Adversarial training (AT) is one of the most effective ways against adversarial attacks. However, multi-step AT is time-consuming while single-step AT is ineffective. In this paper, we propose an ...Energy-AT framework to make single-step AT as effective as multi-step ones, by exploiting the two properties of energy-based models (EBM). First, we utilize the Helmholtz free energy in EBM to push generated examples to be outside of the distribution boundaries of their categories, such that they are more adversarial. Second, we apply an adaptive temperature scheme in EBM to amplify the training gradients of weak adversarial examples targetedly, such that those originally hard-to-learn examples contribute to the robustification of models also. Extensive experiments validate that Energy-AT improves the robustness of models significantly to adversarial attacks in both white-box and black-box settings, and outperforms the state-of-the-art methods.
The paper is aimed to investigate the effect of lamellar structure distribution around elliptical notch in bimodal titanium alloys of Ti-6Al-4V. In this regard, within the framework of crystal ...plasticity based finite element (CPFE), Representative volume element (RVE) model with elliptical notch for bimodal Ti–6Al–4V is developed, to address the effect of lamellar structure on fatigue resistance performance under external fatigue loading. Lamellar structure distribution around elliptical notches with different aspect ratios are investigated. Strain along radial and circular paths are extracted to identify the possible crack initiation points. The numerical results show that, Strain distribution around notches can be adjusted through lamellar structure distribution such that strain uniformity is achieved. Increase of strain oscillation caused by lamellar structure leads to the improvement of fatigue resistance. With the increase of notch aspect ratio, elliptical notch eventually evolves into line crack and tuning performance of lamellar structure appreciably declines. This numerical study provides a new insight into lamellar structure tuning in dual-phase titanium alloys.
Aim
Oxytocin plays an important role in social recognition in rodents, which is mediated predominantly by the olfactory system. Although oxytocin modulates neural activity in the olfactory bulb, the ...underlying mechanism is largely unknown. Here, we studied how direct infusion of oxytocin into the olfactory bulb affect social interactions in mice and modulate the neural activity of mitral/tufted cells in the olfactory bulb.
Methods
A three‐chamber social interaction test was used in the behavioural test. For in vivo studies, single unit recordings, local field potential recordings and fibre photometry recordings were used to record the neural activity of olfactory bulb. For in vitro studies, we performed patch clamp recordings in the slice of the olfactory bulb.
Results
Behaviourally, direct oxytocin infusion in olfactory bulb increased performance in a social interaction task. Moreover, odour‐evoked responses of mitral/tufted cells and neural discrimination of odours were both enhanced by oxytocin, whereas the spontaneous firing rate of mitral/tufted cells was reduced. At the neural network level, oxytocin decreased the amplitude of odour‐evoked high gamma responses. At the cell population level, oxytocin decreased odour‐evoked calcium responses (reflecting neural activity) specifically in granule cells. Moreover, in vitro slice recordings revealed that the inhibitory effect of oxytocin on mitral cell activity is mediated mainly by modulation of ATP‐sensitive potassium channels and involves the oxytocin receptor–Gq–PLC–IP3 signalling pathway.
Conclusion
Oxytocin modulates social interaction, likely by increasing the signal‐to‐noise ratio of odour responses in mitral cells which is partly through ATP‐sensitive potassium channel.
Metamaterials, rationally designed multiscale composite systems, have attracted extensive interest because of their potential for a broad range of applications due to their unique properties such as ...negative Poisson's ratio, exceptional mechanical performance, tunable photonic and phononic properties, structural reconfiguration,
etc.
Though they are dominated by an auxetic structure, the constituents of metamaterials also play an indispensable role in determining their unprecedented properties. In this vein, 2D materials such as graphene, silicene, and phosphorene with superior structural tunability are ideal candidates for constituents of metamaterials. However, the nanostructure-property relationship and composition-property relationship of these 2D material-based metamaterials remain largely unexplored. Mechanical anisotropy inherited from the 2D material constituents, for example, may substantially impact the physical stability and robustness of the corresponding metamaterial systems. Herein, classical molecular dynamics simulations are performed using a generic coarse-grained model to explore the deformation mechanism of these 2D material-based metamaterials with sinusoidally curved ligaments and the effect of mechanical anisotropy on mechanical properties, especially the negative Poisson's ratio. The results indicate that deformation under axial tensile load can be divided into two stages: bending-dominated and stretching-dominated, in which the rotation of junctions in the former stage results in auxetic behavior of the proposed metamaterials. In addition, the auxetic behavior depends heavily on both the amplitude/wavelength ratio of the sinusoidal ligament and the stiffness ratio between axial and transverse directions. The magnitude of negative Poisson's ratio increases from 0 to 0.625, with an associated increase of the amplitude/wavelength ratio from 0 to 0.225, and fluctuates at around 0.625, in good agreement with the literature, with amplitude/wavelength ratios greater than 0.225. More interestingly, the magnitude of negative Poisson's ratio increases from 0.47 to 0.87 with the increase of the stiffness ratio from 0.125 to 8, in good agreement with additional all-atom molecular dynamics simulations for phosphorene and molybdenum disulfide. Overall, these research findings shed light on the deformation mechanism of auxetic metamaterials, providing useful guidelines for designing auxetic 2D lattice structures made of 2D materials that can display a tunable negative Poisson's ratio.
