• Journal of The Korean Society of Grassland and Forage Science
• /
• v.9 no.3
• /
• pp.153-157
• /
• 1989

This experiment was carried out to investigate the effects of the first harvesting times and regrowth periods after the fist harvest on grass regrowth, dry matter (DM) yield and botanical composition in pasture mixtures during 1987 and 1988. For the test, a split plot design with 3 replications was treated with 3 different first harvesting times (vegetative, stem elongation and heading stage) and 3 different regrowth periods (20, 30 and 40 days) after first harvest. Although the total DM yield of grasses was decreased slightly with earlier cutting, the regrowth DM yield and the regrowth plant height was increased significantly with earlier cutting (p < 0.05). Also, the 30 days of regrowth periods was contributed greatly to the regrowth and the DM yield. The percentage of legumes Tmainly red clover) in botanical composition was increased with later initial harvest anrl longer regrowth period after first harvest. Based on the results, it is suggested that good grass regrowth and seasonal distribution could be achieved by the earlier harvest at fist and the regrowth period of 30 days after first harvest in spring.

• Korean Journal of Remote Sensing
• /
• v.34 no.1
• /
• pp.25-43
• /
• 2018

The effects of hydro-meteorological and surface variables on the frequency of Asian dust events (FAE) were investigated using ground station and satellite-based data. Present weather codes 7, 8, and 9 derived from surface synoptic observations (SYNOP)were used for counting FAE. Surface wind speed (SWS), air temperature (Ta), relative humidity (RH), and precipitation were analyzed as hydro-meteorological variables for FAE. The Normalized Difference Vegetation Index (NDVI), land surface temperature (LST), and snow cover fraction (SCF) were used to consider the effects of surface variables on FAE. The relationships between FAE and hydro-meteorological variables were analyzed using Z-score and empirical orthogonal function (EOF) analysis. Although all variables expressed the change of FAE, the degrees of expression were different. SWS, LST, and Ta (indices applicable when Z-score was < 0) explained about 63.01, 58.00, and 56.17% of the FAE,respectively. For NDVI, precipitation, and RH, Asian dust events occurred with a frequency of about 55.38, 67.37, and 62.87% when the Z-scores were > 0. EOF analysis for the FAE showed the seasonal cycle, change pattern, and surface influences related to dryness condition for the FAE. The intensity of SWS was the main cause for change of FAE, but surface variables such as LST, SCF, and NDVI also were expressed because wet surface conditions suppress FAE. These results demonstrate that not only SWS and precipitation, but also surface variables, are important and useful precursors for monitoring Asian dust events.

• Nuclear Engineering and Technology
• /
• v.46 no.4
• /
• pp.557-568
• /
• 2014

This paper presents the results of an analysis of wind characteristics and atmosphere dispersion modeling that are based on computational simulation and part of a preliminary study evaluating environmental radiation monitoring system (ERMS) positions within the Barakah nuclear power plant (BNPP). The return period of extreme wind speed was estimated using the Weibull distribution over the life time of the BNPP. In the annual meteorological modeling, the winds from the north and west accounted for more than 90 % of the wind directions. Seasonal effects were not represented. However, a discrepancy in the tendency between daytime and nighttime was observed. Six variations of cesium-137 ($^{137}Cs$) dispersion test were simulated under severe accident condition. The $^{137}Cs$ dispersion was strongly influenced by the direction and speed of the main wind. A virtual receptor was set and calculated for observation of the $^{137}Cs$ movement and accumulation. The results of the surface roughness effect demonstrated that the deposition of $^{137}Cs$ was affected by surface condition. The results of these studies offer useful information for developing environmental radiation monitoring systems (ERMSs) for the BNPP and can be used to assess the environmental effects of new nuclear power plant.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.44 no.7
• /
• pp.64-73
• /
• 2002

