• Journal of the Microelectronics and Packaging Society
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• v.19 no.3
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• pp.71-76
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• 2012

A chip interconnection technology for smart fabrics was investigated by using flip-chip bonding of SnBi low-temperature solder. A fabric substrate with a Cu leadframe could be successfully fabricated with transferring a Cu leadframe from a carrier film to a fabric by hot-pressing at $130^{\circ}C$. A chip specimen with SnBi solder bumps was formed by screen printing of SnBi solder paste and was connected to the Cu leadframe of the fabric substrate by flip-chip bonding at $180^{\circ}C$ for 60 sec. The average contact resistance of the SnBi flip-chip joint of the smart fabric was measured as $9m{\Omega}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.305-305
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• 2010

In this study, in order to develop excellent lead free piezoelectric ceramics for piezoelectric transformer application (Na,K)(Nb,Sb)$O_3$ ceramics were fabricated using conventional oxides mixed method and their piezoelectric and dielectric characteristics were investigated according to the amount of $Bi_2O_3$ addition.

• Transactions on Electrical and Electronic Materials
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• v.1 no.1
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• pp.12-16
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• 2000

In this paper, we analyze self field effects of Bi-2223 tape-stacked cable assuming constant current density in the cross section of stacked cable. Generally, the critical current of Bi-2223 tape-stacked-cable in much less than the total summation of critical currents of each tape, which is mainly due to the self magnetic fields of the cable itself. Therefore, to predict the critical current of Bi-2223 tape-stacked-cable, we needs to analyze the self filed effects on the stacked cable as well as critical current density data(J$\_$C/) of one tape. To make it more complex, the critical current degradation of Bi-2223 tape is an-isotropic; the critical current is lower in the normal magnetic field(to the tape surface) than in the parallel field. In the paper, a novel approach to predict the critical current of a Bi-2223 tape-stacked-cable from a J$\_$C/-B curve of one tape is presented with the assumption of constant current density across the stacked cable, The approach basically includes the load analysis of the stacked tapes, and its usefulness is confirmed by the experimental data.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.5
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• pp.343-354
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• 2020

Bi-stable mechanism is a system that has two different stable equilibrium positions within its range of motion. It has an ability to stay in two different positions without external power input and despite small disturbances. One of the most bi-stable applied mechanism is a morphing system, such as deployable structures, switch systems, and robot grippers. However, due to the complexity of mechanism and limitation of structure configuration, it is difficult to apply on a morphing system with rotating link mechanism. In this paper, an implementation method of rotational bi-stable mechanism using cylindrical permanent magnets is proposed. The magnetic field and the magnetic force were calculated from electromagnet model of the cylindrical permanent magnet. Based on the model, the force relation between two links containing the cylindrical permanent magnets was estimated. An array of cylindrical permanent magnets was selected for symmetric bi-stability, and an experiment on the link structure with the proposed bi-stable mechanism was performed to investigate the stability against a external torque.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.278-280
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• 2001

BSCCO thin films have been fabricated by co-deposition at an ultralow growth rate using ion beam sputtering(IBS) method. The growth rates of the films was set in the region from 0.17 to 0.27 nm/min. MgO(100) was used as a substrate. In order to appreciate stable existing region of Bi 2212 phase with temperature and ozone pressure, the substrate temperature was varied between 655 and $820^{\circ}C$ and the highly condensed ozone gas pressure($PO_3$) in vacuum chamber was varied between $2.0{\times}10^{-6}$ and $2.3{\times}10^{-5}$ Torr. Bi 2212 phase appeared in the temperature range of 750 and $795^{\circ}C$ and single phase of Bi 2201 existed in the lower region than $785^{\circ}C$. Whereas, $PO_3$ dependance on structural formation was scarcely observed regardless of the pressure variation. And high quality of c-axis oriented Bi 2212 thin film with $T_c$(onset) of about 90 K and $T_c$(zero) of about 45 K is obtained. Only a small amount of CuO in some films was observed as impurity, and no impurity phase such as $CaCuO_2$ was observed in all of the obtained films.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.278-280
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• 2001

BSCCO thin films have been fabricated by co-deposition at an ultralow growth rate using ion beam sputtering(IBS) method. The growth rates of the films was set in the region from 0.17 to 0.27 nm/min. MgO(100) was used as a substrate. In order to appreciate stable existing region of Bi 2212 Phase with temperature and ozone pressure, the substrate temperature was varied between 655 and 820$^{\circ}C$ and the highly condensed ozone gas pressure(PO$_3$) in vacuum chamber was varied between 2.0x10$\^$-6/ and 2.3x10$\^$-5/ Torr. Bi 2212 Phase appeared in the temperature range of 750 and 795$^{\circ}C$ and single phase of Bi 2201 existed in the lower region than 785$^{\circ}C$. Whereas, PO$_3$ dependance on structural formation was scarcely observed regardless of the pressure variation. And high quality of c-axis oriented Bi 2212 thin film with T$\sub$c/(onset) of about 70 K and T$\sub$c/(zero) of about 45 K is obtained. Only a small amount of CuO in some films was observed as impurity, and no impurity phase such as CaCuO$_2$ was observed in all of the obtained films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.2
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• pp.119-125
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• 2017

