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.

Cyclosporin에 의한 치은증식증의 치험 2례

김종배,박효상,김창환,이용규,최봉주,장학원 啓明大學校 醫科大學 1997 계명의대학술지 Vol.16 No.2

Cyclosporin is a relatively new immunosuppressive agent which has been used to prevent organ transplant rejection, to treat type-I diabetes mellitus and several other autoimmune disorders. It is anticipated that the therapeutic use of cyclosporin will increase progressively in the future to treat numerous other disorders. As its clinical use broadens, it will needed for health professionals to be familiar with the beneficial effects as well as some of the undesirable side effects of cyclosporin therapy. A side effect of this drug in dentistry appears to be pronounced gingival hyperplasia. Cyclosporin induced gingival hyperplasia is indistinguishable from gingival hyperplasia induced by phenytoin and nifedipine in clinical and histopathologic finding. We experienced two cases of gingival hyperplasia secondary to cyclosporin therapy in patients, 48-year old & 28-year old females who received a kidney allograft transplant. Clinical examinations revealed a severely overgrown and inflammed gingiva. Surgical excision of the excess tissue was accomplished under local anesthesia. On follow-up check, gingival hyperplasia in a 48-year old patient whose oral hygiene was very poor showed successive recurrence after three times surgical excision, another patient who could control oral hygiene thoroughly showed good healing. Conclusively, it seems to be very important to control oral hygiene thoroughly to decrease occurrence and recurrence of cyclosporin-induced gingival hyperplasia.

돈지, 들깨유 및 달맞이꽃 종자유의 혼합급이가 흰쥐의 간장, 뇌 및 고환의 지질 성분에 미치는 영향

김성희,김한수,서인숙,정효숙,정승용 慶尙大學校 1992 論文集 Vol.31 No.2

돈지 및 들깨유와 달맞이꽃 종자유등 2종 식물 종자유와의 혼합급이가 흰쥐의 체내 조직의 지질 성분에 미치는 영향을 구명하기 위해 S·D계 숫쥐에게 돈지 2.55및 들깨유와 달맞이꽃 종자유의 혼합비율을 달리하여 4주간 급이 사육한 후 간장,뇌 및 고환의 지질 성분을 분석 검토한 결과는 다음과 같다. 간장의 총콜레스테롤 함량은 D군이 대조군에 비해 유의적으로 낮았으며, 인지질 함량은 각 군간의 유의적인 차이가 없었고, 중성지질 함량은 B및 C군이 대조군에 비해 현저하게 낮았다. 콜레스테롤 급이군의 간장 총콜레스테롤 함량은 대조군에 비해 c,d및 e군이 유의적으로 낮았고, 인지질 및 중성지질의 함량은 b군이 낮게 나타났다. 뇌의 총콜레스테롤 함량은 대조군에 비해 B및 C군이 유의적으로 낮았으며, 인지질 및 중성지질의 함량은 대조군에 비해 전 군이 유의적으로 낮데 나타났다. 콜레스테롤 급이군에 있어 뇌의 총콜레스테롤 함량은 각 군간의 유의적인 차이가 없었고, 인지질 함량은 c군이 중성지질 함량은 e군이 대조군에 비해 낮게 나타났다. 고환의 총콜레스테롤 및 인지질 함량은 각 군간의 유의적인 차이가 없었으나, 중성지질 함량은 대조군에 비해 전 군이 유의적으로 낮았다. 콜레스테롤 급이군은 콜레스테롤 무급이군과 거의 유사한 경향을 나타내었다. In order to observe the effects of the feeds mixed with the lard and two vegetable seed oils, which mixed with 2.5% lard and various level of perilla oil and evening primrose oil were administered to the male rats of Sprague Dawley for 4 weeks on lipid components of liver, brain and testes. In livers , total cholesterol contents were remarkably lower in the D group(2.5% lard+2.5% perilla oil+5.0% evening primrose oil,free cholesterol) than in the control group , and phospholipid contents were not significant difference in each groups. Triglyceride contents were remarkably lower in the B(2.5% lard+7.5% perilla oil+5.0% ,free cholesterol) and C(2.5% lard+5.0% perilla oil+2.5% evening primrose oil,free cholesterol) group than in the control group. In the supplemented cholesterol groups, total cholesterol contents were significantly lower in c(C group+cholesterol diet), d(D group+cholesterol diet) and e(2.5% lard+7.5% evening primrose oil,free cholesterol) group, phhspholipid and triglyceride contents were lower in the b group(B group+cholesterol diet) than in the control groups than in the control group, phospholipid and triglyceride contents in brain were considerably lower in the other groups than in the control group. In the supplemented cholesterol groups, total cholesterol contents were not significant difference in each groups. Phospholipid and triglyceride contents were conspicuously lower in the c and e groups. respectively. In testes, total cholesterol and phospholipid contents were not significant difference in the groups, but triglyceride contents were lower in the all groups except for control group The contents of total cholesterlo, phospholipid and triglyceride were similar between the supplimented cholesterol groups and the nonsupplemented cholesterol groups.

