• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.174-177
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• 2003

Cooling load from the top plate to L$N_2$ surface, including wall conduction, gas conduction, radiation, and current leads, is investigated in a closed cooling system for HTS transformer. In general methods of load calculation, individual load is estimated separately, but they are actually coupled each other because of natural convection of nitrogen vapor. Using heat transfer analysis, we calculate cooling load with taking into account the effect of natural convection. Cooling load is under- estimated approximately 2 ％ when the natural convection is ignored. If the operating current is high, there will be a wide difference between actual cooling load and cooling load by individual calculation. Cooling load decreases with increasing number of radiation shield. With production, construction, and cooling load, three radiation shields are proper to 1 MVA HTS transformer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.5-8
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• 1997

A study on the electrical conduction characteristics of the ultrathin organic films is one of the important factors for the development of molecular electronic devices. The Langmuir- Blodgett(LB) technique has recently been attracted interest as a method of the deposition ultrathin films. We hate fabricated N-docosyl N\`-methyl viologen-diTCNQ(DMVT) anion radical LB film and investigated the molecular orientation and electrical conduction characteristics. We have measured infrared transmission-reflection spectra. The alkyl chain is found to he well-ordered with the tilt angle of 13$^{\circ}$ with respect to the substrate surface normal and the TCNQ plane is tilted at 76$^{\circ}$ the surface normal. In ESR spectrum, we confirmed that a half-amplitude linewidth is clearly dependent on the incident angle, which indicates conducting species change. The in-plane conductivity of 31 lagers is approximately 1.33$\times$10$^{-6}$ S/cm. The ohmic behaviour was observed below 0.6 V, when current-voltage(I-V) characteristics was measured verically.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.4
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• pp.49-56
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• 2008

This paper introduces a compact analytical current conduction model of long-channel depletion-mode n-type nanowire field-effect transistors (NWFETs). The NWFET used in this work was fabricated with the bottom-up process and it has a bottom-gate structure. The model includes all current conduction mechanisms of the NWFET operating at various bias conditions. The results simulated from the newly developed NWFET model reproduce a reported experimental results within a 10% error.

• Transactions on Electrical and Electronic Materials
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• v.6 no.5
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• pp.229-232
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• 2005

Direct characterization of band alignment at chemical bath deposition $(CBD)-CdS/Cu_{0.93}(In_{1-x}Ga_x)Se_2$ has been carried out by photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES). Ar ion beam etching at the condition of the low ion kinetic energy of 400 eV yields a removal of surface contamination as well as successful development of intrinsic feature of each layer and the interfaces. Especially interior regions of the wide gap CIGS layers with a band gap of $1.4\~1.6\;eV$ were successfully exposed. IPES spectra revealed that conduction band offset (CBO) at the interface region over the wide gap CIGS of x = 0.60 and 0.75 was negative, where the conduction band minimum of CdS was lower than that of CIGS. It was also observed that an energy spacing between conduction band minimum (CBM) of CdS layer and valance band maximum (VBM) of $Cu_{0.93}(In_{0.25}Ga_{0.75})Se_2$ layer at interface region was no wider than that of the interface over the $Cu_{0.93}(In_{0.60}Ga_{0.40})Se_2$ layer.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1438-1440
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• 1998

In this work, simultaneous measur of space charge and conduction current was c out in LDPE with air gap by Pulsed-Electro-Aco Method. Also, effect of long time charging at con electric field on the formation of space charge conduction was investigated. From the experim results. we knew that the homo space charge formed near the dielectric surfaces and moving the bulk of dielectric as the electric field elevated. This was related with the deep traps b carriers and de trapping by Poole-field lowering conduction current was coincident with the Pool emission. From the long time charging experimen obtained the results that the negative space was moving into the dielectric bulk as the cha continued and the positive space charge accumulated at upper surface of LDPE.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.11
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• pp.727-732
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• 2008

This paper presents a mathematical model to predict the behavior of frost formed on an one-dimensional fin of heat exchanger, considering fin heat conduction under frosting conditions. The computational domain consists of air-side, the frost layer, and fin region, and they are coupled to the frost layer. The frost behavior is more accurately predicted with fin heat conduction considered (Case A) than with constant fin surface temperature assumed (Case B). The results indicate that for Case B, the frost thickness and heat transfer are overpredicted in most regions of the fin, as compared with those for Case A. In addition, for Case A, the maximum frost thickness varies little with the fin length variations, and the extension of the fin length after 30mm contributes insignificantly to heat transfer.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.8
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• pp.404-410
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• 2006

