• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2019년도 학술발표회
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• pp.152-152
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• 2019

This study demonstrates a novel approach of remotely sensed estimates of stream flow at fifteen hydrological station in the Han River Basin, Korea. Multi-temporal data of the European Space Agency's Sentinel-1 SAR satellite from 19 January, 2015 to 25 August, 2018 is used to develop and validate the flow estimation model for each station. The flow estimation model is based on a power law relationship established between the remotely sensed surface area of water at a selected reach of the stream and the observed discharge. The satellite images were pre-processed for thermal noise, radiometric, speckle and terrain correction. The difference in SAR image brightness caused by the differences in SAR satellite look angle and atmospheric condition are corrected using the histogram matching technique. Selective area filtering is applied to identify the extent of the selected stream reach where the change in water surface area is highly sensitive to the change in stream discharge. Following this, an iterative procedure called the Optimum Threshold Classification Algorithm (OTC) is applied to the multi-temporal selective areas to extract a series of water surface areas. It is observed that the extracted water surface area and the stream discharge are related by the power law equation. A strong correlation coefficient ranging from 0.68 to 0.98 (mean=0.89) was observed for thirteen hydrological stations, while at two stations the relationship was highly affected by the hydraulic structures such as dam. It is further identified that the availability of remotely sensed data for a range of discharge conditions and the geometric properties of the selected stream reach such as the stream width and side slope influence the accuracy of the flow estimation model.

• 대한원격탐사학회지
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• 제40권3호
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• pp.257-268
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• 2024

Drone-mounted hyperspectral sensors (DHSs) have revolutionized remote sensing in agriculture by offering a cost-effective and flexible platform for high-resolution spectral data acquisition. Their ability to capture data at low altitudes minimizes atmospheric interference, enhancing their utility in agricultural monitoring and management. This study focused on addressing the challenges of radiometric and geometric distortions in preprocessing drone-acquired hyperspectral data. Radiometric correction, using the empirical line method (ELM) and spectral reference panels, effectively removed sensor noise and variations in solar irradiance, resulting in accurate surface reflectance values. Notably, the ELM correction improved reflectance for measured reference panels by 5-55%, resulting in a more uniform spectral profile across wavelengths, further validated by high correlations (0.97-0.99), despite minor deviations observed at specific wavelengths for some reflectors. Geometric correction, utilizing a rubber sheet transformation with ground control points, successfully rectified distortions caused by sensor orientation and flight path variations, ensuring accurate spatial representation within the image. The effectiveness of geometric correction was assessed using root mean square error(RMSE) analysis, revealing minimal errors in both east-west(0.00 to 0.081 m) and north-south directions(0.00 to 0.076 m).The overall position RMSE of 0.031 meters across 100 points demonstrates high geometric accuracy, exceeding industry standards. Additionally, image mosaicking was performed to create a comprehensive representation of the study area. These results demonstrate the effectiveness of the applied preprocessing techniques and highlight the potential of DHSs for precise crop health monitoring and management in smart agriculture. However, further research is needed to address challenges related to data dimensionality, sensor calibration, and reference data availability, as well as exploring alternative correction methods and evaluating their performance in diverse environmental conditions to enhance the robustness and applicability of hyperspectral data processing in agriculture.

• 한국지리정보학회지
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• 제9권2호
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• pp.159-172
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• 2006

본 연구에서는 광역지역에 대한 지표온도를 추출할 목적으로 대상지역에 대한 시계열 Landsat TM/ETM+영상을 획득하여 기하보정 및 방사보정을 실시하고 NASA모델을 이용하여 지표온도를 추출하였다. 그리고 대상지역에 대한 피복분류를 통하여 이에 따른 고유 방사율을 적용하는 1차 보정을 실시하는 한편, 기상청 기온자료와의 상관관계를 분석하여 보정식을 설정하고 영상으로부터 획득한 지표온도를 2차적으로 보정함으로써 영상을 이용한 지표온도 추출의 정확도를 향상시키고자 하였다. 그 결과, 1,2차 보정에 의해 획득한 지표온도는 기상청자료와 약 ${\pm}3.0^{\circ}C$의 평균편차내에서 보정된 지표온도를 획득할 수 있었다. 연구결과의 재검증을 위하여 다른 시기의 Landsat 영상에 적용함으로써 대상지역에 대한 지표온도를 비교적 높은 정확도로 획득할 수 있었다.

