5,593 research outputs found
Diverse anisotropy of phonon transport in two-dimensional IV-VI compounds: A comparative study
New classes two-dimensional (2D) materials beyond graphene, including layered
and non-layered, and their heterostructures, are currently attracting
increasing interest due to their promising applications in nanoelectronics,
optoelectronics and clean energy, where thermal transport property is one of
the fundamental physical parameters. In this paper, we systematically
investigated the phonon transport properties of 2D orthorhombic group IV-VI
compounds of , , and by solving the Boltzmann transport
equation (BTE) based on first-principles calculations. Despite the similar
puckered (hinge-like) structure along the armchair direction as phosphorene,
the four monolayer compounds possess diverse anisotropic properties in many
aspects, such as phonon group velocity, Young's modulus and lattice thermal
conductivity (), etc. Especially, the along the zigzag and
armchair directions of monolayer shows the strongest anisotropy while
monolayer and shows an almost isotropy in phonon transport. The
origin of the diverse anisotropy is fully studied and the underlying mechanism
is discussed in detail. With limited size, the could be effectively
lowered, and the anisotropy could be effectively modulated by nanostructuring,
which would extend the applications in nanoscale thermoelectrics and thermal
management. Our study offers fundamental understanding of the anisotropic
phonon transport properties of 2D materials, and would be of significance for
further study, modulation and aplications in emerging technologies.Comment: 14 pages, 8 figures, 2 table
Large-time behavior of solutions for the one-dimensional infrarelativistic model of a compressible viscous gas with radiation
AbstractIn this paper, assuming suitable hypotheses on the transport coefficients, we prove the large-time behavior, as time tends to infinity, of solutions in Hi=Hi×H0i×Hi×Hi+1 (i=1,2) for the one-dimensional infrarelativistic model of a compressible viscous gas with radiation
Effective bi-layer model Hamiltonian and density-matrix renormalization group study for the high-Tc superconductivity in LaNiO under high pressure
High-Tc superconductivity has been reported in the single crystal of
LaNiO under high pressure. Based on the electronic structure given
from the density functional theory calculations, we propose an effective
bi-layer model Hamiltonian including both and orbital
electrons of the nickel cations. The main feature of the model is that the
electrons form inter-layer -bonding and anti-bonding bands
via the apical oxygen anions between the two layers, while the
electrons hybridize with the electrons within each NiO plane.
The chemical potential difference of these two orbital electrons ensures that
the orbitals are close to half-filling and the
orbitals are near quarter-filling. The strong on-site Hubbard repulsion of the
orbital electrons gives rise to an effective inter-layer
antiferromagnetic spin super-exchange . Applying pressure can increase the
local coupling strength and self-dope holes on the orbitals with
the same amount of electrons doped on the orbitals
correspondingly. By performing numerical density-matrix renormalization group
calculations on a plaqutte ladder, we find that the charge densities of both
orbitals always have uniform distributions. But a spin-density-wave and a
spin-orbital density-wave are developed in the small limit. In the large
limit, both the spin and spin-orbital density waves get suppressed, and the
electron pairing instability emerges due to the formation of inter-layer
singlets of the electrons. The strongest pairing correlation is
given by the superconducting pair-density wave on the intra-layer vertical
bonds. Our numerical results have provided useful insights in
the high-Tc superconductivity in single crystal LaNiO under high
pressure.Comment: 6 pages, 4 figures; some typos are correcte
Reexamining the doped two-legged Hubbard ladders
We revisit the ground state of the Hubbard model on 2-legged ladders in this
work. We perform DMRG calculation on large system sizes with large kept states
and perform extrapolation of DMRG results with truncation errors in the
converged region. We find the superconducting correlation exponent
extracted from the pair-pair correlation is very sensitive to the position of
the reference bond, reflecting a huge boundary effect on it. By systematically
removing the effects from boundary conditions, finite sizes, and truncation
errors in DMRG, we obtain the most accurate value of and so
far with DMRG. With these exponents, we confirm that the 2-legged Hubbard model
is in the Luther-Emery liquid phase with from tiny
doping near half-filling to hole doping. When the doping is increased to
, the behaviors of charge, pairing, and spin
correlations don't change qualitatively, but the relationship is likely to be violated. With the further increase of the doping
to , the quasi long-ranged charge correlation turns to a true
long-ranged charge order and the spin gap is closed, while the pair-pair
correlation still decays algebraically.Comment: 9 pages,10 figures,4 table
Methodology for determining the electronic thermal conductivity of metals via direct non-equilibrium ab initio molecular dynamics
Many physical properties of metals can be understood in terms of the free
electron model, as proven by the Wiedemann-Franz law. According to this model,
electronic thermal conductivity () can be inferred from the
Boltzmann transport equation (BTE). However, the BTE does not perform well for
some complex metals, such as Cu. Moreover, the BTE cannot clearly describe the
origin of the thermal energy carried by electrons or how this energy is
transported in metals. The charge distribution of conduction electrons in
metals is known to reflect the electrostatic potential (EP) of the ion cores.
