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Dennis D. Keiser,JAN-FONG JUE,BRANDON D. MILLER,JIAN GAN,ADAM B. ROBINSON,PAVEL MEDVEDEV,JAMES MADDEN,DAN WACHS,MITCH MEYER 한국원자력학회 2014 Nuclear Engineering and Technology Vol.46 No.2
In order to investigate how the microstructure of fuel/matrix-interaction (FMI) layers change during irradiation, differentU–7Mo dispersion fuel plates have been irradiated to high fission density and then characterized using scanning electronmicroscopy (SEM). Specifially, samples from irradiated U–7Mo dispersion fuel elements with pure Al, Al–2Si and AA4043(~4.5 wt.%Si) matrices were SEM characterized using polished samples and samples that were prepared with a focused ionbeam (FIB). Features not observable for the polished samples could be captured in SEM images taken of the FIB samples. Forthe Al matrix sample, a relatively large FMI layer develops, with enrichment of Xe at the FMI layer/Al matrix interface andevidence of debonding. Overall, a significant penetration of Si from the FMI layer into the U–7Mo fuel was observed forsamples with Si in the Al matrix, which resulted in a change of the size (larger) and shape (round) of the fission gas bubbles. Additionally, solid fission product phases were observed to nucleate and grow within these bubbles. These changes in thelocalized regions of the microstructure of the U–7Mo may contribute to changes observed in the macroscopic swelling of fuelplates with Al–Si matrices.
Keiser, Dennis D. Jr.,Jue, Jan-Fong,Miller, Brandon D.,Gan, Jian,Robinson, Adam B.,Medvedev, Pavel,Madden, James,Wachs, Dan,Meyer, Mitch Korean Nuclear Society 2014 Nuclear Engineering and Technology Vol.46 No.2
In order to investigate how the microstructure of fuel/matrix-interaction (FMI) layers change during irradiation, different U-7Mo dispersion fuel plates have been irradiated to high fission density and then characterized using scanning electron microscopy (SEM). Specifially, samples from irradiated U-7Mo dispersion fuel elements with pure Al, Al-2Si and AA4043 (~4.5 wt.%Si) matrices were SEM characterized using polished samples and samples that were prepared with a focused ion beam (FIB). Features not observable for the polished samples could be captured in SEM images taken of the FIB samples. For the Al matrix sample, a relatively large FMI layer develops, with enrichment of Xe at the FMI layer/Al matrix interface and evidence of debonding. Overall, a significant penetration of Si from the FMI layer into the U-7Mo fuel was observed for samples with Si in the Al matrix, which resulted in a change of the size (larger) and shape (round) of the fission gas bubbles. Additionally, solid fission product phases were observed to nucleate and grow within these bubbles. These changes in the localized regions of the microstructure of the U-7Mo may contribute to changes observed in the macroscopic swelling of fuel plates with Al-Si matrices.
Christopher M. Hill,Hunter DeBusk,Jeffrey D. Simpson,Brandon L. Miller,Adam C. Knight,John C. Garner,Chip Wade,Harish Chander 한국산업안전보건공단 산업안전보건연구원 2019 Safety and health at work Vol.10 No.3
Background: Performing cognitive tasks and muscular fatigue have been shown to increase muscle activity of the lower extremity during quiet standing. A common intervention to reduce muscular fatigue is to provide a softer shoe-surface interface. However, little is known regarding how muscle activity is affected by softer shoe-surface interfaces during static standing. The purpose of this study was to assess lower extremity muscular activity during erect standing on three different standing surfaces, before and after an acute workload and during cognitive tasks. Methods: Surface electromyography was collected on ankle dorsiflexors and plantarflexors, and knee flexors and extensors of fifteen male participants. Dependent electromyography variables of mean, peak, root mean square, and cocontraction index were calculated and analyzed with a 2×2×3 withinsubject repeated measures analysis of variance. Results: Pre-workload muscle activity did not differ between surfaces and cognitive task conditions. However, greater muscle activity during post-workload balance assessment was found, specifically during the cognitive task. Cognitive task errors did not differ between surface and workload. Conclusions: The cognitive task after workload increased lower extremity muscular activity compared to quite standing, irrespective of the surface condition, suggesting an increased demand was placed on the postural control system as the result of both fatigue and cognitive task.
Hill, Christopher M.,DeBusk, Hunter,Simpson, Jeffrey D.,Miller, Brandon L.,Knight, Adam C.,Garner, John C.,Wade, Chip,Chander, Harish Occupational Safety and Health Research Institute 2019 Safety and health at work Vol.10 No.3
Background: Performing cognitive tasks and muscular fatigue have been shown to increase muscle activity of the lower extremity during quiet standing. A common intervention to reduce muscular fatigue is to provide a softer shoe-surface interface. However, little is known regarding how muscle activity is affected by softer shoe-surface interfaces during static standing. The purpose of this study was to assess lower extremity muscular activity during erect standing on three different standing surfaces, before and after an acute workload and during cognitive tasks. Methods: Surface electromyography was collected on ankle dorsiflexors and plantarflexors, and knee flexors and extensors of fifteen male participants. Dependent electromyography variables of mean, peak, root mean square, and cocontraction index were calculated and analyzed with a $2{\times}2{\times}3$ within-subject repeated measures analysis of variance. Results: Pre-workload muscle activity did not differ between surfaces and cognitive task conditions. However, greater muscle activity during post-workload balance assessment was found, specifically during the cognitive task. Cognitive task errors did not differ between surface and workload. Conclusions: The cognitive task after workload increased lower extremity muscular activity compared to quite standing, irrespective of the surface condition, suggesting an increased demand was placed on the postural control system as the result of both fatigue and cognitive task.