• Bulletin of the Korean Chemical Society
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• v.28 no.9
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• pp.1523-1530
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• 2007

The first reduction peak of the cyclic voltammogram (CV) for sulfur reduction in dimethyl sulfoxide has been studied using time resolved Fourier transform electrochemical impedance spectroscopic (FTEIS) analysis of small potential step chronoamperometric currents. The FTEIS analysis results reveal that the impedance signals obtained during short potential steps can be resolved into electron transfer reactions of two different time constants in a high frequency region. The FTEIS method provides snap shots of impedance profiles during an earlier phase of the reaction, leading to time resolved EIS measurements. Our results obtained by the FTEIS analysis are consistent with a series of electron transfer and chemical equilibrium steps of a complex reaction, making up an ECE (electrochemical-chemical-electrochemical) mechanism postulated from the results of computer simulation.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.2
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• pp.5-9
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• 2000

The visual evoked potential was electrophysiological method for the identify of the EEG response on visual cortex. This test was objective test method on the eye function. This study was used the visual evoked potential for the objective color test. The subjects was a normal color function in Korean adults. The test condition was performed on the differens distance and illumination. According to convergence condition of color vision target. On the appearance of EEG wave of visual stimulation on visual cortex. The most EEG wave style was delta wave, and the next amount wave form was beta wave and theta wave, and the least EEG wave form was alpha wave. The histogram of amplitude of EEG wave form was almost non-Gaussian shape, and the phase diagram of amplitude was almost all linear shape. On the kinds of color vision target, the frequency of EEG wave style appeared a similar results.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.1
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• pp.57-65
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• 2000

In this paper, a model reference adaptive control for the atomic force microscope (AFM) of tapping mode is investigated. The dynamics between the AFM system and al sample is mathematically modeled as a second order spring-mass-damper system with oscillatory inputs. The attractive and repulsive forces between the tip of the AFM system and the sample are derived using the Lennard-Jones potential energy. By non-dimensionalizing the displacement of the tip and the input frequency, the chaotic behavior near a resonance frequency is better depicted through the non-dimensionalized equations. Four nonlinear analysis techniques, a phase portrait, sensitive dependence on initial conditions, a power spectral density function, and a Pomcare map are investigated. Because the equations of motion derived in this paper involve unknown parameter values such as the damping effect of the air and the interaction constants between materials, the standard model reference adaptive control is adopted. Two control objectives, the prevention of chaos and the tracking of reference signal, are pursued. Simulation results are included.

• Biomolecules & Therapeutics
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• v.10 no.4
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• pp.287-292
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• 2002

To find new inhibitory effects from oriental drugs, Albizziae root was extracted in methanol and the extracted was stepwisely fractionated by hexane, chloroform, ethylacetate, butanol and water. In cytotoxic effect of Albizziae root fractions against cancer cell lines including human hepatoma cells(HepG2) were investigated. Expecially the butanol fraction exhibited a inhibition effects on the growth of human hepatoma cells(HepG2). It inhibited of HepG2 cells with the value of IC50. The activities of qutathione after B(a)P treatment were markedly decreased than control, but those levels were increased by the treatment of Albizziae root methanol fraction. The activity of glutathione-S-transferase after B(a)P treatment were markedly decreased than control, but those levels were increased by the treatment of Albizziae root methanol traction. Induction of phase II enzymes is a major mechanism of chemoprevention. The induction levels of quinone reductase(QR) activity in cultured murine hepatoma(Hepa IcIc7)cell by methanol extract of Albizziae root were measured. Among the tested tractions, the extracts of butanol were found to induce QR activities over 2.8 fold than control. These results suggest that Albizziae root has chemopreventive Potential by inducing QR activities and GST levels and increasing GSH

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.741-742
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• 2016

Secure Coding is in the development phase, removing a potential security vulnerability that could lead to attacks such as hacking in advance, says the technique to develop secure software from external attacks. In this paper, we'll learn about the needs and expectations of the effectiveness of these security software development. Due to this, the threat to the safe software development project, and there is an effect to improve quality.

• Food Engineering Progress
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• v.21 no.3
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• pp.215-224
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• 2017

Resveratrol was incorporated into various combinations of single- and double-layer nanoemulsions, prepared by self-assembly emulsification and complex coacervation with chitosan, alginate, and ${\beta}$-cyclodextrin, respectively. Resveratrol nanoemulsions were composed of medium-chain trigacylglycerols (MCTs), $Tween^{(R)}$ 80, water, chitosan, alginate, and ${\beta}$-cyclodextrin. The corresponding mixtures were formulated for the purpose of being used as a nutraceutical delivery system. Resveratrol nanoemulsions were obtained with particle sizes of 10-800 nm, with the size variation dependent on the emulsification parameters including the ratio of aqueous phase and surfactant ratio. Resveratrol nanoemulsions were characterized by evaluating particle size, zeta-potential value, stability, and release rate. There were no significant changes in particle size and zeta-potential value of resveratrol nanoemulsions during storage for 28 days at $25^{\circ}C$. The stability of resveratrol in the double-layer nanoemulsions complexed with chitosan or ${\beta}$-cyclodextrin was higher, compared with the single-layer nanoemulsions.

