• 한국농림기상학회지
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• 제22권1호
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• pp.1-12
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• 2020

토양수분은 농업에서 필수적인 자원으로 이의 변화와 부족을 예측함으로써 관리되어왔다. 최근 현장에서의 적용 용이성과 다양한 지역에 대한 일반화 가능성이 뛰어난 통계 및 기계학습 알고리즘을 활용한 토양수분 예측 연구가 활발히 진행되고 있다. 하지만 국내에서 생성되는 데이터를 이용한 연구들은 부족한 실정이다. 이에 본 연구는 1) 국내 공공기상 데이터만으로 충분한 성능을 내는 토양수분 예측 모델을 만들 수 있는지, 2) 어떠한 기계학습 모델이 국내에서 생산되는 데이터와 토양환경에서 가장 높은 예측 성능을 보이는지, 3) 단일 기계학습 모델을 이용해 다양한 지역에 적용 가능한지를 확인해보려 한다. 본 연구에서 Support Vector Machines (SVM), Random Forest (RF), Extremely Randomized Trees (ET), Gradient Boosting Machines (GBM), and Deep Feedforward Network (DFN) 알고리즘과 종관기상관측 자료, 농업기상관측자료를 활용하여 안동, 보성, 철원, 순천 지역의 토양 수분을 예측하는 모델을 만들었다. 그 결과, GBM을 이용한 모델이 R² : 0.96, Root Mean Squared Error(RMSE) : 1.8로 가장 낮은 예측 오차를 보였다. 또한 GBM을 사용한 모델이 가장 낮은 지역간 예측 오차 분산을 보여 가장 일반화하기에 적절한 모델로 확인되었다.

• 한국잡초학회지
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• 제30권3호
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• pp.258-265
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• 2010

본 연구는 유기질 복합비료가 벼 재배 논에서 잡초 및 벼 생육에 미치는 영향을 파악하기 위하여 수행되었다. 실내 검정 시험에서 유기질 복합비료를 125~250kg $10a^{-1}$ 처리시 이앙벼는 지상부가 10.3~27.2% 증가하였고, 피는 50.3~89.2%의 출현이 억제되었으며, 사마귀풀은 낮은 처리량에서도 높은 감수성을 보였다. 유기질 복합비료는 피, 물달개비, 사마귀풀에 대하여 담수심(1~5cm)이 깊을수록 높게 억제하였으나, 올방개와 같은 사초과 잡초에 대해서는 억제 효과가 나타나지 않았다. 또 $20{\sim}35^{\circ}C$의 비교적 높은 온도에서 피와 물달개비는 각각 75.4~92.2%, 49.5~81.6%의 높은 출현억제율을 나타냈다. 유기질 복합비료 시용 10일 후 낙수 시 피와 물달개비는 각각 33.7%, 23.0%의 출현억제율을 나타내었다. 포장시험에서 시험 후 토양의 유기물은 관행구에서 유기질 복합비료 시용구보다 약간 낮게 나타났다. 벼의 생육은 초장 및 경수가 관행구 대비 적었으며 그 차이는 생육후기에 더 많이 나타났고, 벼의 수량은 관행구 대비 4% 감소하였다. 논잡초 억제 효과는 유기질 복합비료 시용구에서 60.5%로 관행구보다 낮게 나타났다.

• 대한토목학회논문집
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• 제34권5호
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• pp.1489-1504
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• 2014

본 논문은 국내 서남해안 해상풍력발전 하부기초설계 시 신뢰성 기반의 한계상태설계법 적용을 위한 말뚝기초의 부분안전계수를 제안하고자 한다. 우선, 해상풍력관련 국제 설계기준서인 IEC, GL, DNV, API, ISO, EUROCODE 등에서 제시한 다양한 부분안전계수 및 저항계수를 비교 분석하였다. 그리고 부안-영광 및 새만금 해역의 서남해안 해상풍력단지의 지반조사 결과를 가지고 불확실성 분석을 수행하였다. 불확실성 분석 결과를 토대로 신뢰성해석을 수행하여 지반정수에 대한 부분안전계수를 산정하였으며, 서남해안 지역의 해상풍력 말뚝기초의 부분안전계수는 1.3으로 평가되었다. 본 논문에서 제안된 부분안전계수는 서남해안에서의 지반조사 결과를 근거로 산정된 것이므로 기타 광역단위 해역에 활용하기 위해서는 추가적인 조사 및 지반정수에 대한 불확실성 분석을 통해 보정이 필요하다고 판단된다.

