Abstract: Methods and systems for designing electromagnetic wave filters and electromagnetic wave filters designed using the methods and systems are disclosed. In one method, functions are selected whose linear combination define the surface of a filter for producing a desired phase-encoded image. Free parameter values are selected for the function and are varied. The values of the free parameters are observed with regard to an optimization function. Final values of the free parameters are selected based on the optimization function having a specific value or range of values.

Abstract: There is shown and described a shock actuated, shut-off valve for fluid flow lines which includes a valve housing having an inlet conduit, an outlet conduit and a central chamber which communicates between the inlet and outlet conduits. A channel is provided around the interior of the valve above the central chamber. A ball normally rests in the channel. The central chamber is adapted to selectively receive the ball from the channel in a position between the inlet and outlet conduits thereby to selectively interrrupt fluid flow through the valve. A reseating mechanism is provided at the bottom of the valve wherein the ball can be selectively removed from the closure position and returned to the channel.