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Existence of a Thermodynamic Spin-Glass Phase in the Zero-Concentration Limit of Anisotropic Dipolar Systems

Physical Review X 2014年第4期4卷 041016-041016页

作者： Juan Carlos Andresen Helmut G. Katzgraber Vadim Oganesyan Moshe Schechter Theoretische Physik ETH Zurich CH-8093 Zurich Switzerland Department of Theoretical Physics Royal Institute of Technology SE-106 91 Stockholm Sweden Department of Physics and Astronomy Texas A&M University College Station Texas 77843-4242 USA Materials Science and Engineering Program Texas A&M University College Station Texas 77843 USA Santa Fe Institute 1399 Hyde Park Road Santa Fe New Mexico 87501 USA Department of Engineering Science and Physics College of Staten Island CUNY Staten Island New York 10314 USA Initiative for the Theoretical Sciences The Graduate Center CUNY New York New York 10016 USA Department of Physics Ben Gurion University of the Negev Beer Sheva 84105 Israel

The nature of ordering in dilute dipolar interacting systems dates back to the work of Debye and is one of the most basic, oldest and as-of-yet unsettled problems in magnetism. While spin-glass order is readily observed in several RKKY-interacting systems, dipolar spin glasses are the subject of controversy and ongoing scrutiny, e.g., in LiHoxY1−xF4, a rare-earth randomly diluted uniaxial (Ising) dipolar system. In particular, it is unclear if the spin-glass phase in these paradigmatic materials persists in the limit of zero concentration or not. We study an effective model of LiHoxY1−xF4 using large-scale Monte Carlo simulations that combine parallel tempering with a special cluster algorithm tailored to overcome the numerical difficulties that occur at extreme dilutions. We find a paramagnetic to spin-glass phase transition for all Ho+ ion concentrations down to the smallest concentration numerically accessible, 0.1%, and including Ho+ ion concentrations that coincide with those studied experimentally up to 16.7%. Our results suggest that randomly diluted dipolar Ising systems have a spin-glass phase in the limit of vanishing dipole concentration, with a critical temperature vanishing linearly with concentration. The agreement of our results with mean-field theory testifies to the irrelevance of fluctuations in interactions strengths, albeit being strong at small concentrations, to the nature of the low-temperature phase and the functional form of the critical temperature of dilute anisotropic dipolar systems. Deviations from linearity in experimental results at the lowest concentrations are discussed.

关键词： Computational physics Condensed matter physics Magnetism

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Fabrication of graphene by electrochemical exfoliation in alkaline electrolytes

Fabrication of graphene by electrochemical exfoliation in al...

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作者： Chang, Li-Chung Hsieh, Yu-Chi Chen, Yong-Min Wu, Pu-Wei Lee, Jyh-Fu Graduate Program for Science and Technology of Accelerator Light Source China Department of Materials Science and Engineering National Chiao Tung University Hsin-Chu 30010 Taiwan Taiwan National Synchrotron Radiation Research Center Hsin-Chu 30076 Taiwan Taiwan

ISBN: (纸本)9781607685395

Fabrication of graphene was demonstrated by electrochemical exfoliation of graphite in an ammonium hydroxide solution. The processing parameter of applied voltage was optimized to accomplish graphene productivity and desired chemical composition. Images from the atomic force microscopy showed graphene sheets with lateral sizes of several hundred nanometers. Images from the transmission electron microscopy indicated the existence of stacked graphene sheets with thickness of a few graphene layers. Raman spectroscopy confirmed variation of assynthesized graphene and bulk graphite. X-ray photoemission spectroscopy suggested the formation of graphene oxide at large voltage. © 2014 The Electrochemical Society.

关键词： Graphene

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Deformation of porous, nanostructured silver at room temperature and 150C°

Deformation of porous, nanostructured silver at room tempera...

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2012 MRS Fall Meeting

作者： Noiseau, Guillaume Becker, Michael F. Keto, John W. Kovar, Desiderio Materials Science and Engineering Graduate Program University of Texas at Austin Austin TX 78712-1591 United States Department of Electrical and Computer Engineering University of Texas Austin TX United States Department of Physics University of Texas Austin TX United States Department of Mechanical Engineering University of Texas Austin TX United States

ISBN: (纸本)9781632661067

Porous, nanostructured silver samples were produced using a direct-write method where a nanoparticle aerosol consisting of particles with a mean size of approximately 5 nm were accelerated to speeds of approximately 1000 m/sec and impacted onto a translating substrate [1]. The impacting particles have sufficient energy to stick to the substrate, allowing patterned thick films to be directly written from the aerosol without a mask. Unlike other low temperature processing routes for achieving patterned films, no organics are added that can interfere with post-deposition processing. Typical films are 5-100 μm thick, up to several centimeters long, and have an as-deposited relative densities as high as 70% of bulk Ag. Compression tests were carried out in steps at room temperature and at 150°C under constant displacement rates. Local strain and densification were measured by optical profilometry between each compression step. The results can be used as a starting point to better understand the mechanisms that govern plasticity, creep, and sintering in nanostructured, porous silver at low processing temperatures. © 2013 materials Research Society.

