198 research outputs found
Double-distribution-function discrete Boltzmann model for combustion
A 2-dimensional discrete Boltzmann model for combustion is presented.
Mathematically, the model is composed of two coupled discrete Boltzmann
equations for two species and a phenomenological equation for chemical reaction
process. Physically, the model is equivalent to a reactive Navier-Stokes model
supplemented by a coarse-grained model for the thermodynamic nonequilibrium
behaviours. This model adopts 16 discrete velocities. It works for both
subsonic and supersonic combustion phenomena with flexible specific heat ratio.
To discuss the physical accuracy of the coarse-grained model for nonequilibrium
behaviours, three other discrete velocity models are used for comparisons.
Numerical results are compared with analytical solutions based on both the
first-order and second-order truncations of the distribution function. It is
confirmed that the physical accuracy increases with the increasing moment
relations needed by nonequlibrium manifestations. Furthermore, compared with
the single distribution function model, this model can simulate more details of
combustion.Comment: Accepted for publication in Combustion and Flam
Modeling incompressible thermal flows using a central-moment-based lattice Boltzmann method
In this paper, a central-moment-based lattice Boltzmann (CLB) method for
incompressible thermal flows is proposed. In the method, the incompressible
Navier-Stokes equations and the convection-diffusion equation for the
temperature field are sloved separately by two different CLB equations. Through
the Chapman-Enskog analysis, the macroscopic governing equations for
incompressible thermal flows can be reproduced. For the flow field, the tedious
implementation for CLB method is simplified by using the shift matrix with a
simplified central-moment set, and the consistent forcing scheme is adopted to
incorporate forcing effects. Compared with several D2Q5
multiple-relaxation-time (MRT) lattice Boltzmann methods for the temperature
equation, the proposed method is shown to be better Galilean invariant through
measuring the thermal diffusivities on a moving reference frame. Thus a higher
Mach number can be used for convection flows, which decreases the computational
load significantly. Numerical simulations for several typical problems confirm
the accuracy, efficiency, and stability of the present method. The grid
convergence tests indicate that the proposed CLB method for incompressible
thermal flows is of second-order accuracy in space
Time-delayed impulsive control for discrete-time nonlinear systems with actuator saturation
This paper focuses on the problem of time-delayed impulsive control with actuator saturation for discrete-time dynamical systems. By establishing a delayed impulsive difference inequality, combining with convex analysis and inequality techniques, some sufficient conditions are obtained to ensure exponential stability for discrete-time dynamical systems via time-delayed impulsive controller with actuator saturation. The designed controller admits the existence of some transmission delays in impulsive feedback law, and the control input variables are required to stay within an availability zone. Several numerical simulations are also given to demonstrate the effectiveness of the proposed results. 
A semi-free weighting matrices approach for neutral-type delayed neural networks
AbstractIn this paper, a new approach is proposed for stability issues of neutral-type neural networks (DNNs) with constant delay. First, the semi-free weighting matrices are proposed and used instead of the known free weighting matrices to express the relationship between the terms in the LeibnizβNewton formula to simplify the system synthesis and to obtain less computation demand. Second, global exponential stability conditions which are less conservative and restrictive than the known results are derived. At the same time, based on the above approach, fewer variable matrices are introduced in the construction of the Lyapunov functional and augmented Lyapunov functional. Two examples are given to show their effectiveness and advantages over others
Cooperative coloring of some graph families
Given a family of graphs on the vertex set , a
cooperative coloring of it is a choice of independent sets in
such that . For a graph class
, let be the minimum such that every
graph family with and for , has a cooperative coloring. For the class of
trees and the class of wheels, we get that
and . Also, we show that and , where
is the class of graphs whose components are balanced
complete bipartite graphs, and is the class of bipartite graphs
with one part size at most
Fast Successive-Cancellation Decoding of 2 x 2 Kernel Non-Binary Polar Codes: Identification, Decoding and Simplification
Non-binary polar codes (NBPCs) decoded by successive cancellation (SC)
algorithm have remarkable bit-error-rate performance compared to the binary
polar codes (BPCs). Due to the serial nature, SC decoding suffers from large
latency. The latency issue in BPCs has been the topic of extensive research and
it has been notably resolved by the introduction of fast SC-based decoders.
However, the vast majority of research on NBPCs is devoted to issues concerning
design and efficient implementation. In this paper, we propose fast SC decoding
for NBPCs constructed based on 2 x 2 kernels. In particular, we identify
various non-binary special nodes in the SC decoding tree of NBPCs and propose
their fast decoding. This way, we avoid traversing the full decoding tree and
significantly reduce the decoding delay compared to symbol-by-symbol SC
decoding. We also propose a simplified NBPC structure that facilitates the
procedure of non-binary fast SC decoding. Using our proposed fast non-binary
decoder, we observed an improvement of up to 95% in latency concerning the
original SC decoding. This is while our proposed fast SC decoder for NBPCs
incurs no error-rate loss
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