1,228 research outputs found
Methodology for the Diagnosis of Hydromechanical Actuation Loops in Aircraft Engines
No full textThis document provides a method for on-board monitoring and on-ground diagnosis of a hydromechanical actuation loop such as those found in aircraft engines. First, a complete system analysis is performed to understand its behaviour and determine the main degradation modes. Then, system health indicators are defined and a method for their real time on-board extraction is addressed. Diagnosis is performed on-ground through classification of degradation signatures. To parameterize on-ground treatment, both a reference healthy state of indicators and degradations signatures are needed. The healthy distribution of indicators is obtained from data and a physics-based model is used to simulate degradations, quantify indicators sensibility and construct the signatures database. At last, algorithms are deployed and a statistical validation of the performances is conducted
Selection and Validation of Health Indicators in Prognostics and Health Management System Design
No full textHealth Monitoring is the science of system health status evaluation. In the modern industrial world, it is getting more and more importance because it is a powerful tool to increase systems dependability. It is based on the observation of some variables extracted in operation reflecting the condition of a system. The quality of health monitoring strongly depends on the selection of these variables named health indicators. However, the issue in their selection is often underestimated and their validation is, of what is known, an untreated subject. In this paper, the authors introduce a complete methodology for the selection and validation of health indicators in health monitoring systems design. Although it can be applied either downstream on real measured data or upstream on simulated data, the true interest of the method is in the latter application. Indeed, a model-based validation can be integrated in the design phases of the system development process, thereby reducing potential controller retrofit costs and useless data storage. In order to simulate the distribution of health indicators, a well known surrogate model called Kriging is utilized. Eventually, the method is tested on a benchmark system: the high pressure pump of aircraft engines fuel systems. Thanks to the method, the set of health indicators was validated in system design phases and the monitoring is now ready to be implemented for in-service operation
Measurement of the branching fraction B(Bu+→J/ψπ+) and search for Bc+→J/ψπ+
No full textWe report on a measured of the branching fraction of the Cabibbo-suppressed decay B-u(+)-->J/psi pi(+), where J/psi-->mu(+)mu(-). The data were collected by the Collider Detector at Fermilab during 1992-1995 and correspond to an integrated luminosity of 110 pb(-1) in (p) over tildep$ collisions at root s=1.8 TeV. A signal of 28(-9)(+10) events is observed and we demonstrate the ratio of branching fractions B(B-u(+)-->J/psi pi)/B(B-u(+)-->J/psi K+) to be [5.0(-1.7)(+1.9) (stat)+/-0.1(syst)]%. Using the world average value for B(B-u(+)-->J/psi K+), we calculate the branching fraction B(B-u(+)-->J/psi pi(+)) to be (5.0(-1.9)(+2.1))x10(-5). We also search for the decay B-c(+)-->J/psi pi(+) and report a 95% confidence level limit on sigma(B-c(+))B(B-c(+)-->J/psi pi(+)/sigma(B-u(+))B(B-u(+)-->J/psi K+) as a function of the B-c(+) lifetime
Numerical Key Performance Indicators for the Validation of PHM Health Indicators with Application to a Hydraulic Actuation System
No full textIn order to perform Prognostic and Health Management (PHM) of a given system, it is necessary to define some relevant variables sensitive to the different degradation modes of the system. Those variables are named Health Indicators (HI) and they are the keystone of PHM. However, they are subject to a lot of uncertainties when computed in real time and the stochastic nature of PHM makes it hard to evaluate the efficiency of a HI set before the extraction algorithm is implemented. This document introduces Numerical Key Performance Indicators (NKPI) for the validation of HI computed only from data provided by numerical models in the upstream stages of a PHM system development process. In order to match as good as possible the reality, the multiple sources of uncertainties are quantified and propagated into the model. After having introduced the issue of uncertain systems modeling, the different NKPI are defined and eventually an application is performed on a hydraulic actuation system of an aircraft engine
La métaphore vacante : concurrence des images entre 1929 et 1936 : photographie, surréalisme, revue, publicité
No full textLa présente thèse en histoire visuelle réinvestit la photographie surréaliste parisienne de l’entre-deux-guerres, afin de démontrer le rôle moteur des dispositifs de la revue et de la publicité dans la production et la diffusion de la photographie entre 1929 et 1936. Au cours d’une période que nous nommons la « seconde naissance de la photographie », nous établissons une articulation inédite entre les stratégies de diffusion de la photographie dans le contexte des revues surréalistes et les logiques spectaculaires régissant la circulation intensifiée des images à travers les médias imprimés. Notre argument s’appuie sur la notion de concurrence, que nous élaborons en construisant une approche pragmatique et énergétique fondée sur les théories dites de la vie des images (W. J. T. Mitchell entre autres), la conceptualisation du dispositif pulsionnel par Jean-François Lyotard et les études intermédiales qui se formulent autour du Centre de Recherches sur l’Intermédialité (arts, lettres, techniques).
