• Progress in Superconductivity and Cryogenics
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• v.17 no.4
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• pp.25-29
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• 2015

In 1987, M. K. Wu and Paul Chu discovered $Y_{1.2}Ba_{0.8}CuO_4$ (YBCO) with critical temperature ($T_c$) of 93 K. It has significantly lowered the cost of cooling of a material up to the point where superconductivity set in. Utilizing the cost reduction of attaining superconductivity and the vast amount of research to understand characteristics of high temperature oxide superconducting materials, there has been effort to use a high temperature superconductor as a coated conductor. It is important to characterize the materials precisely for stable performance before commercializing. We used polarized Raman scattering spectroscopy to study structural and stoichiometric information regarding $YBa_2Cu_3O_{7-x}$, $GdYBa_2Cu_3O_{7-x}$, and $GdBa_2Cu_3O_{7-x}$ produced by three leading groups of producing commercial grade high temperature superconductor coated conductors American Superconductor Corporation, Superpower, and SuNAM.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.219-226
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• 2003

The fatigue crack growth behavior of the SA516/60 steel used for pressure vessels was examined experimentally at room temperatures $25^{\circ}C$,$-30^{\circ}C$, $-60^{\circ}C$, $-80^{\circ}C$, $-100^{\circ}C$ and $-120^{\circ}C$ with stress ratio of R=0.05, 0.1 and 0.3. fatigue crack propagation rate da/dN related with stress intensity factor range $\Delta$K was influenced by stress ratio in stable than fatigue crack growth (Region II) with an increase in $\Delta$K. The resistance of fatigue crack growth at low temperature is higher compared with that at room temperature, which is attributed to the extent of plasticity-induced by compressive residual stress according to the cyclic loads. Fractographic examinations reveal that the differences of the fatigue crack growth characteristics between room and low temperatures are explained mainly by the crack closure and the strengthening due to the plasticity near the crack tip and roughness of the crack faces induced.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.572-574
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• 1993

In order to obtain superior breakdown properties of Epoxy/$SiO_2$ composite materials at room and high temperature, the simultaneous interpenetrating polymer networks(SIN) is introduced into the Epoxy resin. As a result, it is observed that dielectric breakdown strength tends to increase according to the following order ; Epoxy/$SiO_2$ specimens, specimens treated with coupling agent and SIN introduced specimens which have stable temperature characteristics at room and high temperature. For introducing SIN Epoxy/$SiO_2$ composite material, rise of glass transition temperature and suppression of defects in its internal structure is achieved. This in turn improves the dielectric breakdown strength and the heat proof property of Epoxy/$SiO_2$ composite materials.

• Progress in Superconductivity and Cryogenics
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• v.10 no.1
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• pp.10-14
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• 2008

Differently from BSCCO tapes which are fabricated by powder-in-tube method, the coated conductors are made by the evaporation of YBCO on metal substrate. Due to this structural merit, although the coated conductors are generally used for large current transportation, they are expected to be favorable to the purpose of the fault current limitation as well. In this study, using YBCO coated conductor having copper stabilizer formed by plating technique(produced by Superpower Co.), we investigated the over-current characteristics of the coated conductor. The coated conductors had 85 A $I_c$ and 90 K $T_c$. The resistance of the conductor was 0.93 $m{\Omega}/cm$ at 300 K and 0.17 $m{\Omega}/cm$ at the temperature right above $T_c$. To the coated conductors, we applied the voltages of the range from 150 $V_{rms}$ to 230 $V_{rms}$ and measured the V-I curves using four probe method. From the results, we could analyze the electric behavior of the coated conductor in flux flow state. As the current exceed $I_c$, the currents were distributed into the superconductor and metal stabilizer. The amounts of the currents shared through both current paths were calculated under the assumption that the ,Joule heating was perfectly eliminated by $LN_2$ surrounding the conductor. Finally, the condition for the stable current flowing state which does not affect the conductor was established from the analysis on the over-current characteristics.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.12
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• pp.59-65
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• 2004

A stable reference voltage generator is necessary to the infrared image signal readout circuit(ROIC) to improve noise characteristics of signal originated from infrared devices, that is, to gain good images. In this paper, bandgap circuit operating at cryogenic temperature of 77K for Infrared image ROIC(readout integrated circuit) was first made. It demonstrates practical use possibility through taking measurements and estimations. Bandgap circuit is a representative voltage reference circuit. Most of bandgap reference circuits which are presented so far operate at room temperature, and their characteristic are not suitable for infrared image ROIC operating at liquid nitrogen temperature, 77K. To design bandgap circuit operating at cryogenic temperature, suitable circuit is selected and the parameter characteristics of used devices as temperature change are seen by a theoretical study and fitted at liquid temperature with considering such characteristics. This circuit has been fabricated in the Hynix 0.6um standard CMOS process, and the output voltage measured shows that the stability is 1.042±0.0015V over the temperature range of 60K to 110K and is better than bandgap circuits operated at room temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.9
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• pp.566-571
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• 2017

