2,775 research outputs found
An atomistic investigation of the effect of strain on frictional properties of suspended graphene
We performed molecular dynamics (MD) simulations of a diamond probe scanned on a suspended graphene to reveal the effect of strain on the fictional properties of suspended graphene. The graphene was subjected to some certain strain along the scanning direction. We compared the friction coefficient obtained from different normal loads and strain. The results show that the friction coefficient can be decreased about one order of magnitude with the increase of the strain. And that can be a result of the decreased asymmetry of the contact region which is caused by strain. The synthetic effect of potential energy and the fluctuation of contact region were found to be
the main reason accounting for the fluctuation of the friction force. The strain can reduce the fluctuation of the contact region and improve the stability of friction
Theoretical Model for Subsurface Microstructure Prediction in Micro-Machining Ti-6Al-4V Alloy – Experimental Validation
Insight into perovskite antiferroelectric phases: Landau theory and phase field study
Understanding the appearance of commensurate and incommensurate modulations
in perovskite antiferroelectrics (AFEs) is of great importance for material
design and engineering. The dielectric and elastic properties of the AFE domain
boundaries are lack of investigation. In this work, a novel Landau theory is
proposed to understand the transformation of AFE commensurate and
incommensurate phases, by considering the coupling between the oxygen
octahedral tilt mode and the polar mode. The derived relationship between the
modulation periodicity and temperature is in good agreement with the
experimental results. Using the phase field study, we show that the
polarization is suppressed at the AFE domain boundaries, contributing to a
remnant polarization and local elastic stress field in AFE incommensurate
phases
A Novel Multimodal Approach for Studying the Dynamics of Curiosity in Small Group Learning
Curiosity is a vital metacognitive skill in educational contexts, leading to
creativity, and a love of learning. And while many school systems increasingly
undercut curiosity by teaching to the test, teachers are increasingly
interested in how to evoke curiosity in their students to prepare them for a
world in which lifelong learning and reskilling will be more and more
important. One aspect of curiosity that has received little attention, however,
is the role of peers in eliciting curiosity. We present what we believe to be
the first theoretical framework that articulates an integrated socio-cognitive
account of curiosity that ties observable behaviors in peers to underlying
curiosity states. We make a bipartite distinction between individual and
interpersonal functions that contribute to curiosity, and multimodal behaviors
that fulfill these functions. We validate the proposed framework by leveraging
a longitudinal latent variable modeling approach. Findings confirm a positive
predictive relationship between the latent variables of individual and
interpersonal functions and curiosity, with the interpersonal functions
exercising a comparatively stronger influence. Prominent behavioral
realizations of these functions are also discovered in a data-driven manner. We
instantiate the proposed theoretical framework in a set of strategies and
tactics that can be incorporated into learning technologies to indicate, evoke,
and scaffold curiosity. This work is a step towards designing learning
technologies that can recognize and evoke moment-by-moment curiosity during
learning in social contexts and towards a more complete multimodal learning
analytics. The underlying rationale is applicable more generally for developing
computer support for other metacognitive and socio-emotional skills.Comment: arXiv admin note: text overlap with arXiv:1704.0748
Evolution of surface grain structure and mechanical properties in orthogonal cutting of titanium alloy
In this study, a mesoscale dislocation simulation method was developed to study the orthogonal cutting of Titanium alloy. The evolution of surface grain structure and its effects on the surface mechanical properties were studied by using two-dimensional climb assisted dislocation dynamics technology. The motions of edge dislocations such as dislocation nucleation, junction, interaction with obstacles and grain boundaries, and annihilation were tracked. The results indicated that the machined surface has a microstructure composed of refined grains. The fine-grains bring appreciable scale effect and a mass of dislocations are piled up in the grain boundaries and persistent slip bands. In particular, dislocation climb can induce a perfect softening effect, but this effect is significantly weakened when grain size is less than 1.65 ÎĽm. In addition, a Hall-Petch type relation was predicted according to the arrangement of grain, the range of grain sizes and the distribution of dislocations
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