We study the frictional sliding of two ideally incommensurate surfaces with a third incommensurate sheet – a sort of extended lubricant – in between. When the mutual ratios of the three periodicities in this sandwich geometry are chosen to be the golden mean φ = (1 + √ 5)/2, this system is believed to be statically pinned for any choice of system parameters. In the present study we overcome thi...

A two-step learning method for velocity estimation is presented. First, an efficient representation of velocity is found using a learning technique based on canonical correlation analysis. This results in a spherical representation. Then, given this new representation, the mapping from input data to velocity estimates are learned by minimizing the mean square error between the output and the de...

A video imagery technique for making discharge measurements in streams and waterways is presented and used to estimate low ow discharge for Clear Creek near Oxford, Iowa. A video camera was used to visualize the ow seeded with tracers. Estimates of free surface ow velocities were then made using particle image velocimetry (PIV) techniques. The velocity estimates were used as input to a hydrauli...

The fall velocity of sediment particles plays a key role in sediment transport studies. Researchers have attempted to determine the terminal fall velocity, and most of the studies in this regard have been based on experimental, quasi-experimental, and in-situ measurements. The present study aimed to use a numerical model to estimate the fall velocity of a single sediment particle in distilled a...

We have investigated the scale-invariant solutions of the BBGKY equations for spatial correlation functions of cosmological density fluctuations and the mean relative peculiar velocity in the strongly nonlinear regime. It is found that the solutions for the mean relative physical velocity depend on the three-point spatial correlation function and the skewness of the velocity fields. We find tha...

The effective equation describing the transport of passive tracers in nonsolenoidal velocity fields is determined, assuming that the velocity field U(r,t) is a function of both position r and time t, albeit remaining locally random. Assuming a strong separation of scales and applying the method of homogenization, we find a Fickian constitutive relation for the coarse-grained particle flux, as t...

The retarded Van der Waals force between a polarizable particle and a perfectly conducting plate is re-examined. The expression for this force given by Casimir and Polder represents a mean force, but there are large fluctuations around this mean value on short time scales which are of the same order of magnitude as the mean force itself. However, these fluctuations occur on time scales which ar...

In this paper, we propose a new method for a three dimensional fuzzy modeling of pilot's performance in the dogfight. The dogfight is a short-distance air combat with a gun. A sixth order nonlinear point mass vehicle model is considered for an aircraft's flight dynamics. The desired value of the velocity, the flight path and the heading angles are obtained from some rule bases developed in the ...

Acoustic Doppler Velocity Meters (ADVMs) have become popular for estimating discharge in rivers exhibiting complex flow characteristics. To use the ADVMs for estimating channel discharge, a relation needs to be developed between the mean channel velocity and the index velocity provided by the ADVM. In the past, this relation was primarily developed empirically. To improve the accuracy of ADVM d...

Blood flow velocity in the middle cerebral artery, determined by transcranial Doppler ultrasonography, was monitored during 31 carotid endarterectomies. Electroencephalogram (EEG) was also monitored, and regional cerebral blood flow (rCBF) was measured. The relation between rCBF and mean velocity was dependent on the rCBF level; the correlation was strong if rCBF was less than 20 ml/100 g/min b...