Toward the practical applications, on operation of conduction-cooled HTS SMES at temperatures well below 40[K] should be investigated, in order to take advantage of a greater critical current density of HTS and considerably reduce the size and weight of the system. In order to take advantage of a greater critical current density of high temperature superconducting (HTS) and considerably reduce the size and weight of the system, conduction-cooled HTS superconducting magnetic energy storage (SMES) at temperatures well below 40[K] should be investigated. This work focuses on the breakdown and flashover phenomenology of dielectrics exposed in air and/or vacuum for temperatures ranging from room temperature to cryogenic temperature. Firstly, we summarize the insulation factors of the magnet for the conduction cooled HTS SMES. And Secondly a surface flashover as well as volume breakdown in air and/or vacuum with two kind insulators has been investigated. Finally, we will discuss applications for the HTS SMES including aging studies on model coils exposed in vacuum at cryogenic temperature. The commercial application of many conduction-cooled HTS magnets, however, requires refrigeration at temperatures below 40[K], in order to take advantage of a greater critical current density of HTS and reduce considerably the size and weight of the system. The magnet is driven in vacuum condition. The need to reduce the size and weight of the system has led to the consideration of the vacuum as insulating media. We are studying on the insulation factors of the magnet for HTS SMES. And we experiment the spacer configure effect in the dielectric flashover characteristics. From the results, we confirm that our research established basic information in the insulation design of the magnet.

• The Journal of Information Technology
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• v.9 no.3
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• pp.67-75
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• 2006

This study deals with the computing the temperature change of surface to the increment of time and diffusivity, the heat flux during irradiation of laser. In addition, the computer algorithm for computing the penetration change of the corresponding surface irradiated is developed. The result of this study shows the possibility to treatment of cancer, abnormal cell and biological tissue during irradiation of laser.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.12
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• pp.828-836
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• 2010

The drying is a process that involves coupled and simultaneous heat and mass transfer. When a wet solid is subjected to thermal drying, two processes occur simultaneously. Drying is classified according to heat transfer characteristics in terms of conduction, convection and radiation. In thermal drying, radiation is easier to control than conduction and convection drying and involves a relatively simple structure. In this study, we measured energy consumption, surface hardness of paint and surface gloss with variation of surface temperature of drying materials and drying time. Drying characteristics and energy consumption between heating panels and hot air heating have been presented. The present study shows that a dryer using heating panels is more effective than a hot air dryer from the viewpoint of energy conservation. The hot air dryer, however, was not optimized and more studies on various parameters related to drying will need to be investigated for definite comparison of drying characteristics of the dryers. The result, even if limited, would present the effective availability of paint drying.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.97.2-97.2
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• 2011

Pt-Ru and Pt-Ni bimetallic catalysts were prepared and tested for heavy hydrocarbon reforming. Metals were supported on CGO($Ce_{0.8}Gd_{0.2}O_{2.0-x}$) by incipient wetness method. The prepared catalysts were characterized by Temperature programmed reduction(TPR). Oxidative steam reforming of n-dodecane was conducted to compare the activity of the catalysts. The reforming temperature was varied from $500^{\circ}C$ to $800^{\circ}C$ at fixed $O_2$/C of 0.3, $H_2O$/C of 3.0 and GHSV of 5,000/h.Reduction peaks of metal oxide, surface CGO and bulk CGO were detected. Reduction temperature of metal oxide decreased over the bi-metallic catalysts. It is considered that interaction between metals leads to decrease interaction between metal and oxygen. On the other hands, reduction temperatures of surface CGO were dectected in the order of Pt-Ru > Pt-Ni > Pt. low reduction temperatures of surface CGO indicates the low activation energy for oxygen ion conduction to metal. Oxygen ion conduction is known as de-coking mechanism of ionic conducting supports such as CGO. In activity test, fuel conversion was in the same order of Pt-Ru > Pt-Ni > Pt. Especially, 100% of fuel conversion was obtained over Pt-Ru catalysts at $500^{\circ}C$.