• Structural Engineering and Mechanics
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• v.76 no.3
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• pp.293-310
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• 2020

This study derives the differential equations of free vertical bending and torsional vibrations for two- and three-pylon suspension bridges using d'Alembert's principle. The respective algorithms for natural vibration frequency and vibration mode are established through the separation of variables. In the case of the three-pylon suspension bridge, the effect of the along-bridge bending vibration of the middle pylon on the vertical bending vibration of the entire bridge is considered. The impact of torsional vibration of the middle pylon about the vertical axis on the torsional vibration of the entire bridge is also analyzed in detail. The feasibility of the proposed method is verified by two engineering examples. A comparative analysis of the results obtained via the proposed and more intricate finite element methods confirmed the former feasibility. Finally, the middle pylon stiffness effect on the vibration frequency of the three-pylon suspension bridge is discussed. It is found that the vibration frequencies of the first- and third-order vertical bending and torsional modes both increase with the middle pylon stiffness. However, the increase amplitudes of third-order bending and torsional modes are relatively small with the middle pylon stiffness increase. Moreover, the second-order bending and torsional frequencies do not change with the middle pylon stiffness.

• Composites Research
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• v.35 no.6
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• pp.412-418
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• 2022

Flame-retardant vinyl ester (VE) resin films were developed from the mixtures of brominated and non-brominated epoxy resins via esterification with methacrylic acid without reactive diluents. The films were used to fabricate carbon fiber (CF) prepregs via a hot melt impregnation process. The viscosity of VE resins suitable for film production was optimized by mixing low-viscosity bisphenol-A and high-viscosity brominated bisphenol-A epoxy precursors. Increasing the bromine content of the cured VE resin further increased the limited oxygen index (LOI) (39%), storage modulus (2.4 GPa) at 25℃ and residual carbonization (16.1%) values compared to non-brominated VE. Manual layup of as-prepared VE prepregs with subsequent curing led to the successful fabrication of CF-reinforced composites with high tensile and flexural strength. The results from the study hold high promise for a styrene-free, environmentally friendly VE composite process in the future.

• Korean Journal of Applied Biomechanics
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• v.21 no.4
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• pp.411-420
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• 2011

The purpose of this investigation was to determine whether correlations exist between balance and impact velocity, angular position, and maximum velocity of a club during drive swing. Twelve skilled golfers were recruited in this study. They were asked to perform ten swing trials and two trials were selected for analysis. Balance parameters were calculated via the force platform while kinematic variables were determined by using the Qualisys system. The results of the present study demonstrated that the average of COP velocity was faster in the medio-lateral direction rather than the anterio-posterior direction. Also, left foot's COP velocity and free torque were greater than the right foot's before impact. The range of the right foot's COP in the anterio-posterior direction before impact were correlated with the club velocity and angular position at impact. There was a negative correlation between the left foot's COP velocity before the impact and the velocity at impact. Additionally, the range and RMS of the left foot's free torque affected on the club angular position at impact and the maximum velocity at release, respectively. Finally, a negative correlation existed between the range of the right foot's free torque after the impact and club's maximum velocity at release.

• Bulletin of the Korean Chemical Society
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• v.27 no.6
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• pp.830-834
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• 2006

Lipid peroxidation induced by the reaction of cytochrome c with $H_2O_2$ was investigated. When linoleic acid micelles or phosphatidyl choline liposomes were incubated with cytochrome c and $H_2O_2$, lipid peroxidation was increased in cytochrome c and $H_2O_2$ concentrations-dependent manner. Radical scavengers, azide, formate and ethanol prevented lipid peroxidation induced by the cytochrome c/$H_2O_2$ system. Iron specific chelator, desferoxamine also prevented the cytochrome c/$H_2O_2$ system-mediated lipid peroxidation. These results suggest that lipid peroxidation may be induced by the cytochrome c/$H_2O_2$ system via the generation of free radicals. Carnosine, homocarnosine and anserine are present in the muscle and brain of many animals and human. Previous studies show that these compounds have an antioxidant function. In the present study, carnosine, homocarnosine and anserine significantly prevented the cytochrome c/$H_2O_2$ system-mediated lipid peroxidation. Carnosine and related compounds also inhibited the free radical-generating activity of cytochrome c. The results suggest that carnosine, homocarnosine and anserine may prevent lipid peroxidation induced by the cytochrome c/$H_2O_2$ system through a free radical scavenging.

• Journal of the Korean Chemical Society
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• v.51 no.4
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• pp.346-351
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• 2007

Efficient stereoselective synthesis of α,β-Unsaturated acids, α-Cyanoacrylonitriles and α-Cyanoacrylates has been carried out in the presence of NaHSO4·SiO2 under solvent?free conditions with an E-geometry.

