Study on Microstructure and Mechanical Properties of the Al–25Cr–5Si (at%) Alloy Powder Using Gas-Atomization and SPS Process

Yong‑Ho Kim,Hyo‑Sang Yoo,Jeong‑Han Lee,Ik‑Hyun Oh,Hyun‑Kuk Park,Hyeon‑Taek Son 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7

In order to investigate the microstructure and mechanical properties on Al–25Cr–5Si (at%) alloy, a mixed powder with pureelements and an alloy powder using a gas atomization process were used. Fine and high purity Al–25Cr–5Si (at%) alloypowder was successfully prepared by gas atomization and densified using a spark plasma sintering (SPS) process. The overallpowder size distribution of the mixed Al, Cr, and Si elemental powders was in the range of 10–15 μm. The atomized Al–Cr–Sialloy powder was fine and spherical in morphology and difficult to be formed by intermetallic formation. Densification wasclearly confirmed at 1000 °C, with almost isolated pores formed, by clear removal of pores between particles, deformationof particles, an increase in the number of contacts, and a change in size between particles. As a result of XRD analysis ofthe sintered compacts, single phase was observed using the mixed powder, but the compact using gas atomization remainedthe alloy phase even at the process temperature. The Vickers hardness of the compacts by mixed powder was observed at59.70 Hv and the compact using gas atomized powders on the temperature 1000 °C of the Vickers hardness increased to702.6 Hv. The compressive yield strength of the compact with mixed powder was 195.24 MPa and the compressive strengthof the compact with gas atomized powder increased to 802.07 MPa. It is considered not to be decomposed by the AlCrSi,Al13Cr4Si4and Al8Cr5phases sintering process, resulting from the improvement of mechanical properties.

그람양성구균에 대한 Teicoplanin과 Vancomycin의 시험관내 항균력

최태열,김경숙,전용관,서일혜,김정욱,이웅수,안정열,김홍석,정재용,최효선,김덕언,유진우 대한감염학회 1994 감염 Vol.26 No.1

An increasing frequency of methicillin resistant S. aureus(MRSA), methicillin resistant coagulase negative staphylococci(MRCNS) and Enterococcal infection have been observed in recent years. Teicoplanin is a new glycopeptide antibiotic obstained from the Actinoplanes teicomycetius. The molecular structure and spectrum of antimicrobial activity of teicoplanin is simillar to those of vancomycin, and has been reported to have an excellent in vitro and in vivo effect against various gram-positive infections. Therefore, we evaluated the in vitor susceptibility of gram positive cocci, such as, S. aureus, coagulase negative Staphylococci(CNS), and Enterococci to teicoplanin and vancomycin. The total 253 strains consisted of MSSA(40), MRSA(53), MSCNS(47), MRCNS(48), and Enterococci(65). They were assayed by disc diffusion and agar dilution. During the study, 57% of S. aureus and 49% of CNS showed resistance to methicillin. The inhibitory diameter of teicoplanin was 15-20mm in MSSA, 12-19mm in MRSA, 13-24mm in MSCNS, 11-23mm in MRCNS, and 15-22mm in Enterococci respectively, and showed sensitivity in all but 8 strains(3.2%). The range of the minimum inhibitory concentration (MIC) of teicoplanin to MSSA, MRSA, MSCNS, MRCNS and Enterococci were 9.12-2.0㎍/ml, 0.25-2.0㎍/ml, & 0.25-32㎍/ml, 0.12-1.0㎍/ml respectively. One case of S. haemolyticus was resistant to teicoplanin (32㎍/ml) by the agar dilution method. Eight minor (3.2%) and one major(0.4%) error was observed when the MIC and disk diffusion data were correlated with teicoplanin. As for vancomycin the inhibitory diameter was 17-21mm in MSSA, 15-21mm in MRSA, 18-26mm in MSCNS, 18-25mm in MRCNS, and 16-22mm in Enterococci respectively. The range of the MIC of vancomycin to MSSA, MRSA, MSCNS, MRCNS, and Enterococci were 0.25-1.0㎍/ml, 0.25-4.0㎍/ml, 0.5-2.0㎍/ml and 0.5-2.0㎍/ml respectively. One minor error (0.4%) was seen with the vancomycin disk. The MIC90 of MSSA and MRSA exhibited the same results in teicoplanin (1.0㎍/ml, 1.0㎍/ml), and vancomycin(2.0㎍/ml, 2.0㎍/ml). MSCNS and MRCNS exhibited greater MIC90 with teicoplanin(4.0㎍/ml, 8.0㎍/ml) than vancomycin(2.0㎍/ml, 2.0㎍/ml). Incontrase Enterococci were more susceptible to teicoplanin(0.5㎍/ml) than to vancomucin (2.0㎍/ml). Results from this analysis indicated that both teicoplanin and vancomycin were very excellent for gram positive infections, especially those resistant to methicillin.

