• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3221-3223
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• 2007

Recently, nuclear power plant companies have been extending the turbine valve test interval to reduce the potential of the reactor trip accompanied with a turbine valve test and to improve the NPP's economy through the reduction of unexpected plant trip or decreased operation. In these regards, the extension of the test interval for turbine valves was reviewed in detail. The effect on the destructive overspeed probability due to the test interval change of turbine valves is evaluated by Fault Tree Analysis(FTA) method. Even though the test interval of turbine valves is changed from 1 month to 3 months, the analysis result shows that the reliability of turbine over speed protection system meets acceptance criteria of 1.0E-4/yr. This result will be used as the technical basis on the extension of the test interval for turbine valves. In this paper, the propriety of the turbine valve test interval extension is explained through the review on the turbine valve test interval status of turbine overspeed protection system, the analysis on the annual turbine missile frequency and the probability evaluation of the destructive overspeed due to the test interval extension.

• Corrosion Science and Technology
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• 제22권5호
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• pp.377-386
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• 2023

Aircraft washing is performed periodically for corrosion control. Currently, the aircraft washing interval is qualitatively set according to the geographical conditions of each base. We developed a washing interval determination algorithm based on atmospheric corrosion environment monitoring data at the Republic of Korea Air Force (ROKAF) bases and United States Air Force (USAF) bases to determine the optimal interval. The main factors of the washing interval decision algorithm were identified through hierarchical clustering, sensitivity analysis, and analysis of variance, and criteria were derived. To improve the classification accuracy, we developed a washing interval decision model based on an artificial neural network (ANN). The ANN model was calibrated and validated using the atmospheric corrosion environment monitoring data and washing intervals of the USAF bases. The new algorithm returned a three-level washing interval, depending on the corrosion rate of steel and the results of the ANN model. A new base-specific aircraft washing interval was proposed by inputting the atmospheric corrosion environment monitoring results of the ROKAF bases into the algorithm.

• Journal of applied mathematics & informatics
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• 제29권5_6호
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• pp.1557-1569
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• 2011

In this paper, we consider the oscillation of the following certain second order nonlinear differential equations $(r(t)(x^{\prime}(t))^{\alpha})^{\prime}+q(t)x^{\beta}(t)=0$>, where ${\alpha}$ and ${\beta}$ are ratios of positive odd integers. New oscillation theorems are established, which are based on a class of new functions ${\Phi}={\Phi}(t,s,l)$ defined in the sequel. Also, we establish some interval oscillation criteria for this equation.

• Journal of Information Processing Systems
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• 제14권3호
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• pp.790-800
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• 2018

The simplified neutrosophic set (SNS) is a generalization of fuzzy set that is designed for some practical situations in which each element has truth membership function, indeterminacy membership function and falsity membership function. In this paper, we propose a new method to construct similarity measures of single valued neutrosophic sets (SVNSs) and interval valued neutrosophic sets (IVNSs), respectively. Then we prove that the proposed formulas satisfy the axiomatic definition of the similarity measure. At last, we apply them to pattern recognition under the single valued neutrosophic environment and multi-criteria decision-making problems under the interval valued neutrosophic environment. The results show that our methods are effective and reasonable.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1999년도 추계학술발표회요약집
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• pp.201.2-201
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• 1999

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2012년도 한국컴퓨터종합학술대회논문집 Vol.39 No.1(A)
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• pp.406-408
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• 2012

본 논문의 연구목적은 Grey Relational Analysis와 Interval Weight을 이용하여 다수의 업체가 있는 커뮤니티 환경에서 최적의 업체를 선정하기 위한 방법론을 제공하는 것이다. 일반적으로 하나의 의사를 결정하기 위해서는 대안과 이와 관련된 기준과 같은 다양한 변수들이 고려되어야 한다. 커뮤니티 내의 다수의 업체 평가를 위해 평가기준에 대한 가중치를 도출하고 최종적으로 평가결과를 도출하기 위해 Grey Relational Analysis와 Interval Weight에 기반을 둔 다중의사결정 방법을 제안하였다.

