1,569 research outputs found
Analysis of a VTOL hover task with predictor displays using an optimal control model of the human operator
The influence of different types of predictor displays in a longitudinal VTOL hover task is analyzed in a theoretical study. It was assumed that pitch angle and position are presented to the pilot in separate displays namely the artificial horizon and position display. The predictive information is calculated by means of a Taylor series. From earlier experimental studies it is well known that predictor displays improve human and system performance and result in reducing human workload. In this study, an optimal control model is used to prove this effect theoretically. Several cases with differing amounts of predictive and rate information are compared
The Right Mutation Strength for Multi-Valued Decision Variables
The most common representation in evolutionary computation are bit strings.
This is ideal to model binary decision variables, but less useful for variables
taking more values. With very little theoretical work existing on how to use
evolutionary algorithms for such optimization problems, we study the run time
of simple evolutionary algorithms on some OneMax-like functions defined over
. More precisely, we regard a variety of
problem classes requesting the component-wise minimization of the distance to
an unknown target vector . For such problems we see a crucial
difference in how we extend the standard-bit mutation operator to these
multi-valued domains. While it is natural to select each position of the
solution vector to be changed independently with probability , there are
various ways to then change such a position. If we change each selected
position to a random value different from the original one, we obtain an
expected run time of . If we change each selected position
by either or (random choice), the optimization time reduces to
. If we use a random mutation strength with probability inversely proportional to and change
the selected position by either or (random choice), then the
optimization time becomes , bringing down
the dependence on from linear to polylogarithmic. One of our results
depends on a new variant of the lower bounding multiplicative drift theorem.Comment: an extended abstract of this work is to appear at GECCO 201
Mitigating the Impact of Title VII\u27s New Retaliation Standard: The Americans with Disabilities Act After University of Texas Southwestern Medical Center v. Nassar
Magnetoelastic Coupling in the Spin-Dimer System TlCuCl
We present high-resolution measurements of the thermal expansion and the
magnetostriction of TlCuCl which shows field-induced antiferromagnetic
order. We find pronounced anomalies in the field and temperature dependence of
different directions of the lattice signaling a large magnetoelastic coupling.
The phase boundary is extremely sensitive to pressure, e.g. the transition
field would change by about +/- 185$%/GPa under uniaxial pressure applied along
certain directions. This drastic effect can unambiguously be traced back to
changes of the intradimer coupling under uniaxial pressure. The interdimer
couplings remain essentially unchanged under pressure, but strongly change when
Tl is replaced by K.Comment: 4 pages with 4 figures include
Uniaxial pressure dependencies of the phase boundary of TlCuCl_3
We present a thermal expansion and magnetostriction study of TlCuCl_3, which
shows a magnetic-field induced transition from a spin gap phase to a Neel
ordered phase. Using Ehrenfest relations we derive huge and strongly
anisotropic uniaxial pressure dependencies of the respective phase boundary,
e.g. the transition field changes by about GPa depending on the
direction of uniaxial pressure.Comment: 2 pages, e figures; presented at SCES200
Constraints on the Size of Extra Dimensions from the Orbital Evolution of the Black-Hole X-Ray Binary XTE J1118+480
In a universe of the Randall-Sundrum type, black holes are unstable and emit
gravitational modes in the extra dimension. This leads to dramatically
shortened lifetimes of astrophysical black holes and to an observable change of
the orbital period of black-hole binaries. I obtain an upper limit on the rate
of change of the orbital period of the binary XTE J1118+480 and constrain the
asymptotic curvature radius of the extra dimension to a value that is of the
same order as the constraints from other astrophysical sources. A unique
property of XTE J1118+480 is that the expected rate of change of the orbital
period due to magnetic braking alone is so large that only one additional
measurement of the orbital period would lead to the first detection of orbital
evolution of a black-hole binary and impose the tightest constraint to date on
the size of one extra dimension of the order of 35 microns.Comment: accepted for publication in A&
Mapping land cover from satellite images: A basic, low cost approach
Simple, inexpensive methodologies developed for mapping general land cover and land use categories from LANDSAT images are reported. One methodology, a stepwise, interpretive, direct tracing technique was developed through working with university students from different disciplines with no previous experience in satellite image interpretation. The technique results in maps that are very accurate in relation to actual land cover and relative to the small investment in skill, time, and money needed to produce the products
Non-Linear Effects in Non-Kerr spacetimes
There is a chance that the spacetime around massive compact objects which are
expected to be black holes is not described by the Kerr metric, but by a metric
which can be considered as a perturbation of the Kerr metric. These non-Kerr
spacetimes are also known as bumpy black hole spacetimes. We expect that, if
some kind of a bumpy black hole exists, the spacetime around it should possess
some features which will make the divergence from a Kerr spacetime detectable.
One of the differences is that these non-Kerr spacetimes do not posses all the
symmetries needed to make them integrable. We discuss how we can take advantage
of this fact by examining EMRIs into the Manko-Novikov spacetime.Comment: 8 pages, 3 Figures; to appear in the proceedings of the conference
"Relativity and Gravitation: 100 Years after Einstein in Prague" (2012
Hydrographic, chemical and planktological data from the north-west African upwelling area obtained from February to April 1983 : ("Ostatlantik-Biozirkel")
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