• Title/Summary/Keyword: Double melting

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Electroluminescent Properties of Anthracene Chromophore with Naphthylethenyl Substituents

  • Kim, Hong-Soo;Jeong, Noh-Hee
    • Journal of the Korean Applied Science and Technology
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    • v.21 no.1
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    • pp.24-30
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    • 2004
  • New electroluminescent materials based on anthracene chromophore with naphthylethenyl substituent, 9,10-bis($\alpha$-naphthylethenyl)anthracene (a-BNA), as well as four kinds of its derivatives were synthesized, and luminescent properties of these materials were investigated. Electrolumineecent(EL) emission band was discussed based on their substituent structure differences. It was found that the emission band strongly depends on the molecular structure of introduced substituent. It can be tuned from 557 nm to 591 nm by changing the substituent structures. On the other hand, the anthracene chromophore with bulky substituent possessed high melting point and they gave stable films through vacuum-sublimation. The double layer EL device of ITO/TPD/emission layer/Mg:Ag was employed, and exhibited efficient orange light originating from emitting materials. EL emission with a maximum luminance was observed in the b-BNA emitting material, : maximum luminance was about 8,060 cd $m^{-2}$ at an applied voltage of 10 V and current density of 680 $mA/cm^2$. In conclusion, the electroluminescent properties also showed good difference with their substituent structure.

Manufacturing Process of the Ti-6Al-4V Billet by the Open-die Forging (자유형 단조 공정에 의한 Ti-6Al-4V 빌렛 제조기술)

  • Kim, K.J.;Choi, S.S.;Hwang, C.Y.;Kim, J.S.;Yeom, J.T.;Lee, J.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2006.05a
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    • pp.377-380
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    • 2006
  • Manufacturing process of Ti-6Al-4V alloy billet was investigated with FEM simulation and experimental analysis. Before the breakdown process of Ti-6Al-4V alloy ingot, FEM simulation for the breakdown processes of Ti-6Al-4V alloy ingot was used to calculate the forging load and state variables such as strain, strain rate and temperature. In order to breakdown the ingot structure and make an equiaxed structure billet, two different processes were employed for a VAR/VAR processed Ti-6Al-4V alloy ingot. Firstly, the ingot was cogged in single-phase $\beta$ field at the temperature of $1,100^{\circ}C$. In the process, the coarse and inhomogeneous structure developed by the double melting process was broken down. The second breakdown was performed by upsetting and cogging processes in $\alpha+\beta$ phase field to obtain the microstructure of fine equixed $\alpha$ structure in the matrix of transformed $\beta$. Finally, the mechanical properties of Ti-6Al-4V alloy billet made in this work were compared with those of other billet and ring product.

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A Plastic BGA Singulation using High Thermal Energy of $2^{nd}$ Harmonic Nd:YAG Laser

  • Lee, Kyoung-Cheol;Baek, Kwang-Yeol;Lee, Cheon
    • KIEE International Transactions on Electrophysics and Applications
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    • v.2C no.6
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    • pp.309-313
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    • 2002
  • In this paper, we have studied minimization of the kerf-width and surface burning, which occurred after the conventional singulation process of the multi-layer BGA board with copper, polyethylene and epoxy glass fiber. The high thermal energy of a pulsed Nd:YAG laser is used to cut the multi-layer board. The most considerable matter in the laser cutting of the multi-layer BGA boards is their different absorption coefficient to the laser beam and their different heat conductivity. The cut mechanism of a multi-layer BGA board using a 2$^{nd}$ harmonic Nd:YAG laser is the thermal vaporization by high temperature rise based on the Gaussian profile and copper melting point. In this experiment, we found that the sacrifice layer and Na blowing are effective in minimizing the surface burning by the reaction between oxygen in the air and the laser beam. In addition, N2 blowing reduces laser energy loss by debris and suppresses surface oxidation. Also, the beam incidence on the epoxy layer compared to polyimide was much more suitable to reduce damage to polyimide with copper wire for the multi layer BGA singulation. When the polyester double-sided tape is used as a sacrifice layer, surface carbonization becomes less. The SEM, non-contact 3D inspector and high-resolution microscope are used to measure cut line-width and surface morphology.

