154,228 research outputs found
A simple preconditioned domain decomposition method for electromagnetic scattering problems
We present a domain decomposition method (DDM) devoted to the iterative
solution of time-harmonic electromagnetic scattering problems, involving large
and resonant cavities. This DDM uses the electric field integral equation
(EFIE) for the solution of Maxwell problems in both interior and exterior
subdomains, and we propose a simple preconditioner for the global method, based
on the single layer operator restricted to the fictitious interface between the
two subdomains.Comment: 23 page
Interplay Between Transmission Delay, Average Data Rate, and Performance in Output Feedback Control over Digital Communication Channels
The performance of a noisy linear time-invariant (LTI) plant, controlled over
a noiseless digital channel with transmission delay, is investigated in this
paper. The rate-limited channel connects the single measurement output of the
plant to its single control input through a causal, but otherwise arbitrary,
coder-controller pair. An infomation-theoretic approach is utilized to analyze
the minimal average data rate required to attain the quadratic performance when
the channel imposes a known constant delay on the transmitted data. This
infimum average data rate is shown to be lower bounded by minimizing the
directed information rate across a set of LTI filters and an additive white
Gaussian noise (AWGN) channel. It is demonstrated that the presence of time
delay in the channel increases the data rate needed to achieve a certain level
of performance. The applicability of the results is verified through a
numerical example. In particular, we show by simulations that when the optimal
filters are used but the AWGN channel (used in the lower bound) is replaced by
a simple scalar uniform quantizer, the resulting operational data rates are at
most around 0.3 bits above the lower bounds.Comment: A less-detailed version of this paper has been accepted for
publication in the proceedings of ACC 201
Analysis of new direct sampling indicators for far-field measurements
This article focuses on the analysis of three direct sampling indicators
which can be used for recovering scatterers from the far-field pattern of
time-harmonic acoustic measurements. These methods fall under the category of
sampling methods where an indicator function is constructed using the far-field
operator. Motivated by some recent work, we study the standard indicator using
the far-field operator and two indicators derived from the factorization
method. We show the equivalence of two indicators previously studied as well as
propose a new indicator based on the Tikhonov regularization applied to the
far-field equation for the factorization method. Finally, we give some
numerical examples to show how the reconstructions compare to other direct
sampling methods
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