Spray Pyrolysis에 의한 Manganese Oxide 입자의 제조 및 전기화학적 특성

최원창,변동진,이중기,박달근,김현중,Choi, Won-Chang,Byun, Dong-Jin,Lee, Jung-Kee,Park, Dal-Keun,Kim, Hyeon-Joong 한국재료학회 2001 한국재료학회지 Vol.11 No.11

Spray pyrolysis is a favorable technique to form complex mixed-metal oxide powders with high purity in high temperature region. Manganese oxide powders were prepared by spray pyrolysis from an aqueous solution of $Mn(NO_3)_2$. Powders were formed in the temperature range of 500~$700^{\circ}C$ under the constant pressure of 300torr. All the powders have hydrous forms. When the temperature was increased, the size and the surface area of the particles decreased. An electrochemical capacitors were made with manganese oxide electrodes and KOH electrolyte. With the temperature decreased, capacitors showed high capacitance. Capacitor which was prepared with powders formed in the temperature $500^{\circ}C$ demonstrated specific capacitances as high as 83F/g.

금속 코팅된 흑연 입자로 제조된 전극의 전기화학적 특성

최원창,이중기,변동진,조병원,Choi, Won-Chang,Lee, Joong-Kee,Byun, Dong-Jin,Cho, Byung-Won 한국전기화학회 2003 한국전기화학회지 Vol.6 No.2

리튬이차전지 음극활물질로 사용되는 합성흑연입자에 여러종류금속을 코팅하여 그 전기화학적특성을 조사하였으며, 구체적인 코팅방법으로는 가스분산스프레이 코팅법을 적용하였다. 본 연구범위내에서 금속을 코팅한 입자로 제조된 전극은 충방전시 형성되는 계면저항을 감소시킴으로서 결과적으로 원시료에 비해서 높은 방전용량을 나타내었다. CV실험을 통해서 은과 주석은 리튬과의 합금반응을 확인할 수 있었으나, 2.5 중량$\%$ 이하의 낮은 코팅량을 고려했을 때, 높은 분산도를 지닌 금속 물질의 코팅을 통한 전극 활물질 표면의 균일한 전도도의 증가가 주요원인인 것으로 사료되었다. 단일계 금속으로 코팅하였을 경우 은코팅한 전극활물질이 가장 높은 방전용량과 사이클특성을 나타내었고, 은을 기본으로 하는 이성분계에서는 은-니켈전극이 가장 높은 고율특성을 나타내었다. Various kinds of metals were coated on synthetic graphite in order to investigate the relationship between film characteristics and their electrochemical performance. Gas suspension spray coating method was employed for the coating of synthetic graphite. In our experimental range, all of the metal coated synthetic graphite showed the higher capacity than that of raw material at high C-rate mainly due to decrease in impedance of passivation film. In cyclic voltammetry experiments, silver-coated and tin-coated graphite anodes found the lithium-alloy reaction. Considering smaller amount of metal coating, the most increase in discharge capacity was caused by improvement of conductivity of the electrode. When single-component metal was coated, silver-coated graphite anode exhibited the highest discharge capacity and better cycleability. Double components of silver-nickel coated active material showed the highest discharge capacity, rate capability and the best cycle performance in the range of our experiments.

국제소식 및 국제학회지 주요기사

최원창(Won-Chang Choi),박원준(Wonjun Park) 한국콘크리트학회 2016 콘크리트학회지 Vol.28 No.5

병원환자(病院患者)의 세균배양검사(細菌培養檢査)에서 항생제(抗生劑)에 대(對)한 내성균(耐性菌) 발생빈도(發生頻度)의 변화(變化)

최원창 ( Won Chang Choi ) 대한임상검사과학회 1988 대한임상검사과학회지(KJCLS) Vol.20 No.1

콘크리트관련 도서소개

최원창(Won-Chang Choi) 한국콘크리트학회 2016 콘크리트학회지 Vol.28 No.3

국제소식 및 국제학회지 주요기사

최원창(Won-Chang Choi),박원준(Wonjun Park) 한국콘크리트학회 2016 콘크리트학회지 Vol.28 No.3

금강수역내 항생제 및 중금속내성균의 분포 및 동시내성빈도

이기성,고동규,최원창,오태엽,박영식,최청일,최영길 ( Ki Sung Lee,Dong Kyu Ko,Won Chang Choi,Tae Youp Oh,Young Sik Park,Chung Il Choi,Yong Keel Choi ) 한국환경생물학회 1993 환경생물 : 환경생물학회지 Vol.11 No.2

