• 충청수학회지
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• 제34권3호
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• pp.221-234
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• 2021

We introduce high-order Hopfield neural networks with Leakage delays. Furthermore, we study the uniqueness and existence of Hopfield artificial neural networks having the weighted pseudo almost periodic forcing terms on finite delay. Our analysis is based on the differential inequality techniques and the Banach contraction mapping principle.

• 한국환경과학회지
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• 제23권9호
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• pp.1609-1618
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• 2014

In this study, as a fundamental study for the remediation of the radionuclides-contaminated soil, the adsorption of cobalt, strontium, and cesium on natural soil and kaolin were experimently investigated and adsorption characteristics were evaluated by using several adsorption kinetic and isotherm models. The pseudo-first-order kinetic model (PFOM), pseudo-second-order kinetic model (PSOM), one-site mass transfer model (OSMTM), and two compartment first-order kinetic model (TCFOKM) were used to evaluate the kinetic data and the pseudo-second-order kinetic model was the best with good correlation. The adsorption equilibria of cobalt, strontium, and cesium on natural soil were fitted successfully by Redlich-Peterson and Sips models. For kaolin, the adsorption equilibria of cobalt, strontium, and cesium were fitted well by Redlich-Peterson, Freundlich, and Sips models, respectively. The amount of adsorbed radionuclides on natural soil and kaolin was in the order of cesium > strontium > cobalt. It is considered that these results could be useful to predicting the adsorption behaviors of radionuclides such as cobalt, strontium, and cesium in soil environments.

• 한국대기환경학회지
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• 제18권1호
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• pp.51-58
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• 2002

Destruction process of toluene using a wire-cylindrical BBD (Dielectric Barrier Discharge) reactor packed with catalysts was investigated to characterize the synergetic effects of non-thermal plasma and catalyst process. The catalysts used in the present study were ${\gamma}$-Al$_2$BO$_3$ and Pt/${\gamma}$-Al$_2$O$_3$. Under the numerous test conditions, specific energy density (SED (J/L)) and the conversion of toluene, defined as (1 -[C$_{f}$]/[C$_{i}$]), were measured. The test results showed that toluene decomposition efficiency followed the pseudo-first order in the case of plasma only process. The pseudo-first order process, however, was modified to pseudo-zeroth order reaction in the case of catalyst-assisted plasma process. This modification of the reaction order was verified based on a simple kinetic model proposed in the present study. Owing to the modification of reaction order, which resulted from the catalytic process, the specific energy to achieve the high removal efficiencies, i.e. 80~90%, was reduced significantly.y.y.

• Journal of applied mathematics & informatics
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• 제28권5_6호
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• pp.1323-1329
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• 2010

In this paper, a new fixed point theorem in cone is applied to obtain the existence of at least one positive pseudo-symmetric solution for the second order three-point boundary value problem {x" + f(t, x, x')=0, t $\in$ (0, 1), x(0)=0, x(1)=x($\eta$), where f is nonnegative continuous function; ${\eta}\;{\in}$ (0, 1) and f(t, u, v) = f(1+$\eta$-t, u, -v).

• 충청수학회지
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• 제20권1호
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• pp.11-21
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• 2007

Given a nonlinear function f : $\mathbb{R}{\rightarrow}\mathbb{R}$ that has a simple real zero ${\alpha}$, a new numerical method to be called k-fold pseudo- Halley's method is proposed and it's error analysis is under investigation to confirm the convergence behavior near ${\alpha}$. Under the assumption that f is sufficiently smooth in a small neighborhood of ${\alpha}$, the order of convergence is found to be at least k+3. In addition, the corresponding asymptotic error constant is explicitly expressed in terms of k, ${\alpha}$ and f as well as the derivatives of f. A zero-finding algorithm is written and has been successfully implemented for numerous examples with Mathematica.

• Nuclear Engineering and Technology
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• 제27권4호
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• pp.532-543
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• 1995

의사콜로이드에 의해 매개된 균열 암반 매질에서의 방사성 핵종의 이동 거동을 분석하고 예측하기 위한 이동모델이 개발되었다. 명목적인 의사콜로이드 형성 상수인 $K_{ap}$ (㎥/kg)값이 100보다 클 때 방사성 핵종의 이동에 매우 큰 영향을 미치는 것으로 나타났다. 계산결과에 의하면 Pu-239의 의사콜로이드형성 상수가 Ni-63보다 크기 때문에 Pu-239의 이동이 Ni-63보다 빠른 것으로 나타났다 따라서 결론적으로 균열 암반에서의 방사성 핵종의 가속화는 방사성 핵종과 자연성 참콜로이드와의 의사콜로이드 형성에 따른 용액에서의 유동성 성분의 증가와 방사성 핵종들의 정지된 고체매질로의 흡착양 감소에 기인함을 알 수 있다.

