120,123 research outputs found
Exact Outage Performance Analysis of Multiuser Multi-relay Spectrum Sharing Cognitive Networks
In this paper, we investigate the outage performance of dual-hop multiuser multi-relay cognitive radio networks under spectrum sharing constraints. Using an efficient relay-destination selection scheme, the exact and asymptotic closed-form expressions for the outage probability are derived. From these expressions it is indicated that the achieved diversity order is only determined by the number of secondary user (SU) relays and destinations, and equals to M+N (where M and N are the number of destination nodes and relay nodes, respectively). Further, we find that the coding gain of the SU network will be affected by the interference threshold at the primary user (PU) receiver. Specifically, as the increases of the interference threshold, the coding gain of the considered network approaches to that of the multiuser multi-relay system in the non-cognitive network. Finally, our study is corroborated by representative numerical examples
Quantum Computing via The Bethe Ansatz
We recognize quantum circuit model of computation as factorisable scattering
model and propose that a quantum computer is associated with a quantum
many-body system solved by the Bethe ansatz. As an typical example to support
our perspectives on quantum computation, we study quantum computing in
one-dimensional nonrelativistic system with delta-function interaction, where
the two-body scattering matrix satisfies the factorisation equation (the
quantum Yang--Baxter equation) and acts as a parametric two-body quantum gate.
We conclude by comparing quantum computing via the factorisable scattering with
topological quantum computing.Comment: 6 pages. Comments welcom
The structural, mechanical, electronic, optical and thermodynamic properties of t-XAs (X Si, Ge and Sn) by first-principles calculations
The structural, mechanical, electronic, optical and thermodynamic properties
of the t-XAs (X Si, Ge and Sn) with
tetragonal structure have been investigated by first principles calculations.
Our calculated results show that these compounds are mechanically and
dynamically stable. By the study of elastic anisotropy, it is found that the
anisotropic of the t-SnAs is stronger than that
of t-SiAs and
t-GeAs. The band structures and density of states
show that the t-XAs (Si, Ge and Sn) are
semiconductors with narrow band gaps. Based on the analyses of electron density
difference, in t-XAs As atoms get electrons, X
atoms lose electrons. The calculated static dielectric constants,
, are 15.5, 20.0 and 15.1 eV for
t-XAs (X Si, Ge and Sn), respectively. The
Dulong-Petit limit of t-XAs is about 10 J
molK. The thermodynamic stability successively
decreases from t-SiAs to
t-GeAs to t-SnAs.Comment: 14 pages, 10 figures, 6 table
A fibre optic sensor for the measurement of surface roughness and displacement using artificial neural networks
This paper presents a fiber optic sensor system, artificial neural networks (fast back-propagation) are employed for the data processing. The use of the neural networks makes it possible for the sensor to be used both for surface roughness and displacement measurement at the same time. The results indicate 100% correct surface classification for ten different surfaces (different materials, different manufacturing methods, and different surface roughnesses) and displacement errors less then ±5 μm. The actual accuracy was restricted by the calibration machine. A measuring range of ±0.8 mm for the displacement measurement was achieved
Disentangling the stigma of HIV/AIDS from the stigmas of drugs use, commercial sex and commercial blood donation – A factorial survey of medical students in China
Background: HIV/AIDS related stigma interferes with the provision of appropriate care and
support for people living with HIV/AIDS. Currently, programs to address the stigma approach it as
if it occurs in isolation, separate from the co-stigmas related to the various modes of disease
transmission including injection drug use (IDU) and commercial sex (CS). In order to develop
better programs to address HIV/AIDS related stigma, the inter-relationship (or 'layering') between
HIV/AIDS stigma and the co-stigmas needs to be better understood. This paper describes an
experimental study for disentangling the layering of HIV/AIDS related stigmas.
Methods: The study used a factorial survey design. 352 medical students from Guangzhou were
presented with four random vignettes each describing a hypothetical male. The vignettes were
identical except for the presence of a disease diagnosis (AIDS, leukaemia, or no disease) and a cocharacteristic
(IDU, CS, commercial blood donation (CBD), blood transfusion or no cocharacteristic).
After reading each vignette, participants completed a measure of social distance that
assessed the level of stigmatising attitudes.
Results: Bivariate and multivariable analyses revealed statistically significant levels of stigma associated with AIDS, IDU, CS and CBD. The layering of stigma was explored using a recently
developed technique. Strong interactions between the stigmas of AIDS and the co-characteristics
were also found. AIDS was significantly less stigmatising than IDU or CS. Critically, the stigma of
AIDS in combination with either the stigmas of IDU or CS was significantly less than the stigma of
IDU alone or CS alone.
Conclusion: The findings pose several surprising challenges to conventional beliefs about HIV/
AIDS related stigma and stigma interventions that have focused exclusively on the disease stigma.
Contrary to the belief that having a co-stigma would add to the intensity of stigma attached to
people with HIV/AIDS, the findings indicate the presence of an illness might have a moderating
effect on the stigma of certain co-characteristics like IDU. The strong interdependence between
the stigmas of HIV/AIDS and the co-stigmas of IDU and CS suggest that reducing the co-stigmas
should be an integral part of HIV/AIDS stigma intervention within this context
Research on 2×2 MIMO Channel with Truncated Laplacian Azimuth Power Spectrum
Multiple-input multiple-output (MIMO) Rayleigh fading channel with truncated Laplacian azimuth power spectrum (APS) is studied. By using the power correlation matrix of MIMO channel model and the modified Jakes simulator, into which with random phases are inserted, the effect of the azimuth spread (AS), angle of departure (AOD) and angle of arrival (AOA) on the spatial correlation coefficient and channel capacity are investigated. Numerical results show that larger AS generates smaller spatial correlation coefficient amplitude, while larger average AOD or AOA produces larger spatial correlation coefficient amplitude. The average capacity variation is comprehensively dominated by the average AOD, AOA and AS
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