• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.04a
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• pp.202-205
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• 2001

In this study, the electrokinetic remediation test for the kaolin contaminated by lead was performed and voltage, zeta potential, pH distribution, current, contamination transport in soil sample were studied and finite differential numerical analysis program(HERP) for a contaminated soil were compared with those of test. From the result of HERP, in the anode it was represented that the rest concentration was decreased with the voltage. Hence, if treatment time was continued for a long in the constant voltage, comparing with sample having no change in the rest concentration, it is considered that the voltage gradient is the control factor of the rest concentration.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.723-728
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• 2001

Wind flow perturbations, recirculations and turbulence generated by buildings often dominate air pollutant distributions around buildings. This paper describes dispersion of contaminants in the vicinity of a building by solving the concentration equation based on previously simulated wind flow field. Turbulence closure is achieved by using the standard k-e two-equation model. The paper shows application of the CIP method for solving a species concentration equation of contaminant gas around a rectangular building for two different sources under conditions of neutral atmospheric stratification. Results have been compared to the experimental data and the previous numerical results by hybrid scheme. The computational results of concentration profiles by the CIP method agree well with experimental data.

• Journal of the Korean Chemical Society
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• v.38 no.2
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• pp.129-135
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• 1994

Acyclic polyether dicarboxylic acid have been studied as metal cation carriers in a bulk liquid membrane system. The proton-ionizable ligands feature allows the coupling of a cation transport to reverse proton transport. This feature offers promise for the effective separation and concentration of metal cations with the metal cation transport being driven by a pH gradient. Metal cation transport increased regularly with increasing hydroxide($H^-$) concentration of source phase and with proton($H^+$) concentration of receiving phase. Competitive transport by the acyclic polyether dicarboxylic acids is selective for calcium ion over other alkaline-earth cations.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.11
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• pp.964-969
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• 2003

The objective of this study is to investigate the effect of surfactant on the onset of Marangoni convection adapting a non-linear surface equation of state. The surface tension gradient with respect to the absorbate concentration, ${\gamma}$, is linearly related to the surface concentration of a surfactant with a coeffcient $x_{A}$. The numerical results show that the role of the initial surfactant concentration to Marangoni instability changes from the stabilizer to the destabilizer depending on the change of the sign of $x_{A}$ from negative to positive. It is concluded that for $x_{A}$>0 there is a critical modified Marangoni number of surfactant $M_{Ac}$ $^{*}$ above which liquid layer is always unstable against long wave disturbances.rbances.

• International Journal of Oral Biology
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• v.42 no.4
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• pp.155-161
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• 2017

Teeth and bones are highly mineralized tissues containing inorganic minerals such as calcium phosphate, and a growing number of evidences show that their mineral content is associated with many diseases. Although the quantification of mineral contents by micro-computed tomography(micro- CT) has been used in diagnosis and evaluation for treating bone diseases, its application for teeth diseases has not been well established. In this study, we attempted to estimate a usefulness of a high-resolution micro-CT in analysis of human teeth. The teeth were scanned by using the Skyscan 1172 micro-CT. In order to measure tooth mineral content, beam hardening effect of the machine was corrected with a radiopaque iodine-containing substance, iodoacetamide. Under the maximum resolution of $6.6{\mu}m$, X-ray densities in teeth and hydroxyapatite standards were obtained with Hounsfield unit (HU), and they were then converted to an absolute mineral concentration by a CT Analyzer software. In enamel layer of cusp area, the mean mineral concentration was about $2.14mg/mm^3$ and there was a constant mineral concentration gradient from the enamel surface to the dentinoenamel junction. In the dentin of middle 1/3 of tooth, the mean mineral concentration was approximately $1.27mg/mm^3$ and there was a constant mineral concentration gradient from the outer of root to the pulp side, ranging from 1.3 to $1.06mg/mm^3$. In decay region of dentin, the mineral content was gradually decreased from the intact inner side to the decayed surface. These results suggest that high-resolution micro-CT can be as a useful tool for non-invasive measurement of mineral concentration in teeth.

• Journal of Biomedical Engineering Research
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• v.16 no.2
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• pp.209-216
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• 1995

Recently, a new tailored RF gradient echo (TRFGE) sequence was reported. This technique not only enhances the magnetic susceptibility effect but also allows us to measure local changes in brain oxygenation. In this study, a phantom and cat brain experiments were performed on a 4.7 Tesla BIQSPEC (BRUKER) instrument with a 26 cm gradient system. We have demonstrated that the signal intensity (SI) of the TRFGE sequence varies according to the concentration of susceptibility contrast agent. Three capillary tubes with different concentrations of Gd-DTPA (0.01, 0.05, 0.1 mMOI/l) were placed at the middle of a cylindrical water phantom. Using both TRFGE and conventional gradient echo (CGE) sequences, phantom images of the slices which contain all three tubes were obtained. For the animal experiment, cats were anesthetized and ventilated using halotane (0.5%) and a $N_2O/ O_2$ mixture (2:1), and blood pressure and heart rate were monitored and kept normal. For the observation of tue first pass of Gd- DTPA, imaging was started at t = 0. At t = 8 ~ 12s, 0.2 mMol/Kg Gd-DTPA was manually injected in the femoral vein. The imaging parameters were TRITE = 25/10 msec, flip angle = $30^{\circ}$, FOV = 10cm, image matrix size = $128{\times}128$ with 64 phase encodings and the image data acquisition window was 10 msec. SI-time curves were then obtained from a series of 30 images which were collected at 2 sec intervals using both CGE and TRFGE pulse sequences before, during, and following the contrast injection.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.6
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• pp.531-537
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• 2014

