420 research outputs found
Research on Online Discourse of Cross-Border E-commerce Platform on the Basis of Co-operative Principle
China’s cross-border e-commerce industry has shown a blow-out trend fueled by the rapidly-improved informatization of the society and powerful support of government. However, the increasing platforms in the market, the homogenizing merchandise, and the decreasing of conversion cost bring enormous challenges to the platforms. In order to survive in the fierce competition, they must improve the quality of services in the communication with consumers so as to enhance the core competitiveness centered on consumers. In this research, we compiled 100 real cases of cross-border e-commerce platform online discourse by collecting chat records from the online interaction between 50 college students and the platform merchants on the Tmall international platform. This study analyzes these online discourse cases from the perspective of Grice’s Co-operative principle. The study demonstrates that, the application of Grice’s Co-operative principle can enable cross-border e-commerce platforms to effectively adopt and employ the most appropriate interactive discourse, which exerts an tremendous influence on improving the quality of communication services. And there is a positive correlation between the usage of the Co-operative principle and the monthly sales volume of the platform
The Non-Perturbative Quantum Nature of the Dislocation-Phonon Interaction
Despite the long history of dislocation-phonon interaction studies, there are
many problems that have not been fully resolved during this development. These
include an incompatibility between a perturbative approach and the long-range
nature of a dislocation, the relation between static and dynamic scattering,
and the nature of dislocation-phonon resonance. Here by introducing a fully
quantized dislocation field, the "dislon"[1], a phonon is renormalized as a
quasi-phonon, with shifted quasi-phonon energy, and accompanied by a finite
quasi-phonon lifetime that is reducible to classical results. A series of
outstanding legacy issues including those above can be directly explained
within this unified phonon renormalization approach. In particular, a
renormalized phonon naturally resolves the decades-long debate between dynamic
and static dislocation-phonon scattering approaches.Comment: 5 pages main text, 3 figures, 10 pages supplemental material
Efficiency Limits of Solar Energy Harvesting via Internal Photoemission in Carbon Materials
We describe strategies to estimate the upper limits of the efficiency of
photon energy harvesting via hot electron extraction from gapless absorbers.
Gapless materials such as noble metals can be used for harvesting the whole
solar spectrum, including visible and near-infrared light. The energy of
photo-generated non-equilibrium or hot charge carriers can be harvested before
they thermalize with the crystal lattice via the process of their internal
photo-emission (IPE) through the rectifying Schottky junction with a
semiconductor. However, the low efficiency and the high cost of noble metals
necessitates the search for cheaper abundant alternative materials, and we show
here that carbon can serve as a promising IPE material candidate. We compare
the upper limits of performance of IPE photon energy-harvesting platforms,
which incorporate either gold or carbon as the photoactive material where hot
electrons are generated. Through a combination of density functional theory,
joint electron density of states calculations, and Schottky diode efficiency
modeling, we show that the material electron band structure imposes a strict
upper limit on the achievable efficiency of the IPE devices. Our calculations
reveal that graphite is a good material candidate for the IPE absorber for
harvesting visible and near-infrared photons. Graphite electron density of
states yields a sizeable population of hot electrons with energies high enough
to be collected across the potential barrier. We also discuss the mechanisms
that prevent the IPE device efficiency from reaching the upper limits imposed
by their material electron band structures. The proposed approach is general
and allows for efficient pre-screening of materials for their potential use in
IPE energy converters and photodetectors within application-specific spectral
windows.Comment: 17 pages, 6 figure
In situ study of the mechanical properties of airborne haze particles
Particulate pollution has raised serious concerns regarding its potential impacts on human health in developing countries. However, much less attention has been paid to the threat of haze particles to machinery and industry. By employing a state-of-the-art in situ scanning electron microscope compression testing technique, we demonstrate that iron-rich and fly ash haze particles, which account for nearly 70% of the total micron-sized spherical haze particles, are strong enough to generate abrasive damage to most engineering alloys, and therefore can generate significant scratch damage to moving contacting surfaces in high precision machineries. Our finding calls for preventive measures to protect against haze related threat.National Basic Research Program of China (973 Program) (Grant 2012CB619402)National 111 Project of China (Grant B06025)National Science Foundation (U.S.) (Grants DMR-1120901 and DMR-1410636)National Natural Science Foundation (China) (Grants 51231005, 51471128 and 51321003
Ab initio study of electron mean free paths and thermoelectric properties of lead telluride
Last few years have witnessed significant enhancement of thermoelectric figure of merit of lead telluride (PbTe) via nanostructuring. Despite the experimental progress, current understanding of the electron transport in PbTe is based on either band structure calculation using first principles with constant relaxation time approximation or empirical models, both relying on adjustable parameters obtained by fitting experimental data. Here, we report parameter-free first-principles calculation of electron and phonon transport properties of PbTe, including mode-by-mode electron-phonon scattering analysis, leading to detailed information on electron mean free paths and the contributions of electrons and phonons with different mean free paths to thermoelectric transport properties in PbTe. Such information will help to rationalize the use and optimization of nanostructures to achieve high thermoelectric figure of merit
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