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High temperature ferromagnetic ordering in c-axis orientedZnO:Mnnanoparticle thin films by tailoring substrate temperature

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International Journal of Modern physics: Conference Series 2014年第32期ijmpcs卷

作者： Usman Ilyas P. Lee T. L. Tan R. V. Ramanujan Sam Zhang R. Chen H. D. Sun R. S. Rawat National Institute of Education Nanyang Technological University 1 Nanyang Walk 637616 Singapore Department of Physics University of Engineering & Technology Lahore 54890 Pakistan School of Material Science and Engineering Nanyang Technological University 639798 Singapore School of Mechanical and Aerospace Engineering Nanyang Technological University 639798 Singapore Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link 637371 Singapore

This study reports the enhanced ferromagnetic ordering in ZnO:Mn nanoparticle thin films, grown at different substrate temperatures using pulsed laser deposition. The optimum growth conditions were deduced from X-ray, photoemission and magnetic measurements. The X-ray measurements reveal that there was an optimum substrate temperature where the thin films showed relatively stronger texture, better crystallinity and lower strain. Substrate temperature tuned the deep level recombination centers in ZnO:Mn , which changed the optical quality by altering the electronic structure. The M-H curves, in the present study, revealed superior ferromagnetic response of 20-nm sized particles in ZnO:Mn thin film grown at a substrate temperature of 450 °C. Ferromagnetic ordering becomes weaker at higher/lower substrate temperatures due to the activation of native defects in ZnO host matrix.

关键词： Spintronics ZnO:Mn nanoparticle thin films structural defects substrate temperature

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Unsteady aerodynamic forces and torques on falling parallelograms in coupled tumbling-helical motions

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Physical Review E 2013年第5期87卷 053021-053021页

作者： Kapil Varshney Song Chang Z. Jane Wang Taitem Engineering PC Ithaca New York 14850 USA School of Applied and Engineering Physics Cornell University Ithaca New York 14853 USA Sibley School of Mechanical and Aerospace of Engineering Cornell University Ithaca New York 14853 USA Department of Physics Cornell University Ithaca New York 14853 USA

Falling parallelograms exhibit coupled motion of autogyration and tumbling, similar to the motion of falling tulip seeds, unlike maple seeds which autogyrate but do not tumble, or rectangular cards which tumble but do not gyrate. This coupled tumbling and autogyrating motion are robust, when card parameters, such as aspect ratio, internal angle, and mass density, are varied. We measure the three-dimensional (3D) falling kinematics of the parallelograms and quantify their descending speed, azimuthal rotation, tumbling rotation, and cone angle in each falling. The cone angle is insensitive to the variation of the card parameters, and the card tumbling axis does not overlap with but is close to the diagonal axis. In addition to this connection to the dynamics of falling seeds, these trajectories provide an ideal set of data to analyze 3D aerodynamic force and torque at an intermediate range of Reynolds numbers, and the results will be useful for constructing 3D aerodynamic force and torque models. Tracking these free falling trajectories gives us a nonintrusive method for deducing instantaneous aerodynamic forces. We determine the 3D aerodynamic forces and torques based on Newton-Euler equations. The dynamical analysis reveals that, although the angle of attack changes dramatically during tumbling, the aerodynamic forces have a weak dependence on the angle of attack. The aerodynamic lift is dominated by the coupling of translational and rotational velocities. The aerodynamic torque has an unexpectedly large component perpendicular to the card. The analysis of the Euler equation suggests that this large torque is related to the deviation of the tumbling axis from the principle axis of the card.

关键词： UNSTEADY flow (Aerodynamics) AERODYNAMIC load TUMBLING motion ROTATIONAL motion PARALLELOGRAMS KINEMATICS PARAMETERS (Statistics) TORQUE

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Constrained workspace generation for snake-like manipulators with applications to minimally invasive surgery

Constrained workspace generation for snake-like manipulators...