Mechanical properties, especially negative Poisson's, of 2D sinusoidal lattice metamaterials based on 2D materials depends highly on both geometrical factors and tuned mechanical anisotropy according to our generic coarse-grained molecular dynamics simulations.
The two‐level hierarchical modeling method is developed for damage prognosis on reinforced concrete (RC) industrial buildings, with emphasis on one workshop case. Structural‐level finite element ...analysis is performed first to identify the key components. Subsequently, concrete damaged plasticity (CDP) model is introduced into the component‐level simulation that incorporates preexisting defects. Damage evolution on key components is realized. It is found that the end and middle sections of the beam and upper‐column corbel joint are the dangerous area of the global structure. The whole crane beam and the corbel joint are identified as structural key components. The simulated damage process on local crane beams subjected to the overloaded moving crane is consistent with the experimental results published in literature. The preexisting defects aggravate the unevenness of tensile stresses among steel bars. The work provides a numerical framework for damage prognosis and safety prediction on RC buildings under potentially happened loading scenarios, especially for those old industrial buildings that have been in service for decades.
Manipulation plays a vital role in robotics but is left unsolved. Recent work attempts to leverage the hierarchical structure of tasks via using action primitives. However, due to trajectory ...distribution shift, prior action primitives could hardly be adapted to new tasks. In this letter, we propose the layered action primitive planning from demonstration framework (LAPPLAND) to better utilize prior action primitives while maintaining behavior-interpretability. First, we pretrain goal-conditioned action primitives decoupled with a meta policy and an inverse dynamics model to facilitate interpretable goal state and reachable trajectory. Second, we decompose tasks with logical sub-structure into a sequence of prior action primitives and then align them for better adaption. Third, we execute the action primitives in sequence, conditioned on explicitly assigned goals to lead to the desired states. Extensive experiments in both simulated and real-world environments validate that robotic manipulation planning using LAPPLAND achieves a high success rate and is robust to the variation of the environment. We also compare LAPPLAND with three state-of-the-art methods to demonstrate its superiority.
Fatigue crack growth behaviors of metal alloys are inherently multiscaling. The dual stage advancement in ductile polycrystals can be divided as microstructure‐sensitive stage I and ...microstructure‐independent stage II. Emphasis is placed on stage I of multiscale short fatigue crack growth behaviors in this paper. A microstructure dissimilitude factor p is defined to highlight the effects of microstructural dissimilitude at the stage of the microstructurally small crack (MSC). Fatigue tests of Ti‐6Al‐4V alloy are performed for reference. By incorporating the factor p, the proposed short fatigue crack growth model offers relatively better predictive curves at MSC stage.
Soft-robotic manipulators, with their closed-chamber elastomeric actuators, natural water-sealing and inherent compliance, are ideal for underwater applications for compact, lightweight, and ...dexterous manipulation tasks. However, their low structure rigidity makes soft robots highly prone to underwater disturbances, rendering traditional control methods unreliable, substantially increasing the challenges for high-dexterity control. To address this issue, we proposed an intuitive underwater hybrid manipulator system with a muscle-level mapping design concept. The manipulator was designed to construct an actuator-configuration which could directly map to the main muscles group in the human forearm. Exploiting this analogy, an electromyography-based wearable controller was developed using continuous bio-sensory data from the operator's arm to complement the intuitive manipulator control. A prototype of the proposed manipulator was constructed and validated in various experiments, where a human user could effectively use muscle activations to proportionally drive the soft-robotic manipulator in free-space motions, as well as performing object manipulation tasks both in air and underwater, only using visual feedback, with consistent performances under various time delays. The promising results of this work have demonstrated that the muscle-level analogy of soft robotics could lead to intuitive and effective underwater manipulation with simple structure and low control effort.
To explore the effect of CD4+ CD28null T cell on occurrence and progression of atherosclerosis in patients with type 2 diabetes.
A total of 188 patients who were diagnosed as type 2 diabetes in the ...department of endocrinology were selected in this study.The carotid atherosclerosis was detected using color Doppler ultrasound.The patients with intima-media thickness>1.1 mm or plaques were classified as the carotid atherosclerosis group (95 cases), the others were classified as the control group (93 cases). According to the intima-media thickening and plaques, carotid atherosclerosis group was divided into three subgroups: the thickening group (30 cases), the plaque group (28 cases) and the thickening+plaque group (37 cases). Percentage of CD4+ CD28null T cell in peripheral blood was detected using a flow cytometry, and thus compared and analyzed between the carotid atherosclerosis group and the control group.The relationships between percentage of CD4+ CD28null T cell and age, C-reactive protein (CRP), blood su
PDF
