• 제목/요약/키워드: Round robin

검색결과 340건 처리시간 0.031초

로크웰 경도 국제비교교정 결과 분석 (Analysis on the Results of the World Wide Rockwell Hardness Round Robin Test with Conical Indenters)

  • 방건웅;탁내형
    • 열처리공학회지
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    • 제14권6호
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    • pp.336-344
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    • 2001
  • For the establishment of the world wide unified scales of the Rockwell hardness test with conical indenters, round robin test was carried from 1998 to 2000. The pilot laboratory was MPA-NRW and 12 laboratories from 11 countries participated In this RRT. Rockwell hardness of 74 specially prepared blocks was measured for the scales of C, A, D, 45N, 30N, and 15N and the results were compared. It was found that the geometric form of indenter affects on the results very significantly and standardization in the measurement and evaluation of indenter should be established in short time for the reliable hardness measurement. KRISS showed good results in general for all of the ranges except 15N scale which showed relatively large difference compare to the mean value. It was concluded that poor control in loading velocity of the dash pot was the major reason.

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Round Robin Analyses on Stress Intensity Factors of Inner Surface Cracks in Welded Stainless Steel Pipes

  • Han, Chang-Gi;Chang, Yoon-Suk;Kim, Jong-Sung;Kim, Maan-Won
    • Nuclear Engineering and Technology
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    • 제48권6호
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    • pp.1412-1422
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    • 2016
  • Austenitic stainless steels (ASSs) are widely used for nuclear pipes as they exhibit a good combination of mechanical properties and corrosion resistance. However, high tensile residual stresses may occur in ASS welds because postweld heat treatment is not generally conducted in order to avoid sensitization, which causes a stress corrosion crack. In this study, round robin analyses on stress intensity factors (SIFs) were carried out to examine the appropriateness of structural integrity assessment methods for ASS pipe welds with two types of circumferential cracks. Typical stress profiles were generated from finite element analyses by considering residual stresses and normal operating conditions. Then, SIFs of cracked ASS pipes were determined by analytical equations represented in fitness-for-service assessment codes as well as reference finite element analyses. The discrepancies of estimated SIFs among round robin participants were confirmed due to different assessment procedures and relevant considerations, as well as the mistakes of participants. The effects of uncertainty factors on SIFs were deducted from sensitivity analyses and, based on the similarity and conservatism compared with detailed finite element analysis results, the R6 code, taking into account the applied internal pressure and combination of stress components, was recommended as the optimum procedure for SIF estimation.

Load Balancing Approach to Enhance the Performance in Cloud Computing

  • Rassan, Iehab AL;Alarif, Noof
    • International Journal of Computer Science & Network Security
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    • 제21권2호
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    • pp.158-170
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    • 2021
  • Virtualization technologies are being adopted and broadly utilized in many fields and at different levels. In cloud computing, achieving load balancing across large distributed virtual machines is considered a complex optimization problem with an essential importance in cloud computing systems and data centers as the overloading or underloading of tasks on VMs may cause multiple issues in the cloud system like longer execution time, machine failure, high power consumption, etc. Therefore, load balancing mechanism is an important aspect in cloud computing that assist in overcoming different performance issues. In this research, we propose a new approach that combines the advantages of different task allocation algorithms like Round robin algorithm, and Random allocation with different threshold techniques like the VM utilization and the number of allocation counts using least connection mechanism. We performed extensive simulations and experiments that augment different scheduling policies to overcome the resource utilization problem without compromising other performance measures like makespan and execution time of the tasks. The proposed system provided better results compared to the original round robin as it takes into consideration the dynamic state of the system.

Round robin analysis to investigate sensitivity of analysis results to finite element elastic-plastic analysis variables for nuclear safety class 1 components under severe seismic load

  • Kim, Jun-Young;Lee, Jong Min;Park, Jun Geun;Kim, Jong-Sung;Cho, Min Ki;Ahn, Sang Won;Koo, Gyeong-Hoi;Lee, Bong Hee;Huh, Nam-Su;Kim, Yun-Jae;Kim, Jong-In;Nam, Il-Kwun
    • Nuclear Engineering and Technology
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    • 제54권1호
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    • pp.343-356
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    • 2022
  • As a part of round robin analysis to develop a finite element elastic-plastic seismic analysis procedure for nuclear safety class 1 components, a series of parametric analyses was carried out on the simulated pressurizer surge line system model to investigate sensitivity of the analysis results to finite element analysis variables. The analysis on the surge line system model considered dynamic effect due to the seismic load corresponding to PGA 0.6 g and elastic-plastic material behavior based on the Chaboche combined hardening model. From the parametric analysis results, it was found that strains such as accumulated equivalent plastic strain and equivalent plastic strain are more sensitive to the analysis variables than von Mises effect stress. The parametric analysis results also identified that finite element density and ovalization option in the elbow elements have more significant effect on the analysis results than the other variables.

라운드로빈 평가 결과에 기반한 국내 기관의 용접잔류응력 해석 분포의 불확실성 평가 (Uncertainty Quantification of Welding Residual Stress Analysis based on Domestic Organizations Round-Robin Evaluation)

  • 정성균;전준영;김찬규;오창식;강성식; 오창영
    • 한국압력기기공학회 논문집
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    • 제19권2호
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    • pp.130-139
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    • 2023
  • This paper examines the quantification of uncertainty for welding residual stresses in dissimilar metal welds used in nuclear power plants. A mock-up of a dissimilar metal weld pipe, consisting of carbon and stainless steel pipes, was fabricated to measure the residual stress. A Round-Robin analysis was conducted by Korean institutions to assess the welding residual stress. The analysis was carried out in the second order, and the data obtained by each institution was evaluated based on the information provided. Using the Round-Robin results, the distribution of uncertainty in welding residual stresses among Korean institutions was evaluated. The quantification of uncertainty for Korean institutions was found to have a wider range compared to the distribution of welding residual stresses observed in overseas institutions. This study is considered useful in the establishment of comprehensive strategies for evaluating welding residual stress analysis methods used by domestic institutions.