106,851 research outputs found
Behavior prediction in-the-wild
In this paper, the problem of audio-visual behavior prediction in-the-wild is addressed. In this context, both audio-visual descriptors of behavioral cues (features) and continuous-time real-valued characterizations of behavior (annotations) are (possibly) corrupted by non-Gaussian noise of large magnitude. The modeling assumption behind the proposed framework is that naturalistic affect and behavior captured in audio-visual episodes are smoothly-varying dynamic phenomena and thus the hidden temporal dynamics can be modeled as a generative auto-regressive process. Consequently, continuous-time real-valued characterizations of behavior (annotations) are postulated to be outputs of a low-complexity (i.e., low-order) time-invariant Linear Dynamical System (LDS) when descriptors of behavioral cues (features) act as inputs. To learn the parameters of the LDS, a recently proposed spectral method that relies on Hankel-rank minimization is adopted. Experimental evaluation on a challenging database recorded in the wild demonstrate the effectiveness of the proposed approach in behavior prediction
Dynamic behavior analysis via structured rank minimization
Human behavior and affect is inherently a dynamic phenomenon involving temporal evolution of patterns manifested through a multiplicity of non-verbal behavioral cues including facial expressions, body postures and gestures, and vocal outbursts. A natural assumption for human behavior modeling is that a continuous-time characterization of behavior is the output of a linear time-invariant system when behavioral cues act as the input (e.g., continuous rather than discrete annotations of dimensional affect). Here we study the learning of such dynamical system under real-world conditions, namely in the presence of noisy behavioral cues descriptors and possibly unreliable annotations by employing structured rank minimization. To this end, a novel structured rank minimization method and its scalable variant are proposed. The generalizability of the proposed framework is demonstrated by conducting experiments on 3 distinct dynamic behavior analysis tasks, namely (i) conflict intensity prediction, (ii) prediction of valence and arousal, and (iii) tracklet matching. The attained results outperform those achieved by other state-of-the-art methods for these tasks and, hence, evidence the robustness and effectiveness of the proposed approach
Dynamic behavior analysis via structured rank minimization
Human behavior and affect is inherently a dynamic phenomenon involving temporal evolution of patterns manifested through a multiplicity of non-verbal behavioral cues including facial expressions, body postures and gestures, and vocal outbursts. A natural assumption for human behavior modeling is that a continuous-time characterization of behavior is the output of a linear time-invariant system when behavioral cues act as the input (e.g., continuous rather than discrete annotations of dimensional affect). Here we study the learning of such dynamical system under real-world conditions, namely in the presence of noisy behavioral cues descriptors and possibly unreliable annotations by employing structured rank minimization. To this end, a novel structured rank minimization method and its scalable variant are proposed. The generalizability of the proposed framework is demonstrated by conducting experiments on 3 distinct dynamic behavior analysis tasks, namely (i) conflict intensity prediction, (ii) prediction of valence and arousal, and (iii) tracklet matching. The attained results outperform those achieved by other state-of-the-art methods for these tasks and, hence, evidence the robustness and effectiveness of the proposed approach
The behavioral approach to systems and modeling
An introduction to behavioral system theory, and a brief review of the content of the Special Issue are given
Numerical convergence of the block-maxima approach to the Generalized Extreme Value distribution
In this paper we perform an analytical and numerical study of Extreme Value
distributions in discrete dynamical systems. In this setting, recent works have
shown how to get a statistics of extremes in agreement with the classical
Extreme Value Theory. We pursue these investigations by giving analytical
expressions of Extreme Value distribution parameters for maps that have an
absolutely continuous invariant measure. We compare these analytical results
with numerical experiments in which we study the convergence to limiting
distributions using the so called block-maxima approach, pointing out in which
cases we obtain robust estimation of parameters. In regular maps for which
mixing properties do not hold, we show that the fitting procedure to the
classical Extreme Value Distribution fails, as expected. However, we obtain an
empirical distribution that can be explained starting from a different
observable function for which Nicolis et al. [2006] have found analytical
results.Comment: 34 pages, 7 figures; Journal of Statistical Physics 201
Thermoacoustic instability - a dynamical system and time domain analysis
This study focuses on the Rijke tube problem, which includes features
relevant to the modeling of thermoacoustic coupling in reactive flows: a
compact acoustic source, an empirical model for the heat source, and
nonlinearities. This thermo-acoustic system features a complex dynamical
behavior. In order to synthesize accurate time-series, we tackle this problem
from a numerical point-of-view, and start by proposing a dedicated solver
designed for dealing with the underlying stiffness, in particular, the retarded
time and the discontinuity at the location of the heat source. Stability
analysis is performed on the limit of low-amplitude disturbances by means of
the projection method proposed by Jarlebring (2008), which alleviates the
linearization with respect to the retarded time. The results are then compared
to the analytical solution of the undamped system, and to Galerkin projection
methods commonly used in this setting. This analysis provides insight into the
consequences of the various assumptions and simplifications that justify the
use of Galerkin expansions based on the eigenmodes of the unheated resonator.
We illustrate that due to the presence of a discontinuity in the spatial
domain, the eigenmodes in the heated case, predicted by using Galerkin
expansion, show spurious oscillations resulting from the Gibbs phenomenon. By
comparing the modes of the linear to that of the nonlinear regime, we are able
to illustrate the mean-flow modulation and frequency switching. Finally,
time-series in the fully nonlinear regime, where a limit cycle is established,
are analyzed and dominant modes are extracted. The analysis of the saturated
limit cycles shows the presence of higher frequency modes, which are linearly
stable but become significant through nonlinear growth of the signal. This
bimodal effect is not captured when the coupling between different frequencies
is not accounted for.Comment: Submitted to Journal of Fluid Mechanic
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