• Journal of Korean Society on Water Environment
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• v.30 no.2
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• pp.119-127
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• 2014

The objective of this study is to evaluate and analyze Sumjin River Basin water environment system. It was necessary to improve the water quality. The data were collected from 2010 January to 2012 December including Water Temperature, pH, DO, EC, $BOD_5$, COD, TOC, SS, T-N, T-P. The data were used to study were required to; Correlation Analysis; Principle Component Analysis; Factor Analysis. The results were as followed. According to correlation analysis on $BOD_5$ against COD, TOC it revealed that the each value of correlation coefficient were 0.715 and 0.719; this means the strength of the relationship is strong. The same analysis on T-P against $BOD_5$, COD, TOC, SS has revealed that the range of the correlation coefficient value fell between 0.482 and 0.608 which means strength of the relationship between them remained normal. Through correlation analysis, it has been found that all elements except T-N have high correlation. The results of principal component analysis to target the overall water quality was extracted to three main components. The cumulative contribution rate is 68.990%. In the case of seasonal water quality, Spring and Summer are extracted to each of four main components. The cumulative contribution rate is 81.515% and 73.550% respectively. Fall and Winter are extracted to each of three main components. The cumulative contribution rate is 65.072% and 72.721% respectively. There is no seasonality in the case of factor analysis. The first common factor is $BOD_5$, COD, TOC, SS, T-P, which were classified. Totally speaking, Sumjin River Basin water system gets highly affected by the nutrient salts, organic matter and suspended solid at the same time.

• Atmosphere
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• v.26 no.2
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• pp.227-241
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• 2016

This study investigated the cause of the heavy snowfall that occurred in the East Coast of Korea from 6 February to 14 February 2014. The synoptic conditions were analyzed using blocking index, equivalent potential temperature, potential vorticity, maritime temperature difference, temperature advection, and ground convergence. During the case period, a large blocking pattern developed over the Western Pacific causing the flow to be stagnant, and there was a North-South oriented High-to-Low pressure system over the Korean Peninsula because of this arrangement. The case period was divided into three parts based on the synoptic forcing that was responsible for the heavy snowfall; detailed analyses were conducted for the first and last period. In the first period, a heavy snowfall occurred over the entire Korean Peninsula due to strong updrafts from baroclinic instability and a low pressure caused by potential vorticity located at the mid-troposphere. In the lower atmosphere, a North-South oriented High-to-Low pressure system over the Eastern Korea intensified the easterly airflow and created a convergence zone near the ground which strengthened the upslope effect of the Taebaek Mountain range with a cumulative fresh snowfall amount of 41 cm in the East Coast region. In the last period, the cold air nestled in the Maritime Province of Siberia and Manchuria strengthened much more than that in the first half and extended to the East Sea. The temperature difference between the 850 hPa air and the SST was large and convective clouds developed over the sea. The highest cumulative fresh snow amount of 39.7 cm was recorded in the coastal area during this period. During the entire period, vertically oriented equivalent potential temperature showed neutral stability layer that helped the cloud formation and development in the East Coast. The 2014 heavy snowfall case over the East Coast provinces of Korea were due to: 1) stagnation of the system by blocking pattern, 2) the dynamic effect of mid-level potential vorticity of 1.6 PVU, 3) the easterly air flow from North-South oriented High-to-Low pressure system, 4) the existence of vertically oriented neutral stable layer, and 5) the expansion of strong cold air into the East Sea which created a large temperature difference between the air and the ocean.

• Korean Journal of Agricultural and Forest Meteorology
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• v.23 no.4
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• pp.405-414
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• 2021

This study predicted waxy corn harvest date in South Korea using 30-year (1991-2020) hindcasts (1-6 month lead) produced by the Pusan National University Coupled General Circulation Model (PNU CGCM)-Weather Research and Forecasting (WRF) chain. To estimate corn harvest date, the cumulative temperature is used, which accumulated the daily observed and predicted temperatures from the seeding date (5 April) to the reference temperature (1,650~2,200℃) for harvest. In terms of the mean air temperature, the hindcasts with a bias correction (20.2℃) tends to have a cold bias of about 0.1℃ for the 6 months (April to September) compared to the observation (20.3℃). The harvest date derived from bias-corrected hindcasts (DOY 187~210) well simulates one from observation (DOY 188~211), despite a slight margin of 1.1~1.3 days. The study shows the possibility of obtaining the gridded (5 km) daily temperature and corn harvest date information based on the cumulative temperature in advance for all regions of South Korea.

• The Plant Pathology Journal
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• v.33 no.2
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• pp.206-211
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• 2017

The effect of temperature on the rate of systemic infection of potatoes (Solanum tuberosum L. cv. Chu-Baek) by Potato virus Y (PVY) was studied in growth chambers. Systemic infection of PVY was observed only within the temperature range of $16^{\circ}C$ to $32^{\circ}C$. Within this temperature range, the time required for a plant to become infected systemically decreased from 14 days at $20^{\circ}C$ to 5.7 days at $28^{\circ}C$. The estimated lower thermal threshold was $15.6^{\circ}C$ and the thermal constant was 65.6 degree days. A systemic infection model was constructed based on experimental data, using the infection rate (Lactin-2 model) and the infection distribution (three-parameter Weibull function) models, which accurately described the completion rate curves to systemic infection and the cumulative distributions obtained in the PVY-potato system, respectively. Therefore, this model was useful to predict the progress of systemic infections by PVY in potato plants, and to construct the epidemic models.

