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이경수(Lee Kyoungsoo),김홍덕(Kim Hongdeok),박상규(Park Sangkyu),이요섭(Lee Yoseob),이재곤(Lee Jaegon) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
Recently some of the components serviced in nuclear power plant were identified that the material test reports did not fully satisfy the code requirements. They did not include simulated post weld heat treatment record in detail and raised questions how to apply heat treatment following after repair of the components. Lots of test and analyes were performed to verify that the material met the requirements and to evaluate that the components could be used without replacement. This paper presents the review process and results how to evaluate the integrity of components which have unsatisfied material test report.
용접후열처리가 2.25Cr-1Mo 강 밸브 및 배관재 물성에 미치는 영향
김홍덕,이요섭,이재곤,이경수,Kim, Hongdeok,Lee, Yoseob,Lee, Jaegon,Lee, Kyoungsoo 한국압력기기공학회 2015 한국압력기기공학회 논문집 Vol.11 No.1
The effects of post weld heat treatment(PWHT) on the mechanical properties of 2.25Cr-1Mo steels were investigated. As the PWHT temperature or holding time increased, the strength of low alloy steels progressively decreased due to softening process. After the conventional PWHT, the strength was larger than the minimum value of materials specification. The Charpy impact energy was hardly affected by the conventional PWHT. The trend of mechanical properties was analyzed in terms of tempering parameter. Most materials replaced from a power plant met the requirements of materials specification except for one heat. Same heat of materials with low impact energy were attributed to the voids formed during casting process.
Byun Sang-Min,Na Yong-Su,Chung Kyoung-Jae,Kim Deok-Kyu,Lee Sangjun,Lee Chanyoung,Lee Jaegon,Ryu Jonghyeon 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.9
This paper deals with a newly developed resistive magnetohydrodynamic code, STHENO, for X-pinch analyses on 3D (x, y, z) and 2D (r, z) geometry. The single-fluid two-temperature model is adopted by assuming collisional plasmas. The thermodynamic parameters for various wire materials are employed from the corrected Thomas–Fermi model with the ionization potential in STHENO. The 2D results, which is initially assumed the hollow conical structure for X-pinch, demonstrates the development of the micron Z-pinch and the plasma instability of m = 0. These results are compared with the experiment in Seoul National University, and show a good agreement in the time evolution of the radiation power. The 3D result with STHENO is also found to capture the magnetic field reversal structure and the jet formation.
Synchronization of Nonidentical Phase Oscilators in Directed Networks
Jaegon Um,Sung-Ik Lee,김범준 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2
The synchronization behavior of Kuramoto-type nonidentical oscilators on directed networks is numericaly studied. We start from the pure structure of the directed tre and build directed networks by spliting each edge at a given probability p with the total incoming edge weight of eachvertexpreserved. As more edges are split for a given network size, the synchronization order parameter is found to decrease and then to increase beyond the value for the original tree structure at p = 0. We also investigate the synchronization behaviors of networks in the thermodynamic limit via an analytic approach within the linear approximation and a finite-size scaling numerical analysis: Whereas nonidentical oscilators cannot be synchronized at any fnite coupling strength in the infinite-sized tre networks at p = 0, splitings of sufficient number of edges are shown to lead to ap hase transition at a finite coupling strength. From these findings, we discuss the role of bidirectional information transfer in the synchronization behavior of directed networks.