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Nano Research 2025年第1期18卷 508-519页

作者： Ke Jiang Zhi chen Ji Yu chen zheng Shan Huang Ming Wang Chongqing Key Laboratory of Soft-Matter Material Manufacturing School of Chemistry and Chemical EngineeringSouthwest UniversityChongqing 400715China School of Mechanics Civil Engineering and ArchitecturesNorthwestern Polytechnical UniversityXi’an 710072China Jieyang Branch of Chemistry and Chemical Engineering Guangdong Laboratory(Rongjiang Laboratory) Jieyang 515200China

Herein,the electromagnetic shielding performance of surface concave-convex(SC)and zig-zag micro-arrays was studied by using a simulation prediction and a three-dimensional(3D)printing custom ***,surface stripe concaveconvex(SSC)and surface cylindrical concave-convex(SCC)micro-arrays with or without zig-zag micro-arrays are designed,and their shielding performance is simulated in multi-bands(C-,X-band).The multiwalled carbon nanotubes/polydimethylsiloxane composites(MWCNT/PDMS)with different SC structures and different electrical conductivity are molded in acrylonitrile-butadiene-styrene copolymer(ABS)molds which are printed by a 3D *** results show that the electromagnetic interference shielding effectiveness(EMI SE)of the samples can be enhanced by constructing the SC micro-arrays with zig-zag micro-arrays,and improving with the increase of conductivity and *** addition,the shielding mechanism of the SC-MWCNT/PDMS composites is investigated and discussed by an electromagnetic simulation.

关键词： surface micro-arrays electrical properties electromagnetic interference(EMI)shielding three-dimensional(3D)printing

Linear and non-linear pseudocapacitances with or without diffusion control

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Progress in Natural Science:Materials International 2021年第6期31卷 792-800页

作者： George zheng chen Department of Chemical and Environmental Engineering and Advanced Materials Research Group Faculty of Engineering University of Nottingham

Pseudocapacitance is an important reversible charge storage mechanism in many electrode materials. Although the concept was first proposed in early 1960s, it has been more widely studied following the observation of rectangular cyclic voltammograms(CVs) when testing some transition metal oxides and electronically conducting polymers, and the association with supercapacitor. However, interpretation of pseudocapacitance is inconsistent in the literature. Although all agree that materials are pseudocapacitive if they undergo Faradaic reactions and exhibit rectangular CVs, some have regarded any surface confined Faradaic reactions which may present non-rectangular or even peak-shaped CVs to be pseudocapacitive. In the case of rectangular CVs, the amount of charge stored in the electrode is a linear function of the electrode potential, whilst for non-rectangular or peakshaped CVs, the relationship is non-linear. It is shown in this article that only linear pseudocapacitance is of relevance to supercapacitor, but non-linear pseudocapacitance may find applications in rechargeable battery and supercapattery. Further, it is clarified that the equation i = kv + kvis useful in analysis of electrode kinetics in terms of surface confinement and diffusion control. However, this kinetic equation is blind to the thermodynamically determined charge storage mechanisms as shown by experimental evidence, and should not be used to differentiate non-capacitive Faradaic processes from pseudocapacitance, either linear or non-linear.

关键词： Pseudocapacitance Cyclic voltammetry Galvanostatic charging and discharging Supercapacitor Rechargeable battery Supercapattery

Ignition enhancement of ethylene/air by NO_x addition

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Chinese Journal of Aeronautics 2013年第4期26卷 876-883页

作者： Guo Peng chen zheng State Key Laboratory for Turbulence and Complex Systems College of Engineering Peking University

Recently, non-equilibrium plasma assisted combustion （PAC） has been found to be promising in reducing the ignition delay time in hypersonic propulsion system. NO x produced by non-equilibrium plasma can react with intermediates during the fuel oxidation process and thereby has influence on the combustion process. In this study, the effects of NO x addition on the ignition process of both the homogeneous ethylene/air mixtures and the non-premixed diffusion layer are examined numerically. The detailed chemistry for ethylene oxidization together with the NO x sub-mechanism is included in the simulation. Reaction path analysis and sensitivity analysis are conducted to give a mechanistic interpretation for the ignition enhancement by NO x addition. It is found that for both the homogenous and non-premixed ignition processes at normal and elevated pressures, NO 2 addition has little influence on the ignition delay time while NO addition can significantly promote the ignition process. The ignition enhancement is found to be caused by the promotion in hydroxyl radical production which quickly oxidizes ethylene. The promotion in hydroxyl radical production by NO addition is achieved in two ways：one is the direct production of OH through the reaction HO2＋NO = NO2＋OH, and the other is the indirect production of OH through the reactions NO＋O2=NO2＋O and C2H4＋O = C2H3＋OH. Moreover, it is found that similar to the homogeneous ignition process, the acceleration of the diffusion layer ignition is also controlled by the reaction HO2＋NO = NO2＋OH.

