• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.182-183
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• 2003

• Applied Microscopy
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• v.26 no.2
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• pp.235-241
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• 1996

Amophization and decomposition behaviour in $Mg_{62}Cu_{26}Y_{12}$ alloy prepared by melt spinning method and wedge type metal mold casting method have been investigated by a detailed transmission electron microscopy. Amorphous phase has formed in melt-spun ribbon. In the case of the wedge type specimen, however, the amorphous phase has formed only around the tip area within about 2 mm thickness. The remaining part of the wedge type specimen consists of crystalline phases, $Mg_{2}Cu\;and\;Cu_{2}Y$. The supercooling for crystallization behaviour of the amorphous $Mg_{62}Cu_{26}Y_{12}$ alloy, ${\Delta}T_x$ has been measured to be about 60 K. Such a large undercooling of the crystallization bahaviour enables formation of the amorphous phase in the $Mg_{62}Cu_{26}Y_{12}$ alloy under the cooling rate of $10^{2}K/s$. The amorphous $Mg_{62}Cu_{26}Y_{12}$ has decomposed into crystalline phases, $Mg_{2}Cu\;and\;Cu_{2}Y$ after heat treatment at $170^{\circ}C\;and\;250^{\circ}C$.

• Journal of the Korean Magnetics Society
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• v.2 no.1
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• pp.44-49
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• 1992

Magnetic properties and microstructures of $Nd_{12}Fe_{80}B_{6}(Nb,\;M)$ (M=Ti/Cu/Ga) melt-spun ribbons prepared by single wheel technique have been studied. The results of microstructural study have shown that Ga is effective for the orientation of c-axis normal to the ribbon plane. The Ga-added melt-spun ribbon, $Nd_{12}Fe_{80}B_{6}(Nb,\;Ga)$, quenched at $V_{s}=17.9\;m/s$ was mostly composed of fine grains of about 30 nm in size with the textured free-side surface. The powder of this ribbon aligned in mag-netic field showd a high remanence of 0.87 T which was about 5 % higher than that of ribbon itself. It is believed that there is a possibility to fabricate a new type of HIREM melt-spun ribbon with highly textured free-side surface.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.3
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• pp.240-244
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• 2011

The high cost of crystalline silicon solar cells has been considered as one of the major obstacles to their terrestrial applications. Spin on doping (SOD) is presented as a useful process for the manufacturing of low cost solar cells. Phosphorus (P509) was used as an n-type emitters of solar cells. N-type emitters were formed on p-type EFG ribbon Si wafers by using a SOD at different spin speed (1,000~4,000 rpm), diffusion temperatures ($800^{\circ}C{\sim}950^{\circ}C$), and diffusion time (5~30 min) in $N_2+O_2$ atmosphere. With optimum condition, we were able to achieve cell efficiency of 14.1%.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.1
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• pp.103-111
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• 2017

In this study, the thermomechanical stress and fatigue analysis of a high voltage and high current (3,300 V/1200 A) insulated gate bipolar transistor (IGBT) module used for electric locomotive applications were performed under thermal cycling condition. Especially, the reliability of the copper wire and the ribbon wire were compared with that of the conventional aluminum wire. The copper wire showed three times higher stress than the aluminum wire. The ribbon type wire showed a higher stress than the circular type wire, and the copper ribbon wire showed the highest stress. The fatigue analysis results of the chip solder connecting the chip and the direct bond copper (DBC) indicated that the crack of the solder mainly occurred at the outer edge of the solder. In case of the circular wire, cracking of the solder occurred at 35,000 thermal cycles, and the crack area in the copper wire was larger than that of the aluminum wire. On the other hand, when the ribbon wire was used, the crack area was smaller than that of the circular wire. In case of the solder existing between DBC and base plate, the crack growth rate was similar regardless of the material and shape of the wire. However, cracking occurred earlier than chip solder, and more than half of the solder was failed at 40,000 cycles. Therefore, it is expected that the reliability of the solder between DBC and base plate would be worse than the chip solder.

