구자웅 Koo Ja Woong , 손재권 Son Jae Gwon , 조재영 Cho Jae Young

DOI: JKWST Vol.48(No.1) 3-10, 2006

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The chemical fractions of heavy metals were investigated in the soils of reclaimed and natural tidelands of southwest coastal area of Korea. The distribution pattern of each heavy metal in different fractions was in the order: 1) Cu : organic bound > organic complex > residual > exchangeable = water soluble. 2) Cr : residual > organic bound > organic complex > water soluble > exchangeable. 3) Pb : organic bound > residual > organic complex > water soluble > exchangeable. 4) Cd : residual > organic bound > organic complex > water soluble = exchangeable. 5) Zn : organic bound > residual > organic complex > water soluble > exchangeable. The content of residual Zn showed positive correlation with organic matter content but organic bound Zn showed negative correlation with CEC. The content of residual and exchangeable Cd showed highly positive correlation with organic matter content but residual, organic bound, and exchangeable Cd showed negative correlations with CEC. Water soluble Pb showed positive correlation with CEC but organic bound Pb showed negative correlation with CEC.

유승환 Yoo Seung-hwan , 최진용 Choi Jin-yong , 장민원 Jang Min-won

DOI: JKWST Vol.48(No.1) 13-23, 2006

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In 1998, Food and Agriculture Organization addressed that FAO Modified Penman method possibly over-estimates consumptive use of water comparing to the measured reference crop evapotranspiration (PET) and Penman-Monteith method can be better choice for accurate PET estimation. Nevertheless it is still difficult to find research efforts about paddy rice crop coefficient for Penman-Monteith method. This study aims to estimate paddy rice crop coefficients for Penman-Monteith and FAO modified Penman methods in the manner of comparing two equations. To estimate the crop coefficients, measured evapotranspiration data during 1982-1986 and 1995-1997 were used. The average Penman-Monteith crop coefficients ranged from 0.78 to 1.58 for translated paddy rice and from 0.87 to 1.74 for flood-direct seeded paddy rice. The average FAO Modified Penman crop coefficients ranged from 0.65 to 1.35 for translated paddy rice and from 0.70 to 1.58 for flood-direct seeded paddy rice.

이상진 Lee Sang Jin , 황만하 Hwang Man Ha , 이배성 Lee Bae Sung , 고익환 Ko Ick Hwan

DOI: JKWST Vol.48(No.1) 27-38, 2006

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In this study, we developed a program to estimate discharge efficiently considering major hydraulic characteristic including water level, river bed, water slope and roughness coefficient in a natural river. Stream discharge was measured at Gongju gauge station located in the down stream of the Daechung Dam during normal and dry seasons from 2003 to 2004. The developed model was compared with the results from the existing rating curve at T/M gage stations, and was used for runoff analyses. Evaluating the developed river discharge estimation program, it was applied during 1983-2004 that base flow separation method and RRFS (Rainfall Runoff Forecasting System) which is based on SSARR (Streamflow Synthesis And Resevoir Regulation). The result presents the stage-discharge curve creator range at the Gong-ju is overestimated by approximately 10-20%, especially at the low stage. It is attributed to the hydraulic characteristics at the study. The discharge simulated by the RRFS and base flow separation, which is calibrated using the measurement at the early spring and late fall season during relatively d]v season, shows the least errors. The coefficient of roughness at Gongju station varied with the high and low water level.

정남수 Jung Nam Su , 이정재 Lee Jeong Jae

DOI: JKWST Vol.48(No.1) 41-48, 2006

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In the evaluation of rural amenities, its properties are related with social, cultural, and environmental elements. In this study, Information Measure Model (IMM) and Cultural Property Priority Assessment Model (CPPAM) were developed adapting information measure model with text based surveying data. To apply developed model not only general properties but also specific surveyed data, Specific Information Gathering and Utilizing System (SIGUS) was constructed using the data in Dusan World encyclopedia. IMM shows priorities of cultural property by information in national-designated cultural properties. And CPPAM applied in surveying data in 2004 by Rural Resources Development Institute.

