• Journal of Electrochemical Science and Technology
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• v.11 no.2
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• pp.117-131
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• 2020

The adsorption of N-[(E)-Pyridin-2-ylmethylidene] aniline, a Schiff base, on to mild steel surface in 1M HCl and 0.5 M H₂SO₄ solutions and the consequent corrosion protection were studied employing weight loss method, electrochemical impedance spectroscopy and potentiodynamic polarization measurements. DFT calculations were performed to investigate its interaction with the metal surface at the atomic level to understand its inhibition mechanism. The adsorption process is well described by the Langmuir isotherm. The thermodynamic parameters indicated that the adsorption is spontaneous and the interaction of the inhibitor at the mild steel surface is mainly through physisorption. The R_a values obtained in AFM studies for the uninhibited and inhibited sample in HCl media respectively are 0.756 and 0.559 ㎛, and that in H₂SO₄ media are 0.411 and 0.406 ㎛. The lesser roughness values of the inhibited sample shows the adsorption of the molecules onto the mild surface. The inhibition efficiencies were found to improve with concentration of the inhibitor and the maximum efficiency was observed at 400ppm in all the investigation methods adopted. The inhibitor was found to exhibit a higher efficiency in HCl media (95.7%) than in H₂SO₄ (92.8%). The theoretical and experimental results are found to be in good agreement.

• Journal of Electrochemical Science and Technology
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• v.7 no.4
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• pp.251-262
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• 2016

The corrosion protection of mild steel in 1M HCl and 0.5M $H_2SO_4$ solutions by ethanol extract of Vernonia amygdalina (VA) was studied using a combination of experimental and computational methods. The obtained results revealed that VA reduced the corrosion of mild steel in both environments and inhibition efficiency increased with VA concentration but decreased with prolonged exposure. Electrochemical results showed that the extract functioned via mixed corrosion inhibiting mechanism by adsorption of some organic constituents of the extract on the metal/acid interface. Findings from infrared spectroscopy and electron microscopy all confirmed that VA retarded mild steel corrosion in both 1M HCl and 0.5M $H_2SO_4$ through an adsorption process. The adsorption behavior of selected constituents of the extract was modeled using density functional theory computations.

• Journal of the Korean Mathematical Society
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• v.60 no.3
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• pp.619-634
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• 2023

This paper considers a parabolic-hyperbolic-hyperbolic type chemotaxis system in ℝ^d, d ≥ 3, describing tumor-induced angiogenesis. The global existence result and temporal decay estimate for a unique mild solution are established under the assumption that some Sobolev norms of initial data are sufficiently small.

• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.403-424
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• 1996

Cell culture methods have been used to assess the cytotoxicity of dental materials. Different paramaters are used to monitor cytotoxic effects. But it is difficult to compare each investigator's results with different methods. The objective of this study was to investigate cytotoxic effect of several retrograde filling materials according to cell lines and assay methods. Cytotoxicity of Bestalloy (Dogmyung, Korea), Prisma APH(Densply International Inc., U.S.A.), Clearfil FII (Kuraray Co., Japan), Fuji II (GC Co., Japan), Fuji II LC (GC Co., Japan) and IRM (Densply Co., U.S.A.) on L929, 3T3 and KB permanent cell lines was measured. Radiochromium, Lactate dehydrogenase (LDH) release method and colorimetric assays, namely neutral red (NR) and MTT were used. Each material was mixed according to the manufacturer's instruction. They were tested as solid and extracted state. Cell culture media were added to each mixed or solid materials then the solution was collected and used as extract solutions. Solid Fuji II showed mild cytotoxicity on three cell lines using radiochromium release method. There was no difference in cytotoxicity of extract solution group using radiochromium release method. In colorimetric assay immediate Fuji II group and all the IRM groups showed severe cytotoxic effect. Difference in cyctotoxicity was due to rather kinds of cell lines than assay methods. Solid Fuji II and IRM showed mild cytotoxicity on three cell lines. But extract solutions had different cytotoxic effect according to cell lines using LDH release assay. Light-cured glass ionomer had mild to moderate degree of cytotoxicity on three cell lines. Cytotoxicity was affected by specimen prepaton. Susceptibility of each cell ines were also affected by assay emthods. It was suggested that cytotoxicity study using only one cell line and/or assay method might not accurately reflect the real toxic nature of dental biomaterials.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.1
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• pp.133-138
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• 2008

To analyze incident waves traveling from the deep ocean is very important in that it is based on resolving problems occurred in coastal areas. In general, numerical models and analytical solutions are used to analyze wave transformation. Although a numerical model can be applied to various bottoms and wave conditions, it may have some cumbersome numerical errors. On the other hand, an analytical solution has an advantage of obtaining the solution quickly and accurately without numerical errors. The analytical solution can, however, be utilized only for specific conditions. In this study, the analytical solution of the mild-slope equation has been developed. It can be applied to various conditions combing a numerical technique and an analytical approach while minimizing the numerical errors. As a result of comparing the obtained solutions in this study with those of the previously developed numerical model, A good agreement was observed.

