632 research outputs found
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
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Flow pattern in inner cores of double emulsion droplets
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The efficacy of applications of water-in-oil-in-water (w/o/w) double emulsions
moving in microchannels is significantly impacted by the flow conditions in the inner aqueous cores.
For example in the case of shear sensitive cells transported in the cores, high shear conditions may be
deleterious. This study reports on the flow topology inside w/o/w cores determined by means of
micro-particle image velocimetry (μPIV) and compares it to the flow in single water-in-oil (w/o)
microdroplets with equal sizes moving in a rectangular microchannel. The multiphase flow system
employed in the study had a viscosity ratio, λ, between oil and aqueous phase of the order of unity (λ
= 0.8) and both single and compound droplets filled the channels. This configuration resulted in a
weak recirculating flow inside the w/o single droplet: the measured flow field exhibited a uniform low
velocity flow field in the central region surrounded by small regions of reversed flow near the channel
walls. This flow topology was maintained in the inner cores of w/o/w double emulsions for
intermediate capillary numbers (Ca) ranging from 10-3 to 10-2, and core morphologies varying from
large plug to pancake cores. The core morphology affected the magnitude and distribution of the
velocity in the droplets. The similarity in the flow pattern results from the fact that inner cores were
located at the back of the outer droplet in such a way that inner and outer interfaces were in contact
for half of core surface area and separated by a thin lubricating film
Characterizing Speech Adversarial Examples Using Self-Attention U-Net Enhancement
Recent studies have highlighted adversarial examples as ubiquitous threats to
the deep neural network (DNN) based speech recognition systems. In this work,
we present a U-Net based attention model, U-Net, to enhance adversarial
speech signals. Specifically, we evaluate the model performance by
interpretable speech recognition metrics and discuss the model performance by
the augmented adversarial training. Our experiments show that our proposed
U-Net improves the perceptual evaluation of speech quality (PESQ) from
1.13 to 2.78, speech transmission index (STI) from 0.65 to 0.75, short-term
objective intelligibility (STOI) from 0.83 to 0.96 on the task of speech
enhancement with adversarial speech examples. We conduct experiments on the
automatic speech recognition (ASR) task with adversarial audio attacks. We find
that (i) temporal features learned by the attention network are capable of
enhancing the robustness of DNN based ASR models; (ii) the generalization power
of DNN based ASR model could be enhanced by applying adversarial training with
an additive adversarial data augmentation. The ASR metric on word-error-rates
(WERs) shows that there is an absolute 2.22 decrease under gradient-based
perturbation, and an absolute 2.03 decrease, under evolutionary-optimized
perturbation, which suggests that our enhancement models with adversarial
training can further secure a resilient ASR system.Comment: The first draft was finished in August 2019. Accepted to IEEE ICASSP
202
2DMatPedia: An open computational database of two-dimensional materials from top-down and bottom-up approaches
Two-dimensional (2D) materials have been a hot research topic in the last
decade, due to novel fundamental physics in the reduced dimension and appealing
applications. Systematic discovery of functional 2D materials has been the
focus of many studies. Here, we present a large dataset of 2D materials, with
more than 6,000 monolayer structures, obtained from both top-down and bottom-up
discovery procedures. First, we screened all bulk materials in the database of
Materials Project for layered structures by a topology-based algorithm, and
theoretically exfoliate them into monolayers. Then, we generated new 2D
materials by chemical substitution of elements in known 2D materials by others
from the same group in the periodic table. The structural, electronic and
energetic properties of these 2D materials are consistently calculated, to
provide a starting point for further material screening, data mining, data
analysis and artificial intelligence applications. We present the details of
computational methodology, data record and technical validation of our publicly
available data (http://www.2dmatpedia.org/)
Quantum optical coherence can survive photon losses: a continuous-variable quantum erasure correcting code
A fundamental requirement for enabling fault-tolerant quantum information
processing is an efficient quantum error-correcting code (QECC) that robustly
protects the involved fragile quantum states from their environment. Just as
classical error-correcting codes are indispensible in today's information
technologies, it is believed that QECC will play a similarly crucial role in
tomorrow's quantum information systems. Here, we report on the first
experimental demonstration of a quantum erasure-correcting code that overcomes
the devastating effect of photon losses. Whereas {\it errors} translate, in an
information theoretic language, the noise affecting a transmission line, {\it
erasures} correspond to the in-line probabilistic loss of photons. Our quantum
code protects a four-mode entangled mesoscopic state of light against erasures,
and its associated encoding and decoding operations only require linear optics
and Gaussian resources. Since in-line attenuation is generally the strongest
limitation to quantum communication, much more than noise, such an
erasure-correcting code provides a new tool for establishing quantum optical
coherence over longer distances. We investigate two approaches for
circumventing in-line losses using this code, and demonstrate that both
approaches exhibit transmission fidelities beyond what is possible by classical
means.Comment: 5 pages, 4 figure
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