69 research outputs found
Adaptive Target Recognition: A Case Study Involving Airport Baggage Screening
This work addresses the question whether it is possible to design a
computer-vision based automatic threat recognition (ATR) system so that it can
adapt to changing specifications of a threat without having to create a new ATR
each time. The changes in threat specifications, which may be warranted by
intelligence reports and world events, are typically regarding the physical
characteristics of what constitutes a threat: its material composition, its
shape, its method of concealment, etc. Here we present our design of an AATR
system (Adaptive ATR) that can adapt to changing specifications in materials
characterization (meaning density, as measured by its x-ray attenuation
coefficient), its mass, and its thickness. Our design uses a two-stage cascaded
approach, in which the first stage is characterized by a high recall rate over
the entire range of possibilities for the threat parameters that are allowed to
change. The purpose of the second stage is to then fine-tune the performance of
the overall system for the current threat specifications. The computational
effort for this fine-tuning for achieving a desired PD/PFA rate is far less
than what it would take to create a new classifier with the same overall
performance for the new set of threat specifications
RMPD - A Recursive Mid-Point Displacement Algorithm for Path Planning
Motivated by what is required for real-time path planning, the paper starts
out by presenting sRMPD, a new recursive "local" planner founded on the key
notion that, unless made necessary by an obstacle, there must be no deviation
from the shortest path between any two points, which would normally be a
straight line path in the configuration space. Subsequently, we increase the
power of sRMPD by using it as a "connect" subroutine call in a higher-level
sampling-based algorithm mRMPD that is inspired by multi-RRT. As a consequence,
mRMPD spawns a larger number of space exploring trees in regions of the
configuration space that are characterized by a higher density of obstacles.
The overall effect is a hybrid tree growing strategy with a trade-off between
random exploration as made possible by multi-RRT based logic and immediate
exploitation of opportunities to connect two states as made possible by sRMPD.
The mRMPD planner can be biased with regard to this trade-off for solving
different kinds of planning problems efficiently. Based on the test cases we
have run, our experiments show that mRMPD can reduce planning time by up to 80%
compared to basic RRT
Self-Supervised One-Shot Learning for Automatic Segmentation of StyleGAN Images
We propose a framework for the automatic one-shot segmentation of synthetic
images generated by a StyleGAN. Our framework is based on the observation that
the multi-scale hidden features in the GAN generator hold useful semantic
information that can be utilized for automatic on-the-fly segmentation of the
generated images. Using these features, our framework learns to segment
synthetic images using a self-supervised contrastive clustering algorithm that
projects the hidden features into a compact space for per-pixel classification.
This contrastive learner is based on using a novel data augmentation strategy
and a pixel-wise swapped prediction loss that leads to faster learning of the
feature vectors for one-shot segmentation. We have tested our implementation on
five standard benchmarks to yield a segmentation performance that not only
outperforms the semi-supervised baselines by an average wIoU margin of 1.02 %
but also improves the inference speeds by a factor of 4.5. Finally, we also
show the results of using the proposed one-shot learner in implementing BagGAN,
a framework for producing annotated synthetic baggage X-ray scans for threat
detection. This framework was trained and tested on the PIDRay baggage
benchmark to yield a performance comparable to its baseline segmenter based on
manual annotations
OUTCOME OF MACHINE REASONING IN A NETWORK MANAGEMENT SYSTEM TOPOLOGY VIEW
A technique is described herein to provide a visualization overlaid on a network topology that illustrates the cascading impact of a network event before it happens. The technique may empower a network administrator to perform one or more steps to mitigate the issue and/or minimize its impact before the issue manifests itself into a critical network condition
Attitude, Linear Velocity and Depth Estimation of a Camera observing a planar target using continuous homography and inertial data
International audienceThis paper revisits the problem of estimating the attitude, linear velocity and depth of an IMU-Camera with respect to a planar target. The considered solution relies on the measurement of the optical flow (extracted from the continuous homography) complemented with gyrometer and accelerometer measurements. The proposed deterministic observer is accompanied with an observability analysis that points out camera's motion excitation conditions whose satisfaction grants stability of the observer and convergence of the estimation errors to zero. The performance of the observer is illustrated by performing experiments on a test-bed IMU-Camera system
RVSPY -- Radial Velocity Survey for Planets around Young Stars. Target characterization and high-cadence survey
We introduce our Radial Velocity Survey for Planets around Young stars
(RVSPY), characterise our target stars, and search for substellar companions at
orbital separations smaller than a few au from the host star. We use the FEROS
spectrograph to obtain high signal-to-noise spectra and time series of precise
radial velocities (RVs) of 111 stars most of which are surrounded by debris
discs. Our target stars have spectral types between early F and late K, a
median age of 400 Myr, and a median distance of 45 pc. We determine for all
target stars their basic stellar parameters and present the results of the
high-cadence RV survey and activity characterization. We achieve a median
single-measurement RV precision of 6 m/s and derive the short-term intrinsic RV
scatter of our targets (median 22 m/s), which is mostly caused by stellar
activity and decays with age from >100 m/s at 500 Myr.
We discover six previously unknown close companions with orbital periods
between 10 and 100 days, three of which are low-mass stars, and three are in
the brown dwarf mass regime. We detect no hot companion with an orbital period
<10 days down to a median mass limit of ~1 M_Jup for stars younger than 500
Myr, which is still compatible with the established occurrence rate of such
companions around main-sequence stars. We find significant RV periodicities
between 1.3 and 4.5 days for 14 stars, which are, however, all caused by
rotational modulation due to starspots. We also analyse the TESS photometric
time series data and find significant periodicities for most of the stars. For
11 stars, the photometric periods are also clearly detected in the RV data. We
also derive stellar rotation periods ranging from 1 to 10 days for 91 stars,
mostly from TESS data. From the intrinsic activity-related short-term RV
jitter, we derive the expected mass-detection thresholds for longer-period
companions.Comment: 24 pages, 14 figures, 4 tables; Accepted for publication in A&
Radial Velocity Survey for Planets around Young Stars (RVSPY). Target characterisation and high-cadence survey
We introduce our Radial Velocity Survey for Planets around Young stars (RVSPY), characterise our target stars, and search for substellar companions at orbital separations smaller than a few au from the host star. We use the FEROS spectrograph to obtain high signal-to-noise spectra and time series of precise radial velocities (RVs) of 111 stars most of which are surrounded by debris discs. Our target stars have spectral types between early F and late K, a median age of 400 Myr, and a median distance of 45 pc. We determine for all target stars their basic stellar parameters and present the results of the high-cadence RV survey and activity characterization. We achieve a median single-measurement RV precision of 6 m/s and derive the short-term intrinsic RV scatter of our targets (median 22 m/s), which is mostly caused by stellar activity and decays with age from >100 m/s at 500 Myr. We discover six previously unknown close companions with orbital periods between 10 and 100 days, three of which are low-mass stars, and three are in the brown dwarf mass regime. We detect no hot companion with an orbital period <10 days down to a median mass limit of ~1 M_Jup for stars younger than 500 Myr, which is still compatible with the established occurrence rate of such companions around main-sequence stars. We find significant RV periodicities between 1.3 and 4.5 days for 14 stars, which are, however, all caused by rotational modulation due to starspots. We also analyse the TESS photometric time series data and find significant periodicities for most of the stars. For 11 stars, the photometric periods are also clearly detected in the RV data. We also derive stellar rotation periods ranging from 1 to 10 days for 91 stars, mostly from TESS data. From the intrinsic activity-related short-term RV jitter, we derive the expected mass-detection thresholds for longer-period companions
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