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IEEE International Conference on Robotics and Automation (ICRA)

作者： Ryan J. Murphy Matthew S. Moses Michael D. M. Kutzer Gregory S. Chirikjian Mehran Armand Johns Hopkins University Applied Physics Laboratory Laurel MD US Research and Exploratory Development Department Johns Hopkins University Applied Physics Laboratory Laurel MD USA Department of Mechanical Engineering Johns Hopkins University Baltimore MD USA

ISBN: (纸本)9781467356404

Osteolysis is a debilitating condition that can occur behind the acetabular component of total hip replacements due to wear of the polyethylene liner. Conventional treatment techniques suggest replacing the component, while less-invasive approaches attempt to access and clean the lesion through the screw holes in the component. However, current rigid tools have been shown to access at most 50% of the lesion. Using a recently developed dexterous manipulator, we have adapted a group-theoretic convolution framework to define the manipulator's workspace and its ability to fully explore a lesion. We compared this with the experimental exploration of a printed model of the lesion. This convolution approach successfully contains the experimental results and shows over 98.8% volumetric coverage of a complex lesion. The results suggest this manipulator as a possible solution to accessing much of the area unreachable to the conventional less-invasive technique.

关键词： Manipulators Lesions Convolution Geometry Joints Face Kinematics

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Correlation and relativistic effects in U metal and U-Zr alloy: Validation of ab initio approaches

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Physical Review B 2013年第23期88卷 235128-235128页

作者： Wei Xie (谢玮) Wei Xiong Chris A. Marianetti Dane Morgan Materials Science Program University of Wisconsin-Madison Madison Wisconsin 53706 USA Department of Materials Science and Engineering University of Wisconsin-Madison Madison Wisconsin 53706 USA Department of Applied Physics and Applied Mathematics Columbia University New York New York 10027 USA Department of Engineering Physics University of Wisconsin-Madison Madison Wisconsin 53706 USA

Ab initio calculations have been performed on all solid phases of U metal and U-Zr alloy, the basis of a promising metallic fuel for fast nuclear reactors. Based on generalized gradient approximation, both density functional theory (DFT) in its standard form and the so-called DFT plus Hubbard U (DFT+U) modification are evaluated. The evolution of calculated energetics, volume, magnetic moments, electronic structure, and f-orbital occupation as functions of the effective Hubbard U parameter, Ueff, is carefully examined at Ueff from 0 to 4 eV. DFT is found to overestimate energetics, underestimate volume, downward shift some f bands near Fermi level and overestimate f-orbital occupation against existing experimental and/or computational data. The error is ∼0.07 eV/atom in terms of enthalpy, which affects phase stability modeling for δ(U,Zr) and γ(U,Zr). DFT+U at Ueff=1−1.5 eV offers clear improvement on these calculated properties (∼0.05 eV/atom in terms of enthalpy) and in general still neither promotes ordered magnetic moments nor opens unphysical band gaps, which occur at higher Ueff values. The empirical Ueff values of 1–1.5 eV are close to but smaller than the theoretical estimations of 1.9–2.3 eV that we obtain from the linear response approach. Ueff is found to vary only slightly (≤0.24 eV) between different phases and at different compositions of U and U-Zr; thus, a single Ueff=1.24 eV, which is the statistical optimal from energetic fitting, is suggested for both U and U-Zr. Besides correlation, the relativistic effect of spin-orbit coupling (SOC) is also systematically explored. SOC is found to lower energy, increase volume, and split the 5f shell above Fermi level and reduce f-orbital occupation. The effect predominates in the unoccupied states and is very small on all these calculated ground state properties (∼0.02 eV/atom in terms of enthalpy).

关键词： NUCLEAR reactors HUBBARD model ELECTRONIC structure FERMI level MAGNETIC moments

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Micro-optofluidic ring resonator structures for selective detection of organic vapors

Micro-optofluidic ring resonator structures for selective de...

