• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.276-276
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• 2019

하천에서 신뢰성 있는 유속 및 유량의 측정 자료는 수자원의 효율적인 계획과 관리를 위한 가장 기본적인 사항이다. 유속 및 유량을 측정하기 위해 지금까지는 주로 프로펠러 유속계나 초음파유속계 또는 봉부자 등을 활용해왔으며, 홍수 시에는 봉부자에 의존하고 있다. 봉부자를 이용한 유속 측정은 측정 환경이나 측정자에 따라 정확도 차이가 난다는 한계점이 있다. 뿐만 아니라 실제로 홍수가 발생했을 때는 유량이 매우 크기 때문에 교량으로 접근이 어렵고 현장으로의 접근자체가 제한될 수 있다. 위와 같은 문제들을 해결하기 위한 대안으로 비접촉식 유속 측정방법인 표면영상유속계(LSPIV, Large Scale Particla Image Velocimetry)가 있다. 표면영상유속계는 수면을 촬영한 영상을 분석하여 표면 유속을 측정하는 기법으로, 영상 촬영 장비와 분석 소프트웨어만 있으면 유속을 측정할 수 있다. 유속 및 유량 측정 결과를 보고할 때는 그 결과를 사용하는 사람이 얼마나 믿고 사용해도 좋은가에 관한 신뢰성을 판단할 수 있도록 신뢰도를 나타내는 어떤 정량적인 값인 불확도를 유량 측정 결과와 함께 제시하여야 한다. 표면영상유속계는 매우 간편하고 신속하게 하천의 유속장을 측정하는 기법이지만 측정 불확도 산정에 대한 연구가 미흡하여 정확한 측정 불확도를 제시할 수 없는 실정이다. 표면영상유속계의 불확도 인자는 바람의 영향, 입자 밀도/크기, 촬영시간 간격, 상관영역의 크기, 전단흐름/회전흐름, 참조점 측량/식별, 이동거리 산정 등이 있다. 표면영상유속계의 측정불확도를 제시하기 위해서는 각 불확도 인자에 대한 불확도를 제시하여야 한다. 따라서 본 연구에서는 Matlab을 이용하여 표면영상유속계의 불확도 요인 중 영상에서 참조점식별 시 발생하는 불확도를 분석하고자 한다.

• Analytical Science and Technology
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• v.19 no.6
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• pp.490-497
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• 2006

The sources of uncertainty in the analysis of liquified natural gas (LNG) process are evaluated. The uncertainty sources evaluated are the repeatability of measurement, non-linearity of GC, the uncertainty of standard gas used for calibration, difference of gas sampling and deviation after GC calibration and major revealed sources are the non-linearity of GC, the uncertainty of standard gas and the deviation after GC calibration. The determined values and uncertainties of methane and ethane as the major components are $90.0%mol/mol{\pm}1.9%$ (relative and 95% level of confidence) and $6.26%mol/mol{\pm}0.08$ (relative and 95% level of confidence), respectively. The contribution of uncertainty varies depending on the source of uncertainty and gas component. In the case of methane, non-linearity of GC, the uncertainty of standard gas and deviation after GC calibration contribute 0.28%, 0.25% and 0.24% of relative expanded uncertainty, respectively.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.688-688
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• 2012

불확도의 요인은 유속-면적법에 적용되는 방정식의 일반화된 형태를 고려하여 나타낼 수 있다. 하천에 대한 불확도, 수심에 대한 불확도, 점 유속의 결정에 대한 불확도, 평균유속의 예측과 유량에 대한 불확도가 불확도산정에 많은 영향을 미치는 요소라 할 수 있다. 유량측정을 실시할 때 불확도를 개선하기 위해서는 유속에 비례하여 측선수를 조절함이 좋은 등급을 확보하기에 성과의 품질 향상에 크게 기여하는 결과를 얻을 수 있다. 본 연구에서는 자연하천의 현장지점에서 실시간 수위를 확인하며 유속을 측정하였고, 측정 성과를 이용하여 유량과 불확도를 산정, 비교 분석하였다. 유량측정에 있어 측정 기기로는 국내에서 일반적으로 사용되는 회전식 유속계(PriceAA)를 사용하여 측정을 실시하였으며, 측정방법으로는 도섭법을 기준으로 1점법, 2점법, 3점법에 이르게 다양한 성과를 실측하여 측정한 결과에 적용된 측선수에 따른 불확도를 분석하였다. 그 결과 0.5 m/s 이하의 유속과 $1.5m^3/s$ 의 유량에서는 그림 2에서 제시하였듯 30개 이상의 측선수를 확보하므로 5 % 미만의 2등급을 확보할 수 있었다. 그림 3은 9개의 지점 28회의 측정 결과를 측선수별 평균 불확도를 산정하여 유속 0.5m/s ~ 0.7m/s의 범위에서는 30개 미만의 측선수를 확보하여도 2등급의 품질을 확보할 수 있었으며, 이는 유속과 측선수의 관계를 나타내는 결과이다. 따라서 측정 자료의 신뢰성을 확보할 수 있는 2등급 이상을 얻기 위해서는 국제기준(ISO 748)에 따른 측선수를 적용하되 현장지점의 특성에 따라 유속을 고려한 측선수를 적용하는 것이 필요할 것으로 판단된다.

