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Tribological properties of PTFE-based fabric composites at cryogenic temperature

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Friction 2024年第2期12卷 245-257页

作者： Mingkun XU Zidan WANG Lihe GUO Liming TAO Tianbao MA Tingmei WANG Qihua WANG key laboratory of Science and Technology on Wear and Protection of Materials Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China state key laboratory of Tribology Tsinghua UniversityBeijing 100084China Center of Materials Science and optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

Fabric composites are widely employed in self-lubricating bearing liners as solid lubrication materials.Although the tribological behaviors of fabric composites have been extensively studied,the cryogenic tribological properties and mechanisms have been scarcely reported and are largely unclear to instruct material design for aerospace and other high-tech applications.Herein,the tribological properties of polytetrafluoroethylene(PTFE)-based hybrid-fabric composites were investigated at cryogenic and ambient temperatures in the form of pin-on-disk friction under heavy loads.The results suggest that the friction coefficients of the hybrid-fabric composites obviously increase with a decrease in wear when the temperature drops from 25 to−150°C.Moreover,thermoplastic polyetherimide(PEI),as an adhesive for fabric composites,has better cryogenic lubrication performance than thermosetting phenol formaldehyde(PF)resin,which can be attributed to the flexible chemical structure of PEI.The excellent lubrication performance of hybrid-fabric composites is attributed to the transfer film formed by PTFE fibers on the surface of fabrics.

关键词： cryogenic temperatures fabric composites friction and wear transfer film

70 Gbps PAM-4850-nm oxide-confined VCSEL without equalization and pre-emphasis

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Journal of Semiconductors 2024年第5期45卷 5-7页

作者： Anjin Liu Bao Tang Zhiyong Li Wanhua Zheng key laboratory of Optoelectronic Materials and Devices Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China Center of Materials Science and optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China Accelink technologies co. LtdWuhan 430205China key laboratory of Solid-state optoelectronics Information Technology Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China

Directly modulated 850-nm vertical-cavity surface-emitting lasers(VCSELs)with the advantages of low cost,high modulation speed,good reliability,and low power consumption,are the key sources in the optical interconnects with multimode fibers for the supercomputers,data centers,and machine learning applications[1−3].Typically,non-return-tozero(NRZ)modulation format is used.

关键词： return confined fibers

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Theory and classification of mass extinction causation

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National Science Review 2024年第1期11卷 16-36页

作者： Thomas J.Algeo Jun Shen state key laboratory of Biogeology and Environmental Geology China University of Geosciences—Wuhan state key laboratory of Geological Processes and Mineral Resources China University of Geosciences—Wuhan Department of Geosciences University of Cincinnati

Theory regarding the causation of mass extinctions is in need of systematization, which is the focus of this contribution. Every mass extinction has both an ultimate cause, i.e. the trigger that leads to various climato-environmental changes, and one or more proximate cause(s), i.e. the specific climato-environmental changes that result in elevated biotic mortality. With regard to ultimate causes, strong cases can be made that bolide(i.e. meteor) impacts, large igneous province(LIP) eruptions and bioevolutionary events have each triggered one or more of the Phanerozoic Big Five mass extinctions, and that tectono-oceanic changes have triggered some second-order extinction events. Apart from bolide impacts, other astronomical triggers(e.***.solar flares, gamma bursts and supernova explosions) remain entirely in the realm of speculation. With regard to proximate mechanisms, most extinctions are related to either carbon-release or carbon-burial processes, the former being associated with climatic warming, ocean acidification, reduced marine productivity and lower carbonate δ13C values, and the latter with climatic cooling, increased marine productivity and higher carbonate δ13C values. Environmental parameters such as marine redox conditions and terrestrial weathering intensity do not show consistent relationships with carbon-cycle changes.In this context, mass extinction causation can be usefully classified using a matrix of ultimate and proximate factors. Among the Big Five mass extinctions, the end-Cretaceous biocrisis is an example of a bolide-triggered carbon-release event, the end-Permian and end-Triassic biocrises are examples of LIP-triggered carbon-release events, and the Late Ordovician and Late Devonian biocrises are examples of bioevolution-triggered carbon-burial events. Whereas the bolide-impact and LIP-eruption mechanisms appear to invariably cause carbon release, bioevolutionary triggers can result in variable carbon-cycle changes, e.g. carbon burial during the Late Ordovician and Late Devonian events,

关键词： biocrisis ultimate cause proximate cause bolide large igneous province bioevolutionary event

A highoutput PDMS-MXene/gelatin triboelectric nanogenerator with the petal surface-microstructure

