The average bed shear stress and bed friction factor of samples with any roughness was derived from the head loss between upstream and downstream of a test section in an erosion tunnel. The method was validated in both hydraulically smooth (plexiglass; Reynolds number less than 25,000) and rough regimes (calibrated particles with known roughness). As a first step toward using this method on nat...

In this paper, we present a new mechanism, named the oscillation killer (OSKIL), intended for extinguish limit cycles that may occur as a consequence of: unexpected external disturbances, interactions with the environment, changes in systems set-points and physical parameters, etc. Examples rate from controlled systems with friction, to electrical networks with varying loads and impedances. The...

This paper proposes self-organization as a method to improve the efficiency and adaptability of bureaucracies and similar social systems. Bureaucracies are described as networks of agents, where the main design principle is to reduce local “friction” to increase local and global “satisfaction”. Following this principle, solutions are proposed for improving communication within bureaucracies, se...

The objective of the current experimental program is to generate data for liquid flow through micro-channels. The channel dimensions are 0.9 mm deep x 0.5 mm width. Rectangular seven micro-channels each of 70 mm long were cut on a stainless steel substrate (100 mm x 100 mm x 10 mm) by Electro Discharge Machining (EDM) technique. Covering the top with another plate formed the channels. The liqui...

The non-linear dependence of pre-sliding and sliding friction forces on displacement and velocity is modelled using different physics-based and black-box approaches including various Maxwell-Slip models, neural networks, nonparametric (local) models and recurrent networks. The efficiency and accuracy of these identification methods is compared for an experimental time series where the observed ...

An improved method of measuring the coefficient of sliding friction of floor products is described, whereby similar measurements are made on laboratory samples and floors. An average value over the surface and a trace showing the local variations in friction across the surface are obtained. The latter facilitates studies of the efficiency of geometric projections and other surface effects that ...

The present approach for vibration suppression of flexible structures is based on friction damping in semi-active joints. At optimal locations conventional rigid connections of a large truss structure are replaced by semi-active friction joints. Two different concepts for the control of the normal forces in the friction interfaces are implemented. In the first approach each semi-active joint ha...

This paper deals with the solution of the discretized quasistatic 3D Signorini problems with local Coulomb friction. After a time discretization we obtain a system of static contact problems with Coulomb friction. Each of these problems is decomposed by the TFETI domain decomposition method used in auxiliary contact problemswith Tresca friction. The algebraic formulation of these problems in 3D...

It is shown that the electronic friction between a metallic surface and an open-shell atom or molecule moving perpendicularly to it can be substantially enhanced under experimentally interesting conditions, due to the involvement of the Kondo or correlated mixed-valent state. The region of large friction is shifted from the point where the adsorbate resonance crosses the Fermi level to the poin...

Friction is the result of complex interactions between contacting surfaces in a nanoscale perspective. Depending on the application, the di erent models available are more or less suitable. Available static friction models are typically considered to be dependent only on relative speed of interacting surfaces. However, it is known that friction can be a ected by other factors than speed. In thi...