• Journal of the Korean association of regional geographers
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• 제17권2호
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• pp.167-180
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• 2011

This paper investigates the changes of diurnal temperature range (DTR) by season and region in South Korea using daily maximum temperature and daily minimum temperature from 1954 to 2009. It also attempts to find what causes these changes. The daily minimum temperature distinctively increased during the latter half of the research period (1988~2009) than the first half of the year (1954~1987) leading decreases in DTR, while the rise in daily maximum temperature was not distinct during the research period. The DTR shows slightly increasing trend in spring. but decreasing trend in fall. The DTR is decreasing in urban region while it is increasing in rural area. The degree of the DTR decrease is bigger in large urban region than in medium-small urban region. The DTR in urban region is affected by the amount of clouds in spring and tile duration of sunshine in fall. The DTR in rural area is affected by the amount of clouds in spring and the number of days with precipitation in fall.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.489-492
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• 2008

Adiabatic temperature rise and autogenous shrinkage experiments were performed for three silica-fume included mass concrete mixtures and a reference mixture without silica-fume, in order to investigate the influence of silica-fume on the hydration heat and autogenous shrinkage properties of mass concrete, and to examine applicability of silica-fume to mass concrete. It was revealed from the experiment that, for mass concrete, the rate of hydration was hardly increased while the maximum adiabatic temperature rise decreased about 5$^{\circ}$C by the addition of silica-fume, and the amount of autogenous shrinkage was almost the same regardless of silica-fume replacement. These facts imply that silica-fume can enhance the resistance of mass concrete to temperature cracking as well as the durability.

• Proceedings of the KSME Conference
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• 대한기계학회 2004년도 춘계학술대회
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• pp.2094-2099
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• 2004

An experimental study on heat transfer characteristics near the critical pressure has been performed with an internally-heated vertical annular channel cooled by R-134a fluid. Two series of tests have been completed: (a) steady-state critical heat flux (CHF) and (b) heat transfer tests for pressure reduction transients through the critical pressure. In the present experimental range, the steady-state CHF decreases with the increase of the system pressure For a fixed inlet mass flux and subcooling, the CHF falls sharply at about 3.8 MPa and shows a trend toward converging to zero as the pressure approaches the critical point of 4.059 MPa. The CHF phenomenon near the critical pressure does not lead to an abrupt temperature rise of the heated wall because the CHF occurred at remarkably low power levels. In the pressure reduction transient experiments, as soon as the pressure passed through the critical pressure, the wall temperatures rise rapidly up to a very high value due to the occurrence of the departure from nucleate boiling. The wall temperature reaches a maximum at the saturation point of the outlet temperature, then tends to decrease gradually.

• Journal of the Korean Society for Precision Engineering
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• 제17권8호
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• pp.71-77
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• 2000

The built-in spindle motor for high-speed machine tools is designed and developed by Corporate R&D Institute of DAEWOO Heavy Industries LTD. The heat analysis program for the built-in spindle motor is developed by using lumped method. For the purpose of verification of the program comparison analyses between experiments and calculations are performed on the three motors ; DHI prototype of built-in spindle motor built-in spindle motor sample A and sample B As results calculated temperature distributions are in good agreement with the test results within the average error of 10% Calculated results of all the built-in spindle motors show that maximum temperature rise at high speed remains in the operating condition without exceeding the permitted limit but they exceeded the permitted limit of temperature rise at low speed.

• Nuclear Engineering and Technology
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• 제36권5호
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• pp.403-414
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• 2004

An experimental study of heat transfer characteristics near the critical pressure has been performed with an internally-heated vertical annular channel cooled by R-134a fluid. Two series of tests have been completed: (a) steady-state critical heat flux (CHF) tests, and (b) heat transfer tests for pressure reduction transients through the critical pressure. In the present experimental range, the steady-state CHF decreases with increase of the system pressure for fixed inlet mass flux and subcooling. The CHF falls sharply at about 3.8 MPa and shows a trend towards converging to zero as the pressure approaches the critical point of 4.059 MPa. The CHF phenomenon near the critical pressure does not lead to an abrupt temperature rise of the heated wall, because the CHF occurs at remarkably low power levels. In the pressure reduction transients, as soon as the pressure passes below the critical pressure from the supercritical pressure, the wall temperatures rise rapidly up to very high values due to the departure from nucleate boiling. The wall temperature reaches a maximum at the saturation point of the outlet temperature, and then tends to decrease gradually.

