SEARCH · Engineering Papers
Results for “Lead”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Z-boson production in association with a jet at next-to-next-to-leading order in perturbative QCD
Here, we present the first complete calculation of Z-boson production in association with a jet in hadronic collisions through next-to-next-to-leading order in perturbative QCD. Our computation uses the recently proposed N-jettiness subtraction scheme to regulate the infrared divergences that appear in the real-emission contributions. We present phenomenological results for 13 TeV proton-proton collisions with fully realistic fiducial cuts on the final-state particles. The remaining theoretical uncertainties after the inclusion of our calculations are at the percent level, making the Z+jet channel ready for precision studies at the LHC run II.
Leading and Next-to-Leading Logarithmic Approximations in Quantum Electrodynamics
Abstrac t —Methods: for determination of QED radiative corrections in the leading and next-to- leading logarithmic approximations are described. Analytical solutions to the QED evolution equations for electron structure functions are presented. Some examples of applying the methods described to construction of the high-precision description of processes in high-energy accelerators are considered. A case of the calculation of higher-order corrections to the muon decay spectrum is considered in detail. Use of the approaches developed to justify methods of radiation return and direct measurement of the QED running constant is discussed.
Data for Promoter Deletion in the Soybean Compact Mutant Leads to Overexpression of a Gene with Homology to the C20-Gibberellin 2-Oxidase Family
Height is a critical component of plant architecture, significantly affecting crop yield. The genetic basis of this trait in soybean remains unclear. In this study, we report the characterization of the Compact mutant of soybean, which has short internodes. The candidate gene was mapped to chromosome 17, and the interval containing the causative mutation was further delineated using biparental mapping. Whole-genome sequencing of the mutant revealed an 8.7 kb deletion in the promoter of the Glyma.17g145200 gene, which encodes a member of the class III gibberellin (GA) 2-oxidases. The mutation has a dominant effect, likely via increased expression of the GA 2-oxidase transcript observed in green tissue, as a result of the deletion in the promoter of Glyma.17g145200. We further demonstrate that levels of GA precursors are altered in the Compact mutant, supporting a role in GA metabolism, and that the mutant phenotype can be rescued with exogenous GA3. We also determined that overexpression of Glyma.17g145200 in Arabidopsis results in dwarfed plants. Thus, gain of promoter activity in the Compact mutant leads to a short internode phenotype in soybean through altered metabolism of gibberellin precursors. These results provide an example of how structural variation can control an important crop trait and a role for Glyma.17g145200 in soybean architecture, with potential implications for increasing crop yield.
Measurement of the centrality dependence of the charged particle pseudorapidity distribution in lead-lead collisions at s N N = 2.76 TeV with the ATLAS detector
CERN-LHC. Measurements of the per-event charged particle density distributions - dN/deta - over the |eta| range < 2.0, and the averaged charged particle multiplicity in the central |eta| range < 0.5, in several centrality regions in lead-lead collisions at a centre-of-mass energy of 2.76 TeV/nucleon.
Measurement of the jet radius and transverse momentum dependence of inclusive jet suppression in lead-lead collisions at s N N = 2.76 TeV with the ATLAS detector
CERN-LHC. Measurements of the ratio, Rcp, between jet production in the central to peripheral regions in Lead Lead collisions at a centre of mass energy/nucleon of 2.76 TeV. Jets are reconstructed with |eta|<2.1, covering the jet PT range 38-210 GeV, using the anti-Kt algorithm with norminal jet radii of R=0.2, 0.3, 0.4 and 0.5. Seven regions of centrality are considered from the most peripheral of 60-80% to the most central 0-10%. Rcp is studied as a function of jet PT, number of participating nucleons NPART and R for each of the centrality regions, as well as the ratio of Rcp/Rcp(R=0.2) as a function of jet PT for each R=0.3, 0.4 and 0.5. Finally values of the covariance matrix for staistical correlations between jet PT bins are given. In the tables the first systematic errors are from JES, JER, efficiency, xin and Rcoll and are 100% correlated in PT. The second systematic errors are those that are partially correlated or uncorrelated in pt, taken to be 100% uncorrelated, from the regularization parameter.
