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Research progress of slippage characteristic and gas film stability enhancement methods on biomimetic hydrophobic surfaces

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Journal of Hydrodynamics 2024年第1期36卷 87-101页

作者： Meng-zhuo Zhang Hai-bao Hu Liu-zhen Ren Lu-yao Bao Jun Wen Luo Xie school of marine science and Technology Northwestern Polytechnical UniversityXi’an710072China Research and Development Institute of northwestern polytechnical university in Shenzhen Shenzhen518063China

The biomimetic hydrophobic surface is a potentially efficient underwater drag reduction method and the drag reduction mechanism of this kind of surface comes from the interfacial *** now,it is a hotspot to grasp the slippage characteristic and explore slippage enhancement *** paper not only summarizes our numerical simulation and experimental results of slippage characteristic at the solid-liquid interface(SLI)of hydrophobic surfaces(HS)and the gas-liquid interface(GLI)of superhydrophobic surfaces(SHS)in recent years,but also introduces some innovative methods that can effectively improve the gas film stability and drag reduction effect of ***,we used the molecular dynamics(MD)simulation method to figure out the effect of the solid-liquid interaction strength,the system temperature and the shear rate on the slippage of SLI,and expound their action mechanism from molecular ***,by MD and multibody dissipative particle dynamics(MDPD)method,the slippage behavior at the GLI was studied under the influence of the microstructure size and the flow driving *** proposed a new kind of hybrid slip boundary condition model to describe the slippage characteristic on *** addition,we found through experiment that a three-dimensional backflow will appear on the GLI under the interfacial adsorption of surfactants,and the backflow direction will reverse with the change of GLI ***,we put forward the wettability step structure and gas injection method to enhance the stability and drag reduction effect of the gas film on SHS.

关键词： Hydrophobic surface superhydrophobic surface interfacial slip underwater drag reduction

Nanofluidic memristor based on the elastic deformation of nanopores with nanoparticle adsorption

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National science Review 2024年第4期11卷 46-54页

作者： Xi Zhou Yuanyuan Zong Yongchang Wang Miao Sun Deli Shi Wei Wang Guanghua Du Yanbo Xie Department of Chemistry and Chemical Engineering Northwestern Polytechnical University school of Physical science and Technology Northwestern Polytechnical University school of Aeronautics and Institute of Extreme Mechanics Northwestern Polytechnical University Institute of Modern Physics Chinese Academy of Sciences

The memristor is the building block of neuromorphic computing. We report a new type of nanofluidic memristor based on the principle of elastic strain on polymer nanopores. With nanoparticles absorbed at the wall of a single conical polymer nanopore, we find a pinched hysteresis of the current within a scanning frequency range of 0.01–0.1 Hz, switching to a diode below 0.01 Hz and a resistor above 0.1 Hz. We attribute the current hysteresis to the elastic strain at the tip side of the nanopore, caused by electrical force on the particles adsorbed at the inner wall surface. Our simulation and analytical equations match well with experimental results, with a phase diagram for predicting the system transitions. We demonstrate the plasticity of our nanofluidic memristor to be similar to a biological synapse. Our findings pave a new way for ionic neuromorphic computing using nanofluidic memristors.

关键词： nanofluidics memristor neurocomputing elastic deformation

Logit prototype learning with active multimodal representation for robust open-set recognition

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science China(Information sciences) 2024年第6期67卷 297-312页

作者： Yimin FU Zhunga LIU Zicheng WANG school of Automation Northwestern Polytechnical University

Robust open-set recognition(OSR) performance has become a prerequisite for pattern recognition systems in real-world applications. However, the existing OSR methods are primarily implemented on the basis of single-modal perception, and their performance is limited when single-modal data fail to provide sufficient descriptions of the objects. Although multimodal data can provide more comprehensive information than single-modal data, the learning of decision boundaries can be affected by the feature representation gap between different modalities. To effectively integrate multimodal data for robust OSR performance, we propose logit prototype learning(LPL) with active multimodal representation. In LPL, the input multimodal data are transformed into the logit space, enabling a direct exploration of intermodal correlations without the impact of scale inconsistency. Then, the fusion weights of each modality are determined using an entropybased uncertainty estimation method. This approach realizes adaptive adjustment of the fusion strategy to provide comprehensive descriptions in the presence of external disturbances. Moreover, the single-modal and multimodal representations are jointly optimized interactively to learn discriminative decision ***, a stepwise recognition rule is employed to reduce the misclassification risk and facilitate the distinction between known and unknown classes. Extensive experiments on three multimodal datasets have been done to demonstrate the effectiveness of the proposed method.

