• Tribology and Lubricants
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• 제35권4호
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• pp.229-236
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• 2019

This study investigates the stress singularity that occurs at the contact edge of three bodies in a frictional complete contact. We use the asymptotic analysis method, wherein we constitute an eigenvalue problem and observe the eigenvalue behavior, which we use to obtain the order of the stress singularity. For the present geometry of three bodies in contact, a contact between a cracked indenter and half plane is considered. This is a typical geometry of the PCMI problem of a nuclear fuel rod. Thus, this paper, specifically presents the characteristics of the PCMI problem from the perspective of stress singularity. Consequently, it is noted that the behavior of the stress singularity varies with the difference in the crack angle, coefficient of friction, and material dissimilarity, as is observed in a frictional complete contact of two bodies. In addition, we find that the stress singularity changes essentially linearly with respect to the coefficient of friction, regardless of the variation in the crack angle and material dissimilarity. Concurrently, we find the order of singularity to be 0.5 at a certain coefficient of friction, irrespective of the crack angle, which we also observe in the crack problem of a homogeneous and isotropic body. The order of singularity can also exceed 0.5 in the frictional complete contact problem of three bodies. This implies that the propensity for failure when three bodies are in frictional complete contact can be even worse than that in case of a failure induced by a crack.

• 유통과학연구
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• 제15권5호
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• pp.53-64
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• 2017

Purpose - This study focuses on use intention of mobile travel Apps by Chinese tourists visiting Korea based on UTAUT model, ISS model and ITM model. And the corresponding market promotion schemes are proposed for operators of mobile travel Apps by the research results. Research design, data, and methodology - After collecting 326 respondents in China with cross-sectional questionnaires, this study begins the empirical research with users of mobile travel Apps, and analyzes data with IBM SPSS 23.0 and IBM AMOS 23.0. Results - The results of this study include the following aspects: firstly, the System quality and Information quality are accepted for hypotheses of Satisfaction and Performance expectancy. Secondly, the Personal Propensity to Trust and Firm Reputation are accepted for Initial Trust hypothesis, and the hypotheses of Firm Reputation and Initial Trust are accepted for Use Intention. Thirdly, the Performance expectancy, Effort expectancy, Social influence are accepted for Use Intention hypothesis. Conclusions - With the increase of tourists visiting Korea, it can be predicted that the needs visiting Korea will be increased persistently for Chinese - this trend brings about the increase of the Chinese travel. First, information quality greatly influences satisfaction and performance expectancy. The research result shows that, the higher the mobile traveling App's information quality is, the higher the satisfaction and performance expectancy will be. Therefore, operators of mobile traveling App should have in-depth investigations towards users, to know the latter's real demand to the information quality and then provide corresponding services. Second, performance expectancy and effort expectancy greatly influence users' intention. Therefore, mobile traveling App operators should improve Apps' convenience and efficiency and, in doing so, find an effective method for market expansion. Third, social influence greatly affects users' intention. The result shows that mobile traveling App operators should pay attention to the influence of mass media and friends' recommendation on users, thereby it is necessary to improve advertisement activities. Fourth, initial trust also influences users' intention. The result shows that initial trust is a key element inducing users to generate use intention. Therefore, mobile traveling Apps operators should make efforts to catch elements that influence users' initial trust.

• 한국학교ㆍ지역보건교육학회지
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• 제9권2호
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• pp.65-80
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• 2008

