• Healthcare Informatics Research
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• v.24 no.4
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• pp.346-358
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• 2018

Objectives: The association between obstructive sleep apnea (OSA) and mortality or serious cardiovascular events over a long period of time is not clearly understood. The aim of this observational study was to estimate the clinical effectiveness of continuous positive airway pressure (CPAP) treatment on an outcome variable combining mortality, acute myocardial infarction (AMI), and cerebrovascular insult (CVI) during a follow-up period of 15.5 years ($186{\pm}58$ months). Methods: The data set consisted of 978 patients with an apnea-hypopnea index (AHI) ${\geq}5.0$. One-third had used CPAP treatment. For the first time, a data-driven causal Bayesian network (DDBN) and a hypothesis-driven causal Bayesian network (HDBN) were used to investigate the effectiveness of CPAP. Results: In the DDBN, coronary heart disease (CHD), congestive heart failure (CHF), and diuretic use were directly associated with the outcome variable. Sleep apnea parameters and CPAP treatment had no direct association with the outcome variable. In the HDBN, CPAP treatment showed an average improvement of 5.3 percentage points in the outcome. The greatest improvement was seen in patients aged ${\leq}55$ years. The effect of CPAP treatment was weaker in older patients (>55 years) and in patients with CHD. In CHF patients, CPAP treatment was associated with an increased risk of mortality, AMI, or CVI. Conclusions: The effectiveness of CPAP is modest in younger patients. Long-term effectiveness is limited in older patients and in patients with heart disease (CHD or CHF).

• Genomics & Informatics
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• v.14 no.4
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• pp.149-159
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• 2016

With the success of the genome-wide association studies (GWASs), many candidate loci for complex human diseases have been reported in the GWAS catalog. Recently, many disease prediction models based on penalized regression or statistical learning methods were proposed using candidate causal variants from significant single-nucleotide polymorphisms of GWASs. However, there have been only a few systematic studies comparing existing methods. In this study, we first constructed risk prediction models, such as stepwise linear regression (SLR), least absolute shrinkage and selection operator (LASSO), and Elastic-Net (EN), using a GWAS chip and GWAS catalog. We then compared the prediction accuracy by calculating the mean square error (MSE) value on data from the Korea Association Resource (KARE) with body mass index. Our results show that SLR provides a smaller MSE value than the other methods, while the numbers of selected variables in each model were similar.

• Sleep Medicine and Psychophysiology
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• v.23 no.1
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• pp.5-9
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• 2016

Previous research has identified the biological, psychological, and social factors that confer an elevated risk for suicide. Evidence suggests that sleep disturbances are one of the risk factors that predict an increased risk for suicidal behaviors. Both sleep disorders and general sleep complaints are linked to higher levels of suicidal ideation and depression, as well as increased rates of suicide and suicide attempts. The causal mechanism of this association is not clear. For example, it is not known if insomnia is an independent phenomenon that if interrupted could prevent the emergence of a mental disorder, or if insomnia is a symptom of another developing illness. Hypofrontality, HPA dysfunction, and an impaired serotonergic system are potential mechanisms underlying the association of sleep disturbances and suicidal behavior. Future research is necessary to examine the specific mechanism of this association between sleep and suicide, which may lead to an effective intervention and diminished suicide risk.

• Sleep Medicine and Psychophysiology
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• v.29 no.1
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• pp.1-3
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• 2022

Sleep is associated with Alzheimer's dementia. Many previous researches have shown that inadequate sleep is one of the risk factors that predict Alzheimer's dementia. The causal mechanism of this association is not clear. Slow wave sleep and REM sleep are critical stages in memory consolidation, and by sequential hypothesis both stages are important. Deposition of amyloid beta and tau, the main pathology of Alzheimer's dementia, are also associated with sleep. This review provides the association of sleep and Alzheimer's dementia, and future research is necessary to examine the specific mechanism of this association between sleep and Alzheimer's dementia, which may lead to an early intervention in sleep.

• Journal of Intelligence and Information Systems
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• v.18 no.1
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• pp.23-38
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• 2012

There is a large difference between purchasing patterns in an online shopping mall and in an offline market. This difference may be caused mainly by the difference in accessibility of online and offline markets. It means that an interval between the initial purchasing decision and its realization appears to be relatively short in an online shopping mall, because a customer can make an order immediately. Because of the short interval between a purchasing decision and its realization, an online shopping mall transaction usually contains fewer items than that of an offline market. In an offline market, customers usually keep some items in mind and buy them all at once a few days after deciding to buy them, instead of buying each item individually and immediately. On the contrary, more than 70% of online shopping mall transactions contain only one item. This statistic implies that traditional data mining techniques cannot be directly applied to online market analysis, because hardly any association rules can survive with an acceptable level of Support because of too many Null Transactions. Most market basket analyses on online shopping mall transactions, therefore, have been performed by expanding the co-occurrence criteria of traditional association rule mining. While the traditional co-occurrence criteria defines items purchased in one transaction as concurrently purchased items, the expanded co-occurrence criteria regards items purchased by a customer during some predefined period (e.g., a day) as concurrently purchased items. In studies using expanded co-occurrence criteria, however, the criteria has been defined arbitrarily by researchers without any theoretical grounds or agreement. The lack of clear grounds of adopting a certain co-occurrence criteria degrades the reliability of the analytical results. Moreover, it is hard to derive new meaningful findings by combining the outcomes of previous individual studies. In this paper, we attempt to compare expanded co-occurrence criteria and propose a guideline for selecting an appropriate one. First of all, we compare the accuracy of association rules discovered according to various co-occurrence criteria. By doing this experiment we expect that we can provide a guideline for selecting appropriate co-occurrence criteria that corresponds to the purpose of the analysis. Additionally, we will perform similar experiments with several groups of customers that are segmented by each customer's average duration between orders. By this experiment, we attempt to discover the relationship between the optimal co-occurrence criteria and the customer's average duration between orders. Finally, by a series of experiments, we expect that we can provide basic guidelines for developing customized recommendation systems. Our experiments use a real dataset acquired from one of the largest internet shopping malls in Korea. We use 66,278 transactions of 3,847 customers conducted during the last two years. Overall results show that the accuracy of association rules of frequent shoppers (whose average duration between orders is relatively short) is higher than that of causal shoppers. In addition we discover that with frequent shoppers, the accuracy of association rules appears very high when the co-occurrence criteria of the training set corresponds to the validation set (i.e., target set). It implies that the co-occurrence criteria of frequent shoppers should be set according to the application purpose period. For example, an analyzer should use a day as a co-occurrence criterion if he/she wants to offer a coupon valid only for a day to potential customers who will use the coupon. On the contrary, an analyzer should use a month as a co-occurrence criterion if he/she wants to publish a coupon book that can be used for a month. In the case of causal shoppers, the accuracy of association rules appears to not be affected by the period of the application purposes. The accuracy of the causal shoppers' association rules becomes higher when the longer co-occurrence criterion has been adopted. It implies that an analyzer has to set the co-occurrence criterion for as long as possible, regardless of the application purpose period.

