• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.19.1-19.1
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• 2011

We report on the metal-insulator transition that occurs as a function of film thickness in ultrathin $La_{0.75}Sr_{0.25}VO_3$ films. The metal-insulator transition displays a critical thickness of 5 unit cell. Above the critical thickness, metallic films exhibit a temperature driven metal-insulator transition with weak localization behavior. With decreasing film thickness, oxygen octahedron rotation in the films increases, causing enhanced electron-electron correlation. The electron-electron correlations in ultrathin films induce the transition from metal to insulator in addition to Anderson localization.

• The korean journal of orthodontics
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• v.34 no.4 s.105
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• pp.325-332
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• 2004

A self-etching primer that combines the etchant and primer in one chemical compound saves time and should be mote cost-effective to the clinician and patient. The purpose of this study was to evaluate the clinical effectiveness of a self-etching primer by measuring shear bond strengths according to various conditions and observing adhesive failure patterns. For this Investigation, 120 upper and lower premolars extracted for orthodontic purposes were used and randomly divided into six groups of twenty teeth each. Human premolars were embedded in a metal cylinder with orthodontic resin. Metal brackets and ceramic brackets were bonded with XT primer and self-etching primer by means of XT adhesive. Upon curing, plasma arc light and visible light were used. After bonding, the shear bond strength was tested by Instron universal testing machine, and the amount of residual adhesive that remained on the tooth after debonding was measured by stereoscope and assessed with an adhesive remnant index. The results were as fellows: 1. When brackets were bonded, if other conditions remained the same, there was no significant difference in shear bond strength due to the type of primer - either self-etching primer or XT primer. 2. When metal brackets were bonded, there was no significant difference in shear bond strength according to the source of light - plasma arc light or visible light - and type of primer. 3. There was a very significant difference in shear bond strength according to the type of brackets - metal or ceramic brackets. The shear bond strength of ceramic brackets was stronger than metal brackets. 4. When the adhesive failure patterns of metal brackets bonded with self-etching primer were observed by using the adhesive remnant index, the bond failure of the metal bracket occurred more frequently at the bracket-adhesive. The failure of the ceramic bracket, however, occurred more frequently at the enamel-adhesive interface. The adhesive failure patterns of metal brackets bonded with XT primer observed the same patterns. The above results suggest that self-etching primer can be clinically useful for bonding the brackets without fear of a decrease in shear bond strength.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2570-2575
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• 2021

The exchange behaviors of hydrogen isotopes between protonated lithium metal compounds and deuterated water or tritiated water were investigated. The various protonated lithium metal compounds were prepared by acid treatment of lithium metal compounds with different crystal structures and metal compositions. The protonated lithium metal compounds could more effectively reduce the deuterium concentration in water compared with the corresponding pristine lithium metal compounds. The H⁺ in the protonated lithium metal compounds was speculated to be more readily exchangeable with hydrons in the aqueous solution compared with Li⁺ in the pristine lithium metal compounds, and the exchanged heavier isotopes were speculated to be more stably retained in the crystal structure compared with the light protons. When the tritiated water (157.7 kBq/kg) was reacted with the protonated lithium metal compounds, the protonated lithium manganese nickel cobalt oxide was found to adsorb and retain twice as much tritium (163.9 Bq/g) as the protonated lithium manganese oxide (69.9 Bq/g) and the protonated lithium cobalt oxide (75.1 Bq/g) in the equilibrium state.

• The korean journal of orthodontics
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• v.27 no.5 s.64
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• pp.781-789
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• 1997

The purpose of this study was to evaluate the effects of fluoride relasing orthodontic sealant on the shear bond strength of light-and chemical-cured orthodontic rosins, to compare the shear bond strenth with light-and chemical-cured orthodontic resins, and to identify the changes of shear bond strength by rebonding in vitro. The brackets were divided into eight groups. Each group of metal brackets had different bonding mechanisms with adhesives. Group A : Transbond only Group B : Mono-Lok 2 only Group C : Light cured FluoroBond+Transbond Group D : Light cured FluoroBond+Mono-Lok 2 Group E : Transbond only(rebonded) Group F : Nomo-Lok 2 only(rebonded) Group G : Light cured FluoroBond+Transbond(rebonded) Group H : Light cured FluoroBond+Mono-Lok 2(rebonded) 65 extracted human premolars were prepared for bonding and 65 metal brackets for each group were bonded to prepared enamel surfaces of buccal surfaces as the above prescription. 24 hours bonding after, the Instron universal testing machine was used to test the shear bond strength of metal brackets to enamel. After debonding, same kind of metal brackets for each group were rebonded to prepared enamel surfaces of buccal surfaces to test the shear bond strength at the rebonding to enamel. Statistical analysis of the data was carried out Student's t-test ANOVA test, and Scheffe test using $SPSS/PC^+$ The results were as follows : 1. The order of shear bond strength was Group B(11.84MPa), Group A(10.75MPa), Group, D(9.69MPa), and Group C(9.39MPa)in lst bonded groups. 2. The order of shear bond strength was Group E(7.40MPa), Group G(6.48MPa), Group F(5.89MPa), and Group H(5.15MPa) in rebonded groups. 3. The shear bond strength of chemical cured orthodontic rosins had higher than that of light-cured orthodontic resins in all groups, but there was no statistical significance between groups(P>0.05). 4. In rebonded groups, the shear bond strength of light cured orthodontic rosins had higher than that of chemical cured orthodontic resins, but there was no statistical significance between groups(P>0.05). 5. The shear bond strength of all rebonded groups progressively decreased than that of 1st bonded groups, and there was statistical significance between groups(p<0.05, p<0.001).