Fabrication of Bi2212/Ag HTS Wire with Various Ag Raio (다양한 은비의 Bi2212/Ag 고온초전도 선재의 제조)

  • Kim, Sang-Cheol;Ha, Dong-Woo;Oh, Sang-Soo;Oh, Jae-Geun;Song, Kyu-Jeong;Ha, Hong-Soo;Sohn, Ho-Sang
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.11a
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    • pp.163-164
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    • 2005
  • Round shape Bi2212/Ag is isotropic and can be fabricated Rutherford cable to transport high current. Bi2212/Ag round wires with various Ag ratio were fabricated using powder-in-tube process. Double stacked 385 (55\times$7) filamentary wire of various wire diameter was heat-treated at various melting temperature. Wires which have Ag ratio of 0.3 and 0.42 of Ag tube for monofilament show similar critical current density. As average filament diameter decreases from 33 to 16 \mu$m, critical current density of wires increase, and in case of 16 ${\mu}m$ and $T_m$ 890$^{\circ}C$, critical current density was 2,062 $A/mm^2$ at 4.2 K, 0 T.

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Aging Characteristics of NOx Storage and Reduction Catalyst for Lean-bum Natural Gas Vehicles (린번 천연가스자동차용 NOx 흡장촉매의 열화특성)

  • Choi, Byung-Chul;Lee, Choon-Hee
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.3
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    • pp.147-152
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    • 2007
  • This study investigates the aging characteristics of NOx storage and reduction(NSR) catalyst on the emission conditions of lean burn natural gas vehicles. We designed various NSR catalysts using by the double-layer washcoat technology to increase of a surface area and a thermal durability performance of the catalysts. The experiments were conducted with 3 kinds of the NSR catalysts, which were manufactured using by a honeycomb cordierite substrate. It was found that Ba is weak in the thermal aging because it has lower melting temperature than that of precious metals (PMs). The suitable loading amount of Ba in this study should be about 42 g/L from the results of the NOx adsorption and the NOx reduction efficiency. The major reason in deactivation of the NSR catalyst is the decrease of the adsorption site owing to the agglomeration and sintering of Ba rather than PM aging by hydrothermal aging. It was confirmed by results of BET, SEM and TEM.

The Kinetics and Mechanism of the Hydrolysis to Benzoyl Styrene Derivatives (Benzoyl Styrene 유도체의 가수분해 반응 메카니즘과 그 반응속도론적 연구)

  • Lee, Ki-Chang;Yoon, Chul-Hun;Hwang, Sung-Kwy;Oh, Se-Young
    • Journal of the Korean Applied Science and Technology
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    • v.12 no.1
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    • pp.35-41
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    • 1995
  • The Hydrolysis kinetics of Benzoyl Styrene Derivatives[I]${\sim}$[IV] was investigated by ultraviolet spectrophotometery in 5% dioxane-$H_2O$ at $40^{\circ}C$. The structure of these compounds were ascertained by means of ultraviolet, melting point, IR and NMR spectra. The rate equations which were applied over a wide pH range (pH $1.0{\sim}13.0$) were obtained. The substituent effects on Benzoyl styrene derivatives[I]${\sim}$[IV] were studied, and the hydrolysis were facilitated by electron attracting groups. On the basis of the rate equation and substitutent effect and final product, the plausible hydrolysis reaction mechanism was proposed: At pH 1.0${\sim}$pH 9.0, not relevant to the hydrogenl ion concentration, neutral $H_2O$ molecule competitively attacked on the double bond. By contrary. Above pH 9.0, It was proportional to concentration of hydroxidel ion.

Thermoelectric Properties of Sb Deficiency N-Type Skutterudite Co4Sb12 (Sb가 결핍된 N형 Skutterudite Co4Sb12의 열전 특성)

