• Journal of Conservation Science
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• v.32 no.3
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• pp.417-423
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• 2016

The effect of the glue solution were investigated in the grinding and elutriation process for manufacturing of White clay pigment. In grinding process, glue solution decreased the production of a too fine powder and enhanced the degree of sorting of ground pigments. The grinding performance and limit are generally influenced by the frictional force. Therefore, the friction force was measured in accordance with the grinding conditions. As a result of measuring a friction force, when using glue solution it showed the lowest friction. Finally, the application of glue solution in grinding process is believed to enhance the degree of sorting of ground pigments by reducing frictional force. In elutriation process, the application of glue solution enabled the screening of larger particles in the same conditions by reducing the sedimentation velocity. This result is due to increase in the viscosity of the glue solution according to glue concentration. As a result, the application of glue solution in elutriation process is though to enlarges the range of the selectable particle size and to enable the segmentation of the particles.

• Molecular & Cellular Toxicology
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• v.5 no.1
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• pp.75-82
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• 2009

Saengshik is an uncooked and powdered functional food composed of various edible plants, and has been consumed widely due to its health benefits and convenient uptake. Recently, superfine ground saengshik, which contains a certain extent of nanoscale particles, has been commercialized to enhance efficacy, but its safety has not been determined. This study was conducted to evaluate the food safety of superfine saengshik (SS) through general toxicity examination after oral uptake in mice compared to conventional fine saengshik (FS). The SS particle size distribution was 0.479-26.303 f.1m in diameter, with about 68.92% of particles with a diameter < $0.955{\mu}m$. From our safety evaluation, the number of white blood cells (WBCs) and biochemical values in the serum fell into the normal range, and the weight of organs showed no significant difference between FS and SS groups. Histological observation of the liver, small intestine and large intestine did not show any abnormal or pathological findings under light microscopy. Our results suggest that oral intake of SS is not harmful to mice in terms of general toxicity.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.65-65
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• 2015

In this talk, I will introduce two topics. The first topic is the polymer light emitting diodes (PLEDs) using graphene oxide quantum dots as emissive center. More specifically, the energy transfer mechanism as well as the origin of white electroluminescence in the PLED were investigated. The second topic is the facile synthesis of eco-friendly III-V colloidal quantum dots and their application to light emitting diodes. Polymer (organic) light emitting diodes (PLEDs) using quantum dots (QDs) as emissive materials have received much attention as promising components for next-generation displays. Despite their outstanding properties, toxic and hazardous nature of QDs is a serious impediment to their use in future eco-friendly opto-electronic device applications. Owing to the desires to develop new types of nanomaterial without health and environmental effects but with strong opto-electrical properties similar to QDs, graphene quantum dots (GQDs) have attracted great interest as promising luminophores. However, the origin of electroluminescence (EL) from GQDs incorporated PLEDs is unclear. Herein, we synthesized graphene oxide quantum dots (GOQDs) using a modified hydrothermal deoxidization method and characterized the PLED performance using GOQDs blended poly(N-vinyl carbazole) (PVK) as emissive layer. Simple device structure was used to reveal the origin of EL by excluding the contribution of and contamination from other layers. The energy transfer and interaction between the PVK host and GOQDs guest were investigated using steady-state PL, time-correlated single photon counting (TCSPC) and density functional theory (DFT) calculations. Experiments revealed that white EL emission from the PLED originated from the hybridized GOQD-PVK complex emission with the contributions from the individual GOQDs and PVK emissions. (Sci Rep., 5, 11032, 2015). New III-V colloidal quantum dots (CQDs) were synthesized using the hot-injection method and the QD-light emitting diodes (QLEDs) using these CQDs as emissive layer were demonstrated for the first time. The band gaps of the III-V CQDs were varied by varying the metal fraction and by particle size control. The X-ray absorption fine structure (XAFS) results show that the crystal states of the III-V CQDs consist of multi-phase states; multi-peak photoluminescence (PL) resulted from these multi-phase states. Inverted structured QLED shows green EL emission and a maximum luminance of ~45 cd/m2. This result shows that III-V CQDs can be a good substitute for conventional cadmium-containing CQDs in various opto-electronic applications, e.g., eco-friendly displays. (Un-published results).

