Vibratory Finishing of Stereolithography Parts

Rapid Prototype polymer resin models produced by Stereolithography have, by the nature of the process, a relatively poor surface roughness, particularly on concave and convex surfaces. In many cases this is unacceptable, and slow and tedious manual finishing techniques are often used to improve the surface. An investigation has been conducted into a range of automated finishing techniques with the aim of producing an acceptable surface roughness. This paper presents the results from two techniques, Vibratory Bowl Abrasion and Ultrasonic Abrasion using components made from Ciba-Geigy XB5081-1 and XB 5143 resins. Initial results from Scanning Electron Microscopy and surface topography analyses suggest that both techniques are capable of improving the model surfaces.Mechanical Engineerin

Data Compression System with a Minimum Time Delay Unit-Patent

Minimum time delay unit for conventional time multiplexed data compression channel

Supercritical oxygen heat transfer

Heat transfer to supercritical oxygen was experimentally measured in electrical heated tubes. Experimental data were obtained for pressures ranging from 17 to 34.5 MPa (2460 to 5000 psia), and heat fluxes from 2 to 90 million w/sq cm (1.2 to 55 Btu/(sq in. sec)). Bulk temperatures ranged from 96 to 217 K (173 to 391 R). Experimental data obtained by other investigators were added to this to increase the range of pressure down to 2 MPa (290 psia) and increase the range of bulk temperature up to 566 K (1019 R). From this compilation of experimental data a correlating equation was developed which predicts over 95% of the experimental data within + or - 30%

Keiretsu and Relationship-Specific Investment: Implications for Market-Opening Trade Policy

This paper considers the implications of relationship-specific investment within keiretsu for policies aimed at opening the Japanese market for intermediate goods, such as auto parts. Both VIEs applied to parts and VERs restricting Japanese exports of autos cause the keiretsu to import a wider range of parts, but of a relatively unimportant type, such as seat covers. Since keiretsu investment and output fall, the total value of U.S. parts exports may actually fall. For a given value of these exports, a VIE is less costly for U.S. consumers and Japanese producers, but a VER is preferred by U.S. automakers.