• 농업과학연구
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• 제47권2호
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• pp.381-394
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• 2020

Accelerated soil wind erosion still remains to date to cause severe economic and environmental impacts. Revised and updated models to quantitatively evaluate wind induced soil erosion have been made for specific factors in the wind erosion equation (WEQ) framework. Because of increasing quantities of accumulated data, the WEQ, the revised wind erosion equation (RWEQ), the wind erosion prediction system (WEPS), and other soil wind erosion models have been established. These soil wind erosion models provide essential knowledge about where and when wind erosion occurs although naturally, they are less accurate than the field-scale. The WEQ was a good empirical model for comparing the effects of various management practices on potential erosion before the RWEQ and the WEPS showed more realistic estimates of erosion using easily measured local soil and climatic variables as inputs. The significant relationship between the observed and predicted transport capacity and soil loss makes the RWEQ a suitable tool for a large scale prediction of the wind erosion potential. WEPS developed to replace the empirical WEQ can calculate soil loss on a daily basis, provide capability to handle nonuniform areas, and obtain predictions for specific areas of interest. However, the challenge of precisely estimating wind erosion at a specific regional scale still remains to date.

• 한국토양비료학회지
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• 제41권4호
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• pp.235-238
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• 2008

토양침식을 예측하는 WEPP(Water Erosion Prediction Project)모델은 연방 정부기관이 토양과 물 보전 및 환경을 계획하고 평가하는데 활용하고자 1985년 8월 차세대 물에 의한 토양침식을 예측하기 위해 만들어졌다. 미농무성 농업연구소에 의해 개발된 WEPP 모델은 경험적인 침식 예측을 위한 도구로써 침투, 유거수, 강우와 물에 의한 토양입자의 분리, 침전물의 이동, 퇴적, 작물의 생장 및 수확 후 잔여물의 분해 등을 포함한 토양 침식과 관련된 많은 중요한 물리적 과정을 모의한다. WEPP 모델은 모델을 구성하는 모듈의 입력자료와 모델을 시험하기 위해서 필요한 자료를 경작지, 초지, 산림 등 광대한 현장 실험 결과들로부터 얻었다. 미국내 여러 농업연구소와 협력 대학 등 수 많은 연구소의 큰 노력으로 모델을 만들 수 있었다. WEPP 모델은 경사지 혹은 작은 유역 규모에 적용이 가능하며, 물리적 모델이기 때문에 미국과 다른 여러 나라에서 중요한 자연자원을 효과적으로 평가할 수 있다. 최근 들어 DOS프로그램으로 만들어진 초기 WEPP모델을 윈도우 인터페이스와 GIS프로그램을 통합하여 향상시켰다. 또한, 바람과 물에 의한 침식을 통합 예측하는 시스템을 쉽게 이용할 수 있도록 구축 중에 있다.

• 한국환경농학회지
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• 제27권4호
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• pp.314-320
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• 2008

During the summer season, more than half of the annual precipitation in Korea occurs during the summer season due to the geographical location in the Asian monsoon belt. So, this causes severe soil erosion from croplands, which is directly linked to the deterioration of crop/land productivity and surface water quality. Therefore, much attention has been given to develop accurate estimation tools of soil erosion. The aim of this study is to assess the performance of using the empirical Universal Soil Loss Equation (USLE) and the physical-based model of the Water Erosion Prediction Project (WEPP) to quantify eroded amount of soil from agricultural fields. Input data files, including climate, soil, slope, and cropping management, were modified to fit into Korean conditions. Chuncheon (forest) and Jeonju (level-plain) were selected as two Korean cities with different topographic characteristics for model analysis. The results of this current study indicated that better soil erosion prediction can be achieved using the WEPP model since it has better power to illustrate a higher degree of spatial variability than USLE in topography, precipitation, soils, and crop management practices. These present findings are expected to contribute to the development of the environmental assessment program as well as the conservation of the agricultural environment in Korea.

• 한국전산유체공학회지
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• 제18권3호
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• pp.94-101
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• 2013

In the present study, a practical method to predict cavitation erosion, which caused a critical damage on hydraulic machineries, was developed. Impact and critical velocities were defined to develop a practical method for the prediction of cavitation erosion. To develope the practical method, the computational fluid dynamics (CFD) was introduced. Cavitating flows with erosion in a converging-diverging nozzle and around a hydrofoil were simulated by developed and validated code. Based on the CFD results, the cavitation erosion coefficient was derived by a curve fitting method. The cavitation erosion coefficient was formulated as the function of the cavitation and Reynolds numbers. A cavitating flow in an axisymmetric nozzle followed by radial divergence was simulated to validate the developed practical method. For the application to a propeller, a cavitating flow around a propeller was simulated. Predicted damage extent showed similar with damaged full-scale propeller blade.

• 항공우주시스템공학회지
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• 제14권2호
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• pp.50-56
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• 2020

In this study, we investigated whether long short-term memory (LSTM) can be used in the future to predict F10.7 index data; the F10.7 index is a space environment factor affecting atomic oxygen erosion. Based on this, we compared the prediction performances of LSTM, the Autoregressive integrated moving average (ARIMA) model (which is a traditional statistical prediction model), and the similar pattern searching method used for long-term prediction. The LSTM model yielded superior results compared to the other techniques in the prediction period starting from the max/min points, but presented inferior results in the prediction period including the inflection points. It was found that efficient learning was not achieved, owing to the lack of currently available learning data in the prediction period including the maximum points. To overcome this, we proposed a method to increase the size of the learning samples using the sunspot data and to upgrade the LSTM model.

