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How Reliable Are surface.Tension Data?

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Accounts of Materials Research 2022年第9期3卷 894-899页

作者： Bernette M.Oosterlaken Gijsbertus de With Laboratory of Physical Chemistry Department of Chemical Engineering and ChemistryEindhoven University of Technology5600 MB EindhovenThe Netherlands

surface.Gibbs or Helmholtz)energy is of importance in many areas of science and technology but notoriously difficult to measure.At one time,it was thought that cleavage experiments could yield proper surface.energy values because surface.energy is related to the(reversible)energy needed to create a unit area of surface.As reported in his classic paper,Obreimoff1 was only in a few cases able,after“healing”a cleavage crack,to measure a similar cleavage energy along the same plane as needed in the initial experiment.

关键词： surface. experiment. measure.

Hydrodynamic metasurface.for programming electromagnetic beam scanning on the Azimuth and elevation planes

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Microsystems & Nanoengineering 2022年第2期8卷 217-225页

作者： Aqeel Hussain Naqvi Sungjoon Lim School of Electrical and Electronics Engineering Chung-Ang UniversitySeoul 06974Republic of Korea

The development of multifunctional and reconfigurable metasurface. capable of manipulating electromagnetic waves has created new opportunities for various exciting applications.Extensive efforts have been applied to exploiting active metasurface. with properties that can be controlled by externally controlling active components.However,previous approaches have poor switch isolation,power handling limitations due to nonlinear effects,and complex biasing networks.Therefore,dynamically tunable metasurface. have become a burgeoning field in many research areas.This paper reports a hydrodynamic metasurface.HMS)that can be programmed to realize electromagnetic beam scanning on the azimuth and elevation planes.The proposed HMS platform incorporates four micropumps,each controlling four metasurface.elements via microfluidic channels,built into the HMS base.The proposed platform regulates microfluidic flow through micropumps,causing irregularities in incident wave transmission phase.An HMS was built as a proof of concept,and far-field scanning experiments were performed.Numerical and experimental results verify the feasibility of electromagnetic beam scanning using a hydrodynamic metasurface.This work advances metasurface.research,with very high potential for wide-ranging application and a promising route for replacing bulky cascading active components.

关键词： surface. beam programming

A versatile acoustically active surface.based on piezoelectric microstructures

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Microsystems & Nanoengineering 2022年第3期8卷 51-60页

作者： Jinchi Han Mayuran Saravanapavanantham Matthew R.Chua Jeffrey H.Lang Vadimir Bulovic Department of Electrical Engineering and Computer Science Massachusetts Institute of TechnologyCambridgeMA 02139USA

We demonstrate a versatile acoustically active surface.consisting of an ensemble of piezoelectric microstructures that are capable of radiating and sensing acoustic waves.A freestanding microstructure array embossed in a single step on a flexible piezoelectric sheet of polyvinylidene fluoride(PVDF)leads to high-quality acoustic performance,which can be tuned by the design of the embossed microstructures.The high sensitivity and large bandwidth for sound generation demonstrated by this acoustically active surface.outperform previously reported thin-flm loudspeakers using PVDF,PVDF copolymers,or voided charged polymers without microstructures.We further explore the directivity of this device and its use on a curved surface.In addition,high-fidelity sound perception is demonstrated by the surface.enabling its microphonic application for voice recording and speaker recognition.The versatility,high-quality acoustic performance,minimal form factor,and scalability of future production of this acoustically active surface.can lead to broad industrial and commercial adoption for this technology.

关键词： surface. piezoelectric versatile

Dynamic bifunctional THz metasurface.via dual-mode decoupling

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Photonics Research 2022年第9期10卷 2008-2014页

作者： XUAN CONG HONGXIN ZENG SHIQI WANG QIWU SHI SHIXIONG LIANG JIANDONG SUN SEN GONG FENG LAN ZIQIANG YANG YAXIN ZHANG Terahertz Science and Technology Research Center University of Electronic Science and Technology of ChinaChengdu 610000China College of Materials Science and Engineering Sichuan UniversityChengdu 610065China National Key Laboratory of Application Specific Integrated Circuit Hebei Semiconductor Research InstituteShijiazhuang 050051China Key Laboratory of Nanodevices and Applications Suzhou Institute of Nano-Tech and Nano-Bionics(SINANO)Chinese Academy of SciencesSuzhou 215123China Yangtze Delta Region Institute(HuZhou) University of Electronic Science and Technology of ChinaHuzhou 313001China

Metasurface. have powerful light field manipulation capabilities and have been researched and developed extensively in various fields.With an increasing demand for diverse functionalities,terahertz(THz)metasurface. are also expanding their domain.In particular,integrating different functionalities into a single device is a compelling domain in metasurface..In this work,we demonstrate a functionally decoupled THz metasurface.that can incorporate any two functions into one metasurface.and switch dynamically through external excitation.This proposed metasurface.is formed by the combination of split-ring resonators and phase change material vanadium dioxide(VO_(2)).It operates in the single-ring resonant mode and double-ring resonant mode with varying VO_(2)in insulating and metallic states,respectively.More importantly,the phase modulation is independent in two operating modes,and both cover a 360°cross-polarized phase with efficient polarization conversion.This characteristic makes it obtain arbitrary independent phase information on the metasurface.with different modes to switch dual functions dynamically.Here,we experimentally demonstrate the functions of a tunable focal length and large-angle focus deflection of a THz off-axis parabolic mirror to verify the dual-function switching characteristics of the functionally decoupled metasurface.The functionally decoupled metasurface.developed in this work broadens the way for the research and application of multifunctional modulation devices in the THz band.

