22,446 research outputs found
Microwave oven fabricated hybrid memristor devices for non-volatile memory storage
© 2014 IOP Publishing Ltd. Novel hybrid non-volatile memories made using an ultra-fast microwave heating method are reported for the first time. The devices, consisting of aligned ZnO nanorods embedded in poly (methyl methacrylate), require no forming step and exhibit reliable and reproducible bipolar resistive switching at low voltages and with low power usage. We attribute these properties to a combination of the high aspect ratio of the nanorods and the polymeric hybrid structure of the device. The extremely easy, fast and low-cost solution based method of fabrication makes possible the simple and quick production of cheap memory cells
Discovery of a Non-Thermal Galactic Center Filament (G358.85+0.47) Parallel to the Galactic Plane
We report the discovery of a new non-thermal filament, G358.85+0.47, the
``Pelican'', located ~225 pc in projection from SgrA, and oriented parallel to
the Galactic plane. VLA continuum observations at 20 cm reveal that this 7'
(17.5 pc) structure bends at its northern extension and is comprised of
parallel strands, most apparent at its ends. Observations at 6 and 3.6 cm
reveal that the Pelican is a synchrotron-emitting source and is strongly
linearly polarized over much of its extent. The spectral index of the filament
changes from alpha(20/6)=-0.8 to alpha(6/3.6)=-1.5. The rotation measures
exhibit a smooth gradient, with values ranging from -1000 rad/m2 to +500
rad/m2. The intrinsic magnetic field is well-aligned along the length of the
filament. Based on these properties, we classify the Pelican as one of the
non-thermal filaments unique to the Galactic center. Since these filaments
(most of which are oriented perpendicular to the Galactic plane) are believed
to trace the overall magnetic field in the inner Galaxy, the Pelican is the
first detection of a component of this field parallel to the plane. The Pelican
may thus mark a transition region of the magnetic field orientation in the
inner kiloparsec of the Galaxy.Comment: 6 pages, 4 figures, to appear in ApJ Letters; Figs. 2 & 3 are color
.ps files and best viewed in colo
Corrections to Decay in the 2HDM
QCD corrections to the inclusive decay are
investigated within the two - Higgs doublet extension of the standard model
(2HDM). The analysis is performed in the so - called off-resonance region; the
dependence of the obtained results on the choice of the renormalization scale
is examined in details. It is shown that corrections can suppress
the decay width up to times (depending on the
choice of the dilepton invariant mass and the low - energy scale ). As
a result, in the experimentally allowed range of the parameters space, the
relations between the branching ratio and the new physics
parameters are strongly affected. It is found also that though the
renormalization scale dependence of the branching is
significantly reduced, higher order effects in the perturbation theory can
still be nonnegligible.Comment: 16 pages, latex, including 6 figures and 3 table
Method to reduce the formation of crystallites in ZnO nanorod thin-films grown via ultra-fast microwave heating
© 2018 This paper discusses the nucleation and growth mechanisms of ZnO nanorod thin-films and larger sized crystallites that form within the solution and on surfaces during an ultra-fast microwave heating growth process. In particular, the work focusses on the elimination of crystallites as this is necessary to improve thin-film uniformity and to prevent electrical short circuits between electrodes in device applications. High microwave power during the early stages of ZnO deposition was found to be a key factor in the formation of unwanted crystallites on substrate surfaces. Once formed, the crystallites, grow at a much faster rate than the nanorods and quickly dominate the thin-film structure. A new two-step microwave heating method was developed that eliminates the onset of crystallite formation, allowing the deposition of large-area nanorod thin-films that are free from crystallites. A dissolution-recrystallization mechanism is proposed to explain why this procedure is successful and we demonstrate the importance of the work in the fabrication of low-cost memristor devices
Mechanism of thermally activated c-axis dissipation in layered High-T superconductors at high fields
We propose a simple model which explains experimental behavior of -axis
resistivity in layered High-T superconductors at high fields in a limited
temperature range. It is generally accepted that the in-plane dissipation at
low temperatures is caused by small concentration of mobile pancake vortices
whose diffusive motion is thermally activated. We demonstrate that in such
situation a finite conductivity appears also in -direction due to the phase
slips between the planes caused by the mobile pancakes. The model gives
universal relation between the components of conductivity which is in good
