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arXiv 2017年

作者： Mangolini, Filippo Hilbert, James Brandon McClimon, J. Lukes, Jennifer R. Carpick, Robert W. Institute of Functional Surfaces School of Mechanical Engineering University of Leeds Woodhouse Ln. Leeds West YorkshireLS2 9JT United Kingdom Department of Mechanical Engineering and Applied Mechanics University of Pennsylvania PhiladelphiaPA19104 United States Department of Materials Science and Engineering University of Pennsylvania PhiladelphiaPA19104 United States

The thermally-induced structural evolution of silicon- and oxygen-containing hydrogenated amorphous carbon (a-C:H:Si:O) was investigated by X-ray photoelectron and absorption spectroscopy, as well as molecular dynamics (MD) simulations. The spectroscopic results indicate that the introduction of Si and O in hydrogenated amorphous carbon (a-C:H) increases the activation energy for the conversion of sp3- to sp2-bonded C. MD simulations indicate that the higher thermal stability of a-C:H:Si:O compared to a-C:H derives from the lower fraction of strained C-C sp3 bonds in a-C:H:Si:O. Copyright © 2017, The Authors. All rights reserved.

关键词： Activation energy

Metasurface polarization splitter

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Metasurface polarization splitter

作者： Slovick, Brian A. Zhou, You Yu, Zhi Gang Kravchenko, Ivan I. Briggs, Dayrl P. Moitra, Parikshit Krishnamurthy, Srini Valentine, Jason Applied Optics Laboratory SRI International Menlo ParkCA94025 United States Interdisciplinary Materials Science Program Vanderbilt University NashvilleTN37212 United States Department of Mechanical Engineering Vanderbilt University NashvilleTN37212 United States Institute for Shock Physics Washington State University PullmanWA99164 United States Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak RidgeTN37831 United States Optoelectronics Research Centre University of Southampton SouthamptonSO17 1BJ United Kingdom

Polarization beam splitters, devices that separate the two orthogonal polarizations of light into different propagation directions, are among the most ubiquitous optical elements. However, traditionally polarization splitters rely on bulky optical materials, while emerging optoelectronic and photonic circuits require compact, chip-scale polarization splitters. Here, we show that a rectangular lattice of cylindrical silicon Mie resonators functions as a polarization splitter, efficiently reflecting one polarization while transmitting the other. We show that the polarization splitting arises from the anisotropic permittivity and permeability of the metasurface due to the twofold rotational symmetry of the rectangular unit cell. The high polarization efficiency, low loss and low profile make these metasurface polarization splitters ideally suited for monolithic integration with optoelectronic and photonic circuits. This article is part of the themed issue 'New horizons for nanophotonics'. © 2017 The Author(s) Published by the Royal Society. All rights reserved.

关键词： Polarization

Publisher's Note: "Chemical vapor deposition of monolayer MoS2directly on ultrathin Al2O3for low-power electronics" [Appl. Phys. Lett. 110, 053101 (2016)]

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applied Physics Letters 2017年第9期110卷

作者： Bergeron, Hadallia Sangwan, Vinod K. McMorrow, Julian J. Campbell, Gavin P. Balla, Itamar Liu, Xiaolong Bedzyk, Michael J. Marks, Tobin J. Hersam, Mark C. Department of Materials Science and Engineering Northwestern University EvanstonIllinois60208 United States Applied Physics Graduate Program Northwestern University EvanstonIllinois60208 United States Department of Physics and Astronomy Northwestern University EvanstonIllinois60208 United States Department of Chemistry Northwestern University EvanstonIllinois60208 United States Department of Electrical Engineering and Computer Science Northwestern University EvanstonIllinois60208 United States

This article was originally published online on 30 January 2017. Due to a production error, outdated versions of Figures 1 and 4 appeared in the article as orig

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Valley-selective optical Stark effect probed by Kerr rotation

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arXiv 2017年

作者： LaMountain, Trevor Bergeron, Hadallia Balla, Itamar Stanev, Teodor K. Hersam, Mark C. Stern, Nathaniel P. Applied Physics Program Northwestern University EvanstonIL60208 United States Department of Materials Science and Engineering Northwestern University EvanstonIL60208 United States Department of Physics and Astronomy Northwestern University EvanstonIL60208 United States Department of Chemistry Northwestern University EvanstonIL60208 United States Department of Electrical Engineering and Computer Science Northwestern University EvanstonIL60208 United States

The ability to monitor and control distinct states is at the heart of emerging quantum technologies. The valley pseudospin in transition metal dichalcogenide (TMDC) monolayers is a promising degree of freedom for such control, with the optical Stark effect allowing for valley-selective manipulation of energy levels in WS2 and WSe2 using ultrafast optical pulses. Despite these advances, understanding of valley-sensitive optical Stark shifts in TMDCs has been limited by reflectance-based detection methods where the signal is small and prone to background effects. More sensitive polarization-based spectroscopy is required to better probe ultrafast Stark shifts for all-optical manipulation of valley energy levels. Here, we show time-resolved Kerr rotation to be a more sensitive probe of the valley-selective optical Stark effect in monolayer TMDCs. Compared to the established time-resolved reflectance methods, Kerr rotation is less sensitive to background effects. Kerr rotation provides a five-fold improvement in the signal-to-noise ratio of the Stark effect optical signal and a more precise estimate of the energy shift. This increased sensitivity allows for observation of an optical Stark shift in monolayer MoS2 that exhibits both valley- and energy-selectivity, demonstrating the promise of this method for investigating this effect in other layered materials and heterostructures. Copyright © 2017, The Authors. All rights reserved.

