Adversarial learning games with deep learning models

© 2017 IEEE. Deep learning has been found to be vulnerable to changes in the data distribution. This means that inputs that have an imperceptibly and immeasurably small difference from training data correspond to a completely different class label in deep learning. Thus an existing deep learning network like a Convolutional Neural Network (CNN) is vulnerable to adversarial examples. We design an adversarial learning algorithm for supervised learning in general and CNNs in particular. Adversarial examples are generated by a game theoretic formulation on the performance of deep learning. In the game, the interaction between an intelligent adversary and deep learning model is a two-person sequential noncooperative Stackelberg game with stochastic payoff functions. The Stackelberg game is solved by the Nash equilibrium which is a pair of strategies (learner weights and genetic operations) from which there is no incentive for either learner or adversary to deviate. The algorithm performance is evaluated under different strategy spaces on MNIST handwritten digits data. We show that the Nash equilibrium leads to solutions robust to subsequent adversarial data manipulations. Results suggest that game theory and stochastic optimization algorithms can be used to study performance vulnerabilities in deep learning models

Drying shrinkage of hydrothermally cured cements with reactive magnesia and clay brick waste

In recent years, worldwide research and development in the cement industry has gathered momentum with an aim to explore innovative and sustainable methods to deliver environmentally responsible Portland Cement (PC) based construction products. This study investigated physical and mechanical properties of autoclaved cement-quartz sand blends with the addition of clay-brick waste (CB waste) and reactive magnesia (MgO) with the aim to lower CO2 emissions through the reduction of PC consumption. Mechanical properties and drying shrinkage showed improvements with the incorporation of CB waste due to increased amounts and crystallinity of Al-tobermorite. The addition of reactive MgO to PC in hydrothermal conditions was observed to have a negative effect on the compressive strength. XRD data indicated that MgO did not take part in the reaction during the hydration of the cement and may even retard tobermorite formation. However, the expansive nature from the hydration of MgO to brucite may have compensated for drying shrinkage

Wide-Area Backup Protection Against Asymmetrical Faults Using Available Phasor Measurements

This paper proposes a robust and computationally efficient wide-area backup protection (WABP) scheme against asymmetrical faults on transmission systems using available synchronized/unsynchronized phasor measurements. Based on the substitution theorem, the proposed scheme replaces the faulted line with two suitable current sources. This results in a linear system of equations for WABP, with no need of full system observability by measurement devices. The identification of the faulted line is attributed to the sum of squared residuals (SoSR) of the developed system of equations. To preserve accuracy, the scheme limits the calculations to the assessment of the negative-sequence circuit of the gird. Relevant practical aspects that have not been properly addressed in the literature, namely the non-simultaneous opening of circuit breakers (CBs) and their single-pole tripping for single-phase to ground faults are investigated. The linearity of the formulations derived removes concerns over convergence speed and potential time-synchronization challenges. The proposed scheme is able to identify the faulted line and retain this capability for hundreds of milliseconds following the fault inception. More than 20 000 simulations conducted on the IEEE 39-bus test system verify the effectiveness of the proposed WABP scheme

AKSZ construction from reduction data

We discuss a general procedure to encode the reduction of the target space geometry into AKSZ sigma models. This is done by considering the AKSZ construction with target the BFV model for constrained graded symplectic manifolds. We investigate the relation between this sigma model and the one with the reduced structure. We also discuss several examples in dimension two and three when the symmetries come from Lie group actions and systematically recover models already proposed in the literature.Comment: 42 page

Computing in Additive Networks with Bounded-Information Codes

This paper studies the theory of the additive wireless network model, in which the received signal is abstracted as an addition of the transmitted signals. Our central observation is that the crucial challenge for computing in this model is not high contention, as assumed previously, but rather guaranteeing a bounded amount of \emph{information} in each neighborhood per round, a property that we show is achievable using a new random coding technique. Technically, we provide efficient algorithms for fundamental distributed tasks in additive networks, such as solving various symmetry breaking problems, approximating network parameters, and solving an \emph{asymmetry revealing} problem such as computing a maximal input. The key method used is a novel random coding technique that allows a node to successfully decode the received information, as long as it does not contain too many distinct values. We then design our algorithms to produce a limited amount of information in each neighborhood in order to leverage our enriched toolbox for computing in additive networks

Non-Negative Local Sparse Coding for Subspace Clustering

Subspace sparse coding (SSC) algorithms have proven to be beneficial to clustering problems. They provide an alternative data representation in which the underlying structure of the clusters can be better captured. However, most of the research in this area is mainly focused on enhancing the sparse coding part of the problem. In contrast, we introduce a novel objective term in our proposed SSC framework which focuses on the separability of data points in the coding space. We also provide mathematical insights into how this local-separability term improves the clustering result of the SSC framework. Our proposed non-linear local SSC algorithm (NLSSC) also benefits from the efficient choice of its sparsity terms and constraints. The NLSSC algorithm is also formulated in the kernel-based framework (NLKSSC) which can represent the nonlinear structure of data. In addition, we address the possibility of having redundancies in sparse coding results and its negative effect on graph-based clustering problems. We introduce the link-restore post-processing step to improve the representation graph of non-negative SSC algorithms such as ours. Empirical evaluations on well-known clustering benchmarks show that our proposed NLSSC framework results in better clusterings compared to the state-of-the-art baselines and demonstrate the effectiveness of the link-restore post-processing in improving the clustering accuracy via correcting the broken links of the representation graph.Comment: 15 pages, IDA 2018 conferenc

