• 대한원격탐사학회지
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• 제27권5호
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• pp.573-586
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• 2011

MTF(modulation transfer function)는 광학 시스템의 성능을 평가하기 위하여 사용되는 중요한 파라미터 중 하나이다. 또한 열악한 우주 환경(방사능, 극한 열조건 및 전자기장 등), 대기 영향 및 시스템 성능의 저하 등으로 저하된 영상품질을 복원시켜주기 위한 파라미터로 사용될 수도 있다. 본 논문에서는 소형 지구관측위성인 DubaiSat-1이 발사된 후, 위성영상의 품질을 평가하기 위하여 MTF를 측정하였다. 일반적으로 MTF는 point source 혹은 knife-edge 방법 등과 같은 다양한 방법을 이용하여 측정되어왔다. 그러나 본 논문에서는 ISO에서 line source에 의한 MTF 측정을 표준화한 slanted-edge 방법을 이용하여 MTF를 측정하였다. Slanted-edge 방법은 전자 스틸 카메라(electronic still-picture camera)의 MTF를 측정하기 위한 ISO 12233 표준으로써, 라인스캐닝 망원경(line-scanning telescope)의 MTF를 추정하기 위하여 사용된 방법이다. 또한 PSF(point spread function) 기반으로 제작된 MTF 회선 커널(MTF convolution kernel)에 의한 MTF 보상(MTF compensation)과 영상의 노이즈 제거(image denoising)를 수행하여 영상의 품질 저하(degradation)를 완화시켰다.

• 한국물환경학회지
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• 제32권1호
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• pp.108-114
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• 2016

Sediment-laden water leads to water quality degradation in streams; therefore, best management practices must be implemented in the source area to control nonpoint source pollution. Field monitoring was implemented to measure precipitation, direct runoff, and sediment concentrations at a control plot and straw-applied plot to examine the effect on sediment reduction in this study. A hydrology model, which employs Curve Number (CN) to estimate direct runoff and the Universal Soil Loss Equation to estimate soil loss, was selected. Twenty-five storm events from October 2010 to July 2012 were observed at the control plot, and 14 storm events from April 2011 to July 2011 at the straw-applied plot. CN was calibrated for direct runoff, and the Nash-Sutcliffe efficiency and coefficient of determination were 0.66 and 0.68 at the control plot. Direct runoff at the straw-applied plot was calibrated using the percentage direct runoff reduction. The estimated reduction in sediment load by direct runoff reduction calibration alone was acceptable. Therefore, direct runoff-sediment load behaviors in a hydrology model should be considered to estimate sediment load and the reduction thereof.

• 한국물환경학회지
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• 제37권2호
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• pp.103-113
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• 2021

In this study, an Excel-based model (ROADMOD) was developed to estimate pollutant loading from the road and evaluate BMPs. ROADMOD employs the Chezy-Manning equation and empirical expression for estimating surface runoff, and power function for pollutant buildup, and exponential function for pollutant washoff in SWMM. The results of model calibration for buildup and washoff using observed data revealed a good match between the simulation results and the observed data. The long-term surface runoff and sediment simulated by ROADMOD demonstrated a good match with those by SWMM with 2 ~ 14% of relative error. The shorter sweeping interval (within 8 days) remarkably decreased sediment loads from the road. It was found that the effect of reducing sediment loads from the road was greatly affected not only by the sweeping interval but also by sweeping on the day before a rainfall event. The 48% of removal efficiency of sediment loads from the road was achieved with 26 times of road sweeping per year when sweeping was performed on the day before the rainfall event. A 4-day sweeping interval showed similar removal efficiency (48%) with 96 times of sweeping per year. It is considered that the road sweeping on the day before a rainfall event could maximize the effect of reducing the non-point source pollution from the road with minimization of the number of road sweeping. So, the road sweeping on the day before a rainfall event can be considered as one of the useful and best management practices (BMPs) on road.

• 한국방사선학회논문지
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• 제17권4호
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• pp.531-539
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• 2023

자체흡수는 환경 시료의 감마 분광 측정 정확도에 영향을 미치는 가장 중요한 요소이다. 특히, 샘플의 화학적 구성, 기하학적 모양, 두께, 밀도, 원자 번호, 샘플과 검출기 사이의 거리, 방출된 감마 광자의 에너지 및 샘플 내 습도 계수 또는 백분율과 같은 기타 요인에 의해 영향을 받는다. 보정 방법을 테스트하기 450 ml CRM 표준선원(9개 핵종) 마리넬리 비커를 사용하였다. 보정된 값들을 적용하여 환경시료 중 토양시료 5개를 밀도별로 측정하였다. 따라서, 자체흡수 값은 다소 크고 낮은 광자 에너지에 더 효과적임을 알 수 있다. 환경 시료의 경우 선원자체 흡수를 통한 전체 에너지 피크 효율은 샘플의 밀도에 크게 의존함을 확인하였다.

