• Journal of the Korean Ceramic Society
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• v.51 no.3
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• pp.139-144
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• 2014

Activated carbon fiber (ACF) was modified with MnS nanoparticles to prepare MnS-ACF, and it was employed for preparation of MnS-$ACF/TiO_2$ composites with titanium (IV) n-butoxide (TNB). The properties of MnS-$ACF/TiO_2$ composites were characterized by XRD, SEM, and EDX. EDX results showed the presence of C, O, and Ti as major elements and traces of the metal elements Mn and S. The photocatlytic activity was evaluated by degradation of methyl blue (MB) and methyl orange (MO) dye. The results demonstrated that as-prepared samples could effectively photodegrade MB and MO under UV irradiation. Subsequently, the decomposition of MB solution showed the combined effects of adsorptions by ACF and enhanced photocatalytic effect by $TiO_2$. Finally, the photocatalytic effect increased due to photo-induced-electron absorption effect by ACF and electron trap effect by comodified MnS nanoparticles.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.1
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• pp.6-14
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• 2012

For integrated complementary metal oxide semiconductor (CMOS) circuits, the lateral spread for two-dimensional (2-D) impurity distributions are very important for the analyzing the devices. The measured two-dimensional SEM data obtained using the chemical etching-method matched very well with the results of the Gauss model for boron implanted samples. But the profiles in boron implanted silicon were deviated from the Gauss model. The profiles in boron implanted silicon were shown a little bit steep profile in the deep region due to backscattering effect on the near surface from the bombardments of light boron ions. From the simulated 3-D data obtained using an analytical model, the 1-D and 2-D data were compared with the experimental data and could be verified the justification from the experimental data. The data of 3-D model were also shown good agreements with the experimental and the simulated data. It can be used in the 3-D chip design and the analysis of microelectro-mecanical system (MEMS) and special devices.

• The Journal of Korean Academy of Prosthodontics
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• v.25 no.1
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• pp.41-54
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• 1987

The purposes of this study were to evaluate the color differences those can exist between different brands of porcelain with identical shade designation, and to find their causes. For these purposes the following experiments were executed: The color of each opaque and layered porcelain specimen was determined by spectral reflectance measurements with a spectrophotometer. The compositions of each opaque porcelain powder were analyzed by qualitative, and quantitative analysis. Microscopic structures of each opaque porcelain were observed by scanning electron microscope. The results were as follows: 1. Identical shade of different brands of porcelain produced significantly different colors. 2. Color differences among the three brands were found under different light sources. 3. Color differences among the three brands were mostly a result of differences in kinds and amounts of opacifying agents and fluxes and microstructure of porcelain systems. 4. When porcelain systems have similar compositions and firing cycles, they produced similar colors.

• Composites Research
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• v.27 no.6
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• pp.236-241
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• 2014

This paper aims to evaluate material property variation of polymer concretes under ultra-violet exposure condition. The components and mixing ratio of the polymer composite specimens were determined by the previous research results. The equivalent UV exposure time was calculated with the consideration of the power of metal halide lamp and maximum 3 years were selected for the experiments. From the tests, it was found that the generated heat during UV exposure affected much the material properties of polymer concrete by means of post cure. As a result, the compressive strength increased and ductility factor decreased.

• Journal of the Korean Applied Science and Technology
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• v.37 no.5
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• pp.1100-1105
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• 2020

We investigated the driving force and the required charges for spontaneous reduction of metal nanoparticles (NPs) on a scotch tape induced by mechanochemical activation. The charges were analyzed based on anodic stripping voltammetry (ASV) of silver, which is proportional to the number of charge identities on the tape. The results supported that the driving force is mechanochemical radicals rather than ions in the light of the high charge density on the tape.