关键词： Ethylene/air Ignition enhancement NO x addition Reaction path analysis Sensitivity analysis

Time-optimal guidance for intercepting moving targets with impact-angle constraints

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Chinese Journal of Aeronautics 2022年第7期35卷 157-167页

作者： Yuan zheng zheng chen Xueming SHAO Wenjie ZHAO School of Aeronautics and Astronautics Zhejiang UniversityHangzhou 310027China State Key Laboratory of Fluid Power and Mechatronic Systems Zhejiang UniversityHangzhou 310027China

The minimum-time path for intercepting a moving target with a prescribed impact angle is studied in the *** candidate paths from Pontryagin’s maximum principle are synthesized,so that each candidate is related to a zero of a real-valued *** is found that the real-valued functions or their first-order derivatives can be converted to polynomials of at most fourth *** a result,each candidate path can be computed within a constant time by embedding a standard polynomial solver into the typical bisection *** control strategy along the shortest candidate eventually gives rise to the time-optimal guidance ***,the developments of the paper are illustrated and verified by three numerical examples.

关键词： Dubins vehicle Guidance law Minimum-time path Optimal guidance Path planning

Asymmetric catalytic anhydride openings via carbon-based nucleophiles

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Chinese Chemical Letters 2014年第1期25卷 1-8页

作者： chen zheng Fen-Er chen Department of Chemistry Fudan University

The asymmetric desymmetrization of cyclic anhydrides via the addition of carbon-based nucleophiles has been the focus of considerable levels of interest because it leads to optically active products. Over the past 20 years, a variety of different catalytic asymmetric alkylation reactions have been developed for the desymmetrization of cyclic anhydrides using different metal reagents as nucleophiles and using chiral ligands. The purpose of this review is to provide an overview of significant developments in this field. ~ 2013 Fen-Er chen. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

关键词： Cyclic anhydrides Carbon-based nucleophiles Chiral ligands Asymmetric catalysis Metal reagents

Plasticity of male germline stem cells and their applications in reproductive and regenerative medicine

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Asian Journal of Andrology 2015年第3期17卷 367-372页

作者： zheng chen zheng Li Zuping He State Key Laboratory of Oncogenes and Related Genes Renji-Med X Clinical Stem Cell Research Center Ren Ji Hospital School of Medicine Shanghai Jiao Tong University Shanghai Institute of Cancer Shanghai 200127 China Department of Urology Shanghai Human Sperm Bank Shanghai Institute of Andrology Ren Ji Hospital School of Medicine Shanghai Jiao Tong University Shanghai 200001 China Shanghai Key Laboratory of Assisted Reproduction and Reproductive Genetics Shanghai 200127 China Shanghai Key Laboratory of Reproductive Medicine Shanghai 200025 China

Spermatogonial stem cells （SSCs）, also known as male germline stem cells, are a small subpopulation of type A spermatogonia with the potential of self-renewal to maintain stem cell pool and differentiation into spermatids in mammalian testis. SSCs are previously regarded as the unipotent stem cells since they can only give rise to sperm within the seminiferous tubules. However, this concept has recently been challenged because numerous studies have demonstrated that SSCs cultured with growth factors can acquire pluripotency to become embryonic stem-like cells. The in vivo and in vitro studies from peers and us have clearly revealed that SSCs can directly transdifferentiate into morphologic, phenotypic, and functional cells of other lineages. Direct conversion to the cells of other tissues has important significance for regenerative medicine. SSCs from azoospermia patients could be induced to differentiate into spermatids with fertilization and developmental potentials. As such, SSCs could have significant applications in both reproductive and regenerative medicine due to their unique and great potentials. In this review, we address the important plasticity of SSCs, with focuses on their self-renewal, differentiation, dedifferentiation, transdifferentiation, and translational medicine studies.

关键词： differentiation direct transdifferentiation pluripotency self-renewal spermatogonial stem cells

Asymptotic analysis of outwardly propagating spherical flames

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Acta Mechanica Sinica 2012年第2期28卷 359-366页

作者： Yun-Chao Wu zheng chen State Key Laboratory for Turbulence and Complex SystemsDepartment of Mechanics and Aerospace Engineering Department of Aeronautics and AstronauticsCollege of EngineeringPeking University100871 BeijingChina

Asymptotic analysis is conducted for outwardly propagating spherical flames with large activation energy. The spherical flame structure consists of the preheat zone, reaction zone, and equilibrium zone. Analytical solutions are separately obtained in these three zones and then asymp- totically matched. In the asymptotic analysis, we derive a correlation describing the spherical flame temperature and propagation speed changing with the flame radius. This cor- relation is compared with previous results derived in the limit of infinite value of activation energy. Based on this correla- tion, the properties of spherical flame propagation are inves- tigated and the effects of Lewis number on spherical flame propagation speed and extinction stretch rate are assessed. Moreover, the accuracy and performance of different mod- els used in the spherical flame method are examined. It is found that in order to get accurate laminar flame speed and Markstein length, non-linear models should be used.