Suivant un principe microhistorique, le parcours de la thèse se construit à travers une série d’études de cas qui mettent en jeu des configurations variées entre la photographie, le surréalisme, la revue et la publicité. Nous offrons des analyses détaillées de la revue Le Surréalisme au service de la révolution (1930–1933), des premières années de publication de Minotaure (1933–1935), ainsi que de l’album Électricité (1931), commande publicitaire réalisée par Man Ray, et des projets publicitaires pour Pétrole Hahn (1933–1935) du studio Kéfer-Dora Maar. L’étude de ce corpus ciblé éclaire les relations médiales qui définissent la vitalité des images photographiques dans un contexte de profusion visuelle intensifiée. En proposant de nouveaux outils conceptuels pour l’interprétation des séquences visuelles et des trajectoires d’images, la thèse contribue à l’avancement des études visuelles, en particulier les recherches sur les revues et les modes de diffusion de l’image photographique. L’histoire de la photographie surréaliste que nous restituons dans l’optique nouvelle d’une énergétique des images démontre également la pertinence de réévaluer les avant-gardes historiques à la lumière d’innovations méthodologiques.This thesis in visual history revisits Surrealist photography from interwar Paris in order to demonstrate the role of periodicals and advertising as agents (dispositifs) of photographic production and dissemination between 1929 and 1936. During a period which I refer to as the “second birth of photography,” I identify a previously overlooked relationship between the dissemination strategies used for photography in periodicals produced in the Surrealist context and the logics of the spectacle that governed the intensified circulation of images through print media. To explore this relationship, I draw upon the concept of competition (concurrence), which I elaborate by way of a pragmatic and energetic approach inspired by theories of the “iconic turn” (such as W. J. T. Mitchell’s), by Jean-François Lyotard’s idea of the dispositif, and by intermedial studies of the kind practiced by the Centre de Recherches sur l’Intermédialité (arts, lettres, techniques).
Adopting the tenets of microhistory, this thesis is structured around a series of case studies involving varied configurations between photography, Surrealism, the periodical and advertising. I offer close readings of the Surrealist periodical Le Surréalisme au service de la révolution (1930–1933), the first publication years of Minotaure (1933–1935), as well as the Électricité portfolio (1931), an advertising commission completed by Man Ray, and the advertising projects for Pétrole Hahn (1933–1935) produced by the Kéfer-Dora Maar studio. My analysis of this carefully chosen body of works sheds new light on the medial relations shaping the vitality of photographic images in the context of an intense visual proliferation. By proposing new conceptual tools to interpret visual sequences and image circulation, the thesis contributes to current conversations in visual studies regarding periodicals and the dissemination of photographs. The history of Surrealist photography I offer, with its novel concern for the energetics of images, also demonstrates the value of continuing to re-evaluate historical avant-gardes in the light of methodological innovations
Reconstruction of B-0->J/psi K-S(0) and measurement of ratios of branching ratios involving B->J/psi K* and B+->J/psi K+
No full textWe report on the reconstruction of the decay mode B-0 --> J/psi K-S(0) using 19.3 pb(-1) of data collected by the Collider Detector at Fermilab in collisions at root s = 1.8 TeV. A signal of 41.8 +/- 6.9 events, with a signal-to-background ratio of 9:1, is observed. Three additional decay modes B+ --> J/psi K+, B-0 --> J/psi K*(892)(0), and B+ --> J/psi K*(892)(+) are reconstructed. We measure three ratios of branching ratios, each one relative to the B+ --> J/psi K+ mode. We also report the ratio of decay rates, Gamma(B --> J/psi K*)/Gamma(B --> J/psi K), for the vector-vector relative to the vector-pseudoscalar modes, to be 1.32 +/- 0.23(stat) +/- 0.16(syst)
What is a Good Plan? Cultural Variations in Expert Planners’ Concepts of Plan Quality
No full textThis article presents the results of a field research study examining commonalities and differences between American and British operational planners’ mental models of planning. We conducted Cultural Network Analysis (CNA) interviews with 14 experienced operational planners in the US and UK. Our results demonstrate the existence of fundamental differences between the way American and British expert planners conceive of a high quality plan. Our results revealed that the American planners’ model focused on specification of action to achieve synchronization, providing little autonomy at the level of execution, and included the belief that increasing contingencies reduces risk. The British planners’ model stressed the internal coherence of the plan, to support shared situational awareness and thereby flexibility at the level of execution. The British model also emphasized the belief that reducing the number of assumptions decreases risk. Overall, the American ideal plan serves a controlling function, whereas the British ideal plan supports an enabling function. Interestingly, both the US and UK would view the other’s ideal plan as riskier than their own. The implications of cultural models of plans and planning are described for establishing performance measures and designing systems to support multinational planning teams
<i>Drosophila</i> neurons grow at physiological rates <i>in</i><i>vitro</i>.