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 ℃.

EVA Nanocomposites 제조 및 특성연구

김영용,박일수,정효선,최재곤,김정규,조병욱 조선대학교 생산기술연구소 2003 生産技術硏究 Vol.25 No.1

Ethylene vinyl acetate random copolymer(EVA)/layered-silicate nanocomposites were prepared by melt or solution blending. The TGA thermograms of EVA/ layered-silicate nanocomposites showed an improved thermal stability as the layered-silicate contents increased. The decomposition temperature of nanocomposite was increased around 10℃ compared with pure EVA at 50% weight loss under N_2 atmosphere And in an air atmosphere, temperature difference in 50% wt loss between the nanocomposlte and the virgin EVA was around 100℃ The moduli in their thermomechanical module of nanocomposite are higher than pure EVA. Interlayered spacings of nanosilicates were slightly increased when prepared by melt blending. On the other hand, they were remarkably increased when prepared by solution blending. It may be explained that EVA moiety of the copolymer showed partial adsorption behavior on the surface layer of the silicate. It also revealed that the adsorption is more effective in the solution blending than in the melt blending.

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.

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.

Nylon6,6/Polyaniline 전도성 복합체의 제조 및 전기적 성질에 관한 연구

김효용,허양일,이완진 全南大學校 觸媒硏究所 1998 觸媒硏究 論文集 Vol.20 No.-

The conducting composite using polyaniline as a conducting polymer and nylon6,6 as a matrix by blending method was prepared. The m-cresol was used as a solvent in blending. The PANI was protonated using camphorsulfonic acid(CSA) or dodecylbenzenesulfonic acid (DBSA) such as alkylbenzenesulfonic acid. In the conducting composite, DBSA was found to be more superior dopant to CSA and the electrical conductivity was increased with the amount of PANI complex. Also, in the temperature range of -196℃ to 160℃, the electrical conductivity was measured. The temperature dependency for conducting composites varied with the content of PANI complex and followed variable range hopping model. The electric conductivity was increased up to 0.19 S/cm with the amount of PANI complex protonated with DBSA having long alkyl chain.

빌트인 모터를 이용한 2축 제어 미세 가공기 개발

김건희,김효식,양순철,이상용,국명호,이선규,김윤중,홍권희 한국공작기계학회 2007 한국공작기계학회 추계학술대회논문집 Vol.2007 No.-

This paper describes development of low cost precision machine that has combined the Build-in Motor with a vacuum chuck. This study mainly aims to find out a cutting condition for maintaining optimum surface condition and to examine cutting characteristics of the precision machine that is equipped by diamond bites. The cutting materials is Al alloy. Several experiments were carried out to find out the main factors that affect the surface roughness such as principal axis RPM(rotation per minute), feeding speed, and cutting depth. As a result, we obtain The optimum cutting condition of the developed precision machine.