• Title/Summary/Keyword: Uncertainty Distribution

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Uncertainty Analysis for the Multi-path Ultrasonic Flowmeter UR- 1000 with Dry Calibration (간접 교정에 의한 다회선 초음파유량계 UR-1000 불확도 분석)

  • Hwang, Shang-Yoon;Park, Sung-Ha;Park, Kyung-Am
    • 유체기계공업학회:학술대회논문집
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    • 2002.12a
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    • pp.378-386
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    • 2002
  • Multi-path ultrasonic Sow measurement system uncertainty is determined by assigning an expected error of each component of flow measurement and then defining the total flow measurement uncertainty as square root of the sum of squared values of the individual error. Sources of uncertainty for flow measurement are geometry, transit time and velocity profile integration uncertainty. A theoretical uncertainty model for multi-path ultrasonic transit time flowmeter configured with parallel 5 chords, is derived from and calculated by dry calibration method.

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GEOSTATISTICAL UNCERTAINTY ANALYSIS IN SEDIMENT GRAIN SIZE MAPPING WITH HIGH-RESOLUTION REMOTE SENSING IMAGERY

  • Park, No-Wook;Chi, Kwang-Hoon
    • Proceedings of the KSRS Conference
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    • 2007.10a
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    • pp.225-228
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    • 2007
  • This paper presents a geostatistical methodology to model local uncertainty in spatial estimation of sediment grain size with high-resolution remote sensing imagery. Within a multi-Gaussian framework, the IKONOS imagery is used as local means both to estimate the grain size values and to model local uncertainty at unsample locations. A conditional cumulative distribution function (ccdf) at any locations is defined by mean and variance values which can be estimated by multi-Gaussian kriging with local means. Two ccdf statistics including condition variance and interquartile range are used here as measures of local uncertainty and are compared through a cross validation analysis. In addition to local uncertainty measures, the probabilities of not exceeding or exceeding any grain size value at any locations are retrieved and mapped from the local ccdf models. A case study of Baramarae beach, Korea is carried out to illustrate the potential of geostatistical uncertainty modeling.

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Uncertainty Evaluation of Dynamic Pressure Calibrator by Monte Carlo Simulation (몬테카를로 모사를 이용한 동압력 교정기 불확도 평가)

  • Kim, Moon-Ki
    • Journal of the Korea Institute of Military Science and Technology
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    • v.13 no.4
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    • pp.665-672
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    • 2010
  • This paper describes Monte Carlo Simulation(MCS) to assess the uncertainty of dynamic pressure calibrator and the expanded uncertainty results that were compared by GUM approximation and MCS. MCS uncertainties were computed using defining a domain of possible inputs, generating inputs randomly using probability distribution, performing a deterministic computation repeatedly and aggregating the results. It was revealed that the expanded uncertainty between GUM and MCS was different from each other. the expanded uncertainties were 0.5366%, 0.4856%, respectively. MCS is a suitable method for determining the uncertainty of simple and complex measurement systems. It should be more widely used and studied in measurement uncertainty calculations.

Probabilistic estimation of fully coupled blasting pressure transmitted to rock mass I - Estimation of peak blasting pressure - (암반에 전달된 밀장전 발파압력의 확률론적 예측 I - 최대 발파압력 예측을 중심으로 -)

  • Park, Bong-Ki;Lee, In-Mo;Kim, Dong-Hyun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.5 no.4
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    • pp.337-348
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    • 2003
  • The propagation mechanism of a detonation pressure with fully coupled charge is clarified and the blasting pressure propagated in rock mass is derived from the application of shock wave theory. The blasting pressure was a function of detonation velocity, isentropic exponent, explosive density, Hugoniot parameters, and rock density. Probabilistic distribution is obtained by using explosion tests on emulsion and rock property tests on granite in Seoul and then the probabilistic distribution of the blasting pressure is derived from the above mentioned properties. The probabilistic distributions of explosive properties and rock properties show a normal distribution so that the blasting pressure propagated in rock can be also regarded as a normal distribution. Parametric analysis was performed to pinpoint the most influential parameter that affects the blasting pressure and it was found that the detonation velocity is the most sensitive parameter. Moreover, uncertainty analysis was performed to figure out the effect of each parameter uncertainty on the uncertainty of blasting pressure. Its result showed that uncertainty of natural rock properties constitutes the main portion of blasting pressure uncertainty rather than that of explosive properties. In other words, since rock property uncertainty is much larger than detonation velocity uncertainty the blasting pressure uncertainty is more influenced by the former than by the latter even though the detonation velocity is found to be the most influencing parameter on the blasting pressure.

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Estimation of confidence interval in exponential distribution for the greenhouse gas inventory uncertainty by the simulation study (모의실험에 의한 온실가스 인벤토리 불확도 산정을 위한 지수분포 신뢰구간 추정방법)

  • Lee, Yung-Seop;Kim, Hee-Kyung;Son, Duck Kyu;Lee, Jong-Sik
    • Journal of the Korean Data and Information Science Society
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    • v.24 no.4
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    • pp.825-833
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    • 2013
  • An estimation of confidence intervals is essential to calculate uncertainty for greenhouse gases inventory. It is generally assumed that the population has a normal distribution for the confidence interval of parameters. However, in case data distribution is asymmetric, like nonnormal distribution or positively skewness distribution, the traditional estimation method of confidence intervals is not adequate. This study compares two estimation methods of confidence interval; parametric and non-parametric method for exponential distribution as an asymmetric distribution. In simulation study, coverage probability, confidence interval length, and relative bias for the evaluation of the computed confidence intervals. As a result, the chi-square method and the standardized t-bootstrap method are better methods in parametric methods and non-parametric methods respectively.

