2,243 research outputs found
Speaker change detection using BIC: a comparison on two datasets
Abstract — This paper addresses the problem of unsupervised speaker change detection. We assume that there is no prior knowledge on the number of speakers or their identities. Two methods are tested. The first method uses the Bayesian Information Criterion (BIC), investigates the AudioSpectrumCentroid and AudioWaveformEnvelope features, and implements a dynamic thresholding followed by a fusion scheme. The second method is a real-time one that uses a metric-based approach employing line spectral pairs (LSP) and the BIC criterion to validate a potential change point. The experiments are carried out on two different datasets. The first set was created by concatenating speakers from the TIMIT database and is referred to as the TIMIT data set. The second set was created by using recordings from the MPEG-7 test set CD1 and broadcast news and is referred to as the INESC dataset. I
The Three Dimensional Evolution to Core Collapse of a Massive Star
We present the first three dimensional (3D) simulation of the final minutes
of iron core growth in a massive star, up to and including the point of core
gravitational instability and collapse. We self-consistently capture the
development of strong convection driven by violent Si burning in the shell
surrounding the iron core. This convective burning builds the iron core to its
critical (Chandrasekhar) mass and collapse ensues, driven by electron capture
and photodisintegration. The non-spherical structure and motion (turbulent
fluctuations) generated by 3D convection is substantial at the point of
collapse. We examine the impact of such physically-realistic 3D initial
conditions on the core-collapse supernova mechanism using 3D simulations
including multispecies neutrino leakage. We conclude that non-spherical
progenitor structure should not be ignored, and has a significant and favorable
impact on the likelihood for neutrino-driven explosions.Comment: 7 pages, 5 figures, accepted for publication in ApJ Letters. Movies
may be viewed at http://flash.uchicago.edu/~smc/progen3
Competence-based Curriculum Learning for Neural Machine Translation
Current state-of-the-art NMT systems use large neural networks that are not
only slow to train, but also often require many heuristics and optimization
tricks, such as specialized learning rate schedules and large batch sizes. This
is undesirable as it requires extensive hyperparameter tuning. In this paper,
we propose a curriculum learning framework for NMT that reduces training time,
reduces the need for specialized heuristics or large batch sizes, and results
in overall better performance. Our framework consists of a principled way of
deciding which training samples are shown to the model at different times
during training, based on the estimated difficulty of a sample and the current
competence of the model. Filtering training samples in this manner prevents the
model from getting stuck in bad local optima, making it converge faster and
reach a better solution than the common approach of uniformly sampling training
examples. Furthermore, the proposed method can be easily applied to existing
NMT models by simply modifying their input data pipelines. We show that our
framework can help improve the training time and the performance of both
recurrent neural network models and Transformers, achieving up to a 70%
decrease in training time, while at the same time obtaining accuracy
improvements of up to 2.2 BLEU
Ubiquitous digital technologies and spatial structure; An update
This paper examines the impact of widespread adoption of information and communication technologies (ICT) on urban structure worldwide. Has it offset agglomeration benefits and led to more dispersed spatial structures, or has it strengthened urban externalities and thus resulted in more concentrated spatial structures? Theoretical and empirical studies on this question have produced contradictory findings. The present study recognizes that assumptions made earlier about the evolution of technological capabilities do not necessarily hold today. As cutting-edge digital technologies have matured considerably, a fresh look at this question is called for. The paper addresses this issue by means of several data sets using instrumental variable methods. One is the UN data on Urban Settlements with more than 300, 000 inhabitants. Estimation methods with these data show that increased adoption of ICT has resulted in national urban systems that are less uniform in terms of city sizes and are characterized by higher population concentrations in larger cities, when concentration is proxied the Pareto (Zipf) coefficient for national city size distributions. Two, is disaggregated data for the urban systems of the US, defined as Micropolitan and Metropolitan Areas, and for the UK, defined as Built-up Areas in England and Wales, respectively. These data allow for the impacts to be studied for cities smaller than those included in the cross-country data. Increased internet usage improved a city's ranking in the US urban system. Similarly, increased download speed improves a built-up area's ranking in England and Wales
Can G4-like Composite Ab Initio Methods Accurately Predict Vibrational Harmonic Frequencies?
Minimally empirical G4-like composite wavefunction theories [E. Semidalas and
J. M. L. Martin, \textit{J. Chem. Theory Comput.} {\bf 16}, 4238-4255 and
7507-7524 (2020)] trained against the large and chemically diverse GMTKN55
benchmark suite have demonstrated both accuracy and cost-effectiveness in
predicting thermochemistry, barrier heights, and noncovalent interaction
energies. Here, we assess the spectroscopic accuracy of top-performing methods:
G4-\textit{n}, cc-G4-\textit{n}, and G4-\textit{n}-F12, and validate them
against explicitly correlated coupled cluster CCSD(T*)(F12*) harmonic
vibrational frequencies and experimental data from the HFREQ2014 dataset, of
small first- and second-row polyatomics. G4-T is three times more accurate than
plain CCSD(T)/def2-TZVP, while G4-T is two times superior to
CCSD(T)/ano-pVTZ. Combining CCSD(T)/ano-pVTZ with MP2-F12 in a parameter-free
composite scheme results to a root-mean-square deviation of ~5 cm
relative to experiment, comparable to CCSD(T) at the complete basis set limit.
Application to the harmonic frequencies of benzene reveals a significant
advantage of composites with ANO basis sets -- MP2/ano-pV\textit{m}Z and
[CCSD(T)-MP2]/ano-pVTZ (\textit{m} = Q or 5) -- over similar protocols based on
CCSD(T)/def2-TZVP. Overall, G4-type composite energy schemes, particularly when
combined with ANO basis sets in CCSD(T), are accurate and comparatively
inexpensive tools for computational vibrational spectroscopy.Comment: Molecular Physics, in press [Timothy J. Lee memorial issue
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