• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.160-165
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• 2007

To predict long-term creep life from short-term creep life data, various parametric methods such as Larson-Mille. (L-M), Orr-Sherby-Dorn (O-S-D), Manson-Haferd (M-H) parameters, and a Minimum Commitment Method (MCM) were suggested. A number of the creep data were collected through literature surveys and experimental data produced in KAERI. The polynomial equations for type 316LN SS were obtained by the time-temperature parameters (TTP) and the MCM. Standard error (SE) and standard error of mean (SEM) values were obtained and compared with the each method for various temperatures. The TTP methods showed good creep-life prediction, but the MCM was much superior to the TTP ones at $700^{\circ}C$ and $750^{\circ}C$. It was found that the MCM were lower in the SE values when compared to the TTP methods.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.707-713
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• 2008

Characteristics of minimum fluidization velocity and pressure fluctuations were investigated in an annular fluidized bed whose diameter was 0.102 m and 2.0 m in height. Effects of gas velocity, particle size and bed temperature on the minimum fluidization velocity and pressure fluctuations were examined. The values of minimum fluidization velocity obtained by means of three different methods were very similar each other. The correlation dimension could be a quantitative parameter for expression the resultant complex behavior of gas and solid mixture in the annular fluidized bed. The value of correlation dimension increased with increasing gas velocity, fluidized particle size and temperature in the bed. The minimum fluidization velocity could be determined by means of correlation dimension of pressure fluctuations as well as pressure drop in the bed and standard deviation of pressure fluctuations. The minimum fluidization velocity increased with increasing particle size but decreased with increasing bed temperature in annular fluidized beds. The minimum fluidization velocity was well correlated in therms of correlation dimension as well as operating variables within experimented conditions of this study.

• Journal of Forest and Environmental Science
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• v.39 no.4
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• pp.235-245
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• 2023

Forest fuel moisture content is a crucial factor influencing the combustion rate and fuel consumption during forest fires, significantly impacting the occurrence and spread of wildfires. In this study, meteorological data were gathered using a meteorological measuring device (HOBO data logger) installed in the south and north slopes of Kangwon National University Forest, as well as on bare land outside the forest, from November 1, 2021, to October 31, 2022. The objective was to analyze the relationship between meteorological data and fuel moisture content. Fuel moisture content from the ground cover on the south and north slopes was collected. Fallen leaves on the ground were utilized, with a focus on broad-leaved trees (Prunus serrulata, Quercus dentata, Quercus mongolica, and Castanea crenata) and coniferous trees (Pinus densiflora and Pinus koraiensis), categorized by species. Additionally, correlation analysis with fuel moisture content was conducted using temperature (average, maximum, and minimum), humidity (average, minimum), illuminance (average, maximum, and minimum), and wind speed (average, maximum, and minimum) data collected by meteorological measuring devices in the study area. The results indicated a significant correlation between meteorological factors such as temperature, humidity, illuminance, and wind speed, and the moisture content of fuels. Notably, exceptions were observed for the moisture content of the on the north slope and that of the ground cover of Prunus serrulata and Castanea crenata.

• Journal of Korean Society of Forest Science
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• v.94 no.6
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• pp.468-475
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• 2005

To understand spatiotemporal changes of temperature and humidity in Lentimula edodes cultivation sheds, temperature, relative humidity were measured with HOBO H8 series sensors in log cultivation sheds and sawdust cultivation sheds. The results obtained from October in 2003 to October in 2004 were as follows; 1. Horizontal temperature changes were smaller at center of cultivation shed inside than comer of cultivation shed inside, while relative humidity changes were greater about 3% at center of cultivation shed inside than corner of cultivation shed inside. 2. Vertical temperature changes showed that the temperature was higher at above than at below when the temperature rises, while the temperature was lower at above than at below when the temperature falls. Thus close to soil surface temperature showed a little fluctuation. Vertical relative humidity changes showed that the relative humidity was lower at above than at below when the temperature rises, while the relative humidity was higher at above than at below when the temperature falls. After all temperature and relative humidity was the opposite in cultivation shed. 3. It's showed in log cultivation shed that the minimum temperature was a subzero temperature until the end of April, while the minimum temperature did above zero after the beginning of the May. Besides a winter was the greatest at daily temperature range during the four season, about $30^{\circ}C$. On the other hand the minimum relative humidity was less than 20% at April, May and June but more than 40% after May.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.3
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• pp.398-405
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• 1995

