• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.86-88
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• 1999

We investigated the current limiting characteristics of resistive and inductive SFCLs with $100{\Omega}$ of quench impedance for a line-to-line fault in the 154 kV transmission system. The fault simulation at the phase angles $0^{\circ}$, $45^{\circ}$, and $90^{\circ}$ showed that the resistive SFCL limited the fault current less than 15 kA without any DC component after one half cycle from the instant of the fault. On the other hand, the inductive SFCL suppressed the current below 13 kA, but with $2{\sim}3\;kA$ of DC component which decreased to zero in 6 cycles. We concluded that the inductive SFCL had higher performance in current limiting but the resistive SFCL was better from the view point of DC components.

• Journal of Power System Engineering
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• v.3 no.3
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• pp.76-82
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• 1999

This study presents a methodology to predict the hardenability of quenched carbon steels. The equation of transient heat conduction is analyzed to formulate a cooling curve by a finite element method which incorperates coupled effects of temperature on physical properties, the metallic structures and also the latent heat by phase transformation. The volume traction of martensite and pearlite are the structural analysis for hardenability analysis. In order to demonstrate the feasibility of adopting a full quench model respectively. This procedure could be used as the database for optimal condition of heat treatment processes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.161-163
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• 2001

We present the basic properties of a superconducting current limiting fuse (SCLF) based on YBCO/Au films. The SCLFs consists of YBCO stripes covered with Au layers for current shunt. Under the source voltage of 100 $V_{rms}$, the longer the duration time of fault current was, the shorter its discharge time was. The duration time of fault current and its discharge time were reduced by increased voltages in the range of 200 - 300 $V_{rms}$. We thought that this was because the quench propagation was limited by local melting generated with higher voltage.

• Proceedings of the Membrane Society of Korea Conference
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• 1995.10a
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• pp.5-9
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• 1995

In the dry-jet-wet-spinning process of a hollow fiber membrane, the polymer solution is pumped into a coaxial tube, jet spinneret. The threadline emerging from the spinneret is stabilized by an internal coagulating medium(liquid or gas) as it emerges from the jet orifice. The nascent hollow thread is further stabilized in a quench bath as shown in Fig. 1. In this scheme, three mechanism of formatiota(temperature gradient, solvent evaporation, and solvent-nonsotvent exchange) can be combined. The changes which promote stabilization often play a dominant role in determining the ultimate fiber wall structure as well. Hence, in pratice, hollow fiber stabilization and development of membrane structure are commonly inseparable. However, fiber dimension(the inside diameter and wall thickness of the hollow fiber) is mainly a rheological problem and is determined by dope pumping rate, spinneret diatance from the coagulation bath, inner coagulant flow rate, and fiber draw-rate. Besides rheological phenomena play a prominent part in the final properties of the hollow fiber.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.6
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• pp.673-677
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• 2004

We present the basic properties of a superconductive fuse (SF) based on YBCO/Au films. The SF consists of YBCO stripes covered with Au layers for current shunt. The fault current was limited to a designed value in less than 0.4 msec by resistance development in YBCO/Au upon quenching. This enabled the SF to transfer small fault power and the suppressed current was sustained for more than 0.5 msec while Au layer melting and arcing. The arcing time was less than 2.5 msec, that is short enough to do self-interruption. Under the source voltage of 100 $V_{rms}$, the longer the duration time of fault current was, the shorter its discharge time was. The duration time of fault current and its discharge time were reduced by increased voltages in the range of 200 - 300 $V_{rms}$. We thought that this was because the quench propagation was limited by local melting generated with higher voltage.age.

• Journal of the Korean institute of surface engineering
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• v.17 no.1
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• pp.7-13
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• 1984

Carburizing of a 12%Cr steel containing 0.6%Si was performed at 950$^{\circ}C$ for various times, and the microstructure, hardness and the water characteristics of the carburized chromium steel were examined. The results obtained in this study are as follows: 1. Carbide-dispersed layer (CD layer) with fine dispersion of $Cr_7C_3$ in martensite matrix was formed by carburizing. The radius and amount of the carbides in the surface region of CD layer were about 0.3${\mu}m$ and 35% by volume, respectively. 2. Chromium steel carburized and quench-tempered showed better wear resistance and hardness than ordinary high chromium tool steel. It is concluded from these results that fine dispered carbides are very effective in improving wear resistance and hardness.

