• Membrane and Water Treatment
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• v.9 no.2
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• pp.79-85
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• 2018

In this work, batch adsorption of anionic dye acid green-25 (AG-25) from aqueous solution has been carried out at room temperature using anion exchange membrane (DF-120B) as a noval adsorbent. The effect of various experimental parameters such as contact time, membrane dosage, ionic strength and temperature on the adsorption of dye were investigated. Kinetic models namely pseudo-first-order, pseudo-second-order, Elovich, liquid film diffusion, Bangham and modified freundlich models were employed to evaluate the experimental data. Parameters like adsorption capacities, rate constant and related correlation coefficients for every model are calculated and discussed. It showed that adsorption of AG-25 onto DF-120B followed pseudo-first-order rate expression. Thermodynamic study indicates that adsorption of AG-25 onto DF-120B is an exothermic and spontaneous process.

• Bulletin of the Korean Chemical Society
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• v.14 no.5
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• pp.567-574
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• 1993

Mordant Red 19(MR19) is reduced at mercury electrode at -0.67 V vs. Ag/AgCl with two electrons per molecule in pH 9.2 buffer by differential pulse polarography and linear sweep voltammetry. The peak potential is dependent on the pH of solution. The exhaustive electrolysis, however, gives 4 electrons per molecule because of the disproportionation of the unstable hydrazo intermediate. The electrochemical reduction of lanthanide-MR19 complexes is observed at more cathodic potential than that of free ligand. The difference in peak potentials between complex and free ligand varies from 75 mV for $La^{3+}$ to 165 mV for $Tb^{3+}$ and increases with increasing the atomic number of lanthanide. The electrochemical reduction of lanthanide complexes with MR19 is due to the reduction of ligand itself, and it can be potentially useful as an indirect method for the determination of lanthanides. The shape of i-E curves and the scan rate dependence indicates the presence of adsorption and the adsorption was confirmed by potential double-step chronocoulometry and the effect of standing time. Also the surface excess of the adsorbed species and diffusion coefficients are determined. The composition of the complex is determined to be 1 : 2 by spectrophotometric and electrochemical methods.

• Current Optics and Photonics
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• v.4 no.4
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• pp.368-372
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• 2020

We report the terahertz time-domain spectroscopy (THz-TDS) of transdermal drug delivery in human skin. The time evolution of transdermal nicotine delivery in nicotine patches was assessed by detecting the transmission coefficient of sub-picosecond THz pulses and using a semi-analytic model based on the single-layer effective medium approximation. Using commercial nicotine patches (Nicoderm CQ^®, 7 mg/24 h), THz transmission coefficients were measured to quantitatively analyze the cumulative amounts of nicotine released from the patches in the absence of their detailed specifications, including multilayer structures and optical properties at THz frequencies. The results agreed well with measurements by conventional in vitro and in vivo methods, using a diffusion cell with high-performance liquid chromatography and blood sampling respectively. Our study revealed the ability of the THz-TDS method to be an effective alternative to existing methods for noninvasive and label-free assessments of transdermal drug delivery, showing its high promise for biomedical, pharmaceutical, and cosmetic applications.

• Bulletin of the Korean Chemical Society
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• v.17 no.2
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• pp.162-167
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• 1996

Two redox processes of methyl viologen (+2/+, +/0) in acetonitrile were investigated by using channel electrode voltammetric and in situ electrochemical ESR methods. Two separated unequal plateau currents of the first (+2/+) and second (+/0) redox processes of the viologen were observed in the channel electrode voltammograms and showed a cube-root depedndence on the electrolyte flow rate, respectively. The simple Levich analysis resulted in two different diffusion coefficients of $D_{+2}=2.2{\times}10^{-5}\;cm^2/s$ and $D_+=3.0{\times}10^{-5}cm^2/s$ from the limiting currents. In situ electrochemical ESR studies were performed for the monocation radicals generated at the potentials of the two plateau currents in the electrolyte flow range $1.3{\times}10^{-1}{\geq}v_f{\geq}2.7{\times}10^{-3}\;cm^3/s$. Backward implicitfinite difference method was employed to simulate the electrochemical kinetic problem of two sequential electron transfers ($MV^{+2}+e{\leftrightarrows}MV^+,\;MV^{+}+e{\leftrightarrows}MV^0$) coupled with reversible comproportionation ($MV^{2+}+MV^0{{\leftrightarrows}^{k_f}_{k_b}}2MV^+$). $k_f$ was found to be greater than ($10^6M^{-1}s^{-1}.

• Journal of Korean Port Research
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• v.11 no.2
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• pp.241-255
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• 1997

Three dimensional numerical model is used to simulate the circulation patterns in the Gamcheon Bay located in Pusan, Korea and compared with the observed data. The model is forced by winds, tidal elevation at open boundaries, and warm water discharged from the outfall of power plant, Turbulence mixing coefficients are calculated according to a ${\kippa}-{\varepsilon}$ turbulence closure submodel. Temperature, salinty and current are measuted extensively and these measuted data are compared with the simulation results. Eddy-like features exist both in observed data dna simulation results. These eddies are the results of interaction with the weak tidal current, wind driven current and warm water discharges. Compensational deeects are also found to exit such that while surface current is strong, bottom current tends to weaken and vice versa.

