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Modeling ocean wave propagation under sea ice covers

Acta Mechanica Sinica 2015年第1期31卷 1-15页

作者： Xin Zhao Hayley H. Shen Sukun Cheng Department of Civil and Environmental Engineering Clarkson University

Operational ocean wave models need to work globally, yet current ocean wave models can only treat ice covered regions crudely. The purpose of this paper is to provide a brief overview of ice effects on wave propagation and different research methodology used in studying these effects. Based on its proximity to land or sea, sea ice can be classified as： landfast ice zone, shear zone, and the marginal ice zone. All ice covers attenuate wave energy. Only long swells can penetrate deep into an ice cover. Being closest to open water, wave propagation in the marginal ice zone is the most complex to model. The physical appearance of sea ice in the marginal ice zone varies. Grease ice, pancake ice, brash ice, floe aggregates, and continuous ice sheet may be found in this zone at different times and locations. These types of ice are formed under different thermalmechanical forcing. There are three classic models that describe wave propagation through an idealized ice cover： mass loading, thin elastic plate, and viscous layer models. From physi cal arguments we may conjecture that mass loading model is suitable for disjoint aggregates of ice floes much smaller than the wavelength, thin elastic plate model is suitable for a con tinuous ice sheet, and the viscous layer model is suitable for grease ice. For different sea ice types we may need different wave ice interaction models. A recently proposed viscoelas tic model is able to synthesize all three classic models into one. Under suitable limiting conditions it converges to the three previous models. The complete theoretical framework for evaluating wave propagation through various ice covers need to be implemented in the operational ocean wave models. In this review, we introduce the sea ice types, previous wave ice interaction models, wave attenuation mechanisms,the methods to calculate wave reflection and transmission between different ice covers, and the effect of ice floe breaking on shaping the sea ice morphology. Labora

关键词： Ocean waves Sea ice Cryospheric change

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Forces and energetics of intermittent swimming

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Acta Mechanica Sinica 2017年第4期33卷 725-732页

作者： Daniel Floryan Tyler Van Buren Alexander J.Smits Department of Mechanical and Aerospace Engineering Princeton University Princeton NJ 08544 USA

Experiments are reported on intermittent swimming motions. Water tunnel experiments on a nominally two-dimensional pitching foil show that the mean thrust and power scale linearly with the duty cycle, from a value of 0.2 all the way up to continuous motions, indicating that individual bursts of activity in intermittent motions are independent of each other. This conclusion is corroborated by particle image velocimetry（PIV） flow visualizations, which show that the main vortical structures in the wake do not change with duty cycle. The experimental data also demonstrate that intermittent motions are generally energetically advantageous over continuous motions. When metabolic energy losses are taken into account, this conclusion is maintained for metabolic power fractions less than 1.

关键词： intermittent swimming maintained conclusion cycle thrust favorable producing aquatic circles

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A sharp interface approach for cavitation modeling using volume-of-fluid and ghost-fluid methods

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Journal of Hydrodynamics 2017年第6期29卷 917-925页

作者： Thad Michael Jianming Yang Frederick Stern NSWC Carderock Division 9500 MaeArthur Blvd.West BethesdaMD 20817USA Fidesi Solutions LLC PO Box 734Iowa CityIA 52244USA IIHR-Hydroscience and Engineering University of lowaIowa CityIA 52242USA

This paper describes a novel sharp interface approach for modeling the cavitation phenomena in incompressible viscous flows. A one-field formulation is adopted for the vapor-liquid two-phase flow and the interface is tracked using a volume of fluid（VOF） method. Phase change at the interface is modeled using a simplification of the Rayleigh-Plesset equation. Interface jump conditions in velocity and pressure field are treated using a level set based ghost fluid method. The level set function is constructed from the volume fraction function. A marching cubes method is used to compute the interface area at the interface grid cells. A parallel fast marching method is employed to propagate interface information into the field. A description of the equations and numerical methods is presented. Results for a cavitating hydrofoil are compared with experimental data.