  • Tak, Jang-Yeul;Van Du, Nguyen;Jeong, Min Seok;Lee, NaYoung;Nam, Woo Hyun;Seo, Won-Seon;Cho, Jung Young
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.32 no.6
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    • pp.496-500
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    • 2019
  • In this study, we investigate the effect of an Sb-deficiency on the thermoelectric properties of double-filled n-type skutterudite ($In_{0.05}Yb_{0.15}Co_4Sb_{12-x}$). Samples were prepared by encapsulated induction melting, consecutive long-time annealing, and finally spark plasma sintering processes. The Sb-deficient sample contained a $CoSb_2$ secondary phase. Both the double-filled n-type skutterudite pristine and Sb-deficient samples showed metallic behavior in electrical conductivity with increasing temperature. The carrier concentration of the Sb-deficient sample decreased compared with that of the pristine sample. Due to a decrease in carrier concentration, the Sb deficient sample showed decreased electrical conductivity and an increased Seebeck coefficient compared with the conductivity and coefficient of the pristine sample. Furthermore, the Sb deficient sample showed an increase in the power factor (${\sigma}{\cdot}S^2$); the power factor maximum shifted to athe lower temperature side than ones of the pristine sample. As a result, the Sb-deficient sample represents an improved average figure of merit (ZT) and a $ZT_{max}$ temperature lower than that of the pristine sample. Therefore, we propose that Sb-deficient double-filled n-type skutterudite thermoelectric material ($In_{0.05}Yb_{0.15}Co_4Sb_{12-x}$) be used in the 573~673 K temperature range.

Effects of Alkoxy Side Chain on the Properties of Wholly Aromatic Liquid Crystalline Polyesters with Biphenylene Units (알콕시 곁사슬기가 비페닐렌구조를 갖는 전방향족 액정폴리에스터의 물성에 미치는 영향)

  • Lee, Eung-Jae;Bang, Moon-Soo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.11 no.10
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    • pp.4041-4046
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    • 2010
  • Wholly aromatic polyesters having flexible alkoxy side chain were synthesized by direct polycondensation. The synthetic polymers have been characterized by $^1H$-NMR, FT-IR. DSC, TGA, optical polarizing microscope and X-ray diffractometer. The inherent viscosities (${\eta}_{inh}$) measured in 1,1,2,2-tetrachloroethane (TCE) were 0.46~2.41 dL/g. The polymers having side chain showed double melting transition, ie, solid-sanidic liquid crystalline (LC) phase transition ($T_{m1}$) and sanidic LC phase-nematic LC phase transition ($T_{m2}$). As incresing length of alkoxy side chain, phase transition temperatures decreased and solubilities in organic solvents incresed. The peaks of $2{\theta}\;{\simeq}5$ and $2{\theta}\;{\simeq}20$ in X-ray diffractograms are due to crystallization of polymer main chain and of long side chain, respectively.

A Study on Optimization of Vacuum Glazing Encapsulating Process using Frit inside a Vacuum Chamber (진공챔버 내 프리트 이용 진공유리 봉지공정 최적화에 관한 연구)

  • Park, Sang Jun;Lee, Young Lim
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.2
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    • pp.567-572
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    • 2013
  • In houses that use heating and cooling system, most of heat loss occurs through the windows, so that low-E glass, double-layered glass, and vacuum glazing are used to minimize the heat loss. In this paper, an encapsulating process that is a final process in manufacturing the vacuum glazing has been studied, and bonding in a vacuum chamber rather than atmospheric bonding was considered. For the efficiency of the encapsulating process, frit-melting temperature and bonding time were optimized with heater temperature, and the glass preheating temperature was optimized to prevent glass breakage due to thermal stress. Thus the vacuum glass was successfully manufactured based on these results and heat transmission coefficient measured was about $5.7W/m^2K$ which indicates that the internal pressure of the vacuum glazing is $10^{-2}$ torr.

The Effects of Mass-size Relationship for Snow on the Simulated Surface Precipitation (눈송이의 크기와 질량 관계가 지표 강수 모의에 미치는 영향)

  • Lim, Kyo-Sun Sunny
    • Journal of the Korean earth science society
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    • v.41 no.1
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    • pp.1-18
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    • 2020
  • This study presented the effects of the assumed mass-size relationship for snow on the simulated surface precipitation by using cloud microphysics parameterizations in Weather Research and Forecasting (WRF) model. The selected cloud microphysics parameterizations are WRF Double-Moment 6-class (WDM6) and WRF Single-Moment 6-class (WSM6) in the WRF model. We replaced the mass-size relationship for snow in WDM6 and WSM6 with Thompson's mass-size relationship retrieved from measurement data. The sensitivity of the modified WDM6 and WSM6 was tested for the idealized 2-dimensional squall line and winter precipitation system over the Korean peninsula, respectively. The modified WDM6 and WSM6 resulted in the increase of graupel/rain mixing ratios and the decrease of snow mixing ratio in the low atmosphere. The changes of hydrometeor mixing ratio and surface precipitation could be due to the collision-coalescence process between raindrops and snow and the graupel melting process.