• 대한금속재료학회지
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• 제46권7호
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• pp.449-457
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• 2008

Compression deformation behaviors at high temperature as a function of temperature and strain rate were investigated in the 6061 aluminum alloy, which is used for automobile wheel. Compression tests were carried out in the range of temperatures $300{\sim}475^{\circ}C$ and strain rate $10^{-3}{\sim}10^{-1}sec^{-1}$. By analyzing these results, strain rate sensitivity, deformation temperature sensitivity, the efficiency of power dissipation, Ziegler's instability criterion, etc were calculated, which were plastic deformation instability parameters as suggested by Ziegler, Malas, etc. Furthermore, deformation processing map was drawn by introducing dynamic materials model (DMM) and Ziegler's Continuum Criteria. This processing map was evaluated by relating the deformation instability conditions and the real microstructures. As a result, the optimum forging condition for the automobile wheel with the 6061 aluminum alloy was designed at temperature $450^{\circ}C$, strain rate $1.0{\times}10^{-1}sec^{-1}$. It was also confirmed by DEFORM finite element analysis tool with simulation process.

• Journal of Microbiology and Biotechnology
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• 제26권10호
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• pp.1765-1773
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• 2016

Wastewater containing kraft lignin (KL) discharged from pulp and paper industries could cause serious environmental contamination. Appropriate effluent treatment is required to reduce the pollution. Investigations on anaerobic bacteria capable of degrading KL are beneficial to both lignin removal and biofuel regeneration from the effluent. In this paper, an anaerobic strain capable of degrading KL was isolated from the sludge of a pulp and paper mill and identified as Dysgonomonas sp. WJDL-Y1 by 16S rRNA analysis. Optimum conditions for KL degradation by strain WJDL-Y1 were obtained at initial pH of 6.8, C:N ratio of 6 and temperature of 33℃, based on statistical analyses by response surface methodology. For a 1.2 g/l KL solution, a COD removal rate of 20.7% concomitant with biomass increase of 17.6% was achieved after 4 days of incubation under the optimum conditions. After the treatment by strain WJDL-Y1, KL was modified and degraded.

• Applied Biological Chemistry
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• 제13권2호
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• pp.111-129
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• 1970

