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열분석 방법을 이용한 AISI 5160스프링강의 용접시 Heat Affected Zone에서의 결합규명과 수소취성에 관한 연구
김민태,이재영 대한용접접합학회 1987 대한용접·접합학회지 Vol.5 No.1
To explore the possible application of thermal analysis technique as a probe for finding weld defects, Hydrogen trapping phenomena in Heat Affected Zone (HAZ) of the AISI 5160 spring steel were investigated. HAZ was divided into five parts, which were used as thermal analysis specimens. Two types of trap sites were found in HAZ, ferrite/cementin interface and microvoid. The thermal analysis peak due to the ferrite/cementite interface increased its height toward the weld deposit. The thermal analysis peak due to the microvoid was the highest where the grain size was the smallest. The correspondence between the cold cracking and hydrogen trap nature is also discussed.
김민태,이재훈,Nathaniel T. Carpena,이민영,정필상,정재윤 대한이비인후과학회 2021 Clinical and Experimental Otorhinolaryngology Vol.14 No.1
Objectives. The relationship of estrogen (the primary female sex hormone) with hearing function has been studied in both humans and animals. However, whether estrogen levels affect hearing remains uncertain. Therefore, in this study, we investigated changes in the vulnerability of hearing to acoustic overexposure in ovariectomized female rats. Methods. Eighteen 8-week-old female Sprague-Dawley rats were separated into four groups as follows: sham ovariectomy (OP), OP only, and OP treated with low (10 μg/kg) or high doses (100 μg/kg) of estrogen. Rats in the estrogen replacement groups were given two intraperitoneal injections. Hearing thresholds were measured before noise exposure, and at 1 day and 2 weeks after exposure. Results. The hearing thresholds of the sham OP and OP-only groups were not significantly different. However, both estrogen groups showed a lower threshold shift than the OP-only group. Histological immunostaining analyses showed that hair cell loss in the 32 kHz region was more severe in the sham OP group than in the OP-only group. Furthermore, there was little or no hair cell loss in either estrogen replacement group and significantly more hair cell loss in the OP-only group. Conclusion. These results suggest that estrogen replacement may reduce the vulnerability of hearing to noise exposure in menopausal women.
수평 반고리관 양성돌발성두위현훈에서 아형에 따른 등속회전검사의 비교
김민태,최지은,이민영,정재윤 대한평형의학회 2019 Research in Vestibular Science Vol.18 No.4
Objectives: The nystagmus evoked by an angular velocity step is influenced by the cupula dynamics and the status of velocity storage mechanisms. This study questioned whether the cupulolithiasis of horizontal canal benign paroxysmal positional vertigo (HC-BPPV) affects the time constant or gain of the velocity step test.Methods: We performed a retrospective study of 30 patients who diagnosed with HC-BPPV and performed rotary chair test at Dankook University Hospital from June 2010 to May 2017. All patients had normal vestibular function on the si-nusoidal harmonic acceleration test. According to the direction of nystagmus on the head roll test, we further divided the patients into “geotrophic” (canalo-lithiasis) and “apogeotrophic” (cupulolithiasis) groups. We compared the time constant (Tc), gain, and directional preponderance (DP) between the 2 groups. We also compared the time constant and gain between lesion side of BPPV and normal side in each group.Results: In the supine head roll, geotrophic nystagmus observed in 14 patients and apogeotrophic nystagmus observed in 16 patients. When parameters of the velocity step test compared according to lesion side of BPPV (per-rotary of lesion side, postrotary of lesion side, per-rotary of normal side, and postrotary of normal side), there were no significant differences in Tc, gain, and DP between the 2 groups. There were also no significant differences in Tc and gain between lesion side and normal side in each group.Conclusions: We assumed that cupulolithiasis of HC-BPPV could affect the cu-pular deflection evoked by an angular velocity step, but there were no significant differences in Tc and gain between patients with cupulolithiasis and canalolithi-asis.
석면 슬레이트 지붕 가옥 거주자의 지붕 개량 인식도 조사
김민태,박소영,김미경,함다솜,윤은영,김윤재,장봉기 순천향대학교 기초과학연구소 2019 순천향자연과학연구 논문집 Vol.25 No.1
In addition to the Saemaul Movement, slate roof houses containing asbestos used for the improvement of thatched roofs are exposed to air as the slate is corroded and weathered over time. This study was carried out to obtain the data that help the slate roof demolition support project by grasping the roof improvement awareness of the resident of the slate roof house and residents of the house with layering sheathing on top of an asbestos slated roof. We surveyed 42 residents living on slate roofs in September 2017 and 41 residents of houses living on the slate with steel plates and galvanized iron on top of the asbestos slate roofs in Asan city, Chungnam province. In the 30-59 year residence period, they were more likely to live in houses that were the house with layering sheathing on top of an asbestos slated roof. The rate of respondents who did not know the risk of asbestos was 45.2%, which was higher than that of the house without layering sheathing group, 26.8%. Among the residents of 41 houses that were of the house with layering sheathing group, 87.8% said the reason for the sheathing was 'due to old roofs' and 9.8% said 'because of poor appearance,' while only one person responded to the reason for the low awareness of the risk of asbestos. Among the reasons for sheathing the slate roof, 56.1% said that it was cheaper than other methods, and 22.0% said that they wanted to demolish but the cost was too high. The satisfaction level for sheathing the slate roof instead of demolition was high at 53.7%, with the ratio of "unsatisfied" being very low at 7.3%. As a reason for not sheathing the slate roof, 64.3% said that there was no inconvenience in staying and that it was due to the cost burden. 54.6% of the respondents did not know about the project to support the removal of asbestos slate roofs from the government and 56.6% of the respondents answered that the support project is not helpful because they can not provide the support to all the applicants. As a result, it is costly to remove the slate roof and use new roofing material. Therefore, the slate roof is used as it is, or it is used by sheathing with steel plate or galvanized iron. In order to remove the slate and improve with other roofing material, and expansion of the target and active publicity are needed.