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325 results on '"Bourgault D"'

4. Thermal detector based on a suspended polyimide membrane for infrared radiation applications.

Author

Bourgault, D., Paul, G., Latargez, C., Moiroux, G., Jegouso, D., Felix, C., Guttin, C., and Garden, J.-L.

Subjects
*NEAR infrared radiation, *INFRARED detectors, *INFRARED radiation, *DETECTORS, *THIN films, *NANOFABRICATION, *INFRARED absorption
Abstract

This Letter details a pioneering study on the design and nanofabrication process of a thermoelectric infrared radiation detector using a suspended polyimide membrane. The research includes a comprehensive analysis of thermoelectric doped Bi2Te3 thin films, comparing their expected performance regarding noise and specific detectivity with other infrared detectors, particularly those in the silicon sector. Experimental results and calculations shed light on responsivity and time constants. In the absence of absorption layers, specific detectivity values for visible and near infrared radiation are measured at 9.2 × 107 and 2.9 × 107 cm Hz / W , respectively, with a time constant nearing 20 ms. Calculations show that introducing an optimized absorption layer with ε = 1 significantly improves specific detectivity, reaching 9.0 × 108 cm Hz / W. Subsequent calculations also show that further enhancement can be obtained by etching the polyimide membrane to a 1-micron thickness, resulting in an exceptional specific detectivity value of 8.4 × 109 cm Hz / W , placing it among the best in the current state-of-the-art. [ABSTRACT FROM AUTHOR]

Published
2024
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13. Internal Solitary Waves within the Cold Tongue of the Equatorial Pacific Generated by Buoyant Gravity Currents

Author

Santos-Ferreira, A. M., Silva, J. C. B. da, St-Denis, B., Bourgault, D., Maas, L. R. M., Santos-Ferreira, A. M., Silva, J. C. B. da, St-Denis, B., Bourgault, D., and Maas, L. R. M.

Abstract

The equatorial cold tongue in the Pacific Ocean has been intensely studied during the last decades as it plays an important role in air–sea interactions and climate issues. Recently, Warner et al. revealed gravity currents apparently originating in tropical instability waves. Both phenomena have strong dissipation rates and were considered to play a significant role in cascading energy from the mesoscale to smaller horizontal scales, as well as to vertical scales less than 1 m. Here, we present Sentinel-3 satellite observations of internal solitary waves (ISWs) in the Pacific cold tongue near the equator, in a zonal band stretching from 210° to 265°E, away from any steep bottom topography. Within this band these waves propagate in multiple directions. Some of the waves’ characteristics, such as the distance between wave crests, crest lengths, and time scales, are estimated from satellite observations. In total we identify 116 ISW trains during one full year (2020), with typical distances between crests of 1500 m and crest lengths of hundreds of kilometers. These ISW trains appear to be generated by buoyant gravity currents having sharp fronts detectable in thermal infrared satellite images. A 2D numerical model confirms that resonantly generated nonlinear internal waves with amplitudes of O(10) m may be continuously initiated at the fronts of advancing gravity currents.

Published
2023

23. Dynamic heat treatment of BSCCO-2212 tapes with homogeneous properties and high critical current density

Author

Flahaut, E., Bourgault, D., Bruzek, C.E., Rikel, M.O., Herrmann, P., Soubeyroux, J.L., and Tournier, R.

Subjects
Melting points -- Research, Critical phenomena (Physics) -- Observations, Adhesive tape -- Research, Business, Electronics, Electronics and electrical industries
Abstract

The investigation shows the outline design of the developed reel-to-reel system and presenting the results on transport critical currents and microstructure in Bi2212/Ag tapes as function of processing parameters characterizing the melting step is conducted. It is concluded that further development such as optimization of the cooling rate in order to increase the performance of the tape is required.

Published
2003

24. Current limitation with bulk Y-Ba-Cu-O

Author

Tixador, P., Porcar, L., Floch, E., Buzon, D., Isfort, D., Bourgault, D., Chaud, X., and Tournier, R.

