537 research outputs found
Polyphonic audio tagging with sequentially labelled data using CRNN with learnable gated linear units
Audio tagging aims to detect the types of sound events occurring in an audio
recording. To tag the polyphonic audio recordings, we propose to use
Connectionist Temporal Classification (CTC) loss function on the top of
Convolutional Recurrent Neural Network (CRNN) with learnable Gated Linear Units
(GLU-CTC), based on a new type of audio label data: Sequentially Labelled Data
(SLD). In GLU-CTC, CTC objective function maps the frame-level probability of
labels to clip-level probability of labels. To compare the mapping ability of
GLU-CTC for sound events, we train a CRNN with GLU based on Global Max Pooling
(GLU-GMP) and a CRNN with GLU based on Global Average Pooling (GLU-GAP). And we
also compare the proposed GLU-CTC system with the baseline system, which is a
CRNN trained using CTC loss function without GLU. The experiments show that the
GLU-CTC achieves an Area Under Curve (AUC) score of 0.882 in audio tagging,
outperforming the GLU-GMP of 0.803, GLU-GAP of 0.766 and baseline system of
0.837. That means based on the same CRNN model with GLU, the performance of CTC
mapping is better than the GMP and GAP mapping. Given both based on the CTC
mapping, the CRNN with GLU outperforms the CRNN without GLU.Comment: DCASE2018 Workshop. arXiv admin note: text overlap with
arXiv:1808.0193
Decreasing the uncertainty of atomic clocks via real-time noise distinguish
The environmental perturbation on atoms is the key factor restricting the
performance of atomic frequency standards, especially in long term scale. In
this letter, we demonstrate a real-time noise distinguish operation of atomic
clocks. The operation improves the statistical uncertainty by about an order of
magnitude of our fountain clock which is deteriorated previously by extra
noises. The frequency offset bring by the extra noise is also corrected. The
experiment proves the real-time noise distinguish operation can reduce the
contribution of ambient noises and improve the uncertainty limit of atomic
clocks.Comment: 5 pages, 4 figures, 1 tabl
Practical color-based motion capture
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 93-101).Motion capture systems track the 3-D pose of the human body and are widely used for high quality content creation, gestural user input and virtual reality. However, these systems are rarely deployed in consumer applications due to their price and complexity. In this thesis, we propose a motion capture system built from commodity components that can be deployed in a matter of minutes. Our approach uses one or more webcams and a color garment to track either the user's upper body or hands for motion capture and user input. We demonstrate that custom designed color garments can simplify difficult computer vision problems and lead to efficient and robust algorithms for hand and upper body tracking. Specifically, our highly descriptive color patterns alleviate ambiguities that are commonly encountered when tracking only silhouettes or edges, allowing us to employ a nearest-neighbor approach to track either the hands or the upper body at interactive rates. We also describe a robust color calibration system that enables our color-based tracking to work against cluttered backgrounds and under multiple illuminants. We demonstrate our system in several real-world indoor and outdoor settings and describe proof-of-concept applications enabled by our system that we hope will provide a foundation for new interactions in computer aided design, animation control and augmented reality.by Robert Yuanbo Wang.Ph.D
Deep Generative Imputation Model for Missing Not At Random Data
Data analysis usually suffers from the Missing Not At Random (MNAR) problem,
where the cause of the value missing is not fully observed. Compared to the
naive Missing Completely At Random (MCAR) problem, it is more in line with the
realistic scenario whereas more complex and challenging. Existing statistical
methods model the MNAR mechanism by different decomposition of the joint
distribution of the complete data and the missing mask. But we empirically find
that directly incorporating these statistical methods into deep generative
models is sub-optimal. Specifically, it would neglect the confidence of the
reconstructed mask during the MNAR imputation process, which leads to
insufficient information extraction and less-guaranteed imputation quality. In
this paper, we revisit the MNAR problem from a novel perspective that the
complete data and missing mask are two modalities of incomplete data on an
equal footing. Along with this line, we put forward a generative-model-specific
joint probability decomposition method, conjunction model, to represent the
distributions of two modalities in parallel and extract sufficient information
from both complete data and missing mask. Taking a step further, we exploit a
deep generative imputation model, namely GNR, to process the real-world missing
mechanism in the latent space and concurrently impute the incomplete data and
reconstruct the missing mask. The experimental results show that our GNR
surpasses state-of-the-art MNAR baselines with significant margins (averagely
improved from 9.9% to 18.8% in RMSE) and always gives a better mask
reconstruction accuracy which makes the imputation more principle
Flat Chern Band From Twisted Bilayer MnBiTe
We construct a continuum model for the Moir\'e superlattice of twisted
bilayer MnBiTe, and study the band structure of the bilayer in both
ferromagnetic (FM) and antiferromagnetic (AFM) phases. We find the system
exhibits highly tunable Chern bands with Chern number up to . We show that a
twist angle of turns the highest valence band into a flat band with
Chern number that is isolated from all other bands in both FM and AFM
phases. This result provides a promising platform for realizing time-reversal
breaking correlated topological phases, such as fractional Chern insulator and
topological superconductor. In addition, our calculation indicates that
the twisted stacking facilitates the emergence of quantum anomalous Hall effect
in MnBiTe.Comment: 7+6 pages, 3+2 figure
Colloquium: Graphene spectroscopy
Spectroscopic studies of electronic phenomena in graphene are reviewed. A
variety of methods and techniques are surveyed, from quasiparticle
spectroscopies (tunneling, photoemission) to methods probing density and
current response (infrared optics, Raman) to scanning probe nanoscopy and
ultrafast pump-probe experiments. Vast complimentary information derived from
these investigations is shown to highlight unusual properties of Dirac
quasiparticles and many-body interaction effects in the physics of graphene.Comment: 36 pages, 16 figure
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