• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1179-1184
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• 1998

Mesogenic and azo monomers were synthesized and copolymerized to obtain two copolymers composed of methacrylate and itaconate backbone. Glass transition temperatures of the copolymers were found to be slightly higher than ambient temperature. Both the copolymers showed liquid crystalline properties. Trans-cis isomerization in film state was observed under UV-irradiation with a light of 365 nm. Regarding the photochemical phase transition behavior, the transition rate of nematic-to-isotropic state was slightly faster in the methacrylate copolymer during irradiation at 365 nm and the rate of the reverse transition was much faster in itaconate copolymer under thermal effect.

• Korean Journal of Materials Research
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• v.23 no.7
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• pp.373-378
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• 2013

In order to clarify the effect of C/Ti atom ratios(${\chi}$) on the deformation behavior of $TiC_{\chi}$ at high temperature, single crystals having a wide range of ${\chi}$, from 0.56 to 0.96, were deformed by compression test in a temperature range of 1183~2273 K and in a strain rate range of $1.9{\times}10^{-4}{\sim}5.9{\times}10^{-3}s^{-1}$. Before testing, $TiC_{\chi}$ single crystals were grown by the FZ method in a He atmosphere of 0.3MPa. The concentrations of combined carbon were determined by chemical analysis and the lattice parameters by the X-ray powder diffraction technique. It was found that the high temperature deformation behavior observed is the ${\chi}$-less dependent type, including the work softening phenomenon, the critical resolved shear stress, the transition temperature where the deformation mechanism changes, the stress exponent of strain rate and activation energy for deformation. The shape of stress-strain curves of $TiC_{0.96}$, $TiC_{0.85}$ and $TiC_{0.56}$ is seen to be less dependent on ${\chi}$, the work hardening rate after the softening is slightly higher in $TiC_{0.96}$ than in $TiC_{0.85}$ and $TiC_{0.56}$. As ${\chi}$ decreases the work softening becomes less evident and the transition temperature where the work softening disappears, shifts to a lower temperature. The ${\tau}_c$ decreases monotonously with decreasing ${\chi}$ in a range of ${\chi}$ from 0.86 to 0.96. The transition temperature where the deformation mechanism changes shifts to a lower temperature as ${\chi}$ decreases. The activation energy for deformation in the low temperature region also decreased monotonously as ${\chi}$ decreased. The deformation in this temperature region is thought to be governed by the Peierls mechanism.

• Journal of Microbiology and Biotechnology
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• v.17 no.11
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• pp.1751-1757
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• 2007

Elastin-like polypeptides (ELPs) undergo a reversible inverse phase transition upon a change in temperature. This thermally triggered phase transition allows for a simple and rapid means of purifying a fusion protein. Recovery of ELPs-tagged fusion protein was easily achieved by aggregation, triggered either by raising temperature or by adding salt. In this study, levansucrase has been used as a model enzyme in the development of a simple one-step purification method using ELPs. The levansucrase gene cloned from Pseudomonas aurantiaca S-4380 was tagged with various sizes of ELPs to functionally express and optimize the purification of levansucrase. One of two ELPs, ELP[V-20] or ELP[V-40], was fused at the C-terminus of the levansucrase gene. A levansucrase-ELP fusion protein was expressed in Escherichia coli $DH5{\alpha}$ at $37^{\circ}C$ for 18 h. The molecular masses of levansucrase-ELP[V-20] and levansucrase-ELP[V-40] were determined as 56 kDa and 65 kDa, respectively. The phase transition of levansucrase-ELP[V-20] occurred at $20^{\circ}C$ in 50 mM Tris-Cl (pH 8) buffer with 3 M NaCl added, whereas the phase transition temperature ($T_t$) of levansucrase-ELP[V-40] was $17^{\circ}C$ with 2 M NaCl. Levansucrase was successfully purified using the phase transition characteristics of ELPs, with a recovery yield of higher than 80%, as verified by SDS-PAGE. The specific activity was measured spectrophotometrically to be 173 U/mg and 171 U/mg for levansucrase-ELP[V-20] and levansucrase-ELP[V-40], respectively, implying that the ELP-tagging system provides an efficient one-step separation method for protein purification.

• Journal of the Korean Vacuum Society
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• v.6 no.2
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• pp.109-113
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• 1997

PR spectra of MBE grown AlGaAs/GaAs MQW have been measured at room temperature using the He-Ne laser and the Ar laser as the pump source. We have observed various subband transition peaks and PR spectra were fitted to standard analytic line shape. Above that results, obtained us transition energy from n=1 conduction band to heavy hole(C1-H1) and to light hole(C1-L1) subband. Photoluminescence(PL) at room temperature showed main peak with a shoulder. Good agreement between PL and PR measured n=1 intersubband transition energies was confirmed that PL main peak with a shoulder is associated with the C1-H1, C1-L1 transition. Additionally, we have calculated the C1-H1 and C1-L1 intersubband energy within envelope function approximation(EFA).

