• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.527-527
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• 2016

최근 급증하는 이상기후 등으로 인하여, 가뭄 및 홍수 등의 자연재해가 반복적으로 발생하는 등 수자원관리에 어려움이 증대되고 있다. 본 연구는 토양수분량, 강우량, 수위관측 및 증발산량 관측이 수행되고 있는 용담-구량천 유역을 대상으로, PDM 토양저류 함수 모형을 습윤(6월~9월) 및 건조(10월~5월)기로 분리 적용하여 기간에 따른 유역 유출 특성을 분석하였다. 습윤 및 건조기의 유출률(유량/총강우량)은 각각 0.61~0.65와 0.31~0.42으로 서로 다른 유출 특성을 나타내고 있다. 2014~2015년 유역의 관측 토양 수분 자료(심도 100~200mm)와 PDM 토양저류 함수를 활용한 모의 결과가 습윤기에서 유사한 경향성을 보이고 있다(R2=0.9). 이를 바탕으로 용담-구량천 유역의 토양 저류 및 유출 특성을 분석한 결과, 기간을 습윤기 및 건조기로 분리하여 각각의 유역 유출 모형을 구축하는 것이 필요하다고 판단된다. 향후 단기 홍수 사상의 분석을 통한 홍수 유출 및 토양 저류 분석을 위한 모형을 제시하고자 한다.

• Water for future
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• v.29 no.6
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• pp.179-188
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• 1996

The chronical sequences of daily precipitation are of great practical importance in the planning and operational processes of water resources system. A sequence of days with alternate dry day and wet day can be generated by two state Markov chain model that establish the subsequent daily state as wet or dry by previously calculated vconditional probabilities depending on the state of previous day. In this study, a synthetic generation model for obtaining the daily precipitation series is presented by classifying the precipitation amount in wet days into multi-states. To apply multi-state Markov chain model, the daily precipitation amounts for wet day are rearranged by grouping into thirty states with intervals for each state. Conditional probabilities as transition probability matrix are estimated from the computational scheme for stepping from the precipitation on one day to that on the following day. Statistical comparisons were made between the historical and synthesized chracteristics of daily precipitation series. From the results, it is shown that the proposed method is available to generate and simulate the daily precipitation series with fair accuracy and conserve the general statistical properties of historical precipitation series.

• Journal of the Korean Geotechnical Society
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• v.33 no.6
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• pp.37-48
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• 2017

Soil-water characteristic curve (SWCC) has been widely used to estimate the shear strength and coefficient of permeability for unsaturated soils. In general, it is divided into the drying path in which the water is discharged and the wetting path in which the water is permeated, and it has a hysteresis indicating different suctions at the same volumetric water content. In reality the field behavior of unsaturated soils is much closer to the wetting path during the infiltration. The drying path has been practically used for various analyses because obtaining the wetting path takes longer than the drying path. Although many approaches for estimating wetting path have been studied till now, these are complex and do not fit well. Therefore, a simple method for estimating wetting path based on empirical approach in this study is proposed in unsaturated soils, and a feasibility study is conducted as well.

• The Journal of Engineering Geology
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• v.28 no.1
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• pp.25-34
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• 2018

The physical properties and unsaturated characteristics of acid sulfate soils were investigated and analyzed. As the results of measuring physical properties of the acid sulfate soils obtained around the Ilkwang mine area, the dry unit weight is $1.246t/m^3$ and this soil is classified into the silty sand (SM) by USCS. Soil Water Characteristics Curves (SWCC) of the drying and wetting paths were measured by the automated SWCC apparatus. Also, Hydraulic Conductivity Functions (HCF) of the drying and wetting paths were estimated by the van Geunchten (1980) model which is the most well-known parameter estimation method. The hydraulic conductivity of acid sulfate soils in the dry path was continuously decreased with increasing the matric suction. However, the hydraulic conductivity in the wetting path was decreased relatively small with increasing matric suction and decreased suddenly just before water entry value of matric suction. Meanwhile, the hysteresis phenomenon was occurred in SWCCs and HCFs during the drying and wetting paths.

• Research in Plant Disease
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• v.24 no.2
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• pp.132-137
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• 2018

Melanose caused by Diaporthe citri is a serious disease on yuzu fruits. Moisture is the most important to infect after the pycnidiospores are released. In order to understand how dryness and moisture interruption affect on germination, the conidial suspensions on slide glass were dried for 0-48 h. For the moisture interruption experiment, moisture was supplied for 10 h then interrupted for 0-6 h depending on the treatments. Germinations on the treatments with longer than 15 h of dryness were less than 10%. And those with longer than 3 h of moisture interruption were less than 30%. Compared with other fungal phytopathogens, D. citri was xero-sensitive. Germination on yuzu feel medium was measured under 15, 20, 25, 30, $35^{\circ}C$ with 3, 6, 9, 12, 15, 18, and 24 h of wetness. The minimum wetness periods achieving 10% and 50% germinations were 4.5 and 13 h, and the optimum temperatures were $29.1^{\circ}C$ and $29.2^{\circ}C$, respectively. From the yuzu medium study, the regression equations to be required wetness period achieving 10% and 50% germinations on various temperatures were $Wh_{50%}=0.1093{\times}T^2-6.3762{\times}+106.08$ and $Wh_{10%}=0.082{\times}T^2-4.8025{\times}T+74.861$.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.411-411
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• 2023