Objectives: To identify the relationship between the internet addition of elementary school students, and their health behavior and VDT syndrome, and thereby to detect the impact of internet addiction on the health behavior of elementary school students, to get the basic information necessary to develop a prevention program for internet addiction and to plan for VDT syndrome prevention program. Methods: We conducted this study during the period from jun 27, 2007 through July 8, 2007. The subjects of this study were 416 children whose grades were in 4th through 6th grades of elementary schools located in the city A in Kyung Pook Providence. Data were obtained from self-rating questionnaires. The questionnaires were composed of Korean Internet Addiction Self-examination on Internet Use Patterns (K-scale), Health Behavior Profile, VDT Syndrome, and general characteristics. We used t-test, AVOVA with Ducan method for Post-hoc comparison in means comparison between groups, $X^2$-test for frequency analysis and Pearson's correlation coefficient. We used SPSS/PC(12.0 ver) program and the LISREL 8.53 Win program for covariance structural analysis. Results: Major results were as follows. 1. The internet addiction propensity distribution based on the distribution of scores were investigated according to the self diagnosis scale on internet addiction. 6.5% of them were high risk user group, 14.4% were potential risk users and 79.1% of them were common user groups. 2. Internet addictions by sex, internet use duration, frequency (days/week), time(hours/day), purpose, position, brightness of internet, attitude of parents and frequency of conversation of family members were statistically significant(p<0.01). 3. There was a statistically significant difference in VDT syndrome according to internet addiction groups(p<0.001) besides ocular symptoms, dry mouth and GI troubles. 4. The health behavior score was the lowest in high risk user group(p<0.001). There were significant differences between internet addiction groups in personal hygiene and habits of daily living(p<.002), the prevention of accidents(p<.002), the practice concerned with the prevention of infectious disease(p=.002), and mental health(p<.001). 5. There was also a significant negative correlation between internal addiction and health profile(r=-0.365, p<0.01) and a significant positive correlation between internal addiction and VDT syndrome(r=0.331, p<0.01). 6. As the result of structural model analysis, internet use time(/day), days of internet use(/1week), conversation frequency among family members, degree of brightness of internet use had significant direct effects on internet addiction. Conclusions: The results will help the development of an effective intervention program for the prevention and treatment of internal addiction by clarifying the effect of the internal addiction upon elementary school students' VDT syndrome and health behavior.

• Journal of Chest Surgery
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• 제55권1호
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• pp.69-76
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• 2022

Background: While the use of bioprosthetic valves for mitral valve replacement (MVR) is increasing, very few studies have compared bovine pericardial and porcine valves in the mitral position to help guide bioprosthetic selection. Methods: In the present study, patients who underwent MVR using bovine pericardial valves were compared with those who underwent MVR with porcine bioprostheses between January 1996 and July 2018. Those with prior MVR, infective endocarditis, congenital mitral valve disease, or ischemic mitral regurgitation were excluded. The primary outcomes were structural valve deterioration (SVD) and mitral valve reoperation from any cause, and death was regarded as a competing risk. Competing risk analysis and propensity score-matching were used for comparisons. Results: Among the 388 patients enrolled, pericardial and porcine bioprostheses were implanted in 217 (55.9%) and 171 (44.1%), respectively. Propensity score-matching yielded 122 pairs of patients that were well-balanced for all baseline covariates. No significant differences were observed between the groups in unadjusted (p=0.09) and adjusted overall survival (hazard ratio [HR], 1.13; 95% confidence interval [CI], 0.72-1.76; p=0.60). Competing risk analysis revealed no significant differences in the risks of mitral reoperation (HR, 1.07; 95% CI, 0.50-2.27; p=0.86) and development of SVD (HR, 1.57; 95% CI, 0.56-4.36; p=0.39) between the groups. Matched population analysis confirmed similar results regarding reoperation (HR, 0.99; 95% CI, 0.40-3.22; p=0.98) and SVD (HR, 1.39; 95% CI, 0.41-4.73; p=0.60). Conclusion: No significant differences in survival or valve durability were observed between bovine pericardial and porcine bioprosthetic MVR. These findings require further validation through studies with larger sample sizes.

• Tuberculosis and Respiratory Diseases
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• 제80권3호
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• pp.296-303
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• 2017

