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447 results on '"Brun, N."'

1. Crystallinity in Niobium oxides: A pathway to mitigate Two-Level System Defects in Niobium 3D Resonator for quantum applications

Author

Kalboussi, Y., Curci, I., Miserque, F., Troadec, D., Brun, N., Walls, M., Jullien, G., Eozenou, F., Baudrier, M., Maurice, L., Bertrand, Q., Sahuquet, P., and Proslier, T.

Subjects
Physics - Applied Physics, Quantum Physics
Abstract

Materials imperfections in Nniobium based superconducting quantum circuits, in particular, two-level-system (TLS) defects, are a major source of decoherence, ultimately limiting the performance of quantum computation and sensing. Thus, identifying and understanding the microscopic origin of possible TLS defects in these devices and developing strategies to eliminate them is key to superconducting qubit performance improvement. In this paper, we demonstrate the reduction of two-level system losses in three-dimensional superconducting radio frequency (SRF) niobium resonators by a 10-hour high vacuum (HV) heat treatment at 650{\deg}C, even after exposure to air and high pressure rinsing (HPR). By probing the effect of this annealing on niobium samples using X-ray photoelectron spectroscopy (XPS) and high-resolution scanning transmission electron microscopy (STEM), we witness an alteration of the native oxide composition re-grown after air exposure and HPR and the creation of nano-scale crystalline oxide regions, which correlates with the measured tenfold quality factor enhancement at low fields of the 1.3 GHz niobium resonator.

Published
2024

2. Deep Learning for EELS hyperspectral images unmixing -- using autoencoders

Author

Brun, N., Lambert, G., and Bocher, L.

Subjects
Physics - Data Analysis, Statistics and Probability, Condensed Matter - Materials Science
Abstract

Spatially resolved Electron Energy-Loss Spectroscopy (EELS) conducted in a Scanning Transmission Electron Microscope (STEM) enables the acquisition of hyperspectral images (HSIs). Spectral unmixing (SU) is the process of decomposing each spectrum of an HSI into a combination of representative spectra (endmembers) corresponding to compounds present in the sample along with their local proportions (abundances). SU is a complex task, and various methods have been developed in different communities using HSIs. However, none of these methods fully satisfy the STEM-EELS requirements. Recent advancements in remote sensing, which focus on Deep Learning techniques, have the potential to meet these requirements, particularly Autoencoders (AEs). In this study, the performance of Deep Learning methods using AE for SU is evaluated, and their results are compared with traditional methods. Synthetic HSIs have been created to quantitatively assess the outcomes of the unmixing process using specific metrics. The methods are subsequently applied to a series of experimental data. The findings demonstrate the promising potential of AE as a tool for STEM-EELS SU, marking a starting point for exploring more sophisticated Neural Networks., Comment: 39 pages, 11 figures To be published in Journal of Spectral Imaging

Published
2023

4. Role of interfaces in the biased composition of TbFe(Co) thin films

Author

Haltz, E., Weil, R., Sampaio, J., Pointillon, A., Rousseau, O., March, K., Brun, N., Li, Z., Briand, E., Bachelet, C., Dumont, Y., and Mougin, A.

Subjects
Condensed Matter - Materials Science
Abstract

Ferrimagnetic TbFe or TbFeCo amorphous alloy thin films have been grown by co-evaporation in ultra-high vacuum. They exhibit an out-of-plane magnetic anisotropy up to their Curie temperature with a nucleation and propagation reversal mechanism suitable for current induced domain wall motion. Rutherford back scattering experiments confirmed a fine control of the Tb depth-integrated composition within the evaporation process. However, a large set of experimental techniques were used to evidence an interface related contribution in such thin films as compared to much thicker samples. In particular, scanning transmission electron microscopy experiments evidence a depth dependent composition and perturbed top and bottom interfaces with preferential oxidation and diffusion of terbium. Despite of that, amorphous and homogeneous alloy film remains in a bulk-like part. The composition of that bulk-like part of the magnetic layer, labeled as effective composition, is biased when compared with the depth-integrated composition. The magnetic properties of the film are mostly dictated by this effective composition, which we show changes with different top and bottom interfaces., Comment: 9 figures

Published
2018
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10. Risk factors for bleeding, including platelet count threshold, in newly diagnosed immune thrombocytopenia adults