• Nuclear Engineering and Technology
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• v.16 no.2
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• pp.70-79
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• 1984

With the help of the nuclear computational system for a large LMFBR (KAERI-26 group cross section library/1DX/2DB), the reactivity coefficients for the diagrid expansion and the pad expansion at the beginning of cycle of the equilibrium core of SUPER-PHENIX I are calculated and reviewed. the core is described using R-Z geometry model, and a two-dimensional multigroup diffusion theory is used. For reference cases, reactivity calculations for radial and axial uniform expansion are performed, and also calculated are reactivity variations due to changes in material density and core volume. The reactivity coefficient for the diagrid expansion is calculated to be -0.553pcm/mil. The temperature coefficient corresponding to the above value is -1.0766pcm/$^{\circ}C$ and is well in accord with the French datum of -1.09pcm/$^{\circ}C$ within 1.2% difference. With the use of 4he calculational method for the diagrid expansion effect, reactivity calculations for the pad expansion bringing about nonuniform expansion are performed, which show that the calculational method is very useful in the analysis of the pad expansion effect. The reactivity coefficients for the pad expansion are calculated to be -0.2743 pcm/mil and -0.2786pcm1mi1 for the averaged expansion model and for the integrated pancake model, respectively. Under the assumption of the free expanding core the temperature reactivity coefficients for each model are obtained to be -0.5766pcm/$^{\circ}C$ and -0.5858pcm/$^{\circ}C$, both of which agree with the French datum of -0.574pcm/$^{\circ}C$ within 2% difference.

• Journal of Navigation and Port Research
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• v.34 no.10
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• pp.787-792
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• 2010

It is necessary to predict the penetration of chloride ions for designing RC construction in marine environments. However, it takes a long time to obtain chloride migration coefficients. Therefore, the rapid chloride penetration test (RCPT) is generally used to shorten the test time. But there is a difference between chloride migration coefficients determined by rapid chloride penetration tests and those based on exposure in marine environments. In this study, we evaluated the effect on the chloride ion migration coefficient caused by a change in voltage and NaCl concentration. We also compared the relationship between the chloride ion migration coefficient by RCPT and that by exposure in marine environments. As a result of the experiments, we found that there is only a small change in the experimental factors based on changes in voltage and NaCl concentration and since they are so small, we can conclude that they are in the range of experimental error and test results from chloride ion migration coefficients by RCPT and exposure were very different from each other. In the exposure experiments, when the water-cement ratio was increased, the smaller fine air gaps in concrete affected the chloride ion migration coefficient.

• Journal of Soil and Groundwater Environment
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• v.11 no.6
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• pp.28-34
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• 2006

Laboratory column tests using $Cl^-$ tracer were conducted to study the correlation of soil particle distribution and hydrodynamic dispersion mechanism with three kinds of ununiformed soil samples, in which the ratio of gravel and sand versus silt and clay is 24.5 for S-1 soil, 4.48 for S-2 soil, and 0.4 for S-3 soil. Chloride breakthrough curves with time were fitted with gaussian functions. The relative concentrations of chloride were converged to 1.0 after 0.7 hours for S-1, 6.3 hours for S-2, and 389 hours for S-3. Average linear velocity, longitudinal dispersion coefficient, and longitudinal dispersivity were calculated by chloride breakthrough curves. Longitudinal dispersion coefficients were $1.20{\times}10^{-4}\;m^2/sec$ for S-1, $8.87{\times}10^{-7}\;m^2/sec$ for S-2, and $1.94{\times}10^{-9}\;m^2/sec$ for S-3. Peclet numbers calculated by the molecular diffusion coefficient of chloride and the mean grain diameters of soils were $2.59{\times}10^2$ for S-1, $6.27{\times}10^0$ for S-2, and $1.35{\times}10^{-4}$ for S-3. Mechanical dispersion was dominant for the hydrodynamic dispersion mechanism of S-1. Both mechanical dispersion and molecular diffusion were dominant for the hydrodynamic dispersion mechanism of S-2, but mechanical dispersion was ascendant over molecular diffusion. Hydrodynamic dispersion in S-3 was occurred mainly by molecular diffusion. When plotting three soils on the graph of $D_L/D_m$ versus Peclet number produced by Bijeljic and Blunt (2006), the values of $D_L/D_m$ for S-1 and S-2 were more than 2.0 order compared to their graph. S-3 was not plotted on their graph because the Peclet number was as small as $1.35{\times}10^{-4}$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.2
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• pp.113-120
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• 2010

An experimental investigation was carried out to examine the evaporative heat transfer characteristics of R-134a in a micro-channel heat exchanger. The micro-channel heat exchanger used in this study was a sort of plate heat exchanger. Micro-channels were fabricated on the SUS304 plate by the photo-etching process: 13 sheets of plates were stacked and bonded by the diffusion bonding process. The effects of the evaporating temperature, mass flux of R-134a, and inlet temperature of water were examined. As the difference between the inlet temperatures of R-134a and water increased, the heat transfer rate increased. The evaporative heat transfer coefficients obtained in this study range from 0.67 to 6.23 kW/$m^2{\cdot}^{\circ}C$. The experimental correlation for the Nusselt number as a function of the Reynold number and $\Theta$ was suggested for the micro-channel heat exchanger.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.3
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• pp.149-157
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• 2005

Typical water quality (WQ) parameters defined in the governing equation of the WQ model are the pollutant loads from atmosphere and watersheds, pollutant release rates from sediment, diffusion coefficient and reaction coefficient etc. The direct measurement of these parameters is very difficult as well as requires high cost. In this study, the pollutant budget equation including these parameters was used to construct the linear simultaneous equations. Based on these equations, the inverse problems were constructed and WQ parameter estimation method minimizing the sum of squared errors between the computed and observed amounts of the mass changes was suggested. WQ parameters, i.e., the atmospheric pollutant loads, sediment release rates, diffusion coefficients and reaction coefficient, were estimated using .this method by utilizing the vertical concentration profile data which has been observed in Cheonsu Bay and Ulsan Port. Values of the estimated parameters show a large temporal variation. However, this technique is persuasive in that the RHS (root mean square) error was less than $5.0\%$ of the observed value ranges and the agreement index was greater than 0.95.