32,888 research outputs found
Transmission Game in MIMO Interference Channels With Radio-Frequency Energy Harvesting
For multi-user transmissions over MIMO interference channels, each user
designs the transmit covariance matrix to maximize its information rate. When
passive radio-frequency (RF) energy harvesters are present in the network, the
transmissions are constrained by both the transmit power limits and the energy
harvesting requirements. A passive RF energy harvester collects the radiated
energy from nearby wireless information transmitters instead of using a
dedicated wireless power source. It needs multiple transmitters to concentrate
their RF radiation on it because typical electric field strengths are weak. In
this paper, strategic games are proposed for the multi-user transmissions.
First, in a non-cooperative game, each transmitter has a best-response strategy
for the transmit covariance matrix that follows a multi-level water-filling
solution. A pure-strategy Nash equilibrium exists. Secondly, in a cooperative
game, there is no need to estimate the proportion of the harvested energy from
each transmitter. Rather, the transmitters bargain over the unit-reward of the
energy contribution. An approximation of the information rate is used in
constructing the individual utility such that the problem of network utility
maximization can be decomposed and the bargaining process can be implemented
distributively. The bargaining solution gives a point of rates that is superior
to the Nash equilibria and close to the Pareto front. Simulation results verify
the algorithms that provide good communication performance while satisfying the
RF energy-harvesting requirements.Comment: 13 pages, 13 figures. Submitted to IEEE Transactions on Green
Communications and Networkin
Effect of Pauli principle on the deformed QRPA calculations and its consequence in the -decay calculations of deformed even-even nuclei
In this work, we take into consideration of Pauli Exclusion Principle(PEP) in
the quasi-particle random phase approximation (QRPA) calculations for the
deformed systems by replacing the traditional Quasi-Boson Approximation(QBA)
with the renormalized one. With this new formalism, the parametrization of QRPA
calculations has been changed and the collapse of QRPA solutions could be avoid
for realistic values. We further find that the necessity of
renormalization parameter of particle-particle residual interaction in
QRPA calculations is due to the exclusion of PEP. So with the inclusion of PEP,
we could easily extend the deformed QRPA calculations to the less explored
region where lack of experimental data prevent effective parametrization of
for QRPA methods. With this theoretical improvement, we give
predictions of weak decay rates for even-even isotopes in the rare earth region
and the results are then compared with existing calculations.Comment: 8 Pages, 4 Figures, Accepted by PR
A discussion of deuteron transverse charge densities
The deuteron transverse charge density is the two-dimensional
Fourier transform of its charge form factor in the impact space. We show that
different parameterizations of the charge form factors provide different
, in particular at the central value of impact parameter (),
although all the parameterizations can well reproduce the form factors in the
region of small . In addition, we also check the explicit contributions
from the different coordinate intervals of the deuteron wave function to its
root-mean-square radius.Comment: 6 pages, 5 tables, 3 figure
Bardeen-Cooper-Schrieffer formalism of superconductivity in carbon nanotubes
We develop the Bardeen-Cooper-Schrieffer (BCS) formalism for the
superconductivity of carbon nanotubes. It is found that the superconducting
transition temperature Tc of single-wall carbon nanotubes decreases
exponentially with the increase of the tube diameter because the density of
states near the Fermi energy is inversely proportional to the tube diameter.
For the multi-wall carbon nanotubes, the Cooper paring hopping between layers
enhances the superconducting correlation and increases the superconducting
transition temperature, which is consistent with the experimental observation.Comment: 11 page
Deuteron electromagnetic form factors in transverse plane with a phenomenological Lagrangian approach
A phenomenological Lagrangian approach is employed to study the
electromagnetic properties of deuteron. The deuteron is regarded as a loosely
bound state of a proton and a neutron. The deuteron electromagnetic form
factors are expressed in light-front representation in the transverse plane.
