• Journal of the Korean Child Neurology Society
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• v.26 no.4
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• pp.251-262
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• 2018

Purpose: This study aimed to identify changes in smart device usage trends of young children using two studies conducted in 2015-2016 and 2017 respectively. Methods: We compared the data of the previous study of 130 children (Group A) and the new study of 162 children (Group B). The children and parents were recruited from kindergartens in Seoul and Guri/Namyangju cities. We used the "Parental questionnaire for smart device usage status." Results: There were some changes in the smart device usage in young children and parental perception. In the 2017 study, smart device usage time increased during weekends (P<0.05) and the usage with siblings decreased (P<0.05). In 2017, the smart device was mostly used when children had to be quiet without disturbing others (36.8%). No significant difference existed in the main purpose of use: watching video clips (79.3% vs 76.6%). Overall control of the usage was still largely exercised by mothers; however, when using applications, mothers still only helped the children on request (51.8% vs 49.7%). Regarding the effect of smart device on children, responses of "not knowing" decreased and "will be negative" and "will be positive" increased (P<0.05). Additionally, most mothers thought that "Although the smart device is currently unnecessary, it will be needed in future" in 2017 (46.3%). Conclusion: Limiting the smart device usage time during the weekends and increasing parental involvements are recommended. Guidelines for smart devices usage in young children are also necessary considering the changes in parental attitudes in recognizing the smart device usage as unavoidable.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.871-885
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• 2023

In 2022, the total of 129 million m³ of aggregate was produced in Korea, a slightly decrease from the total production of 2021. Of these, about 44 million m³ of sand and about 84 million m³ of gravel were produced. About 41% of total quantity of aggregates were produced by permission and the rest were produced after declaration. It estimated that of the 129 million m³ of aggregates in Korea in 2022, about 54.9% was produced by screening crushed aggregate, by 32.8% by forest aggregate, 2.2% by land aggregate, 6.2% by marine aggregate and 3.1% by washing aggregate, and 0.3% by river aggregate. This indicates that screening crushed and forest aggregate are the main producers of domestic aggregate in 2022. Leading producing metropolitan governments were Gyeonggi-do, Gyeongsangnam-do, Chungcheongnam-do, Incheon, Jeollanam-do, Chungcheongbuk-do, Gangwon-do, Gyeongsangbuk-do in order decreasing volume. In 2022, aggregates were produced in 147 local governments, and the 10 leading producing local governments were, in descending order of volume, Hwaseong, Pocheon, Paju, Ongjin, Youngin, Gwangju, west EEZ, Incheon Seo-gu, Namyangju, Asan. The combined production of the 10 leading local governments accounted for 31% of the national total. And 44 local governments have produced aggregates of more than 1 million m³ each other. In 148 local governments that produced aggregate, a total of 800 active operations produced aggregate with 350 operations by river, land and forest aggregate, 450 operations by selective crushed and washing aggregate.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.41 no.3
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• pp.47-58
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• 2023

This study was conducted through reviewing Aspects of Design and Construction in Entrance Space of the World Heritage Royal Tombs of the Joseon Dynasty, which is equipped with parking lots, ticket offices, toilets, exhibition halls, information boards, and rest facilities for the convenience of visitors and the purpose of this study was to propose a direction for improvement. The results of the study are as follows: First, the reduced area of Royal Tombs of the Joseon Dynasty was unable to fully accommodate the ritual movement line, and as a result, the location of the entrance space in the current royal tomb was decided to accommodate minimal convenience functions. In the meantime, the entrance space of the royal tombs has been relocated or renovated in order to achieve its integrity as a World Heritage Site, rational arrangement of movement lines and spatial utility. Second, the size of the entrance space ranges from 1,000 square meters in Jeongneung in Seoul to 16,000 square meters in Hongyuneung in Namyangju, and the number of annual users varies greatly from 12,000 in Onneung in Yangju to 410,000 in Seonjeongneung in Seoul. Considering the conditions of the 16 royal tombs, the entrance space should be provided at an appropriate scale, reflecting the surrounding land use and accessibility that affect the influx of users, the size of the site, and the king's awareness and preferences. Third, the location of the parking lot, the presence or absence of an outer courtyard and an internal courtyard bordering the ticket and check offices, and the location of the Historical and Cultural Museum made it possible to know the aspects of entrance space of the Joseon Royal Tombs, where the spatial configuration is determined Fourth, according to the royal tombs, it was found that the entrance space should have essential parking, access control, information, and convenience functions, and that support, exhibition, passage, and recess functions should be optional. At this time, the management office and the Historical and Cultural Center are in charge of support and exhibition functions. The function of passage can be a strategy that provides a sense of entry and the function of recess which has been introduced in only four royal tombs requires an appropriate location and landscape access.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.1195-1206
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• 2011

This study was conducted to apply LCA (Life cycle assessment) methodology to lettuce (Lactuca sativa L.) production systems in Namyang-ju as a case study. Five lettuce growing farms with three different farming systems (two farms with organic farming system, one farm with a system without agricultural chemicals and two farms with conventional farming system) were selected at Namyangju city of Gyeonggi-province in Korea. The input data for LCA were collected by interviewing with the farmers. The system boundary was set at a cropping season without heating and cooling system for reducing uncertainties in data collection and calculation. Sensitivity analysis was carried out to find out the effect of type and amount of fertilizer and energy use on GHG (Greenhouse Gas) emission. The results of establishing GTG (Gate-to-Gate) inventory revealed that the quantity of fertilizer and energy input had the largest value in producing 1 kg lettuce, the amount of pesticide input the smallest. The amount of electricity input was the largest in all farms except farm 1 which purchased seedlings from outside. The quantity of direct field emission of $CO_2$, $CH_4$ and $N_2O$ from farm 1 to farm 5 were 6.79E-03 (farm 1), 8.10E-03 (farm 2), 1.82E-02 (farm 3), 7.51E-02 (farm 4) and 1.61E-02 (farm 5) kg $kg^{-1}$ lettuce, respectively. According to the result of LCI analysis focused on GHG, it was observed that $CO_2$ emission was 2.92E-01 (farm 1), 3.76E-01 (farm 2), 4.11E-01 (farm 3), 9.40E-01 (farm 4) and $5.37E-01kg\;CO_2\;kg^{-1}\;lettuce$ (farm 5), respectively. Carbon dioxide contribute to the most GHG emission. Carbon dioxide was mainly emitted in the process of energy production, which occupied 67~91% of $CO_2$ emission from every production process from 5 farms. Due to higher proportion of $CO_2$ emission from production of compound fertilizer in conventional crop system, conventional crop system had lower proportion of $CO_2$ emission from energy production than organic crop system did. With increasing inorganic fertilizer input, the process of lettuce cultivation covered higher proportion in $N_2O$ emission. Therefore, farms 1 and 2 covered 87% of total $N_2O$ emission; and farm 3 covered 64%. The carbon footprints from farm 1 to farm 5 were 3.40E-01 (farm 1), 4.31E-01 (farm 2), 5.32E-01 (farm 3), 1.08E+00 (farm 4) and 6.14E-01 (farm 5) kg $CO_2$-eq. $kg^{-1}$ lettuce, respectively. Results of sensitivity analysis revealed the soybean meal was the most sensitive among 4 types of fertilizer. The value of compound fertilizer was the least sensitive among every fertilizer imput. Electricity showed the largest sensitivity on $CO_2$ emission. However, the value of $N_2O$ variation was almost zero.