• Journal of the Korea Safety Management & Science
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• v.25 no.1
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• pp.67-74
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• 2023

This study aims to measure sedimentation status change with the changes in internal pressure for dry chemical extinguishers of various use periods and analyze the suitability of the fire extinguishers' performance criteria. When the internal pressure of the fire extinguisher is 0%, 2 out of 10 new dry chemical powders for the 5 elapsed years were noted to be suitable, including 3 recycled dry chemical powders with 5 elapsed years that were found eligible. One out of 10 new dry chemical powders for 10 elapsed years was shown as suitable. Also, one new dry chemical powder for 13 elapsed years was suitable. When the internal pressure of the fire extinguisher was 50%, all 10 out of 10 new dry chemical powders for 5 years, recycled one with 5 elapsed years, and a new one with 10 elapsed years were found to be suitable, while 9 new dry chemical powders for 13 years were shown as suitable. When the internal pressure of the fire extinguisher was normal, new ones with 5 elapsed years, recycled ones with 5 elapsed years, new ones with 10 elapsed years, and new ones with 13 elapsed years were all 10 out of 10 samples noted as suitable. In summarizing the experiment results, it was found that the sedimentation status, one of the fire extinguisher's physical properties experiments, affects the fire extinguisher's performance criteria rather than the change with use periods.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.4
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• pp.693-702
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• 2005

Accurate timing and sequence of eruption of permanent teeth are indicies of growth and essential for pediatric dentistry and pediatric clinical orthodontics. From the children brought to the Yonsei Dental Hospital during 2001 to 2003, 654 boys and 542 girls, ranging in age from five to fourteen years, were selected and analysed. The following was concluded. 1. Eruption time of maxillary teeth is 6.81 years in boys, 6.78 years in girls for central incisor, 8.30 years in boys, 7.98 years in girls for lateral incisor, 10.28 years in boys, 10.04 years in girls for canine, 9.74 years in boys, 9.90 years in girls for first premolar, 10.87 years in boys, 10.41 years in girls for second premolar, 6.25 years in boys, 6.54 years in girls for first permanent molar, 12.21 years in boys, 12.03 years in girls for second permanent molar 2. Eruption time of mandibular teeth is 6.00 years in boys, 6.06 years in girls for central incisor, 6.99 years in boys, 6.74 years in girls for lateral incisor, 9.83 years in boys, 9.17 years in girls for canine, 9.92 years in boys, 9.75 years in girls for first premolar, 10.66 years in boys, 10.39 years in girls for second premolar, 5.99 years in boys, 5.75 years in girls for first permanent molar, 11.92 years in boys, 12.17 years in girls or second permanent molar. 3. The following eruption sequence was observed the first permanent molar erupted first, followed by the central incisor, the lateral incisor, the first premolar, the canine, the second premolar and the second permanent molar in the maxilla. The first permanent molar erupted first, followed by the central incisor, the lateral incisor, the canine, the first premolar, the second premolar and the second permanent molar in the mandible.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.4
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• pp.389-397
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• 2010

Purpose: This study was to investigate the changes of refractive error and astigmatism associated with age in Korean subjects between the ages of 6 and 80 years during 10-year period. Methods: 220 normal subjects (345 eyes) who visited ophthalmic clinic was recruited and followed for 10 years between 1999 and 2009, cycloplegic manifest refraction being performed annually. Visual acuity was tested on a Han's chart. Results: The mean 10-year change in the spherical equivalent refraction (SER) of age 6 to 10 years old and 10 to 20 years was -3.649D and -2.165D respectively. There was no change of refractive error in age 21 to 40 years. The myopic shift decreased with age from 41 up to 69 years but increased slightly in patients 70 years and older; the hyperopic shift showed the opposite trend. The distribution of refractive error over the 10 years in aged 6 to 10 and 11 to 20 years was shifted myopic. The incidence of medium (> -3.01D) to high myopia at age 6 to 10 years was 4.8% and after 10 years was 62.5%. The 10-year change of astigmatism axis was in "with the rule" direction for younger age group and in a "against the rule" direction for older subjects. Conclusions: This study has documented refractive error changes in Korean subjects and confirmed reported trends of myopic shift from age 6-20 years and hyperopic shift before age 70 years and a myopic shift thereafter. The axis of astigmatism turns to "against the rule" after 40's.

