8,894 research outputs found
Coded Modulation Assisted Radial Basis Function Aided Turbo Equalisation for Dispersive Rayleigh Fading Channels
In this contribution a range of Coded Modulation (CM) assisted Radial Basis Function (RBF) based Turbo Equalisation (TEQ) schemes are investigated when communicating over dispersive Rayleigh fading channels. Specifically, 16QAM based Trellis Coded Modulation (TCM), Turbo TCM (TTCM), Bit-Interleaved Coded Modulation (BICM) and iteratively decoded BICM (BICM-ID) are evaluated in the context of an RBF based TEQ scheme and a reduced-complexity RBF based In-phase/Quadrature-phase (I/Q) TEQ scheme. The Least Mean Square (LMS) algorithm was employed for channel estimation, where the initial estimation step-size used was 0.05, which was reduced to 0.01 for the second and the subsequent TEQ iterations. The achievable coding gain of the various CM schemes was significantly increased, when employing the proposed RBF-TEQ or RBF-I/Q-TEQ rather than the conventional non-iterative Decision Feedback Equaliser - (DFE). Explicitly, the reduced-complexity RBF-I/Q-TEQ-CM achieved a similar performance to the full-complexity RBF-TEQ-CM, while attaining a significant complexity reduction. The best overall performer was the RBF-I/Q-TEQ-TTCM scheme, requiring only 1.88~dB higher SNR at BER=10-5, than the identical throughput 3~BPS uncoded 8PSK scheme communicating over an AWGN channel. The coding gain of the scheme was 16.78-dB
Chiral Electronics
We consider the properties of electric circuits involving Weyl semimetals.
The existence of the anomaly-induced chiral magnetic current in a Weyl
semimetal subjected to magnetic field causes an interesting and unusual
behavior of such circuits. We consider two explicit examples: i) a circuit
involving the "chiral battery" and ii) a circuit that can be used as a "quantum
amplifier" of magnetic field. The unique properties of these circuits stem from
the chiral anomaly and may be utilized for creating "chiral electronic"
devices.Comment: 5 pages, 2 figures; final version to appear in Physical Review
Superdiffusive heat conduction in semiconductor alloys -- II. Truncated L\'evy formalism for experimental analysis
Nearly all experimental observations of quasi-ballistic heat flow are
interpreted using Fourier theory with modified thermal conductivity. Detailed
Boltzmann transport equation (BTE) analysis, however, reveals that the
quasi-ballistic motion of thermal energy in semiconductor alloys is no longer
Brownian but instead exhibits L\'evy dynamics with fractal dimension . Here, we present a framework that enables full 3D experimental analysis by
retaining all essential physics of the quasi-ballistic BTE dynamics
phenomenologically. A stochastic process with just two fitting parameters
describes the transition from pure L\'evy superdiffusion as short length and
time scales to regular Fourier diffusion. The model provides accurate fits to
time domain thermoreflectance raw experimental data over the full modulation
frequency range without requiring any `effective' thermal parameters and
without any a priori knowledge of microscopic phonon scattering mechanisms.