In termperate zone planting rice at different date subjects the crop to different climatic condition. This study aimed at comparison of the change in source-sink relationship of the Japonica(J) and that of Indica Japonica(I$\times$J) type rice cultivars caused by shift of heading date. Two J-and two I$\times$J-type cultivars were made to head on Aug. 16, Aug. 26 and Sep. 5. Percent grain fertility was not changed in response to shift of heading date. Ripening patterns of 4 rice cultivars were similar to sigmoid curve type but when the heading date was delayed to Sep. 5, the form is changed to log type of curve. In J-type, physiological maturity was delayed about 5 day when headed at Sep. 5, in compare to headed at Aug. 16 and Aug. 26. However ripening was continued about 10 days when the diurnal, nocturnal and minimum temperature was above 17, 12$^{\circ}C$ and about 3~8$^{\circ}C$. In I$\times$J hybrid, real ripening was continued when the diurnal, nocturnal and minimum temperature was over 20, 17$^{\circ}C$, but if the minimum temperature was downed bellow 1$0^{\circ}C$, it was impossible. Simulated photosynthetic amount based on photosynthetic ability, temperature, leaf area and day length was varied according to changes in heading date and it was decreased seriously if the minimum temperature was fall down bellow 4$^{\circ}C$ in field, that's why decrease in photosynthetic ability and aging. The temperature range of optimum ripening was 21~26$^{\circ}C$, if there is nothing hindering factor.

• Korean Journal of Agricultural and Forest Meteorology
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• v.24 no.4
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• pp.244-255
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• 2022

This study estimated and evaluated the high resolution (1km) gridded mountain meteorology data of daily mean, maximum and minimum temperature based on ASOS (Automated Surface Observing System), AWS (Automatic Weather Stations) and AMOS (Automatic Mountain Meteorology Observation System) in South Korea. The ASOS, AWS, and AMOS meteorology data which were located above 200m was classified as mountainous area. And the ASOS, AWS, and AMOS meteorology data which were located under 200m was classified as non-mountainous area. The bias-correction method was used for correct air temperature over complex mountainous area and the performance of enhanced daily coefficients based on the AMOS and mountainous area observing meteorology data was evaluated using the observed daily mean, maximum and minimum temperature. As a result, the evaluation results show that RMSE (Root Mean Square Error) of air temperature using the enhanced coefficients based on the mountainous area observed meteorology data is smaller as 30% (mean), 50% (minimum), and 37% (maximum) than that of using non-mountainous area observed meteorology data. It indicates that the enhanced weather coefficients based on the AMOS and mountain ASOS can estimate mean, maximum, and minimum temperature data reasonably and the temperature results can provide useful input data on several climatological and forest disaster prediction studies.

• Atmosphere
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• v.33 no.5
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• pp.477-492
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• 2023

