• Proceedings of the Korean Society of Rheology Conference
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• 2002.05a
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• pp.65-68
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• 2002

• Korea-Australia Rheology Journal
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• v.21 no.3
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• pp.193-200
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• 2009

We present a direct simulation technique for two-dimensional mold-filling simulations of fluids filled with a large number of circular disk-like rigid particles. It is a direct simulation in that the hydrodynamic interaction between particles and fluid is fully considered. We employ a pseudo-concentration method for the evolution of the flow front and the DLM (distributed Lagrangian multipliers)-like fictitious domain method for the implicit treatment of the hydrodynamic interaction. Both methods allow the use of a fixed regular discretization during the entire computation. The discontinuous Galerkin method has been used to solve the concentration evolution equation and the rigid-ring description has been introduced for freely suspended particles. A buffer zone, the gate region of a finite area subject to the uniform velocity profile, has been introduced to put discrete particles into the computational domain avoiding any artificial discontinuity. From example problems of 450 particles, we investigated the particle motion and effects of particles on the flow for both Newtonian and shear-thinning fluid media. We report the prolonged particle movement toward the wall in case of a shear-thinning fluid, which has been interpreted with the shear rate distribution.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3391-3398
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• 2013

The carboxylated multiwall carbon nanotubes (MWCNT-COOH) and functionalized with isatin derivative (MWCNT-isatin) have been used as efficient adsorbents for the removal of lead (Pb) from aqueous solutions. The influence of variables including pH, concentration of the lead, amount of adsorbents and contact time was investigated by the batch method. The adsorption of the lead ions from aqueous solution by modified MWCNTs was studied kinetically using different kinetic models. The kinetic data were fitted with pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. The sorption process with MWCNT-COOH and MWCNT-isatin was well described by pseudo-second-order and pseudo-first-order kinetics, respectively which it was agreed well with the experimental data. Also, it involved the particle-diffusion mechanism. The values of regression coefficient of various adsorption isotherm models like Langmuir, Freundlich and Tempkin to obtain the characteristic parameters of each model have been carried out. The Langmuir isotherm was found to best represent the measured sorption data for both adsorbent.

• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.291-294
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• 2002

The reactions of triplet oxygen atom with halomethanes as a potential fire extinguisher were studied by a discharge flow-chemiluminescence imaging method. The experiments were carried out under second order conditions. The bimolecular atom-molecule reaction rate constants were determined in terms of the initial rate method. The initial concentration of oxygen atom was also determined under second order rate law instead of the pseudo-first order conditions with $[O(^3P)]_0{\ll}[sample]_0$. The second order conditions were more reliable than pseudo-first order conditions for the determinations of rate constants. The rate constants of the reactions $CF_3I\;+\;O(^3P)$, $CH_3PI\;+\'O(^3P)$, and $CHBrCl_2\;+\;O(^3P)$ were determined to be $5.0\;{\times}\;10^{-12}$ , $1.1\;×\;0^{-11}$ , and $1.9\;{\times}\;10^{-14}cm^3molecule^{-1}s^{-1}$, respectively.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1006-1011
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• 2010

This study was focused on the reactivity of furnace slag against cadmium to design the vertical drain method with reactive column for improving contaminated sea shore sediment. The removal capacity of furnace slag was analyzed using pseudo-second-order model. And the effective parameters of removal test were initial concentration and initial pH. According to equilibrium removal amount and reactive constant calculated by pseudo-second-order model, the removal capacity was analyzed. Equilibrium removal amount of furnace slag was linearly increased as increasing intial cadmium concentration. Because the pH was around 11, the removal mechanism of furnace slag could be both sorption and precipitation. Therefore the removal amount was increased due to initial concentration. pH was increased to around 11 in the case of "No treat", but the pH were 3.8 in the case of "HAc added" and 0.7 in the case of "HCl added". The removal amount was different 4.8, 1.19 and 0.27 mg/g. This results show the pH was major factor to remove cadmium using furnace slag.

• Journal of Korean Society for Atmospheric Environment
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• v.2 no.3
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• pp.11-18
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• 1986

In order to evaluate the state of the environmental pollution by vehicle exhaust in Seoul area the correlation between lead in air and leaves of roadside trees has been investigated during August in 1985. The dust in the atmosphere was collected by high volume air sampler to measure the concentration of lead. On the other hand, lead as a pollution indicator was extracted from the leaves of roadside trees (Ginkgo biloba, Salix pseudo/lasiogyne, platanus occidentalis) by conventional method and their concentrations were determined. The following results were obtained : 1. Lead concentrations in the leaves of roadside trees varied with trees, for example, the average concentrations of lead in each of the leaves of Ginkgo biloba, Salix pseudo/lasiogyne and Platanus occidentalis were 20.66 ppm, 9.37 ppm, and 10.58 ppm, respectively. 2. The dust sampled along heavily traveled highways showed that lead content tended to increase with traffic volume. 3. The correlation coefficients between lead correlation in air and leaves of Gingo biloba, Salix pseudo/lasiogyne, and Platanus orientalis were 0.80, 0.85, and 0.87, respectively.

