the downstream flow section v another advantage is that the cooling fluid flowing in the annular passage also cools the corrugations 30 and 32 that might be caused to heat up this makes it possible to control the lifetime of the corrugations by optimizing their operating temperature finally in fig3 it can be seen that the positioning member 10 and more precisely the corrugations 24 of the first arm 14 serves to keep a plate 54 radially against the contiguous ends of the first and second ring segments 50 and 50 u2032 this plate 54 covers the junction 56 defined between the ends 50 a and 50 u2032 a of the two ring segments as to improve sealing between the annular passage and the flow section in which the blades 64 of the turbine wheel move another advantage of the positioning member 10 is that it pushes the ring segment at each of its axial ends in an azimuth direction thereby improving contact between the ring segment 50 and the downstream portion 62 b of the casing 62 and thus improving sealing the positioning of the bearing at the ends of the segments 50 and 50 u2032 also serves to reduce any risk of the segments jamming in the grooves of the casing 62 with reference to fig4 and 5 there follows a description of a second embodiment of a positioning member 110 in accordance with the present invention in this embodiment elements that are identical to those of the first embodiment are given the same numerical references plus one hundred the positioning member 110 is in the form of a single arm 114 constituted by a tongue like the first embodiment the arm or tongue 114 presents a resilient portion 124 forming a compression.