• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.5
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• pp.83-91
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• 2015

With varying conditions of concrete surface, induced chloride contents are changed and this is a key parameter for steel corrosion and service life in RC (Reinforced Concrete) structures. Many surface enhancement techniques using impregnation have been developed, however the evaluation techniques for chloride behavior through doubly layered media and time-dependent diffusion are rarely proposed. This paper presents an analysis technique considering double-layer concrete and time-dependent diffusion behavior, and the results are compared with those from the previous test results through reverse analysis. The chloride profiles from the surface-impregnated concrete exposed to atmospheric, tidal, submerged zone for 2 years are adopted. Furthermore surface chloride contents and diffusion coefficients are obtained, and are compared with those from Life365. Through consideration of time effect, the relative error decreases from 0.28 to 0.20 in atmospheric, 0.29 to 0.11 in tidal, and 0.54 to 0.40 in submerged zone, respectively, which shows more reasonable results. Utilizing the diffusion coefficients from Life365, relative errors increases and it needs deeper penetration depth (e) and lower diffusion coefficient ratio ($D_1/D_2$) due to higher diffusion coefficient.

• Journal of Physiology & Pathology in Korean Medicine
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• v.18 no.3
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• pp.863-867
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• 2004

Herba Patriniae(HP) has been known to exert anti-inflammation and -tumoral activity in Korea. However, its molecular mechanism of action is not understood. In this study, we found that HP extract induced apoptosis in androgen-dependent prostate cancer LNCaP cells as evidenced by DNA fragmentation. Our data demonstrated that HP extract-induced apoptotic cell death was accompanied by inhibition of NF- κB activation, lowering effects of intracellular prostate specific antigen(PSA) and androgen reoeptor(AR) expression in a time dependent manner. Taken together, HP extract may inhibit the proliferation of prostate cancer LNCaP cell associated with inhibition of NF- κB activation, PSA and AR expression and that of apoptosis.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.236-236
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• 2006

Time-resolved photoluminescence spectroscopy measurements of oligofluorenes with various side chains were studied. With extremely pure oligofluorenes, two kinds of red-shifted green emission were observed which have different origins; aggregate formation and on-chain chemical defect. The green emission around 490 nm was largely dependent upon the intermolecular interaction of oliglfuorene molecules. Moreover, by using oligofluorene with high-order liquid crystalline phase, we observed that the green emission was strongly dependent upon the molecular packing in solid films.

• Transactions on Control, Automation and Systems Engineering
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• v.2 no.2
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• pp.98-103
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• 2000

This paper is concerned with a delay-dependent sliding mode scheme for the robust stabilization of input-delay systems with bounded unknown uncertainties. A sliding surface based ona predictor is proposed to minimize the effect of the input delay. Then, a robust control law is derived to ensure the existence of a sliding mode on the surface. In input-delay systems, uncertainties given during te delayed time are not directly controlled by the switching control because of causality prolem of them. They can influence the stability of the system in the sliding mode. Hence, a delay-dependent stability analysis for reduced order dynamics is employed to estimate maximum delay bound such that the system is globally asymptotically stable in the sliding mode. A numerical example is given to illustrate the design procedure.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.579-585
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• 2008

Numerous experimental investigations on metallic materials and solid polymers have shown that relaxation behavior is nonlinearly dependent on prior strain rate. The stress drops in a constant time interval nonlinearly increase with an increase of prior strain rate. And the relaxed stress associated with the fastest prior strain rate has the smallest stress magnitude at the end of relaxation periods. This paper deals with the performance of three classes of unified constitutive models in predicting the characteristic behaviors of relaxation. The three classes of models are categorized by a rate sensitivity of kinematic hardening rule. The first class uses rate-independent kinematic hardening rule that includes the competing effect of strain hardening and dynamic recovery. In the second class, a stress rate term is incorporated into the rate-independent kinematic hardening rule. The final one uses a rate-dependent format of kinematic hardening rule.

