Showing papers on "Thesaurus (information retrieval) published in 1990"

An approach to the automatic construction of global thesauri

Abstract: The benefits of a well constructed thesaurus to an information retrieval system have long been recognized by both researchers and practitioners in the field. Previous experiments have investigated the construction of thesauri by manual, semiautomatic, and automatic means. Automatic thesaurus generation in particular has proven to be an especially difficult problem. This paper examines both early and current approaches to automatic thesaurus construction and describes an approach to the automatic generation of global thesauri based on the term discrimination value model of Salton, Yang, and Yu and on an appropriate clustering algorithm. This method has been implemented and applied to two document collections. Preliminary results indicate that this method, which produces improvements in retrieval performance in excess of 10 and 15 percent in the test collections, is viable and worthy of continued investigation.

New gears profile having zero relative curvature at many contact points (LogiX tooth profile)

Abstract: We have successfully developed a tooth profile which enables a spur gear having zero relative curvature at contact points under the engagement through the concave/convex pattern of contact and further enables a single flank of the tooth profile to have the infinite number of points where the relative curvature and specific sliding are zero values. We have given a name of “LogiX” to this tooth profile. A W-N (Wildhaber-Novikov) tooth profile has been known as that having the concave/convex pattern of contact. The tooth profile, however, is applied only to a helical gear due to its feature of a point contact. While, on the LogiX tooth profile, an improvement has been made so that a pair of spur gears having the tooth profile may contact each other through the concave/convex pattern of a line-contact which cannot be achieved by the W-N tooth profile. Therefore, the LogiX tooth profile has realized a spur gear whose surface durability is as high as that of the W-N tooth profile. Since the results of durability tests show slightly higher than an involute one, it is expected that a new type heavy duty gear of this tooth profile puts into practical use. Furthermore, the tooth profile will have the possibility of creating the new era in the history of tooth profile theory.

Developing a New Thesaurus for Art and Architecture

Abstract: THE ART AND ARCHITECTURE currently consisting of THESAURUS, almost 40,000 terms, is midway in its development. Methods for constructing the thesaurus were modeled on existing standards and on other thesauri such the National Library of Medicine’s MeSH Thesaurus.It was designed to provide the “hinge” between the object, its images, and related bibliographic material. In the decade since it was begun, however, attitudes toward the use of terminology to describe visual images and museum objects have changed, impelling AAT constructors to develop policies that would make the thesaurus flexible enough to meet the needs of a new generation of database producers. This article describes the processes and policies that were developed to construct a language that would represent knowledge in the field of art and architecture as well as be surrogates for the images and objects being described. The AAT’s presentation of an “atomized” or faceted language is detailed.

Pentacoordinated molecules. 82. Conformational preferences of monocyclic pentaoxyphosphoranes varying in ring size

Abstract: New monocyclic pentaoxyphosphoranes 1-4, 6 and the furanosyl derivative, 7, were synthesized from the reaction of tris(2,6-dimethylphenyl) phosphite (5) with a diol or a quinone. The pentacoordinated derivatives 1-4 were studied by X-ray analysis and represent the first structurally characterized monocyclic oxyphosphoranes that have six-, seven-, and eight-membered rings. All possess trigonal-bipyramidal geometries with the rings spanning apical-equatorial positions. Retention of these structures in solution is indicated by 1 H, 13 C, and 31 P NMR. Twist-boat, rowboat, and distorted-tub conformations are found for the six- (1), seven- (2), and eight- (4) membered ring derivatives, respectively. Phosphorane 3 has a more planar phosphorinane ring, a consequence of ring unsaturation. Variable-temperature 1 H and 13 C NMR establish nonrigid behavior supporting a simple Berry pseudorotation in which the rings exchange apical-equatorial positions. It is concluded that six-membered rings of pentaoxyphosphoranes prefer apical-equatorial sites of a TBP. The preferred conformation of saturated six-membered rings is generally that of a boat. Phosphorane 1 crystallizes in the monoclinic space group C 2 /c with a = 29.392 (8), b = 11.420 (5), c = 16.379 (2) A, β = 92.22 (1)°, and Z = 8. Compound 2 crystallizes in the monoclinic space group P2 1 with a = 12.268 (2), b = 9.916 (3), c = 12.625 (2) A, β = 91.79 (1)°, and Z = 2. The monocyclic derivative 3 crystallizes in the monoclinic space group P2 1 /c with a = 20.114 (6), b = 9.554 (2), c = 17.178 (3) A, β = 114.24 (2)° and Z = 4. Phosphorane 4 crystallizes in the triclinic space group P1 with a = 9.690 (2), b = 15.414 (4), c = 21.350 (5) A, α = 93.07 (2)°, β = 90.17 (2)°, γ = 99.97 (2)°, and Z = 4. The final conventional unweighted residuals are 0.056 (1), 0.039 (2), 0.038 (3), and 0.076 (4).

Automatic Syntactic Analysis of Free Text.

Abstract: Problems encountered under the syntactic analysis of free text documents are discussed. The system called COPSY (context operator syntax), which uses natural language processing techniques during fully automatic syntactic analysis (indexing and search) of free text documents is described. Applications under real world conditions are mentioned as well as evaluation and technical aspects. Further developments in the field of thesaurus building and full-text analysis using the linguistic algorithms of the syntactic retrieval system are outlined. COPSY was developed as part of a text processing project at Siemens, called TINA (Text-Inhalts-Analyse: text content analysis)