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Primary water stress corrosion cracking incidents have been reported in nuclear reactors over the past several decades. Garud et al developed an empirical equation to express primary water stress corrosion cracking (PWSCC) initiation time by using experimental data. This strain rate damage model has been used in multiple simulation studies. Some of these studies used the extended finite element method (XFEM) to simulate the PWSCC propagation in Alloy 600. However, several studies showed that the accuracy of XFEM depends on the mesh quality. Different mesh qualities can change the heat flux of a welding procedure, leading to different weld residual stresses. We performed a parametric study on PWSCC initiation and propagation of a control rod driving mechanism by using different mesh qualities.The major variables explored here are number of elements per bead, number of circumferential elements, and number of weld beads. Finally, an XFEM-based representative model was suggested for PWSCC initiation and propagation simulation.

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This article presents an ultrabroadband balun with 1:4 impedance transformation ratio using transmission‐line transformers. The proposed ultrabroadband balun consists of one 1:1 transmission‐line transformer as a balun and two 1:4 transmission‐line transformers for impedance transformation. Each transmission‐line transformer is based on a coaxial line, which is wound around a ferrite core to extend the bandwidth to the lower frequency region. Experimentally optimized offset transmission lines are used to compensate for the phase imbalance characteristics at the high frequency band. The implemented ultrabroadband balun operates from 300 kHz to 400 MHz with a return loss of below 12 dB and an insertion loss of less than 1 dB. The magnitude and phase imbalance for the balanced signal output are both less than 0.5 dB and 2.0°, respectively. An outstanding relative bandwidth (the ratio of the highest frequency to the lowest frequency in the operational band) of 1330 was achieved. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1974–1978, 2014