• 한국산림과학회지
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• 제96권3호
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• pp.300-306
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• 2007

본 연구는 산지사면에 시공되어 있는 사방댐내의 퇴사량에 영향을 미치는 산림환경 및 하천형태학적 인자를 분석하고 수량화이론(I)을 이용하여 예방적인 측면에서 사방댐의 시공 적지를 선정하고 예측하였다. 각 인자의 category별 상대점수를 262개 사방댐의 각종 인자에 반응시켜 사방댐의 시공적지를 예측할 수 있는 판정표를 개발하였고 또한 판정표를 이용하여 시공적지를 I급지(Very suitable site), II급지(Suitable site), III급지(Poor suitable site)로 구분하였다. 따라서 각종 산지재해로부터 예방적인 차원의 사방사업인 사방댐을 건설하고자 할 때 객관적인 지표가 될 수 있는 판정표를 이용하여 시공에 따른 타당성과 시공적지를 예측함으로서 주관적 판단에 의한 불합리성과 시공 후 적지로 판정되지 못할 경우 발생하는 막대한 예산낭비를 막을 수 있고 사방댐에 의한 토사조절을 극대화함으로서 산지사면에서 발생하는 각종 재해에 대한 피해를 최소화할 수 있어 산림유역 관리에 많은 기여를 할 수 있을 것으로 사료된다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.1057-1058
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• 2012

• Corrosion Science and Technology
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• 제12권3호
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• pp.125-131
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• 2013

The most common pipe wall thinning degradation mechanisms that can occur in the steam and feedwater systems are FAC (Flow Acceleration Corrosion), cavitation, flashing, and LDIE (Liquid Droplet Impingement Erosion). Among those degradation mechanisms, FAC has been investigated by many laboratories and industries. Cavitation and flashing are also protected on the piping design phase. LDIE has mainly investigated in aviation industry and turbine blade manufactures. On the other hand, LDIE has been little studied in NPP (Nuclear Power Plant) industry. This paper presents the development of prediction system for pipe wall thinning caused by LDIE in terms of erosion rate based on air-water ratio and material. Experiment is conducted in 3 cases of air-water ratio 0.79, 1.00, and 1.72 using the three types of the materials of A106B, SS400, and A6061. The main control parameter is the air-water ratio which is defined as the volumetric ratio of water to air (0.79, 1.00, 1.72). The experiments were performed for 15 days, and the surface morphology and hardness of the materials were examined for every 5 days. Since the spraying velocity (v) of liquid droplets and their contact area ($A_c$) on specimens are changed according to the air-water ratio, we analyzed the behavior of LDIE for the materials. Finally, the prediction equations(i.e. erosion rate) for LDIE of the materials were determined in the range of the air-water ratio from 0 to 2%.

• 농업과학연구
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• 제47권4호
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• pp.803-814
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• 2020

Managing erosion control dams requires the annual average sediment yield to determine their storage capacity and time to full sediment-fill and dredging. The GeoWEPP (Geo-spatial interface for Water Erosion Prediction Project) model can predict the annual average sediment yield from various land uses and vegetation covers at a watershed scale. This study assessed the GeoWEPP to determine the annual average sediment yield for managing erosion control dams by applying it to five erosion control dams and comparing the results with field observations using ground-based LiDAR (light detection and ranging). The modeling results showed some differences with the observed sediment yields. Therefore, GeoWEPP is not recommended to determine the annual average sediment yield for erosion control dams. Moreover, when using the GeoWEPP, the following is recommended :1) use the US WEPP climate files with similar latitude, elevation and precipitation modified with monthly average climate data in Korea and 2) use soil files based on forest soil maps in Korea. These methods resulted in GeoWEPP predictions and field observations of 0 and 63.3 Mg·yr-1 for the Gangneung, 142.3 and 331.2 Mg·yr-1 for the Bonghwa landslide, 102.0 and 107.8 Mg·yr-1 for the Bonghwa control, 294.7 and 115.0 Mg·yr-1 for the Chilgok forest fire, and 0 and 15.0 Mg·yr-1 for the Chilgok control watersheds. Application of the GeoWEPP in Korea requires 1) building a climate database fit for the WEPP using the meteorological data from Korea and 2) performing further studies on soil and streamside erosion to determine accurate parameter values for Korea.

• Tribology and Lubricants
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• 제25권3호
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• pp.171-175
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• 2009

One of the critical issues associated with the 40mm long hollow cylinder's development and maintenance is the prediction of cylinder erosion. The actual firing test is the most accurate method to measure the cylinder erosion rate. But it costs a great deal and requires a long measurement time. Hence many empirical methods have been proposed to predict the erosion rate and life span of long hollow cylinders. An EFC formula is calculated. An approximate erosion formula for the ammunition type A is derived to interpolate 16 observation values up to 4,000 rounds. A new erosion equation and muzzle velocity formula are also suggested. Several numerical results are presented.