• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1303-1304
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• 2006

The type, volume fraction, size, shape and arrangement of embedded particles influence the mechanical properties of the particle reinforced metal matrix composites. This presents the investigation of the SiC particle and porosity distributions in various aluminum matrix composites produced by cold- and hot-pressing. The microstructures were characterized by optical microscopy and stereological parameters. SiC and porosity volume fractions, and the anisotropy distribution function were measured to establish the influence of the consolidation method.

• Journal of Magnetics
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• v.14 no.1
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• pp.15-17
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• 2009

The magnetostatic interaction between the two magnetic nanowires was studied by using the longitudinal magneto-optical Kerr effect (MOKE). For this purpose two magnetic nanowires having different widths (400 nm, 800 nm) were fabricated on an Si substrate with electron beam lithography and the lift-off method. Magnetic hysteresis loops measured by MOKE showed double switching behavior, corresponding to the separated switching fields of each wire. The switching field of the narrow wire was greatly affected by the separation between the two wires. Based on how the switching field changes with decreasing separation, it is concluded that the magnetostatic field of the 800-nm wire strongly affects the switching of the 400-nm wire when the separation is less than $0.5{\mu}m$.

• Carbon letters
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• v.5 no.3
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• pp.113-117
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• 2004

The mesophase pitch was prepared by adding 1~10 wt% of the borane-pyridine complex (BPC) to decant oil. It was prepared in a reactor held at $450^{\circ}C$ for 2 h in $N_2$ atmosphere. The mesophase pitches were analyzed using thermogravimetric analyzer (TGA), melting point apparatus, X-ray diffraction (XRD) and polarized optical microscope. The coke yield, softening point, toluene insoluble, density and content of anisotropy in the mesophase pitches were increased with BPC contents. The XRD profiles did not show any effect of addition of BPC on the formation of mesophase pitch, while the crystallinity of mesophase pitches was increased when the materials were heat treated with boron compound.

• Bulletin of the Korean Chemical Society
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• v.20 no.9
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• pp.1010-1016
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• 1999

We synthesized the photoresponsive side chain polymers containing aminonitro azobenzene for studying the effect of temperature on photoinduced birefringence. Four different copolymers were prepared using methacrylate, α-methylstyrene, and itaconate monomer. Photoisomerization was observed under the exposure of UV light using UV-VIS absorption spectroscopy. Reorientation of polar azobenzene molecules induced optical anisotropy under a linearly polarized light at 532 nm. The change of the birefringence was observed with increasing the sample temperature under a continuous irradiation of excitation light. We could estimate the activation energy of molecular motion in thermal and photochemical mode. Besides the effect of glass transition temperature on the activation energy, we focused our interests on the effect of geometrical hindrance of polar azobenzene molecules and cooperative motion of environmental mesogenic molecules in the vicinity of polar azobenzene molecules.

• Bulletin of the Korean Chemical Society
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• v.20 no.10
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• pp.1186-1194
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• 1999

Photoresponsive side chain polymers containing aminonitro azobenzene were synthesized for studying optically induced birefringence. Four different copolymers were prepared using methacrylate, a-methylstyrene, and itaconate monomer. Two copolymers are totally amorphous and the other two are liquid crystalline in nature. Trans-to-cis photoisomerization was observed under the exposure of UV light with UV-VIS absorption spectroscopy. Reorientation of polar azobenzene molecules induced optical anisotropy under a linearly polarized light at 532 nm. The dynamic parameters of optically induced birefringence let us compare the effect of polymeric structure on the rate of growth and decay of the birefringence. Besides the effect of glass transition temperature on the dynamics of photoinduced birefringence, we focused our interests on the geometrical hindrance of polar azobenzene molecules and cooperative motion of environmental mesogenic molecules in the vicinity of polar azobenzene moiety.

