• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.88.2-88.2
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• 2012

We investigate solar flare occurrence rate and daily flare probability depending on McIntosh sunspot classification, its area, and its area change. For this we use the NOAA active region and GOES solar flare data for 15 years (from January 1996 to December 2010). We consider the most flare-productive 10 sunspot classification: 'Dko', 'Dai', 'Eai', 'Fai', 'Dki', 'Dkc', 'Eki', 'Ekc', 'Fki', and 'Fkc'. Sunspot area and its change can be a proxy of magnetic flux and its emergence/cancellation, respectively. we classify each sunspot group into two sub-groups: 'Large' and 'Small'. In addition, for each group, we classify it into three sub-groups according to sunspot group area change: 'Decrease', 'Steady', and 'Increase'. As a result, in the case of compact groups, their flare occurrence rates and daily flare probabilities noticeably increase with sunspot group area. We also find that the flare occurrence rates and daily flare probabilities for the 'Increase' sub-groups are noticeably higher than those for the other sub-groups. In case of the (M+X)-class flares of 'Dkc' group, the flare occurrence rate of the 'Increase' sub-group is three times higher than that of the 'Steady' sub-group. Mean flare occurrence rates and flare probabilities for all sunspot regions increase with the following order: 'Steady', 'Decrease', and 'Increase'. Our results statistically demonstrate that magnetic flux and its emergence enhance major solar flare occurrence. We are going to forecast solar flares based on these results and NOAA scale.

• Journal of Environmental Impact Assessment
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• v.28 no.6
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• pp.568-579
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• 2019

The present study aims to identify the effect of land cover categories on particulate matter (PM) concentrations by analyzing the correlation between monthly PM concentrations in Seoul's air quality monitoring network and the percentages of land cover categories by buffers around air quality monitoring stations. According to a monthly correlation analysis between land cover categories and PM concentrations, in the buffer 3km, PM₁₀ showed a better correlation than PM_2.5, there was a clear negative correlation with the forest area, the grassland and the urbanized area had some positive correlation with PM₁₀, and the barren land and the urbanized area had some positive correlation with PM_2.5. According to a monthly correlation analysis of dominant land cover sub-categories and sub-sub-categories within the buffer 3km, PM₁₀ showed a clear negative correlation with the broad-leaved forest, and some positive correlation with the road was dominant. PM_2.5 showed partly negative correlation with the broad-leaved forest and partly positive correlation with the commercial area. There was a very low or no correlation with other grassland and bare land subcategories. A monthly stepwise regression analysis on noticeable land cover sub-categories and sub-sub-categories with positive or negative correlations revealed that an increasing percentage of the broad-leaved forest had a clear effect on reducing PM₁₀ concentrations, and the road was excluded from the selected variables. Although an increasing percentage of the commercial area had some effect on increasing monthly PM_2.5 concentrations and an increasing percentage of the broad-leaved forest had an effect on decreasing the PM_2.5 concentrations, their effect size was smaller than that on PM₁₀. The forest area around the city center had the largest and clearest effect on reducing PM concentrations. The urbanized area's sub-categories and sub-sub-categories were also confirmed to have some effect on increasing PM concentrations.

• Journal of the Korean Wood Science and Technology
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• v.52 no.3
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• pp.289-299
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• 2024

The current study aimed to investigate the impact of CO₂ enrichment on the width of annual tree rings, earlywood and latewood, and the area of annual growth of Pinus densiflora Siebold & Zucc. grown in open-top chamber (OTC). To this end, two CO₂ enrichment cases were considered, namely 1.4 × increment (560 ppm in OTC-II) and 1.8 × (720 ppm in OTC-III) were compared with the current atmosphere (400 ppm in OTC-I). The CO₂ enrichment conditions for a period of 12 years (2010-2021) were considered, and all measurements were done through image analysis. The study showed that the increment in CO₂ concentrations positively affected the tree growth. The measurement data from the trees in OTC-III were considerably higher than those from OTC-I, whereas those from OTC-II were slightly higher than those from OTC-I. Decreasing patterns of the measured widths and area in 6-7 years after the beginning of CO₂ enrichment was found for all the OTCs. These patterns were possibly due to changes in the physiological features, such as aging. The findings of the present study can have potential uses as fundamental data for forest management considering CO₂ concentrations.