Fasciola의 간농양에서 Praziquantel 7일 요법의 임상

김정룡,이효석,채종일,김선미,김찬규 대한감염학회 1997 감염 Vol.29 No.5

목 적 : Fasciola hepatica에 의한 간농양으로 진단 받은 환자에게 장기간 praziquantel을 투여하여, fasciola에 의한 간농양에 대한 장기간의 Praziquantel두여 효과를 알아보고자 하였다. 방 법 : F. hepatica에 의한 간농양으로 진단 받은 3명의 환자를 대상으로 하였다. F. hepatica에 의한 간농양으로 진단한 기준은 1) micro-ELISA에 의한 기생충에 대한 항체검사에서 fasciola 항원에 대한 반응이 양성이고 2) 말초 혈액 검사상 호산구증다증 을 보이며 3) 복부초음파 또는 복부컴퓨터단층촬영상 간질에 의한 간농양의특징적 소견을 보이며 4) 간내점 유병소에 대한 조직검사상 호산구성 농양을 보이는 경우로 하였다. Praziquantel의 투여는 하루 70-84mg/kg으로 7일간 투여 하였다. Praziquantel 투여 후 치료 효과 유무의 판정은 3개월 내에 말초혈액 호산구수의 500/㎣ 이하로의 감소 및 1년 이내에 간농양 의 소멸 여부로 결정하였다. 결 과 : 호산구다증은 2-3개월 내에 정상화 되었고, 간농양은 1예에서 치료 5개월 후에 병변의 크기가 90%이하로 감소하였고 나머지 2예에서 1년 이내에 소실되었다. Praziquantel의 투여를 중단할만한 심각한 부작용은 없었다. 결 론 : 7일간의 praziquantel 투여는 간질증에 의한 간농양에 대해 효과가 있으리라 생각되며 안전하다. Background : Fascioliasis is a zoonotic helminthiasis by fasciola species and is occasionally complicated by liver abscess, and the treatment of choice is oral bithionol, which is not available in Korea. Most clinical reports showed that praziquantel given at usual dosage(75mg/kg for 1day) failed to cure Fasciola fepatica infections, however, it has not been investigated whether long term praziquantel(70mg/kg/d for 7 days) would be effective. We evaluated the effectiveness of long term praziquantel therapy in patients with Fasiola liver abscess. Method : There patients were included in the current study who were diagnosed as liver abscess by F. hepatica. The diagnostic criteria for inclusion were 1) hypereosinophilia, 2) positive serologic test for F. hepatica antigen, 3) characteristic findings on CT scan and 4) demonstration of aggregates of eosinophils on ultrasonography-guided aspirates of the abscess. Praziquantel was given orally to patients at the daily does of 70-84mg/kg for 7 days. the effectiveness was assessed by the normalization of count at the end of 3 months and the disappearance of abscess cavity on ultrasonography or CT scam one year after treatment. Results : Blood eosinophil count decreased to less than 500/mm³ in all patient within 2 to 3 months. The liver abscesses reduced in size by 90% in 5 months in one patient and disappeared within a year in two patients. No major adverse effects were observed. Conclusion : We conclude that 7-day praziquantel therapy may be effective and safe in the treatment of liver abscess caused by F. hepatica.