Author

Piel‐Julian, M.‐L., Mahévas, M., Germain, J., Languille, L., Comont, T., Lapeyre‐Mestre, M., Payrastre, B., Beyne‐Rauzy, O., Michel, M., Godeau, B., Adoue, D., Moulis, G., Alric, L., Arista, S., Astudillo, L., Balardy, L., Betrian, S., Bonnet, D., Borel, C., Brechemier, D., Brun, N., Carreiro, M., Castel, B., Caudrelier, L., Cougoul, P., Danu, A., Delavigne, K., Dingremont, C., Faurie, T., Gaches, F., Gaspard, M.‐H., Gaudin, C., Godel‐Labouret, A., Giraud, P., Hadj‐Khelifa, S., Hebraud, B., Khatibi, S., Leplay, L., Leveneur, Y., Limal, N., Ollier, S., Madaule, S., Marchou, B., Martel, C., Martin‐Blondel, G., Montane De La Roque, P., Michaud, M., Moeglin, J., Nuccio, F., Prudhomme, L., Pugnet, G., Recher, C., Remy, V., Sailler, L., Sire, S., Sommet, A., Tavitian, S., Thiercelin‐Legrand, M.‐F., and Vaillant, W.

Published
2018
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16. Reducing two-level systems dissipations in 3D superconducting niobium resonators by atomic layer deposition and high temperature heat treatment.

Author

Kalboussi, Y., Delatte, B., Bira, S., Dembele, K., Li, X., Miserque, F., Brun, N., Walls, M., Maurice, J. L., Dragoe, D., Leroy, J., Longuevergne, D., Gentils, A., Jublot-Leclerc, S., Jullien, G., Eozenou, F., Baudrier, M., Maurice, L., and Proslier, T.

Subjects
ELECTRON energy loss spectroscopy, ATOMIC layer deposition, SUPERCONDUCTING resonators, HEAT treatment, HIGH resolution electron microscopy, QUANTUM coherence
Abstract

Superconducting qubits have arisen as a leading technology platform for quantum computing, which is on the verge of revolutionizing the world's calculation capacities. Nonetheless, the fabrication of computationally reliable qubit circuits requires increasing the quantum coherence lifetimes, which are predominantly limited by the dissipations of two-level system defects present in the thin superconducting film and the adjacent dielectric regions. In this paper, we demonstrate the reduction of two-level system losses in three-dimensional superconducting radio frequency niobium resonators by atomic layer deposition of a 10 nm aluminum oxide Al2O3 thin films, followed by a high vacuum heat treatment at 650 °C for few hours. By probing the effect of several heat treatments on Al2O3-coated niobium samples by x-ray photoelectron spectroscopy plus scanning and conventional high resolution transmission electron microscopy coupled with electron energy loss spectroscopy and energy dispersive spectroscopy, we witness a dissolution of niobium native oxides and the modification of the Al2O3-Nb interface, which correlates with the enhancement of the quality factor at low fields of two 1.3 GHz niobium cavities coated with 10 nm of Al2O3. [ABSTRACT FROM AUTHOR]

Published
2024
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25. The Energetic Particle Telescope: First Results

Author

Pierrard, V., Lopez Rosson, G., Borremans, K., Lemaire, J., Maes, J., Bonnewijn, S., Van Ransbeeck, E., Neefs, E., Cyamukungu, M., Benck, S., Bonnet, L., Borisov, S., Cabrera, J., Grégoire, G., Semaille, C., Creve, G., De Saedeleer, J., Desoete, B., Preud’homme, F., Anciaux, M., Helderweirt, A., Litefti, K., Brun, N., Pauwels, D., Quevrin, C., Moreau, D., Punkkinen, R., Valtonen, E., Hajdas, W., and Nieminen, P.

Published
2014
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29. Response of the CALICE Si-W electromagnetic calorimeter physics prototype to electrons

