• Korean Journal of Mathematics
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• 제9권2호
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• pp.115-121
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• 2001

In this paper, we establish the conditions that a mild C-existence family yields a solution to the abstract Cauchy problem. And we show the relation between mild C-existence family and C-regularized semigroup if the family of linear operators is exponentially bounded and C is a bounded injective linear operator.

• 한국해안·해양공학회논문집
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• 제20권5호
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• pp.461-471
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• 2008

WKB 방법에 의한 일차원 완경사 파랑식의 해석해를 유도하였고 이는 Porter(2003)의 해와 유사한 형태를 갖는다. 적용적 측면에서 본 해석해는 관련 수치해에 견줄 만큼 해석상의 일반성을 갖는다. 유도과정에서 해면함수로 표현된 굴절 방정식의 해도 얻었다. Bremmer 방법을 이용한 본 해석해에 대한 수치계산 결과를 제시하였고 이들은 기존 결과와 일치한다.

• 한국콘텐츠학회논문지
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• 제12권3호
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• pp.434-441
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• 2012

축대칭 함몰지형 위를 통과하는 파의 변형에 관한 확장형 완경사 방정식의 해석해를 유도하였다. 함몰지형내의 수심은 함몰지형의 중심으로부터의 거리의 멱에 비례하여 변화된다. 지배방정식은 변수분리법을 이용하여 상미분방정식으로 변환되었으며 Hunt(1979)의 근사식을 이용하여 계수들을 파속과 군속도의 항으로 이뤄진 양함수의 형태로 나타냈다. 확장형 완경사 방정식의 바닥의 곡률과 경사의 제곱으로 이뤄진 항은 멱급수형태로 변환하였다. 마지막으로 Frobenius 급수를 사용하여 확장형 완경사 방정식의 해석해를 유도하였다. 유도된 해석해는 FEM으로 도출된 수치해와 기존의 완경사 방정식의 해석해와 비교하여 검증하였다.

• Corrosion Science and Technology
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• 제23권1호
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• pp.20-32
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• 2024

Metal corrosion in acidic environments is a major issue in various industrial applications. This study evaluates the 4-piperonylideneaminoantipyrine (PPDAA) corrosion inhibition efficiency for mild steel in a hydrochloric acid (HCl) solution. The weight loss method was used to determine the corrosion inhibition efficiency at different concentrations and immersion time periods. Results revealed that the highest inhibition efficiency (94.3%) was achieved at 5 mM concentration after 5 hours of immersion time. To inspect the surface morphology of the inhibitor film on the mild steel surface, scanning electron microscopy (SEM) was used before and after immersion in 1.0 M HCl. Density functional theory (DFT) calculations were performed to investigate the molecular structure and electronic properties of the inhibitor molecule to understand the corrosion inhibition mechanism. Theoretical results showed that the inhibitor molecule can adsorb onto the mild steel surface through its nitrogen and oxygen atoms, forming a protective layer that prevents HCl corrosive attack. These findings highlight the potential of PPDAA as an effective corrosion inhibitor for mild steel in HCl solution. Moreover, combining experimental and theoretical approaches provides insights into the mechanism of corrosion inhibition, which is essential for developing effective strategies to prevent metal corrosion in acidic environments.

• 대한수학회보
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• 제38권1호
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• pp.175-182
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• 2001

In this paper we prove the existence and uniqueness of a mild solution of a functional differential equation with nonlocal condition using the semigroup theory and the Banach fixed point principle.

• Corrosion Science and Technology
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• 제18권5호
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• pp.155-167
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• 2019

In this study, two novel Schiff base compounds including (3-(4-Chlorophenyl isoxazole-5-yl) methanol and (3-(2,4 dichlorophenol isoxazole-5-yl) methanol as corrosion inhibitors for mild steel in 1 M hydrochloric acid solution were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and density functional theory (DFT) computations. The results showed that the corrosion inhibition efficiency (IE) is remarkably enhanced with the growing concentration of the Schiff base inhibitors. The results from Tafel polarization and EIS methods showed that IE decreases with gradual increments of temperature. This process can be attributed to the displacement of the adsorption/desorption balance and hence to the diminution of the level of a surface coating. Also, the adsorption of two inhibitors over mild steel followed the Langmuir adsorption isotherm. Too, the results of the scanning electron microscope (SEM) images showed that the Schiff base inhibitors form an excellent protective film over mild steel and verified the results by electrochemical techniques. Additionally, the results from the experimental and those from DFT computations are in excellent accordance.

• 동의신경정신과학회지
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• 제12궈1호
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• pp.123-135
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• 2001

Objective: This study was designed to assess antidepressant effects of Quibitang on an Animal Model of Depression induced by Chronic Mild Stress. Method: The consumption of 1% sucrose solution and active avoidance learning test were used to evaluate antidepressant effect of Quibitang. The consumption of 1% sucrose solution was measured every week for 8 weeks, and active avoidance learning test was executed after 4 weeks treatment of saline or Quibitang. Result: 1. The consumption of 1% sucrose solution was significantly reversed in test group (Quibitang-treated group) at 5th, 7th, 8th weeks, but there was no significant change in control group. 2. Chronic Mild Stress was found to suppress the increase of body weight at 5th, 6th, 7th, 8th weeks. Treatment of Quibitang did not enhanced the body weigt, but it enhanced the consumption of sucrose solution. 3. In order to measure the learning ability of rat which drived to be depressed, we executed active avoidance test. The result revealed that depressed rat showed impaired acquisition than control group, and the treatment of Quibitang restored the learning activity. Conclusion: These results suggest that Quibitang may have antidepressant effects on depression induced by chronic mild stress.

• 충청수학회지
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• 제23권4호
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• pp.793-800
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• 2010

We investigate the existence and uniqueness of almost automorphic mild solutions of the semilinear abstract differential equations.

• 한국해안해양공학회지
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• 제5권2호
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• pp.84-90
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• 1993

구형 해저지형과 이안제를 가진 해안에 대한 완경사방정식의 해를 구하는데 반복기법(Conjugate Gradient Method, Panchang et al., 1991)을 사용하였다. 지형 및 구조물로 인한 파랑의 전파변형에 대한 계산결과가 실험치와도 잘 일치하였다. 종내 과도한 기억용량 때문에 광역에는 완경사방정식을 그대로 사용하기가 어려웠지만 이 기법을 사용하면 그런 어려움은 해결된 것으로 판단된다. 특히 소요되는 계산시간이 짧고 복잡한 지형 및 구조물에 대해서도 별 어려움 없이 적용할 수 있는 것이 큰 장점이다.

• 대한화학회지
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• 제57권2호
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• pp.264-271
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• 2013

Corrosion inhibition of mild steel used in water station in 35 ppm aluminum sulfate and 10 ppm chloride solution by Camellia sinensis leaves extract was studied using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy techniques at $30^{\circ}C$. Results show that the inhibition efficiency increases with increasing concentration of the extract and decreases with increasing temperature. Inhibitive effect was afforded by adsorption of the extract's components which was found to accord with Langmuir adsorption isotherm. Inhibition mechanism is deduced from the temperature dependence of the inhibition efficiency and was further corroborated by the values of activation parameters obtained from the experimental data.