Terrestrial vegetation has been known as a main source of biogenic volatile organic compounds (BVOCs). Isoprene and monoterpene among the BVOCs are most abundant species emitted by forests, and have a significant impact on atmospheric chemistry. Abundancy of these species could lead to an increase or decrease in the production of natural tropospheric ozone in forests, depending on the nitric oxide (NO) concentration. Soil is the most significant source of natural NO. Understanding of NO emission from forest soil could be critical in evaluation of air quality in the forest area. Flux-gradient similarity theory (FGST) was applied for practical use to estimate forest soil NO emission at Mt. Taewha where is available micro-meteorological data near surface monitoring from flux tower. NO fluxes calculated by FGST were compared to flux results by flow-through dynamic chamber (FDC) measurement. Surface NO emission trends were shown between two different techniques, however their magnitudes were found to be different. NO emissions measured from FDC technique were relatively higher than those from theoretical results. Daily mean NO emissions resulted from FGST during Aug. 13, 14 and 15 were $0.28{\pm}8.45$, $2.17{\pm}15.55$, and $-3.18{\pm}13.65{\mu}gm^{-2}hr^{-1}$, respectively, while results from FDC were $2.26{\pm}1.44$, $5.11{\pm}3.85$, and $2.23{\pm}6.45{\mu}gm^{-2}hr^{-1}$. Trends of daily means were shown in similar pattern, which NO emissions were increasing during late afternoon ($r^2$=0.04). These emission trends could be because soil temperature and moisture influence importantly soil microbiology.

• Journal of Soil and Groundwater Environment
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• v.19 no.5
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• pp.26-34
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• 2014

A $1.5m(L){\times}1.0m(W){\times}1.1m(H)$ polypropylene (PP) field scale electroniketic system coupled with stainless steel electrodes was designed to examined metal removal performance applied 0.2-0.35 V/cm potential gradient and 0.05-0.5M lactic acid for 20 day. Electroosmosis permeabilities of $2.2{\times}10^{-5}cm^2/V-s$ to $4.8{\times}10^{-5}cm^2/V-s$ were observed and it increased with the potential gradient increased. The reservoir pH controlled at $7.0{\pm}1.0$ has been effectively diminished the clogging of most metal oxides. The best removal efficiency of Zn, Pb, and Ni was 78.4%, 84.3%, and 40.1%, respectively, in the field scale EK system applied 0.35 V/cm and 0.05M lactic acid for 20 days. Increasing potential gradient would more effectively enhance metal removal than increasing concentration of processing fluid. The reservoir and soil temperatures were majorly related to potential gradient and power consumptio. A $4-16^{\circ}C$ above room temperature was observed in the investigated system. It was found that the temperature increase in soil transported the pore water and metals from bottom to the topsoil. This vertical transport phenomenon is critical for the electrokinetic process to remediate in-situ deep pollution.

• The Korean Journal of Ecology
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• v.23 no.6
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• pp.423-429
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• 2000

To understand the effects of elevated $CO_2$ concentration and temperature on seedling emergence of seven herbaceous species, the seedling emergence was monitored between November 1997 and May 1998 using a temperature gradient chamber and a $CO_2$-temperature gradient chamber. Experiment was conducted under current ambient condition (Control plot), 2$^{\circ}C$-warmed condition with ambient $CO_2$ (T2 Plot), 4$^{\circ}C$-warmed condition with ambient $CO_2$ (T4 plot). and 4$^{\circ}C$-warmed condition with 1.8 fold of ambient $CO_2$ (CT4 plot). Species tested in this study were Digitaria adscendens, Echinochloa crus-galli, Panicum bisulcatum, Setaria viridis. Oenothera biennis, Andropogon virginicus, and Imperata cylindrica. Each species often dominates in the herbaceous stage of secondary succession in Japan. The mean seedling emergence times for all species were significantly increased to 23.6 and 32.2 d in the T2 and T4 plot compared to the Control plot, respectively. The most sensitive and insensitive species in seedling emergence time in T2 plot were O. biennis and D. adscendens, respectivel.y, and those in the T4 and CT4 plot were I. cylindrica and D. adscendens, E. crus-galli and A. virginicus, respectively. All experimental species showed no significant difference in the seedling emergence rate between treatments except for O. biennis and I. cylindrica. O. biennis showed a great decrease in the seedling emergence rate from 83.3% in the Control plot to 38.0%, 14.7%, and 29.3% in the T2, T4, and CT4 plot, respectively. Elevated $CO_2$ had very little effect on the seedling emergence. From these observations, it is expected that increased temperature would greatly advance the vegetative recovery time after disturbance through the advancement of seedling emergence time.

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.733-738
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• 2013

Sediment contains a high fraction of organic matter, high buffering capacity, and a large portion of fine grained particles such as silt and clay, which are major barriers to remove heavy metals from sediments. In this study, a lab-scale electrokinetic (EK) technique was applied to remove heavy metals effectively from marine sediment at a constant voltage gradient of 2 V/cm. A concentration of 0.1 M of ethylenediaminetetraacetic acid (EDTA), citric acid (CA), $HNO_3$, and HCl were circulated in the cathode, and tap water was circulated in the anode. CA extracted 92.4% of Ni, 96.1% of Cu, 97.1% of Zn, and 88.1% of Pb from marine sediment. A higher voltage gradient enhanced the transport of citrate and EDTA into the sediment and, therefore, increased metal extraction from the marine sediment through a complexation reaction between metals and the chelates. Based on these results, the electrokinetic process using a high voltage gradient with EDTA and CA might be useful to extract heavy metals from marine sediment.