关键词： Room temperature

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Flexible Electronics: Extremely Flexible Transparent Conducting Electrodes for Organic Devices (Adv. Energy Mater. 1/2014)

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Advanced Energy materials 2014年第1期4卷

作者： Sunghoon Jung Sunghun Lee Myungkwan Song Do‐Geun Kim Dae Sung You Jong‐Kuk Kim Chang Su Kim Tae‐Min Kim Kwon‐Hyeon Kim Jang‐Joo Kim Jae‐Wook Kang Surface Technology Division Korea Institute of Materials Science (KIMS) Changwon 641‐831 Republic of Korea OLEDs Center WCU Hybrid Materials Program Department of Materials Science and Engineering Seoul National University Seoul 151‐744 Republic of Korea Professional Graduate School of Flexible and Printable Electronics Department of Flexible and Printable Electronics Chonbuk National University Jeonju 561‐756 Republic of Korea

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Deformation of Porous, Nanostructured Silver at Room Temperature and 150 °C

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MRS Online Proceedings Library 2013年第1期1513卷 1-6页

作者： Noiseau, Guillaume Becker, Michael F. Keto, John W. Kovar, Desiderio Materials Science and Engineering Graduate Program The University of Texas at Austin Austin USA Department of Electrical and Computer Engineering The University of Texas Austin USA Department of Physics The University of Texas Austin USA Department of Mechanical Engineering The University of Texas Austin USA

Porous, nanostructured silver samples were produced using a direct-write method where a nanoparticle aerosol consisting of particles with a mean size of approximately 5 nm were accelerated to speeds of approximately 1000 m/sec and impacted onto a translating substrate [1]. The impacting particles have sufficient energy to stick to the substrate, allowing patterned thick films to be directly written from the aerosol without a mask. Unlike other low temperature processing routes for achieving patterned films, no organics are added that can interfere with postdeposition processing. Typical films are 5- 100 μm thick, up to several centimeters long, and have an as-deposited relative densities as high as 70% of bulk Ag. Compression tests were carried out in steps at room temperature and at 150°C under constant displacement rates. Local strain and densification were measured by optical profilometry between each compression step. The results can be used as a starting point to better understand the mechanisms that govern plasticity, creep, and sintering in nanostructured, porous silver at low processing temperatures.

关键词： Ag densification nanoscale

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Reactivity of Ti-B, Cr-S, and Mn-S powder systems during explosively-driven collapse

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Journal of Physics: Conference Series 2014年第18期500卷

作者： M Serge P H Chiu A J Higgins V F Nesterenko Mechanical Engineering Department McGill University Montreal QC H3A 0C3 Canada Department of Mechanical and Aerospace Engineering UCSD La Jolla CA 92093-0411 USA Materials Science and Engineering Graduate Program UCSD La Jolla CA 92093-0411 USA

Metal-metal and metal-sulfur reactive powder mixtures have been previously tested for initiation of reaction via planar, normal-shock loading. In addition to reacting under shock, such powder mixtures may undergo exothermic reaction from other types of mechanical loading. The thick-walled cylinder technique was performed on samples of Ti-B (1:2 molar ratio), Cr-S (1.15:1 molar ratio), and Mn-S (1:1 molar ratio). These experiments were aimed to determine the effect of large shear strains exerted on reactive metal powder mixtures and to establish the relative effectiveness of shear loading in comparison to shock loading for initiating reaction. Recovered samples were analyzed via SEM and XRD to determine the degree of reaction.

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Multi-hole defect photonic crystals with enhanced surface area for biosensing applications

Multi-hole defect photonic crystals with enhanced surface ar...

