107 research outputs found
Ultrafast pump-probe spectroscopic signatures of superconducting and pseudogap phases in YBa2Cu3O7-{\delta} films
Femtosecond pump-probe spectroscopy is applied to identify transient optical
signatures of phase transitions in optimally doped YBa2Cu3O7-{\delta} films. To
elucidate the dynamics of superconducting and pseudogap phases, the slow
thermal component is removed from the time-domain traces of photo-induced
reflectivity in a high-flux regime with low frequency pulse rate. The rescaled
data exhibit distinct signatures of the phase separation with abrupt changes at
the onsets of TSC and TPG in excellent agreement with transport data. Compared
to the superconducting phase, the response of the pseudogap phase is
characterized by the strongly reduced reflectivity change accompanied by a
faster recovery time.Comment: 14 pages, 3 figure
Uniaxial Tension Simulation Using Real Microstructure-based Representative Volume Elements Model of Dual Phase Steel Plate
AbstractDual-phase steels have become a favored material for car bodies. In this study, the deformation behavior of dual-phase steels under uniaxial tension is investigated by means of 2D Representative Volume Elements (RVE) model. The real metallographic graphs including particle geometry, distribution and morphology are considered in this RVE model. Stress and strain distributions between martensite and ferrite are analyzed. The results show that martensite undertakes most stress without significant strain while ferrite shares the most strain. The tensile failure is the result of the deforming inhomogeneity between martensite phase and ferrite phase, which is the key factor triggering the plastic strain localization on specimen section during the tensile test
Vertical Ferroelectricity in Van der Waals Materials: Models and Devices
Ferroelectricity has a wide range of applications in functional electronics
and is extremely important for the development of next-generation information
storage technology, but it is difficult to achieve due to its special symmetry
requirements. In this letter, based on van derWaals stacking, a generic model
is proposed for realizing ferroelectric devices, where a freely movable center
layer is packaged in two fixed and symmetrically stacked layers. In this model,
the ferroelectric phase transition can be realized between the two equivalent
and eccentric ground stacking-states with opposite polarizations. By means of
first-principles calculations, taking the h-BN/h-BN/h-BN and h-BN/Graphene/h-BN
as feasible models, we carefully evaluate the magnitude of ferroelectricity.
The corresponding polarizations are estimated as 1.83 and 1.35 pC/m,
respectively, which are comparable to the sliding ferroelectricity. Such a new
tri-layer model of vertical ferroelectricity can be constructed by arbitrary
van derWaals semiconducting materials, and usually holds low switching barrier.
Optimized material combinations with remarkable polarization are highly
expectable to be discovered from the huge candidate set for future information
storage.Comment: 5 pages;4 figure
Comparison between Numerical and Analytical Analysis of the Dynamic Behavior of Circular Tunnels
Dynamic behavior of underground structures is controlled by the strain field imposed by wave propagation and by the interaction between rock mass and structures. Shear and pressure waves propagating in the plane of the cross-section of the tunnel generate ground distortions, which tend to cause ovaling deformations of the lining. In this paper, the seismic response of a circular tunnel subjected respectively to shear waves and pressure waves will be analyzed both analytically and numerically at first, and then a complete 3D analysis will be given to show the overall effects on a tunnel induced by seismic events considering seismic inputs in three directions.El comportamiento dinámico de estructuras subterráneas se controla por el campo de deformación impuesta por la propagación de ondas y por la interacción entre la masa rocosa y las estructuras. La onda de cizallamiento y la onda de presión en el plano de sección transversal del túnel generan distorsiones del terreno que tienden a causar deformaciones ovaladas del revestimiento de la estructura. En este artÃculo se analiza la respuesta sÃsmica de un túnel circular sujeto respectivamente a ondas de cizallamiento y ondas de presión tanto analÃtica como numéricamente. Luego se muestra un análisis tridimensional completo para mostrar los efectos generales en un túnel producidos por eventos sÃsmicos y donde se consideran registros en tres direcciones
