8,058 research outputs found
Decentralized Formation Control with A Quadratic Lyapunov Function
In this paper, we investigate a decentralized formation control algorithm for
an undirected formation control model. Unlike other formation control problems
where only the shape of a configuration counts, we emphasize here also its
Euclidean embedding. By following this decentralized formation control law, the
agents will converge to certain equilibrium of the control system. In
particular, we show that there is a quadratic Lyapunov function associated with
the formation control system whose unique local (global) minimum point is the
target configuration. In view of the fact that there exist multiple equilibria
(in fact, a continuum of equilibria) of the formation control system, and hence
there are solutions of the system which converge to some equilibria other than
the target configuration, we apply simulated annealing, as a heuristic method,
to the formation control law to fix this problem. Simulation results show that
sample paths of the modified stochastic system approach the target
configuration
On the Coordinate System of Space-Weather HMI Active Region Patches (SHARPs): A Technical Note
We describe the coordinate systems of two streams of HMI active region vector
data. A distinction is made between (a) the 2D grid on which the field vector
is measured (or sampled), and (b) the 3D coordinate established at each grid
point, in which the field vector is presented. The HMI data reduction can
involve coordinate changes on both, with those performed on the former termed
"remapping", the latter "vector transformation". Relevant pipeline procedures
are described. Useful examples are given for data analysis.Comment: Technical note for the HMI vector data pipeline. Containing data
analysis example. Corrected typo in Eq(6
On Coding Efficiency for Flash Memories
Recently, flash memories have become a competitive solution for mass storage.
The flash memories have rather different properties compared with the rotary
hard drives. That is, the writing of flash memories is constrained, and flash
memories can endure only limited numbers of erases. Therefore, the design goals
for the flash memory systems are quite different from these for other memory
systems. In this paper, we consider the problem of coding efficiency. We define
the "coding-efficiency" as the amount of information that one flash memory cell
can be used to record per cost. Because each flash memory cell can endure a
roughly fixed number of erases, the cost of data recording can be well-defined.
We define "payload" as the amount of information that one flash memory cell can
represent at a particular moment. By using information-theoretic arguments, we
prove a coding theorem for achievable coding rates. We prove an upper and lower
bound for coding efficiency. We show in this paper that there exists a
fundamental trade-off between "payload" and "coding efficiency". The results in
this paper may provide useful insights on the design of future flash memory
systems.Comment: accepted for publication in the Proceeding of the 35th IEEE Sarnoff
Symposium, Newark, New Jersey, May 21-22, 201
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