유찬 Yu Chan , 윤성욱 Yun Sung Wook

DOI: JKWST Vol.54(No.3) 1-9, 2012

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As topographic characteristics of Korea where 64 % of the national land area is forest and only 17 % is being used as farmland, remediation of farmland contaminated by heavy metals is a considerably important issue. In this study, as an alternative of practically and effectively remediating farmland which was abandoned as its crop plants exceeded maximum residue limit of heavy metals due to mining impact, applicability of stabilization method was examined through the pilot-scale field experiment. Three plots (L×W×D＝ 3 m×2 m×0.3 m) were installed at the selected farmland and in plot 1, only soil of the selected farmland was applied, in pilot 2, soil of the selected farmland plus 3 % limestone (w/w) was applied and in pilot 3, soil of the selected farmland plus 3 % limestone was applied and then uncontaminated soil was covered thereon (0.3 m). After that, seeds of radish, Korean cabbage and soybean of which characteristics of edible portions are different were sowed on each plot and cultivated. Afterwards, at a proper harvesting time (app. 80 days later), crop plants and soil were collected and phytoavailability (0.11 M HOAc extractable) of heavy metals in soil and accumulated concentration of heavy metal in edible portion of crop plants were examined. As a result, it was revealed that phytoavailability of heavy metals in soil added with limestone (plot 2) was clearly reduced compared with plot 1 (untreated) and owing to this treatment, accumulated concentration of heavy metals in edible portion of crops was also clearly reduced compared with plot 1. While radish cultivated in plot 1 had exceeded maximum residue limit of agricultural products, in particular, plot 2 using limestone had shown concentration lower than maximum residue limit and this plot had shown little difference with 3 plot where crop was cultivated in uncontaminated soil cover. Therefore, it was considered that for abandoned farmland like the selected farmland, reducing mobility and phytoavailability of heavy metals and reducing crop uptake through stabilization method would be an effective and practical alternative for producing safe agricultural products on a sustained basis.

이달원 Lee Dal Won , 이영학 Lee Young Hak

DOI: JKWST Vol.54(No.3) 11-17, 2012

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In this study, an experiment with large-scale model was performed according to raising embankment in order to investigate the cause of collapse by a change in water level of reservoir. Also, the settlement and pore water pressure by high water level and a rapid drawdown were compared and analyzed. After raising embankment for inclined core, there was no infiltration by leakage. For the vertical core, the pore water pressure showed a largely change by faster infiltration of pore water than in the inclined core. In a rapid drawdown, inclined core was remained stable but vertical core showed a largely change in pore water pressure. A settlement after a raising embankment showed a larger measure of settlement than before the raising embankment. The leakage quantity before a raising embankment and an inclined extension showed no leakage. Leakage in vertical extension was measured 160 l. From the result, a instrument system that can accurately estimate a change of pore water pressure shall be established for a rational maintenance and stabilization of raising embankment for agricultural reservoir.

최순군 Choi Soon-kun , 최진용 Choi Jin-yong , 남원호 Nam Won-ho , 허승오 Hur Seung-oh , 김학진 Kim Hak-jin , 정선옥 Chung Sun-ok , 한경화 Han Kyung-hwa

DOI: JKWST Vol.54(No.3) 19-28, 2012

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Greenhouse cultivation has been increasing for high quality and four season crop production in South Korea. For the cultivation in a greenhouse, maintaining adequate soil moisture at each crop growth stage is quite important for yield stability and quality while the behavior of moisture movement in the soil has complexity and adequate moisture conditions for crops are vary. Drip irrigation systems have been disseminated in the greenhouse cultivation due to advantages including irrigation convenience and efficiency without savvy consideration of the soil moisture redistribution. This study aims to evaluate soil moisture movement of drip irrigation according to the soil moisture uniformity assessment. Richards equation and finite difference scheme were adapted to simulate soil moisture behavior in soil. Soil container experiment was conducted and the model was validated using the data from the experiment. Two discharge rate (1 ℓ/hr and 2 ℓ/hr) and three spaces between the emitters (10 cm, 20 cm, and 30 cm) were used for irrigation system evaluation. Christiansen uniformity coefficient was also calculated to assess soil moisture redistribution uniformity. The results would propose design guidelines for drip irrigation system installation in the greenhouse cultivation.

