서교 Kyo Suh , 이정재 Jeong-jae Lee , 김태곤 Tae-gon Kim , 이호재 Ho-jae Yi

DOI: JKWST Vol.47(No.4) 3-12, 2005

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The object of this study is to develop simulation model using GASS for analyzing complex agricultural marketing. It's hard to analyze agricultural marketing system which consists of many marketing unit by economic mathematical model. This paper proposes simulation model based on GASS which can reduce complexity of system, and applies the national average wholesale cost and retail cost of alpine Chinese cabbage at 2001, 2002 to proposed simulation model.

조진구 Cho Jin Goo , 박진환 Park Jin Hwan

DOI: JKWST Vol.47(No.4) 15-24, 2005

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This study is focused on modeling to predict the behavior of two-way RC slabs. A new finite element model will be presented to analyze the nonlinear behavior of RC slabs. The numerical approach is based on the p-version degenerate shell element including theory of anisotropic laminated composites, theory of materially and geometrically nonlinear plates. In the nonlinear formulation of this model, the total Lagrangian formulation is adopted with large deflections and moderate rotations being accounted for in the sense of von Karman hypothesis. The material model is based on the Kuper's yield criterion, hardening rule, and crushing condition. The validity of the proposed p-version nonlinear RC finite element model is demonstrated through the load-deflection curves and the ultimate loads. It is shown that the proposed model is able to adequately predict the deflection and ultimate load of two-way slabs with respect to steel arrangements and steel ratios.

성찬용 Sung Chan Yong , 백승출 Back Seung Chul

DOI: JKWST Vol.47(No.4) 25-32, 2005

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This study was performed to evaluate the strength properties of polymer concrete using recycled aggregate. The compressive strength, splitting tensile strength, flexural strength and pulse velocity of polymer concrete were decreased with increasing the content of recycled aggregate. At the curing age of 7days, the compressive strength was 80.5~88.3MPa, the splitting tensile strength was 9.1~10.6MPa, the flexural strength was 19.2~21.5MPa and the pulse velocity was 3,931~4,041 m/s, respectively. Also, the compressive strength, splitting tensile strength, flexural strength and pulse velocity of concrete using recycled fine aggregate were higher than that of the silica sand. Therefore, these recycled aggregate polymer concretes were estimated for high strength concrete without major problem.

송창섭 Song Chang Seob , 신창섭 Shin Chang Seob

DOI: JKWST Vol.47(No.4) 35-41, 2005

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In order to analyse the flow problems for an unsaturated soil, it is required to examine closely the characteristics of the coefficient of permeability which is changing with the matric suction. To this ends, a permeability test was conducted on the three samples;granular soil, cohesive soil and silty soil. The specimen was made by pressing the static pressure on the mold filled with soil and the void ratio was controled with the different compaction ratio. And the test was performed by using the modified apparatus of the steady state method which was proposed by flute (1972). The range of matric suction was 0-90 kPa. The measured results for the coefficients of permeability were analysed with the void ratio and the compaction ratio, and it was examined closely the characteristics of the permeability for an unsaturated soil.

임성훈 Eam Sung Hoon

DOI: JKWST Vol.47(No.4) 43-52, 2005

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It is known in some literatures that the B value is not equal to unity in saturated soil when effective stress is given, in which the B Value is the ratio of measured excess pore water pressure and isometric loading pressure. In this study the B value was measured on various effective stresses and on various incremental loading stresses in various grain size of specimens with saturated sand. The test results showed that the B value was affected largely by grain size of sand in specimen and the amount of effective stress. There was the semi-logarithmic relationship between B value and effective stress, and also there was the linear relationship between the gradient of the former semi-logarithmic relationship and grain size of specimen.

이행우 Lee Haeng Woo , 장병욱 Chang Pyoung Wuck , 장웅희 Chang Woong Hee , 김시운 Kim See-woon

DOI: JKWST Vol.47(No.4) 53-61, 2005

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A series of laboratory tests was carried out fur analyzing of seepage characteristics of two-layers embankment model which consists of gravel and earth fill layers. Gravel layers were built under the earth fill for a half and one-third width of earth fill of the model. Permeability of earth fill was ranged between 5.00×10^-5~3.00×10^-4 m/s. The tests were performed with hydraulic gradients(i), 0.10~0.55. From the test results, hydraulic head of earth fill with gravel layer was 1.6 times higher than that of earth fill without gravel layer. Seepage rate was increased up to 4~22 times and safety factor for piping was decreased to 13~43% comparing the earth fill with gravel layer to that without gravel layer. The gravel layer under the earth fill could, in general, give some serious seepage problems to seadike embankment.

최경숙 Kyung-sook Choi

DOI: JKWST Vol.47(No.4) 65-74, 2005

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AnnAGNPS model was applied to a catchment mainly occupied with bushland for modeling non-point source pollution. Since the single event model cannot handle events longer than 24 hours duration, the event-based calibration was carried out using the continuous mode. As event flows affect sediment and nutrient generation and transport, the calibration of the model was performed in three steps: Hydrologic, Sediment and Nutrient calibrations. The results from hydrologic calibration for the catchment indicate a good prediction of the model with average ARE(Absolute Relative Error) of 24.6% fur the runoff volume and 12% for the peak flow. For the sediment calibration, the average ARE was 198.8% indicating acceptable model performance for the sediment prediction. The predicted TN(Total Nitrogen) and TP(Total Phosphorus) were also found to be acceptable as the average ARE for TN and TP were 175.5% and 126.5%, respectively. The AnnAGNPS model was therefore approved to be appropriate to model non-point source pollution in bushland catchments. In general, the model was likely to result in underestimation for the larger events and overestimation fur the smaller events for the water quality predictions. It was also observed that the large errors in the hydrologic prediction also produced high errors in sediment and nutrient prediction. This was probably due to error propagation in which the error in the hydrologic prediction influenced the generation of error in the water quality prediction. Accurate hydrologic calibration should be hence obtained for a reliable water quality prediction.

정광욱 Jung Kwang-wook , 윤춘경 Yoon Chun-gyeong , 장재호 Jang Jae-ho , 김형철 Kim Hyung-chul , 전지홍 Jeon Ji-hong

DOI: JKWST Vol.47(No.4) 75-85, 2005

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A study was performed to examine the effects of reclaimed-water irrigation on microorganism con-centration in ponded-water of paddy rice plots. Several treatments were used and each one was triplicated to evaluate the change of indicator microorganisms (total coliforms (TC), fecal coliforms FC), and E. coli) concentrations in 2003 and 2004 growing seasons. Their concentrations increased significantly right after irrigation, but decreased about 45% in 24 hours. It implies that agricultural activities such as plowing and fertilizing should be practiced one or two days after irrigation considering health-risks. Treatments with UV-disinfected water irrigation demonstrated significantly lower concentrations than others including control plots where natural surface water was irrigated. The monitoring results from actual paddy rice fields and experimental paddy plots showed that concentrations of indicator microorganisms ranged from 10² to 10⁵ MPN/100mL. A comprehensive assessment of existing agricultural practices and a thorough monitoring in the field as well as treatment-plots are recommended to make more realistic national guidelines more applicable. UV-disinfected water irrigation reduced microorganism concentrations in paddy fields down to below the concentration of conventional paddy rice culture, and is thought to be an effective and feasible measure fur agricultural reuse of secondary effluent.