We show that the solid-solid friction between bulk chiral molecular solids can depend on the relative chirality of the two materials. In menthol and 1-phenyl-1-butanol, heterochiral friction is smaller than homochiral friction, while in ibuprofen, heterochiral friction is larger. Chiral asymmetries in the coefficient of sliding friction vary with temperature and can be as large as 30%. In the t...

The subloading-friction model is capable of describing static friction, the smooth transition from static to kinetic friction and the recovery to static friction after sliding stops or sliding velocity decreases. This causes a negative rate sensitivity (i.e. a decrease in friction resistance with increasing sliding velocity). A generalized subloading-friction model is formulated in this article...

A friction identification method in a frequency domain is proposed for a precision servomechanism. A nonlinear friction model including static, Coulomb, and viscous friction as well as Stribeck effect is considered in this paper. Friction models are formulated by using describing functions. Friction elements are estimated through the limit cycle analysis in a velocity control loop. A Butterwort...

This paper aims to investigate the microscopic friction mechanism based on in situ microscopic observation in order to record the deformation and contact situation of friction lining during the frictional process. The results show that friction coefficient increased with the shear deformation and energy loss of the surfacee, respectively. Furthermore, the friction mechanism mainly included adhe...

Two distinct regimes are considered when it comes to friction: gross-sliding regime and presliding regime [1]. Friction in the gross-sliding regime contains familiar and classic concepts of static friction, Coulomb friction, and Stribeck curve. It is more intriguing, on the other hand, that friction in the pre-sliding regime behaves like a non-linear spring with hysteresis, significantly impact...

The effect of a height-dependent asperity radius of curvature is accounted for in a recently developed scaledependent model of contact and friction. The contact and friction model includes the effects of adhesion, using the Maugis model, and of scale-dependent friction, using the Hurtado and Kim single asperity friction model. This multiasperity model has been modified to include the effect of ...

This paper reports on research aimed at providing a more realistic simulation model of crowd behavior under both panic and non-panic conditions by modifying the Helbing-Molnar-Farkas-Vicsek (HMFV) model. Such simulations will be of great value both in operational and training contexts. Many operations deal with crowd control and accurate simulations of crowd dynamics. The approach is based on a...

A plethora of media platforms were involved in communicating recent protests across the MENA, though it remains unclear exactly how these interacted. This qualitative paper, based primarily on interviews with BBC newsworkers, explores the networked linkages between social and broadcast media, asking how social media content moved into broadcast news, which standards shaped the interface between...

This paper presents a new methodology for friction compensation that is not based on any friction model. This is done by using finite-terms Fourier series to approximate the friction term. Updating laws for the coefficients of the series are easily derived from a Lyapunov approach to guarantee asymptotic convergence of the tracking error. Computer simulations are then proposed in which friction...

This contribution presents a friction estimator for industrial purposes which identifies Coulomb friction in a steering system. The estimator only needs a few, usually known, steering system parameters. Friction occurs on almost every mechanical system and has a negative influence on high-precision position control. This is demonstrated on a steering angle controller for highly automated drivin...