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Now showing items 33 - 48 of 70

  • Location,Occupation,and Semantics based Socioeconomic Status Inference on Twitter

    Abitbol, Jacob Levy   Karsai, Marton   Fleury, Eric  

    The socioeconomic status of people depends on a combination of individual characteristics and environmental variables, thus its inference from online behavioral data is a difficult task. Attributes like user semantics in communication, habitat, occupation, or social network are all known to be determinant predictors of this feature. In this paper we propose three different data collection and combination methods to first estimate and, in turn, infer the socioeconomic status of French Twitter users from their online semantics. Our methods are based on open census data, crawled professional profiles, and remotely sensed, expert annotated information on living environment. Our inference models reach similar performance of earlier results with the advantage of relying on broadly available datasets and of providing a generalizable framework to estimate socioeconomic status of large numbers of Twitter users. These results may contribute to the scientific discussion on social stratification and inequalities, and may fuel several applications.
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  • Grain-Size Effects on the High-Temperature Oxidation of Modified 304 Austenitic Stainless Steel

    Kim, Ju-Heon   Kim, Dong-Ik   Suwas, Satyam   Fleury, Eric   Yi, Kyung-Woo  

    The high-temperature oxidation behavior of modified 304 austenitic stainless steels in a water vapor atmosphere was investigated. Samples were prepared by various thermo mechanical treatments to result in different grain sizes in the range 8-30 mu m. Similar I 3 pound grain boundary fraction was achieved to eliminate any grain-boundary characteristics effect. Samples were oxidized in an air furnace at 700 A degrees C with 20 % water vapor atmosphere. On the fine-grained sample, a uniform Cr2O3 layer was formed, which increased the overall oxidation resistance. Whereas on the coarse-grained sample, an additional Fe2O3 layer formed on the Cr-rich oxide layer, which resulted in a relatively high oxidation rate. In the fine-grained sample, grain boundaries act as rapid diffusion paths for Cr and provided enough Cr to form Cr2O3 oxide on the entire sample surface.
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  • Surface properties of Ti(N,C,O) thin coating layers deposited by PA-MOCVD for bipolar plates used PEMFC

    Kwon, Oh-Jib   Fleury, Eric   Han, Seung-Hee  

    Ti(N,C,O) thin films were deposited by means of metal-organic chemical vapor deposition using a glow discharge with the aim of enhancing the corrosion resistance and electrical contact conductivity of austenitic stainless steel as a candidate materials for the bipolar plates used in polymer electrolyte membrane fuel cells. The corrosion properties were found to be dependent on the composition, i.e., the precursor source, and on the thickness of the thin films. Tetrakis(diethylamino) titanium used as a liquid metal organic source for the deposition of thin Ti(N,C,O) layers onto austenitic stainless steel provided a significant improvement of the corrosion resistance, which resulted in superior interfacial electrical conductivity after corrosion tests.
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  • Worldsens: From Lab to Sensor Network Application Development and Deployment

    Fournel, Nicolas   Fraboulet, Antoine   Chelius, Guillaume   Fleury, Eric   Allard, Bruno   Brevet, Olivier  

    We present Worldsens; a prototyping and development framework for wireless sensor protocols and applications. Our environment relies on two simulators; WSim and WSNet; and proposes a full simulation and performance estimation of embedded platforms with instruction and radio byte accuracy. During this demo; we propose to demonstrate the interest of the two simulators in stand-alone and in cooperative use.
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  • Worldsens: Development and Prototyping Tools for Application Specific Wireless Sensors Networks

    Fraboulet, Antoine   Chelius, Guillaume   Fleury, Eric  

    In this paper we present Worldsens, an integrated environment for development and rapid prototyping of wireless sensor network applications. Our environment relies on software simulation to help the designer during the whole development process. The refinement is done starting from the high level design choices down to the target code implementation, debug and performance analysis. In the early stages of the design, high level parameters, like for example the node sleep and activity periods, can be tuned using WS-Net, an event driven wireless network simulator. WSNet uses models for applications, protocols and radio medium communication with a parameterized accuracy. The second step of the sensor network application design takes place after the hardware implementation choices. This second step relies on the WSim cycle accurate hardware platform simulator. WSim is used to debug the application using the real target binary code. Precise performance evaluation, including real-time analysis at the interrupt level, are made possible at this low simulation level. WSim can be connected to WSNet, in place of the application and protocol models used during the high level simulation to achieve a full distributed application simulation. WSNet and WSNet;WSim allow a continuous refinement from high level estimations down to low level real-time validation. We illustrate the complete application design process using a real life demonstrator that implements a hello protocol for dynamic neighborhood discovery in a wireless sensor network environment.
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  • Tracking Clinical Staff Behaviors in an Operating Room

