• Journal of Advanced Marine Engineering and Technology
• /
• 제20권2호
• /
• pp.48-56
• /
• 1996

This paper is concerned with a method for calibrating five-hole probes of both angle-tube and prismatic geometries to measure local total and static pressures and the magnitude and direction of the mean velocity vector. Descriptions of the calibration technique, the typical calibration data, and an accompanying discussion of the interpolation procedure are included. The flow properties are determined explicitly from measured probe pressures using calibration data. Flow angles are obtained within the deviation angle of 1.0 degree and dynamic pressures within 0.03 with 95% certainty. The variations in the calibration data due to Reynolds number are also discussed. For the range of Reynolds number employed, no effect was detected on the pitch, yaw abd total pressure coefficients. However, the static pressure coefficient showed change to cause minor variations in the magnitude of the calculated velocity vector. To account for these variations, average correction factors need to be incorporated into the static pressure coefficient.

• 대한원격탐사학회지
• /
• 제24권2호
• /
• pp.213-222
• /
• 2008

초분광영상의 활용 가능성은 증대하고 있으나, 연구에 필요한 초분광센서의 공급은 비교적 제한되어 있다. 초분광영상으로부터 정보 획득을 위한 처리와 분석은 대부분 영상에서 획득되는 분광반사율에 기반을 두고 있다. 본 연구의 목표는 사전 복사보정 자료가 없는 지상 초분광카메라 영상의 복사보정 과정을 개발하여 영상의 화소값을 분광반사율로 변환하고자 한다. 다양한 분광반사특성을 가진 22개 클래스로 구성된 모의지표물을 대상으로 분광측정기를 이용한 대리 복사보정 절차를 수행하였다 분광측정기로 측정된 복사량과 영상의 화소값의 관계를 이용하여 120개 밴드 초분광영상의 화소값을 센서감지 복사량(radiance)로 변환하는 보정계수를 도출하였다. 영상 촬영 및 분광측정이 대기의 영향이 거의 없는 지상 근접 촬영으로 이루어졌기 때문에, 화소값을 반사율(reflectance)로 직접 변환하는 보정계수도 산출하였다. 그러나 원거리 촬영이나 공중 촬영으로 획득된 영상의 경우 산출된 복사보정 계수는 센서감지 복사량 변환에만 유효하며, 반사율을 얻기 위해서는 추가적인 대기보정 절차가 별도로 수행되어야 한다.

• 한국농림기상학회지
• /
• 제2권3호
• /
• pp.75-79
• /
• 2000

Calibrations of fast-response krypton hygrometers were carried out using a dew-point hygrometer to investigate the changes in their absorption coefficients due to long-term field operation. Absorption coefficients changed proportionally with the number of hours of field operation. The increase in absorption coefficient indicates that the water vapor flux, calculated with the original absorption coefficient, would underestimate the true flux in the field. To minimize the uncertainty in quantifying evapotranspiration and surface energy budget studies, frequent calibrations (for example, every 1500 hours of field operation) of krypton hygrometer are recommended.

• Environmental Analysis Health and Toxicology
• /
• 제17권1호
• /
• pp.63-71
• /
• 2002

The thermal desorption-gas chromatographic (TD-GC) system has been constructed for the measurement of volatile organic compounds. The thermal desortion unit is composed of four major parts: 1) the control part; 2) the thermal desorption part; 3) the focusing part; and 4) the injection part. The peltier element was introduced to the focusing part for the temperature of the focusing tube to reach-35$^{\circ}C$. The system was tested for the linearity of the calibration curves and reproducibility of instrumental analyses using some disinfection by-products (DBPs) and BTXs (benzene, toluene and p-xylene). The coefficients of determination (r$^2$) for all the calibration curves made were higher than 0.998, and the coefficients of variation (CV) for triplicate measurements were all within 10％. The system also has been tested for field applicability. The analysis of field samples showed that there was no breakthrough problem in the sampling system and that the system could be applied to field measurements.

• 해양환경안전학회지
• /
• 제24권3호
• /
• pp.295-301
• /
• 2018

This study compares optimization algorithms for efficient estimations of ship's hydrodynamic coefficients. Two constrained algorithms, the interior point and the sequential quadratic programming, are compared for the estimation. Mathematical optimization is designed to get optimal hydrodynamic coefficients for modelling a ship, and benchmark data are collected from sea trials of a training ship. A calibration for environmental influence and a sensitivity analysis for efficiency are carried out prior to implementing the optimization. The optimization is composed of three steps considering correlation between coefficients and manoeuvre characteristics. Manoeuvre characteristics of simulation results for both sets of optimized coefficients are close to each other, and they are also fit to the benchmark data. However, this similarity interferes with the comparison, and it is supposed that optimization conditions, such as designed variables and constraints, are not sufficient to compare them strictly. An enhanced optimization with additional sea trial measurement data should be carried out in future studies.

