395 research outputs found
Potential high- superconductivity in YCeH and LaCeH under pressure
Lanthanum, yttrium, and cerium hydrides are the three most well-known
superconducting binary hydrides, which have gained great attention in both
theoretical and experimental studies. Recent studies have shown that ternary
hydrides composed of lanthanum and yttrium can achieve high superconductivity
around 253 K. In this study, we employ the evolutionary-algorithm-based crystal
structure prediction (CSP) method and first-principles calculations to
investigate the stability and superconductivity of ternary hydrides composed of
(Y, Ce) and (La, Ce) under high pressure. Our calculations show that there are
multiple stable phases in Y-Ce-H and La-Ce-H hydrides, among which
-YCeH, -LaCeH, -YCeH, and
-LaCeH possessing H or H clathrate structures
can maintain both of the thermodynamic and dynamic stabilities. In addition, we
also find that these phases also maintain a strong resistance to decomposition
at high temperature. Electron-phonon coupling calculations show that all of
these four phases can exhibit high-temperature superconductivity.
-YCeH is predicted to have a superconducting transition
temperature () as high as 246 K at 350 GPa. The value of
-LaCeH at 250 GPa is about 233 K, which is slightly smaller
than that of -YCeH. However, it is found that
-LaCeH can be stabilized at 200 GPa, making the high-pressure
synthesis of LaCeH easier.Comment: 5 figure
A General Class of Transfer Learning Regression without Implementation Cost
We propose a novel framework that unifies and extends existing methods of
transfer learning (TL) for regression. To bridge a pretrained source model to
the model on a target task, we introduce a density-ratio reweighting function,
which is estimated through the Bayesian framework with a specific prior
distribution. By changing two intrinsic hyperparameters and the choice of the
density-ratio model, the proposed method can integrate three popular methods of
TL: TL based on cross-domain similarity regularization, a probabilistic TL
using the density-ratio estimation, and fine-tuning of pretrained neural
networks. Moreover, the proposed method can benefit from its simple
implementation without any additional cost; the regression model can be fully
trained using off-the-shelf libraries for supervised learning in which the
original output variable is simply transformed to a new output variable. We
demonstrate its simplicity, generality, and applicability using various real
data applications.Comment: 31 pages, 6 figure
The brightest UV-selected galaxies in protoclusters at : Ancestors of Brightest Cluster Galaxies?
We present the results of a survey of the brightest UV-selected galaxies in
protoclusters. These proto-brightest cluster galaxy (proto-BCG) candidates are
drawn from 179 overdense regions of -dropout galaxies at from the
Hyper Suprime-Cam Subaru Strategic Program identified previously as good
protocluster candidates. This study is the first to extend the systematic study
of the progenitors of BCGs from to . We carefully remove
possible contaminants from foreground galaxies and, for each structure, we
select the brightest galaxy that is at least 1 mag brighter than the fifth
brightest galaxy. We select 63 proto-BCG candidates and compare their
properties with those of galaxies in the field and those of other galaxies in
overdense structures. The proto-BCG candidates and their surrounding galaxies
have different rest-UV color distributions to field galaxies and
other galaxies in protoclusters that do not host proto-BCGs. In addition,
galaxies surrounding proto-BCGs are brighter than those in protoclusters
without proto-BCGs. The image stacking analysis reveals that the average
effective radius of proto-BCGs is larger than that of field
galaxies. The color differences suggest that proto-BCGs and their
surrounding galaxies are dustier than other galaxies at . These results
suggest that specific environmental effects or assembly biasses have already
emerged in some protoclusters as early as , and we suggest that
proto-BCGs have different star formation histories than other galaxies in the
same epoch.Comment: 18 pages, 11 figures, Accepted for publication in Ap
Cross-Speaker Emotion Transfer for Low-Resource Text-to-Speech Using Non-Parallel Voice Conversion with Pitch-Shift Data Augmentation
Data augmentation via voice conversion (VC) has been successfully applied to
low-resource expressive text-to-speech (TTS) when only neutral data for the
target speaker are available. Although the quality of VC is crucial for this
approach, it is challenging to learn a stable VC model because the amount of
data is limited in low-resource scenarios, and highly expressive speech has
large acoustic variety. To address this issue, we propose a novel data
augmentation method that combines pitch-shifting and VC techniques. Because
pitch-shift data augmentation enables the coverage of a variety of pitch
dynamics, it greatly stabilizes training for both VC and TTS models, even when
only 1,000 utterances of the target speaker's neutral data are available.
Subjective test results showed that a FastSpeech 2-based emotional TTS system
with the proposed method improved naturalness and emotional similarity compared
with conventional methods.Comment: Submitted to Interspeech 202
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