14,204 research outputs found
Improved three-dimensional color-gradient lattice Boltzmann model for immiscible multiphase flows
In this paper, an improved three-dimensional color-gradient lattice Boltzmann
(LB) model is proposed for simulating immiscible multiphase flows. Compared
with the previous three-dimensional color-gradient LB models, which suffer from
the lack of Galilean invariance and considerable numerical errors in many cases
owing to the error terms in the recovered macroscopic equations, the present
model eliminates the error terms and therefore improves the numerical accuracy
and enhances the Galilean invariance. To validate the proposed model, numerical
simulation are performed. First, the test of a moving droplet in a uniform flow
field is employed to verify the Galilean invariance of the improved model.
Subsequently, numerical simulations are carried out for the layered two-phase
flow and three-dimensional Rayleigh-Taylor instability. It is shown that, using
the improved model, the numerical accuracy can be significantly improved in
comparison with the color-gradient LB model without the improvements. Finally,
the capability of the improved color-gradient LB model for simulating dynamic
multiphase flows at a relatively large density ratio is demonstrated via the
simulation of droplet impact on a solid surface.Comment: 9 Figure
Co-doped Ceria: Tendency towards ferromagnetism driven by oxygen vacancies
We perform an electronic structure study for cerium oxide homogeneously-doped
with cobalt impurities, focusing on the role played by oxygen vacancies and
structural relaxation. By means of full-potential ab-initio methods, we explore
the possibility of ferromagnetism as observed in recent experiments. Our
results indicate that oxygen vacancies seem to be crucial for the appearance of
a ferromagnetic alignment among Co impurities, obtaining an increasing tendency
towards ferromagnetism with growing vacancy concentration. The estimated
couplings cannot explain though, the experimentally observed room-temperature
ferromagnetism. In this systematic study, we draw relevant conclusions
regarding the location of the oxygen vacancies and the magnetic couplings
involved. In particular, we find that oxygen vacancies tend to nucleate in the
neighborhood of Co impurities and we get a remarkably strong ferromagnetic
coupling between Co atoms and the Ce^{3+} neighboring ions. The calculated
magnetic moments per cell depend on the degree of reduction which could explain
the wide spread in the magnetization values observed in the experiments
Differences in thermal-acoustic perception in various office behaviors
Thermal-acoustic interaction has vital research value in the development of soundscape prediction models. Previous studies on thermal-acoustic interaction have been focused mainly on perceptual changes. However, the differences in office behaviors warrant attention. We conducted an experimental study to explore the effects of various office behaviors (such as resting, reading, writing, and typing) on the thermal-acoustic interactive perception. The results showed that (at near thermal neutral temperature) (1) sound types affected thermal evaluation, acoustic evaluation, and overall evaluation. The sound of water significantly reduced the score for thermal sensation. (2) Behavior types affected thermal sensation, acoustic comfort, and overall comfort. Reading contributed to significantly lower scores than other behaviors for the three indicators. This indicated that when reading, people are more demanding of the environment. (3) The interaction of sound types and behavior types affected overall annoyance. Therefore, we recommend adjusting the office environment effectively and establishing more effective soundscape prediction models
Megabits secure key rate quantum key distribution
Quantum cryptography (QC) can provide unconditional secure communication
between two authorized parties based on the basic principles of quantum
mechanics. However, imperfect practical conditions limit its transmission
distance and communication speed. Here we implemented the differential phase
shift (DPS) quantum key distribution (QKD) with up-conversion assisted hybrid
photon detector (HPD) and achieved 1.3 M bits per second secure key rate over a
10-km fiber, which is tolerant against the photon number splitting (PNS)
attack, general collective attacks on individual photons, and any other known
sequential unambiguous state discrimination (USD) attacks.Comment: 14 pages, 4 figure
2013年中国建筑工人劳动合同的状况
2013-2014 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
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