• Journal of Microbiology and Biotechnology
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• 제11권5호
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• pp.781-787
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• 2001

The binding of heavy metals by a biosorbent with binary functional groups was mathematically modeled. An FT-IR spectrophotometer analysis was employed to determine the stoichiometry between the protons in the functional groups of alginic acid and lead ions as a model system. The results calculated using an equilibrium constant agreed well with the experimental results obtained under various operating conditions, such as pH and metal ion concentration. It was also shown that the overall adsorption phenomenon of alginic acid was mainly due to its carboxyl groups. The equilibrium constants for each functional group successfully predicted the lead adsorption of ${\alpha}$-cellulose. Furthermore, the biosorption model could predict the adsorption phenomena of two metal ions, lead ions and calcium ions, relatively.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1372-1377
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• 2008

Since metallic foam will increase the performance of heat exchanger, it have caused many researcher's attention recently. Our research base on the model that metallic foams applied to heat exchanger. In this case, there is three kind of heat transfer mechanisms, heat conduction in fibers, heat transfer by conduction in fluid phase, and internal heat change between solid and fluid phases. In this paper, we first discuss the acceptance of applying thermal equilibrium among the two phases. then to calculate the dimensionless temperature profile along 7 metallic foams. The 7 samples have different characteristics, such as area ratio, effective conductivity, porosity, etc.

• 한국세라믹학회지
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• 제48권3호
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• pp.205-210
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• 2011

The dependence of sulfur redox behavior and its diffusivity on temperature and composition was studied in mixed alkali silicate melts by means of square wave voltammetry (SWV) at different frequencies in a temperature range of $1000^{\circ}C$ to $1400^{\circ}C$. The voltammograms showed two reduction peaks at high frequency but only one peak at low frequency. Irrespective of $K_2O/(Na_2O+K_2O)$, each peak potential due to reduction of $S^{6+}$ to $S^{4+}$ and $S^{4+}$ to $S^0$ moved toward a negative direction with temperature decrease, and the peak current showed a strong dependence on frequency at a constant temperature. However, the compositional dependence of the peak potential showed an inconsistent behavior with an increase of $K_2O$. The mixed alkali effect was not observed in sulfur diffusion. This inconsistency of both peak potential and diffusion for compositional dependence may be derived from the strong volatilization of sulfur in melts.

• Korean Chemical Engineering Research
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• 제56권5호
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• pp.732-737
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• 2018

Experimental data of phase equilibria are reported for the binary mixture of 1-phenyl-2-pyrrolidone in supercritical carbon dioxide. Phase behavior data was measured in a synthetic method at a temperature ranging from 333.2 to 393.2 K and at pressures up to 97.14 MPa. The solubility of 1-phenyl-2-pyrrolidone in the carbon dioxide + 1-phenyl-2-pyrrolidone system increased as temperature increased at a constant pressure and it exhibited the type-I phase behavior. The experimental data for the binary mixture were correlated with the Peng-Robinson equation of state using mixing rule and the critical properties of 1-phenyl-2-pyrrolidone were predicted with the Joback and Lyderson method.

• 대한수학회논문집
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• 제34권2호
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• pp.685-699
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• 2019

This research is focused on a continuous epidemic model of transmission of Plasmodium vivax malaria with a time delay. The model is represented as a system of ordinary differential equations with delay. There are two equilibria, which are the disease-free state and the endemic equilibrium, depending on the basic reproduction number, $R_0$, which is calculated and decreases with the time delay. Moreover, the disease-free equilibrium is locally asymptotically stable if $R_0<1$. If $R_0>1$, a unique endemic steady state exists and is locally stable. Furthermore, Hopf bifurcation is applied to determine the conditions for periodic solutions.

• Bulletin of the Korean Chemical Society
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• 제24권10호
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• pp.1495-1500
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• 2003

Equilibria and applications of a synergistic extraction were studied for the determination of a trace lithium by using thenoyltrifluoroacetone (TTA) and trioctylphosphine oxide (TOPO) as ligands. Several equations were derived for the extraction of lithium into m-xylene as a phase of Li-TTA·mTOPO adduct. Distribution coefficients and extraction constant were determined together with a stability constant of the adduct. The adduct was quantitatively extracted from the basic solution of higher than pH 9 by shaking for 30 minutes. m-Xylene was selected as an optimum solvent by comparing the extraction efficiency among several kinds of organic solvents. The stability constant (${\Beta}_2$) for Li-TTA/2TOPO was 150 times higher than Li-TTA/TOPO. The distribution coefficient of Li-TTA/2TOPO into m-xylene was 9.12 and the logarithmic extraction constant (log $K_{ex}$) was 6.76. Trace lithium of sub-ppm level in seawater samples could be determined under modified conditions and a detection limit equivalent to 3 times standard deviation for background absorption was 0.42 ng/mL.