• Journal of Korea Multimedia Society
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• v.16 no.12
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• pp.1465-1474
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• 2013

In this paper, air pollutant tracing models using perceptron neural network(PNN) and non-negative least square(NNLS) are proposed. When the measured values of the air pollution and the contribution concentration of each source by chemical transport modeling are given, they estimate and trace the amount of the air pollutants emission from each source. Two kinds of emissions data are used in the experiments : CH4 and N2O of Geumgo-dong landfill greenhouse gas, and PM10 of 17 areas in Northeast Asia and eight regions of the Korean Peninsula. Emission values were calculated using pseudo inverse method, PNN and NNLS. Pseudo inverse method could be used for the model, but it may have negative emission values. In order to deal with the problem, we used the PNN and NNLS methods. As a result, the estimation using the NNLS is closer to the measured values than that using PNN. The proposed tracing models have better utilization and generalization than those of conventional pseudo inverse model. It could be used more efficiently for air quality management and air pollution reduction.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.5
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• pp.118-123
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• 2001

Most structures of automobile are composed of many substructures connected to one another by various types of mechanical joints. In automotive engineering, it is important to study these connected structures under various dynamic farces for the evaluations of fatigue life and stress concentration exactly. It is rarely obtained the accurate load history of specified positions because of the errors such as modeling, measurement, and etc. In the beginning of design, exact load data are actually necessary for the fatigue strength and life analysis to minimize the cost and time of designing. In this paper, the procedure of practical dynamic load determination is developed by the combination of the principal stresses of F.E. analysis and experiment. Inverse problem and least square pseudo inverse matrix are adopted to obtain an inverse matrix of analyzed stresses matrix. Pseudo-Practical dynamic load was calculated for Lab. Test of sub-structure. GUI program(PLODAS) was developed for whole of above procedure. This proposed method could be extended to any geometric shape of structure.

• Advances in environmental research
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• v.6 no.2
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• pp.113-125
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• 2017

Santa Barbara Amorphous-15(SBA-15) nanoparticles were utilized as the inexpensive and effective adsorbents to remove methylene blue dye from the aqueous solution.SBA-15 was created by Zhao et al method. Infrared spectroscopy, X-ray diffraction and scanning electron microscopy (SEM) were used for the evaluated physical properties of SBA-15. The results of diffraction X-ray indicated that was the crystalline structure for it. Also IR spectroscopy indicated was a silica the whole structure of the groups and SEM image verify the structure of relatively identical particles size of SBA-15. Factors affecting adsorption including the amounts of adsorbent, pH and contact time were investigated by a SBA-15 nanomaterial design. The extent of dye removal enhanced with increasing initial dye concentration and pH from 4 to 10. The higher percentage adsorption were obtained under optimum conditions of variables (sorbent dose of 200 mg/liter, initial MB concentration 10 mg/liter, initial pH of 10 and temperature of $25^{\circ}C$). Maximum adsorption happened after the 2 hour and the kinetic processes of the dyes adsorption were described by applying the pseudo-first-order and the pseudo-second-order and the relatively High correlation with the kinetic Ellovich models. It was found that the pseudo-second-order models kinetic equation described the data of dye adsorption with a good correlation (R2>0.999) which indicated chemisorption mechanism. Freundlich and Langmuir adsorption models were investigated in conditions of variables (adsorbent dose 0.01 gr/liter, MB concentration 10, 20, 30 mg/liter, pH of 4, 7, 10, contact time 90 min and temperature of $27^{\circ}C$). The adsorption data were represented by Langmuir isotherm model. These values are higher than the adsorption capacities of some other adsorbents that have recently been published in the literature.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.11
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• pp.2037-2046
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• 2000

It has been reported that the inhibition effect of pH on activated sludge follows noncompetitive inhibition kinetics. However. the noncompetitive inhibition kinetic equation can not be directly applied to pH inhibition because of the difficulty in quantification of pH in terms of inhibitor concentration. So, many empirical equations have been developed to describe the pH inhibition effect especially for acidic condition. In this research. the pseudo toxic concentration ($C_{PT}$) concept model to quantify pH inhibition effect on activated sludge was proposed and compared to other existing models. The $C_{PT}$ concept model can explain the reduction of the maximum specific growth rate (${\mu}_{max}$) caused by the pH inhibition more accurately than any other models, at a wide range of pH. The only model parameter. $K_I$ can be easily estimated by Lineweaver-Burk linearization method.