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Now showing items 17 - 32 of 70

  • Surface Modification by Carbon Ion Implantation for the Application of Ni-Based Amorphous Alloys as Bipolar Plate in Proton Exchange Membrane Fuel Cells

    Kim, Min-Uk   Kim, Do-Hyang   Han, Seung-hee   Fleury, Eric   Seok, Hyun-Kwang   Cha, Pil-Ryung   Kim, Yu-Chan  

    Ni-based amorphous alloys with surface modification by carbon ion implantation are proposed as an alternative bipolar plate material for polymer electrolyte membrane fuel cells (PEMFCs). Both Ni60Nb20Ti10Zr10 alloys with and without carbon ion implantation have corrosion resistance as good as graphite as well as much lower contact resistance than 316L stainless steel in the PEMFC environment. The formation of conductive surface carbide due to carbon ion implantation results in a decrease in the contact resistance to a level comparable to that of graphite. This combination of excellent properties indicates that carbon ion implanted Ni-based amorphous alloys can be potential candidate materials for bipolar plates in PEMFCs.
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  • Paradoxical phenomena between the homogeneous and inhomogeneous deformations of metallic glasses RID A-8478-2008

    Park, Kyoung-Won   Lee, Chang-Myeon   Lee, Mi-Rim   Fleury, Eric   Falk, Michael L.   Lee, Jae-Chul  

    Experiments in binary alloys demonstrate that metallic glasses exhibiting more plastic strain during homogeneous deformation tend to show lower global plasticity during inhomogeneous deformation. Testing of Cu-Zr binary alloys supports the hypothesis that the formation energy of a shear transformation zone, as extracted from the experimental data, is related to the homogeneous flow rate. We also report the microstructural aspects that control the global plasticity of metallic glasses in the light of structural disordering, softening, and shear localization.
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  • Correlations and dynamics of consumption patterns in social-economic networks

    Leo, Yannick   Karsai, Marton   Sarraute, Carlos   Fleury, Eric  

    We analyse a coupled dataset collecting the mobile phone communications and bank transactions history of a large number of individuals living in a Latin American country. After mapping the social structure and introducing indicators of socioeconomic status, demographic features, and purchasing habits of individuals, we show that typical consumption patterns are strongly correlated with identified socioeconomic classes leading to patterns of stratification in the social structure. In addition, we measure correlations between merchant categories and introduce a correlation network, which emerges with a meaningful community structure. We detect multivariate relations between merchant categories and show correlations in purchasing habits of individuals. Finally, by analysing individual consumption histories, we detect dynamical patterns in purchase behaviour and their correlations with the socioeconomic status, demographic characters and the egocentric social network of individuals. Our work provides novel and detailed insight into the relations between social and consuming behaviour with potential applications in resource allocation, marketing, and recommendation system design.
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  • Plasticity of amorphous alloys assessed by their homogeneous flow rate

    Park, Kyoung-Won   Lee, Chang-Myeon   Fleury, Eric   Lee, Jae-Chul  

    We explored the sole effect exerted by the packing density of an amorphous alloy on its homogeneous deformation and subsequent inhomogeneous deformation. The experiments demonstrated that an alloy with higher packing exhibits a greater degree of homogeneous deformation, whereas the same alloy exhibits less global plasticity associated with inhomogeneous deformation in a typical compression test. We clarify this paradoxical relationship between homogeneous and inhomogeneous deformation by exploring the relationship between the homogeneous flow rate and its effect on shear localization. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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  • A modified embedded-atom method interatomic potential for the V-H system

    Shim, Jae-Hyeok   Lee, Young-Su   Fleury, Eric   Cho, Young Whan   Ko, Won-Seok   Lee, Byeong-Joo  

    An interatomic potential for the vanadium-hydrogen binary system has been developed based on the second nearest-neighbor modified embedded-atom method (2NN MEAM) potential formalism, in combination with the previously developed potentials for V and H. Also, first-principles calculation has been carried out to provide data on the physical properties of this system, which are necessary for the optimization of the potential parameters. The developed potential reasonably reproduces the fundamental physical properties (thermodynamic, diffusion, elastic and volumetric properties) of V-rich bcc solid solution and some of the vanadium hydride phases. The applicability of this potential to the development of V-based alloys for hydrogen applications is discussed. (C) 2011 Elsevier Ltd. All rights reserved.
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  • Translation on Graphs: An Isometric Shift Operator

    Girault, Benjamin   Goncalves, Paulo   Fleury, Eric  

    In this letter, we propose a new shift operator for graph signals, enforcing that our operator is isometric. Doing so, we ensure that as many properties of the time shift as possible get carried over. Finally, we show that our operator behaves reasonably for graph signals.
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  • Origin of the plasticity in bulk amorphous alloys

