Improving the SLA-based management of QoS for secure multimedia services

This paper proposes to integrate security parameters into the Service Level Specification (SLS) template proposed in the Tequila project to improve SLA-based management of QoS [8], [21]. Integrating those parameters in the QoS part of the Service Level Agreement (SLA) specification is essential in particular for secure multimedia services since the QoS is negotiated when the multimedia service is deployed. Security mechanisms need to be negotiated at deployment time when sensible multimedia information is exchanged. In this paper we show that including security parameters in the SLA specification improves the SLA-based management of QoS and therefore the negotiation, deployment and use of the secure multimedia service. The parameters this paper proposes to integrate have the advantage to be understandable by both the end-users and service providers. © IFIP International Federation for Information Processing 2005

Oxidation of UC: an in-situ high temperature environmental scanning electron microscopy study

Uranium carbide (UC) has the potential to be used as fuel in Generation IV nuclear reactors thanks to its higher metal atom density and better thermal conductivity when compared to the most commonly used fuel: uranium dioxide (UO2) [1]. Although UC offers improved properties during operation, it needs to be converted into an oxide form after usage as it is reactive and potentially pyrophoric [2] in oxidising environments. Previous oxidation studies on UC, performed over a range of oxygen atmospheres and temperatures, suggest different mechanisms lead to the formation of either a protective or a pulverised non-protective oxide layer [3]. New experimental observations of the oxidation and self-ignition of UC were reported in our previous work [4] involving a combination of state-of-the-art techniques: high temperature environmental scanning electron microscopy (HT-ESEM), high-resolution transmission electron microscopy (HRTEM) combined with an image analysis technique (ImageJ). In situ HT-ESEM oxidation of sintered UC fragments from 723 to 848 K in 10 to 100 Pa oxygen atmosphere revealed the morphological changes to the oxide during the transformations between UC to UO2 and UO2 to U3O8. Oxidation at 723 K in a low O2 atmosphere (≤ 25 Pa O2) produced a compact UO2+x oxide layer, confirmed by post mortem HRTEM analysis. The oxide formed after an induction period and it was accompanied by an exponential followed by logarithmic sample area expansion and crack propagation. Furthermore, samples oxidised at 50 Pa O2 at 723 K and at 773-848 K in an oxygen atmosphere of 10 to 100 Pa O2 showed “explosive” oxidation (see Figure 1). Sample expansion and crack propagation are well described by an exponential law until the “explosion” occurred causing a transformation to a popcorn-like morphology which is typical for oxidation from UO2 to U3O8. HRTEM analysis on the sample powder showed the oxide to be formed of a mixture of U3O7/U3O8 with U3O8 showing preferential growth in the [001] direction. The explosive nature of the oxide is triggered by ignition of UC, which set off this reaction throughout the entire sample with a propagation speed of 150-500 ± 50 µm/s, which shows similarities to a self-propagating high-temperature synthesis reaction. Please click Additional Files below to see the full abstract

On the stoichiometry of zirconium carbide.

The dependencies of the enhanced thermomechanical properties of zirconium carbide (ZrCx) with sample purity and stoichiometry are still not understood due to discrepancies in the literature. Multiple researchers have recently reported a linear relation between the carbon to zirconium atomic ratio (C/Zr) and the lattice parameter, in contrast with a more established relationship that suggests that the lattice parameter value attains a maximum value at a C/Zr ~ 0.83. In this study, the relationship between C/Zr atomic ratio and the lattice parameter is critically assessed: it is found that recent studies reporting the thermophysical properties of ZrCx have unintentionally produced and characterised samples containing zirconium oxycarbide. To avoid such erroneous characterization of ZrCx thermophysical properties in the future, we propose a method for the accurate measurement of the stoichiometry of ZrCx using three independent experimental techniques, namely: elemental analysis, thermogravimetric analysis and nuclear magnetic resonance spectroscopy. Although a large scatter in the results (ΔC/Zr = 0.07) from these different techniques was found when used independently, when combining the techniques together consistent values of x in ZrCx were obtained

Contribution of Energetically Reactive Surface Features to the Dissolution of CeO2 and ThO2 Analogues for Spent Nuclear Fuel Microstructures

