the equations governing the motion of steel balls and their impact onto shell liners in industrial semi-autogenous grinding (sag) mills are derived in full details by the authors and are used in order to determine the effective design variables for optimizing the working conditions of the mill and to avoid severe impacts which lead to the breakage of sag mill shell liners. these design variable...

Orthodontic tooth movement can be regarded as teeth sliding on a wire like pearls on a string, the force being supplied by springs or elastics. The movement implies friction between wire and bracket, taking up part of the force and leaving an uncontrolled amount to act on the teeth. The friction is likely to depend on bracket construction and wire material. Therefore, in this investigation the ...

Our recent experimental work showed that asymmetry is needed for surface textures to decrease friction in full-film lubricated sliding (e.g. thrust bearings) with Newtonian fluids; textures reduce the shear load and produce a separating normal force [1]. However, standard slider bearing theory cannot explain the sign of the observed normal thrust, and any effort to optimize surface textures wou...

The effect of variety and moisture content on some engineering properties of five improved paddy rice varieties was investigated within moisture content range of 10% and 30% dry basis (d.b.). Increase in moisture content was found to increase the linear dimensions, mass of 100 seeds, surface area, apparent volume, true volume, arithmetic mean diameter, effective geometric diameter, sphericity, ...

In this paper, a simple model for the prediction of centrifuge cone penetration tip resistance in sand is presented. The proposed method, which relates the tip resistance to the pressure to expand a spherical cavity, refines and simplifies Greeuw’s original equations. The method assumed the failure mode of a spherical cavity expansion pressure given as a function of shear stiffness, angle of fr...

In the present investigation, unidirectional grinding marks were attained on the steel plates. Experiments were then conducted using pins of high purity Al, pure Mg and Al-Mg alloys against the prepared steel plates using an inclined pin-on-plate sliding tester. The inclination angle of the plate was varied in the tests and for each inclination angle, the pins were slid both perpendicular and p...

Internal friction is an important contribution to protein dynamics at all stages along the folding reaction. Even in unfolded and intrinsically disordered proteins, internal friction has a large influence, as demonstrated with several experimental techniques and in simulations. However, these methods probe different facets of internal friction and have been applied to disparate molecular system...

The friction of surfaces moving relative to each other must derive from the atomic interaction at interfaces. However, recent experiments bring into question the fundamental understanding of this phenomenon. The analytic theories predict that most perfect clean incommensurate interfaces would produce no static friction, whereas commensurate aligned surfaces would have very high friction. In con...

An outstanding challenge in protein folding is understanding the origin of "internal friction" in folding dynamics, experimentally identified from the dependence of folding rates on solvent viscosity. A possible origin suggested by simulation is the crossing of local torsion barriers. However, it was unclear why internal friction varied from protein to protein or for different folding barriers ...

In contrast to most fluids, flowing powders do not exhibit viscosity such that a Newtonian rheology cannot accurately describe granular flow. Assuming that the material is incompressible, dry, cohesionless, and perfectly rigid-plastic, generalized Navier-Stokes equations (’Schaeffer Model’) have been derived where the velocity gradient has been replaced by the shear rate, and the viscosity depe...