    Lee, Jae-Chul   Park, Kyoung-Won   Kim, Kyou-Hyun   Fleury, Eric   Lee, Byeong-Joo   Wakeda, Masato   Shibutani, Yoji  

    Unlike the dislocation-based plasticity in crystalline metals, which can be readily explained by their crystal structure and the presence of defects, the nature of the plasticity in amorphous alloys is not completely understood. Experiments have shown that the plasticity in amorphous alloys is strongly dependent on their atomic packing density. This study, based on the combination of experimental and computational techniques, examines the origin of the plasticity in amorphous alloys considering characteristics of the inherent atomic-scale structure as defined by short-range ordered (SRO) clusters. The role of various SRO atomic clusters in creating free volume during shear deformation is discussed. We report that the plasticity exhibited by amorphous alloys is very sensitive to the characteristics of the atomic packing state, which can be described by various SRO atomic structures and quantified by the effective activation energy for crystallization.
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  • Embrittlement of Pd-Coated Ni-Nb-Ti-Zr Amorphous Alloys during Hydrogen Permeation

    Lee, Dock-Young   Fleury, Eric  

    In this study, we report results of an investigation into the failure of Ni60Nb15Ti15Zr10 amorphous alloys occurring during hydrogen permeation performed at 473 K and 573 K. However, the amorphous membrane did not fail during test performed at higher temperatures (673 K and 773 K). The failure of the Pd-coated Ni60Nb15Ti15Zr10 amorphous ribbon is attributed to the cracking of the hydrogenated Pd coating induced by the formation of alpha' hydride phase in the low temperature range.
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  • Attitudes, risk of infection and behaviours in the operating room (the ARIBO Project): a prospective, cross-sectional study.

    Birgand, Gabriel   Azevedo, Christine   Toupet, Gaelle   Pissard-Gibollet, Roger   Grandbastien, Bruno   Fleury, Eric   Lucet, Jean-Christophe  

    INTRODUCTION: Inappropriate staff behaviours can lead to environmental contamination in the operating room (OR) and subsequent surgical site infection (SSI). This study will focus on the continued assessment of OR staff behaviours using a motion tracking system and their impact on the SSI risk during surgical procedures.; METHODS AND ANALYSIS: This multicentre prospective cross-sectional study will include 10 ORs of cardiac and orthopaedic surgery in 12 healthcare facilities (HCFs). The staff behaviour will be assessed by an objective, continued and prolonged quantification of movements within the OR. A motion tracking system including eight optical cameras (VICON-Bonita) will record the movements of reflective markers placed on the surgical caps/hoods of each person entering the room. Different configurations of markers positioning will be used to distinguish between the staff category. Doors opening will be observed by means of wireless inertial sensors fixed on the doors and synchronised with the motion tracking system. We will collect information on the OR staff, surgical procedures and surgical environment characteristics. The behavioural data obtained will be compared (1) to the 'best behaviour rules' in the OR, pre-established using a Delphi method and (2) to surrogates of the infectious risk represented by microbiological air counts, particle counts, and a bacteriological sample of the wound at closing. Statistics will be performed using univariate and multivariate analysis to adjust on the aerolic and architectural characteristics of the OR. A multilevel model will allow including surgical specialty and HCFs effects. Through this study, we will develop an original approach using high technology tools associated to data processing techniques to evaluate 'automatically' the behavioural dynamics of the OR staff and their impact on the SSI risk.; ETHICS AND DISSEMINATION: Approbation of the Institutional Review Board of Paris North Hospitals, Paris 7 University, AP-HP (no 11-113, 6 April 2012). The findings will be disseminated through peer-reviewed journals, and national and international conference presentations.=20
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  • Hydrogen permeation of Pd-coated V(90)Al(10) alloy membranes at different pressures in the presence and absence of carbon dioxide

    Il Jeon, Sung   Park, Jung Hoon   Magnone, Edoardo   Lee, Yong Taek   Fleury, Eric  

    The hydrogen permeation characteristics of alloy membranes based on Pd-coated V(90)Al(10) alloy membrane have been investigated in the pressure range 1-3 atm under pure hydrogen and hydrogen -carbon dioxide gas mixture at 450 degrees C. Hydrogen permeation experiments have been confirmed that hydrogen flux was 21.1 ml/min/cm(2) for a Pd-coated V(90)Al(10) alloy membrane (thickness: 0.5 mm) using pure hydrogen as the feed gas. It has been found that Pd-coated V(90)Al(10) alloy membranes exhibit good resistance to hydrogen embrittlement in pure hydrogen atmosphere. After different hydrogen permeation flux tests under different pressure condition in presence of hydrogenecarbon dioxide gas mixture, the characteristics of the Pd-coated V(90)Al(10) alloy membranes were examined by ex-situ analysis techniques. The loss of cell performance observed in the presence of hydrogenecarbon dioxide gas mixture is mainly attributed to both physical and chemical degradations of membrane, which led to structural changes in the Pd-coated V(90)Al(10) xalloy membrane. (C) 2011 Elsevier B. V. All rights reserved.
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  • Close proximity interactions support transmission of ESBL-K. pneumoniae but not ESBL-E. coli in healthcare settings

