Abstract: Spoken-language instruction method and apparatus employ context-based speech recognition for instruction and evaluation, particularly language instruction and language fluency evaluation. A system can administer a lesson, and particularly a language lesson, and evaluate performance in a natural interactive manner while tolerating strong foreign accents, and produce as an output a reading quality score. A finite state grammar set corresponding to the range of word sequence patterns in the lesson is employed as a constraint on a hidden Markov model (HMM) search apparatus in an HMM speech recognizer which includes a set of hidden Markov models of target-language narrations produced by native speakers of the target language. The invention is preferably based on use of a linguistic context-sensitive speech recognizer.

Abstract: A process is provided for separating benzene from non-aromatics in a highly aromatic stream containing olefins in a concentration range of from about 0.05 to about 5.0, which process comprises predistilling said highly aromatic stream to produce a distilled fraction having a concentration of C.sub.8 and heavier compounds of less than about 0.1 wt percent; and extracting said distilled fraction with a solvent comprising substituted morpholines in an extractive distillation zone to produce a highly-pure benzene stream.