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

    Inadequate staff behaviors in an operating room (OR) may lead to environmental contamination and increase the risk of surgical site infection. In order to assess this statement objectively, we have developed an approach to analyze OR staff behaviors using a motion tracking system. The present article introduces a solution for the assessment of individual displacements in the OR by: (1) detecting human presence and quantifying movements using a motion capture (MOCAP) system and (2) observing doors' movements by means of a wireless network of inertial sensors fixed on the doors and synchronized with the MOCAP system. The system was used in eight health care facilities sites during 30 cardiac and orthopedic surgery interventions. A total of 119 h of data were recorded and analyzed. Three hundred thirty four individual displacements were reconstructed. On average, only 10.6% individual positions could not be reconstructed and were considered undetermined, i.e., the presence in the room of the corresponding staff member could not be determined. The article presents the hardware and software developed together with the obtained reconstruction performances.
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  • Documents Diplomatiques Suisses - Diplomatische Dokumente der Schweiz - Documenti Diplomatici Svizzeri. Bd. 16: 9.5. 1945-31.5. 1947by Antoine Fleury; Mauro Cerutti; Michele Coduri; Eric Flury-Dasen

    Review by: Silvia Pfeiffer-Herkenrath  

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  • A distributed policy scheduling for wireless sensor networks

    Chen, Yu   Fleury, Eric  

    We aim to save energy by scheduling periodic sensors' duty cycles. Different from existing works, we integrate two important tasks, collision avoidance and duty cycling, into one scheduling of sensors' activities. Our scheme consists of two parts: a coloring scheme that assigns a "color" to each sensor and a color scheduling scheme that associates each color with a schedule. Each sensor switches between sleep and active modes according to the schedule associated with its color. We propose a coloring definition. Theoretical analyses and simulation results show that, if this coloring is used by collision avoidance schemes such as TDMA or CDMA, connectivity can be guaranteed by using much less colors than traditional colorings. Theoretical analyses and simulation evaluations are presented for our scheduling. As compared to handling collision avoidance and duty cycling separately, performances can be improved by integrating these two tasks into one carefully designed schedule of sensors' activities. In particular, in duty cycled dense networks, in order to reduce packet latency and save energy, it is desirable to guarantee the communication connectivity of links only in a sparse connected subgraph.
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  • Elaboration of AlSi10Mg casting alloys using directional solidification processing

    Ghedjati, Khadoudja   Fleury, Eric   Hamani, Mohamed Seghir   Benchiheub, Mostefa   Bouacha, Khaider   Bolle, Bernard  

    The effects of pulling velocity on the solidification behavior and microstructural parameters of AlSi10Mg alloys prepared in a Bridgman-type directional solidification furnace were investigated. The microstructure, particularly the secondary dendritic arm spacing (SDAS), and the Brinell hardness (BH) of the solidified AlSi10Mg alloys were characterized for samples with cylindrical shapes and different conicities (theta =3D 0A degrees, 5A degrees, and 10A degrees). Microstructural studies revealed an increased density of alpha-Al phase dendrites and a decreased interdendritic distance with increasing pulling velocity. The dendrites were found to be preferentially oriented along the pulling direction for low pulling velocities. For larger pulling velocities, the dendrites grew first in the cooling direction but then broke as others nucleated and coarsened. The HB values of the solidified samples increased as the pulling velocity increased. In regard to sample conicity, smaller dendrites were observed for an apex angle of theta =3D 5A degrees, resulting in the largest HB value. This result was interpreted in terms of the favorable orientation of the dendrite along the pulling direction.
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  • Role of alloying elements in vanadium-based binary alloy membranes for hydrogen separation

    Lee, Young-Su   Ouyang, Chuying   Suh, Jin-Yoo   Fleury, Eric   Cho, Young Whan   Shim, Jae-Hyeok  

