Behavior of unirradiated Zr based uranium metal fuel under reactivity initiated accident conditions

Reactivity initiated accident (RIA) tests with 4 unirradiated Zr based uranium metal fuel rods were performed to establish a criterion which should be observed under RIA conditions. Of the four tests, fuel failures were observed in the two tests that experienced the maximum energy depositions of 188 and 212 cal/g, respectively. However, the fuel failures were not observed at the place of a maximum energy deposition but at the position where the thermocouples were installed; one failed at the position whose local energy deposition was 150 cal/g, and the other one at the place with energy deposition of 170 cal/g. The fuel failures seem to have occurred because excessive pressure, which was caused by the partial melting of the fuel meat, was applied to the cladding with a reduced thickness. However, other parts of the fuel rods including the place of a maximum energy deposition maintained their integrity and a big change in the temperature and pressure in the internal capsule, which would be an indication of the fragmentation and dispersion of the fuel meat into the internal capsule, was not observed. Visual inspection also showed that, except for the thermocouple positions, there was no trace of clad failure such as the formation of brittle cracks in the cladding or melting of the cladding. Therefore, for the Zr based uranium metal fuel rods, it can be concluded that the threshold energy deposition above which fragmentation and dispersion of fuel meat into the primary coolant system is expected to occur could be higher than 212 cal/g.     

Fabrication and microstructure of the d.c.-magnetron-sputtered YBa2Cu3O7 − x superconducting thin films

Systematic investigations were conducted to determine the effect of deposition conditions on the microstructure and superconducting properties of YBa₂Cu₃O_{7 – x} thin films produced by d.c. magnetron sputtering on (001) MgO substrate. The films were c-axis preferentially oriented with respect to the (001) MgO surface at substrate temperatures of 680–700 C. X-ray diffraction patterns clearly indicated the existence of the c-axis alignment normal to the substrate surface and some second phases. The second phases, including a Cu-rich phase and Y₂O₃, were identified by energy dispersive X-ray spectrometer and the microstructures were analysed by electron and atomic force microscopes.     

Measurement of nonlinear mechanical properties of PDMS elastomer

This paper presents the measurement of the nonlinear mechanical properties of polydimethylsiloxane (PDMS) elastomer based on the mixing ratio of base polymer to curing agent. Strip-type PDMS samples with different mixing ratios were prepared using a simple coating, curing, and cutting process. A cyclic uniaxial tension test with a fixed magnitude of applied strain and a single-pull-to-failure tension test were performed with a micro-tensile tester at room temperature.Our new finding is that when the PDMS is mixed with excessive curing agent, stress softening occurs and residual strain exists in cyclic tension tests when the magnitude of the applied strain increases. For the PDMS-05 samples, in which the mixing ratio of base polymer to curing agent was 5 to 1, there were large differences in the stresses for the same strain level under loading and unloading during the first cycle with a 100% fixed strain amplitude, but the softening effect of the stress in the PDMS dropped rapidly starting from the second cycle.Nonlinear mechanical Neo-Hookean, third-order Mooney, and second-order Ogden models of three different PDMS films were computed from the stress-strain data. The results showed that all models were preferable for the small strain region of PDMS compared with other models. In the nonlinear, large strain region, only the second-order Ogden model properly described the mechanical behavior of the PDMS, while the Neo-Hookean and third-order Mooney-Rivlin models were too stiff or flexible in the measurement range. The bulk modulus of PDMS increased with the amount of curing agent in it. Therefore, the second-order Ogden model is preferable for analyzing the PDMS structure over the entire measurement range. This could provide reasonable mechanical models of PDMS for rapid computational prototyping and for designing active and passive components from PDMS.     

Pursuing goals with others: Group identification and motivation resulting from things done versus things left undone.

This article addresses what factors best motivate individuals to work toward shared goals. We propose that when individuals do not identify highly with a group, their contributions will mimic others': An emphasis on things done will increase their contributions toward achieving a goal, because such emphasis suggests the goal is worth pursuing. Conversely, we propose that when individuals identify highly with a group, their contributions will compensate for others': An emphasis on things left undone will increase their own contributions, because missing contributions suggest insufficient progress toward a goal they already consider worthwhile. Five studies lend support to these predictions by measuring contributions to goals centered on idea generation and helping victims of various global disasters (earthquake in Haiti, wildfires in Southern California, rioting in Kenya). (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Analysis of PLR for Shared Switch Fabrics

A modular upgrade design for packet transport switch nodes is presented where packet loss is dramatically reduced by intra‐module and inter‐module buffer sharing. This modular design offers significant cost and power reduction in a high‐data‐rate system where buffers are highly costly and power‐greedy.     

Magnetic Polishing of Titanium-Nickel Alloy Stents: Surface Characterization and Catheter Deployment Test

We report here for the first time the use of magnetic polishing to improve the surface finish of titanium-nickel (TiNi) stents for better performance. We investigated the effects of polishing time and rotational speed on the average surface roughness, surface chemical contents, and push-out load of stents. The magnetically polished stents show a decrease of 2.3 to 17.9?pct in surface roughness and a lower push-out load for stent deployment from the catheter.     

Study of impact energy propagation phenomenon and modal characteristics of an armored vehicle undergoing high velocity impact

A new manufacturing technology is being employed to build a new type of armored vehicle. While thick panels are welded together in the old manufacturing technology, relatively thin panels are welded to a frame structure in the new manufacturing technology. The structural integrity of the new type of armor vehicles can be maintained mainly by the frame structures while the panel thickness is reduced significantly to reduce the total vehicle weight. Since the dynamic characteristics of a frame-panel hybrid structure are different from those of the old type of structure which consists of only thick panels, they should be identified to achieve a good performance of the vehicle. For this purpose, a proper FE model of the hybrid type of structure needs to be developed. In the present study, FE models are proposed to represent the frame-panel hybrid type structure efficiently. The impact energy propagation, the transient response and the modal characteristics are investigated with the FE models. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Hong-Hee Yoo received a B.S. and M.S. degree in Mechanical Engineering from Seoul National University in 1980 and 1982. He then went on to receive his Ph.D. degree from Michigan State University in 1989. Dr. Yoo is currently a Professor at the School of Mechanical Engineering at Hanyang University in Seoul, Korea. His research interests are in the area of Flexible body dynamics, vibration.     

Konjac flour improved textural and water retention properties of transglutaminase-mediated,heat-induced porcine myofibrillar protein gel: Effect of salt level and transglutaminase incubation

Functional properties of heat-induced gels prepared from microbial transglutaminase (TG)-treated porcine myofibrillar protein (MP) containing sodium caseinate with or without konjac flour (KF) under various salt concentrations (0.1, 0.3 and 0.6 M NaCl) were evaluated. The mixed MP gels with KF exhibited improved cooking yields at all salt concentrations. TG treatment greatly enhanced gel strength and elasticity (storage modulus, G′) at 0.6 M NaCl, but not at lower salt concentrations. The combination of KF and TG improved the gel strength at 0.1 and 0.3 M NaCl and G′ at all salt concentrations, when compared with non-TG controls. Incubation of MP suspensions (sols) with TG promoted the disappearance of myosin heavy chain and the production of polymers. The TG-treated MP mixed gels had a compact structure, compared to those without TG, and the KF incorporation modified the gel matrix and increased its water-holding capacity. Results from differential scanning calorimetry suggested possible interactions of MP with KF, which may explain the changes in the microstructure of the heat-induced gels.