The diarthrodial, knee joint is a remarkably efficient bearing system; articulating cartilage surfaces provide nearly frictionless performance with minimal wear. The low friction properties of the cartilage surfaces are due in part to the boundary lubricant, superficial zone protein (SZP); also known as lubricin or proteoglycan 4 (PRG4). In previous work, SZP localization and cartilage friction...

The modern active systems and the advanced driver assistance systems have certainly reduced the amount of accidents. However these systems are still lacking one major information, which is the friction between the tyre-road interface. The performance of these systems could be enhanced substantially if this information was known. Rather simple methods can be used to determine the friction coeffi...

Processes on different length scales affect the dynamics of chain molecules. In this work, we focus on structures on the scale of a monomer and investigate polyolefins, i.e., hydrocarbon chains with different small-scale architectures. We present an exact enumeration scheme for the simulation of interactions and relative motion of two short chain sections on a lattice and employ it to deduce th...

Tetraalkylammonium salts have larger ions than metal ions, which can greatly change the interlayer space and energy, and then potentially tune the properties of graphite. In this work, various graphite intercalation compounds (GICs) have been synthesized by intercalating tetraoctylammonium bromide (TOAB) ions into graphite through electrochemical interactions under different reduction potential...

Stick-slip friction was observed in articular cartilage under certain loading and sliding conditions and systematically studied. Using the Surface Forces Apparatus, we show that stick-slip friction can induce permanent morphological changes (a change in the roughness indicative of wear/damage) in cartilage surfaces, even under mild loading and sliding conditions. The different load and speed re...

One of the great enemies of rubber compounds is heat. Heat will cause chemical and physical degradation of vulcanized rubber as well as a considerable loss in its strength. A major source of heat generation in a tire is due to internal friction resulting from the viscoelastic deformation of the tire as it rolls along the road. Another source of heat generation in a tire is due to its contact fr...

Energy dissipation via spin excitations is investigated for a hard ferromagnetic tip scanning a soft magnetic monolayer. We use the classical Heisenberg model with Landau-LifshitzGilbert (LLG) dynamics including a stochastic field representing finite temperatures. The friction force depends linearly on the velocity (provided it is small enough) for all temperatures. For low temperatures, the co...

Here we address the comments by Iverson (2016) on our recent work concerning the reduction of friction in long runout landslides. Iverson (2016) questions the veracity of our models and suggests that high basal pore fluid pressure is the dominant mechanism reducing friction in long runout landslides. The main goal of our work was to elucidate the mechanism responsible for the apparent reduction...

The mismatched perturbations and system chattering are the two main challenging problems in sliding mode control. This paper tries to solve these problems by deriving the invariant sets created by the sliding mode controller where the present work is devoted to a second order nonlinear affine system. If the state started in these sets it will not leave it for all future time. The first invarian...