3,364 research outputs found
DualApp: Tight Over-Approximation for Neural Network Robustness Verification via Under-Approximation
The robustness of neural networks is fundamental to the hosting system's
reliability and security. Formal verification has been proven to be effective
in providing provable robustness guarantees. To improve the verification
scalability, over-approximating the non-linear activation functions in neural
networks by linear constraints is widely adopted, which transforms the
verification problem into an efficiently solvable linear programming problem.
As over-approximations inevitably introduce overestimation, many efforts have
been dedicated to defining the tightest possible approximations. Recent studies
have however showed that the existing so-called tightest approximations are
superior to each other. In this paper we identify and report an crucial factor
in defining tight approximations, namely the approximation domains of
activation functions. We observe that existing approaches only rely on
overestimated domains, while the corresponding tight approximation may not
necessarily be tight on its actual domain. We propose a novel
under-approximation-guided approach, called dual-approximation, to define tight
over-approximations and two complementary under-approximation algorithms based
on sampling and gradient descent. The overestimated domain guarantees the
soundness while the underestimated one guides the tightness. We implement our
approach into a tool called DualApp and extensively evaluate it on a
comprehensive benchmark of 84 collected and trained neural networks with
different architectures. The experimental results show that DualApp outperforms
the state-of-the-art approximation-based approaches, with up to 71.22%
improvement to the verification result.Comment: 13 pages, 9 fugures, 3 table
BBReach: Tight and Scalable Black-Box Reachability Analysis of Deep Reinforcement Learning Systems
Reachability analysis is a promising technique to automatically prove or
disprove the reliability and safety of AI-empowered software systems that are
developed by using Deep Reinforcement Learning (DRL). Existing approaches
suffer however from limited scalability and large overestimation as they must
over-approximate the complex and almost inexplicable system components, namely
deep neural networks (DNNs). In this paper we propose a novel, tight and
scalable reachability analysis approach for DRL systems. By training on
abstract states, our approach treats the embedded DNNs as black boxes to avoid
the over-approximation for neural networks in computing reachable sets. To
tackle the state explosion problem inherent to abstraction-based approaches, we
devise a novel adjacent interval aggregation algorithm which balances the
growth of abstract states and the overestimation caused by the abstraction. We
implement a tool, called BBReach, and assess it on an extensive benchmark of
control systems to demonstrate its tightness, scalability, and efficiency
Kerr-Sen Black Hole as Accelerator for Spinning Particles
It has been proved that arbitrarily high-energy collision between two
particles can occur near the horizon of an extremal Kerr black hole as long as
the energy and angular momentum of one particle satisfies a critical
relation, which is called the BSW mechanism. Previous researchers mainly
concentrate on geodesic motion of particles. In this paper, we will take
spinning particle which won't move along a timelike geodesic into our
consideration, hence, another parameter describing the particle's spin
angular momentum was introduced. By employing the Mathisson-Papapetrou-Dixon
equation describing the movement of spinning particle, we will explore whether
a Kerr-Sen black hole which is slightly different from Kerr black hole can be
used to accelerate a spinning particle to arbitrarily high energy. We found
that when one of the two colliding particles satisfies a critical relation
between the energy and the total angular momentum , or has a critical
spinning angular momentum , a divergence of the center-of-mass energy
will be obtained.Comment: Latex,17 pages,1 figure,minor revision,accepted by PR
Architecture Design for Particle Transport Code Acceleration
The stochastic simulation method of particle transport is usually used to solve the characteristic quantity of a large number of moving particles.Particle transport problems are widely found in the fields of medicine,astrophysics and nuclear phy-sics.The main challenge of current stochastic simulation methods for particle transport is the gap between the number of simulation samples supported by computers,the simulation timescale,and researchersâ needs to study practical problems.Since the development of processor performance has entered a new historical stage with the stagnation of process size progress,the integration of complex on-chip structures no longer meets the current requirements.For particle transport programs,this paper carries out a series of architecture design works.By analyzing and using the parallelism and access characteristics of the program,simplified kernel and reconfigurable cache are designed to speed up the program.Experiments show that compared to the traditional architecture composed of multiple out-of-order cores,this architecture can obtain more than 4.5x in performance per watt and 2.78x in performance per area,which lays a foundation for the further study of large-scale many-nucleus particle transport acce-lerator
1-Methyl-1H-indazole-3-carboxylic acid
The asymmetric unit of the title compound, C9H8N2O2, contains two molÂecules. In the crystal structure, both molÂecules form inversion dimers via pairs of OâHâŻO hydrogen bonds, and a CâHâŻO interÂation is also seen
Identification of the chemical components of ethanol extract of Chenopodium ambrosioides and evaluation of their in vitro antioxidant and anti tumor activities
Purpose: To determine the characteristic chemical components of the ethanol extract of Chenopodium ambrosioides and evaluate their antioxidant and anti-tumor effects in vitro.