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2013 17th International Conference on Solid-State Sensors, Actuators and Microsystems, TRANSDUCERS and EUROSENSORS 2013

作者： Scholten, K. Reddy, K. Fan, X. Zellers, E.T. Applied Physics Program University of Michigan Ann Arbor MI United States Department of Biomedical Engineering University of Michigan Ann Arbor MI United States Department of Environmental Health Sciences University of Michigan Ann Arbor MI United States Center for Wireless Integrated MicroSensing and Systems University of Michigan Ann Arbor MI United States

ISBN: (纸本)9781467359818

A microfabricated optofluidic ring resonator (μOFRR) sensor for volatile organic compounds (VOC) is described. SiOx optical resonators integrated into a microfluidic pathway were defined lithographically and fabricated via Si micromachining. Whispering gallery mode resonances with quality factors exceeding 104 were excited in devices with diameters of 50-250 μm and wall thicknesses of 1.5-2 μm. Fluidic interconnections and structures for alignment of optical fiber waveguides were integrated into the larger μOFRRs. Devices coated internally with a thin PDMS layer exhibit shifts in resonant wavelengths during VOC exposure with sub-ng detection limits. In related work, selective VOC measurements obtained with plasmonic films of functionalized nanoparticles are described, with a goal of using them in place of polymer coatings in the μOFRR. A thin film of octanethiolate monolayer protected gold nanoparticles (MPN) was coated on a planar substrate and capped with a microfluidic cell. Reflected light from one of two single wavelength sources (783 nm and 488 nm) was measured during separate dynamic exposures to two VOCs. The decrease in reflected light intensity, due to film selling and changes in the local surface plasmon resonance band, was proportional to the VOC concentration. The ratio of responses at each wavelength provided a pattern unique to each VOC. © 2013 IEEE.

关键词： Optical fibers

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Erratum: “Electronic structure and thermoelectric properties of p-type Ag-doped Mg2Sn and Mg2Sn1−xSix (x = 0.05, 0.1)” [J. Appl. Phys. 116, 153706 (2014)]

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Journal of applied physics 2014年第17期116卷

作者： Sunphil Kim Bartlomiej Wiendlocha Hyungyu Jin Janusz Tobola Joseph P. Heremans 1Department of Mechanical and Aerospace Engineering The Ohio State University Columbus Ohio 43210 USA 2AGH University of Science and Technology Faculty of Physics and Applied Computer Science Al. Mickiewicza 30 30-059 Krakow Poland 3Department of Physics The Ohio State University Columbus Ohio 43210 USA

One reference is missing in the original publication.1 Reference 15 should contain two articles:

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Radon entrance and its daily movement into a closed detached of three level house

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Physica Medica 2014年 30卷 e91-e91页

作者： Efstratios Vogiannis Dimitrios Nikolopoulos Maria Koukou Sofia Kottou Michail Vrachopoulos Evangeliki Model School of Smyrna Lesvou 4 17123 Nea Smyrni Greece TEI of Piraeus Department of Electronic Computer Systems Engineering Petrou Ralli & Thivon 250 12244 Aigaleo Greece University of Applied Sciences Mechanical Engineering Department Energy and Environmental Research Laboratory Central Greece 34400 Psachna Evia Greece Department of Mechanical Engineering TEI of Halkis 34400 Psachna Evia Greece Medical Physics Department Medical School University of Athens Mikras Asias 75 11527 Athens Greece

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Nanoindentation investigation of the reactive pulsed laser deposited superconducting niobium nitride thin films

Nanoindentation investigation of the reactive pulsed laser d...

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142nd Annual Meeting and Exhibition: Linking Science and Technology for Global Solutions, TMS 2013

作者： Mamun, M.A. Farha, A.H. Ufuktepe, Y. Kimura, S.I. Hajiri, T. Imura, K. Karadag, F. Elsayed-Ali, H.E. Elmustafa, A.A. Department of Mechanical and Aerospace Engineering Old Dominion University Norfolk VA 23529 United States Department of Electrical and Computer Engineering Old Dominion University Norfolk VA 23529 United States Department of Physics Cukurova University Adana 01330 Turkey UVSOR Facility Institute for Molecular Science Okazaki 444-8585 Japan Okazaki 444-8585 Japan Graduate School of Engineering Nagoya University Nagoya 464-8601 Japan Department of Physics Nagoya University Nagoya 464-8601 Japan Applied Research Center Thomas Jefferson National Accelerator Facility Newport News VA 23606 United States

