94,477 research outputs found
From Instantly Decodable to Random Linear Network Coding
Our primary goal in this paper is to traverse the performance gap between two
linear network coding schemes: random linear network coding (RLNC) and
instantly decodable network coding (IDNC) in terms of throughput and decoding
delay. We first redefine the concept of packet generation and use it to
partition a block of partially-received data packets in a novel way, based on
the coding sets in an IDNC solution. By varying the generation size, we obtain
a general coding framework which consists of a series of coding schemes, with
RLNC and IDNC identified as two extreme cases. We then prove that the
throughput and decoding delay performance of all coding schemes in this coding
framework are bounded between the performance of RLNC and IDNC and hence
throughput-delay tradeoff becomes possible. We also propose implementations of
this coding framework to further improve its throughput and decoding delay
performance, to manage feedback frequency and coding complexity, or to achieve
in-block performance adaption. Extensive simulations are then provided to
verify the performance of the proposed coding schemes and their
implementations.Comment: 30 pages with double space, 14 color figure
A Variational r-Adaption and Shape-Optimization Method for Finite-Deformation Elasticity
This paper is concerned with the formulation of a variational r-adaption method for finite-deformation elastostatic problems. The distinguishing characteristic of the method is that the variational principle simultaneously supplies the solution, the optimal mesh and, in problems of shape optimization, the equilibrium shapes of the system. This is accomplished by minimizing the energy functional with respect to the nodal field values as well as with respect to the triangulation of the domain of analysis. Energy minimization with respect to the referential nodal positions has the effect of equilibrating the energetic or configurational forces acting on the nodes. We derive general expressions for the configuration forces for isoparametric elements and nonlinear, possibly anisotropic, materials under general loading. We illustrate the versatility and convergence characteristics of the method by way of selected numerical tests and applications, including the problem of a semi-infinite crack in linear and nonlinear elastic bodies; and the optimization of the shape of elastic inclusions
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