关键词： Incompressible flow two-phase flow cavitation modeling sharp interface method ghost fluid method volume of fluidmethod level set method parallel fast marching method marching cubes method

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Organic semiconductor-incorporated two-dimensional halide perovskites

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National Science Review 2022年第5期9卷 17-19页

作者： Yao Gao Letian Dou Davidson School of Chemical Engineering Purdue University Birck Nanotechnology Center Purdue University

Recently,the search for novel two-dimensional (2D) organic-inorganic halide perovskite materials has come to a *** is significant interest not only in terms of their intriguing optoelectronic properties,but also their structural diversity and improved *** 2D perovskite structure can be visualized as atomically thin slabs cut from 3D parent structures along different crystal directions that are sandwiched between two layers of large organic *** bulky organic cations/ligands play a governing role in2D structure formation via suppression of the out-of-plane growth and promotion of in-plane ***,

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Enhancing von Neumann entropy by chaos in spin–orbit entanglement

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Chinese Physics B 2019年第10期28卷 153-159页

作者： Chen-Rong Liu Pei Yu Xian-Zhang Chen Hong-Ya Xu Liang Huang Ying-Cheng Lai School of Physical Science and Technology and Key Laboratory for Magnetism and Magnetic Materials of MOELanzhou UniversityLanzhou 730000China School of Electrical Computerand Energy EngineeringArizona State UniversityTempeAZ 85287USA Department of Physics Arizona State UniversityTempeAZ 85287USA

For a quantum system with multiple degrees of freedom or subspaces, loss of coherence in a certain subspace is intimately related to the enhancement of entanglement between this subspace and another one. We investigate intra-particle entanglement in two-dimensional mesoscopic systems, where an electron has both spin and orbital degrees of freedom and the interaction between them is enabled by Rashba type of spin-orbit coupling. The geometric shape of the scattering region can be adjusted to produce a continuous spectrum of classical dynamics with different degree of chaos. Focusing on the spin degree of freedom in the weak spin-orbit coupling regime, we find that classical chaos can significantly enhance spin-orbit entanglement at the expense of spin coherence. Our finding that classical chaos can be beneficial to intra-particle entanglement may have potential applications such as enhancing the bandwidth of quantum communications.

关键词： spin-orbit entanglement chaos von Neumann entropy spin decoherence

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On 2-Site Voronoi Diagrams Under Geometric Distance Functions

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Journal of Computer Science & Technology 2013年第2期28卷 267-277页

作者： Gill Barequet Matthew Dickerson David Eppstein David Hodorkovsky Kira Vyatkina Department of Computer Science Technion-Israel Institute of Technology Department of Mathematics and Computer Science Middlebury College Department of Mathematics and Computer Science University of California Department of Applied Mathematics Technion-Israel Institute of Technology Algorithmic Biology Laboratory St.Petersburg Academic University Russian Academy of Sciences

We revisit a new type of Voronoi diagram, in which distance is measured from a point to a pair of points. We consider a few more such distance functions, based on geometric primitives, namely, circles and triangles, and analyze the structure and complexity of the nearest- and furthest-neighbor 2-site Voronoi diagrams of a point set in the plane with respect to these distance functions. In addition, we bring to notice that 2-point site Voronoi diagrams can be alternatively interpreted as 1-site Voronoi diagrams of segments, and thus, our results also enhance the knowledge on the latter.

关键词： distance function lower envelope Davenport-Schinzel theory crossing-number lemma

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Constructing of highly porous thermoelectric structures with improved thermoelectric performance

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Nano research 2021年第10期14卷 3608-3615页

作者： Peilei He Yue Wu Department of Chemical and Biological Engineering Iowa State UniversityAmesIowa 50011USA

As more than 60%of worldwide consumed energy is unused and becomes waste heat every year,high-efficiency waste heat to power technologies are highly demanded for the conversion of wasted heat to *** which can convert the wasted heat directly into electricity represent a promising approach for energy *** technology has existed for several decades,but its usage has been limited due to low *** advances in nanotechnology have enabled the improving of thermoelectric properties which open up the thermoelectrics’feasibility in *** this paper,we present an overview of recent progress in increasing the porosity of thermoelectric materials from atomic scale to microscale,leading to the enhancement of figure of merit.

