370 research outputs found
Designing Sparse Reliable Pose-Graph SLAM: A Graph-Theoretic Approach
In this paper, we aim to design sparse D-optimal (determinantoptimal)
pose-graph SLAM problems through the synthesis of sparse graphs with the
maximum weighted number of spanning trees. Characterizing graphs with the
maximum number of spanning trees is an open problem in general. To tackle this
problem, several new theoretical results are established in this paper,
including the monotone log-submodularity of the weighted number of spanning
trees. By exploiting these structures, we design a complementary pair of
near-optimal efficient approximation algorithms with provable guarantees. Our
theoretical results are validated using random graphs and a publicly available
pose-graph SLAM dataset.Comment: WAFR 201
Complex Periodic Potentials with a Finite Number of Band Gaps
We obtain several new results for the complex generalized associated Lame
potential V(x)= a(a+1)m sn^2(y,m)+ b(b+1)m sn^2(y+K(m),m) + f(f+1)m
sn^2(y+K(m)+iK'(m),m)+ g(g+1)m sn^2(y+iK'(m),m), where y = x-K(m)/2-iK'(m)/2,
sn(y,m) is a Jacobi elliptic function with modulus parameter m, and there are
four real parameters a,b,f,g. First, we derive two new duality relations which,
when coupled with a previously obtained duality relation, permit us to relate
the band edge eigenstates of the 24 potentials obtained by permutations of the
four parameters a,b,f,g. Second, we pose and answer the question: how many
independent potentials are there with a finite number "a" of band gaps when
a,b,f,g are integers? For these potentials, we clarify the nature of the band
edge eigenfunctions. We also obtain several analytic results when at least one
of the four parameters is a half-integer. As a by-product, we also obtain new
solutions of Heun's differential equation.Comment: 33 pages, 0 figure
One-step-ahead kinematic compressive sensing
A large portion of work on compressive sampling and sensing has focused on reconstructions from a given measurement set. When the individual samples are expensive and optional, as is the case with autonomous agents operating in a physical domain and under specific energy limits, the CS problem takes on a new aspect because the projection is column-sparse, and the number of samples is not necessarily large. As a result, random sampling may no longer be the best tactic. The underlying incoherence properties in l0 reconstruction, however, can still motivate the purposeful design of samples in planning for CS with one or more agents; we develop here a greedy and computationally tractable sampling rule that will improve errors relative to random points. Several example cases illustrate that the approach is effective and robust.United States. Office of Naval Research (Grant N00014-09-1-0700
Correction for Self-Heating When Using Thermometers as Heaters in Precision Control Applications
In precision control applications, thermometers have temperature-dependent electrical resistance with germanium or other semiconductor material thermistors, diodes, metal film and wire, or carbon film resistors. Because resistance readout requires excitation current flowing through the sensor, there is always ohmic heating that leads to a temperature difference between the sensing element and the monitored object. In this work, a thermistor can be operated as a thermometer and a heater, simultaneously, by continuously measuring the excitation current and the corresponding voltage. This work involves a method of temperature readout where the temperature offset due to self-heating is subtracted exactly
The Mid-Infrared Instrument for the James Webb Space Telescope, VII: The MIRI Detectors
The MIRI Si:As IBC detector arrays extend the heritage technology from the
Spitzer IRAC arrays to a 1024 x 1024 pixel format. We provide a short
discussion of the principles of operation, design, and performance of the
individual MIRI detectors, in support of a description of their operation in
arrays provided in an accompanying paper (Ressler et al. (2015)). We then
describe modeling of their response. We find that electron diffusion is an
important component of their performance, although it was omitted in previous
models. Our new model will let us optimize the bias voltage while avoiding
avalanche gain. It also predicts the fraction of the IR-active layer that is
depleted (and thus contributes to the quantum efficiency) as signal is
accumulated on the array amplifier. Another set of models accurately predicts
the nonlinearity of the detector-amplifier unit and has guided determination of
the corrections for nonlinearity. Finally, we discuss how diffraction at the
interpixel gaps and total internal reflection can produce the extended
cross-like artifacts around images with these arrays at short wavelengths, ~ 5
microns. The modeling of the behavior of these devices is helping optimize how
we operate them and also providing inputs to the development of the data
pipeline
The Mid-Infrared Instrument for the James Webb Space Telescope, VIII: The MIRI Focal Plane System
We describe the layout and unique features of the focal plane system for
MIRI. We begin with the detector array and its readout integrated circuit
(combining the amplifier unit cells and the multiplexer), the electronics, and
the steps by which the data collection is controlled and the output signals are
digitized and delivered to the JWST spacecraft electronics system. We then
discuss the operation of this MIRI data system, including detector readout
patterns, operation of subarrays, and data formats. Finally, we summarize the
performance of the system, including remaining anomalies that need to be
corrected in the data pipeline
Magnetic susceptibility of insulators from first principles
We present an {\it ab initio} approach for the computation of the magnetic
susceptibility of insulators. The approach is applied to compute
in diamond and in solid neon using density functional theory in the local
density approximation, obtaining good agreement with experimental data. In
solid neon, we predict an observable dependence of upon pressure.Comment: Revtex, to appear in Physical Review Lette
Slowly Rotating Homogeneous Stars and the Heun Equation
The scheme developed by Hartle for describing slowly rotating bodies in 1967
was applied to the simple model of constant density by Chandrasekhar and Miller
in 1974. The pivotal equation one has to solve turns out to be one of Heun's
equations. After a brief discussion of this equation and the chances of finding
a closed form solution, a quickly converging series solution of it is
presented. A comparison with numerical solutions of the full Einstein equations
allows one to truncate the series at an order appropriate to the slow rotation
approximation. The truncated solution is then used to provide explicit
expressions for the metric.Comment: 16 pages, uses document class iopart, v2: minor correction
Peculiarities of the hidden nonlinear supersymmetry of Poschl-Teller system in the light of Lame equation
A hidden nonlinear bosonized supersymmetry was revealed recently in
Poschl-Teller and finite-gap Lame systems. In spite of the intimate
relationship between the two quantum models, the hidden supersymmetry in them
displays essential differences. In particular, the kernel of the supercharges
of the Poschl-Teller system, unlike the case of Lame equation, includes
nonphysical states. By means of Lame equation, we clarify the nature of these
peculiar states, and show that they encode essential information not only on
the original hyperbolic Poschl-Teller system, but also on its singular
hyperbolic and trigonometric modifications, and reflect the intimate relation
of the model to a free particle system.Comment: 10 pages, typos corrected; to appear in J. Phys.
The decay of homogeneous anisotropic turbulence
We present the results of a numerical investigation of three-dimensional
decaying turbulence with statistically homogeneous and anisotropic initial
conditions. We show that at large times, in the inertial range of scales: (i)
isotropic velocity fluctuations decay self-similarly at an algebraic rate which
can be obtained by dimensional arguments; (ii) the ratio of anisotropic to
isotropic fluctuations of a given intensity falls off in time as a power law,
with an exponent approximately independent of the strength of the fluctuation;
(iii) the decay of anisotropic fluctuations is not self-similar, their
statistics becoming more and more intermittent as time elapses. We also
investigate the early stages of the decay. The different short-time behavior
observed in two experiments differing by the phase organization of their
initial conditions gives a new hunch on the degree of universality of
small-scale turbulence statistics, i.e. its independence of the conditions at
large scales.Comment: 9 pages, 17 figure
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