• 한국초전도학회:학술대회논문집
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• v.10
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• pp.272-275
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• 2000

We investigated a resistive superconducting fault current limiter (SFCL) fabricated using YBCO thin films on 2-inch diameter sapphire substrates. Nearly identical SFCL units were prepared and tested. The units were connected in series and parallel to increase the current and voltage ratings. A serial connection of the units showed significantly unbalanced power dissipation between the units. This imbalance was removed by introducing a shunt resistor to the firstly quenched unit. Parallel connection of the units increased the current rating. An SFCL module of 4 units in parallel, each of which has minimum quench current 25 Ap, was produced and successfully tested at a 220 V circuit. From the resistance increase, we estimated that the film temperature increases to 200 K in 5 msec, and 300 K in 120 msec. Successive quenches revealed that this system is stable without degradation in the current limiting capability under such thermal shocks as quenches at 220 V.

• Journal of Information Display
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• v.4 no.1
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• pp.17-23
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• 2003

A thermoset type anisotropic conductive adhesive film (ACAF) comprising epoxy resin and natural butyl rubber (NBR) as the binder, micro-encapsulated imidazole as the curing agent, and Ni/Au coated polymer bead as a conductive particle has been studied. These films have been prepared to respond to requirements such as improved contact resistance, current status less of than 60 ${\mu}m$ and reliability. These films can also be used for connection between the ITO glass for LCD panel and the flexible circuit board. The curing conditions for the connection were 40, 20 and 15 seconds at 150, 170 and 190 $^{\circ}C$, respectively. The initial contact resistance and adhesion strength were 0.5 ${\Omega}/square$ and 0.4 kg/cm under the condition of 30 kgf/$^{cm}^2}$, respectively. After completing one thousand thermal shock cycling tests between -15 $^{\circ}C$ and 100 $^{\circ}C$, the contact resistance was maintained below 0.7 ${\Omega}/square$. Durability against high temperature (80$^{\circ}C$) and high humidity (85 % RH) was also tested to confirm long-term stability (1000 hrs) of the conduction.

• Journal of Hydrogen and New Energy
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• v.34 no.1
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• pp.26-31
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• 2023

In this study, in order to propose a modular method for type IV high aspect ratio modular hydrogen storage vessel, a numerical analysis was conducted on the heat transfer behavior in series and parallel connection methods, and the differences according to each connection method were reviewed. Computational fluid dynamics software was used to check the internal temperature and pressure values of the hydrogen storage container under charging conditions. In terms of thermal safety when charging hydrogen gas, it was confirmed that the parallel modularization method was superior.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.145-156
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• 1990

In this study, thermophysical properties of the engineering ceramic materials such as $Al_{2}$O$_{3}$, Si$_{3}$N$_{4}$ and SiC were measured b y a single rectangular pulse heating method. The values of thermal diffusivities, specific heats, and thermal conductivities were measured as a function of temperature ranging form room temperature to 1300K. The measured thermal properties of one group of ceramic material were compared with those of other group and discussed in detail in connection with the chemical composition. Thus, some criteria for thermal design with the engineering ceramic materials were proposed.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.2
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• pp.114-118
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• 2017

Purpose: The aim of this study was to investigate the effects of a titanium component for the zirconia abutment in the internal connection implant system on screw loosening under thermocycling conditions. Materials and Methods: Internal connection titanium abutments and external connection zirconia abutments with titanium sockets were connected respectively to screw-shaped internal connection type titanium implants with 30 Ncm tightening. These implant-screw-abutment assemblies were divided into two groups of five specimens each; titanium abutments as control and zirconia abutments with titanium sockets as experimental group. The specimens were subjected to 2,000 thermocycles in water baths at $5^{\circ}C$ and $55^{\circ}C$, with 60 seconds of immersion at each temperature. The removal torque values (RTVs) of the abutment screws of the specimen were measured before and after thermocycling. RTVs pre- and post-thermocycling were investigated in statistics. Results: There was not screw loosening identified by tactile and visual inspection in any of the specimens during or after thermocycling. The mean RTV difference for the control group and the experimental group were $-1.34{\pm}2.53Ncm$ and $-1.26{\pm}2.06Ncm$, respectively. Statistical analysis using an independent t-test revealed that no significant differences were found in the mean RTV difference of the groups (P > 0.05). Conclusion: Within the limitations of this in vitro study, the titanium socket for the zirconia abutment did not show a significant effect on screw loosening under thermal stress compared to the titanium abutment in the internal connection implant.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.11
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• pp.1922-1928
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• 2008

The thermal rating of a conductor are maximum continuous current capacity and short time emergency current capacity. The overload operation for a faults have an effect on a conductor lifetime. Its time duration and overload level are limited to facility conditions of transmission lines. The short time emergency current capacity in KOREA observe the KEPCO's DESIGN RULE 1210, but its rules are not included to concept of an allowable short time duration. This papers are described to the calculation concept of short time emergency current capacity considering a time duration and an overload level. And we suggested a operation grouping and its maximum conductor temperature considering facility conditions - conductor lifetime, stability of connection points, conductor height above ground and clearance, in the operating and new T/L.