Author

Adloff, C., Karyotakis, Y., Repond, J., Yu, J., Eigen, G., Hawkes, C.M., Mikami, Y., Miller, O., Watson, N.K., Wilson, J.A., Goto, T., Mavromanolakis, G., Thomson, M.A., Ward, D.R., Yan, W., Benchekroun, D., Hoummada, A., Krim, M., Benyamna, M., Boumediene, D., Brun, N., Cârloganu, C., Gay, P., Morisseau, F., Blazey, G.C., Chakraborty, D., Dyshkant, A., Francis, K., Hedin, D., Lima, G., Zutshi, V., Hostachy, J.-Y., Morin, L., D’Ascenzo, N., Cornett, U., David, D., Fabbri, R., Falley, G., Gadow, K., Garutti, E., Göttlicher, P., Jung, T., Karstensen, S., Korbel, V., Lucaci-Timoce, A.-I., Lutz, B., Meyer, N., Morgunov, V., Reinecke, M., Sefkow, F., Smirnov, P., Vargas-Trevino, A., Wattimena, N., Wendt, O., Feege, N., Groll, M., Haller, J., Heuer, R.-D., Richter, S., Samson, J., Kaplan, A., Schultz-Coulon, H.-Ch., Shen, W., Tadday, A., Bilki, B., Norbeck, E., Onel, Y., Kim, E.J., Baek, N.I., Kim, D.-W., Lee, K., Lee, S.C., Kawagoe, K., Tamura, Y., Bowerman, D.A., Dauncey, P.D., Magnan, A.-M., Yilmaz, H., Zorba, O., Bartsch, V., Postranecky, M., Warren, M., Wing, M., Faucci Giannelli, M., Green, M.G., Salvatore, F., Bedjidian, M., Kieffer, R., Laktineh, I., Bailey, D.S., Barlow, R.J., Kelly, M., Thompson, R.J., Danilov, M., Tarkovsky, E., Baranova, N., Karmanov, D., Korolev, M., Merkin, M., Voronin, A., Frey, A., Lu, S., Prothmann, K., Simon, F., Bouquet, B., Callier, S., Cornebise, P., Fleury, J., Li, H., Richard, F., de la Taille, Ch., Poeschl, R., Raux, L., Ruan, M., Seguin-Moreau, N., Wicek, F., Anduze, M., Boudry, V., Brient, J.-C., Gaycken, G., Mora e Freitas, P., Musat, G., Reinhard, M., Rougé, A., Vanel, J.-Ch., Videau, H., Park, K.-H., Zacek, J., Cvach, J., Gallus, P., Havranek, M., Janata, M., Marcisovsky, M., Polak, I., Popule, J., Tomasek, L., Tomasek, M., Ruzicka, P., Sicho, P., Smolik, J., Vrba, V., Zalesak, J., Belhorma, B., Belmir, M., Nam, S.W., Park, I.H., Yang, J., Chai, J.-S., Kim, J.-T., Kim, G.-B., Kang, J., and Kwon, Y.-J.

Published
2009
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33. Modelling of a CO2 refrigerant booster system for waste heat recovery applications in retail for space heating provision

Author

Sarabia, EJ, Acha Izquierdo, S, Le Brun, N, Soto, V, Jose Manuel, P, Shah, N, Markides, C, and Sainsbury's Supermarkets Ltd

Abstract

This paper compares and quantifies the energy, environmental and economic benefits of various control strategies for recovering heat from a supermarket’s CO2 booster refrigeration system. There covered heat is used for space heating, with the goal of displacing natural gas fueled boilers. A theoretical model with thermal storage is presentedbased on a previous validated model from an existing refrigeration system in a food-retail building located in the UK. Sixheat recovery strategies are analysed by modifying thermal storage volumes and pressure levels in the gas-cooler/condenser. The model shows that a reduction of 30-40% in natural-gasc onsumption is feasible by the installation of a de-superheater and without any advanced operating strategy, and 40-50% by using a thermal storage tank. However, the CO2 system can fully supply the entire space-heating requirement by adopting alternative control strategies, albeit by penalising the coefficient of performance (COP) of the compressor. Results show that the best energy strategy can reduce total consumption by 35%, while the best economic strategy can reduce costs by 11%. Findings from this work suggest that heat recovery systems can bring substantial benefits to improve the overall efficiency of energy-intensive buildings,although trade-offs need to be carefully considered and further analysed before embarking on such initiatives.

Published
2020

41. Modelling of a real CO2 booster installation and evaluation of control strategies for heat recovery applications in supermarkets

Author

Universitat Politècnica de València. Departamento de Termodinámica Aplicada - Departament de Termodinàmica Aplicada, Engineering and Physical Sciences Research Council, Reino Unido, Sarabia Escrivà, Emilio José, Acha, S., Le Brun, N., Soto Francés, Víctor Manuel, Pinazo Ojer, José Manuel, Markides, C., Shah, N., Universitat Politècnica de València. Departamento de Termodinámica Aplicada - Departament de Termodinàmica Aplicada, Engineering and Physical Sciences Research Council, Reino Unido, Sarabia Escrivà, Emilio José, Acha, S., Le Brun, N., Soto Francés, Víctor Manuel, Pinazo Ojer, José Manuel, Markides, C., and Shah, N.

