• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.93-93
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• 2020

미래 기후변화로 인해 집중 호우, 가뭄의 발생 빈도가 증가하고, 물 부족, 수질 오염 등으로 인해 합리적인 수자원 계획 및 관리의 중요성이 증가하고 있다. 기후변화는 유역간 물 이동량 뿐만 아니라 유역의 하천 유량 및 수질에 영향을 미치기 때문에, 물 이동량이 많은 유역에서는 기후변화 시나리오를 고려한 하천 유량 및 수질 변화를 정량적으로 평가해야 한다. 만경강 유역(1,602 ㎢)은 하류 지역에 비옥한 평야가 분포되어 있어 농업이 발달한 유역이나, 유역 내 가용 용수가 부족하여 인근에 위치한 금강 용담댐의 발전용수를 공급받아 사용하고 있다. 발달된 농경지로부터 발생되는 비점오염, 축산 점오염원으로 인한 수질 문제가 심각할 뿐만 아니라, 만경강의 수질은 궁극적으로 새만금호에 영향을 미치기 때문에 더욱 엄격한 관리가 필요하다. 따라서, 본 연구에서는 유역간 물이동량, 취수량 등을 고려하여 Soil and Water Assessment Tool(SWAT) 모형을 구축하였다. 2개의 수위-유량 관측소의 일자료와 2개의 수질관측소 월자료를 이용하여 보정(2012~2014) 및 검증(2016~2018)을 수행한 결과 유출량의 평균 Nash-Sutcliffe model Efficiency (NSE)는 0.49 ~ 0.51, SS, T-N, 그리고 T-P에 대한 평균 결정계수(Coefficient of determination, R²)는 0.73, 0.78, 0.72였다. 미래 기후변화에 따른 유역의 수문 및 수질 변화 분석을 위해 증발산량 산정이 가능한 RCP 8.5 기후변화 시나리오에 STARDEX를 활용하여 가장 습윤한 시나리오 및 가장 건조한 기후변화 시나리오를 각각 1개를 선정할 것이다. 선정된 시나리오를 구축된 SWAT 모형에 적용하여 미래 유역간 물이동이 유역의 하천 유량 및 수질에 미치는 영향을 미래 평가기간(S1:2011~2040, S2:2041~2070, S3:2071~2100)으로 구분하여 분석할 것이다.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.315-315
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• 2020

기후변화로 인하여 전 세계적으로 이상기후가 진행되고 있다. 우리나라의 경우 홍수와 가뭄 등의 이상 강수가 빈번히 발생하고 있으며, 이로 인한 비점오염물질의 유출과 집적이 발생하고 있다. SWAT (Soil and Water Assessment Tool)과 HSPF (Hydrological Simulation Program)등의 다양한 모델이 비점오염의 유출을 모의하기 위하여 활용되고 있으나, 농장 단위에서 유역 단위까지 다양한 대상지역에 대한 장기 모의와 BMP적용에 따른 효율평가가 어려운 실정이다. Texas A&M Agrilife Research에서 개발한 APEX(Agricultural Policy Environmental eXtender model) 모형의 경우, 농장 단위에서 유역 단위의 대상지역에 대하여 최대 100년까지 일단위 모의가 가능한 특징이 있다. 하지만 APEX 모형은 개발된지 상당한 시간이 지났으며, 데스크탑 기반의 모형이므로 다양한 플랫폼에서의 활용이 어려운 한계점이 있다. 따라서 본 연구에서는 1. 기존 데스크탑 기반의 APEX 모형을 웹에서 구동할 수 있도록 웹 기반 시스템을 구축하였으며, 2. 양분유출에 대한 모의 평가가 가능하도록 결과를 시스템화하는 모듈을 추가하였다. 또한, 3. 웹 기반 APEX 모형의 활용도를 위하여 최적관리기법을 적용할 수 있는 모듈을 개발 및 추가하였다. 본 연구의 결과는 향후 농업비점오염원 지역의 양분유출을 확인·예측하고 관리하기 위한 기초자료로 활용될 것으로 기대하며, 최적관리기법을 활용한 저감 정책을 수립하기 위한 평가도구로 활용될 수 있을 것이다. 또한, 기존 데스크탑 기반의 모형을 웹 기반으로 이전하였으므로, APEX 모형 혹은 다른 데스크탑 기반 모형들의 웹 이전을 통한 사용자 편의성 증대를 위한 기초자료로 활용될 수 있을 것이다. 아울러 본 연구의 결과는 APEX 모형의 작물 매개변수가 국내 환경에 최적화 되어있지 않으므로 정확한 BMP 저감효과 모의에는 한계가 있으므로, 이에 대한 추가적인 연구가 필요할 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.401-401
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• 2021

