ABSTRACT
A straight filamentary spark produced by a laser has been used to image the spatial distribution of gases in a jet of methane in air. The technique provides a direct map of a conserved scalar quantity useful in modeling turbulent reacting flows and may have other experimental advantages.
ABSTRACT
Sparks in the form of long, thin filaments having quasi-periodic longitudinal light and dark regions (striations) in time-integrated images have been observed in various gases using a CO(2) TEA laser. Typically, a 50-mJ pulse will produce a filament 1 cm long and 130 microm in diameter, with more than 150 striations spaced 50 microm apart in atmospheric air. Each striation is associated with the formation of a plasma region by one pulse in a train of pulses from the mode-locked laser, and the filament results from the formation of successive (nearly identical) regions, each displaced from the previous one toward the laser. The possible use of these sparks as a light source in diagnostics is noted.
ABSTRACT
A terminology limited to point objects is introduced to distinguish between finite and infinite, transparent and opaque mirrors. A basic image-producing operator is defined, and its properties are examined in detail. An operational form of the basic operator is derived, two general definitions are presented, and a formal expression for the images of a system of plane mirrors is written. Some simple systems are analyzed in detail to illustrate the applications of the theory. Finally, indication is given of possible directions for future development of the subject, and of its relationship to existing mathematical theories.