• 한국소음진동공학회논문집
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• 제12권6호
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• pp.453-460
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• 2002

In this paper, vibration criteria for fresh concrete are suggested considering relationship of strength and ages of concrete. Vibration criteria of fresh concrete subjected to construction vibration are not to be certain in abroad countries without question within a country. Before 12 hours cured, vibration criterion is suggested 0.25 cm/s. Used 4.0 cm/s by vibration criterion after 28 days. And the interval extent used relation with strength and ages of concrete. Vibration criteria proposed in this paper are thought may satisfy properties of fresh concrete as well as generally used those in domestic. Also, the actual ground vibrations due to pile driving have been measured, and data are analyze using the nitration equation applying to reliability index.

• CRM연구
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• 제4권2호
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• pp.19-29
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• 2011

오프라인 쇼핑몰에 비해 온라인 쇼핑몰은 빠르게 접근이 가능하기 때문에 처음 구매의사를 생성하고 실제 구매가 이루어지기까지의 기간이 오프라인 쇼핑몰에 비해 매우 짧게 나타난다. 즉 오프라인 쇼핑몰의 경우 구매 희망물건을 바로 구매하기 보다는 몇 개의 물건들을 모두 모아서 구매하는 행태가 일반적이다. 하지만, 인터넷 쇼핑몰의 경우 단 하나의 물품만을 포함하고 있는 주문이 전체 주문의 절반이상을 차지한다. 이러한 차이는 온라인 쇼핑몰 거래데이터의 분석을 위해서는 데이터 마이닝 분석에서 사용되어 온 장바구니의 정의에 대한 확장이 필요함을 의미한다. 하지만 현재까지 온라인 데이터를 대상으로 한 장바구니 분석 연구는, 장바구니의 기준 즉 동시구매의 기준에 대한 명확한 근거나 합의 없이 연구자의 선택에 따라 서로 다른 기준으로 수행되어왔다. 따라서 본 연구에서는 온라인 쇼핑몰 분석에 적용되는 동시에 구매되는 물건들에 대한 기준을 고찰해보고 연구모형을 마련하고자 한다.

• International Journal of Advanced Culture Technology
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• 제8권4호
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• pp.64-76
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• 2020

Purpose: Several screening tools have been developed to identify sarcopenia in rural community-dwelling older adults. We aimed to compare the diagnostic accuracy of two such tools, namely the SARC-F and SARC-CalF assessments. Methods: This cross-sectional study on 388 community-dwelling older adults comprised 254 women and 134 men with a mean age of 77.8 ± 6.26 year in Korea. We assessed muscle mass, muscle strength, and physical performance using a bioimpedance analysis device, hydraulic hand dynamometer, and 4 m gait speed test, respectively. Three widely-used diagnostic criteria [the Asian Working Group for Sarcopenia (AWGS), European Working Group on Sarcopenia in Older People, and the International Working Group on Sarcopenia] were applied. Sensitivity and specificity analyses were performed on the SARC-CalF and SARC-F tests. We used receiver-operating characteristic curves and the area under the curves (AUCs) to compare the diagnostic accuracy of the assessments with regard to sarcopenia. Results: An analysis using four sets of diagnostic criteria showed that the prevalence of sarcopenia was 27.6% to 41.0%. Using the AWGS 2019 criteria as a reference standard, the SARC-CalF had a sensitivity of 83.02% and a specificity of 53.71% in the entire study population, whereas the SARC-F had a sensitivity of 79.87% and a specificity of 41.92%. The AUCs for the SARC-CalF and SARC-F tests were 0.725 (95% confidence interval 0.678-0.769) and 0.645 (95% confidence interval 0.595-0.693), respectively (p<001). In the analyses using the other three diagnostic criteria, similarity was also confirmed. Conclusion: SARC-CalF showed better sensitivity than did SARC-F when diagnosing sarcopenia in rural community-dwelling older adults. Further studies are needed to verify this finding in different populations.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1542-1550
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• 2013

This paper presents new results on delay-dependent global exponential stability for uncertain linear systems with interval time-varying delay. Based on Lyapunov-Krasovskii functional approach, some novel delay-dependent stability criteria are derived in terms of linear matrix inequalities (LMIs) involving the minimum and maximum delay bounds. By using delay-partitioning method and the lower bound lemma, less conservative results are obtained with fewer decision variables than the existing ones. Numerical examples are given to illustrate the usefulness and effectiveness of the proposed method.