• Geomechanics and Engineering
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• 제34권2호
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• pp.187-195
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• 2023

Intensive rainfall during the summer season in Korea has triggered numerous devastating landslides outside of downtown in mountainous areas. The 2D slope stability analysis that is generally used for cut slopes and embankments is inadequate to model slope failure in mountainous areas. This paper presents a new 3D slope stability formulation using the global sliding vector in the limit equilibrium method, and it uses an ellipsoidal slip surface for static and quasi-static analyses. The slip surface's flexibility of the ellipsoid shape gives a lower FS than the spherical failure shape in the Fellenius, Bishop, and Janbu's simplified methods. The increasing sub-columns of each column tend to increase the FS and converge to a steady value. The symmetrical geometric conditions of the convex turning corners do not indicate symmetrical failure of the surface in 3D analysis. Pseudo-static analysis shows that the horizontal seismic force decreases the FS and increases the mass volume at the critical failure state. The stability index takes the FS and corresponding sliding mass into consideration to assess the potential risk of slope failure in complex mountainous terrain. It is a valuable parameter for selecting a vulnerable area and evaluating the overall risk of slope failure.

• 한국의류산업학회지
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• 제15권2호
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• pp.302-308
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• 2013

This study is a preliminary investigation of the influence of surface characteristics of substrates on detergency of particulate soil. The surface of PET film was modified with NaOH and NaOH+ethylene diamine on different times. The surface morphology of the film was scanned by AFM and surface energies were calculated from measured contact angles between several solutions and film based on the geometric mean and a Lewis acid base method. The surface morphology of PET film treated with NaOH and NaOH+ethylene diamine became more etched, and the surface area, surface roughness and the coefficient of friction of film increased with treatment of NaOH and NaOH+ethylene diamine. The contact angle of film treated with NaOH and NaOH+ethylene diamine decreased in water and surfactant solution; in addition, the surface energy increased was largely attributed to the increased portion on the polar surface energy of film. However, the effect of the diamine addition to the NaOH treatment solution on surface characteristics of PET film was insignificant.

• 한국의류학회지
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• 제34권11호
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• pp.1880-1888
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• 2010

This study was a preliminary investigation of the influence of surface characteristics of substrates on the detergency of particulate soil. A PET film was surface modified with NaOH and DMF for different times. The surface morphology of the film was scanned by AFM and the surface energies were calculated from the measured contact angles between several solutions and film based on a geometric mean and the Lewis acid base method. The surface morphology of the PET film treated with NaOH and DMF became more etched and swelled with an increased treatment time, respectively. The surface roughness and surface area of film treated with NaOH enlarged with increased treatment time. However, the coefficient of friction of film treated with NaOH and coefficient of friction, surface roughness, and surface area of film treated with DMF increased and then decreased with increased treatment time. The contact angle of film treated with DMF decreased with increased treatment time in water and surfactant solution; however, the effect of treatment time on the contact angle was different in both solutions for film treated with NaOH. By the treatment of PET film with NaOH and DMF, the polar group of the surface energy increased and the nonpolar group decreased; however, the change of total surface energy was not significant.