• Journal of Korean Society for Atmospheric Environment
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• v.4 no.1
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• pp.1-12
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• 1988

This study was carried out to measure the contents of soluble sulfur and heavy metals in the leaves of roadside tree at 34 sampling sites of Seoul area from the Sep. 1 to Sep. 30 during 1985 and 1986. The results were as follows; 1. Average contents of soluble sulfur at all sampling sites were; Plantanus orientalis 0.474%, Ginkgobioloba 0.562%, and Salix pseudolasiogyne 0.566%. 2. Correlation between sulfur dioxide concentration in the air and soluble sulfur in the leaves by area were; Green belt area R = 0.985, Residential area R = 0.856, Commercial area R = 0.668, Industrial area R = 0.886. Correlation by species were ; Platanus orientalis R = 0.817, Ginkgobiloba R = 0.771, Salix pseudo-lasiogyne R = 0.824. 3. Correlation between $SO_X$ concentration in the air and sulfur contents in the leaves showed positive significance. 4. Contents of soluble sulfur in the heavy traffic area were higher than that of light traffic area. 5. Heavy metal contents of 1986 were higher than that of 1985; Fe> Mn > Zn > Pb > Cu > Cd > Cr. 6. Lead contents in the leaves of 1986 were; Platanus orientalis 16, 701 ppm, Gingobiloba 21,729ppm, Salix Pseudo-lasiogyne 12.418 ppm.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.2
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• pp.346-351
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• 1997

The creep characteristics of an Al-5wt.% Ag alloy including the stress exponent, the activation energy for creep and the shape of the creep curve were investigated at a normalized shear stress extending from $ 10^{-5}{\;}to{\;}3{\times}10^{-4}$ and in the temperature range of 640-873 K, where silver is in solid solution. The experimental results shows that the stress exponent is 4.6, the activation energy is 141 kJ/mole, and the stacking fault energy is $180{\;}mJ/m^2$, suggesting that the creep behavior of Al-5 wt.% Ag is similiar to that reported for pure aluminum, and that under the current experimental conditions, the alloy behaves as a class II(metal class). The above creep characteristics obtained for Al-5 wt.% Ag are discussed in the light of prediction regarding deformation mechanisms in solid solution alloys.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.736-742
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• 2000

Mass removed from crystalline silicon samples during high power single-pulse laser ablation was studied by measuring the resulting crater morphology with a white light interferometric microscope. The volume and depth of the craters show a strong nonlinear change as the laser irradiance increases across a threshold value, that is, approximately $2.2{\times}10^{10}\;W/cm^2$. Time-resolved shadowgraph images of the ablation plume show the ejection of large particulates from the sample for laser irradiance above the threshold, with a time delay of about 300-400 nsec. The thickness of superheated liquid layer near the critical temperature was numerically estimated, considering the transformation of liquid metal into liquid dielectric near the critical state (i.e., induced transparency). The estimated thickness of the superheated layer at a delay time of 200 nsec agreed with the measured crater depths, suggesting that induced transparency promotes the formation of a deep superheated liquid layer which leads to an explosive boiling responsible for the sudden increase of crater volume and depth.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.407-412
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• 2000

In this study, a research for process design in bending of structural frame of AA6061-T6 with rubber pad was conducted. In this process, the conventional lower die made of metal is replaced with a polyurethane pad, resulting in high flexibility during bending. Vulcanized polyurethane rubber with shore A hardness of 60 was used for the pad. Experiments on a newly developed bending machine were carried out by controlling the stroke of the roller and horizontal movement of roller pad lower die. From this, the relation between roller path and geometry of the materials bent was obtained for the process design of producing roof rail part of a passenger car and the experimental result was compared with the target profile. For more accurate process design, it is required to control the roller path interactively. Based on the experience in developing the prototype bending machine, it is construed that a fully automated bending system with rubber pad to produce various light-weight components for automotive body frames can be successfully developed.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.207-207
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• 2010

Both ZnO and GaN have excellent physical properties in optoelectronic devices such as blue light emitting diode (LED), blue laser diode (LD), and ultra-violet (UV) detector. The ZnO/GaN heterostructure, which has a potential to achieve the cost efficient LED technology, has been fabricated by using radio frequency (RF) sputtering, pyrolysis, metal organic chemical vapor deposition (MOCVD), direct current (DC) arc plasmatron, and pulsed laser deposition (PLD) methods. Among them, the PLD system has a benefit to control the composition ratio of the grown film from the mixture target. A 500-nm-thick ZnO film was grown by PLD technique on c-plane GaN/sapphire substrates. The post annealing process was executed at some varied temperature between from $300^{\circ}C$ to $900^{\circ}C$. The morphology and crystal structural properties obtained by using atomic force microscope (AFM) and x-ray diffraction (XRD) showed that the crystal quality of ZnO thin films can be improved as increasing the annealing temperature. We will discuss the post-treatment effect on film quality (uniformity and reliability) of ZnO/GaN heterostructures.