• Journal of the Korean Chemical Society
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• v.36 no.3
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• pp.360-365
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• 1992

We constructed a photoacoustic cell and dewar in order to investigate the phase transition of the solids. The solid-liquid phase transition of a wood's metal was measured by a temperature controlled photoacoustic apparatus. It showed a good agreement with the reported value of the melting point, 343 K. The phase transiton of the wood's metal has been determined to be the first order transition, existing a latent heat, which is typical in the solid-liquid transition. In addition, a supercooling effect was observed by monitoring the photoacoustic signal as the temperature of the sample was decreased. The experiments have demonstrated the photoacoustic detection is an appropriate method to determine the order of transition in solid samples.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1828-1833
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• 2003

In a foaming process of microcellular plastics (MCPs) with a batch process, amorphous plastics and crystalline plastics have different characteristics for a foaming temperature. It is known that a foaming of amorphous plastics occurs at the temperature above a glass transition temperature, however, it is discovered that crystalline plastics do not take place above a glass transition temperature without exception, and even though the foaming occurs, it does not in all the range. In this research, to measure foaming temperature of crystalline polymer, a foaming experiment was performed using one of the typical crystalline polymer, polypropylene. To analyze whether the foaming occurs both at amorphous and crystalline fields, SEM was applied

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.11
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• pp.556-560
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• 2004

In this paper, thermal and structural properties of epoxy/elastomer blend were measured by DSC, TGA and FESEM. Specimens were made of dumbbell forms by the ratio of 5, 10, 15, and 20[phr] by changing elastomer content. The measuring temperature ranges of DSC were from -20[℃] to 150[℃] and heating rate was 4[℃/min]. And the measuring temperature ranges of TGA were from 0[℃] to 800[℃], and heating rate was 5[℃/min]. Also we observed structure of specimens through FESEM with magnification of 1000 times and voltage of 15[kV] by breaking quenched specimens. As experimental results, we could know that thermal and structural properties were improved according to decrease of elastomer content. Because it increased glass transition temperature, high temperature and structure of elastic epoxy.

• Journal of the Korean Magnetics Society
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• v.8 no.4
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• pp.179-184
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• 1998

Colossal magnetoresistance is closely related to (but is not) the abrupt change of electrical resistivity in the vicinity of Curie temperature, which is caused by the temperature dependent paramagnetic-ferromagnetic phase transition and concurrent change of electrical conducting mechanism. A resistivity-temperature equation is presented to fully describe the overall behavior, especially the abrupt change. The main ingredients of the equation are a simple effective media theory and a function for the temperature dependent fraction of ferromagnetic phase. The model fits very well to the measured resistivity-temperature curve of $La_{0.7}Ca_{0.3}MnO_3$.

• Journal of Korea Foundry Society
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• v.2 no.2
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• pp.2-9
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• 1982

This paper is concerned with the improvement of impact and tensile Properties of spheroidal graphite cast iron of the following duplex matricess which were heat treated in the eutectic transformation temperature range (that is, $({\alpha}+{\gamma})$ coexisting range) ; ferrite-martensite, ferrite-bainite and ferrite-pearlite. The absorbed energy and maximum load was measured by recording the load-deflection curve with instrumented Charpy impact testing machine in the temperature range from $+100^{\circ}C$ to $-196^{\circ}C$. It was found the ferrite-bainite duplex matrix showed the highest toughness among the above matrices in the room temperature and the low temperature range. Comparison of this matrix to ferrite-pearlite matrix(that is, as cast) showed a lowering of $27^{\circ}C$ in the nil-ductility transition temperature (NDT) and a lowering of $40^{\circ}C$ in the ductile-brittle transition temperature (TrE), Which seems to result from the finner dimple pattern observed using miorofractography.

• Journal of the Korean Ceramic Society
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• v.32 no.8
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• pp.915-921
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• 1995

The morphotropic phase boundary and phase transitions of the solid solutiion system, (1-x)(Na1/2Bi1/2)TiO3-PbTiO3＋xPbTiO3 were studied by investigating changes in crystal structure, variations in permittivity with temperature, and calorimetric behavior. It was observed that the morphotropic phase boundary (MPB) of this solid solutiion system was at near 14 mol% of PbTiO3. Compositions containing less than 10mol% PbTiO3 (x<0.1) exhibited a phase transition, i.e. ferroelectric rhombohedrallongrightarrowparaelectric paraelectric cubic, with increasing temperature. Composition containing more than 14 mol% PbTiO3 (x 0.14) showed a phase transition from ferroelectric tetragonal to paraelectric cubic. In the composition range of 0.1$\varepsilon$ (T) curve, which coincided with a phase transition from ferroelectric rhombohedral to an intermediate phase, was also found.