• Journal of Advanced Research in Ocean Engineering
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• v.2 no.2
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• pp.48-60
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• 2016

Accurate simulation of free-surface wave flows around a ship is very important for better hull-form design. In this paper, a computational fluid dynamics (CFD) code which is based on the open source libraries, OpenFOAM, was developed to predict the wave patterns around a ship. Additional anti-diffusion source term for minimizing a numerical diffusion, which was caused by convection differencing scheme, was considered in the volume-fraction transport equation. The influence of the anti-diffusion source term was tested by applying it to free-surface wave flow around the Wigley and KCS model ships. In results, the wave patterns and hull wave profiles of the Wigley and KCS model ships for various anti-diffusion coefficients showed quite close patterns. While, the band width of the water volume-fraction values between 0.1 to 0.9 at the Wigley and KCS model hull surfaces was narrowed by considering the anti-diffusion term. From the results, anti-diffusion source term decreased free-surface smearing.

• Journal of computational fluids engineering
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• v.19 no.1
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• pp.15-20
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• 2014

Accurate simulation of free-surface wave flows around a ship is very important for better hull-form design. In this paper, a computational fluid dynamics (CFD) code, termed SNUFOAM, which is based on the open source libraries, OpenFOAM, was developed to predict the wave patterns around a ship. Additional anti-diffusion source term for minimizing a numerical diffusion, which was caused by convection differencing scheme, was considered in the volume-fraction transport equation. The influence of the anti-diffusion source term was tested by applying it to free-surface wave flow around the Wigley model ship. In results, the band width of the volume fraction contours between 0.1 to 0.9 at the hull surface was narrowed by considering the anti-diffusion term.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.104-105
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• 2014

In this study, fundamental properties of mortar with the variation of dosage of anti-rust agent has been tested to evaluate the effect of the anti-rust agent. Dosage of anti-rust agent was fixed as 0,3,6,9%, respectively. The variation of the flow, compressive strength and diffusion speed of chloride ion has been tested to evaluate the effect of the anti-rust agent. Results showed that flow has been smally increased. For the compressive strength, compressive strength increased with the increase of dosage of agent. For the diffusion speed of chloride, the speed decreased with the increase of dosage of the anti-rust agent. For the overall consideration, it could be identified that when the dosage of anti-rust agent was fixed as 3-6%, the mortar showed the optimum performances.

• Journal of Ocean Engineering and Technology
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• v.23 no.4
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• pp.64-68
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• 2009

It has been observed that coated steel structures deteriorate more rapidly than the designed lifetime due to acid rain caused by air pollution, etc. Therefore, improving the corrosion resistance of anti-corrosive paint is very important in terms of safety and the economic point of view. In this study, the corrosion resistance of five kinds of anti-corrosive paints, including the Acryl, Fluorine, and Epoxy resin series, were investigated with electrochemical methods, such as corrosion potential measurements, polarization curves, diffusion limiting current density, etc. As a result, the corrosion resistance of the F101 specimen with the fluorine resin series was found to be superior to the other specimens, while E100 with the epoxy resin series also showed a somewhat good corrosion resistance. Furthermore, it was observed that the amount of water and oxygen entering the inner side of a painted film increased with an increase in immersion time, irrespective of the kind of resin series. However, the oxygen diffusion limiting current density of a specimen with good corrosion resistance was relatively decreased compared to other specimens, because of the difficulty of oxygen diffusion penetrating to the inner side of the film. Consequently it is suggested that we can qualitatively evaluate the corrosion resistance of an anti-corrosive paint by measuring the diffusion limiting current density as an electrochemical method.

• Journal of the Korean institute of surface engineering
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• v.51 no.5
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• pp.297-302
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• 2018

The important drawback of hardware fasteners consisted of 304 stainless steel (STS) is a frequent galling caused by a combination of friction and adhesion between the sliding surface. To improve the anti-galling effect, Sn-Al coatings by a thermal diffusion have been developed. The thermal diffusion by pack cementation with an $AlCl_3$ activator at $250^{\circ}C$ for 1 hour produced an Sn-Al alloy coating layer with an average thickness of $9.9{\pm}0.5{\mu}m$ on the surface of 304 STS fasteners. Compared with the galling frequency of the 304 STS fasteners, Sn-Al coatings on the surface of 304 STS fasteners demonstrated about 2.8-time reduction of the galling frequency.

