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From ultra-low friction to superlubricity state of black phosphorus:Enabled by the critical oxidation and load

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Friction 2023年第10期11卷 1829-1844页

作者： Qiang LI Fenghua SU yanjun chen Jianfang SUN School of Mechanical&Automotive Engineering South China University of TechnologyGuangzhou 510641China Guangdong Provincial Key Laboratory of Technique and Equipment for Macromolecular Advanced Manufacturing South China University of TechnologyGuangzhou 510640China

Based on the density functional theory(DFT),we investigate the friction properties of inevitable oxidized black phosphorus(o-BP).o-BP with the weaker interlayer adhesion exhibits their great potential as a solid *** the zero load,the friction property of o-BP is adjusted by its oxidation ***,ultra-low friction of P4O2(50%oxidation,O:P=2:4=50%)is obtained,which is attributed to the upper O atoms with lower sliding resistance in the O channel formed by lower layer O *** attractive,we observe superlubricity behavior of o-BP at the critical load/distance due to the flattening potential energy surface(PES).The flattening PES is controlled by the electrostatic role for the high-load(P4O3,O:P=3:4=75%),and by the electrostatic and dispersion roles for the low-load(P4O2).Distinctly,the transform from ultra-low friction to superlubricity state of black phosphorus(BP)can be achieved by critical oxidation and load,which shows an important significance in engineering *** addition,negative friction behavior of o-BP is a general phenomenon(Z>Z_(min),Z_(min)is the interlayer distances between the outermost P atoms of minimum load.),while its surface-surface model is different from the fold mechanism of the tip-surface model(Z_(0)Z_(min)).In summary,o-BP improves the friction performance and reduces the application limitation,comparing to graphene(Gr),MoS2,and their oxides.

关键词： oxidized black phosphorus(o-BP) ultra-low friction superlubricity critical load/distance first-principles

Skin-integrated stretchable actuators toward skin-compatible haptic feedback and closed-loop human-machine interactions

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npj Flexible Electronics 2023年第1期7卷 555-566页

作者： Si chen yanjun chen Ji Yang Teng Han Shanshan Yao Department of Mechanical Engineering Stony Brook UniversityStony BrookNY 11794USA Institute of Software Chinese Academy of Sciences100190 BeijingChina Meta Platforms Menlo ParkCA 94025USA

Skin-integrated haptic interfaces that can relay a wealth of information from the machine to the human are of great ***,existing haptic devices are not yet able to produce haptic cues that are compatible with the *** this work,we present the stretchable soft actuators for haptic feedback,which can match the perception range,spatial resolution,and stretchability of the ***-amplification structures are fabricated using a scalable self-assembly process to ensure an output pressure beyond the skin perception *** to the minimized device size,the actuator array can be fabricated with a sufficiently high spatial resolution,which makes the haptic device applicable for skin locations with the highest spatial acuity.A haptic feedback system is demonstrated by employing the developed soft actuators and highly sensitive pressure *** proof-ofconcept applications are developed to illustrate the capability of transferring information related to surface textures and object shapes acquired at the robot side to the user side.

关键词： robot Skin stretch

Rendering discrete participating media using geometrical optics approximation

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Computational Visual Media 2022年第3期8卷 425-444页

作者： Jie Guo Bingyang Hu yanjun chen Yuanqi Li Yanwen Guo Ling-Qi Yan State Key Lab for Novel Software Technology Nanjing UniversityNanjing 210023China Department of Computer Science UC Santa BarbaraUSA

We consider the scattering of light in participating media composed of sparsely and randomly distributed discrete *** particle size is expected to range from the scale of the wavelength to several orders of magnitude greater,resulting in an appearance with distinct graininess as opposed to the smooth appearance of continuous *** fundamental issue in the physically-based synthesis of such appearance is to determine the necessary optical properties in every local *** these properties vary spatially,we resort to geometrical optics approximation(GOA),a highly efficient alternative to rigorous Lorenz–Mie theory,to quantitatively represent the scattering of a single *** enables us to quickly compute bulk optical properties for any particle size *** then use a practical Monte Carlo rendering solution to solve energy transfer in the discrete participating *** proposed framework is the first to simulate a wide range of discrete participating media with different levels of graininess,converging to the continuous media case as the particle concentration increases.