    We investigate the metal-hydrogen interaction in vanadium alloyed with X =3D Fe, Ni, Al, Ti, and Nb using first-principles calculations. The site energy of interstitial hydrogen depends on both the volume and the presence of a nearby alloying element; the two effects are analyzed separately. The effective volume of the alloying element follows the sequence Nb > Ti > Al > V > Ni > Fe, and a larger volume lowers the site energy on average. Locally, Al appears to be the strongest hydrogen repellent, and Ti exhibits the strongest affinity for hydrogen. The original tetrahedral coordination by the metal atoms is also affected and the effect is the most pronounced in Ni, where the hydrogen atom in the octahedral interstitial site is strongly stabilized. A 16-atom body centered cubic special quasi-random structure is utilized to obtain the statistical distribution of site energies in V12X4. The obtained site energies at 673 K have the following sequence: Ti < Nb < Al < Ni < Fe. This result indicates that the strongest local repulsion brought by Al is not necessarily correlated to the largest drop in solubility due to the compensation by the elastic effect. The strong repulsion, however, would cause a pronounced decrease in the configurational entropy. (c) 2012 Elsevier B.V. All rights reserved.
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  • Worldsens: Development and prototyping tools for application specific wireless sensors networks

    Fraboulet, Antoine   Chelius, Guillaume   Fleury, Eric  

    In this paper we present Worldsens, an integrated environment for development and rapid prototyping of wireless sensor network applications. Our environment relies on software simulation to help the designer during the whole development process. The refinement is done starting from the high level design choices down to the target code implementation, debug and performance analysis. In the early stages of the design, high level parameters, like for example the node sleep and activity periods, can be tuned using WSNet, an event driven wireless network simulator. WSNet uses models for applications, protocols and radio medium communication with a parameterized accuracy. The second step of the sensor network application design takes place after the hardware implementation choices. This second step relies on the WSim cycle accurate hardware platform simulator. WSim is used to debug the application using the real target binary code. Precise performance evaluation, including real-time analysis at the interrupt level, are made possible at this low simulation level. WSim can be connected to WSNet, in place of the application and protocol models used during the high level simulation to achieve a full distributed application simulation. WSNet and WSNet+WSim allow a continuous refinement from high level estimations down to low level real-time validation. We illustrate the complete application design process using a real life demonstrator that implements a hello protocol for dynamic neighborhood discovery in a wireless sensor network environment.
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  • Interindividual Contacts and Carriage of Methicillin-Resistant Staphylococcus aureus: A Nested Case-Control Study.

    Obadia, Thomas   Opatowski, Lulla   Temime, Laura   Herrmann, Jean-Louis   Fleury, Eric   Boelle, Pierre-Yves   Guillemot, Didier  

    BACKGROUND: Reducing the spread of multidrug-resistant bacteria in hospitals remains a challenge. Current methods are screening of patients, isolation, and adherence to hygiene measures among healthcare workers (HCWs). More specific measures could rely on a better characterization of the contacts at risk of dissemination.; OBJECTIVE: To quantify how close-proximity interactions (CPIs) affected Staphylococcus aureus dissemination. DESIGN Nested case-control study.; SETTING: French long-term care facility in 2009.; PARTICIPANTS: Patients (n=3D329) and HCWs (n=3D261).; METHODS: We recorded CPIs using electronic devices together with S. aureus nasal carriage during 4 months in all participants. Cases consisted of patients showing incident S. aureus colonization and were paired to 8 control patients who did not exhibit incident colonization at the same date. Conditional logistic regression was used to quantify associations between incidence and exposure to demographic, network, and carriage covariables.; RESULTS: The local structure of contacts informed on methicillin-resistant S. aureus (MRSA) carriage acquisition: CPIs with more HCWs were associated with incident MRSA colonization in patients (odds ratio [OR], 1.10 [95% CI, 1.04-1.17] for 1 more HCW), as well as longer CPI durations (1.03 [1.01-1.06] for a 1-hour increase). Joint analysis of carriage and contacts showed increased carriage acquisition in case of CPI with another colonized individual (OR, 1.55 [1.14-2.11] for 1 more HCW). Global network measurements did not capture associations between contacts and carriage.; CONCLUSIONS: Electronically recorded CPIs inform on the risk of MRSA carriage, warranting more study of in-hospital contact networks to design targeted intervention strategies.=20
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  • The role of Fe particle size and oxide distribution on the hydrogenation properties of ball-milled nano-crystalline powder mixtures of Fe and Mg

    Fadonougbo, Julien O.   Jung, Jee Yun   Suh, Jin-Yoo   Lee, Young-Su   Shim, Jae-Hyeok   Fleury, Eric   Cho, Young Whan  