핵산 및 그 관련물질 연구의 일환으로서 미생물 효소에 의하여 핵산을 분해하여 5'-mononucleotides 생성을 목적으로 미생물에서 5'-phosphodiesterase 생성균주를 얻기위하여 전국 각지 76개 지역에서 논, 밭, 산, 하천의 토양 그리고 퇴비, 누룩, 메주 등 시료 210종을 수집하였다. 이 수집 시료로 부터 dilution pour plate method 로서 Aspergillus속 240주, Penicillium속 232주, Neurospora속, 19주, Monascus속 16주, 그리고 Streptomyces속 265주로 총 758주를 순수 분리하였다. 분리된 모든 균주에 대하여 RNA-depolymerase 균의 crude enzyme 중에는 5'-AMP deaminase가 공존하고 있으므로 효소반응 중에 RNA 가 5'-mononucleotide로 분해 축적하는 동안에 5'-AMP의 adenine의 6위치에 붙은 $NH_2$기를 탈아미노하여 hypoxanthine으로 하기 때문에 5'-IMP 로 되는 것이라 생각된다. 분리 동정 된 Penicillium citreo-viride PO 2-11 strain과 Streptomyces aureus SOA 4-21 strain 이 생성한 5'-phosphodiesterase 로서 RNA를 효소 분해하여 5'-mononucleotide 의 정량한 결과는 Table 10과 같다. productivities를 1차 screening 하고 5'-phosphodiesterase productivities로서 2차 screening 하여 우수균주를 얻고 동정하였다. 우수균주의 5'-phosphodiesterase productivity에 대하여 배양상의 optimum condition을 검토하고 5'-phosphodiesterse activity에 미치는 여러 화합물의 영향과 효소반응의 최적 조건을 구명하였다. 우수균주가 생성한 5'-phosphodiesterase에 의하여 RNA 분해로 반응 최종 산물을 ion exchange column chromatography법으로 정량하고 최종 분해 산물엔 5'-mononucleotide를 paper chromatography, thinlayer chromatography, UV-absorption spectra, carbazole reaction 및 Schiff's reaction 등으로 동정한 결과는 다음과 같다. [1] 5'-phosphodiesterase productivity가 가장 우수한 두 균주를 선정하였고 이들은 토양에서 분리 되었으며 선정된 푸른 곰팡이는 Penicillium citreoviride PO 2-11로 동정되었고 방사선균은 Streptomyces aureus SOA 4-21로 동정되었다. [2] 분리 선정 된 Penicillium citreo-viride PO 2-11 strain은 배양상의 optimum condition 이 pH 5.0이고 temperature는 $30^{\circ}C$이었고 이 균이 생성한 5'-phosphodiesterase의 효소 반응상의 optimum condition 이 pH 4.2이고 temperature는 $60^{\circ}C$이었다. 그리고 5'-phosphodiesterase 생성에서 최적 탄소원은 sucrose이고 질소원은 $NH_4NO_3$이고 corn steep liquor나 혹은 yeast extract를 각각 0.01%씩 첨가한 구는 첨가하지 않은 control 구보다 20%의 5'-phosphodiesterase 생성 증가를 나타 내었다. 이 균이 생성한 5'-phosphodiestrase는 $Mg^{++},\;Ca^{++},\;Zn^{++},\;Mn^{++}$ 등 금속이온은 activator이고 EDTA, citrate, $Cu^{++},\;Co^{++}$ 등은 inhibitor 임을 알았다. 이 균이 생성한 5'-phosphodiesterase는 RNA를 분해하여 분해율 65.81%이었고 5'-AMP, 5'-GMP, 5'-UMP 및 5'-CMP를 생성하며 이때 축적되는 5'-mononucleotides중 5'-GMP 만이 정미성이 있음을 알았고 이균은 5'-AMP deamaminase가 없음을 확인하였다. 이 균의 효소에 의하여 RNA에서 정미성 5'-GMP 186.7 mg/RNA(g)를 생산할수 있음을 알았다. [3] 분리 선정된 Streptomyces aureus SOA 4-21 strain은 배양상의 optimum condition이 pH 7.0이고 temperature는 $28^{\circ}C$이었고 이 균이 생성한 5'-phosphodiesterase의 효소반응상의 optimum condition이 pH 7.3이고 temperature는 $50^{\circ}C$이었다. 그리고 5'-phosphodiesterase 생성에서 최적탄소원은 glucose이고 질소원은 asparagine이고 yeast extract 0.01%첨가구가 control 구보다 40%의 5'-phosphodiesterase 생성증가를 나타내었다. 이 균이 생성한 5'-phosphodiesterase는 $Ca^{++},\;Zn^{++},\;Mn^{++}$ 등 금속이온은 activator 이고 citrate, EDTA, $Cu^{++}$ 등은 inhibitor 임을 알았다. 또한 이 균은 5'-phosphodiesterase 뿐만 아니라 5'-AMP deaminase도 생성함을 확인하였다. 그러므로 RNA 분해율은 63.58% 이었고 RNA를 분해하여 5'-AMP, 5'-CMP, 5'-GMP 및 5'-UMP로 축적시키고 RNA가 효소 분해됨과 동시에 5'-AMP deaminase도 작용하며 생성된 5'-AMP 의 60% 상당을 5'-IMP로 전환시키는 특성이 있어서 정미성 5'-mononucleotide 생성이 전자의 균보다 두드러지게 증가함을 밝혔다. 이 균에 의하여 RNA에서 정미성 5'-IMP 171.8 mg/RNA(g) 및 5'-GMP 148.2 mg/RNA(g)생산할 수 있어 정미성 5'-mononucleotide 320mg/RNA(g)를 생산할 수 있음을 알았다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1995년도 춘계학술대회논문집
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• pp.155-161
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• 1995

Superplastic forming/diffusion bonding(SPF/DB) processes are analyzed using a rigid visco-plastic finite element method. The optimum pressure-time relationship for a target strain rate and thickness distributions were predicted using two-node line element based on membrane approximation for plane strain shapes. Material behavior during SPF/DB of the integral structures with complicated shapes are investigated. The tying condition is employed for the analysis inter-sheet contact problems. A movement of rib structure is successfully prodicted during the forming.

• 소성∙가공
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• 제5권1호
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• pp.37-46
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• 1996

Superplastic forming/diffusion bonding (SPF/DB) processes were analyzed using a rigid visco-plastic finite element method. The optimum pressure-time relationship for a target strain rate and thickness distributions were predicted by two-node line elements based on the membrane approximation for plane strain. Material behavior during SPF/DB of the integral structures having complicated shapes was investigated. The tying condition is employed for the analysis of inter-sheet contact problems. A movement of rib structure is successfully predicted during the forming.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 춘계학술대회논문
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• pp.172-184
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• 1996

Superplastic forming of thin sheet into complex shape is an important manufacturing process especially in aerospace industry. The main interest in modeling the superplastic forming process is to predict the forming pressure cycle to maintain optimum strain rate and the resulting thickness distribution. Many researchers have attemped to model superplastic forming using the various techniques including finite element method. But in most of their researches have disregarded the strain hardening effect which which occurs in several superplastic materials. In this study ABAQUS finite element code was used for prediction of process variables for axisymmetric cup forming of Supral 100 and 7075Al alloys considereing strain hardening. The performance of numerical results were compared with the experimental results.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2007년 추계학술발표대회 개요집
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• pp.263-265
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• 2007

