• Journal of Korea Water Resources Association
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• v.51 no.spc
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• pp.1079-1089
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• 2018

The majority of existing studies for quantifying uncertainties in climate change impact assessments suggest only the uncertainties of each stage, and not the total uncertainty and its propagation in the whole procedure. Therefore, this study has proposed a new method, the Uncertainty Delta Method (UDM), which can quantify uncertainties using the variances of projections (as the UDM is derived from the first-order Taylor series expansion), to allow for a comprehensive quantification of uncertainty at each stage and also to provide the levels of uncertainty propagation, as follows: total uncertainty, the level of uncertainty increase at each stage, and the percentage of uncertainty at each stage. For quantifying uncertainties at each stage as well as the total uncertainty, all the stages - two emission scenarios (ES), three Global Climate Models (GCMs), two downscaling techniques, and two hydrological models - of the climate change assessment for water resources are conducted. The total uncertainty took 5.45, and the ESs had the largest uncertainty (4.45). Additionally, uncertainties are propagated stage by stage because of their gradual increase: 5.45 in total uncertainty consisted of 4.45 in emission scenarios, 0.45 in climate models, 0.27 in downscaling techniques, and 0.28 in hydrological models. These results indicate the projection of future water resources can be very different depending on which emission scenarios are selected. Moreover, using Fractional Uncertainty Method (FUM) by Hawkins and Sutton (2009), the major uncertainty contributor (emission scenario: FUM uncertainty 0.52) matched with the results of UDM. Therefore, the UDM proposed by this study can support comprehension and appropriate analysis of the uncertainty surrounding the climate change impact assessment, and make possible a better understanding of the water resources projection for future climate change.

• YAKHAK HOEJI
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• v.52 no.6
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• pp.480-487
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• 2008

We described an estimation of measurement uncertainty in quantitative analysis of 11-nor-9-carboxy-${\Delta}^9$-tetrahydrocannabinol (THCCOOH), the major metabolite of ${\Delta}^9$-tetrahydrocannabinol, in urine sample by solid-phase extraction (SPE) and GC/MS detection. The analytical results were compared and the different contributions to the uncertainty were evaluated. Inter-day and inter-person validation were performed using statistical analysis of several indicative factors. Measurement uncertainty associated with target analyte in real forensic samples was estimated using quality control (QC) data. Traceability of measurement was established through traceable standards, calibrated volumetric glassware and volume measuring device. The major factors of contribution to combined standard uncertainty, were calibration linearity, inter-day repeatability and inter-person reproducibility, while those associated with preparation of analytical standards and sampling volume were not so important considering the degree of contribution. Relative combined standard uncertainties associated with the described method was 12.05% for THCCOOH.

• Journal of Korea Water Resources Association
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• v.51 no.5
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• pp.439-449
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• 2018

Many potential sources of bias are used in several steps of the radar-rainfall estimation process because the hydrological and meteorological radars measure the rainfall amount indirectly. Previous studies on radar-rainfall uncertainties were performed to reduce the uncertainty of each step by using bias correction methods in the quantitative radar-rainfall estimation process. However, these studies do not provide comprehensive uncertainty for the entire process and the relative ratios of uncertainty between each step. Consequently, in this study, a suitable approach is proposed that can quantify the uncertainties at each step of the quantitative radar-rainfall estimation process and show the uncertainty propagation through the entire process. First, it is proposed that, in the suitable approach, the new concept can present the initial and final uncertainties, variation of the uncertainty as well as the relative ratio of uncertainty at each step. Second, the Maximum Entropy Method (MEM) and Uncertainty Delta Method (UDM) were applied to quantify the uncertainty and analyze the uncertainty propagation for the entire process. Third, for the uncertainty quantification of radar-rainfall estimation at each step, two quality control algorithms, two radar-rainfall estimation relations, and two bias correction methods as post-processing through the radar-rainfall estimation process in 18 rainfall cases in 2012. For the proposed approach, in the MEM results, the final uncertainty (from post-processing bias correction method step: ME = 3.81) was smaller than the initial uncertainty (from quality control step: ME = 4.28) and, in the UDM results, the initial uncertainty (UDM = 5.33) was greater than the final uncertainty (UDM = 4.75). However uncertainty of the radar-rainfall estimation step was greater because of the use of an unsuitable relation. Furthermore, it was also determined in this study that selecting the appropriate method for each stage would gradually reduce the uncertainty at each step. Therefore, the results indicate that this new approach can significantly quantify uncertainty in the radar-rainfall estimation process and contribute to more accurate estimates of radar rainfall.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.204-204
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• 2018

