418 research outputs found
LC4SV: A Denoising Framework Learning to Compensate for Unseen Speaker Verification Models
The performance of speaker verification (SV) models may drop dramatically in
noisy environments. A speech enhancement (SE) module can be used as a front-end
strategy. However, existing SE methods may fail to bring performance
improvements to downstream SV systems due to artifacts in the predicted signals
of SE models. To compensate for artifacts, we propose a generic denoising
framework named LC4SV, which can serve as a pre-processor for various unknown
downstream SV models. In LC4SV, we employ a learning-based interpolation agent
to automatically generate the appropriate coefficients between the enhanced
signal and its noisy input to improve SV performance in noisy environments. Our
experimental results demonstrate that LC4SV consistently improves the
performance of various unseen SV systems. To the best of our knowledge, this
work is the first attempt to develop a learning-based interpolation scheme
aiming at improving SV performance in noisy environments
Pervasive brain monitoring and data sharing based on multi-tier distributed computing and linked data technology
EEG-based Brain-computer interfaces (BCI) are facing grant challenges in their real-world applications. The technical difficulties in developing truly wearable multi-modal BCI systems that are capable of making reliable real-time prediction of users’ cognitive states under dynamic real-life situations may appear at times almost insurmountable. Fortunately, recent advances in miniature sensors, wireless communication and distributed computing technologies offered promising ways to bridge these chasms. In this paper, we report our attempt to develop a pervasive on-line BCI system by employing state-of-art technologies such as multi-tier fog and cloud computing, semantic Linked Data search and adaptive prediction/classification models. To verify our approach, we implement a pilot system using wireless dry-electrode EEG headsets and MEMS motion sensors as the front-end devices, Android mobile phones as the personal user interfaces, compact personal computers as the near-end fog servers and the computer clusters hosted by the Taiwan National Center for High-performance Computing (NCHC) as the far-end cloud servers. We succeeded in conducting synchronous multi-modal global data streaming in March and then running a multi-player on-line BCI game in September, 2013. We are currently working with the ARL Translational Neuroscience Branch and the UCSD Movement Disorder Center to use our system in real-life personal stress and in-home Parkinson’s disease patient monitoring experiments. We shall proceed to develop a necessary BCI ontology and add automatic semantic annotation and progressive model refinement capability to our system
Giant X-ray circular dichroism in a time-reversal invariant altermagnet
X-ray circular dichroism, arising from the contrast in X-ray absorption
between opposite photon helicities, serves as a spectroscopic tool to measure
the magnetization of ferromagnetic materials and identify the handedness of
chiral crystals. Antiferromagnets with crystallographic chirality typically
lack X-ray magnetic circular dichroism because of time-reversal symmetry, yet
exhibit weak X-ray natural circular dichroism. Here, we report the observation
of giant natural circular dichroism in the Ni -edge X-ray absorption of
NiTeO, a polar and chiral antiferromagnet with effective time-reversal
symmetry. To unravel this intriguing phenomenon, we propose a phenomenological
model that classifies the movement of photons in a chiral crystal within the
same symmetry class as that of a magnetic field. The coupling of X-ray
polarization with the induced magnetization yields giant X-ray natural circular
dichroism, revealing the altermagnetism of NiTeO. Our findings provide
evidence for the interplay between magnetism and crystal chirality in natural
optical activity. Additionally, we establish the first example of a new class
of magnetic materials exhibiting circular dichroism with time-reversal
symmetry.Comment: Accepted by Advanced Materials (2024.2.16) Revised title: Giant X-ray
circular dichroism in a time-reversal invariant altermagnet Revised drafts:
Main 14 pages, 4 figures, and SI 20 pages, 8 figure
Association of Suicide Risk With Headache Frequency Among Migraine Patients With and Without Aura
Background: Migraines with aura have been associated with suicide in adolescents and young adults, but the association between suicide and migraine frequency has not been determined. This study investigated suicidal ideation and suicide attempts among patients with varying frequencies of migraines, with and without auras.Methods: This cross-sectional study analyzed 528 patients aged between 20 and 60 years from a headache outpatient clinic in Taiwan. All patients completed a set of questionnaires, including a demographic questionnaire, the Migraine Disability Assessment questionnaire, the Hospital Anxiety and Depression Scale, the Beck Depression Inventory, and the Pittsburgh Sleep Quality Index. Suicide risk was evaluated by self-reported lifetime suicidal ideation and attempts. Patients were divided into low-frequency (1–4 days/month), moderate-frequency (5–8 days/month), high-frequency (9–14 days/month), and chronic (≥15 days/month) migraine groups. The association between migraine frequency and suicidality was investigated using multivariable linear regression and logistic regression.Results: The rates of suicidal ideation and suicide attempts were the highest for chronic migraine with aura (ideation: 47.2%; attempts: 13.9%) and lowest in migraine-free controls (2.8%). Migraine frequency was an independent risk factor for suicidal ideation and attempts in patients with aura (both Ptrend < 0.001), but not in patients without auras. Migraine aura and depression were associated with higher risks of suicidal ideation and suicide attempts in patients with migraine.Conclusion: High migraine frequency has a correlation with high suicide risk in patients who experience an aura, but not in other patients with migraine
Anapole mediated giant photothermal nonlinearity in nanostructured silicon
Featured with a plethora of electric and magnetic Mie resonances, high index
dielectric nanostructures offer a versatile platform to concentrate
light-matter interactions at the nanoscale. By integrating unique features of
far-field scattering control and near-field concentration from radiationless
anapole states, here, we demonstrate a giant photothermal nonlinearity in
single subwavelength-sized silicon nanodisks. The nanoscale energy
concentration and consequent near-field enhancements mediated by the anapole
mode yield a reversible nonlinear scattering with a large modulation depth and
a broad dynamic range, unveiling a record-high nonlinear index change up to 0.5
at mild incident light intensities on the order of MW/cm2. The observed
photothermal nonlinearity showcases three orders of magnitude enhancement
compared with that of unstructured bulk silicon, as well as nearly one order of
magnitude higher than that through the radiative electric dipolar mode. Such
nonlinear scattering can empower distinctive point spread functions in confocal
reflectance imaging, offering the potential for far-field localization of
nanostructured Si with an accuracy approaching 40 nm. Our findings shed new
light on active silicon photonics based on optical anapoles
AMiBA: Broadband Heterodyne CMB Interferometry
The Y. T. Lee Array for Microwave Background (AMiBA) has reported the first
science results on the detection of galaxy clusters via the Sunyaev Zel'dovich
effect. The science objectives required small reflectors in order to sample
large scale structures (20') while interferometry provided modest resolutions
(2'). With these constraints, we designed for the best sensitivity by utilizing
the maximum possible continuum bandwidth matched to the atmospheric window at
86-102GHz, with dual polarizations. A novel wide-band analog correlator was
designed that is easily expandable for more interferometer elements. MMIC
technology was used throughout as much as possible in order to miniaturize the
components and to enhance mass production. These designs will find application
in other upcoming astronomy projects. AMiBA is now in operations since 2006,
and we are in the process to expand the array from 7 to 13 elements.Comment: 10 pages, 6 figures, ApJ in press; a version with high resolution
figures available at
http://www.asiaa.sinica.edu.tw/~keiichi/upfiles/AMiBA7/mtc_highreso.pd
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