• Journal of the korean academy of Pediatric Dentistry
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• v.3 no.1
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• pp.52-62
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• 1976

The purpose of this paper is to present the clinical findings obtained from the fourth year epidemiological study on dental caries prevalence in Korean children and to compare them with those from the first year study made in 1973 by Paik. The oral examination was performed for this study on 1,451 children, composed of 808 boys and 643 girls, at "K" elementary school located in Seoul, Korea. The following conclusions are drawn: 1. The df person rate of primary teeth is 90.30% for boys, 90.67% for girls, and 90.43% for all, which is 7.41% higher than the first year value. 2. The dft index per child of primary teeth is 4.26 for boys, 4.30 for girls, and 4.28 for all, which is 0.42 higher than the first year value. The dt index is 2.49 for boys, 2.44 for girls, and 2.47 for all, which is 0.59 lower than the first year value. The ft index is 1.77 for boys, 1.86 for girls, and 1.81 for all, which is 1.01 higher than the first year value. 3. The DMF person rate of permanent teeth is 70.24% for boys, 73.05% for girls, and 71.49% for all, which is 16.28% lower than the first year value. 4. The DMFT index per child of permanent teeth is 2.08 for boys, 2.50 for girls, and 2.27 for all, which is 1.31 lower than the first year value. The DT index is 1.44 for boys, 1.64 for girls, and 1.53 for all, which is 1.53 lower than the first year value. The FT index is 0.61 for body, 0.85 for girls, and 0.71 for all, which is 0.21 higher than the first year value. The MT index is 0.02 for all, which is statistically the same as the first year value.

• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.988-992
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• 2011

$CO_2$ adsorption on mineral sorbents has a potential to sequester $CO_2$. This study used a density functional theory (DFT) study of $CO_2$ adsorption on barium oxide (BaO) in the presence of $H_2O$ to determine the role of $H_2O$ on the $CO_2$ adsorption properties on the ($2{\times}2$; $11.05\;{\AA}{\times}11.05\;{\AA}$) BaO (100) surface because BaO shows a high reactivity for $CO_2$ adsorption and the gas mixture of power plants generally contains $CO_2$ and $H_2O$. We investigated the adsorption properties (e.g., adsorption energies and geometries) of a single $CO_2$ molecule, a single $H_2O$ molecule on the surface to achieve molecular structures and molecular reaction mechanisms. In order to evaluate the coordinative effect of $H_2O$ molecules, this study also carried out the adsorption of a pair of $H_2O$ molecules, which was strongly bounded to neighboring (-1.91 eV) oxygen sites and distant sites (-1.86 eV), and two molecules ($CO_2$ and $H_2O$), which were also firmly bounded to neighboring sites (-2.32 eV) and distant sites (-2.23 eV). The quantum mechanical calculations show that $H_2O$ molecule does not influence on the chemisorption of $CO_2$ on the BaO surface, producing a stable carbonate due to the strong interaction between the $CO_2$ molecule and the BaO surface, resulting from the high charge transfer (-0.76 e).

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.391-402
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• 2001

The reports concerning dental disease in handicapped children are contentious, and there are many differences of opinion as to what extent handicapped children differ in oral health and disease from healthy children. The present study was done by conducting a comprehensive study and evaluation of the oral health between the 267 handicapped and the 128 normal persons with regard to caries rate, occlusion and the condition of the periodontium. The result showed that the dft, the dfs and DMFT indices of handicapped persons according to age were significantly lower than those of normal persons(p<0.05). The prevalence of gingivitis in handicapped persons increased with age and was significantly higher than those reported for normal persons(p<0.001). It was found that the handicapped group had a significant difference in the class distribution of occlusion, with a higher percentage of Class II and Class III occlusion from that observed in the control group(p<0.05).