• 한국환경농학회지
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• 제28권4호
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• pp.378-385
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• 2009

Arsenic (As) is known to be very toxic and carcinogenic to human beings. Arsenic contaminated soil was collected from a timber mill site at Busan Metropolitan City, Korea, where chromated copper arsenate (CCA) had been used to protect wood from rotting caused by insects and microbial agents. The soil was stabilized using both natural oyster shells (NOS) and calcinated oyster shells (POS). The calcination of natural oyster shells was accomplished at a high temperature in order to activate quicklime from calcite. Two different oyster shell particle sizes (-#10 mesh and -#20 mesh) and curing periods of up to 28 days were investigated. The stabilization effectiveness was evaluated based on the Korean Standard Test (KST) method (1N HCl extraction). The stabilization results showed that the POS treatment was more effective than the NOS treatment at immobilizing the As in the contaminated soils. A significant As reduction (96%) was attained upon a POS treatment at 20 wt% and passed the Korean warning standard of 20 mg/kg ('Na' area). However, an As reduction of only 47% (169 mg/kg) was achieved upon a NOS treatment at 20 wt%. The -#20 mesh oyster shells seem to perform better than the -#10 materials. The scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDX) results showed that As immobilization was strongly associated with Ca and O in the presence of Al and Si.

• Structural Engineering and Mechanics
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• 제52권6호
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• pp.1069-1084
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• 2014

The long-term performance of plates resting on viscoelastic foundations is a major concern in the analysis of soil-structure interaction. As a powerful mathematical tool, fractional calculus may address these plate-on-foundation problems. In this paper, a fractionalized Zener model is proposed to study the time-dependent behavior of a uniformly loaded rectangular thin foundation plate. By use of the viscoelastic-elastic correspondence principle and the Laplace transforms, the analytical solutions were obtained in terms of the Mittag-Leffler function. Through the analysis of a numerical example, the calculated plate deflection, bending moment and foundation reaction were compared to those from ideal elastic and standard viscoelastic models. It is found that the upper and lower bound solutions of the plate response estimated by the proposed model can be determined using the elastic model. Based on a parametric study, the impacts of model parameters on the long-term performance of a foundation plate were systematically investigated. The results show that the two spring stiffnesses govern the upper and lower bound solutions of the plate response. By varying the values of the fractional differential order and the coefficient of viscosity, the time-dependent behavior of a foundation plate can be accurately captured. The fractional differential order seems to be dependent on the mechanical properties of the ground soil. A sandy foundation will have a small fractional differential order while in order to simulate the creeping of clay foundation, a larger fractional differential order value is needed. The fractionalized Zener model is capable of accounting for the primary and secondary consolidation processes of the foundation soil and can be used to predict the plate performance over many decades of time.

• Structural Engineering and Mechanics
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• 제61권4호
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• pp.527-538
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• 2017

The evaluation of the loss-of-support conditions of frictional beam-to-column connections using simplified numerical models describing the transverse response of a portal-like structure is presented in this paper considering the effects of the seismic-hazard disaggregation. Real earthquake time histories selected from European Strong-motion Database (ESD) are used to show the effects of the seismic-hazard disaggregation on the beam loss-of-support conditions. Seismic events are classified according to different values of magnitudes, epicentral distances and soil conditions (stiff or soft soil) highlighting the importance of considering the characteristics of the seismic input in the assessment of the loss-of-support conditions of frictional beam-to-column connections. A rigid and an elastic model of a frame of a precast industrial building (2-DoF portal-like model) are presented and adopted to find the minimum required friction coefficient to avoid sliding. Then, the mean value of the minimum required friction coefficient with an epicentral distance bin of 10 km is calculated and fitted with a linear function depending on the logarithm of the epicentral distance. A complete parametric analysis varying the horizontal and vertical period of vibration of the structure is performed. Results show that the loss-of-support condition is strongly influenced by magnitude, epicentral distance and soil conditions determining the frequency content of the earthquake time histories and the correlation between the maxima of the horizontal and vertical components. Moreover, as expected, dynamic characteristics of the structure have also a strong influence. Finally, the effect of the column nonlinear behavior (i.e. formation of plastic hinges at the base) is analyzed showing that the connection and the column are a series system where the maximum force is limited by the element having the minimum strength. Two different longitudinal reinforcement ratios are analyzed demonstrating that the column strength variation changes the system response.