A soft baking process was used to enhance the electrical characteristics of solution-processed indium-zincoxide (IZO) thin-film transistors (TFTs). We demonstrate a stable soft baking process using a hot plate in air to maintain the electrical stability and improve the electrical performance of IZO TFTs. These oxide transistors exhibited good electrical performance; a field-effect mobility of $7.9cm^2/Vs$, threshold voltage of 1.4 V, sub-threshold slope of 0.5 V/dec, and a current on/off ratio of $2.9{\times}10^7$ were measured. To investigate the static response of our solutionprocessed IZO TFTs, simple resistor load type inverters were fabricated by connecting a resistor (5 or $10M{\Omega}$). Our IZO TFTs, which were manufactured using the soft baking process at a baking temperature of $120^{\circ}C$, performed well at the operating voltage, and are therefore a good candidate for use in advanced logic circuits and transparent display backplanes.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.102-108
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• 2006

On the refutation demanded for a control of various toxic substances. PCBs(poly chlorinated biphenyl) has a fatal poisonous matter in the ecosystem and the environmental pollution as it Is a kind of stable chemical substance. Especially, the gross Product of PCBs is estimated at about one million tonnage all over the world. However it is kept on storing in untreated state, then has a deterioration by the Prolonged storage and a risk of overflowing. Therefore, this research examined the fundamental characteristics of combustion and emission for the target of using the IPA (iso-propyl alcohol) solution as a part of PCBs control. IPA was filled to three kinds of Vessel, i.e. Vessel I, II, and III, and then was investigated as follows combustion shape, flame temperature. mass burning velocity, and PM(Particulate matter). A radial thermometer and a C-A thermocouple measured the flame temperature, and the optical extinction method by using He-Ne laser and the filter weight method used in the PM measurement. As a result, with an increasing of L/S ratio, the flame length become shorter and the burning velocity is more rapid, but the particulate matters is higher. It is supposed that the air flow rate is high on Vessel. and then the combustion is Promoted in the surface area of the upstream zone. The future works plan to investigate the characteristics with an using of the mixing of IPA and PCBs

• Tribology and Lubricants
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• v.22 no.3
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• pp.149-154
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• 2006

This paper presents the braking friction and wears on the rubbing surfaces of a friction pad-disk brake. In this study, four friction disk specimens are sampled from unused and used disks in which are taken from the disk brake system when the friction induced vibration and noise problems have been occurred during a braking period at a running period of 10,000 km, 20,000 km, and 30,000 km in random. The experimental results indicate that the tribological characteristics of an unused disk brake shows equal and stable as a friction coefficient and temperature distributions during a braking friction/wear test period including a total friction mode from the start to running periods. But the used disk brake shows unstable and uneven friction modes between an outside and inside rubbing surfaces of a disk brake in terms of a friction coefficient and wears. This may lead to a friction induced friction vibration and noise problems of a used disk brake.

• Journal of Environmental Science International
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• v.21 no.6
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• pp.705-711
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• 2012

Adsorption experiment of carbon dioxide was performed on MCM41 silica with a 30 wt.% EDA(ethylenediamine) loading at different $CO_2$ inlet concentration and various adsorption temperature. The surface characteristics of $CO_2$ capturing agent were carried out using BET analysis, X-ray diffraction and FT-IR. The results of BET showed 781 $m^2/g$ for MCM41 and 464 $m^2/g$ for EDA/MCM41. X-ray diffraction results reveled typical hexagonal pore system. The higher sorption capacity of EDA/MCM41 was about 80 $mg_{CO2}/g_{sorbent}$ with 50% $CO_2$ inlet concentration and 303 K adsorption temperature. The isosteric heat of adsorption in 303-353 K ranged from -25.47 to -28.24 KJ/mole for EDA/MCM41, which indicates $CO_2$-EDA/MCM41 interaction with exothermic adsorption process. Finally, the performance of EDA/MCM41 in 10 consecutive sorption-desorption runs was a stable with only a minor drop in its sorption capacity.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.605-608
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• 2008

The preparation and characteristics of flexible indium tin oxide electrodes grown on polyethylene terephthalate (PET) substrates using a specially designed roll-to-roll sputtering system for use in flexible optoelectronics In spite of low a PET substrate temperature, we can obtain the flexible electrode with a sheet resistance of 47.4 ohm/square and an average optical transmittance of 83.46 % in the green region of 500~550 nm wavelength. Both x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) analysis results showed that all flexible ITO electrodes grown on the PET substrate were an amorphous structure with a very smooth and featureless surface, regardless of the Ar/$O_2$ flow ratio due to the low substrate temperature, which is maintained by a cooling drum. In addition, the flexible ITO electrode grown on the Ar ion beam treated PET substrates showed more stable mechanical properties than the flexible ITO electrode grown on the wet cleaned PET substrate, due to an increased adhesion between the flexible ITO and the PET substrates.