• Journal of the Korean Ceramic Society
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• v.53 no.3
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• pp.282-287
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• 2016

This study involves enhancing the performance of the $Na(Li,Ti)O_2$ system as an Na-ion battery anode with the addition of Mg, which partially replaces Li ions. We perform both computational and experimental approaches to achieve a higher reversible capacity and a faster transport of Na ions for the devised system. Computational results indicate that the $Na(Li,Mg,Ti)O_2$ system can provide a lower-barrier path for Na-ion diffusion than can a system without the addition of Mg. Experimentally, we synthesize various $Na_z(Li_y,Mg_x,Ti)O_2$ systems and evaluate their electrochemical characteristics. In agreement with the theoretical study, Mg addition to such systems improves general cell performance. For example, the prepared $Na_{0.646}(Li_{0.207}Mg_{0.013}Ti_{0.78})O_2$ system displays an increase in reversible capacity of 8.5% and in rate performance of 13.5%, compared to those characteristics of a system without the addition of Mg. Computational results indicate that these improvements can be attributed to the slight widening of the Na-$O_6$ layer in the presence of Mg in the $(Li,Ti)O_6$ layer.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3285-3292
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• 2012

The interaction of thiazole drug with (6,0) zigzag single-walled boron nitride nanotube of finite length in gas and solvent phases was studied by means of density functional theory (DFT) calculations. In both phases, the binding energy is negative and presenting characterizes an exothermic process. Also, the binding energy in solvent phase is more than that the gas phase. Binding energy corresponding to adsorption of thiazole on the BNNT model in the gas and solvent phases was calculated to be -0.34 and -0.56 eV, and about 0.04 and 0.06 electrons is transferred from the thiazole to the nanotube in the phases. The significantly changes in binding energies and energy gap values by the thiazole adsorption, shows the high sensitivity of the electronic properties of BNNT towards the adsorption of the thiazole molecule. Frontier molecular orbital theory (FMO) and structural analyses show that the low energy level of LUMO, electron density, and length of the surrounding bonds of adsorbing atoms help to the thiazole adsorption on the nanotube. Decrease in global hardness, energy gap and ionization potential is due to the adsorption of the thiazole, and consequently, in the both phases, stability of the thiazole-attached (6,0) BNNT model is decreased and its reactivity increased. Presence of polar solvent increases the electron donor of the thiazole and the electrophilicity of the complex. This study may provide new insight to the development of functionalized boron nitride nanotubes as drug delivery systems for virtual applications.

• International Journal of Highway Engineering
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• v.16 no.5
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• pp.59-66
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• 2014

PURPOSES : This study is to predict the Sound Pressure Level(SPL) obtained from the Noble Close ProXimity(NCPX) method by using the Extended Kalman Filter Algorithm employing the taylor series and Linear Regression Analysis based on the least square method. The objective of utilizing EKF Algorithm is to consider stochastically the effect of error because the Regression analysis is not the method for the statical approach. METHODS : For measuring the friction noise between the surface and vehicle's tire, NCPX method was used. With NCPX method, SPL can be obtained using the frequency analysis such as Discrete Fourier Transform(DFT), Fast Fourier Transform(FFT) and Constant Percentage Bandwidth(CPB) Analysis. In this research, CPB analysis was only conducted for deriving A-weighted SPL from the sound power level in terms of frequencies. EKF Algorithm and Regression analysis were performed for estimating the SPL regarding the vehicle velocities. RESULTS : The study has shown that the results related to the coefficient of determination and RMSE from EKF Algorithm have been improved by comparing to Regression analysis. CONCLUSIONS : The more the vehicle is fast, the more the SPL must be high. But in the results of EKF Algorithm, SPLs are irregular. The reason of that is the EKF algorithm can be reflected by the error covariance from the measurements.