• 펄프종이기술
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• 제47권5호
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• pp.15-22
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• 2015

The crop production technologies keep in improving and the cultivation becomes more standardization owing to the significant developments of various agricultural materials. The artificial soil and base system for root could be one of the major technologies for the modern cultivation especially for controlled horticulture. Although the perlite, cocopeat, and peat moss are the major components of the artificial soil and are broadly used for various application, there is a great need for the new alternative materials for overcoming the low nutrition and the possible shortage of raw materials. In this study, the application of oil palm EFB fiber as an alternative materials for artificial soil especially for the seeding pad components was evaluated. The changes in the structural properties and the functional properties such as moisture holding properties were compared by laboratory produced seeding pads with different mixture of oil palm EFB fiber. The addition of fibrillated EFB fiber resulted in the significant increase in durability of the seeding pad, which showed the possible application of EFB fiber to the seeding pad instead of the wood fiber (UBKP). The moisture holding properties and the germination condition characteristics of the EFB fiber showed the slight less than those of the cocopeat, which require more sophisticated study for improving the functional properties of seeding pad made of the EFB fiber.

• 한국지반공학회논문집
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• 제27권1호
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• pp.87-97
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• 2011

본 연구에서는 산업 전분야에 걸쳐 다양하게 활용되고 있는 X-ray CT의 지반분야 적용을 위해 X-ray CT를 이용한 사질토의 간극비 측정에 관한 연구를 수행하였다. 이를 위해 고분해능 X-ray CT 시스템의 적용에 문제가 되는 빔하드닝(Beam hardening) 및 동심원상 화상결함(Ring artifact) 등에 대한 문제점 지적 및 해결방안을 제시하였다. 또한 X-ray CT를 이용한 간극비 산정을 위한 알고리즘 및 프로그램을 개발하였으며, 이를 이용하여 주문진 표준사의 간극비를 측정하여 신뢰성을 검토하였다.

• 한국터널지하공간학회 논문집
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• 제22권3호
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• pp.311-321
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• 2020

본 연구에서는 쉴드 터널 세그먼트 라이닝의 한계상태설계 시 세그먼트 라이닝에 작용하는 지진하중에 대한 변동계수를 산정하였다. 지반 정수의 통계적 특성치는 국내 지반의 확률특성치를 분석하여 단위중량에 대한 통계적 특성치를 산정하였으며, 전단탄성파 속도를 산정하기 위해 N값과 확률 특성치를 이용하였다. 지진하중 효과에 대한 변동계수를 산정하기 위하여 MCS기법을 적용하였으며, 지진하중 효과 산정에는 closed-form식을 적용하였다. 변동계수 산정결과, 풍화토 지반에서 지진하중 효과의 변동계수는 0.06~0.15의 범위로 분석되었고, 변동계수는 지진을 고려한 쉴드 터널의 한계상태설계 시 기본자료로 활용할 수 있을 것으로 판단된다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제17권1호
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• pp.13-21
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• 2012

This study reports a surfactant-enhanced in-situ remediation treatment at a test site which is located in a hilly terrain. The leakage oils from a storage tank situated on the top of the hill contaminated soils and groundwater in the lower elevation. Sixteen vertical injection wells (11 m deep) were installed at the top of the hill to introduce 0.1-0.5 vol.% of non-ionic Tween-80 surfactant. The contaminated area that required remediation treatment was about $1,650\;m^2$. Two cycles of injecting surfactant solution followed by water were repeated over approximately 7.5 months: first cycle with 0.5 month of surfactant injection followed by 3 months of water injection, and second cycle with 1 month of surfactant followed by 3 months of water injection. The seasonal fluctuation in groundwater table was also considered in the selection of periods for surfactant and water injection. The results showed that the initial Total Petroleum Hydrocarbon (TPH) concentration of 1,041 mg/kg (maximum 3,605 mg/kg) was reduced significantly down to 76.6 mg/kg in average. After 2nd surfactant injection process finished, average TPH concentration of soils was reduced to 7.5% compared to initial concentration. Also, average BTEX concentration of soils was reduced to 10.8%. This resultes show that the surfactant enhanced in-situ remediation processes can be applicable to LNAPL contaminated site in field scale.