• Title/Summary/Keyword: Calibration uncertainty

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Development of linear measuring system (선형측정장치 개발)

  • Eom, Tae-Bong;Kim, Goo-Young;Chung, Myung-Sai
    • Journal of the Korean Society for Precision Engineering
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    • v.10 no.4
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    • pp.104-108
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    • 1993
  • The linear length measurements are most frequently performed and should be most accurate among other parts in dimensional metrology. We developed the linear measuring system using a laser interferometer to improve the accuracy and to shorten the calibration time. The uncertainty of the system is 0.01 .mu. for 500mm steel gage block. The range of the measurement and resolution of the system are 1000mm and 0.01 .mu. m, respectively.

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SWAT model calibration/validation using SWAT-CUP I: analysis for uncertainties of objective functions (SWAT-CUP을 이용한 SWAT 모형 검·보정 I: 목적함수에 따른 불확실성 분석)

  • Yu, Jisoo;Noh, Joonwoo;Cho, Younghyun
    • Journal of Korea Water Resources Association
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    • v.53 no.1
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    • pp.45-56
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    • 2020
  • This study aims to quantify the uncertainty that can be induced by the objective function when calibrating SWAT parameters using SWAT-CUP. SWAT model was constructed to estimate runoff in Naesenong-cheon, which is the one of mid-watershed in Nakdong River basin, and then automatic calibration was performed using eight objective functions (R2, bR2, NS, MNS, KGE, PBIAS, RSR, and SSQR). The optimum parameter sets obtained from each objective function showed different ranges, and thus the corresponding hydrologic characteristics of simulated data were also derived differently. This is because each objective function is sensitive to specific hydrologic signatures and evaluates model performance in an unique way. In other words, one objective function might be sensitive to the residual of the extreme value, so that well produce the peak value, whereas ignores the average or low flow residuals. Therefore, the hydrological similarity between the simulated and measured values was evaluated in order to select the optimum objective function. The hydrologic signatures, which include not only the magnitude, but also the ratio of the inclining and declining time in hydrograph, were defined to consider the timing of the flow occurrence, the response of watershed, and the increasing and decreasing trend. The results of evaluation were quantified by scoring method, and hence the optimal objective functions for SWAT parameter calibration were determined as MNS (342.48) and SSQR (346.45) with the highest total scores.

Evaluation of the Output Dose of a Linear Accelerator Photon Beams by Using the Ionization Chamber TM31010 Series through TG-51 Protocol to Postal Monitoring Output of RPC for 5 Years (TM31010 계열의 공동이온전리함과 TG-51을 이용한 선형가속기광자선의 5년간 출력선량 평가)

  • Choi, Tae-Jin;Kim, Ok-Bae
    • Progress in Medical Physics
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    • v.22 no.2
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    • pp.92-98
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    • 2011
  • This study is to keep the accuracy and stability of the output dose evaluations for linear accelerator photon beams by using the air ionization chambers (TM31010, 0.125 cc, PTW) through the Task Group 51 protocol. The absorbed dose to water calibration factor $N_{dw}{^{Co-60}}$ was delivered from the air kerma calibration factor $N_k$ which was provided from manufacture through SSDL calibration for determination of output factor. The ionization chamber of TM31010 series was reviewed the calibration factor and other parameters for reduce the uncertainty within ${\pm}2%$ discrepancy and we found the supplied $N_{dw}{^{Co-60}}$ which was derived from Nk has shown a -2.8% uncertainty compare to that of PSDL. The authors provided the program to perform the output dosimetry with TG-51 protocol as it is composed same screen of TG-51 worksheets. The evaluated dose by determination of output factor delivered to postal TLD block for comparison the output dose to that of MDACC (RPC) in postal monitoring program. The results have shown the $1.001{\pm}0.013$ for 6 MV and $0.997{\pm}0.012$ discrepancy for 15 MV X rays for 5 years followed. This study shows the evaluated outputs for linear accelerate photon beams are very close to that of international output monitor with small discrepancy of ${\pm}1.3%$ with high reliability and showing the gradually stability after 2010.

