• Journal of Korea Water Resources Association
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• v.55 no.8
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• pp.623-634
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• 2022

Due to river maintenance projects such as the creation of hydrophilic areas around rivers and the Four Rivers Project, the flow characteristics of rivers are continuously changing, and the risk of water quality accidents due to the inflow of various pollutants is increasing. In the event of a water quality accident, it is necessary to minimize the effect on the downstream side by predicting the concentration and arrival time of pollutants in consideration of the flow characteristics of the river. In order to track the behavior of these pollutants, it is necessary to calculate the diffusion coefficient and dispersion coefficient for each section of the river. Among them, the dispersion coefficient is used to analyze the diffusion range of soluble pollutants. Existing experimental research cases for tracking the behavior of pollutants require a lot of manpower and cost, and it is difficult to obtain spatially high-resolution data due to limited equipment operation. Recently, research on tracking contaminants using RGB drones has been conducted, but RGB images also have a limitation in that spectral information is limitedly collected. In this study, to supplement the limitations of existing studies, a hyperspectral sensor was mounted on a remote sensing platform using a drone to collect temporally and spatially higher-resolution data than conventional contact measurement. Using the collected spatio-temporal hyperspectral images, the tracer concentration was calculated and the transverse dispersion coefficient was derived. It is expected that by overcoming the limitations of the drone platform through future research and upgrading the dispersion coefficient calculation technology, it will be possible to detect various pollutants leaking into the water system, and to detect changes in various water quality items and river factors.

• Korean Journal of Remote Sensing
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• v.13 no.2
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• pp.99-120
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• 1997

Solar radiation is scattered and absorbed atmospheric compositions in the atmosphere before it reaches the surface and, then after reflected at the surface, until it reaches the satellite sensor. Therefore, consideration of the radiative transfer through the atmosphere is essential for the quantitave analysis of the satellite sensed data, specially at shortwave region. This study examined a feasibility of using radiative transfer code for estimating the atmospheric effects on satellite remote sensing data. To do this, the flux simulated by LOWTRAN7 is compared with CAGEX data in shortwave region. The CAGEX (CERES/ARM/GEWEX Experiment) data provides a dataset of (1) atmospheric soundings, aerosol optical depth and albedo, (2) ARM(Aerosol Radiation Measurement) radiation flux measured by pyrgeometers, pyrheliometer and shadow pyranometer and (3) broadband shortwave flux simulated by Fu-Liou's radiative transfer code. To simulate aerosol effect using the radiative transfer model, the aerosol optical characteristics were extracted from observed aerosol column optical depth, Spinhirne's experimental vertical distribution of scattering coefficient and D'Almeida's statistical atmospheric aerosols radiative characteristics. Simulation of LOWTRAN7 are performed on 31 sample of completely clear days. LOWTRAN's result and CAGEX data are compared on upward, downward direct, downward diffuse solar flux at the surface and upward solar flux at the top of the atmosphere(TOA). The standard errors in LOWTRAN7 simulation of the above components are within 5% except for the downward diffuse solar flux at the surface(6.9%). The results show that a large part of error in LOWTRAN7 flux simulation appeared in the diffuse component due to scattering mainly by atmispheric aerosol. For improving the accuracy of radiative transfer simulation by model, there is a need to provide better information about the radiative charateristrics of atmospheric aerosols.

• Korean Journal of Remote Sensing
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• v.37 no.3
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• pp.531-542
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• 2021

Open-pit mines require constant monitoring as they can cause surface changes and environmental disturbances. In open-pit mines, there is little vegetation at the mining site and can be monitored using InSAR (Interferometric Synthetic Aperture Radar) coherence imageries. In this study, activities occurring in mine were analyzed by applying the recently developed InSAR coherence-based NDAI (Normalized Difference Activity Index). The March 5 Youth Mine is a North Korean mine whose development has been expanded since 2008. NDAI analysis was performed with InSAR coherence imageries obtained using Sentinel-1 SAR images taken at 12-day intervals in the March 5 Youth Mine. First, the area where the elevation decreased by about 75.24 m and increased by about 9.85 m over the 14 years from 2000 was defined as the mining site and the tailings piles. Then, the NDAI images were used for time series analysis at various time intervals. Over the entire period (2017-2019), average mining activity was relatively active at the center of the mining area. In order to find out more detailed changes in the surface activity of the mine, the time interval was reduced and the activity was observed over a 1-year period. In 2017, we analyzed changes in mining operations before and after artificial earthquakes based on seismic data and NDAI images. After the large-scale blasting that occurred on 30 April 2017, activity was detected west of the mining area. It is estimated that the size of the mining area was enlarged by two blasts on 30 September 2017. The time-averaged NDAI images used to perform detailed time-series analysis were generated over a period of 1 year and 4 months, and then composited into RGB images. Annual analysis of activity confirmed an active region in the northeast of the mining area in 2018 and found the characteristic activity of the expansion of tailings piles in 2019. Time series analysis using NDAI was able to detect random surface changes in open-pit mines that are difficult to identify with optical images. Especially in areas where in situ data is not available, remote sensing can effectively perform mining activity analysis.