We have studied the effects of Ag on the characteristics of $Sn_{43}Bi_{57}Ag_x$(wt%) lead-free solders for photovoltaic ribbon. Ag atoms in the solder formed an alloy phase of Ag3Sn after reacting with some part of Sn atoms, while they did not react with Bi atoms, but decreased the mean size of Bi solid phase and the thickness of solder. When Ag atoms of 3.0 wt% was added to eutectic $Sn_{43}Bi_{57}$(wt%) solder, it showed the optimally useful results that the peel strength of photovoltaic ribbon greatly increased and the sheet resistance of the solder decreased. In the meanwhile, the eutectic $Sn_{43}Bi_{57}$(wt%) solder showed a low melting temperature of $138.9^{\circ}C$, and showed a very similar result regardless of the added amount of Ag atoms.

• Archives of Plastic Surgery
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• v.37 no.3
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• pp.207-212
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• 2010

Purpose: The object of this study is to develop a novel BMP-2 delivery system for continuous osteogenic differentiation and to induce osteogenesis of stem cells using a bi-phase alginate carrier in vitro. Methods: Alginate nanoparticle loaded BMP-2 was prepared by the reverse emulsification-diffusion technique. Physical properties and release profiles of alginate carriers were measured by Instron and ELISA kit, respectively. Cell viability and alkaline phosphate activity of hBMSCs differentiation was also evaluated by MTS and Metra BAP assays, respectively. Results: Optimal concentration for bi-phase alginate carrier was determined as 2 wt% by evaluating mechanical and biological properties, and differentiation of BMSCs for bone regeneration. The 2% bi-phase alginate carrier had the lowest initial and final release ratio. In addition, the 2% bi-phase alginate carrier had a little higher ALP activity than the homogeneous carrier. An improved controlled release profile was obtained by combining alginate hydrogel with lyophilized particles. Conclusion: Bi-phase alginate carrier has many advantages such as biocompatibility and controlled release capability. It is expected to be effective as a scaffold and carrier in bone tissue engineering.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.11
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• pp.878-885
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• 2012

In this study we aims to examine the co-doping effects of 1/3 mol% $Mn_3O_4+Co_3O_4$ (1:1) on the reaction, microstructure, and electrical properties such as the bulk defects and grain boundary properties of $ZnO-Bi_2O_3-Sb_2O_3$ (ZBS; Sb/Bi=0.5, 1.0, and 2.0) varistors. The sintering and electrical properties of Mn,Co-doped ZBS, ZBS(MCo) varistors were controlled by Sb/Bi ratio. Pyrochlore ($Zn_2Bi_3Sb_3O_{14}$) was decomposed and promoted densification at lower temperature on heating in Sb/Bi=1.0 by Mn rather than Co. Pyrochlore on cooling was reproduced in all systems however, spinel (${\alpha}$- or ${\beta}$-polymorph) did not formed in Sb/Bi=0.5. More homogeneous microstructure was obtained in $Sb/Bi{\geq}1.0$ In ZBS(MCo), the varistor characteristics were improved drastically (non-linear coefficient, ${\alpha}$=30~49), and seemed to form $Zn_i^{..}$(0.17 eV) and $V_o^{\bullet}$(0.33 eV) as dominant defects. From impedance and modulus spectroscopy (IS & MS), the grain boundaries have divided into two types, i.e. the one is tentatively assign to $ZnO/Bi_2O_3(Mn,Co)/ZnO$ (0.47 eV) and the other ZnO/ZnO (0.80~0.89 eV) homojunctions.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.1
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• pp.17-22
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• 2003

The experimental FT-IR spectra and DTA curves of the $PbO-Bi_2O_3-B_2O_3-SiO_2$ glasses have been investigated. The composition ratio dependence of glass transition temperature showed that the structure of this glass system changes at 60 mol% $Bi_2O_3$. We have observed that the FT-IR spectra of the investigated samples with high bismuth content are dominated by bands associated to the structural units of the heaviest cation, $Bi^{3+}$ and the boron atoms in the treated samples are three and four coordinated even for very high $Bi_2O_3$ content. The low intensity of these non-bridging oxygen bands, for high PbO content glasses, can be attributed to the strong network-forming roles of PbO. The glasses absorption bands exhibited a greater change in intensities on crystallization.