• Environmental Analysis Health and Toxicology
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• v.24 no.1
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• pp.63-70
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• 2009

Naringenin, major one of the citrus flavonoids, have been identified that exert antioxidative, anticancer effects. The present study investigated the effects of naringenin on tumor invasion and matrix metalloproteinases(MMPs) activities. Naringenin inhibited cell invasion of HT-1080 fibrosarcoma cells in a dose-dependent manner. The activities of MMP-2 and MMP-9 were inhibited by naringenin as demonstrated by gelatin zymography assay. Furthermore, the amounts of MMP-2, MMP-9, and MT1-MMP mRNA were analyzed in the cells. MMP-2, MMP-9, and MT1-MMP mRNA expression were suppressed by naringenin with time and dose-dependent. These results demonstrate that anti-metastatic activities of naringenin resulted from blocking of invasion of the HT-1080 cells. Taken together, the results of this studies provide evidence that naringenin possess an anti-metastatic activity.

• YAKHAK HOEJI
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• v.39 no.3
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• pp.337-345
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• 1995

The effects of ginkgolides(natural mixture of ginkgolides, ginkgolide B, ginkgolide C) and flavonoids(quercetin, kaempferol, myricetin), extracted from Ginkgo biloba, on ADP and PAF-induced platelet aggregation in vitro and ex vivo were investigated. In these experiments, both of ginkgolides and ginkgoflavonoids did not affect the ADP(5 $\mu{M}$) induced platelet aggregation in vitro. The IC$_{50}$ value on PAF (0.3 $\mu{M}$) induced platelet aggregation were 2.52 $\mu{M}$ (ginkgolide B) and 6.35 $\mu{M}$ (natural mixture of ginkgolides) and 2.80 $\mu{M}$ (mixture of ginkgolide B and quercetin). Oral administration of ginkgolide B (1 and 3 mg/kg) and quercetin (3 and 9 mg/kg) to rabbits inhibited ex vivo PAF induced platelet aggregation in a dose-dependent manner. Ginkomin-F tablets administered to the diabetic patients showed inhibitory activities on the ADP and PAF induced platelet aggregation in a dose and time dependent manner.

• Journal of the Korean Physical Society
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• v.73 no.11
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• pp.1675-1678
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• 2018

Methylammonium lead halide ($MAPbI_3$) perovskites are considered as promising materials owing to their excellent optical and electrical properties. However, perovskite materials suffer from degradation in air, which limits their practical applications. Here, we demonstrate successful passivation of the $MAPbI_3$ photodetectors through monochloro-para-xylylene (Parylene-C) deposition. The time-dependent photocurrent characteristics were systematically investigated, and we achieved significantly improved device performance and stability with Parylene-C passivation. Based on the excitation-power-dependent photoluminescence (PL) data, we confirmed that Parylene-C can reduce the carrier losses in $MAPbI_3$, leading to the enhancement of photocurrent and PL in $MAPbI_3$ photodetectors.

• Steel and Composite Structures
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• v.46 no.5
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• pp.637-647
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• 2023

Nonlinear free vibration and stability responses of a carbon nanotube reinforced composite beam under temperature rising are investigated in this paper. The material of the beam is considered as a polymeric matrix by reinforced the single-walled carbon nanotubes according to different distributions with temperature-dependent physical properties. With using the Hamilton's principle, the governing nonlinear partial differential equation is derived based on the Euler-Bernoulli beam theory. In the nonlinear kinematic assumption, the Von Kármán nonlinearity is used. The Galerkin's decomposition technique is utilized to discretize the governing nonlinear partial differential equation to nonlinear ordinary differential equation and then is solved by using of multiple time scale method. The critical buckling temperatures, the nonlinear natural frequencies and the nonlinear free response of the system is obtained. The effect of different patterns of reinforcement on the critical buckling temperature, nonlinear natural frequency, nonlinear free response and phase plane trajectory of the carbon nanotube reinforced composite beam investigated with temperature-dependent physical property.

• Structural Engineering and Mechanics
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• v.73 no.6
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• pp.725-735
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• 2020

The present investigation deals with the thermomechanical interactions in an orthotropic thermoelastic homogeneous body in the context of fractional order theory of thermoelasticity due to time harmonic sources. The application of a time harmonic concentrated and distributed sources has been considered to show the utility of the solution obtained. Assuming the disturbances to be harmonically time dependent, the expressions for displacement components, stress components and temperature change are derived in frequency domain. Numerical inversion technique has been used to determine the results in physical domain. The effect of frequency on various components has been depicted through graphs.