5,422 research outputs found
An end-to-end machine learning system for harmonic analysis of music
We present a new system for simultaneous estimation of keys, chords, and bass
notes from music audio. It makes use of a novel chromagram representation of
audio that takes perception of loudness into account. Furthermore, it is fully
based on machine learning (instead of expert knowledge), such that it is
potentially applicable to a wider range of genres as long as training data is
available. As compared to other models, the proposed system is fast and memory
efficient, while achieving state-of-the-art performance.Comment: MIREX report and preparation of Journal submissio
Harmonic-seeded remote laser emissions in N2-Ar, N2-Xe and N2-Ne mixtures: a comparative study
We report on the investigation on harmonic-seeded remote laser emissions at
391 nm wavelength from strong-field ionized nitrogen molecules in three
different gas mixtures, i.e., N2-Ar, N2-Xe and N2-Ne. We observed a decrease in
the remote laser intensity in the N2-Xe mixture because of the decreased
clamped intensity in the filament; whereas in the N2-Ne mixture, the remote
laser intensity slightly increases because of the increased clamped intensity
within the filament. Remarkably, although the clamped intensity in the filament
remains nearly unchanged in the N2-Ar mixture because of the similar ionization
potentials of N2 and Ar, a significant enhancement of the lasing emission is
realized in the N2-Ar mixture. The enhancement is attributed to the stronger
third harmonic seed, and longer gain medium due to the extended filament.Comment: 10 pages, 5 figure
A doubly stochastic rainfall model with exponentially decaying pulses
We develop a doubly stochastic point process model with exponentially decaying pulses to describe the statistical properties of the rainfall intensity process. Mathematical formulation of the point process model is described along with second-order moment characteristics of the rainfall depth and aggregated processes. The derived second-order properties of the accumulated rainfall at different aggregation levels are used in model assessment. A data analysis using 15 years of sub-hourly rainfall data from England is presented. Models with fixed and variable pulse lifetime are explored. The performance of the model is compared with that of a doubly stochastic rectangular pulse model. The proposed model fits most of the empirical rainfall properties well at sub-hourly, hourly and daily aggregation levels
The Effect of Tantalum Incorporation on the Physical and Chemical Properties of Ternary Silicon–calcium–phosphorous Mesoporous Bioactive Glasses
Synthesis and characterization of the first mesoporous bioactive glasses (MBGs) containing tantalum are reported here, along with their potential application as hemostats. Silica MBGs were synthesized using with the molar composition of (80-x)% Si, 15% Ca, 5% P, and x% Ta. It was found that incorporation of \u3e1 mol % Ta into the MBGs changes their physical and chemical properties. Increasing Ta content from 0 to 10 mol % causes a decrease in the surface area and pore volume of ~20 and ~35%, respectively. This is due to the increase in nonbridging oxygens and mismatch of thermal expansion coefficient which created discontinuities in the ordered channel structure. However, the effect is not significant on the amount of ions (Si, Ca, P, and Ta) released, from the sample into deionized water, for short durations (\u3c60 \u3emin). In a mouse tail-cut model, a significant decrease in bleeding time (≥50% of average bleeding time) was found for Ta-MBGs compared to having no treatment, Arista, and MBG without Ta. Further studies are proposed to determine the mechanism of Ta involvement with the hemostatic process. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2229–2237, 2019
Giant Asymmetric Radiation from an Ultrathin Bianisotropic Metamaterial
Unidirectional radiation is of particular interest in high-power lasing and
optics. Commonly, however, it is difficult to achieve a unidirectional profile
in such a system without breaking reciprocity. Recently, assisted by
metamaterials without structural symmetry, antennas that radiate asymmetrically
have been developed, hence providing the possibility of achieving
unidirectionality. Nevertheless, it has been challenging to achieve extremely
high radiation asymmetry in such antennas. Here, we demonstrate that this
radiation asymmetry is further enhanced when magnetic plasmons are present in
the metamaterials. Experimentally, we show that a thin metamaterial with a
thickness of approximately {\lambda}_0/8 can exhibit a forward-to-backward
emission asymmetry of up to 1:32 without any optimization. Our work paves the
way for manipulating asymmetric radiation by means of metamaterials and may
have a variety of promising applications, such as directional optical and
quantum emitters, lasers, and absorbers.Comment: 22pages, 5figures, Journal Articl
Competing source and loss mechanisms due to wave-particle interactions in Earth’s outer radiation belt during the 30 September to 3 October 2012 geomagnetic storm
Abstract Drastic variations of Earth’s outer radiation belt electrons ultimately result from various competing source, loss, and transport processes, to which wave-particle interactions are critically important. Using 15 spacecraft including NASA’s Van Allen Probes, THEMIS, and SAMPEX missions and NOAA’s GOES and POES constellations, we investigated the evolution of the outer belt during the strong geomagnetic storm of 30 September to 3 October 2012. This storm’s main phase dropout exhibited enhanced losses to the atmosphere at L*\u3c 4, where the phase space density (PSD) of multi-MeV electrons dropped by over an order of magnitude in1 MeV electrons and energetic protons, SAMPEX \u3e1 MeV electrons, and ground observations of band-limited Pc1-2 wave activity, we show that this sudden loss was consistent with pitch angle scattering by electromagnetic ion cyclotron waves in the dusk magnetic local time sector at 3\u3c L*\u3c 4. At 4\u3c L*\u3c 5, local acceleration was also active during the main and early recovery phases, when growing peaks in electron PSD were observed by both Van Allen Probes and THEMIS. This acceleration corresponded to the period when IMF Bz was southward, the AE index was \u3e300 nT, and energetic electron injections and whistler-mode chorus waves were observed throughout the inner magnetosphere for \u3e12 h. After this period, Bz turned northward, and injections, chorus activity, and enhancements in PSD ceased. Overall, the outer belt was depleted by this storm. From the unprecedented level of observations available, we show direct evidence of the competitive nature of different wave-particle interactions controlling relativistic electron fluxes in the outer radiation belt
Fanning the flames: How the European Union is fuelling a new arms race - Executive Summary
At the time of writing in March 2022, a war has broken out in eastern Europe following the illegal invasion of Ukraine by Russian troops. Towards the end of 2021 unrest in the Balkans came close to boiling point. Tensions in the South China Sea continue to simmer and threaten regional and global stability. Wars and violence continue in Afghanistan, in Central Africa, Iraq, several countries across the Sahel, Syria, and Yemen among other countries and regions experiencing constant violence and consequent displacement. Some of the world's most powerful nations are sabre-rattling, drafting and deploying troops, stockpiling military materiel, and actively preparing for war – including the European Union (EU) and some of its member states. Contrary to the EU's founding principle of promoting peace, it too has been charting a course to establish itself as a global military power. History has shown, however, that far from contributing to stability and peace, militarism fuels tension, instability, destruction and devastation.In a 'watershed moment', in response to the war in Ukraine, the EU announced that it would, for the first time, fund and supply lethal weapons to a country under attack through the European Peace Facility (EPF). While this move is unprecedented, it is not unexpected. The EU has been pursuing a military path since the entry in to force of the Lisbon Treaty in 2009, which provides the legal underpinning to create a common security and defence policy. Less than a decade later, in a new point of departure, the EU created specific budget lines to allocate funding to military-related projects. This decision firmly set the EU on a new and deeply worrying trajectory, where international political and social problems were to be addressed not only through dialogue and diplomacy, but also through the threat of military solutions
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