24,779 research outputs found
The observed by the BES Collaboration
In the framework of the meson decay model, the strong decays of the
and states are investigated. It is found that in
the presence of the initial state mass being 2.24 GeV, the total widths of the
and states are about 438 MeV and 125 MeV,
respectively. Also, when the initial state mass varies from 2220 to 2400 MeV,
the total width of the state varies from about 100 to 132
MeV, while the total width of the state varies from about
400 to 594 MeV. A comparison of the predicted widths and the experimental
result of GeV, the width of the
with a mass of GeV recently observed by the
BES Collaboration in the radiative decay , suggests that it would be very difficult to identify the
as the state, and the seams a
good candidate for the state.Comment: 14 pages, 3 figures, typos corrected, Accepted by Physical Review
Applications of FEM and BEM in two-dimensional fracture mechanics problems
A comparison of the finite element method (FEM) and boundary element method (BEM) for the solution of two-dimensional plane strain problems in fracture mechanics is presented in this paper. Stress intensity factors (SIF's) were calculated using both methods for elastic plates with either a single-edge crack or an inclined-edge crack. In particular, two currently available programs, ANSYS for finite element analysis and BEASY for boundary element analysis, were used
Squeezed-state generation in optical bistability
Experiments to generate squeezed states of light are described for a collection of two-level atoms within a high-finesse cavity. The investigation is conducted in a regime for which the weak-field coupling of atoms to the cavity mode produces a splitting in the normal mode structure of the atom-field system that is large compared with the atomic linewidth. Reductions in photocurrent noise of 30% (-1.55 dB) below the noise level set by the vacuum state of the field are observed in a balanced homodyne detector. A degree of squeezing of approximately 50% is inferred for the field state in the absence of propagation and detection losses. The observed spectrum of squeezing extends over a very broad range of frequencies (~±75 MHz), with the frequency of best squeezing corresponding to an offset from the optical carrier given by the normal mode splitting
Communication-Efficient Federated Learning for Wireless Edge Intelligence in IoT
This is the author accepted manuscript. The final version is available from IEEE via the DOI in this recordThe rapidly expanding number of IoT devices is
generating huge quantities of data, but public concern over
data privacy means users are apprehensive to send data to a
central server for Machine Learning (ML) purposes. The easilychanged behaviours of edge infrastructure that Software Defined
Networking provides makes it possible to collate IoT data at
edge servers and gateways, where Federated Learning (FL) can
be performed: building a central model without uploading data to
the server. FedAvg is a FL algorithm which has been the subject
of much study, however it suffers from a large number of rounds
to convergence with non-Independent, Identically Distributed
(non-IID) client datasets and high communication costs per
round. We propose adapting FedAvg to use a distributed form
of Adam optimisation, greatly reducing the number of rounds
to convergence, along with novel compression techniques, to
produce Communication-Efficient FedAvg (CE-FedAvg). We perform extensive experiments with the MNIST/CIFAR-10 datasets,
IID/non-IID client data, varying numbers of clients, client participation rates, and compression rates. These show CE-FedAvg
can converge to a target accuracy in up to 6Ă less rounds than
similarly compressed FedAvg, while uploading up to 3Ă less data,
and is more robust to aggressive compression. Experiments on
an edge-computing-like testbed using Raspberry Pi clients also
show CE-FedAvg is able to reach a target accuracy in up to 1.7Ă
less real time than FedAvg.Engineering and Physical Sciences Research Council (EPSRC
Error Propagation Mitigation in Sliding Window Decoding of Braided Convolutional Codes
We investigate error propagation in sliding window decoding of braided
convolutional codes (BCCs). Previous studies of BCCs have focused on iterative
decoding thresholds, minimum distance properties, and their bit error rate
(BER) performance at small to moderate frame length. Here, we consider a
sliding window decoder in the context of large frame length or one that
continuously outputs blocks in a streaming fashion. In this case, decoder error
propagation, due to the feedback inherent in BCCs, can be a serious problem.In
order to mitigate the effects of error propagation, we propose several schemes:
a \emph{window extension algorithm} where the decoder window size can be
extended adaptively, a resynchronization mechanism where we reset the encoder
to the initial state, and a retransmission strategy where erroneously decoded
blocks are retransmitted. In addition, we introduce a soft BER stopping rule to
reduce computational complexity, and the tradeoff between performance and
complexity is examined. Simulation results show that, using the proposed window
extension algorithm, resynchronization mechanism, and retransmission strategy,
the BER performance of BCCs can be improved by up to four orders of magnitude
in the signal-to-noise ratio operating range of interest, and in addition the
soft BER stopping rule can be employed to reduce computational complexity.Comment: arXiv admin note: text overlap with arXiv:1801.0323
Constraining the Atmospheric Composition of the Day-Night Terminators of HD 189733b : Atmospheric Retrieval with Aerosols
A number of observations have shown that Rayleigh scattering by aerosols
dominates the transmission spectrum of HD 189733b at wavelengths shortward of 1