• Journal of the Korea Safety Management & Science
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• 제23권3호
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• pp.97-102
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• 2021

This study developed a scenario to understand the reaction rate and operational time according to RTI value of rate of rise detector in each type in case of fire mattress. In the results of analyzing the reaction rate and operational time of detector in each scenario, in case when installing a single detector, the elevated temperature per minute was raised to 8℃/min ~ 9℃/min. In case when installing two detectors, it was raised to 9℃/min ~ 10℃/min. In case when installing three detectors, it was raised to 10℃/min. The horizontal distance between detector and mattress was 1.8m~2.5m. Whenever the number of detectors was increased, the horizontal distance was decreased. The operational time of detector was within maximum 540 seconds and minimum 420 seconds. As the research tasks in the future, there should be the researches on the effects of reaction rate of detector on the evacuation in case of fire through the result value of RSET by setting up the latency until the detector operates, and the researches on the safety by understanding if the operational time of detector is suitable for the evaluation standard of performance-centered design.

• Proceedings of the KSME Conference
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1250-1254
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• 2004

To develop more compact and light generators which have high capacity, the most important thing that should be considered is the inner cooling system. Under all circumstances, the temperature of rotor and stator windings must be kept below the maximum temperature of insulation to maintain reliability and prolong durability of the machine. Therefore, the development of more effective cooling system and the exact prediction of windings are essential to produce our unique generator model which is reliable and competitive in international market. In this study, the flow of cooling air and the temperature distribution of winding is analyzed by using computational fluid dynamics. This analysis can lead to optimize the structure of cooling system and predict a local temperature rise.

• Proceedings of the Korean Institute of Building Construction Conference
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• 한국건축시공학회 2021년도 봄 학술논문 발표대회
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• pp.114-115
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• 2021

The research team conducted a series of studies to use CGS as fine aggregate for concrete. In this paper, through the adiabatic temperature rising test, CGS' hydration heating performance and its usability as a mass concrete hydration heating agent were reviewed. According to the analysis, the maximum temperature of the mix of OPC 100 was 53.7℃, and the temperature of CGS 50% was 45.2℃, which was 8.5℃ lower than the OPC 100.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제64권10호
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• pp.1517-1522
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• 2015

Since electric railroad vehicle pass through repeatedly on the railroad bridge, the dynamic load that causes the change of tension of contact wire affect it constantly. In this paper, we measured the dynamic displacement of the railroad bridges to analyze the effect of tension in the catenary. A result of dynamic measurement of the longitudinal displacement, it's maximum value was 39.9mm which was lower than the primary management criteria 378mm. Also on the based of a maximum temperature, it shows a feature that the longitudinal displacement value increased as temperature rise from April to October. In terms of behavior characteristics of a tensioning device, it was confirmed to be the value of 50mm stroke movement when the temperature changes ±5℃.

• Journal of Chest Surgery
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• 제40권2호
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• pp.122-127
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• 2007

Background: Spontaneous pneumothorax is a common respiratory condition and has been postulated that it develops because of rupture of subpleural blebs. Although the morphology and ultrastructure of causative lesions are well known, the reason for rupture of sbupleural blebs is not absolutely clear. Broad consensus concerning the role of meteorological factors in spontaneous pneumothorax dose not exist. The aim of the study was to examine the influence of change of atmospheric pressure and temperature on the occurrence of spontaneous pneumothorax. Material and Method: One hundred twenty eight consecutive spontaneous pnemothorax events that occurred between January 2003 and December 2004 were selected. Changes of meteorological factors of particular days from the day before for 5 consecutive days were calculated and compared between the days with pneumothorax occurrence (SP days) and the days without pneumothorax occurrence (Non SP days). The correation between change of pressure and temperature and the occurrence of SP was evaluated. Result: SP occurred on 117 days (16.0%) in the 2-year period. Although there was no significant differences in change of pressure factors prior 4 days of SP occurrence compare to the 4 days prior Non SP day, change of mean pressure was higher (+0.934 vs. -0.191hPa, RR 1.042, Cl $1.003{\sim}1.082$, p=0.033), and change of maximum pressure fall was lower (3.280 vs. 4.791 hPa, RR 1.051, Cl $1.013{\sim}l.090$, p=0.009) on the 4 days prior SP day. There were significant differences in change of temperature factors prior 2 days and the day of SP, Changes of mean temperature (-0.576 vs.+$0.099^{\circ}C$, RR 0.886, 95% Cl $0.817{\sim}0.962$, p=0.004) and maximum temperature rise (7.231 vs. $8.079^{\circ}C$, RR 0.943 Cl $0.896{\sim}0.993$, p=0.027) were lower on the 2 days prior SP. But changes of mean temperature (0.533 vs. $-0.103^{\circ}C$, RR 1.141, Cl $1.038{\sim}l.255$, p=0.006) and maximum temperature rise (9.209 vs. $7.754^{\circ}C$, RR 1.123, Cl $1.061{\sim}1.190$, p=0.006) and maximum temperature rise (9.209 vs. $7.754^{\circ}C$ RR 1.123, Cl $1.061{\sim}l.190$, p=0.000) were higher on the SP days. Conclusion: Charge of atmospheric pressure and temperature seems to influence the chance of occurrence of SP. Meteorological phenomena that pressure rise 4 day prior to SP and following temperature fall and rise might explain the occurrence of SP. Further studies should be continued in the future.