• Economic and Environmental Geology
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• v.9 no.3
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• pp.127-134
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• 1976

The K-Ar age determined on six granitic rocks samples from the Eonyang- and the northwestern part of Ulsan-quardrangle, Kyeongsang-nam-do, Korea, ranges from $87{\times}10^6$ years to $58{\times}10^6$ years. Three of the samples belong to the upper Cretaceous ($87{\times}10^6-71{\times}10^6years$) and three to the late Cretaceous-early Tertiary ($63{\times}10^6-58{\times}10^6years$) in age. The early Tertiary ages are measured first on the "Younger Granites" in Korea. These two emplacement periods of granitic rocks are representative that the former is correlated to north Kyushu-Seto Inland belt ($95{\times}10^6-75{\times}10^6years$) and the later to Sanin-central Honshu belt ($65{\times}10^6-50{\times}10^6years$), in southwestern Japan.

• Journal of Chest Surgery
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• v.22 no.6
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• pp.980-989
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• 1989

The Hancock porcine xenograft valves had been used in Seoul National University Hospital, mainly because of their antithrombogenicity despite of the predicted failure, from March 1976 to April 1984, and a total and consecutive 163 patients were retrospectively studied for late results with the special stress on the structural failure. The hospital mortality rate [within 30 days] was 6.1 %, and the 153 early survivors were followed up for a total of 822.9 patient-years [p-y][Mean * SD 5.38 * 3.02 years]. The linealized late mortality was 1.823%/p-y. Four major complications related to the Hancock valve were: 1.822% thromboembolism/p-y; 0.729 % bleeding/p-y; 0.972% endocarditis/p-y; 3.646% overall valve failure/p-y and 2.187 % primary tissue failure [PTF]/p-y. The actuarial survival rates at 5 and 10 years were 94.90 * 1.89% and 80.58 * 5.21 %; and the probabilities of freedom from thromboembolism at 5 and 10 years were 90.93 * 2.63% and 83.35 * 7.64 9o respectively. The probabilities from PTF at 5, 10 and 12 years were 98.02 * 1.39%, 60.62 * 8.89% and 49.60 * 12.34 %. One hundred-eighteen patients [72.4%] had single MVR [age, 34.0 * 10.9 years] with the operative mortality rate of 4.2%; and 113 early survivors were followed up for a total 616.4 patient-years[5.46 * 2.96 years]. The late mortality rate was 1.460 %/p-y. The major complications were: 1.622 % thromboembolism /p-y; 0.487% bleeding/p-y; 0.649 % endocarditis/p-y; 2.920% primary valve failure/p y and 1.785% PTF/p-y. The actuarial survival rates were 97.08 * 1.67%[at 5 years] and 81.27 * 6.64%[at 10 years], and the probabilities of freedom from thromboembolism 92.44 * 2.76 %[at 5 years] and 80.89 * 11.08%[at 10 years]. The probabilities of freedom from PTF at 5 and 10 years were 98 70 * 1.29% and 65.59 * 9.78% respectively. The mean age of 11 patients of PTF was 25.7 * 8.8 years and the valve extraction period 7.16 * 1.45 years. Failure of bioprosthetic xenograft valves are reportedly known to occur earlier in young patients in an accelerated fashion. The study with two groups divided into the cumulative younger and the cumulative older patients according to the age limits of 5-year interval strongly suggested these tendency. Although PTF began to occur past postoperative 5 years and the probabilities of freedom from PTF increased as the age limits raised and the number of patients increased in the cumulative younger patients while they decreased as the age limits lowered and the number of patients increased in the cumulative older patients, the definite age limits from which the Hancock valve can be safely recommended could not be obtained. From the results, the Hancock valves are contraindicated in patients younger than 20 to 25 years and may be safely recommended in patients older than 45 years as a tentative conclusion. Further longitudinal study may define these age factors.

