• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.5
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• pp.435-440
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• 2002

In this study, we have investigated photo-induced changes of optical energy gap( $E_{OP)}$ and photoluminescence (PL) in amorphous ($\alpha$-) S $e_{100-x}$G $e_{x}$ (x=5, 25 and 33) thin films prepared by conventional thermal evaporation method. In the $\alpha$-S $e_{100-x}$G $e_{x}$ thin film, the $E_{OP}$ is obtained by a linear extrapolation of the ($\alpha$hν)$^{\frac{1}{2}}$ versus hν plot to the energy axis using the optical absorption coefficient ($\alpha$) calculated from the extinction coefficient k measured in the wavelength range of 290~900nm. Although the values of $\Delta$ $E_{OP}$ are very different, all films exhibit photo-induced photo-darkening (PD) effect that is a red shift of $E_{OP}$ . In particular, $\Delta$ $E_{OP}$ in $\alpha$-S $e_{75}$ G $e_{25}$ thin film exhibits the largest value (i, e., $\Delta$ $E^{OP}$ ~40meV for $\alpha$-S $e_{95}$ G $e_{5}$ , $\Delta$ $E_{OP}$ ~200meV for $\alpha$-S $e_{75}$ G $e_{25}$ , $\Delta$ $E_{OP}$ ~130meV for $\alpha$-S $e_{67}$ G $e_{33}$ ). PL spectra in $\alpha$-SeGe by hν$_{HeCd}$ have no-Stokes shift (SS) and show a tendency dependent on both composition and illumination time. We explain the energy-induced phenomena such as the PD and thermal bleaching, the native charged-defect generation and the no-SS PL, etc..the PD and thermal bleaching, the native charged-defect generation and the no-SS PL, etc..tc..

• Journal of the Korea Institute of Building Construction
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• v.17 no.4
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• pp.385-391
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• 2017

The warranty liability period for defects in apartment buildings by work type is not based on scientific analysis, making the appropriateness of the term a culprit behind the lawsuits. Therefore, this research aims to evaluate the appropriateness of the warranty liability term of apartment buildings by identifying the current status of defects, in particular, caused by finishing works. That is because the number of defects, caused during the finishing works, accounted for the largest portion of the total defect cases of apartment buildings reported to the Apartment Defect Dispute Mediation Committee under the Ministry of Land, Infrastructure, and Transport of Korea between 2010 and 2011. The result from analyzing claims for defect repairs of the finishing works showed that most cases by work type continued to be made after two years, and only about 60% were charged within the warranty period. And, defects by work type have correlation, which needs to be considered for a better construction technique. Considering a low correlation between the possibility of defects and the construction performance rankings, which are highly relevant to the apartment preference. It is believed that there needs to be a qualification process for agencies that actually performs finishing works.

• Bulletin of the Korean Chemical Society
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• v.13 no.2
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• pp.127-131
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• 1992

Changes in network structures of ${\alpha}-Nb_2O_5$ in the X MgO+(1-X) ${\alpha}-Nb_2O_5$ solid solutions occurring as the MgO doping level (X) was varied were investigated by means of infrared spectroscopy and X-ray analysis. X-ray diffraction revealed that all the synthesized specimens have the monoclinic structure. The FT-IR spectroscopy showed that the system investigated forms the solid solutions in which $Mg^{2+}$ ions occupy the octahedral sites in parent crystal lattice. Electrical conductivities were measured as a function of temperature from 600 to $1050{\circ}$ and $P_{O2}$ form $1{\times}10^{-5}$ to $2{\times}10^{-1}$ atm. The defect structure and conduction mechanism were deduced from the results. The $1}n$ value in ${\alpha}{\propto}{P_{O2}^{1}n}}$ is found to be -1/4 with single possible defect model. From the activation energy ($E{\alpha}$ = 1.67-1.73 eV) and the1/n value, electronic conduction mechanism is suggested with a doubly charged oxygen vacancy.

• Nuclear Engineering and Technology
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• v.41 no.1
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• pp.21-38
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• 2009

The use of multi scale modeling concepts and simulation techniques to study the destabilization of an ultrathin layer of oxide interface between a metal substrate and the surrounding environment is considered. Of particular interest are chemo-mechanical behavior of this interface in the context of a molecular-level description of stress corrosion cracking. Motivated by our previous molecular dynamics simulations of unit processes in materials strength and toughness, we examine the challenges of dealing with chemical reactivity on an equal footing with mechanical deformation, (a) understanding electron transfer processes using first-principles methods, (b) modeling cation transport and associated charged defect migration kinetics, and (c) simulation of pit nucleation and intergranular deformation to initiate the breakdown of the oxide interlayer. These problems illustrate a level of multi-scale complexity that would be practically impossible to attack by other means; they also point to a perspective framework that could guide future research in the broad computational science community.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.660-665
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• 1996

Thin films of indium oxide and indium tin oxide have been prepared by d.c. magnetron sputtering onto the fused silica substrates kept at 90, 200 and $300^{\circ}C$. In order to elucidate the optical absorption process in low energy region below 3 eV, we have analyzed the absorption coefficients obtained from reflectance and transmittance measurements for these films based on the Lucovsky model. It has been found for the first time that a defect center in the band gap is located at 0.8~1.4 eV below the Fermi level in all films and arises from oxygen vacancies in their films. The optical absorption in low energy region is explained to be dominated by the transition of electrons trapped at the positively charged (+2e) oxygen vacancies with s-like nature to the conduction band formed from the 5s-orbit in indium atoms.

