87 research outputs found
Etude de la répartition des génotypes du virus de l'hépatite B en Aquitaine
No full textBORDEAUX2-BU Santé (330632101) / SudocPARIS-BIUM (751062103) / SudocPARIS-Bib. Serv.Santé Armées (751055204) / SudocSudocFranceF
Von Neumann equivalence and properly proximal groups
Get PDFWe introduce a new equivalence relation on groups, which we call von Neumann
equivalence, that is coarser than both measure equivalence and
-equivalence. We introduce a general procedure for inducing actions in
this setting and use this to show that many analytic properties, such as
amenability, property (T), and the Haagerup property, are preserved under von
Neumann equivalence. We also show that proper proximality, which was defined
recently by Boutonnet, Ioana, and the second author using dynamics, is also
preserved under von Neumann equivalence. In particular, proper proximality is
preserved under both measure equivalence and -equivalence, and from this
we obtain examples of non-inner amenable groups that are not properly proximal.Comment: Updates based on recommendations from the referees. We have added a
section at the end with open problem
Methods for assessing the coverage performance of satellite constellations
Get PDFLAUREA MAGISTRALELe costellazioni sono un gruppo di satelliti che lavorano assieme come un sistema coordinato al fine di raggiungere un unico obiettivo. In generale vengono usate per rispondere a requisiti di copertura spaziale e temporale che non possono essere soddisfatti da un singolo satellite.
Il lavoro svolto in questa tesi è un’analisi delle geometrie di costellazioni esistenti e dei relativi metodi di progettazione, con lo scopo di realizzare un confronto facilmente comprensibile tra i vari approcci e di determinare i più efficienti. Gli obiettivi del processo di ottimizzazione di un metodo sono la minimizzazione del costo computazionale e la presenza di simulazioni grafiche esplicative e rappresentative. In più, sono considerati di primaria importanza anche il numero di casi in cui questi metodi possono essere applicati e l’esattezza dei risultati.
Tra tutte le figure di merito che caratterizzano una costellazione di satelliti, le condizioni e i requisiti di visibilità sono stati il filo conduttore dello studio svolto e quindi i metodi analizzati sono basati sulla valutazione delle prestazioni di copertura delle costellazioni.
L’innovazione del presente lavoro di tesi è rappresentata dal fatto che tutti i metodi sono descritti e trattati attraverso una nomenclatura standardizzata in modo da poter effettuare un confronto diretto, intuitivo e semplice. I corrispondenti algoritmi sono stati realizzati allo scopo di testare l’efficienza e la precisione dei risultati ottenuti, ma anche per visualizzare tali risultati graficamente.
Lo scopo di questa tesi è anche l’introduzione di un approccio innovativo per le determinazione dell’area di copertura, basato su calcoli analitici che partono dalla conoscenza del vettore di posizione dei satelliti, dalle relative coordinate geografiche e dall’angolo di semiapertura dell’antenna di navigazione. I calcoli analitici permettono di ridurre il costo computazionale e di aumentare la precisione dei risultati.
Come casi studio, i metodi presentati sono stati applicati a due missioni cui l’autore ha avuto possibilità di contribuire durante l’Internship presso l’Agenzia Spaziale Europea, la prima relativa a una mega-costellazione attorno alla Terra e l’altra a una piccola costellazione attorno alla Luna.
L’implementazione dei diversi metodi di progettazione ha evidenziato alcuni limiti nei vari approcci e possibili campi di sviluppo per investigazioni future.Satellite constellations are a set of satellites working together as a coordinated system to achieve a unique objective, in general used to fulfill spatial and temporal coverage and observation requirements which can not be met with a single satellite.
The aim of this thesis is to perform an analysis of the geometries and the design methods for satellite constellations, to make a simple and clear comparison among the existing design approaches and to determine the most efficient and optimal ones. Either minimisation of the computational effort or development of graphical representations aimed at clarifying the underlying physics are considered as targets of the optimisation process, and field of applicability as well as accuracy of the results are judged of primary importance.
Among all figures of merit that characterise a constellation, visibility conditions and coverage requirements have been the common thread throughout all the work presented as the methods studied are focused on assessing the coverage performance of satellite constellations.