As the basic study to solve the recent big problems upon the bacterial multi-drug resistance recognizing seriously from the viewpoint of microbial ecology, clinical medicine and public health, this study was carried out temporally and spatially upon Kum river area that has been recently accelerated the pollution for the purpose of analysis such as distribution of heterotrophic bacteria, distribution of resistant bacteria upon prevalently utilizing antibiotics(Ampicillin, Amp ; Chloramphenicol, Cm ; Tetracycline, Tc ; Kanamycin, Km ; Streptomycin, Sm) and heavy metal(mercury, Hg ; cadmium, Cd), frequency of multi-drug resistances, frequency of resistant factor transfer, compatibility and/or incompatibility. In May, 1992, community sizes of total heterotrophic bacteria reached to 5×10 exp (7)CFU/㎖ in site 1(1S, Kapchun stream`s water), 5×10 exp (8)CFU/㎖ in site 2(2S, Kapchun soil) where industrial and domestic sewages were chiefly flowed, and reached to 1×10 exp (8)CFU/㎖ in site 3(3S, Sanne stream`s water), 1×10 exp (7)CFU/㎖ in site 4(4S, Sanne soil) where agricultural domestic sewages were. Total heterotrophic bacteria in Kapchun area(1S, 2S) were distributed 50 times higher than those in Sanne area(3S, 4S) respectively. Compared with water, soil contained 10 times higher in heterotrophic bacteria. Of heterotrophic bacteria, compositional ratios of resistant bacteria upon antibiotics and heavy metals were shown to the level of 0.07% in May, 1992 and to the level of 0.2% in October, 1992. So, frequency of resistant bacteria increased in October about 3 times higher than in May. The frequent order of resistant factor was Tc, Km, Cd, Amp, Hg, Cm, in May, 1992 and was Cd, Amp, Sm, Hg, Km, Tc, Cm, in October, 1992, respectively. Especially, Cd resistant bacteria were distributed upon all experimental sites more frequently in October, 1992 than in May, 1992. Passing through the rainy period in summer, the distributional change of resistant bacteria indicate strong evidence for the influx of large amount of sewage containing lots of resistant bacteria and of pollutants to the Kum river area. Considering the genetic linkage between antibiotics resistance and heavy metal resistance and distributional change of multi-drug resistant bacteria, resistant factor such as Tc, Amp, Cd were shown the highest frequency of simultaneous coexistence, so they are closely linked with other resistant factors the most from the viewpoint of molecular genetics. Most of resistant bacteria comprise generally simultaneous multi-drug resistance upon 5 to 3 drugs. As especial results, considering the relationship of simultaneous coexistence in antibiotics and heavy metal resistance, Cd resistance bacteria comprise other resistance factors such as Tc(70%) and Amp(68%) simultaneously and frequently and Hg resistant bacteria, such as Tc(80%) and with Cd(70%). In the transferability and incompatibility upon resistant factors, only 1% of resistant factors was the conjugative, transferable type plasmid, and 99% of them showed the incompatibility in the other strains.

금강수역내에서 분리된 몇 종의 Ampicillin 내성균의 β-Lactamase 발현양상

이기성,고동규,최원창,문영길,박영식,최청일,최영길 ( Ki Sung Lee,Dong Kyu Ko,Won Chang Choi,Yong Keel Mun,Young Sik Park,Chung Il Choi,Yong Keel Choi ) 한국환경생물학회 1994 환경생물 : 환경생물학회지 Vol.12 No.1

