• 대한금속재료학회지
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• 제46권12호
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• pp.780-787
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• 2008

For the advanced high strength steels (AHSS), high-manganese TWIP (twinning induced plasticity) steels exhibit high tensile strength (800-1000 MPa) and high elongation (50-60%). However, the TWIP steels need to be understood of delayed fracture following the cup drawing test. Among the factors to cause delayed fracture, i.e, martensite transformation, hydrogen embrittlement and residual stress, the effects of martensite transformation (${\gamma}{\rightarrow}{\varepsilon}$ or ${\gamma}{\rightarrow}{\alpha}^{\prime}$) were investigated on the delayed fracture phenomenon. Microstructural phase analysis was conducted for cold rolled (20, 60, 80% reduction ratio) steels and tensile deformed (20, 40, 60% strain) steels. For the Al-added TWIP steels, no martensite phase was found in the cold rolled and tensile deformed specimen. But, the TWIP steels with no Al addition indicated the martensite transformation. The cup drawing specimens showed the martensite transformation irrespective of the Al-addition to the TWIP steel. However, the TWIP steel with no Al exhibited the larger amount of martensite than the case of the TWIP steel with Al addition. For the reason, it was possible to conclude that the Al addition suppressed the martensite transformation in TWIP steels, therefore preventing the delayed fracture effectively. However, it was interesting to note that the mechanism of delayed fracture should be incorporated with hydrogen embrittlement and/or residual stress as well as the martensite transformation.

• 한국어류학회지
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• 제19권2호
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• pp.83-87
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• 2007

어류 에드워드감염증에 대한 예방 재조합 ghost 백신을 개발하기 위한 연구의 일환으로 어류 병원성 세균인 Edwardsiella trada를 대상으로 플라스미드 형질전환을 실시하고 형질전환 안정성을 평가하였으며, 형질 도입된 재조합 ghost 세균의 E-lysis 유전자 발현을 분석하였다. E. tarda를 대상으로 한 ghost 유도는 대장균에 비해 상대적으로 장시간의 반응 시간이 요구되며 lysis의 개시가 지연된 점을 고려 시 발현된 E protein의 용해 능력 또는 E-gene의 전사발현 양이 E. tarda에서 다소 약화되는 것으로 나타났다. 그러나 대장균에 비해 ghost 유도 속도가 다소 낮음에도 불구하고 반응이 완성되었을 시점에서의 E. tarda의 ghost 효율은 대장균과 전혀 차이가 없이 99.99% 이상의 유도효율을 나타내었다.

• 열처리공학회지
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• 제13권4호
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• pp.265-271
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• 2000

The microstructural change and transformation characteristics with cooling rate i.e. wheel speed were investigated in 82.8wt%Cu-12.8wt%Al-4.3wt%Ni SMA ribbons fabricated by melt-spinning. The thickness and width of ribbon were decreased with increasing wheel speed, while the uniformity of it was improved. At same wheel speed, the grain size of the contact surface of ribbon was smaller than that of free surface. The mean grain size was decreased with increasing wheel speed, resulted in obtaining grains with $3{\mu}m$ in mean diameter in the wheel speed of 30 m/s. However, micro-voids and cracks at grain boundary could be observed at higher wheel speed. $M_s$ and $A_s$ temperatures were decreased, and $M_s{\sim}M_f$ and $A_s{\sim}A_f$ temperature ranges were broadened with increasing wheel speed. All the ribbons were retained the ordered $D0_3$ due to rapid cooling, the volume fraction of it was increased with increasing wheel speed.

• International Journal of Ocean System Engineering
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• 제1권1호
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• pp.28-31
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• 2011

An attempt was made to compute the free surface deformation due to the impact of a water droplet. The Cauchy Poisson, i.e. the initial value problem, was solved with the kinematic and dynamic free surface boundary conditions linearized. The zero order Hankel transformation and Laplace transform were applied to the related equations. The initial condition for the free surface profile was derived from a captured video image. The effect of the surface tension was not significant with the water mass used in this investigation. The computed and observed free surface deformations were compared.