The transverse charge density of the deuteron is discussed.Comment: 13 pages, 9 figures, submitted to Chinese Physics
Clarifying Trust in Social Internet of Things
A social approach can be exploited for the Internet of Things (IoT) to manage
a large number of connected objects. These objects operate as autonomous agents
to request and provide information and services to users. Establishing
trustworthy relationships among the objects greatly improves the effectiveness
of node interaction in the social IoT and helps nodes overcome perceptions of
uncertainty and risk. However, there are limitations in the existing trust
models. In this paper, a comprehensive model of trust is proposed that is
tailored to the social IoT. The model includes ingredients such as trustor,
trustee, goal, trustworthiness evaluation, decision, action, result, and
context. Building on this trust model, we clarify the concept of trust in the
social IoT in five aspects such as (1) mutuality of trustor and trustee, (2)
inferential transfer of trust, (3) transitivity of trust, (4) trustworthiness
update, and (5) trustworthiness affected by dynamic environment. With network
connectivities that are from real-world social networks, a series of
simulations are conducted to evaluate the performance of the social IoT
operated with the proposed trust model. An experimental IoT network is used to
further validate the proposed trust model.Comment: 14 pages, 16 figures. Submitted to IEEE Transactions on Knowledge and
Data Engineerin
Energy Efficiency in Multiuser Transmission Over Parallel Frequency Channels
Energy efficiency is an important design criterion for wireless
communications. When parallel frequency channels are used for multiuser
transmission, the channel bandwidths and user power are adjusted to maximize
the sum information rate with the bandwidth budget, the transmit power budget,
and the user-specific rate requirements. The maximum sum rate is used in
measuring the energy efficiency. With fixed or flexible bandwidths of the
frequency channels, practical methods are developed to find the total transmit
power with the unique optimal resource (bandwidth and power) allocation for
maximum energy efficiency. This resource allocation ensures that, while each
user's minimum rate requirement is satisfied, all the excess resource of the
spectrum and transmit power is dedicated to the one user with the best channel
quality. Simulation results validate the optimal solutions of total transmit
power and resource allocation that support the energy-efficient multiuser
transmission.Comment: 10 pages, 9 figure
Secure Location-Aided Routing Protocols With Wi-Fi Direct For Vehicular Ad Hoc Networks
Secure routing protocols are proposed for the vehicular ad hoc networks. The
protocols integrate the security authentication process with the Location-Aided
Routing (LAR) protocol to support Wi-Fi Direct communications between the
vehicles. The methods are robust against various security threats. The security
authentication process adopts a modified Diffie-Hellman key agreement protocol.
The Diffie-Hellman protocol is used with a short authentication string
(SAS)-based key agreement over Wi-Fi Direct out-of-band communication channels.
It protects the communication from any man-in-the-middle security threats. In
particular, the security process is integrated into two LAR routing schemes,
i.e., the request-zone LAR scheme and the distance-based LAR scheme. We conduct
extensive simulations with different network parameters such as the vehicular
node density, the number of the malicious nodes, and the speed of the nodes.
Simulation results show that the proposed routing protocols provide superior
performance in secure data delivery and average total packet delay. Also, the
secure distance-based LAR protocol outperforms the secure request-zone LAR
protocol.Comment: 10 pages, 14 figure
Quantum Szilard engines with arbitrary spin
The quantum Szilard engine (QSZE) is a conceptual quantum engine for
understanding the fundamental physics of quantum thermodynamics and information
physics. We generalize the QSZE to an arbitrary spin case, i.e., a spin QSZE
(SQSZE), and we systematically study the basic physical properties of both
fermion and boson SQSZEs in a low-temperature approximation. We give the
analytic formulation of the total work. For the fermion SQSZE, the work might
be absorbed from the environment, and the change rate of the work with
temperature exhibits periodicity and even-odd oscillation, which is a
generalization of a spinless QSZE. It is interesting that the average absorbed
work oscillates regularly and periodically in a large-number limit, which
implies that the average absorbed work in a fermion SQSZE is neither an
intensive quantity nor an extensive quantity. The phase diagrams of both
fermion and boson SQSZEs give the SQSZE doing positive or negative work in the
parameter space of the temperature and the particle number of the system, but
they have different behaviors because the spin degrees of the fermion and the
boson play different roles in their configuration states and corresponding
statistical properties. The critical temperature of phase transition depends
sensitively on the particle number. By using Landauer's erasure principle, we
give the erasure work in a thermodynamic cycle, and we define an efficiency (we
refer to it as information-work efficiency) to measure the engine's ability of
utilizing information to extract work. We also give the conditions under which
the maximum extracted work and highest information-work efficiencies for
fermion and boson SQSZEs can be achieved.Comment: 24 pages, 11 figure
Multiscale analysis for convection dominated transport equations
In this paper, we perform a systematic multiscale analysis for convection dominated transport equations with a weak diffusion and a highly oscillatory velocity field. The paper primarily focuses on upscaling linear transport equations. But we also discuss briefly how to upscale two-phase miscible flows, in which case the concentration equation is coupled to the pressure equation in a nonlinear fashion. For the problem we consider here, the local Peclet number is of O(ε^(-m+1)) with m is an element of [2, infinity] being any integer, where ε characterizes the small scale in the heterogeneous media. Due to the presence of the nonlocal memory effect, upscaling a convection dominated transport equation is known to be very difficult. One of the key ideas in deriving a well-posed homogenized equation for the convection dominated transport equation is to introduce a projection operator which projects the fluctuation onto a suitable subspace. This projection operator corresponds to averaging along the streamlines of the flow. In the case of linear convection dominated transport equations, we prove the well-posedness of the homogenized equations and establish rigorous error estimates for our multiscale expansion
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