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Particuology 2017年第1期15卷 92-101页

作者： Bellamarie Ludwia Jennifer L. Gray Applied research Laboratory The Pennsylvania State University North Atherton Street State College PA 16801 USA Materials research Institute The Pennsylvania State University USA

Aluminum particles were exposed to gaseous polydimethylsiloxane （PDMS） to produce a hydropho- bic surface coating for enhanced flow and fluidity. Surface retention of the intact PDMS was confirmed through infrared and X-ray photoelectron spectroscopy. Transmission electron microscopy was used to image cross-sections of the treated particles and energy dispersive spectroscopy element maps demon- strated the presence of a surface layer consisting of silicon and oxygen. Density measurements provided evidence for improvements in the Hausner ratio and Carr index of the PDMS-treated aluminum, indicating a reduction in inter-particulate cohesion through increased bulk density. Stability, compressibility, shear, aeration, and permeability of the particles were assessed by powder rheometer. The compressibility was reduced by approximately 32% following surface treatment, revealing a reduction in void space, while Mohr＇s circle analysis and shear testing determined that the extrapolated cohesion value was reduced by approximately 53% and the flow factor at 6 kPa was doubled. Aeration testing showed that the air velocity required to obtain a fluidized bed was on the order of 0.35 mm/s for the treated powder, whereas the raw powder could not be uniformly fluidized. PDMS may be a viable option for the large-scale treatment of aluminum powder for flow applications.

关键词： Aluminum powder Polydimethylsiloxane X-ray photoelectron spectroscopy Diffuse reflectance infrared Fourier transform spectroscopy Flowability FT4 powder rheometer

Optomechanical control of stacking patterns of h-BN bilayer

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Nano research 2019年第10期12卷 2634-2639页

作者： Haowei Xu Jian Zhou Yifei Li Rafael Jaramillo Ju Li Department of Nuclear Science and Engineering Massachusetts Institute of TechnologyCambridgeMA 02139USA Center for Advancing Materials Performance from the Nanoscale State Key Laboratory for Mechanical Behavior of MaterialsXi'an Jiaotong UniversityXi'an 710049China Department of Materials Science and Engineering Massachusetts Institute of TechnologyCambridgeMA 02139USA

Few-layer two-dime nsion al(2D)materials usually have differe nt(meta)-stable stacking patterns,which have distinet electronic and optical *** spired by optical tweezers,we show that a laser with selected freque ncy can modify the gen eralized stacking-fault en ergy Iandscape of bilayer hexagonal boron nitride(BBN),by coupling to the slip-dependent dielectric ***,BBN can be reversibly and barrier-freely switched betwee n its stacking patter ns in a controllable *** simulate the dyn amics of the stacki ng transition with a simplified equati on of motion and dem on strate that it happe ns at picosec ond *** one layer of BBN has a nearly-free surface boundary condition,BBN can be locked in its metastable stacking modes for a long *** a fast,reversible and non-volatile transition makes BBN a potential media for data storage and optical phase mask.

关键词： phase change materials two-dimensional materials opto-mechanics density functional theory

Practical evaluation of the drag of a ship for design and optimization

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Journal of Hydrodynamics 2013年第5期25卷 645-654页

作者： YANG Chi HUANG Fuxin NOBLESSE Francis Center for Computational Fluid DynamicsGeorge Mason University State Key Laboratory of Ocean Engineering and School of naval Architecture Ocean and Civil EngineeringShanghai Jiao Tong University

We consider two major components of the drag of a ship, the ＂friction drag＂ and the ＂wave drag＂, that are related to viscous friction at the hull surface and wavemaking, and mostly depend on the Reynolds number and the Froude number, respectively. We also consider the influence of sinkage and trim, viscosity, and nonlinearities on the drag. The sum of the friction drag given by the classical ITTC friction formula and the wave drag predicted by the modification, called Neumann-Michell （NM） theory, of the classical Neumann-Kelvin theory of ship waves is found to be within about 10% of experimental drag measurements for four ship hulls for which theoretical predictions and experimental measurements are compared. The sum of the ITTC friction drag and the NM wave drag can then be expected to yield realistic practical estimates that can be useful for routine applications to design and hull- form optimization of a broad range of displacement ships. Furthermore, we note several simple extensions of this highly simplified approach that can be expected to significantly improve accuracy.

关键词： friction drag wave drag Neumann-Michell (NM) theory sinkage and trim nonlinear effects

Pressure-dependent phase transition of 2D layered silicon telluride(Si2le3)and manganese intercalated silicon telluride

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Nano research 2019年第9期12卷 2373-2377页

作者： Virginia L. Johnson Auddy Anilao Kristie J. Koski Department of Chemistry University of CaliforniaDavisDavisCA 95616USA

Two-dimensional(2D)layered silicon telluride(SizTes)nanocrystals were compressed to 12 GPa using diamond anvil cell *** measurements show a color change from transparent red to opaque black indicating a semiconductor-to-metal phase *** scattering was used to observe the stiffening of the crystal lattice and subsequent phase behavior.A possible phase transition was *** 9.5±0.5 GPa evidenced by the disappearance of the Atg stretching *** was intercalated with elemental manganese to^1 at.%.Intercalation lowers the pressure of the proposed phase transition to 7.5±1 *** modes show both phonon stiffening and phonon softening,suggesting negative linear *** results provide fundamental insight into the high-pressure optical phonon behavior of silicon telluride and illuminate how a specific electron-donating intercalant can chemically alter pressure-dependent optical phonon behavior.

