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17th National Congress of the Fluid Dynamics Division of the Mexican Physical Society, 2011

作者： Speetjens, Michel F. M. Clercx, Herman J. H. Department of Mechanical Engineering Energy Technology and J.M. Burgers Center for Fluid Dynamics P.O. Box 513 Eindhoven5600 Netherlands Department of Applied Physics Fluid Dynamics Laboratory and J.M. Burgers Center for Fluid Dynamics P.O. Box 513 Eindhoven5600 Netherlands

ISBN: (纸本)9783642277221

The formation of coherent structures in three-dimensional (3D) unsteady laminar flows in a cylindrical cavity is reviewed. The discussion concentrates on two main topics: the role of symmetries and fluid inertia in the formation of coherent structures and the ramifications for the Lagrangian transport properties of passive tracers. We consider a number of time-periodic flows that each capture a basic dynamic state of 3D flows: 1D motion on closed trajectories, (quasi-)2D motion within (approximately) 2D subregions of the flow domain and truly 3D chaotic advection. It is shown that these states and their corresponding coherent structures are inextricably linked to symmetries (or absence thereof) in the flow. Symmetry breaking by fluid inertia and the resulting formation of intricate coherent structures and (local) onset of 3D chaos is demonstrated. Finally, first experimental analyses on coherent structures and the underlying role of symmetries are discussed. © Springer-Verlag Berlin Heidelberg 2013.

关键词： Laminar flow

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Optical Third-Harmonic Generation in Graphene

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Physical Review X 2013年第2期3卷 021014-021014页

作者： Sung-Young Hong Jerry I. Dadap Nicholas Petrone Po-Chun Yeh James Hone Richard M. Osgood, Jr. Department of Chemistry Columbia University New York New York 10027 USA Department of Applied Physics and Applied Mathematics Columbia University New York New York 10027 USA Department of Mechanical Engineering Columbia University New York New York 10027 USA Department of Electrical Engineering Columbia University New York New York 10027 USA

We report strong third-harmonic generation in monolayer graphene grown by chemical vapor deposition and transferred to an amorphous silica (glass) substrate; the photon energy is in three-photon resonance with the exciton-shifted van Hove singularity at the M point of graphene. The polarization selection rules are derived and experimentally verified. In addition, our polarization- and azimuthal-rotation-dependent third-harmonic-generation measurements reveal in-plane isotropy as well as anisotropy between the in-plane and out-of-plane nonlinear optical responses of graphene. Since the third-harmonic signal exceeds that from bulk glass by more than 2 orders of magnitude, the signal contrast permits background-free scanning of graphene and provides insight into the structural properties of graphene.

关键词： Graphene Optics

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Nitrogen-vacancy center creation with helium-ion microscope

Nitrogen-vacancy center creation with helium-ion microscope

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2013 Conference on Lasers and Electro-Optics, CLEO 2013

作者： Huang, Zhihong Li, Wen-Di Santori, Charles Acosta, Victor M. Faraon, Andrei Williams, R. Stanley Beausoleil, Raymond G. He Wlett-Packard Laboratories 1 501 Page Mill Rd. Palo Alto CA 94304 United States Department of Mechanical Engineering University of Hong Kong Pokfulam Hong Kong Applied Physics and Materials Science California Institute of Technology Pasadena CA United States

We investigate a method to create nitrogen-vacancy (NV) centers in diamond using a focused-heliu m-ion-microscopy. Near-surface NV centers can be created with spatial resolution below 0.6μm. NV center spectral line w... 详细信息

ISBN: (纸本)9781557529725

关键词： Helium

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Application of TDGL Model to B2 Type Ordering with Two Step Phase Separation in Fe-Ni-Al Alloys

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MRS Online Proceedings Library (OPL) 2013年第1期1535卷 mmm12-a-0255-mmm12-a-0255页

作者： Ryuichiro Oguma Syo Matsumura Minoru Doi Satoshi Hata Keisuke Ogata Department of Applied Physics. Fukuoka University Fukuoka 814-0180 Japan Department of Applied Quantum Physics and Nuclear Engineering Kyushu University Fukuoka 819-0395 Japan Department of Mechanical Engineering Aichi Institute of Technology Toyota 470-0392 Japan Department of Electrical and Material Science Kyushu University Kasuga 816-8580 Japan Interdisciplinary Graduate School of Engineering Science Kyushu University Kasuga 816-8580 Japan

Formation of domain structures in two-step phase separation in Fe-based Fe-Ni-Al alloys are investigated by applying a time-dependent Ginzburg-Landau (TDGL) model. The present authors recently developed a TDGL formulation for ordering processes of B2 and D03 in binary alloys, taking into account the symmetrical relationships between these ordered phases. In this formulation, multiple types of variants of the structures are represented by three order parameters which can be measured independently through crystal structure factors. Mean-field free energies are defined in a form of Landau type expansion with the order parameters and a composition parameter. Interfacial energies due to local variations of degrees of order and composition are given in a gradient square approximation. Kinetic equations for time-evolution of the order parameters and the composition one are derived from the Ginzburg-Landau type potential consisting of the mean-field free energies and the interfacial energy terms. On the other hand, coauthors have investigated domain structures in two-step phase separation of Fe-based Fe-Ni-Al alloys. The evolution of three-dimensional domain structures and composition profiles has been analyzed by electron tomography imaging and energy-dispersive X-ray spectroscopy. In this work the authors performed three-dimensional numerical simulations assuming the thermal processing. The results of the simulations well reproduced the characteristics of the micro-structures obtained from the observations.