• Proceedings of the Korea Association of Information Systems Conference
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• 2004.05a
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• pp.316-335
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• 2004

This paper builds a system dynamics model analyzing first mover effect and growth strategy of online retailer, a major segment of B2C e-commerce. The dynamic model in this paper is calibrated to the online book market and Yes24.com as major test cases. The model consists of eight key value chain sectors. Five of these(Users, Site Operations, Human Resources, Financial Accounting, and Fundraising) are internal to the company, and three others(Market, Financial Market, and Relative Performance) are external to the company. With the model, this paper suggests research propositions representing positive feedback loops and negative feedback loops that lead to corporate growth and limits to growth according to dynamic causal relationships among eight key value chain sectors, and simulate these propositions.

• Proceedings of the Korea Association of Information Systems Conference
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• 1996.11a
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• pp.29-48
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• 1996

Previous studies on user training have largely focused on assessing models which describe the determinants of information technology usage or examined the effects of training on user satisfaction, productivity, performance, and so on. Scant research efforts have been made, however, to examine those effects of training by using theoretical models. This study presented a conceptual model to predict intention to use information technology and conducted an experiment to understand how training for computer skill acquisition affects primary variables of the model. The data were obtained from 32 student subjects of an experimental group and 31 students of a control group, and the information technology employed for this study was a university's electronic mail system. The study results revealed that attitude toward usage and perceived behavioral control helped to predict user intentions; outcome expectations were positively related to attitude toward usage; and self - efficacy and perceived behavioral control. The changes in those variables suggest more causal effects of user training than other survey studies.

• Journal of the Korean Home Economics Association
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• v.29 no.2
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• pp.169-184
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• 1991

The purpose of this study is to analyze urban housewives' home management behavioral patterns focusing on the morphostatic and morphogenic in continuum, to estimate the level of their family life satisfaction and to determine the variables affecting family life satisfaction. The major findings of this study can be summarized as follows: 1. The tendency is that the wives have controlled in value orientation, and home management behavioral patterns are neutral, and they are somewhat satisfied in terms of family life satisfaction. 2. As for the causal variables, marriage duration, the number of children education, employment status of wives, and value orientation influence on home management behavioural patterns. 3. The variables which affect family life satisfaction significantly are number of children, wives' education level, family income, employment status of wives and value orientation. 4. In analyzing relation between wives' home management behavioual patterns and their family life satisfaction, those who prefer morphostatic patterns have higer level of life satisfaction. 5. From the path analysis, it was found that monthly family income, employment status of wives, wives' educationn level, and value orientation had positive effects on family life satisfaction, and home management behavioral patterns had negative effects on family life satisfaction.

• Journal of the Korean Home Economics Association
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• v.35 no.1
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• pp.443-459
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• 1997

The purpose of this study were (1) to investigate the effect of environments on the ecological value orientation (2) to examine the effect of environments and ecological value orientation on housewives' recycling behavior and (3) to analyze the hypothesized causal model of the housewives' recycling behavior in order to explain direct and indirect effects of the selected variables. 687 samples were selected from housewives living in Seoul. Cronbach's a, descriptive statistics and stepwise multiple regression were used for data analysis The major findings are as follows: Housewives' recycling behavior In conclusion the result of the path analysis explained the contribution of variables on housewives' household recycling. It was found that the ecological value orientation makes the most significant contribution to household recycling.

• Journal of the Korean Home Economics Association
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• v.35 no.6
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• pp.157-171
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• 1997

The purpose of this study was (1) to assess the level of financial management and financial goal attainment on housing purchase and children's educational expenditure, (2) to identify individual, family and environment variables which influence financial goal attainment, and (3) to investigate causal relation of variables which affect financial goal attainment. Data were collected from questionnaire with 772 married women who were residents of Jeonju. The major finding were as follows; (1) The levels of financial management and financial goal attainment on housing purchase and children's educational expenditure were middle. (2) The variables which exerted direct effects on financial goal attainment on housing purchase were time orientation of consumption life, asset, income stability, easiness in extending credit, financial planning, and financial implementing. the most powerful predictor of financial goal attainment on housing purchase was asset. (30 The variables which exerted direct effects on financial goal attainment on children's educational expenditure were time orientation of consumption life, asset, children's presence on the camp8us, easiness I extending credit, financial planning, and financial implementing. The most powerful predictor of financial goal attainment on children's educational expenditure was financial planning.