Abstract: In one aspect, the present invention provides a subsurface heater comprising: a combustible gas supply conduit; an oxygen supply conduit and a heat transmissive external housing encompassing a porous refractory medium. The combustible gas supply conduit and the oxygen supply conduit are configured as a concentric pair disposed within the porous refractory medium and coupled to a plurality of gas jets disposed within the porous refractory medium. The porous refractory medium has disposed within it a plurality of combustion product gas return conduits. The combustion product gas return conduits are configured to receive combustion product gases from the porous refractory medium. Also provided in another aspect of the present invention, is a method for heating a subsurface zone.

Abstract: A method estimates a signal to noise ratio (SNR) of a received direct sequence spread spectrum (DSSS) signal. Using the estimated SNR, a control signal is determined that is suitable for modifying a position of a directional antenna. The control signal may be used to modify the position of the directional antenna. In another method, a first estimated SNR is determined for a received radio frequency (RF) signal. An output voltage of an AGC circuit is converted to a second estimated SNR. Using at least the first estimated SNR when the first estimated SNR is within a first range and using at least the second estimated SNR when the second estimated SNR is within a second range, an output SNR is determined. The output SNR may be used to determine the at least one control signal, which may then be used to modify the position of the directional antenna.

Abstract: A method of making a boron carbide article by sintering includes mixing boron carbide with an epoxidized resin in solution and drying to form a granulated homogenized mixture and a carbonization cycle in which the mixture is maintained at at least two constant temperatures for predetermined times. The rates of temperature rise are at controlled rates sufficient to allow outgassing of the gases evolved during the decomposition of the resin.