Abstract: A focus improver for a concave reflector having a circular cross section. It has an array of plane mirrors diametrically across the mouth of the reflector. The angle of tilt of the mirrors is relative to parallel rays incident upon the reflector, and each mirror has an angle of tilt such that a central parallel ray reflected therefrom will focus at a common location.An application of the focus improver provides a solar energy collector that employs a cylindrical reflector which may be oriented in an east-west direction. The mirrors are thin strips that are coextensive in length with the cylindrical reflector. And, a solar energy utilization device may be located along the focal line that is created.

Abstract: Hereinafter disclosed is methodology and apparatus for converting wide dynamic amplitude range digital data recorded in floating point digital word form, comprising a binary coded mantissa and a binary coded exponent, to an analog signal, or oscillogram, of compressed dynamic amplitude range. The digital word, occupying a number of binary bit positions, is, in algebraic form, .+-.AG.sup..sup.-E ; where A represents the mantissa, or argument, G represents the base, or radix, of the number system used and E represents the exponent. Since the base G is constant at 8, for example, the only binary bits that need to be recorded are those representing the mantissa A and the exponent E. In reconverting the digital data to analog form for making an oscillogram, or wiggle trace, it is proposed to compress the dynamic range and, yet, at the same time avoid introducing serious distortion. Apparatus for performing the aforesaid changes, among other things, is disclosed.

Abstract: A competent permeable communication zone connecting injection and production wells completed in a tar sand which communication zone will be rigid and will not tend to slump or heal may be developed by injecting a fluid in the injection well under such pressure so as to fracture the tar sand formation between the injection well and the production well and circulating a fluid between the injection and production wells which is at a temperature sufficiently low to freeze the water in tar sands. The fluid may contain propping agents to hold the fracture surfaces apart. This procedure will rigidify the hydrocarbon portion of the tar sand formation in the vicinity of the fracture zone as well as freeze the water in the tar sand formation. Once the fracture is established a solvent for the hydrocarbon in the tar sands may be circulated preferably at a temperature below the freezing point of the water in the tar sands to extract the bitumen therefrom.