3,693 research outputs found
Attitude controls for VTOL aircraft Patent
Development of attitude control system for vertical takeoff aircraft using reaction nozzles displaced from various axes of aircraf
Attitude controls for VTOL aircraft
Systems consist of single duct system with two sets of reaction control nozzles, one linked mechanically to pilot's controls, and other set driven by electric servomotors commanded by preselected combinations of electrical signals
On the Transition from Confinement to Screening in QCD_{1+1} Coupled to Adjoint Fermions at Finite N
We consider SU(N) QCD_{1+1} coupled to massless adjoint Majorana fermions,
where N is finite but arbitrary. We examine the spectrum for various values of
N, paying particular attention to the formation of multi-particle states, which
were recently identified by Gross, Hashimoto and Klebanov in the N -> infinity
limit of the theory. It is believed that in the limit of vanishing fermion
mass, there is a transition from confinement to screening in which string-like
states made out of adjoint fermion bits dissociate into stable constituent
``single particles''. In this work, we provide numerical evidence that such a
transition into stable constituent particles occurs not only at large N, but
for any finite value of N. In addition, we discuss certain issues concerning
the ``topological'' properties exhibited by the DLCQ spectrum.Comment: 14 pages, Late
A (1+1)-Dimensional Reduced Model of Mesons
We propose an extension of 't Hooft's large- light-front QCD in two
dimensions to include helicity and physical gluon degrees of freedom, modelled
on a classical dimensional reduction of four dimensional QCD. A
non-perturbative renormalisation of the infinite set of coupled integral
equations describing boundstates is performed. These equations are then solved,
both analytically in a phase space wavefunction approximation and numerically
by discretising momenta, for (hybrid) meson masses and (polarized) parton
structure functions.Comment: LaTex 13 pages; 2 figures, uuencoded file (PostScript
On the Size of Hadrons
The form factor and the mean-square radius of the pion are calculated
analytically from a parametrized form of a wave function. The
numerical wave function was obtained previously by solving numerically an
eigenvalue equation for the pion in a particular model. The analytical formulas
are of more general interest than just be valid for the pion and can be
generalized to the case with unequal quark masses. Two different
parametrizations are investigated. Because of the highly relativistic problem,
noticable deviations from a non-relativistic formula are obtained.Comment: 14 pages, minor typos corrected, several points clarified, results
unchange
Thermal, electric and spin transport in superconductor/ferromagnetic-insulator structures
A ferromagnetic insulator (FI) attached to a conventional superconductor (S)
changes drastically the properties of the latter. Specifically, the exchange
field at the FI/S interface leads to a splitting of the superconducting density
of states. If S is a superconducting film, thinner than the superconducting
coherence length, the modification of the density of states occurs over the
whole sample. The co-existence of the exchange splitting and superconducting
correlations in S/FI structures leads to striking transport phenomena that are
of interest for applications in thermoelectricity, superconducting spintronics
and radiation sensors. Here we review the most recent progress in understanding
the transport properties of FI/S structures by presenting a complete
theoretical framework based on the quasiclassical kinetic equations. We discuss
the coupling between the electronic degrees of freedom, charge, spin and
energy, under non-equilibrium conditions and its manifestation in
thermoelectricity and spin-dependent transport.Comment: 117 pages, 33 figures. arXiv admin note: substantial text overlap
with arXiv:1706.0824
Theory of Microwave-Assisted Supercurrent in Diffusive SNS Junctions
The observation of very large microwave-enhanced critical currents in
superconductor-normal metal-superconductor (SNS) junctions at temperatures well
below the critical temperature of the electrodes has remained without a
satisfactory theoretical explanation for more than three decades. Here we
present a theory of the supercurrent in diffusive SNS junctions under microwave
irradiation based on the quasiclassical Green's function formalism. We show
that the enhancement of the critical current is due to the energy
redistribution of the quasiparticles in the normal wire induced by the
electromagnetic field. The theory provides predictions across a wide range of
temperatures, frequencies, and radiation powers, both for the critical current
and the current-phase relationship.Comment: 4 pages, 4 figure
Quantum Continuum Mechanics Made Simple
In this paper we further explore and develop the quantum continuum mechanics
(CM) of [Tao \emph{et al}, PRL{\bf 103},086401] with the aim of making it
simpler to use in practice. Our simplifications relate to the non-interacting
part of the CM equations, and primarily refer to practical implementations in
which the groundstate stress tensor is approximated by its Kohn-Sham version.
We use the simplified approach to directly prove the exactness of CM for
one-electron systems via an orthonormal formulation. This proof sheds light on
certain physical considerations contained in the CM theory and their
implication on CM-based approximations. The one-electron proof then motivates
an approximation to the CM (exact under certain conditions) expanded on the
wavefunctions of the Kohn-Sham (KS) equations. Particular attention is paid to
the relationships between transitions from occupied to unoccupied KS orbitals
and their approximations under the CM. We also demonstrate the simplified CM
semi-analytically on an example system
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