• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.1105-1107
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• 1999

The purpose of termination for high voltage tests of XLPE power cable is to prevent flashover during the breakdown test of specimen as well as to withstand the specified voltage between its conductor and screen without failure. For easier treatment and simpler construction of testing termination, resistivity grading method using semi-conductive material was employed. Based on the fundamental theory, its failure characteristics by changing the resistivity of semi-conductive material on the insulation surface was investigated. With two layers construction by difference resistivity on their surfaces, much improved result than that of one resistivity was obtained through the experiment for MV cable.

• Journal of Wetlands Research
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• v.25 no.2
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• pp.91-98
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• 2023

Some concrete wastewater generated during construction is in the form of non-point pollution sources that workers, managers, and users are unaware of, and it is not easy to manage as it flows through sewage pipes. Due to these characteristics, construction sludge is inflow into rivers and sewage pipes in the form of non-point pollution sources in an unmanaged state. This study applied the D.W.S method to the concrete retaining wall removal method installed on the road, and the resulting concrete wastewater was physically and chemically treated through a mobile sewage treatment facility, and it was examined whether it met the removal efficiency and wastewater discharge acceptance standards. Accordingly, it is intended to meet the standards for effluent concentration of wastewater during construction by removing 73.5% of BOD and 89.1% of SS through physical and chemical treatment through portable sewage treatment facilities during construction. In addition, we would like to review the adequacy and economic analysis of calculating environmental conservation costs for physicochemical treatment through portable sewage treatment facilities and sewage treatment generated during construction.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.276-279
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• 2000

When high temperature superconducting tapes is fabricated using the PIT (Powder In Tube) method, the length of HTS tapes is increased more than 500 ${\sim}$ 1,000 times of initial powder packed billet. On mechanical processing, heterogeneous properties between the ceramic superconducting core and Ag/Ag alloy sheath occur the non-uniformity deformation as like sausaging that deteriorate the critical current properties of HTS tapes. In this study, we investigated the workability of Bi-2223/Ag/Ag alloy sheath tapes fabricated by the PIT method involving a number of different mechanical processes, multi drawing and rolling. In order to obtain the high critical current density and high uniformity of Bi-2223/Ag sheath tapes, the influences of powder packing density, drawing die angle and rolling parameters were studied. We found that the roll diameter is an important variable in the rolling process, as critical current of tapes rolled using 250 mm rolls was higher than that using 150 mm rolls.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.138-141
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• 2004

Finite element method is very effective method to simulate the forming processes with good prediction of the deformation behaviour. For the finite element modeling of sheet mental forming the accurate tool model is required. Due to the geometrical complexity of real-size part stamping tools it is hard to make FE model for real-size auto-body stamping parts. In this paper, it was focussed on the drawability factors on auto-body panel stamping by AUTOFORM with using tool planing alloy to reduce law price as well as high precision from Design Optimization of die. According to this study, the results of simulation will give engineers good information to access the Design Optimization of die.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.414-417
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• 2005

Many process parameters have an effect on the auto-body panel forming process. A well-designed blank shape causes the material to flow smoothly, reduces the punch and yields a product with uniform thickness distribution. Therefore, the determination of an initial blank shape plays the important role of saving time and cost in the auto-body panel forming process. For these reasons, some approaches to estimate the initial blank shape have been implemented in this paper, the one-step approach by using a finite element inverse method will be introduced to predict the initial blank shape the developed program is applied to auto-body panel forming.

• Progress in Superconductivity and Cryogenics
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• v.8 no.3
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• pp.9-12
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• 2006

Batch type co-evaporation EDDC (Evaporation using Drum in Dual Chambers) system was recently manufactured to fabricate 100m - long SmBCO superconducting coated conductor. As a preliminary study before the fabrication of long tape. short CC samples have been fabricated using the EDDC system and their crystal texture and $I_c$ properties were investigated. $1.2 {\mu}m$-thick SmBCO layers were deposited on $CeO_2/YSZ/CeO_2$ buffered Ni-W tapes. $I_c$ of 128A/cm-w and corresponding $J_c$ of $1.1 MA/cm^2$ at 77K in self-field were obtained for SmBCO CC tape. In-field property of SmBCO CC was confirmed to be better than that of YBCO deposited by PLD.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.10a
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• pp.123-127
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• 1997

Various recrystallization techniques has been applied to control morphology and size of NTO(3-nitro-1, 2, 4-triazole-5-one) crystals. With cooling method, it was found that the size of NTO at aqueous solution was controlled in the range of 5 to 500 $\mu\textrm{m}$. The spherical or cubic shapes of particles were obtained by adjusting operating conditions. Hexagonal and cubic shaped crystals of NTO were also obtained by sonication and evaporative method using aqueous solution of NTO. Their particle sizes were ranged 20 to 30 $\mu\textrm{m}$. In gas anti-solvent method with NTO/DMF and NTO/DMSO solutions, cubic type of NTO was obtained and the range of their sizes was 0.5-2$\mu\textrm{m}$.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.624-629
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• 2001

An experimental study was performed to investigate adiabatic wall temperature and heat transfer coefficient around on a module with longitudinal fin heat sink cooled by forced air flow. In the first method, inlet air flow(1-7m/s) and input power(3-5W) was varied after a heated module were placed on an adiabatic floor($320{\times}550{\times}1mm^{3}$). An adiabatic wall temperature was determinated to use liquid crystal film(LCF). In the second method to determinate heat transfer coefficient, inlet air flow(1-7m/s) and the heat flux of rubber heater($0.031-0.062\;W/cm^{2}$) was varied after an adiabatic module was placed on rubber heater covering up an adiabatic floor. In addition, surface oil-film visualization were performed to characterize the macroscopic flow-field around a module.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.881-886
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• 2003

In spite of its simple design, structure and operating mechanism, swing check valves are one of the critical components which adversely affect the safety of the nuclear power plants if they fail to function properly. Therefore, it is important to evaluate the performance condition of the swing check valves in safety-related systems. The performance characteristics of swing check valves include opening characteristics, the minimum required flow velocity, the pressure drop at design flow, the disc stability, and the effect of the upstream disturbances. Among factors to identify the performance of a swing check valve, a method to evaluate the opening characteristics and the minimum required flow velocity, which guarantees to fully open the disc and hold the disc without motion, are presented to determine the operating region of the swing check valve, such as stable, tapping, or oscillation. Based on the determined operating region and opening characteristics, the simple methods of wear and fatigue analyses of the specific parts of the valve are also described.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.346-351
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• 2018

Metal three-dimensional (3D) printing technologies are mainly classified as powder bed fusion (PBF) and direct energy deposition (DED) methods according to the method of application of a laser beam to metallic powder. The DED method can be used to fabricate fine and hard 3D metallic structures by applying a strong laser beam to a thin layer of metallic powder. The PBF method involves slicing 3D graphics to be a certain height, laminating metal powders, and making a 3D structure using a laser. While the DED method has advantages such as laser cladding and metallic welding, it causes problems with low density when 3D shapes are created. The PBF method was introduced to address the structural density issues in the DED method and makes it easier to produce relatively dense 3D structures. In this paper, thin lines were produced by using PBF 3D printers with stainless-steel powder of roughly $30{\mu}m$ in diameter with a galvano scanner and fiber-transferred Nd:YAG laser beam. Experiments were carried out to find the optimal conditions for the width of a line depending on the processing times, laser power, spot size, and scan speed. The optimal conditions were two scanning processes in one line structure with a laser power of 30 W, spot size of $28.7{\mu}m$, and scan speed of 200 mm/s. With these conditions, a minimum width of about $85.3{\mu}m$ was obtained.