• Resources Recycling
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• v.19 no.3
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• pp.62-70
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• 2010

As the demand for paper continues to grow and the importance of recycled paper, white ledgar(WL) and old newspaper pulp(ONP), continuously increase. In addition, usage of recycled paper is essential in terms of forest conservation and environmental protection issues. However, optical and mechanical properties of recycled paper have some drawbacks than regular paper's properties that is indispensable. In order to complement these problems of recycled paper, precipitated calcium carbonate (PCC) was synthesized by the In-situ process with a recycled pulp. Depending on the size of PCC is divided into 2 types, $0.01{\mu}m{\sim}0.09{\mu}m$ colloid type ultra-fine particle and $0.1{\mu}m{\sim}0.9{\mu}m$ cubic type particles. In this study, we analyze how the different shape and size of precipitated calcium carbonate affects in the optical and mechanical properties of the recycled paper used as a filler. Furthermore, we mixed with chemical pulp for overcome reduce of mechanical properties, without using other chemicals, when we use PCC as a filler. The results has the possibility to meet in GR excellent recycling certification mark, standard was proposed.

• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.299-306
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• 2016

In this study, new hydroxyapatite powder surface composites were investigated for protective effects against ultraviolet rays. Hydroxyapatite (HAp) is biocompatible and does not cause nebula phenomenon on skin. We investigated the surface modification of hydroxyapatite to improve UV block and skin usage. Dimethicone, lauroyl lysine, triethoxycaprylylsilane and silica were used as coating agents for the surface modification of HAp. To prepare the composite complex of the modified surface, the dimethicone, lauroyl lysine and triethoxycaprylylsilane were prepared by a dry process, and silica by a hydrothermal synthesis method. The HAp-silica was chosen as the best composite powder when measuring its sun protection levels. We investigated the characteristics of the surface of HAp-silica by SEM, particle size analyzer and energy dispersive spectrometry (EDS). Additionally, the stability in the formulation, UV block effect, and safety in BB creams were investigated. In conclusion, HAp-silica prepared by the modification of HAp complex surface improved the skin usage and UV block effect by enhancing the white cloudy phenomenon. These results indicate that HAp-silica may be used for UV block cosmetics.

• Applied Microscopy
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• v.42 no.2
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• pp.87-93
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• 2012

In this study, fine structures of silica, titanium dioxide, talc and kaolin used in decorative cosmetics and the mixture extracted from BB cream cosmetics were observed by scanning electron microscopy. Kaolin had plate like shape structures of polygon with smooth surface and edge of kaolin had a relatively smooth appearance in comparison with talc. Also, thickness of each layer was estimated to about $0.1{\mu}M$ in the lump formed in stratum of several layers. Talc was observed by lumps shape phase of layering very thin flake. Boundary of thin flake was sharp or angular phase and thickness of flake was approximately 600 nm in diameter. When comparing the thickness of kaolin and talc, we was confirmed that kaolin was thicker than talc. Diameter of titanium dioxide was estimated to 0.2~0.3 ${\mu}M$ and surface of particle was a soft cubic form. Silica was confirmed that variety of size from 200 nm to $15{\mu}M$ of globular shape was measured. From the observation of inorganic pigments, silica was homogeneous dispersed in the BB cream cosmetics and among each other was filled with relatively small size like talc, kaolin, titanium dioxide and iron oxide. In conclusion, we suggest that silica at decorative cosmetics were formed in cosmetic coat at the skin as the minimum thickness.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.388-388
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• 2016