Background: Acute respiratory distress syndrome (ARDS) is related to high mortality and morbidity. There are no proven therapeutic measures however, to improve the clinical course of ARDS, except using low tidal volume ventilation. Metformin is known to have pleiotropic effects including anti-inflammatory activity. We hypothesized that pre-admission metformin might alter the progress of ARDS among intensive care unit (ICU) patients with diabetes mellitus (DM). Methods: We performed a retrospective cohort study from January 1, 2005, to April 30, 2005 of patients who were admitted to the medical ICU at Seoul National University Hospital because of ARDS, and reviewed ARDS patients with DM. Metformin use was defined as prescribed within 3-month pre-admission. Results: Of 558 patients diagnosed with ARDS, 128 (23.3%) patients had diabetes and 33 patients were treated with metformin monotherapy or in combination with other antidiabetic medications. Demographic characteristics, cause of ARDS, and comorbid conditions (except chronic kidney disease) were not different between metformin users and nonusers. Several severity indexes of ARDS were similar in both groups. The 30-day mortality was 42.42% in metformin users and 55.32% in metformin nonusers. On multivariable regression analysis, use of metformin was not significantly related to a reduced 30-day mortality (adjusted ${\beta}-coefficient$, -0.19; 95% confidence interval, -1.76 to 1.39; p=0.816). Propensity score-matched analyses showed similar results. Conclusion: Pre-admission metformin use was not associated with reduced 30-day mortality among ARDS patients with DM in our medical ICU.

• 한국산업정보학회논문지
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• 제22권5호
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• pp.85-100
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• 2017

택배사들은 지속적으로 늘어나는 택배 수요와 이를 처리할 배송 인력의 부족, 배송 난(難) 지역의 해소 및 택배거점 확보의 필요성, 배송비용 상승에 대한 대응 등 사업 수행상의 어려움에 직면하고 있는 상황에서 노인의 일자리를 창출하는 실버택배 서비스를 도입하는 CSV 활동을 진행하고 있다. 본 연구에서는 실버택배 서비스 품질과 택배사의 CSV 활동 및 소비자 개인특성요인이 택배사에 대한 신뢰 및 사용의도에 미치는 영향을 살펴보았다. 본 연구의 실증분석에서는 택배서비스를 이용해본 경험이 있는 개인을 대상으로 온 오프라인으로 설문조사를 실시하였으며, 최종적으로 216개의 표본으로 실증분석 하였다. 연구결과를 살펴보면 먼저, 실버택배 서비스 품질인 신속성은 신뢰에 유의한 영향을 미치는 것으로 나타났으나 안전성은 유의한 영향을 미치지 않는 것으로 나타났다. 둘째, 실버택배 서비스 업체의 CSV 활동의 진정성은 신뢰에 유의한 영향을 미치는 것으로 나타났으나, CSV 활동의 적합성은 유의한 영향을 미치지 않는 것으로 나타났다. 또한 소비자 개인 특성인 소비가치와 윤리적 소비성향은 신뢰에 유의한 영향을 미치는 것으로 나타났으며, 실버 택배사에 대한 신뢰 또한 사용의도에 유의한 영향을 미치는 것으로 나타났다.

• Journal of Korean Neurosurgical Society
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• 제30권sup2호
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• pp.228-234
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• 2001

Objective : The goal of this study was to identify variables that were predictive of recurrence in primary intracranial ependymomas. Methods : We analyzed variables affecting recurrence in 30 patients with primary intracranial ependymomas. Age, location, CSF cytology, seeding on neuroimaging study, tumor grade, extent of surgery, use of chemotherapy, chemotherapy regimen, use of radiotherapy, and radiotherapy field were entered to test their impacts on recurrence. Results : Follow-up ranged from 2 to 110 months. Tumors were recurred at the primary tumor site only in 13 patients (43.3%). The overall average recurrence free period was 55 months, with overall recurrence free rates at 3 and 6 years of 61.0% and 20.9%, respectively. Extent of surgery was the strongest variable affecting recurrence. The median recurrence free period and 3-year recurrence free rate were 72 months and 78.4% for patients having complete excision and 33 months and 0% for those having incomplete excision(p=0.05). Other prognostic variables like age, location, tumor grade, use of chemotherapy, and use of radiotherapy did not affect recurrence(p=0.2848, 0.7899, 0.1714, 0.2157, 0.7076, respectively). Conclusions : Intracranial ependymomas have a propensity to recur after treatment, and recurrence at the primary site is still the main obstacle to cure. Among various variables, only extent of resection had the strongest impact on recurrence. Additional studies may still be needed to precisely define the prognostic variables on recurrence in intracranial ependymomas.