• Journal of the Korean earth science society
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• v.41 no.2
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• pp.129-136
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• 2020

Drought is an environmental disaster typically defined as an unusual deficiency of water supply over an extended period. Satellite remote sensing provides an alternative approach to monitoring drought over large areas. In this study, we monitored drought patterns over about 30 years (1985-2015), using satellite imagery of Lake Soyang, Gangwondo, South Korea. Landsat images were classified using ISODATA, maximum likelihood analysis, and an artificial neural network to derive the lake area. In addition, the relationship between areas of Lake Soyang and the Standardized Precipitation Index (SPI) was analyzed. The results showed that the artificial neural network was a better method for determining the area of the lake. Based on the relationship between the SPI value and changes in area, the R² value was 0.52. This means that the area of the lake varied depending on SPI value. This study was able to detect and monitor drought conditions in the Lake Soyang area. The results of this study are used in the development of a regional drought monitoring program.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.36-36
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• 2003

목적 : 고감도 형광판과 필름을 이용하여 실시간으로 선량을 측정하여 IMRT 선량분포를 검증하는데 사용하는 가능성을 알아보고자 하였다. 대상 및 방법 : 본 연구에서 개발한 물팬텀은 지름 25cm 아크릴 원통과 원통의 중앙부분에 삽입되는 고감도 형광판으로 구성되어 있다. 이를 사용하여 dose linearity correction factor를 구하기 위해 dmax 지점에서 6MV x-ray를 고감도형광판에 조사하여 blurring correction factor를 구하였다. CCD를 이용하여 고감도 형광판에서 나오는 영상을 수집하였다. 고감도 형광판에서 수집한 영상의 x축 profile은 RTP에서 얻은 profile과 비교하였고, 이온전리함으로 scanning한 데이터를 이용하여 고감도 형광판과 물에서 빛에 의한 산란선 때문에 발생하는 blurring effect를 교정하였다. 여기서 계산된 blurring effect factor를 고감도 형광판에서 수집된 영상에 적용하였다. 결과 : CCD 카메라는 형광판의 전 영역을 감지할 수 있고, 조사시간은 형광판의 중첩된 영상의 선량에 비례하였다. 물팬텀에서 형광판의 blurring effect 는 가우시안 분포로 표현할 수 있었다. 또한 Deconvolution kernel은 원통 팬텀에서 지름 $\pm$5cm 이내의 범위에 위치하였고, 따라서 형광판 영상으로부터의 실제 선량분 포를 뽑아낼 수 있었다. RTP 에서 계산된 선량분포와 blurring correction factor로 교정한 후 중첩시켜 얻은 고감도 형광판 영상의 선량분포는 일치하였다. 결론 : 정기적인 IMRT 선량 검증에 대한 실시간 선량측정 방법이 개발되었다. 고감도 형광판 영상과 CCD 카메라를 사용한 물팬텀으로, IMRT 치료계획에 대한 선량분포를 검증할 수 있는 가능성을 보였다.비의 회전에 의한 오차 보정, 필름의 광학적 밀도에 관한 보정 등 여러 가지 계통적 오차들에 대한 보정들이 선량분포 확인과정의 이해와 그 기준마련에 도움이 되겠지만 우리가 다룬 원점 불일치에 비해서 상대적으로 무시할 수 있었다. 마지막으로 선량분포 확인의 최종목표인 3 차원 선량분포 확인의 실제 적용을 위한 연구가 최적화 알고리듬을 이용하여 실험 중에 있다.\times$5cm, 10$\times$10cm, 15$\times$l5cm, 20$\times$20cm인 경우, 측정하여 얻은 PSF가 0.8%, 0.2%, 0.4%, 0.2%로 약간 높지만, 두 값은 매우 유사한 것으로 나타났다. 그리고, 기존의 BSF를 이용해 구한 TAR과 BJR 25에서 권고하는 PSF를 이용해 구한 TAR을 비교한 결과 field size 에 따라 약 1%-1.5% 정도로 BSF를 이용하여 구한 TAR보다 PSF를 이용하여 구한 TAR이 1.3% 정도 높게 나타났지만, 이것은 두 값의 절대적인 차이일 뿐, 실제로는 PSF를 이용하여 구한 TAR이 측정해서 구한 TAR과는 매우 유사한 값을 보여주고 있다. 결론 : 기존의 BSF를 이용해 구한 TAR과 PSF를 이용해 구한 TAR을 비교하였을 때, 약 1.3% 정도 높게 내고 있지만, 기존의 TAR보다는 PSF를 이용해 구한 TAR이 BJR 25와 잘 일치하고 있으므로 Co-60 원격치료용 방사선 조사장치를 사용할 경우 BSF보다는 PSF를 사용하는 것이 타당한 것으로 사료된다.tokines의 변화는 비록 통계학적인 차이는 없지만 비타민 C를 사용한 환자의 cytokines이 모두 사용하지 않은 환자에 비해 감소하였음을 보였다. 비타민 C는 부작용이 거의 없는 안전한 약으로서 말기 암 환자에서 비타민 C사용은 임상 증상을 호전시키는 데 도움

