• Journal of the Korean Society of Industry Convergence
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• v.7 no.1
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• pp.25-31
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• 2004

The heat transfer characteristics of a plasma display panel has been investigated for cooling an electronic module. Hence, a two dimensional $\kappa-{\varepsilon}$ turbulent model was developed to predict the temperatures of the panel and module. The heat conduction was solve for the material region. To consider the mixed convection at the solid-fluid interfaces between the air and the panel and module, the energy equation was solved simultaneously. When the electronic module stands face to face with the panel, the temperatures of panel and module are lower than other arrangement due to the chimney effect. However the gap between the panel and module does not affect significantly the maximum temperature when the aspect ratio is less than 0.1. To maintain the maximum temperature of the module under a certain limit, the passage of air should be well designed by the optimal layout of electronic modules which have different heat emission.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.5
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• pp.145-150
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• 2013

Recently, many vehicles have applied electric parts for saving fuel consumption and reducing levels of environmental pollution. ISG (integrated starter & generator) is one of main electric parts and can improve fuel efficiency by using idle stop & go function and regenerative braking system. However, if ISG driving inverter works under the continuously high load condition, it will make the performance and durability of the inverter decreased with rising temperature. In this study, we carried out the analysis on the fluid flow and thermal characteristics of the inverter. As a result, we found the MOSFET of the air cooled inverter was increased up to $116^{\circ}C$ over the limit temperature. On the other hand, the liquid cooled type inverter's MOSFET was decreased by about $17^{\circ}C$ compared to that of the air cooled inverter. Therefore, we verified the feasibility of the liquid cooled type using the present cooling structure.

• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.156-161
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• 2011

In case of newly constructed buildings, the construction type is almost Curtain-wall system or large window in building skin. However, these kind of buildings have problems with regulations on building energy efficiency. And national regulations on building energy efficiency limit only the V-factor of window(except infiltration), it is hard to predict energy consumption of Curtain-wall buildings which gain large solar energy in summer. In this study, the influence of LSG(Light to Solar Gain) on energy performance was theoretically analyzed with simulation. LSG is the value of VLT divide SHGC and represents the optical performance of the glass or glazing. The Window & Therm program developed in LBNL was used to analyze window systems and EnergyPlus was used to building energy. Cases of glazing are three types; single coated Low-e clear glazing, tripple coated Low-e clear glazing, tripple coated Low-e tinted glazing. The results of this study are follows; 1) The building energy consumption of Alt-l, 2, 3 were about 300, 253, $259kWh/m^2{\cdot}yr$ respectively. Therefore, improvement of LSG could save the energy up to 16%. 2) The saved energy could be converted 1 billion won as annual benefit of total energy costs 3) SHGC and LSG more influence on cooling energy than heating energy in office buildings.

• Journal of Advanced Marine Engineering and Technology
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• v.10 no.1
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• pp.74-84
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• 1986

Ejectors, having no moving, lubricating and leaking parats, are widely used as marine pumps because of its high working confidence. For instance, uses in ships are stripping in crude oil tank, bilge discharge in engine room, ballast water pumping on are carrier, and brine discharge from fresh water generator. And it is also used as cooling water recirculating pump in boiling water type nuclear reactor and deep-well pump. It is not easy to determine the optimal dimension for designing each ejector agreed with its suggested performance condition, because complicated calculations must be repeated to obtain the maximum efficiency affected by flowrate ratio, head ratio, area ratio and so on. Therefore, it is considered that the CAD (Computer-Aided Design) for ejector is a powerful method for design according to the individual design condition. In this paper, a computer program for water ejector design is developed based on the previous paper on theoretical analysis and experimental results for water ejector. And from the theoretical approach, an equation for the working limit and an equation for determing the shape of throat are obtained. The validity of the present computer program is sufficiently confirmed through the comparison of the computed results with the main dimension of the previous manufactured water ejector. This program will be easily developed as the CAD for various kinds of ejectors, including steam ejector.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.295-296
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• 2006

High hardness of P/M parts can be obtained in the cooling section of the sintering furnace by using sinter hardenable materials, thus the post-sintering heat treatment can be eliminated. However, the sinter hardened materials would have difficulties in secondary machining if it is required, which will limit the applications of sinter hardenable materials in the machined parts. Recent development in warm compaction technology can enable us not only to achieve the high green density up to $7.4\;g/cm^3$, but also the high green strength which is needed for green machining. Therefore by using warm compaction technology, the green machining can be applied to sinter hardenable materials for the high density, strength and hardness P/M parts. In the present study, a pre-alloyed steel powder, ATOMET4601, was used by mixing with 2.0% copper, 1.0% nickel, 0.9% graphite and a proprietary lubricant using a binder treatment process - FLOMET. The specimens were compacted and green machined with different machining parameters. The machined surface finish and part integrity were evaluated in selecting the optimal conditions for green machining. The possibility of applying the green machining to the high-density structural parts was explored.

• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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• pp.30-34
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• 2021

Superconducting magnets have paved the way for opening new horizons in designing an electromagnet of a high field magnetic resonance imaging (MRI) device. In the first phase of the superconducting MRI magnet era, low-temperature superconductor (LTS) has played a key role in constructing the main magnet of an MRI device. The highest magnetic resonance (MR) field of 11.7 T was indeed reached using LTS, which is generated by the well-known Iseult project. However, as the limit of current carrying capacity and mechanical robustness under a high field environment is revealed, it is widely believed that commercial LTS wires would be challenging to manufacture a high field (>10 T) MRI magnet. As a result, high-temperature superconductor together with the conducting cooling approach has been spotlighted as a promising alternative to the conventional LTS. In 2020, the Korean government launched a national project to develop an HTS magnet for a high field MRI magnet as an extent of this interest. We have performed a design study of a 7 T 320 mm winding bore HTS MRI magnet, which may be the ultimate goal of this project. Thus, in this paper, design study results are provided. Electromagnetic design and analysis were performed considering the requirements of central magnetic field and spatial field uniformity.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.498-505
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• 2024

In this paper, a cable-driven endoscopic manipulator (CEM) is designed for the Chinese latest compact fusion reactor. The whole CEM arm is more than 3000 mm long and includes end vision tools, an endoscopic manipulator/control system, a feeding system, a drag chain system, support systems, a neutron shield door, etc. It can cover a range of ±45° of the vacuum chamber by working in a wrap-around mode, etc., to meet the need for observation at any position and angle. By placing all drive motors in the end drive box via a cable drive, cooling, and radiation protection of the entire robot can be facilitated. To address the CEM motion control problem, a discrete trajectory tracking method is proposed. By restricting each joint of the CEM to the target curve through segmental fitting, the trajectory tracking control is completed. To avoid the joint rotation angle overrun, a joint limit rotation angle optimization method is proposed based on the equivalent rod length principle. Finally, the CEM simulation system is established. The rationality of the structure design and the effectiveness of the motion control algorithm are verified by the simulation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.4
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• pp.405-413
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• 2015

In the US, the number of cases of subterranean water contamination from tritium leaking through a damaged buried nuclear power plant pipe continues to increase, and the degradation of the buried metal piping is emerging as a major issue. A pipe blocked from corrosion and/or degradation can lead to loss of cooling capacity in safety-related piping resulting in critical issues related to the safety and integrity of nuclear power plant operation. The ASME Boiler and Pressure Vessel Codes Committee (BPVC) has recently approved Code Case N-755 that describes the requirements for the use of polyethylene (PE) pipe for the construction of Section III, Division 1 Class 3 buried piping systems for service water applications in nuclear power plants. This paper contains tensile and slow crack growth (SCG) test results for high-density polyethylene (HDPE) pipe welds under the environmental conditions of a nuclear power plant. Based on these tests, the fracture surface of the PENT specimen was analyzed, and the fracture mechanisms of each fracture area were determined. Finally, by using 3D finite element analysis, limit loads of HDPE related to premature failure were verified.

• Journal of Astronomy and Space Sciences
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• v.17 no.1
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• pp.77-86
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• 2000

There have been a few attempts to measure diffuse line emission between 900 $\AA$ and 1200 $\AA$, and only in a limited number of sight lines has it been detected. The main contributions to the equilibrium radiative cooling curve between $10^{4.5}K\;to\;10^6K$ are from the doublet of Ovi ${lambda}{lambda}1032;and;{lambda}{lambda}1038$ in the FUV spectral region. There are several bright airglow lines which could interfere with attempts to observe the OVI lines. The nearest lines HI 1025 $\AA$, OI 1027 $\AA$ have a combined intensity of about $10^{5.5}$ photons/s/$cm^2$/sr. In the present study, the detectability simulation of OVI doublet is performed using a Monte-Carlo technique and chi-square statistics. The analysis results are compared with the previous observations and with the predictions of several interstellar medium models, and are used to limit manufacturing and alignment errors of FIMS optical system.

• Transactions of the KSME C: Technology and Education
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• v.5 no.2
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• pp.135-143
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• 2017

The domestic unique research reactor, HANARO (Hi-flux Advanced Neutron Application ReactOr), has been constructed with the open-pool, the core is submerged in, for the multi-purpose neutron application. The reactor has a primary cooling system to remove the fission heat from the core and its connected fluidic systems. Since the works are required at the reactor pool top as a characteristic of the research reactor, the radiation shall be minimized with the operation of the hot water layer system to avoid unnecessary radiation exposure on the workers during work at the pool top. Moreover, the pool water management system is connected to the reactor pool to maintain the pool temperature below $50^{\circ}C$ to minimize the uprising radioactive gas or impurity from the colder pool bottom. For the efficient flow rate of the PWMS, the thermal capacity of heat exchanger is selected with 260 kW in the normal operation condition. In this paper, the modeling is formulated to figure out whether or not each pool temperature maintains below the temperature limit and the calculation results show that the designed PWMS heat exchanger has enough capacity with the design margin regardless of the reactor operation mode.