• 산경연구논집
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• 제11권3호
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• pp.51-62
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• 2020

Purpose - This study examined the relationship between individual creativity and its related variables to observe how individual creativity contributes to organizational performance. In addition, this study strived to explore how to maximize the utilization of individual creativity and innovate the structure of the organization itself so that teams and organizations can respond more effectively to new rising trends. this study aimed to examine whether the value congruence between individuals and organizations (propensity congruence, goal congruence has a significant impact on knowledge sharing and innovation behavior as dependent variables by exerting individual creativity and synergy as independent variables. Research design, data and methodology - SPSS 24.0 program were used to analyze the data. Descriptive Statistics and correlation analysis were performed, and the reliability factor (Cronbach's α) was calculated. Afterwards, we analyzed the moderating effects of structural equation model analysis and hierarchical regression analysis. The number of samples used in the study were 309 copies. Results - First, Individual creativity had a positive effect on knowledge sharing and innovative behavior. In other words, it was confirmed that decision-making processes fused with individual creativity could create an atmosphere of knowledge sharing and transform the organization. Second, value congruence adjusted the influence of individual creativity on knowledge sharing and innovation behavior. Conclusions - First, it is important for managers to recognize the value and secure the pool of creative talents who will be a potential future basic source of organizational success and competitive advantage. Second, managers should be able to identify those with creative talents and expertise, and use them to increase their knowledge sharing performance, while also developing emotional and motivational creativity. Third, in order improve knowledge sharing performance, managers should pay attention to the emotional aspect of creativity. Fourth, managers should strive to create an environment that is beneficial for the reinforcement of individual self-management capabilities. Fifth, managers should be able to develop decision-making processes to develop potential creativity and encourage creative thinking, opinions, or solutions. Sixth, managers should promote the dissemination and integration of new knowledge based on the creative views and attitudes of team members.

• 한국조사연구학회지:조사연구
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• 제4권1호
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• pp.1-29
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• 2003

모바일 조사방법은 유선전화조사와는 달리 응답대상자에 대한 접촉가능성이 높기 때문에 새로운 조사방법으로 활용되기 시작하였다. 그러나 모바일 조사방법의 표본 대표성을 확보할 수 있는 방법론이 아직 정립되지 않았다. 이 연구는 성향지수를 이용한 가중치를 사용하는 것이 모바일 조사의 표본편향을 제거해 줄 수 있는지 검토해 보았다. 성, 연령, 학력 등의 인구학적 속성과 기타 태도변인을 이용하여 성향지수를 산출하여 가중치로 사용하였다. 그 결과 선거예측조사와 과학 여론조사 등에서 표본의 편향이 감소되는 것으로 나타났다. 그러나 이러한 본 연구의 결과가 일반성을 어느 정도 가지는가는 좀더 검토되어야 할 것이다.

• Nutrition Research and Practice
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• 제7권1호
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• pp.59-65
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• 2013

Excessive sodium intake leading to hypertension, stroke, and stomach cancer is mainly caused by excess use of salt in cooking. This study was performed to estimate the salt content in school meals and to compare differences in perceptions related to sodium intake between students and staffs working for school meal service. We collected 382 dishes for food from 24 schools (9 elementary, 7 middle, 8 high schools) in Gyeonggi-do and salt content was calculated from salinity and weight of individual food. The average salt content from elementary, middle, and high school meals were 2.44 g, 3.96 g, and 5.87 g, respectively. The amount of salt provided from the school lunch alone was over 80% of the recommended daily salt intake by WHO. Noodles, stews, sauces, and soups were major sources of salt intake at dish group level, while the most salty dishes were sauces, kimchies, and stir-fried foods. Dietary knowledge and attitude related to sodium intake and consumption frequency of the salty dishes were surveyed with questionnaire in 798 students and 256 staffs working for school meal service. Compared with the staffs, the students perceived school meals salty and the proportions of students who thought school meals were salty increased with going up from elementary to high schools (P < 0.001). Among the students, middle and high school students showed significant propensity for the preference to one-dish meal, processed foods, eating much broth and dipping sauce or seasoning compared with the elementary students, although they had higher nutrition knowledge scores. These results proposed that monitoring salt content of school meals and consideration on the contents and education methods in school are needed to lower sodium intake.