• KIEE International Transactions on Electrophysics and Applications
• /
• 제5C권1호
• /
• pp.18-22
• /
• 2005

We developed a new systematic calibration procedure and applied it to the calibration of the diffusivity, segregation and TED model of the indium impurity. The TED of the indium impurity was studied under 4 different experimental conditions. Although the indium proved to be susceptible to the TED, the RTA was effective in suppressing the TED effect and in maintaining a steep retrograde profile. Just as in the case of boron, indium demonstrated significant oxidation-enhanced diffusion in silicon and its segregation coefficients at the Si/SiO₂ interface were significantly below 1. In contrast, the segregation coefficient of indium decreased as the temperature increased. The accuracy of the proposed technique has been validated by SIMS data and 0.13-㎛ device characteristics such as Vth and Idsat with errors less than 5% between simulation and experiment.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
• /
• pp.390-393
• /
• 2007

KOMPSAT-2, the first Korean high resolution earth observing satellite, continuously acquires high resolution images since July 2006. The quality of satellite images should be geometrically and radiometrically ensured before distribution to users. This study focused on absolute radiometric calibration which is a prerequisite procedure to ensure the radiometric quality of optical satellite images. In this study, we performed reflectance-based vicarious calibration methods on several uniform targets collected through several field campaigns in 2007. The radiative transfer model, MODTRAN, was used to estimate the amount of energy received at the sensor. The energy reached at the sensor are affected by several factors such as reflectance of targets, atmospheric condition, geometry condition between Sun and the sensor, etc. This study proposes the absolute radiometric calibration coefficients of KOMPSAT-2 MSC images combining several types of collected data through field works and tried to compare dynamic range of sensor-detected energy with other commercial high resolution sensors.

• 대한원격탐사학회지
• /
• 제23권1호
• /
• pp.55-58
• /
• 2007

The prototype radiometric calibration algorithm of the imagers for IR channels has been developed according to the Weinreb's method. Applying the algorithm to the GOES-12 count data, we have shown that the calibration coefficients (slope and intercept) evaluated by the algorithm gives good agreement with the NESDIS's ones, and that the scanning error due to the scan mirror emissivity and stripe error are almost eliminated by the East/West angle dependent scan-mirror correction and the respective calculation of intercept for each North/South scan line, respectively.

• 대한원격탐사학회지
• /
• 제39권6_1호
• /
• pp.1273-1281
• /
• 2023

절대복사검보정은 위성 센서에서 얻은 전자기 신호의 물리량 변환을 위해 절대복사보정 계수를 결정하는 작업으로 위성 데이터의 정확도 개선 및 다른 위성 데이터와의 비교 및 통합을 위해 수행되어야 한다. 또한, 위성 센서는 시간에 따른 센서 노후화나 환경 조건의 영향을 받아 초기 설정된 보정 계수가 변화할 수 있으므로 주기적으로 이러한 변화를 모니터링 하는 것이 필수적이다. 이 연구에서는 차세대중형위성 1호(CAS500-1)의 다중 분광 채널에 대한 vicarious calibration을 수행하기 위해 필드 캠페인을 수행하였다. 구름이 없는 맑은 날의 조건 하에 총 두 차례의 유효한 현장 관측 자료를 얻었으며, MODTRAN 6 복사전달모델을 활용하여 대기 상단(top-of-atmosphere, TOA) radiance를 모의하였다. 모의된 TOA radiance와 CAS500-1의 digital number (DN)는 선형성은 보였지만, CAS500-1 영상의 넓은 시야각과 saturation 발생으로 향후 변환 계수의 보완이 필요한 것으로 보인다. 하지만, 본 연구는 CAS500-1의 절대복사보정에 대한 첫 시도를 하였으며, 향후 높은 신뢰성을 가진 계수 결정을 목표로 하는 연구들에 유용한 정보를 제공할 것으로 기대된다.

• 한국수자원학회논문집
• /
• 제31권3호
• /
• pp.235-242
• /
• 1998

본 연구의 목적은 낙동강 하류부의 감조구간에 대하여 실시간 홍수예보를 위한 수리학적 홍수추적 모형의 적용성을 검토하고 홍수시 감조구간내의 주요 홍수 예보지점에 대한 조위의 영향을 분석하는 것이다. 또한 모형의검증을 위하여 부정류 해석법에 의하여 하도구간별, 유량규모별 최적 조도계수를 추정하였으며 추정된 최적 조도계수를 적용한 부정류 해석 결과가 관측 수위수문곡선의 전반적인 형태를 매우 잘 재현하는 것으로 나타났다.