김태곤 Taegon Kim , 이정재 Jeongjae Lee , 서교 Kyo Suh

DOI: JKWST Vol.56(No.3) 1-9, 2014

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The aim of this study is to develop a simulation model for analyzing 2D truss structure using Generic Agricultural System Simulator (GASS). Although the truss is simple structure, numerical methods based on matrix analysis are cumbersome and complicated. This study suggests simple and convenient methods to remove calculating steps for whole stiffness matrices. The simulation environment based on independency of object-oriented components on GASS consists of component development and component deploy stages. A component for a truss structure is implemented based on equilibrium equations at nodes. The simulator can analyze truss structures through deploying components with attributes and links. The examples using GASS show intuitive graphical results of the movements of truss nodes.

조성욱 Jo Sung-wook , 박성직 Park Seong-jik

DOI: JKWST Vol.56(No.3) 11-17, 2014

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We investigated the applicability of steel slag as a capping material in order to minimize phosphorus(P) release into seawater. Steel slag is a byproduct from the iron and steel industries and the use of steel slag has some advantages in respect of both cost and environmental concern. P removal by steel slag were studied in a batch system with respect to changes in contact time and initial concentration. Kinetic adsorption data were described well by pseudo 2nd order model, indicating rate limiting step for P adsorption to steel slag is chemical sorption. Equilibrium adsorption data fitted well to Langmuir isotherm model which describes for single layer adsorption. The maximum P adsorption capacity of steel slag was 7.134 mg-P/L. Increasing the depth of steel slag produced a positive effect on interruption of P release. More than 3 cm of steel slag was effective for blocking P release and 5 cm of steel slag was recommended as the depth for capping of P contaminated marine sediments. Increasing P concentration and flow rate had a negative effect on P removal ratio. It was concluded that the steel slag has a potential capping material for blocking P release from marine sediments.

박종윤 Jong-yoom Park , 정혁 Hyuk Jung , 장철희 Cheol-hee Jang , 김성준 Seong Joon Kim

DOI: JKWST Vol.56(No.3) 19-29, 2014

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This study was to evaluate the potential climate change impact on watershed hydrological components of evapotranspiration, surface runoff, lateral flow, return flow, and streamflow using Soil and Water Assessment Tool (SWAT). For Yongdam dam watershed (930 ㎢), the SWAT model was calibrated for five years (2002-2006) and validated for three years (2004-2006) using daily streamflow data at three locations and daily soil moisture data at five locations. The Nash-Sutcliffe model efficiency (NSE) and coefficient of determination (R²) were 0.43-0.67 and 0.48-0.70 for streamflow, and 0.16-0.65 and 0.27-0.76 for soil moisture, respectively. For future evaluation, the HadGEM3-RA climate data by Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios were adopted. The biased future data were corrected using 30 years (1982-2011, baseline period) of ground weather data. The HadGEM3-RA 2080s (2060-2099) temperature and precipitation showed increase of +4.7 ℃ and +22.5 %, respectively based on the baseline data. The impacts of future climate change on the evapotranspiration, surface runoff, baseflow, and streamflow showed changes of ＋11.8 %, ＋36.8 %, ＋20.5 %, and ＋29.2 %, respectively. Overall, the future hydrologic results by RCP emission scenarios showed increase patterns due to the overall increase of future temperature and precipitation.

신민환 Shin Min Hwan , 장정렬 Jang Jeong Ryeol , 정영훈 Jung Young Hun , 금동혁 Kum Dong Hyuk , 원철희 Won Chul Hee , 이수인 Lee Su In , 임경재 Lim Kyoung Jae , 최중대 Choi Joong Dae

