7,707 research outputs found
Clean relaying aided cognitive radio under the coexistence constraint
We consider the interference-mitigation based cognitive radio where the
primary and secondary users can coexist at the same time and frequency bands,
under the constraint that the rate of the primary user (PU) must remain the
same with a single-user decoder. To meet such a coexistence constraint, the
relaying from the secondary user (SU) can help the PU's transmission under the
interference from the SU. However, the relayed signal in the known dirty paper
coding (DPC) based scheme is interfered by the SU's signal, and is not "clean".
In this paper, under the half-duplex constraints, we propose two new
transmission schemes aided by the clean relaying from the SU's transmitter and
receiver without interference from the SU. We name them as the clean
transmitter relaying (CT) and clean transmitter-receiver relaying (CTR) aided
cognitive radio, respectively. The rate and multiplexing gain performances of
CT and CTR in fading channels with various availabilities of the channel state
information at the transmitters (CSIT) are studied. Our CT generalizes the
celebrated DPC based scheme proposed previously. With full CSIT, the
multiplexing gain of the CTR is proved to be better (or no less) than that of
the previous DPC based schemes. This is because the silent period for decoding
the PU's messages for the DPC may not be necessary in the CTR. With only the
statistics of CSIT, we further prove that the CTR outperforms the rate
performance of the previous scheme in fast Rayleigh fading channels. The
numerical examples also show that in a large class of channels, the proposed CT
and CTR provide significant rate gains over the previous scheme with small
complexity penalties.Comment: 30 page
Entropy and Its Quantum Thermodynamical Implication for Anomalous Spectral Systems
The state function entropy and its quantum thermodynamical implication for
two typical dissipative systems with anomalous spectral densities are studied
by investigating on their low-temperature quantum behavior. In all cases it is
found that the entropy decays quickly and vanishes as the temperature
approaches zero. This reveals a good conformity with the third law of
thermodynamics and provides another evidence for the validity of fundamental
thermodynamical laws in the quantum dissipative region.Comment: 10 pages, 3 figure
BRYNTRN: A baryon transport computer code, computation procedures and data base
The development is described of an interaction data base and a numerical solution to the transport of baryons through the arbitrary shield material based on a straight ahead approximation of the Boltzmann equation. The code is most accurate for continuous energy boundary values but gives reasonable results for discrete spectra at the boundary with even a relatively coarse energy grid (30 points) and large spatial increments (1 cm in H2O)
HZETRN: A heavy ion/nucleon transport code for space radiations
The galactic heavy ion transport code (GCRTRN) and the nucleon transport code (BRYNTRN) are integrated into a code package (HZETRN). The code package is computer efficient and capable of operating in an engineering design environment for manned deep space mission studies. The nuclear data set used by the code is discussed including current limitations. Although the heavy ion nuclear cross sections are assumed constant, the nucleon-nuclear cross sections of BRYNTRN with full energy dependence are used. The relation of the final code to the Boltzmann equation is discussed in the context of simplifying assumptions. Error generation and propagation is discussed, and comparison is made with simplified analytic solutions to test numerical accuracy of the final results. A brief discussion of biological issues and their impact on fundamental developments in shielding technology is given
An experimental approach to quantify strain transfer efficiency of fibre bragg grating sensors to host structures
This paper developed a method to evaluate the strain transfer efficiency of
fibre Bragg grating sensors to host structures. Various coatings were applied to
fibre Bragg grating sensors after being fabricated. They were epoxy, silane
agent and polypropylene, representing different surface properties. A neat epoxy
resin plate was used as the host in which the coated fibre sensors were embedded
in the central layer. The tensile strain output from the FBGs was compared with
that obtained from electrical strain gauges which were attached on the surface
of the specimen. A calculating method based on the measured strains was
developed to quantify the strain transfer function of different surface
coatings. The strain transfer coefficient obtained from the proposed method
provided a direct indicator to evaluate the strain transfer efficiency of
different coatings used on the FBG sensors, under either short or long-term
loading. The results demonstrated that the fibre sensor without any coating
possessed the best strain transfer, whereas, the worst strain transfer was
created by polypropylene coating. Coatings play a most influential role in
strain measurements using FBG sensors
Horizontal divergence of typhoon-generated gravity waves in the upper troposphere and lower stratosphere (UTLS) and its influence on typhoon evolution
The characteristics of horizontal divergence induced by typhoon-generated
gravity waves (HDTGWs) and the influence of HDTGW on typhoon evolution are
investigated based on the simulation results of Typhoon Saomai (2006) using
the Weather Research and Forecasting (WRF) model. The power spectral density
of HDTGW shows dominant powers at horizontal wavelengths of 20–30 km and at
periods of less than 1 h. This is associated with gravity waves
generated by vigorous convective clouds in an inner core region of the
typhoon. However, the domain-averaged HDTGW in the upper troposphere and
lower stratosphere had a spectral peak at 24 h, which is well correlated
with the minimum sea-level pressure of the typhoon, especially during a
rapidly developing period. The 24 h period of the averaged HDTGW stems
from the inertia–gravity waves generated by the convective clouds in the
spiral rainbands, and showed no clear association with the thermal tides or
the diurnal variation of precipitation
The Neutrino Magnetic Moment Induced by Leptoquarks
Allowing leptoquarks to interact with both right-handed and left-handed
neutrinos (i.e., ``non-chiral'' leptoquarks), we show that a non-zero neutrino
magnetic moment can arise naturally. Although the mass of the non-chiral vector
leptoquark that couples to the first generation fermions is constrained
severely by universality of the leptonic decays and is found to be
greater than 50 TeV, the masses of the second and third generation non-chiral
vector leptoquarks may evade such constraint and may in general be in the range
of TeV. With reasonable input mass and coupling values, we find
that the neutrino magnetic moment due to the second generation leptoquarks is
of the order of while that caused by the
third generation leptoquarks, being enhanced significantly by the large top
quark mass, is in the range of .Comment: 11 pages, 3 eps figures, uses revte
Preparation and characterization of antigenic properties of gramicidin A- keyhole limpet hemocyanin and gramicidin A- ovalbumin conjugates
A rapid, simple and low cost procedure for preparing hapten-protein conjugates was developed using gramicidin A (GA) and two other water-soluble proteins, keyhole limpet hemocyanin (KLH) and ovalbumin (OVA). GA was a kind of antimicrobial peptides. Two lysines and a cysteine were linked to amino- terminus and carboxyl-terminus of the peptide chain, respectively, in order to form sulfhydryl groups and improve its water solubility. And the molecule weight and purity of the modified peptidechain were checked by electron spray ionization mass spectrometry (ESI-MS) and high performance liquid chromatography (HPLC). Then the activated KLH and OVA were conjugated to GA by using 4-(Nmaleimidomethyl) cyclohexane-1-carboxylic acid 3-sulfo-N-hydroxysuccinimide ester sodium salt (sulfo-SMCC) to form disulfide linkage. In order to obtain artificial antigen of GA, GA was linked to KLHand OVA by sulfo-SMCC coupling at room temperature. The conjugates of KLH-Peptide and OVAPeptide were identified by infrared and ultraviolet spectrophotometry SDS-PAGE and DTNB method, which could prove the activity of the sulfhydryl-groups. In this way, we have obtained a novel artificial immunogen and coating antigen that could be used to raise polyclonal antibody through immunized rabbits
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