• Journal of Environmental Science International
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• v.29 no.2
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• pp.177-189
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• 2020

We analyzed the recent characteristics of Particulate Matter (PM) including PM₁₀ (PM with diameter of less than 10 ㎛) and PM_2.5 (PM with diameter of less than 2.5 ㎛) observed in Busan metropolitan area, and compared them with those measured in Seoul metropolitan area. This analysis includes the monthly, seasonal, and annual variations and differences, in emissions and chemical compositions observed in both Busan and Seoul areas. Synoptic meteorological conditions were investigated at the time when high PM concentrations occurred in each of the two areas. The results showed clearly decreasing trends of annual mean concentrations with strong seasonal variations: lower in summer and higher in winter in both areas. In comparison with Seoul, the seasonal variation in Busan demonstrated relatively lower, but showed greater summer fluctuations than in Seoul metropolitan area. This is implying the importance of secondary generation of PM in summer via active photochemical reaction in Busan area. In high concentration days, Busan's chemical composition of sulfate was higher than that of nitrate in summer, whereas nitrate was higher than sulfate in Seoul. The ratios of NO₃^- to SO₄^2-(N/S ratio) showed lower in Busan approximately by a factor of 1/2(half of N/S ratio) in Busan compared with that in Seoul. Others such as synoptic characteristics and emission differences were also discussed in this study.

• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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• pp.14-18
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• 2021

The Mg-Powder-Compaction (MPC) process is proposed to fabricate the MgB₂ superconducting wires. Mg powder wall, similar to the Mg metal tube, inside the Nb outer sheath has been made and the stochiometric B powder was inserted into the wall. Even though the very high MgB₂ core density of 2.53 g/cm³ is obtained, the superconducting area fraction of MgB₂ is not high enough for the applications. In this work, an advanced MPC process was adopted by adding Mg powder into B powder. The Mg powder wall in the initial wire was fabricated by controlling the wall thickness while maintaining a constant density, and the mixture of B and Mg powder was filled into the Mg powder wall with the same filling density. It is found that the reduction in the area of the Mg powder wall proceeds similar to the wire, and the Mg powder wall is well maintained at the final wire diameter, which is advantage for the fabrication of long wires. With the advanced MPC process, as the added Mg is increased the densities of MgB₂ core is decreased and the porous structure is formed, it is found that the area fraction of superconducting MgB₂ increase up to the 37.7 % with the improved high critical current density (J_c) and the engineering critical current density (J_e).

• Journal of Korean Society of Transportation
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• v.22 no.2 s.73
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• pp.109-119
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• 2004

In COSMOS, an area for signal coordination is divided into subareas composed of several signalized intersections that share a common cycle time. Each subarea contains only one critical intersection having heavy traffic load. Subarea is a basic unit of control. The performance of COSMOS is highly dependent on the linkage rule between adjacent subareas. The purpose of this study is to provide an appropriate subarea linkage rule in COSMOS. This study developed a control strategy for Critical Intersection and Sub Area linkage. Critical Intersections calculate the Offset Pattern both East-West Axis and North-South Axis, and the coordination direction either East-West Axis or North-South Axis. Subarea can be combined with other one in all directions. The performance of the suggested linkage rule was evaluated on the real network in Gangnam-Gu. The result was that travel time was reduced by the suggested linkage rule.

• Journal of the Korean Home Economics Association
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• v.37 no.1
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• pp.29-44
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• 1999

The objectives of this study are (1) to identify sub-areas of the pro-environmental behavior, (2) to examine the level of the pro-environmental attitude and behavior, (3) to examine the degree of inconsistency between attitude and behavior, and (4) to investigate the reasons of the inconsistency. Data was collected from the questionnares with 299 married men and 378 married women and the deep interviews with 10 married women. The major findings are follows : (1) The pro-environmental behavior can be classified into 2 sub-areas : social-oriented area and individual-oriented area. (2) The level of pro-environmental attitude and behavior in the social-oriented area is lower than those in individual-oriented area. (3) The attitude-behavior inconsistency in the social-oriented sub-area is stronger than that in the individual-oriented sub-area. (4) The reasons of the pro-environmental attitude-behavior inconsistency are the lack of the sincere environmental consciousness and the existence of the pro-environmental behavior restriction factors.