• Clean Technology
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• v.27 no.3
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• pp.217-222
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• 2021

Although monolayer black phosphorus (BP) and few-layer BP nanosheets (NSs) have been extensively studied as promising alternatives to graphene, research has focused primarily on atomically thin-layered BP in an isolated form. In order to realize the practical applications of BP-related devices, a BP film based on continuous networking of few-layer BP NSs should be developed. In this study, a transparent BP film with high quality was fabricated via a vacuum filtration method. An oxygen-free water solvent was used as an exfoliation medium to avoid significant oxidation of the few-layer BP NSs in liquid-phase exfoliation. The exfoliation efficiency from bulk BP to the few-layer BP NSs was estimated at 22%, which is highly efficient for the production of continuous BP film. The characteristics of the high-quality BP film were determined as 98% transparency, minimum oxidation of 18%, structural stability, and an appropriate bandgap of about 1.8 eV as a semiconductor layer. In order to demonstrate the potential of the BP film for photocatalytic activity, we performed photoelectrochemical water oxidation of the transparent BP film. Although its performance should be improved for practical applications, the BP film could function as a photoanode, which offers a new potential semiconductor in water oxidation. We believe that if the BP film is adequately engineered with other catalysts the photocatalytic activity of the BP film will be improved.

• Biomolecules & Therapeutics
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• v.30 no.3
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• pp.257-264
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• 2022

Colorectal cancer (CRC) is one of the most common malignant tumor. 5-FU is commonly used for the treatment of CRC. However, the development of drug resistance in tumor chemotherapy can seriously reduce therapeutic efficacy of 5-FU. Recent data show that FoxM1 is associated with 5-FU resistance in CRC. FoxM1 plays a critical role in the carcinogenesis and drug resistance of several malignancies. It has been reported that urushiol V isolated from the cortex of Rhus verniciflua Stokes is cytotoxic to several types of cancer cells. However, the underlying molecular mechanisms for its antitumor activity and its potential to attenuate the chemotherapeutic resistance in CRC cells remain unknown. Here, we found that urushiol V could inhibit the cell proliferation and induced S-phase arrest of SW480 colon cancer cells. It inhibited protein expression level of FoxM1 through activation of AMPK. We also investigated the combined effect of urushiol V and 5-FU. The combination treatment reduced FoxM1 expression and consequently reduced cell growth and colony formation in 5-FU resistant colon cancer cells (SW480/5-FUR). Taken together, these result suggest that urushiol V from Rhus verniciflua Stokes can suppress cell proliferation by inhibiting FoxM1 and enhance the antitumor capacity of 5-FU. Therefore, urushiol V may be a potential bioactive compound for CRC therapy.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.1
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• pp.56-65
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• 2022

The electrochemical corrosion properties of austenitic AISI 304 steel subjected to a long-term-aging heat treatment were investigated. AISI 304 steel was aged at 700 ℃ for up to 10,000 h. The variation in the microstructure of the aged specimens was observed by optical microscopy and scanning electron microscopy. Electrochemical polarization experiments were performed to obtain the corrosion current density (Icorr) and corrosion potential (Ecorr). Analyses indicated that the metastable intermetallic carbide M₂₃C₆ formed near the γ/γ grain boundary and coarsened with increasing aging time; meanwhile, the δ-ferrite decomposed into the σ phase and into M₂₃C₆ carbide. As the aging time increased, the current density increased, but the corrosion potential of the austenitic specimen remained high (at least 0.04 ㎛/cm²). Because intergranular carbide was absent, the austenitic annealed specimen exhibited the highest pitting resistance. Consequently, the corrosion resistance of austenitic AISI 304 steel decreased as the aging heat treatment time increased.

• Current Optics and Photonics
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• v.7 no.5
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• pp.545-556
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• 2023

This paper introduces volume-sharing multi-aperture imaging (VMAI), a potential approach proposed for volume reduction in space-borne imagers, with the aim of achieving high-resolution ground spatial imagery using deep learning methods, with reduced volume compared to conventional approaches. As an intermediate step in the VMAI payload development, we present a phase-1 design targeting a 1-meter ground sampling distance (GSD) at 500 km altitude. Although its optical imaging capability does not surpass conventional approaches, it remains attractive for specific applications on small satellite platforms, particularly surveillance missions. The design integrates one wide-field and three narrow-field cameras with volume sharing and no optical interference. Capturing independent images from the four cameras, the payload emulates a large circular aperture to address diffraction and synthesizes high-resolution images using deep learning. Computational simulations validated the VMAI approach, while addressing challenges like lower signal-to-noise (SNR) values resulting from aperture segmentation. Future work will focus on further reducing the volume and refining SNR management.