21,303 research outputs found
An Analytical Link Loss Model for On-Body Propagation Around the Body Based on Elliptical Approximation of the Torso with Arms' Influence Included
An analytical model for estimating the link loss for the on-body wave
propagation around the torso is presented. The model is based on the
attenuation of the creeping waves over an elliptical approximation of the human
torso and includes the influence of the arms. The importance of including the
arms' effect for a proper estimation of the link loss is discussed. The model
is validated by the full-wave electromagnetic simulations on a numerical
phantom
A Link Loss Model for the On-body Propagation Channel for Binaural Hearing Aids
Binaural hearing aids communicate with each other through a wireless link for
synchronization. A propagation model is needed to estimate the ear-to-ear link
loss for such binaural hearing aids. The link loss is a critical parameter in a
link budget to decide the sensitivity of the transceiver. In this paper, we
have presented a model for the deterministic component of the ear-to-ear link
loss. The model takes into account the dominant paths having most of the power
of the creeping wave from the transceiver in one ear to the transceiver in
other ear and the effect of the protruding part of the outer ear called pinna.
Simulations are done to validate the model using in-the-ear (ITE) placement of
antennas at 2.45 GHz on two heterogeneous phantoms of different age-group and
body size. The model agrees with the simulations. The ear-to-ear link loss
between the antennas for the binaural hearing aids in the homogeneous SAM
phantom is compared with a heterogeneous phantom. It is found that the absence
of the pinna and the lossless shell in the SAM phantom underestimate the link
loss. This is verified by the measurements on a phantom where we have included
the pinnas fabricated by 3D-printing
Statistical Analysis in Art Conservation Research
Evaluates all components of data analysis and shows that statistical methods in conservation are vastly underutilized. Also offers specific examples of possible improvements
Generalized Interlinked Cycle Cover for Index Coding
A source coding problem over a noiseless broadcast channel where the source
is pre-informed about the contents of the cache of all receivers, is an index
coding problem. Furthermore, if each message is requested by one receiver, then
we call this an index coding problem with a unicast message setting. This
problem can be represented by a directed graph. In this paper, we first define
a structure (we call generalized interlinked cycles (GIC)) in directed graphs.
A GIC consists of cycles which are interlinked in some manner (i.e., not
disjoint), and it turns out that the GIC is a generalization of cliques and
cycles. We then propose a simple scalar linear encoding scheme with linear time
encoding complexity. This scheme exploits GICs in the digraph. We prove that
our scheme is optimal for a class of digraphs with message packets of any
length. Moreover, we show that our scheme can outperform existing techniques,
e.g., partial clique cover, local chromatic number, composite-coding, and
interlinked cycle cover.Comment: Extended version of the paper which is to be presented at the IEEE
Information Theory Workshop (ITW), 2015 Jej
A New Index Coding Scheme Exploiting Interlinked Cycles
We study the index coding problem in the unicast message setting, i.e., where
each message is requested by one unique receiver. This problem can be modeled
by a directed graph. We propose a new scheme called interlinked cycle cover,
which exploits interlinked cycles in the directed graph, for designing index
codes. This new scheme generalizes the existing clique cover and cycle cover
schemes. We prove that for a class of infinitely many digraphs with messages of
any length, interlinked cycle cover provides an optimal index code.
Furthermore, the index code is linear with linear time encoding complexity.Comment: To be presented at the 2015 IEEE International Symposium on
Information Theory (ISIT 2015), Hong Kon
Giant Radio Sources
We present multi-frequency VLA observations of two giant quasars, 0437-244
and 1025-229, from the Molonglo Complete Sample. These sources have
well-defined FRII radio structure, possible one-sided jets, no significant
depolarization between 1365 and 4935 MHz and low rotation measure (). The giant sources are defined to be those whose overall
projected size is 1 Mpc. We have compiled a sample of about 50 known
giant radio sources from the literature, and have compared some of their
properties with a complete sample of 3CR radio sources of smaller sizes to
investigate the evolution of giant sources, and test their consistency with the
unified scheme for radio galaxies and quasars. We find an inverse correlation
between the degree of core prominence and total radio luminosity, and show that
the giant radio sources have similar core strengths to the smaller sources of
similar total luminosity. Hence their large sizes are unlikely to be due to
stronger nuclear activity. The degree of collinearity of the giant sources is
also similar to the sample of smaller sources. The luminosity-size diagram
shows that the giant sources are less luminous than our sample of smaller-sized
3CR sources, consistent with evolutionary scenarios where the giants have
evolved from the smaller sources losing energy as they expand to these large
dimensions. For the smaller sources, radiative losses due to synchrotron
radiation is more significant while for the giant sources the equipartition
magnetic fields are smaller and inverse Compton losses with the microwave
background radiation is the dominant process. The radio properties of the giant
radio galaxies and quasars are consistent with the unified scheme.Comment: 14 pages with 12 figures, MNRAS LaTex. Accepted for publication in
MNRAS. Minor changes in the text and couple of references adde
Graph-Theoretic Approaches to Two-Sender Index Coding
Consider a communication scenario over a noiseless channel where a sender is
required to broadcast messages to multiple receivers, each having side
information about some messages. In this scenario, the sender can leverage the
receivers' side information during the encoding of messages in order to reduce
the required transmissions. This type of encoding is called index coding. In
this paper, we study index coding with two cooperative senders, each with some
subset of messages, and multiple receivers, each requesting one unique message.
The index coding in this setup is called two-sender unicast index coding
(TSUIC). The main aim of TSUIC is to minimize the total number of transmissions
required by the two senders. Based on graph-theoretic approaches, we prove that
TSUIC is equivalent to single-sender unicast index coding (SSUIC) for some
special cases. Moreover, we extend the existing schemes for SSUIC, viz., the
cycle-cover scheme, the clique-cover scheme, and the local-chromatic scheme to
the corresponding schemes for TSUIC.Comment: To be presented at 2016 IEEE Global Communications Conference
(GLOBECOM 2016) Workshop on Network Coding and Applications (NetCod),
Washington, USA, 201
Frustrated spin ladder with alternating spin-1 and spin-1/2 rungs
We study the impact of the diagonal frustrating couplings on the quantum
phase diagram of a two-leg ladder composed of alternating spin-1 and spin-1/2
rungs. As the coupling strength is increased the system successively exhibits
two gapped paramagnetic phases (a rung-singlet and a Haldane-like
non-degenerate states) and two ferrimagnetic phases with different
ferromagnetic moments per rung. The first two states are similar to the phases
studied in the frustrated spin-1/2 ladder, whereas the magnetic phases appear
as a result of the mixed-spin structure of the model. A detailed
characterization of these phases is presented using density-matrix
renormalization-group calculations, exact diagonalizations of periodic
clusters, and an effective Hamiltonian approach inspired by the analysis of
numerical data. The present theoretical study was motivated by the recent
synthesis of the quasi-one-dimensional ferrimagnetic material
FeFe (trans-1,4-cyclohexanedicarboxylate) exhibiting a similar
ladder structure.Comment: 10 pages, 8 figure
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