Effect Evaluation by Activity and Geometry Difference in Calibration on LSC (LSC 장비를 이용한 교정시 Activity 및 Geometry 차이에 의한 영향 평가)

  • Han, Sang-Jun;Lee, Kyung-Jin;Lee, Seung-Jin;Kim, Hee-Gang;Park, Eung-Seop
    • Journal of Radiation Protection and Research
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    • v.33 no.1
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    • pp.21-26
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    • 2008
  • When the calibration on Liquid Scintillation Counter using the Solid $^3H$ Standard Source of 200,000DPM is executed, the uncertainty due to activity and geometry difference, exists. Therefore, this paper intends to evaluate environmental samples comparatively accurately as decreasing this uncertainty existing in the process of calibration. For this, measurements on samples manufactured by $^3H$ Standard Source and sensitivity study were performed. Also, this paper verified calibration results using Radioactivity-Error-Analysis Method, and evaluated quantitatively the effect by geometry and activity difference based on verification result. According to the result of sensitivity study, in case of using the exposure time of 75 sec and Repeat method, the measuring accuracy and precision of about $1{\sim}3%$ were increased in comparison with the existing method. By analysis result, the effect by activity difference did not appear, and a plastic cell existing into Teflon vial made a role as reflector. The less the effect of plastic cells are decreased, the more activity is high, and the effect of those can be neglected at the activity of 200,000 DPM.

Simulation of TOA Visible Radiance for the Ocean Target and its Possible use for Satellite Sensor Calibration (해양 표적을 이용한 대기 상단 가시영역에서의 복사휘도 모의와 위성 센서 검보정에의 활용 가능성 연구)

  • Kim, Jung-Gun;Sohn, Byung-Ju;Chung, Eui-Seok;Chun, Hyoung-Wook;Suh, Ae-Sook;Kim, Kum-Lan;Oh, Mi-Lim
    • Korean Journal of Remote Sensing
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    • v.24 no.6
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    • pp.535-549
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    • 2008
  • Vicarious calibration for the satellite sensor relies on simulated TOA (Top-of-Atmosphere) radiances over various targets. In this study, TOA visible radiance was calculated over ocean targets which are located in five different regions over the Indian and Pacific ocean, and its possible use for the satellite sensor calibration was examined. TOA radiances are simulated with the 6S radiative transfer model for the comparison with MODIS/Terra and SeaWiFS measurements. Geometric angles and sensor characteristics of the reference satellites were taken into account for the simulation. AOT (Aerosol Optical Thickness) from MODIS/Terra, pigment concentrations from Sea WiFS, and ozone amount from OMI measurements were used as inputs to the model. Other atmospheric input parameters such as surface wind and total column water vapor were taken from NCEP/NCAR reanalysis data. The 5-day averaged radiances over all targets show that the percent differences between simulated and observed radiances are within about ${\pm}5%$ in year 2005, indicating that the calculated radiances are in good agreement with satellite measurements. It has also been shown that the algorithm can produce the SeaWiFS radiances within about ${\pm}5%$ uncertainty range. It has been suggested that the algorithm can be used as a tool for calibrating the VIS bands within about 5% uncertainty range.

Generation of calibration standard gases using capillary gas divider: uncertainty measurement and method validation (다중 모세관을 이용한 교정용 표준가스의 제조: 불확도와 유효성 평가)

  • Lee, Sangyun;Hwang, Eun-Jin;Jung, Hye-Ja;Lee, Kwang-Woo;Chun, Ki-Joon
    • Analytical Science and Technology
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    • v.19 no.5
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    • pp.369-375
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    • 2006
  • Calibration gas mixtures were prepared using dynamic volumetric method according to ISO 6145-5 and the uncertainty was evaluated. Ten identical capillaries with 0.25 mm in inner diameter and 50 cm in length were applied in this system. Dilution ratio of parent gas was determined by the number of capillaries that passes parent gas and that passes balance gas through. Capillaries were made of Teflon which had good chemical stability against adsorption of gaseous substances. Mechanical valves were introduced in this system in order to minimize the thermal effect of solenoid valves. Concentration of prepared gases were compared with master grade standard gases in cylinders made by RiGAS Co. and calibration of the instrument were completed using comparison method according to ISO 6143. Experimental results showed that the coefficient of variance of diluted oxygen standard gases showed less then 0.2% in most dilution range, that of diluted hydrogen sulfide standard gases showed less then 1.0%. Therefore, it is proven that the standard gases prepared by this system are appropriate to be used as a calibration standards in ambient monitoring, etc.

