equilibrium and is also unique. The best response algorithm is used to achieve the green connection between players. As a result, the results obtained from the proposed model and algorithm show the advantages as well as the effectiveness of the proposed study. Moreover, energy consumption was reduced significantly (12%) compared to the benchmark algorithm because the proposed algorithm succeeded in delivering energy in micro which is much better compared to previous studies. Considering the reduction and improvement in power consumption, we could say the proposed model is suitable for the next wireless environment represented in 5G.

• Journal of the Korea Society of Computer and Information
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• v.28 no.11
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• pp.53-63
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• 2023

This study developed a cognitive impairment predictive model as one of the screening tests for preventing dementia in the elderly by using Automated Machine Learning(AutoML). We used 'Wearable lifelog data for high-risk dementia patients' of National Information Society Agency, then conducted using PyCaret 3.0.0 in the Google Colaboratory environment. This study analysis steps are as follows; first, selecting five models demonstrating excellent classification performance for the model development and lifelog data analysis. Next, using ensemble learning to integrate these models and assess their performance. It was found that Voting Classifier, Gradient Boosting Classifier, Extreme Gradient Boosting, Light Gradient Boosting Machine, Extra Trees Classifier, and Random Forest Classifier model showed high predictive performance in that order. This study findings, furthermore, emphasized on the the crucial importance of 'Average respiration per minute during sleep' and 'Average heart rate per minute during sleep' as the most critical feature variables for accurate predictions. Finally, these study results suggest that consideration of the possibility of using machine learning and lifelog as a means to more effectively manage and prevent cognitive impairment in the elderly.

• Proceedings of the Korean Society for Cognitive Science Conference
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• 2005.05a
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• pp.202-205
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• 2005

대부분의 실험상황과 달리 실제 상황에서 사람들은 의사결정에 필요한 정보를 직접 획득해야 한다. 기존의 연구는 정보 획득 방략이 고정된 것으로 간주하였다. 그러나 반복적인 의사결정은 환경에 대한 피드백 학습을 가능케 하여 심적 모형 형성에 영향을 미치며, 심적 모형의 변화는 정보 획득 방략의 변화를 초래한다. 이 연구에서는 심적 모형 형성과 정보 획득 방략의 변화에 대해 고찰하였다.

• East Asian mathematical journal
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• v.29 no.1
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• pp.101-107
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• 2013

We consider a cognitive network with a primary and a secondary channel. Primary users have higher priority on the usage of the primary channel, and secondary users are allowed to opportunistically access the primary channel at times when the channel is not occupied by primary users. The secondary channel is dedicated only to secondary users. An analytical model is presented to obtain the performance of an opportunistic spectrum access using both the primary and secondary channels, and is validated by simulations.

• Therapeutic Science for Rehabilitation
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• v.11 no.1
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• pp.87-99
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• 2022

Objective : Through the application of the Anderson model, this study provides an empirical analysis of the decision-making factors for participation in cognitive improvement programs for the elderly living in the community. Methods : This study was conducted through an online survey. The participants were elderly people aged 65 years or older living in the community. The survey had 154 participants and was conducted over a two-month period from August to September 2020. Results : The main results of this study were as follow: first, there was no correlation between the predisposing factors and cognitive improvement program; second, among the enabling factors, diversity, interest, and effectiveness of the program were correlated with the cognitive improvement program; and third, there was no correlation between participation in the cognitive improvement program and need factors. Conclusion : This study shows that the results of basic information and evidence will be identified through analysis of the results of the study and that the implications for the development of cognitive improvement programs will be obtained in the future.