• Bulletin of the Korean Chemical Society
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• 제23권3호
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• pp.469-476
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• 2002

Photocrosslinkable soluble polyimide and polymethacrylate compound were synthesized for studying the optically induced anisotropy of the thin films. Chalcone group was introduced into the side chain unit of two polymers. We observed a photodimerization behavior between the double bonds in the chalcone group and an optical anisotropy of these materials by irradiation of a linearly polarized UV light (LPL). Optical anisotropy of the thin film was also investigated by using polarized UV absorption spectroscopy. The dynamic property of optical anisotropy in photoreactive polyimide was compared to that in polymethacrylate containing chalcone group in the side chain.

• Fibers and Polymers
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• 제2권1호
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• pp.123-130
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• 2001

Photoresponsive side chain copolymer and homopolymer containing an aminonitroazobenzene were synthesized for studying photoisomerization behavior and photo-induced anisotropy. Trans-to-cis photoisomerization was observed under the exposure of a circularly polarized visible light with UV-Vis absorption spectroscopy. Reorientation of polar azobenzene molecules induced optical anisotropy under a linearly polarized light at 532nm. Polarized absorption spectroscopy was employed to investigate the anisotropy of the polymer film during irradiationg of the excitation light. Layers of two photosensitive polymers were used for aligning liquid crystal(LC) molecules instead of one of the rubbed polyimide layers in the conventional twisted nematic cell. For producing homogeneous alignment of a nematic LC molecule, a linearly polarized light was exposed to the films of two polymers. The stability of the LC alignment upon the linearly polarized light exposure was also studied.

• Advances in nano research
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• 제1권3호
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• pp.153-158
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• 2013

An approach to achieving of spatially homogeneous, ordered ensemble of semiconductor quantum rods in polymer film of polyvinyl butyral is reported. The CdSe/ZnS quantum rods are embedded to the polymer film. Obtained film is stretched up to four times to its initial length. A concentration of quantum rods in the samples is around $2{\times}10^{-5}$ M. The absorption spectra, obtained in the light with orthogonal polarization, confirm the occurrence of spatial ordering in a quantum rod ensemble. Anisotropy of the optical properties in the ordered quantum rod ensemble is examined. The presented method can be used as a low-cost solution for preparing the nanostructured materials with anisotropic properties and high concentration of nanocrystals.

• Advanced Composite Materials
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• 제17권4호
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• pp.359-372
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• 2008

The moisture absorption behavior of carbon fiber-reinforced plastic (CFRP) and its effect on dimensional stability were examined. Moisture diffusivity in CFRP was determined by measuring a specimen's weight during the moisture absorption test. Three types of CFRP specimens were prepared: a unidirectionally reinforced laminate, a quasi-isotropic laminate and woven fabric. Each CFRP was processed into two geometries - a thin plate for determination of diffusivity and a rod with a square cross-section for the discussion of two-dimensional diffusion behavior. By solving Fick's law expanded to 3 dimensions, the diffusivities in the three orthogonal directions were obtained and analyzed in terms of the anisotropy of CFRP moisture diffusion. Coefficients of moisture expansion (CMEs) were also obtained from specimen deformation caused by moisture absorption. During moisture absorption, the specimen surfaces showed larger deformation near the edges due to the distribution of moisture contents. This deformation was reasonably predicted by the finite element analysis using experimentally determined diffusivities and CMEs. For unidirectional CFRP, the effect of the fiber alignment on CME was analyzed by micromechanical finite element analysis (FEA) and discussed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.687-694
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• 1997

The anisotropy and shape of distributed piezopolymer actuator have advantages over isotropic piezo ceramic materials, since these features of PVDF can be utilized as another design variable in control application. This study is interested in the reduction of sound transmission through elastic plate into interior space by using the PVDF actuator. The plate-cavity system is adopted as a test problem. The vibration of composite plate and the sound fields through plate are analyzed by using the coupled finite element and boundary element method. Some numerical simulations are performed on sound transmission through elastic plates. To investigate the effects of anisotropy and shape of distributed piezopolymer actuator, various kinds of distributed PVDF actuators are applied in sound control simulation for isotropic and anisotropic plates. The PVDF actuators applied are different from each other in their shapes and laminate angles. The results of control simulation show that the control effectiveness of distributed PYDF actuator can be enhanced by using the coupling between shape of actuator and vibration modes of structure and the anisotropy of piezoelectric properties of PVDF.

