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The evolution of frictional strength has great fundamental and practical importance. Applications range from earthquake dynamics to hard-drive read/write cycles. Frictional strength is governed by the resistance to shear of the large ensemble of discrete contacts that forms the interface that separates two sliding bodies. An interface's overall strength is… (More)
The way in which a frictional interface fails is critical to our fundamental understanding of failure processes in fields ranging from engineering to the study of earthquakes. Frictional motion is initiated by rupture fronts that propagate within the thin interface that separates two sheared bodies. By measuring the shear and normal stresses along the… (More)
Experiments of pure tensile fracture in thin brittle gels reveal a new dynamic oscillatory instability whose onset occurs at a critical velocity, VC=0.87CS, where CS is the shear wave speed. Until VC, crack dynamics are well described by linear elastic fracture mechanics (LEFM). These extreme speeds are obtained by suppression of the microbranching… (More)
The color gamut of RGB primaries displays can be increased by using more saturated primaries, with the penalty of a corresponding significant decrease in brightness. We present a multiple primaries technology that enables substantial increase in both the color gamut and brightness of projection displays and describes results of prototype projection systems… (More)
The static friction coefficient between two materials is considered to be a material constant. We present experiments demonstrating that the ratio of shear to normal force needed to move contacting bodies can, instead, vary systematically with controllable changes in the external loading configuration. Large variations in both the friction coefficient and… (More)
The excitation of large amplitude nonlinear waves is achieved via parametric autoresonance of Faraday waves. We experimentally demonstrate that phase locking to low amplitude driving can generate persistent high-amplitude growth of nonlinear waves in a dissipative system. The experiments presented are in excellent agreement with theory.
We present an experimental study of the dynamics of rapid tensile fracture in brittle amorphous materials. We first compare the dynamic behavior of " standard " brittle materials (e.g. glass) with the corresponding features observed in " model " materials, polyacrylamide gels, in which the relevant sound speeds can be reduced by 2-3 orders of magnitude. The… (More)