关键词： logit prototype learning multimodal perception open-set recognition uncertainty estimation

Turbulence Statistics of Thermo-Buoyancy Supercritical Fuel Flow in a Regenerative Cooling Channel

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Journal of Thermal science 2024年第1期33卷 126-137页

作者： SUN Feng XIE Gongnan school of marine science and Technology Northwestern Polytechnical UniversityXi'an 710072China Department of Thermal Engineering Tsinghua UniversityBeijing 100084China

Active regenerative cooling with supercritical hydrocarbon fuel is considered as the most promising thermal protection *** existence of buoyancy force would lead to strongly anisotropic flow and thermal transport *** is closely related to the cooling performance of the *** elucidate the mechanisms of turbulent transport,the large eddy simulation(LES) was performed to assess turbulence statistics within different turbulence *** results indicated that the buoyancy and inertial force together dominated the change of turbulent ***,the spatial thermal buoyancy effect significantly suppressed the vertical velocity *** is due to the laminar motion caused by the buoyancy force,thereby weakening the thermal *** the statistics of velocity fluctuation,it was found that the buoyancy force and inertial force greatly weaken the vertical and streamwise velocity fluctuation,*** the statistics of thermal transport,the results pointed out that the near-wall heat transport characteristics need to be paid more *** thickness of the temperature mixing boundary layer led to the attenuation of vertical heat flux,which inhibited vertical temperature diffusion and predisposed to extreme conditions of heat transfer *** results can enhance the academic understanding of the heat transfer mechanism of supercritical fluids,and give guidance for further applications of thermal protection.

关键词： active regenerative cooling large eddy simulation(LES) buoyancy force turbulence statistics

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Dynamic analysis of beta oscillations in Parkinsonian neural networks with the pedunculopontine nucleus under optogenetic control

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Acta Mechanica Sinica 2024年第6期40卷 125-140页

作者： Yuzhi Zhao Honghui Zhang Ying Yu Lin Du Zichen Deng school of Mathematics and Statistics Northwestern Polytechnical UniversityXi’an710072China school of Aeronautic science and Engineering Beihang UniversityBeijing100191China school of Aeronautics Northwestern Polytechnical UniversityXi’an710072China

Clinical experiments have proven that the pedunculopontine nucleus(PPN)plays a crucial role in the modulation of beta oscillations in Parkinson’s disease(PD).Here,we propose a new computational framework by introducing the PPN and related synaptic connections to the classic basal ganglia-thalamo-cortical ***,the improved model can not only simulate the basic saturated and beta activities mentioned in previous studies but also produce the normal alpha rhythm that is much closer to physiological ***,the results show that Parkinsonian oscillation activities can be controlled and modulated by the connection strength between the PPN and the globus pallidus internal nucleus(GPi)and the subthalamic nucleus(STN),supporting the fact that PPN is overinhibited in ***,the internal mechanism underlying these state transitions is further explained from the perspective of ***,both deep brain stimulation(DBS)and optogenetic technology are considered effective in terms of abnormal *** when a low-frequency DBS is added to the PPN,beta oscillations can be suppressed,but it is excited again as the DBS’s frequency gradually increases to a larger *** results coincide with the experimental results that low-frequency stimulation of the PPN is effective,and verify the rationality of the ***,we show that optogenetic stimulation of the globus pallidus external(GPe)expressing excitatory channelrhodopsin(ChR2)can effectively inhibit beta oscillations,whereas exciting the STN and PPN has a limited *** results are consistent with experimental reports suggesting that the symptoms of PD’s movement disorder can be alleviated under the GPe-ChR2,but not STN-ChR2,*** the functional role of the PPN and the feasibility of optogenetic stimulation remain to be clinically explored,the results obtained help us understand the mechanisms of beta oscillations in PD.

关键词： Pedunculopontine nucleus Beta oscillations Optogenetic Deep brain stimulation Parkinson’s disease

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Frontiers of Computer science 2024年第3期18卷 227-229页

作者： Qianwen GOU Yunwei DONG YuJiao WU Qiao KE school of Computer science Northwestern Polytechnical UniversityXi’an 710129China school of Mathematics and Statistics Northwestern Polytechnical UniversityXi’an 710129China

1 Introduction Program retrieval aims to enable the flexible retrieval of program snippets based on a natural language query,significantly accelerating software development *** shows that over 60%of developers perform program retrieval daily[1].Recent years have witnessed an increasing interest in deep learning-based program retrieval,which aims to construct embedding representations for program snippets and ***,the distribution of natural languages and programs is inconsistent,resulting in a semantic *** critical challenge is to bridge the semantic gap between the programming language and natural language,and accurately measure their similarity.

