356 research outputs found
RawNet: Fast End-to-End Neural Vocoder
Neural networks based vocoders have recently demonstrated the powerful
ability to synthesize high quality speech. These models usually generate
samples by conditioning on some spectrum features, such as Mel-spectrum.
However, these features are extracted by using speech analysis module including
some processing based on the human knowledge. In this work, we proposed RawNet,
a truly end-to-end neural vocoder, which use a coder network to learn the
higher representation of signal, and an autoregressive voder network to
generate speech sample by sample. The coder and voder together act like an
auto-encoder network, and could be jointly trained directly on raw waveform
without any human-designed features. The experiments on the Copy-Synthesis
tasks show that RawNet can achieve the comparative synthesized speech quality
with LPCNet, with a smaller model architecture and faster speech generation at
the inference step.Comment: Submitted to Interspeech 2019, Graz, Austri
Unquantized thermal Hall effect in quantum spin liquids with spinon Fermi surfaces
Recent theoretical studies have found quantum spin liquid states with spinon
Fermi surfaces upon the application of a magnetic field on a gapped state with
topological order. We investigate the thermal Hall conductivity across this
transition, describing how the quantized thermal Hall conductivity of the
gapped state changes to an unquantized thermal Hall conductivity in the gapless
spinon Fermi surface state. We consider two cases, both of potential
experimental interest: the state with non-Abelian Ising topological order on
the honeycomb lattice, and the state with Abelian chiral spin liquid
topological order on the triangular lattice.Comment: 20 pages, 9 figure
Quantifying Coherence with Untrusted Devices
Device-independent (DI) tests allow to witness and quantify the quantum
feature of a system, such as entanglement, without trusting the implementation
devices. Although DI test is a powerful tool in many quantum information tasks,
it generally requires nonlocal settings. Fundamentally, the superposition
property of quantum states, quantified by coherence measures, is a distinct
feature to distinguish quantum mechanics from classical theories. In
literature, witness and quantification of coherence with trusted devices have
been well-studied. However, it remains open whether we can witness and quantify
single party coherence with untrusted devices, as it is not clear whether the
concept of DI tests exists without a nonlocal setting. In this work, we study
DI witness and quantification of coherence with untrusted devices. First, we
prove a no-go theorem for a fully DI scenario, as well as a semi DI scenario
employing a joint measurement with trusted ancillary states. We then propose a
general prepare-and-measure semi DI scheme for witnessing and quantifying the
amount of coherence. We show how to quantify the relative entropy and the
norm of single party coherence with analytical and numerical methods. As
coherence is a fundamental resource for tasks such as quantum random number
generation and quantum key distribution, we expect our result may shed light on
designing new semi DI quantum cryptographic schemes.Comment: 14 pages, 7 figures, comments are welcome
Transport of ion beam in an annular magnetically expanding helicon double layer thruster
An ion beam generated by an annular double layer has been measured in a helicon thruster, which
sustains a magnetised low-pressure (5.0 104 Torr) argon plasma at a constant radio-frequency
(13.56 MHz) power of 300 W. After the ion beam exits the annular structure, it merges into a solid
centrally peaked structure in the diffusion chamber. As the annular ion beam moves towards the
inner region in the diffusion chamber, a reversed-cone plasma wake (with a half opening angle of
about 30 ) is formed. This process is verified by measuring both the radial and axial distributions
of the beam potential and beam current. The beam potential changes from a two-peak radial profile
(maximum value 30 V, minimum value 22.5 V) to a flat ( 28 V) along the axial direction;
similarly, the beam current changes from a two-peak to one-peak radial profile and the maximum
value decreases by half. The inward cross-magnetic-field motion of the beam ions is caused by a
divergent electric field in the source. Cross-field diffusion of electrons is also observed in the inner
plume and is determined as being of non-ambipolar origin
Principle of radial transport in low temperature annular plasmas
Radial transport in low temperature annular plasmas is investigated theoretically in this paper. The electrons are assumed to be in quasi-equilibrium due to their high temperature and light inertial mass. The ions are not in equilibrium and their transport is analyzed in three different situations: a low electric field (LEF) model, an intermediate electric field (IEF) model, and a high electric field (HEF) model. The universal IEF model smoothly connects the LEF and HEF models at their respective electric field strength limits and gives more accurate results of the ion mobility coefficient and effective ion temperature over the entire electric field strength range. Annular modelling is applied to an argon plasma and numerical results of the density peak position, the annular boundary loss coefficient and the electron temperature are given as functions of the annular geometry ratio and Paschen number
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