Based on this premise, we develop a new methodology for evaluating
by combining the free electron model and non-equilibrium ab
initio molecular dynamics (NEAIMD) simulations. We demonstrate that the kinetic
energy of thermally excited electrons originates from the energy of the spatial
electrostatic potential oscillation (EPO), which is induced by the thermal
motion of ion cores. This method directly predicts the of pure
metals with a high degree of accuracy.Comment: 7 pages, 3 figures, with Supplementary Information of 19 pages, 7
figures and 7 table
The Hazards of Growing Up: A Study of the Changing Mechanisms of Bullying Among Girls in Shenzhen
Among the many contending theories of bullying, the widely accepted thesis known as frustration-aggression assumes that bullying is a form of aggressive behavior induced by external stress. Recently, researchers have discovered that the relationship between external stressors and bullying is sometimes moderated by internal frustration. The present investigation is an attempt to examine which of the above mechanisms can better explain female students’ bullying behaviors. Data analysis, using structural equation modeling, was based on 1,069 girls selected from 14 primary schools and 16 junior secondary schools in Shenzhen, China. The result of the analysis suggests that while bullying by girls in primary schools is directly related to external stress, bullying in secondary schools is moderated by internal frustration. The authors suggest that several risk factors, namely, (a) the competitiveness of the education system, (b) socialization processes within families and schools, and (c) developmental changes in females during puberty, may be contributing to the difference between bullying mechanisms in primary and secondary schools. Parmi les nombreuses théories contraires portant sur l'intimidation, la thèse largement acceptée, connue sous le nom de frustration-agression postule que l'intimidation est une forme de comportement agressif provoqué par le stress externe. Les chercheurs ont récemment découvert que le rapport entre les agents de stress externes et l'intimidation est parfois modéré par la frustration interne. La présente étude vise à déterminer lesquels de ces mécanismes expliquent le mieux les comportements d'intimidation par les élèves. L'analyse de données, suivant la modélisation par équation structurelle, était basée sur 1 069 filles sélectionnées de 14 écoles primaires et 16 écoles secondaires à Shenzhen, en Chine. Les résultats de l'analyse donnent à penser que l'intimidation par les filles à l'école primaire est directement liée au stress externe, alors que l'intimidation à l'école secondaire est modérée par la frustration interne. Les auteurs proposent qu'il est possible que plusieurs facteurs de risque, notamment (a) la compétitivité du système d'éducation, (b) les processus de socialisation en sein des familles et des écoles et (c) les changements de croissance chez les filles pendant la puberté, contribuent aux différences entre les mécanismes d'intimidation à l'école primaire et à l'école secondaire
SIG-VC: A Speaker Information Guided Zero-shot Voice Conversion System for Both Human Beings and Machines
Nowadays, as more and more systems achieve good performance in traditional
voice conversion (VC) tasks, people's attention gradually turns to VC tasks
under extreme conditions. In this paper, we propose a novel method for
zero-shot voice conversion. We aim to obtain intermediate representations for
speaker-content disentanglement of speech to better remove speaker information
and get pure content information. Accordingly, our proposed framework contains
a module that removes the speaker information from the acoustic feature of the
source speaker. Moreover, speaker information control is added to our system to
maintain the voice cloning performance. The proposed system is evaluated by
subjective and objective metrics. Results show that our proposed system
significantly reduces the trade-off problem in zero-shot voice conversion,
while it also manages to have high spoofing power to the speaker verification
system
The influence of additive content on microstructure and mechanical properties on the Csf/SiC composites after annealed treatment
AbstractIn this paper, micrometers long and 20–100nm diameter SiC nanowires had been synthesized in the short cut fiber toughened SiC composites (Csf/SiC) by annealing treatment. The present work demonstrated that it was possible to fabricate the in situ SiC nanowires toughened Csf/SiC composites by annealed treatment. The “vapor–liquid–solid” growth mechanism of the SiC nanowires was proposed. The mainly toughened mechanism concluded grain bridging, crack deflection, fiber debonding and SiC nanowires, which can improve fracture toughness
The DKU-DukeECE Diarization System for the VoxCeleb Speaker Recognition Challenge 2022
This paper discribes the DKU-DukeECE submission to the 4th track of the
VoxCeleb Speaker Recognition Challenge 2022 (VoxSRC-22). Our system contains a
fused voice activity detection model, a clustering-based diarization model, and
a target-speaker voice activity detection-based overlap detection model.
Overall, the submitted system is similar to our previous year's system in
VoxSRC-21. The difference is that we use a much better speaker embedding and a
fused voice activity detection, which significantly improves the performance.
Finally, we fuse 4 different systems using DOVER-lap and achieve 4.75 of the
diarization error rate, which ranks the 1st place in track 4.Comment: arXiv admin note: substantial text overlap with arXiv:2109.0200
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