최진규 Choi Jin Kyu , 손재권 Son Jae Gwon , 윤광식 Yoon Kwang Sik , 이현정 Lee Hyun Jeong , 김영주 Kim Young Joo

DOI: JKWST Vol.54(No.3) 29-36, 2012

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This study was carried out to investigate the runoff characteristics in paddy field using livestock compost fertilizer. Irrigation, runoff and water quality data in the paddy field were analyzed periodically from May to September in 2011. The observed amounts of rainfall, irrigation, runoff for the experimental paddy field during the irrigation period were 1,148.2 mm, 523.9 mm, and 344.7 mm, respectively. T-N concentrations ranged from 2.28 mg/L to 11.75 mg/L, which was generally higher than the quality standard of agricultural water (1.0 mg/L). T-P concentrations ranged from 0.018 mg/L to 0.241 mg/L and the average was 0.122 mg/L. The runoff loads of T-N and T-P were 15.7 kg/ha and 0.4 kg/ha, respectively. The runoff pollutants loadings in T-N and T-P in this study were much lower values than the loads of T-N and T-P from the paddy field presented by others‘ studies. We are considering that these results were affected by rainfall as well as hydrological condition, irrigation water, fertilizer application, rice straw and plowing.

송상현 Song Sang-hyeon , 이인복 Lee In-bok , 권경석 Kwon Kyeong-seok , 하태환 Ha Tae-hwan , Bitog Jessie P. , 홍세운 Hong Se-woon , 서일환 Seo Il-hwan , 문운경 Moon Oun-kyeong , 김연주 Kim Yeon-joo , 최은진 Choi Eun-jin

DOI: JKWST Vol.54(No.3) 37-45, 2012

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Recently, the livestock industry in Korea was heavily affected by the outbreak of official livestock diseases such as foot and mouse disease, high pathogenic avian influenza, swine influenza, and so on. It has been established that these diseases are being spread through direct contact, droplet and airborne transmission. Among these transmissions, airborne transmission is very complex in conducting field investigation due to the invisibility of the pathogens and unstable weather conditions. In this study, the airborne transmission was thoroughly investigated inside a pig house by conducting tracer gas (CO2) experiment because experiment with real pathogen is limited and dangerous. This is possible as it can be assumed that the flow is similar pattern very fine particles and gas. In the experiment, the ventilation structure as well as the location of gas emission were varied. The CO2 detection sensors were installed at 0.5 and 1.3 m height from the floor surface. The tracer gas level was measured every second. Results revealed that the direction of spread can be determined by the response time. Response time refers to the time to reach 150 ppm from the gas emission source at each measuring points. The location of the main flow as well as the gas emission was also found to be very important factor causing the spread.

서동욱 Seo Dong Uk , 유봉선 Yu Bong Seon

DOI: JKWST Vol.54(No.3) 47-54, 2012

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As a large construction such as highway, dam, reclaimed land etc. increase in number more and more, large amount of fill materials are required. It is needed to utilize a gypsum which is a by-product yielded from chemical plants, as fill materials. Though some studies have been conducted to know a engineering characteristic of gypsum, it is not certain that water contents were checked at 45 ℃ dry oven. This study proposed that water contents must be measured at 45 ℃ dry condition because gypsum is changed to other types as a dry temperature. As the results obtained by compaction tests, it is found that moisture of gypsum in compaction must be within －5.0∼2.5 % O.M.C (optimal moisture content).

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

DOI: JKWST Vol.54(No.3) 55-63, 2012

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Soil properties are not random values which is represented by mean and standard deviation but show spatial correlation. Especially, soils are highly variable in their properties and rarely homogeneous. Thus, the accuracy and reliability of probabilistic analysis results is decreased when using only one random variable as design parameter. In this paper, to consider spatial variability of soil property, one-dimensional random fields of coefficient of consolidation (C_u) were generated based on a Karhunen-Loeve expansion. A Latin hypercube Monte Calro simulation coupled with finite difference method for Terzaghi's one dimensional consolidation theory was then used to probabilistic analysis. The results show that the failure probability is smaller when consider spatial variability of(C_u)than not considered and the failure probability increased when the autocorrelation distance increased. Thus, the uncertainty of soil can be overestimated when spatial variability of soil property is not considered, and therefore, to perform a more accurate probabilistic analysis, spatial variability of soil property needed to be considered.