• Journal of Environmental Science International
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• v.17 no.2
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• pp.239-248
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• 2008

The purpose of this study is to examine appropriate sub-basin division numbers that best reflect the hydrological characteristics of the basin so as to propose the criterion for dividing the sub-basin in analyzing flood runoff in the future. The characteristics of flood runoff variations were based on the WMS HEC-1 model, and the area in the upstream of the Dongbyeon water level observatory and the Geum-ho water level observatory was chosen for analysis, and examined the characteristics of the changes in flood runoff. First of all, in the targeted basin, if the sub-basin division number was 4 (that is, the area of the divided sub-basin was about 25% of the total area). Next, as the sub-basin division number gradually increased, the peak rate of runoff increased as well, and in case the sub-basin was not divided, the peak rate of runoff occurred at the earliest time. Given these results, the spatial change characteristics will be best reflected when the sub-basin is divided for analysis of flood runoff in such a way that the area of the divided sub-basin is about 25% of the total area of the basin. However, as these results are based on a limited number (4) of storms, more storm events and other basins need to be included in the review of the sub-basin division methodology.

• Journal of Environmental Health Sciences
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• v.47 no.3
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• pp.279-291
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• 2021

Objectives: This study investigated the association between air pollutant levels and medical usage rates for environmental disease in a general residential area during the period 2015-2017. Methods: Air pollutant (PM₁₀, PM_2.5, SO₂, NO₂, CO, O₃) data were collected from Air-Korea. Medical usage data on environmental disease (asthma, allergic rhinitis, atopic dermatitis) for the period 2015-2017 in a general residential area in Gyeongsangnam-do Province were provided by the National Health Insurance Corporation. Pearson correlation analysis and multiple regression analysis were conducted to investigate the association between air pollutant levels and medical usage rates (SAS 9.4). In the multiple regression analysis, environmental disease was set as the dependent variable and air pollutants were set as independent variables and analyzed using the General Linear Model. Results: Except for PM_2.5, the average concentration of air pollutants in the surveyed area was below than the air environment standards of Korea. NO₂ was higher than Korea's national average, but CO was similar. The others were lower than the Korea's national average. The daily medical usage rates for environmental disease were 1.38‰ for asthma, 9.90‰ for allergic rhinitis, and 0.32‰ for atopic dermatitis. As a result of correlation analysis, PM₁₀ and SO₂, NO₂ and CO were significantly correlated with asthma, PM₁₀ and NO₂ and CO were correlated with allergic rhinitis, and PM₁₀ and PM_2.5, SO₂, NO₂ and CO were correlated with atopic dermatitis. As a result of multiple regression analysis, PM₁₀ and SO₂ were found to have a higher effect on asthma, PM₁₀ and NO₂ on allergic rhinitis, and SO₂ and NO₂ on atopic dermatitis, compared to other air pollutants. Conclusion: According to these results, air pollutants such as PM₁₀ and SO₂ and NO₂ were associated with the medical usage rates of environmental disease even in relatively low concentrations. Therefore, continuous monitoring will be required for general residential areas.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.5
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• pp.218-227
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• 2021

A thick film NTC thermistor for low temperature co-firing was manufactured by printing and sintering a paste prepared using NTC powder of Mn_1.5Ni_0.4Co_0.9Cu_0.4O₄ composition, lead free frit, and RuO₂ on a 96 % alumina substrate. The effect of frit and RuO₂ on the electrical properties of thick film NTC thermistor was studied. The resistance of the thick film NTC thermistor was higher than that of the bulk phase sintered at the same temperature, but it was found that the negative resistance temperature characteristic appeared more clearly and linearly in the resistance - temperature characteristic. On the other hand, the area resistance decreased as the sintering temperature increased, and the area resistance increased as the amount of frit added increased. The B constant of the thick film NTC thermistor was 3000 K or higher. Among them, it was found that the B constant of the thick film NTC thermistor made of paste with 5 wt% of frit added and sintered at 900℃ showed the highest B constant. Also, it can be seen that the area resistance decreased with the addition of RuO₂, and the change in the area resistance decrease of the thick film NTC thermistor obtained by sintering the paste containing 5 wt% of RuO₂ at 900℃ is the most obvious.