关键词： thermoelectrics semiconductors porous structures thermal conductivity

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Plasma Spray Forming of Nanostructured Composite Coatings

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Journal of Materials Science & Technology 2002年第3期18卷 287-288页

作者： XianliangJIANG EricH.Jordan 等 InstituteofSurfaceandCoatingsTechnology CentralSouthUniversityChangsha410083China InstituteofMatrialsScience UniversityofConnecticutStorrsCT06269USA

The nanostructure composite coating is obtained via plasma spraying of Al2O3-13 wt pct TiO2 powder. Brittle and hard lamella results from melted nanostructured powder. Ductile nanostructured matrix forms from unmelted nanostructured particles. Through the adjustment of constituent and nanostructure, hardness/strength and toughness/ductility are balanced and overall properties of the structure composite are achieved.

关键词： Plasma spray forming Nanostructured coating Mechanical Property

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Synthesis of surface controlled nickel/palladium hydride nanodendrites with high performance in benzyl alcohol oxidation

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Nano research 2019年第6期12卷 1467-1472页

作者： Zipeng Zhao Michelle M.Flores Espinosa Jihan Zhou Wang Xue Xiangfeng Duan Jianwei Miao Yu Huang Department of Materials Science and Engineering University of CaliforniaLos AngelesCA 90095USA Department of Physics and Astronomy University of CaliforniaLos AngelesCA 90095USA Department of Chemistry and Biochemistry University of CaliforniaLos AngelesCA 90095USA California Nanosystems Institute University of CaliforniaLos AngelesCA 90095USA

Benzaldehyde byproduct is an imperative intermediate in the production of fine chemicals and *** selectivity to benzaldehyde is therefore critical in alcohol oxidation reactions at the industrial ***,we report a simple but innovative method for the synthesis of palladium hydride and nickel palladium hydride nanodendrites with controllable morphology,high stability,and excellent catalytic *** synthesized dendrites can maintain the palladium hydride phase even after their use in the chosen catalytic ***,the high surface area morphology and unique interaction between nickel-rich surface and palladium hydride (β-phase) of these nanodendrites are translated in an enhanced catalytic activity for benzyl alcohol oxidation *** Ni/PdH0.43 nanodendrites demonstrated a high selectivity towards benzaldehyde of about 92.0% with a conversion rate of 95.4%,showing higher catalytic selectivity than their PdH0.43 counterparts and commercial Pd/*** present study opens the door for further exploration of metal/metal-hydride nanostructures as next-generation catalytic materials.

关键词： benzyl alcohol selectivity benzaldehyde palladium hydride oxidation nanodendrites

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Distributed Control of Multiple-Bus Microgrid With Paralleled Distributed Generators

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IEEE/CAA Journal of Automatica Sinica 2019年第3期6卷 676-684页

作者： Bo Fan Jiangkai Peng Jiajun Duan Qinmin Yang Wenxin Liu IEEE the State Key Laboratory of Industrial Control Technology College of Control Science and Engineering Zhejiang University the Smart Microgrid and Renewable Technology (SMRT) research Laboratory Department of Electrical and Computer Engineering Lehigh University the Global Energy Interconnection research Institute North America (GEIRINA)

A microgrid is hard to control due to its reduced inertia and increased uncertainties. To overcome the challenges of microgrid control, advanced controllers need to be *** this paper, a distributed, two-level, communication-economic control scheme is presented for multiple-bus microgrids with each bus having multiple distributed generators(DGs) connected in parallel. The control objective of the upper level is to calculate the voltage references for one-bus subsystems. The objectives of the lower control level are to make the subsystems' bus voltages track the voltage references and to enhance load current sharing accuracy among the local DGs. Firstly, a distributed consensusbased power sharing algorithm is introduced to determine the power generations of the subsystems. Secondly, a discrete-time droop equation is used to adjust subsystem frequencies for voltage reference calculations. Finally, a Lyapunov-based decentralized control algorithm is designed for bus voltage regulation and proportional load current sharing. Extensive simulation studies with microgrid models of different levels of detail are performed to demonstrate the merits of the proposed control scheme.

关键词： Coordinate control decentralized control multiple-bus microgrid paralleled distributed generations power sharing algorithm

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