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Laser science, LS 2013

作者： Hu, S. Kang, C. Zhao, Y. Mares, J.W. Vlasov, Y.A. Assefa, S. Weiss, S.M. Department of Physics and Astronomy Vanderbilt University Nashville TN 37235 United States Interdisciplinary Graduate Program in Materials Science Vanderbilt University Nashville TN 37235 United States Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN 37235 United States IBM T.J. Watson Research Center Yorktown Heights NY 10536 United States

Multi-hole defect (MHD) photonic crystal cavities functionalized with in situ synthesized DNA bioreceptors are demonstrated for biosensing applications. By significantly increasing light interaction with target biomol... 详细信息

ISBN: (纸本)9781557529879

关键词： Photonic crystals

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Mechanical Behavior of Yttria-Stabilized Zirconia Aqueous Cast Tapes and Laminates

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Journal of Ceramics 2014年第1期2014卷

作者： V. Moreno R. M. Bernardino D. Hotza Graduate Program on Materials Science and Engineering (PGMAT) Federal University of Santa Catarina 88040-900 Florianópolis SC Brazilufsc.br Department of Mechanical Engineering Federal University of Santa Catarina 88040-900 Florianópolis SC Brazilufsc.br Department of Chemical Engineering Federal University of Santa Catarina 88040-900 Florianópolis SC Brazilufsc.br

Aqueous tape casting was used to produce yttria-stabilized zirconia films for electrolyte-supported solid oxide fuel cell (SOFC). Tape casting slurries were prepared varying the binder content between 20 and 25 wt%. A commercial acrylic emulsion served as binder. Rheological measurements of the two slurries were performed. Both slurries showed a shear-thinning behavior. Tapes with 25 wt% binder exhibited adequate flexibility and a smooth and homogeneous surface, free of cracks and other defects. Suitable conditions of lamination were found and a theoretical density of 54% in the laminates was achieved. Laminated tapes showed higher tensile strength compared to single sheets. Tape orientation has a significant influence on the mechanical properties. Tensile strength, elongation to strain, and Young’s modulus measured in samples produced in the direction of casting showed higher property values.

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Modeling and simulation of the microalgae derived hydrogen process in compact photobioreactors

Modeling and simulation of the microalgae derived hydrogen p...

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IEEE Conference on Technologies for Sustainability

作者： J. V. C. Vargas D. A. Mitchell A. B. Mariano D. O. Correa J. C. Ordonez Graduate Program in Engineering and Materials Science PIPE and Sustainable Energy Research and Development Center NPDEAS Federal University of Parana Department of Mechanical Engineering Energy and Sustainability Center and Center for Advanced Power Systems Florida State University FSU

ISBN: (纸本)9781467346290

A general transient mathematical model for managing microalgae derived hydrogen production, with temperature dependence of the cultivation medium is developed. For that, the simplified physical model combines principles of classical thermodynamics, mass, species and heat transfer, resulting in a system of differential equations which are discretized in space using a three-dimensional cell-centered finite volume scheme. A Michaelis-Menten type expression is proposed for modeling the rate of H_2 production with dependence on O_2 inhibition. Tridimensional simulations are performed in order to determine the mass fractions distributions inside a compact photobioreactor (PBR), under different operating conditions. A relatively coarse mesh was used (6048 volume elements) to obtain converged results for a large compact PBR computational domain (5m×2m×8m). The largest computational time required for obtaining results was 560 s, i.e., less than 10 min. The numerical results for microalgal growth are validated by direct comparison to experimental measurements. Hydrogen production simulations are conducted to demonstrate PBR intermittent operation (aerobic and anaerobic stages) feasibility and adequate species evolution trends in an indirect biophotolysis approach. Therefore, after experimental validation for a particular H_2 production system, it is reasonable to state that the model could be used as an efficient tool for PBR systems thermal design, control and optimization for maximum H_2 production.

关键词： Chlamydomonas reinhardtii Scenedesmus sp. Photobioreactor architecture Early stage design tool

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An evaluation of the corrosion behavior of orthodontic Ni-Ti archwires as a function of residence time the oral cavity

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ECS Transactions 2012年第50期50卷 99-112页

作者： Britto, Káthia M.F. Macedo, Daniel A. Nascimento, Rubens M. Martinelli, Antonio E. Júnior, Hélio S. Materials Science and Engineering Post-Graduate Program Federal University of Rio Grande Do Norte 59072-970 Natal Brazil

The objective of the present study was to evaluate the effect of the residence time in the oral cavity on the electrochemical and microstructural properties of nickel-titanium superelastic and thermoelastic archwires aiming at establishing optimum treatment parameters regarding materials selection and maintenance of orthodontic apparatus. The corrosion behaviour of commercial archwires of different diameters was studied after periods of use from 1 to 3 months in the oral cavity of patients submitted to orthodontic treatment. Electrochemical measurements and scanning electron microscopy (SEM) were performed. The results revealed that the stiffness of superelastic archwires increased upon use, making it unnecessary to replace archwires in the early stages of treatment with the objective of adapting the diameter of the wire. Electrochemical tests suggested extremely high corrosion resistance of the nickel-titanium alloy even in severe acid environment. SEM images revealed limited pit formation concentrated in the archwire-bracket contacts. © The Electrochemical Society.

关键词： Dental orthoses

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