• Proceedings of the Korean Magnestics Society Conference
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• 2000.05a
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• pp.82-83
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• 2000

• BMB Reports
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• v.40 no.4
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• pp.453-458
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• 2007

Bacterial luciferase is a heterodimeric enzyme, which catalyzes the light emission reaction, utilizing reduced FMN (FMNH2), a long chain aliphatic aldehyde and $O_2$, to produce green-blue light. This enzyme can be readily classed as slow or fast decay based on their rate of luminescence decay in a single turnover. Mutation of Glu175 in $\alpha$ subunit to Gly converted slow decay Xenorhabdus Luminescence luciferase to fast decay one. The following studies revealed that changing the luciferase flexibility and lake of Glu-flavin interactions are responsible for the unusual kinetic properties of mutant enzyme. Optical and thermodynamics studies have caused a decrease in free energy and anisotropy of mutant enzyme. Moreover, the role of Glu175 in transition state of folding pathway by use of stopped-flow fluorescence technique has been studied which suggesting that Glu175 is not involved in transition state of folding and appears as surface residue of the nucleus or as a member of one of a few alternative folding nuclei. These results suggest that mutation of Glu175 to Gly extended the structure of Xenorhabdus Luminescence luciferase, locally.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.535-538
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• 2003

Liquid crystal molecules with a new fluoro-isothiocyanate moiety were synthesized. They showed remarkably high $T_{NI}$ (>190 $^{\circ}C$), wide mesophase range of 170 $^{\circ}C$, high dielectric anisotropy (>14) and high optical anisotropy (>0.28). New LC Mixtures of the high $T_{NI}$ (>$85^{\circ}C$) was blended with the novel fluoro-isothiocyanate containing LC molecules, phenylcyclohexanes, bicyclohexanes and ester compounds. The LC mixtures show a fast speed (<10ms) of the below one frame rate in 17" WXGA panel.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06a
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• pp.147-152
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• 2006

Restoration of historical documents and arts has become important to inherit cultural properties. Most of historical documents were recorded on paper. Therefore, restoration of ancient papers is demanded and techniques for this purpose must be developed and sophisticated. In our study, several nondestructive methods for analyzing ancient paper have been developed. Image analysis using fast Fourier transform with suitable modifications was applied to optical micrographs of traditionally-handmade Korean and Japanese papers. This analysis determines the angle and anisotropy of fiber orientation of paper surfaces. Fiber orientation of traditionally-handmade Korean and Japanese papers was found to show their own characteristics in accordance with the motion of a papermaking screen made of bamboo splints. Consequently, the information on fiber orientation was found to be possible to distinguish the flow-sheet forming typical of Japanese paper and still-sheet forming typical of Korean paper. Moreover, the anisotropy was always higher for the screen side than for the top side, thus meaning that surface fiber orientation is possible to distinguish the two sides of paper of which papermaking history is unknown. An application of this technique to actual historical documents evidenced that wrapping papers were used as envelops with a lateral side up, namely, after rotating 90 degrees. A variety of cultural habits in writing letters was revealed by discrimination of the two sides.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.276-276
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• 2010

Large-area micropatterned array of Co/Ni bilayer anti-dots was fabricated using photolithography and wet etching process. The surface morphology as well as the surface topography was checked by scanning electron microscopy and atomic force microscopy, whereas the magnetic properties were studied by magneto-optical Kerr effect (MOKE) and magnetic force microscopy (MFM). Systematic studies of the magnetic-reversal mechanism, the in-plane anisotropy and the switching field properties were carried out. To get a comprehensive knowledge about the domain configuration, we also employed OOMMF simulations. It was found from the MOKE measurements that a combined effect of configurational and the magneto-crystalline anisotropy simultaneously works in such micropatterned bilayer structures. In addition, the inclusion of holes in the uniform magnetic film drastically affected the switching field. The MFM images show well-defined domain structures which are periodic in nature. The micromagnetic simulations indicate that the magnetization reversal of such a structure proceeds by formation and annihilation of domain walls, which were equally manifested by the field-dependent MFM images. The observed changes in the magnetic properties are strongly related to both the patterning that hinders the domain-wall motion and to the magneto-anisotropic bilayered structure.