In the safety case for the geological disposal of nuclear waste, the release of radioactivity from the repository is controlled by the dissolution of the spent fuel in groundwater. There remain several uncertainties associated with understanding spent fuel dissolution, including the contribution of energetically reactive surface sites to the dissolution rate. In this study, we investigate how surface features influence the dissolution rate of synthetic CeO2 and ThO2, spent nuclear fuel analogues that approximate as closely as possible the microstructure characteristics of fuel-grade UO2 but are not sensitive to changes in oxidation state of the cation. The morphology of grain boundaries (natural features) and surface facets (specimen preparation-induced features) was investigated during dissolution. The effects of surface polishing on dissolution rate were also investigated. We show that preferential dissolution occurs at grain boundaries, resulting in grain boundary decohesion and enhanced dissolution rates. A strong crystallographic control was exerted, with high misorientation angle grain boundaries retreating more rapidly than those with low misorientation angles, which may be due to the accommodation of defects in the grain boundary structure. The data from these simplified analogue systems support the hypothesis that grain boundaries play a role in the so-called “instant release fraction” of spent fuel, and should be carefully considered, in conjunction with other chemical effects, in safety performance assessements for the geological disposal of spent fuel. Surface facets formed during the sample annealing process also exhibited a strong crystallographic control and were found to dissolve rapidly on initial contact with dissolution medium. Defects and strain induced during sample polishing caused an overestimation of the dissolution rate, by up to 3 orders of magnitude

The hidden curriculum and integrating cure- and care-based approaches to medicine

Although current literature about the “cure versus care” issue tends to promote a patient-centered approach, the disease-centered approach remains the prevailing model in practice. The perceived dichotomy between the two approaches has created a barrier that could make it difficult for medical students and physicians to integrate psychosocial aspects of patient care into the prevailing disease-based model. This article examines the influence of the formal and hidden curricula on the perception of these two approaches and finds that the hidden curriculum perpetuates the notion that “cure” and “care” based approaches are dichotomous despite significant changes in formal curricula that promote a more integrated approach. The authors argue that it is detrimental for clinicians to view the two approaches as oppositional rather than complementary and attempt to give recommendations on how the influence of the hidden curriculum can be reduced to get a both-cure-and-care-approach, rather than an either-cure-or-care-approach

Actes du deuxième colloque africain sur la recherche en informatique = Proceedings of the second African Conference on research in computer science

Les performances des applications distribuées sont fonction des performances des ressources qu'elles consomment, principalement du système d'exploitation du réseau. Les performances de ces ressources imposent des limites. La littérature présente un certain nombre de travaux d'optimisation portant sur l'architecture des ordinateurs, des protocoles et de leur implémentation, sur la régulation de charge, etc. Ce papier propose un controle des processus liés aux applications distribuées à partir des informations d'état des ressources. Il explique l'intéret de cette idée et propose à cet effet l'extension du système de nommage des ressources du réseau Internet pour gérer l'état des ressources. (Résumé d'auteur

An Object-Oriented Information Model for Policy-based Management of Distributed Applications

International audienceThis paper presents an object-oriented information model to support a policy-based management for distributed multimedia applications. The information base contains application-level information about the users, the applications, and their profile. Our Information model is described in details and its specification in UML is provided. This paper presents our approach, methodology and results. This research work has been conducted in the context of the RTIPA (Real-Time Internet Platform Architecture) European project

An Active Network Architecture Allowing Mobile Agents Construction to Improve Quality of Service

NRC publication: Ye

Semantic Techniques for Reconfiguring and Adapting Networks in Pervasive Environments

Computing and networking technologies are becoming ever more pervasive in order to support their users ’ increasingly dynamic lifestyles. These technologies aim to increase the networks ’ awareness of their users ’ requirements. At the same time, they strive to reduce the amount of manual reconfiguration and explicit interaction between the users and the network resources. The main problem is the extreme difficulty in reconfiguring the network’s resources at runtime and in adapting the network’s behaviour automatically according to the changes happening in the surroundings. To address these issues, we investigated the use of the emerging semantic web technologies, policies, and context information. We also developed an ontology-based reasoning machinery to address the problem of automated adaptability. In this paper, we provide an analysis of the ontologies we developed and the reasoning machinery required to increase the network’s awareness of its context. We report on the experiments we conducted to evaluate the techniques we are proposing