关键词： silicon telluride Si2Te3 high pressure diamond anvil cell two-dimensional(2D)layered material

Spatio-temporal breather dynamics in microcomb soliton crystals

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Light(Science & Applications) 2024年第11期13卷 2620-2633页

作者： Futai Hu Abhinav Kumar Vinod Wenting Wang Hsiao-Hsuan Chin James F.McMillan Ziyu Zhan Yuan Meng Mali Gong Chee Wei Wong Fang Lu Mesoscopic Optics and Quantum Electronics Laboratory University of CaliforniaLos AngelesCAUSA State Key Laboratory of Precision Measurement Technology and Instruments Tsinghua UniversityBeijingChina

Solitons,the distinct balance between nonlinearity and dispersion,provide a route toward ultrafast electromagnetic pulse shaping,high-harmonic generation,real-time image processing,and RF photonic *** we uniquely explore and observe the spatio-temporal breather dynamics of optical soliton crystals in frequency microcombs,examining spatial breathers,chaos transitions,and dynamical deterministic switching–in nonlinear measurements and *** understand the breather solitons,we describe their dynamical routes and two example transitional maps of the ensemble spatial breathers,with and without chaos *** elucidate the physical mechanisms of the breather dynamics in the soliton crystal microcombs,in the interaction plane limit cycles and in the domain-wall understanding with parity symmetry breaking from third-order *** present maps of the accessible nonlinear regions,the breather frequency dependences on third-order dispersion and avoided-mode crossing strengths,and the transition between the collective breather spatio-temporal *** range of measurements matches well with our first-principles theory and nonlinear *** image these soliton ensembles and their breathers,we further constructed panoramic temporal imaging for simultaneous fast-and slow-axis two-dimensional mapping of the *** the phasedifferential sampling,we present two-dimensional evolution maps of soliton crystal breathers,including with defects,in both stable breathers and breathers with *** fundamental studies contribute to the understanding of nonlinear dynamics in soliton crystal complexes,their spatio-temporal dependences,and their stability-existence zones.

关键词： theory. soliton dynamics

Nanosecond mid-infrared pulse generation via modulated thermal emissivity

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Light(Science & Applications) 2019年第1期8卷 724-731页

作者： Yuzhe Xiao Nicholas A.Charipar Jad Salman Alberto Pique Mikhail A.Kats Department of Electrical and Computer Engineering University of Wisconsin-MadisonMadisonWI 53706USA naval research Laboratory 4555 Overlook Ave.SWWashingtonDC 20375USA Department of Materials Science and Engineering University of Wisconsin-MadisonMadisonWI 53706USA Department of Physics University of Wisconsin-MadisonMadisonWI 53706USA

We demonstrate the generation of nanosecond mid-infrared pulses via fast modulation of thermal emissivity enabled by the absorption of visible pump pulses in unpatterned silicon and gallium *** free-carrier dynamics in these materials result in nanosecond-scale modulation of thermal emissivity,which leads to nanosecond pulsed thermal *** our knowledge,the nanosecond thermal-emissivity modulation in this work is three orders of magnitude faster than what has been previously *** also indirectly observed subnanosecond thermal pulses from hot carriers in *** experiments are well described by our multiphysics *** method of converting visible pulses into the mid infrared using modulated emissivity obeys different scaling laws and can have significant wavelength tunability compared to approaches based on conventional nonlinearities.

关键词： pump emissivity thermal

Effect of particle size distribution on particle based composite anode models

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Acta Mechanica Sinica 2013年第3期29卷 357-369页

作者： Vaughan L.Thomas 148. 3400 Charles Street 031 Latrobe Hall Baltimore Maryland 21218 USA

Particle based models of composite anodes are useful tools for exploring the behavior of SOFC systems. As part of our efforts to develop models for understanding fuel cells, we have been building models of Ni-YSZ composite anodes using experimentally measured particle size distributions. The objectives of this study were to characterize the percolation threshold and conductivity of these models in comparison to simpler mono dispersed and biphasic particle size distributions from the literature. We found that the average values for the onset of percolation and the measured conductivity of the models with experimentally measured particle size distributions are similar to those for the simple distributions and the experimentally measured distributions. For all of the configurations evaluated, the onset of percolation in the Nickel phase occurred at a solid fraction of Nickel between 20% and 25%. This corresponded almost exactly to the point at which the coordination number between Nickel phase particles reached 2.2. The significant finding was that the variation in the value for the conductivity, as measured by the standard deviation of the results, was several orders of magnitude higher than for the simpler systems. We explored the validity of our assumptions, specifically the assumption of random particle placement, by building a particle model directly from FIB-SEM data. In this reconstruction, it was clear that the location of particles was not random. Particles of the same type and size had much likelihood of contact higher than would indicated by random location.

