• Journal of Electrochemical Science and Technology
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• 제11권2호
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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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• 제7권4호
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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.

• 대한수학회지
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• 제60권3호
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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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• 제21권1호
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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.

• 한국방재학회 논문집
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• 제8권1호
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• pp.133-138
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• 2008

외해에서 내습하는 파랑 자료를 분석하는 일은 연안에서 발생하는 문제를 해결함에 있어 기본이 되기 때문에 매우 중요하다. 파랑을 해석하는 방법에는 크게 수치 모델을 이용하는 방법과 해석 해를 이용하는 방법이 있다. 수치 모델의 경우, 다양한 지형과 파랑 조건에 대해 적용할 수 있다는 장점이 있지만 수치 오차를 고려해야 하는 번거로움이 있다. 반면, 해석 해의 경우 수치 오차 없이 빠르고 정확하게 해를 구할 수 있다는 장점이 있지만 특정한 지형 및 파랑 조건에서만 성립한다는 단점이 있다. 본 연구에서는 수치적인 기법과 해석적인 접근을 혼합하여 수치 오차를 최소화시키면서 다양한 조건에 적용이 가능한 완경사 방정식의 해를 유도하였다. 유도된 해를 기존의 수치 해와 비교한 결과 매우 잘 일치한다는 알 수 있었다.

• Journal of applied mathematics & informatics
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• 제33권5_6호
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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.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2006년도 PAN PACIFIC CONFERENCE vol.1
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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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• 제18권1호
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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).

• 한국해안·해양공학회논문집
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• 제21권2호
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• pp.117-126
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• 2009

억류파를 제외한 수정 완경사파랑식과 고유함수 전개법의 평면파 근사식에 대한 정밀도를 검토하기 위해 다수의 수치실험 결과를 제시하였다. 본 연구에서 두 해석해가 사용되었으며 하나는 수정 완경사파랑식에 대한 Porter(2003)의 해이고 다른 하나는 평면파 근사식에 산란체법을 적용한 서(2008a)의 해이다. 급변 지형에서의 파랑변형에 대한 기존 결과와의 직접 비교를 통해 평면파 근사식 모형이 수정 완경사파랑식 보다 잘 기술하는 것으로 나타났다.

• 한국해안해양공학회지
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• 제13권1호
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• pp.46-55
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• 2001

비선형 파랑 모형을 이용하여 해안류를 산정하는 모형이 소개되었다. 기존의 잉여응력을 이용한 수치모형 결과와 비교하였으며, 두 수치모형의 타당성 검토를 위하여 PIV 시스템으로 획득한 실험자료와도 비교하였다. 방파제 및 잠제 후면에서 형성되는 해안류에 대하여 서로 비교한 결과, 소용돌이 흐름의 형태는 유사하나 관측 결과와 비교하여 수치 모형 결과가 대체로 과소평가되고 있다.