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Note added at 11 mins (2007-09-24 13:54:48 GMT)
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Insert densité air...

Il nécessite l’acquisition d’images TDM puis TEP sur un fantôme d’eau chargé de Fluor et présentant trois inserts de densité différente : air, ...
www.utc.fr/~Farges/dess_tbh/03-04/stages/carriere/carriere.... - 563k -

Just in case this helps, and there should be a grave accent on the "a" before "sec"..

http://64.233.183.104/search?q=cache:ucJmc7RNpHkJ:radiologys...

air-core transformer

Air cores
A physical core is not an absolute requisite and a functioning transformer can be produced simply by placing the windings in close proximity to each other, an arrangement termed an "air-core" transformer. The air which comprises the magnetic circuit is essentially lossless, and so an air-core transformer eliminates loss due to hysteresis in the core material.[9] The leakage inductance is inevitably high, resulting in very poor regulation, and so such designs are unsuitable for use in power distribution.[9] They have however very high bandwidth, and are frequently employed in radio-frequency applications,[40] for which a satisfactory coupling coefficient is maintained by carefully overlapping the primary and secondary windings.

EN) In an air-core transformer provided with a magnetic circuit with columns around which are arranged electric coils, the 'low voltage' stage is composed, at each phase of the electricity supply, of an electroconductive metal coil (4) embedded in a heat conducting polymer resin matrix (2, 5) moulded on each column (1) of the magnetic circuit. Preferably, the resin is a thermoplastic polymer. Also preferably, the resin is slightly electroconductive. A more compact transformer is thus obtained, in which the thickness of the air layers required for ventilating the installation is reduced as much as possible.
(FR) Dans un transformateur sec pourvu d'un circuit magnétique à colonnes autour desquelles sont disposés les enroulements électriques, l'étage 'basse tension' de l'invention est constitué, au niveau de chaque phase de l'alimentation électrique, par un enroulement métallique électroconducteur (4) noyé dans une masse de résine polymère thermoconductrice (2, 5) moulée sur chaque colonne (1) du circuit magnétique. De préférence, la résine est un polymère thermoplastique. De préférence également, la résine est faiblement conductrice de l'électricité. On réalise ainsi un transformateur plus compact, où les épaisseurs des couches d'air nécessaires à la ventilation de l'appareil sont réduites au maximum.

WO/1994/014040) INDUSTRIAL MOBILE PROCESS MONITOR SYSTEM
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... primary and secondary windings (40) of an air-core transformer (36). ... les enroulements primaire et secondaire (40) d'un transformateur à sec (36). ...
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Note added at 3 hrs (2007-09-24 16:49:32 GMT)
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Listing for Engineering (General)The suspended element is a cylinder which is composed of permanent magnet material and the magnetic actuators are air core electromagnets mounted in a ...
aerade.cranfield.ac.uk/subject-listing/nasa/n31.html - 46k - Cached - Similar pages


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Note added at 3 hrs (2007-09-24 16:50:11 GMT)
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CAT.INIST... spin resonance computed tomography system using and air-core electromagnet ... A rapid field scan L-band electron spin resonance computed tomography ...
cat.inist.fr/?aModele=afficheN&cpsidt=2963888 - Similar pages