• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4A
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• pp.355-363
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• 2009

When water inside the concrete member evaporates by high temperature, the evaporation heat which absorbs surrounding temperature occurs. The rate of increment of the internal temperature in concrete is reduced due to the evaporation heat in spite of continuously increasing external temperature. In this paper, the prediction method of internal temperature of concrete members considering the evaporation heat under the high temperature is presented. Finite element method is employed to facilitate thermal analysis for any position of member. And the thermal characteristics models of high strength concrete affected by high temperature are proposed. To demonstrate the validity of this numerical procedure, the prediction by the proposed algorithm is compared with the test results of other researchers. The proposed algorithm shows a good agreement with the experimental results including the phenomenon that temperature is lost by the evaporation heat.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4561-4569
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• 2023

A correct understanding of vibration-based degradation is crucial from the standpoint of maintenance for Steam Generators (SG) as crucial mechanical equipment in nuclear power plants. This study has established a novel approach to developing a model for investigating tube bundle degradation according to crack growth caused by two-phase Flow-Induced Vibration (FIV). An important step in the approach is to calculate the two-phase flow field parameters between the SG tube bundles in various zones using the porous media model to determine the velocity and vapor volume fraction. Afterward, to determine the vibration properties of the tube bundles, the Fluid-Solid Interaction (FSI) analysis is performed in eighteen thermal-hydraulic zones. Tube bundle degradation based on crack growth using the sixteen most probable initial cracks and within each SG thermal-hydraulic zone is performed to calculate useful lifetime. Large Eddy Simulation (LES) model, Paris law, and Wiener process model are considered to model the turbulent crossflow around the tube bundles, simulation of elliptical crack growth due to the vibration characteristics, and estimation of SG tube bundles degradation, respectively. The analysis shows that the tube deforms most noticeably in the zone with the highest velocity. As a result, cracks propagate more quickly in the tube with a higher height. In all simulations based on different initial crack sizes, it was observed that zone 16 experiences the greatest deformation and, subsequently, the fastest degradation, with a velocity and vapor volume fraction of 0.5 m/s and 0.4, respectively.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.1
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• pp.16-22
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• 2018

Silicon carbide (SiC) is used in various semiconductor processes because it has superior thermal, mechanical, and electrical characteristics as well as higher chemical and corrosion resistance than existing materials. Due to these characteristics, various manufacturing technologies have been developed for SiC. A recent development among these technologies is Chemical Vapor Deposition SiC (CVD-SiC). Many studies have been carried out on the processing and manufacturing of CVD-SiC due to its different material characteristics compared to existing materials like RB-SiC or Sintered-SiC. CVD-SiC is physically stable and has excellent chemical and corrosion resistance. However, there is a problem with increasing the thickness, because it is manufactured through a deposition process. Additionally, due to its high strength and hardness, it is difficult to subject to machining.

• Journal of Hydrogen and New Energy
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• v.33 no.5
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• pp.525-533
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• 2022

In this study, in order to numerically analyze the heat flow characteristics in the valve according to the opening rate for the solenoid valve for hydrogen supply applied to the hydrogen storage tank, flow characteristics were comparatively analyzed. Through the analysis of pressure and temperature distributions within the valve according to the high-pressure supply condition of 70 MPa or more, the heat flow characteristics in the valve, inlet and outlet passage according to the opening rate of the valve were identified. As a result a sudden change in the fluid behavior appears in the neck region of the valve, and it is understood that the flow separation caused by the flow path shape of the expanded tube has a dominant influence on the flow characteristics. And, it was confirmed that the shape of the valve seat is a factor significantly affecting the improvement of flow rate and differential pressure performance.

• Korean Journal of Remote Sensing
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• v.35 no.6_4
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• pp.1403-1415
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• 2019

Urban population growth and consequent rapid urbanization involve some thermal environmental problems in the cities. Monitoring of thermal environments in urban areas such as hot spot analysis is required for effective actions to resolve these problems. This study selected 14 dongs and surrounding administrative districts of Sejong city as study areas and analyzed the characteristics of changes in surface temperature due to the urban expansion in the summer from 2013 to 2018. In the study, the surface temperature distributions in the study areas were plotted using surface temperature values from Landsat 8 and NDVI (Normalized Difference Vegetation Index) and NDBI (Normalized Difference Built-up Index) based on KOMPSAT 2/3 data, and the patterns of surface temperature changes with urban expansion were discussed using the estimated NDVI and NDBI. In particular, the distinct urbanization in the study areas were selected for case studies, and the cause of the changes in the hot spots in the regions was analyzed using high-resolution KOMPSAT images. This study results present that hot spots appeared in urbanized regions within the study areas, and it was plotted that the lower the NDVI values and the higher the NDBI values indicate the temperature values are high. The land surface temperature and satellite-based products were used to divide the study areas into continuously urbanized regions and rapidly urbanized regions and to identify the different characteristics depending on land covers. In the regions with distinct surface temperature changes by urbanization, the analysis using high-resolution KOMPSAT images as presented in this study could provide effective information for urban planning and policy utilization in the future.

