2,749 research outputs found
Bank-to-turn control technology survey for homing missiles
The potential advantages of bank-to-turn control are summarized. Recent and current programs actively investigating bank-to-turn steering are reviewed and critical technology areas concerned with bank-to-turn control are assessed
Imaging of microwave fields using ultracold atoms
We report a technique that uses clouds of ultracold atoms as sensitive,
tunable, and non-invasive probes for microwave field imaging with micrometer
spatial resolution. The microwave magnetic field components drive Rabi
oscillations on atomic hyperfine transitions whose frequency can be tuned with
a static magnetic field. Readout is accomplished using state-selective
absorption imaging. Quantitative data extraction is simple and it is possible
to reconstruct the distribution of microwave magnetic field amplitudes and
phases. While we demonstrate 2d imaging, an extension to 3d imaging is
straightforward. We use the method to determine the microwave near-field
distribution around a coplanar waveguide integrated on an atom chip.Comment: 11 pages, 4 figure
Towards designing robust coupled networks
Natural and technological interdependent systems have been shown to be highly
vulnerable due to cascading failures and an abrupt collapse of global
connectivity under initial failure. Mitigating the risk by partial
disconnection endangers their functionality. Here we propose a systematic
strategy of selecting a minimum number of autonomous nodes that guarantee a
smooth transition in robustness. Our method which is based on betweenness is
tested on various examples including the famous 2003 electrical blackout of
Italy. We show that, with this strategy, the necessary number of autonomous
nodes can be reduced by a factor of five compared to a random choice. We also
find that the transition to abrupt collapse follows tricritical scaling
characterized by a set of exponents which is independent on the protection
strategy
Coherent manipulation of Bose-Einstein condensates with state-dependent microwave potentials on an atom chip
Entanglement-based technologies, such as quantum information processing,
quantum simulations, and quantum-enhanced metrology, have the potential to
revolutionise our way of computing and measuring and help clarifying the
puzzling concept of entanglement itself. Ultracold atoms on atom chips are
attractive for their implementation, as they provide control over quantum
systems in compact, robust, and scalable setups. An important tool in this
system is a potential depending on the internal atomic state. Coherent dynamics
in this potential combined with collisional interactions allows entanglement
generation both for individual atoms and ensembles. Here, we demonstrate
coherent manipulation of Bose-condensed atoms in such a potential, generated in
a novel way with microwave near-fields on an atom chip. We reversibly entangle
atomic internal and motional states, realizing a trapped-atom interferometer
with internal-state labelling. Our system provides control over collisions in
mesoscopic condensates, paving the way for on-chip generation of many-particle
entanglement and quantum-enhanced metrology with spin-squeezed states.Comment: 9 pages, 6 figure
On the General Analytical Solution of the Kinematic Cosserat Equations
Based on a Lie symmetry analysis, we construct a closed form solution to the
kinematic part of the (partial differential) Cosserat equations describing the
mechanical behavior of elastic rods. The solution depends on two arbitrary
analytical vector functions and is analytical everywhere except a certain
domain of the independent variables in which one of the arbitrary vector
functions satisfies a simple explicitly given algebraic relation. As our main
theoretical result, in addition to the construction of the solution, we proof
its generality. Based on this observation, a hybrid semi-analytical solver for
highly viscous two-way coupled fluid-rod problems is developed which allows for
the interactive high-fidelity simulations of flagellated microswimmers as a
result of a substantial reduction of the numerical stiffness.Comment: 14 pages, 3 figure
A thermodynamically self-consistent theory for the Blume-Capel model
We use a self-consistent Ornstein-Zernike approximation to study the
Blume-Capel ferromagnet on three-dimensional lattices. The correlation
functions and the thermodynamics are obtained from the solution of two coupled
partial differential equations. The theory provides a comprehensive and
accurate description of the phase diagram in all regions, including the wing
boundaries in non-zero magnetic field. In particular, the coordinates of the
tricritical point are in very good agreement with the best estimates from
simulation or series expansion. Numerical and analytical analysis strongly
suggest that the theory predicts a universal Ising-like critical behavior along
the -line and the wing critical lines, and a tricritical behavior
governed by mean-field exponents.Comment: 11 figures. to appear in Physical Review
Synthesis and characterization of precursors for group II metal aluminates
Precursors to Group II metal aluminates (MAI 2 O 4 , M=Mg, Ca, Ba, Sr) are synthesized from inexpensive starting materials including Group II metal oxides/hydroxides, Al(OH) 3 , triethanolamine (TEA) and ethylene glycol, in a one-pot synthesis process. The precursors are soluble in common organic solvents and can be handled in moist air for a reasonable period of time. On pyrolysis in air to 1200 °C, all three precursors transform to the corresponding Group II metal aluminates. A termetallic double alkoxide, ‘ionomer-like’ structure is proposed, wherein the alkaline-earth metal is encapsulated by a TEA molecule bridging two alumatrane units. The precursors were characterized using TGA, NMR, mass spectroscopy and elemental analyses, and the pyrolysed precursors were briefly characterized using x-ray diffraction analysis. © 1997 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38300/1/666_ftp.pd
Josephson effect in SXS junctions
We investigate the Josephson effect in SXS junctions,
where S is a superconducting material with a ferromagnetic exchange
field, and X a weak link. The critical current increases with the
(antiparallel) exchange fields if the distribution of transmission eigenvalues
of the X-layer has its maximum weight at small values. This exchange field
enhancement of the supercurrent does not exist if X is a diffusive normal
metal. At low temperatures, there is a correspondence between the critical
current in an SIS junction with collinear orientations of
the two exchange fields, and the AC supercurrent amplitude in an SIS tunnel
junction. The difference of the exchange fields in an SIS junction corresponds to the potential difference in
an SIS junction; i.e., the singularity in [in an SIS
junction] at is the analogue of the Riedel peak.
We also discuss the AC Josephson effect in SIS junctions.Comment: 5 pages, 5 figure
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