• Korean Journal of Remote Sensing
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• v.33 no.5_1
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• pp.537-546
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• 2017

This study aims to develop the floating debris detection algorithm using a Unmanned Aerial Vehicle (UAV) and multispectral sensors. In addition, the occurrence range of floating debris was estimated by applying the algorithm. An aerial photograph using an unmanned aerial vehicle was used to generate an orthoimage that can calculate the area. A spectrum survey of water, plants litter, polystyrene foam etc. was conducted. After obtaining spectroscopic characteristics of floating debris and water, the River Floating Debris (RFD) index was calculated. And we detected the floating debris through band combination of sensor using RFD. As a result of the RFD application, accumulation zone of floating debris was confirmed at three sites in the orthoimage. It was estimated that a lot of floating debris was accumulated at 0.82 ha ($8,200m^2$), which is corresponding to 3.6% including the accumulation zone.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.583-587
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• 2006

국부세굴의 발생은 일반적으로 흐름조건, 구조물 조건과 하상재료 세 가지의 주 원인으로 구분할 수 있다. 흐름조건의 경우 구조물 영향으로 발생되는 3차원적인 와류가 주요원인이며 하상재료의 경우 여러 요인이 있겠지만 비중이 같은 입자라 가정할 경우 입자의 크기를 주요 변수로 정할 수 있다. 교각 국부세굴에 관한 연구는 1960년대 이후 연구자들에 의해 매우 다양하게 수행되어 졌으며 많은 산정공식도 제시되었다. 하지만 기존 연구는 최대세굴심 조건으로 다양한 하상재료와 시간에 대한 세굴변동(홍수사상 등)에 대한 영향을 고려하는데 어려움이 있다. 특히 국내의 경우 다양한 하상재료와 홍수빈도를 고려할 때 이에 대한 세굴적용은 매우 중요한 인자라 할 수 있다. 따라서 교각세굴에 대한 궁극적인 목적은 다양한 하상재료와 홍수빈도를 고려할 수 있는 세굴평가를 제안하는데 있다. 이를 위해 본 연구에서는 우선적인 연구로 입자의 다양성과 이미지 기법을 이용한 실시간 측정을 통해 보완하여 입자에 따른 시간적 변화를 분석하였다. 현재 4가지의 하상재료의 입경차이에 따른 국부세굴의 시간적 변화와 초기세굴 발생의 수리적 조건을 파악하고 기존연구와 비교분석하였으며, 이를 기초자료로 세굴심$(S,\;S_{max})$, 교량주변 전단력$({\tau}_p,\;{\tau}_{pc})$, 접근수로부 전단력$({\tau}_a)$와 입자한계전단력$({\tau}_c)$에 대한 시간분석 (time effect)을 통해 다양한 하상재료와 홍수빈도를 해석을 위한 초기분석을 수행하는데 목적이 있다. 수리모형실험에 사용된 가변경사수로의 제원은 $0.6m(W){\times}20m(L){\times}2m(H)$이며 모형구조물은 투명한 아크릴로 제작하였다. 실험방법은 교각 내부에 CC카메라를 전 후면 및 상측면에 설치하여 세굴 발생을 실시간으로 촬영한 후 이미지 분석을 통해 분석하였다.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.4 s.15
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• pp.35-42
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• 2004

Accurate classification of water area is a preliminary step to analyze the flooded area and damages caused by flood. This is essential process for monitoring the region where annually repeating flood is a problem. The accurate estimation of flooded area can ultimately be utilized as a primary source of information for the policy decision. In this paper, flooded areas was classified using 1:25,000 land use map and a RADARSAT image of Ok-Chun and Bo-Eun located in Chung-Book province taken in 12th of August, 1998. Then we analyzed the flood area based on GIS. A RADARSAT image was used to classify the flooded areas with slope theme generated from digital elevation model. In processing on a RADARSAT image, the geometric correction was performed by a backwardgeocoding method based on ephemeris data and one control point for near real time flood area analysis.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.1
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• pp.9-14
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• 1999

The effect of operating condition was studied experimently on the characteristics of twin sprays ejected from two airblast atomizers, within the range of the mass air-fuel ratio 1.36∼3.54. Water and nitrogen gas were used as test fluids for the experiments. Spray characteristics of liquid spray were measured with measurement of mass distribution and instantaneous image of the spray cone. Experimental results show that the maximum specify of the distribution were lowered but distributed over the larger area when the ROA ratio increased, Center of mass position did not change with increasing water mass flow, Increase of the nozzle distance has an small effect on mass distribution of interaction area but distributed over the larger area. It was also conformed that the effect of interaction near central point of collision decreased with the increase of the ROA ratio on interaction area from comparison using superposition method

