Dynamic Trust Federation in Grids

Grids are becoming economically viable and productive tools. Grids provide a way of utilizing a vast array of linked resources such as computing systems, databases and services online within Virtual Organizations (VO). However, today’s Grid architectures are not capable of supporting dynamic, agile federation across multiple administrative domains and the main barrier, which hinders dynamic federation over short time scales is security. Federating security and trust is one of the most significant architectural issues in Grids. Existing relevant standards and specifications can be used to federate security services, but do not directly address the dynamic extension of business trust relationships into the digital domain. In this paper we describe an experiment in which we highlight those challenging architectural issues and we will further describe how the approach that combines dynamic trust federation and dynamic authorization mechanism can address dynamic security trust federation in Grids. The experiment made with the prototype described in this paper is used in the NextGRID project for the definition of requirements for next generation Grid architectures adapted to business application need

Physical Dissipation and the Method of Controlled Lagrangians

We describe the effect of physical dissipation on stability of equilibria which have been stabilized, in the absence of damping, using the method of controlled Lagrangians. This method applies to a class of underactuated mechanical systems including “balance” systems such as the pendulum on a cart. Since the method involves modifying a system’s kinetic energy metric through feedback, the effect of dissipation is obscured. In particular, it is not generally true that damping makes a feedback-stabilized equilibrium asymptotically stable. Damping in the unactuated directions does tend to enhance stability, however damping in the controlled directions must be “reversed” through feedback. In this paper, we suggest a choice of feedback dissipation to locally exponentially stabilize a class of controlled Lagrangian systems

Dissipation and Controlled Euler-Poincaré Systems

The method of controlled Lagrangians is a technique for stabilizing underactuated mechanical systems which involves modifying a system’s energy and dynamic structure through feedback. These modifications can obscure the effect of physical dissipation in the closed-loop. For example, generic damping can destabilize an equilibrium which is closed-loop stable for a conservative system model. In this paper, we consider the effect of damping on Euler-Poincaré (special reduced Lagrangian) systems which have been stabilized about an equilibrium using the method of controlled Lagrangians. We describe a choice of feed-back dissipation which asymptotically stabilizes a sub-class of controlled Euler-Poincaré systems subject to physical damping. As an example, we consider intermediate axis rotation of a damped rigid body with a single internal rotor

Optical polarimetric monitoring of the type II-plateau SN 2005af

Aims. Core-collapse supernovae may show significant polarization that implies non-spherically symmetric explosions. We observed the type II-plateau SN 2005af using optical polarimetry in order to verify whether any asphericity is present in the supernova temporal evolution. Methods. We used the IAGPOL imaging polarimeter to obtain optical linear polarization measurements in R (five epochs) and V (one epoch) broadbands. Interstellar polarization was estimated from the field stars in the CCD frames. The optical polarimetric monitoring began around one month after the explosion and lasted ~30 days, between the plateau and the early nebular phase. Results. The weighted mean observed polarization in R band was [1.89 +/- 0.03]% at position angle (PA) 54 deg. After foreground subtraction, the level of the average intrinsic polarization for SN 2005af was ~0.5% with a slight enhancement during the plateau phase and a decline at early nebular phase. A rotation in PA on a time scale of days was also observed. The polarimetric evolution of SN 2005af in the observed epochs is consistent with an overall asphericity of ~20% and an inclination of ~30 deg. Evidence for a more complex, evolving asphericity, possibly involving clumps in the SN 2005af envelope, is found.Comment: 6 pages, 5 figures, to be published A&

AGRICULTURAL TRANSITION: ITS IMPLICATIONS FOR AGRICULTURAL ECONOMICS EXTENSION IN THE SOUTHEAST

Teaching/Communication/Extension/Profession,

Accessing Patient Records in Virtual Healthcare Organisations

The ARTEMIS project is developing a semantic web service based P2P interoperability infrastructure for healthcare information systems that will allow healthcare providers to securely share patient records within virtual healthcare organisations. Authorisation decisions to access patient records across organisation boundaries can be very dynamic and must occur within a strict legislative framework. In ARTEMIS we are developing a dynamic authorisation mechanism called PBAC that provides a means of contextual and process oriented access control to enforce healthcare business processes. PBAC demonstrates how healthcare providers can dynamically share patient records for care pathways across organisation boundaries