An extendable auger conveyor including a screw thread sleeve snugly and slidably receiving a rotary drive shaft having a non-round cross section, both housed within a pair of telescoping sections of a casing having an infeed port intermediate the length of the supporting casing section. A sorting station may be subdivided into two or more modular bins. A source gas containing a metal material and a second oxidant having a second oxidation force stronger than the first oxidation force are alternately supplied to form a second insulating film on the first insulating film. A modified term distribution is produced by operating on the first statistical distribution of at least one of the terms in the query using the second statistical distribution, responsively to the category restriction.