• Journal of Integrative Natural Science
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• v.14 no.4
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• pp.162-175
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• 2021

Recently, due to global warming, the average temperature of the earth has risen, and the glaciers in the Antarctic and Arctic melt, leading to a rise in sea level, which is accompanied by powerful natural disasters such as strong typhoons and tsunamis around the world. Accordingly, a precipitation in summer in Korea also increased, and changes in the form of precipitation were showed with the increase. Compared to the past, the frequency of localized heavy rain is increasing, and the damage from flooding and flooding is increasing day by day. In this study, based on the precipitation data measured in hours from May to September from 2016 to 2021 according to the change in the precipitation form, according to the nature of the torrential rain investigated the change in the summer precipitation form. In addition, the trend of localized heavy rain from 2016 to 2021 was confirmed by classifying them into two types: localized heavy rains caused by cyclones and weather front, and by typhoons and large-scale cyclones. Through this, the change in precipitation due to the climate crisis should not be viewed as a single phenomenon, it should be reflected and discussed on our life focused on scientific and technological development, and it should be used as a stepping stone for realizing a humanistic.

• Water Engineering Research
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• v.5 no.2
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• pp.55-68
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• 2004

The GLEAMS (Groundwater Loading Effects of Agricultural Management System, version 3.0) water quality model was used to predict hydrology and water quality and to evaluate the effects of soil types from a cattle-grazed pasture field of Bermuda-Rye grass rotation with poultry litter application as a fertilizer in North Alabama. The model was applied and evaluated by using four years (1999-2002) of field-measured data to compare the simulated results for the 2.71- ha Summerford watershed. $R^2$ values between observed and simulated runoff, sediment yields, TN, and TP were 0.91, 0.86, 0.95, and 0.69, respectively. EI (Efficiency Index) of these parameters were 0.86, 0.67, 0.70, and 0.48, respectively. The statistical parameters indicated that GLEAMS provided a reasonable estimation of the runoff, sediment yield, and nutrient losses at the studied watershed. The soil infiltration rates were compared with the rainfall events. Only high intensity rainfall events generated runoff from the watershed. The measured and predicted infiltration rates were higher during dry soil conditions than wet soil conditions. The ratio of runoff to precipitation was ranging from 2.2% to 8.8% with average of 4.3%. This shows that the project site had high infiltration and evapotranspiration which generated the low runoff. The ratio of runoff to precipitation according to soil types by the GLEAMS model appeared that Sa (Sequatchie fine sandy loam) soil type was higher and Wc (Waynesboro fine sandy loam, severely eroded rolling phase) soil type relatively lower than the weighted average of the soil types in the watershed. The model under-predicted runoff, sediment yields, TN, and TP in Wb (Waynesboro fine sandy loam, eroded undulating phase) and Wc soil types. General tendency of the predicted data was similar for all soil types. The model predicted the highest runoff in Sa soil type by 105% of the weighted average and the lowest runoff in Wc soil type by 87% of the weighted average

• Environmental Engineering Research
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• v.18 no.2
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• pp.85-90
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• 2013

This study is an attempt to quantify rainwater utilization and miscellaneous water demand in Tokyo's 23 special wards, the core of the urban area in Tokyo, Japan, in order to elucidate the potential of further rainwater utilization. The rainwater utilization for miscellaneous appropriate water demands, including toilet flushing, air conditioning, and garden irrigation, were calculated for six different types of building: residential house, office, department store, supermarket, restaurant, and accommodation. Miscellaneous water demands in these different types of building were expressed in terms of equivalent rainfall of 767, 1,133, 3,318, 1,887, 16,574, and 2,227 (mm/yr), respectively, compared with 1,528 mm of Tokyo's average annual precipitation. Building types, numbers and its height were considered in this study area using geographic information system data to quantify miscellaneous water demands and the amount of rainwater utilization in each ward. Area precipitation-demand ratio was used to measure rainwater utilization potential for miscellaneous water demands. Office and commercial areas, such as Chiyoda ward, showed rainwater utilization potentials of <0.3, which was relatively low compared to those wards where many residential houses are located. This is attributed to the relatively high miscellaneous water demand. In light of rainwater utilization based on building level, the introduction of rainwater storage mechanisms with a storage depth of 50 mm for six different types of buildings was considered, and calculated as rainfall of 573, 679, 819, 766, 930, and 787 (mm), respectively. Total rainwater utilization using such storage facilities in each building from 23 wards resulted in the retention of 102,760,000 $m^3$ of water for use in miscellaneous applications annually, and this volume corresponded to 26.3% of annual miscellaneous water demand.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.1
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• pp.128-135
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• 2015