关键词： Landforms

Hypostatic jammed packings of frictionless nonspherical particles

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arXiv 2017年

作者： VanderWerf, Kyle Jin, Weiwei Shattuck, Mark D. O'Hern, Corey S. Department of Physics Yale University New HavenCT06520 United States Benjamin Levich Institute and Physics Department City College of New York New YorkNY10031 United States Department of Mechanics and Engineering Science Peking University Beijing100871 China Department of Mechanical Engineering & Materials Science Yale University New HavenCT06520 United States Department of Applied Physics Yale University New HavenCT06520 United States Graduate Program in Computational Biology and Bioinformatics Yale University New HavenCT06520 United States

We perform computational studies of static packings of a variety of nonspherical particles including circulo-lines, circulo-polygons, ellipses, asymmetric dimers, dumbbells, and others to determine which shapes form packings with fewer contacts than degrees of freedom (hypostatic packings) and which have equal numbers of contacts and degrees of freedom (isostatic packings), and to understand why hypostatic packings of nonspherical particles can be mechanically stable despite having fewer contacts than that predicted from naïve constraint counting. To generate highly accurate force- and torque-balanced packings of circulo-lines and -polygons, we developed an interparticle potential that gives continuous forces and torques as a function of the particle coordinates. We show that the packing fraction and coordination number at jamming onset obey a master-like form for all of the nonspherical particle packings we studied when plotted versus the particle asphericity A, which is proportional to the ratio of the squared perimeter to the area of the particle. Further, the eigenvalue spectra of the dynamical matrix for packings of different particle shapes collapse when plotted at the same A. For hypostatic packings of nonspherical particles, we verify that the number of "quartic" modes along which the potential energy increases as the fourth power of the perturbation amplitude matches the number of missing contacts relative to the isostatic value. We show that the fourth derivatives of the total potential energy in the directions of the quartic modes remain nonzero as the pressure of the packings is decreased to zero. In addition, we calculate the principal curvatures of the inequality constraints for each contact in circulo-line packings and identify specific types of contacts with inequality constraints that possess convex curvature. These contacts can constrain multiple degrees of freedom and allow hypostatic packings of nonspherical particles to be mechanically stable. C

关键词： Degrees of freedom (mechanics)

Mechanical Behaviour of 304 Austenitic Stainless Steel Processed by Room Temperature Rolling

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IOP Conference Series: materials science and engineering 2018年第1期330卷

作者： Rahul Singh Sunkulp Goel Raviraj Verma R Jayaganthan Abhishek Kumar Department of Applied Mechanics Motilal Nehru National Institute of technology Allahabad Allahabad-211004 India Herbert Gleiter Institute of Nanoscience Nanjing University of Science and Technology Nanjing-210094 China Department of Metallurgical and Materials Engineering Indian Institute of Technology Roorkee Roorkee-247667 India Department of Engineering Design Indian Institute of Technology Madras Chennai-600036 India

To study the effect of room temperature rolling on mechanical properties of 304 Austenitic Stainless Steel, the as received 304 ASS was rolled at room temperature for different percentage of plastic deformation (i.e. 30, 50, 70 and 90 %). Microstructural study, tensile and hardness tests were performed in accordance with ASTM standards to study the effect of rolling. The ultimate tensile strength (UTS) and hardness of a rolled specimen have enhanced with rolling. The UTS has increased from 693 MPa (as received) to 1700 MPa (after 90% deformation). The improvement in UTS of processed samples is due to combined effect of grain refinement and stress induced martensitic phase transformation. The hardness values also increases from 206 VHN (as received) to 499 VHN (after 90% deformation). Magnetic measurements were also conducted to confirm the formation of martensitic phase.

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Nano-rheology of hydrogels using direct drive force modulation atomic force microscopy 71

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Nano-rheology of hydrogels using direct drive force modulati...

