• Journal of the Korean Chemical Society
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• v.65 no.1
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• pp.37-47
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• 2021

In this study, the model cognition level of high school science-gifted students about the two types of acid-base models taught in secondary schools was analyzed. In order to find out the model cognition level of students, 12 items were developed based on the acid-base reaction and the dissociation reaction of acids and bases. The subjects of the study were 95 students of two science-gifted schools. As a result of the questionnaire analysis, model cognition levels were analyzed 6 levels in the context of consistency, inconsistency, and unexplainable scope of the two models. In the acid-base reaction item, the largest percentage of students cognized only understanding of the two models. In the acid-base dissociation reaction item, they understood the two models and perceived the 'Known Ignorance' that cognizes the limitations of one model. However, there was only one student who perceived the limitations of both models and all of the 'Unknown Ignorance' that the model could not explain. Through this, we argued that there is a need for educational efforts to raise the model cognition level of science-gifted students.

• Journal of Korea Soil Environment Society
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• v.3 no.3
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• pp.3-10
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• 1998

Acid/Base buffer capacity of soil is very important in prediction of contaminant transport for its direct impact on pH change of the system composed of soil-contaminant-water, In this research, diffuse double layer theory as well as two layer electrostatic adsorption model are applied to develop a theoretical model of buffer capacity of soil. Model application procedures are presented as well. Buffer capacity of Georgia kaolinite and Milwhite kaolinite was measured by acid-base titration. Model prediction and experimental results are compared.

• Journal of the Korean Chemical Society
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• v.64 no.5
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• pp.267-276
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• 2020

This study analyzed the level of chemistry teachers' cognition related to two types of acid-base models taught in secondary schools. For the purpose, a questionnaire was developed to identify teachers' cognitions based on previous studies that analyzed the 'Ignorance' of each model. The questionnaire consisted of two items, one related to acid and base reactions and one related to acid and base dissociation, which suggested inconsistencies between the two models. The subjects were 15 chemistry teachers, and as a result, teachers' cognitions were analyzed at four levels. The four levels are: if they don't know the two models, if they only understand one model, if they understand the two models, and perceived the 'Ignorance' of one model, and if they understand the two models and perceived the 'Ignorance' of the two models. The largest proportion of teachers understood the two models and perceived the 'Ignorance' of one model. However, the proportion of understanding the two models and perceiving the 'Ignorance' of the two models was very small. Through this, we argued that efforts to increase the level of chemistry teachers' cognition of the model and 'Ignorance' were necessary.

• Journal of the Korean Chemical Society
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• v.63 no.1
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• pp.56-65
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• 2019

This study investigated the perceptions of the relationship among the three acid-base models of chemistry teachers. In addition, we examined how the perception of the relationship between models affected on the interpretation of concepts in each model. To investigate teachers' perceptions and interpretations, a questionnaire and interviews were conducted for 24 chemistry teachers. As results, most of the chemistry teachers recognized the three models as cumulative extension relationships. The perceptions were related to the contents of textbooks. The perception of the relationship of these models influenced on interpretations of the models' acid-base concept. In this study, we suggested that science teachers need to be aware of diverse models' roles.

• Journal of Environmental Science International
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• v.17 no.8
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• pp.919-924
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• 2008

The surface properties and adsorption rates of activated carbon modified with acid and base were compared. The distribution ratio of C and C-H on the surface of activated carbon were decreased by modification with acid and base, but the distribution ratio of C-O, C=O, and O=C-O were increased. Base modification damaged the surface of activated carbon more than acid modification, it caused the effect of 6 percent increments of surface area. Adsorption rate model was more suitable to second order equation than first order equation. Adsorption rate was controlled by adsorption in pore better than in surface.

• Journal of the Korean Applied Science and Technology
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• v.25 no.2
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• pp.123-129
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• 2008

Transdermal therapeutic system(TTS) is often used as the method of drug dosage into the epidermic skin. Natural polymer were selected as ointment material of TTS. We investigated the permeation of natural polymer ointment containing drug in rat skin using horizontal membrane cell model. Permeation properties of materials were investigated for water-soluble drug such as Nicotinic acid N-oxide in vitro. These results showed that skin permeation rate of drug across the composite was mainly dependent on the property of ointment base and drug. Proper selection of the polymeric materials which resemble and enhance properties of the delivering drug was found to be important in controlling the skin permeation rate. This result suggests a possible use of natural polymer ointment base as TTS of antihyperlipoproteinemic agent.