In this study, we develop the very short-term precipitation forecasting model as well as classifier based on polynomial radial basis function neural networks by using AWS(Automatic Weather Station) and KLAPS(Korea Local Analysis and Prediction System) meteorological data. The polynomial-based radial basis function neural networks is designed to realize precipitation forecasting model as well as classifier. The structure of the proposed RBFNNs consists of three modules such as condition, conclusion, and inference phase. The input space of the condition phase is divided by using Fuzzy C-means(FCM) and the local area of the conclusion phase is represented as four types of polynomial functions. The coefficients of connection weights are estimated by weighted least square estimation(WLSE) for modeling as well as least square estimation(LSE) method for classifier. The final output of the inference phase is obtained through fuzzy inference method. The essential parameters of the proposed model and classifier such ad input variable, polynomial order type, the number of rules, and fuzzification coefficient are optimized by means of Particle Swarm Optimization(PSO) and Differential Evolution(DE). The performance of the proposed precipitation forecasting system is evaluated by using KLAPS meteorological data.

• Journal of the Korean Ceramic Society
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• v.27 no.8
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• pp.991-1003
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• 1990

A precipitation method, one of the most effective liquid phase reaction methods, was adopted in order to prepare high-tech Al2O3/ZrO2 composite ceramics. Al2(SO4)3.18H2O, ZrOCl2.8H2O and YCl3.6H2O were used as starting materials and NH4OH as a precipitation agent, various types of metal hydroxides were obtained by single precipitation(series A) and co-precipitation(series B) method at the pH condition between 7 and 11. Fine Al2O3-ZrO2 powders were prepared at optimum calcination condition and the effects of ZrO2 on microstructures and mechanical properties of Al2O3 were investigated. The composition of Al2O3/ZrO2 composites wax fixed as Al2O3-15 v/o ZrO2(＋3m/o Y2O3). ZrO2 limited the grain growth of Al2O3 and increased grain size homogeneity of Al2O3 more effectively than MgO.Flexural strength values in Al2O3 and Al2O3/ZrO2 composites were 340-430 MPa and 540-820 MPa, respectively, and the effect of strength improvement showed 20-50% by adding ZrO2 to Al2O3. Fracture toughness of Al2O3/ZrO2 composites was improved by stress-induced phase transformation of tetragonal ZrO2 and toughening effect by microcrack was not observed. Also, ZrO2 particles located at Al2O3 grain junction contributed to toughening, while spherical ZrO2 particles located within Al2O3 grain did not contribute to toughening. Weibull moduli of Al2O3 ceramics and Al2O3/ZrO2 composites of series A and series B were 4.34, 5.17 and 9.06, respectively. Above 0.5 of failure probability, strength values in Al2O3 ceramics and Al2O3/ZrO3 composites of series A and series B were above 400 MPa, 700 MPa and 650 MPa, respectively.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.2
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• pp.9-15
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• 2018

This study is intended to investigate that it is possible to analyze the public awareness and satisfaction of the weather forecast service provided by the Korea Meteorological Administration (KMA) through social media data as a way to overcome limitations of the questionnaire-based survey in the previous research. Sentiment analysis and association rule mining were used for Twitter data containing opinions about the weather forecast service. As a result of sentiment analysis, the frequency of negative opinions was very high, about 75%, relative to positive opinions because of the nature of public services. The detailed analysis shows that a large portion of users are dissatisfied with precipitation forecast and that it is needed to analyze the two kinds of error types of the precipitation forecast, namely, 'False alarm' and 'Miss' in more detail. Therefore, association rule mining was performed on negative tweets for each of these error types. As a result, it was found that a considerable number of complaints occurred when preventive actions were useless because the forecast predicting rain had a 'False alarm' error. In addition, this study found that people's dissatisfaction increased when they experienced inconveniences due to either unpredictable high winds and heavy rains in summer or severe cold in winter, which were missed by weather forecast. This study suggests that the analysis of social media data can provide detailed information about forecast users' opinion in almost real time, which is impossible through survey or interview.

