Effect of Heat Treatment on Microstructure and Fracture Behavior of STS304-Zr Alloys for Metal Waste Forms

Three kinds of STS304-Zr alloys were fabricated by varying the Zr content, and their microstructure and fracture properties were analyzed. Moreover, we performed heat treatment to improve their properties and studied their microstructure and fracture properties. The microstructure of the STS304-Zr alloys before and after the heat treatment process consisted of α-Fe and intermetallics: Zr(Cr, Ni, Fe)2 and Zr6Fe23. The volume fraction of the intermetallics increased with an increasing Zr content. The 11Zr specimen exhibited the lowest hardness and fine dimples and cleavage facets in a fractured surface. The 15Zr specimen had high hardness and fine cleavage facets. The 19Zr specimen had the highest hardness and large cleavage facets. After the heat treatment process, the intermetallics were spheroidized and their volume fraction increased. In addition, the specimens after the heat treatment process, the Laves phase (Zr(Cr, Ni, Fe) 2) decreased, the Zr6Fe23 phase increased and the Ni concentration in the intermetallics decreased. The hardness of all the specimens after the heat treatment process decreased because of the dislocations and residual stresses in α-Fe, and the fine lamellar shaped eutectic microstructures changed into large α-Fe and spheroidized intermetallics. The cleavage facet size increased because of the decomposition of the fine lamellarshaped eutectic microstructures and the increase in spheroidized intermetallics.11Yscopuskc

과거 10년간의 Neisseria gonorrhoeae 분리와 penicillinase 생성 및 항균제 감수성에 관한 연구

보건학과/석사[한글] 임질은 성병중 흔한 것이지만 우리나라에 있어서의 환자 발생수는 파악이 되어 있지 않다. Penicillinase-producing Neisseria gonorrhoeae(PPNG)의 출현은 임질의 증가를 염려하게 하고 있도 또한 치료약의 선택을 어렵게 하고 있다. 이 연구에서는 연세의료원의 1975년에서 1984년의 부인과 검체와 눈 검체에서의 임균분리와 근년의 PPNG의 비율을 검토하였고 최근 분리된 임균의 항균제 감수성을 한천 희석법으로 시험하여 다음과 같은 결과를 얻었다. 1. 이 기간에 한국인 여자환자의 생식기 검체의 4.8%(340명)와 눈 검체의 3.3%(43명)에서 임균이 분리되었다. 분리수는 1975년에 가장 많았고 그 이후 약간의 감소 경향을 보였다. 2. 남자 생식기에서는 20대가 60.6%, 여자는 30대가 40.3%, 눈 검체에서는 1/12세 미만에서 69.8%가 분리되었다. 3. 한국인 환자에서의 최초의 PPNG는 1979년에 분리되었고 1983년에는 그 비율이 38.6%에 달하였으며 1984년에는 19.5%이었다. 4. Penicillin G의 MIC는 non-PPNG에 대해 2㎍/ml 이하였으나 PPNG에 대해서는 4㎍/ml 이상이었다. β-lactamase 생성에 관계없이 spectinomycin의 MIC는 32㎍/ml 이하이고 cef operazone, cefotaxime, moxalactam의 MIC는 대단히 낮았다. 5. Non-PPNG는 13.6%가 penicillin G에, 75%가 tetracycline에 감수성이었고, PPNG는 81.3%가 tetracycline에 감수성이었다. Spectinomycin등 다른 모든 항균제는 시험균주 모두가 감수성이었다. 이 연구에서 임질이 드물지 않은 성병임에는 화가 없으며, 감염되었음을 모르는 임신부가 계속해서 있고, PPNG의 비율은 상당히 높으며, tetracycline 내성균주가 흔하다는 결론을 얻었다. [영문] Incidence of gonorrhea Is difficult to estimate in Korea. A gradual increase of the penicillin-resistant strains and the emergence of β-lactamase-producting strains(PPNG) became a serious problem in many parts of the world. In this study, an analysis was made on the isolation of Neisseria gonorrhoeae obtained at Yonsei Medical center from 1975 to 1984. The follwing results were obtained. 1. Among the female genital specimens of Korean, 4.8%(340 patients) yielded gonococci. The isolation rate from eye specimens was 3.3%(43 patients). The number of isolation was greatest in 1975 and thereafter it was slightly decreased. 2. The isolation rate was highest in genital specimens of 20-29 year old group tn male. while in female it was 30-39 year old group. Majority (69.8%) of the eye isolates came from infants aged less than one month old. 3. The first PPNG from Korean was isolated in 1979. The proportion reached 38.6% of all gonococci in 1983 and then slight decline to 19.5% was noted in 1984. 4. The MIC of penicillin G against non-PPHG was ≤ 2 ㎍/ml, while against PPNG it was ≥ 4 ㎍/ml. Regardless of the β-lactamase production, the MIC of spectinomycin was ≤ 32 ㎍/ml and those of cefoperazone, cefotaxime and moxalactam were all very low. 5. The prevalence of isolates susceptible to penicillin G was 13.6% of non-PPNG and to tetracycline 75% of non-PPNG and 81.3% of PPNG. All of the isolates tested were susceptible to spectinomycin and rest of antimicrobial agent. From this study it is concluded that gonorrhea remaines to be a relatively common serious infection in Korean, some pregnant women are not aware of their infections, and that PPNG is quite prevalent arid tetracycline resistant strains are very common.restrictio

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