수문 기상레이더는 강우량을 바로 추정하지 못하고 여러 단계의 정량적 강우량 추정과정을 거치게 되므로 많은 불확실성 발생요소가 존재한다. 불확실성 관련한 기존 연구들은 정량적 레이더 기반 강우량 추정과정에서 보정방법을 이용하여 각 단계별 불확실성을 줄이는 연구들을 수행하였다. 하지만 기존 연구들은 전체 과정에 대한 포괄적인 불확실성을 나타내지 못하고 각 단계별 불확실성의 상대적인 비율도 제시하지 못하는 단점이 있다. 본 연구에서는 정량적 레이더강우량 추정과정의 각 단계별 불확실성을 정량화하고 불확실성 전파를 나타낼 수 있는 적합한 방법을 제시하였다. 첫 번째로 초기와 최종 불확실성, 각 단계별 불확실성의 변동과 상대적인 비율을 나타낼 수 있는 새로운 개념을 제안하였다. 두 번째로 레이더기반 추정과정의 불확실성 정량화와 전파과정을 분석하기 위해 Maximum Entropy Method (MEM), Uncertainty Delta Method (UMD), Modified-Narrow Uncertainty Method (M-NUM)를 적용하였다. 세 번째로 레이더기반 강우량 추정과정의 불확실성 정량화를 위해 2개 품질관리 알고리즘, 2개 강우량 추정방법, 2개 후처리 강우량 보정방법을 2012년 여름철 18개 사례에 대하여 사용하였다. 적용결과, 최종 불확실성(후처리 강우량 보정 불확실성)이 초기 불확실성(품질관리 불확실성)보다 작게 나타나 불확실성이 감소하는 것으로 나타났다. 하지만 레이더강우량 추정단계의 불확실성은 증가하는 것으로 나타났다. 또한 레이더강우량 추정과정에서 각 단계별로 적합한 방법을 선정하는 것이 각 단계별로 불확실성이 감소시킬 수 있음을 확인하였다. 따라서 본 연구는 새로운 방법이 명확히 불확실성을 정량화할 수 있으며 정확한 정량적 레이더 강우추정에 기여할 것으로 판단한다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.4
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• pp.202-208
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• 2005

In Korea it tends to rely on foreign standards for the stability management of the embankment slope on the soft clay layer. The Matsuo-Kawamura's method, the Kurihara's method, the Tominaga- Hashimoto's method and the Shibata-Sekiguchi's method are generally employed at site. In this study these slope stability methods are investigated and the applicability of the stability management methods is evaluated through numerical analysis. It is evaluated that stability is overestimated to some degree by the Matsuo-Kawamura method. According to the result by the Tominaga-Hashimoto method there is some risk of sudden failure. This implies that the careful attention is necessary for the management of monitoring the field data. Even though the stability tends to be underestimated by the Kurihara's method, however, it is estimated that this method is applicable to the field when the probable uncertainty at site is considered. For the Shibata-Sekiguchi's method, there is some difficulties in determining the failure index for the practical application, it is considered as safe when the existing estimated failure index is greater than ${\Delta}_q/{\Delta}{\delta}$. In this study, however, it is evaluated to be safe as well when ${\Delta}_q/{\Delta}{\delta}$ to load shows the tendency of constant increase.

• Publications of The Korean Astronomical Society
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• v.32 no.3
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• pp.407-420
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• 2017

