1,032 research outputs found
Aircraft control system
An aircraft control system is described which is particularly suited to rotary wing aircraft. Longitudinal acceleration and course rate commands are derived from a manual control stick to control translational velocity of the aircraft along a flight path. In the collective channel the manual controls provide vertical velocity commands. In the yaw channel the manual controls provide sideslip or heading rate commands at high or low airspeeds, respectively. The control system permits pilots to fly along prescribed flight paths in a precise manner with relatively low work load
Quantum phases of hardcore bosons with repulsive dipolar density-density interactions on two-dimensional lattices
We analyse the ground-state quantum phase diagram of hardcore Bosons
interacting with repulsive dipolar potentials. The bosons dynamics is described
by the extended-Bose-Hubbard Hamiltonian on a two-dimensional lattice. The
ground state results from the interplay between the lattice geometry and the
long-range interactions, which we account for by means of a classical spin
mean-field approach limited by the size of the considered unit cells. This
extended classical spin mean-field theory accounts for the long-range
density-density interaction without truncation. We consider three different
lattice geometries: square, honeycomb, and triangular. In the limit of zero
hopping the ground state is always a devil's staircase of solid (gapped)
phases. Such crystalline phases with broken translational symmetry are robust
with respect to finite hopping amplitudes. At intermediate hopping amplitudes,
these gapped phases melt, giving rise to various lattice supersolid phases,
which can have exotic features with multiple sublattice densities. At
sufficiently large hoppings the ground state is a superfluid. The stability of
phases predicted by our approach is gauged by comparison to the known quantum
phase diagrams of the Bose-Hubbard model with nearest-neighbour interactions as
well as quantum Monte Carlo simulations for the dipolar case on the square
lattice. Our results are of immediate relevance for experimental realisations
of self-organised crystalline ordering patterns in analogue quantum simulators,
e.g., with ultracold dipolar atoms in an optical lattice.Comment: 31 pages, 9 figure
Systematic Analysis of Crystalline Phases in Bosonic Lattice Models with Algebraically Decaying Density-Density Interactions
We propose a general approach to analyse diagonal ordering patterns in
bosonic lattice models with algebraically decaying density-density interactions
on arbitrary lattices. The key idea is a systematic search for the
energetically best order on all unit cells of the lattice up to a given extent.
Using resummed couplings we evaluate the energy of the ordering patterns in the
thermodynamic limit using finite unit cells. We apply the proposed approach to
the atomic limit of the extended Bose-Hubbard model on the triangular lattice
at fillings and . We investigate the ground-state properties of
the antiferromagnetic long-range Ising model on the triangular lattice and
determine a six-fold degenerate plain-stripe phase to be the ground state for
finite decay exponents. We also probe the classical limit of the
Fendley-Sengupta-Sachdev model describing Rydberg atom arrays. We focus on
arrangements where the atoms are placed on the sites or links of the Kagome
lattice. \changed{Our method provides a general framework to treat cristalline
structures resulting from long-range interactions.Comment: 35 pages, 11 figure
What Does an Exemplary Middle School Mathematics Teacher Look Like? The Use of a Professional Development Rubric
A School University Research Network (SURN) committee composed of current mathematics teachers, central office math supervisors, building administrators, mathematicians, and mathematics educators researched numerous sources regarding best practices in mathematics instruction. The resulting professional development rubric synthesizes their findings and can serve a professional development role by providing teachers and administrators with a tool to develop clarity and consensus on best mathematics instructional practices, and how these practices are implemented in the classroom. It is also being used as a tool for cooperating teachers in their supervision of student teachers and as a reflective method for self-evaluation
Impurity effects in superconducting UPt3
Superconducting UPt3 is characterized by a novel and complex magnetic field‐temperature phase diagram, with two superconducting transitions at Tc1 and Tc2 in zero field. We have studied the effects of Pd and Y impurities on the zero field superconducting properties of UPt3. Resistance measurements show that both dopants increase the residual resistivity and decrease the spin fluctuation temperature in the normal state. Tc1 is depressed by both dopants, but more effectively by Pd. ‖Tc1 − Tc2‖ is essentially unaffected by Y doping, but increases dramatically with Pd doping.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70706/2/JAPIAU-69-8-5487-1.pd
FlashCam: A fully digital camera for CTA telescopes
The future Cherenkov Telescope Array (CTA) will consist of several tens of
telescopes of different mirror sizes. CTA will provide next generation
sensitivity to very high energy photons from few tens of GeV to >100 TeV.
Several focal plane instrumentation options are currently being evaluated
inside the CTA consortium. In this paper, the current status of the FlashCam
prototyping project is described. FlashCam is based on a fully digital camera
readout concept and features a clean separation between photon detector plane
and signal digitization/triggering electronics.Comment: In Proceedings of the 2012 Heidelberg Symposium on High Energy
Gamma-Ray Astronomy. All CTA contributions at arXiv:1211.184
Identification of genes encoding squalestatin S1 biosynthesis and in vitro production of new squalestatin analogues
A gene cluster responsible for the biosynthesis of squalestatin S1 (SQS1, 1) was identified by full genome sequencing of two SQS1-producing ascomycetes: Phoma sp. C2932 and unidentified fungus MF5453. A transformation protocol was established and a subsequent knockout of one PKS gene from the cluster led to loss of SQS1 production and enhanced concentration of an SQS1 precursor. An acyltransferase gene from the cluster was expressed in E. coli and the expressed protein MfM4 shown to be responsible for loading acyl groups from CoA onto the squalestatin core as the final step of biosynthesis. MfM4 appears to have a broad substrate selectivity for its acyl CoA substrate, allowing the in vitro synthesis of novel squalestatins
- …