259,919 research outputs found
Classification methods for noise transients in advanced gravitational-wave detectors
Noise of non-astrophysical origin will contaminate science data taken by the
Advanced Laser Interferometer Gravitational-wave Observatory (aLIGO) and
Advanced Virgo gravitational-wave detectors. Prompt characterization of
instrumental and environmental noise transients will be critical for improving
the sensitivity of the advanced detectors in the upcoming science runs. During
the science runs of the initial gravitational-wave detectors, noise transients
were manually classified by visually examining the time-frequency scan of each
event. Here, we present three new algorithms designed for the automatic
classification of noise transients in advanced detectors. Two of these
algorithms are based on Principal Component Analysis. They are Principal
Component Analysis for Transients (PCAT), and an adaptation of LALInference
Burst (LIB). The third algorithm is a combination of an event generator called
Wavelet Detection Filter (WDF) and machine learning techniques for
classification. We test these algorithms on simulated data sets, and we show
their ability to automatically classify transients by frequency, SNR and
waveform morphology
EXAMINING THE IMPACT OF DISCRETE AND CONTEXTUAL STRESS FACTORS ON MEMORY
Stress is a complex and multifaceted process which is often not perceived as such. Therefore, given the unidimensional conceptualization of stress in previous research the current understanding of the associations between stress and memory are not well understood. This study investigates the association between stress and memory by capturing the complexity of stress through discrete and contextual stress factors. The current study used ecological momentary assessment (EMA) and geocoded indices (i.e., zip codes) of population density (i.e., urbanicity) and deprivation (socioeconomic disadvantage) in a large and diverse sample of U.S. participants (N = 8817) to examine the relationship between markers of daily stress (i.e., detection and intensity) and contextual factors (i.e., urbanicity and deprivation) on a well-established assessment of memory recall. Analyses examined models of cumulative stress reports and event-based stress reports. Results revealed significant main effects and interactions between our discrete and contextual stress factors highlighting that both factors contribute to the relationship between stress and memory. Additionally, examining the cumulative impact of stress across several days on a single memory test revealed to be more effective in assessing the impact of stress on memory compared to examining stress occurring at the same instance of test. Overall, this study provided new evidence in the way stress impacts memory thus suggesting the importance of examining cumulative stress over time and examining contextual factors of stress
Properties of Sequential Chromospheric Brightenings and Associated Flare Ribbons
We report on the physical properties of solar sequential chromospheric
brightenings (SCBs) observed in conjunction with moderate-sized chromospheric
flares with associated CMEs. To characterize these ephemeral events, we
developed automated procedures to identify and track subsections (kernels) of
solar flares and associated SCBs using high resolution H-alpha images.
Following the algorithmic identification and a statistical analysis, we compare
and find the following: SCBs are distinctly different from flare kernels in
their temporal characteristics of intensity, Doppler structure, duration, and
location properties. We demonstrate that flare ribbons are themselves made up
of subsections exhibiting differing characteristics. Flare kernels are measured
to have a mean propagation speed of 0.2 km/s and a maximum speed of 2.3 km/s
over a mean distance of 5 x 10^3 km. Within the studied population of SCBs,
different classes of characteristics are observed with coincident negative,
positive, or both negative and positive Doppler shifts of a few km/s. The
appearance of SCBs precede peak flare intensity by ~12 minutes and decay ~1
hour later. They are also found to propagate laterally away from flare center
in clusters at 41 km/s or 89 km/s. Given SCBs distinctive nature compared to
flares, we suggest a different physical mechanism relating to their origin than
the associated flare. We present a heuristic model of the origin of SCBs.Comment: 24 pages, 17 figure
Indexing of fictional video content for event detection and summarisation
This paper presents an approach to movie video indexing that utilises audiovisual analysis to detect important and meaningful temporal video segments, that we term events. We consider three event classes, corresponding to dialogues, action sequences, and montages, where the latter also includes musical sequences. These three event classes are intuitive for a viewer to understand and recognise whilst accounting for over 90% of the content of most movies. To detect events we leverage traditional filmmaking principles and map these to a set of computable low-level audiovisual features. Finite state machines (FSMs) are used to detect when temporal sequences of specific features occur. A set of heuristics, again inspired by filmmaking conventions, are then applied to the output of multiple FSMs to detect the required events. A movie search system, named MovieBrowser, built upon this approach is also described. The overall approach is evaluated against a ground truth of over twenty-three hours of movie content drawn from various genres and consistently obtains high precision and recall for all event classes. A user experiment designed to evaluate the usefulness of an event-based structure for both searching and browsing movie archives is also described and the results indicate the usefulness of the proposed approach
Identification of unusual events in multi-channel bridge monitoring data
Peer reviewedPostprin
Indexing of fictional video content for event detection and summarisation
This paper presents an approach to movie video indexing that utilises audiovisual analysis to detect important and meaningful temporal video segments, that we term events. We consider three event classes, corresponding to dialogues, action sequences, and montages, where the latter also includes musical sequences. These three event classes are intuitive for a viewer to understand and recognise whilst accounting for over 90% of the content of most movies. To detect events we leverage traditional filmmaking principles and map these to a set of computable low-level audiovisual features. Finite state machines (FSMs) are used to detect when temporal sequences of specific features occur. A set of heuristics, again inspired by filmmaking conventions, are then applied to the output of multiple FSMs to detect the required events. A movie search system, named MovieBrowser, built upon this approach is also described. The overall approach is evaluated against a ground truth of over twenty-three hours of movie content drawn from various genres and consistently obtains high precision and recall for all event classes. A user experiment designed to evaluate the usefulness of an event-based structure for both searching and browsing movie archives is also described and the results indicate the usefulness of the proposed approach
Indexing of fictional video content for event detection and summarisation
This paper presents an approach to movie video indexing that utilises audiovisual analysis to detect important and meaningful temporal video segments, that we term events. We consider three event classes, corresponding to dialogues, action sequences, and montages, where the latter also includes musical sequences. These three event classes are intuitive for a viewer to understand and recognise whilst accounting for over 90% of the content of most movies. To detect events we leverage traditional filmmaking principles and map these to a set of computable low-level audiovisual features. Finite state machines (FSMs) are used to detect when temporal sequences of specific features occur. A set of heuristics, again inspired by filmmaking conventions, are then applied to the output of multiple FSMs to detect the required events. A movie search system, named MovieBrowser, built upon this approach is also described. The overall approach is evaluated against a ground truth of over twenty-three hours of movie content drawn from various genres and consistently obtains high precision and recall for all event classes. A user experiment designed to evaluate the usefulness of an event-based structure for both searching and browsing movie archives is also described and the results indicate the usefulness of the proposed approach
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