• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.16 no.6
• /
• pp.130-136
• /
• 2002

A novel ozonizer has been developed using a high frequency surface discharge and a high purity Ti-Si-Al ceramic catalyst as its dielectric component. A cylindrical thin compound ceramic catalyst in reactor is adhered to inside of the film-like outside electrode. And, when experiment condition are oxygen gas temperature of 20 ［$^{\circ}C$］, inner reactor pressure of 1.6 atm 600［Hz］ and flow late of 2［l/min］. the ozonizer can easily produce ozone concentration(50～60［g/㎥］for oxygen) and power efficiency(180［g/kWh］for oxygen) without using a special enrichment means. At 2［l/min］, 20［$^{\circ}C$］, 1.6［atm］, 600［Hz］and 40［W］, the result of simulation to gas temperature of reactor using general code Phoenics, the maximum temperature of reactor was 132［$^{\circ}C$］in reactor. Ant the result electric field simulation of Ti-Si-Al type reactor using general code Flux 2D, maximum electric field was 0.131E.08［V/m］.

• Korean Journal of Metals and Materials
• /
• v.48 no.10
• /
• pp.901-906
• /
• 2010

The first stage blade of a gas turbine was operated under a severe environment which included both $1300^{\circ}C$ hot gas and thermal stress. To obtain high efficiency, a thermal barrier coating (TBC) and an internal cooling system were used to increase the firing temperature. The TBC consists of multi-layer coatings of a ceramic outer layer (top coating) and a metallic inner layer (bond coat) between the ceramic and the substrate. The top and bond coating layer respectively act as a thermal barrier against hot gas and a buffer against the thermal stress caused by the difference in the thermal expansion coefficient between the ceramic and the substrate. Particularly, the bondcoating layer improves the resistance against oxidation and corrosion. An inter-diffusion layer is generated between the bond coat and the substrate due to the exposure at a high temperature and the diffusion phenomenon. A thickness measurement result showed that the bond coat of the suction side was thicker than that of the pressure side. The thickest inter-diffusion zone was noted at SS1 (Suction Side point 1). A chemical composition analysis of the bond coat showed aluminum depletion around the inter-diffusion layer. In this study, we evaluated the properties of the bond coat and the degradation of the coating layer used on a $1300^{\circ}C$-class gas turbine blade. Moreover, the operation temperature of the blade was estimated using the Arrhenius equation and this was compared with the result of a thermal analysis.

• Journal of Aerospace System Engineering
• /
• v.11 no.4
• /
• pp.15-21
• /
• 2017

In this study, the surface heat transfer coefficient of the 3D model of a thruster regulator in the high temperature and high pressure environment was estimated using the commercial CFD code. The thermal barrier coating (TBC) on the surface of the thruster regulator was modeled and the effect of the thickness of the TBC on the temperature of the thruster regulator was investigated. The thickness of the TBC was varied from $100{\mu}m$ to $500{\mu}m$. Results showed that the temperature of the surface and the inside the thruster regulator was lower for the thicker TBC case.

• Journal of Hydrogen and New Energy
• /
• v.32 no.3
• /
• pp.156-162
• /
• 2021

Mg hydride has a relatively high hydrogen storage amount of 7.6wt%, and inexpensive due to abundant resources, but has high reaction temperature and long reaction time because of treble oxidation reactivity and upper activation energy. Their range of applications could be further extended if their hydrogenation kinetics and degradation behavior could be improved. Therefore, the effect of CaO has improved the hydrogenation kinetics and slowed down the degradation. This study focused on investigating whether to improve the hydrogenation kinetics by synthesizing Mg₂NiH_x-5wt% CaO composites. The Mg₂NiH_x-5wt% CaO composites have been synthesized by hydrogen induced mechanical alloying. The synthesized composites were characterized by performing X-ray diffraction, Scanning Electron Microscopy, Brunauer-Emmett-Teller, Thermogravimetric, and Sivert's type automatic pressure-composition-temperature analysis. Hydriding kinetics were performed using an automatic PCT measurement system and evaluated over the temperature range of 423 K, 523 K, and 623 K. As a result of calculating the hydrogen adsorption amount through the hydrogenation kinetics curve, it was calculated as about 0.42wt%, 0.91wt%, and 1.15wt%, the highest at 623 K and the lowest at 423 K.

• Transactions of Materials Processing
• /
• v.31 no.3
• /
• pp.124-128
• /
• 2022

NdFeB magnets have been positioned as the core materials in advanced technologies such as MRI (magnetic resonance imaging), FA (factory automation system), robot, motors, and so on based on the highest magnetic properties. To effectively improve the refined microstructure, the plastic deformation has been known as the good alternatives by the recrystallization. However, it has been regarded as being impossible because of the few slip systems in the RE-Fe-B magnets at room temperature. The purpose of this study was to investigate the possibility of control of grain refinement and magnetic anisotropy of NdFeB alloy powder by the severe plastic deformation. The NdFeB magnet powder was fabricated by gas atomization process, and the powder was pre-compacted at high temperature. The pre-compacted billets were deformed by HPT (high pressure torsion), and then the deformed billets were observed microstructure and magnetic properties. After the HPT process at room temperature, the grain size decreased with increasing because of the melted Nd-rich phase, and the anisotropy of Nd₂Fe₁₄B phase was formed after the HPT process.

