Computing an Upper Bound for SVS(gg) by Abstract Interpretation.

A fire hose nozzle having a central tubular body member and tubular forward and rear body members carried at the respsective ends of said central body member. A pressure control cylinder is coaxially mounted in the tubular body member and a hydraulically balanced, tubular, slider member is mounted in the central body member for axial movement between an upstream position wherein the downstream end of the slider member is spaced from a cone on the upstream end of the pressure control cylinder, and a downstream position wherein the downstream end of the slider member engages the cone of the pressure control cylinder and shuts off flow through the nozzle. Manually movable means on the exterior of the central tubular body member is connected to the slider member and permits a user of the nozzle to vary the position of the downstream end of the slider member in the tubular body member with respect to the cone of the pressure control cylinder to thus modulate the rate of the flow of fluid through the nozzle.