    Duval, Audrey   Obadia, Thomas   Boelle, Pierre-Yves   Fleury, Eric   Herrmann, Jean-Louis   Guillemot, Didier   Temime, Laura   Opatowski, Lulla   Alvarez, Anne Sophie   Baraffe, Audrey   Beiro, Mariano   Bertucci, Inga   Boelle, Pierre-Yves   Cyncynatus, Camille   Dannet, Florence   Delaby, Marie Laure   Denys, Pierre   de Celles, Matthieu Domenech   Fleury, Eric   Fraboulet, Antoine   Gaillard, Jean-Louis   Labrador, Boris   Lasley, Jennifer   Lawrence, Christine   Legrand, Judith   Le Minor, Odile   Ligier, Caroline   Martinet, Lucie   Mignon, Karine   Sacleux, Catherine   Salomon, Jerome   Obadia, Thomas   Perard, Marie   Petit, Laure   Remy, Laeticia   Thiebaut, Anne   Thomas, Damien   Tronchet, Philippe   Villain, Isabelle  

    Antibiotic-resistance of hospital-acquired infections is a major public health issue. The worldwide emergence and diffusion of extended-spectrum -lactamase (ESBL)-producing Enterobacteriaceae, including Escherichia coli (ESBL-EC) and Klebsiella pneumoniae (ESBL-KP), is of particular concern. Preventing their nosocomial spread requires understanding their transmission. Using Close Proximity Interactions (CPIs), measured by wearable sensors, and weekly ESBL-EC-and ESBL-KP-carriage data, we traced their possible transmission paths among 329 patients in a 200-bed long-term care facility over 4 months. Based on phenotypically defined resistance profiles to 12 antibiotics only, new bacterial acquisitions were tracked. Extending a previously proposed statistical method, the CPI network's ability to support observed incident-colonization episodes of ESBL-EC and ESBL-KP was tested. Finally, mathematical modeling based on our findings assessed the effect of several infection-control measures. A potential infector was identified in the CPI network for 80% (16/20) of ESBL-KP acquisition episodes. The lengths of CPI paths between ESBL-KP incident cases and their potential infectors were shorter than predicted by chance (P =3D 0.02), indicating that CPI-network relationships were consistent with dissemination. Potential ESBL-EC infectors were identified for 54% (19/35) of the acquisitions, with longer-than-expected lengths of CPI paths. These contrasting results yielded differing impacts of infection control scenarios, with contact reduction interventions proving less effective for ESBL-EC than for ESBL-KP. These results highlight the widely variable transmission patterns among ESBL-producing Enterobacteriaceae species. CPI networks supported ESBL-KP, but not ESBL-EC spread. These outcomes could help design more specific surveillance and control strategies to prevent in-hospital Enterobacteriaceae dissemination. Author summary Tracing extended-spectrum -lactamase (ESBL) dissemination in hospitals is an important step in the fight against the spread of multi-drug resistant bacteria. Indeed, understanding ESBL spreading dynamics will help identify efficient control interventions. In the i-Bird study, patients and hospital staff from a French long-term care facility carried a wearable sensor to capture their interactions at less than 1.5 meters, every 30 seconds over a 4-month period. Every week, patients were also swabbed to detect carriage of ESBL-producing Enterobacteriaceae. Based on the analysis of these longitudinal data, this study shows that ESBL-producing Klebsiella pneumoniae (ESBL-KP) mostly spreads during close-proximity interactions between individuals, while this is not the case for ESBL-producing Escherichia coli (ESBL-EC), suggesting that ESBL-KP but not ESBL-EC may be controlled by contact reduction interventions.
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  • Determination of orientation relationships between FCC-hydride and HCP-titanium and their correlation with hydrides distribution

    Wen, Jing   Allain, Nathalie   Fleury, Eric  

    Since the crystallographic orientation relationships (ORs) play an important role in the hydrides precipitation as well as in the deformation behavior of alpha-titanium alloys containing hydrides, the present work aimed at exploring thoroughly the ORs and their interface planes between the fcc-hydride and the alpha-titanium using the stereographic projections of the corresponding OR plane and OR direction and a trace analysis. In addition to the general reported two ORs in the alpha-titanium, a new OR closely related to the texture component of the rolled Ti-sheet is also determined in the present work. The overall identified ORs and their interface planes are accounted for by edge-to-edge matching model. Furthermore, a quantitative analysis using the high-angular resolution SEM-EBSD highlighted the dependency of hydride distribution on the ORs and the parent grain orientation. (C) 2019 Elsevier B.V. All rights reserved.
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  • Performance evaluation of DTN protocols to deliver sluts in dense mobile network :Empirical proofs