关键词： light scattering geometrical optics approximation(GOA) discrete participating media volume rendering

Influence of Pseudoelasticity on Mechanical Behavior of TiNi Alloy under Dynamic Impact Loading

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Petroleum Science 2007年第1期4卷 86-89页

作者： Xu Renbo Cui Lishan Zheng yanjun chen Hongling Department of Materials Science and Engineering China University of Petroleum Beijing 102249 China

The mechanical behavior of TiNi alloy and Cr12MoV alloy under dynamic impact loading was investigated with a self-made impact testing system. The real-time contact force was measured with a piezoelectric force sensor and digital signal processing system during impact. Equations for predicting instantaneous velocity anti displacement were presented. The results showed that the TiNi alloy exhibited a plateau of maximum contact force with increasing impact height. At the plateau stage, TiNi alloy in the parent phase can absorb impact energy and keep the maximum contact force nearly identical due to its pseudoelasticity.

关键词： TiNi alloy mechanical behavior contact force impact energy pseudoelasticity

Nanocomposite Polymer Hydrogels Reinforced by Carbon Dots and Hectorite Clay

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Journal of Wuhan University of Technology(Materials Science) 2020年第2期35卷 287-292页

作者： MA Shuai ZHENG Hang chen yanjun ZOU Jincheng ZHANG Chaocan WANG Yifeng School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China

Herein, two nanoparticles with different dimensions, spherical carbon dots (C-dots) and sheetlike hectorite clay, were used as physical crosslinkers to fabricate C-dots-clay-poly(N-isopropylacrylamide)nanocompositehydrogels (coded as C-dots-clay-PNIPAm hydrogels). The mechanical properties, fluorescence features and thermal-responsive properties of the C-dots-clay-PNIPAm hydrogels were evaluated. The experimental results indicate that synergistic effects of C-dots and hectorite clay nanoparticles are able to significantly enhance mechanical properties of the hydrogels. The hydrogels can be stretched up to 1730%with strength as high as 250 kPa when the C-dots concentration is 0.1wt%and the clay concentration is 6wt%. The hydrogels exhibit complete self-healing through autonomic reconstruction of crosslinked network a damaged interface. The hydrogels show favorable thermal-responsive properties with the volume phase transition around 34℃. In addition, the hydrogels are endowed with fluorescence features that are associated with C-dots in the hydrogels. It can be expected that the as-fabricated C-dots-clay-PNIPAm hydrogels are promising for applications in sensors, biomedical carriers and tissue engineering.

关键词： polymer hydrogels nanocomposite reinforcement carbon dots hectorite clay

Optimal Energy-Efficient Operation of a Metro Train on a Long and Steep Downhill Segment

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CSEE Journal of Power and Energy Systems 2023年第6期9卷 2356-2365页

作者： Deqiang He Hanqing Jian yanjun chen Jian Miao Zhixiao Luo Chonghui Ren Lang Zhang the department of State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures Guangxi Key Laboratory of Manufacturing System&Advanced Manufacturing TechnologySchool of Mechanical EngineeringGuangxi UniversityNanning 530004China the department of Guangxi Police College Nanning 530028China. the department of Nanning Rail Transit Co. Ltd.Nanning 530029China

Because the standard four-stage operation and con-trol strategy cannot fully utilize the gravitational potential energy of a train operating on a long and steep downhill segment,this paper further improves the method for train operation and control *** improved operation includes three stages of acceleration,coasting-speed limit cruising,and *** the speed limit,time limit,and distance limit as the constraints,the coasting condition switching point,braking condition switching point,traction coefficient,and braking force coefficient are used as the decision ***,an improved train traction energy consumption model is constructed,and an improved differential evolution algorithm is designed to solve this *** improved method is used to simulate two long and steep downhill segments of the Nanning *** results show that the improved method can meet the requirements of speed limit,time limit,and distance *** with the standard four-stage operation,the improved train operation and control strategy can reduce train energy consumption by more than 40%on the two long and steep downhill segments;compared with other similar algorithms,the improved algorithm is more suitable for solving the model.

关键词： Energy-efficient operation improved differential evolution algorithm long and steep downhill segment metro train

Combination of Silica Sol and Potassium Silicate via Isothermal Heat Conduction Microcalorimetry

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Chinese Journal of Chemistry 2011年第2期29卷 356-362页

作者： Tian Hebao Zhang Chaocan Liu Peng Li Xi Wu Lili chen yanjun School of Materials Science and Engineering Wuhan University of Technology Wuhan Hubei 430070 China Department of Chemistry School of Sciences Wuhan University of Technology Wuhan Hubei 430070 China

