This paper discusses problems inherent in retrieval from multimedia information systems. These problems stem from the diverse and inherently unstructured nature of multimedia. We examine some problems in this area, identify some notable successes, and present a set of user interface design principles for creating effective interfaces to multimedia information. We then discuss information retrie...

Over the past two decades, some very efficient techniques for the numerical solution of partial differential equations have been developed. We are especially interested in adaptive local grid refinement on unstructured meshes, multigrid solvers and parallelization techniques. Up to now, these innovative techniques have been implemented mostly in university research codes and only very few comme...

This paper presents some linear adaptive non-nested multigrid methods which are applied to linear elastic problems discretized with triangular and tetrahedral nite elements using unstructured and Delaunay mesh generators. The Zienkiewicz-Zhu error estimator and a h-re nement procedure are used to obtain the non-nested meshes used by the multigrid methods. We solve problems with a speci ed perce...

The article describes development of a high order finite volume method for solution of transonic flow problems. The method is based on a reconstruction procedure similar to weighted ENO. Our reconstruction procedure is based on least square method with data dependent weights which is much simpler to implement than ENO scheme. The computational results demonstrate the usability of this approach ...

We present a chart of structured backward errors for approximate eigenpairs of singly and doubly structured eigenvalue problems. We aim to give, wherever possible, formulae that are inexpensive to compute so that they can be used routinely in practice. We identify a number of problems for which the structured backward error is within a factor √ 2 of the unstructured backward error. This paper c...

We propose a family of mimetic discretization schemes for elliptic problems including convection and reaction terms. Our approach is an extension of the mimetic methodology for purely diffusive problems on unstructured polygonal and polyhedral meshes. The a priori error analysis relies on the connection between the mimetic formulation and the lowest order Raviart–Thomas mixed finite element met...

An edge-based three-dimensional interface element for simulation of joints, faults and other discontinuities present in several geomechanical applications is proposed. Edge-based data structures are used to improve computational efficiency of Inexact Newton methods for solving finite element nonlinear problems on unstructured meshes. Numerical experiments in the solution of three-dimensional pr...

We present the Discrete Duality Finite Volume method (DDFV) for solving the linear elasticity problem on unstructured mesh applied to solids undergoing mechanical loads. The procedure is described in detail for three dimensional problems and some theoretical results are provided: the discrete problem is well-posed, stable and convergent. A number of numerical test problems demonstrates the abil...

We study large, sparse generalized eigenvalue problems for matrix pencils, where one of the matrices is Hamiltonian and the other skew Hamiltonian. Problems of this form arise in the numerical simulation of elastic deformation of anisotropic materials, in structural mechanics and in the linear-quadratic control problem for partial diierential equations. We develop a structure-preserving skew-Ha...

The control of autonomous intelligent robotic agent operating in unstructured changing environments includes many objective difficulties. One major difficulty concerns the characteristics of the environment that the agent should operate in. In unstructured and changing environments the inconsistency of the terrain, the irregularity of the product and the open nature of the working environment r...