• Journal of applied mathematics & informatics
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• v.33 no.5_6
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• pp.699-721
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• 2015

This paper investigates the existence of mild solution for a fractional integro-differential equations with a deviating argument and nonlocal initial condition in an arbitrary separable Hilbert space H via technique of approximations. We obtain an associated integral equation and then consider a sequence of approximate integral equations obtained by the projection of considered associated nonlocal fractional integral equation onto finite dimensional space. The existence and uniqueness of solutions to each approximate integral equation is obtained by virtue of the analytic semigroup theory via Banach fixed point theorem. Next we demonstrate the convergence of the solutions of the approximate integral equations to the solution of the associated integral equation. We consider the Faedo-Galerkin approximation of the solution and demonstrate some convergenceresults. An example is also given to illustrate the abstract theory.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06a
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• pp.67-71
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• 2006

Strong oxidizing biocides are commonly used to control biofilm formation in alkaline papermaking systems. However, paper streams contain many substances that react with or consume oxidizers (e.g., fiber and starch, Therefore, to achieve effective microbiological control, the oxidizer must be overfed to overcome the effect of these substances. When dosed in this manner, the oxidizer can cause many unwanted reactions and adverse side effects, including the consumption of costly papermaking additives increased corrosion rates, and reduced felt life. Some oxidizers also contribute to the formation of halogenated organic compounds. When used for biofilm control, strong oxidizers can cause more problems than they remedy. A patented biocide that effectively controls biofilm without the adverse side effects associated with strong oxidizing biocides is available from Hercules. $Spectrum^{(R)}$ XD3899 Ammonium Bromide Technology, which can be described as a mild oxidizer, is currently used on more than 300 machines globally and has resulted in numerous production and/or machine efficiency records since its introduction in 2001.

• Restorative Dentistry and Endodontics
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• v.18 no.1
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• pp.95-102
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• 1993

Two functions of root canal medicaments and irrigants are to reduce microorganisms and to encourge the repair of apical tissues. The biocompatibility of endodontic materials has been tested using in vitro cell culture techniques. The purpose of this study Was to evaluate and compare the cytotoxic effects of 2 root canal irrigation solutions and 4 antiseptics on HEp-2 and McCoy cells. Two irrigation solutions were sodium hypochlorite. $H_2O_2$ and 4 antiseptics were povidone, ethanol, glutaraldehyde and benzalkonium chloride. Each solutions were serially diluted to 1:1, 1:10, 1:$10^2$, 1:$10^3$, 1:$10^4$, 1:$10^5$, 1:$10^6$. And each diluted solutions were added to the cells and cytotoxic effects were measured with the absorbance of formazan formed cells by ELISA READER. The results were as follows : 1. Benzalkonium chloride was the most cytotoxic on HEp-2 cell. (P<0.05) 2. $H_2O_2$ was the most cytotoxic on McCoy cell. (P<.05) 3. Povidone and ethanol showed mild cytotoxic effect on HEp-2 and McCoy cell. (P<0.05).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.2
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• pp.117-126
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• 2009

In order to test the accuracy between the modified mild slope equation (MMSE) without evanescent modes and the plane-wave approximation (PA) of eigenfunction expansion method, various numerical results from both models are presented. In this study, analytical solutions of two models are employed, one based on the MMSE derived by Porter (2003) and the other on the scatterer method of PA by Seo (2008a). Judging from direct comparisons against existing results of rapidly varying topography, the PA model gives better predictions of the wave propagation than the MMSE model.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.1
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• pp.46-55
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• 2001

An approach using the nonlinear wave model in predicting wave-induced currents is presented. The model results were compared with those of the conventional model using phase-averaged radiation stress, and in addition with experimental data captured by a PIV system. As a result of comparison of wave-induced currents generated behind the surface-piercing breakwater and submerged breakwater, eddy patterns appeared to be similar each other but in general numerical solutions of both models were underestimated.