24,950 research outputs found
Rapid Online Analysis of Local Feature Detectors and Their Complementarity
A vision system that can assess its own performance and take appropriate actions online to maximize its effectiveness would be a step towards achieving the long-cherished goal of imitating humans. This paper proposes a method for performing an online performance analysis of local feature detectors, the primary stage of many practical vision systems. It advocates the spatial distribution of local image features as a good performance indicator and presents a metric that can be calculated rapidly, concurs with human visual assessments and is complementary to existing offline measures such as repeatability. The metric is shown to provide a measure of complementarity for combinations of detectors, correctly reflecting the underlying principles of individual detectors. Qualitative results on well-established datasets for several state-of-the-art detectors are presented based on the proposed measure. Using a hypothesis testing approach and a newly-acquired, larger image database, statistically-significant performance differences are identified. Different detector pairs and triplets are examined quantitatively and the results provide a useful guideline for combining detectors in applications that require a reasonable spatial distribution of image features. A principled framework for combining feature detectors in these applications is also presented. Timing results reveal the potential of the metric for online applications. © 2013 by the authors; licensee MDPI, Basel, Switzerland
WiFi emission-based vs passive radar localization of human targets
In this paper two approaches are considered for human targets localization based on the WiFi signals: the device emission-based localization and the passive radar. Localization performance and characteristics of the two localization techniques are analyzed and compared, aiming at their joint exploitation inside sensor fusion systems. The former combines the Angle of Arrival (AoA) and the Time Difference of Arrival (TDoA) measures of the device transmissions to achieve the target position, while the latter exploits the AoA and the bistatic range measures of the target echoes. The results obtained on experimental data show that the WiFi emission-based strategy is always effective for the positioning of human targets holding a WiFi device, but it has a poor localization accuracy and the number of measured positions largely depends on the device activity. In contrast, the passive radar is only effective for moving targets and has limited spatial resolution but it provides better accuracy performance, thanks to the possibility to integrate a higher number of received signals. These results also demonstrate a significant complementarity of these techniques, through a suitable experimental test, which opens the way to the development of appropriate sensor fusion techniques
A Two-stage Method for Inverse Medium Scattering
We present a novel numerical method to the time-harmonic inverse medium
scattering problem of recovering the refractive index from near-field scattered
data. The approach consists of two stages, one pruning step of detecting the
scatterer support, and one resolution enhancing step with mixed regularization.
The first step is strictly direct and of sampling type, and faithfully detects
the scatterer support. The second step is an innovative application of
nonsmooth mixed regularization, and it accurately resolves the scatterer sizes
as well as intensities. The model is efficiently solved by a semi-smooth
Newton-type method. Numerical results for two- and three-dimensional examples
indicate that the approach is accurate, computationally efficient, and robust
with respect to data noise.Comment: 18 pages, 5 figure
Manifestation of fundamental quantum complementarities in time-domain interference experiments with quantum dots: A theoretical analysis
A theoretical analysis is presented showing that fundamental complementarity
between the particle-like properties of an exciton confined in a semiconductor
quantum dot and the ability of the same system to show interference may be
studied in a time domain interference experiment, similar to those currently
performed. The feasibility of such an experiment, including required pulse
parameters and the dephasing effect of the environment, is studied.Comment: Final, considerably extended version; 8 pages, 3 figure
Planning the Future of U.S. Particle Physics (Snowmass 2013): Chapter 4: Cosmic Frontier
These reports present the results of the 2013 Community Summer Study of the
APS Division of Particles and Fields ("Snowmass 2013") on the future program of
particle physics in the U.S. Chapter 4, on the Cosmic Frontier, discusses the
program of research relevant to cosmology and the early universe. This area
includes the study of dark matter and the search for its particle nature, the
study of dark energy and inflation, and cosmic probes of fundamental
symmetries.Comment: 61 page
The complementarity of astrometric and radial velocity exoplanet observations - Determining exoplanet mass with astrometric snapshots
We obtain full information on the orbital parameters by combining radial
velocity and astrometric measurements by means of Bayesian inference. We sample
the parameter probability densities of orbital model parameters with a Markov
chain Monte Carlo (McMC) method in simulated observational scenarios to test
the detectability of planets with orbital periods longer than the observational
timelines. We show that, when fitting model parameters simultaneously to
measurements from both sources, it is possible to extract much more information
from the measurements than when using either source alone. We demonstrate this
by studying the orbit of recently found extra-solar planet HD 154345 b.Comment: 6 pages, 9 figures. Accepted to A&
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