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2002.04a
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• pp.33-40
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• 2002

We, Tong Yang Moolsan Co. Ltd. (TYM) set up the mass-production system for virus-free seed garlic via tissue culture technique. TYM's tissue culture technique is called as 'Multiple shoot propagation technique'. This technique can lead mass propagation of genetically homogeneous seed garlic in a short period because of its highly proliferation rate of in vitro shoots ($15^{10}$ /year). TYM researchers applied the technique to some selected garlic cultivars with superior characteristics and carried out field test of productivity in the inside and outside of the country for several years. According to the yearly results of field test with virus-free seed garlic, we ascertained that virus-free seed garlic can produce the highly yield increase (max. above $50\%$) and also can enhance the product quality. Consequently, we estimated that TYM's seed garlic will contribute to farmers with increase of income and can elevate the national position of garlic market in the world for its competitive power of technical and production cost.

• BMB Reports
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• v.45 no.2
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• pp.114-119
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• 2012

Salsolinol (1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline) is a compound derived from dopamine metabolism and is capable of causing dopaminergic neurodegeneration. Oxidative modification of neurofilament proteins has been implicated in the pathogenesis of neurodegenerative disorders. In this study, oxidative modification of neurofilament-L (NF-L) by salsolinol and the inhibitory effects of histidyl dipeptides on NF-L modification were investigated. When NF-L was incubated with 0.5 mM salsolinol, the aggregation of protein was increased in a time-dependent manner. We also found that the generation of hydroxyl radicals (${\bullet}OH$) was linear with respect to the concentrations of salsolinol as a function of incubation time. NF-L exposure to salsolinol produced losses of glutamate, lysine and proline residues. These results suggest that the aggregation of NF-L by salsolinol may be due to oxidative damage resulting from free radicals. Carnosine, histidyl dipeptide, is involved in many cellular defense processes, including free radical detoxification. Carnosine, and anserine were shown to significantly prevent salsolinol-mediated NF-L aggregation. Both compounds also inhibited the generation of ${\bullet}OH$ induced by salsolinol. The results indicated that carnosine and related compounds may prevent salsolinol-mediated NF-L modification via free radical scavenging.

• Advances in Traditional Medicine
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• v.10 no.4
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• pp.271-277
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• 2010

We tested to determine if Mori Cortex Radicis extract has antioxidant activities and its potential mechanism of action was explored. Anti-oxidative effects were tested by measuring free radical and nitric Oxide (NO) scavenging activity, and reducing power. Since iNOS and COX-2 are important enzymes responsible for the production of free radicals in the cell, Mori Cortex Radicis extract was tested as to whether it could inhibit iNOS and COX-2 expression in LPS stimulated Raw cells. 70% methanolic extract of Mori Cortex Radicis exerted significant DPPH free radical and NO scavenging activities. In addition, the Mori Cortex Radicis extract exerted dramatic reducing power with maximal activity observed at 1 mg/ml (11-fold over control). Production of iNOS induced by LPS was significantly inhibited by the Mori Cortex Radicis extract, suggesting it could inhibit NO production by suppressing iNOS expression. COX-2 induced by LPS was also significantly inhibited by the Mori Cortex Radicis extract. The extract contains well known antioxidant components including phenolics, flavonoids and anthocyanin at the concentration of 0.23 mg/g, 42.97 mg/g and 12.08 mg/g, respectively. These results suggest that 70% methanolic extract of Mori Cortex Radicis exerts significant anti-oxidant activity via inhibiting iNOS and COX-2 induction.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.41.3-42
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• 2016

No matter how intense magnetic flux it contains, a coronal magnetic structure has little free magnetic energy when a composing magnetic field is close to a potential field, or current-free field where no volume electric current flows. What kind of electric current system is developed is therefore a key to evaluating the activity of a coronal magnetic structure. Since the corona is a highly conductive medium, a coronal electric current tends to survive without being dissipated, so the free magnetic energy provided by a coronal electric current is normally hard to release in the corona. This work aims at clarifying how a coronal electric current system is structurally developed into a system responsible for producing a flare. Toward this end, we perform diffusive MHD simulations for the emergence of a magnetic flux tube with different twist applied to it, and go through the process of structuring a coronal electric current in a twisted flux tube emerging to form a coronal magnetic structure. Interestingly, when a strongly twisted flux tube emerges, there spontaneously forms a structure inside the flux tube, where a coronal electric current changes flow pattern from field-aligned dominant to cross-field dominant. We demonstrate that this structure plays a key role in releasing free magnetic energy via rapid dissipation of a coronal electric current, thereby producing a flare.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.5-14
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• 1999

Free vibration characteristics of a cantilevered laminated composite beam with multiple non-propagating transverse open cracks are investigated. In the present analysis a special ply-angle distribution referred to as asymmetric stiffness configuration inducing the elastic coupling between chord-wise bending and extension is considered. The multiple open cracks are modelled as equivalent rotational springs whose spring constants are calculated based on the fracture mechanics of composite material structures. Governing equations of a composite beam with open cracks are derived via Hamilton's Principle and Timoshenko beam theory encompassing transverse shear and rotary inertia effect is adopted. The effects of various parameters such as the ply angle, fiber volume fraction, crack numbers, crack positions and crack depthes on the free vibration characteristics of the beam with multiple cracks are highlighted. The numerical results show that the existence of the multiple cracks in an anisotropic composite beam affects the free vibration characteristics in a more complex fashion compared with the beam with a single crack.