• Journal of Welding and Joining
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• 제19권2호
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• pp.182-190
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• 2001

A marine structural material was well known to have high tensile strength, good weldability and proper corrosion resistance. Cu-containing high strength low alloy(HSLA) steel was recently developed for their purposes mentioned above. And the steel is free about preheating for welding, therefore it is reported that shipbuilding cost by using it can be saved more or less. However the marine structural materials like Cu-containing HSLA steel are being generally adopted with cathodic protection method in severe corrosive environment like natural sea water but the high strength steel may give rise to Hydrogen Embrittlement due to over protection at high cathodic current density for cathodic protection. In this study Cu-containing HSLA steel using well for marine atructure was investigated about the susceptibility of Hydrogen Embrittlement as functions of tensile strength, strain ratio, fracture time, and fracture mode, etc. and an optimum cathodic protection potential by slow strain rate test(SSRT) method as well as corrosion properties in natural sea water. And its corrosion resistance was superior to SS400 steel, but Hydrogen Embrittlement susceptibility of Cu-containing HSLA steel was higer than that of SS400 steel. However Hydrogen Embrittlement of its steel by SSRT method was showed with pheonomena such as decreasing of fracture time, strain ratio and fracture mode of QC(quasi-cleavage). Eventually it is suggested that an optimum cathodic protection potential not presenting Hydrogen Embrittlement of Cu-containing of HSLA steel by SSRT method was from-770mv(SCE) to - 900mV(SCE)under natural sea water.

• Journal of Advanced Marine Engineering and Technology
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• 제30권1호
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• pp.157-168
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• 2006

Recently, interest in using Al alloys in ship construction instead of fiber-reinforced plastic (FRP) has increased because of the advantages of A) alloy ships over FRP ships, including high speed, increased load capacity. and ease of recycling. This paper investigated the mechanical and electrochemical properties of Al alloys in a slow strain rate test under various potential conditions. These results will provide reference data for ship design by determining the optimum protection potential regarding hydrogen embrittlement and stress corrosion cracking. In general, Al and Al alloys do not corrode on formation of a film that has resistance to corrosion in neutral solutions. In seawater, however, $Cl^-$ ions lead to the formation and destruction of a Passive film. In a potentiostatic experiment. the current density after 1200 sec in the Potential range of $-0.68\~-1.5\;V$ was low. This low current density indicates the protection potential range. Elongation at an applied potential of 0 V was high in this SSRT. However, corrosion protection under these conditions is impossible because the mechanical properties are worse owing to decreased strength resulting from the active dissolution reaction in parallel parts of the specimen. A film composed of $CaCO_3\;and\;Mg(OH)_2$ confers corrosion resistance. However, at potentials below -1.6 V forms non-uniform electrodeposition coating, since there is too little time to form a coating. Therefore, we concluded that the mechanical properties are poor because the effect of hydrogen gas generation exceeds that of electrodeposition. Comparison of the maximum tensile strength, elongation, and time to fracture indicated that the optimum protection potential range was from -1.45 to -0.9 V (SSCE).

• 한국지반공학회지:지반
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• 제12권3호
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• pp.17-34
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• 1996

본 논문의 주된 목적은 폐자원(첨가제로서 pyrolyzed carbon black과 굵을 골재로서 aircooled iron blast furnace slag)을 사용한 아스팔트 콘크리트의 기본특성을 설명하는 것이다. 최적의 아스팔트 함유량을 결정하기 위하여 Marshall Mik Design방법을 이용하였고, 최적의 아스팔트 함유량은 첨가제의 양에 따라 변하며,그 범위는 6.7%에서 7.57%로 나타났다. 최적의 아스팔트 함유량을 이용하여 아스팔트 콘크리트 시편을 제작하였고, dynamic creep 실험을 수행하였다. Pyrolyzed carbon black과 Furnace slag의 사용은 Marshall stability를 증가시켰고, 비교적 높은 온도(5$0^{\circ}C$)와 137.gkpa의 구속 압력하에서 아스팔트 콘크리트의 시간에 따른 변형률을 감소시켰고, 또한 시간에 따른 아스팔트 콘크리트의 stiffness감소 비율을 줄여주는 역할을 하였다. 본 실험결과로 부터 첨가제로서의 pyrolyzed carbon black과 굵은 골재로서의 slag의 사용은 Marshall stability, stiffness, rutting resistance에 좋은 결과를 나타내는 것으로 밝혀졌다.