• Membrane and Water Treatment
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• v.2 no.3
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• pp.187-205
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• 2011

The electric transport of the mixture of hydrochloric and phosphoric acids through strong base (Neosepta ACM) and weak base (Selemion AAV) anion-exchange membranes was investigated. The instantaneous efficiency of HCl removal from the cathode solution, $CE_{Cl}$, with and without $H_3PO_4$ was determined. It was found that $CE_{Cl}$ was 0.8-0.9 if the number of moles of elementary charge passed through the system, $n_F$, did not exceed ca. 80% of the initial number of HCl moles in the cathode solution, $n_{Cl,ca,0}$. The retention efficiency of $H_3PO_4$ in that range was close to one. The transport of acid mixtures was satisfactorily described by a model based on the extended Nernst-Planck and Donnan equations for $n_F$ not exceeding $n_{Cl,ca,0}$. Among the tested model parameters, most important were: concentration of fixed charges, the porosity-tortuosity coefficient, and the partition coefficient of an undissociated form of $H_3PO_4$. For the both membranes, the obtained optimal values of fixed charge concentration, $\bar{c}_m$, were up to 40% lower than the literature values of $\bar{c}_m$ obtained from the equilibrium measurements. Regarding the $H_3PO_4$ equilibria, it was sufficient to consider $H_3PO_4$ as a monoprotic acid.

• Korean Chemical Engineering Research
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• v.54 no.2
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• pp.255-261
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• 2016

Adsorption experiments of Acid Yellow 14 dye using activated carbon were carried out as function of adsorbent dose, pH, initial concentration, contact time and temperature. The equilibrium adsorption data were analyzed by Langmuir, Freundlich and Temkin isotherm model. The experimental data were best represented by Freundlich isotherm model. Base on the estimated Freundlich constant (1/n=0.129~0.212) and Langmuir separation factor ($R_L=0.202{\sim}0.243$), this process could be employed as effective treatment method. The heat of adsorption of Temkin isotherm model was 5.101~9.164 J/mol indicated that the adsorption process followed a physical adsorption. Adsorption kinetics experimental data were modeled using the pseudo-first-order and pseudo-second-order kinetic equation. It was shown that pseudo-second-order kinetic equation could best describe the adsorption kinetics. Base on the negative Gibbs free energy (-4.81~-10.33 kJ/mol) and positive enthalpy (+78.59 kJ/mol) indicate that the adsorption is spontaneous and endothermic process.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.3
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• pp.205-211
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• 2005

Water-soluble polyethyleneimine (PE) derivatives containing nucleic acid bases and hydrophilic amino acids such as homoserine (Hse) and serine were prepared by the activated ester method as nucleic acid models. From spectroscopic measurements, the polymers were found to interact with DNA accompanied by an induction of conformational change. Hypochromicity in UV spectra indicated that a stable polymer complex was formed between poly (A) with PEI­Hse-Ura by complementary hydrogen bonding with equimolar nucleic base units (adenine:uracil=1:1). The induced conformation of DNA by the interaction with the polymer containing uracil and homoserine (PEI-Hse-Ura) was concluded to be a super triple helical structure. The formation of the polymer complex, DNA: PEI-Hse-Ura, was found to be affected by the presence of metal ions such as $Ca^{2+}\;and\;Cu^{2+}$.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.786-789
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• 1989

A nonlinear self-tuning regulator for a neutralization process of a weak acid and strong base system is proposed. Rearranging the state equation of the process model, we first obtain equations which are linear for a manipulated variable or unknown parameters. Then to these equations we apply the standard procedure used in designing linear self-tuning regulators. Simulation results show that the regulator provides very good performances for various realistic situations and traces variations of the unknown parameters. Since computations are simple and additional measurements except the effluent pH value are only flow rates of influent streams, it can be easily applied to real processes such as a waste water treatment process.