关键词： Propagating spherical flames Asymptotic anal- ysis Lewis number Stretch rate

Energy-saving and accurate motion control of a hydraulic actuator with uncertain negative loads

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Chinese Journal of Aeronautics 2021年第5期34卷 253-264页

作者： Bobo HELIAN zheng chen Bin YAO State Key Laboratory of Fluid Power and Mechatronic Systems Zhejiang UniversityHangzhou 310027China Ocean College Zhejiang UniversityZhoushan 316021China School of Mechanical Engineering Purdue UniversityWest LafayetteIN 47907USA

Pump controlled hydraulic actuators are wildly used in the aerospace industry owing to the advantages of energy-saving and integrated *** loads may occur to actuators due to external force loads or the inertial force when the actuator decelerates *** negative load working conditions may cause cavitation,actuator vibration,and even instability to the motion control if the actuator is without sufficient meter-out *** types of hydraulic configuration schemes have been proposed to deal with negative loads of hydraulic ***,few of them can simultaneously achieve energy saving and high control *** study proposes an energy-saving and accurate motion tracking strategy for a hydraulic actuator with uncertain negative *** actuator’s motion is driven by a servomotor pump,which gives full play to the advantage of *** meter-out pressure is controlled by proportional valves to provide the optimized meter-out *** nonlinear adaptive robust control law is designed,which guarantees the control stability and achieve high tracking *** integrated direct/indirect adaptation law obtains satisfactory parameter estimations and model compensation for asymptotic motion *** experiments under different working conditions were performed to validate the advantages of the proposed control strategy.

关键词： Adaptive robust control Hydraulic actuator Meter-out throttling Motion control Servomotor pump

Evolution of microstructure and texture of cold-drawn polycrystalline Ag with low stacking fault energy

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Science China(Technological Sciences) 2015年第7期58卷 1146-1153页

作者： MA XiaoGuang chen Jian chen zheng YAN Wen State Key Laboratory of Solidification Processing School of Materials Science and Engineering Northwestern Polytechnical University School of Materials Science and Chemical Engineering Xi'an Technological University

The evolution of microstructure and texture for drawn polycrystalline Ag was investigated by transmission electron microscopy and electron backscattering *** results show that there are deformation twins and some un-tangled discrete dislocations at low *** the strain is increased to 0.58,a lot of high density dislocation walls and microbands come into *** the same time,some twins lose the twinning relationship of 60°.At a strain of 0.94,both dislocation boundaries and twin boundaries will rotate to the axis direction of wires and the shear bands start to *** the strain is higher than 1.96,most of the boundaries are parallel to the drawn *** analysis indicates that with the strain increasing,the volume fraction of complex texture component decreases,butandtexture components ***,the variation in the volume fraction of each texture component as strains is not evident when the strains are higher than *** polycrystalline Ag with low stacking fault energy,complex texture components are easily formed.

关键词： polycrystalline Ag cold-drawn deformation microstructure deformation twinning stacking fault energy

Nanoporous Versus Nanoparticulate Carbon-Based Materials for Capacitive Charge Storage

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Energy & Environmental Materials 2020年第3期3卷 247-264页

作者： Yao chen Xiaoyue Hao George zheng chen The State Key Laboratory of Refractories and Metallurgy College of Materials and MetallurgyWuhan University of Science and TechnologyWuhan 430081China Department of Chemical and Environmental Engineering Faculty of EngineeringUniversity of NottinghamNottingham NG27RDUK Department of Chemical and Environmental Engineering Faculty of Science and EngineeringUniversity of Nottingham Ningbo ChinaNingbo 315100China

This article reviews recent progresses in the preparation and supercapacitor applications of selected nanoporous and nanoparticulate carbon-based materials,namely activated carbons,graphenes and carbon nanotubes and their composites with redox *** processing steps and graphitization are crucial for making activated *** liquid processing and furnace technology are mainly used in graphene preparation,including curlization,electrolyte incorporation,self-propagating hightemperature synthesis,molten salt technology,and flash Joule *** deposition and new dispersion methods open better routes to making carbon nanotube composites of high charge *** storage mechanisms are compared with attention to the facts that activated carbons store ionic charges largely in desirable nanopores,while the ion-accessible external surfaces of nanoparticulates affect the storage performance of graphenes and composites of carbon ***,it is explained that pseudocapacitance can result from partial(or zone)delocalization of electrons in graphenes caused by hetero atoms,oxygen in particular.A highlight of this review is on novel molten salt densified holey graphene that has enabled a high specific energy of 618 Wh kg-1 in supercapattery.

关键词： activated carbon carbon nanotube electrolyte graphene supercapacitor