Key statement: The semi-hollow pneumatic tire has an

axis of revolution and comprises a sole mountable on the periphery of a rotary support, a tread opposite the sole, and two sidewalls each connecting the sole and the tread so as to form together a cover which defines an uninflated chamber inside the pneumatic tire.

The particle would rotate around its

axis of revolution aligned to the vorticity direction when the shear rate is low, while aligning on the flow-gradient plane beyond a critical shear rate value.

The most convenient way to define a surface of revolution is to prescribe the (planar) generating curve, or generatrix, given by g(v) = [(r(v), 0, z(v)).sup.T] (take the curve in xoz plane as an example) and by the

axis of revolution, in the same plane as

One exemplary embodiment provides a system comprising: a light source; an image producing unit, which produces an image upon interaction with light approaching the image producing unit from the light source; an eyepiece; and a mirror, directing light from the image to a surface of the eyepiece, wherein the surface has a shape of a solid of revolution formed by revolving a planar curve at least 180 DEG around an

axis of revolution.

Hence, without loss of generality, we may consider as the

axis of revolution with the [x.sub.0]-axis or [x.sub.2]-axis if l is not null.

We allow (in fact, require) the

axis of revolution to intersect the graph of the function or parametric curve; and we wish to find which such line yields the minimum unsigned surface area.

1, R represents the distance of one of its points from the axis of rotation x - axis , and x represents the distance of its points from the R - axis [phi] is the angle between the normal to the meridian curve and the

axis of revolution. [R.sub.1] and [R.sub.2], shown in Fig.