    Leo, Yannick   Busson, Anthony   Sarraute, Carlos   Fleury, Eric  

    In urban areas, the population density is still growing (the population density starts exceeding 20.000 inhabitants per km(2)), and so, the density of mobile users becomes very important. People are moving from home to work, from work to active places. One can take benefit of the mobility and the density to justify DTN (Delay Tolerant Network) approach protocol to convey SMS (or alternative messaging services) traffic. Indeed, the mobility of users, especially during the day, create an ad hoc mobile network where the nodes are the smartphones hold by mobile clients. In this paper, their performance evaluations are based on a measurement and analysis of SMS traces coming from a nationwide cellular telecommunication operator during a two month period, we propose several DTN like basic network protocols for delivering SMS. We perform a temporal and spatial analysis of the Mexico City cellular network considering geolocalized SMS to characterize the traffic. Such key characterization allows us to answer the question: is it possible to transmit SMS using phones as relay in a large city such as Mexico City? We define four network protocols to transmit SMS from a source to a destination. We study a mobile dataset including 8 Million users living in Mexico city. This gives us a precise estimation of the average transmission time and the global performance of our approach. Our analysis shows that after 30 min, half of the SMS are delivered successfully to destination. On the contrary to the cellular networks, we explain how much the potentiality of the mobile users network can take benefit from complementary properties such a the locality of SMS, the density of phones in Mexico City and the mobility of phone users. Moreover, we show that in a realistic scenario, our approach induces reasonable storage cost. (C) 2016 Elsevier B.V. All rights reserved.
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  • Oxide dependent wear mechanisms of titanium against a steel counterface:Influence of SMAT nanostructured surface

    Maurel, Pierre   Weiss, Laurent   Bocher, Philippe   Fleury, Eric   Grosdidier, Thierry  

    The analysis of the tribological behavior of a steel ball on pure titanium has been carried out under alternative motion on both, a coarse grained Ti surface and its nanostructured derivative obtained by surface mechanical attrition treatment (SMAT). Along the duration of the tribology test, variations in friction behavior were interpreted as a three stages sequence of different wear mechanisms that were controlled by the successive formation of Ti-rich and Fe-rich oxides. Surface nanostructures appeared to change the oxide formation kinetics and delay the formation of a protective Fe-rich third body oxide layer on Ti. The results indicate that apparently contradicting literature results can be explained by taking into account the contamination induced during the SMAT process.
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  • Improvement in cardiac sympathetic nerve activity in responders to resynchronization therapy

    Burri, Haran   Sunthorn, Henri   Somsen, Aernout   Fleury, Eric   Stettler, Carine   Shah, Dipen   Righetti, Alberto  

    Aims To assess changes in cardiac adrenergic activity with cardiac resynchronization therapy (CRT), and to investigate whether these changes are related to improvement in left ventricular ejection fraction (LVEF). Methods and results Sixteen patients (13 mates, age 66 +/- 7 years) were studied at baseline and after >= 6 months of CRT (mean follow-up 9.2 +/- 3.2 months). LVEF was assessed by nuclear angiography. Responders were defined as patients showing 5% absolute increase in LVEF + improvement in >= 1 NYHA class + absence of heart failure hospitalization. Cardiac sympathetic nerve activity was studied by (123)I-metaiodobenzyl-guanidine ((123)I-MIBG) scintigraphy. Responders (n = 8) showed lower (123)I-MIBG washout at follow-up when compared with non-responders (P = 0.002), indicating tower cardiac sympathetic nerve activity. The decrease in (123)I-MIBG washout at follow-up when compared with baseline was only seen in the responder group (P = 0.036). There was a moderate correlation between increase in LVEF and decrease in (123)I-MIBG washout (r = 0.52, P = 0.04). Conclusion CRT induces a reduction in cardiac sympathetic nerve activity in responders, that parallels an improvement in LVEF, whereas non-responders do not show any significant changes.
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  • Analysis of Dynamic Sensor Networks: Power Law Then What?

    Fleury, Eric   Guillaume, Jean-Loup   Robardet, Celine   Scherrer, Antoine  

    Recent studies on wireless sensor networks (WSN) have shown that the duration of contacts and inter-contacts are power law distributed. While this is a strong property of these networks; we will show that this is not sufficient to describe properly the dynamics of sensor networks. We will present some coupled arguments from data mining; random processes and graph theory to describe more accurately the dynamics with the use of a random model to show the limits of an approach limited to power law contact durations.
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