Thermomechanical simulation of an industrial quenching process applied to a centrifugal pump impeller

En este trabajo se estudia el comportamiento termomecánico durante el tratamiento térmico de templado de un rodete de una bomba centrífuga fabricada en fundición blanca. El análisis se realiza mediante una formulación termomecánica acoplada discretizada mediante el método de elementos finitos. La respuesta del material se describe por medio de un modelo termoplástico que incorpora efectos de cambio de fase. En particular, se presenta el proceso de templado desde la austenización hasta el enfriamiento del rodete con la finalidad de evaluar la ocurrencia de falla en la pieza al final del proceso. Para la determinación del daño mecánico se comparan 3 criterios diferentes escritos en función de las tensiones y de las deformaciones plásticas desarrolladas durante el proceso. El estudio se enfoca en 2 tipos de configuración de rodetes, con 4 y 5 álabes, donde la primera de ellas experimenta fractura en el proceso industrial de producción. Los resultados numéricos obtenidos en este trabajo confirman que la metodología propuesta permite predecir de manera realista las posibilidades de falla para los 2 casos analizados.The thermomechanical behaviour during the quenching process of a centrifugal pump impeller made of white iron is studied in this work. The analysis is carried out using a coupled thermomechanical formulation that is discretized within the context of the finite element method. The material response is described by means of a thermoplastic model that includes phase-change effects. In particular, a heat treatment consisting in cooling from the austenizing temperature is presented with the aim of assessing the failure occurrence of the part at the end of the process. Three different criteria written in terms of the stresses and plastic deformations developed during the cooling stage are specifically compared to evaluate the final mechanical damage. The study is focused on two impeller configurations, with 4 and 5 blades, where fracture occurs in the former during its industrial production. The numerical results obtained in this work for these two cases confirm that the proposed methodology realistically predicts their failure possibilities.Peer Reviewe

Changes in pools of organic matter and major elements in the soil following prescribed pastoral burning in the central Pyrenees

High-mountain soils are rich in partially decomposed organic matter, which is highly sensitive to mineralization and fire. Prescribed burning is performed in the Pyrenees to keep subalpine grasslands open for grazing. The compositions of the ash, litter and duff layers, and the particulate organic matter (POM) of the topsoil in the 0–1, 1–2, 2–3, and 3–5 cm depths were analyzed in relation to the nutrient availability after the prescribed burning of a stand encroached by erizón (Echinospartum horridum). The concentrations of C, N, P, and S and organic components (nonstructural, hemicellulose, cellulose, and lignin-type) were determined before the prescribed burn and 0, 6, 12, 18, and 24 months after the prescribed burn. The fire consumed the aboveground biomass, the litter and part of the duff layer, and the most thermostable (i.e., lignin-type) components and the least volatile elements (P, S) were selectively preserved in the resulting ash. Prescribed burning caused significant losses of organic-C and N only in the 0–1 cm depth (–72% and –68%, respectively). The organic-C loss was mostly (82%) from the POM, whereas the N loss was from more similar proportions of the POM (57%) and the nonparticulate organic matter (NPOM) (43%). However, few changes were observed in the composition of the organic matter, which pointed to a largely uneven combustion that resulted in a substantial part of the organic matter remaining largely untouched by the fire. After 6 months, the duff layer was depleted in hemicellulose by 32% compared to immediately after the burn, and fragmentation of the POM into the NPOM was observed. During the second spring, N- and P-rich charred POM were incorporated into the top 1 cm, while C-rich charcoal particles underwent fragmentation and vertical transport into the deeper soil. The preburn ecosytem was limited by P, and likely also by S. The plant available N showed transient increases of 1.5–2.1 times the immediate postburn levels for nitrate-N at 12 months after burning, and of up to 10–20 times for ammonium-N at 18 months. In contrast, the concentrations of plant-available P and S gradually declined to 1.8–3.3 and 1.8–4.0 times, respectively, lower at 24 months after the burn. Results indicated that fire-induced increases in the nutrient availability can be short-lived in high-mountain habitats, but steadier and likely more persistent nutrient inputs can derive from the gradual breakdown of charred organic matter. © 2021 Elsevier B.V

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

European Red List of Marine Fishes

The European Red List is a review of the conservation status of European species according to IUCN regional Red Listing guidelines. It identifies those species that are threatened with extinction at the regional level, so that appropriate conservation action can be taken to improve their status. This Red List publication summarises results for all described native European marine fishes.Postprin

Observation of inverse Compton emission from a long γ-ray burst.