Measurement of the azimuthal anisotropy for charged particle production in s N N = 2.76 TeV lead-lead collisions with the ATLAS detector
Differential measurements of charged particle azimuthal anisotropy are presented for lead-lead collisions at a centre-of-mass energy of 2.76 TeV/nucleon. The anisotropy is characterized via a Fourier expansion of the distribution of charged particles in azimuthal angle relative to the reaction plane, with the coefficients V_n denoting the magnitude of the anisotropy. A Fourier analysis of the charged particle pair distribution in relative angle is performed extracting the coefficients V_nn.
Measurement of event-plane correlations in s N N = 2.76 TeV lead-lead collisions with the ATLAS detector
Experimental measurements of event-plane correlations in lead-lead collisions. The correlation data are presented as a function of centrality for 14 different correlators. The data tables are linked to the corresponding figure number in the paper as well as additional plots in reference.
Lead in zircon at the atomic scale
Lead-doped zircon crystals, which were synthesized under three different conditions (Watson et al. 1997): dry at 1430 °C at atmospheric pressure without P2O5; wet at 900 °C at 1.5 GPa in the presence of P2O5; and wet at 800 °C at 1.0 GPa without P2O5, have been investigated to understand the mechanisms of Pb incorporation into zircon at the sub-micrometer scale, using various electron microscopy techniques including high-resolution transmission electron microscopy (HRTEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Four different mechanisms in which Pb may be incorporated into zircon have been identified. In the P-free synthesis, Pb-oxide hydrate particles, 50–200 nm in size, are embedded in zircon. Each Pb-particle is associated with a single vesicle, ~50 nm. Lead in the zircon structure is possibly incorporated under the detection limit value of energy-dispersive X-ray analysis (EDX) by means of: (1) Zr4+ = Pb2+ + 2H+ at less than ~0.1 wt%. In the system with P, Pb-phases occur in three different forms: Pb-rich domains concentrated along cleavage planes or grain boundaries without any evident crystal form; numerous Pb-phosphate particles, as large as 100 nm, embedded heterogeneously in the zircon crystal; and homogeneous distribution of Pb in the zircon structure at less than ~1 wt% as determined by EDX. These results suggest that charge balance is maintained by the xenotime-type coupled substitution: (2) Zr4+ + 2Si4+ = Pb2+ + 2P5+ with a possible minor contribution from mechanism 1. The apparent solubility limit of Pb, <1 wt%, is constrained mainly by the xenotime-type coupled substitution mechanism, which is probably due to increasing strain at higher Pb-concentrations. The presence of Pb2+ in natural zircon is consistent with the low-level Pb allowed by substitution mechanism 2, with only a minor contribution from substitution mechanism 1, the latter of which causes distortion in the local structure.
Lead-lead age of the Bondoc meteorite.
Bondoc meteorite lead-lead age determined by isotopic dilution technique
Result of Monte-Carlo simulation of electron-photon cascades in lead and layers of lead-scintillator
Results of Monte-Carlo simulation of electromagnetic cascade development in lead and lead-scintillator sandwiches are analyzed. It is demonstrated that the structure function for core approximation is not applicable in the case in which the primary energy is higher than 100 GeV. The simulation data has shown that introducing an inhomogeneous chamber structure results in subsequent reduction of secondary particles.
