• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.37.2-37.2
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• 2014

Gas in disk galaxies interacts nonlinearly with a underlying stellar spiral potential to form galactic spiral shocks. Numerical simulations typically show that these shocks are unstable to the wiggle instability, forming non-axisymmetric structures with high vorticity. While previous studies suggested that the wiggle instability may arise from the Kelvin-Helmholtz instability or orbit crowding of gas elements near the shock, its physical nature remains uncertain. It was even argued that the wiggle instability is of numerical origin, caused by the inability of a numerical code to resolve a shock that is inclined to numerical grids. In this work, we perform a normal-mode linear stability analysis of galactic spiral shocks as a boundary-value problem. We find that the wiggle instability originates physically from the potential vorticity generation at a distorted shock front. As the gas follows galaxy rotation, it periodically passes through multiple shocks, successively increasing its potential vorticity. This sets up a normal-mode that grows exponentially, with a growth rate comparable to the orbital angular frequency. We show that the results of our linear stability analysis are in good agreement with the those of local hydrodynamic simulations of the wiggle instability.

• Journal of the Korean Institute of Landscape Architecture
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• v.22 no.3
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• pp.151-162
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• 1994

This is a comparative study on the use pattern and satisfaction of skiers between the suburban skiing ground and the resort one. The purpose of this study is to provide basic data for the planning and the management of skiing ground. The sites of case study are Yong Pyung Ski Resort (Resort type) and Bears Town(Suburban type). Data were collected from questionaire. A total of 420 questionaires were completed. And data were subjected to following analysis: First, the descriptive statistics(mean, chi-square analysis etc.) were used to compare the characteristics of the users and the use pattern of two sites. Second, factor analysis was utilized to reduce 22 satisfaction items into the smaller number of factors. Third, regression analysis was used to find the factors affecting users' overall satisfaction in each skiing ground. The findings of this study are as follows: First, it was proved that the characteristics of users between tow sites were different in terms of age, income, and skill level. Second, it was proved that the use pattern between two sites were different in terms of travel distance from home, traffic mode, length of stay, accommodation type, and the money spent per day. Third, By a principal component factor analysis several factors of satisfaction are found: In physical terms, they are 'slope and life facilities', 'recreation and lodge facilities', 'accessibility', 'crowding', and 'landscape'. In psychological terms, they are 'skiing skills and thrills', and 'relaxation and freedom'. Forth, As the result of the stepwise regression analysis, it was yielded that 'relaxation/and freedom' was most important factor to predict the overall satisfaction in both skiing ground. And it was proved that not only physical factors but also phychological(need gratifying) factors were important sources of the satisfaction.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.4 no.2
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• pp.161-166
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• 2001

Purpose: Poor living conditions such as overcrowding and sharing a bed are reported to be significant risk factors for H. pylori infection throughout childhood. We investigated the prevalence of Helicobacter pylori infection in Korean athletes who are obliged to live together in training camps over six months a year. Methods: Blood sampling and surveying through questionnaire were performed on 440 regular high school students (228 boys and 212 girls) and 220 athletes (148 boys and 72 girls) of a physical education high school. We measured serum IgG Ab to H. pylori in order to compare the prevalence of H. pylori infection between normal adolescents and athletes. In addition, we conducted a nutritional analysis and questionnaire survey for socioeconomic status in order to compare other risk factors that might influence H. pylori infection between groups. Results: The prevalence (43.2%) of H. pylori infection in athletes was higher than that (22.7%) in the controls. No significant differences in the nutritional factors or socioeconomic status, such as Hollingshead index, type of house, and crowding index, were found between the groups. Multivariate analysis showed that crowding and the difference in school type were the significant predictors of H. pylori seropositivity after controlling for dietary and socioeconomic factors. Conclusion: Living together in training camps might be a significant risk factor for H. pylori infection in athletes.

• Journal of the Korean Institute of Landscape Architecture
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• v.20 no.2
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• pp.27-42
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• 1992

IN urban areas, public outdoor recreation opportunities are limited, traditional funding sources are being eraded, and crowding as well as ecological damage appear inevitable, these developments may require new analysis on the prospective policy of park, with the evaluation of the trend of amenity resources and recreation values, 16 parks were taken as informants in Deagu city area, the data for this research were collected 2,942 samples by the on-site-interview. The abstracted results of amenity elements were revealed as institutions and resource types, the attraction of resources was about twice as much as that of institutions. The resources is to be classified into two items ; national resources and human resources. The former is about five times as mcuh atractive as the latter. The attraction of natural resources consists in the atmospheric factors(35%), the biological factors(28%), the topographical factors(19%), and the scenery factors(18%). While, the attraction of human resources consists in the cultural factors(54%), the social factors(46%). The attraction of the base institutions is very low. The attraction of the static institution is three times as much as that of that of the dynamic institution. The above tendency is a general trend in Daegu city. But when we are taking into consideration in datail, we find that there is great difference among the green tract of land of the park. When the amenity resources of one's destination was used for the value of recreation, the pattern of attraction variables as a physical characteristics could explain 58%. Based on those result, this study is a small but important guidence for decision makings concerning to the allocation of scarce amenity resources.

• Journal of The Korean Dental Society of Anesthesiology
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• v.13 no.1
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• pp.13-18
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• 2013

CATCH 22 syndrome is a one of the most common chromosome microdeletion syndrome with multiple organ anomalies in humans, with an incidence of approximately 1:4,000 to 1:5,000 live births. It is caused by a microdeletion of 1.5 to 3.0 megabases on the long arm of chromosome 22. The phenotypic spectrum of this disorder is wide and various. A 19-year-old patient who showed delayed growth and development (Height; 110 cm, Weight; 18 kg) was referred to our department for the treatment of dental cavities. She was diagnosed as CATCH 22 syndrome in 2004. Physical examination revealed hypertelorism, a short philtrum, thick reflected lips and a small mouth. She underwent cleft palate surgery at 1 year of age and heart valve surgery due to the cardiovascular abnormality at 13 years of age. Convulsive seizures had persisted until 5 years ago but are well controlled at present. Oral examination showed poor oral hygiene, crowding, prolonged retention on #65, 75 and dental cavities on #16, 21, 65, 26, 36, and 46. Cavity treatment and prophylaxis were performed under general anesthesia. Also continuous follow-up checks have been carrying out with the periodic prophylaxis and dental home education. Problems with numerous cavities and gingivitis which can lead to specific risks are common for CATCH 22 syndrome patients. It is therefore of great importance that these patients are referred to foremost physician and dental specialist for the oral care. In addition, preventive treatment targeting the risk of dental cavities and gingivitis is especially important and, as the syndrome involves many different medical problems, the dental treatment should be carried out in collaboration with the patient's physician.

• The Journal of Korea Assosiation for Disability and Oral Health
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• v.5 no.1
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• pp.23-26
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• 2009

Mental retardation is defined by the American Psychiatric Association as" subnormal general intellectual functioning which originates during the developmental period and is associated with impairment of either learning and social adjustment or maturation, or both." A patient with mild to moderate mental retardation can be managed adequately using restraints and medications. However, in case of severe or profound mental disability, dental treatment cannot be accomplished even with the use of behavior modification, physical restraints and sedation techniques. When treatment in the dental office has much difficulty, hospitalization for dental treatment under general anesthesia can and should be considered. This case presents the treatment of a patient with mental retardation who was referred to our department for comprehensive dental care. Dental examination revealed widespread dental caries and a severe anterior open bite with crowding problems. Under general anesthesia, generalized caries treatment was performed by our department, and the anterior dental esthetics was achieved in collaboration with the department of prosthodontic dentistry.