• Journal of the Korean Institute of Landscape Architecture
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• v.32 no.6 s.107
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• pp.82-94
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• 2005

This study was undertaken to measure and analyze the thermal environment characteristics of the grey permeable cement concrete pavement(GPCCP), the permeable cement concrete brick pavement(PCCBP) compared with impermeable cement concrete pavement(ICCP) and bare soil(BS) under the summer outdoor environment. Following is a summary of major results. 1) The peak surface temperature was greatest in the GPCCP$(54.2^{\circ}C)$ followed by ICCP$(47.2^{\circ}C)$ rut August 2, 2002, the hottest day$(35.3^{\circ}C\;of\;highest\;temperature)$ during the experiment; peak temperature in the ICCP and BS were $45.5^{\circ}C)$ and $45.3^{\circ}C)$ respectively. 2) Analysis of heat budget of the pavements has revealed that the heat environment was worse in the GPCCP than that in the ICCP and that this was mainly due to a low albedo in the former(0.2) relative to that of the latter(0.4). 3) Analysis of heat budget of the pavements has revealed that the heat environment was worse in the GPCCP than that in the PCCBP, BS and that this was mainly due to a decreased latent heat resulting from a time dependent decreasing impact of rainfall. 4) It is necessary to make cool pavements to further studies on light-colored surface materials for attaining high albdo and construction methods which can enhance the latent heat through the continuous evaporation from pavements surface. 5) Vertical arrangement of pavement layers has not been considered in the present study, which has been focuses on the heat characteristics of the surface layer materials. Accordingly, future studies will have to be empasized on pavement methods including the vertical arrangement of the pavement layers.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.12
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• pp.80-90
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• 1994

To develop VLSI of higher packing density with 0.5.mu.m gate length of less, semiconductor devices require shallow junction with higher doping concentration. the most common method to form the shallow junction is ion implantation, but in order to remove the implantation induced defect and activate the implanted impurities electrically, ion-implanted Si should be annealed at high temperature. In this annealing, impurities are diffused out and redistributed, creating deep PN junction. These make it more difficult to form the shallow junction. Accordingly, to miimize impurity redistribution, the thermal-budget should be kept minimum, that is. RTA needs to be used. This paper reports results of the diffusion characteristics of PSG film by varying Phosphorus weitht %/ Times and temperatures of RTA. From the SIMS.ASR.4-point probe analysis, it was found that low sheet resistance below 100 .OMEGA./ㅁand shallow junction depths below 0.2.mu.m can be obtained and the surface concentrations are measured by SIMS analysis was shown to range from 2.5*10$^{17}$ aroms/cm$^{3}$~3*10$^{20}$ aroms/cm$^{3}$. By depending on the RTA process of PSG film on Si, LDD-structured nMOSFET was fabricated. The junction depths andthe concentration of n-region were about 0.06.mu.m. 2.5*10$^{17}$ atom/cm$^{-3}$ , 4*10$^{17}$ atoms/cm$^{-3}$ and 8*10$^{17}$ atoms/cm$^{3}$, respectively. As for the electrical characteristics of nMOS with phosphorus junction for n- region formed by RTA, it was found that the characteristics of device were improved. It was shown that the results were mainly due to the reduction of electric field which decreases hot carriers.

• Journal of Ocean Engineering and Technology
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• v.32 no.5
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• pp.310-323
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• 2018

In order to protect lives and prevent large-scale injuries in the event of a fire on a ship or an offshore plant, most classification societies are strengthening their fire resistance designs of relevant cargo holds and accommodation compartments to keep flames from being transferred from a fire point to other compartments. Particularly in critical compartments, where flames should not propagate for a certain period of time, such as the A60 class division, both the airtightness and fire-resistant design of a piece passing through a bulkhead are subject to the Safety of Life at Sea Convention (SOLAS) issued by the International Maritime Organization (IMO). In order to verify the suitability of a fire-resistant design for such a penetrating piece, the fire test procedure prescribed by the Maritime Safety Committee (MSC) must be carried out. However, a numerical simulation should first be conducted to minimize the time and cost of the fire resistance test. In this study, transient thermal analyses based on the finite element method were applied to investigate the heat transfer characteristics of a bulkhead penetration piece for the A60 class compartment. In order to determine a rational bulkhead penetration piece design, the transient heat transfer characteristics according to the variation of design parameters such as the diameter, length, and material were reviewed. The verification of the design specification based on a numerical analysis of the transient heat transfer performed in this study will be discussed in the following research paper for the actual fire protection test of the A60 class bulkhead penetration piece.

• Journal of Hydrogen and New Energy
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• v.16 no.1
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• pp.66-73
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• 2005

Hydrogen linear power system is estimated as the next generation power system which can obtain a performance as same as fuel cell. In order to develop Hydrogen combustion power system with high thermal efficiency, it is very important to understand the basic characteristics of hydrogen combustion and establish combustion stabilization technique of its system. In this study, RICEM(Rapid Intake Compression Expansion Machine) for researching of hydrogen combustion linear power system was manufactured and evaluated, and the basic characteristics of linear RICEM were analyzed.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.5 no.4
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• pp.35-42
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• 1991

Recently, HID lamps have been considered as important in regard to the trend of energy saving, and increasingly and diversely used in various ways. This paper will show the simulating models concerning high-pressure arc discharge system directly applicable for its design and manufacture, and analyze its various characteristics. For warm-up characteristics, the evaporating process of inner atoms is described in terms of second-order differential equation: for the thermal conduction from are axis to discharge wall and outer bulb, its transfer process is introduced according to five first-order differential equations. Under the steady state satisfying LTE, the time-variant characteristics are suggested by means of time-dependent energy balance equation derived from fluid equations, approximation of radiation energy and material functions in the discharge tube. The simulating models concerning these equations are then applied for high-pressure mercury lamp.