• Journal of Korea Water Resources Association
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• v.50 no.8
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• pp.521-535
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• 2017

Acoustic Doppler Current Profilers (ADCPs) have been widely utilized for assessing streamflow discharge, yet few comprehensive studies were conducted to evaluate discharge uncertainty in consideration of individual uncertainty components. It could be mostly because it was not easy to determine which uncertainty framework can be appropriate to rigorously analyze streamflow discharge driven by ADCPs. In this regard, considerable efforts have been made by scientific and engineering societies to develop a standardized theoretical framework for uncertainty analysis in hydrometry. One of the well-established UA methodology based on sound statistical and engineering concepts is Guide to the Expression of Uncertainty Measurement (GUM) adopted widely by various scientific and research communities. This research fundamentally adapted the GUM framework to assess individual uncertainty components of ADCP discharge measurements, and subsequently provided results of a customized experiment in a controllable real-scale artificial river channel. We focused particularly upon sensitivities of uncertainty components in the GUM framework driven by ADCPs direct measurements such as depths, edge distance, submerged depth, velocity gap, sampling time, repeatability, bed roughness and so on. Section-by-Section method for ADCP discharge measurement was applied for uncertainty analysis for this study. All of measurements were carefully compared with data using other instrumentations such as ADV to evaluate individual uncertainty components.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.1
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• pp.47-52
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• 2002

It was virtually declared that measurement science must abandon the error analysis of measurement when ISO had published "Guide to Expression of uncertainty in Measurement" International inclination of measurement field in order to guarantee the traceability and confidence of measurement results discards the error concept and instead analyzes the measurement uncertainty. In this paper we establish a mathematical model of measurement and analyze all uncertainty factors as possible as for yielding the measurement uncertainty in the course of the calibration of RF multimeter using Transfer Standard, Thermal Voltage Converter We produce the expanded uncertainty by analyzing cable effects, correlation of thermocoupler and DC meter, DC source, RF source, attenuator, reflection coefficients and DUT.s and DUT.

• Analytical Science and Technology
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• v.27 no.6
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• pp.269-276
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• 2014

A short study for the uncertainty of post column isotope dilution method has been performed for the analysis of Selenomethionine in HPLC-ICP/MS. Major error sources studied were concentration and the flow rate of Se isotope solution, atomic weights of Se in spike and sample, and isotope ratio measured for the spiked sample. Uncertainties were obtained for each factor and the contribution for the total concentration uncertainty was 54.4% and 0.61%, 0.0072% and 0.018%, and 45.0%, respectively. The biggest contribution factor was concentration of the spike solution and the second was the isotopic ratio measured for the spiked sample solution. The mass flow rate of spike and atomic weights did not show much contribution. The calculated total uncertainty was $1.46ng{\cdot}g^{-1}$ for the standard SeMet ($126.30ng{\cdot}g^{-1}$). The experimental result was $127.09{\pm}1.46ng{\cdot}g^{-1}$ and the relative uncertainty was 1.20%.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.6
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• pp.1139-1144
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• 2019

A calibration system for diagnosing and confirming the performance of precision measuring instruments minimizes the risk of misjudgment of calibration resulted by complying with international standard requirements in order to ensure the reliability of calibration results. This paper uses a proposed calibration system suitability assessment and a guard-band technique through an analysis of uncertainty factors when it is impossible to acquire and operate high-performance equipment at a calibration laboratory, and proposes an optimized test limit output model substituting performance standards. The proposed method provides an optimized test standard to meet the quantitative evaluation criteria of the calibration system and the probability of false acceptance risk required by international standards.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.4
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• pp.346-354
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• 2020

Nowadays, it is required to apply low observable technology to weapon systems in operation or under development. Radar Cross Section(RCS) is a measure of the scattered power in an given direction when a target is illuminated by an incident wave and used as a parameter to estimate the low observable performance of weapon system. RCS of a target can be calculated by various numerical methods. However, measurement is also needed to estimate RCS of a complex target because it is difficult to estimate theoretically. To acquire reliable measurement results, an analysis of measurement uncertainty is essential. In this paper, error components and uncertainties of near-field RCS measurement system which was constructed in ASTEC(Aerospace System Test & Evaluation Center) were analyzed based on the IEEE recommended practice for radar cross-section test procedures(IEEE Std. 1502-2007) which describes the uncertainty of RCS measurement and unique error components of this near-field measurement system were also identified.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.11
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• pp.1123-1131
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• 2008

In this study, measurement uncertainty of instrumental neutron activation analysis was evaluated for ambient As concentration in PM2.5. Expanded uncertainties of the measurements were calculated by applying both ISO-GUM approximation and Monte Carlo Simulation(MCS). The estimate of As concentration on a specific day by the Monte Carlo Simulation differed from that of ISO-GUM approximation by less than 4%. Relative expanded uncertainties of As concentrations from a total number of 60 PM2.5 samples were also estimated to be more or less than 10% with 95% confidence level using the Monte Carlo Simulation. Sensitivity test of the measurement uncertainties showed that $\gamma$-ray counting error(62.3%), efficiency(18.5%), air volume(12.3%), neutron flux(2.3%), and absolute gamma-intensity(1.8%) are major factors of uncertainty variations.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.7
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• pp.625-638
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• 2014

In this study, the uncertainties in the critical flow functions (CFFs) calculated by the AGA8-dc equation of state were estimated. To this end, the formulas for enthalpy, entropy, and speed of sound, which are used in calculating the CFF, were expressed in the form of dimensionless Helmholtz free energy and its derivatives, and the uncertainty in Helmholtz free energy was inferred. To consider the variations in the compressibility-dependent variables induced by the variation (i.e., uncertainty) in compressibility, the form of the AGA8-dc equation was modified to have a deviation equal to the uncertainty under each flow condition. For each independent uncertainty component of the CFF, a model for uncertainty contribution was developed. All these changes were applied to GASSOLVER, which is KOGAS's thermodynamic database. As a result, the uncertainties in the CFF were estimated to be 0.025, 0.055, and 0.112 % at 10, 50, and 100 bar, respectively, and are seen to increase with the increase in pressure. Furthermore, these results could explain the deviations in the CFFs across the different labs in which the CFF international comparison test was conducted under the ISO management in 1999.