최근 급격한 기후변화로 인한 기온, 강수량 등의 시·공간적 변화는 홍수, 가뭄 등과 같은 자연재해의 빈도와 규모를 증가시키고 있다. 특히 한강수계 주요 하천에서는 급격한 도시화 및 산업화로 인한 물 수요의 증가와 기후변화로 인한 강수량 감소 그리고 하천변 시설에서의 과다한 지하수 이용으로 인해 지하수위 변동이 발생하고 있다. 2017년 국가 지하수관측연보 및 지하수조사연보에 따르면 한강수계에 위치한 전체 569개 관정 중 암반층 관정과 충적층 관정의 최근 5년간 지하수위 평균 변동폭은 각각 3.91 m, 2.73 m로 조사되었으며, 10년 이상 장기관측 자료를 보유한 430개소 관정 중 228개소 관정에서 지하수위 하강 추세를 보이는 것으로 조사된 바 있다. 이처럼 강우나 하천수위 등 자연적인 원인과 양수, 유출 등 인위적인 원인에 의해 발생하는 지하수위의 하강은 지반 침하의 주요 원인이 되며, 하천 기저유출의 변화에도 큰 영향을 미치고 있다. 기저유출은 하천으로 단기 유출되는 지하수로 평수기 및 갈수기 하천 유량의 대부분을 차지하고 있기 때문에 건기시 하천 수질과 수생태계 관리에 있어 매우 중요한 요소에 해당된다. 따라서, 기후변화에 의한 이상가뭄 발생 등을 대비하기 위한 비상용수 또는 대체수자원으로서의 지하수 개발수요가 증가하는 추세에 따라 기저유량 확보 및 수질 개선 방안을 수립하는 것은 지속가능한 수자원 이용·관리 측면에 있어서 매우 중요하다. 현재 활용되는 SWAT(Soil and Water Assessment Tool)과 HSPF(Hydrological Simulation Program Fortran) 수문모형의 경우 지표유출 모의에 있어서 다양하게 활용되고 있으나 기저유량의 특성을 고려하기 위해서는 지표하 수문거동 모의가 어렵다는 한계가 있다. 또한 지표하 수문거동 모의가 가능한 MODFLOW의 경우 지표유출을 모의하기 어려운 한계가 있다. 이를 극복하기 위하여 SWAT-MODFLOW 모형이 개발되었으며, 본 연구에서는 SWAT-MODFLOW 모형을 활용하여 신둔천 유역을 대상으로 유량 및 지하수위 모의결과를 검보정하여 기저유량을 산정하고 변동특성을 분석하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3B
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• pp.233-240
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• 2006

One of the main factor that effects on the CN's value in SCS Curve Number method for the estimation of direct runoff is the antecedent soil moisture condition (AMC). It is also common to use the AMC-III in hydrologic practice, which provides the largest runoff as possible. In this paper, AMC defending on the rainfall characteristics is analyzed using daily rainfall data at rainy season (June~September) of the Seoul station from 1961 to 2002. The probability mass function of AMC is also investigated to analyze the variation of AMC based on climate change, scenarios from several General Circulation Model (GCM) predictions. As a results we can find that the occurrence of AMC-I is reduced, and AMC-III is increased, whereas AMC-II does not change.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6C
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• pp.349-358
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• 2008

In performing the reliability analysis for predicting the settlement with time of alluvial clay layer at Kobe airport, the uncertainties of geotechnical properties were examined based on the stochastic and probabilistic theory. By using Terzaghi's consolidation theory as the objective function, the failure probability was normalized based on AFOSM method. As the result of reliability analysis, the occurrence probabilities for the cases of the target settlement of ${\pm}10%,\;{\pm}25%$ of the total settlement from the deterministic analysis were 30~50%, 60%~90%, respectively. Considering that the variation coefficients of input variable are almost similar as those of past researches, the acceptable error range of the total settlement would be expected in the range of 10% of the predicted total settlement. As the result of sensitivity analysis, the factors which affect significantly on the settlement analysis were the uncertainties of the compression coefficient Cc, the pre-consolidation stress Pc, and the prediction model employed. Accordingly, it is very important for the reliable prediction with high reliability to obtain reliable soil properties such as Cc and Pc by performing laboratory tests in which the in-situ stress and strain conditions are properly simulated.

• Computers and Concrete
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• v.32 no.1
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• pp.15-26
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• 2023

In order to study the anti-seismic performance of full light-weight concrete utility tunnel, EL Centro seismic waves were input, and the seismic simulation shaking table test was carried out on the four utility tunnel models. The dynamic characteristics and acceleration response of the system consisting of the utility tunnel structure and the soil, and the interlayer displacement response of the structure were analyzed. The influence law of different construction methods, haunch heights and concrete types on the dynamic response of the utility tunnel structure was studied. And the experimental results were compared with the finite element calculation results. The results indicated that with the increase of seismic wave intensity, the natural frequency of the utility tunnel structure system decreased and the damping ratio increased. The assembling composite construction method could be equivalent to replace the integral cast-in-place construction method. The haunch height of the assembling composite full light-weight concrete utility tunnel was increased from 30 mm to 50 mm to enhance the anti-seismic performance during large earthquakes. The anti-seismic performance of the full light-weight concrete utility tunnel was better than that of the ordinary concrete utility tunnel. The peak acceleration of the structure was reduced by 21.8% and the interlayer displacement was reduced by 45.8% by using full light-weight concrete. The finite element simulation results were in good agreement with the experimental results, which could provide reference for practical engineering design and application.

