• Progress in Superconductivity and Cryogenics
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• v.21 no.3
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• pp.1-5
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• 2019

The superconductor stability theories are consistently described by the integral formula. If the defined stability function is a simple decreasing function, it becomes a cryogenic stability condition. If the stability function has a maximum value and a minimum value, and the maximum value is less than 0, then it is a cold-end recovery condition. If the maximum value is more than 0, it can be shown that the unstable equilibrium temperature, that is, the MPZ (minimum propagation zone) temperature distribution can exist. The MPZ region is divided into two regions according to the current ratio. At the low current ratio, the maximum dimensionless temperature is greater than 1, and at the relatively high current ratio, the maximum dimensionless temperature is less than 1. In order to predict the minimum quench energy, the dimensionless energy was obtained for the MPZ temperature distribution. In particular, it was shown that the dimensionless energy can be obtained even when the MPZ maximum temperature is 1 or more.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.9 no.3
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• pp.137-152
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• 2004

The climatological characteristics of coastal zone over the southwestern coast of Korea peninsula were investigated using the data observed by AWS (automatic weather system) and 4 buoy points. Coastal zone is climatologically defined as the region bounded by the distinct contrast of temperature gradient and wind speed across coastline. In the southwest of peninsula four cross-lines consisted of AWS aligned with each buoy were selected as Geojedo buoy line, Geomundo buoy line, Chilbaldo buoy line and Dukjukdo buoy line. Analysis on the diurnal cycle and intra-month variation, monthly mean and maximum value, the temperature gradient with distance between buoy and each station and the accumulative frequency of wind speed were applied to find out the characteristics and the range of coast zone. The maximum ranges of coastal zone vary from offshore to Sanglim (about 34 km distance from coastline) for Geojedo buoy line, to Sunchun (about 52 km) for Geo-mundo buoy line, to Jaeundo (about 27 km) for chilbaldo buoy line and to Yongin (about 65 km) for Dukjukdo buoy line. The modification of coastal zone according to synoptic flow was investigated for the onshore, off-shore and calm cases. The ranges of coastal zone are significantly changed with the distance between 65∼90 km for the case of onshore. In addition, we tried to find out the variation of the wind and temperature and the wind ratio of wind speed at ocean to land stations along Geojedo buoy line during 12∼13 Sep. 2003 affected by typhoon (MAEMI).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1289-1295
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• 2012

A process heat exchanger (PHE) in a nuclear hydrogen system is a key component for transferring the considerable heat generated in a very high temperature reactor (VHTR) to a chemical reaction that yields a large quantity of hydrogen. A performance test on a small-scale PHE prototype made of Hastelloy-X is underway in a small-scale gas loop at the Korea Atomic Energy Research Institute. Previous research on the high-temperature structural analysis of the small-scale PHE prototype had been performed using base material properties. In this study, a high-temperature structural analysis considering the mechanical properties in the weld zone was performed, and the obtained results were compared with those of the previous research.

• Journal of Bio-Environment Control
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• v.7 no.1
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• pp.25-33
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• 1998

Root zone temperature have influenced on protected cultivation in winter season. Especially root zone temperature is acted on limiting factor in crop cultivation. This study was conducted to obtain optimum temperature of root zone in Protected cultivation Root zone was warmed by heated water($28^{\circ}C$) flowing through the PPC pipe(${\phi}15$) buried depth 40 cm. And the flowing water was heated by solar system. Minimum air temperature during night time was set at $14^{\circ}C$ and maximum air temperature during day time was set at $28~30^{\circ}C$ the growing period of cucumber was from Nov. 6, 1996 to Jan. 30, 1997. The results are summarized as follows. 1. Average soil temperature at 15~20 cm depth was $22^{\circ}C$ at warming plots, $17~18^{\circ}C$ at non-warming plots 2. Early growth in leaf length, stem diameter, number of leaves and leaf area for 30 days after planting were accelerated by root zone warming. Especially, the grawing rate of soil warming plots was higher 27% in leaf length, 51% in leaf number, 150% in leaf area than non-warming Plots. Above-ground and underground part of warming plots was higher 117%, 56% than non-warming plots. 3. In total yield analysis, number of fruits were 614 in soil warming and 313 in non-warming plots. In the result, total yield of soil warming plots was increased with 196% than non-warming plots. 3. In total yield analysis. number of fruits were 614 in soil warming and 313 in non-warming plots. In the result. total yield of soil warming plots was increased with 196% than non-warming plots.

• Journal of Urban Science
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• v.9 no.1
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• pp.17-31
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• 2020

This study aims to analyze the relations among greenbelt, urban land surface temperature empirically in order to assess the environmental effects of the greenbelt in the Seoul metropolitan area, objectively. For this purpose, this study conducts an empirical analysis of impacts of greenbelt on urban land surface temperature using a multiple-regression model. The main data employed in the analysis include real-time air pollution data, Landsat 8-OLI Landsat imagery data, KLIS data and Jip-gye-gu data. The major findings are summarized as follows. NDVI has a negative (-) correlation with the land surface temperature, and the urban temperature is high in areas with poor vegetation. The land surface temperature is low in residential or commercial areas, while the temperature is high in industrial areas. The temperature is low in green fields, open spaces, and river areas. it is found that the urban land surface temperature is low in the greenbelt zone. In the greenbelt zone, there is an effect that reduces the land surface temperature by 1% on average, as compared to that at the center of the Seoul metropolitan area. Especially, the center of the Seoul metropolitan area, in a range from 0.6% to 1.9% of the average temperature, the temperature gets lower up to approximately 3km from the greenbelt boundary.