김성민 Kim Sung Min , 김성재 Kim Sung Jae , 김상민 Kim Sang Min

DOI: JKWST Vol.54(No.3) 65-74, 2012

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In this study, three different unit hydrograph methods (NRCS, Snyder and Clark) in the HEC-HMS were compared to find better fit with the observed data in the Namgang-Dam watershed. The Sancheong, Shinan, and Changchon in Namgang-Dam watershed were selected as the study watersheds. The input data for HEC-HMS were calculated land use, digital elevation map, stream, and watershed map provided by WAter Management Information System (WAMIS). Sixty six storms from 2004 to 2011 were selected for model calibration and validation. Three unit hydrograph methods were compared with the observed data in terms of simulated runoff volume, and peak runoff for the selected storms. The results showed that the coefficient of determination (R²) for the peak runoff was 0.8295∼0.9999 and root mean square error (RMSE) was 0.029∼0.086 mm/day for calibration stages. In the model validation, R² for the peak runoff was 0.9061∼0.9916 and RMSE was 0.030∼0.088 mm/day which were more accurate than calibrated data. Analysis of variance showed that there was no significant difference among the three unit hydrograph methods.

홍성구 Hong Seong Gu

DOI: JKWST Vol.54(No.3) 75-80, 2012

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Gasification is a therm-chemical conversion process to convert various solid fuels into gaseous fuels under limited supply of oxygen in high temperature environment. Considering current availability of biomass resources in this country, the gasification is more attractive than any other technologies in that the process can accept various combustible solid fuels including plastic wastes. Mixed fuels of biomass and polyethylene pellets were used in gasification experiments in this study in order to assess their potential for synthesis gas production. The results showed that higher reaction temperatures were observed in mixed fuel compared to woodchip experiments. In addition, carbon monoxide, hydrogen, and methane concentrations were increased in the synthesis gas. Heating values of the synthesis gas were also higher than those from woodchip gasification. There are hundred thousand tons of agricultural plastic wastes generated in Korea every year. Co-gasification of biomass and agricultural plastic waste would provide affordable gaseous fuels in rural society.

김한중 Kim Han Joong

DOI: JKWST Vol.54(No.3) 81-89, 2012

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This paper presents a set of controlled simulated statical and engineering mechanical experiments accessible via the virtual world environment (VWE) and virtual physics lab S/W. Online courses of the university offering courses and/or programs online are growing and the number of students want education in ways which fit their personal places, e-learning is becoming more important and ubiquitous each year. In this study, first of all, question is rather ‘How do we execute the learning effectiveness of e-learning courses?’ than ‘Why does they need e-learnig or VW-learning?’. In particular, is it possible to effectively teach mechanical engineering courses online? The answer was ‘No’. So, there is little research on many of these questions. And another important question is ‘Is e-learning cost effective?’. For the answer, This research provided that an instructional design model is used to ‘How to think and apply the Newtonian forces’ in the virtual physics lab S/W. Collected data from student are administered in the spring semester when students studied ‘Introduction to Bio-resources and Systems Engineering’. Results show that a cadre of students can take highly interactively physical properties of mechanical engineering in the virtual laboratory environment. Those show that VWE is greater than that of a similar real world presentation or experimental lab, since most of students are delighted to modify and retry modeling works in the VWE.

정충길 Jung Chung Gil , 조형경 Joh Hyung Kyung , 박종윤 Park Jong Yoon , 김성준 Kim Seong Joon

DOI: JKWST Vol.54(No.3) 91-101, 2012

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This study is to assess the runoff characteristics of nonpoint source pollution loads for Jecheon and Jangpyeong stream watersheds located in the upstream of Chungju lake. The SWAT (Soil and Water Assessment Tool), a physically based distributed hydrological model was calibrated and verified using 5 years (2006 to 2010) streamflow and water quality data. The Nash-Sutcliffe model efficiency for streamflow was 0.60～0.92 and the determination coefficients for sediment, Total Nitrogen (T-N), and Total Phosphorous (T-P) were 0.53～0.71, 0.51～0.91 and 0.38～0.85 respectively. The results showed that the Sediment, T-N, and T-P of Jangpyeong stream were 40.0～60.9 %, 34.8～64.1 % and 76.5～83.9 % higher than Jecheon stream watershed during wet days. The results evaluated high NPS loads at Jangpyeong stream because the percentage of urban and upland crop cultivation area Jangpyeong stream watershed was higher than Jecheon stream watershed.