Based on the new climate normals (1991~2020), annual mean, maximum and minimum temperature is 12.5℃, 18.2℃, and 7.7℃, respectively while annual precipitation is 1,331.7 mm, the annual mean wind speed is 2.0 m s^-1, and the relative humidity is 67.8% in the Republic of Korea. Compared to 1981~2010 normal, annual mean temperature increased by 0.2℃, maximum and minimum temperatures increased by 0.3℃, while the amount of precipitation (0.7%) and relative humidity (1.1%) decreased. There was no distinct change in annual mean wind speed. The spatial range of the annual mean temperature in the new normals is large from 7.1 to 16.9℃. Annual precipitation showed a high regional variability, ranging from 787.3 to 2,030.0 mm. The annual mean relative humidity decreased at most weather stations due to the rise in temperature, and the annual mean wind speed did not show any distinct difference between the new and old normals. With the addition of a warmer decade (2011~2020), temperatures all increased consistently and in particular, the increase in the maximum temperature, which had not significantly changed in previous decades, was evident. The increasing trend of annual and summer precipitation by the 2010s has disappeared in the new normals. Among extreme climate indices, MxT30 (Daily maximum temperature ≥ 33℃ days), MnT25 (Daily minimum temperature ≥ 25℃ days), and PH30 (1 hour maximum precipitation ≥ 30 mm days) increased while MnT-10 (Daily minimum temperature < -10℃ days) and W13.9 (Daily maximum wind speed ≥ 13.9 m/s days) decreased at a statistically significant level. It is thought that a detailed study on the different trends of climate elements and extreme climate indices by region should be conducted in the future.

• Journal of Astronomy and Space Sciences
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• v.30 no.2
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• pp.101-106
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• 2013

The length of solar cycle 23 has been prolonged up to about 13 years. Many studies have speculated that the solar cycle 23/24 minimum will indicate the onset of a grand minimum of solar activity, such as the Maunder Minimum. We check the trends of solar (sunspot number, solar magnetic fields, total solar irradiance, solar radio flux, and frequency of solar X-ray flare), interplanetary (interplanetary magnetic field, solar wind and galactic cosmic ray intensity), and geomagnetic (Ap index) parameters (SIG parameters) during solar cycles 21-24. Most SIG parameters during the period of the solar cycle 23/24 minimum have remarkably low values. Since the 1970s, the space environment has been monitored by ground observatories and satellites. Such prevalently low values of SIG parameters have never been seen. We suggest that these unprecedented conditions of SIG parameters originate from the weakened solar magnetic fields. Meanwhile, the deep 23/24 solar cycle minimum might be the portent of a grand minimum in which the global mean temperature of the lower atmosphere is as low as in the period of Dalton or Maunder minimum.

• Atmosphere
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• v.17 no.3
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• pp.255-268
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• 2007

This study generated and evaluated the high resolution (5 km) gridded data of monthly mean, maximum and minimum temperature from 2002 to 2005 over South Korea using a modified PRISM(Parameter-elevation Regressions on Independent Slopes Model: K-PRISM) developed by Daly et al. (2003). The performance of K-PRISM was evaluated by qualitative and quantitative ways using the observations and gridded data derived by inverse distance weighting (IDW) and hypsometric methods (HYPS). For the generation of high resolution gridded data, geographic informations over South Korea, such as the digital elevation, topographic facet and coastal proximity, are derived from the 1 km digital elevation data. The spatial patterns of temperature derived by K-PRISM were more closely linked to topography and coastal proximity than those by IDW. The K-PRISM performed much better than IDW for all months and temperatures, but it was equal to or slightly better than the HYPS. And the performances of K-PRISM were better in the minimum and mean temperature (winter) than the in maximum temperature (summer).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.321-322
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• 2007

In this thesis, the sintering properties and piezoelectric properties of $Pb[(Co_{0.5}W_{0.5})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.07}(Zr_{0.52}Ti_{0.48})_{0.9}]O_3+0.5[wt%]MnO_2$ ceramics has been systematically investigated as a function of the sintering temperature after manufacturing the specimens with a general method. The lattice constant from the analysis of crystal structure showed that the pychlore structure was decreased with the increase of the sintering temperature. Density was decreased by increasing $B_2O_3$. TCFr was showed its minimum variation rate of 0.35~-0.52[%] in the sintered temperature 950[$^{\circ}C$], $B_2O_3$ 3[wt%]. The electromechanical coupling coefficient (Kp) showed its maximum of 31.116[%] in the sintered temperature 1050[$^{\circ}C$], and its minimum of 20.220[%] in the sintered temperature 1150[$^{\circ}C$].