关键词： phase transformation metal diffusion

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Simulations of structure formation in B2 type ordering with two step phase separation in Fe-Ni-Al alloys

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AIP Conference Proceedings 2013年第1期1518卷 703-709页

The present authors recently developed a time-dependent Ginzburg-Landau (TDGL) formulation for ordering processes of B2 and D03 in binary alloys, taking into account the symmetrical relationships between these ordered phases. In this formulation, mean-field free energies are defined in a form of Landau type expansion with order parameters and a composition parameter. Interfacial energies due to local variations of degrees of order and composition are given in a gradient square approximation. Kinetic equations for time-evolution of the order parameters and the composition one are derived from the Ginzburg-Landau type potential consisting of the mean-field free energies and the interfacial energy terms. On the other hand, coauthors have investigated domain structures in two-step phase separation of Fe-based Fe-Ni-Al alloys. Micro-structures in the super alloys consist of B2 ordered domains and A2 disordered matrices in the first stage of phase separation. The second stage during a subsequent aging leads to formation of B2 domains and A2 phase regions in the former A2 matrices and B2 domains, respectively. The evolution of three-dimensional domain structures and composition profiles has been analyzed by electron tomography imaging and energy-dispersive X-ray spectroscopy. In this work the authors have applied the TDGL formulation to this alloy system, and performed three-dimensional numerical simulations assuming the thermal processing. The results of the simulations well reproduced the characteristics of the micro-structures obtained from the observations.

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Hypoxic intrusions to Puget Sound from the ocean

Hypoxic intrusions to Puget Sound from the ocean

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OCEANS

作者： R. Walt Deppe Jim Thomson Brian Polagye Christopher Krembs Mechanical Engineering Department University of Washington Seattle Washington Applied Physics Lab University of Washington Seattle Washington Washington State Department of Ecology Olympia Washington

ISBN: (纸本)9781479913084

Oceanic intrusions of dense, hypoxic water regularly occur at the entrance to Puget Sound, WA (USA), and may be significant to regional dissolved oxygen levels. Seabed observations at Admiralty Inlet from 2009 to 2013 show a strong correlation of low dissolved oxygen concentrations with high salinity, coincident with residual currents directed inward to Puget Sound. These intrusions of dense water to Puget Sound likely are related to estuarine exchange flows, which are expected to occur during conditions for minimal tidal mixing. Observations are consistent with minimal mixing, which occurs during the neap tides and maximum diurnal inequalities (and especially during solar equinoxes, when these effects are combined). However, tidal conditions alone cannot predict intrusions of hypoxic ocean water to Puget Sound. Coastal upwelling and Fraser River discharge influence the availability of dense, hypoxic water outside of Puget Sound. This likely is related to the larger-scale exchange flow in the Strait of Juan de Fuca, which connects Puget Sound to the North Pacific Ocean. This large scale process adds a strong seasonal modulation to the intrusion of hypoxic water. This paper develops a method to diagnose hypoxic intrusion events at Admiralty Inlet. The method is based, empirically, on seabed observations, but application of the method relies on operational data products. Using only tidal elevation datum and indices for coastal upwelling and river discharge, 100% of events with dissolved oxygen less than 4.0 mg/L are identified in the 3 year record.

关键词： Indexes Tides Rivers Sea measurements Availability Modulation Time series analysis

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The Fragmentation of Al-W Granular Composites Under Explosive Loading

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MRS Online Proceedings Library 2013年第1期1521卷 1-6页

作者： Karl L. Olney Po-Hsun Chiu Vitali F. Nesterenko David J. Benson Chris Braithwaite Adam Collins David Williamson Francesca McKenzie Department of Mechanical and Aerospace Engineering University of California San Diego USA Material Science and Engineering program University of California San Diego USA Department of Structural Engineering University of California San Diego USA Fracture and Shock Physics SMF Group Department of Physics Cavendish Laboratory Cambridge United Kingdom Imperial College London Institute of Shock Physics London United Kingdom

Small scale explosively driven fragmentation experiments have been performed on Aluminum (Al)-Tungsten (W) granular composite rings processed using cold isostatic compression of Al and W powders with a particle size of 4-30 microns. Fragments collected from the experiments had a maximum size of the order of a few hundred micrometers. This is a dramatic reduction in the fragment size when compared to the 1-10 mm typical for a homogeneous material such as solid aluminum under similar loading conditions. Numerical simulations of the experiment were performed to elucidate the mechanisms of fragmentation that were responsible for this shift in fragmentation size scales. Simulations were performed with a significantly stronger explosive driver to examine how the mechanisms of fragmentation change when the detonation pressure increases.

