44,510 research outputs found
A study of noise metric and tone correction accuracy
Methods currently used to measure human response to aircraft flyover noise were investigated. Response to high level aircraft noise usually experienced outdoors was obtained. Response to aircraft flyover noise typical of indoor exposure was also investigated. It was concluded that current methods for evaluating response to aircraft flyover are more accurate for outdoor noise
On Rendering Synthetic Images for Training an Object Detector
We propose a novel approach to synthesizing images that are effective for
training object detectors. Starting from a small set of real images, our
algorithm estimates the rendering parameters required to synthesize similar
images given a coarse 3D model of the target object. These parameters can then
be reused to generate an unlimited number of training images of the object of
interest in arbitrary 3D poses, which can then be used to increase
classification performances.
A key insight of our approach is that the synthetically generated images
should be similar to real images, not in terms of image quality, but rather in
terms of features used during the detector training. We show in the context of
drone, plane, and car detection that using such synthetically generated images
yields significantly better performances than simply perturbing real images or
even synthesizing images in such way that they look very realistic, as is often
done when only limited amounts of training data are available
Airborne forward pointing UV Rayleigh lidar for remote clear air turbulence (CAT) detection: system design and performance
A high-performance airborne UV Rayleigh lidar system was developed within the
European project DELICAT. With its forward-pointing architecture it aims at
demonstrating a novel detection scheme for clear air turbulence (CAT) for an
aeronautics safety application. Due to its occurrence in clear and clean air at
high altitudes (aviation cruise flight level), this type of turbulence evades
microwave radar techniques and in most cases coherent Doppler lidar techniques.
The present lidar detection technique relies on air density fluctuations
measurement and is thus independent of backscatter from hydrometeors and
aerosol particles. The subtle air density fluctuations caused by the turbulent
air flow demand exceptionally high stability of the setup and in particular of
the detection system. This paper describes an airborne test system for the
purpose of demonstrating this technology and turbulence detection method: a
high-power UV Rayleigh lidar system is installed on a research aircraft in a
forward-looking configuration for use in cruise flight altitudes. Flight test
measurements demonstrate this unique lidar system being able to resolve air
density fluctuations occurring in light-to-moderate CAT at 5 km or moderate CAT
at 10 km distance. A scaling of the determined stability and noise
characteristics shows that such performance is adequate for an application in
commercial air transport.Comment: 17 pages, 19 figures. Pre-publish to Applied Optics (OSA
Feasibility of an onboard wake vortex avoidance system
It was determined that an onboard vortex wake detection system using existing, proven instrumentation is technically feasible. This system might be incorporated into existing onboard systems such as a wind shear detection system, and might provide the pilot with the location of a vortex wake, as well as an evasive maneuver so that the landing separations may be reduced. It is suggested that this system might be introduced into our nation's commuter aircraft fleet and major air carrier fleet and permit a reduction of current landing separation standards, thereby reducing takeoff and departure delays
Index to NASA Tech Briefs, 1975
This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs
Interpretable Aircraft Engine Diagnostic via Expert Indicator Aggregation
Detecting early signs of failures (anomalies) in complex systems is one of
the main goal of preventive maintenance. It allows in particular to avoid
actual failures by (re)scheduling maintenance operations in a way that
optimizes maintenance costs. Aircraft engine health monitoring is one
representative example of a field in which anomaly detection is crucial.
Manufacturers collect large amount of engine related data during flights which
are used, among other applications, to detect anomalies. This article
introduces and studies a generic methodology that allows one to build automatic
early signs of anomaly detection in a way that builds upon human expertise and
that remains understandable by human operators who make the final maintenance
decision. The main idea of the method is to generate a very large number of
binary indicators based on parametric anomaly scores designed by experts,
complemented by simple aggregations of those scores. A feature selection method
is used to keep only the most discriminant indicators which are used as inputs
of a Naive Bayes classifier. This give an interpretable classifier based on
interpretable anomaly detectors whose parameters have been optimized indirectly
by the selection process. The proposed methodology is evaluated on simulated
data designed to reproduce some of the anomaly types observed in real world
engines.Comment: arXiv admin note: substantial text overlap with arXiv:1408.6214,
arXiv:1409.4747, arXiv:1407.088
A Methodology for the Diagnostic of Aircraft Engine Based on Indicators Aggregation
Aircraft engine manufacturers collect large amount of engine related data
during flights. These data are used to detect anomalies in the engines in order
to help companies optimize their maintenance costs. This article introduces and
studies a generic methodology that allows one to build automatic early signs of
anomaly detection in a way that is understandable by human operators who make
the final maintenance decision. The main idea of the method is to generate a
very large number of binary indicators based on parametric anomaly scores
designed by experts, complemented by simple aggregations of those scores. The
best indicators are selected via a classical forward scheme, leading to a much
reduced number of indicators that are tuned to a data set. We illustrate the
interest of the method on simulated data which contain realistic early signs of
anomalies.Comment: Proceedings of the 14th Industrial Conference, ICDM 2014, St.
Petersburg : Russian Federation (2014
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