• 한국태양에너지학회:학술대회논문집
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• 2008.11a
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• pp.214-219
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• 2008

This study is describes thermal performance of solar cooling and hot water for demonstration system with ETSC(Evacuated tubular solar collector) installed at Seo-gu culture center of Kwanju. Control condition for solar cooling and hot water system is changed by connection of auxiliary heater. Demonstration system was connected to central air conditioning system. Demonstration system was operated by two types. First type(A) was operated to cooling and hot water supply in that order. Second type(B) was operated to hot water supply and cooling in that order. As a result. it was indicated that the total solar energy consumption of (A) was 799 MJ and the solar energy consumption rate for the cooling and hot water supply was 70% and 30% respectively. Total solar energy consumption of (b) was 898 MJ and the solar energy consumption rate for the cooling and hot water supply was 31% and 69% respectively.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1845-1850
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• 2003

The underground utility tunnels are important facility as a mainstay of country because of communication developments. The communication and electrical duct banks as well as various utility lines for urban life are installed in the underground utility tunnel systems. If a fire breaks out in this life-line tunnel, the function of the city will be discontinued and the huge damages are occurred. In order to improve the safety of life-line tunnel systems and the fire detection, the behaviors of the fire-induced smoke flow and temperature distribution are investigated. In this study we assumed that the fire is occurred at the contact or connection points of cable. Numerical calculations are carried out using different velocity of ventilation in utility tunnel. The fire source is modeled as a volumetric heat source. Three-dimensional flow and thermal characteristics in the underground tunnel are solved by means of FVM (Finite Volume Method) using SIMPLE algorithm and standard ${\kappa}-{\varepsilon}$ model for Reynolds stress terms. The numerical results of the fire-induced flow characteristics in an underground utility tunnel with different velocity of ventilation are graphically prepared and discussed.

• Journal of the Korean Society of Safety
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• v.29 no.2
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• pp.1-6
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• 2014

In this paper, safety certification products and safety condition of small transformer is analyzed in industries field and educational facilities. In transformer of 50places, absolute majority is step down transformer to measure of instrument. Most transformers were below 5kVA and 1~3kVA capacity was the mainstream. In industries field, 5 transformers were found without safety certification according to the Electrical Appliances Safety Control Act as cheap product prefer and lack of safety consciousness. Mark & number, voltage, date of manufacture of safety certification must show item of certification. However date of manufacture showed in product of 18%, 9places. As result of thermal imaging camera, running temperature of transformer was showed in below of target temperature. However as a narrow space of transformer and wall, power cable was touched on a ventilating flue in transformer. It was simple carelessness case that surface fouling and temperature ageing of transformer accelerate. Power poor connection, neglect of transformer in production equipment, fall damage by setup incongruity and ground omission were found in case of illogicality item of transformer.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.1
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• pp.121-133
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• 2020

Underwater cutting has a different mechanism than dry cutting, and there are more restrictions than benefits. Due to these constraints, research and development of underwater cutting has been very limited. At present, reactor dismantling is emerging as an important task worldwide, and reactor pressure containers, a key part of the reactor, are decommissioned based on underwater cutting. Reactor pressure containers are high-level radioactive waste, which is one of the main goals of today, such as to bridge the gap between environmental, safety, and cutting performance; hence, a process suitable for cutting should be applied. Therefore, many studies are being conducted on underwater cutting in connection with the dismantling of nuclear reactors in various areas in order to find appropriate processes. This paper first introduces the core technology of underwater cutting processes and discusses various processes. The emphasis is then placed on the adequacy of the reactor dismantling application. More specifically, we examine the suitability for the mechanical and thermal cutting processes, respectively, to find a solution suitable for dismantling a reactor. We discuss how each solution can sufficiently perform the specified functions at each stage of reactor dismantling and suggest that these processes can perform all of the work of underwater cutting.