• Analytical Science and Technology
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• v.8 no.3
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• pp.341-350
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• 1995

$Nd_{14}Fe_{80}B_6$ ribbon alloy was manufactured with using melt-spinning method and analyzed the magnetic properties according to the manufacturing conditions. The microstructure and magnetic properties of melt-spun ribbons are sensitively dependent on the quench rate and annealing conditions. As-quenched $Nd_{14}Fe_{80}B_6$ ribbons with optimum magnetic properties are obtained at wheel speed($v_s$) of about 20m/sec and over quenched ribbons show optimum magnetic properties at $v_s$=22m/see when annealed for 30 minutes at $600^{\circ}C$ under vacuum. The crystallization temperature($T_k$) of $Nd_2Fe_{14}B$ phase is about $595^{\circ}C$ in the DTA analysis.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1673-1678
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• 2013

Lumazine protein is a member of the riboflavin synthase superfamily and the intense fluorescence is caused by non-covalently bound to 6,7-dimethyl 8-ribityllumazine. To figure out the binding modes and the structure of the N-terminal domain of lumazine protein, the wild type of protein extending to amino acid 118 (N-LumP 118 Wt) and mutants of N-LumP 118 V41W, S48W, T50W, D64W, and A66W from Photobacterium leiognathi were purified. The biochemical properties of the wild type and mutants of N-LumP 118 proteins were analyzed by absorbance and fluorescence spectroscope. The peak of absorbance and fluorescence of lumazine ligand were shifted to longer wavelength on binding to N-LumPs. The observed absorbance value at 410 nm of lumazine bound to N-LumP 118 proteins indicate that one mole of N-LumP 118 proteins bind to one mole of ligand of lumazine. Fluorescence analysis show that the maximum peak of fluorescence of N-LumP S48W was shifted to the longest wavelength by binding with 6,7-dimethyl 8-ribityllumazine and was shown to the greatest quench effect by acrylamide among all tryptophan mutants.

• Journal of the Korean Magnetics Society
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• v.7 no.4
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• pp.173-179
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• 1997

Change in phases, microstructures, and magnetic properties by the variation of quench rate and heat treatment were investigated for melt-spun $Fe_{77}Pr_{15}C_8$ ribbons. The amorphization of as-spun ribbons increased as the quench rate increased. As a result, the ribbon quenched at 40 m/s was almost entirely amorphous. Similarly to cast alloys, the primary phase in crystalline ribbons quenched at 10 m/s was $\alpha$-Fe followed by the secondary $Fe_{17}Pr_2C_x$. Crystalline phases were still dominant in the ribbon spun at 20 m/s, but in this case crystallization of $Fe_{17}Pr_2C_x$ was remarkable with a little suppression of $\alpha$-Fe. At 30 m/s an amorphous phase obviously dominated in the as-spun ribbons with small fraction of crystals. Therefore, substantial amount of hard magnetic $Fe_{14}Pr_2C$ was not obtained from the as-spun state but, as in cast alloys, produced only by a solid-state transformation. Within a few minutes fine grains of $Fe_{14}Pr_2C$ were easily obtained at relatively low temperature when the degree of amorphization of as-spun ribbons was higher. The grain size of $Fe_{14}Pr_2C$ was well less than 1${\mu}{\textrm}{m}$. The ribbons quenched at 20 or 30 m/s yielded higher coercivities after heat treatment.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1562-1563
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• 2011

Partial discharge measurement is one of the effective diagnostic techniques to predict abnormal high voltage dielectric insulation conditions of the electric equipments. Recently partial discharge diagnostic techniques were also utilized to evaluate the cryogenic dielectric insulation of high temperature superconducting electric equipment in liquid nitrogen. Generally, liquid nitrogen at 77 K is used used as the cryogenic and dielectric media for many high temperature superconducting high voltage applications. When a quench in the superconductor occurs, bubbles are generated which can affect the dielectric properties of the liquid nitrogen. So in order to reduce the bubble formation, subcooled nitrogen was also employed for this purpose. In this work, investigation of partial discharge characteristics of subcooled liquid nitrogen were conducted in order to clarify the retardation of partial discharge initiation voltage according to the different subcooling temperature of liquid nitrogen. And also the relation of partial discharge phenomena and the activities of bubbles were analyzed. It was observed that PD inception voltages shows rather different characteristics according to the decrease of subcooling temperature and the activities of bubbles were strongly influenced by temperature of the subcooled liquid nitrogen.