Chemical mist deposition (CMD) of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was investigated with cavitation frequency f, solvent, flow rate of nitrogen, substrate temperature $T_s$, and substrate dc bias $V_s$ as variables for efficient PEDOT:PSS/crystalline (c-)Si heterojunction solar cells (Fig. 1). The high-speed camera and differential mobility analysis characterizations revealed that average size and flux of PEDOT:PSS mist depend on f, solvent, and $V_s$. The size distribution of mist particles including EG/DI water cosolvent is also shown at three different $V_s$ of 0, 1.5, and 5 kV for a f of 3 MHz (Fig. 2). The size distribution of EG/DI water mist without PEDOT:PSS is also shown at the bottom. A peak maximum shifted from 300-350 to 20-30 nm with a narrow band width of ~150 nm for PEDOT:PSS solution, whose maximum number density increased significantly up to 8000/cc with increasing $V_s$. On the other hand, for EG/water cosolvent mist alone, the peak maximum was observed at a 72.3 nm with a number density of ~700/cc and a band width of ~160 nm and it decreased markedly with increasing $V_s$. These findings were not observed for PEDOT:PSS/EG/DI water mist. In addition, the Mie scattering image of PEDOT:PSS mist under white bias light was not observed at $V_s$ above 5 kV, because the average size of mist became smaller. These results imply that most of solvent is solvated in PEDOT:PSS molecule and/or solvent is vaporized. Thus, higher f and $V_s$ generate preferentially fine mist particle with a narrower band width. Film deposition occurred when $V_s$ was impressed on positive to a c-Si substrate at a Ts of $30-40^{\circ}C$, whereas no deposition of films occurred on negative, implying that negatively charged mist mainly provide the film deposition. The uniform deposition of PEDOT:PSS films occurred on textured c-Si(100) substrate by adjusting $T_s$ and $V_s$. The adhesion of CMD PEDOT:PSS to c-Si enhanced by $V_s$ conspicuously compared to that of spin-coated film. The CMD PEDOT:PSS/c-Si solar cell devices on textured c-Si(100) exhibited a ${\eta}$ of 11.0% with the better uniformity of the solar cell parameters. Furthermore, ${\eta}$ increased to 12.5% with a $J_{sc}$ of $35.6mA/cm^2$, a $V_{oc}$ of 0.53 V, and a FF of 0.67 with an antireflection (AR) coating layer of 20-nm-thick CMD molybdenum oxide $MoO_x$ (n= 2.1) using negatively charged mist of 0.1 wt% 12 Molybdo (VI) phosphoric acid n-Hydrate) $H_3(PMo_{12}O_40){\cdot}nH_2O$ in methanol. CMD. These findings suggest that the CMD with negatively charged mist has a great potential for the uniform deposition of organic and inorganic on textured c-Si substrate by adjusting $T_s$ and $V_s$.

• Korean Journal of Heritage: History & Science
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• v.50 no.4
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• pp.148-165
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• 2017

Mural paintings drawn inside ancient tombs are very sensitive to changes in the environment such as temperature and humidity, especially the finish layer of the tomb murals differ in preservability depending on the material properties and humidity conditions. In this study, I examined the mural painting of Songsan-ri Tomb No.6, where the finish layer was made of earth, and identified the physical changes that can occur due to drying, depending on the material properties of the finish layer. I found out through particle size analysis that the finish layer of the mural painting in Songsan-ri Tomb No.6 is about 85.0wt% below silt, about 14.0wt% clay therein, mostly composed of silt and below clay. I also found out through physical property evaluation that surface change rate of samples showed the largest change at 15.5% in reproduced finish layer sample made up of bentonite, followed by 7.8% of reproduced finish layer sample made up of celadon soil, 6.3% of reproduced finish layer sample made up of loess, 6.2% of reproduced finish layer sample composed of white clay and the same order of change in appearance was confirmed in each sample consisted of soil. In addition, it showed the same trend of surface change rate, and the bentonite condition showed the largest change, in the measurement of shrinkage rate and expansion rate. The experiment shows that the finish layer composed of soil is affected by cohesion among particles according to the content of fine parts and the relationship between the agglomeration due to the content of the differentiated part and the stress due to the expansibility depending on the kind of the clay mineral etc. Therefore, it can be concluded that the physical damage occurred in the mural painting finish layer of the Songsan-ri Tomb No.6 is related to the factors such as the material characteristics of the soil and the highly humid environmental change inside the tomb.