m. In this study, we retrieve a range of aerosol distributions consistent
with transmission spectroscopy between 0.3-24 m that were recently
re-analyzed by Pont et al. (2013). To constrain the particle size and the
optical depth of the aerosol layer, we investigate the degeneracies between
aerosol composition, temperature, planetary radius, and molecular abundances
that prevent unique solutions for transit spectroscopy. Assuming that the
aerosol is composed of MgSiO, we suggest that a vertically uniform aerosol
layer over all pressures with a monodisperse particle size smaller than about
0.1 m and an optical depth in the range 0.002-0.02 at 1 m provides
statistically meaningful solutions for the day/night terminator regions of HD
189733b. Generally, we find that a uniform aerosol layer provide adequate fits
to the data if the optical depth is less than 0.1 and the particle size is
smaller than 0.1 m, irrespective of the atmospheric temperature, planetary
radius, aerosol composition, and gaseous molecules. Strong constraints on the
aerosol properties are provided by spectra at wavelengths shortward of 1 m
as well as longward of 8 m, if the aerosol material has absorption
features in this region. We show that these are the optimal wavelengths for
quantifying the effects of aerosols, which may guide the design of future space
observations. The present investigation indicates that the current data offer
sufficient information to constrain some of the aerosol properties of
HD189733b, but the chemistry in the terminator regions remains uncertain.Comment: Transferred to ApJ and accepted. 11 pages, 10 figures, 1 tabl
The First Calculation for the Mass of the Ground Glueball State on Lattice
Under the quenched approximation, we perform a lattice calculation for the
mass of the ground glueball state in channel on a
lattice. Our calculation shows that the mass of this state is
, which rules out the or mainly
glueball interpretation for .Comment: 10 pages and 1 figur
Kinetic stabilization of Fe film on (4 by 2)-GaAs(100)
We grow Fe film on (4 by 2)-GaAs(100) at low temperature, (~ 130 K) and study
their chemical structure by photoelectron spectroscopy using synchrotron
radiation. We observe the effective suppression of As segregation and
remarkable reduction of alloy formation near the interface between Fe and
substrate. Hence, this should be a way to grow virtually pristine Fe film on
GaAs(100). Further, the Fe film is found stable against As segregation even
after warmed up to room temperature. There only forms very thin, ~ 8 angstrom
thick interface alloy. It is speculated that the interface alloy forms via
surface diffusion mediated by interface defects formed during the low
temperature growth of the Fe film. Further out-diffusion of both Ga and As are
suppressed because it should then proceed via inefficient bulk diffusion.Comment: 4 figure
Dust composition and mass-loss return from the luminous blue variable R71 in the LMC
We present an analysis of mid-and far-infrared (IR) spectrum and spectral
energy distribution (SED) of the LBV R71 in the LMC.This work aims to
understand the overall contribution of high-mass LBVs to the total dust-mass
budget of the interstellar medium (ISM) of the LMC and compare this with the
contribution from low-mass asymptotic giant branch (AGB) stars. As a case
study, we analyze the SED of R71. We compiled all the available photometric and
spectroscopic observational fluxes from various telescopes for a wide
wavelength range (0.36 -- 250\,m). We determined the dust composition from
the spectroscopic data, and derived the ejected dust mass, dust mass-loss rate,
and other dust shell properties by modeling the SED of R71. We noted nine
spectral features in the dust shell of R71 by analyzing Spitzer spectroscopic
data. Among these, we identified three new crystalline silicate features. We
computed our model spectrum by using 3D radiative transfer code MCMax. Our
model calculation shows that dust is dominated by amorphous silicates, with
some crystalline silicates, metallic iron, and a very tiny amount of polycyclic
aromatic hydrocarbon (PAH) molecules. The presence of both silicates and PAHs
indicates that the dust has a mixed chemistry. We derived a dust mass of 0.01
M, from which we arrive at a total ejected mass of 5
M. This implies a time-averaged dust mass-loss rate of
2.510 M\,yr with an explosion about 4000 years
ago. We assume that the other five confirmed dusty LBVs in the LMC loose mass
at a similar rate, and estimate the total contribution to the mass budget of
the LMC to be 10 M\,yr, which is comparable to
the contribution by all the AGB stars in the LMC. Based on our analysis on R71,
we speculate that LBVs as a class may be an important dust source in the ISM of
the LMC.Comment: 10 pages, 6 figures, 2 table
Magnetic properties of a novel Pr Fe Ti phase
In a systematic study of the (Pr1âxTix)Fe5 alloy series, the (Pr0.65Ti0.35)Fe5 alloy has been
found to have a dominant phase with either the rhombohedral Th2Zn17 structure or the
newly discovered Nd2(Fe,Ti)19 (S. J. Collocott, R. K. Day, J. B. Dunlop, and R. L. Davis,
in Proceedings of the Seventh International Symposium on Magnetic Anisotropy and
Coercivity in RâT Alloys, Canberra, July 1992, p. 437) structure, depending on the
annealing procedure. Powderâxârayâdiffraction patterns and scanning electron
microscopy show that the sample annealed at a temperature of 850â°C followed by
1000â°C has the 2:17 structure whereas annealing at 1000â°C directly leads to the new
2:19 structure. Energyâdispersive xâray analysis yields Pr:Fe:Ti ratios of 10.7:86.2:3.1
for the Pr2(Fe,Ti)17 phase and 9.2:85.9:4.9 for the Pr2(Fe,Ti)19 phase.
57
Fe Mössbauer
spectroscopy (at 295 K) gives values for the average
57
Fe hyperfine field of 15.7 T for the
2:17 phase and 17.5 T for the 2:19 phase, respectively
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