• Journal of Environmental Science International
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• v.29 no.7
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• pp.785-788
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• 2020

We investigated the oviposition characteristics of Protaetia brevitarsis seulensis, focusing on zone breeding throughout the year in terms of the development and utilization of insect resources. To select Protaetia brevitarsis seulensis individuals laying a large number of eggs, the number of eggs laid for each individual was measured for each individual after emergence as adults from larvae grown at room temperature in five farmhouses. The five study zone included Gongju (Tancheon), Gyeonggi (Himsen), Chungnam (Gyeryong), Taean (Wonbuk), and Siheung (Baekse). The average oviposition tendency during a 12-week period obtained from the five regions was somewhat different; however, there was no remarkable difference in overall tendency. The maximum oviposition in Protaetia brevitarsisseulensis in the five regions occurred between 6 and 7 weeks. Compared toother regions, the average cumulative number of eggs laid during the 12-week period was higher (40%-60%) in Gongju (Tancheon) and Gyeonggi (Himsen). These results indicate that in two regions, zone breeding is selected as a system for increasing the demand for insects.

• Transactions of Materials Processing
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• v.20 no.4
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• pp.296-302
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• 2011

The objective of this paper is to determine the effect of process parameters on the behavior of a 18Cr-10Mn-$0.44N_2$ nitrogen steel sample deformed by hot rolling. Compression tests were carried out at high temperatures to determine the flow stresses needed for a finite element(FE) analysis. The strain rate, ranging from 0.1 to $1.0s^{-1}$, significantly affected the flow stress at temperatures higher than $1,000^{\circ}C$. Non-isothermal rolling simulations and laboratory rolling tests were performed with plate specimens 14.5mm thick, 135mm wide and 226mm long. A rolling reduction of 15% per pass leading to a cumulative rolling reduction of 60% was determined as optimal. The extension ratio of 176.5% in the length direction was about 30.4 times greater than the extension ratio of 5.8% in the width direction. Isotropic properties for tensile strength, microstructure and grain size were measured after mock-up hot rolling tests. The results from the mockup tests were found to be in good agreement with those of the simulations.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.75-80
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• 2011

The main objective of this research is to develop fatigue prediction model for flexible pavements using energy ratio factor and phase angle. The two parameters are considered as fundamental properties of time and temperature dependent viscoelastic asphalt concrete materials. The energy ratio factor is defined as the ratio of the pseudo-total cumulative dissipated energy to the cumulative dissipated energy to failure during the test. The phase angle between the stress and strain ware signals stems from the intrinsic the dependent asphalt mixture behavior. The phase angle was computed and the relationship between the initial mixture stiffness and the initial phase angle is presented. As a result, fatigue prediction model for flexible pavements was proposed using intrinsic properties of viscoelastic asphalt concrete materials.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.6
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• pp.534-539
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• 2003

The yield and quality characteristics of three rice varieties(Seojinbyeo, Ilpumbyeo, and Chuchungbyeo) in reclaimed saline paddy field were investigated under different cultural practices, three transplanting times (May 15, May 30 and June 15) and four harvest times (40, 50, 60 and 70days after heading) in order to obtain basic information for the production of high quality rice. Brown rice yield of three rice varieties were significantly higher in early and medium than late season cultivation. The protein content of milled rice showed high interaction effect between transplanting time and harvest time. Palatability values of Seojinbyeo and Ilpumbyeo were significantly higher in late than medium season cultivation, but Chucheongbyeo did not show any difference in its palatability value by different transplanting time. The palatability values of three rice variety was the highest in the harvest at 40 days after heading. The grain yield of three rice varieties were higher in early and medium than late season cultivation, whereas palatability values of three rice varieties were significantly higher in the early and late season cultivation than medium season cultivation. The palatability value measured by rice taster showed a highly negative correlation(r=$0.43^{**}$) with cumulative air temperature during ripening period.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.47 no.3
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• pp.254-258
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• 2002

The characteristics of yield and quality in 3 rice varieties according to harvest time of 40, 50, 60 and 70days after heading(DAH) was investigated to obtain basic information for the production of high quality rice. The protein content of milled rice increased significantly as increase the ripening period from 40 to 70DAH. The palatability value measured by rice taster was the highest in ripening period of 40DAH and decreased with increase of ripening period. The optimum time for harvest in terms of both rice yield and quality was 4050DAH in Daejinbyeo, and 4060DAH in Seojinbyeo and Chucheongbyeo, however, it was considered to be 4050DAH only for rice quality. The palatability value measured by rice taster showed a highly negative correlation with protein content of milled rice(1=-0.94$^{**}$) and cumulative ripening temperature(r=-0.79$^{**}$).

• Korean Journal of Agricultural and Forest Meteorology
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• v.17 no.4
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• pp.340-347
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• 2015

This study was conducted to analyze the relationship between climate factors and fruit characteristics of 'Sangjudungsi' persimmon (Diospyros kaki THUNB) has been mainly cultivated in Sangju of Korea. We has been surveyed the yield and fruit characteristics such as fruit weight and soluble solids of 'Sangjudungsi' persimmon from 2010 to 2015 for five years. Also, as major meteorological factor, mean air temperature, cumulative temperature and days, the data of sunshine duration, diurnal range, and rainfall were collected from Sangju Regional Meteorological Administration. As result of that, the annual variation of fruit weight was affected by sunshine duration for April and October related starting point of fruit weight increase. The content of soluble solids was affected by sunshine duration for April and October similarly with fruit weight and was negatively correlated with the number of days with precipitation in the year. These results indicate the characteristics related to fruit quality like the above were affected by the sunshine duration and precipitation which is critical factor for the intensity of radiation during rapid growth period (April and October). Fruit number and yield per tree was commonly affected by mean air temperature of April and cumulative temperature days of October. These results also indicate that temperature for period of rapid growth stage of persimmon may have an important role in the fruit number and yield per tree.