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Seasonal Variability of the Yellow Sea/East China Sea Surface Fluxes and Thermohaline Structure

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Advances in Atmospheric Sciences 2005年第1期22卷 1-20页

作者： Peter CHU 陈玉春 Akira KUNINAKA naval Ocean Analysis and Prediction Laboratory Institute of Cold and Arid Environment and Engineering

We use the U.S. Navy's Master Oceanographic Observation Data Set (MOODS) forthe Yellow Sea/ East China Sea (YES) to investigate the climatological water mass features and theseasonal and non-seasonal variabilities of the thermohaline structure, and use the ComprehensiveOcean-Atmosphere Data Set (COADS) from 1945 to 1989 to investigate the linkage between the fluxes(momentum, heat, and moisture) across the air-ocean interface and the formation of the water massfeatures. After examining the major current systems and considering the local bathymetry and watermass properties, we divide YES into five regions: East China Sea (ECS) shelf, Yellow Sea (YS) Basin,Cheju bifurcation (CB) zone, Taiwan Warm Current (TWC) region, Kuroshio Current (KC) region. Thelong term mean surface heat balance corresponds to a heat loss of 30 W m^(-2) in the ESC and CBregions, a heat loss of 65 W m^(-2) in the KC and TWC regions, and a heat gain of 15 W m^(-2) in theYS region. The surface freshwater balance is defined by precipitation minus evaporation. The annualwater loss from the surface for the five subareas ranges from 1.8 to 4 cm month^(-1). The freshwater loss from the surface should be compensated for from the river run-off. The entire watercolumn of the shelf region (ECS, YS, and CB) undergoes an evident seasonal thermal cycle withmaximum values of temperature during summer and maximum mixed layer depths during winter. However,only the surface waters of the TWC and KC regions exhibit a seasonal thermal cycle.. We also foundtwo different relations between surface salinity and the Yangtze River run-off, namely, out-of-phasein the East China Sea shelf and in-phase in the Yellow Sea. This may confirm an earlier study thatthe summer fresh water discharge from the Yangtze River forms a relatively shallow, low salinityplume-like structure extending offshore on average towards the northeast.

关键词： yellow sea east China sea surface net heat flux fresh water flux seasonalvariability thermohaline structure

An overview of simulation-based hydrodynamic design of ship hull forms

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Journal of Hydrodynamics 2016年第6期28卷 947-960页

作者： Chi YANG Fuxin HUANG Center for Computational Fluid Dynamics George Mason University

This review paper presents an overview of simulation-based hydrodynamic design optimization of ship hull forms. A computational tool that is aimed to accomplishing early-stage simulation-based design in terms of hydrodynamic performance is discussed in detail. The main components of this computational tool consist of a hydrodynamic module, a hull surface modeling module, and an optimization module. The hydrodynamic module includes both design-oriented simple CFD tools and high-fidelity CFD tools. These integrated CFD tools are used for evaluating hydrodynamic performances at different design stages. The hull sur- face modeling module includes various techniques for ship hull surface representation and modification. This module is used to automatically produce hull forms or modify existing hull forms in terms of hydrodynamic performance and design constraints. The optimization module includes various optimization algorithms and surrogate models, which are used to determine optimal designs in terms of given hydrodynamic performance. As an illustration of the computational tool, a Series 60 hull is optimized for reduced drag using three different modification strategies to outline the specific procedure for conducting simulation-based hydrodynamic design of ship hull forms using the present tool. Numerical results show that the present tool is well suited for the hull form design optimization at early design stage because it can produce effective optimal designs within a short period of time.

关键词： simulation based design ship hull form optimization radial basis function NURBS hydrodynamics

The effect of gas phase polydimethylsiloxane surface treatment of metallic aluminum particles： Surface characterization and flow behavior

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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

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

Ultrathin wavy Rh nanowires as highly effective electrocatalysts for methanol oxidation reaction with ultrahigh ECSA

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Nano research 2019年第1期12卷 211-215页

作者： Xiaoyang Fu Zipeng Zhao Chengzhang Wan Yiliu Wang Zheng Fan Frank Song Bocheng Cao Mufan Li Wang Xue Yu Huang Xiangfeng Duan Department of Chemistry and Biochemistry University of CaliforniaLos AngelesLos AngelesCalifornia 90095USA Department of Materials Science and Engineering University of CaliforniaLos AngelesLos AngelesCalifornia 90095USA California Nanosystems Institute University of CaliforniaLos AngelesLos AngelesCalifornia 90095USA

Direct methanol fuel cells (DMFCs) have received tremendous research interests because of the facile storage of liquid methanol ***,the DMFC today is severely plagued by the poor kinetics and rather high overpotential in methanol oxidation reaction (MOR).Here we report the investigation of the ultrathin Rh wavy nanowires as a highly effective MOR *** show that ultrathin wavy Rh nanowires can be robustly synthesized with 2-3 nm *** studies show a current peak at the potential of 0.61 V *** hydrogen electrode (RHE),considerably lower than that of Pt based catalysts (~ 0.8-0.9 V ***).Importantly,with ultrathin diameters and favorable charge transport,the Rh nanowires catalysts exhibit an ultrahigh electrochemically active surface area determined from CO-stripping (ECSAco) of 144.2 m2/g,far exceeding that of the commercial Rh black samples (20 m2/g).Together,the Rh nanowire catalysts deliver a mass activity of 722 mA/mg at 0.61 V,considerably higher than many previously reported electrocatalysts at the same *** chronoamperometry studies also demonstrate good stability and CO-tolerance compared with the Rh black control sample,making ultrathin Rh wavy nanowires an attractive electrocatalyst for MOR.

关键词： rhodium nanowires electrocatalysis methanol oxidation reaction (MOR)

Hydrodynamic optimization of a triswach

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Journal of Hydrodynamics 2014年第6期26卷 856-864页

作者： YANG Chi HUANG Fuxin KIM Hyunyul School of Physics Astronomy and Computational Sciences George Mason University NAVATEK South KingstownRI 02879USA

A new methodology for hydrodynamic optimization of a Tri SWACH is developed, which considers not only the positions of the side hulls but also the shape of the side hulls. In order to account for the strong near-field interference effects between closely-spaced multihulls, an integrated hydrodynamic computational tool that consists of a potential-flow based simple CFD tool and an Euler/RANS/Navier-Stokes based advanced CFD tool has been further developed and integrated into a practical multiobjective hydrodynamic optimization tool. The other components of this hydrodynamic optimization tool consist of a hull shape representation and modification module and an optimization module. This enhanced multi-objective hydrodynamic optimization tool has been applied to the hydrodynamic design optimization of the Tri SWACH for reduced drag by optimizing the side hulls only. A new methodology is developed to optimize side hull forms so that the Tri SWACH has a minimal drag for a wide speed range and for various side hull positions. Two sets of the side hulls are developed and used for the design of two optimal Tri SWACH models. Model tests are carried out for two optimal Tri SWACH models at Webb Institute for validations. Substantial drag reductions have been obtained for a wide range of speed.

关键词： hydrodynamics optimization drag reduction CFD trimaran surface modification

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