71st Society of Tribologists and Lubrication Engineers Annual Meeting and Exhibition 2016

作者： Nalam, P.C. Gosvami, N. Caporizzo, M. Composta, R.J. Carpick, R.W. Civil and Environmental Engineering University of Illinois Urbana Champaign ChampaignIL United States Department of Mechanical Engineering and Applied Mechanics University of Pennsylvania PhiladelphiaPA United States Department of Materials Science and Engineering University of Pennsylvania PhiladelphiaPA United States

ISBN: (纸本)9781510825048

Hydrogels are widely used soft materials in cartilage tribology, among other applications. We present a magnetic force-based direct drive modulation method to measure local nano-rheological properties of Polyacrylamide hydrogels across a broad frequency range (10 Hz - 2 kHz) using colloid-attached AFM probes in liquid. The frequency bandwidth was extended to lower frequencies (upto 0.1 Hz) by acquiring slow force-displacement which show loading-direction mechanical behavior dependence: approach curves showed Hertzian while retraction curves fit JKR model. Using small amplitude modulation at faster rates, the load dependence of the storage stiffness transitioned from Hertzian to a dynamic punch-type model, indicating significant influence of material dissipation coupled with adhesion. The study highlights possible transitions in the probe-material contact mechanical behavior of soft matter especially when the applied strain rates and the material relaxation rates become comparable.

关键词： Hydrogels

Jamming of Deformable Polygons

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arXiv 2018年

作者： Boromand, Arman Signoriello, Alexandra Ye, Fangfu O'Hern, Corey S. Shattuck, Mark D. Beijing Natl. Laboratory for Condensed Matter Physics and Cas Key Laboratory of Soft Matter Physics Institute of Physics Chinese Academy of Sciences Beijing China Department of Mechanical Engineering and Materials Science Yale University New HavenCT06520 United States Program in Computational Biology and Bioinformatics Yale University New HavenCT06520 United States School of Physical Sciences University of Chinese Academy of Sciences Beijing China Department of Physics Yale University New HavenCT06520 United States Department of Applied Physics Yale University New HavenCT06520 United States Benjamin Levich Institute and Physics Department City College of City University of New York New YorkNY10031 United States

Multi-instrument multi-scale experimental damage mechanics for fibre reinforced composites

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IOP Conference Series: materials science and engineering 2018年第1期406卷

作者： Stepan V Lomov Christian Breite Delphine Carrella-Payan Valter Carvelli Nuri Ersoy Marco Gigliotti Raquel Antoranz Gonzalez Sergey Ivanov Malika Kersani Marie-Christine Lafarie-Frenot Mark Mavrogordato Mahoor Mehdikhani Arsen Melnikov Francisco Mesquita Fatih Oz Yannick Pannier Lincy Pyl Erich Schöberl Ian Sinclair S Mark Spearing Yentl Swolfs Danny Van Hemelrijk Man Zhu Larissa Gorbatikh Department of Materials Engineering KU Leuven Belgium Siemens PLM Software Leuven Belgium Department of ABC Politecnico di Milano Italy Department of Mechanical Engineering Bogazici University Istanbul Turkey Institut Pprime CNRS ISAE-ENSMA Université de Poitiers France Faculty of Physics University of Science & Technology Houari Boumediene Algiers Algeria Department of Engineering and Environment University of Southampton UK SIM M3 program Zwijnaarde Belgium Department Mechanics of Materials and Constructions Vrije Universiteit Brussel Belgium

Reliable investigation of damage in fibre reinforced composites requires concurrent in- and ex-situ application of multiple instruments at different scale: digital image correlation, acoustic emission registration, optical/electron microscopy, C-scan, X-ray imaging and micro-computed tomography. The multi-instrument experimental mechanics allows detailed damage monitoring and inspection.

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Local and global avalanches in a two-dimensional sheared granular medium

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Physical Review E 2017年第5期96卷 052902-052902页

作者： Jonathan Barés Dengming Wang Dong Wang Thibault Bertrand Corey S. O'Hern Robert P. Behringer Department of Physics and Center for Nonlinear and Complex Systems Duke University Durham North Carolina 27708 USA Key Laboratory of Mechanics on Western Disaster and Environment Ministry of Education of China Lanzhou University 730000 Lanzhou China Department of Mechanical Engineering and Materials Science Yale University New Haven Connecticut 06520-8286 USA Department of Physics Yale University New Haven Connecticut 06520-8286 USA Department of Applied Physics Yale University New Haven Connecticut 06520-8286 USA

We present the experimental and numerical studies of a two-dimensional sheared amorphous material composed of bidisperse photoelastic disks. We analyze the statistics of avalanches during shear including the local and global fluctuations in energy and changes in particle positions and orientations. We find scale-free distributions for these global and local avalanches denoted by power laws whose cutoffs vary with interparticle friction and packing fraction. Different exponents are found for these power laws depending on the quantity from which variations are extracted. An asymmetry in time of the avalanche shapes is evidenced along with the fact that avalanches are mainly triggered by the shear bands. A simple relation independent of the intensity is found between the number of local avalanches and the global avalanches they form. We also compare these experimental and numerical results for both local and global fluctuations to predictions from mean-field and depinning theories.

关键词： Classical statistical mechanics Self-organized criticality Shear deformation Granular materials