DOI: JKWST Vol.56(No.3) 31-38, 2014

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Four actual cultivations were prepared and a variety of soybean was cultivated. A H-flume, an automatic water level gauge and an automatic water sampler were installed at the outlet of each plot equipped for the measurement of flow rate and its water quality. The amount of rainfall of the study area in 2013 was measured as 975.6 mm which was much lower than the annual average rainfall of 1,271.8 mm, resulting in less occurrences in rainfall-runoff events. Rainfall-runoff events were occurred three times during the rainfall event of 4~5 July, 23 and 24 August. The characteristics of NPS pollution discharge of the plots and the reduction effect of the selected BMPs were analyzed during these events. The reduction effect of straw mat and soil amendments (Polyacrylamide (PAM) and Gypsum) on runoff ratio ranged between 38.2 and 92.9% (average 71.6%). The NPS pollution load reduced between 27.7 and 95.1% (average 70.0%) by the application of rice straw mat and soil conditioner when compared with that of control plot. Soybean yield (2,133.3 kg/ha) of the straw mat covered plots increased by 14.3% when compared with control (1,866.7 kg/ha). The effect of straw mat on the yield was not economically viable if the material and accompanying labor costs were considered. The data collected and analyzed on different soil textures and crops in this study are expected to be a fundamental reference for the expansion of the results to the application nationwide and the development of NPS pollution management policies.

민슬기 Min Seul-gi , 손영환 Son Young-hwan , 박재성 Park Jae-sung , 노수각 Noh Soo-kack , 봉태호 Bong Tae-ho

DOI: JKWST Vol.56(No.3) 39-45, 2014

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Dust is mostly caused by human activity. The effect of natural factors on dust emission were studied in many research, but the little effort in researching artificial factors of dust emission. The object of study is to analysis dust emission characteristic by drop impact. Particle matter 10μm (PM₁₀) was measured by drop impact on paved soil with changing drop height, weight and drop size. Increasing drop height cause more PM₁₀ emission. Increasing drop weight cause more PM₁₀ emission but had limit weight for increasing dust emission. Because the exceed kinetic energy of drop weight penetrate the soil surface. The limit perimeter was exist that separating PM₁₀ emission aspect. Under limit perimeter, PM₁₀ emission was increasing while perimeter was increasing, but over limit perimeter showed the opposite aspect. Regression equations for estimating PM₁₀ with kinetic energy and perimeter were made under limit perimeter and over limit perimeter. The R² of those equations were 0.784, 0.743. The error has occurred between measured PM₁₀ and calculated PM₁₀ in the equation under limit perimeter. But using equation of case for over limit perimeter, PM10 can be estimated with kinetic energy and drop perimeter.

원철희 Chul-hee Won , 신민환 Min-hwan Shin , 이수인 Su-in Lee , 금동혁 Dong-hyuk Kum , 임경재 Kyoung-jae Lim , 최중대 Joong-dae Choi

DOI: JKWST Vol.56(No.3) 47-53, 2014

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We investigated the effect of straw mat cover and soil amendments on the reduction of runoff, non-point source pollution load and yield of a Chinese cabbage from alpine fields. Two plots on sandy loam soil were prepared. Experimental treatments were control and rice straw mat cover (3,300 kg/ha)＋Polyacrylamide (PAM) (5 kg/ha)＋Gypsum (1 ton/ha) (SPG). A variety of Chinese cabbage was cultivated and runoff was monitored during a growing season in 2012. Monitoring was conducted to seven times. Runoff rate of SPG plot was lower than those of control plot. The reduction rate of runoff from SPG plot was 29.4 % compared to control plot. The reduction rate of suspended solids (SS), total nitrogen (TN) and total phosphorus (TP) load of SPG plot was 86.5 %, 34.7 % and 39.1 %, respectively. Yield of a Chinese cabbage from SPG plot (39,646 kg/ha) was greater than that of control plots (28,482 kg/ha). It was concluded that the use of SPG on soil surface could not only reduce the NPS pollution loads in receiving waters but also help increase the crop yield.

