Shopping Cart System: Load Balancing and Fault Tolerance in the OSGi Service Platform

The main purpose of this paper was to find a simple solution for load balancing and fault tolerance in OSGi. The challenge was to implement a highly available web application such as a shopping cart system with load balancing and fault tolerance, without having to change the core of OSGi.

Greece, global fault-lines and the disintegrative logics of Germany’s primacy in Europe

Post-Keynesian, heterodox and Marxist political economists have rightly argued that the eurozone crisis is not a fiscal crisis but a balance of payments crisis, mainly caused by the pivotal position of Germany in the European Monetary Union (EMU) and its neo-mercantilist model of growth (low wage, low inflation and export-led). This view, however, sees the split between core and periphery in the European Union as something created with the introduction of the EMU in 1999. This chapter contends that this is not the case. By putting forth a global fault-lines historical perspective and focusing on the case of Greece, it is argued that the problem is not the introduction of the EMU but the geopolitical and macroeconomic asymmetries between core and periphery in Europe since the inception of what vaguely – and even inaccurately – can be defined as ‘European modernity’. Global fault-lines offer a macro-historical and macroeconomic understanding of crises seen as structural events generated by the evolving and contradictory tendencies of capitalism as a world system. It is not just a political economy perspective but a perspective that encompasses many instances of the social, especially geopolitical and geocultural structures.

Early analysis of fault-attack effects for cryptographic hardware

International audience

Fault tolerance logging-based model for deterministic systems

Fault tolerance allows a system to remain operational to some degree when some of its components fail. One of the most common fault tolerance mechanisms consists on logging the system state periodically, and recovering the system to a consistent state in the event of a failure. This paper describes a general fault tolerance logging-based mechanism, which can be layered over deterministic systems. Our proposal describes how a logging mechanism can recover the underlying system to a consistent state, even if an action or set of actions were interrupted mid-way, due to a server crash. We also propose different methods of storing the logging information, and describe how to deploy a fault tolerant master-slave cluster for information replication. We adapt our model to a previously proposed framework, which provided common relational features, like transactions with atomic, consistent, isolated and durable properties, to NoSQL database management systems.

Ground fault protectionmethods for distribution systems

The system grounding method option has a direct influence on the overall performance of the entire medium voltage network as well as on the ground fault current magnitude. For any kind of grounding systems: ungrounded system, solidly and low impedance grounded and resonant grounded, we can find advantages and disadvantages. A thorough study is necessary to choose the most appropriate grounding protection system. The power distribution utilities justify their choices based on economic and technical criteria, according to the specific characteristics of each distribution network. In this paper we present a medium voltage Portuguese substation case study and a study of neutral system with Petersen coil, isolated neutral and impedance grounded.

Fault detection with Conditional Gaussian Network

International audience

Effect on the disability index of adult patients with benign paroxysmal positional vertigo using vestibular rehabilitation and human movement

Objective: determine the effect on the disability index of adult patients with benign paroxysmal positional vertigo (BPPV) using vestibular rehabilitation therapy (VRT) and human movement. Subjects: six subjects with an average age of 49.5 ± 14.22 years who have been diagnosed with benign paroxysmal positional vertigo by an otolaryngologist. Instruments: the Dizziness Handicap Inventory and a questionnaire to determine impact on the quality of life of patients with this pathology (Ceballos and Vargas, 2004). Procedure: subjects underwent vestibular therapy for four weeks together with habituation and balance exercises in a semi-supervised manner. Two measurements were performed, one before and one after the vestibular therapy and researchers determined if there was any improvement in the physical, functional, and emotional dimensions. Statistical analysis: descriptive statistics and Student’s t-test of repeated measures were applied to analyze results obtained. Results: significant statistical differences were found in the physical dimension between the pre-test (19.33 ± 4.67 points) and post-test (13 ± 7.24 points) (t = 2.65; p < 0.05).  In contrast, no significant statistical differences were found in the functional (t = 2.44; p>0.05), emotional (t = 2.37; p>0.05) or general dimensions (t = 2.55; p>0.05). Conclusion: vestibular therapy with a semi-supervised human movement program improved the index of disability due to vertigo (physical dimension) in BPPV subjects.

