We reduce the question of local nonsolvability of the Darboux equation, and hence of the isometric embedding problem for surfaces, to the local nonsolvability of a simple linear equation whose type is explicitly determined by the Gaussian curvature. Let (M, g) be a two-dimensional Riemannian manifold. A well-known problem is to ask, when can one realize this locally as a small piece of a surfac...

— The paper describes a back-projection based algorithm, improved by adaptive techniques, able to reconstruct a high-resolution image from multiple low-resolution frames. The proposed approach is mainly based on a specific metric, the uncertainty degree, used in pixel reconstruction and on a local Auto-iterative approach for error correction. Using uncertainty the amount of computation is sensi...

This paper presents novel adaptive reduced-rank filtering algorithms based on joint iterative optimization of adaptive filters. The novel scheme consists of a joint iterative optimization of a bank of fullrank adaptive filters that constitute the projection matrix and an adaptive reduced-rank filter that operates at the output of the bank of filters. We describe least squares (LS) expressions f...