• Journal of the Korean Society of Combustion
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• v.11 no.3
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• pp.1-7
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• 2006

A reaction mechanism of methane partial oxidation, which consists of thermal and plasma chemistry reaction pathways, has been investigated using with an arc-jet reactor. The reaction zone of the arc-jet reactor is spatially separated into thermal and non-thermal plasma zone. Methane conversion rates, selectivity of $H_2$ and $C_2$ chemicals in each zone are obtained, which reveals clearly different characteristics of reaction pathways depending on the temperature conditions. The conversion rates obtained in thermal plasma zone is higher than those in non-thermal plasma zone. The selectivity, however, obtained in non-thermal plasma zone is significantly higher than those in thermal plasma zone. Further parametric study on $O_2/C$ ratio, arc length and SED shows that the present process is mainly governed by thermal chemistry pathways.

• Economic and Environmental Geology
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• v.32 no.5
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• pp.519-535
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• 1999

Precambrian metasedimetay rocks in the Sunchang Shear Zone (so-called Seologri and Yongamsan Formation) consist of black slate, phylite, mica schistm quartzite and rarely calc schist. The metamorphic rocks in the area have undergone at least three stages of metamorphism, which are two prograde (M1 and M2) and one contact metamorphism (M3). The metamorphism which made the most prevailing mineral assemblages in the area, is M2 stage metamorphism. The metamorphic grade of M2 methamorphism in metapelites increases from the Chlorite zone through Biotituzone, Garnet zone to Staurolite zone. The M1 stage metamorphism is recognized by kyanite and sillimanite pressure type regional metamorphism. The M3 stage methamorphism is represented in the contact boundary, which area is the chlorite zone and biotite zone near the Sunchang foliated granite and the namwon granite. The M3 stage methamorphism is characterized by andalusite bearing mineral assemblages. The peak temperature condition of M2 metamorphism estimated from coexising garnet and biotite (Kretz, 1990) is 518~598$^{\circ}C$.

• Journal of Welding and Joining
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• v.10 no.4
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• pp.222-229
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• 1992

A prediction of penetration and heat affected zone by using Finite Element Method in CO$_{2}$ Arc Welding has been discussed this paper. The temperature distribution of a base metal produced by the CO$_{2}$ arc welding processing is analyzed by using a three dimensional finite element model. The common finite element program ANSYS 4.4A was employed to obtain the numerical results. Temperature dependent material properties, effect of latent heat, and the convective boundary conditions are included in the model. Numerically predicted sizes of the penetration and the heat affected zone are compared with the experimentally observed values. As a result, there was a slight difference between numerical analysis values and experimentally observed values. For in the case of heat affected zone, it was not considered a precise forced convective coefficient value, and in the case of penetration, it was not, considered a arc force.

• Safety and Health at Work
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• v.12 no.3
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• pp.416-420
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• 2021

Hazardous area classification design is required to reduce the explosion risk in process plants. Among the international design guidelines, only IEC 60079-10-1 proposes a new type of zone, namely zone 2 NE, to prevent explosion hazards. We studied how to meet the zone 2 NE grade for a facility handling hydrogen gas, which is considered as most dangerous among explosive gases. Zone 2 NE can be achieved considering the grade of release, as well as the availability and effectiveness of ventilation, which are factors indicative of the facility condition and its surroundings. In the present study, we demonstrate that zone 2 NE can be achieved when the degree of ventilation is high by accessing temperature, pressure, and size of leak hole. The release characteristic can be derived by substituting the process condition of the hydrogen gas facility. The equations are summarized considering relation of the operating temperature, operating pressure, and size of leak hole. Through this relationship, the non-hazardous condition can be realized from the perspective of inherent safety by the combination of each parameter before the initial design of the hydrogen gas facility.

• Journal of Welding and Joining
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• v.31 no.1
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• pp.58-64
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• 2013

The following results were obtained, microstructures and tensile properties in arc brazed joints of DP(dual phase) steel using Cu-5.3wt%Sn insert metal was investigated as function of brazing current. 1) The Fusion Zone was composed of ${\alpha}Fe+{\gamma}Cu$ and Cu23Sn2. The reason for the formation of these solid solutions. Despite, Fe & Cu were impossible to solid solution at room temperature. It's melting & reaction to something of insert metal & Base Metal (DP Steel) by Arc. Brazing Process has faster cooling rate then Cast Process, Supersaturated solid solution at room temperature. 2) The increase Hardness of Fusion Zone was directly proportional to the rise of welding current. Because, ${\alpha}Fe+{\gamma}Cu$ phase (higher hardness than the Cu23Sn2.(104.1Hv < 271.9Hv)) Volume fraction was Growth, due to increasing the amount of base metal melting by High current. 3) The results of tensile shear test by Brazing, All specimens happen to fracture in Fusion Zone. On the other hand, when Brazing Current increasing tend to rise tensile load. but it was very small, about 26-30% of the base metal. 4) The result of fracture analysis, The crack initiate at Triple Point for meet to Upper B.M/Under B.M/Fusion Zone. This Crack propagated to Fusion zone. So ruptured by tensile strength. The Reason to in the fusion zone fracture, Fusion zone by Brazing of hardness (strength) was very lower then the base metal (DP steel). In addition the Fusion Zone's thickness in triple point was thin than the base metal's thickness in triple point.