• Macromolecular Research
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• 제9권6호
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• pp.339-344
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• 2001

In order to investigate the photoalignment mechanism of nematic liquid crystals on a polymer film, a new photoreactive polymer having chalcone groups as side chains was synthesized. Linearly polarized UV light causes preferential photoreactions of the chalcone unit along the polarization direction and thus induces the anisotrpy in the polymer alignment layer resulting in homogeneous LC alignment perpendicular to the polarization direction. The sequential investigations of photoalignment generated by the preferential E/Z isomerization and (2+2) cycloaddition reactions show that either photoreaction can solely induce the LC alignment in the direction perpendicular to UV polarization.

• Natural Product Sciences
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• 제8권4호
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• pp.147-151
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• 2002

In the course of our work on anti-platelet constituents from plants, eight phenolic compounds, $({\pm})-syringaresinol$ (1), 4-hydroxybenzaldehyde (2), 4-hydroxybenzoic acid (3), vanillic acid (4), 4-hydroxy cinnamic acid (5), quercetin 3-O-rhamnoside (6), rutin (7), and quercetin $3-(2^G-rhamnosylrutinoside)$ (8) were isolated from the methanol extract of the leaves of Magnolia obovata. The compounds were identified based on the spectroscopic data. Compound 2, 3, 5, 6, 7 and 8 were isolated for the first time from genus Magnolia. 1 and 6 showed same order of inhibitory potencies as acetylsalicylic acid (ASA) to rat platelet aggregation induced by all the stimulators tested. The remaining six compounds showed only mild effects.

• 한국해양공학회지
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• 제27권5호
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• pp.36-42
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• 2013

We present the optimum design for the cross-sectional(sizing) and shape optimization of truss structures with natural frequency constraints. The optimum design method used in this paper employs continuous design variables and the Harmony Search Algorithm(HSA). HSA is a meta-heuristic search method for global optimization problems. In this paper, HSA uses the method of random number selection in an update process, along with penalty parameters, to construct the initial harmony memory in order to improve the fitness in the initial and update processes. In examples, 10-bar and 72-bar trusses are optimized for sizing, and 37-bar bridge type truss and 52-bar(like dome) for sizing and shape. Four typical truss optimization examples are employed to demonstrate the availability of HSA for finding the minimum weight optimum truss with multiple natural frequency constraints.

• Bulletin of the Korean Chemical Society
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• 제2권2호
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• pp.56-59
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• 1981

In this paper a further generalization of the theory of multilayer physical adsorption previously developed by the authors is attempted so that the effect of vertical interactions between adsorbent and adsorbate can be explicitly taken into account. In this attempt we have to discard the previously adopted assumption that the molecules in the second layer or above are all in the same physical state. In order to estimate the effect of vertical interactions on the adsorption isotherm the interaction energy between an adsorbed molecule and the adsorbent surface is assumd to vary as $r^{-3}$ where r is the distance that the molecule under consideration is separated from the adsorbent surface. Resulting adsorption isotherm is applied to interpret the adsorption data of tetramethylsilane vapor on iron film and good agreements between observed and calculated values are obtained over wide range of pressure.

• Nuclear Engineering and Technology
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• 제51권5호
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• pp.1272-1278
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• 2019

A lumped kinetic modeling platform is developed to investigate the coupled nuclear/thermo-fluid features of the closed natural circulation loop in a low power lead cooled fast reactor. This coolant material serves a reliable choice with noticeable thermo-physical safety characteristics in terms of natural convection. Boussienesq approximation is resorted to appropriately reduce the governing partial differential equations (PDEs) for the fluid flow into a set of ordinary differential equations (ODEs). As a main contributing step, the coolant circulation speed is accordingly correlated to the loop operational power and temperature levels. Further temporal analysis and control synthesis activities may thus be carried out within a more consistent state space framework. Nyquist stability criterion is thereafter employed to carry out a sensitivity analysis for the system stability at various power and heat sink temperature levels and results confirm a widely stable natural circulation loop.