关键词： semantic similarity retrieval

Global dynamics and noise-induced transitions for a two-dimensional panel system in subsonic flow

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Acta Mechanica Sinica 2024年第8期40卷 253-264页

作者： Xiaole Yue Huikang Zhang Yongge Li Yong Xu school of Mathematics and Statistics Northwestern Polytechnical UniversityXi’an710129China MOE Key Laboratory for Complexity science in Aerospace Northwestern Polytechnical UniversityXi’an710129China

A two-dimensional panel in subsonic flow with stochastic excitation is studied by assuming that the aerodynamic pressure contains random pressure *** on the global properties,the sensitivities of system parameters and noise intensities are ***,the parameter region with multiple coexisting attractors under different dynamic pressures is *** is found that the coexistence of multiple attractors extensively appears and the basin structure may be *** the periodic time history diagrams are calculated by simulating the random pressure fluctuation as Poisson white *** results show that under typical bistable conditions,the noise sensitivity of the subsonic panel system is related to the basin structures and the disposition of the coexisting attractors to the *** transition between two attractors diffuses along the unstable manifold and tends to the position where the basin boundary curvature is relatively *** findings underscore the importance of global analysis in assessing the noise load carrying capacity,which provides some valuable insights into the safety design of subsonic panel systems.

关键词： Global analysis Transition Subsonic panel Multistability

A new local resonance metamaterial for flat and cylindrical structures depended on elastic chiral spiral beams

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science China Technological sciences 2024年第11期67卷 3597-3611页

作者： LIU Jing ZENG Tan NI HengTai HOU YingYing PAN Guang school of marine science and Technology Northwestern Polytechnical University Research & Development Institute of northwestern polytechnical university in Shenzhen Northwestern Polytechnical University

In practical engineering structures, complex low-frequency vibrations are often encountered. However, most reported elastic metamaterials are designed for high-frequency ranges or rely on substantial additional mass to control low-frequency vibrations,making them difficult to apply in real-world engineering scenarios. To address this limitation, we propose a homogeneous locally resonance metamaterial with tunable low-frequency bandgaps. This design overcomes the challenges associated with conventional local resonators, which are often large and heavy, making them impractical for engineering applications. By integrating resonator structures composed of elastic chiral spiral beams and mass blocks onto the supporting structure, we achieve lowfrequency vibration control within limited spaces, broadband absorption with gradient parameter units, and vibration control under different curvatures. The effectiveness of the proposed design is validated through comparative computational methods,dispersion curve calculations, frequency response simulations, and experimental tests. This study proposes a novel LRM structure with a full bandgap from 96.9 to 124 Hz. The transmittance is negative in most of the band gap range, which has been verified through numerical and experimental results. This approach effectively meets the complex low-frequency vibration control requirements of various curved structures in engineering applications, providing a viable solution for low-frequency vibration control of structures such as flat and cylindrical shells.

关键词： local resonance metamaterial chiral spiral elastic beams flat structures cylindrical structures low-frequency vibrations

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Patterning single-layer materials by electrical breakdown using atomic force microscopy

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Nanotechnology and Precision Engineering 2024年第1期7卷 71-77页

作者： Yajie Yang Jiajia Lu Yanbo Xie Libing Duan school of Physical science and Technology Northwestern Polytechnical UniversityXi’an 710072China school of Aeronautics and Institute of Extreme Mechanics Northwestern Polytechnical UniversityXi’an 710072China

The development of nanoelectronics and nanotechnologies has been boosted signiﬁcantly by the emergence of 2D materials because of their atomic thickness and peculiar properties,and developing a universal,precise patterning technology for single-layer 2D materials is critical for assembling *** here is a nanomachining technique using electrical breakdown by an AFM tip to fabricate nanopores,nanostrips,and other nanostructures on *** can be achieved by voltage scanning or applying a constant voltage while moving the *** measuring the electrical current,the formation process on single-layer materials was shown *** present results provide evidence of successful pattern fabrication on single-layer MoS2,boron nitride,and graphene,although further conﬁrmation is still *** proposed method holds promise as a general nanomachining technology for the future.

关键词： 2D material Nanopattern AFM Electrical breakdown Lithography

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