Functional central limit theorem with mean-uncertainty under sublinear expectation

In this paper, we introduce a fundamental model for independent and identically distributed sequence with model uncertainty on the canonical space $(\mathbb{R}^\mathbb{N},\mathcal{B}(\mathbb{R}^\mathbb{N}))$ via probability kernels. Thanks to the well-defined upper and lower variances, we obtain a new functional central limit theorem with mean-uncertainty on the canonical space by the method based on the martingale central limit theorem and stability of stochastic integral in the classical probability theory. Then we extend it to the general sublinear expectation space through a new representation theorem. Our results generalize Peng's central limit theorem with zero-mean to the case of mean-uncertainty and provides a purely probabilistic proof instead of the existing nonlinear partial differential equation approach. As an application, we consider the two-armed bandit problem and generalize the corresponding central limit theorem from the case of mean-certainty to mean-uncertainty.Comment: 31 pages. arXiv admin note: substantial text overlap with arXiv:2203.0017

Physical Invisible Backdoor Based on Camera Imaging

Backdoor attack aims to compromise a model, which returns an adversary-wanted output when a specific trigger pattern appears yet behaves normally for clean inputs. Current backdoor attacks require changing pixels of clean images, which results in poor stealthiness of attacks and increases the difficulty of the physical implementation. This paper proposes a novel physical invisible backdoor based on camera imaging without changing nature image pixels. Specifically, a compromised model returns a target label for images taken by a particular camera, while it returns correct results for other images. To implement and evaluate the proposed backdoor, we take shots of different objects from multi-angles using multiple smartphones to build a new dataset of 21,500 images. Conventional backdoor attacks work ineffectively with some classical models, such as ResNet18, over the above-mentioned dataset. Therefore, we propose a three-step training strategy to mount the backdoor attack. First, we design and train a camera identification model with the phone IDs to extract the camera fingerprint feature. Subsequently, we elaborate a special network architecture, which is easily compromised by our backdoor attack, by leveraging the attributes of the CFA interpolation algorithm and combining it with the feature extraction block in the camera identification model. Finally, we transfer the backdoor from the elaborated special network architecture to the classical architecture model via teacher-student distillation learning. Since the trigger of our method is related to the specific phone, our attack works effectively in the physical world. Experiment results demonstrate the feasibility of our proposed approach and robustness against various backdoor defenses

Anti-hepatotoxic and anti-oxidant effects of extracts from Piper nigrum L. root

The aim of this study was to investigate the effect of Piper nigrum L. root extracts on carbon tetrachloride (CCl4)-induced rat liver injury. Among the three different extracts (water, ethanol and chloroform extract), ethanol extract exhibits the highest hepatoprotective activity (p < 0.05). When using the ethanol extract at a dose of 120 mg/ kg to treat the CCl4-intoxicated rat, the activities of alanine transaminase (ALT) and aspartate transanimase (AST) in rat serum decreased to 65.7 and 84.5%, respectively. At the same time, the lipid peroxidation (MDA) decreased to 52.3% and glutathione (GSH) increased to 55.8% in the rats liver homogenate, as compared with those of the CCl4 positive control rats. The hepatoprotective effect of ethanol extract was also supported by the histopathological observations. Moreover, the ethanol extract was studied for its in vitro antioxidant activity using the methods of ferric thiocyanate (FTC) and thiobarbituric acid (TBA). The findings indicate that the ethanol extract of P. nigrum L. root is an efficient hepatoprotective and antioxidant agent against CCl4-induced liver injury.Keywords: Piper nigrum L. root, ethanol extract, carbon tetrachloride (CCl4), hepatoprotective, antioxidan

Attention-TCN-BiGRU: An Air Target Combat Intention Recognition Model

The prerequisite for victory in war is the rapid and accurate identification of the tactical intention of the target on the battlefield. The efficiency of manual recognition of the combat intention of air targets is becoming less and less effective with the advent of information warfare. Moreover, if the traditional method of combat intention of air targets is based only on data from a single moment in time, the characteristic information on the time-series data is difficult to capture effectively. In this context, we design a new deep learning method attention mechanism with temporal convolutional network and bidirectional gated recurrent unit (Attention-TCN-BiGRU) to improve the recognition of the combat intent of air targets. Specifically, suitable characteristics are selected based on the combat mission and air posture to construct a characteristic set of air target intentions and encode them into temporal characteristics. Each characteristic in the characteristic set is given an appropriate weight through the attention mechanism. In addition, temporal convolutional network (TCN) is used to mine the data for latent characteristics and bidirectional gated recurrent unit (BiGRU) is used to capture long-term dependencies in the data. Experiments comparing with other methods and ablation demonstrate that Attention-TCN-BiGRU outperforms state-of-the-art methods in terms of accuracy in recognizing target intent in the air