• Journal of Electrochemical Science and Technology
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• 제13권3호
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• pp.347-353
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• 2022

Agarose hydrogel, a solid electrolyte, was investigated voltammetrically in terms of transport properties and natural convection effects using a ferrocenyl compound as a redox probe. To confirm the diffusion properties of solute on the agarose interface, the diffusion coefficients (D) of ferrocenemethanol in agarose hydrogel were determined by cyclic voltammetry (CV) according to the concentration of agarose hydrogel. While the value of D on the agarose interface is smaller than that in the bulk solution, the square root of the scan rate-dependent peak current reveals that the mass transport behavior of the solute on the agarose surface shows negligible convection or migration effects. In order to confirm the reduced natural convection on the gel interface, scan rate-dependent CV was performed in the solution phase and on the agarose surface, respectively. Slow scan voltammetry at the gel interface can determine a conventional and reproducible diffusion-controlled current down to a scan rate of 0.3 mV/s without any complicated equipment.

• 한국토양동물학회지
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• 제2권1호
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• pp.41-58
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• 1997

According to the related references, up to now the systematic studies on the ants from Mt. Moak have not been professionally surveyed yet. On order to classify the the ants from Mt. Moak, authors had collected the ants in this area from Octorber, 1993 to June, 1995. Examining all the collections, 44 species of 23 genera of 17 tribes under 3 subfamilies were identified.

• 풍력에너지저널
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• 제4권2호
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• pp.17-24
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• 2013

Idealized PID-controlled rotor-speed error for blade pitch control of wind turbines responds as a second-order system with natural frequency and damping ratio for closed-loop system. RISO National Laboratory has recommended specific natural frequency(=0.6 rad/s) and damping ratio(=0.7) for 2 MW wind turbine. The baseline controller for 5 MW wind turbine of NREL(National Renewable Energy Laboratory) is designed based on the same values of RISO recommendation. This study investigates the effect of the natural frequency and damping ratio of the controller for NREL 5 MW wind turbine. It is confirmed that RISO recommendation shall be tuned for each wind turbine.

• 한국강구조학회 논문집
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• 제9권4호통권33호
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• pp.601-609
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• 1997

본 연구에서는 4개의 변수로 구성된 단순화된 고차전단변형이론에 근거한 복합적층판의 휨과 진동결과를 해석하였으며 적층판의 배열형태는 중립축을 중심으로 역대칭으로 적층되어있고 변수를 1개 줄여 해석하여도 기존의 고차전단변형이론의 결과와 비교하여 정확도에 큰 차이가 없음을 알 수 있었다. 단순화된 고차전단변형이론에 의한 결과를 1차전단변형이론과 3차전단변형이론에 의한 해와 비교 분석하였으며 복합재료 설계자나 이론과 실험의 상관관계를 연구하는 연구자 혹은 프로그램의 정확도를 검증하려고 하는 수치해석자들을 위해 결과자료들을 도표화하였다.

• 한국약용작물학회지
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• 제18권5호
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• pp.291-297
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• 2010

Liriope platyphylla has been though as an useful medical plant to improve the cough, sputum, neurodegenerative disorders, obesity, and diabetes in Korea and China from old times. In order to investigate the effects of Liriope platyphylla on expression and secretion of nerve growth factor (NGF), the mRNA expression and protein secretion were detected in the neuronal cell (B35) and neuroglial cell (C6) cultured with three differences concentration (5%, 10%, 15%) of Liriope platyphylla. In MTT assay and FACS anslysis, the some death of some B35 and C6 cells were observed in 15% extract-treated group, while other groups did not induce the death. Also, the mRNA expression of NGF were significantly increased in 5% and 10% extracts treated-group. Furthermore, the NGF protein concentration in supernatant collected from cultured cells showed the very similar pattern with mRNA expression. In order to verify the activity of secreted NGF, the culture supernatant collected from B35 and C6 cells cultured with Liriope platyphylla extracts for 24 hrs were treated into undifferentiated PC12 cells, and the differentiation level of PC12 cell were also observed with microscopes. The differentiation level of PC12 cell were significantly increased depend on the dose of extract. Therefore, these results suggested that the water extracts of Liriope platyphylla may contribute the regulation of NGF expression and secretion in the neuronal cell and be considered as an excellent candidate for a neurodegenerative disease-therapeutic drug.