• Korean Journal of Remote Sensing
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• v.32 no.4
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• pp.383-401
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• 2016

In this paper, we described the statistical modeling of crop yields using satellite images, climatic datasets, soil property maps, and fertilizer data for the Midwestern United States during 2001-2012. Satellite images were obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS), and climatic datasets were provided by the Parameter-elevation Regressions on Independent Slopes Model (PRISM) Climate Group. Soil property maps were derived from the Harmonized World Soil Database (HWSD). Our multivariate regression models produced quite good prediction accuracies, with differences of approximately 8-15% from the governmental statistics of corn and soybean yields. The unfavorable conditions of climate and vegetation in 2012 could have resulted in a decrease in yields according to the regression models, but the actual yields were greater than predicted. It can be interpreted that factors other than climate, vegetation, soil, and fertilizer may be involved in the negative biases. Also, we found that soybean yield was more affected by minimum temperature conditions while corn yield was more associated with photosynthetic activities. These two crops can have different potential impacts regarding climate change, and it is important to quantify the degree of the crop sensitivities to climatic variations to help adaptation by humans. Considering the yield decreases during the drought event, we can assume that climatic effect may be stronger than human adaptive capacity. Thus, further studies are demanded particularly by enhancing the data regarding human activities such as tillage, fertilization, irrigation, and comprehensive agricultural technologies.

• Proceedings of the Korean Society of Crop Science Conference
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• 2019.09a
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• pp.19-19
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• 2019

It is necessary to maintain stable crop productions under the unsuitable environments, because the drought and flood may be frequently caused by the global warming. Therefore, it is agent to improve the crop growth model corresponded to soil moisture status. Chili pepper (Capsicum annuum) is one of the useful crop in Asia, and then it is affected by change of precipitation in consequence drought and flood occur however crop model to evaluate water stresses on chili pepper is not enough yet. In this study, development of crop model under different soil moisture status was attempted. The experiment was conducted on the slope fields in the greenhouse. The water level was kept at 20cm above the bottom of the container. Habanero (C. chinense) was used as material for crop model. Sap bleeding rate, SPAD value, chlorophyll content, stomatal conductance, leaf water potential, plant height, leaf area and shoot dry weight were measured at 10 days after treatment (DAT) and 13 DAT. Moreover, temperature and RH in the greenhouse, soil volume water contents (VWC) and soil water potential were measured. As a result, VWC showed 4.0% at the driest plot and 31.4% at the wettest plot at 13 DAT. The growth model was calculated using WVC and the growth analysis parameters. It was considered available, because its coefficient of determination showed 0.84 and there are significant relationship based on plants physiology among the parameters and the changes over time. Furthermore, we analyzed the important factors for higher accuracy prediction using multiple regression analysis.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.4
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• pp.456-462
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• 2014

Infrared(IR) guided heat-seeking missiles uses IR emissions from aircraft to detect and track a target. Due to passive characteristic of the IR guidance, early detection of the missile is difficult and it is significant threat to aircraft survivability. Therefore, IR signature prediction of the aircraft is an important aspect of the stealth technology. In this study, we simulated IR signature of the aircraft in real atmospheric conditions. Aircraft surface temperature distribution was calculated by using RadthermIR code. Based on temperature distribution, IR radiance and BRDF(Bidirectional Reflectance Distribution Function) image were simulated for different weather(seasonal) and background(sky/soil) conditions. The IR contrast tendencies are not aligned with surface temperature or magnitude of target IR radiance. Therefore, it is essential to simulate IR signature with various conditions and background to acquire reliable database.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.3
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• pp.360-369
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• 2012

