• Journal of the Korean Ceramic Society
• /
• 제36권3호
• /
• pp.231-236
• /
• 1999

냉각속도가 재열처리가 AFD 방법에 의해 제작된 76SiO2-14B2O3-6Na2O-4Al2O3 유리박막의 광학적 특성에 미치는 영향을 조사하였다. 유리박막의 열팽창계수는 30$0^{\circ}C$부터 전이온도 사이에서 약 5$\times$10-6/$^{\circ}C$이었으며, 전이온도는 62$0^{\circ}C$였다. 유리박막을 전이온도 이하에서 열처리할 경우 열처리 시간이 증가함에 따라 굴절률은 증가하였으며, 열처리 온도가 증가함에 따라 굴절률의 증가속도는 더 컸다. 열처리온도에 따른 유리박막의 복굴절(TE-TM)감소는 굴절률이 가장 크게 증가하는 온도인 $600^{\circ}C$에서 가장 효과적이다. 한편, 냉각속도가 증가함에 따라 유리박막의 두께는 증가하였으며, 굴절류른 감소하였다.

• Journal of Animal Science and Technology
• /
• 제47권4호
• /
• pp.491-500
• /
• 2005

To test applicability to the Hanwoo traceability system, twenty microsatellite markers were selected and analyzed. MSA, CERVUS, FSTAT, GENEPOP, API_CALC and PHYLIP software was employed serially to estimate heterozygosity, polymorphic information content, F-statistics, identity probability, exclusion probability and genetic distance. Eleven microsatellite markers(TGLA53, TGLA227, ETH185, TGLA122, BM4305, INRA23, ILSTS013, BMS1747, BM2113, BL1009, and ETH3) were selected based on their high heterozygosity values. Identity probability using these markers is one hundred times higher than when using StockMakersTM of Applied Biosystems. This indicates the selected microsatellite markers are appropriate and effective for use in the Hanwoo traceability system. Additionally, estimates of DA genetic distance and pairwise-FST can be utilized to identify genetic relationships between adjacent farms.

• Journal of the Korean Society of Safety
• /
• 제14권1호
• /
• pp.208-215
• /
• 1999

The creep behavior of a rapidly solidified and consolidated Al-9.45wt%Fe-4.45wt%Cr alloy were investigated in the stress range 40 to 115 MPa and temperature range 300(0.53Tm) to 441$^{\circ}C$(0.66Tm). It is of use to available aerospace and automobile industries for the improved performance of materials used at high temperature. Because Al alloys with improved creep resistance offer the potential for lower weight and reduced costs in aerospace and automobile components (e.g., structural members and engine parts) through the replacement of heavier and more costly materials, the safety in use at high temperature is good. The alloy is characterized by high stress exponents and activation energies for creep, which are greatly dependent on the stress and temperature. Because the creep stress is seen to cause a strongly significant enhancement of coarsening, the coarsening rate of the dispersed particles in all crept specimens is faster than that in isothermally annealed specimens. Dislocations connecting dispersoids are observed more cofrequently in crept specimens with higher stress and lower temperature. The creep strain rates in the power law creep regime were found to be predicted much better by the Shorty and Rosler/Arzt equation with the inclusion of a threshold stress and dislocation detachment mechanism. The dispersoids in this alloy were acting a source of void nucleation that finally leaded to ductile fracture within the grain so called intergranular. Each void was initiated, grown and failed at the dispersoids in the aluminium matrix. Grain boundary accommodation of the slip produced, which result in initiation of the void and then final transgranular fracture. Therefore, it was confirmed that these dispersoids played an important role in the fracture mechanism by the formation of $Al_{13}Fe_4$, $Al_{13}Cr_2$ and $Al_2O_3$.

• Nuclear Engineering and Technology
• /
• 제52권8호
• /
• pp.1742-1748
• /
• 2020

TSSD, TSSP, and TSSP2 of hydrogen for optimized-Zirlo (Zirlo™) alloy were measured by DSC in the range of 53-457 wppm. Solvus curves of the TSSs are derived and proposed in this study. The results show that the temperature gap between TSSD and TSSP solvus lines of Zirlo™ are similar to those of other zirconium alloys, but another gap between the TSSD and TSSP2 line differs significantly. In particular, the TSSP2 solvus line becomes closer to the TSSD solvus line than to TSSP unlike Zircaloy-4, so ΔT_TSSD-TSSP2 of Zirlo™ decreases with decreasing temperature. This implies that hydride reorientation can take place more significantly in Zirlo™ than in Zircaloy-4, and the limited temperature variation of 65 ℃ during the vacuum drying and the cooling-down process may not be sufficient to prevent the triggering of hydride reorientation in Zirlo™ cladding under long-term dry storage.

• Journal of Mechanical Science and Technology
• /
• 제20권8호
• /
• pp.1209-1216
• /
• 2006

An AZ31 magnesium alloy was tested at constant temperatures ranging from 423 to 473 K (0.46 to 0.51 Tm) under constant stresses. All of the creep curves exhibited two types depending on stress levels. At low stress (${\sigma}/ G < 4 {\times}10^{-3}$), the creep curve was typical of class A (Alloy type) behavior. However, at high stresses (${\sigma}/ G > 4 {\times}10^{-3}$), the creep curve was typical of class M (Metal type) behavior. At low stress level, the stress exponent for the steady-state creep rate was of 3.5 and the true activation energy for creep was 101 kJ/mole which is close to that for solute diffusion. It indicates that the dominant deformation mechanism was glide-controlled dislocation creep. At low stress level where n=3.5, the present results are in good agreement with the prediction of Fridel model.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 한국재료학회 1993년도 춘계학술발표회
• /
• pp.99-100
• /
• 1993

