• Nuclear Engineering and Technology
• /
• v.52 no.8
• /
• pp.1862-1870
• /
• 2020

The purpose of this study is to investigate the effect of welding residual stress on operating stress in designing a nuclear turbine welded rotor. A two-dimensional axisymmetric finite element model is employed to calculate the residual stress before and after post weld heat treatment (PWHT), and then the superposition of residual stress after PWHT and operating stress at normal speed and overspeed were discussed. The investigated results show that operating stress can be affected significantly by welding residual stress, and the distribution trend of superposition stress at the weld area is mainly determined by welding residual stress. The superposition of residual stress and operating stress is linear superposition, and the hoop stress distribution of superposition stress is similar with the distribution of residual stress. With the increasing overspeed, the distribution pattern of the hoop superimposed stress remains almost unchanged, while the stress level increases.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.8 s.251
• /
• pp.976-984
• /
• 2006

Time-temperature superposition has been studied to determine the long-term fatigue life over millions of cycles for glassy polymers. π le superposition is supposed to make an accelerated lifetime testing (ALT) technique possible. Dog-bone shaped specimens made of carbon filled Polycarbonate (PC) were tested under fatigue, based on the stress-lifetime approach (S-N curve). Fatigue-induced localized yield-like deformation is considered as the defect leading to fatigue and its evolution behavior is characterized by a modified energy activation model in which temperature is considered as fatigue acceleration factor. This model allows the reduced time concept to account for effects of different temperature in short-term fatigue data to determine long-term fatigue life through the use of time-temperature superposition that is applicable under a low frequency and isothermal conditions. The experimental results validated that the proposed technique could be a possible method for accelerated lifetime testing (ALT) of time-dependent polymeric materials.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.7 no.3
• /
• pp.39-45
• /
• 2003

Modified Lanczos vector superposition method is proposed for efficient dynamic analysis of structures, The proposed method is based on the modified Lanczos algorithm that generates stiffness-orthonormal Lanczos vectors. The proposed Lanczos vector superposition method has the same accuracy and efficiency as the conventional Lonczos vector superposition method in the analysis of structures under single input loads. On the other hand, the proposed method is more efficient than the conventional method in the analysis of structures under multi-input loads. The effectiveness of the proposed method is verified by analyzing two numerical examples.

• Journal of Ocean Engineering and Technology
• /
• v.20 no.1 s.68
• /
• pp.43-47
• /
• 2006

Superposition of three wave trains on finite depth is investigated. This paper is focused on how to improve the linear superposition of three waves. This was realized by introducing the scheme. The idea of the scheme is based on a fixed point approach. Application of the scheme to the superposition makes it possible to obtain a wave profile of wave-wave interaction. With the help of FFT, it was possible to analyze high-order nonlinear frequencies for three interacting Stokes' waves on finite depth.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1608-1609
• /
• 2011

In this study, in order to develop the evaluation method for XLPE materials for HVDC cables, DC/Impulse superposition testing system was builded up. Throughout the P-spice simulation, optimal values of the protection resistor for the DC generation system and the blocking capacitor for the Impulse generator were calculated. DC/Impulse superposition system showed good result maintaining their proper wave shapes and amplitudes. This system would be planned to apply to the evaluation of XLPE materials for HVDC cables.

• Journal of IKEEE
• /
• v.24 no.1
• /
• pp.360-363
• /
• 2020

We present the power of the correlated superposition coding (SC) in non-orthogonal multiple access (NOMA). This paper derives closed-form expressions for the total allocated power with the constant total transmitted power. It is shown that the total allocated power is the function of a correlation coefficient. In result, the correlated SC NOMA should be designed with consideration of the correlation coefficient.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2000.04a
• /
• pp.89-92
• /
• 2000

In this paper, an effective procedure is presented for the local recovery of displacements and stresses in multilayered composite panels, which incorporate the local refinement using mesh superposition. The mesh superposition method is used to refine the global coarse mesh by superimposing refined mesh to the localized zone of interest without transition zones. The finite element model used is a solid element based on the Hellinger-Reissner variational principle. The a posteriori computation of the through-the-thickness distributions of displacements and stresses is achieved using a predictor-corrector procedure. The procedure utilizes the superconvergent stresses and nodal displacements of the finite element patch. The element patch is generated by locally superimposing a refined local mesh to the coarse global mesh.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2003.04a
• /
• pp.11-18
• /
• 2003

This paper proposes modified Lanczos vector superposition method for efficient dynamic analysis of structures. Proposed method is based on the modified Lanczos algorithm that generates stiffness-orthonormal Lanczos vectors. Proposed method has better computing efficiency than the conventional Lanczos vector superposition method in the analysis of multi-input-loaded structures. The efficiency of proposed method is verified through numerical examples. Comparison with other vector superposition methods is also presented through numerical examples.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.10
• /
• pp.1934-1936
• /
• 2015

This paper proposes an optimal relay selection and adaptive throughput enhancement scheme utilizing superposition modulation in cooperative communication. The optimal relay is selected and the channel state is estimated by utilizing superposition modulation. The source determines the number of superimposed signal in accordance with the estated channel state. As a result, throughput is increased in accordance with the channel state.

• Steel and Composite Structures
• /
• v.20 no.2
• /
• pp.295-316
• /
• 2016

This paper presents the results of experimental investigation, numerical calculation and theoretical analysis on axial compression ratio limit values for steel reinforced concrete (SRC) special shaped columns. 17 specimens were firstly intensively carried out to investigate the hysteretic behavior of SRC special shaped columns subjected to a constant axial load and cyclic reversed loads. Two theories were used to calculate the limits of axial compression ratio for all the specimens, including the balanced failure theory and superposition theory. It was found that the results of balanced failure theory by numerical integration method cannot conform the reality of test results, while the calculation results by employing the superposition theory can agree well with the test results. On the basis of superposition theory, the design limit values of axial compression ratio under different seismic grades were proposed for SRC special shaped columns.