This study was performed to evaluate effects of physical characteristics of both watershed and reservoir on nutrient-chlorophyll relationship in Korean reservoirs. Simple linear models were developed with published data in Korea including 415 reservoirs and 11 multi-purpose dams, and physico-chemical parameters of reservoirs and characteristics relationship of models were analyzed. Theoretical residence time in Korean reservoirs was strongly correlated with the ratio of TA/ST (drainage area + surface area / storage volume) in the logarithmic function. As a result of monthly nutrients-chlorophyll-a regression analysis, significant Chl-a-TP relationship appeared during May～July. The high Chl-a yields per total phosphorus appeared during this time (R$\^$2/=0.51, p<0.001, N= 1088). Chlorophyll-a demonstrated much stronger relationship with TP. than TN. Seasonal algal-nutrient coupling were closely related with N:P ratio in the reservoir water, and it was, in turn, dependent on the monsoon climatic condition (precipitation). Based on the results of regression analysis and high N:P ratio, a major limiting factor of algal growth appeared to be phosphorus during this time. Unlikely TA/ST ratio, DA/SA ratio (drainage area f surface area) was likely to influence directly on the nutrient-Chl-a relationship, indicating that if storage volume and inflowing water volume were the same, algal biomass could be developed more in reservoirs with large surface area. Thus, DA/SA ratio seemed to be an important factor to affect the development of algal biomass in Korean reservoirs. With low determination coefficient of TP-Chl-a relationship, our findings indicated not only nutrient (phosphorus) but also other physical factors, such as DA/SA ratio, may affect algal biomass development in Korean reservoirs, where actual residence time appears to be more closely related to reservoir surface area rather than storage volume.

• Korean Journal of Community Nutrition
• /
• v.19 no.5
• /
• pp.468-478
• /
• 2014

Objectives: Intake of fruits and vegetables has protective effects against stroke attack. This study intended to examine the status of consuming fruits and vegetables and to find out which factors may influence the frequency of consumption of fruits and vegetables in individuals with a history of stroke. Methods: The data of 208 subjects from 5th (2010, 2011) Korea National Health and Nutrition Examination Survey (KNHNES) who reported a stroke diagnosis was used for analysis. To identify major factors influencing the consumption of fruits and vegetables, a classification-tree analysis was carried out. Results: Among those who reported a stroke diagnosis, the frequencies of consumption of fruits and vegetables were influenced by their age, place of residence (urban or rural), economic status, educational level, occupation, number of family members, frequency of eating out, and having meals (breakfast or lunch) with family members. Two factors from fruits and three factors from vegetables were generated by exploratory factor analyses. Urban residents ate fruits and vegetables more frequently in all factors than rural residents. Eating frequencies of 'seasonal fruits (orange, apple, strawberry, melon, pear and watermelon)', 'easily-accessible fruits (persimmon, tangerine, grape, peach, banana)', and 'Western-style vegetables (cabbage, mushroom, carrot, tomato, spinach)' were influenced by the socioeconomic status. Eating frequencies of 'Korean-style vegetables (bean sprout, radish leaves, pumpkin/squash, sea weed)', 'preserved vegetables (Korean cabbage, radish, laver, cucumber)' were influenced by having breakfast with family members. Conclusions: The results of this study suggested that by eating more fruits and vegetables, more preventive effects against secondary stroke attack are expected in stroke patients who live in the rural areas and who do not eat breakfast with family members. In addition, more outreach and education programs are needed for them.

• Journal of Korean Society of Water and Wastewater
• /
• v.27 no.5
• /
• pp.591-601
• /
• 2013

In modern society, we are living indoor at 80 - 90 % or more of the day, therefore most people are exposed to unconscious indoor air pollutants by various causes. When mother and infant, whose level of immunity are weak, are exposed to polluted indoor air, respiratory diseases and atopy can occur by the growth of bacteria. Therefore, appropriate indoor air quality management is important especially at nursery, elementary school and postpartum clinic etc. In this study, we compared the characteristics of the indoor air qualities of primary school facilities and infant facilities. In this study, seasonal effects were investigated. Also the effects of individual activity area were studied for indoor air quality. During summer season(May-August), the air qualities of each 16 elementary school and nursery school were investigated. During winter season(October-december), the air qualities of each 10 elementary school and nursery school were investigated. As a result, during winter season in 10 of 16 nursery school, $CO_2$ concentration exceeded regulation level of 1000 ppm. This resulted from the operation of heating system and poor ventilation. Also the air quality of all parameters during winter season were worse than during summer, maybe due to poor ventilation. Except HCHO, the concentrations of other parameters were higher in nursery school. This seems to result from relatively low individual activity area of nursery school than elementary school. From this research, more strong regulation for ventilation and installation of air purifier should be implemented.

