James W. Welch

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In several file systems, the data in a file is described by constructing lists of records. Each list contains exactly those records for which some property is true. The motivation for constructing and maintaining these lists is to facilitate the processing of retrieval requests -- in many situations only a subset of the file need be searched in order to(More)
Single-cycle terahertz fields generated by coherent transition radiation from a relativistic electron beam are used to study the high field optical response of single crystal GaAs. Large amplitude changes in the sub-band-gap optical absorption are induced and probed dynamically by measuring the absorption of a broad-band optical beam generated by transition(More)
A number of file structures (e.g., inverted files and multilist files) can be modelled as a collection of records whose contents are described using sets. With each of these sets is associated a definition which is stated as a Boolean expression of attributes. The contents of a set logically consist of all records in the file for which the associated(More)
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