Single Laboratory Validation and Uncertainty Estimation of a HPLC Analysis Method for Deoxynivalenol in Noodles (면류에서 HPLC를 이용한 데옥시니발레놀 분석법의 검증과 불확도 산정)

  • Ee, Ok-Hyun;Chang, Hyun-Joo;Kang, Young-Woon;Kim, Mee-Hye;Chun, Hyang-Sook
    • Journal of Food Hygiene and Safety
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    • v.26 no.2
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    • pp.142-149
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    • 2011
  • An isocratic high performance liquid chromatography (HPLC) method for routine analysis of deoxynivalenol in noodles was validated and estimated the measurement uncertainty. Noodles (dried noodle and ramyeon) were analyzed by HPLC-ultraviolet detection using immunoaffinity column for clean-up. The limits of detection (LOD) and quantification (LOQ) were 7.5 ${\mu}g$/kg and 18.8 ${\mu}g$/kg, respectively. The calibration curve showed a good linearity, with correlation coefficients $r^2$ of 0.9999 in the concentration range from 20 to 500 ${\mu}g$/kg. Recoveries and Repeatabilities expressed as coefficients of variation (CV) spiked with 200 and 500 ${\mu}g$/kg were $82{\pm}2.7%$ and $87{\pm}1.3%$% in dried noodle, and $97{\pm}1.6%$ and $91{\pm}12.0%$ in ramyeon, respectively. The uncertainty sources in measurement process were identified as sample weight, final volume, and sample concentration in extraction volume as well as components such as standard stock solution, working standard solution, 5 standard solutions, calibration curve, matrix, and instrument. Deoxynivalenol concentration and expanded uncertainty in two matrixes spiked with 200 ${\mu}g$/kg and 500 ${\mu}g$/kg were estimated to be $163.8{\pm}52.1$ and $435.2{\pm}91.6\;{\mu}g$/kg for dried noodle, and $194.3{\pm}33.0$ and $453.2{\pm}91.1\;{\mu}g$/kg for ramyeon using a coverage factor of two which gives a level of statistical confidence with approximately 95%. The most influential component among uncertainty sources was the recovery of matrix, followed by calibration curve.

KFDA TLD Dose Quality Audit and Measurement Uncertainty (식품의약품안전청의 치료방사선 선량보증과 측정불확도)

  • Jeong, Hee-Kyo;Lee, Hyun-Ku;Kim, Gwe-Ya;Yang, Hyun-Kyu;Lim, Chun-Il
    • Proceedings of the Korean Society of Medical Physics Conference
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    • 2004.11a
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    • pp.153-156
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    • 2004
  • Korea Food and Drug Administration(KFDA) has peformed the calibration of therapy level dosimeters for Co-60 radiation since 1979. The reference standard ionization chamber has been calibrated at BIPM in France. The uncertainty on the KFDA calibration coefficients is 0.9 %(k=2) for air kerma and absorbed dose to water. Since 1999 a national quality audit program for ensuring dosimetry accuracy in Korea radiotherapy centers has been performed by the KFDA. The uncertainty associated with the determination of the absorbed dose to water from the TLD readings for high energy x-ray is 1.6 %(k=1). The correction factors for energy, non-linearity dose response, and TLD holder are used in the dose determination. Agreement between the user stated dose and KFDA measured dose within ${\pm}$ 5 % is considered acceptable. KFDA TLD postal dose quality audit program was peformed for 71 beam qualities of 53 domestic radiotherapy centers in 2003. The results for quality assurance showed that 63 out of 71 beam qualifies (89 %) satisfied the acceptance limit. The second audit was carried out for the centers outside the limit and ail of them have been corrected.