• Journal of the Korean Magnetics Society
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• v.13 no.4
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• pp.160-164
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• 2003

The external magnetic field dependency of the impedance, resistance, and inductance of the meander pattern fabricated by using Co-base amorphous ribbon has been investigated in the frequency range of 300 ㎑∼1 ㎓. The amorphous ribbon was patterned to the meander pattern through conventional photolithography and wet etching process. The extremely high sensitivity in impedance changing ratio by external magnetic field was observed. This is due to the transverse magnetic anisotropy the pattern which was induced by magnetic field annealing. The impedance had peak value at the external field of -13 Oe and the impedance changing ratio 100 ${\times}$ (Z$\_$13/-Z$\_$0/)/Z$\_$0/) was about 210％ at the frequency of 50 MHz.

• Korean Journal of Breeding Science
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• v.43 no.3
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• pp.214-217
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• 2011

A light pink double freesia (Freesia hybrida Hort.) 'Pink Ribbon' was developed from a cross of breeding a line, 'Pink Jewel' derived 'Michelle' and 'Rossini' and 'Purple Rain' followed by seedling and line selections at the National Institute of Horticultural and Herbal Science (NIHHS), Rural Development Administration (RDA) in 2008. Growth and flowering characteristic tests were conducted from 2004 to 2007. 'Pink Ribbon' has double type flower with light pink color (RHS, RP66C). It has simultaneous flowering of many florets, good flower shape, upright leaves and stalks. The average cut flower yield of 'Purple Rain' observed in the greenhouse from 2005 to 2007 was 7.7 cuttings per plant. It has good production of cormlets, vigorous growth, too. 'Purple Rain' could be cultured under greenhouse conditions in Korea.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.202-203
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• 2002

Ribbon type nanocrystalline alloy cores have shown excellent soft magnetic properties in the high frequency range because of small crystalline anisotropy and nearly zero magnetostriction[1]. In present, however ribbon alloys gives some limit in applications such as a large inductor and reactors of PFC circuit, which are required good DC bias property and low loss in the high frequency. Powder alloys with ultra fine grain structure can be an important way to overcome this kind of disadvantage, and to improve the high frequency soft magnetic properties in conventional metallic powder cores[2]. (omitted)

• Structural Engineering and Mechanics
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• v.34 no.2
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• pp.213-229
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• 2010

An analytical method is proposed for the evaluation of the static response of a prestresse-dribbon concrete pedestrian bridge, which may also be applied for the roofing of large areas. On the basis of an established analogy with a suspension bridge system, a procedure is presented for the prestresse-dribbon direct analysis, leading to the introduction of two dimensionless parameters as governing factors of the design, namely the thinness and the prestressing steel ratio. The exposed procedure, applied by a simple computer program, allows a quick evaluation of the response and permits the investigation of the influence of the aforementioned parameters on it, by means of comprehensive diagrams. The presented diagrams may be directly used for the preliminary design of a pedestrian bridge of this type, for the whole practical range of span lengths. A design example is also included, showing the applicability of the proposed procedure.

• Journal of Korea Foundry Society
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• v.15 no.5
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• pp.459-468
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• 1995

For high performance aerospace structures, the properties of highest priority are low density, high strength, and high stiffness(modulus of elasticity). Addition of beryllium decrease the density of the aluminum alloy and increase the strength and the stiffness of the alloy. However it is very difficult to produce the Al-Be alloy having useful engineering properties by conventional ingot casting, because of the extremely limited solid solubility of beryllium in aluminum. So, rapid solidification processing is necessary to obtain extended solid solubility. In this study, rapidly solidified Al-6 at% Be alloy were prepared by twin roll melt spinning process and single roll melt spinning process. Twin roll melt spun ribbons were extruded at $450^{\circ}C$ with reduction in area of 25 : 1 after vacuum hot pressing at $550^{\circ}C and 375^{\circ}C$. The microstructure of melt spun ribbon exhibited a refined cellular microstructure with dispersed Be particles. As advance velocity of liquid/solid interface increase, the morphology of Be particle vary from rod-like type to spherical type and the crystal structure of Be particle from HCP to BCC. These microstructural characteristics of rapidly solidified Al-6at.%Be alloy were described on the basis of metastable phase diagram proposed by Perepezko and Boettinger. The extruded ribbon consisted of recrystallized grains dispersed with Be particles and exhibited improved tensile property compared with that of extruded ingot.