• Nuclear Engineering and Technology
• /
• v.56 no.9
• /
• pp.3950-3960
• /
• 2024

As a solution to the problem of spent nuclear fuels (SNFs), the disposal of SNF has gained attention from nations using nuclear energy because of hazards posed to the ecosystem. Among many proposed solutions, the most promising method is to dispose of SNF in a deep geological repository (DGR) which utilizes the multi-barrier concept developed by Finland and Sweden. Here, a new fully-coupled Thermal-Hydraulic (TH) code HADES (High-level rAdionuclide Disposal Evaluation Simulator) is developed using the MOOSE framework. This new code suggests basic numerical tools, such as a non-linear solver and finite element discretization, to assess the safety performance of disposal systems. The new TH code considered various TH behavior using Richards' flow approach, assuming gas pressure is constant. The HADES showed promising results when it was compared to various TH codes validated from DECOVAELX-THMC projects. When the single-canister model was utilized to estimate the TH behavior of the Korean Reference disposal System, although it showed significant saturation reduction due to the evaporation of water, the temperature was maintained under the thermal criteria limit, which is 100 ℃. In addition, the new code estimated temperature and degree of saturation of the multi-canisters model, considering two or three canisters, it showed a slightly lower temperature, 5 ℃, than the single-canister model. From these results, the following are concluded: (1) the new TH code contribute to an additional integrity by estimating TH behavior of KRS; (2) however, due to limitations in single-canister simulation, it is recommended to use multi-canisters simulation to estimate TH behavior accurately. Therefore, this model is anticipated not only to help licensing applications and estimation of various multi-physics phenomena and multi-canister at the disposal site.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.28 no.2
• /
• pp.414-421
• /
• 2022

Subsea oil and gas exploration is increasingly moving into deeper water depths, and typically, subsea pipelines operate under high pressure and temperature conditions. Owing to the difference in these components, the axial force in the pipe is accumulated. When a pipeline is operated at a high internal pressure and temperature, it will attempt to expand and contract for differential temperature changes. Typically, the line is not free to move because of the plane strain constraints in the longitudinal direction and soil friction effects. For a positive differential temperature, it will be subjected to an axial compressive load, and when this load reaches a certain critical value, the pipe may experience vertical (upheaval buckling) or lateral (snaking buckling) movements that can jeopardize the structural integrity of the pipeline. In these circumstances, the pipeline behavior should be evaluated to ensure the pipeline structural integrity during operation in those demanding loading conditions. Performing this analysis, the correct mitigation measures for thermal buckling can be considered either by accepting bar buckling but preventing the development of excessive bending moment or by preventing any occurrence of bending.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.10 no.5
• /
• pp.9-15
• /
• 2010

Recently, the high-compressive strength concrete where the use is extending was weak in fire because of spalling that was occurring with rise of internal vapor pressure by high temperature. For preventing spalling of high-strength concrete in fire, Organic fibers have been using in concrete generally. By melting of organic fibers in concrete in fire, the internal moistures of concrete moves quickly to the outside, and so, preventing of spalling of high-strength concrete. But this method will be able to prevent the spalling of high-strength concrete, but makes the decrease of the concrete strength after fire. This study make a comparison between properties of preventing of spalling and remaining compressive strength of concrete using intumescence Alkali-Silicates fire-resistant material and that of concrete with organic fibers. Using organic fibers for preventing of spalling of concrete are P.P and Nylon fibers, and anti-fire intumescence material for protection of concrete surface is alkali-silicate materials. Fire resistance test executed as long as 3 hr under the flame temperature $1,200^{\circ}C$ over. In the case of concrete with P.P fibers, don't occurred the spalling, but the remaining compressive strength will not be able to measure, the concrete using intumescence Alkali-Silicates system fire-resistant material is not only preventing of the spalling but also the remaining compressive strength maintained until the maximum 96%.

• Journal of the Korean earth science society
• /
• v.23 no.5
• /
• pp.424-435
• /
• 2002

This study analyzes the surface ozone and meteorological data in Daegu for a period from 1997 to 1999. It also investigates the meteorological characteristics of high ozone episodes. For this study the high ozone episode has been defined as a daily maximum ozone concentration higher than 100ppb in at least one station among six air quality monitoring stations in Daegu, Korea. The frequency of episodes is 13 days. The frequency is the highest in May and September. The average value of daily maximum ozone concentration is 81.6ppb, and 8-hour average ozone concentration is 58.6ppb for the high episodes. This shows that ozone pollution is continuous and wide-ranging in Daegu. The daily maximum ozone concentration is positively correlated to solar radiation and daily maximum temperature, but negatively correlated to relative humidity, wind speed and cloud amount. The maximal correlation coefficient to solar radiation is 0.45. The differences between high ozone episode day's daily mean meteorological value and monthly mean value are +1.58hPa for sea level pressure, +3.45${\circ}$C for maximum temperature, -5.69% for relative humidity, -0.46ms$^{-1}$ for wind speed, -1.79 for cloud amount, and +3.97MJm$^{-2}$ for solar radiation, respectively. This shows that strong solar radiation, low wind speed and no precipitation between 0700${\sim}$1100LST are favorite conditions for high ozone episodes. It is related to the morning stagnant condition.

• Analytical Science and Technology
• /
• v.15 no.6
• /
• pp.502-508
• /
• 2002

See-through hollow cathode glow discharge cell has been developed for the trace analysis of metal ions. The systems consists of new glow discharge cell improved the cooling system. In the case of previous type of hollow cathode glow discharge cell, it had been utilized for the trace analysis of metal ions but it had a problem that the plasma becomes unstable by air-cooled device. In this study, the modified hollow cathode glow discharge cell has been developed in order to minimize the problem associated with the air-cooled device. thus the stability of the plasma with water-cooling device has been improved and also the higher plasma temperature has been measured. The fundamental characteristics of modified systems have been investigated. And the discharge parameters, such as discharge pressure, material, and diameter of cathode, have been studied to find optimum discharge conditions.