Isothermal heat conduction microcalorimetry was utilized as a novel characterization method to investigate the polymerization processes of silica with both thermodynamic and kinetic parameters when the combination of silica sol and potassium silicate was stirred at temperatures of 25.0, 35.0, and 45.0 ℃. The silica polymerization was characterized by the greater enthalpy change at each higher temperature and by the reaction orders of the silica sol and potassium silicate, which varied rapidly, instantaneously, and constantly from low to high all the time, up and down in an alternate manner. When the reaction order of the silica sol and potassium silicate was 3.0, the maximum rate constant occurred at 25.0℃ （k= 1.22 × 10 ^-4 mol-2·dm6·s-1）. The two temperature regions （25.0-35.0 ℃ region with a faster rate and 35.0-45.0℃ region with a lower rate） reflected a two-stage oligomerization of silica monomers with different oligomers formed in a two-step anionic mechanism. The measurements of particle size and pH value showed that the colloidal particles in the mixed silica sol and potassium silicate first dissolved, then ＂active＂ silica in the potassium silicate redeposited to make a distinct particle size distribution （Z-average size, 33.0-14.9 nm at 25.0 ℃） influenced both by pH value （9.82--11.97 at 25.0 ℃） and the mass fraction （53, 65, 75, and 85 mass/%） of the silica sol in the mixture. The processes of combination of the silica sol and potassium silicate did not result from acid-base neutralization reactions but from a complex polymerization of the ＂active＂ silica components which relate to silica monomers oligomerization with heat evolved （the total enthalpy changes, 1.6234-3.3882 J）.

关键词： silica sol silicates nanoparticles microcalorimetry thermodynamics kinetics

Molecular studies of cellulose synthase supercomplex from cotton fiber reveal its unique biochemical properties

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Science China(Life Sciences) 2022年第9期65卷 1776-1793页

作者： Xingpeng Wen Yufeng Zhai Li Zhang yanjun chen Zhiyuan Zhu Gang chen Kun Wang Yuxian Zhu Institute for Advanced Studies Wuhan UniversityWuhan 430072China Hubei Hongshan Laboratory Wuhan 430070China College of Life Sciences Wuhan UniversityWuhan 430072China School of Physical Science and Technology ShanghaiTech UniversityShanghai 201210China

Cotton fiber is a highly elongated and thickened single cell that produces large quantities of cellulose,which is synthesized and assembled into cell wall microfibrils by the cellulose synthase complex(CSC).In this study,we report that in cotton(Gossypium hirsutum)fibers harvested during secondary cell wall(SCW)synthesis,GhCesA 4,7,and 8 assembled into heteromers in a previously uncharacterized 36-mer-like cellulose synthase supercomplex(CSS).This super CSC was observed in samples prepared using cotton fiber cells harvested during the SCW synthesis period but not from cotton stem tissue or any samples obtained from ***-out of any of GhCesA 4,7,and 8 resulted in the disappearance of the CSS and the production of fiber cells with no SCW *** fiber CSS showed significantly higher enzyme activity than samples prepared from knock-out cotton *** found that the microfibrils from the SCW of wild-type cotton fibers may contain 72 glucan chains in a bundle,unlike other plant materials ***4,7,and 8 restored both the dwarf and reduced vascular bundle phenotypes of their orthologous Arabidopsis mutants,potentially by reforming the CSC *** complementation was not observed when non-orthologous CesA genes were used,indicating that each of the three subunits is indispensable for CSC formation and for full cellulose synthase *** of cotton CSS will increase our understanding of the regulation of SCW biosynthesis.

关键词： cotton fiber cellulose synthase supercomplex(CSS) GhCesA 36-mer-like SCW 72 chain model microfibril

Probing the structure of multi-center molecules with odd–even high harmonics

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Chinese Physics B 2018年第5期27卷 274-280页

作者： Ning Su Shujuan Yu Weiyan Li Shiping Yang yanjun chen College of Physics and Information Technology Shaan'xi Normal UniversityXi'an 710119China College of Physics and Information Engineering Hebei Normal UniversityShijiazhuang 050024China School of Mathematics and Science Hebei GEO UniversityShijiazhuang 050031China

We study high-order harmonic generation(HHG)from multi-center asymmetric linear molecules numerically and *** simulations show that odd and even HHG spectra of the asymmetric multi-center system respond differently to the change of the molecular ***,when the internuclear distances between these nuclei of the molecule have a small change,the odd spectra usually do not change basically,but the even spectra differ *** on this phenomenon,a simple procedure is proposed to probe the positions of these nuclei with odd–even *** results shed light on attosecond probing of the structure of multi-center molecules using HHG.

关键词： odd-even harmonics multi-center asymmetric molecules molecular structure