• Corrosion Science and Technology
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• v.13 no.5
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• pp.195-203
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• 2014

Modern industry has a wide variety of application areas such as ocean industry, construction and automobile industry. With the current circumstances, the need for anti-corrosion technology that can be used on materials to withstand in harsh environments, is increasing. In this study, we have sought to develop a metal coating technology with zinc and aluminum powders as a potential anti-corrosion material. To make a coating on metal products, a thermal diffusion coating method was used under the conditions of $350^{\circ}C$ for 30 minutes. Optical microscope, Field emission scanning electron microscope (FE-SEM&EDX) and X-ray diffraction analysis were used to analyze a coating layer. As a result, we have confirmed that the generated amount of rust on metal parts coated with thermal diffusion coating method decreased dramatically compared with non-coated metal parts. Furthermore, the anti-corrosion performance was evaluated according to the different ratio of zinc and aluminum. Finally, we confirmed the possibility of application and commercialization of our coating technique on metal parts used in harsh industrial based on the results of these performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.12
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• pp.2271-2282
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• 2006

This paper is concerned with simulation issues arising in the PDE-based image restoration such as the total variation minimization(TVM) and its generalizations. In particular, we study the issues of staircasing and excessive dissipation of TVM-like smoothing operators. A strategy of scaling the algebraic system and a non-convex minimization are considered respectively for anti-staircasing and anti-diffusion. Furthermore, we introduce a variable constraint parameter to better preserve image edges. The resulting algorithm has been numerically verified to be efficient and reliable in denoising. Various numerical results are shown to confirm the claim.

• Journal of Korea Multimedia Society
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• v.22 no.6
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• pp.684-694
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• 2019

Information spread in networks is universal in many real-world phenomena such as propagation of infectious diseases, diffusion of a new technology, computer virus/spam infection in the internet, and tweeting and retweeting of popular topics. The problem of finding the information source is to pick out the true source if information spread. It is of practical importance because harmful diffusion can be mitigated or even blocked e.g., by vaccinating human or installing security updates. This problem has been much studied, where it has been shown that the detection probability cannot be beyond 31% even for regular trees if the number of infected nodes is sufficiently large. In this paper, we study the impact of an anti-information spreading on the original information source detection. We consider an active defender in the network who spreads the anti-information against to the original information simultaneously and propose an inverse Voronoi partition based inference approach, called Voronoi Inference to find the source. We perform various simulations for the proposed method and obtain the detection probability that outperforms to the existing prior work.

• Journal of the East Asian Society of Dietary Life
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• v.26 no.3
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• pp.215-222
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• 2016

This study was carried out to investigate the antimicrobial and anti-inflammatory activities of ethanol extract from Glycyrrhizae radix (GR) and ethanol extract from Glycyrrhizae radix cultured with Paecilomyces japonica mycelium (GRPM). Antimicrobial activity was measured by paper disc diffusion assay and minimum inhibitory concentration (MIC). Anti-inflammatory activity was evaluated by measurement of NO production in LPS-stimulated RAW264.7 cells. For the results of the paper disc diffusion assay, GRPM showed high antimicrobial activities against Bacillus cereus, Listeria monocytogenes, and Staphylococcus aureus. In addition, the MIC of GRPM (100 ppm) was lower than that of GR (200 ppm) against L. monocytogenes. When the morphology of L. monocytogenes treated with GRPM was observed using a FE-SEM, the surface of cells treated with GRPM were damaged, and some parts of the cell wall were destroyed. The inhibitory effect on NO production in LPS-stimulated RAW264.7 cells was significantly increased by GRPM treatment. In conclusion, GRPM is superior to GR in terms of antimicrobial and anti-inflammatory activities.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.32 no.1 s.55
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• pp.53-58
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• 2006

Agrimonia pilosa Ledeb. is a perennial plant, which naturally habitats in whole area of Korea, and where it is popularly used for the traditional remedies. In the present study, A. pilosa Ledeb. extract was prepared to determine the anti-acne effects and application possibility as a cosmetic resource. A pilosa Ledeb. was extracted with methanol and its anti-acne effect against Propionibacterium acnes was investigated via minimum inhibitory concentration (MIC) and paper disk diffusion method. The MIC of A. pilosa Ledeb. extract and triclosan was 0.05 mg/mL and 0.04 mg/mL, respectively. This implies that A. pilosa Ledeb. extract nay be an efficient anti-acne ingredient for cosmetics, considering that it is a crude extract. The paper disk diffusion assay showed that its anti-acne effect was similar to that of triclosan. Furthermore, A. pilosa Ledeb. extract effectively inhibited the growth of several aerobic microorganisms including Staphylococcus aureus. Finally, we examine the stability of the extract to temperature and pH. The extract was very stable to high temperatures ($70{\sim}121^{\circ}C$) and to pH ($pH 2{\sim}11$), suggesting its utilization for cosmetics.