Parent material, climate, topography, biological factors, and time are considered five soil forming factors. This study was conducted to elucidate the effects of several environment factors on soil distribution using quantitative analysis method, called soil series estimation algorithm in the soils of Jeju Island. We selected environment factors including mean temperature, annual precipitation, surface geology, altitude, slope, aspect, altitude difference within 1 $km^2$ area, topographic wetness index, distance from the shore, distance from the mountain peak, and landuse for a quantitative analysis. We analyzed the ranges of environment factors for each soil series and calculated probabilities of possible-soil series for certain locations using estimation algorithm. The algorithm can predicted exact soil series on the soil map with correctness of 33% on $1^{st}$ ranking, 62% within $2^{nd}$ ranking, 74% within $5^{th}$ ranking after estimating using randomly extracted environment factors. In predicted soil map, soil sequences of Entisols-Alfisols-Andisols on northern area and Alfisols-Ultisols-Andisols on western area can be suggested along increasing altitude. More modeling studies will be needed for the genesis process of soils in Jeju Island.

• Proceedings of the Korean Reliability Society Conference
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• 2005.06a
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• pp.69-73
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• 2005

The failure of geogrids used for soil reinforcement application can be defined as an excessive creep strain which causes the collapse of slopes and embankments. Accordingly, the lifetime is evaluated as a time to reach the excessive creep strain using two accelerated creep testing methods, time-temperature superposition(TTS) and stepped isothermal methods(SIM). TTS is a well-accepted acceleration method to evaluate creep behavior of polymeric materials, while SIM was developed in the last ten years mainly to shorten testing time and minimize the uncertainty associated with inherent variability of multi-specimen tests. The SIM test is usually performed using single rib of geogrids for temperature steps of $14^{\circ}C$ and a dwell time of 10,000 seconds. However, for multi-ribs of geogrids, the applicability of the SIM has not been well established. In this study, the creep behaviors are evaluated using multi-ribs of polyester geogrids using SIM and TTS creep procedures and the newly designed test equipment. Then the lifetime of geogrids are predicted by analyzing the failure times to reach the excessive creep strains through reliability analysis.

• Journal of the Korean Geosynthetics Society
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• v.12 no.1
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• pp.93-100
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• 2013

Frost heave occurs when ground temperature decreases under $0^{\circ}C$ and soil volume expands, which causes roadway and buried pipe line failure due to differential heaving. There are several models to predict volumetric strain caused by frost heave, but they requires expertises who have professional background and experience related to numerical analysis. This study presents an evaluation method to predict volumetric strain caused by frost heave with fundamental physical properties of soils. The evaluation method is assessed with experimental results.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.439-439
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• 2015

The temporal and spatial relationship of the weather elements such as rainfall and temperature is closely linked to the streamflow simulation, especially, to the flood forecasting problems. For the study area, Imjin river basin, which has the specific characteristics in geography with river cross operation between North and South Korea, the meteorological information in the northern area is totally deficiency, lead to the inaccuracy of streamflow estimation. In the paper, this problem is solved by using the combination of global (such as soil moisture content, land use) and local hydrologic components data such as weather data (precipitation, evapotranspiration, humidity, etc.) for the model-driven runoff (surface flow, lateral flow and groundwater flow) data in each subbasin. To compute the streamflow in Imjin river basin, this study is applied the hydrologic model SURR (Sejong Univ. Rainfall-Runoff) which is the continuous rainfall-runoff model used physical foundations, originally based on Storage Function Model (SFM) to simulate the intercourse of the soil properties, weather factors and flow value. The result indicates the spatial variation in the runoff response of the different subbasins influenced by the input data. The dependancy of runoff simulation accuracy depending on the qualities of input data and model parameters is suggested in this study. The southern region with the dense of gauges and the adequate data shows the good results of the simulated discharge. Eventually, the application of SURR model in Imjin riverbasin gives the accurate consequence in simulation, and become the subsequent runoff for prediction in the future process.

