We use medium-resolution Keck/Echellette Spectrograph and Imager spectroscopy of bright quasars to study cool gas traced by Ca
The ballistic performance of edge-clamped monolithic polyimide aerogel blocks (12 mm thickness) has been studied through a series of impact tests using a helium-filled gas gun connected to a vacuum chamber and a spherical steel projectile (approximately 3 mm diameter) with an impact velocity range of 150–1300 m s−1. The aerogels had an average bulk density of 0.17 g cm−3with high porosity of approximately 88%. The ballistic limit velocity of the aerogels was estimated to be in the range of 175–179 m s−1. Moreover, the aerogels showed a robust ballistic energy absorption performance (e.g., at the impact velocity of 1283 m s−1at least 18% of the impact energy was absorbed). At low impact velocities, the aerogels failed by ductile hole enlargement followed by a tensile failure. By contrast, at high impact velocities, the aerogels failed through an adiabatic shearing process. Given the substantially robust ballistic performance, the polyimide aerogels have a potential to combat multiple constraints such as cost, weight, and volume restrictions in aeronautical and aerospace applications with high blast resistance and ballistic performance requirements such as in stuffed Whipple shields for orbital debris containment application.
- Publication Date:
- NSF-PAR ID:
- 10369704
- Journal Name:
- Scientific Reports
- Volume:
- 12
- Issue:
- 1
- ISSN:
- 2045-2322
- Publisher:
- Nature Publishing Group
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract ii λλ 3934, 3969 and Nai λλ 5891, 5897 absorption in the interstellar/circumgalactic media of 21 foreground star-forming galaxies at redshifts 0.03 <z < 0.20 with stellar masses 7.4 ≤ logM */M ⊙≤ 10.6. The quasar–galaxy pairs were drawn from a unique sample of Sloan Digital Sky Survey quasar spectra with intervening nebular emission, and thus have exceptionally close impact parameters (R ⊥< 13 kpc). The strength of this line emission implies that the galaxies’ star formation rates (SFRs) span a broad range, with several lying well above the star-forming sequence. We use Voigt profile modeling to derive column densities and component velocities for each absorber, finding that column densitiesN (Caii ) > 1012.5cm−2(N (Nai ) > 1012.0cm−2) occur with an incidencef C(Caii ) = 0.63+0.10−0.11(f C(Nai ) = 0.57+0.10−0.11). We find no evidence for a dependence off Cor the rest-frame equivalent widthsW r (Caii K) orW r (Nai 5891) onR ⊥orM *. Instead,W r (Caii K) is correlated with local SFR at >3σ significance, suggesting that Caii traces star formation-driven outflows. While most of the absorbers have velocities within ±50 km s−1of the host redshift, their velocity widths (characterized by Δv 90) are universally 30–177 km s−1larger than that implied by tilted-ring modeling of the velocities of interstellar material. These kinematics mustmore » -
Metal oxide (MO) semiconductor thin films prepared from solution typically require multiple hours of thermal annealing to achieve optimal lattice densification, efficient charge transport, and stable device operation, presenting a major barrier to roll-to-roll manufacturing. Here, we report a highly efficient, cofuel-assisted scalable combustion blade-coating (CBC) process for MO film growth, which involves introducing both a fluorinated fuel and a preannealing step to remove deleterious organic contaminants and promote complete combustion. Ultrafast reaction and metal–oxygen–metal (M-O-M) lattice condensation then occur within 10–60 s at 200–350 °C for representative MO semiconductor [indium oxide (In2O3), indium-zinc oxide (IZO), indium-gallium-zinc oxide (IGZO)] and dielectric [aluminum oxide (Al2O3)] films. Thus, wafer-scale CBC fabrication of IGZO-Al2O3thin-film transistors (TFTs) (60-s annealing) with field-effect mobilities as high as ∼25 cm2V−1s−1and negligible threshold voltage deterioration in a demanding 4,000-s bias stress test are realized. Combined with polymer dielectrics, the CBC-derived IGZO TFTs on polyimide substrates exhibit high flexibility when bent to a 3-mm radius, with performance bending stability over 1,000 cycles.
-
Abstract Solar filaments exist as stable structures for extended periods of time before many of them form the core of a coronal mass ejection (CME). We examine the properties of an erupting filament on 2017 May 29–30 with high-resolution He
i 10830 Å and Hα spectra from the Dunn Solar Telescope, full-disk Dopplergrams of Hei 10830 Å from the Chromospheric Telescope, and EUV and coronograph data from SDO and STEREO. Pre-eruption line-of-sight velocities from an inversion of Hei with the HAZEL code exhibit coherent patches of 5 Mm extent that indicate counter-streaming and/or buoyant behavior. During the eruption, individual, aligned threads appear in the Hei velocity maps. The distribution of velocities evolves from Gaussian to strongly asymmetric. The maximal optical depth of Hei 10830 Å decreased fromτ = 1.75 to 0.25, the temperature increased by 13 kK, and the average speed and width of the filament increased from 0 to 25 km s−1and 10 to 20 Mm, respectively. All data sources agree that the filament rose with an exponential acceleration reaching 7.4 m s−2that increased to a final velocity of 430 km s−1at 22:24 UT; a CME was associated with this filament eruption. The properties during the eruption favor a kink/torus instability, which requires the existence of amore » -
ABSTRACT The radial velocity method is amongst the most robust and most established means of detecting exoplanets. Yet, it has so far failed to detect circumbinary planets despite their relatively high occurrence rates. Here, we report velocimetric measurements of Kepler-16A, obtained with the SOPHIE spectrograph, at the Observatoire de Haute-Provence’s 193cm telescope, collected during the BEBOP survey for circumbinary planets. Our measurements mark the first radial velocity detection of a circumbinary planet, independently determining the mass of Kepler-16 (AB) b to be $0.313 \pm 0.039\, {\rm M}_{\rm Jup}$, a value in agreement with eclipse timing variations. Our observations demonstrate the capability to achieve photon-noise precision and accuracy on single-lined binaries, with our final precision reaching $\rm 1.5~m\, s^{-1}$ on the binary and planetary signals. Our analysis paves the way for more circumbinary planet detections using radial velocities which will increase the relatively small sample of currently known systems to statistically relevant numbers, using a method that also provides weaker detection biases. Our data also contain a long-term radial velocity signal, which we associate with the magnetic cycle of the primary star.
-
Abstract Few published ultraviolet (UV) spectra exist for stripped-envelope supernovae and none to date for broad-lined Type Ic supernovae (SNe Ic-bl). These objects have extremely high ejecta velocities and are the only supernova type directly linked to gamma-ray bursts (GRBs). Here we present two epochs of HST/STIS spectra of the SN Ic-bl 2014ad, the first UV spectra for this class. We supplement this with 26 new epochs of ground-based optical spectra, augmenting a rich spectral time series. The UV spectra do not show strong features and are consistent with broadened versions of other SN Ic spectra observed in the UV. We measure Fe
ii 5169 Å velocities and show that SN 2014ad has even higher ejecta velocities than most SNe Ic both with and without observed GRBs. We construct models of the SN 2014ad UV+optical spectra usingtardis , a 1D Monte Carlo radiative-transfer spectral synthesis code. The models fit the data well at multiple epochs in the optical but underestimate the flux in the UV, likely due to simplifying assumptions. We find that high densities at high velocities are needed to reproduce the spectra, with ∼3M ⊙of material atv > 22,000 km s−1, assuming spherical symmetry. Our nebular line fits suggest a steep density profilemore »