• 청정기술
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• 제25권3호
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• pp.198-205
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• 2019

야자계 입상활성탄에 대한 Brilliant Green의 흡착 평형과 동역학 및 열역학 파라미터들을 다양한 초기농도($300{\sim}500mg\;L^{-1}$), 접촉시간(1 ~ 12 h) 및 흡착온도(303 ~ 323 K)를 변수로 하여 회분식 실험을 통하여 연구하였다. 흡착평형 값들은 Langmuir, Freundlich, Temkin, Harkins-Jura 및 Elovich 식으로 해석하였다. 그 결과는 Langmuir 식에 가장 잘 맞았으며, 평가된 Langmuir 무차원 분리계수 값($R_L=0.018{\sim}0.040$)과 Freundlich 상수값(1/n = 0.176 ~ 0.206)은 활성탄에 의한 Brilliant Green의 흡착이 효과적인 공정임을 보여주었다. Temkin 식에 의해 평가된 흡착열 관련상수($B=12.43{\sim}17.15J\;mol^{-1}$)는 물리흡착에 해당하였다. Harkins-Jura 식에 의한 등온선 매개변수($A_{HJ}$)는 온도가 증가할수록 이종 기공 분포도 증가함을 나타내었고, Elovich 식에 의한 최대흡착용량은 실험값보다 매우 적은 것으로 나타났다. 흡착공정은 유사이차반응속도식에 더 잘 맞았으며, 흡착과정은 입자내 확산이 율속단계였다. 입자내 확산속도 상수는 초기 농도가 커질수록 염료의 운동이 활발해졌기 때문에 증가하였다. 그리고 초기농도가 커질수록 경계층의 영향이 커졌다. Gibbs 자유에너지($-3.46{\sim}-11.35kJ\;mol^{-1}$), 엔탈피($18.63kJ\;mol^{-1}$) 및 활성화에너지($26.28kJ\;mol^{-1}$)는 흡착공정이 자발적이고, 흡열 및 물리흡착임을 나타냈다.

• Computers and Concrete
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• 제32권3호
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• pp.287-302
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• 2023

Corrosion of reinforcing bars in reinforced concrete structures due to chloride attack in environments containing chloride ions is one of the most important factors in the destruction of concrete structures. According to the abundant reports that the corrosion rate around the repair area has increased due to the macro-cell current known as the incipient anode, it is necessary to understand the effective parameters. The main objective of this paper is to investigate the effect of the kinetic parameters of corrosion including the cathodic Tafel slope, exchange current density, and equilibrium potential in repair materials on the total corrosion rate and maximum corrosion rate in the patch repair system. With the numerical simulation of the patch repair system and concerning the effect of parameters such as electromotive force (substrate concrete activity level), length of repair area, and resistivity of substrate and repair concrete, and with constant other parameters, the sensitivity of the macro-cell current caused by changes in the kinetic parameters of corrosion of the repairing materials has been investigated. The results show that the maximum effect on the macro-cell current values occurred with the change of cathodic Tafel slope, and the effect change of exchange current density and the equilibrium potential is almost the same. In the low repair extant and low resistivity of the repairing materials, with the increase in the electromotive force (degree of substrate concrete activity) of the patch repair system, the sensitivity of the total corrosion current reduces with the reduction in the cathode Tafel slope. The overall corrosion current will be very sensitive to changes in the kinetic parameters of corrosion. The change in the cathodic Tafel slope from 0.16 to 0.12 V/dec and in 300 mV the electromotive force will translate into an increase of 200% of the total corrosion current. While the percentage of this change in currency density and equilibrium potential is 53 and 43 percent, respectively. Moreover, by increasing the electro-motive force, the sensitivity of the total corrosion current decreases or becomes constant. The maximum corrosion does not change significantly based on the modification of the corrosion kinetic parameters and the modification will not affect the maximum corrosion in the repair system. Given that the macro-cell current in addition to the repair geometry is influenced by the sections of reactions of cathodic, anodic, and ohmic drop in repair and base concrete materials, in different parameters depending on the dominance of each section, the sensitivity of the total current and maximum corrosion in each scenario will be different.

• 한국지반공학회지:지반
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• 제13권6호
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• pp.25-36
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• 1997

피에조콘을 이용하면 연약지반 개량후 임의의 시점에서 지반의 압밀도를 파악할 수가 있다. 이 경우 임의의 심도에서 피에조콘의 관입을 멈추고 간극수압이 일정한 값에 이를 때까지 간극 수압 소산시험을 실시하는데, 연약지반의 투수계수가 작기 때문에 대체적으로 상당히 오랜 시간 동안 소산시험을 하게 된다. 본 논문에서는 침하 분석기법 가운데 일반적으로 널리 알려져 있는 쌍곡선법, 아사오카법, 호시노법을 이용하여 간극수압 소산시험시의 평형간극수압을 각각 추정한 후 장시간에 걸친 실제 시험결과와 비교함으로써 간극수압 소산시험에 소요되는 시간을 단축할 수 있는 방법을 연구하였다. 그 결과, 호시노법을 이용한 추정방법이 가장 적합한 방법임을 알 수 있었으며 이를 이용한 효율적인 간극수압 소산시험 방법을 제시하였다.

• 대한환경공학회지
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• 제27권11호
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• pp.1238-1243
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• 2005

본 연구에서는 해안가에서 자생하는 두 종의 해조류(Laminaria japonica와 Kjellmaniella crassifolia)를 생체흡착제로 사용하여 용액중의 중금속(납) 제거 실험을 통해 생체흡착제의 납의 흡착속도와 흡착평형 특성을 연구하였다. 두 종의 해조류을 사용한 납의 생체흡착은 흡착초기 2시간 이내에 평형에 도달하였다. 흡착속도는 유사 2차 흡착속도식에 의해 거의 정확한 모사가 가능하였으며, 여기에서 산출된 속도상수, $k_{2,ad.}$는 각각 $0.883{\times}10^{-3}$와 $0.628{\times}10^{-3}\;g/mg/min$이었다. 흡착평형은 Langmuir, Redlich-Peterson 및 Koble-Corrigan (Langmuir-Freundlich) 모델식에 의해 잘 모사되었다. 또한, L. japonica와 K. crassifolia의 4가지 중금속에 대한 선택성은 Pb>Cd>Cr>Cu와 Pb>Cu>Cd>Cr순으로 나타났다. 본 실험에 사용된 L. japonica는 pH의 증가에 따라 납의 흡착량도 증가되었다.