• Environmental Engineering Research
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• 제25권2호
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• pp.178-185
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• 2020

The aim of this study is to investigate the degradation of ciprofloxacin (CIP) from its aqueous solutions via different advanced oxidation processes (AOP). The effects of persulfate (PS) concentration, pH, zinc oxide nanoparticles (ZnO-NPs) dose, initial CIP concentration, and reaction time on the degradation of CIP were studied. It was found that the sonochemical (US) degradation is a less efficient process (with removal efficiency of 36%) compared to the sono-nano-chemical (US/ZnO) process which resulted in removal efficiency of 70%. Maximum removal of 99% was obtained using the sono-nano-chemical/PS (US/ZnO/PS) process at a frequency of 60 kHz, time of 10 min, pH of 7, initial CIP concentration of 25 mg/L, and PS concentration of 476.06 mg/L. The addition of PS and ZnO-NPs to the process enhanced the rate of US degradation of CIP. In addition, the kinetic parameters for the US/ZnO/PS process were obtained by fitting the kinetic data into the pseudo-first-order and pseudo-second-order kinetic models. The kinetic data was found to fit into the pseudo-first-order kinetic model than the pseudo-second-order model. The results showed that the AOP using US/ZnO/PS is a promising technique for the treatment of ciprofloxacin containing solutions.

• 한국환경과학회지
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• 제25권12호
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• pp.1717-1726
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• 2016

In this study, the reductive decolorization of three acid and basic dyes using modified zero-valent iron (i.e., acid-washed iron (Aw/Fe) and palladium coated iron (Pd/Fe)) at various pH conditions (pH 3~5) was experimentally investigated and the decolorization characteristics were evaluated by analyzing the absorbance spectra and reaction kinetics. In the case of acid dyes such as methyl orange and eriochrome black T, color removal efficiencies increased as initial pH of the dye solution decreased. However, the color removal of methylene blue, a basic dye, was not affected much by the initial pH and more than 70% of color was removed within 10 min. During the decolorization reaction, the absorbance of methyl orange (${\lambda}_{max}=464nm$) and eriochrome black T (${\lambda}_{max}=528nm$) decreased in the visible range but increased in the UV range. The absorbance of methylene blue (${\lambda}_{max}=664nm$) also decreased gradually in the visible range. Pseudo-zero order, pseudo-first order, and pseudo-second order kinetic models were used to analyze the reaction kinetics. The pseudo-second order kinetic model was found to be the best with good correlation. The decolorization reaction rate constants ($k_2$) of methylene blue were relatively higher than those of methyl orange and eriochrome black T. The reaction rate constants of methyl orange and eriochrome black T increased with a decrease in the initial pH.

• Environmental Engineering Research
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• 제19권3호
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• pp.247-253
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• 2014

The aim of this study was to characterize quintinite in fluoride removal from aqueous solutions, using batch experiments. Experimental results showed that the maximum adsorption capacity of fluoride to quintinite was 7.71 mg/g. The adsorption of fluoride to quintinite was not changed at pH 5-9, but decreased considerably in highly acidic (pH < 3) and alkaline (pH > 11) solution conditions. Kinetic model analysis showed that among the three models (pseudo-first-order, pseudo-second-order, and Elovich), the pseudo-second-order model was the most suitable for describing the kinetic data. From the nonlinear regression analysis, the pseudo-second-order parameter values were determined to be $q_e=0.18mg/g$ and $k_2=28.80g/mg/hr$. Equilibrium isotherm model analysis demonstrated that among the three models (Langmuir, Freundlich, and Redlich-Peterson), both the Freundlich and Redlich-Peterson models were suitable for describing the equilibrium data. The model analysis superimposed the Redlich-Peterson model fit on the Freundlich fit. The Freundlich model parameter values were determined from the nonlinear regression to be $K_F=0.20L/g$ and 1/n=0.51. This study demonstrated that quintinite could be used as an adsorbent for the removal of fluoride from aqueous solutions.

• 공업화학
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• 제34권2호
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• pp.153-160
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• 2023

본 논문에서는 미이용 바이오매스로부터 바이오차를 생산하고 메틸렌블루 흡착 특성을 평가하였다. 바이오매스는 주로 셀룰로오스, 헤미셀룰로오스, 리그닌으로 구성되어 있으며 회분의 함량은 벌채부산물에서 가장 높았다. 탄화 온도가 증가할수록 탄화 수율은 감소하였으며, 수소와 산소 함량도 감소하였다. 반면, 탄소 함량은 증가하였다. 탄화 온도가 증가할수록 바이오차의 비표면적과 미세기공은 증가하였다. 바이오차 비표면적은 탄화 온도 600 ℃에서 가장 높았다(216.15~301.80 m² /g). 600 ℃에서 탄화한 바이오차를 이용하여 메틸렌블루 흡착 실험을 수행한 결과, 참나무, 벌채부산물, 사과 전정가지의 흡착 거동은 Freundlich model, 복숭아 전정가지는 Langmuir model에 적합하였다. 흡착 동역학에서 참나무와 복숭아 전정가지는 pseudo-first-order model, 벌채부산물과 사과 전정가지는 pseudo-second-order model에 적합하였다.