Distribution of impurities in steam-generating equipment with estimating the efficiency of their removal during the power unit shutdown process

The sludge distribution patterns in the volume of a steam generator and in the near-wall region of its heat-transfer surface are obtained. Recommendations for removing sludge in the power unit shutdown mode are given.     

Ellipsometry of chemically deposited PbS-ZnS films

The optical and dielectric characteristics of hydrochemically deposited films of lead sulfide (PbS) and supersaturated substitutional solid solutions of the PbS-ZnS system have been studied by the ellipsometry techniques. It is established that the formation of solid solutions leads to an increase in the refractive index and a decrease in the imaginary part of the complex dielectric constant as compared to those of pure PbS films. An increase in the content of ZnS in the solid solution us accompanied by a significant decrease in the dielectric loss tangent.     

Diffusional Boriding of Subeutectoidal Tool Steels: Technology and Outcome

Structural, subeutectoidal structural, and tool steels are studied. Their boriding is considered. Equipment for electrolytic boriding and a modernized high-temperature casting crucible are presented. The conditions of electrolytic boriding are established. Shortcomings of electrolytic boriding are noted.     

Immunolocalization of the cellular prion protein in normal brain

We examined the localization of PrP(c) in normal brain using free-floating section immunohistochemistry and monclonal antibody 3F4. In the mature hamster and baboon brain, PrP(c) is localized to the neuropil with a synaptic distribution and the PrP(c) immunoreactivity is denser in regions known for ongoing plasticity. Cell bodies and major fiber tracts have little or no PrP(c) immunoreactivity. At the electron microscopic level, PrP(c) immunoreactivity decorates synaptic profiles, both pre- and postsynaptically. Results obtained with two additional antibodies, 3B5 and Pri-304, showed similar patterns of PrP(c) bands on Western blots, although Pri-304 was less sensitive. On sections through the adult hamster hippocampus, 3B5 and Pri-304 both stained the synaptic neuropil while cell bodies in the pyramidal and dentate granule cell layers were not immunoreactive. Pri-304 differentiated between synaptic layers in the hippocampus and closely resembled the pattern of staining obtained with 3F4. Preliminary results of developing brain showed that PrP(c) is initially localized along fiber tracts in the neonate brain. These results show that PrP(c) has a synaptic distribution in the adult brain and suggest that there are important changes in its distribution during brain development. These results also characterize two additional reagents for studies of PrP(c) localization.     

Exhaust-line performance in a gas-pumping system

A promising means of determining exhaust-line performance in a gas-pumping system is to analyze the passage of the sound wave formed by the action of dynamic loads at the channel wall; the dynamic loads are due to pressure fluctuation in the gas flux.     

Numerical investigation of potential elimination of ‘hot streaking’ and stratification in the VHTR lower plenum using helicoid inserts

The helium-cooled, high temperature Next Generation Nuclear Plant (NGNP) and Very High Temperature Reactor (VHTR) with prismatic type cores are being designed to operate at reactor exit temperatures ranging from 873 to 923 K and 1123 to 1223 K, respectively. The helium flow velocity in the coolant channels of the core is ∼70 m/s. The high-temperature helium jets exiting the coolant channels impinge onto the bottom plate in the lower plenum (LP), causing “hot spots” (“hot streaking”) and stratification due to the absence of proper mixing and the obstruction caused by the graphite support columns. In order to minimize or eliminate hot streaking and enhance helium mixing in the LP, this work investigates using static, quadruple helicoid inserts at the exit of the coolant channels. These inserts introduce radial and azimuthal momentum flow components, which result in extensive entrainment and mixing of the surrounding gas in the LP, significantly reducing the impingement onto the bottom plate, thereby minimizing hot streaking and stratification. Results of parametric analyses and a comparison of the flow fields of helium free conventional and swirling jets, and of a convectional jet in cross flow are presented and discussed. The analyses with helium at 1273 K and the dynamic Smagorinsky turbulence model are conducted using Fuego, a 3D, finite element, incompressible, reactive flow, massively parallel code with state-of-the-art turbulence models developed at Sandia National Laboratories. The calculations are benchmarked successfully by comparing the numerical results with experimental data and semi-empirical analytical expressions.     

Post-mortem evolution of rheological properties of the myofibrillar structure

The post-mortem evolution of the rheological behaviour of beef muscle has been studied with the SATA compressive device. The resistance and elasticity of the muscle tissue, measured at low strain, refer to the myofibrillar structure and provide an indication of the advance of the rigor maturation process. These parameters have been used to quantify the electrical stimulation effect on Longissimus dorsi and Semi-membranosus muscles. An empirical model is proposed for the post-mortem evolution of the resistance and provides three parameters-the initial rate of rigor onset, the time of rigor and the residual stress after ageing. On the other hand, parameters obtained at high strain refer mainly to the connective tissue. The particularly high stress developed by the pre-rigor muscle, however, is presumed to be associated with the myofibrillar component.     

Nanoindentation of Al2O3/Al2TiO5 composites: Small-scale mechanical properties of Al2TiO5 as reinforcement phase

The mechanical properties of alumina/aluminum titanate composites (Al₂O₃/Al₂TiO₅) were evaluated and analyzed by nanoindentation. Indentations with different penetration depths were performed, and residual imprints on specimens were located and observed by combining complementary characterization techniques. The mechanical response of composites was found to be determined by grain size of alumina and aluminum titanate, as evaluated from indentations performed at 1500 nm of penetration depth. On the other hand, small indents in individual grains permitted to assess the hardness as well as the elastic modulus of non-cracked particles of Al₂TiO₅ through implementation of different analytical indentation models. The attained values for the local mechanical properties were validated through critical comparison of them with those predicted by the rule of mixtures. Results showed no evidence of microcracking on grains of the reinforcing phase for all the tested composites, before and after low penetration depth indentations. Elastic modulus of Al₂TiO₅ was found to be higher than the values reported on bulk aluminum titanate, presumably because of the absence of microcracking for small grain sizes. The bulk composite mechanical response is finally discussed on the basis of contributions from those of the individual phases.