    In the aim of evidencing the relationship between Mg2FeH6 synthesis and the size of Fe particles, several specimens have been prepared by applying various milling energies (milling time) on a 2.1 Mg and 1Fe powder mixture doped with a small fraction of Unsaturated Fatty Amine (UFA). The resulting nanocrystalline composite structures display a broad Fe particle size distribution as a function of milling time. The hydrogenation of those complex powders has been conducted at temperatures lower than 400 degrees C under 60 bar of hydrogen pressure. As expected, the Fe particle size significantly influenced the hydrogenation kinetics. Also, the inevitable distribution of a minor fraction of oxides occurring during the milling process affected greatly the hydrogen storage capacity. Under the low pressure and temperature conditions selected in the frame of this study, lower than 100 bar and 500 degrees C conventionally used for synthesis of high purity Mg2FeH6, the hydrogenation reaction was demonstrated to be almost completed within 6 h, confirming the fast hydrogen absorption capability of the prepared materials. Plus, nearly 84 wt% of Mg2FeH6 was achieved under the afore mentioned moderate conditions and a minor fraction of unreacted Fe still remained due to diffusion constraints existing at low temperatures. (C) 2019 Elsevier B.V. All rights reserved.
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  • Dependency of the corrosion properties of in-situ Ti-based BMG matrix composites with the volume fraction of crystalline phase

    Debnath, Mukta Rani   Kim, Do-Hyang   Fleury, Eric  

    The chemical and electrochemical corrosion properties of in-situ Ti-45(Zr-Be-Cu-Ni)(55-x)Nb-x BMG matrix composites, with x = 0, 5, 10, 15 at.% and containing different volume fractions of crystalline beta-(Ti,Zr,Nb) phase, have been investigated in a hydrogenated 1 M H2SO4 + 2 ppm F- electrolyte at 80 degrees C. In comparison to monolithic Ti-based BMGs and Ti-6Al-4V alloy, the in-situ BMG matrix composite with similar to 20% volume fraction of beta-(Ti,Zr,Nb) phase exhibits a high corrosion resistance characterized by a low value of corrosion current density, a stable passivation behavior in both potentiodynamic and potentiostatic polarization and low weight loss during immersion tests. The enhancement of the corrosion resistance is attributed to Ti-, Zr- and Nb-rich oxide layers produced on top of both the dendrite and amorphous matrix. However, for the BMG composite with a large (similar to 41.5%) volume fraction of Nb-rich dendrites the corrosion resistance was reduced leading to the dissolution of the amorphous matrix during immersion tests. (C) 2011 Elsevier Ltd. All rights reserved.
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  • Strain localization in annealed Cu(50)Zr(50) metallic glass

    Park, Kyoung-Won   Park, Hogun   Fleury, Eric  

    A molecular dynamics simulation technique was used to investigate the atomic structural changes in Cu(50)Zr(50) metallic glass during isothermal annealing, with the aim of clarifying the mechanism responsible for the reduction of the plasticity experimentally observed during uniaxial loading of heat-treated Cu(50)Zr(50). The atomic strain during shear deformation was calculated for the as-cast and annealed samples to evaluate the degree of strain localization, which affects the global plasticity of the alloys. The validity of the normalized relaxation heat parameter used to evaluate the degree of strain localization has been verified during elastostatic compression. The variation of the potential energy in the elastic regime, which was found to be correlated to the degree of strain localization, is proposed as parameter to evaluate by computational simulation the ability of an amorphous alloy to deform plastically. (C) 2011 Elsevier B.V.. All rights reserved.
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  • Optimal Proxy Selection for Socioeconomic Status Inference on Twitter

    Abitbol, Jacob Levy   Fleury, Eric   Karsai, Marton  

    Individual socioeconomic status inference from online traces is a remarkably difficult task. While current methods commonly train predictive models on incomplete data by appending socioeconomic information of residential areas or professional occupation profiles, little attention has been paid to how well this information serves as a proxy for the individual demographic trait of interest when fed to a learning model. Here we address this question by proposing three different data collection and combination methods to first estimate and, in turn, infer the socioeconomic status of French Twitter users from their online semantics. We assess the validity of each proxy measure by analyzing the performance of our prediction pipeline when trained on these datasets. Despite having to rely on different user sets, we find that training our model on professional occupation provides better predictive performance than open census data or remote sensed expert annotation of habitual environments. Furthermore, we release the tools we developed in the hope it will provide a generalizable framework to estimate socioeconomic status of large numbers of Twitter users as well as contribute to the scientific discussion on social stratification and inequalities.
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