4,089 research outputs found
Low-Latency Millimeter-Wave Communications: Traffic Dispersion or Network Densification?
This paper investigates two strategies to reduce the communication delay in
future wireless networks: traffic dispersion and network densification. A
hybrid scheme that combines these two strategies is also considered. The
probabilistic delay and effective capacity are used to evaluate performance.
For probabilistic delay, the violation probability of delay, i.e., the
probability that the delay exceeds a given tolerance level, is characterized in
terms of upper bounds, which are derived by applying stochastic network
calculus theory. In addition, to characterize the maximum affordable arrival
traffic for mmWave systems, the effective capacity, i.e., the service
capability with a given quality-of-service (QoS) requirement, is studied. The
derived bounds on the probabilistic delay and effective capacity are validated
through simulations. These numerical results show that, for a given average
system gain, traffic dispersion, network densification, and the hybrid scheme
exhibit different potentials to reduce the end-to-end communication delay. For
instance, traffic dispersion outperforms network densification, given high
average system gain and arrival rate, while it could be the worst option,
otherwise. Furthermore, it is revealed that, increasing the number of
independent paths and/or relay density is always beneficial, while the
performance gain is related to the arrival rate and average system gain,
jointly. Therefore, a proper transmission scheme should be selected to optimize
the delay performance, according to the given conditions on arrival traffic and
system service capability
Consistency of field-theoretical and kinetic calculations of viscous transport coefficients for a relativistic fluid
The transport coefficients of causal relativistic dissipative fluid dynamics
are calculated both in a field-theoretical and a kinetic approach. We find that
the results from the traditional kinetic calculation by Israel and Stewart are
modified. The new expressions for the viscous transport coefficients agree with
the results obtained in the field-theoretical approach when the contributions
from pair creation and annihilation are neglected.Comment: 4 pages, 2 figure
Consistency of field-theoretical and kinetic calculations of viscous transport coefficients for a relativistic fluid
The transport coefficients of causal relativistic dissipative fluid dynamics
are calculated both in a field-theoretical and a kinetic approach. We find that
the results from the traditional kinetic calculation by Israel and Stewart are
modified. The new expressions for the viscous transport coefficients agree with
the results obtained in the field-theoretical approach when the contributions
from pair creation and annihilation are neglected.Comment: 4 pages, 2 figure
On the Nature of X(4260)
We study the property of resonance by re-analyzing all experimental
data available, especially the cross section data. The final state
interactions of the , couple channel system are also taken
into account. A sizable coupling between the and is
found. The inclusion of the data indicates a small value of
eV.Comment: Refined analysis with new experimental data included. 13 page
Topological energy gaps in the [111]-oriented InAs/GaSb and GaSb/InAs core-shell nanowires
The [111]-oriented InAs/GaSb and GaSb/InAs core-shell nanowires have been
studied by the Luttinger-Kohn Hamiltonian to
search for non-vanishing fundamental gaps between inverted electron and hole
bands. We focus on the variations of the topologically nontrivial fundamental
gap, the hybridization gap, and the effective gap with the core radius and
shell thickness of the nanowires. The evolutions of all the energy gaps with
the structural parameters are shown to be dominantly governed by quantum size
effects. With a fixed core radius, a topologically nontrivial fundamental gap
exists only at intermediate shell thicknesses. The maximum gap is
meV for GaSb/InAs and meV for InAs/GaSb core-shell nanowires, and
for the GaSb/InAs core-shell nanowires the gap persists over a wider range of
geometrical parameters. The intrinsic reason for these differences between the
two types of nanowires is that in the shell the electron-like states of InAs is
more delocalized than the hole-like state of GaSb, while in the core the
hole-like state of GaSb is more delocalized than the electron-like state of
InAs, and both features favor stronger electron-hole hybridization. Since
similar features of the electron- and hole-like states have been found in
nanowires of other materials, it could serve as a common rule to put the
hole-like state in the core while the electron-like state in the shell of a
core-shell nanowire to achieve better topological properties.Comment: 10 pages, 10 figure
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