1,860 research outputs found
Quality interoperability within digital libraries: the DL.org perspective
Quality is the most dynamic aspect of DLs, and becomes even more complex with respect to interoperability. This paper formalizes the research motivations and hypotheses on quality interoperability conducted by the Quality Working Group within the EU-funded project DL.org (<a href="http://www.dlorg.eu">http://www.dlorg.eu/</a>). After providing a multi-level interoperability framework – adopted by DL.org - the authors illustrate key-research points and
approaches on the way to the interoperability of DLs quality, grounding them in the DELOS Reference Model. By applying the DELOS Reference Model Quality Concept Map to their interoperability motivating scenario, the authors subsequently present the two main research outcomes of their investigation - the Quality Core Model and the Quality Interoperability Survey
Rate-dependent morphology of Li2O2 growth in Li-O2 batteries
Compact solid discharge products enable energy storage devices with high
gravimetric and volumetric energy densities, but solid deposits on active
surfaces can disturb charge transport and induce mechanical stress. In this
Letter we develop a nanoscale continuum model for the growth of Li2O2 crystals
in lithium-oxygen batteries with organic electrolytes, based on a theory of
electrochemical non-equilibrium thermodynamics originally applied to Li-ion
batteries. As in the case of lithium insertion in phase-separating LiFePO4
nanoparticles, the theory predicts a transition from complex to uniform
morphologies of Li2O2 with increasing current. Discrete particle growth at low
discharge rates becomes suppressed at high rates, resulting in a film of
electronically insulating Li2O2 that limits cell performance. We predict that
the transition between these surface growth modes occurs at current densities
close to the exchange current density of the cathode reaction, consistent with
experimental observations.Comment: 8 pages, 6 fig
Surface resonance of the (2×1) reconstructed lanthanum hexaboride (001)-cleavage plane : a combined STM and DFT study
We performed a combined study of the (001)-cleavage plane of lanthanum hexaboride (LaB6) using scanning tunneling microscopy and density-functional theory (DFT). Experimentally, we found a (2×1) reconstructed surface on a local scale. The reconstruction is only short-range ordered and tends to order perpendicularly to step edges. At larger distances from surface steps, the reconstruction evolves to a labyrinthlike pattern. These findings are supported by low-energy electron diffraction experiments. Slab calculations within the framework of DFT show that the atomic structure consists of parallel lanthanum chains on top of boron octahedra. Scanning tunneling spectroscopy shows a prominent spectral feature at −0.6eV. Using DFT, we identify this structure as a surface resonance of the (2×1) reconstructed LaB6 (100) surface which is dominated by boron dangling bond states and lanthanum d states
Rieger, Schwabe, Suess-de Vries: The Sunny Beats of Resonance
We propose a self-consistent explanation of Rieger-type periodicities, the
Schwabe cycle, and the Suess-de Vries cycle in terms of resonances of various
wave phenomena with gravitational forces exerted by the orbiting planets.
Starting on the high-frequency side, we show that the two-planet spring tides
of Venus, Earth and Jupiter are able to excite magneto-Rossby waves which can
be linked with typical Rieger-type periods. We argue then that the 11.07-year
beat period of those magneto-Rossby waves synchronizes an underlying
conventional -dynamo, by periodically changing either the field
storage capacity in the tachocline or some portion of the -effect
therein. We also strengthen the argument that the Suess-de Vries cycle appears
as an 193-year beat period between the 22.14-year Hale cycle and a spin-orbit
coupling effect related with the 19.86-year rosette-like motion of the Sun
around the barycenter.Comment: 31 pages, 12 figure
Hawking Radiation on an Ion Ring in the Quantum Regime
This paper discusses a recent proposal for the simulation of acoustic black
holes with ions. The ions are rotating on a ring with an inhomogeneous, but
stationary velocity profile. Phonons cannot leave a region, in which the ion
velocity exceeds the group velocity of the phonons, as light cannot escape from
a black hole. The system is described by a discrete field theory with a
nonlinear dispersion relation. Hawking radiation is emitted by this acoustic
black hole, generating entanglement between the inside and the outside of the
black hole. We study schemes to detect the Hawking effect in this setup.Comment: 42 pages (one column), 17 figures, published revised versio
On the robustness of entanglement in analogue gravity systems
We investigate the possibility of generating quantum-correlated quasi-particles utilizing analogue gravity systems. The quantumness of these correlations is a key aspect of analogue gravity effects and their presence allows for a clear separation between classical and quantum analogue gravity effects. However, experiments in analogue systems, such as Bose–Einstein condensates (BECs) and shallow water waves, are always conducted at non-ideal conditions, in particular, one is dealing with dispersive media at non-zero temperatures. We analyse the influence of the initial temperature on the entanglement generation in analogue gravity phenomena. We lay out all the necessary steps to calculate the entanglement generated between quasi-particle modes and we analytically derive an upper bound on the maximal temperature at which given modes can still be entangled. We further investigate a mechanism to enhance the quantum correlations. As a particular example, we analyse the robustness of the entanglement creation against thermal noise in a sudden quench of an ideally homogeneous BEC, taking into account the super-sonic dispersion relations
Wavelet Analysis for Wind Fields Estimation
Wind field analysis from synthetic aperture radar images allows the estimation of wind direction and speed based on image descriptors. In this paper, we propose a framework to automate wind direction retrieval based on wavelet decomposition associated with spectral processing. We extend existing undecimated wavelet transform approaches, by including à trous with B3 spline scaling function, in addition to other wavelet bases as Gabor and Mexican-hat. The purpose is to extract more reliable directional information, when wind speed values range from 5 to 10 ms−1. Using C-band empirical models, associated with the estimated directional information, we calculate local wind speed values and compare our results with QuikSCAT scatterometer data. The proposed approach has potential application in the evaluation of oil spills and wind farms
Coherent control of a surface structural phase transition
Active optical control over matter is desirable in many scientific disciplines, with prominent examples in all-optical magnetic switching1,2, light-induced metastable or exotic phases of solids3,4,5,6,7,8 and the coherent control of chemical reactions9,10. Typically, these approaches dynamically steer a system towards states or reaction products far from equilibrium. In solids, metal-to-insulator transitions are an important target for optical manipulation, offering ultrafast changes of the electronic4 and lattice11,12,13,14,15,16 properties. The impact of coherences on the efficiencies and thresholds of such transitions, however, remains a largely open subject. Here, we demonstrate coherent control over a metal–insulator structural phase transition in a quasi-one-dimensional solid-state surface system. A femtosecond double-pulse excitation scheme17,18,19,20 is used to switch the system from the insulating to a metastable metallic state, and the corresponding structural changes are monitored by ultrafast low-energy electron diffraction21,22. To govern the transition, we harness vibrational coherence in key structural modes connecting both phases, and observe delay-dependent oscillations in the double-pulse switching efficiency. Mode-selective coherent control of solids and surfaces could open new routes to switching chemical and physical functionalities, enabled by metastable and non-equilibrium states
- …