21,407 research outputs found
Defect Induced Resonances and Magnetic Patterns in Graphene
We investigate the effects of point and line defects in monolayer graphene
within the framework of the Hubbard model, using a self-consistent mean field
theory. These defects are found to induce characteristic patterns into the
electronic density of states and cause non-uniform distributions of magnetic
moments in the vicinity of the impurity sites. Specifically, defect induced
resonance bound states in the local density of states are observed at energies
close to the Dirac points. The magnitudes of the frequencies of these resonance
states are shown to decrease with the strength of the scattering potential,
whereas their amplitudes decay algebraically with increasing distance from the
defect. For the case of defect clusters, we observe that with increasing defect
cluster size the local magnetic moments in the vicinity of the cluster center
are strongly enhanced. Furthermore, non-trivial impurity induced magnetic
patterns are observed in the presence of line defects: zigzag line defects are
found to introduce stronger-amplitude magnetic patterns than armchair line
defects. When the scattering strength of these topological defects is
increased, the induced patterns of magnetic moments become more strongly
localized
Threshold Effects in Cigarette Addiction: An Application of the Threshold Model in Dynamic Panels
We adopt the threshold model of myopic cigarette addiction to US state-level panel data. The threshold model is used to identify the structural effects of cigarette demand determinants across the income stratification. Furthermore, we apply a bootstrap approach to correct for the small-sample bias that arises in the dynamic panel threshold model with fixed effects. Our empirical results indicate that there exists the heterogeneity of smoking dynamics across consumers.Cigarettes demand, price elasticity, threshold regression model, dynamic panel model, bias correction, bootstrap
Antidumping Petition: To File or Not To File
Given the ââŹĹnormal valueâ⏠of a product as common knowledge in an import-competing market, the profitability of a home firm in filing an antidumping (AD) petition against its foreign rival is shown to depend on the marginal cost differential between the home and foreign firms. When the marginal cost differential is ââŹĹsignificantly large,â⏠the home firm's ability to put the foreign firm at the risk of an AD violation is limited. But when the marginal cost differential is ââŹĹsignificantly small,â⏠the home firm is able to increase its output and lower the price of the product below its normal value, putting the foreign firm in the situation of an illegal dumping. One interesting implication is that, relative to the case without an AD law, the home firm has a stronger incentive to undertake cost-reducing activities (e.g., R&D investment or the adoption of a more efficient technology) under the law.antidumping laws, antidumping duties, dumping margins
When Causal Intervention Meets Adversarial Examples and Image Masking for Deep Neural Networks
Discovering and exploiting the causality in deep neural networks (DNNs) are
crucial challenges for understanding and reasoning causal effects (CE) on an
explainable visual model. "Intervention" has been widely used for recognizing a
causal relation ontologically. In this paper, we propose a causal inference
framework for visual reasoning via do-calculus. To study the intervention
effects on pixel-level features for causal reasoning, we introduce pixel-wise
masking and adversarial perturbation. In our framework, CE is calculated using
features in a latent space and perturbed prediction from a DNN-based model. We
further provide the first look into the characteristics of discovered CE of
adversarially perturbed images generated by gradient-based methods
\footnote{~~https://github.com/jjaacckkyy63/Causal-Intervention-AE-wAdvImg}.
Experimental results show that CE is a competitive and robust index for
understanding DNNs when compared with conventional methods such as
class-activation mappings (CAMs) on the Chest X-Ray-14 dataset for
human-interpretable feature(s) (e.g., symptom) reasoning. Moreover, CE holds
promises for detecting adversarial examples as it possesses distinct
characteristics in the presence of adversarial perturbations.Comment: Noted our camera-ready version has changed the title. "When Causal
Intervention Meets Adversarial Examples and Image Masking for Deep Neural
Networks" as the v3 official paper title in IEEE Proceeding. Please use it in
your formal reference. Accepted at IEEE ICIP 2019. Pytorch code has released
on https://github.com/jjaacckkyy63/Causal-Intervention-AE-wAdvIm
Construction of a Fish-like Robot Based on High Performance Graphene/PVDF Bimorph Actuation Materials.
Smart actuators have many potential applications in various areas, so the development of novel actuation materials, with facile fabricating methods and excellent performances, are still urgent needs. In this work, a novel electromechanical bimorph actuator constituted by a graphene layer and a PVDF layer, is fabricated through a simple yet versatile solution approach. The bimorph actuator can deflect toward the graphene side under electrical stimulus, due to the differences in coefficient of thermal expansion between the two layers and the converse piezoelectric effect and electrostrictive property of the PVDF layer. Under low voltage stimulus, the actuator (length: 20 mm, width: 3 mm) can generate large actuation motion with a maximum deflection of about 14.0 mm within 0.262 s and produce high actuation stress (more than 312.7 MPa/g). The bimorph actuator also can display reversible swing behavior with long cycle life under high frequencies. on this basis, a fish-like robot that can swim at the speed of 5.02 mm/s is designed and demonstrated. The designed graphene-PVDF bimorph actuator exhibits the overall novel performance compared with many other electromechanical avtuators, and may contribute to the practical actuation applications of graphene-based materials at a macro scale
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