• Bulletin of the Korean Chemical Society
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• v.13 no.3
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• pp.248-252
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• 1992

$ZrO_2-dopedYb_2O_3solid$ solutions containing 1, 3, 5, 7 and 9 mol% $ZrO_2were$ synthesized from spectroscopically pure $Yb_2O_3$ and $ZrO_2$ powders and found to be rare earth C-type structure by XRD technique. Electrical conductivities were measured as a function of temperatures from 700 to $1050^{\circ}C$ and oxygen partial pressures from 1${\times}$$10^-5$ to 2${\times}$ $10^-1$atm. The electrical conductivities depend simply on temperature and the activation energies are determined to be 1.56-1.68 $_eV$. The oxygen partial pressure dependence of the electrical conductivity shows that the conductivity increases with increasing oxygen partial pressure, indicating p-type semiconductor. The $PO_2$ dependence of the system is nearly power of 1/4. It is suggested from the linearity of the temperature dependence of electrical conductivity and only one value of 1/n that the solid solutions of the system have single conduction mechanism. From these results, it is concluded that the main defects of the system are negatively doubly charged oxygen interstitial in low. $ZrO_2doping$ level and negatively triply charged cation vacancy in high doping level and the electrical conduction is due to the electronic hole formed by the defect structure.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.254.2-254.2
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• 2014

The Transmission Fourier Transform Infrared spectroscopy (FTIR) of SiOx charge storage layer with the richest silicon content showed an assignment at peaks around 2000~2300 cm-1. It indicated that the existence of many silicon phases and defect sources in the matrix of the SiOx films. The total hysteresis width is the sum of the flat band voltage shift (${\Delta}VFB$) due to electron and hole charging. At the range voltage sweep of ${\pm}15V$, the ${\Delta}VFB$ values increase of 0.57 V, 1.71 V, and 13.56 V with 1/2, 2/1, and 6/1 samples, respectively. When we increase the gas ratio of SiH4/N2O, a lot of defects appeared in charge storage layer, more electrons and holes are charged and the memory window also increases. The best retention are obtained at sample with the ratio SiH4/N2O=6/1 with 82.31% (3.49V) after 103s and 70.75% after 10 years. The high charge storage in 6/1 device could arise from the large amount of silicon phases and defect sources in the storage material with SiOx material. Therefore, in the programming/erasing (P/E) process, the Si-rich SiOx charge-trapping layer with SiH4/N2O gas flow ratio=6/1 easily grasps electrons and holds them, and hence, increases the P/E speed and the memory window. This is very useful for a trapping layer, especially in the low-voltage operation of non-volatile memory devices.

• Journal of the Korean Chemical Society
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• v.37 no.4
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• pp.390-395
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• 1993

The x values and electrical conductivities of the nonstoichiometric compounds$ CeO_{2-x} have been measured in a temperature range from 600 to 1200$^{\circ}C$ under oxygen partial pressure of $2{\times}10^{-1}{\sim}1{\times}10^{-4}$ atm. The enthalpy of the defect formation shows an endothermic process with the oxygen partial pressure dependence (1/n value) of -1/3.18 ∼ -1/3.69. The activation energy and 1/n value for the electrical conductivity are estimated as 1.75 eV and -1/4, respectively. According to the x values, the $\sigma$ values, and the thermodynamic data, the defect structure of the ceria seems to be the formation of singly charged negative oxygen vacancies. The n-type semiconducting behaviors could be explained by the presence of excess metals in the lattice as the conduction electron donor.

• The Journal of the Korea Contents Association
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• v.1 no.1
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• pp.8-14
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• 2001

In this paper, we suggests a algorithms of recognizing the disease region by extracting particular organ from medical image. This method can extract liver region in spite of input image including many organs and charged format by using multi-threshold of feed-back-structure for segmentation liver region, and suggest the recognition of disease region in extracted liver, using multi-neural network structured by RBF and BP, overcoming the defect of single-neural network. The algorithm in this paper is proficient in adaptation for a multi form change of input medical image. This algorithm can be used at tole-medicine through automatic recognition after recognizing of the disease region by real-tire medical Image.

• Journal of the Korean Ceramic Society
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• v.47 no.1
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• pp.19-25
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• 2010

Traditional Kr$\ddot{o}$ger-Vink (K-V) notation defines sites in ionic crystals as interstitial or belonging to host ions. It enables description and calculations of combinations of native and foreign defects, including dopants and substituents. However, some materials exhibit inherently disordered partial occupancy of ions and vacancies, or partial occupancy of two types of ions. For instance, the high temperature disordered phases of $Bi_2O_3$, $Ba_2In_2O_5$, $La_2Mo_2O_9$, mayenite $Ca_{12}Al_{14}O_{33}$, AgI, and $CsHSO_4$ are all good ionic conductors and thus obviously contain charged point defects. But traditional K-V notation cannot account for a charge compensating defect in each case, without resorting to terms like "100% substitution" or "Frenkel disorder". the former arbitrary and awkward and the latter inappropriate. Instead, a K-V compatible nomenclature in which the partially occupied site is defined as the perfect site, has been proposed. I here introduce it thoroughly and provide a number of examples.