Polar phase transitions in heteroepitaxial stabilized La0.5Y0.5AlO3 thin films
PAPER
Polar phase transitions in heteroepitaxial stabilized La0.5Y0.5AlO3 thin films
Shenghua Liu1, Chunfeng Zhang1, Mengya Zhu1, Qian He2, Jak Chakhalian3, Xiaoran Liu3,4, Albina Borisevich2, Xiaoyong Wang1 and Min Xiao1,4
Published 1 September 2017 • © 2017 IOP Publishing Ltd
Journal of Physics: Condensed Matter, Volume 29, Number 40
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Abstract
We report on the fabrication of epitaxial La0.5Y0.5AlO3 ultrathin films on (001) LaAlO3 substrates. Structural characterizations by scanning transmission electron microscopy and x-ray diffraction confirm the high quality of the film with a − b + c − AlO6 octahedral tilt pattern. Unlike either of the nonpolar parent compound, LaAlO3 and YAlO3, second harmonic generation measurements on the thin films suggest a nonpolar–polar phase transition at T c near 500 K, and a polar–polar phase transition at T a near 160 K. By fitting the angular dependence of the second harmonic intensities, we further propose that the two polar structures can be assigned to the Pmc2 1 and Pmn2 1 space group, while the high temperature nonpolar structure belongs to the Pbnm space group
Mega-TTS 2: Zero-Shot Text-to-Speech with Arbitrary Length Speech Prompts
Zero-shot text-to-speech aims at synthesizing voices with unseen speech
prompts. Previous large-scale multispeaker TTS models have successfully
achieved this goal with an enrolled recording within 10 seconds. However, most
of them are designed to utilize only short speech prompts. The limited
information in short speech prompts significantly hinders the performance of
fine-grained identity imitation. In this paper, we introduce Mega-TTS 2, a
generic zero-shot multispeaker TTS model that is capable of synthesizing speech
for unseen speakers with arbitrary-length prompts. Specifically, we 1) design a
multi-reference timbre encoder to extract timbre information from multiple
reference speeches; 2) and train a prosody language model with arbitrary-length
speech prompts; With these designs, our model is suitable for prompts of
different lengths, which extends the upper bound of speech quality for
zero-shot text-to-speech. Besides arbitrary-length prompts, we introduce
arbitrary-source prompts, which leverages the probabilities derived from
multiple P-LLM outputs to produce expressive and controlled prosody.
Furthermore, we propose a phoneme-level auto-regressive duration model to
introduce in-context learning capabilities to duration modeling. Experiments
demonstrate that our method could not only synthesize identity-preserving
speech with a short prompt of an unseen speaker but also achieve improved
performance with longer speech prompts. Audio samples can be found in
https://mega-tts.github.io/mega2_demo/
Anisotropic ultrafast spin/valley dynamics in WTe2 films
WTe2 Weyl semimetal hosts the natural broken inversion symmetry and strong
spin orbit coupling, making it promising for exotic spin/valley dynamics within
a picosecond timescale. Here, we unveil an anisotropic ultrafast spin/valley
dynamics in centimeter-scale, single-crystalline Td-WTe2 films using a
femtosecond pump-probe technique at room temperature. We observe a transient
(~0.8 ps) intra-valley transition and a subsequent polarization duration (~5
ps) during the whole spin/valley relaxation process. Furthermore, the
relaxation exhibits the remarkable anisotropy of approximately six-fold and
two-fold symmetries due to the intrinsic anisotropy along the crystalline
orientation and the extrinsic matrix element effect, respectively. Our results
offer a prospect for the ultrafast manipulation of spin/valleytronics in
topological quantum materials for dissipationless high-speed spin/valleytronic
devices.Comment: 21 pages, 4 figure
MicroRNA-124 Functions as a Tumor Suppressor by Regulating CDH2 and Epithelial-Mesenchymal Transition in Non-Small Cell Lung Cancer
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