9,179 research outputs found
Euler solution of multiblade rotor flow
A numerical method for solving the Euler equations for multiblade rotors has been developed and some preliminary results reported. The numerical scheme is a combination of several recent methods and algorithm improvements, adapted to the particular requirements of rotor-body interactions. A cylindrical basic grid has been used to study conventional multiblade helicopter rotors. Test calculations have been made for two- and six-blade rotors in hover and for a two-blade rotor in forward flight, under transonic tip conditions but without lift. The results show good agreement with experimental data
Quantum phase diagram of an exactly solved mixed spin ladder
We investigate the quantum phase diagram of the exactly solved mixed
spin-(1/2,1) ladder via the thermodynamic Bethe ansatz (TBA). In the absence of
a magnetic field the model exhibits three quantum phases associated with su(2),
su(4) and su(6) symmetries. In the presence of a strong magnetic field, there
is a third and full saturation magnetization plateaux within the strong
antiferromagnetic rung coupling regime. Gapless and gapped phases appear in
turn as the magnetic field increases. For weak rung coupling, the fractional
magnetization plateau vanishs and exhibits new quantum phase transitions.
However, in the ferromagnetic coupling regime, the system does not have a third
saturation magnetization plat eau. The critical behaviour in the vicinity of
the critical points is also derived systematically using the TBA.Comment: 20 pages, 2 figure
Fully gapped superconducting state in Au2Pb: a natural candidate for topological superconductor
We measured the ultra-low-temperature specific heat and thermal conductivity
of AuPb single crystal, a possible three-dimensional Dirac semimetal with a
superconducting transition temperature 1.05 K. The electronic
specific heat can be fitted by a two-band s-wave model, which gives the gap
amplitudes (0)/ = 1.38 and (0)/ = 5.25.
From the thermal conductivity measurements, a negligible residual linear term
in zero field and a slow field dependence of at low
field are obtained. These results suggest that AuPb has a fully gapped
superconducting state in the bulk, which is a necessary condition for
topological superconductor if AuPb is indeed one.Comment: 6 pages, 4 figure
Hysteresis in the quantum Hall regimes in electron double quantum well structures
We present in this paper experimental results on the transport hysteresis in
electron double quantum well structures. Exploring the measurement technique of
fixing the magnetic field and sweeping a front gate voltage (Vg), we are able
to study the hysteresis by varying the top layer Landau level fillings while
maintaining a relatively constant filling factor in the bottom layer, allowing
us to tackle the question of the sign of Rxx(up)-Rxx(down), where Rxx(up) is
the magnetoresistance when Vg is swept up and Rxx(down) when Vg swept down.
Furthermore, we observe that hysteresis is generally stronger in the even
integer quantum Hall effect (IQHE) regime than in the odd-IQHE regime. This, we
argue, is due to a larger energy gap for an even-IQHE state, determined by the
Landau level separation, than that for an odd-IQHE state, determined by the
Zeeman splitting
Phase diagram as a function of doping level and pressure in EuLaFeAs system
We establish the phase diagram of EuLaFeAs system as a
function of doping level x and the pressure by measuring the resistivity and
magnetic susceptibility. The pressure can suppress the spin density wave (SDW)
and structural transition very efficiently, while enhance the antiferromagnetic
(AFM) transition temperature T of Eu. The superconductivity coexists
with SDW order at the low pressure, while always coexists with the Eu
AFM order. The results suggests that Eu spin dynamics is disentangeld
with superconducting (SC) pairing taken place in the two-dimensional
\emph{Fe-As} plane, but it can strongly affect superconducting coherence along
c-axis
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