연규석 Yeon Kyu Seok , 주명기 Joo Myung Ki , 이현종 Lee Hyun Jong , 김성기 Jin Xing Qi , 이지원 Lee Chi Won

DOI: JKWST Vol.48(No.1) 51-60, 2006

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This study was conducted to investigate experimentally the drying shrinkage and the strength properties of redispersible SBR and PAE powder-modified mortars. Polymer-cement ratio, content of shrinkage-reducing agent and antifoamer content were manipulated as the experimental variables. The peculiarity of this study is to obtain a high early-age strength by using the portland cement and alumina cement with the ratio of 8 : 2. Until 7 days of age, the drying shrinkage remarkably increased up to 1~2×10^-4, while it tended to decrease as the ratio of polymer to cement ratio and the content of shrinkage-reducing agent increased. Polymer-cement ratio was effective in improving the flexural, tensile and adhesive strengths: As the ratio increased, the strengths correspondingly increased. The flexural strength was in the range of 7~11MPa, the tensile strength was 3.5~5MPa and the adhesive strength was 1.2~3.9MPa. On the other hand, the compressive strength tended to decrease as the polymer-cement ratio increased, and it was in the range of 23~39MPa. All strengths, flexural, tensile, adhesive and compressive strengths, decreased as the content of powder shrinkage-reducing agent increased. It turned out that the polymer-cement ratio influenced more on the behavior of drying shrinkage and the properties of strength than the powder shrinkage-reducing agent did.

조진구 Cho Jin Goo , 박진환 Park Jin Hwan

DOI: JKWST Vol.48(No.1) 61-68, 2006

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The p-version nonlinear finite element model has been developed to analyze the nonlinear behavior of simply supported RC slabs strengthened with carbon fiber reinforced plastic sheets. The shape function is adopted with integral of Legendre polynomials. The compression model of concrete is based on the Kupfer's yield criterion, hardening rule, and crushing condition. The cracking behavior is modeled by a smeared crack model. In this study, the fixed crack approach is adopted as being geometrically fixed in direction once generated. Each steel layer has a uniaxial behavior resisting only the axial force in the bar direction. Identical behavior is assumed for tension and compression of steel according to the elastic modulus. The carbon fiber reinforced plastic sheets are considered as reinforced layers of equivalent thickness with uniaxial strength and rigidity properties in the present model. It is shown that the proposed model is able to adequately predicte the displacement and ultimate load of nonlinear simply supported RC slabs by a patch with respect to reinforcement ratio, thickness and angles of CFRP sheets.

김웅구 Kim Woong Ku , 장병욱 Chang Pyoung Wuck , 차경섭 Cha Kyung Seob

DOI: JKWST Vol.48(No.1) 71-79, 2006

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In Korea, most landslides occurred during the rainy season and had a shallow failure plane parallel to the slope. For these types of rainfall-induced failures, the most important factor triggering slope unstability is decrease in the matric suction of unsaturated soils with increasing saturation depth by rainfall infiltration. The saturation depth was readily estimated using modified Green-Ampt model proposed by Chu et al. (Chu Model) at present. But Chu Model involves some problems for application, because water-redistribution phenomena were not reflected. So the modified Chu Model (MCGAM) which reflect water redistribution pheno mena was developed. The results showed that the MCGAM had a better agreement with measured volumetric water contents than existing Chu Model.

이행우 Lee Haeng Woo , 장병욱 Chang Pyoung Wuck , 송창섭 Song Chang Seob , 원정윤 Won Jeong Yun

DOI: JKWST Vol.48(No.1) 81-88, 2006

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Numerical analyses were carried out for studying on seepage problems due to seawater intrusion through the embedded rock layers of the sea-dike. A seepage analysis model, SAMTLE was developed for two-layer embankment system. The analyses by SAMTLE showed that the size of embedded rock layer had a significant effect on the seepage problems of sea-dike. If the embedded rock layer is longer and thicker, the seepage problems become more serious to water head, seepage rate and safety factor of piping in embankment. On the other hand, if the width of embedded rock layer is equivalent to the sea-dike's bottom width, the water head becomes lower and seepage rate and safety factor of piping are dramatically increasing. This makes another seepage problems such that the fresh water becomes saltier and higher seepage rates result in internal erosion of sea-dike.

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

DOI: JKWST Vol.48(No.1) 91-102, 2006

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Most projects of tideland reclamation with dike construction produce estuarine reservoirs, which may result in water quality problems due to blocking of natural flow of stream water to the sea. External loadings to the reservoirs through tributaries are major concerns in a concerned water quality management. The water quality of a reservoir is greatly influenced by watershed drainage, and accurate estimation of pollutant is indispensable for in the reservoir management. Concentrations of the microorganisms in stream water and conventional parameters were monitored in the 13 water quality monitoring sites located in a rural watershed of Hwaong estuarine reservoir. The indicator of microorganisms showed strong correlation between them, and regression equations with R²≥0.70 may be used for estimating one from other microorganisms. The relationships between water quality parameters obtained in this study may be used to infer one unknown pollutant concentrations from the measured pollutant loadings. This methodology could be applied to other areas where the watershed characteristics are not significantly different from the study area. High concentrations of nitrogen was observed in water quality monitoring sites affected by urban land uses and numbers of livestock in wet day as well as dry day, due to the influent of diffuse sources.