Long-duration γ-ray bursts (GRBs) originate from ultra-relativistic jets launched from the collapsing cores of dying massive stars. They are characterized by an initial phase of bright and highly variable radiation in the kiloelectronvolt-to-megaelectronvolt band, which is probably produced within the jet and lasts from milliseconds to minutes, known as the prompt emission1,2. Subsequently, the interaction of the jet with the surrounding medium generates shock waves that are responsible for the afterglow emission, which lasts from days to months and occurs over a broad energy range from the radio to the gigaelectronvolt bands1-6. The afterglow emission is generally well explained as synchrotron radiation emitted by electrons accelerated by the external shock7-9. Recently, intense long-lasting emission between 0.2 and 1 teraelectronvolts was observed from GRB 190114C10,11. Here we report multi-frequency observations of GRB 190114C, and study the evolution in time of the GRB emission across 17 orders of magnitude in energy, from 5 × 10-6 to 1012 electronvolts. We find that the broadband spectral energy distribution is double-peaked, with the teraelectronvolt emission constituting a distinct spectral component with power comparable to the synchrotron component. This component is associated with the afterglow and is satisfactorily explained by inverse Compton up-scattering of synchrotron photons by high-energy electrons. We find that the conditions required to account for the observed teraelectronvolt component are typical for GRBs, supporting the possibility that inverse Compton emission is commonly produced in GRBs

Measurement of event-shape observables in Z→ℓ+ℓ− events in pp collisions at √ s=7 TeV with the ATLAS detector at the LHC

Event-shape observables measured using charged particles in inclusive $Z$-boson events are presented, using the electron and muon decay modes of the $Z$ bosons. The measurements are based on an integrated luminosity of $1.1 {\rm fb}^{-1}$ of proton--proton collisions recorded by the ATLAS detector at the LHC at a centre-of-mass energy $\sqrt{s}=7$ TeV. Charged-particle distributions, excluding the lepton--antilepton pair from the $Z$-boson decay, are measured in different ranges of transverse momentum of the $Z$ boson. Distributions include multiplicity, scalar sum of transverse momenta, beam thrust, transverse thrust, spherocity, and $\mathcal{F}$-parameter, which are in particular sensitive to properties of the underlying event at small values of the $Z$-boson transverse momentum. The Sherpa event generator shows larger deviations from the measured observables than Pythia8 and Herwig7. Typically, all three Monte Carlo generators provide predictions that are in better agreement with the data at high $Z$-boson transverse momenta than at low $Z$-boson transverse momenta and for the observables that are less sensitive to the number of charged particles in the event.Comment: 36 pages plus author list + cover page (54 pages total), 14 figures, 4 tables, submitted to EPJC, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2014-0

Measurement of jet suppression in central Pb-Pb collisions at root s(NN)=2.76 TeV

The transverse momentum(p(T)) spectrum and nuclear modification factor (R-AA) of reconstructed jets in 0-10% and 10-30% central Pb-Pb collisions at root s(NN) = 2.76 TeV were measured. Jets were reconstructed using the anti-k(T) jet algorithm with a resolution parameter of R = 0.2 from charged and neutral particles, utilizing the ALICE tracking detectors and Electromagnetic Calorimeter (EMCal). The jet p(T) spectra are reported in the pseudorapidity interval of \eta(jet)\ 5 GeV/c to suppress jets constructed from the combinatorial background in Pb-Pb collisions. The leading charged particle requirement applied to jet spectra both in pp and Pb-Pb collisions had a negligible effect on the R-AA. The nuclear modification factor R-AA was found to be 0.28 +/- 0.04 in 0-10% and 0.35 +/- 0.04 in 10-30% collisions, independent of p(T), jet within the uncertainties of the measurement. The observed suppression is in fair agreement with expectations from two model calculations with different approaches to jet quenching. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V.Peer reviewe

Measurement of the azimuthal anisotropy of Y(1S) and Y(2S) mesons in PbPb collisions at √S^{S}NN = 5.02 TeV

The second-order Fourier coefficients (υ$_{2}$) characterizing the azimuthal distributions of Υ(1S) and Υ(2S) mesons produced in PbPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV are studied. The Υmesons are reconstructed in their dimuon decay channel, as measured by the CMS detector. The collected data set corresponds to an integrated luminosity of 1.7 nb$^{-1}$. The scalar product method is used to extract the υ$_{2}$ coefficients of the azimuthal distributions. Results are reported for the rapidity range |y| < 2.4, in the transverse momentum interval 0 < p$_{T}$ < 50 GeV/c, and in three centrality ranges of 10–30%, 30–50% and 50–90%. In contrast to the J/ψ mesons, the measured υ$_{2}$ values for the Υ mesons are found to be consistent with zero