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STS 316L 소결재료의 내식특성에 미치는 합금원소 첨가방법의 영향
김혜성,김유영,박동규,안인섭,Kim, Hye Seong,Kim, Yoo Young,Park, Dong Kyu,Ahn, In Shup 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.3
In this study, STS 316L powders with 3 wt.% Cu and 1 wt.% Sn known as corrosion-resistance reinforcement elements, are prepared to make different kinds of specimens, in which, 3 wt.% Cu and 1 wt.% Sn are added in different forms by mixing, alloying and fully alloying. After sintering in the same condition, the corrosion resistance, wear resistance and their mechanical properties of specimens are tested respectively. According to the comparison, STS 316L specimen sintered at $1270^{\circ}C$ showed the most excellent mechanical property: HRB 78 (hardness), 1130.7 MPa (RCS), 26.6% (Fraction Wear), It was similar with the specimen made of STS316L and fully alloyed Cu and Sn powders, meanwhile, the latter one appears the best corrosion resistance, 75hrs-salt immersion test results. In addition, the specimens with Cu and Sn powders additive showed relatively worse wear resistance in compared with STS316L specimen.
김혜성,김병재,오소희,이다영,황규리,전혜원,이승미 대한의학회 2015 Journal of Korean medical science Vol.30 No.9
During the first trimester of pregnancy, thyroid-stimulating hormone (TSH) > 2.5 mIU/L has been suggested as the universal criterion for subclinical hypothyroidism. However, TSH levels change continuously during pregnancy, even in the first trimester. Therefore the use of a fixed cut-off value for TSH may result in a different diagnosis rate of subclinical hypothyroidism according to gestational age. The objective of this study was to obtain the normal reference range of TSH during the first trimester in Korean gravida and to determine the diagnosis rate of subclinical hypothyroidism using the fixed cut-off value (TSH > 2.5 mIU/L). The study population consisted of pregnant women who were measured for TSH during the first trimester of pregnancy (n = 492) and nonpregnant women (n = 984). Median concentration of TSH in pregnant women was lower than in non-pregnant women. There was a continuous decrease of median TSH concentration during the first trimester of pregnancy (median TSH concentration: 1.82 mIU/L for 3+0 to 6+6 weeks; 1.53 mIU/L for 7+0 to 7+6 weeks; and 1.05 mIU/L for 8+0 to 13+6 weeks). Using the fixed cut-off value of TSH > 2.5 mIU/L, the diagnosis rate of subclinical hypothyroidism decreased significantly according to the gestational age (GA) at TSH (25% in 3+0 to 6+6 weeks, 13% in 7+0 to 7+6 weeks, and 9% for 8+0 to 13+6 weeks, P < 0.001), whereas the diagnosis rate was 5% in all GA with the use of a GA-specific cut-off value (P = 0.995). Therefore, GA-specific criteria might be more appropriate for the diagnosis of subclinical hypothyroidism.
Sebaceous Hyperplasia of the Scrotum and Penile Shaft
김혜성,이준영,김형옥,박영민 대한피부과학회 2011 Annals of Dermatology Vol.23 No.-
Sebaceous hyperplasia (SH) is a proliferative abnormality of sebaceous glands, most often seen in elderly individuals. It consists of single or multiple, asymptomatic, small yellow papules with a central depression. The face is most commonly affected, but there have been reports of SH on the chest or genitalia. A lobular array of well-differentiated mature sebaceous lobules is noted on histological preparations. In this report, we describe a patient with SH on the penile shaft and parts of the scrotum. (Ann Dermatol 23(S3) S341∼S342, 2011)
급냉응고법에 의한 In-Situ 복합재료로서의 과포정 Al-10wt%Ti 합금(I)
김혜성,금동화,김긍호,Kim, Hye-Seong,Geum, Dong-Hwa,Kim, Geung-Ho 한국재료학회 1999 한국재료학회지 Vol.9 No.3
In this study, a new concept of aluminum-matrix composites and the possibility of in-situ processing are suggested, and preliminary results on AI- Ti system are presented. Fine powders of AI-lO% Ti were prepared by the gas atomization so that fine $Al_3Ti$ formed into flake shape. A 25v/o $Al_3Ti/Al$ composite sample was made by the powd er metallurgy process involving hot extrusion. Microstructure and mechanical behavior both at room temperature and high temperatures were analysed by OM, SEM, TEM and tension test. Microstructural characteristics and mechanical properties of the composites exhibited similar behavior to those of $SiC_w/2124$ composites. Merits and drawbacks of the $Al_3Ti/Al$ composites are discussed together with a possibility of further improvement. 본 연구에서는 Al-기지 복합재료의 새로운 개념과 in-situ 공정의 가능성을 Al-Ti계의 연구결과들을 토대로 제시하고자 하였다. 가스아토마이제이션법에의해 $Al_3Ti$가 미세한 편상형상을 갖도록 Al-10%Ti 조성의 합금분말을 제조하고, 고온 압출 공정을통하여 25V/o $Al_3Ti/Al $ 복합재를 제조하였다. 복합재의 미세구조를 광학현미경, SEM, TEM 등을 이용하여 조사하였고, 상온과 고온에서의 기계적 특성을 인장시험을 통하여 측정하였다. 제조된 복합재료의 미세구조 및 고온 기계적 성질을 상용되고 있는 $SiC_w/2124$ 복합재료와 유사한 거동을 보여준다. 제조된 $Al_3Ti/Al$ 복합재료의 장점과 단점이 물성향상의 가능성과 더불어 제시되었다.