关键词： surface. functional resonant

Partial discharge measurement and analysis under lightning impulse superimposed DC voltage in SF6 gas

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High Voltage 2022年第4期7卷 744-752页

作者： Haotian Wang Cong He Ruochen Guo Xuan Meng Wenze Yuan Junhao Li State Key Laboratory of Electrical Insulation and Power Equipment Xi'an Jiaotong UniversityXi'anChina

The presence of lightning impulses(LIs)on the DC waveform can seriously influence the insulation performance of a GIL system.The waveshape can be a superposition of the DC and impulse waveform.In this study,the behaviour of partial discharge(PD)on an epoxy surface.is investigated under DC and LI superimposed voltage in SF6.The lightning impulses with different polarities are superimposed on the epoxy surface.under both positive and negative DC voltages,respectively.Positive lightning impulses are superimposed on a negative DC voltage with a 90%of the partial discharge inception voltage(PDIV)magnitude.The number and amplitude of the PDs are used to evaluate the insulation performance.The experimental results show that the LI with a different polarity applied to DC can excite the PDs on the epoxy surface.The excitation effect of positive LI superimposed on negative DC is more significant.According to the impulse amplitude and PD characteristics,the influence of superimposed LI on PD excitation can be divided into three stages.As the superimposed LI increases,the amplitude of the excited PD increases gradually,while the PD number first increases and then decreases.This study is expected to provide reference for manufacture and protection of power equipment.

关键词： surface. excitation insulation

Transmissive metasurface.for multi-channel and full-polarization modulation of electromagnetic wavefronts

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Photonics Research 2023年第2期11卷 245-251页

作者： LINDA SHAO ZHENFEI LI JIALIN FENG JIN ZHANG HONGYU SHI XUDONG BAI WEIREN ZHU Department of Electronic Engineering Shanghai Jiao Tong UniversityShanghai 200240China School of Information and Communications Engineering Xi’an Jiaotong UniversityXi’an 710049China School of Microelectronics Northwestern Polytechnical UniversityTaicang 215400China

Metasurface. have great potential for flexible manipulation of electromagnetic wave polarizations and wavefronts.Here, we propose a general method for achieving independent wavefront manipulation in a single polarizationmultiplexing transmissive metasurface. As a proof of concept, we design a transmission-type anisotropic metasurface.for independent wavefront manipulation in full-polarization channels. An x-polarized wave transmitted through such a metasurface.could be converted into four outgoing beams with delicately designed polarization states that converge to specific positions for holographic imaging. The measured results are in good agreements with simulated ones, verifying the independent wavefront manipulations with arbitrary polarization conversions.Compared with the existing traditional meta-devices with single-polarization modulation, we achieve polarization-multiplexed metasurface. with mixed polarization and phase control, which can greatly improve the functional richness of the system.

关键词： surface. proof holographic

Abnormal nonlinear optical responses on the surface.of topological materials

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npj Computational Materials 2022年第1期8卷 1045-1052页

作者： Haowei Xu Hua Wang Ju Li Department of Nuclear Science and Engineering Massachusetts Institute of TechnologyCambridgeMA02139USA Department of Materials Science and Engineering Massachusetts Institute of TechnologyCambridgeMA02139USA

The nonlinear optical(NLO)responses of topological materials are under active research.Most previous works studied the surface.and bulk NLO responses separately.Here we develop a generic Green’s function framework to investigate the surface.and bulk NLO responses together.We reveal that the topological surface.can behave disparately from the bulk under light illumination.Remarkably,the photocurrents on the surface.can flow in opposite directions to those in the bulk interior,and the light-induced spin current on the surface.can be orders of magnitude stronger than its bulk counterpart on a per-volume basis.We also study the responses under inhomogeneous field and higher-order NLO effect,which are all distinct on the surface.These anomalous surface.responses suggest that light can be a valuable tool for probing the surface.states of topological materials.Besides,the surface.effects should be prudently considered when investigating the optical properties of topological materials.

关键词： materials. surface. topological

Effects of Magnetic Field on Entropy Generation in Flow and Heat Transfer due to a Radially Stretching surface

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Chinese Physics Letters 2013年第2期30卷 155-159页

作者： Adnan Saeed Butt Asif Ali Department of Mathematics Quaid-I-Azam University 45320Islamabad 44000Pakistan

We investigate the effects of magnetic field on the entropy generation during fluid flow and heat transfer due to the radially stretching surface.The partial differential equations governing the flow and heat transfer phenomenon are transformed into nonlinear ordinary differential equations by using suitable similarity transformations.These equations are then solved by the homotopy analysis method and the shooting technique.The effects of the magnetic field parameter M and the Prandtl number Pr on velocity and the temperature profiles are presented.Moreover,influence of the magnetic field parameter M and the group parameter Br/Ω on the local entropy generation number Ns as well as the Bejan number Be are inspected.It is observed that the magnetic field is a strong source of entropy production in the considered problem.

关键词： technique. surface. entropy

Adatom self-diffusion on Pt (100) surface.by an ad-dimer migrating

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Science China Mathematics 2000年第10期43卷 1108-1113页

作者：庄军刘磊 Department of Physics State Key Joint Laboratory for Materials Modification by Laser Ion and Electron Beams Fudan University Shanghai 200433 China

We study the self-diffusion of adatom on Pt(100) surface.by molecular dynamics. The metal is modeled by the surface.embedded-atom potential. Besides the conventional concerted exchange mechanism, a new exchange mechanism in which an ad-dimer diffuses by a concerted motion of three atoms is observed. The importance is that it could become a dominant diffusion mechanism in some cases.

关键词： self-diffusion exchange mechanism metal surface.