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.86-86
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• 2012

The new approaches for silicon solar cell of new concept have been actively conducted. Especially, solar cells with wire array structured radial p-n junctions has attracted considerable attention due to the unique advantages of orthogonalizing the direction of light absorption and charge separation while allowing for improved light scattering and trapping. One-dimenstional semiconductor nano/micro structures should be fabricated for radial p-n junction solar cell. Most of silicon wire and/or pillar arrays have been fabricated by vapour-liquid-solid (VLS) growth because of its simple and cheap process. In the case of the VLS method has some weak points, that is, the incorporation of heavy metal catalysts into the growing silicon wire, the high temperature procedure. We have tried new approaches; one is electrochemical etching, the other is noble metal catalytic etching method to overcome those problems. In this talk, the silicon pillar formation will be characterized by investigating the parameters of the electrochemical etching process such as HF concentration ratio of electrolyte, current density, back contact material, temperature of the solution, and large pre-pattern size and pitch. In the noble metal catalytic etching processes, the effect of solution composition and thickness of metal catalyst on the etching rate and morphologies of silicon was investigated. Finally, radial p-n junction wire arrays were fabricated by spin on doping (phosphor), starting from chemical etched p-Si wire arrays. In/Ga eutectic metal was used for contact metal. The energy conversion efficiency of radial p-n junction solar cell is discussed.

• Bulletin of the Korean Chemical Society
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• v.24 no.1
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• pp.49-54
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• 2003

TiO₂nanoparticles were synthesized using the metallorganic chemical vapor deposition process. Particles with and without metal ion dopants were obtained. X-ray photoelectron and energy dispersive X-ray spectroscopic measurements confirmed the stoichiometry of the TiO₂nanoparticles. X-ray diffraction patterns showed a polycrystalline anatase structure of TiO₂. Transmission electron microscopy revealed that these particles are of nanoscale dimensions. Exact particle size and size distribution analyses were carried out by dynamic light scattering. The average particle size was determined to be 22 nm. The nanosize particles provided large surface area for photocatalysis and a large number of free surface-charge carriers, which are crucial for the enhancement of photocatalytic activity. To improve the photocatalytic activity, metal ions, including transition metal ions $(Pd^{2+},\;Pt^{4+},\;Fe^{3+})$ and lanthanide ion $(Nd^{3+})$ were added to pure TiO₂nanoparticles. The effects of dopants on photocatalytic kinetics were investigated by the degradation of 2-chlorophenol under an ultraviolet light source. The results showed that the TiO₂nanoparticles with the metal ion dopants have higher photocatalytic activity than undoped TiO₂. The $Nd^{3+}$ ion of these dopant metal ions showed the highest catalytic activity. The difference in the photocatalytic activity with different dopants is related to the different ionic radii of the dopants.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.2
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• pp.142-147
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• 2009

Conventional HP(high pressure) sodium or Metal-halide lamps have a life span of around one year requiring at least annual replacement and maintenance. High Power LED lights require no regular maintenance further increasing savings on replacement bulbs, access equipment and labour costs. New installations benefit from a substantial reduction in the cost of expensive heavy duty cable required for sodium lighting. Especially, LED light can achieve variable color temperature, high functional performance in the field of street light. There are two main method to achieve variable color temperature function of the street light. one method is using RGB multi-chip LED, the other is using Orange-White LED method. In this paper, it was compare RGB Multi-chip LED with white-orange LED for there characteristics performance.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.307-309
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• 2005

We investigated light absorption layer effect on metal-induced lateral crystallization (MILC) growth rate and MILC thin films transistors (TFTs). As annealing method, we used scanning-rapid thermal annealing (RTA). MILC growth rate which was crystallized by light absorption layer and using scanning-RTA was 3 times than normal MILC which was without light absorption layer growth rate. Also we compared MILC TFTs characteristics which were combined to light absorption layer with conventional MILC TFTs. After scanning-RTA process, MILC-TFTs which were with light absorption layer were superior to conventional MILC-TFTs. With this new MILC-TFTs structure, we could reduced crystallization time and obtain good electrical properties.