N,N-Dimethylaniline의 아조커플링 반응에 關한 硏究

金容仁,明孝信 弘益大學校 1982 弘大論叢 Vol.14 No.2

The coupling reaction of N, N-dimethylaniline with several monosubstituted benzenediazonium salts has been studied kinetically in aqueous buffered solution. The activation evergies measured in the coupling reaction of N, N-dimethylaniliine with diazotized p-nitroaniline, m-nitroaniline, sulfanilic acid, m-anisidine,p-anisidine, p-bromoaniline, p-chloroaniline, m-toluidine, p-toluidine are 8.46, 8.05, 9.20, 12.32, 15.91, 10.86, 11.54, 13.80, 14.35, 15.47Kcal/mole, respectively. The coupling reactionis more favorable in the presence of an electron-withdrawing group in active components than in the presence of electron-donating group. It has been observed that the coupling reaction with diazotized p-nitroaniline proceeds 1000 times more rapidly than that with the benzenediazonium salt, which is coupled 40 times faster than diazotized p-anisidine. In our experiments, the formation of triazene, the diazoamino compound has not been observed, and the experimental result that the ionic strength of the medium didn't give any influence on the coupling reaction rate leads to the confirmation of the neutral free amine being one of the reasonable reactive species in the coupling reaction. A linear free energy relationship has been essentially observed except for three para substituted active components, for which the extended Hammett plot treated by Yukawa-Tsuno permits a good log k/k??=ρ(σ+ rㆍ????) linear relationship when considering the mesomeric effect. The calculated reaction constant of these azocoupling reaction is ρ=3.92, and the reaction constant of resonance contribution is calculated as r=0.32 at 20 ℃.

加味金櫃腎氣丸의 抗癌 및 抗轉移 效果에 關한 硏究

김용태,전영수,김정효,김성훈 대한한방종양학회 1999 대한한방종양학회지 Vol.5 No.1

To evaluate the antitumor activity and antimetastatic effats of Kamigumgusingihwan(KGSH) studies have ken dom. The results were obtained as follows: 1. KGSH extras exhibited a weak cytotoxicity against A549, SK-OV-3, B16-F10, and SK-MEL-2 cell lines. But exhibited potent cytotoxicity against P388 cell line in a dose-dpendent manner. 2. The concentration inhibiting adhesion of A549 to complex extracellular maMx up to below 30% of control was recognized at 10^-3g/ml of KGSH 3. KGSH extrats showed a wed inhibitoty effect on DNA topo- isomerase I from calf thyus. 4. The T/C% wa 137% in KGSH treated group in S-180 bearing ICR mice. 5. In pulmonary colonization assay. a number of colonies in the lungs were decreased sigruncanny in KGSH treated group as compared with control group. 6. In hematological changes in Bl6-BL6 injected C57BL/6, numbers of WBC were decreased insignificantly in KGSH treated groups, and also those of platelet were inoeased insignificantly in KGSH treated groups as compared with control. 7. In CAM asay, KGSH extracts inhibited angiogenesis at 15ug/egg concentration significantly as compared with control. Taken together these results, it is strongly demonstrated that KGSH significantly suppressed tumor metastasis by blpcking cell adheion to exuaalula matrix. Therefore. KGSH is expected to be clinically a potem antimetastatic drug for the prevention and treatment of cancer.