황순호 Hwang Soon Ho , 강문성 Kang Moon Seong , 김지혜 Kim Ji Hye , 송정헌 Song Jung Hun , 전상민 Jun Sang Min , 이상현 Lee Sang-hyun , 최진용 Choi Jin-yong

DOI: JKWST Vol.54(No.3) 103-111, 2012

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Works for dam heightening plan have dual purposes: flood disaster prevention by securing additional storage volume and river ecosystem conservation by supplying stream maintenance flow. Now, the dam heightening project is in progress and there are 93 dam heightened reservoir. After the dam heightening project, 2.2 hundred million ton of flood control volume in reservoirs will be secured. Thus it is necessary to evaluate the effects of the dam heightening project on watershed hydrology and stream hydraulics, and resulting flood damages. This study was aimed to assess the impact of outflow from the dam heightened reservoir group on the Whangryong river design flood. The HEC-HMS (Hydrologic Engineering Center-Hydrologic Modeling System) model was used for estimating flood discharge, while HEC-5 (Hydrologic Engineering Center-5) was used for reservoir routing. This study analysed flood reduction effect on 100yr and 200yr return periods about the before and after heightening of agricultural dams. Based on the results of this study, the reduction of flood peak discharge at downstream of the reservoir group was estimated to be about 41% and 53% for 100yr and 200yr frequencies, respectively.

이성복 Lee Sung-bok , 이인복 Lee In-bok , 홍세운 Homg Se-woon , 서일환 Seo Il-hwan , Bitog P. Jessie , 권경석 Kwon Kyeong-seok , 하태환 Ha Tae-hwan , 한창평 Han Chang-pyoung

DOI: JKWST Vol.54(No.3) 113-124, 2012

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Reliable estimation of energy load inside the greenhouse and the selection of cooling and heating facilities are very important preceding factors to save energy as well as initial and maintenance costs of operating a greenhouse. Recently, building energy simulation (BES) technique to simulate a model similar to the actual conditions through a variety of dynamic simulation methods, and predict and analyze the flow of energy is being actively introduced and developed. As a fundamental research to apply the BES technique which is mainly used for analysis of general buildings, to greenhouse, this research designed four types of naturally-ventilated greenhouses using one of commercial programs, TRNSYS, and then compared and analyzed their energy load properties, by applying meteorological data collected from six regions in Korea. When comparing the greenhouse load of each region depending on latitude and topographical characteristics through simulation, Chuncheon had nearly 9∼49 % higher heating load per year than other regions, but its annual cooling load was the reverse to it. Except for Jeju, 1-2W type greenhouses in five regions showed about 17 % higher heating load than a widespan type greenhouse, and 1-2W type greenhouses in Chuncheon, Suwon, Cheongju, Daegu, Cheonju and Jeju had 23 %, 20 %, 17 %, 16 %, 18 % and 20 % higher cooling load respectively than a wide span-type one. Glasshouse and vinyl greenhouse showed 8∼11 % and 10∼12 % differences respectively in heating load, while 2∼10 % and 7∼10 % differences in cooling load respectively.

최경숙 Choi Kyung-sook , 김해도 Kim Hae-do

DOI: JKWST Vol.54(No.3) 125-132, 2012

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Saemangeum development project is the world's largest tidal flat reclamation project. It is currently under construction, and proceeding with phased developments. The construction of agricultural areas within the Saemangeum reclamed lands is also a part of this project. These areas will have multi-functional complexes aiming to produce mainly eco-friendly horticultural crops and livestock products for the purpose of export. The major concern is to obtain sufficient water with appropriate quality to supply to those areas. The objective of this study is therefore to provide available water supply plans for agricultural purpose, especially for horticulture and livestock complexes. Alternative methods for water supply are purifying water from the Saemangenm lake or using water supply services providing by K-water or local governments. This study investigates to find an economical water supply plan through comparisons of these methods. As a result, the water purification method with Saemangeum lake water could be advantageous for given water supply conditions to horticulture and livestock complexes.