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Nano Research 2024年第5期17卷 4151-4162页

作者： Zekun Wang Congcong Hao Mingzhe Cai Juan Cui Yongqiu Zheng Chenyang Xue key laboratory of Instrumentation Science&Dynamic Measurement Ministry of Education North University of ChinaTaiyuan 030051China state key laboratory of Electronic Thin Films and integrated Devices University of Electronic Science and Technology of ChinaChengdu 611731China

Triboelectric nanogenerator(TENG)has a promising future in the field of energy harvesting and self-powered sensing due to their simplicity in structure,low cost,and efficient energy harvesting from the surrounding environment.The output electrical performance of TENG can be improved by doping the friction material with functional materials and modifying the surface of the friction material.However,the current method of adding functional materials to friction materials is costly and wasteful,and the method of modifying the surface structure of friction materials is cumbersome and not easy to operate.In this work,we present a polydimethylsiloxane(PDMS)-MXene/gelatin triboelectric nanogenerator(PMMG-TENG)based on petal surface-microstructures,which has the advantages of low cost,simple preparation,high output performance,and ecological friendliness.By doping 0.03 wt.%of MXene in PDMS,the output electrical performance of TENG can be significantly improved,with an output current increase of up to 139.7%.Four different petals are used as natural molds to prepare PMMG-TENG.The results show that PMMG-TENG with peony petal surface microstructure has the best electrical performance,and the output current increase of up to 228.17%compared with PMMG-TENG without structure.The PMMG-TENG with peony petal surface-microstructure exhibits excellent electrical performance,demonstrating a maximum open-circuit voltage of 417.39 V and a maximum short-circuit current of 12.01μA at a size of 3 cm×3 cm,and a maximum power density of 170μW/cm^(2) at a load resistance of 107Ω.The PMMG-TENG’s output performance after 10,000 cycles is consistent with the initial state,highlighting excellent output stability.The PMMG-TENG can easily light up at least 100 light emitting diodes(LEDs).(operating voltage 3V.)Gelatin film exhibits excellent degradation performance,with complete degradation time of only 150 s in water at a constant temperature of 75℃.PMMG-TENG not only shows excellent performance in the field of energy harvesting,but also has a br

关键词： triboelectric nanogenerator(TENG) petal surface-microstructure gelatin MXene energy harvesting

Macro-superlubricity in sputtered MoS_(2)-based films by decreasing edge pinning effect

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Friction 2024年第1期12卷 52-63页

作者： Chunmeng DONG Dong JIANG Yanlong FU Desheng WANG Qinqin WANG Lijun WENG Ming HU Xiaoming GAO Jiayi SUN state key laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China Center of Materials Science and optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

To date,MoS_(2) can only be achieved at microscale.Edge pinning effect caused by structure defects is the most obvious barrier to expand the size of structural superlubricity to macroscale.Herein,we plan to pin edge planes of MoS_(2) with nanospheres,and then the incommensurate structure can be formed between adjacent rolling nanoparticles to reduce friction.The sputtered MoS_(2) film was prepared by the physical vapor deposition(PVD)in advance.Then enough Cu_(2)O nanospheres(~40 nm)were generated in situ at the edge plane of MoS_(2) layers by liquid phase synthesis.An incommensurate structure(mismatch angle(θ)=8°)caused by MoS_(2) layers was formed before friction.The friction coefficient of the films(5 N,1,000 r/min)was~6.0×10^(−3) at the most.During friction,MoS_(2) layers pinned on numerous of Cu_(2)O nanoparticles reduced its edge pinning effect and decreased friction.Moreover,much more incommensurate was formed,developing macro-superlubricity.

关键词： sputtered MoS_(2)film Cu_(2)O nanospheres edge pinning effect macro-superlubricity

Recent advances in protein conformation sampling by combining machine learning with molecular simulation

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Chinese Physics B 2024年第3期33卷 80-87页

作者：唐一鸣杨中元姚逸飞周运谈圆王子超潘瞳熊瑞孙俊力韦广红 Department of Physics State Key Laboratory of Surface Physicsand Key Laboratory for Computational Physical Sciences (Ministry of Education)Shanghai 200438China

The rapid advancement and broad application of machine learning(ML)have driven a groundbreaking revolution in computational biology.One of the most cutting-edge and important applications of ML is its integration with molecular simulations to improve the sampling efficiency of the vast conformational space of large biomolecules.This review focuses on recent studies that utilize ML-based techniques in the exploration of protein conformational landscape.We first highlight the recent development of ML-aided enhanced sampling methods,including heuristic algorithms and neural networks that are designed to refine the selection of reaction coordinates for the construction of bias potential,or facilitate the exploration of the unsampled region of the energy landscape.Further,we review the development of autoencoder based methods that combine molecular simulations and deep learning to expand the search for protein conformations.Lastly,we discuss the cutting-edge methodologies for the one-shot generation of protein conformations with precise Boltzmann weights.Collectively,this review demonstrates the promising potential of machine learning in revolutionizing our insight into the complex conformational ensembles of proteins.