Vanadate가 집토끼의 심근수축력과 활동전압에 미치는 효과

김충수,방효원,엄대용,이상돈 중앙대학교 의과대학 의과학연구소 1985 中央醫大誌 Vol.10 No.1

Rabbit papillary muscle preparations were used to investigate the effects of vanadate on isometric contractility and variabilities of action potential. To record the myocardial contractility and action potential of rabbit papillary muscles, 3M KCI-filled glass microelectrodes were directly introduced into the muscle cells. The following results were obtained: 1. By increase of concentration of vanadate, myocardial isometric contractility increased but action potential did not change. 2. In case of preparation with the calcium antagonist(Diltiazem) myocardial contractility decreased and the overshoot potential and APD50 also decreased. 3. In case of preparations simultaneously with vanadate and Diltianzem, the effect in case of initial treatment with vanadate was completely reversed ay later treatment with Diltiazem. Above results could be interpreted as that the inflow of calcium ion was increased at the myocardial cell membrane level and then the myocardial contractility was increased by vanadate.

PECVD법으로 증착된 전자소자용 thiophene 박막의 전기화학적 신뢰성에 관한 연구

김정구,박진택,최윤석,부진효,유용재 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.6

The corrosion failure of electronic devices has been a major reliability concern lately. This failure is an ongoing concern because of miniaturization of integrated circuits(IC) and the increased use of polymers in electronic packaging. In this paper plasma-polymerized thiophene films were considered as a possible candidate for an interlayer dielectric for multilever metallization of ultra large scale integrated (ULSI) semiconductor devices. The protective ability of above films as a function RF power in an 3.5 wt.% NaCl solution was examined by electrochemical methods and contact angle measurement. The protective efficiency of the film increased with increasing RF power, which induced the higher degree of cross-linking and hydrophobicity of the films.

"人類의 共同遺産" 槪念의 法的 意味

김효진,엄응용 경운대학교 산업기술연구소 2001 産業技術硏究論文誌 Vol.3 No.2(B)

After the world war Ⅱ, an international society has been concerned about the outside region of national jurisdiction(Deep seabed, Outer Space, Moon, South Pole etc), and the development and conservation of its resources. As a result, Antarctic Treaty(1959), Outer Space Treaty(1967), the Moon Treaty(1979), and UNCLOS(1982) were concluded. Above all, through the treaties common Heritage of Mankind(CHM) was induced expressly or analogically as a new approach for the development and conservation of International Common Spaces. However, the question at issue is that the concept, character , extent, and regulations of CHM which was induced by the treaties have been interpreted and applied according to each treaty or standpoint of each nation. This lead to denunciation on the status of the CHM in international law. By the way, the core cause of this denunciation could be that there's no right legal definition on the terms of the CHM. It means that a prior question on the status of the CHM from the point of the international law is to analyze and examine closely the terms of this concept and define the legal implication. Therefore, I am willing to describe the appearance and development of the concept of CHM, analyze the legal significance on each term of the concept and evaluate generally the legal position of it through this study.

