• Korean Journal of Agricultural Science
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• v.41 no.3
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• pp.205-211
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• 2014

Focused on Mt. Bogdkhan nature reserve in Mongolia, this study was conducted as a fundamental research to discover a tendency and characteristics of forest damage and to draw up measures for proper plans of forest restoration through an analysis of year-to year change using satellite images. In specific, land cover mapping was conducted by using Landsat images from 1994 to 2011, and then year-to year change was analyzed to investigate the features of forest damage in Mt. Bogdkhan. The results showed that the whole area of a reservation in Mongolia in 2011 was about $416.89km^2$; among them, forest area was $167,87km^2$, accounting for about 40.3%, followed by bare patch and grassland area (58.6%) and urban dry area (1.1%). In particular, compared in 1994, the area of forest in 2011 has increased by $6.12km^2$; while bare patch and grassland area has decreased by $10.81km^2$. Primary causes of forest degradation occurred in Mt. Bogdkhan nature reserve included illegal logging for fuel, forest and grassland degradation caused by domestic animals grazing, man-made forest fire, and disaster caused by insect pest.

• Korean Journal of Agricultural Science
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• v.48 no.3
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• pp.433-446
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• 2021

In this study, the future flood inundation changes under a climate change were simulated in the Tonle Sap basin in Cambodia, one of the countries with high vulnerability to climate change. For the flood inundation simulation using the rainfall-runoff-inundation (RRI) model, globally available geological data (digital elevation model [DEM]; hydrological data and maps based on Shuttle elevation derivatives [HydroSHED]; land cover: Global land cover facility-moderate resolution imaging spectroradiometer [GLCF-MODIS]), rainfall data (Asian precipitation-highly-resolved observational data integration towards evaluation [APHRODITE]), climate change scenario (HadGEM3-RA), and observational water level (Kratie, Koh Khel, Neak Luong st.) were constructed. The future runoff from the Kratie station, the upper boundary condition of the RRI model, was constructed to be predicted using the long short-term memory (LSTM) model. Based on the results predicted by the LSTM model, a total of 4 cases were selected (representative concentration pathway [RCP] 4.5: 2035, 2075; RCP 8.5: 2051, 2072) with the largest annual average runoff by period and scenario. The results of the analysis of the future flood inundation in the Tonle Sap basin were compared with the results of previous studies. Unlike in the past, when the change in the depth of inundation changed to a range of about 1 to 10 meters during the 1997 - 2005 period, it occurred in a range of about 5 to 9 meters during the future period. The results show that in the future RCP 4.5 and 8.5 scenarios, the variability of discharge is reduced compared to the past and that climate change could change the runoff patterns of the Tonle Sap basin.

• Journal of The Korean Society of Agricultural Engineers
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• v.63 no.2
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• pp.75-84
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• 2021

As the weather changes become frequent, weather disasters are increasing, causing more damage to plastic greenhouses. Among the damage caused by various disasters, damage by snow to the greenhouse takes a relatively long time, so if an alarm system is properly prepared, the damage can be reduced. Existing greenhouse design standards and snow warning systems are based on snow depth. However, even in the same depth, the load on the greenhouse varies depending on meteorological characteristics and snow density. Therefore, this study aims to secure the structural safety of greenhouses by developing sensors that can directly measure snow loads, and analysing the warning criteria for load using a stochastic model. Markov chain was applied to estimate the failure probability of various types of greenhouses in various regions, which let users actively cope with heavy snowfall by selecting an appropriate time to respond. Although it was hard to predict the precise snow depth or amounts, it could successfully assess the risk of structures by directly detecting the snow load using the developed sensor.

• Journal of Korea Water Resources Association
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• v.56 no.12
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• pp.929-937
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• 2023

This study aims to develop rules for the Determination of Drought Stages at the Local Level based on the drought cases in Gwangju and Jeollanam-do in 2022-2023. Among the eight drought indicators provided, six indicators (Agricultural drought stage (for paddy), Residential & industrial drought stage, SPI-12, Relative agricultural water storage, Residential water consumption change (for domestic use), Residential water consumption change (for non-domestic use) were confirmed to have statistical correlations with the perceptions of local government officials and experts. Additionally, this drought indicator was applied to a decision tree algorithm to develop rules for determining the severity of drought. Although it presented results similar to those of the existing method presented in previous studies, it showed a significant comparative advantage in explaining the temporal and spatial patterns of drought in the Gwangju and Jeollanam-do.