关键词： Resistor network Composite electrodes 3D particle packing Solid oxide fuel cells

Technical cross-fertilization between terrestrial microgrids and ship power systems

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Journal of Modern Power Systems and Clean Energy 2016年第2期4卷 161-179页

作者： Robert E.HEBNER Fabian M.URIARTE Alexis KWASINSKI Angelo L.GATTOZZI Hunter B.ESTES Asif ANWAR Pietro CAIROLI Roger A.DOUGAL Xianyong FENG Hung-Ming CHOU Laurence J.THOMAS Manisa PIPATTANASOMPORN Saifur RAHMAN Farid KATIRAEI Michael STEURER M.Omar FARUQUE Mario A.RIOS Gustavo A.RAMOS Mirrasoul J.MOUSAVI Timothy J.MCCOY Center for Electromechanics The University of Texas at AustinAustinTXUSA Department of Electrical and Computer Engineering University of PittsburghPittsburghPAUSA University of South Carolina ColumbiaSCUSA ABB Inc. RaleighNCUSA Texas A&M University College StationTXUSA Lauren Engineers and Constructors Inc.AbileneTXUSA Virginia Tech’s Advanced research Institute ArlingtonVAUSA Quanta Technology Inc.RaleighNCUSA Center for Advanced Power Systems Florida State UniversityTallahasseeFLUSA Universidad de los Andes Bogota´Colombia McCoy Consulting LLCMontrossVAUSA

Aspects of terrestrial microgrids and ship power systems are *** work exposes a variety of technical synergies from these two power systems to effectively advance their *** their overlap allows congruent efforts to target both systems;understanding their differences hinders conflict and redundancy in early-stage *** paper concludes by highlighting how an understanding of both systems can reduce the investment in research resources.

关键词： Microgrid Power systems Ship power systems

STABILITY OF EQUILIBRIA OF NEMATIC LIQUID CRYSTALLINE POLYMERS

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Acta Mathematica Scientia 2011年第6期31卷 2289-2304页

作者： Hong Zhou Hongyun Wang Department of Applied Mathematicsnaval Postgraduate School Monterey CA 93943 USA Department of Applied Mathematics and StatisticsUniversity of California Santa Cruz CA 95064 USA

We provide an analytical study on the stability of equilibria of rigid rodlike nematic liquid crystalline polymers （LCPs） governed by the Smoluchowski equation with the Maier-Saupe intermolecular potential. We simplify the expression of the free energy of an orientational distribution function of rodlike LCP molecules by properly selecting a coordinate system and then investigate its stability with respect to perturbations of orientational probability density. By computing the Hessian matrix explicitly, we are able to prove the hysteresis phenomenon of nematic LCPs： when the normalized polymer concentration b is below a critical value b＊（6.T314863965）, the only equilibrium state is isotropic and it is stable; when b＊〈 b 〈 15/2, two anisotropic （prolate） equilibrium states occur together with a stable isotropic equilibrium state. Here the more aligned prolate state is stable whereas the less aligned prolate state is unstable. When b 〉 15/2, there are three equilibrium states： a stable prolate state, an unstable isotropie state and an unstable oblate state.

关键词： equilibria stability nematic liquid crystalline polymers hysteresis phenomenon

Thermal transports in the MXenes family:Opportunities and challenges

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Nano research 2024年第8期17卷 7700-7716页

作者： Yurui Liu Yue Wu Xinwei Wang Department of Chemical and Biological Engineering Iowa State University618 Bissell AmesIA 50011USA Department of Mechanical Engineering 271 Applied Science Complex II1915 Scholl RoadIowa State UniversityAmesIA 50011USA

The carbides and nitrides of transition metals known as“MXenes”refer to a fast-growing family of two-dimensional materials discovered in *** to their unique nanolayer structure,superior electrical,mechanical,and thermal properties,MXenes have shown great potential in addressing the critical overheating issues that jeopardize the performance,stability,and lifetime of high-energy-density components in modern devices such as microprocessors,integrated circuits,and capacitors,*** outstanding intrinsic thermal conductivity of MXenes has been proved by experimental and theoretical *** MXenes-enabled high thermal conductivity composites incorporated with polymer matrix have also been reported and widely used as thermal management *** the booming heat dissipation demands,MXenes-enabled thermal management material is an extremely valuable and scalable option for modern electronics ***,the fundamental thermal transport mechanisms behind the MXenes family remain *** MXene thermal conductivity disparities between the theoretical prediction and experimental results are still *** better understand the thermal conduction in MXenes and provide more insights for engineering high-performance MXene thermal management materials,in this article,we summarize recent progress on thermal conductive *** essential factors that affect MXenes intrinsic thermal conductivities are tackled,selected MXenes-polymer composites are highlighted,and prospects and challenges are also discussed.

关键词： transition metal carbide(MXene) thermal transport two-dimensional materials thermally conductive composites