• Journal of the Korea Organic Resources Recycling Association
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• v.26 no.1
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• pp.47-53
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• 2018

Recovery of lactic acid from fermentation broth using chemical precipitation was investigated with various chemicals. Effects of chemical types, mixing speeds, settling duration, and solvent addition were evaluated to improve the recovery rates of lactic acid. Overall, recovery efficiencies increased as the dosage of chemicals increased. Recovery rate of lactic acid by CaO was higher than those of $Ca(OH)_2$ and $CaCO_3$. Recovery of lactic acid increased by 48% under the optimized reaction conditions which included a mixing speed at 180 rpm, a settling duration of 24 h, and addition of ethanol at 25%(v/v). Practical application needs to consider types and concentrations of other organic acids as well as lactic acid. Based upon the results of fluorescence excitation emission matrix (FEEM), size exclusion chromatography (SEC), characteristics of recovered lactic acid were same as that in the fermentation broth.

• Journal of the Korean institute of surface engineering
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• v.48 no.6
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• pp.329-334
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• 2015

The aim of this paper is to determine the proper heat treatment temperature for SDSS tube production without ${\sigma}$-phase precipitation. When Mother steel tube was heat treated at $800^{\circ}C$ temperature, relatively a large amount of ${\sigma}$-phase precipitated and grain refinement of ferrite phase occurred simultaneously. However, in Pilgered and Drawn steel tubes, grain refinement of the ferrite phase did not occur and a small amount of ${\sigma}$-phase precipitated. For all three types of steel tubes, the pitting potential was reduced to 2/5 or less compared with the untreated one and corrosion also occurred in the salt spray test due to the precipitation of ${\sigma}$-phase. When heat treatment temperature was $900^{\circ}C$, grain refinement of the ferrite phase occurred and very little ${\sigma}$-phase precipitated in Pilgered and Drawn steel tubes. But when heat treatment was done at $1,000^{\circ}C$ temperature, all three types of steel tubes had a similar corrosion properties of that of untreated one and also corrosion did not occur in the salt spray test, as ${\sigma}$-phase did not precipitate. Therefore, the optimum heat treatment temperature range is determined to be more than $1000^{\circ}C$ for the SDSS at which corrosion does not occur.

• Journal of Radiation Protection and Research
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• v.30 no.3
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• pp.99-105
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• 2005

A model for evaluating radioactive contamination in the urban environment, named METRO-K, was developed as a basic step for accident consequence analysis in case of an accidental release. The three kind of radionuclides $(^{137}Cs,\;^{106}Ru,\;^{131}I)$ and the different chemical forms of iodine (particulate, organic and elemental forms) are considered in the model. The radioactive concentrations are evaluated for the five types of surface (roof, paved road, wall, lawn/soil, tree) as a function of time. Using the model, the contaminative impacts of the surfaces were intensively investigated with respect to with and without precipitation during the measurement periods of radionuclides in air. In addition, a practical application study was conducted using $^{137}Cs$ concentration in air and precipitation measured in an European country at the Chernobyl accident. As a result precipitation was an influential factor in surface contamination. The degree of contamination was strongly dependent on the types of radionuclide and surface. Precipitation was more influential in contamination of $^{137}Cs$ than that of $^{131}I$ (elemental form).

• Journal of Korea Water Resources Association
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• v.56 no.10
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• pp.655-665
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• 2023

In this study, unit hydrographs are calculated when precipitations of 10 scales instantaneously occurs in a virtual watershed with a constant slope and roughness. Then, the relationship between the peak flow rate and the peak occurrence time of the unit hydrograph was calculated for the precipitation scale, respectively. At this time, the virtual watershed simplified with a rhombic shape, a constant slope, and a flow condition with a certain roughness was applied instead of a natural watershed in order to understand the effect the precipitation scale has on the peak value of the unit hydrograph. And it was assumed that the precipitation in the basin was effective rainfall and the runoff was direct runoff, and the runoff flowed in a straight, uniform flow from the drop point to the outlet. The relationship between the peak flow and the peak occurrence time of the unit hydrograph was calculated in the case of 10 types of precipitation scales of 10 mm, 40 mm, 90 mm, 160 mm, 250 mm, 360 mm, 640 mm, 1,000 mm, 1,210 mm, and 1,690 mm of effective precipitation. A noteworthy achievement of this study is that, even without the storage effect of the watershed, as the scale of precipitation increases, the depth of runoff increases, so the flow rate in the watershed increases and the distance per unit time increases, so the peak flow rate increases and the peak occurrence time increases. This is a nonlinear characteristic of watershed runoff.