• Journal of the Optical Society of Korea
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• 제2권2호
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• pp.74-79
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• 1998

The use of a fiber Fabry-Perot interferometer (FFPI) as an optical current transducer is demonstrated. A conventional inductive pickup coil converts the time-varying current I(t) being measured to a voltage waveform V(t) applied across a piezeolectric strip to which the FFPI is bonded. The strip experiences a longitudinal expansion and contraction, resulting in an optical phase shift ${\phi}(t)$ in the fiber proportional to V(t). This phase shift is measured using a frequency-modulated semiconductor light source, photodiodes to monitor the reflected light from the FFPI and the laser power, and a digital signal processor. Calibration routines compute V(t) and I(t) from the measured phase shift at a l KHz rate. Response to 60 Hz ac over the design range 0-1300A rms is characterized Transient response of the FFPI transducer is also measured.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.1870-1875
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• 2007

The microchannel heat sink is promising heat dissipation method for high heat flux source. Contrary to conventional circular channel, MEMS based microchannel had rectangular or trapezoidal cross-sectional shape. In our study, we conducted three dimensional conjugate heat transfer calculation for rectangular shape microchannel. First, we simulated that channel was completely drained with known heating power. As a result we obtained calibration line, which indicates heat loss was function of temperature. Second, we simulated single phase heat transfer with various mass flux, 100-400 $kg/m^2s$. In conclusion, the single phase test verified that the present heat loss evaluation method is applicable to micro scale heat transfer devices. Heat fluxes from each side wall shows difference due to non-uniform heating. However those ratios were correlated with supplied total heat. Finally, we proposed effective area correction factor to evaluate appropriate heat flux.

• Journal of Astronomy and Space Sciences
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• 제18권1호
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• pp.71-80
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• 2001

KITSAT-1에 탑재된 Total Dose Experiment (TDE)로 부터 관측된 RADFET의 문턱전압 변화를 원자력 연구소 조사실의 Co-60 감마선 조사 장치를 이용한 보정 실험을 통해 총 방사능양으로 환산하였다. 위성 내 센서의 위치에 따라 측정되는 총 방사능양이 다르게 나타났으며, 지구 자기권에서의 NASA 방사선 모델을 이용한 시뮬레이션을 통해 이러한 차이가 센서 위치에 따라 위성체에 의한 차폐 효과가 다르기 때문에 나타나는 현상임을 확인하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.548-553
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• 2011

The lock-in thermography was employed to evaluate the defects in railway bogies. Prior to the actual application on railway bogies, in order to assess the detectability of known flaws, the calibration reference panel was prepared with various dimensions of artificial flaws. The panel was composed of polymer matrix composites, which were the same material with actual bogies. Through lock-in thermography evaluation, the optimal frequency of heat source was determined for the best flaw detection. Based on the defects information, the actual defect assessments on railway bogie were conducted with different types of railway bogies, which were used for the current operation. In summary, it was found that the novel infrared thermography technique could be an effective way for the inspection and the detection of surface defects on bogies since the infrared thermography method provided rapid and non-contact investigation of railway bogies.

• 전자공학회논문지
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• 제52권5호
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• pp.183-189
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• 2015

본 논문에서는 LED에 전류 또는 전압을 공급하고, 이에 따라 나타나는 전기적 특성을 분석하는 시스템에서 기존의 (+),(-) 전류 또는 전압을 공급하는 방식과 (+),(-) 전류 또는 전압을 측정 방식에서, 회로의 오차를 감소시키고, 하드웨어의 복잡도를 개선시킬 수 있으며, 시스템의 보정을 절반으로 줄일 수 있는 방법으로 (+) 단일 전원을 이용하여 전류 또는 전압을 공급하고, 측정할 수 있는 방법을 제안한다.

• Journal of Radiation Protection and Research
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• 제9권1호
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• pp.11-18
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• 1984

Well type 전리함과 미세전류 측정희로를 사용하여 표준 감마선 전리함 장치를 개발하였다. 미세전류는 automatic Townsend balance with stepwise compensation방법을 사용하여 측정하였다. $^{226}Ra$을 기준 선원으로 택하여 감마 방출핵종인 $^{241}Am,\;^{133}Ba,\;^{60}Co,\;^{134}Cs,\;^{137}Cs^{22}Na$에 대한 비교 교정인자를 산출하였으며, 감마에너지의 함수로서 검출 효율 곡선을 구하였다.