Preliminary Research on the Uncertainty Estimation in the Probabilistic Designs

  • Youn Byung D.;Lee Jae-Hwan
    • Journal of Ship and Ocean Technology
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    • v.9 no.1
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    • pp.64-71
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    • 2005
  • In probabilistic design, the challenge is to estimate the uncertainty propagation, since outputs of subsystems at lower levels could constitute inputs of other systems or at higher levels of the multilevel systems. Three uncertainty propagation estimation techniques are compared in this paper in terms of numerical efficiency and accuracy: root sum square (linearization), distribution-based moment approximation, and Taguchi-based integration. When applied to reliability-based design optimization (RBDO) under uncertainty, it is investigated which type of applications each method is best suitable for. Two nonlinear analytical examples and one vehicle crashworthiness for side-impact simulation example are employed to investigate the unique features of the presented techniques for uncertainty propagation. This study aims at helping potential users to identify appropriate techniques for their applications in the multilevel design.

Power Performance Testing and Uncertainty Analysis for a 3MW Wind Turbine (3MW 풍력발전시스템 출력 성능시험 및 불확도 분석)

  • Kim, Keon-Hoon;Hyun, Seung-Gun
    • Journal of the Korean Solar Energy Society
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    • v.30 no.6
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    • pp.10-15
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    • 2010
  • The installed capacity of wind turbines in KOREA are growing and enlarging by the central government's support program. Thus, the importance of power performance verification and its uncertainty analysis are recognizing rapidly. This paper described the power testing results of a 3MW wind turbine and analysed an uncertainty level of measurements. The measured power curves are very closely coincide with the calculated one and the annual power production under the given Rayleigh wind speed distribution are estimated with the 3.6~12.7% of uncertainty but, in the dominant wind speed region as 7~8m/s, the uncertainty are stably decreased to 6.3~5.3%.

Comparison among Methods of Modeling Epistemic Uncertainty in Reliability Estimation (신뢰성 해석을 위한 인식론적 불확실성 모델링 방법 비교)

  • Yoo, Min Young;Kim, Nam Ho;Choi, Joo Ho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.27 no.6
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    • pp.605-613
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    • 2014
  • Epistemic uncertainty, the lack of knowledge, is often more important than aleatory uncertainty, variability, in estimating reliability of a system. While the probability theory is widely used for modeling aleatory uncertainty, there is no dominant approach to model epistemic uncertainty. Different approaches have been developed to handle epistemic uncertainties using various theories, such as probability theory, fuzzy sets, evidence theory and possibility theory. However, since these methods are developed from different statistics theories, it is difficult to interpret the result from one method to the other. The goal of this paper is to compare different methods in handling epistemic uncertainty in the view point of calculating the probability of failure. In particular, four different methods are compared; the probability method, the combined distribution method, interval analysis method, and the evidence theory. Characteristics of individual methods are compared in the view point of reliability analysis.

Private Equity Valuation under Model Uncertainty

  • BIAN, Yuxiang
    • The Journal of Asian Finance, Economics and Business
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    • v.9 no.1
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    • pp.1-11
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    • 2022
  • The study incorporates model uncertainty into the private equity (PE) valuation model (SWY model) (Sorensen et al., 2014) to evaluate how model uncertainty distorts the leverage and valuations of PE funds. This study applies a continuous-time model to PE project valuation, modeling the LPs' goal as multiplier preferences provided by Anderson et al. (2003), and assuming that LPs' aversion to model uncertainty causes endogenous belief distortions with entropy as a measure of model discrepancies. Concerns regarding model uncertainty, according to the theoretical model, have an unclear effect on LPs' risk attitude and GPs' decision, which is based on the value of the PE asset. It also demonstrates that model uncertainty lowers the certainty-equivalent valuation of the LPs. Finally, we compare the outcomes of the Full-spanning risk model with the Non-spanned risk model, and they match the intuitive economic reasoning. The most important implication is that model uncertainty will have negative effects on the LPs' certainty-equivalent valuation but has ambiguous effects on the portfolio allocation choice of liquid wealth. Our works contribute to two literature streams. The first is the literature that models the PE funds. The second is the literature introduces model uncertainty into standard finance models.

Comparison of ISO-GUM and Monte Carlo Method for Evaluation of Measurement Uncertainty (몬테카를로 방법과 ISO-GUM 방법의 불확도 평가 결과 비교)

  • Ha, Young-Cheol;Her, Jae-Young;Lee, Seung-Jun;Lee, Kang-Jin
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.7
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    • pp.647-656
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    • 2014
  • To supplement the ISO-GUM method for the evaluation of measurement uncertainty, a simulation program using the Monte Carlo method (MCM) was developed, and the MCM and GUM methods were compared. The results are as follows: (1) Even under a non-normal probability distribution of the measurand, MCM provides an accurate coverage interval; (2) Even if a probability distribution that emerged from combining a few non-normal distributions looks as normal, there are cases in which the actual distribution is not normal and the non-normality can be determined by the probability distribution of the combined variance; and (3) If type-A standard uncertainties are involved in the evaluation of measurement uncertainty, GUM generally offers an under-valued coverage interval. However, this problem can be solved by the Bayesian evaluation of type-A standard uncertainty. In this case, the effective degree of freedom for the combined variance is not required in the evaluation of expanded uncertainty, and the appropriate coverage factor for 95% level of confidence was determined to be 1.96.