• Journal of Advanced Navigation Technology
• /
• v.25 no.5
• /
• pp.320-326
• /
• 2021

In airlines, on-time performance (OTP) is a measure of an airline's reliability and can be used as an important indicator when compared to other airlines. This study analyzed the effects and strength of delay factors on airline punctuality by analyzing the data of domestic K airlines for one year before and after March 2020, when the number of flights drastically decreased due to the corona virus. In addition, delays caused by seasonal weather effects were analyzed, and how the number of passengers who plummeted due to the corona situation had an effect on delay factors was studied. As for the delay factors, the delay codes of K airline which added its own codes to the delay codes of IATA, were applied. Based on the results of the analysis, we would like to suggest a method to minimize the delay.

• Journal of Korean Society on Water Environment
• /
• v.37 no.5
• /
• pp.369-380
• /
• 2021

In this work, we analyzed the effects of drought on the water temperature (WT) of Nakdong river basin major river sections using Standardized Precipitation Index (SPI) and WT data. The analysis was carried out on a seasonal basis. After calculating the optimal time scale of the SPI through the correlation between the SPI and WT data, we used the copula theory to model the joint probability distribution between the WT and SPI on the optimal time scale. During spring and fall, the possibility of environmental drought caused by high WT increased in most of the river sections. Notably, in summer, the possibility of environmental drought caused by high WT increased in all river sections. On the other hand, in winter, the possibility of environmental drought caused by low WT increased in most river sections. From the risk map, which quantified the sensitivity of WT to the risk of environmental drought, the river sections Nakbon C, Namgang E, and Nakbon K showed increased stress in the water ecosystem due to high WT when drought occurred in summer. When drought occurred in winter, an increased water ecosystem stress caused by falling WT was observed in the river sections Gilan A, Yongjeon A, Nakbon F, Hwanggang B, Nakbon I, Nakbon J, Nakbon K, Nakbon L, and Nakbon M. The methodology developed in this study will be used in the future to quantify the effects of drought on water quality as well as WT.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.4B
• /
• pp.405-411
• /
• 2008

The Nakdong River Estuary Barrage (NREB) was constructed in 1987 to prevent saltwater intrusion and to provide the sustainable water supply in the upstream channel. Sediment dredging has been conducted to eliminate deposited sediments in the approached upstream channel of the NREB. Fluvial changes and sedimentation problems have been continued due to urbanization and development in the watershed as well as construction of the NREB. However, the sufficient field monitoring and researches for sedimentation characteristics and bed changes have not been performed after construction of the NREB. Therefore, bed elevation changes and seasonal sediment concentration distribution were analyzed using the quasi-steady state model with historical field data in this study. The water surface elevation changes with and without sediment dredging operation were calculated using the developed quasi-steady state model and finally the sediment dredging effects were evaluated.

• Journal of Korean Society of Rural Planning
• /
• v.29 no.4
• /
• pp.127-135
• /
• 2023

This study examined the impact of changes in agricultural production methods on society, the economy, and the environment. While traditional open-field farming relied heavily on natural conditions, modern approaches, including greenhouse and smart farming, have emerged to mitigate the effects of climate and seasonal variations. Facility horticulture has been on the rise since the 1990s, and recently, there has been a growing interest in smart farms due to reasons such as climate change adaptation and food security. We compared open-field spinach and greenhouse spinach using agricultural income survey data, and we also compared greenhouse tomato cultivation with smart farming tomato cultivation, utilizing data from the smart farm survey reports. The economic results showed that greenhouse spinach increased yield by 25.8% but experienced a 29% decrease in income due to equipment depreciation. In the case of tomato production in smart farms, both yield and income increased by 36-39% and 34-46%, respectively. In terms of environmental impact, we also compared fertilizer and energy usage. It was found that greenhouse spinach used 29% less fertilizer but 14% more energy compared to open-field spinach. Smart farming for tomatoes saw a negligible decrease in electricity and fuel costs. Regarding the social impact, greenhouse spinach reduced labor hours by 31%, and the introduction of smart farming for tomatoes led to an average 11% reduction in labor hours. This reduction is expected to have a positive effect on sustainable farming. In conclusion, the transition from open-field to greenhouse cultivation and from greenhouse cultivation to smart farming appears to yield positive effects on the economy, environment, and society. Particularly, the reduction in labor hours is beneficial and could potentially contribute to an increase in rural populations.