Evaluation of cloud detection instruments and performance of laminar-flow leading-edge test articles during NASA Leading-Edge Flight-Test Program
Summary evaluations of the performance of laminar-flow control (LFC) leading edge test articles on a NASA JetStar aircraft are presented. Statistics, presented for the test articles' performance in haze and cloud situations, as well as in clear air, show a significant effect of cloud particle concentrations on the extent of laminar flow. The cloud particle environment was monitored by two instruments, a cloud particle spectrometer (Knollenberg probe) and a charging patch. Both instruments are evaluated as diagnostic aids for avoiding laminar-flow detrimental particle concentrations in future LFC aircraft operations. The data base covers 19 flights in the simulated airline service phase of the NASA Leading-Edge Flight-Test (LEFT) Program.
The Detection of CO(4 [leads into, converted to] 3) and CO(5 [leads into, converted to] 4) Emission from B2 0902+34, A Powerful Radio Galaxy at Z= 3.3995
We report on the detection of CO(4 [leads into, converted to] 3) and CO(5 [leads into, converted to] 4) emission from the powerful radio galaxy B2 0902+34 at a redshift < z(sub co) > = 3.3995 +/- )0.0002.
Luminosity measurement for lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV in 2015 and 2018 at CMS
Measurements of the luminosity delivered to the CMS experiment during the lead-lead data-taking periods in 2015 and 2018 are presented for the first time. The collisions were recorded at a nucleon-nucleon center-of-mass energy of 5.02 TeV; the 2018 data sample is three times larger than the 2015 data sample. Three subdetectors are used: the pixel luminosity telescope, the forward hadron calorimeters, and the fast beam conditions monitor. The absolute luminosity calibration is determined using the van der Meer technique that relies on transverse beam separation scans. The dominant sources of uncertainty are the transverse factorizability of the bunch density profiles and, in 2015, the difference between the results obtained using various detectors. The total uncertainty in the integrated luminosity, including the stability of the calibrated subdetector response over time, amounts to 3.0% for 2015, 1.7% for 2018, and 1.6% for the combined data sample.
One-group fission cross sections for plutonium and minor actinides inserted in calculated neutron spectra of fast reactor cooled with lead-208 or lead-bismuth eutectic
The paper is dedicated to one-group fission cross sections of Pu and MA in LFRs spectra with the aim to increase these values by choosing a coolant which hardens neutron spectra. It is shown that replacement of coolant from Pb-Bi with Pb-208 in the fast reactor RBEC-M, designed in Russia, leads to increasing the core mean neutron energy. As concerns fuel Pu isotopes, their one-group fission cross sections become slightly changed, while more dramatically Am-241 one-group fission cross section is changed. Another situation occurs in the lateral blanket containing small quantities of minor actinides. It is shown that as a result of lateral blanket mean neutron energy hardening the one-group fission cross sections of Np-237, Am-241 and Am-243 increases up to 8-11%. This result allows reducing the time of minor actinides burning in FRs. (authors)
Development of phenomena identification and ranking table for Westinghouse lead fast reactor’s safety
The Westinghouse Lead-cooled Fast Reactor (LFR) is a medium-size, passively safe, economic, Gen-IV nuclear reactor. An important effort within the Westinghouse LFR program is the development of the safety analysis methodology, which comprises computer code development, model development, and experimental testing. A key initial task associated with the development of the safety analysis methodology is the identification of processes and phenomena that affect the plant's capability to meet selected safety performance indicators. This is accomplished through the development of a Phenomena Identification and Ranking Table (PIRT) for selected accident scenarios which, for this specific PIRT effort, included selected postulated design basis accidents and hypothetical beyond design basis accidents in LFRs. This paper describes the role of PIRT in the development of the Westinghouse LFR safety analysis methodology and the process used in the PIRT development. Specifically, the Westinghouse LFR PIRT assessed importance of pertinent phenomena and identified gaps in their knowledge-base by evaluating current modeling capabilities and data available for validation. The ultimate goal was to provide guidance on computer code development and validation efforts and to prioritize testing to support LFR design and licensing. The key phenomena and processes that are deemed highly important for the safety performance indicators, but for which the state of knowledge is low, are presented. The testing program and analyses development are planned to address significant phenomena in the PIRT.