Diffusive tomography methods : special boundary conditions and characterization of inclusions

This thesis presents mathematical analysis of optical and electrical impedance tomography. We introduce papers [I-III], which study these diffusive tomography methods in the situation where the examined object is contaminated with inclusions that have physical properties differing from the background.reviewe

Best bilinear shell element: flat, twisted or curved?

This thesis concerns the accuracy of finite element models for shell structures. The focus is on low-order approximations of layer and vibration modes in shell deformations with particular reference to problems with concentrated loads. It is shown that parametric error amplification, or numerical locking, arises in these cases when bilinear elements are used and the formulation is based on the so-called degenerated solid approach. Furthermore, an alternative way for designing bilinear shell elements is discussed. The procedure is based on a refined shallow shell model which allows for an effective coupling between the membrane and bending strain in the energy expression

PRIVACY AND ACCOUNTABILITY IN CERTIFICATE SYSTEMS Tuomas Aura and Carl Ellison

ABSTRACT: Discretionary access right management on the Internet and inother distributed communications systems is increasingly based on public-key identity and authorization certificates. The certificates pose a threat to pri-vacy because they identify the owners and reveal the authorization relations between them. This paper overviews the privacy concerns and describes tech-niques for minimizing the amount of confidential information leaked about individuals and organizations. We also show how identity escrow certificatescan ensure individual accountability without identity authentication. All the techniques can be implemented with SPKI certificates

EXTENSIONS AND APPLICATIONS OF THE A * ALGORITHM Antti Autere

ABSTRACT: In this thesis we investigate path finding problems, that is, plan-ning routes from a start node to some goal nodes in a graph. Such problems arise in many fields of technology, for example, production planning,energy-aware message routing in large networks, resource allocation, and vehicle navigation systems. We concentrate mostly on planning a minimumcost path using the A * algorithm.We begin by proving new theorems comparing the performance of A * toother (generalized) path finding algorithms. In some cases, A * is an optimalmethod in a large class of algorithms. This means, roughly speaking, that A*explores a smaller region of the search space than the other algorithms in the given class.We develop a new method of improving a given (static) heuristic for A*dynamically, during search. A heuristic controls the search of A * so thatunnecessary branches of the tree of nodes that A * visits are pruned. The newmethod also finds an optimal path to any node it visits for the first time s