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SM45C강의 Tempering 온도 변화에 따른 상온 및 300℃에서의 피로균열전파특성
장천수,김현철,임병수 成均館大學校 科學技術硏究所 1993 論文集 Vol.44 No.2
The effect of micros tructural and tempering temperature change on ΔK_th has been investigated at room temperature and 300℃ For the experiments, using SM4OC steel, specimens of different grain sizes, spacings between ΔK_th particles and tempering temperatures were prepared. Some of the conclusions obtained are as follows ; 1. ΔK_th values were greater at 300℃ when compared with those at room temperature and the crack growth rate decreased as test temperature increased. 2. ΔK_th was observed to increase with tempering temperature. However, ΔK_th value of 450℃ tempered specimen was very low, which is believed to be the result of Tempered Martensite Embrittlement(T.M.E.).
용접공에서 혈중 중금속 농도와 혈장중 Malondialdehyde, α-tocopherol 및 적혈구내 Superoxide Dismutase 활성도에 관한 연구
이원진,장성훈,황천현,천병철,김해준 大韓産業醫學會 1998 대한직업환경의학회지 Vol.10 No.2
We investigated the association between the oxidative stress and the concentration of heavy metals in blood among welders. The study subjects were male manual CO₂welders(N=127) exposed to several heavy metals. The age distribution was from 20 to 63(GM=33.7) and the geometric mean(GM) of work duration was 4.2 years. We analyze the level of blood lead, cadmium, manganese and chromium which was related with the oxidative stress in the animal studies. Blood selenuim, plasma malondialdehyde(MDA), plasma α-tocopherol and erythrocyte superoxide dismutase(SOD) were analyzed as biological markers of the oxidative stress. The results of univariate analysis showed that the plasma MDA was significantly correlated with α-tocopherol(r=0.327) and blood selenium(r=0.313) concentration. But we could not find out any relationship between the erythrocyte SOD activities and those metal concentrations. Neither smoking nor alcohol consumption was related to the level of heavy metals and the oxidative stress biomarkers. As the results of multiple regression analysis with stepwise selection method, 1) the change of MDA level were dependent with the level of α-tocopherol and blood selenium concentration(R²=19.7), 2) the plasma α-tocopherol level was dependant with MDA and blood chromium concentration(R²=15.6), 3) in case of erythrocyte SOD activity, only the duration of work was significantly selected.
Cheon, Jeong Hyun,Lee, Hyung Chul,Im, Gi Jung,Park, Jung Youl,Park, Chul Korean Society of Plastic and Reconstructive Surge 2019 Archives of Plastic Surgery Vol.46 No.6
Background In microtia patients with bilateral hearing impairment, hearing improvement is crucial for language development and performance. External auditory canal reconstruction (EACR) has been performed to improve hearing, but often results in complications. We performed transcutaneous bone conduction implant (TBCI) surgery in these patients. This study aimed to evaluate the safety and efficacy of TBCI surgery. Methods A retrospective review was performed of five patients who underwent auricular reconstruction and TBCI surgery and 12 patients who underwent EACR between March 2007 and August 2018. Hearing improvement was measured based on the air-bone gap values using pure-tone audiometry over a 6-week postoperative period. We reviewed other studies on hearing improvement using EACR and compared the findings with our results. The surgical techniques for TBCI were reviewed through case analyses. Results Postoperative hearing outcomes showed a significant improvement, with a mean gain of 34.1 dB in the TBCI cohort and 14.1 dB in the EACR cohort. Both gains were statistically significant; however, the TBCI cohort showed much larger gains. Only three of the 12 patients who underwent EACR achieved hearing gains of more than 20 dB, which is consistent with previous studies. All patients who underwent TBCI surgery demonstrated hearing gains of more than 20 dB and experienced no device-related complications. Conclusions TBCI is a safe and effective method of promoting hearing gains in microtia patients with bilateral hearing impairment. TBCI surgery provided better hearing outcomes than EACR and could be performed along with various auricular reconstruction techniques using virgin mastoid skin.
Jeong Hyun Cheon,Hyung Chul Lee,Gi Jung Im,Jung Youl Park,Chul Park 대한성형외과학회 2019 Archives of Plastic Surgery Vol.46 No.6
Background In microtia patients with bilateral hearing impairment, hearing improvement iscrucial for language development and performance. External auditory canal reconstruction(EACR) has been performed to improve hearing, but often results in complications. We performedtranscutaneous bone conduction implant (TBCI) surgery in these patients. This studyaimed to evaluate the safety and efficacy of TBCI surgery. Methods A retrospective review was performed of five patients who underwent auricularreconstruction and TBCI surgery and 12 patients who underwent EACR between March 2007and August 2018. Hearing improvement was measured based on the air-bone gap values usingpure-tone audiometry over a 6-week postoperative period. We reviewed other studies onhearing improvement using EACR and compared the findings with our results. The surgicaltechniques for TBCI were reviewed through case analyses. Results Postoperative hearing outcomes showed a significant improvement, with a meangain of 34.1 dB in the TBCI cohort and 14.1 dB in the EACR cohort. Both gains were statisticallysignificant; however, the TBCI cohort showed much larger gains. Only three of the 12patients who underwent EACR achieved hearing gains of more than 20 dB, which is consistentwith previous studies. All patients who underwent TBCI surgery demonstrated hearinggains of more than 20 dB and experienced no device-related complications. Conclusions TBCI is a safe and effective method of promoting hearing gains in microtia patientswith bilateral hearing impairment. TBCI surgery provided better hearing outcomes thanEACR and could be performed along with various auricular reconstruction techniques usingvirgin mastoid skin.