• Geomechanics and Engineering
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• v.35 no.6
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• pp.603-615
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• 2023

Population growth and urbanization prompted engineers to propose more sophisticated and efficient transportation methods, such as underground transit systems. However, due to limited urban space, it is necessary to construct these tunnels in close proximity to existing infrastructure like high-rise buildings and bridges. Battered piles have been widely used for their higher stiffness and bearing capacity compared to vertical piles, making them effective in resisting lateral loads from winds, soil pressures, and impacts. Considerable prior research has been concerned with understanding the vertical pile response to tunnel excavation. However, the three-dimensional effects of tunnelling on adjacent battered piled foundations are still not investigated. This study investigates the response of a single battered pile to tunnelling at three critical depths along the pile: near the pile shaft (S), next to the pile (T), and below the pile toe (B). An advanced hypoplastic model capable of capturing small strain stiffness is used to simulate clay behaviour. The computed results reveal that settlement and load transfer mechanisms along the battered pile, resulting from tunnelling, depend significantly on the tunnel's location relative the length of the pile. The largest settlement of the battered pile occurs in the case of T. Conversely, the greatest pile head deflection is caused by tunnelling near the pile shaft. The battered pile experiences "dragload" due to negative skin friction mobilization resulting from tunnel excavation in the case of S. The battered pile is susceptible to induced bending moments when tunnelling occurs near the pile shaft S whereas the magnitude of induced bending moment is minimal in the case of B.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1269-1276
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• 2023

Crop estimation is essential for the multinational meal and powerful demand due to its numerous aspects like soil, rain, climate, atmosphere, and their relations. The consequence of climate shift impacts the farming yield products. We operate the dataset with temperature, rainfall, humidity, etc. The current research focuses on feature selection with multifarious classifiers to assist farmers and agriculturalists. The crop yield estimation utilizing the feature selection approach is 96% accuracy. Feature selection affects a machine learning model's performance. Additionally, the performance of the current graph classifier accepts 81.5%. Eventually, the random forest regressor without feature selections owns 78% accuracy and the decision tree regressor without feature selections retains 67% accuracy. Our research merit is to reveal the experimental results of with and without feature selection significance for the proposed ten algorithms. These findings support learners and students in choosing the appropriate models for crop classification studies.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.6
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• pp.447-458
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• 2023

In this study, a comparison model considering the stochastic characteristics of the load and member resistance of the shield tunnel segment lining as well as the variability of the boundary condition was selected and reliability analysis was performed, and the adequacy of the limit state design was analyzed by calculating the probability of failure and reviewing the structural safety. For the analysis considering the probability characteristics of these ground constants, the ground spring coefficient was considered as the mean value by calculating the quantitative value by applying the Muirwood formula, and the coefficient of variation was selected based on the existing research data to review the models according to the change of ground boundary conditions. Through the structural analysis of these models and the reliability analysis using MCS technique, the failure probability and reliability index were calculated to examine the changes in the failure probability due to changes in ground boundary conditions.

• Animal Bioscience
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• v.37 no.7
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• pp.1196-1203
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• 2024

Objective: A study was conducted to quantify the performance differences of the near-infrared spectroscopy (NIRS) calibration models developed with different degrees of hay sample preparations. Methods: A total of 227 imported alfalfa (Medicago sativa L.) and another 360 imported timothy (Phleum pratense L.) hay samples were used to develop calibration models for nutrient value parameters such as moisture, neutral detergent fiber, acid detergent fiber, crude protein, and in vitro dry matter digestibility. Spectral data of hay samples prepared by milling into 1-mm particle size or unground were separately regressed against the wet chemistry results of the abovementioned parameters. Results: The performance of the developed NIRS calibration models was evaluated based on R², standard error, and ratio percentage deviation (RPD). The models developed with ground hay were more robust and accurate than those with unground hay based on calibration model performance indexes such as R² (coefficient of determination), standard error, and RPD. Although the R² of calibration models was mainly greater than 0.90 across the feed value indexes, the R² of cross-validations was much lower. The R² of cross-validation varies depending on feed value indexes, which ranged from 0.61 to 0.81 in alfalfa, and from 0.62 to 0.95 in timothy. Estimation of feed values in imported hay can be achievable by the calibrated NIRS. However, the NIRS calibration models must be improved by including a broader range of imported hay samples in the modeling. Conclusion: Although the analysis accuracy of NIRS was substantially higher when calibration models were developed with ground samples, less sample preparation will be more advantageous for achieving rapid delivery of hay sample analysis results. Therefore, further research warrants investigating the level of sample preparations compromising analysis accuracy by NIRS.