The novelty proposed in the presented work is directed towards the development of a standardised nomenclature and treatment in order to make a direct, intuitive and simple comparison. The proposed algorithms have been created for the purpose of testing the efficiency and the accuracy of the results, but also to graphically visualise numerical results.
In addition, an innovative approach for the determination of the coverage area is introduced, that relies on an analytical method based on the knowledge of the satellite’s position vectors, the relative geographical coordinates of the sub-satellite points and the half-aperture angle of the navigation antenna. The analytical formulations reduce the computational cost and increase the accuracy of the results.
A feasibility analysis of the proposed approaches is also performed, by applying the methods to two missions in which the author was able to contribute during the Internship at the European Space Agency, one dealing with a mega-constellation around the Earth and the other with a small constellation around the Moon.
However, the development of the different design methods and the relative results showed some particular peculiarities and sometimes limit in the methodology treated, hinting some possible fields for future investigations
The difficult airway in obstetrical anesthesia: advocacy to improve the quality of assessment
No full textCombinatorial therapy with two pro-coagulants and one osmotic agent reduces the extent of the lesion in the acute phase of spinal cord injury in the rat
No full textAcier Thomas soufflé au mélange oxygène - gaz carbonique (Élaboration - Essais de laboratoire - Résultats industriels)
No full textTraumatismes thoraciques pénétrants : analyse rétrospective de 69 cas civils et militaires pris en charge dans un centre de traumatologie français
No full textIntroduction: Penetrating Thoracic Injuries (PTIs) are a medico-surgical challenge for trauma teams. Few european studies focus on the specificity of PTIs. The aim of this study was to analyse the demographic, injury patterns, surgical management and clinical outcomes of civilian and military patients who were admitted to a French Military Teaching Hospital with PTIs over a twelve-year period. Patients and methods: all patients with PTIs admitted to a Level I Trauma Centre and to Role-2 facilities in war theatres between January 1, 2004 and May 31, 2016 were included. Results: a total of 69 patients were included, of whom 17 were military casualties. Mechanisms of injury were first stabwounds for civilian patients (63%), gunshotwounds (59%) and shrapnel (41%) for military casualties. NISS was 35,6 ± 13,5 for military casualties, 21,2 ± 12,2 for civils. 29 (33%) patients were unstable or in cardiac arrest on admission. 30 (43%) were transfused. 38 (55%) patients had thoracic surgery, 25 thoracotomy were performed. 13 thoracoscopies were performed in stable patients. Intra-hospital mortality was 18,8%. Conclusion: an anticipated medico-surgical and protocol approach must allow the effective management of severe and hemorrhagic patients who require frequent recourse to surgery.Introduction : les Traumatismes Thoraciques Pénétrants (TTP) sont un challenge médico-chirurgical pour les équipes de traumatologie. Il existe peu de données européennes publiées s’y intéressant. Le but de l’étude était d’analyser les critères démographiques, les mécanismes lésionnels, la prise en charge médico-chirurgicale et la morbimortalité de patients militaires et civils, pris en charge dans un Hôpital d’Instruction des Armées (HIA) sur une période de 12 ans. Patients et méthodes : tous les patients présentant un TTP admis à l’HIA Percy et en rôle 2 en opération extérieure entre le 1er janvier 2004 et le 31 mai 2016 ont été inclus. Résultats : soixante-neuf patients ont été inclus, dont 17 patients militaires. Les mécanismes lésionnels étaient majoritairement par arme blanche chez les patients civils (63%), par arme à feu (59%) et polycriblage (41%) chez les patients militaires. Le NISS était de 35,6 ± 13,5 chez les militaires et de 21,2 ± 12,2 chez les civils. Vingt-neuf (33%) patients étaient instables ou en arrêt cardio-respiratoire à l’admission, 30 (43%) ont été transfusés. Trente-huit (55%) patients ont bénéficié de chirurgie thoracique, 25 thoracotomies ont été réalisées. Treize thoracoscopies ont été réalisées chez des patients stables. La mortalité intra-hospitalière était de 18,8%. Conclusion : une approche médico-chirurgicale anticipée et protocolisée doit permettre une prise en charge efficace de patients graves, hémorragiques et nécessitant un recours fréquent à la chirurgie
- …
