Grain boundary segregation in UFG alloys processed by severe plastic deformation

Grain boundary segregations were investigated by Atom Probe Tomography in an Al-Mg alloy, a carbon steel and Armco\trademark Fe processed by severe plastic deformation (SPD). In the non-deformed state, the GBs of the aluminium alloy are Mg depleted, but after SPD some local enrichment up to 20 at.% was detected. In the Fe-based alloys, large carbon concentrations were also exhibited along GBs after SPD. These experimental observations are attributed to the specific structure of GBs often described as "non-equilibrum" in ultra fine grained materials processed by SPD. The grain boundary segregation mechanisms are discussed and compared in the case of substitutional (Mg in fcc Al) and interstitial (C in bcc Fe) solute atoms

Риск, связанный с выпуском воздушного судна в соответствии с перечнем минимального оборудования (MEL)

The article covers the problem of understanding of risk assessment necessity connected with aircraft production in accordance with Minimum Equipment List (MEL). The article presents calculation of fail-safe performance probability of Airbus A320 Family fuel system in the event of defect which rectification is postponed in accordance with MEL. The article also presents the results of risk assessment connected with aircraft production in accordance with MEL.Статья посвящена осмыслению необходимости оценки риска, связанного с выпуском ВС в соответствии с перечнем минимального оборудования (MEL). Проведен расчет вероятности безотказной работы топливной системы ВС Airbus A320 Family при наличии дефекта в одном из ее элементов, устранение которого отложено в соответствии с MEL. Представлены результаты оценки риска, связанного с выпуском ВС в соответствии с MEL

Факторы опасности при использовании перечня минимального оборудования (MEL)

The article covers the problem of understanding of hazard identification necessity by using Minimum Equipment List (MEL) in civil aviation of the Russian Federation. The examples of hazards by using MEL are given in the article. It is also pointed out the seriousness of the consequences associated with the hazards and necessity of subsequent risk assessment.Статья посвящена осмыслению необходимости выявления и учета факторов опасности при использовании перечня минимального оборудования (MEL) в гражданской авиации Российской Федерации. Показаны примеры факторов опасности, возникающих при использовании MEL. Обращено внимание на серьезность последствий, связанных с указанными факторами опасности, и на необходимость последующей оценки соответствующего риска

Shape of primary proton spectrum in multi-TeV region from data on vertical muon flux

It is shown, that primary proton spectrum, reconstructed from sea-level and underground data on muon spectrum with the use of QGSJET 01, QGSJET II, NEXUS 3.97 and SIBYLL 2.1 interaction models, demonstrates not only model-dependent intensity, but also model-dependent form. For correct reproduction of muon spectrum shape primary proton flux should have non-constant power index for all considered models, except SIBYLL 2.1, with break at energies around 10-15 TeV and value of exponent before break close to that obtained in ATIC-2 experiment. To validate presence of this break understanding of inclusive spectra behavior in fragmentation region in p-air collisions should be improved, but we show, that it is impossible to do on the basis of the existing experimental data on primary nuclei, atmospheric muon and hadron fluxes.Comment: Submitted to Phys. Rev.

THERMAL STABILITY AND EXTRA-STRENGTH OF AN ULTRAFINE GRAINED STAINLESS STEEL PRODUCED BY HIGH PRESSURE TORSION

International audienceInvestigations of an ultrafine-grained (UFG) Cr-Ni austenitic stainless steel produced by high pressure torsion (HPT) at room and elevated (400 C) temperatures followed by series of annealing up to 700 C are reported. The grain size of the alloy processed at room temperature (55 nm) was found to be about twice lower than the grain size of the alloy (90 nm) processed at elevated temperature. Besides, both as-processed states demonstrated a very high value of microhardness (~590 Hv) , while the steel in initial quenched state had the microhardness about 155 Hv. It is shown that the hardness of the steel in both UFG states does not decrease with annealing up to 650 C, and even a certain increase in hardness was observed for the steel produced at room temperature. At higher temperature (700 C), the recrystallization starts, and precipitation was observed

Influence of hadronic interaction models and the cosmic ray spectrum on the high energy atmospheric muon and neutrino flux

The recent observations of muon charge ratio up to about 10 TeV and of atmospheric neutrinos up to energies of about 400 TeV has triggered a renewed interest into the high-energy interaction models and cosmic ray primary composition. A reviewed calculation of lepton spectra produced in cosmic-ray induced extensive air showers is carried out with a primary cosmic-ray spectrum that fits the latest direct measurements below the knee. In order to achieve this, we used a full Monte Carlo method to derive the inclusive differential spectra (yields) of muons, muon neutrinos and electron neutrinos at the surface for energies between 80 GeV and hundreds of PeV. The air shower simulator {\sc corsika} 6.990 was used for showering and propagation of the secondary particles through the atmosphere, employing the established high-energy hadronic interaction models {\sc sibyll} 2.1, {\sc qgsjet-01} and {\sc qgsjet-ii 03}. We show that the performance of the interaction models allows makes it possible to predict the spectra within experimental uncertainties, while {\sc sibyll} generally yields a higher flux at the surface than the qgsjet models. The calculation of the flavor and charge ratios has lead to inconsistent results, mainly influenced by the different representations of the K/$\pi$ ratio within the models. Furthermore, we could quantify systematic uncertainties of atmospheric muon- and neutrino fluxes, associated to the models of the primary cosmic-ray spectrum and the interaction models. For most recent parametrizations of the cosmic-ray primary spectrum, atmospheric muons can be determined with an uncertainty smaller than $^{+15}_{-13}$% of the average flux. Uncertainties of the muon- and electron neutrino fluxes can be calculated within an average error of $^{+32}_{-22}$% and $^{+25}_{-19}$%, respectively.Comment: 16 pages, 10 figures, version 2 includes analytic approximatio

Microstructural changes and strengthening of austenitic stainless steels during rolling at 473 k

The microstructural changes in 304L and 316L austenitic stainless steels during plate rolling with 95% rolling reduction at a temperature of 473 K and their effect on strengthening were studie

Predicting Neutron Production from Cosmic-ray Muons

Fast neutrons from cosmic-ray muons are an important background to underground low energy experiments. The estimate of such background is often hampered by the difficulty of measuring and calculating neutron production with sufficient accuracy. Indeed substantial disagreement exists between the different analytical calculations performed so far, while data reported by different experiments is not always consistent. We discuss a new unified approach to estimate the neutron yield, the energy spectrum, the multiplicity and the angular distribution from cosmic muons using the Monte Carlo simulation package FLUKA and show that it gives a good description of most of the existing measurements once the appropriate corrections have been applied.Comment: 8 pages, 7 figure