135 research outputs found
Classes of low-frequency earthquakes based on inter-time distribution reveal a precursor event for the 2011 Great Tohoku Earthquake
Recently, slow earthquakes (slow EQ) have received much attention relative to
understanding the mechanisms underlying large earthquakes and to detecting
their precursors. Low-frequency earthquakes (LFE) are a specific type of slow
EQ. In the present paper, we reveal the relevance of LFEs to the 2011 Great
Tohoku Earthquake (Tohoku-oki EQ) by means of cluster analysis. We classified
LFEs in northern Japan in a data-driven manner, based on inter-time, the time
interval between neighboring LFEs occurring within 10 km. We found that there
are four classes of LFE that are characterized by median inter-times of 24
seconds, 27 minutes, 2.0 days, and 35 days, respectively. Remarkably, in
examining the relevance of these classes to the Tohoku-oki EQ, we found that
activity in the shortest inter-time class (median 23 seconds) diminished
significantly at least three months before the Tohoku-oki EQ, and became
completely quiescent 30 days before the event (p-value = 0.00014). Further
statistical analysis implies that this class, together with a similar class of
volcanic tremor, may have served as a precursor of the Tohoku-oki EQ. We
discuss a generative model for these classes of LFE, in which the shortest
inter-time class is characterized by a generalized gamma distribution with the
product of shape parameters 1.54 in the domain of inter-time close to zero. We
give a possible geodetic interpretation for the relevance of LFE to the
Tohoku-oki EQ
Seismic-phase detection using multiple deep learning models for global and local representations of waveforms
The detection of earthquakes is a fundamental prerequisite for seismology and
contributes to various research areas, such as forecasting earthquakes and
understanding the crust/mantle structure. Recent advances in machine learning
technologies have enabled the automatic detection of earthquakes from waveform
data. In particular, various state-of-the-art deep-learning methods have been
applied to this endeavour. In this study, we proposed and tested a novel phase
detection method employing deep learning, which is based on a standard
convolutional neural network in a new framework. The novelty of the proposed
method is its separate explicit learning strategy for global and local
representations of waveforms, which enhances its robustness and flexibility.
Prior to modelling the proposed method, we identified local representations of
the waveform by the multiple clustering of waveforms, in which the data points
were optimally partitioned. Based on this result, we considered a global
representation and two local representations of the waveform. Subsequently,
different phase detection models were trained for each global and local
representation. For a new waveform, the overall phase probability was evaluated
as a product of the phase probabilities of each model. This additional
information on local representations makes the proposed method robust to noise,
which is demonstrated by its application to the test data. Furthermore, an
application to seismic swarm data demonstrated the robust performance of the
proposed method compared with those of other deep learning methods. Finally, in
an application to low-frequency earthquakes, we demonstrated the flexibility of
the proposed method, which is readily adaptable for the detection of
low-frequency earthquakes by retraining only a local model
Performance Evaluation of The Speaker-Independent HMM-based Speech Synthesis System "HTS-2007" for the Blizzard Challenge 2007
This paper describes a speaker-independent/adaptive HMM-based speech synthesis system developed for the Blizzard Challenge 2007. The new system, named HTS-2007, employs speaker adaptation (CSMAPLR+MAP), feature-space adaptive training, mixed-gender modeling, and full-covariance modeling using CSMAPLR transforms, in addition to several other techniques that have proved effective in our previous systems. Subjective evaluation results show that the new system generates significantly better quality synthetic speech than that of speaker-dependent approaches with realistic amounts of speech data, and that it bears comparison with speaker-dependent approaches even when large amounts of speech data are available
The HTS-2008 System: Yet Another Evaluation of the Speaker-Adaptive HMM-based Speech Synthesis System in The 2008 Blizzard Challenge
For the 2008 Blizzard Challenge, we used the same speaker-adaptive approach to HMM-based speech synthesis that was used in the HTS entry to the 2007 challenge, but an improved system was built in which the multi-accented English average voice model was trained on 41 hours of speech data with high-order mel-cepstral analysis using an efficient forward-backward algorithm for the HSMM. The listener evaluation scores for the synthetic speech generated from this system was much better than in 2007: the system had the equal best naturalness on the small English data set and the equal best intelligibility on both small and large data sets for English, and had the equal best naturalness on the Mandarin data. In fact, the English system was found to be as intelligible as human speech
Speaker-Independent HMM-based Speech Synthesis System
This paper describes an HMM-based speech synthesis system
developed by the HTS working group for the Blizzard Challenge
2007. To further explore the potential of HMM-based
speech synthesis, we incorporate new features in our conventional
system which underpin a speaker-independent approach:
speaker adaptation techniques; adaptive training for HSMMs;
and full covariance modeling using the CSMAPLR transforms
An Excitation Model for HMM-Based Speech Synthesis Based on Residual Modeling
SSW6: 6th ISCA Speech Synthesis Workshop, August 22-24, 2007, Bonn, Germany.This paper describes a trainable excitation approach to eliminate the unnaturalness of HMM-based speech synthesizers. During the waveform generation part, mixed excitation is constructed by state-dependent filtering of pulse trains and white noise sequences. In the training part, filters and pulse trains are jointly optimized through a procedure which resembles analysis-bysynthesis speech coding algorithms, where likelihood maximization of residual signals (derived from the same database which is used to train the HMM-based synthesizer) is pursued. Preliminary results show that the novel excitation model in question eliminates the unnaturalness of synthesized speech, being comparable in quality to the the best approaches thus far reported to eradicate the buzziness of HMM-based synthesizers
Sutimlimab suppresses SARS-CoV-2 mRNA vaccine-induced hemolytic crisis in a patient with cold agglutinin disease
Cold agglutinin disease (CAD) is a rare form of acquired autoimmune hemolytic anemia driven mainly by antibodies that activate the classical complement pathway. Several patients with CAD experience its development or exacerbation of hemolysis after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or after receiving the SARS-CoV-2 mRNA vaccine. Therefore, these patients cannot receive an additional SARS-CoV-2 mRNA vaccination and have a higher risk of severe SARS-CoV-2 infection. Sutimlimab is a monoclonal antibody that inhibits the classical complement pathway of the C1s protein and shows rapid and sustained inhibition of hemolysis in patients with CAD. However, whether sutimlimab could also inhibit hemolysis caused by SARS-CoV-2 mRNA vaccination is uncertain. Here, we present the case of a 70-year-old man with CAD who repeatedly experienced a hemolytic crisis after receiving SARS-CoV-2 mRNA vaccines. The patient eventually underwent SARS-CoV-2 mRNA vaccination safely, without hemolytic attack, under classical pathway inhibition therapy with sutimlimab. This report suggests that appropriate sutimlimab administration can suppress SARS-CoV-2 mRNA vaccination-induced CAD exacerbation, and that it could be a preventive strategy to minimize hemolytic attacks in susceptible populations
Recent development of the HMM-based speech synthesis system (HTS)
A statistical parametric approach to speech synthesis based on hidden Markov models (HMMs) has grown in popularity over the last few years. In this approach, spectrum, excitation, and duration of speech are simultaneously modeled by context-dependent HMMs, and speech waveforms are generate from the HMMs themselves. Since December 2002, we have publicly released an open-source software toolkit named “HMM-based speech synthesis system (HTS)” to provide a research and development toolkit for statistical parametric speech synthesis. This paper describes recent developments of HTS in detail, as well as future release plans
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