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Theory of linear G-difference equations
(Journal article; Tidsskriftartikkel; Peer reviewed, 1997-12-17)
We introduce the notion of difference equation defined on a structured set. The symmetry group of the structure determines the set of difference operators. All main notions in the theory of difference equations are introduced as invariants of the action of the symmetry group. Linear equations are modules over the skew group algebra, solutions are morphisms relating a given equation to other ...
Understanding the Cool DA White Dwarf Pulsator, G29–38
(Journal article; Tidsskriftartikkel; Peer reviewed, 1997-10-10)
The white dwarfs are promising laboratories for the study of cosmochronology and stellar evolution. Through observations of the pulsating white dwarfs, we can measure their internal structures and compositions, critical to understanding post main sequence evolution, along with their cooling rates, allowing us to calibrate their ages directly. The most important set of white dwarf variables to ...
3D visualization of weather forecasts and topography
(Research report; Forskningsrapport, 1994-09)
Advances in computing power and graphics have increased the use of graphics in weather forecasting. This includes 3D animation sequences and geographical information systems. The paper addresses the main problems and presents preliminary results of the visualization of atmospheric models in conjunction with the underlying topography. The goal is among others to make a sort of 3D satellite pictures ...
Security in the PASTA project
(Research report; Forskningsrapport, 1997-02-04)
This paper presents the system model for the work on security in the Pasta project. We present the objectives of the security effort, the threats we will consider, and those we will not consider. As such, the paper describes the environment which applications must be prepared to face, and still provide users with the desired degree of privacy.
Cooperation through information interchange in StormCast
(Research report; Forskningsrapport, 1990)
This paper addresses the cooperation between different expert system modules in a networking environment. StormCast - a distributed artificial intelligence application for severe storm forecasting is used as a case to obtain practical results. Two key aspects is investigated, first the representation of knowledge in this kind of environment is outlined. Then the cooperating nature of a group of ...
Superposed epoch analysis applied to large-amplitude travelling convection vortices.
(Journal article; Tidsskriftartikkel, 1998)
For the six months from 1 October 1993 to 1 April 1994 the recordings of the IMAGE magnetometer network have been surveyed in a search for large- amplitude travelling convection vortices (TCVs). The restriction to large amplitudes (>100 nT) was chosen to ensure a proper detection of evens also during times of high activity. Readings of all stations of the northern half of the IMAGE network ...
An approach towards an agent computing environment
(Research report; Forskningsrapport, 1998)
We devise a mobile agent middleware architecture for supporting distributed applications in a wide-area network. The architecture provides a structural framework for functional components that are needed to support mobile agents in asymmetric networking environments.
QoS applied to security in mobile computing
(Research report; Forskningsrapport, 1997-06-30)
Hand-held mobile computers have the potential to become important communication tools for roaming users. As such, they will also become very personal. They will be used under a wide range of operating conditions, and tight user control will be enforced on issues like power consumption, consistency control, and trust management. Their ability to adapt will be the key to their success. In this paper ...
Quick- instead of Merge-sort for pipelines systems
(Research report; Forskningsrapport, 1997-05)
This paper proposes an external sorting algorithm for large data as an alternative to the widely used merge-sort algorithm. The algorithm we present is an application of the widely known quick-sort algorithm to large sequences of data stored externally on a disk device. The problem with the merge-sort algorithm is not its time complexity but the large amount of time it requires to output its first ...
File repository transfer protocol. Version 1
(Research report; Forskningsrapport, 1995-02)
This document presents and specifies the protocol that interfaces clients and servers in the File Repository (FR). The FR is a software system that supports sharing of files. The protocol is modelled after Smtp and Nntp and is encoded in Ascii. No details of server implementation is visible in the protocol description, but we state our intentions at several occasions.