Subjects
Superconductors -- Research, Business, Electronics, Electronics and electrical industries
Abstract

The use of bulk Y-Ba-Cu-O in fault current limitation is considered, and results under steady state operations on the assembly are reported.

Published
2001

30. Annealing effect on the magnetic induced austenite transformation in polycrystalline freestanding Ni-Co-Mn-In films produced by co-sputtering.

Author

Croügneau, G., Porcar, L., Courtois, P., Pairis, S., Mossang, E., Eyraud, E., and Bourgault, D.

Subjects
AUSTENITE, ANNEALING of metals, MAGNETOCALORIC effects, ENERGY dispersive X-ray spectroscopy, POLYCRYSTALLINE semiconductors, SCANNING electron microscopy, SPUTTERING (Physics), THIN films
Abstract

Ni-Co-Mn-In freestanding films, with a magneto-structural transformation at room temperature were successfully produced by co-sputtering and post-annealing methods leading to film composition mastering. For a post-annealing temperature of 700 °C, the phase transformation occurs slightly above room temperature, with a twisted martensitic microstructure phase observed at 300K by Field Emission Scanning Electron Microscopy. Magnetization measurements on a polycrystalline film showed a phase transformation from a weakly magnetic martensite to a magnetic austenite phase. Moreover, an inverse magnetocaloric effect with an entropy variation of 4 J/kgK under 5 T was also measured. A simple magneto-actuation experiment based on the magnetic induced austenite transformation was also successfully completed. The possibility to insert such films in microsystems is clearly demonstrated in this work. [ABSTRACT FROM AUTHOR]

Published
2015
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47. On the influence of cold-water coral mound size on flow hydrodynamics, and vice versa

Author

Cyr, F., van Haren, H., Mienis, F., Duineveld, G., Bourgault, D., Cyr, F., van Haren, H., Mienis, F., Duineveld, G., and Bourgault, D.

Abstract

Using a combination of in situ observations and idealistic 2-D nonhydrostatic numericalsimulations, the relation between cold-water coral (CWC) mound size and hydrodynamics is explored forthe Rockall Bank area in the North Atlantic Ocean. It is shown that currents generated by topographicallytrapped tidal waves in this area cause large isopycnal depressions resulting from an internal hydrauliccontrol above CWC mounds. The oxygen concentration distribution is used as a tracer to visualize the flowbehavior and the turbulent mixing above the mounds. By comparing two CWC mounds of different sizesand located close to each other, it is shown that the resulting mixing is highly dependent on the size of themound. The effects of the hydraulic control for mixing, nutrient availability, and ecosystem functioning arealso discussed.

Published
2016

50. Turbulent nitrate fluxes in the Lower St. Lawrence Estuary, Canada

Author

Cyr, F., Bourgault, D., Galbraith, P.S., Gosselin, M., Cyr, F., Bourgault, D., Galbraith, P.S., and Gosselin, M.

Abstract

Turbulent vertical nitrate fluxes were calculated using new turbulent microstructure observations in the Lower St. Lawrence Estuary (LSLE), Canada. Two stations were compared: the head of the Laurentian Channel (HLC), where intense mixing occurs on the shallow sill that marks the upstream limit of the LSLE, and another station located about 100 km downstream (St. 23), more representative of the LSLE mean mixing conditions. Mean turbulent diffusivities and nitrate fluxes at the base of the surface layer for both stations were, respectively (with 95% confidence intervals): inline image and inline image. Observations suggest that the interplay between large isopleth heaving near the sill and strong turbulence is the key mechanism to sustain such high turbulent nitrate fluxes at the HLC (two to three orders of magnitude higher than those at Station 23). Calculations also suggest that nitrate fluxes at the HLC alone can sustain primary production rates of inline image over the whole LSLE, approximately enough to account for a large part of the phytoplankton bloom and for most of the postbloom production. Surfacing nitrates are also believed to be consumed within the LSLE, not leaving much to be exported to the rest of the Gulf of St. Lawrence.

Published
2015

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