4,521 research outputs found
A Novel Stealthy Target Detection Based on Stratospheric Balloon-borne Positional Instability due to Random Wind
A novel detection for stealthy target model F-117A with a higher aspect vision is introduced by using Stratospheric Balloon-borne Bistatic system. The potential problem of proposed scheme is platform instability impacted on the balloon by external wind force. The flight control system is studied in detail under typical random process, which is defined by Dryden turbulence spectrum. To accurately detect the stealthy target model, a real Radar Cross Section (RCS) based on physical optics (PO) formulation is applied. The sensitivity of the proposed scheme has been improved due to increasing PO – scattering field of stealthy model with higher aspect angle comparing to the conventional ground -based system. Simulations demonstrate that the proposed scheme gives much higher location accuracy and reduces location errors
Scenic: A Language for Scenario Specification and Scene Generation
We propose a new probabilistic programming language for the design and
analysis of perception systems, especially those based on machine learning.
Specifically, we consider the problems of training a perception system to
handle rare events, testing its performance under different conditions, and
debugging failures. We show how a probabilistic programming language can help
address these problems by specifying distributions encoding interesting types
of inputs and sampling these to generate specialized training and test sets.
More generally, such languages can be used for cyber-physical systems and
robotics to write environment models, an essential prerequisite to any formal
analysis. In this paper, we focus on systems like autonomous cars and robots,
whose environment is a "scene", a configuration of physical objects and agents.
We design a domain-specific language, Scenic, for describing "scenarios" that
are distributions over scenes. As a probabilistic programming language, Scenic
allows assigning distributions to features of the scene, as well as
declaratively imposing hard and soft constraints over the scene. We develop
specialized techniques for sampling from the resulting distribution, taking
advantage of the structure provided by Scenic's domain-specific syntax.
Finally, we apply Scenic in a case study on a convolutional neural network
designed to detect cars in road images, improving its performance beyond that
achieved by state-of-the-art synthetic data generation methods.Comment: 41 pages, 36 figures. Full version of a PLDI 2019 paper (extending UC
Berkeley EECS Department Tech Report No. UCB/EECS-2018-8
RUR53: an Unmanned Ground Vehicle for Navigation, Recognition and Manipulation
This paper proposes RUR53: an Unmanned Ground Vehicle able to autonomously
navigate through, identify, and reach areas of interest; and there recognize,
localize, and manipulate work tools to perform complex manipulation tasks. The
proposed contribution includes a modular software architecture where each
module solves specific sub-tasks and that can be easily enlarged to satisfy new
requirements. Included indoor and outdoor tests demonstrate the capability of
the proposed system to autonomously detect a target object (a panel) and
precisely dock in front of it while avoiding obstacles. They show it can
autonomously recognize and manipulate target work tools (i.e., wrenches and
valve stems) to accomplish complex tasks (i.e., use a wrench to rotate a valve
stem). A specific case study is described where the proposed modular
architecture lets easy switch to a semi-teleoperated mode. The paper
exhaustively describes description of both the hardware and software setup of
RUR53, its performance when tests at the 2017 Mohamed Bin Zayed International
Robotics Challenge, and the lessons we learned when participating at this
competition, where we ranked third in the Gran Challenge in collaboration with
the Czech Technical University in Prague, the University of Pennsylvania, and
the University of Lincoln (UK).Comment: This article has been accepted for publication in Advanced Robotics,
published by Taylor & Franci
Novel directed search strategy to detect continuous gravitational waves from neutron stars in low- and high-eccentricity binary systems
We describe a novel, very fast and robust, directed search incoherent method
for periodic gravitational waves (GWs) from neutron stars in binary systems. As
directed search, we assume the source sky position to be known with enough
accuracy, but all other parameters are supposed to be unknown. We exploit the
frequency-modulation due to source orbital motion to unveil the signal
signature by commencing from a collection of time and frequency peaks. We
validate our pipeline adding 131 artificial continuous GW signals from pulsars
in binary systems to simulated detector Gaussian noise, characterized by a
power spectral density Sh = 4x10^-24 Hz^-1/2 in the frequency interval [70,
200] Hz, which is overall commensurate with the advanced detector design
sensitivities. The pipeline detected 128 signals, and the weakest signal
injected and detected has a GW strain amplitude of ~10^-24, assuming one month
of gapless data collected by a single advanced detector. We also provide
sensitivity estimations, which show that, for a single- detector data covering
one month of observation time, depending on the source orbital Doppler
modulation, we can detect signals with an amplitude of ~7x10^-25. By using
three detectors, and one year of data, we would easily gain more than a factor
3 in sensitivity, translating into being able to detect weaker signals. We also
discuss the parameter estimate proficiency of our method, as well as
computational budget, which is extremely cheap. In fact, sifting one month of
single-detector data and 131 Hz-wide frequency range takes roughly 2.4 CPU
hours. Due to the high computational speed, the current procedure can be
readily applied in ally-sky schemes, sieving in parallel as many sky positions
as permitted by the available computational power
P-CNN: Pose-based CNN Features for Action Recognition
This work targets human action recognition in video. While recent methods
typically represent actions by statistics of local video features, here we
argue for the importance of a representation derived from human pose. To this
end we propose a new Pose-based Convolutional Neural Network descriptor (P-CNN)
for action recognition. The descriptor aggregates motion and appearance
information along tracks of human body parts. We investigate different schemes
of temporal aggregation and experiment with P-CNN features obtained both for
automatically estimated and manually annotated human poses. We evaluate our
method on the recent and challenging JHMDB and MPII Cooking datasets. For both
datasets our method shows consistent improvement over the state of the art.Comment: ICCV, December 2015, Santiago, Chil
Improving the sensitivity to gravitational-wave sources by modifying the input-output optics of advanced interferometers
We study frequency dependent (FD) input-output schemes for signal-recycling
interferometers, the baseline design of Advanced LIGO and the current
configuration of GEO 600. Complementary to a recent proposal by Harms et al. to
use FD input squeezing and ordinary homodyne detection, we explore a scheme
which uses ordinary squeezed vacuum, but FD readout. Both schemes, which are
sub-optimal among all possible input-output schemes, provide a global noise
suppression by the power squeeze factor, while being realizable by using
detuned Fabry-Perot cavities as input/output filters. At high frequencies, the
two schemes are shown to be equivalent, while at low frequencies our scheme
gives better performance than that of Harms et al., and is nearly fully
optimal. We then study the sensitivity improvement achievable by these schemes
in Advanced LIGO era (with 30-m filter cavities and current estimates of
filter-mirror losses and thermal noise), for neutron star binary inspirals, and
for narrowband GW sources such as low-mass X-ray binaries and known radio
pulsars. Optical losses are shown to be a major obstacle for the actual
implementation of these techniques in Advanced LIGO. On time scales of
third-generation interferometers, like EURO/LIGO-III (~2012), with
kilometer-scale filter cavities, a signal-recycling interferometer with the FD
readout scheme explored in this paper can have performances comparable to
existing proposals. [abridged]Comment: Figs. 9 and 12 corrected; Appendix added for narrowband data analysi
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