1,467 research outputs found
A Trajectory Prediction Method of Ship-to-air Missiles for Dynamic Firepower Compatibility
AbstractFor the question of warship's air-defence firepower compatibility, a trajectory prediction method of ship-to-air missiles for dynamic firepower compatibility is put forward. Ship-to-air missiles’ ideal trajectories are simulated based on targets’ typical flight paths and missiles’ guidance law, and missile's ideal position coordinates expression of time is obtained at the same time. Then trajectory distribution error sources which affect missiles’ position coordinates are analysed. This method can predict trajectory efficiently before ship-to-air missiles’ launch and help to avoid firepower interaction during warships’ air-defence
Transition of stoichiometricSr2VO3FeAs to a superconducting state at 37.2 K
The superconductor Sr4V2O6Fe2As2 with transition temperature at 37.2 K has
been fabricated. It has a layered structure with the space group of p4/nmm, and
with the lattice constants a = 3.9296Aand c = 15.6732A. The observed large
diamagnetization signal and zero-resistance demonstrated the bulk
superconductivity. The broadening of resistive transition was measured under
different magnetic fields leading to the discovery of a rather high upper
critical field. The results also suggest a large vortex liquid region which
reflects high anisotropy of the system. The Hall effect measurements revealed
dominantly electron-like charge carriers in this material. The
superconductivity in the present system may be induced by oxygen deficiency or
the multiple valence states of vanadium.Comment: 5 pages, 4 figure
Superconductivity at 15.6 K in Calcium-doped Tb_{1-x}Ca_xFeAsO: the structure requirement for achieving superconductivity in the hole-doped 1111 phase
Superconductivity at about 15.6 K was achieved in Tb_{1-x}Ca_xFeAsO by
partially substituting Tb^{3+} with Ca^{2+} in the nominal doping region x =
0.40 \sim 0.50. A detailed investigation was carried out in a typical sample
with doping level of x = 0.44. The upper critical field of this sample was
estimated to be 77 Tesla from the magnetic field dependent resistivity data.
The domination of hole-like charge carriers in the low-temperature region was
confirmed by Hall effect measurements. The comparison between the calcium-doped
sample Pr_{1-x}Ca_xFeAsO (non-superconductive) and the Strontium-doped sample
Pr_{1-x}Sr_xFeAsO (superconductive) suggests that a lager ion radius of the
doped alkaline-earth element compared with that of the rare-earth element may
be a necessary requirement for achieving superconductivity in the hole-doped
1111 phase.Comment: 7 pages, 7 figure
2,2′,4,4′,6,6′-Hexamethyl-N-(3-phthalimidopropyl)-N,N′-(propane-1,3-diyl)dibenzenesulfonamide
In the title compound, C32H38N3O6S2, an intermediate in the synthesis of polyamine drugs, the dihedral angle between the phenyl rings of the two 2,4,6-trimethylbenzenesulfonyl groups is 27.1 (3)°. In the crystal structure, molecules are linked by intermolecular N—H⋯O hydrogen bonds, thereby forming an infinite one-dimensional chain propagating along [010]
N,N′-Bis(2-cyanoethyl)-4,4′-dimethyl-N,N′-(butane-1,4-diyl)dibenzenesulfonamide
The complete molecule of the title compound, C24H30N4O4S2, is generated by a crystallographic inversion centre. In the crystal, weak C—H⋯O interactions link the molecules, forming infinite sheets
Doping effect of Cu and Ni impurities on the Fe-based superconductor Ba0.6K0.4Fe2As2
Copper and Nickel impurities have been doped into the iron pnictide
superconductor Ba0.6K0.4Fe2As2. Resistivity measurements reveal that Cu and Ni
impurities suppress superconducting transition temperature T_c with rates of
\Delta T_c/Cu-1% = -3.5 K and \Delta T_c/Ni-1% = -2.9 K respectively.
Temperature dependence of Hall coefficient R_H of these two series of samples
show that both Cu-doping and Ni-doping can introduce electrons into
Ba0.6K0.4Fe2As2. With more doping, the sign of R_H gradually changes from
positive to negative, while the changing rate of Cu-doped samples is much
faster than that of Ni-doped ones. Combining with the results of
first-principles calculations published previously and the non-monotonic
evolution of the Hall coefficient in the low temperature region, we argue that
when more Cu impurities were introduced into Ba0.6K0.4Fe2As2, the removal of
Fermi spectral weight in the hole-like Fermi surfaces is much stronger than
that in the electron-like Fermi surfaces, which is equivalent to significant
electron doping effect. DC magnetization and the lattice constants analysis
reveal that static magnetic moments and notable lattice compression have been
formed in Cu-doped samples. It seems that the superconductivity can be
suppressed by the impurities disregard whether they are magnetic or nonmagnetic
in nature. This gives strong support to a pairing gap with a sign reversal,
like S^\pm. However, the relatively slow suppression rates of T_c show the
robustness of superconductivity of Ba0.6K0.4Fe2As2 against impurities, implying
that multi-pairing channels may exist in the system.Comment: 7 pages, 7 figure
2-(3-Bromopropyl)isoindoline-1,3-dione
In the title compound, C11H10BrNO2, the dihedral angle between the five- and six-membered rings of the phthalamide system is 1.00 (16)°. There are no significant intermolecular interations except for van der Waals contacts
A -ray Quasi-Periodic modulation in the Blazar PKS 0301243?
We report a nominally high-confidence -ray quasi-periodic modulation
in the blazar PKS 0301243. For this target, we analyze its \emph{Fermi}-LAT
Pass 8 data covering from 2008 August to 2017 May. Two techniques, i.e., the
maximum likelihood optimization and the exposure-weighted aperture photometry,
are used to build the -ray light curves. Then both the Lomb-Scargle
Periodogram and the Weighted Wavelet Z-transform are applied to the light
curves to search for period signals. A quasi-periodicity with a period of
yr appears at the significance level of , although it
should be noted that this putative quasi-period variability is seen in a data
set barely four times longer. We speculate that this -ray
quasi-periodic modulation might be evidence of a binary supermassive black
hole.Comment: 9 pages, 8 figures; Accepted for publication in Ap
The role of lake heat flux in the growth and melting of ice
For shallow lakes, ice mass balance is largely dominated by thermodynamic processes. The heat flux from lake water plays a critical role for ice growth and melting. In this study, we applied a numerical thermodynamic lake model to investigate the sensitivity of the lake ice mass balance to the lake heat flux during the growth and melting periods. Several groups of modelling experiments forced by simplified climatological weather data have been carried out. Two sites, Lake Wuliangsuhai in Inner Mongolia, China’s arid region and Lake Orajärvi in snowy Finnish Lapland, were investigated. Lake heat flux affects inversely proportional maximum ice thickness followed by ice break-up date. The solar radiation and surface albedo complicate the effect of lake heat flux on lake ice mass balance during melting season. With heavy snowfall, the increase of lake heat flux adds on the formation of granular ice but reduces the formation of columnar ice. Under climatological weather conditions, the ice cover winter seasonal mean lake heat flux were 14 W·m−2 and 4 W·m−2 in Lake Wuliangsuhai and Lake Orajärvi, respectively.Peer reviewe
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