Abstract
Researching the aerodynamic characteristic of projectile at high angle of attack could serve to determine the launching condition and the design method of aerodynamic configuration. The ...aerodynamic coefficients of a kind of spin-stabilized projectile were calculated and analyzed by CFD. An efficient and precise method of calculating the pitching damping moment was obtained to research the aerodynamic coupling characteristic of spinning motion and pitching motion. The results showed that the aerodynamic coefficients of projectile at high angle of attack was nonlinear, the pitching damping moment was proportional to the pitching angular velocity, magnus force had hysteresis characteristic which was affected by pitching amplitude and frequency.
Because of the half-filled t_{2g}-electron configuration, the BO_{6} octahedral distortion in a 3d^{3} perovskite system is usually very limited. In this Letter, a perovskitelike oxide ...Hg_{0.75}Pb_{0.25}MnO_{3} (HPMO) with a 3d^{3} Mn^{4+} state was synthesized by using high pressure and high temperature methods. This compound exhibits an unusually large octahedral distortion enhanced by approximately 2 orders of magnitude compared with that observed in other 3d^{3} perovskite systems like RCr^{3+}O_{3} (R=rare earth). Essentially different from centrosymmetric HgMnO_{3} and PbMnO_{3}, the A-site doped HPMO presents a polar crystal structure with the space group Ama2 and a substantial spontaneous electric polarization (26.5 μC/cm^{2} in theory) arising from the off-center displacements of A- and B-site ions. More interestingly, a prominent net photocurrent and switchable photovoltaic effect with a sustainable photoresponse were observed in the current polycrystalline HPMO. This Letter provides an exceptional d^{3} material system which shows unusually large octahedral distortion and displacement-type ferroelectricity violating the "d^{0}-ness" rule.
.
Five-dimensional collective Hamiltonian based on the covariant density functional theory has been applied to study the low-lying states of even-even
148-162
Gd isotopes. The shape evolution from
...148
Gd to
162
Gd is presented. The experimental energy spectra and intraband
B
(
E
2) transition probabilities for the
148-162
Gd isotopes are reproduced by the present calculations. The relative
B
(
E
2) ratios in present calculations are also compared with the available interacting boson model results and experimental data. It is found that the occupations of neutron
1
i
13
/
2
orbital result in the well-deformed prolate shape, and are essential for Gd isotopes.
The compression deformation behavior and deformation mechanisms of 001-oriented single crystal CM247LC are investigated at 600 °C and at the strain rate of 5 × 10−6 to 5 × 10−3 s−1. We found that ...although the Protevin-Le Châtelier effect appears during plastic deformation under the investigated strain rates, its yield strength is strain-rate insensitive. Transmission electron microscopy observations on the slightly deformed specimens reveal that in contrast to previous findings, shearing of γ′ precipitates is accomplished by pairs of a/2 dislocations as well as partial dislocations, which result in the formation of superlattice stacking faults and extended stacking faults, in the experimental alloy at the early stage of plastic deformation at all the strain rates. Meanwhile, it is also found that the frequency of occurrence of the two shear processes is not influenced by the strain rate. Based on these observations, the formation of stacking faults and the relationship between operative deformation mechanisms and the yield strength of the experimental alloy are discussed.
•The PLC effect appears in CM247LC during compressive deformation at 600 °C.•The yield strength of CM247LC is strain-rate insensitive.•Stacking fault shearing operates in CM247LC at all the studied strain rates.•The process of stacking fault shearing is not rate-controlled.
The hadronic interaction of cosmic rays with solar atmosphere can produce high energy gamma-rays. The gamma-ray luminosity is correlated both with the flux of primary cosmic rays and the intensity of ...the solar magnetic field. The gamma-rays below 200 GeV have been observed by Fermi without any evident energy cutoff. The bright gamma-ray flux above 100 GeV has been detected only during solar minimum. The only available data in the TeV range come from the HAWC observations, however, outside the solar minimum. The ARGO-YBJ data set has been used to search for sub-TeV/TeV gamma-rays from the Sun during the solar minimum from 2008 to 2010, the same time period covered by the Fermi data. A suitable model containing the Sun shadow, solar disk emission, and inverse-Compton emission has been developed, and the chi-square minimization method was used to quantitatively estimate the disk gamma-ray signal. The result shows that no significant gamma-ray signal is detected and upper limits to the gamma-ray flux at 0.3-7 TeV are set at the 95% confidence level. In the low energy range these limits are consistent with the extrapolation of the Fermi-LAT measurements taken during solar minimum and are compatible with a softening of the gamma-ray spectrum below 1 TeV. They also provide an experimental upper bound to any solar disk emission at TeV energies. Models of dark matter annihilation via long-lived mediators predicting gamma-ray fluxes >10−7 GeV cm−2 s−1 below 1 TeV are ruled out by the ARGO-YBJ limits.