Study on the solid solution temperature of achieving ultra-high strength in wire-arc additive manufactured Al-Zn-Mg-Cu aluminum alloy

Al-Zn-Mg-Cu aluminum alloys are typically heat-treatable aluminum alloys. The heat treatment has a significant effect on the microstructure and mechanical properties of Al-Zn-Mg-Cu alloy. In this study, the solid solution temperature of achieving ultra-high strength in wire-arc additive manufactured 7B55 aluminum alloy was systematically investigated. The results showed that the microstructure of the as-deposited 7B55 aluminum alloy was composed of equiaxed grains with an average grain size of 4.2 ± 0.5 μm. A large number of the second phases were continuously distributed along grain boundaries. The precipitated phases within grains were mainly composed of the larger η phases and the smaller η′ phases, and the amount of precipitated phases was fewer. The second phases distributed along grain boundaries gradually dissolved into α-Al matrix with the increase of solid solution temperature, resulting in a higher supersaturation of the α-Al matrix and more homogeneous distribution of alloy elements. Combined with the results of DSC analysis, the optimal solid solution temperature of the 7B55 aluminum alloy was determined to be 480 °C. After solid solution of 480 °C，the microstructure was still composed of equiaxed grains with an average grain size of 4.8 ± 0.4 μm. The size of the grain did not grow significantly. A larger number of nanoscale fine GP zones, η′ phases and secondary Al3(Sc,Zr) particles were precipitated within the grains during subsequently artificial aging process, resulting in a significant increase in tensile properties. The ultimate tensile strength (UTS), yield strength (YS) and elongation (EL) reached 621 MPa, 555 MPa and 5.73%, respectively, which was significantly higher than the strength level of WAAM aluminum alloy reported among all the existing literature

Achieving high strength-ductility properties of wire-arc additive manufactured Al-Mg-Sc aluminum alloy via friction stir processing post-treatment and high temperature aging treatment

In this study, the high strength-ductility properties of wire-arc additive manufactured (WAAM) Al-Mg-Sc aluminum alloy were achieved by friction stir processing post-treatment (FSPPT) and high temperature aging treatment (HTAT). The FSPPT significantly refined the microstructure and eliminated porosity defects, which the average grain size was about 2.4 ± 0.2 μm in stirring zone (SZ). There was no obvious growth in grain size after HTAT and the average grain size was about 2.7 ± 0.4 μm in SZ. Many fine secondary Al3(Sc,Zr) phases were precipitated. Compared to WAAM sample, the average ultimate tensile strength (UTS), yield strength (YS) and elongation (EL) of FSPPT + HTAT sample increased by 57.9%, 54.7% and 205.9%, respectively

xNi/Ni0.05Ce0.20Zr0.75O2 Solid Solution over a CO2 Methanation Reaction

A Ni-modified ceria-zirconia support with Ni impregnation at different Ni-loading catalysts for a CO2 methanation reaction was systematically studied. The corresponding structures of each catalyst were characterized by Brunauer-Emmett-Teller surface area analysis, X-ray powder diffraction, X-ray fluorescence, H-2 temperature-programmed reduction, CO2 temperature-programmed desorption, Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric/differential thermal analysis. The results showed that Ni-modified Ce-Zr oxide improved the basic properties as well as the oxygen vacancies. A gradual increase in Ni loading from 15 to 45 wt % was found to increase medium-strong basic sites, and surface Ce3+ and Ni-0 species along with oxygen vacancies favor high activity. The CO2 methanation activity was related to the amount of Ni loadings where the 45Ni/Ni005CZO catalyst was reported to be the most active catalyst. This is due to the high amount of Ni surface suitable for H-2 activation and high medium basic sites to accommodate CO2 activation, leading to high catalytic activity