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.12
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• pp.55-63
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• 2015

Recently, terroristic threats using a radio controlled improvised explosive device (RCIED) that is remotely controlled and exploded have been increased around the world. In order to prevent the explosion of an RCIED, jamming techniques that interrupt an RCIED receiver can be used, so that the receiver can not demodulate the trigger code. Conventional jamming technique is a type of active barrage jamming that always emits the noise jamming signal for all the frequency band. However, it needs large power consumption and thus is limited in operation time for a vehicle. In order to overcome the shortage of the active barrage jamming, reactive jamming technique has drawn attention. In reactive jamming, all the frequency band is firstly scanned, and then if any trigger signal exists, one emits the jamming signal to the corresponding frequency band. Therefore, the reactive jamming is superior to the active barrage jamming in terms of power efficiency. However, a reactive jammer emits a jamming signal only after the trigger signal is intercepted, which means that the jamming signal may be late for interrupting an RCIED receiver. In this sense, it is needed to evaluate a delay in an RCIED receiver. To achieve this, we analyze the reaction time and present the simulation result for jamming performance of reactive jamming against an RCIED using mobile devices.

• The KIPS Transactions:PartD
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• v.13D no.6 s.109
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• pp.775-788
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• 2006

Many disaster monitoring systems are constantly studied to prevent disasters such as environmental pollution, the breaking of a tunnel and a building, flooding, storm earthquake according to the progress of wireless telecommunication, the miniaturization of terminal devices, and the spread of sensor network. A disaster monitoring system can extract information of a remote place, process sensor data with rules to recognize disaster situation, and provide work for preventing disaster. However existing monitoring systems are not enough to predict and prevent disaster, because they can only process current sensor data through utilizing simple aggregation function and operators. In this paper, we design and implement a disaster prevention system to predict near future dangerous area through using outside sensor network and spatial Information. The provided prediction technique considers the change of spatial information over time with current sensor data, and indicates the place that could be dangerous in near future. The system can recognize which place would be dangerous and prepare the disaster prevention. Therefore, damage of disaster and cost of recovery would be reduced. The provided disaster prevention system and prediction technique could be applied to various disaster prevention systems and be utilized for preventing disaster and reducing damages.

• Fire Science and Engineering
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• v.29 no.6
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• pp.51-56
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• 2015

In Korea, measures to maintain sustainable fire safety performance for apartment buildings are insufficient in terms of fire-fighting products, skilled personnel, and maintenance status. Also, because of the particular features of a fire compartment, it has structural problems that are very likely to cause damage to human life when a fire occurs. Currently, problems with the fire supervisory system installed in an apartment building cannot be checked in real time, so it is difficult to identify the location of a fire accurately. Protected areas are also not assigned to each household, and residents cannot be clearly informed of the occurrence of a fire. As a consequence, safety evacuation cannot be secured. In addition, it is impossible to test the operation performance for water detectors in sprinkler fire extinguishing systems outside of the household. Therefore, an experiment was conducted to evaluate the performance of a remote fire supervisory system. The results show that the system satisfies all performance requirements. Also, an household alarm system was installed in each household to alert of any occurrence of a fire accurately, and the performance of the alarm system was improved to ensure that residents were quickly evacuated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.7
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• pp.630-642
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• 2013

To transmit vital signal stream of mobile patients remotely, it requires mobility of patient and watcher, sensing function of patient's abnormal symptom and self-organizing service binding of related computing resources. In the existing relative researches, the vital signal stream is transmitted as a centralized approach which exposure the single point of failure itself and incur data traffic to central server although it is localized service. Self-organizing middleware platform based on heterogenous overlay network is a middleware platform which can transmit real-time data from sensor device(including vital signal measure devices) to Smartphone, TV, PC and external system through overlay network applied self-organizing mechanism. It can transmit and save vital signal stream from sensor device autonomically without arbitration of management server and several receiving devices can simultaneously receive and display through interaction of nodes in real-time.

• Journal of Sensor Science and Technology
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• v.8 no.3
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• pp.239-246
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• 1999

A highly sensitive photovoltaic infrared photodiode was fabricated for detecting infrared light in $3{\sim}5\;{\mu}m$ wavelength range on InSb wafer with p-i-n structure grown by MOCVD. Silicon dioxide($SiO_2$) insulating films for the junction interface and surface of photodiode were prepared using RPCVD because InSb has low melting point and evaporation temperature. After formation of In ohmic contacts by thermal evaporation, the electrical properties of the photodiode were characterized in dark state at 77K. A product of zero-bias resistance and area($R_0A$) showed $1.56{\times}10^6\;{\Omega}{\cdot}cm^2$ that satisfied BLIP(background limited infrared photodetector) condition. When the photodiode was tested under infrared light, the normalized detectivity of about $10^{11}\;cm{\cdot}Hz^{1/2}{\cdot}W^{-1}$ was obtained. we successfully fabricated a unit cell with InSb IR array with good quantum efficiency and high detectivity.