217 research outputs found
Atomistic potential for graphene and other sp carbon systems
We introduce a torsional force field for sp carbon to augment an in-plane
atomistic potential of a previous work (Kalosakas et al, J. Appl. Phys. {\bf
113}, 134307 (2013)) so that it is applicable to out-of-plane deformations of
graphene and related carbon materials. The introduced force field is fit to
reproduce DFT calculation data of appropriately chosen structures. The aim is
to create a force field that is as simple as possible so it can be efficient
for large scale atomistic simulations of various sp carbon structures
without significant loss of accuracy. We show that the complete proposed
potential reproduces characteristic properties of fullerenes and carbon
nanotubes. In addition, it reproduces very accurately the out-of-plane ZA and
ZO modes of graphene's phonon dispersion as well as all phonons with
frequencies up to 1000~cm.Comment: 9 pages, 6 figure
Knowledge-aware Complementary Product Representation Learning
Learning product representations that reflect complementary relationship
plays a central role in e-commerce recommender system. In the absence of the
product relationships graph, which existing methods rely on, there is a need to
detect the complementary relationships directly from noisy and sparse customer
purchase activities. Furthermore, unlike simple relationships such as
similarity, complementariness is asymmetric and non-transitive. Standard usage
of representation learning emphasizes on only one set of embedding, which is
problematic for modelling such properties of complementariness. We propose
using knowledge-aware learning with dual product embedding to solve the above
challenges. We encode contextual knowledge into product representation by
multi-task learning, to alleviate the sparsity issue. By explicitly modelling
with user bias terms, we separate the noise of customer-specific preferences
from the complementariness. Furthermore, we adopt the dual embedding framework
to capture the intrinsic properties of complementariness and provide geometric
interpretation motivated by the classic separating hyperplane theory. Finally,
we propose a Bayesian network structure that unifies all the components, which
also concludes several popular models as special cases. The proposed method
compares favourably to state-of-art methods, in downstream classification and
recommendation tasks. We also develop an implementation that scales efficiently
to a dataset with millions of items and customers
Predicting Evoked Emotions in Conversations
Understanding and predicting the emotional trajectory in multi-party
multi-turn conversations is of great significance. Such information can be
used, for example, to generate empathetic response in human-machine interaction
or to inform models of pre-emptive toxicity detection. In this work, we
introduce the novel problem of Predicting Emotions in Conversations (PEC) for
the next turn (n+1), given combinations of textual and/or emotion input up to
turn n. We systematically approach the problem by modeling three dimensions
inherently connected to evoked emotions in dialogues, including (i) sequence
modeling, (ii) self-dependency modeling, and (iii) recency modeling. These
modeling dimensions are then incorporated into two deep neural network
architectures, a sequence model and a graph convolutional network model. The
former is designed to capture the sequence of utterances in a dialogue, while
the latter captures the sequence of utterances and the network formation of
multi-party dialogues. We perform a comprehensive empirical evaluation of the
various proposed models for addressing the PEC problem. The results indicate
(i) the importance of the self-dependency and recency model dimensions for the
prediction task, (ii) the quality of simpler sequence models in short
dialogues, (iii) the importance of the graph neural models in improving the
predictions in long dialogues
Wrinkled few-layer graphene as highly efficient load bearer
Multilayered graphitic materials are not suitable as load-bearers due to
their inherent weak interlayer bonding (for example, graphite is a solid
lubricant in certain applications). This situation is largely improved when
two-dimensional (2-D) materials such as a monolayer (SLG) graphene are
employed. The downside in these cases is the presence of thermally or
mechanically induced wrinkles which are ubiquitous in 2-D materials. Here we
set out to examine the effect of extensive large wavelength/ amplitude
wrinkling on the stress transfer capabilities of exfoliated simply-supported
graphene flakes. Contrary to common belief we present clear evidence that this
type of "corrugation" enhances the load bearing capacity of few-layer graphene
as compared to 'flat' specimens. This effect is the result of the significant
increase of the graphene/polymer interfacial shear stress per increment of
applied strain due to wrinkling and paves the way for designing affordable
graphene composites with highly improved stress-transfer efficiency.Comment: 20 pages, 6 figure
The Role of Preprocessing for Word Representation Learning in Affective Tasks
Affective tasks, including sentiment analysis, emotion classification, and sarcasm detection have drawn a lot of attention in recent years due to a broad range of useful applications in various domains. The main goal of affect detection tasks is to recognize states such as mood, sentiment, and emotions from textual data (e.g., news articles or product reviews). Despite the importance of utilizing preprocessing steps in different stages (i.e., word representation learning and building a classification model) of affect detection tasks, this topic has not been studied well. To that end, we explore whether applying various preprocessing methods (stemming, lemmatization, stopword removal, punctuation removal and so on) and their combinations in different stages of the affect detection pipeline can improve the model performance. The are many preprocessing approaches that can be utilized in affect detection tasks. However, their influence on the final performance depends on the type of preprocessing and the stages that they are applied. Moreover, the preprocessing impacts vary across different affective tasks. Our analysis provides thorough insights into how preprocessing steps can be applied in building an effect detection pipeline and their respective influence on performance
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