Experimental study of durable low-friction concrete contacts for precast segmental columns with resettable sliding joints

An experimental study has been made of the friction of real ski and of smaller models sliding on snow and ice at various temperatures. On cold snow the static friction is high. When the sliding speed is appreciable the friction falls to a low value, and experiments support the view, put forward earlier, that this low friction is due to a localized surface melting produced by frictional heating. Measurements are made on a variety of surfaces including metals, synthetic polymers and waxes. The contact angle which water makes with the surface is important, and there is evidence that this can decrease during sliding. In general, the solids with a high contact angle give a lower friction. The behaviour is also influenced by the relative hardness of ice and of the ski surface at the temperature of sliding. Polytetrafluoroethylene gives a very low friction on snow and ice under all conditions.

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The Elastohydrodynamic Performance of Low-Friction, Zero-Leakage Metal Seals

Journal of Mechanical Engineering Science ◽

10.1243/jmes_jour_1979_021_045_02 ◽

1979 ◽

Vol 21 (4) ◽

pp. 275-285

Author(s):

L. E. C. Ruskell

Keyword(s):

Experimental Study ◽

Fluid Flow ◽

Hydraulic Actuator ◽

Low Friction ◽

Oil Film

Part 1 discusses the requirements for the satisfactory operation of a reciprocating metal rod seal for a hydraulic actuator. Elastohydrodynamic theory is used to predict seal performance, and results indicate that with a suitable geometry good lubrication is possible in both stroking directions of the jack rod, even when the fluid flow is against the sealed pressure. In Part 2, an experimental study of the lubrication of these seals is described. They exhibited low friction and zero net leakage, and measurements of oil film shape are presented which illustrate why this is so.

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Experimental study on the restoration from a tilt-azimuth series for improvement in resolution

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010013955x ◽

1995 ◽

Vol 53 ◽

pp. 636-637

Author(s):

Norio Baba ◽

Norihiko Ichise ◽

Syunya Watanabe

Keyword(s):

Experimental Study ◽

Spherical Aberration ◽

Incident Beam ◽

Optical Parameters ◽

Beam Tilting ◽

Illumination Method ◽

Restoration Method ◽

Illumination Mode

The tilted beam illumination method is used to improve the resolution comparing with the axial illumination mode. Using this advantage, a restoration method of several tilted beam images covering the full azimuthal range was proposed by Saxton, and experimentally examined. To make this technique more reliable it seems that some practical problems still remain. In this report the restoration was attempted and the problems were considered. In our study, four problems were pointed out for the experiment of the restoration. (1) Accurate beam tilt adjustment to fit the incident beam to the coma-free axis for the symmetrical beam tilting over the full azimuthal range. (2) Accurate measurements of the optical parameters which are necessary to design the restoration filter. Even if the spherical aberration coefficient Cs is known with accuracy and the axial astigmatism is sufficiently compensated, at least the defocus value must be measured. (3) Accurate alignment of the tilt-azimuth series images.

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