The catastrophic phase transformation of yttria partially stabilized zirconia (YSZ) is considered to be the main reason that leads to the failure of YSZ based thermal barrier coatings (TBCs) when ...their service temperatures are higher than 1200°C, which greatly limits the application of YSZ in the new-generation aero engines. In the present work, a fine-lamellar structured YSZ coating that consisted of submicro-/nano-grains showed good phase stability during a burner-rig test at 1270±20°C. The results from X-ray diffraction and Raman spectroscopy confirmed that the phase compositions of as-sprayed or failed coatings fully consisted of the t′ phase. The catastrophic tetragonal-monoclinic (t→m) phase transformation did not occur, indicating it was not the main reason for the spallation of YSZ coating. However, the analysis of residual stress within YSZ coating suggested that the failure of coating was associated with the severe sintering of YSZ and thermal expansion mismatch at high temperatures.
•Fine-lamellar structured YSZ coating with submicro/nano-grains was fabricated.•Coating showed a good phase stability and thermal insulation property at 1270±20°C.•The t′ phase was confirmed in as-sprayed and failed YSZ coatings.•Evolution of stress transformed from tensile to compressive.•Link-up of vertical and transverse cracks led to the failure of coating.
AZ80 cast magnesium alloy has been fabricated by a combination of ECAE (equal channel angular extrusion) and subsequent forging processing to investigate the effect of second forging processing on ...the evolution of microstructure, texture and tensile properties. The AZ80 alloy produced by this process exhibited the ultimate tensile strength (UTS) of 434MPa, yield strength (YS) of 347MPa, and elongation-to-failure of 6%. The observed high strength in this sample has been ascribed to the effect of grain refinement and the formation of sharp basal texture by the subsequent forging processing. The contribution of second-phase particles to the mechanical properties was also discussed in this paper.
We have developed and implemented an iterative algorithm of flux calibration for the LAMOST Spectroscopic Survey of the Galactic anticentre (LSS-GAC). For a given LSS-GAC plate, the spectra are first ...processed with a set of nominal spectral response curves (SRCs) and used to derive initial stellar atmospheric parameters (effective temperature T
eff, surface gravity log g and metallicity Fe/H) as well as dust reddening E(B − V) of all targeted stars. For each of the 16 spectrographs, several F-type stars with good signal-to-noise ratios are selected as flux standard stars for further, iterative spectral flux calibration. Comparison of spectrophotometric colours, deduced from the flux-calibrated spectra, with the photometric measurements yield average differences of 0.02 ± 0.07 and −0.04 ± 0.09 mag for (g − r) and (g − i), respectively. The relatively large negative offset in (g − i) is because we have opted not to correct for the telluric bands, most notably the atmospheric A band in the wavelength range of the i band. Comparison of LSS-GAC multi-epoch observations of duplicate targets indicates that the algorithm has achieved an accuracy of about 10 per cent in relative flux calibration for the wavelength range 4000–9000 Å. The shapes of SRCs deduced for individual LAMOST spectrographs vary by up to 30 per cent for a given night, and larger for different nights, indicating that the derivation of SRCs for the individual plates is essential to achieve accurate flux calibration for the LAMOST spectra.
Interfacial engineering toward the perovskite layer/electron transporting layer (ETL) interface has been demonstrated to be critical for achieving highly efficient perovskite solar cells (PSCs). In ...this work, PSCs with ETL/perovskite interfacial modification by benzoic acid derivatives are fabricated. No obvious influence of this interfacial modification on optical properties, crystal structure and surface morphology of perovskite films are found. Enhancement of the charge extracting ability of treated TiO
2
and passivation toward trap states of the TiO
2
surface are confirmed from transient PL spectra and EIS measurements. Besides, the effect of different groups on the
para
-position is also investigated. A PCE as high as 18.43% with a maximal steady-state output PCE of 17.19% has been achieved for the PSCs treated with
para
-Cl substituted benzoic acid.
Enhanced performance of a perovskite solar cell
via
simple interfacial modification onto a mesoporous TiO
2
layer.
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