Chercheur postdoctoral

Résumé

On appelle souvent chercheur postdoctoral (ou, improprement, postdoctorant ou encore chercheur postdoctorat, souvent en abrégé en « postdoc ») un chercheur titulaire d'une thèse de doctorat (généralement depuis moins de dix ans) engagé en contrat à durée déterminée dans un laboratoire de recherche. Apparus d'abord dans le domaine de la biologie dans le monde anglo-saxon, les postdocs se sont généralisés dans la recherche académique à la fin des années 1990. Ces chercheurs sont généralement embauchés pour un à cinq ans sur un poste associé à un contrat de recherche propre à l'unité de recherche ou bien obtenu à titre personnel via un organisme de financement de la recherche. Certaines institutions proposent des contrats postdoctoraux dans la perspective d'une titularisation ; c'est en particulier le cas des universités américaines avec les systèmes de tenure track pour les enseignants-chercheurs. Le statut précaire de chercheur postdoctoral fait l'objet de critiques émanant des cherch

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https://fr.wikipedia.org/wiki/Chercheur_postdoctoral

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This course is an introduction to the methodological issues of scientific research. The objective is to help doctoral students conduct a scientifically robust research.

The course is an introduction to the epistemological stakes of science, questioned in particular through the construction of a research object. The aim is to help PhD students to build a scientifically robust project. The course alternates : didactical input, guest lectures and debate

The course deals with the role of digital culture in Architecture and Sciences of the city research. Stories of the vicissitudes, the potential for innovation and the research problems related to digital culture and technology will be at the centre of the presentations and debates.

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Documenting the effects of climate change in Siberia

Sandrine Perroud

Annelen Kahl, a post-doc in environmental sciences and engineering at EPFL, will oversee a group of four EPFL students during a three-week stint at a high-tech research station on a Siberian island. She will post updates on the EPFL Out There blog.

2018

Chargement

The Super Proton Synchrotron (SPS) at CERN is the injector of the Large Hadron Collider (LHC), the world's largest particle collider. The High-Luminosity LHC (HL-LHC) project is a major step forward in the improvement of the LHC performances and it requires a doubling of the nominal bunch intensity of the current LHC beam. In the SPS, multi-bunch instabilities and particle losses limit the beam intensity that can be accelerated to 450 GeV/c and transferred to the LHC. Without mitigation measures, the bunch intensity threshold for longitudinal instabilities is three times below the nominal intensity of the LHC beam. Moreover, the present limited RF power is not sufficient to accelerate beams with intensities well above nominal without substantial particle losses and a reduction of the RF voltage available for the beam at the flat top energy. The SPS will undergo significant upgrades but they may not be sufficient to ensure the stability of the HL-LHC beam. The objectives of this doctoral research are to study the longitudinal intensity limitations of the LHC proton beam in the SPS and to find possible mitigation measures to ensure the beam stability and quality at HL-LHC intensity. Beam measurements and particle simulations are used in conjunction with analytical estimations to study the multi-bunch instabilities during the cycle in the SPS. This work attempts to identify the main sources of instabilities and beam quality degradation. Possible scenarios of mitigation measures are investigated to explore the future beam parameters achievable after upgrades. The effects on beam stability of the foreseen RF upgrade, the double RF operation and the reduction of various longitudinal beam-coupling impedances are analysed in detail. The scenario of a lower-harmonic RF system in the SPS, for particle losses reduction, is also studied.

EPFL2019

Chargement

Use of compact Laser Doppler Velocimetry in reduced scale model testing of hydraulic machines

Loïc Andolfatto, François Avellan, Vincent Berruex, Andres Müller, Masashi Sakamoto

Laser based flow survey methods such as Laser Doppler Velocimetry (LDV) or Particle Image Velocimetry (PIV) have long been used for studying the flow in hydraulic machines. Even if the results have crucially improved our understanding of potentially destabilizing flow patterns in the draft tube at off-design conditions and the prediction of the stable operating range, these techniques are not systematically used for reduced scale model measurements in the frame of customer acceptance tests or development projects. In a not too distant past, the price, size and complexity of the necessary equipment and procedures exceeded the acceptable range for these projects. Recent developments however made them more accessible. Furthermore, the collaboration with experienced research institutes provides the necessary know-how as well as an added academic value by providing researchers with realistic test cases. This work reports a case study for which a compact LDV probe was used to measure the velocity field in the draft tube cone of a reduced scale physical model of a Francis turbine. The axial and tangential velocity profiles were established by performing measurements at several radial positions between the turbine centreline and the cone wall. The overall objective was the validation of numerical flow simulations across the entire operating range of the turbine, from partial to full load.

2018

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