• 열처리공학회지
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• 제5권3호
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• pp.149-156
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• 1992

Transformation behavior and reversible shape memory effct of Ti-Ni-Cu alloys with various Cu content has been investigated by means of electrical resistivity measurement, differential scanning calorimetry. X-ray diffraction and strain gage sensor. The transformation sequence in Ti-Ni-Cu alloys substituted by Cu for Ni up to 5at.% occurs to $B2{\leftrightarrow}B19^{\prime}$ and it proceeds in two stages by addition of 10 at.%Cu. i.e. $B2{\leftrightarrow}B19{\leftrightarrow}B19^{\prime}$. But the content of Cu increases up to 20at.%, it has been transformed in one stage ; $B2{\leftrightarrow}B19$. The shape change of Ti-40Ni-10Cu alloy which was constrain aged in circular form bended in $B2{\leftrightarrow}B19$ transformation but it spreaded out in $B19{\leftrightarrow}B19^{\prime}$ transformation. The amount of reversible shape change (${\Delta}{\varepsilon}$) of Ti-47Ni-3Cu alloy constrain aged at $400^{\circ}C$ after solution treatment has a maximum value of about $5.6{\times}10^{-3}$, but that of cold rolled and constrain aged specimens exhibits a little value independent of Cu concentrations.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2008년도 학술논문요약집
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• pp.191-192
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• 2008

• 한국전자거래학회:학술대회논문집
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• 한국전자거래학회 2005년도 e-Biz World Conference 2005
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• pp.143-148
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• 2005

The purpose of this paper is to analyze pricing strategies between conventional offline retailers and Internet retailers and discuss which strategy is more profitable when a bricks-and-mortar firm transforms into a clicks-and-mortar firm.

• Archives of Pharmacal Research
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• 제4권1호
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• pp.25-31
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• 1981

The ginsenosides of Korean ginseng decomposed profoundly to produce artifact products of prosapogenin $A_{1}$, $A_{2}$ and $A_{3}$ from ginsenoside Rg$_{1}$, prosapogenin $C_{1}$, $C_{2}$ and $C_{3}$ from ginsenoside Re, and prosapogenin E$_{1}$, E$_{2}$ and E$_{3}$ from ginsenoside Rb$_{1}$ by the acid treatment under physiological condition such as 37.deg.C incubation in 0.1 N HCI. 2. The chemical structures of the artifact substances were determined by the analysis CMR and mass spectra of TMS derivatives as following; table omitted.

• Natural Product Sciences
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• 제26권4호
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• pp.283-288
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• 2020

Microbial transformation of a potent progestin, norethisterone (17��-hydroxy-19-nor-17α-pregn-4-en-20-yn-3-one) (1) was carried out by using two filamentous fungi Aspergillus niger and Penicillium citrinum. Biotransformation of 1 with A. niger yielded a hydroxylated transformed product 10��,17��-diydroxy-19-nor-17α-pregn-4-en-20-yn-3-one (2) whereas 11��,17��-diydroxy-19-nor-17α-pregn-4-en-20-yn-3-one (3) was obtained through microbial transformation of 1 by P. citrinum. It is the first report of their production from 1 by using A. niger and P. citrinum with complete 1H- and 13C-NMR assignment. The structures of both metabolites were characterized by various spectroscopic techniques and reported data.

• Journal of Korean Vacuum Science & Technology
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• 제5권2호
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• pp.43-46
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• 2001

Fe-Au alloys are characterized by the complete solubility, and exhibit an fcc-bcc structural transformation at the Fe-rich side. The magneto-optical(equatorial Ken effect : EKE) and optical properties of Fe$\_$1-x/Aux (0 < x < 1) were investigated in the 0.5 - 5.0 eV energy range. The x-ray diffraction study shows the structural fcc-bcc transformation about 80 at. % of Fe. Noticeable changes in the optical properties caused by the fcc-bcc structural transformation was observed. The shape and intensity of the EKE spectra as well as the field dependence of the magneto-optical response were also significantly changed. It is thought that these changes are mainly comes from the induced magnetic moment in Au(and/or the emhanced magnetic moment of Fe). The nature of the prominent structure observed in the UV range of the magneto-optical Ken effect of Au/Fe multilayered films are disscussed in connection with the above results.