• Polymer(Korea)
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• v.34 no.1
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• pp.69-73
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• 2010

Effects of reaction time and temperature on the isomerization and dehydrobromination reactions of brominated butyl rubber were investigated. The structural composition of brominated butyl rubber was determined by Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance spectroscopy($^1H$-NMR), Density functional theory (DFT) was used to study on the isomerization and dehydrobromination mechanisms of model compounds. The geometries for model compounds of 3-bromo-5,5,7,7-tetramethyl-2(2',2',4',4'-tetramethyl)pentyl-1-octylene (3BrOE), 1-bromo-5,5,7,7-tetramethyl-2(2',2',4',4'-tetramethyl)pentyl-2-octylene (1Br2OE) and 5,5,7,7-tetramethyl-2(2',2', 4',4'-tetramethyl)pentyl-1,3-octadiene (CD) had been optimized by using density functional theory at B3LYP/3-21G and B3LYP/6-31G levels. The predicted energy of 3BrOE lies higher than that of 1Br2OE which suggests that 1Br2OE configuration is more stable than the 3BrOE configuration. Compared with the energy barrier, the pathway of dehydrobromination is less competitive than that of isomerization. This is qualitatively consistent with the experimental results.

• Proceedings of the Korean Magnestics Society Conference
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• 2011.06a
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• pp.129-129
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• 2011

The limited understanding of the surface properties of $Pt_3Ni$ for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cell (PEMFC) has motivated the study of properties and electronic structures of seven layered $Pt_3Ni$ (001), (110), and (111) surfaces. The first principle method based on density functional theory (DFT) is carried out. It is found that the bulk $Pt_3Ni$ has a ferromagnetic ground state with the ordered fcc type L12 structure, which is in good agreement with other results. Non magnetic Pt has the induced magnetic moment due to the strong hybridization between 3d Ni and 5d Pt. The magnetic moment of Pt and Ni enhanced on the surface of each due to surface effect however the magnetic moment of surface Pt in the Pt-segregated Pt3Ni (111) decreased and the magnetic moment of Ni in Ni rich subsurface increased significantly. The calculated d band centers of Pt explain the possibilities for oxygen absorption and play the important roles in altering the catalytic properties. The spin polarized densities of states are presented in order to understand physical properties of Pt in different surfaces in detail.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.109-110
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• 2008

We have performed a density functional theory study to investigate the reaction of the $HfCl_4$ molecule on $H_2O$ terminated Si (001)-$(2\times1)$ surface. The reaction of the $HfCl_4$ molecule is more favorable on OH-terminated site than H-terminated site. The first $HfCl_4$ molecule is adsorbed on a OH-terminated site with 0.21 eV energy benefit. The second $HfCl_4$ molecule is adsorbed on the most adjacent OH-terminated site of the first molecule and the energy benefit is 0.28 eV. The third and forth molecules have same tendency with the first and second ones. The adsorption energies of the fifth and sixth $HfCl_4$ molecules are 0.01 eV, -0.06 eV respectively. Therefore, we find that the saturation Hf coverage is approximately 5/8 of the available hydroxyl site, which is $2.08\times10^{14}/cm^2$. Our model is well matched with an experimental study by reference.

• The Korean Journal of Pesticide Science
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• v.9 no.3
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• pp.191-198
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• 2005

Hippuryl-L-histidyl-L-leucine (Hip-L-His-L-Leu, HHL) is the known substrate of ACE, which used often in inhibition kinetic study to design new inhibitor. Here we use HHL molecule as a template to predict pharmacophore which can interact with residues in active site of AnCE, new potential insecticide target protein. To explain physicochemical properties related to molecular geometry and conformational change in reaction field as well as electron density of atoms associated to pharmacophores, geometry optimization, NMR chemical shifts and natural population analysis were performed by ab initio and DFT method. Calculated NMR chemical shifts showed good agreement with the experimental ones and obtained electron densities were used for analyzing pharmacophores of corresponding atoms. Finally, we could extract aye pharmacophores related to hydrophobic aliphatic and aromatic site, hydrogen bonding donor and acceptor site and Zn binding site from the HHL molecule.