Power Extraction Strategy of a Robust kW Range Marine Tidal Turbine Based on Permanent Magnet Synchronous Generators and Passive Rectifiers

This paper presents a kW range marine tidal current power generation system consisting of a fixed pitch marine current turbine (MCT) with two permanent magnet synchronous generators in the turbine shaft, two diode rectifiers (each rectifier is associated with a permanent magnet synchronous generator) and a DC source voltage. This system is designed for a kW range robust power supply. The specificity of the proposed system is that the two generators have different numbers of turns in their windings and the two rectifiers are in parallel in the same DC source. It has been demonstrated that the proposed system is able to harness very efficiently the energy of the turbine in the whole tidal cycle. The proposed system is interesting because it does not need complex control system and it allows minimizing converter losses costs due to electronic devices as controlled IGBT PWM converters usually used in conventional power generation systems. The analytical results have been confirmed numerically using PSIM software for two kW range generators with the same magnetic circuit and different winding number of turns

Category-based Tail Comovement

Traditional …financial theory predicts that comovement in asset returns is due to fundamentals. An alternative view is that of Barberis and Shleifer (2003) and Bar- beris, Shleifer and Wurgler (2005) who propose a sentiment based theory of comovement, delinking it from fundamentals. In their paper they view comovement under the prism of the standard Pearson's correlation measure, implicitly excluding extreme market events, such as the latest …financial crisis. Poon, Rockinger and Tawn (2004) have shown that under such events different types of comovement or dependence may co-exist, and make a clear distinction between the four types of dependence: perfect dependent, independent, asymptotically dependent and asymptotically independent. In this paper we extend the sentiment based theory of comovement so as to cover the whole spectrum of dependence, including extreme comovement such as the one that can be observed in …financial crises. One of the key contributions of this paper is that it formally proves that assets belonging to the same category comove too much in the tail and reclassifying an asset into a new category raises its tail dependence with that category.Interest rates ; Yield curve ; ICA ; PCA

GRID Storage Optimization in Transparent and User-Friendly Way for LHCb Datasets

The LHCb collaboration is one of the four major experiments at the Large Hadron Collider at CERN. Many petabytes of data are produced by the detectors and Monte-Carlo simulations. The LHCb Grid interware LHCbDIRAC is used to make data available to all collaboration members around the world. The data is replicated to the Grid sites in different locations. However the Grid disk storage is limited and does not allow keeping replicas of each file at all sites. Thus it is essential to optimize number of replicas to achieve a better Grid performance. In this study, we present a new approach of data replication and distribution strategy based on data popularity prediction. The popularity is performed based on the data access history and metadata, and uses machine learning techniques and time series analysis methods

Category-based Tail Comovement

Traditional financial theory predicts that comovement in asset returns is due to fundamentals. An alternative view is that of Barberis and Shleifer (2003) and Bar- beris, Shleifer and Wurgler (2005) who propose a sentiment based theory of comovement, delinking it from fundamentals. In their paper they view comovement under the prism of the standard Pearson's correlation measure, implicitly excluding extreme market events, such as the latest financial crisis. Poon, Rockinger and Tawn (2004) have shown that under such events different types of comovement or dependence may co-exist, and make a clear distinction between the four types of dependence: perfect dependent, independent, asymptotically dependent and asymptotically independent. In this paper we extend the sentiment based theory of comovement so as to cover the whole spectrum of dependence, including extreme comovement such as the one that can be observed in financial crises. One of the key contributions of this paper is that it formally proves that assets belonging to the same category comove too much in the tail and reclassifying an asset into a new category raises its tail dependence with that category

Influence of etching processes on electronic transport in mesoscopic InAs/GaSb quantum well devices

We report the electronic characterization of mesoscopic Hall bar devices fabricated from coupled InAs/GaSb quantum wells sandwiched between AlSb barriers, an emerging candidate for two-dimensional topological insulators. The electronic width of the etched structures was determined from the low field magneto-resistance peak, a characteristic signature of partially diffusive boundary scattering in the ballistic limit. In case of dry-etching the electronic width was found to decrease with electron density. In contrast, for wet etched devices it stayed constant with density. Moreover, the boundary scattering was found to be more specular for wet-etched devices, which may be relevant for studying topological edge states.Comment: 5 pages, 2 figure

Capteurs Intelligents : Nouvelles Technologies et Nouvelles Problématiques pour la Sûreté de Fonctionnement

New technology allows intelligent sensors by integrating new functionalities: error measure correction, self-calibration, self-diagnosis of measures and sensor status, reconfiguration, digital communication. Industrialists take advantage of more accurate measurements, cost reductions and use facilities. For industrial safety, new dependability issues appear. Some functionalities as self-diagnosis and digital communication seem to be in favour of control systems availability. On the other hand, the high amount of electronics and programmable units implies new failure causes and modes. Availability assessments of intelligent sensors are quite low in literature. Moreover, “intelligent” functionalities are usually not taken into account. In this paper, a discussion about dependability issues and modelling is presented. An approach is proposed. Both functional and structural decompositions of the system are included which allow representing sensor functionalities and types of dependencies. Failures make up the third part of the model. First analyses show the consequences of these failures on sensor functions and the corresponding failure modes during time. An infrared gas sensor is used for example. Some tools for availability assessment of complex systems can take advantage of these results, especially when dysfunctional behaviour is not well known

Fiabilité des Capteurs-Transmetteurs intégrant des Fonctionnalités Numériques

These works are part of a PhD thesis performed at the INERIS, under the scientific supervision of the UTT, and about the reliability of digital-based transmitters. These systems are commonly described as “intelligent” since they are able to perform innovative functionalities such as self-diagnoses, error measurement corrections, self-adjustments, and on-line reconfigurations. Moreover, they may take advantage of a bidirectional digital communication to perform “cooperating” operations. First, an “intelligent transmitter” modelling has been developed, which includes material and functional interactions, and reliability analyses have been proposed based on this model, dealing with uncertainties linked to system behaviours under faulty conditions. Then, “intelligent transmitters” taking part of control systems have been considered, taking the system elements interactions into account, as well as the process influences, using a dynamic reliability framework

Dependability Issues for Intelligent Transmitters and Reliability Pattern Proposal

International audienceNew technologies make way for "intelligent" transmitters by integrating new functionalities: error measurement corrections, self-adjustment, self-diagnosis for measurement and transmitter status, on-line reconfiguration, and digital bidirectional communication. Industrialists are taking advantage of more accurate measurements, cost reductions and facilities. For industrial risk prevention, new dependability issues are arising. Functionalities such as self-diagnosis and digital communication seem to be in favour of control systems availability. On the other hand, the high amount of electronics and programmable units implies new failure causes and modes which are usually not well known. In this paper, dependability issues for intelligent transmitters are discussed and a reliability model is proposed. By using a Goal Tree - Success Tree (GTST) technique, both functional and material aspects of an intelligent transmitter pattern are included. Material-material, material-function, and function-function relationships are then demonstrated in Master Logic Diagrams (MLD). These results are proposed as support for further case studies. For example, the impact of any material failure on any function, and the reliability of the main functions, can be assessed using this kind of model. Other dependability tools can take advantage of this reliability pattern, for example when the behavioural aspects of complex systems are undetermined