CNS/ATM 구축을 위한 항공 이동 데이터 링크 응용 시스템의 구축에 관한 연구

김용중,박효달 한국항행학회 1999 韓國航行學會論文誌 Vol.3 No.2

항공이동통신분야에서는 아날로그형 음성통신의 한계점을 극복하고, 운용자의 업무 부담을 경감할 목적으로 항공이동데이터통신망(VDL)을 이용한 데이터 통신이 항공운용통신(AOC) 분야에서 발전되었으며, 이를 항공교통서비스(ATS) 분야에 적용하기 위한 연구가 국제민간항공기구(ICAO)의 CNS/ATM 구축 권고에 의하여 미국, 유럽 등 항공 선진국에서 진행되고 있다. 본 논문은 항공교통서비스 분야에 VDL을 이용한 데이터 링크 서비스를 제공하기 위하여 디지털형의 출발전비행허가(PDC) 시스템을 개발한 내용의 결과이다. 개발된 PDC 시스템은 하나의 PC급 단일 시스템으로 항공교통관 제소, VDL 통신망, 관제사 등이 원격으로 연동되어 실시간 및 동시에 PDC 정보를 처리하여야 한다. 이를 위하여 제안된 기법은 하나의 프로세서에 여러 개의 쓰레드를 갖는 멀티 쓰레드 방식이 도입되어 설계되었다. 멀티 쓰레드 방식이 사용된 이유는 시스템의 간소화, 효율적인 내부 자원의 이용, 데이터 처리에 있어서 우수한 성능을 발휘하기 때문이다. 본 논문은 김포공항 PDC 시스템의 구조 및 설계 내용을 기술하고, 실제 운용 결과에 대한 데이터를 분석하였다. 김포공항 PDC 시스템의 운용결과를 이용한 분석한 결과, 운용초기단계로 모든 항공기에 시스템이 구축되지 않아 매일 평균 25대의 항공기가 운용하여 평균 10%의 이용률을 나타내며, 최대 34대의 항공기가 이용하고 있다. 메시지 송/수신에 걸리는 시간을 분석한 결과, 항공기의 PDC 요청부터 MAS의 수신에 소요되는 시간은 최소 14초부터 최대 983초(16분 23초)까지로써, 평균 122초(2분 2초)의 시간을 나타내었다. 또한 신뢰성을 확인하기 위하여 가용도를 계산한 결과 99.7%로써 상당히 신뢰할 수 있는 수준이었다. 또한, 다중 처리를 위하여 사용된 방식인 멀티 쓰레드 방식이 적절히 동작함을 확인할 수 있었다. 앞으로, 전체 연동 시스템이 자동화로 구축될 경우, PDC의 요청부터 발송 및 확인까지 상당히 짧은 시간 내에 이루어져 관제업무 능률을 향상시킬 수 있을 것이다.

시차주사열량분석기를 이용한 치과용 접착시멘트의 경화기전 및 반응열에 관한 연구

김철위,이용근,윤태호,김효종,남세진 大韓齒科器材學會 2000 대한치과재료학회지 Vol.27 No.3

The working time of dental cement has a close relation with the setting time, where the setting reaction can be said as the result of the chemical reaction between cement liquid and powder. The purpose of this experiment was to investigate the setting characteristics and setting rate of dental cements by measuring the exothermic heat(Joule/gram) from the setting reaction at specified times using a differential scanning calorimeter (Differential Scanning Calorimeter, DSC 204, TASC 414/3A Controller, Netzche, Germany). Graphs of time-exothermic heat at 37℃ isothermal condition, showing the setting reaction of dental cements were plotted. Three types of luting cements studied were zinc-phosphate cement (ZPC), polycarboxylate cement (PCC), and glass ionomer cement (GIC). The effects of powder-liquid ratio on the setting characteristics of cements were also included. The amount of heat (calory) released per one gram of cement was calculated at each specified time, and was analyzed. ANOVA and Scheff's multiple comparison test (p=0.05) were used for statistical analysis using SPSS/PC+. The setting rate of cement was not constant during the setting reaction, and different setting characteristics were observed depending on the type of cement and powder/liquid ratio. Generally, 70∼90% of the setting reaction, measured by the exothermic heat release, occurred within 5 minutes after mixing. The exothermic heat released by ZPC was very high immediately after mixing, and the duration of the heat release was prolonged compared with other cements. The exothermic heat release of PCC finished most rapidly. It was generally observed that the amount of heat release (rise in temperature) per one gram of cement was highest for ZPC, followed by GIC, and then PCC. However, heat release during the first 2∼5 minutes after mixing was highest for GIC, followed by ZPC and then PCC. According to the Scheff's multiple comparison test, the duration of the total setting reaction did not show any significant difference among the cements(p>0.05), and also among the different power/liquid ratio groups(p>0.05). It was observed that more heat was released with the lower powder/liquid ratio than the higher powder/liquid ratio.