1,721,134 research outputs found
Scan Patterns Predict Sentence Production in the Cross-Modal Processing of Visual Scenes
No full textSimulation of bipolar charge transport in graphene on h-BN
No full textPurpose: The purpose of this paper is to simulate charge transport in monolayer graphene on a substrate made of hexagonal boron nitride (h-BN). This choice is motivated by the fact that h-BN is one of the most promising substrates on account of the reduced degradation of the velocity due to the remote impurities. Design/methodology/approach: The semiclassical Boltzmann equations for electrons in the monolayer graphene are numerically solved by an approach based on a discontinuous Galerkin (DG) method. Both the conduction and valence bands are included, and the inter-band scatterings are taken into account as well. Findings: The importance of the inter-band scatterings is accurately evaluated for several values of the Fermi energy, addressing the issue related to the validity of neglecting the generation-recombination terms. It is found out that the inclusion of the inter-band scatterings produces sizable variations in the average values, like the current density, at zero Fermi energy, whereas, as expected, the effect of the inter-band scattering becomes negligible by increasing the absolute value of the Fermi energy. Research limitations/implications: The correct evaluation of the influence of the inter-band scatterings on the electronic performances is deeply important not only from a theoretical point of view but also for the applications. In particular, it will be shown that the time necessary to reach the steady state is greatly affected by the inter-band scatterings, with not negligible consequences on the switching on/off processes of realistic devices. As a limitation of the present work, the proposed approach refers to the spatially homogeneous case. For the simulation of electron devices, non-homogenous numerical solutions are required. This last case will be tackled in a forthcoming paper. Originality/value: As observed in Majorana et al. (2019), the use of a Direct Simulation Monte Carlo (DSMC) approach, which properly describes the inter-band scatterings, is computationally very expensive because the valence band is highly populated and a huge number of particles is needed. Even by simulating holes instead of electrons does not overcome the problem because there is a certain degree of ambiguity in the generation and recombination terms of electron-hole pairs. The DG approach, used in this paper, does not suffer from the previous drawbacks and requires a reasonable computing effort
Simulation of electron-phonon coupling and heating dynamics in suspended monolayer graphene including all the phonon branches
No full textThermal effects in monolayer graphene due to an electron flow are investigated with a direct simulation Monte Carlo (DSMC) analysis. The crystal heating is described by simulating the phonon dynamics of the several relevant branches, acoustic, optical, K and Z phonons. The contribution of each type of phonon is highlighted. In particular, it is shown that the Z phonons, although they do not enter the scattering with electrons, play a non-negligible role in the determination of the crystal temperature. The phonon distributions are evaluated by counting the emission and absorption processes during the MC simulation. The crystal temperature raise is obtained for several applied electric fields and for several positive Fermi energies. The latter produces the effect of a kind of n-doping in the graphene layer. Critical temperatures can be reached in a few tens of picoseconds posing remarkable issues regarding the cooling system in view of a possible application of graphene in semiconductor devices. Moreover, a significant influence of the lattice temperature on the characteristic curves is observed only for long times, confirming graphene rather robust as regards the electrical performance
Assessment of the Constant Phonon Relaxation Time Approximation in Electron–Phonon Coupling in Graphene
No full textThe importance of the correct determination of the relaxation times, entering the electron–phonon coupling, is crucial for a proper evaluation of the rise of the crystal lattice temperature induced by a flow of electrons that undergo an external electric field. We describe the crystal heating by simulating the dynamics of all the phonon branches, i.e. acoustic, optical, K and Z phonons in a suspended monolayer graphene. At each time step the charge transport is determined by means of a direct simulation Monte Carlo procedure while the evolution of the phonon distributions is evaluated by counting the emission and absorption processes in the electron–phonon scatterings. For several applied electric fields and for several positive Fermi energies, the behaviors of the crystal lattice temperature, obtained with different models of the relaxation times, are compared and discussed. The contribution of each type of phonon is highlighted as well
When Expectancies Collide: Action Dynamics reveal the Interaction of Plausibility and Congruency
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The Interaction of Visual and Linguistic Saliency during Syntactic Ambiguity Resolution
No full textPsycholinguistic research using the visual world paradigm has shown that the processing of sentences is
constrained by the visual context in which they occur. Recently, there has been growing interest in the
interactions observed when both language and vision provide relevant information during sentence processing.
In three visual world experiments on syntactic ambiguity resolution, we investigate how visual
and linguistic information influence the interpretation of ambiguous sentences. We hypothesize that (1)
visual and linguistic information both constrain which interpretation is pursued by the sentence processor,
and (2) the two types of information act upon the interpretation of the sentence at different
points during processing. In Experiment 1, we show that visual saliency is utilized to anticipate the
upcoming arguments of a verb. In Experiment 2, we operationalize linguistic saliency using intonational
breaks and demonstrate that these give prominence to linguistic referents. These results confirm prediction
(1). In Experiment 3, we manipulate visual and linguistic saliency together and find that
both types of information are used, but at different points in the sentence, to incrementally update
its current interpretation. This finding is consistent with prediction (2). Overall, our results suggest
an adaptive processing architecture in which different types of information are used when they
become available, optimizing different aspects of situated language processing
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