Methods: The plant powder (5 g) was extracted with 1 L of 80 % ethanol at room temperature for 45 min, and then placed at 60 oC at varying microwave power and duration to obtain optimal extraction conditions. Characteristic chemical components were detected using ultra-high performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-Q-TOF-MS/MS). Kaempferitrin was isolated from the 80 % ethanol extract using a D101 macroporous resin column, and its content was assessed by high performance liquid chromatography (HPLC). The antioxidant effect of kaempferitrin was evaluated by its ability to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) radicals, while its anti-proliferation activity in human liver cancer cells SMMC-7721 was determined using cell counting kit-8 (CCK-8) reagent.
Results: Three characteristic components of ethanol extract of C. ambrosioides were obtained, namely, kaempferitrin, kaempferol-3-O-apigenin-7-O-rhamnoside and kaempferol-3-O-acetylapigenin-7-O-rhamnoside. Kaempferitrin was shown to possess strong DPPH radical and moderate ABTS radical scavenging activities. Kaempferitrin significantly inhibited the proliferation of SMMC-7721 cells at doses of 4 and 8 ÎŒg/mL, with half-maximal concentration (IC50) of 0.38 ÎŒM (p < 0.05).
Conclusion: Kaempferitrin extracted from C. ambrosioides has antioxidant and anti-tumor activities. The results reported here indicate that C. ambrosioides may have potential use in herbal medicine practice
Multisite rTMS combined with cognitive training modulates effective connectivity in patients with Alzheimer's disease
PurposeTo investigate the effective connectivity (EC) changes after multisite repetitive transcranial magnetic stimulation (rTMS) combined with cognitive training (COG).MethodWe selected 51 patients with mild or moderate Alzheimer's disease (AD) and delivered 10 Hz rTMS over the left dorsal lateral prefrontal cortex (DLPFC) and the lateral temporal lobe (LTL) combined with COG or sham stimulation for 4 weeks. The selected AD patients were divided into real (real rTMS+COG, n = 11) or sham (sham rTMS+COG, n = 8) groups to undergo neuropsychological assessment, resting-state fMRI, and 3D brain structural imaging before (T0), immediately at the end of treatment (T4), and 4 weeks after treatment (T8). A 2 Ă 3 factorial design with âtimeâ as the within-subjects factor (three levels: T0, T4, and T8) and âgroupâ as the between-subjects factor (two levels: real and sham) was used to investigate the EC changes related to the stimulation targets in the rest of the brain, as well as the causal interactions among seven resting-state networks based on Granger causality analysis (GCA).ResultsAt the voxel level, the EC changes from the left DLPFC out to the left inferior parietal lobe and the left superior frontal gyrus, as well as from the left LTL out to the left orbital frontal cortex, had a significant group Ă time interaction effect. At the network level, a significant interaction effect was identified in the increase in EC from the limbic network out to the default mode network. The decrease in EC at the voxel level and the increase in EC at the network level were both associated with the improved ability to perform activities of daily living and cognitive function.ConclusionMultisite rTMS combined with cognitive training can modulate effective connectivity in patients with AD, resulting in improved ability to perform activities of daily living and cognitive function
Enhancement of thermophilic anaerobic sludge digestion by 70ÂșC pre-treatment : energy considerations
The objective of this work was to investigate the effect of a low temperature pre-treatment (70°C) on the thermophilic anaerobic digestion of sewage sludge. Experimental results were used for the calculation of theoretical energy balances of full-scale digesters with and without pre-treatment step. The 70°C sludge pre-treatment increased sludge solubilization by 10 times and enhanced volatile fatty acids generation. Biogas production increased up to 30-40% and methane content in biogas from 64 to 68-70%. Theoretical calculations showed that additional surplus energy production would be expected by incorporating a 70°C pre-treatment step to a thermophilic reactor
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