• Korean Journal of Remote Sensing
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• v.28 no.2
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• pp.181-189
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• 2012

Recently, interest in potential for estimating water quality using high resolution satellite images is increasing. However, low SNR(Signal to Noise Ratio) over inland water and radiometric errors such as non-linearity of brightness value of high resolution satellite images often lead to accuracy degradation in water quality estimation. Therefore radiometric correction should be carried out to estimate water quality for high resolution satellite images. For KOMPSAT-2 images parameters for brightness value-radiance conversion are not available and precise radiometric correction is difficult. To exploit KOMPSAT-2 images for water quality monitoring, it is necessary to investigate non-linearity of brightness value and noise over inland water. In this paper, we performed brightness value comparison between KOMPSAT-2 images and IKONOS/GeoEye-1, which are known to show the linearity. We used the images obtained over the same area and on the same date for comparison. As a result, we showed that although KOMPSAT-2 images are more noisy;the trend of brightness value and pattern of noise are almost similar to reference images. The results showed that appropriate target area to minimize the impact of noise was $5{\times}5$. Non-linearity of brightness value between KOMPSAT-2 and reference images was not observed. Therefore we could conclude that KOMPSAT-2 may be used for estimation of water quality parameters such as concentration of chlorophyll.

• Korean Journal of Remote Sensing
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• v.29 no.1
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• pp.11-20
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• 2013

Space-borne Synthetic Aperture Radar(SAR) has been one of the most effective tools for monitoring quantitative oceanographic physical parameters. The Doppler information recorded in single-channel SAR raw data can be useful in estimating moving velocity of water mass in ocean. The Doppler shift is caused by the relative motion between SAR sensor and the water mass of ocean surface. Thus, the moving velocity can be extracted by measuring the Doppler anomaly between extracted Doppler centroid and predicted Doppler centroid. The predicted Doppler centroid, defined as the Doppler centroid assuming that the target is not moving, is calculated based on the geometric parameters of a satellite, such as the satellite's orbit, look angle, and attitude with regard to the rotating Earth. While the estimated Doppler shift, corresponding to the actual Doppler centroid in the situation of real SAR data acquisition, can be extracted directly from raw SAR signal data, which usually calculated by applying the Average Cross Correlation Coefficient(ACCC). The moving velocity was further refined to obtain ocean surface current by subtracting the phase velocity of Bragg-resonant capillary waves. These methods were applied to Envisat ASAR raw data acquired in the East Sea, and the extracted ocean surface currents were compared with the current measured by HF-radar.

• Journal of the Korean Geophysical Society
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• v.9 no.2
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• pp.121-128
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• 2006

Recently, spillways are need to control stable water level for supporting main dams because of floods by unusual change of weather such as Typhoon Rusa. This study has been focused on the amount of leakage through the rock mass distributed fractures and joints under the opened emergency spillway. It is very important to evaluate the amount of leakage as these affect stability of spillway by interaction between effective stress and pore pressure. The commercial program MAFIC has been used for analyzing groundwater flow in fractured rock mass. The results showed that the values of range, average and deviation of leakage were 2.85∼ 3.79×10-1, 3.32×10-1 and 1.70×10-2 m3/day/m2 respectively. Secondary, we have estimated the effect of grouting after the transmissivity(Tf) of joint 1 as main pathway of leakage known from above results was changed from 1.78×10-7 to 1.59×10-9 m2/s. The results showed that the values of range, average and deviation of leakage were 7.80×10-4∼1.53×10-3, 1.18×10-3 and 1.32×10-4 m3/day/m2 respectively. As the result, the amount of leakage after grouting has been decreased by a ratio of 1 to 277.

