791 research outputs found
Sparsity prior for electrical impedance tomography with partial data
This paper focuses on prior information for improved sparsity reconstruction
in electrical impedance tomography with partial data, i.e. data measured only
on subsets of the boundary. Sparsity is enforced using an norm of the
basis coefficients as the penalty term in a Tikhonov functional, and prior
information is incorporated by applying a spatially distributed regularization
parameter. The resulting optimization problem allows great flexibility with
respect to the choice of measurement boundaries and incorporation of prior
knowledge. The problem is solved using a generalized conditional gradient
method applying soft thresholding. Numerical examples show that the addition of
prior information in the proposed algorithm gives vastly improved
reconstructions even for the partial data problem. The method is in addition
compared to a total variation approach.Comment: 17 pages, 12 figure
Distinguishability revisited: depth dependent bounds on reconstruction quality in electrical impedance tomography
The reconstruction problem in electrical impedance tomography is highly
ill-posed, and it is often observed numerically that reconstructions have poor
resolution far away from the measurement boundary but better resolution near
the measurement boundary. The observation can be quantified by the concept of
distinguishability of inclusions. This paper provides mathematically rigorous
results supporting the intuition. Indeed, for a model problem lower and upper
bounds on the distinguishability of an inclusion are derived in terms of the
boundary data. These bounds depend explicitly on the distance of the inclusion
to the boundary, i.e. the depth of the inclusion. The results are obtained for
disk inclusions in a homogeneous background in the unit disk. The theoretical
bounds are verified numerically using a novel, exact characterization of the
forward map as a tridiagonal matrix.Comment: 25 pages, 6 figure
Intercropping wheat with pea for improved wheat baking quality
Field pea (Pisum sativum L.) and wheat (Triticum sativum L.) were either sole cropped or intercropped in a complete design of five relative proportions and five density levels to determine the effects of interspecific interaction in an intercrop on wheat baking quality. It is shown how pea interspecific competitive ability for factors such as light and water results in an increase in wheat protein content without reducing other important quality parameters. Density and relative crop frequency can be used as “regulators” when specific objectives such as bread making quality are wante
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