• 한국전기전자재료학회논문지
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• 제16권3호
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• pp.238-246
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• 2003

We have performed the simulation of ferromagnetic resonance spectra on the exchange coupled bilayer thin films at perpendicular configuration. Variables considered in spectrum calculation were the interfacial exchange constants per unit area, the layer thickness, and the surface anisotropy constants. In case of antiferromagnetic coupling, variation of exchange constant gave a great effect to the absorption spectra of the low and the high magnetization layer. Variation of thickness in low magnetization layer did nt nearly influenced the resonated field of the high magnetization layer. Also, the increase of negative surface anisotropy increased the resonance field of the low and the high magnetization layer.

• Journal of Magnetics
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• 제11권3호
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• pp.130-134
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• 2006

The microwave power absorption for the patterned CoNbZr magnetic film has been investigated by coplanar waveguide method. The power absorption peaks of the patterned CoNbZr film (50 ${\mu}m$ ${\times}$ 2 mm ${\times}$ 2 ${\mu}m$), were observed at around 5.7 GHz. The observed resonance peak was in good agreement with calculated ferromagnetic resonance frequency including magnetic shape anisotropy effects. Compared with the coplanar waveguide without a magnetic film, the characteristic impedance of patterned film was shown to be increased. This resulted from the large increment of inductance up to 33 % without any significant changes of the capacitance.

• 한국가구학회지
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• 제19권6호
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• pp.420-427
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• 2008

To study the suitability of chestnut as a cask for ripening traditional liquors, the absorption property for pure water, liquor with 30% alcohol content and ethanol with 95% alcohol content were investigated for five species. Oriental oak had the greatest amount of liquid absorption while chestnut had the smallest amount. The absorption amount linearly increased with increasing soaking time. The absorption amounts for each section were greatest in RT plane, and the difference between LR plane and LT plane was very small for all soaking conditions. The anisotropy of absorption amount for five species was greatest in Japanese cedar and was smallest in white mulberry on the whole. And the change of absorption amounts according to soaking conditions tended to decrease in softwoods and increase in hardwoods, and the difference among wood species was not clear. From this result, it was found that chestnut with a small absorption amount, regarding of soaking behavior, was a good material as a cask for ripening traditional liquors, whereas small diameter oriental oak with a great absorption amount was not suitable in this purpose.

• Bulletin of the Korean Chemical Society
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• 제24권11호
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• pp.1675-1679
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• 2003

The photodynamics of excited-state intramolecular proton transfer reaction of 1-hydroxyanthraquinone (1-HAQ) and 1-deuterioanthraquinone was investigated in toluene with time-resolved emission and femtosecond transient transmittance techniques at room temperature. The temporal profiles of transient transmittance of 1-HAQ could be well described with multi-decaying time constants. The ultrafast time constant within ca. 260 fs reflects the dynamics of proton transfer. The decay component of 2 ps is assigned to an additional proton translocation process induced by the intramolecular vibrational relaxation, whereas the decay component of 18 ps is assigned to the vibrational cooling process, while the long component (200 ps) can be explained in terms of the relaxation from excited-state keto-tautomer to its ground state. Time-resolved anisotropy decay dynamics and isotope effects on the photodynamics reveals that the ESIPT from enol-tautomer to keto-one of 1-HAQ is barrierless reaction and coupled to a vibrational relaxation process.

• 한국초전도ㆍ저온공학회논문지
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• 제24권2호
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• pp.19-22
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• 2022

We studied the effect of substrate-induced strain state on the superconducting transition in GdBa₂Cu₃O_7-x(GdBCO)/La_0.7Sr_0.3MnO₃ (LSMO) bilayers deposited on a LaAlO₃ (LAO) substrate. The stain state of LSMO is controlled by increasing the thickness from 20 nm to 80 nm. Analyses on the extended X-ray absorption fine structure (EXAFS) measurements reveal difference in the direction of MnO₆ octahedral distortion depending on the LSMO thickness, which leads to a difference in anisotropy of magnetization of LSMO layer. The superconducting transitions of our system are strongly correlated with the magnetic anisotropy accompanied by the MnO₆ octahedron distortion in a specific direction. This result suggests the possibility of improving the superconducting transition in the GdBCO/LSMO bilayer system by controlling the degree of competition between superconductivity and ferromagnetism via adjusting strain state in the LSMO layer.