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Flow Calibration and Validation of Daechung Lake Watershed, Korea Using SWAT-CUP (SWAT-CUP을 이용한 대청호 유역 장기 유출 유량 보정 및 검증)

  • Lee, Eun-Hyoung;Seo, Dong-Il
    • Journal of Korea Water Resources Association
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    • v.44 no.9
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    • pp.711-720
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    • 2011
  • SWAT (Soil and Water Assessment Tool) model was calibrated for the flow rate of the Deachung lake with a large area of 3108.29 $km^2$. Application of SWAT model requires significant number of input data and is prone to result in uncertainties due to errors in input data, model structure and model parameters. The SUFI-2 (Sequential Uncertainty Fitting Ver. 2) program and GLUE (Generalized Likelihood Uncertainty Estimation) program in SWAT-CUP (SWAT-Calibration and Uncertainty Program) are used to select the best parameters for SWAT model. Optimal combination of parameter values was determined through 2,000 iterative SWAT model runs. The Nash-Sutcliffe values and $R^2$ values were 0.87 and 0.89 respectively indicating both methods show good agreements with observed data successfully. RMSE and MSE values also showed similar results for both programs. It seems the SWAT-CUP has a great practical appeal for parameter optimization especially for large basin area and it also can be used for less experienced SWAT model users.

The Uncertainty Analysis of SWAT Simulated Streamflow Applied to Chungju Dam Watershed (충주댐 유역의 유출량에 대한 SWAT모형의 예측불확실성 분석)

  • Joh, Hyung-Kyung;Park, Jong-Yoon;Shin, Hyung-Jin;Lee, Ji-Wan;Kim, Seong-Joon
    • Proceedings of the Korea Water Resources Association Conference
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    • 2011.05a
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    • pp.29-29
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    • 2011
  • SWAT (Soil and Water Assessment Tool) 모형은 물리적 기반의 준분포형 강우-유출 모형으로서, 대규모의 복잡한 유역에서 장기간에 걸친 다양한 종류의 토양과 토지이용 및 토지관리 상태에 따른 유출과 유사 및 오염물질의 거동에 대한 토지관리 방법의 영향을 예측이 가능하여, 수자원 관리 계획 및 유역관리를 위한 의사결정 지원 등 그 적용 범위가 매우 광범위하다. 이러한 모형의 적용성 검증을 위해서는 매개변수 민감도 분석 및 검 보정, 예측 불확실성 분석을 필요로 한다. 최근 수문 모델의 불확실성을 분석하기 위한 다양한 기법들이 개발 되었는데, 본 연구는 충주댐 유역(6,581.1 m)을 대상으로 유역출구점의 실측 일 유출량 자료(1998~2003)를 바탕으로 SWAT 모형의 유출관련 매개변수(총 18개)에 대한 불확실성 분석을 실시하였다. 이때 사용된 분석 기법으로는 SUFI2 (Sequential Uncertainty FItting algorithm 2), GLUE (Generalized Likelihood Uncertainty Estimation), ParaSol (Parameter Solution)등을 적용 하였다. 이러한 기법은 모두 SWAT-CUP (SWAT-Calibration Uncertainty Program, Abbaspour, 2007) 모형에 탑재되어있으며, 모형의 결과로써 검 보정, 매개변수의 민감도 분석, 각종 목적 함수 및 불확실성의 범위 등이 자동으로 산출 되므로 모형의 사용자가 불확실성 평가 기법의 분석 및 비교를 손쉽게 할 수 있다. 그 결과 대표적인 목적 함수인 결정 계수( $^2$)와 NSE (Nash-Sutcliffe Model Efficiency)는 모두 0.65에서 0.92사이의 값을 나타내어 대체적으로 모의가 잘 이루어졌음을 알 수 있었다. 그러나 불확실성의 범위를 나타내는 지표인 p-factor 및 r-factor에서는 평가 기법 별로 그 차이가 확연하게 드러났다. 여기서 p-factor는 불확실성 범위에 실측치가 포함되는 비율이며, r-factor는 불확실성의 상대적인 범위로 각각 1과 0에 가까울수록 모의 기법의 성능이 우수함을 의미한다. 세 가지 알고리듬 중에서 SUFI2의 p-factor가 약 0.51로 가장 높게 나타났으며, ParaSol의 r-factor가 0.00으로 가장 작게 나타났다. 여기서 p-factor는 불확실성 범위에 실측치가 포함되는 비율이며, r-factor는 불확실성의 상대적인 범위를 의미한다. 본 연구의 결과는 SWAT 모형을 이용한 수문모델링에서 수문분석에 따른 예측결과의 불확실성을 정량적으로 평가함으로서, 모형의 적용성 평가 및 모의결과의 신뢰성 확보에 근거자료로 활용이 가능할 것으로 판단된다.

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