• 한국정밀공학회지
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• 제21권12호
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• pp.100-108
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• 2004

In reverse engineering, data acquisition methodology can generally be categorized into contacting and non-contacting types. Recently, researches on hybrid or sensor fusion of the two types have been increasing. In addition, efficient construction of a geometric model from the measurement data is required, where considerable amount of user interaction to classify and localize regions of interest is inevitable. Our research focuses on the classification of each bounded region into a pre-defined feature shape fer a hybrid measuring scheme, where the overall procedures are described as fellows. Firstly, the physical model is digitized by a non-contacting laser scanner which rapidly provides cloud-of-points data. Secondly, the overall digitized data are approximated to a z-map model. Each bounding curve of a region of interest (featured area) can be 1.aced out based on our previous research. Then each confined area is systematically classified into one of the pre-defined feature types such as floor, wall, strip or volume, followed by a more accurate measuring step via a contacting probe. Assigned to each feature is a specific digitizing path topology which may reflect its own geometric character. The research can play an important role in minimizing user interaction at the stage of digitizing path planning.

• 한국멀티미디어학회논문지
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• 제5권5호
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• pp.552-561
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• 2002

본 논문은 쾌속조형(rapid prototyping) 시스템에서 사용되며 3D 기하학적 형상을 가지는 STL 파일에 워터마크를 삽입하고 추출하는 방법에 관한 연구이다. 제안된 알고리즘은 3D 형상의 왜곡이 없도록 하기위해, 패싯의 법선 영역과 꼭지점 영역에 워터마크를 삽입한다. 워터마크 비트들은 법선의 위치와 꼭지점의 순서 정보를 이용하여 삽입된다 제안된 알고리즘은 패싯의 저장 순서에 대한 종속성이 없으며, 워터마크의 비가시성 (invisibility)을 충족한다. 제안된 알고리즘으로 3D 기하학적 형상에 워터마크를 삽입하고 추출하는 실험 결과들은 STL로 표현된 3D원형상에 영향을 주지 않고 워터마크의 삽입과 추출이 가능함을 보여준다.

• 농업과학연구
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• 제49권4호
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• pp.857-869
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• 2022

Eggs are considered an excellent complete food because they contain many major energy sources, including protein. Eggs are one of the most widely consumed foods worldwide, and egg consumption is steadily increasing. Eggs are generally classified according to their quality and weight. Various characteristics of eggs must be considered for the design and effective utilization of equipment used for the transport, processing, packaging, and storage of eggs. In this study, egg surface area, volume, density, etc. were measured according to the grade of the egg. The values of several geometrical properties that were measured tended to increase with increasing egg grade. The smallest grade eggs had the lowest shell thickness and density. The electrical conductivity of the eggshell and its contents was measured with a self-made electrode and equipment. The egg shell showed properties similar to insulators, and as the thickness increased, the electrical conductivity tended to increase. The electrical conductivity of the egg yolk showed almost constant values under all conditions. The electrical conductivity of the egg white and mixture was particularly low at 0.1 kHz. Fouling and electrode corrosion occurred in a low frequency region due to the egg white. In this study, various geometric and electrical characteristics of eggs were measured, and based on this, factors that could serve as new indicators for egg processed production were analyzed and investigated.

• 한국정밀공학회지
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• 제6권3호
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• pp.68-77
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• 1989

The surface rolling for cylindrical surface of a grey cast iron was carried out using a lathe with a simple newly-designed tool system. A surface rolling tool used was steel ball whose diameter was 3/8 inch (9.525mm) The effects of rolling feeds and number of rolling on surface rolling were investigated. The contact pressure between ball and workpiece which was considered as Hertz's contact problem was examined and the track of motion of a ball on the cylindrical surface of a work- piece was measured according to the rolling feed. The results obtained were as follows; 1. The roughness of the machined surface which was originally 5.3 .approx. 28 umRz decreased to 1.2 .approx. 5 umRz according to rolling feeds and numbers of rolling. 2. The hardness increased from Hv 260 to Hv 290 .approx. 310 through 2 .approx. 4 rollings according to the roughness of machined surfaces. 3. The reduction of diameter was found to be proportional to the variations of roughness of previous machined surfaces. About 60% to 90% of reduction in diameter was made during the first rolling process. 4. An equation relating the reduction of diameter and the variation of surface roughness after surface rolling was presented using a geometric surface model. 5. An equation for the calculation of dynamic contact area between pressure ball and workpiece according to the rolling feed was presented.