• The korean journal of orthodontics
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• v.30 no.5 s.82
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• pp.613-623
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• 2000

The purpose of this study was to amount of the frictional forces with the brackets and wires, ligation methods, dry/wet, offsets, interbracket distances, velocity and to compare them each other by different conditions. This study tested 0.018'x0.025' slot sized 8 types of orthodontic bracket systems and 0.016', 0.016'x0.022' sized stainless steel, NiTi, Cu-NiTi orthodontic wires. One cuspid bracket were positioned on the slide glass and archwire was engaged into bracket and ligated with elastomeric modules. The values of frictional forces were measured with the instron universal testing machine. The results were as follows; 1. Polycrystalline ceramic bracket had the highest mean frictional forces and followed and by ceramic reinforced plastic bracket, metal bracket, plastic bracket with metal slot, monocrystalline ceramic bracket, single bracket, self-ligating bracket, friction free bracket in descending order. The self-ligating bracket showed low frictional forces in the round wires and high frictional forces in the rectangular wires. 2. Stainless steel wires had the least frictional forces and followed by NiTi, Cu-NiTi wires in descending order. Round wires had lower frictional forces then that of rectangular wires. 3. The stainless steel ligation method had significantly greater mean frictional forces them the elastomeric module ligation method. 4. Artificial saliva statistically increased the frictional forces in stainless steel wire, NiTi wire and Cu-NiTi wire. 5. There was a statistically significant difference with offset change 6. There was no statistically significant difference with interbracket distance in stainless steel wires but a significant difference in NiTi wires as the interbracket was decreased. 7 There was no statistically significant difference with velocity change. From the above findings, self-ligating bracket, stainless steel wires and the elastomeric module ligation method might be effective than any other materials to reduce the frictional forces in the orthodontic treatment and can be correlated to clinical situations seen in orthodontic patient care.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.8 no.2
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• pp.242-253
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• 1998

South Korea has been producing asbestos over 60 years. The use of asbestos was over 50 years for production of asbestos slate and 27 years for asbestos friction materials including asbestos textile and brake-lining. Thus, it can be supposed that asbestos related diseases such as asbestosis, lung cancer and mesothelioma could be found in the vulnerable workers exposed to asbestos in 1955-1975, given the average latency period of 10-30 years. Asbestos was produced primarily by Japanese during World War II In Korea. The production of chrysotile peaked to 4,815 tons in 1944. From 1978 to 1984, 10,000 tons of asbestos were produced annually. However, the production was interrupted by raising labor costs and extinction of mine reserves, and finally they had to depend on import for the need of asbestos. In 1945, there were 16 asbestos mines, in total, with the addition of new asbestos mines in South Korea. Imports of asbestos was increased from 74,000 tons to 95,000 tons during the period of 1976 - 1992. But the imports was reduced to 88,000 tons in 1995. Since, in addition to the import of asbestos itself, the imports of asbestos products were increased as well and the accumulation of asbestos reached to 30,000 tons during the period of 1964 to 1993. In 1965, there was only one asbestos company with 207 employees. But the size of asbestos industry has been expanded so much that 118 asbestos companies could be found in 1993 with 1,476 workers. However, there was no record on the survey of asbestos concentration to which workers were exposed in any companies in 1983. The record of the air-borne concentration of the asbestos in textile working places in 1984 showed 6.7 fibers/cc by geometric mean(GM), but it was reduced to 1.2 fibers/cc in 1993. GMs of asbestos in working places for construction materials and asbestos textiles were also decreased from 1.7 fibers/cc to 0.55 fibers/cc during the period of 1984 - 1996.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.31 no.4
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• pp.113-122
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• 2013

In this study, the traditional structure of the impact on the stability analysis. Korean traditional landscape architecture column space of stonework stable composition as the foundation of the fence for a long time been known to fall down and not maintained. The destination of research Ohgokmun Damyang Soswaewon fence which is in harmony with nature is one of the traditional structures that affect its shape without being kept so far came true. This includes our ancestral wisdom and that wisdom can guess guesswork. But I let the traditional reproduction incidence structures frequently. This deviation from the traditional method of construction application of shorthand stand. Thus, the subject of this study, the factors that do not fall down fences Ohgokmun solution is to indirectly gain the weak. In addition, epidemiological studies and the methods of calculation of the inferred physical examination, the results of the analysis were derived through the following. First, the internal factors of the fence Ohgokmun constituting the structural member and the coupling of the scheme. 1) based on stable ground. Greater role in the country rock The fact that the settlement will have no symptoms. 2) to minimize the friction caused by hydrological water to remove the two-pronged process through stone work building form and menu sustaining power in hydrology and flooding made against the bypass channel. 3) due to the load bearing capacity and durability to withstand the strength of the material and the construction of structures in the form of a dispersion of power between each individual to maximize the process of getting traction was applied. Second, external factors Ohgokmun fence the results obtained through the calculation of the dynamics of repair, is greatly affected by the wind and the water gate of the fence, but the action of the structural stability of the lack of power that hurt enough conclusion. In this study, the results of the structure of internal and external influence as well through the structure can be viewed as composed consisting. However, over the next follow-up in terms of climate and environmental factors due to the fact that the fall might.