406 research outputs found
Analysis of pressure blips in aft-finocyl solid rocket motor
Ballistic anomalies have frequently occurred during the firing of several solid rocket motors (SRMs) (Inertial Upper Stage, Space Shuttle Redesigned SRM (RSRM) and Titan IV SRM Upgrade (SRMU)), producing even relevant and unexpected variations of the SRM pressure trace from its nominal profile. This paper has the purpose to provide a numerical analysis of the following possible causes of ballistic anomalies in SRMs: an inert object discharge, a slag ejection, and an unexpected increase in the propellant burning rate or in the combustion surface. The SRM configuration under investigation is an aft-finocyl SRM with a first-stage/small booster design. The numerical simulations are performed with a quasi-one-dimensional (Q1D) unsteady model of the SRM internal ballistics, properly tailored to model each possible cause of the ballistic anomalies. The results have shown that a classification based on the head-end pressure (HEP) signature, relating each other the HEP shape and the ballistic anomaly cause, can be made. For each cause of ballistic anomalies, a deepened discussion of the parameters driving the HEP signatures is provided, as well as qualitative and quantitative assessments of the resultant pressure signals
Characterization of SABRE crystal NaI-33 with direct underground counting
Published online: 09 April 2021Ultra-pure NaI(Tl) crystals are the key element for a model-independent verification of the long standing DAMA result and a powerful means to search for the annual modulation signature of dark matter interactions. The SABRE collaboration has been developing cutting-edge techniques for the reduction of intrinsic backgrounds over several years. In this paper we report the first characterization of a 3.4 kg crystal, named NaI-33, performed in an underground passive shielding setup at LNGS. NaI-33 has a record low ³⁹K contamination of 4.3 ± 0.2 ppb as determined by mass spectrometry. We measured a light yield of 11.1 ± 0.2 photoelectrons/keV and an energy resolution of 13.2% (FWHM/E) at 59.5 keV. We evaluated the activities of ²²⁶Ra and ²²⁸Th inside the crystal to be 5.9±0.6 μBq/kg and 1.6±0.3 μBq/kg, respectively, which would indicate a contamination from ²³⁸U and ²³²Th at part-per-trillion level. We measured an activity of 0.51 ± 0.02 mBq/kg due to ²¹⁰Pb out of equilibrium and a α quenching factor of 0.63 ± 0.01 at 5304 keV. We illustrate the analyses techniques developed to reject electronic noise in the lower part of the energy spectrum. A cut-based strategy and a multivariate approach indicated a rate, attributed to the intrinsic radioactivity of the crystal, of ∼1 count/day/kg/keV in the [5–20] keV region.M. Antonello ... I. Bolognino ... A. G. Williams ... et al
Characterization of SABRE crystal NaI-33 with direct underground counting
Ultra-pure NaI(Tl) crystals are the key element for a model-independent
verification of the long standing DAMA result and a powerful means to search
for the annual modulation signature of dark matter interactions. The SABRE
collaboration has been developing cutting-edge techniques for the reduction of
intrinsic backgrounds over several years. In this paper we report the first
characterization of a 3.4 kg crystal, named NaI-33, performed in an underground
passive shielding setup at LNGS. NaI-33 has a record low K contamination
of 4.30.2 ppb as determined by mass spectrometry. We measured a light
yield of 11.10.2 photoelectrons/keV and an energy resolution of 13.2%
(FWHM/E) at 59.5 keV. We evaluated the activities of Ra and Th
inside the crystal to be Bq/kg and Bq/kg,
respectively, which would indicate a contamination from U and
Th at part-per-trillion level. We measured an activity of 0.510.02
mBq/kg due to Pb out of equilibrium and a quenching factor of
0.630.01 at 5304 keV. We illustrate the analyses techniques developed to
reject electronic noise in the lower part of the energy spectrum. A cut-based
strategy and a multivariate approach indicated a rate, attributed to the
intrinsic radioactivity of the crystal, of 1 count/day/kg/keV in the
[5-20] keV region
Short-Run Regional Forecasts: Spatial Models through Varying Cross-Sectional and Temporal Dimensions
In any economic analysis, regions or municipalities should not be regarded as isolated spatial units, but rather as highly interrelated small open economies. These spatial interrelations must be considered also when the aim is to forecast economic variables. For example, policy makers need accurate forecasts of the unemployment evolution in order to design short- or long-run local welfare policies. These predictions should then consider the spatial interrelations and dynamics of regional unemployment. In addition, a number of papers have demonstrated the improvement in the reliability of long-run forecasts when spatial dependence is accounted for. We estimate a heterogeneouscoefficients dynamic panel model employing a spatial filter in order to account for spatial heterogeneity and/or spatial autocorrelation in both the levels and the dynamics of unemployment, as well as a spatial vector-autoregressive (SVAR) model. We compare the short-run forecasting performance of these methods, and in particular, we carry out a sensitivity analysis in order to investigate if different number and size of the administrative regions influence their relative forecasting performance. We compute short-run unemployment forecasts in two countries with different administrative territorial divisions and data frequency: Switzerland (26 regions, monthly data for 34 years) and Spain (47 regions, quarterly data for 32 years)
Borexino's search for low-energy neutrinos associated with gravitational wave events from GWTC-3 database
The search for neutrino events in correlation with gravitational wave (GW)
events for three observing runs (O1, O2 and O3) from 09/2015 to 03/2020 has
been performed using the Borexino data-set of the same period. We have searched
for signals of neutrino-electron scattering with visible energies above 250 keV
within a time window of 1000 s centered at the detection moment of a particular
GW event. The search was done with three visible energy thresholds of 0.25, 0.8
and 3.0 MeV.Two types of incoming neutrino spectra were considered: the
mono-energetic line and the spectrum expected from supernovae. The same spectra
were considered for electron antineutrinos detected through inverse beta-decay
(IBD) reaction. GW candidates originated by merging binaries of black holes
(BHBH), neutron stars (NSNS) and neutron star and black hole (NSBH) were
analysed separately. Additionally, the subset of most intensive BHBH mergers at
closer distances and with larger radiative mass than the rest was considered.
In total, follow-ups of 74 out of 93 gravitational waves reported in the GWTC-3
catalog were analyzed and no statistically significant excess over the
background was observed. As a result, the strongest upper limits on
GW-associated neutrino and antineutrino fluences for all flavors (\nu_e,
\nu_\mu, \nu_\tau) have been obtained in the (0.5 - 5.0) MeV neutrino energy
range.Comment: 13 pages, 8 figure
Short-Run Regional Forecasts: Spatial Models Through Varying Cross-Sectional and Temporal Dimensions
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