In order to characterize the bacterial β-lactamase types occurred in Kum river area, this research was designed to analyze with identification upon ampicillin (Amp) resistant bacteria, and was investigated into relationships between β-lactamase expression (inducibility) and growth phase under ampicillin shift and with restriction patterns of R-plasmids. As the identification result upon 4 strains of Amp resistant bacteria, KL 601 is identified as Pasteurella maltocida, KL 602 as Enterobacter agglomerans, KL 609 as Pseudomonas maltophilia and KL 611 as Acinetobactor calcoaceticus, respectively. In order to investigate Amp effect upon growth, when the Amp resistant bacteria were cultivated in nutrient liquid LB medium, in LB medium added with Amp, or in LB medium in the manner of Amp shift, the changes in growth rate and lag phase could not be observed. However, upon the prototrophic strains, KL 602 and KL 609, examining Amp effect upon these two strains in minimal GM63 liquid media, even though there was no change of maximum growth yield, the latent lag phase become very lengthened. In nutrient medium, β-lactamase activities of these 4 strains were metabolically regulated in accordance with growth phase, on the other hand, in minimal medium were differently regulated in accordance with growth phase and with strains. It could be postulated that KL 609 strain has the M.W.24,000, β-lactamase type which E. coli comprise, however, that KL 601, KL 602 and KL 611 have the M.W.35,000, β-lactamase type which E. cloacae or C. freundii comprise. Through the whole growth phase, since Amp did not affect to phosholipid metabolism, there is no change in phospholipid compisition upon Amp effect. Main phospholipid are the phosphatidyl glycerol and cardiolipin in all 4 Amp resistant strains. So, it was very significant that there were no changes in phospholipid composition and in growth rate upon nutrient medium under Amp stress. In order to recognize whether Amp resistant strains comprise the plasmid or not, preparation of plasmids and restriction digestion with Bam H1 were carried out, KL 601 strain has about 30 Kb of plasmid, KL 609 and KL 611 strain have about 25 Kb of plasmid and KL 602 does not have the plasmid, however. Hence, it will be predicted strongly that β-lactamase gene in KL 602 might be encoded chromosomally. Moreover, considering the results upon the changes of β-lactamase acticity, upon β-lactamase inducibility and upon changes of periplasmic protein profile under Amp stress, its prediction is very recognizable.

최근 충북지역에서 분리된 Gram 양성 세균종과 항생물질의 감수성 양상

황석연(Seock-Yeon Hwang),최원창(Won-Chang Choi) 대한의생명과학회 1999 Biomedical Science Letters Vol.5 No.2

임상검체에서 분리되는 병원균을 주기적으로 분석하고 이에 대한 항균제 감수성의 변화 양상을 파악하는 것은 임상에서의 적절한 항균제의 선택이나 내성균의 감독과 조절을 위해 필수적이라 할 수 있다. 저자들은 충북대학병원에 1996년 1년간 내원 환자의 미생물 배양 검사에서 분리, 동정된 1,689 균주중 Gram 양성인 542 균주의 분리 빈도 및 주요 균종에 대하여 항생제 감수성 양상을 조사하였다. Gram 양성 균종은 S. aureus, S. pneumoniae, S. epidermidis, S. hemolyticus, coagulase negative Staphylococcus (CNS), Enterococcus faecalis 순으로 분리되었다. 한편, 항생제 감수성 시험 결과 S. aureus의 항생제 감수성은 penicillin과 gentamicin에 대한 저항성이 현저히 높았으며, teicoplanin과 vancomycin (MIC?? 0.5㎍/㎖)에 감수성이 높은 것으로 나타났다. CNS의 경우도 S. aureus와 대동소이한 결과를 보였으나, S. epidermidis의 경우에는 ciprofloxacin과 clindamycin에 감수성이 높은 것으로 나타났다. Enterococcus spp.는 vancomycin, penicillin, tetracycline 등에 저항성이 매우 높았으며 , 검사한 모든 항생제에 대하여 대부분의 감수성이 zig-zag pattern을 보였다. In order to control resistant strains and to properly select the antimicrobial agents, it is of quite importance to know current trends of bacterial species and changing patterns of antimicrobial resistance rates. The authors studied the results of 542 Gram-positive strains among 1,689 strains isolated at Chung-buk National University Hospital in 1996. The frequently isolated Gram-positive microorganisms were Staphylococcus aureus, Streptococcus pneumoniae, Staphylococcus epidermidis and Enterococcus faecalis in descending order. S. aureus showed high resistance to penicillin, gentamicin, and susceptibility to teicoplanin and vancomycin. Coagulase negative Staphylococcus was highly resistant to all of the antibiotics used in this experiment except teicoplanin and vancomycin. Enterococcus were highly resistant to vancomycin, penicillin and tetracycline. MIC of Gram- positve oaganisms was appeared to be zig-zag pattern.

비대칭 연단보강재가 설치된 직교이방성 ㄷ형 단면 압축재의 탄성국부좌굴

윤순종(Yoon Soon Jong),최원창(Choi Won Chang) 대한토목학회 2002 대한토목학회논문집 A Vol.22 No.5A