• Journal of the korean academy of Pediatric Dentistry
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• v.1 no.1
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• pp.19-29
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• 1974

Surveying the root resorption of the mandibular deciduous teeth in 967 children, (Male 493 Female 474) from 3 to 12 years old by orthopantomography, the author obtained the following results. 1) Female in the root resorption of the deciduous teeth was earlier than male. 2) The stages of initial resorption of the deciduous teeth were as follow. central incisor 4 years lateral incisor 4 years 2 months cuspid 6 years first decid uous molar 6 years second deciduous molar 6 years 5 months 3) The exfoliational stages ($R_5$) of the deciduous teeth were as follow. central incisor 6 years 8 months lateral incisor 7 years 2 months cuspid 9 years 10 months first deciduous molar 10 years 3 months second deciduous molar 11 years.

• Korean Journal of Clinical Laboratory Science
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• v.46 no.1
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• pp.17-21
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• 2014

The prevalence of hepatitis A virus (HAV) in a certain community reflects that community's living standard and hygienic condition. The seroprevalence rate of IgG anti-HAV has been changing with regions and times. In this study, we aimed to study the difference of seroprevalence of IgG anti-HAV according to sex, age and type of drinking water, and to know the vaccination rate and seroconversion rate for vaccinated subjects in Busan. A total of 644 samples were analyzed. The overall seroprevalence rate of IgG anti-HAV was 35.4% (228/644). There was no significant difference in sex (male 39.8%, female 32.7) (p>0.05). According to age, seroprevalence rate of anti-HAV were 55.0% in subjects aged 5~9 years old, 47.8% in 10~14 years old, decreced to 10.6% in 15~19 years old, 1.0% in 20~24 years old, 0.0% in 25~29 years old and increced with advacing ages ; 14.7% in 30~34 years old, 39.4% in 35~39 years old, 67.3% in 40~44 years old, 94.1% in 45~49 years old, 100.0% over 50 years (p<0.001). The seroprevalence of IgG anti-HAV was no statistical difference according to the types of drinking water (p>0.05). The vaccinated subject was 42 case only in below 25 years old. The seroconversion rate after vaccination was 88.1%.

• Journal of Chest Surgery
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• v.25 no.5
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• pp.494-503
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• 1992

The durability of the xenograft cardiac substitute valves is of a great concern on the clinical grounds. Four groups of tc tal and consecutive patients to the end of study operated on between 1976 and 1984 were Group ISM, 291 patients of MVR, ISA, 65 patients of AVR, and ISMA, 107 patients of MVR+AVR with the standard Ionescu-Shiley bovine pericardial valve, and H, 163 patients of valve replacement with the Hancock porcine aortic vlave. Operative mortality was 5.2%[ISM], 10.8%[ISA], 7.5%[ISMA] and 6.1%[H]. Early survivors were followed up for a total of 1148.3 patient-years[pt-yrs] [ISM], 271.2 pt-yrs [ISA], 488.1 pt-yrs[ISMA] and 822.9 pt-yrs[H]. Linearized late mortality was 2.1% /pt-yr [ISM], 1.l%/pt-yr[ISA], 1.8%/pt-yr[ISMA] and 1.8% /pt-yr[H]. Thromboembolic complication was experienced at the linearized rate of 1.045% /pt-yr [ISM], 1.475%/pt-yr[ISA], 0.615%/pt-yr[ISMA] and 1.822%/pt-yr[H], and bleeding complication at the rate of 0.871% /pt-yr[ISM], 0.63% /pt-yr[ISA], 0.205% /pt-yr [ISMA] and 0.729%a /pt-yr[H], respectively. Prosthetic valve endocarditis occurred at the rate of 0.610% /pt-yr[ISM], 1.475% /pt-yr[ISA], 1.639% /pt-yr[ISMA] and 0.972% /pt-yr[H]. The linearized annual incidence of primary tissue failure was 1.655%/pt-yr[ISM], l. 475%/pt-yr[ISA], 1.639% /pt-yr[ISMA], 2.187% /pt-yr[H] and 1.785% /pt-yr[Group HM : MVR with Hancock valve]. The incidence of tissue failure was significantly high in the patients younger than 30 years of age compared with the older patients. The actuarial survival was 87.7$\pm$2.5% at 10 years[ISM], 94.3$\pm$3.2% at 11 years[ISA], 89.6$\pm$3.4% at 10 years[ISMA] and 81.3$\pm$6.6% at 12 years[HM], The freedom from thromboembolism was 93.2$\pm$2.0% at 10 years[ISM], 90.6$\pm$4.6% at 11 years[ISA], 95.8$\pm$2.6% at 10 years[ISMA] and 80.9$\pm$11.1% at 12 years[HM], And, the freedom from primary tissue failure was 84.2$\pm$3.8% and 28.1$\pm$23.0% at 9 and 10 years[ISM], 60.4$\pm$16.9% at 11 years[ISA], 62.3$\pm$12.7 at 10 years[ISMA] and 65.6$\pm$9.8% at 12 years[HM]. In conclusion, the standard Ionescu-Shiley and the Hancock bioprosthetic valves are excellent in their antithrombogenicity and long-term survival. However, the features of the structural failure with the prolonged follow-up beyond 10 years appear to be guarding, and the clinical indications of these bioprostheses seem to be quite limited.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.5
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• pp.647-654
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• 2005