미래 대기 이산화탄소 농도가 증가함에 따라 강수 등 기후의 변화하고, 이는 유출량을 포함한 수문 순환 뿐 아니라 지면 식생 생장에 영향을 줄 것으로 예상된다. 이에 본 연구에서는 미래 CO2 증가에 따른 식생의 변화와 이로 인한 지표 유출량의 변화에 대해 이해하고자 한다. Intergovernmental Panel on Climate Change (IPCC) 6차 평가보고서에서 제시한 표준 온실가스 경로 중 탄소 모듈이 포함된 Coupled Model Intercomparison Project phase 6 biogeochemistry (CMIP6-BGC) 모델과 탄소 모듈이 포함안된 CMIP6 모델 결과를 활용하였다. 공통 사회경제경로 시나리오(Shared Socio-economic Pathway; SSP) 중 고탄소 시나리오인 SSP585에 따른 모델 결과물을 활용하였다. 표면 유출량 자료에 과거 기간 임계수준 방법을 (Threshold Level Method) 적용하여 동아시아 지역 극한 건조 및 습윤 상태의 빈도와 강도를 CMIP6-BGC와 CMIP6에 대해 평가하였다. CMIP6-BGC 경우, 건조 및 습윤 상태의 빈도는 각각 6.17%, 5.03% , CMIP6 경우 각각 9.29%, 6.70% 으로 예측되어, CMIP6-BGC가 CMIP6 보다 극한 상태를 과소평가하는 경향을 보였다. 또한, 잎 면적 지수(Leaf Area Index; LAI), 증산량 등의 변수를 분석하여, 기 도출된 CMIP6-BGC와 CMIP6 간의 극한 건조 및 습윤 상태 예측의 차이가 발생한 메카니즘을 이해하고자 하였다.

• Journal of Sericultural and Entomological Science
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• v.14 no.1
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• pp.43-47
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• 1972

The tensile properties of cocoon filament obtained from the dried cocoon were studied by deniroscope and tensilon with special attachments. The strength and dried elongation at break feint with dry and swollen samples were observed. The apparent young's modulus was also calculated with the dry samples. The results obtained are as follows. 1) The breaking strength of dry and swollen samples decreased in parallel with denier decreasing ratio in the whole length of a cocoon filament. 2) Tensile strength of inner-layer filament, when treated at the temperature of 95$^{\circ}C$ for 15 min., was 37 per cent of outer-layer filament. 3) By swelling treatment, the breaking strength of the filament was decreased but the elongation was increased. 4) Apparent young's modulus and tensile strength per denier of inner-layer filament were higher than those of the rest cocoon layer.

• Water for future
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• v.21 no.2
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• pp.193-201
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• 1988

A simplified model for higher order scanning curves in the soil water characteristic function is suggested. The conceptual hysteresis models developed by $Mualem_{8,9}$ are simplied for higher order scanning curves. Higher order drying curves are regarded as primary drying curves and the last wetting reversal point is assumed to be on the main wetting curve by moving that point vertically downward. For the higher order wetting curves, it is assumed that these curves can be regarded as primary curves and the last wetting reversal point sits on the imaginary main drying curve which passes through the last wetting reversal point. The water content computed from the simplified model are compared with those obtained from Mualem's original model for second order scanning curves. It is found that absolute differences between the two methods aree relatively small and the simplified model always underestimates for higher order drying curves while it overestimates for higher order wetting curves. Hence, those two tend to compensate each other for repeated drying-wetting processes. The simplified model approximates higher order scanning curves well and reduces computation considerably.

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.27-37
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• 2001

본 연구에서는 지금까지 수행한 건조토 지반에 대한 말뚝의 수평거동 연구의 연속된 연구로서 지반내에 함수비가 존재하는 포화토 및 습윤토 지반에서의 수평거동에 대한 지반내 함수비의 영향성을 평가하고자 함이 목적이다. 말뚝의 수평거동을 고찰하기 위하여 각각 다른 함수비를 갖는 네 종류의 지반과 말뚝의 두부 및 선단 구속조건이 다른 네 종류의 말뚝조건으로 모형실험을 수행하였다. 본 연구에서 1회의 지하수 상승과 하강을 반복하는 모형실험결과에 의하면, 포화토와 습윤토 지반의 수평지지력은 건조토 지반에 비하여 각각 26%~45% 감소와 20%~36%정도 증가하는 것으로 나타났다. 말뚝두부 고정과 선단 자유조건의 경우, 동일 수평변위 1mm에서의 최대 휨모멘트는 건조토 지반에 비하여 25%의 함수비를 갖는 습윤토 지반에서 약 48% 증가하나, 34.06%의 함수비를 갖는 포화토 지반에서는 반대로 68% 감소하였다. 이는 지하수의 존재로 인한 입자간 인력에 의한 유효응력과 겉보기강도의 증가 그리고 단위중량의 증가로 설명할 수가 있다. 지속수평하중에 대한 수평변위와 최대 휨모멘트의 변화를 포화토 및 습윤토 지반에서 관찰할 수 있었다.

• Journal of Korea Water Resources Association
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• v.41 no.2
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• pp.173-184
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• 2008

Climatic water balance has been applied to obtain quantity of various hydrologic components. Hydrologic information is estimated by comparison between rainfall and evapotranspiration under complex terrain condition. Water deficit is defined as that subtraction of actual supply from climatic demand. The water deficit will occur, when monthly evapotranspiration exceed monthly rainfall. Contrary water surplus is defined as that surplus water after meeting the demand by plants. The water surplus will be occurred when monthly rainfall exceeds monthly evapotranspiration. Finally, the discrete moisture indices were calculated and mapped for the whole watershed to estimate dryness and wetness status using the climatic water balance approach. The result of this study can properly interpret the real drought and non drought. Based upon the results, it can be concluded that the climatic water balance model is useful to monitor water conditions for the watershed.