agreement with experimental data.Comment: RevTeX, 4 pages, 2 Postscript figure
Coupling rheology and segregation in granular flows
During the last fifteen years there has been a paradigm shift in the continuum modelling of granular materials; most notably with the development of rheological models, such as the μ(I) μ(I) -rheology (where μ μ is the friction and I is the inertial number), but also with significant advances in theories for particle segregation. This paper details theoretical and numerical frameworks (based on OpenFOAM) which unify these currently disconnected endeavours. Coupling the segregation with the flow, and vice versa, is not only vital for a complete theory of granular materials, but is also beneficial for developing numerical methods to handle evolving free surfaces. This general approach is based on the partially regularized incompressible μ(I) μ(I) -rheology, which is coupled to the gravity-driven segregation theory of Gray & Ancey (J. Fluid Mech., vol. 678, 2011, pp. 353–588). These advection–diffusion–segregation equations describe the evolving concentrations of the constituents, which then couple back to the variable viscosity in the incompressible Navier–Stokes equations. A novel feature of this approach is that any number of differently sized phases may be included, which may have disparate frictional properties. Further inclusion of an excess air phase, which segregates away from the granular material, then allows the complex evolution of the free surface to be captured simultaneously. Three primary coupling mechanisms are identified: (i) advection of the particle concentrations by the bulk velocity, (ii) feedback of the particle-size and/or frictional properties on the bulk flow field and (iii) influence of the shear rate, pressure, gravity, particle size and particle-size ratio on the locally evolving segregation and diffusion rates. The numerical method is extensively tested in one-way coupled computations, before the fully coupled model is compared with the discrete element method simulations of Tripathi & Khakhar (Phys. Fluids, vol. 23, 2011, 113302) and used to compute the petal-like segregation pattern that spontaneously develops in a square rotating drum
Volume Fractions of the Kinematic "Near-Critical" Sets of the Quantum Ensemble Control Landscape
An estimate is derived for the volume fraction of a subset in the neighborhood
of the critical set
of the kinematic quantum ensemble control landscape J(U) = Tr(U\rho U' O),
where represents the unitary time evolution operator, {\rho} is the initial
density matrix of the ensemble, and O is an observable operator. This estimate
is based on the Hilbert-Schmidt geometry for the unitary group and a
first-order approximation of . An upper bound on these
near-critical volumes is conjectured and supported by numerical simulation,
leading to an asymptotic analysis as the dimension of the quantum system
rises in which the volume fractions of these "near-critical" sets decrease to
zero as increases. This result helps explain the apparent lack of influence
exerted by the many saddles of over the gradient flow.Comment: 27 pages, 1 figur
Using mental-modelling to explore how irrigators in the Murray-Darling Basin make water-use decisions
Study region: Water stress and over-allocation are at the forefront of water management and policy challenges in Australia, especially in the Murray–Darling Basin (MDB). Because irrigated agriculture is a major social and economic component of the MDB, farmer decision-making plays a major role in water sustainability in the region. Study focus: This study used a fuzzy cognitive mapping methodology, ‘mental modeling’, to understand the perceived constraints of irrigator water-use decisions in the MDB, for two different types of irrigation: permanent and annual crops. The approach elicits and documents irrigator insights into the complex and networked nature of irrigation water use decisions in relation to farm-based dynamics. New hydrological insights for the region:
Results suggest support for greater local and irrigator involvement in water management decisions. Many, if not most, of the irrigators understood the need for, or at least the inevitability of, governmental policies and regulations. However, a lack of accountability, predictability, and transparency has added to the uncertainty in farm-based water decision-making. Irrigators supported the concept of environmental sustainability, although they might not always agree with how the concept is implemented. The mental modelling approach facilitated knowledge sharing among stakeholders and can be used to identify common goals. Future research utilizing the mental modelling approach may encourage co-management and knowledge partnerships between irrigators, water managers and government officials.Ellen M. Douglas, Sarah Ann Wheeler, David J. Smith, Ian C. Overton, Steven A. Gray, Tanya M. Doody, Neville D. Crossma
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