• Journal of the Korean Society of Radiology
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• v.10 no.4
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• pp.255-261
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• 2016

In this study, among various factors having influence on SUV, we intended to compare and analyze the change of SUV using CT(4 type) and MRI(3 type) contrast agents which are commercialized now. We used Discovery 690 PET/CT(GE) and NEMA NU2 - 1994 PET phantom as experimental equipment. We have conducted a study as follows; first, we filled distilled water to phantom about two-thirds and injected radioisotope(18F-FDG 37 MBq), contrast agent. Second, we mixed CT contrast agent with distilled water and MRI contrast agent with that water separately. And then, we stirred the fluid and filled distilled water fully not to make air bubble. In emission scan, we had 15minutes scanning time after 40 minutes mixing contrast agent with distilled water. In transmission scan, we used CT scanning and its measurement conditions were tube voltage 120 kVp, tube current 40 mA, rotation time 0.5 sec, slice thickness 3.27 mm, DFOV 30 cm. Analyzing results, we set up some ROIs in 10th, 15th, 20th, 25th, 30th slice and measured SUVmean, SUVmax. Consequently, all images mixed 3 types of MRI contrast agent with distilled water have high SUVmean as compared with pure FDG image but there was no statistical significance. In SUVmax, they have high score and there was statistical significance. And other 4 images mixed 4 types of CT contrast agent with distilled water have significance in both SUVmean and SUVmax. Attenuation correction in PET/CT has been executed through various methods to make high quality image. But we figured out that using CT and MRI contrast agents before PET/CT scanning could make distortion of image and decrease diagnostic value. In that reason, we have to sort out the priority of examination in hospital not to disturb other examination's results. Through this process, we will be able to give superior medical service to our customers.

• Radiation Oncology Journal
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• v.26 no.3
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• pp.189-194
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• 2008

Purpose: We designed a water-based bolus device for radiation therapy in Kaposi's sarcoma. This study evaluated the usefulness of this new device and compared it with the currently used rice-based bolus. Materials and Methods: We fashioned a polystyrene box and cut a hole in order to insert patient's extremities while the patient was in the supine position. We used a vacuum-vinyl based polymer to reduce water leakage. Next, we eliminated air using a vacuum pump and a vacuum valve to reduce the air gap between the water and extremities in the vacuum-vinyl box. We performed CT scans to evaluate the density difference of the fabricated water-based bolus device when the device in which the rice-based bolus was placed directly, the rice-based bolus with polymer-vinyl packed rice, and the water were all put in. We analyzed the density change with the air gap volume using a planning system. In addition, we measured the homogeneity and dose in the low-extremities phantom, attached to six TLD, and wrapped film exposed in parallel-opposite fields with the LINAC under the same conditions as the set-up of the CT-simulator. Results: The density value of the rice-based bolus with the rice put in directly was 14% lower than that of the water-based bolus. Moreover, the value of the other experiments in the rice-based bolus with the polymer-vinyl packed rice showed an 18% reduction in density. The analysis of the EDR2 film revealed that the water-based bolus shows a more homogeneous dose plan, which was superior by $4{\sim}4.4%$ to the rice-base bolus. The mean TLD readings of the rice-based bolus, with the rice put directly into the polystyrene box had a 3.4% higher density value. Moreover, the density value in the case of the rice-based bolus with polymer-vinyl packed rice had a 4.3% higher reading compared to the water-based bolus. Conclusion: Our custom-made water-based bolus device increases the accuracy of the set-up by confirming the treatment field. It also improves the accuracy of the therapy owing to the reduction of the air gap using a vacuum pump and a vacuum valve. This set-up represents a promising alternative device for delivering a homogenous dose to the target volume.

• Journal of the East Asian Society of Dietary Life
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• v.23 no.5
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• pp.654-661
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• 2013

The current research is designed to analyze sterilization effects on mulberries in terms of storage temperature and storage period after treating with tap water (TW), electrolyzed water (EW) and aqueous chlorine dioxide ($ClO_2$). The treated $ClO_2$ concentrations are 10, 50, 100 and 200 ppm. In each concentration, the mulberries are soaked for 30 seconds respectively. The sterilization effects are being compared at room temperature ($25^{\circ}C$) and at $4^{\circ}C$, respectively. And the enzyme activity related to quality is also being investigated and analyzed about for browning inhibition effects. Microbial sterilizing power increases more in treating plots with EW and $ClO_2$ than treating plot with TW. Futhermore sterilizing power of $ClO_2$ increased sharply on high concentration treatment plot as well. Sterilization effects of $ClO_2$ during storage time are better at cold temperature. Pictures taken from scanning electron microscope reveal that there are no microbes in sterilizing solutions treatment plots. From measurement of the enzyme activity, it is concluded that activities decrease more in sterilizing solutions treatment plots as comparing with TW treated plot during the time. The amount of total polyphenolics decrease with the time passing and EW and $ClO_2$ treatment shows less contents than TW treatment. Thus, EW and $ClO_2$ treatment of mulberris are considered as method to improve safety by reducing total plate count and to contribute to quality maintenance and to extend storage time.