Abstract

[EN] This paper compares and quantifies the energy, environmental and economic benefits of various control strategies recovering heat from a CO2 booster system in a supermarket for space heating with the purpose of understanding its potential for displacing natural gas fuelled boilers. A theoretical steady-state model that simulates the behaviour of the CO2 system is developed and validated against field measurements obtained from an existing refrigeration system in a food-retail building located in the United Kingdom. Five heat recovery strategies are analysed by modifying the mass flow and pressure level in the condenser. The model shows that a reduction of 48% in natural-gas consumption is feasible by the installation of a de-superheater and without applying any advanced operating strategy. However, the CO2 system can fully supply the entire space-heating requirements by adopting alternative control strategies, albeit by penalising the coefficient of performance (COP) of the compressor. Results show that the best energy strategy can reduce total consumption by 32%, while the best economic strategy can reduce costs by 6%. Findings from this work suggest that heat recovery systems can bring substantial benefits to improve the overall efficiency of energy-intensive buildings; nevertheless trade-offs need to be carefully considered and analysed on a site by site basis before embarking on such initiatives.

Published
2019

46. Fuel cells as CHP systems in commercial buildings: a case study for the food retail sector

Author

Acha Izquierdo, S, Shah, N, Markides, C, Le Brun, N, Lambert, R, and Sainsbury's Supermarkets Ltd

Abstract

This study investigates fuel cells as combined heat and power systems (CHPs) for distributed applications in commercial buildings, specifically supermarkets. Up-to-date technical data from a specialized manufacturing company wasinvestigated and used to conduct a case study analysis on several food retail buildings using half-hourly historical data. A detail mathematical model, described in previous publications (Cedillos et al. 2016, Achaet al.2018), was used to simulate the performance of fuel cells through a year of operation in each supermarket. The simulations employ comprehensive energy market costing data and practical informationto evaluate project feasibility such as installation workcosts. The results of the simulations are discussed and a techno-economic assessment is conducted to evaluate the main factors affecting the economics of fuel cell projects.In addition, a comparative analysis with competing CHP technologies (internal combustion engines) is covered. Results show that fuel cells are becoming financially competitivealthough combustion engines are still amoreviableoption. For large-size supermarketsthe payback time forinstalling a fuel cell system is 4.7-5.6years versus 3.6-5.6years for internal combustion engines. The work alsodiscusses the prospects of fuel cells under different market and policy scenariosas well astechnologicalimprovements; thus,offering insights in what are the key aspects which can foster fuel cell installations

Published
2018

47. Optimal CHP investments applying sensitivity analyses and financial risk management indicators

Author

Acha Izquierdo, S, Lambert, R, Le Brun, N, Markides, C, Shah, N, and Sainsbury's Supermarkets Ltd

Abstract

Evaluating combined heat and power (CHP) investments for commercial applications is not a straightforward task.This work assesses the impact multipletechno-economicuncertainties can have on CHP investments.Understanding the impact these uncertaintiescanhave on projectviabilityallows decision-makers to make informed decisions on capital intensive projects. In this work,amathematical model described previously (Cedillos et al.)wasused to select the optimal CHP size and calculate a reference solution on the financial viability of such investments in a set of buildings. After generating these reference CHP solutions, the impact of uncertainty is then assessed by applying Monte-Carlo based sensitivity analyses and financial and risk management key performance indicators (KPIs). Results suggest thefour most influential parameters in CHP priojects areheating demand, installation costs, electricity prices, and electricity demand. For attractive investments cost uncertainty made projects vary in their payback from2.6 to 6.9years, while for unattractive investments payback ranged from 4 to 11.3 years. Furthermore, Monte-Carlo results illustrate thedifferent distributions of each project, with significant variations in tails risks; indicating which sites are more suitable than others. Results presented show the economic impactuncertainties have onCHP projects, hence allowing decision-makers to make informed decisions before committing their resources to such capital-intensive projects.

Published
2018

48. Rentabilité diagnostique du myélogramme systématique chez les patients de plus de 60 ans au diagnostic de purpura thrombopénique immunologique pour rechercher une cause secondaire

Author

Comont, T., primary, Brun, N., additional, Germain, J., additional, Dingremont, C., additional, Castel, B., additional, Arista, S., additional, Madaule, S., additional, Montané De La Roque, P., additional, Prudhomme, L., additional, Sailler, L., additional, Balardy, L., additional, Alric, L., additional, Gaches, F., additional, Lapeyre-Mestre, M., additional, Beyne-Rauzy, O., additional, Adoue, D., additional, and Moulis, G., additional

Published
2019
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