• International conference on construction engineering and project management
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• 2024.07a
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• pp.1317-1317
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• 2024

As climate change escalates extreme weather events, the structural durability of plastic greenhouses, constituting 90% of Korea's facility agriculture, emerges as a critical issue. These greenhouses are pivotal for year-round crop cultivation and high-quality agricultural production. In 2021, collapses caused around US$2 million in damages, mainly due to heavy snowfall and strong winds, accounting for 97% of incidents. The Korean Ministry of Agriculture responded by disseminating disaster-resistant standardized designs, yet more robust standards are needed. Current designs rely on elastic analysis, but plastic greenhouses display nonlinear behavior due to factors like residual stress and local buckling. Our study employs a refined plastic hinge method and finite element analysis to analyze structures, considering progressive yielding. We conducted loading tests using scale down models of plastic greenhouses in accordance with similitude laws. Based on these tests, the deformation of models under different load conditions was measured and compared with the deformation of greenhouse using our nonlinear structural analysis. This study will contribute to the development of reliable design criteria for plastic greenhouses in response to climate extremes such as heavy snowfall and typhoons. In addition, by identifying the deformation characteristics of plastic greenhouses due to loads, it can contribute to establishing usability standards for greenhouses, and reinforcement measures for vulnerable areas which are easily deformed under load can be considered.

• Korean Journal of Agricultural and Forest Meteorology
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• v.26 no.2
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• pp.127-139
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• 2024

Climate change has increased extreme weather events likewise heatwaves, heavy rain, and drought. Unlike other natural disaster, drought is a slowly developing phenomenon and thus drought damage increases as the drought continues. Therefore, it is necessary to understand the characteristics and mechanism of drought occurrence. Agricultural drought occurs when the water supply needed by crops becomes insufficient due to lack of soil water. Therefore, soil water is used as a key variable affecting agricultural drought. In this study, we examined the spatio-temporal distribution and trends of drought across the Korean Peninsula by determining the soil available water content (SAWC) through a model that integrated soil, meteorological, and crop data. Moreover, an investigation into the correlation between meteorological variables and the SAWC was conducted to assess how meteorological characteristics influence the nature of drought occurrences. During the soybean cultivation period, the average SAWC was lowest in 2018 at 88.6% and highest in 2021 at 103.2%. Analysis of the spatial distribution of SAWC by growth stage revealed that the lowest SAWC occurred during the flowering stage (S3) in 2018, during the leaf extension stage (S2) in 2019, during the seedling stage (S1) in 2020, again during the flowering stage (S3) in 2021, and during the seedling stage (S1) in 2022. Based on the average SAWC across different growth stages, the frequency of upland drought was the highest at 22 times during the S3 in 2018. The lowest SAWC was primarily influenced by a significant negative correlation with rainfall and evapotranspiration, whereas the highest SAWC showed a significant positive correlation with rainfall and relative humidity, and a significant negative correlation with reference evapotranspiration.

• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.3
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• pp.120-129
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• 2017

Agrometeorological advisories for farms and orchards are issued when daily weather exceeds a predefined range of the local reference climate, which is a long-term average of daily weather for the location. The reference climate at local scales is prepared by various simplification methods, resulting in uncertainty in the agrometeorological advisories. We restored daily weather data for the 1981-2010 period and analyzed the differences in prediction results of weather risk by comparing with the temporal and spatial simplified normal climate values. For this purpose, we selected the agricultural drought index (ADI) among various disaster related indices because ADI requires many kinds of weather data to calculate it. Ten rural counties within the Seomjin River Basin were selected for this study. The normal value of 'temporal simplification' was calculated by using the daily average value for 30 years (1981-2010). The normal value of 'spatial simplification' is the zonal average of the temporally simplified normal values falling within a standard watershed. For residual moisture index, temporal simplification normal values were overestimated, whereas spatial simplification normal values were underestimated in comparison with non-simplified normal values. The ADI's calculated from January to July 2017 showed a significant deviation in terms of the extent of drought depending on the normal values used. Through this study, we confirmed that the result of weather risk calculation using normal climatic values from 'simplified' methods can affect reliability of the agrometeorological advisories.

• The Korean Journal of Mycology
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• v.46 no.1
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• pp.58-68
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• 2018

Sunn hemp (Crotalaria juncea) is used as a nitrogen-fixing green manure in Korea to improve soil quality, reduce soil erosion, and suppress weeds and nematodes. In 2014, wilting sunn hemp plants were observed in green manure-cultivated fields in Wanju, Korea. Leaves of the infected plants began yellowing, starting with the lower leaves, eventually leading to their death. Moreover, a number of dark perithecia were observed on the wilting stems. Six isolates were obtained from these perithecia by single spore isolation. Based on their morphological characteristics, the isolates were identified as Fusarium udum (teleomorph: Gibberella indica). Macroconidia were slightly curved with almost hooked apical cell, and microconidia were formed on false heads by monophialides. Chlamydospores were produced abundantly in the hyphae, either singly or in clusters. To confirm the identification, multilocus sequence analysis was conducted using translation elongation factor 1 alpha (TEF), calmodulin (CAL), and histone 3 (HIS3). The sequences of TEF, CAL, and HIS3 showed 94.4~96.2%, 99.7%, and 99.6~99.8% similarity to the reference sequences of F. udum in NCBI GenBank, respectively. Pathogenicity was tested on sunn hemp and two soybean cultivars using the inoculation method of soil drenching with spore suspension. The wilting symptoms were observed only in sunn hemp and one cultivar of soybean (cv. Teagwang) after 14~21 days of inoculation. This is the first report of wilt disease in sunn hemp caused by Fusarium udum in Korea.