199 research outputs found
A comparison of linear and non-linear calibrations for speaker recognition
In recent work on both generative and discriminative score to
log-likelihood-ratio calibration, it was shown that linear transforms give good
accuracy only for a limited range of operating points. Moreover, these methods
required tailoring of the calibration training objective functions in order to
target the desired region of best accuracy. Here, we generalize the linear
recipes to non-linear ones. We experiment with a non-linear, non-parametric,
discriminative PAV solution, as well as parametric, generative,
maximum-likelihood solutions that use Gaussian, Student's T and
normal-inverse-Gaussian score distributions. Experiments on NIST SRE'12 scores
suggest that the non-linear methods provide wider ranges of optimal accuracy
and can be trained without having to resort to objective function tailoring.Comment: accepted for Odyssey 2014: The Speaker and Language Recognition
Worksho
Toroidal Probabilistic Spherical Discriminant Analysis
In speaker recognition, where speech segments are mapped to embeddings on the
unit hypersphere, two scoring back-ends are commonly used, namely cosine
scoring and PLDA. We have recently proposed PSDA, an analog to PLDA that uses
Von Mises-Fisher distributions instead of Gaussians. In this paper, we present
toroidal PSDA (T-PSDA). It extends PSDA with the ability to model within and
between-speaker variabilities in toroidal submanifolds of the hypersphere. Like
PLDA and PSDA, the model allows closed-form scoring and closed-form EM updates
for training. On VoxCeleb, we find T-PSDA accuracy on par with cosine scoring,
while PLDA accuracy is inferior. On NIST SRE'21 we find that T-PSDA gives large
accuracy gains compared to both cosine scoring and PLDA.Comment: Submitted to ICASSP 202
On the physics behind coastal morphodynamic patterns
Peer ReviewedPostprint (published version
The role of surface rollers on the formation of surfzone transverse sand bars
A morphodynamic model has been developed to gain more fundamental knowledge about the formation of transverse finger sand bars. The model describes the feedback between waves, rollers, depth-averaged currents and bed evolution, so that self-organized processes can develop. The wave and bathymetric conditions measured at Egmond site are firstly applied and the modeled longshore current and wave height are compared with field data of that beach. Subsequently, the wave and bathymetric conditions measured at Noordwijk site are used to compare model results with the up-current oriented bars observed there. Realistic positive feedback leading to formation of the observed bars only occurs if the resuspension of sediment due to bore turbulence is included in the model. The modeled wavelength, crest orientation and growth rate agree with data but the model overestimates the migration rates.Peer ReviewedPostprint (published version
The role of surface rollers on the formation of surfzone transverse sand bars
Peer ReviewedPostprint (published version
Modeling and analyzing observed transverse sand bars in the surf zone
A morphodynamic model has been applied to explain the characteristics of
transverse sandbars observed in the inner surf zone of open beaches. The model describes
the feedback between waves, rollers, depth-averaged currents and bed evolution, so that
self-organized processes can develop.Postprint (published version
Understanding coastal morphodynamic patterns from depth-averaged sediment concentration
This review highlights the important role of the depth-averaged sediment concentration (DASC) to understand the formation of a number of coastal morphodynamic features that have an alongshore rhythmic pattern: beach cusps, surf zone transverse and crescentic bars, and shoreface-connected sand ridges. We present a formulation and methodology, based on the knowledge of the DASC (which equals the sediment load divided by the water depth), that has been successfully used to understand the characteristics of these features. These sand bodies, relevant for coastal engineering and other disciplines, are located in different parts of the coastal zone and are characterized by different spatial and temporal scales, but the same technique can be used to understand them. Since the sand bodies occur in the presence of depth-averaged currents, the sediment transport approximately equals a sediment load times the current. Moreover, it is assumed that waves essentially mobilize the sediment, and the current increases this mobilization and advects the sediment. In such conditions, knowing the spatial distribution of the DASC and the depth-averaged currents induced by the forcing (waves, wind, and pressure gradients) over the patterns allows inferring the convergence/divergence of sediment transport. Deposition (erosion) occurs where the current flows from areas of high to low (low to high) values of DASC. The formulation and methodology are especially useful to understand the positive feedback mechanisms between flow and morphology leading to the formation of those morphological features, but the physical mechanisms for their migration, their finite-amplitude behavior and their decay can also be explored
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