No full text<p>(<b>A</b>) Coomassie stain of DECM purified from Kc167 conditioned media. Bands identified as Laminin A, Tiggrin, Laminin B1, and Laminin B2 by mass spectroscopy. Unsequenced band at 50 kDa corresponds to glutactin based on previous reports [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080136#B44" target="_blank">44</a>]. Phase images of <i>Drosophila</i> neurons grown <i>in </i><i>vitro</i> on (<b>B</b>) poly-ornithine and (<b>C</b>) DECM. Axonal length at 24 hours increases with concentrations of DECM at 2 µg/ml and higher (<b>D</b>). The numbers in the bars in (<b>D</b>) represent <i>n</i> for each group. The graph in (<b>E</b>) shows axonal initiation is asynchronous, occurring over a period of ~12 hours, and is not substrate dependent. The arrow marks the time point where 50% of the neurons had initiated axons. Representative examples of growth cone position over time are shown for neurons grown on (<b>F</b>) poly-ornithine and (<b>G</b>) DECM. By aligning individual growth cone positions so initiation is at t = 0, accurate depictions of cone advance can be more clearly seen. (<b>H</b>) poly-ornithine alignment, (<b>I</b>) DECM alignment. Averaging axonal length over time without accounting for differences in initiation (<b>J</b>) yields rates of elongation similar to previous reports, whereas analysis of synchronized average axonal length (<b>K</b>) reveals elongation occurs at rates similar to those observed <i>in </i><i>vivo</i>. All error bars are 95% CI. Scale bar = 70 µm.</p
Role of glutathione transferases in herbicide detoxification in weeds
No full textGlutathione transferases (GSTs) catalyse the conjugation of the electrophilic herbicides atrazine, metolachlor, alachlor and fluorodifen with the tripeptide glutathione (GSH). Maize (Zea mays L), contains multiple GSTs with differing substrate specificities which confer tolerance to a variety of herbicides. In contrast far less is known regarding the GSTs in competing weed species. In vivo metabolism studies using seedlings of maize and the weeds Panicum miliaceum. Digitaria sanguinalis, Sorghum bicolor. Setaria faberi. Abutilon theophrasti and Echinochloa crus-galli demonstrated that all species were capable of metabolising radiolabelled atrazine to GSH conjugates and the relative rates of metabolism related well to GST activities. Similarly, GST activities toward atrazine, metolachlor and alachlor correlated well with herbicide tolerance, with GSH availability being less important. GST activities towards metolachlor, alachlor and atrazine were highest in young maize plants and decreased with age, whilst GST activities in S.faberi remained unchanged. At 35 days GST activities were similar in the two species and the atrazine selectivity was lost. GSH content decreased with age in both species. Protein purification studies showed that S.faberi contains 4 GST isoenzymes with differing substrate specificities. The major GST was estimated to account for 0.1 % of die total soluble protein in S.faberi. PCR-amplification of a cDNA prepared from mRNA showed that S.faberi contains a GST with 88% identity to GST I from maize at the nucleotide level and 82% identity at the amino acid level. Similarly antibodies raised to maize and wheat GSTs recognised GSTs in S.faberi. It is concluded that GSTs determine the relative tolerance to chloroacetanilides and atrazine in weed seedlings but may be less important in older plants. The GSTs in S.faberi are similar in complexity to those determined in maize but are expressed at lower levels
Diagnostics of an Aircraft Engine Pumping Unit Using a Hybrid Approach based-on Surrogate Modeling
No full textThis document introduces a hybrid approach for fault detection and identification of an aircraft engine pumping unit. It is based on the complementarity between a model-based approach accounting for uncertainties aimed at quantifying the degradation modes signatures and a data-driven approach aimed at recalibrating the healthy syndrome from measures. Because of the computational time costs of uncertainties propagation into the physics based model, a surrogate modeling technic called Kriging associated to Latin hypercube sampling is utilized. The hybrid approach is tested on a pumping unit of an aircraft engine and shows good results for computing the degradation modes signatures and performing their detection and identification
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