Calorimetric (D.S.C) studies were carried out on the nylon 4,6 single crystals grown from 1,4-butanediol solution at various crystallisation temperatures, based on the assessment of the lamellar thickness by small angle x-ray scattering. Samples were annealed mainly ot get rid of residual solvents inside the crystals. The effect of annealing on the crystal perfection is inferred from the measured thermal properties of the crystals. Accordig to the scanning rates less than 80 K/min., D. S C. melting peaks indicate that changes in the internal morphology of nylon 4,6 crystals preapred at different crystallisation temeratures yield a thermodynamic melting temperature. Tm, of 319 $^{\circ}C$, for the infinitely extended crystal thickness (1/ι). The obtained heat of fusion value for the inginite crystal thickness, Ho, was 270 J/g from the plot of measured feat of fusion ($\Delta$Hm) vs. reciprocal crystal thickness (1/ι). based on these values, the fold surface energy, $\delta$e. of 65.4 erg/$\textrm{cm}^2$ was obtained from Hoffman-Waeeks equation. The thermodynamic melting temperature and heat of fusion of the infinite crystal thickness for the solution grow nylon 4,6 single crystals are found to be higher than of the reported corresponding solution grown nylon 6,6 single crystals. pbtained crystallinity from D. S. C measurements ranges from 40 to 50 %, which is close to the reported yalue for the nylon 6,6 single ctystals but lower than we expected.

• Journal of the Korean Society for Heat Treatment
• /
• 제17권2호
• /
• pp.94-100
• /
• 2004

In order to improve the wear resistance of Ti-6Al-4V alloy, plasma carburization treatment was newly carried out without consumption of its good specific strength and fatigue life over the temperature. Effect of the plasma carburization was analyzed and compared with the non-treated alloy by microstructural observation, structure characterization and mechanical test. The plasma treated alloy formed a carburized layer of about $150{\mu}m$ in depth from the surface, where a fine and hard particles of TiC and $V_4C_3$ were homogeneously dispersed through the layer. The steady-static creep behaviors of Ti-6Al-4V alloy, using the constant stress creep tester, were investigated over the temperature range of $510{\sim}550^{\circ}C$(0.42~0.44Tm) and the stress range of 200~275 MPa. Stress exponent(n) was decreased from 9.32 of non-treatment specimen to 8.95 of carburized, however, the activation energy(Q) increased from 238 to 250 kJ/mol with the same condition as indicated above. From the above results, it can be concluded that the static creep deformation for Ti-6Al-4V alloy was controlled by the dislocation climb over the ranges of the experimental conditions.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제10권4호
• /
• pp.427-438
• /
• 2018

The reduction of $CO_2$ emissions has been a key target in the marine industry since the IMO's MEPC published its findings in 2009. Air lubrication method is one of the mature technologies for commercialization to reduce the frictional resistance and enhance fuel efficiency of ships. Air layer is formed by the coalescence of the injected air bubbles beyond a certain air flow rate. In this study, a model ship (${\lambda}=33.33$) of a 50,000 ton medium range tanker is equipped with an air lubrication system. The experiments were conducted in the 100 m long towing tank facility at the Pusan National University. By selecting optimal air injector configuration and distribution ratio between two injectors, the total resistance of model $R_{TM}$ was able to be reduced down to 18.1% in the model scale. Key issue was found to suppress the sideway leakage of injected air by appropriate injection parameters.

• Laser Solutions
• /
• 제8권3호
• /
• pp.5-10
• /
• 2005

[ $InxGa_{1-x}P/GaAs$ ] structures were grown by chemical beam epitaxy(CBE), Pure phosphine($PH_3$) gases were used as group V sources. for the group III sources, TEGa, TmIn were used. $InxGa_{1-x}P$ epilayer was grown on SI-GaAs substrate and has a 1-${\mu}m$ thick. We have investigated the characteristics of $InxGa_{1-x}P$ by the photoreflectance(PR) spectroscopy, The PR spectrum of $InxGa_{1-x}P$ shows third-derivative feature whose Peaks Provide energy gap. The energy gap of $InxGa_{1-x}P$ has deduced composition x. From temperature dependance of PR spectra, temperature coefficient is $dEg/dT=-3.773{\times}10^{-4}$ eV/K, and Varshni coefficients $\alpha$ and $\beta$ values obtained $4{\times}10^4$ eV/K and 267 K respectively. Also, interaction $\alpha$B was 19.4 meV using the Bose-Einstein temperature relation, and $\Theta$ value related the average phonon frequency were 101.4 K. In particular, shoulder peak related to defects observed in PR signal that measured in temperature 82 K.

• Proceedings of the SCSK Conference
• /
• 대한화장품학회 2003년도 IFSCC Conference Proceeding Book II
• /
• pp.184-191
• /
• 2003

New pyranone derivative, 2-((3E)-4(2H, 3H, -benzo[3, 4-d] 1, 3-dioxolan-5-yl)-2-oxo-but-3-enyloxy)-5-hydroxy-4H-pyran-4-one (Seletinoid $G^{TM}$), was designed as a novel retinoid on the assumption that the pyranone ring may mimic the carboxylic acid moiety in retinoid structure. The enolic hydroxy of pyranone at five position was easily deprotonated to form an enolate. The role of enolate was similar to that of carboxylic acid. To evaluate the value of Seletinoid G as an anti-aging ingredient, various tests were performed for example inhibitory effect for MMP-l expression, anti-oxidative activity, procollagen synthesis in hairless mouse and primary skin irritation. The result of this study suggested that our new synthetic retinoid could be used as a safe material for anti-aging cosmetics.