이성행 Lee Seong Haeng , 양동운 Yang Dong Woon , 함형길 Hahm Hyung Gil , 공보성 Kong Bo Sung , 신동욱 Shin Dong Wook

DOI: JKWST Vol.54(No.3) 133-139, 2012

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Dynamic characteristic of lift gate supported by plane truss is studied by a model test scaled with the ratio of 1：31.25 in the four major rivers project. The vibrations of gate supported by the plane truss is assessed in comparison with those of gate supported by the space truss which was tested formerly. The gate model is made of acryl panel and calibrated by lead. A model test is conducted under the different gate opening and upstream water levels conditions in the concrete test flume dimensioned 1.6 m in width, 0.8 m in height and 24 m in length. In order to verify the model, natural frequencies of the model gate are measured, and compared with the numerical results. The vibrations of gate model supported by the plane truss in opening height of 1.0 cm∼2.0 cm shows greater than one supported by the space truss. It is found that the gate model supported by the plane truss is less desirable than one supported by the space truss. thus, the latter type of gate model is requested to design.

나상일 Na Sang Il , 박종화 Park Jong Hwa , 박진기 Park Jin Ki

DOI: JKWST Vol.54(No.3) 141-148, 2012

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Food policy is considered as the most basic and central issue for all countries, while making efforts to keep each country’s food sovereignty and enhance food self-sufficiency. In the case of Korea where the staple food is rice, the rice yield prediction is regarded as a very important task to cope with unstable food supply at a national level. In this study, Korean paddy Rice yield Prediction Model (KRPM) developed to predict the paddy rice yield using meteorological element and MODIS NDVI. A multiple linear regression analysis was carried out by using the NDVI extracted from satellite image. Six meteorological elements include average temperature; maximum temperature; minimum temperature; rainfall; accumulated rainfall and duration of sunshine. Concerning the evaluation for the applicability of the KRPM, the accuracy assessment was carried out through correlation analysis between predicted and provided data by the National Statistical Office of paddy rice yield in 2011. The 2011 predicted yield of paddy rice by KRPM was 505 kg/10a at whole country level and 487 kg/10a by agroclimatic zones using stepwise regression while the predicted value by KOrea Statistical Information Service was 532 kg/10a. The characteristics of changes in paddy rice yield according to NDVI and other meteorological elements were well reflected by the KRPM.

지용근 Jee Yong Keun , 이진희 Lee Jin Hee , 김상단 Kim Sang Dan

DOI: JKWST Vol.54(No.3) 149-157, 2012

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For the systemic management and planning of future agricultural water resources, deriving and analyzing the various results of climate change are necessary to respond the uncertainties of climate change. This study assessed the impact of climate change on the rainfall, temperature, and agricultural water requirement targeting in the Nakdong-river's basin periodically according to socioeconomic driving factors under the scenarios A1B, A2 and B1 of the Special Report on Emission Scenarios (SRES) through the various IPCC GCMs. As a result of future rainfall change (2011∼2100), increasing or decreasing tendency of rainfall change for future periods did not show a clear trend for three rainfall observatories, Daegu, Busan and Gumi. The characteristics of the temperature change consistently show a tendency to increase, and in the case of Daegu observatory, high temperature growth was shown. Especially, it was increased by 93.3 % in the period of future3 (2071∼2100) for A2 scenario. According to the scenario and periodic analyses on the agricultural water demand, which was thought to be dependent on rainfall and temperature, the agricultural water demand increased at almost every period except during the Period Future1 (2011∼2040) with different increase sizes, and the scenario-specific results were shown to be similar. As for areas, the agricultural water demand showed more changes in the sub-basin located by the branch of Nakdong-river than at the mainstream of the River.

김용성 Kim Yong Seong , 서민우 Seo Min Woo , 오상은 Oh Sang Eun

DOI: JKWST Vol.54(No.3) 159-168, 2012

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