220 research outputs found
A New Achievable Scheme for Interference Relay Channels
We establish an achievable rate region for discrete memoryless interference
relay channels that consist of two source-destination pairs and one or more
relays. We develop an achievable scheme combining Han-Kobayashi and noisy
network coding schemes. We apply our achievability to two cases. First, we
characterize the capacity region of a class of discrete memoryless interference
relay channels. This class naturally generalizes the injective deterministic
discrete memoryless interference channel by El Gamal and Costa and the
deterministic discrete memoryless relay channel with orthogonal receiver
components by Kim. Moreover, for the Gaussian interference relay channel with
orthogonal receiver components, we show that our scheme achieves a better sum
rate than that of noisy network coding.Comment: 18 pages, 4 figure
Hierarchical Coding for Distributed Computing
Coding for distributed computing supports low-latency computation by
relieving the burden of straggling workers. While most existing works assume a
simple master-worker model, we consider a hierarchical computational structure
consisting of groups of workers, motivated by the need to reflect the
architectures of real-world distributed computing systems. In this work, we
propose a hierarchical coding scheme for this model, as well as analyze its
decoding cost and expected computation time. Specifically, we first provide
upper and lower bounds on the expected computing time of the proposed scheme.
We also show that our scheme enables efficient parallel decoding, thus reducing
decoding costs by orders of magnitude over non-hierarchical schemes. When
considering both decoding cost and computing time, the proposed hierarchical
coding is shown to outperform existing schemes in many practical scenarios.Comment: 7 pages, part of the paper is submitted to ISIT201
Wall-mediated self-diffusion in slit and cylindrical pores
Analytical and numerical simulation studies are performed on the diffusion of simple fluids in both thin slits and long cylindrical pores. In the region of large Knudsen numbers, where the wall-particle collisions outnumber the intermolecular collisions, we obtain analytical results for the self-diffusion coefficients for both slit and cylindrical pore shapes. The results show anomalous behavior of the mean square displacement and the velocity autocorrelation for the case of slits, unlike the case of cylindrical pores which shows standard Fick's law. Molecular dynamics simulations confirm the analytical results. We further study the wall-mediated diffusion behavior conducted by a Smoluchowski thermal wall and compare with our analytical results obtained from the stochastic thermal wall model proposed by Mon and Percus
Nature of self-diffusion in two-dimensional fluids
Self-diffusion in a two-dimensional simple fluid is investigated by both
analytical and numerical means. We investigate the anomalous aspects of
self-diffusion in two-dimensional fluids with regards to the mean square
displacement, the time-dependent diffusion coefficient, and the velocity
autocorrelation function using a consistency equation relating these
quantities. We numerically confirm the consistency equation by extensive
molecular dynamics simulations for finite systems, corroborate earlier results
indicating that the kinematic viscosity approaches a finite, non-vanishing
value in the thermodynamic limit, and establish the finite size behavior of the
diffusion coefficient. We obtain the exact solution of the consistency equation
in the thermodynamic limit and use this solution to determine the large time
asymptotics of the mean square displacement, the diffusion coefficient, and the
velocity autocorrelation function. An asymptotic decay law of the velocity
autocorrelation function resembles the previously known self-consistent form,
, however with a rescaled time.Comment: 10 pages, to appear in New Journal of Physic
Real-time Near-infrared Virtual Intraoperative Surgical Photoacoustic Microscopy
AbstractWe developed a near infrared (NIR) virtual intraoperative surgical photoacoustic microscopy (NIR-VISPAM) system that combines a conventional surgical microscope and an NIR light photoacoustic microscopy (PAM) system. NIR-VISPAM can simultaneously visualize PA B-scan images at a maximum display rate of 45Hz and display enlarged microscopic images on a surgeon's view plane through the ocular lenses of the surgical microscope as augmented reality. The use of the invisible NIR light eliminated the disturbance to the surgeon's vision caused by the visible PAM excitation laser in a previous report. Further, the maximum permissible laser pulse energy at this wavelength is approximately 5 times more than that at the visible spectral range. The use of a needle-type ultrasound transducer without any water bath for acoustic coupling can enhance convenience in an intraoperative environment. We successfully guided needle and injected carbon particles in biological tissues ex vivo and in melanoma-bearing mice in vivo
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