• Journal of Technologic Dentistry
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• v.32 no.3
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• pp.195-207
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• 2010

Purpose: The purpose of this study was to observe the microstructural changes of surface in the specimens, performing the shear bond strength testing. The currently most used non-precious alloys are nickel-chromium based alloys with or without beryllium. However, their biocompatibility has been questioned concerning possible damages to the health of the patient and professionals involved in the fabrication of prosthesis caused by long exposure to Ni and Be. An option to nickel-chromium alloys is the cobalt-chromium alloy, an alternative that does not sacrifice the physical properties of the metal porcelain systems. Studies in the animals substantially show that the cobalt-chromium alloys are relatively well tolerated, being therefore more biocompatible than the nickel-chromium alloys. Methods: Non-addition Be to nickel-chromium based alloy(Bellabond plus) and cobalt-chromium alloy which has been widely used(Wirobond C) fused with ZEO light porcelain classified control group and cobalt-chromium alloy which is developing alloy of Alphadent company in Korea(Alphadent alloy) fused with ZEO light porcelain classified experimental group. The specimens of $4mm{\times}4mm{\times}0.5mm$ were prepared as-cast and as-opaque to cast body to analyze the mechanical characteristic change, the microstructure of alloy surface. The phase change was used to observe through XRD analysis and OM/SEM was used to observe the surface of specimens as-cast and as-opaque to cast body. Chemical formation of their elements was measured with EDS. Then hardness was measured with Micro Vicker's hardness tester. Shear bond strength test thirty specimens of $10mm{\times}10mm{\times}2mm$ was prepared, veneered, 3mm high and 3mm in diameter, over the alloy specimens. The shear bond strength test was performed in a universal testing machine(UTM) with a cross head speed of 0.5mm/min. Ultimate shear bond strength data were analyzed with one-way ANOVA and the Scheffe's test (P<0.05). Within the limits of this study, the following conclusions were drawn: The X-ray diffraction analysis results for the as-cast and as-opaque specimens showed that the major relative intensity of Bellabond plus alloy were changed smaller than Wirobond C and Alphadent Co-Cr based alloys. Results: Microstructural analysis results for the opaque specimens showed all the alloys increased carbides and precipitation(PPT). Alphadent Co-Cr based alloy showed the carbides of lamellar type. The Vickers hardness results for the opaque specimens showed Wirobond C and Alphadent Co-Cr based alloys were increaser than before ascast, but Bellabond plus alloy relatively decreased. The mean shear bond strengths (MPa) were: 33.11 for Wirobond C/ZEO light; 25.00 for Alphadent Co-Cr alloy/ZEO light; 18.02 for Bellabond plus/ZEO light. Conclusion: The mean shear bond strengths for Co-Cr and Ni-Cr based alloy were significantly different. But the all groups showed metal-metal oxide modes in shear bond strengths test at the interface.

• 한국태양에너지학회:학술대회논문집
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• 2009.04a
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• pp.214-219
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• 2009

In high-efficiency crystalline silicon solar cells, If high-efficiency solar cells are to be commercialized. It is need to develop superior contact formation method and material that can be inexpensive and simple without degradation of the solar cells ability. For reason of plated metallic contact is not only high metallic purity but also inexpensive manufacture. It is available to apply mass production. Especially, Nickel, Copper and Silver are applied widely in various electronic manufactures as easily formation is available by plating. The metallic contact system of silicon solar cell must have several properties, such as low contact resistance, easy application and good adhesion. Ni is shown to be a suitable barrier to Cu diffusion as well as desirable contact metal to silicon. Nickel monosilicide(NiSi) has been suggested as a suitable silicide due to its lower resistivity, lower sintering temperature and lower layer stress than $TiSi_2$. Copper and Silver can be plated by electro & light-induced plating method. Light-induced plating makes use the photovoltaic effect of solar cell to deposite the metal on the front contact. The cell is immersed into the electrolytic plating bath and irradiated at the front side by light source, which leads to a current density in the front side grid. Electroless plated Ni/ Electro&light-induced plated Cu/ Light-induced plated Ag contact solar cells result in an energy conversion efficiency of 14.68 % on $0.2{\sim}0.6{\Omega}{\cdot}cm,\;20{\times}20mm^2$, CZ(Czochralski) wafer.