• Journal of the Korea Concrete Institute
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• v.15 no.5
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• pp.759-767
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• 2003

This paper presents the simplified but more rational analysis method for the prediction of additional internal forces induced in integral abutment bridges. These internal forces depend upon the degree of restraint provided tc the deck by the backfill soil adjacent to the abutments and piles. In addition, effect of the relative flexural stiffness ratio among pile foundations, abutment, and superstructure on the structural behavior is also an important factor. The first part of the paper develops the stiffness matrices, written in terms of the soil stiffness, for the lateral and rotational restraints provided by the backfill soil adjacent to the abutment. The finite difference analysis is conducted and it is confirmed that the results are agreed well with the predictions obtained by the proposed method. The simplified spring model is used in the parametric study on the behavior of simple span and multi-span continuous integral abutment PSC beam bridges in which the abutment height and the flexural rigidity of piles are varied. These results are compared with those obtained by loading Rankine passive earth pressure according to the conventional method. From the results of parametric study, it was shown that the abutment height, the relative flexural rigidity of superstructure and piles, and the earth pressure induced by temperature change greatly affect the overall structural response of the bridge system. It may be possible to obtain more rational and economical designs for integral abutment bridges by the proposed method.

• Journal of Korean Society of Forest Science
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• v.99 no.2
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• pp.163-171
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• 2010

Forest fires have potentials to change the structure and function of forest ecosystems and significantly influence on atmosphere and biogeochemical cycles. Forest fire also affects the quality of public benefits such as carbon sequestration, soil fertility, grazing value, biodiversity, or tourism. The prediction of fire occurrence and its spread is critical to the forest managers for allocating resources and developing the forest fire danger rating system. Most of fires were human-caused fires in Korea, but meteorological factors are also big contributors to fire behaviors and its spread. Thus, meteorological factors as well as social factors were considered in the fire danger rating systems. A total of 298 forest fires occurred during the fall season from 2002 to 2006 in South Korea were considered for developing a logistic model of forest fire occurrence. The results of statistical analysis show that only effective humidity and temperature significantly affected the logistic models (p<0.05). The results of ROC curve analysis showed that the probability of randomly selected fires ranges from 0.739 to 0.876, which represent a relatively high accuracy of the developed model. These findings would be necessary for the policy makers in South Korea for the prevention of forest fires.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.284-288
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• 2012

토양온도는 기후변화, 지역기상모형, 수생태 영향과 밀접한 상관성을 가지고 있으며 이에 대한 연구들이 활발하게 진행 중에 있다. 특히 기후는 토양의 분포와 성장, 그리고 소멸에 영향을 미치고, 식생은 증산과정에 의해 대기로 수분을 내보내는 과정을 통해 기후에 영향을 미치고 있다. 이 때, 지표면의 토양온도는 토양수분 및 식생의 성장에 영향을 미치게 된다. 이에 본 연구에서는 격자기반 일 지표면 토양온도 모형이 제안되며, 이를 이용하여 한반도 남동쪽에 위치한 낙동강 유역 내 안동댐 상류지역에 대한 지표면 토양온도가 모의된다. 제안된 모형의 구동을 위해 필요한 입력 자료는 일평균기온 및 관측 NDVI 자료이다. 전국 60개 지점에서 관측된 일 평균기온은 고도가 고려된 Krignig기법을 이용하여 격자별로 구축되며, NDVI 및 지표면 토양온도를 위한 위성자료는 적절한 전처리 과정을 거쳐 자료를 구축한다. 전반적으로 모의된 일 지표면 토양온도는 관측 자료를 잘 재현하고 있는 것으로 분석된다. 추가적으로 감쇠율을 적용하여 토양온도를 토양깊이에 따라 예측하는 방법이 제안되며, 토양깊이에 따라 토양온도가 감소하는 경향을 살펴볼 수 있을 것이다. 이상과 같이 본 연구에서 제안된 모형은 추후 하천수온예측 및 격자기반의 수문모형의 구성을 위한 기초자료를 제공할 것으로 기대된다. 더 나아가 본 연구는 기후-토양-식생의 관계를 바탕으로 미래기후에 대한 물 환경 영향을 평가하는데 있어서 기여할 수 있을 것으로 판단된다.