Recently, the economic losses caused by inundation are increasing due to the urbanization and industrialization, i.e., intensive land utilization and concentration of population and properties. It is regarded that the role of the storm sewer systems in urban areas becomes more important as one of the effective countermeasures for reducing the inundation losses. In this study, the effects of rainfall design frequency enhancement on the construction cost of the storm sewer systems were analyzed by increasing the design frequency from the present design frequency of the sewer systems, which is 5~10 years, to 15 years, 20 years and 30 years. The change rate functions of the design discharge and construction cost based on the various design frequencies were derived by regression analysis. According to the analysis, change the rate of design discharge at 15, 20, 30 years rainfall design frequencies were increased by 10%, 17.1%, and 27.2%, respectively, when compared to that at 10 year frequency. Furthermore, it was found that by increasing the design frequency from 10 years to 15 years, 20 years and 30 years, the construction costs were increased by 5.0%, 8.0% and 12.4%, respectively. Finally, their reliabilities need to be tested by applying the rate functions to the real storm sewer districts.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.04a
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• pp.44-44
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• 2018

The seeds of soybean (Glycine max), adzuki bean (Vigna angularis), mung bean (Vigna radiata), and kidney bean (Phaseolus vulgaris L.) were examined the germination rate after 10 years of long-term storage ($-18^{\circ}C$) conservation. For soybean seeds, 2,313 accessions were examined and germination rate of 1,082 accessions was decreased with below 15% of initial germination rate. For 227 accessions of soybean, germination rate was decreased with above 15% of initial germination rate after 10 years of long-term storage, which is needed to be rejuvenated. Germination rate of 589 accessions was increased and showed no change for 415 accessions after 10 years of long-term storage. For adzuki bean seeds, 2,058 accessions were examined and germination rate of 739 accessions was decreased with below 15% of initial germination rate. For 63 accessions of adzuki bean, germination rate was decreased with above 15% of initial germination rate after 10 years of long-term storage, which is needed to be rejuvenated. Germination rate of 535 accessions was increased and showed no change for 721 accessions after 10 years of long-term storage. For mung bean seeds, 438 accessions were examined and germination rate of 139 accessions was decreased with below 15% of initial germination rate. For 5 accessions of mung bean, germination rate was decreased with above 15% of initial germination rate after 10 years of long-term storage, which is needed to be rejuvenated. Germination rate of 155 accessions was increased and showed no change for 139 accessions after 10 years of long-term storage. For kdney bean seeds, 366 accessions were examined and germination rate of 7 accessions was decreased with below 15% of initial germination rate. For 65 accessions of kidney bean, germination rate was decreased with above 15% of initial germination rate after 10 years of long-term storage, which is needed to be rejuvenated. Germination rate of 201 accessions was increased and showed no change for 93 accessions after 10 years of long-term storage.