We study the operation of a lunisolar calendar in Korea and its time data calculation method. The dates based on the lunisolar calendar have been conventionally used in Korea after the Gregorian calendar was introduced in 1896. With the Astronomy Act enacted in 2010, the lunisolar calendar is presently being used as an official calendar along with the Gregorian calendar. However, no institutionalized regulations have been provided on the time data calculation method by the lunisolar calendar. The Korea Astronomy and Space Science Institute very recently established the regulations on the lunisolar calendar operation in Korea. We introduce the regulations together with historical substances and analyze the time data calculated according to the regulations for 600 years from 1901 to 2500. From our study, we find that the value of ${\Delta}T$ (i.e., the difference between the terrestrial time and the universal time) is the most critical parameter causing uncertainty on the data. We also find that all new Moon days in the almanacs agree with our calculations since 1912. Meanwhile, we find that new Moon and winter solstice times are found to be very close to midnight in 38 and five cases, respectively. For instance, the new Moon time on January 14, 2097 is 0 h 0 min 8 s. In this case, deciding the first day (i.e., new moon day) in a lunar month is difficult because of the large uncertainty in the value of ${\Delta}T$. Regarding with a lunar leap month, we find that the rules of inserting the leap month do not apply for 17 years. In conclusion, we believe that our findings are helpful in determining calendar days by using the lunisolar calendar.

• Journal of Power System Engineering
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• v.11 no.3
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• pp.35-40
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• 2007

Leak would happen because of the damage of high temperature and high-pressure valve in nuclear power plant. condition based prevention maintenance is essential by using the suitable method based on local condition. Energy loss prevention can prevent from an accurate test, Local actually and ability. The methods of test for high energy fluid leak at present are analysis of ${\Delta}T$, AE(Acoustic Emission) analysis, and thermal image. The result for test of secondary system in nuclear power plant Unit reveals that the AE occurred clearly in leakage situation, but thermal image didn't occur. It is identified that leak is occurred when the orifice located front and back of valve operates. It shows that making a impatient judgment by using the single method if it is leakage is containing uncertainty. So we think that using the Multi-Measuring method is more sound judgment than single-measuring method.

• Journal of Applied Reliability
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• v.18 no.3
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• pp.271-279
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• 2018

Purpose: Probabilistic safety analysis was performed to enhance the safety and reliability of nuclear power plants because traditional deterministic approach has limitations in predicting the risk of failure by crack growth. The study introduces a probabilistic approach to establish a basis for probabilistic safety assessment of passive components. Methods: For probabilistic modeling of fatigue crack growth rate (FCGR), various FCGR tests were performed either under constant load amplitude or constant ${\Delta}K$ conditions by using heat treated X-750 at low temperature with adequate cathodic polarization. Bayesian inference was employed to update uncertainties of the FCGR model using additional information obtained from constant ${\Delta}K$ tests. Results: Four steps of Bayesian parameter updating were performed using constant ${\Delta}K$ test results. The standard deviation of the final posterior distribution was decreased by a factor of 10 comparing with that of the prior distribution. Conclusion: The method for developing a probabilistic crack growth model has been designed and demonstrated, in the paper. Alloy X-750 has been used for corrosion fatigue crack growth experiments and modeling. The uncertainties of parameters in the FCGR model were successfully reduced using the Bayesian inference whenever the updating was performed.

• Journal of the Korean Data and Information Science Society
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• v.26 no.4
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• pp.971-984
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• 2015

Imputation procedures fill-in missing values, thereby enabling complete data analyses. Fully efficient fractional imputation (FEFI) and multiple imputation (MI) create multiple versions of the missing observations, thereby reflecting uncertainty about their true values. Methods have been described for hypothesis testing with multiple imputation. Fractional imputation assigns weights to the observed data to compensate for missing values. The focus of this article is the development of tests of independence using FEFI for partially classified two-way contingency tables. Wald and deviance tests of independence under FEFI are proposed. Simulations are used to compare type I error rates and Power. The partially observed marginal information is useful for estimating the joint distribution of cell probabilities, but it is not useful for testing association. FEFI compares favorably to other methods in simulations.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3458-3463
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• 2007

Leakage would happen because of the damage of high temperature and high-pressure valve in nuclear power plant. condition based prevention maintenance is essential by using the suitable method based on local condition. Energy loss prevention can prevent from an accurate test, Local actually and ability. The methods of test for high energy fluid leakage at present are analysis of ${\Delta}$T, AE(Acoustic Emission) analysis, and thermal image. The result for test of AC (Main steam) system in YNG 2 Unit reveals that the AE occurred clearly in leakage situation, but thermal image didn't occur. It is identified that leakage is occurred when the orifice located front and back of valve operates. It shows that making a impatient judgment by using the single method if it is leakage is containing uncertainty. So I think that using the Multi-Measuring method is more sound judgment than Single-Measuring method.