Abstract: A method of prestack reverse-time migration of seismic data that yields significant gains in computer storage and memory bandwidth efficiency is disclosed. The values only of the source wave incident on the boundaries of a simulation domain are saved, rather than all of the values of the wavefield throughout the entire simulation domain. This data allows an accurate and robust approximation of the forward propagated source wave for all finite-difference approximation orders of the acoustic wave equation. The method reduces the amount of data storage required by an order of magnitude and overcomes the present challenge of requiring special large memory hardware while allowing for the implementation of 3D prestack reverse-time migration on off-the-shelf platforms.

Abstract: A method and apparatus for improved dewatering of a papermaking stock in a web forming section of a papermaking machine including directing a stock jet stream into the head end of a run between opposed looped forming wires traveling in a substantially parallel forming run passing over a curved vacuum forming box and thereafter passing over one or more pressure locations with a pressure dome on one side and a water collecting chamber at the other side of the wires with the pressure dome in one form divided into compartments each applying an increasing pressure to the wire and stock between the wires with the air pressure being heated such as by being delivered from the dryer section and the wires separated slightly following the pressure location with a last smaller pressure compartment transferring the web to one of the wires and the wire carrying the web thereafter turning over a couch roll and the other wire carried over a turning roll.

Abstract: In a papermaking machine, a method and mechanism for delivering stock to a dewatering web including a pressure headbox with a narrowing slice opening, a receiving throat either with a single traveling forming wire or a pair of traveling forming wires, bridging the space between the headbox opening and the wire so that the stock jet is contained without a free surface, and applying a trailing flexible element opposite the stock in a single wire machine or against one wire in a twin wire machine with the force and location of the trailing element controlled by a series of push rods arranged parallel in a cross machine direction.