Contact area

About: Contact area is a research topic. Over the lifetime, 12358 publications have been published within this topic receiving 256401 citations. The topic is also known as: contact patch & contact region.

Evolution of permeability in a natural fracture: Significant role of pressure solution

Abstract: [1] A mechanistic model is presented to describe closure of a fracture mediated by pressure solution; closure controls permeability reduction and incorporates the serial processes of dissolution at contacting asperities, interfacial diffusion, and precipitation at the free face of fractures These processes progress over a representative contacting asperity and define compaction at the macroscopic level, together with evolving changes in solute concentration for arbitrarily open or closed systems for prescribed ranges of driving effective stresses, equilibrium fluid and rock temperatures, and fluid flow rates Measured fracture surface profiles are applied to define simple relations between fracture wall contact area ratio and fracture aperture that represents the irreversible alteration of the fracture surface geometry as compaction proceeds Comparisons with experimental measurements of aperture reduction conducted on a natural fracture in novaculite [Polak et al, 2003] show good agreement if the unknown magnitude of microscopic asperity contact area is increased over the nominal fracture contact area Predictions of silica concentration slightly underestimate the experimental results even for elevated microscopic contact areas and may result from the unaccounted contribution of free face dissolution For the modest temperatures (20–150°C) and short duration (900 hours) of the test, pressure solution is demonstrated to be the dominant mechanism contributing to both compaction and permeability reduction, despite net dissolution and removal of mineral mass Pressure solution results in an 80% reduction in fracture aperture from 12 μm, in contrast to a ∼10 nm contribution by precipitation, even for the case of a closed system For the considered dissolution-dominated system, fracture closure rates are shown to scale roughly linearly with stress increase and exponentially with temperature increase, taking between days and decades for closure to reach completion

Methods for navigating a touch screen device in conjunction with gestures

Abstract: A method for navigating a touch screen interface associated with a touch screen device including activating a first contact indicator within an object contact area on a touch screen interface of the touch screen device, in which the object contact area is configured to move within the touch screen interface in response to movement of the first contact indicator. The method further includes activating a point indicator within the object contact area away from the first contact indicator, in which the point indicator is configured to move within the object contact area in response to the movement of the first contact indicator. The method further includes positioning the point indicator over a target position associated with the touch screen interface and selecting a target information for processing, in which the target information is selected in reference to the target position.

A Theoretical Review of Particle Adhesion

Abstract: This paper constitutes a theoretical review of the forces of adhesion of small particles to surfaces. The primary force of adhesion of small, less than 50 micron diameter, particles on a dry surface are van der Waals forces. These van der Waals forces can be increased due to particle and/or surface deformations which increase the particle contact area. Particles less than 1 micron diameter can be held to surfaces by forces exceeding 100 dynes, which corresponds to forces per unit area of 109 dyn/cm2 or more. Total forces of adhesion for 1 micron diameter particles can exceed the gravitational force acting on that particle by factors greater than 106. Electrostatic forces, although they only become important and predominate for particles larger than 50 microns diameter, may play a significant role in bringing particles to surfaces for adhesion. The presence of a liquid between the particle and surface, due to either immersion and subsequent removal from a liquid or due to high humidity conditions, can add a very large capillary force to the total force of adhesion. This capillary force is known to remain, in some cases, even after baking at above the liquid boiling point for many hours. Although some possibilities exist for particle removal, removal of small particles has been in practice extremely difficult due to these large forces. Each of these forces will be discussed theoretically with some attempts at quantification versus particle diameter. Some data will also be presented on attempted particle removal as a function of removal method. Clearly, emphasis should be placed on prevention of particle deposition on surfaces rather than relying on achieving subsequent removal.