Identified values for InGaAs and SiGe match ab initio BTE predictions
within a few percent. Our results provide experimental evidence of fractal
L\'evy heat conduction in semiconductor alloys. The formalism additionally
indicates that the transient temperature inside the material differs
significantly from Fourier theory and can lead to improved thermal
characterization of nanoscale devices and material interfaces
1/2 BPS Geometries of M2 Giant Gravitons
We construct the general 1/2 BPS M2 giant graviton solutions asymptotic to
the eleven-dimensional maximally supersymmetric plane wave background, based on
the recent work of Lin, Lunin and Maldacena. The solutions have null
singularity and we argue that it is unavoidable to have null singularity in the
proposed framework, although the solutions are still physically relevant. They
involve an arbitrary function F(x) which is shown to have a correspondence to
the 1/2 BPS states of the BMN matrix model. A detailed map between the 1/2 BPS
states of both sides is worked out.Comment: 21 pages and 1 figure. v2: references added, comments adde
Retail event: A comparative study between local residents and tourists in spontaneous purchase
Research on festivals and cultural events draw considerable attention among academics
and practitioners. The relationships between marketing influence and spontaneous purchase have been studied in general retail setting; however, there is dearth knowledge of purchase patterns in a festive setting. This study aims to identify what factors motivate attendees to spontaneous purchase and to investigate how local residents and tourists respond in their spontaneous purchase when exposed to stimuli at a special event held infrequently for a short period of time. The flower market at the Chinese New Year Festival was chosen as the study context as it is one of the most popular events in Macau, in which spontaneous purchases are made. A quota sample of 150 local residents and 100 tourists was recruited in November, 2007. The results indicate that product quality, price, and variety are the top three priorities among both local residents and tourists when making purchasing decision at the flower market. Significant differences of free sample tasting and cultural tradition were found between the two segments in purchase intention. The findings allow marketing activities to be highly targeted according to the difference response of local residents and tourists. Future research is also recommended
The age and abundance structure of the stellar populations in the central sub-kpc of the Milky Way
The four main findings about the age and abundance structure of the Milky Way
bulge based on microlensed dwarf and subgiant stars are: (1) a wide metallicity
distribution with distinct peaks at [Fe/H]=-1.09, -0.63, -0.20, +0.12, +0.41;
(2) a high fraction of intermediate-age to young stars where at [Fe/H]>0 more
than 35 % are younger than 8 Gyr, (3) several episodes of significant star
formation in the bulge 3, 6, 8, and 11 Gyr ago; (4) the `knee' in the
alpha-element abundance trends of the sub-solar metallicity bulge appears to be
located at a slightly higher [Fe/H] (about 0.05 to 0.1 dex) than in the local
thick disk.Comment: 4 pages, contributed talk at the IAU Symposium 334 "Rediscovering our
Galaxy" in Potsdam, July 10-14, 201
Multiwavelength Mass Comparisons of the z~0.3 CNOC Cluster Sample
Results are presented from a detailed analysis of optical and X-ray
observations of moderate-redshift galaxy clusters from the Canadian Network for
Observational Cosmology (CNOC) subsample of the EMSS. The combination of
extensive optical and deep X-ray observations of these clusters make them ideal
candidates for multiwavelength mass comparison studies. X-ray surface
brightness profiles of 14 clusters with 0.17<z<0.55 are constructed from
Chandra observations and fit to single and double beta-models. Spatially
resolved temperature analysis is performed, indicating that five of the
clusters in this sample exhibit temperature gradients within their inner 60-200
kpc. Integrated spectra extracted within R_2500 provide temperature, abundance,
and luminosity information. Under assumptions of hydrostatic equilibrium and
spherical symmetry, we derive gas and total masses within R_2500 and R_200. We
find an average gas mass fraction within R_200 of 0.136 +/- 0.004, resulting in
Omega_m=0.28 +/- 0.01 (formal error). We also derive dynamical masses for these
clusters to R_200. We find no systematic bias between X-ray and dynamical
methods across the sample, with an average M(dyn)/M(X-ray) = 0.97 +/- 0.05. We
also compare X-ray masses to weak lensing mass estimates of a subset of our
sample, resulting in a weighted average of M(lens)/M(X-ray) of 0.99 +/- 0.07.
We investigate X-ray scaling relationships and find powerlaw slopes which are
slightly steeper than the predictions of self-similar models, with an E(z)^(-1)
Lx-Tx slope of 2.4 +/- 0.2 and an E(z) M_2500-Tx slope of 1.7 +/- 0.1.
Relationships between red-sequence optical richness (B_gc,red) and global
cluster X-ray properties (Tx, Lx and M_2500) are also examined and fitted.Comment: Astrophysical Journal, 48 pages, 11 figures, LaTeX. Added correction
to surface brightness normalization of MS1512.4+3647, corrections to sample
gas mass fractions and calculated value of Omega_m. Figure resolution has
been reduced to comply with astro-ph upload requirement
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