关键词： machine learning molecular simulation protein conformational space enhanced sampling

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Discontinuous phase diagram of amorphous carbons

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National Science Review 2024年第4期11卷 164-171页

作者： YinBo Zhu ZhouYu Fang ZhongTing Zhang HengAn Wu CAS key laboratory of Mechanical Behavior and Design of Materials Department of Modern MechanicsUniversity of Science and Technology of China state key laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences

The short-range order and medium-range order of amorphous carbons demonstrated in experiments allow us to rethink whether there exist intrinsic properties hidden by atomic disordering. Here we presented six representative phases of amorphous carbons（0.1–3.4 g/cm3）, namely, disordered graphene network（DGN）, high-density amorphous carbon（HDAC）, amorphous diaphite（a-DG）, amorphous diamond（a-D）, paracrystalline diamond（p-D）, and nano-polycrystalline diamond（NPD）, respectively, classified by their topological features and microstructural characterizations that are comparable with experiments. To achieve a comprehensive physical landscape for amorphous carbons, a phase diagram was plotted in the sp3/sp2versus density plane, in which the counterintuitive discontinuity originates from the inherent difference in topological microstructures, further guiding us to discover a variety of phase transitions among different amorphous carbons. Intriguingly, the power law, log（sp3/sp2） ∝ ρn, hints at intrinsic topology and hidden order in amorphous carbons, providing an insightful perspective to reacquaint atomic disorder in non-crystalline carbons.

关键词： amorphous carbons disordered carbons phase diagram microstructural topology phase transition

Large-inductance superconducting microstrip photon detector enabling 10 photon-number resolution

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Advanced Photonics 2024年第1期6卷 96-105页

作者： Ling-Dong Kong Tian-Zhu Zhang Xiao-Yu Liu Hao Li Zhen Wang Xiao-Ming Xie Li-Xing You Chinese Academy of Sciences(CAS) Shanghai Institute of Microsystem and Information TechnologyNational Key Laboratory of Materials for Integrated CircuitsShanghaiChina CAS Center for Excellence in Superconducting Electronics ShanghaiChina University of Chinese Academy of Sciences Center of Materials Science and Optoelectronics EngineeringBeijingChina

Efficient and precise photon-number-resolving detectors are essential for optical quantum information science.Despite this,very few detectors have been able to distinguish photon numbers with both high fidelity and a large dynamic range,all while maintaining high speed and high timing precision.Superconducting nanostrip-based detectors excel at counting single photons efficiently and rapidly,but face challenges in balancing dynamic range and fidelity.Here,we have pioneered the demonstration of 10 true photon-number resolution using a superconducting microstrip detector,with readout fidelity reaching an impressive 98%and 90%for 4-photon and 6-photon events,respectively.Furthermore,our proposed dual-channel timing setup drastically reduces the amount of data acquisition by 3 orders of magnitude,allowing for real-time photon-number readout.We then demonstrate the utility of our scheme by implementing a quantum random-number generator based on sampling the parity of a coherent state,which guarantees inherent unbiasedness,robustness against experimental imperfections and environmental noise,as well as invulnerability to eavesdropping.Our solution boasts high fidelity,a large dynamic range,and real-time characterization for photon-number resolution and simplicity with respect to device structure,fabrication,and readout,which may provide a promising avenue towards optical quantum information science.

关键词： superconducting microstrips single-photon detector photon-number resolution quantum random number

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Two-dimensional ballistic transistors for advanced-node integrated circuits

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National Science Review 2024年第3期11卷 9-10页

作者： Jia Li Xidong Duan Hunan Provincial key laboratory of Two-Dimensional Materials State Key Laboratory for Chemo/Biosensing and Chemometrics College of Chemistry and Chemical Engineering Hunan University

As the feature size of metal-oxide-semiconductor-field-effect-transistors(MOSFETs) in integrated circuits(ICs)is reduced to sub-10-nm, the traditional channel materials are plagued by enhanced scattering and short-cha... 详细信息

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