关键词： energetic material simulation shock loading

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Prediction of organ geometry from demographic and anthropometric data based on supervised learning approach using statistical shape atlas

Prediction of organ geometry from demographic and anthropome...

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2nd International Conference on Pattern Recognition Applications and Methods, ICPRAM 2013

作者： Otake, Yoshito Carneal, Catherine Lucas, Blake Thawait, Gaurav Carrino, John Corner, Brian Carboni, Marina DeCristofano, Barry Maffeo, Michale Merkle, Andrew Armand, Mehran Department of Computer Science Johns Hopkins University Baltimore MD United States Department of Mechanical Engineering Johns Hopkins University Baltimore MD United States Applied Physics Laboratory Johns Hopkins University Laurel MD United States Department of Radiology Johns Hopkins Hospital Baltimore MD United States US Army Natick Soldier Research Development and Engineering Center Natick MA United States

ISBN: (纸本)9789898565419

We propose a method relating internal human organ geometries and non-invasively acquired information such as demographic and anthropometric data. We first apply a dimensionality reduction technique to a training dataset to represent the organ geometry with low dimensional feature coordinates. Regression analysis is then used to determine a regression function between feature coordinates and the external measurements of the subjects. Feature coordinates for the organ of an unknown subject are then predicted from external measurements using the regression function, subsequently the organ geometry is estimated from the feature coordinates. As an example case, lung shapes represented as a point distribution model was analyzed based on demographic (age, gender, race), and several anthropometric measurements (height, weight, and chest dimensions). The training dataset consisted of 124 topologically consistent lung shapes created from thoracic CT scans. The prediction error of lung shape of an unknown subject based on 11 demographic and anthropometric information was 10.71 ± 5.48 mm. This proposed approach is applicable to scenarios where the prediction of internal geometries from external parameters is of interest. Examples include the use of external measurements as a prior information for image quality improvement in low dose CT, and optimization of CT scanning protocol.

关键词： Regression analysis

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The fragmentation of Al-W granular composites under explosive loading

The fragmentation of Al-W granular composites under explosiv...

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2012 MRS Fall Meeting

作者： Olney, Karl L. Chiu, Po-Hsun Nesterenko, Vitali F. Benson, David J. Braithwaite, Chris Collins, Adam Williamson, David McKenzie, Francesca Department of Mechanical and Aerospace Engineering University of California San Diego San Diego CA United States Material Science and Engineering Program University of California San Diego San Diego CA United States Department of Structural Engineering University of California San Diego San Diego CA United States Fracture and Shock Physics Department of Physics Cavendish Laboratory Cambridge CB3 0HE United Kingdom Institute of Shock Physics Imperial College London South Kensington Campus London SW7 2AZ United Kingdom

ISBN: (纸本)9781632661111

Small scale explosively driven fragmentation experiments have been performed on Aluminum (Al)-Tungsten (W) granular composite rings processed using cold isostatic compression of A1 and W powders with a particle size of 4-30 microns. Fragments collected from the experiments had a maximum size of the order of a few hundred micrometers. This is a dramatic reduction in the fragment size when compared to the 1-10 mm typical for a homogeneous material such as solid aluminum under similar loading conditions. Numerical simulations of the experiment were performed to elucidate the mechanisms of fragmentation that were responsible for this shift in fragmentation size scales. Simulations were performed with a significantly stronger explosive driver to examine how the mechanisms of fragmentation change when the detonation pressure increases. © 2013 Materials Research Society.

关键词： Binary alloys

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Dynamic inductive tuning of Fano-resonant meta-surfaces using plasmonic response of graphene in mid-infrared

Dynamic inductive tuning of Fano-resonant meta-surfaces usin...

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International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (METAMATERIALS)

作者： N. Dabidian S. H. Mousavi I. Kholmanov K. Alici D. Purtseladze N. Arju K. Tatar J. W. Suk Y. Hao A. B. Khanikaev R. S. Ruoff G. Shvets Physics Department University of Texas at Austin Austin TX USA Department of Mechanical Engineering and Materials Science Program University of Texas at Austin Austin TX USA

We demonstrate theoretically and experimentally that electrically gated single-layer graphene can be used to inductively tune the infrared optical response of Fano-resonant meta-surfaces. Several implementations will be introduced: graphene of the meta-surface, graphene directly under the meta-surface, and graphene separated by a thin spacer from the meta-surface. Both electrostatic and chemical doping of graphene will be discussed and supporting experimental results presented. Finally, we will demonstrate how the spectral shifts of metamaterials resonances introduced by the graphene can be utilized to extract graphene's electronic properties such as the complex-valued resistivity.

关键词： Graphene Metamaterials Plasmons Reflectivity Tuning Conductivity

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