Controlling Spatiotemporal Mechanics of Supramolecular Hydrogel Networks with Highly Branched Cucurbit[8]uril Polyrotaxanes

Attempts to rationally tune the macroscopic mechanical performance of supramolecular hydrogel networks through noncovalent molecular interactions have led to a wide variety of supramolecular materials with desirable functions. While the viscoelastic properties are dominated by temporal hierarchy (crosslinking kinetics), direct mechanistic studies on spatiotemporal control of supramolecular hydrogel networks, based on host-guest chemistry, have not yet been established. Here, supramolecular hydrogel networks assembled from highly branched cucurbit[8]uril-threaded polyrotaxanes (HBP-CB[8] ) and naphthyl-functionalized hydroxyethyl cellulose (HECNp) are reported, exploiting the CB[8] host-guest complexation. Mechanically locking CB[8] host molecules onto a highly branched hydrophilic polymer backbone, through selective binary complexation with viologen derivatives, dramatically increases the solubility of CB[8]. Additionally, the branched architecture enables tuning of material dynamics of the supramolecular hydrogel networks via both topological (spatial hierarchy) and kinetic (temporal hierarchy) control. Relationship between macroscopic properties (time- and temperature-dependent rheological properties, thermal stability, and reversibility), spatiotemporal hierarchy, and chain dynamics of the highly branched polyrotaxane hydrogel networks is investigated in detail. Such kind of tuning of material mechanics through spatiotemporal hierarchy improves our understanding of the challenging relationship between design of supramolecular polymeric materials and their complex viscoelasticity, and also highlights a facile strategy to engineer dynamic supramolecular materials.Ministry of Education of Malaysia and Universiti Teknologi MARA, Marie Curie Fellowship. Grant Number: 65836

Creep characterisation of Inconel 718 lattice metamaterials manufactured by laser powder bed fusion

Lattice metamaterials manufactured by laser powder bed fusion (LPBF) are limited by their performance for critical applications. LPBF materials have microstructural or macroscale anomalies, such as suboptimal grain size, morphology, and lack of fusion. This results in LPBF metamaterials performance degradation for various mechanical properties, such as creep, which has seldom been researched. To understand the creep behavior of LPBF Inconel 718, body-centered cubic metamaterials are fabricated for creep test at 650 °C. Kachanov's damage modeling is used to predict the creep performance of the metamaterials under different loading conditions. Microstructural characterization is performed with scanning electron microscopy to identify critical microstructure defects affecting the failure mechanisms and creep behaviors of the metamaterials. It is shown in the results that the loading conditions affect the fracture process of the metamaterials owing to different failure mechanisms. In the simulation and test results, the logarithmic decline in creep life is shown when loading increases; also, logarithmic increase in the creep life is shown when relative density increases

Tuberculosis incidence correlates with sunshine : an ecological 28-year time series study

Birmingham is the largest UK city after London, and central Birmingham has an annual tuberculosis incidence of 80 per 100,000. We examined seasonality and sunlight as drivers of tuberculosis incidence. Hours of sunshine are seasonal, sunshine exposure is necessary for the production of vitamin D by the body and vitamin D plays a role in the host response to tuberculosis. Methods: We performed an ecological study that examined tuberculosis incidence in Birmingham from Dec 1981 to Nov 2009, using publicly-available data from statutory tuberculosis notifications, and related this to the seasons and hours of sunshine (UK Meteorological Office data) using unmeasured component models. Results: There were 9,739 tuberculosis cases over the study period. There was strong evidence for seasonality, with notifications being 24.1% higher in summer than winter (p<0.001). Winter dips in sunshine correlated with peaks in tuberculosis incidence six months later (4.7% increase in incidence for each 100 hours decrease in sunshine, p<0.001). Discussion and Conclusion: A potential mechanism for these associations includes decreased vitamin D levels with consequent impaired host defence arising from reduced sunshine exposure in winter. This is the longest time series of any published study and our use of statutory notifications means this data is essentially complete. We cannot, however, exclude the possibility that another factor closely correlated with the seasons, other than sunshine, is responsible. Furthermore, exposure to sunlight depends not only on total hours of sunshine but also on multiple individual factors. Our results should therefore be considered hypothesis-generating. Confirmation of a potential causal relationship between winter vitamin D deficiency and summer peaks in tuberculosis incidence would require a randomized-controlled trial of the effect of vitamin D supplementation on future tuberculosis incidence