A brief review on offshore wind turbine fault detection and recent development in condition monitoring based maintenance system

Offshore wind turbine requires more systematized operation and maintenance strategies to ensure systems are harmless, profitable and cost-effective. Condition monitoring and fault diagnostic systems ominously plays an important role in offshore wind turbine in order to cut down maintenance and operational costs. Condition monitoring techniques which describing complex faults and failure mode types and their generated traceable signs to provide cost-effective condition monitoring and predictive maintenance and their diagnostic schemes. Continuously monitor the condition of critical parts are the most efficient way to improve reliability of wind turbine. Implementation of Condition Based Maintenance (CBM) strategy provides right time maintenance decisions and Predictive Health Monitoring (PHM) data to overcome breakdown and machine downtime. Fault detection and CBM implementation is challenging for off shore wind farm due to the complexity of remote sensing, components health and predictive assessment, data collection, data analysis, data handling, state recognition, and advisory decision. The rapid expansion of wind farms, advanced technological development and harsh installation sites needs a successful CM approach. This paper aims to review brief status of recent development of CM techniques and focusing with major faults takes place in gear box and bearing, rotor and blade, pitch, yaw and tower system and generator and control system.

Functional observer-based fault detection of time-delay systems via an LMI approach

This paper presents a novel residual generator that uses minimum-order functional observers to trigger actuator and component faults in time-delay systems. We first present a fault detection scheme and derive existence conditions of the residual generator and functional observer. The observer and residual parameters are then systematically determined via solving some coupled generalized Sylvester matrix equations. To deal with the time-delay issue, a stabilizability condition expressed in terms of linear matrix inequality (LMI) is derived to ensure the time-delay observer error system converges to zero with a prescribed convergence rate. Our design approach has the advantage that the designed fault detection scheme has lower order than existing results in the literature. Two numerical examples are given to illustrate the effectiveness of our results.

Fault tolerance in data gathering wireless sensor networks

In data gathering wireless sensor networks, data loss often happens due to external faults such as random link faults and hazard node faults, since sensor nodes have constrained resources and are often deployed in inhospitable environments. However, already known fault tolerance mechanisms often bring new internal faults (e.g. out-of-power faults and collisions on wireless bandwidth) to the original network and dissipate lots of extra energy and time to reduce data loss. Therefore, we propose a novel Dual Cluster Heads Cooperation (CoDuch) scheme to tolerate external faults while introducing less internal faults and dissipating less extra energy and time. In CoDuch scheme, dual cluster heads cooperate with each other to reduce extra costs by sending only one copy of sensed data to the Base Station; also, dual cluster heads check errors with each other during the collecting data process. Two algorithms are developed based on the CoDuch scheme: CoDuch-l for tolerating link faults and CoDuch-b for tolerating both link faults and node faults; theory and experimental study validate their effectiveness and efficiency. © 2010 The Author Published by Oxford University Press on behalf of The British Computer Society. All rights reserved.

Minimal-order functional observer-based residual generators for fault detection and isolation of dynamical systems

This paper examines the design of minimal-order residual generators for the purpose of detecting and isolating actuator and/or component faults in dynamical systems. We first derive existence conditions and design residual generators using only first-order observers to detect and identify the faults. When the first-order functional observers do not exist, then based on a parametric approach to the solution of a generalized Sylvester matrix equation, we develop systematic procedures for designing residual generators utilizing minimal-order functional observers. Our design approach gives lower-order residual generators than existing results in the literature. The advantages for having such lower-order residual generators are obvious from the economical and practical points of view as cost saving and simplicity in implementation can be achieved, particularly when dealing with high-order complex systems. Numerical examples are given to illustrate the proposed fault detection and isolation schemes. In all of the numerical examples, we design minimum-order residual generators to effectively detect and isolate actuator and/or component faults in the system.