ISBN: (纸本)9781118605813

Nanomechanical properties were investigated for the reactive pulsed laser deposited (PLD) superconducting NbNx thin films grown on Si(100) at constant substrate temperature of 800°C using three different background nitrogen gas pressures (200, 400 and 500 mTorr). The Cross-sectional transmission electron microscopy (TEM), X-ray diffraction (XRD), and atomic force microscopy (AFM) were employed to characterize the films' surface structure and morphology. Superconductivity was determined by performing resistance measurements. Nanoindentation technique was used to evaluate the hardness and modulus of the films. The results indicate that the background pressure impacted the crystalline quality, morphology, superconductivity and the hardness of the films. As the background pressure increases to 500 mTorr, improved superconducting properties and higher hardness (17.5±1.5 GPa at 20 nm depth) values were reported as compared to the other two samples.

关键词： Atomic force microscopy

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Nano-engineered composites: Interlayer carbon nanotubes effect

Nano-engineered composites: Interlayer carbon nanotubes effe...

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作者： Carleya, Glaucio Geraldo, Viviany De Oliveira, Sergio Avila, Antonio Ferreira Mechanical Engineering Graduate Studies Program Universidade Federal de Minas Gerais - UFMG Av. Antonio Carlos 6627 CEP 31270-901 Belo Horizonte MG Brazil Physics Department Universidade Federal de Minas Gerais - UFMG Av. Antonio Carlos 6627 CEP 31270-901 Belo Horizonte Brazil Mechanical Engineering Department Universidade Federal de Minas Gerais - UFMG Av. Antonio Carlos 6627 CEP 31270-901 Belo Horizonte Brazil

The concept of carbon nanotube interlayer was successfully introduced to carbon fiber/epoxy composites. This new hybrid laminated composites was characterized by Raman spectroscopy, X-ray diffraction, scanning electron microscopy and tensile tests. An increase on peak stress close to 85% was witnessed when CNTs interlayer with 206.30 mg was placed to carbon fiber/epoxy laminates. The failure mechanisms are associated to CNTs distribution between and around carbon fibers. These CNTs are also responsible for crack bridging formation and the increase on peak stress. Initial stiffness is strongly affected by the CNT interlayer, however, changes on stiffness is associated to changes on nano/micro-structure due to damage. Three different behaviors can be described, i.e. for interlayers with ≈ 60 mg of CNT the failure mode is based on cracks between and around carbon fibers, while for interlayers with CNT contents between 136 mg and 185 mg cracks were spotted on fibers and inside the CNT/matrix mix. Finally, the third failure mechanism is based on carbon fiber breakage, as a strong interface between CNT/matrix mix and carbon fibers is observed. © 2013.

关键词： Raman spectroscopy

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Nonlinear Elastic Instability in Channel Flows at Low Reynolds Numbers

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Physical Review Letters 2013年第17期110卷 174502-174502页

作者： L. Pan A. Morozov C. Wagner P. E. Arratia Department of Mechanical Engineering and Applied Mechanics University of Pennsylvania Philadelphia 19141 USA SUPA School of Physics and Astronomy University of Edinburgh Mayfield Road Edinburgh EH9 3JZ United Kingdom Experimental Physics Saarland University 66123 Saarbrucken Germany

It is presently believed that flows of viscoelastic polymer solutions in geometries such as a straight pipe or channel are linearly stable. Here we present experimental evidence that such flows can be nonlinearly unstable and can exhibit a subcritical bifurcation. Velocimetry measurements are performed in a long, straight microchannel; flow disturbances are introduced at the entrance of the channel system by placing a variable number of obstacles. Above a critical flow rate and a critical size of the perturbation, a sudden onset of large velocity fluctuations indicates the presence of a nonlinear subcritical instability. Together with the previous observations of hydrodynamic instabilities in curved geometries, our results suggest that any flow of polymer solutions becomes unstable at sufficiently high flow rates.

关键词： NONLINEAR elastic fracture CHANNEL flow (Fluid dynamics) REYNOLDS number VISCOELASTIC materials POLYMERS VELOCIMETRY

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