Risk based resilient network design

This paper presents a risk-based approach to resilient network design. The basic design problem considered is that given a working network and a fixed budget, how best to allocate the budget for deploying a survivability technique in different parts of the network based on managing the risk. The term risk measures two related quantities: the likelihood of failure or attack, and the amount of damage caused by the failure or attack. Various designs with different risk-based design objectives are considered, for example, minimizing the expected damage, minimizing the maximum damage, and minimizing a measure of the variability of damage that could occur in the network. A design methodology for the proposed risk-based survivable network design approach is presented within an optimization model framework. Numerical results and analysis illustrating the different risk based designs and the tradeoffs among the schemes are presented. © 2011 Springer Science+Business Media, LLC

Effects Of Iron Implantation On The Aqueous Corrosion Of Magnesium

The influence of the implantation of iron ions on the corrosion of magnesium and an AlZn-rich magnesium alloy (AZ91C) has been studied. Anodic polarization measurements in a dilute chloride-containing alkaline solution were used to evaluate corrosion resistance. A range of ion energies (50-180 keV) and doses (1016-2 x 1017 Fe+ ions cm-2) have been evaluated. Both the iron-implanted pure magnesium and the alloy AZ91C gave improved polarization measurements. A systematic positive shift of the open-circuit potential with increasing iron dose was found. In AZ91C at a dose of 1017 Fe+ ions cm-2, there was a + 0.6 V more noble shift in the open-circuit potential and a nearly equivalent shift of the pitting potential. In addition, there was a reduction of more than an order of magnitude in the current densities at all potentials. The ion energy did not have a large effect on the corrosion behavior. Annealing the samples did not further improve the corrosion resistance. The results from characterizing the corroded samples using Auger spectroscopy and scanning electron microscopy are also presented. © 1985

Comparison of the Full Outline of UnResponsiveness and Glasgow Liege Scale/Glasgow Coma Scale in an Intensive Care Unit Population.

peer reviewedBACKGROUND: The Full Outline of UnResponsiveness (FOUR) has been proposed as an alternative for the Glasgow Coma Scale (GCS)/Glasgow Liege Scale (GLS) in the evaluation of consciousness in severely brain-damaged patients. We compared the FOUR and GLS/GCS in intensive care unit patients who were admitted in a comatose state. METHODS: FOUR and GLS evaluations were performed in randomized order in 176 acutely (<1 month) brain-damaged patients. GLS scores were transformed in GCS scores by removing the GLS brainstem component. Inter-rater agreement was assessed in 20% of the studied population (N = 35). A logistic regression analysis adjusted for age, and etiology was performed to assess the link between the studied scores and the outcome 3 months after injury (N = 136). RESULTS: GLS/GCS verbal component was scored 1 in 146 patients, among these 131 were intubated. We found that the inter-rater reliability was good for the FOUR score, the GLS/GCS. FOUR, GLS/GCS total scores predicted functional outcome with and without adjustment for age and etiology. 71 patients were considered as being in a vegetative/unresponsive state based on the GLS/GCS. The FOUR score identified 8 of these 71 patients as being minimally conscious given that these patients showed visual pursuit. CONCLUSIONS: The FOUR score is a valid tool with good inter-rater reliability that is comparable to the GLS/GCS in predicting outcome. It offers the advantage to be performable in intubated patients and to identify non-verbal signs of consciousness by assessing visual pursuit, and hence minimal signs of consciousness (11% in this study), not assessed by GLS/GCS scales

Emerging semantic communities in peer web search

Peer network systems are becoming an increasingly important development in Web search technology. Many studies show that peer search systems perform better when a query is sent to a group of peers semantically similar to the query. This suggests that semantic communities should form so that a query can quickly propagate to many appropriate peers. For the network to be functional, its dynamic communication topology must match the semantic clustering of peers. We introduce two criteria to evaluate a peer search network based on the concept of semantic locality: first, the “smallworld” topology of the network; second, we use topical semantic similarity to monitor the quality of a peer’s neighbors over time by looking at whether a peer chooses semantically appropriate neighbors to route its queries. We present several simulation experiments conducted with different peer search algorithms on our peer Web search system, 6S. The results suggest that 6S, despite its use of an unstructured overlay network; can effectively foster the spontaneous formation of semantic communities through local peer interactions alone

A risk management approach to resilient network design

This paper considers the problem of where a survivability technique should be deployed in a network based on managing risk given a limited financial budget. We formulate three novel risk management resilient network design techniques: (1) minimize the maximum damage that could occur in the network, (2) minimize the maximum risk in the network and (3) minimize the root mean squared damage. The first two approaches try to minimize the damage/risk from the worst case failure scenario, where as the third technique minimizes the variability of damage across all failure scenarios. Numerical results for a sample network show the tradeoffs among the schemes. ©2010 IEEE

Jelasity: “Overlay Management for Fully Distributed User-Based Collaborative Filtering

Abstract. Offering personalized recommendation as a service in fully distributed applications such as file-sharing, distributed search, social networking, P2P television, etc, is an increasingly important problem. In such networked environments recommender algorithms should meet the same performance and reliability requirements as in centralized services. To achieve this is a challenge because a large amount of distributed data needs to be managed, and at the same time additional constraints need to be taken into account such as balancing resource usage over the network. In this paper we focus on a common component of many fully distributed recommender systems, namely the overlay network. We point out that the overlay topologies that are typically defined by node similarity have highly unbalanced degree distributions in a wide range of available benchmark datasets: a fact that has important—but so far largely overlooked—consequences on the load balancing of overlay protocols. We propose algorithms with a favorable convergence speed and prediction accuracy that also take load balancing into account. We perform extensive simulation experiments with the proposed algorithms, and compare them with known algorithms from related work on wellknown benchmark datasets.