이상현 Lee Sang-hyun , 오윤경 Oh Yun-gyeong , 박나영 Park Na-young , 이성학 Lee Sung Hack , 최진용 Choi Jin-yong

DOI: JKWST Vol.56(No.3) 55-64, 2014

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While utilizing high resolution satellite image for land use classification has been popularized, object-oriented classification has been adapted as an affordable classification method rather than conventional statistical classification. The aim of this study is to extract the paddy field area using object-oriented classification with time series NDVI from high-resolution satellite images, and the RapidEye satellite images of Jaeryung-gun in North Korea were used. For the implementation of object-oriented classification, creating objects by setting of scale and color factors was conducted, then 3 different land use categories including paddy field, forest and water bodies were extracted from the objects applying the variation of time-series NDVI. The unclassified objects which were not involved into the previous extraction classified into 6 categories using unsupervised classification by clustering analysis. Finally, the unsuitable paddy field area were assorted from the topographic factors such as elevation and slope. As the results, about 33.6 % of the total area (32313.1 ha) were classified to the paddy field (10847.9 ha) and 851.0 ha was classified to the unsuitable paddy field based on the topographic factors. The user accuracy of paddy field classification was calculated to 83.3 %, and among those, about 60.0 % of total paddy fields were classified from the time-series NDVI before the unsupervised classification. Other land covers were classified as to upland(5255.2 ha), forest (10961.0 ha), residential area and bare land (3309.6 ha), and lake and river (1784.4 ha) from this object-oriented classification.

유승환 Yoo Seung-hwan , 이상현 Lee Sang-hyun , 최진용 Choi Jin-yong

DOI: JKWST Vol.56(No.3) 65-74, 2014

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Water footprint is defined as the total volume of direct and indirect water used to produce a good and service by consumer or producer, and measured at the point of production based on virtual water concept. The green and blue water footprint refers to the volume of the rainwater and the irrigation water consumed, respectively. Crop water footprint is expected to be used as the basic data for agricultural water resources policies at production, consumption and trade aspect. Thus, it is necessary to estimate suitable green and blue water footprint for South Korea. The objective of this paper is to quantify the green and blue water footprint and usage of upland crops during the period 2001-2010. To estimate the water footprint, 43 upland crop production quantity and harvested area data were collected for 10 years and FAO Penman-Monteith equation was adopted for calculating crop water requirement. As the results, the water footprint of cereals, vegetables, fruits and oil crops accounted for 1,994, 165, 605, and 4,226 ㎥/ton, respectively. The usage of water footprint for crop production has been estimated at 3,499 (green water) and 216 (blue water) M㎥/yr on average showing a tendency to decrease. Fruits and vegetables have the largest share in the green water usage, consuming about 1,200 and 1,060 M㎥/yr which are about 65 % of gross usage. The results of this study are expected to be understood by the agricultural water footprint as well as by the total water footprint from both a production and consumption perspective in Korea.

이종원 Lee Jong Won

DOI: JKWST Vol.56(No.3) 75-81, 2014

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Fossil energy is needed for a whole year greenhouse cropping due to climate in South Korea. Because the most of the fossil energy resources is imported, it is necessary to develop technology to be able to reduce the energy cost in order to manage greenhouse profitably. The greenhouse commonly consume less amount of energy as compared to other industrial sectors. Replacement of fossil fuel with solar thermal storage, therefore, can be an economical as well as environmentally sustainable option for greenhouse heating. The fluid flow, heat storage and radiation characteristic of the gravel bed model were analyzed to provide basic data for design of the experimental solar heated greenhouse with underground thermal storage using gravel. The air flow velocity in the gravel storage bed was proven to be affected from the capacity of circulation fan and the circulation method and the positive pressure method was proven to be the best among the different air circulation methods. The initial air temperature of the thermal storage bed of 1.2 m wide×9 m long×0.9 m deep was 10 ℃. After the thermal storage bed is heated by air of the mean temperature 41 ℃ during 9 hours, the temperature has increased about 20.3 ℃ and the storage of heat was about 33,000 kcal. The important factors should be taken into consideration for design of the solar heated greenhouse with underground thermal storage using gravel are insulation of rock storage, amount of storing heat, inflow rate and direction of inlet and outlet duct.