Report on the formal specification and partial verification of the VIPER microprocessor

The formal specification and partial verification of the VIPER microprocessor is reviewed. The VIPER microprocessor was designed by RSRE, Malvern, England, for safety critical computing applications (e.g., aircraft, reactor control, medical instruments, armaments). The VIPER was carefully specified and partially verified in an attempt to provide a microprocessor with completely predictable operating characteristics. The specification of VIPER is divided into several levels of abstraction, from a gate-level description up to an instruction execution model. Although the consistency between certain levels was demonstrated with mechanically-assisted mathematical proof, the formal verification of VIPER was never completed

A new approach to mass spectrometer measurements of thermospheric density

The gas sampling problem in satellite and high velocity probes was investigated by applying the theory of a drifting Maxwellian gas. A lens system using a free stream ion source was developed and experimentally evaluated over the pressure range of 0.00001 to 0.01 N/m sq (approx. 10 to the minus 7th power to 0.0001 torr). The source has high beam transparency, which minimizes gas-surface collisions within, or near, the ionization volume. It is shown that for high ion energy (60 eV), the extracted ion beam has an on-axis energy spread of less than 4 eV, and that 90 percent of the ions are within 2.5 deg of the beam axis. It is concluded that the molecular beam mass spectrometer concept, developed for gas density measurements in the upper atmosphere, substantially reduces gas-surface scattering and gas-surface reactions in the sample, and preserves the integrity of the gas sample during the analysis process. Studies show that both the Scout and Delta launch vehicles have adequate volume, control, velocity, and data acquisition capability necessary to obtain thermospheric number density in real time

Carbon Fiber Reinforced Carbon Foams for Repair and Reconstruction of Bone Defects

The present invention relates to a tissue scaffold and a method of preparing a tissue scaffold for implantation. The tissue scaffold includes a body having a graphite foam core. At least a first portion of the external surface of that graphite foam core is covered by a composite material to provide additional mechanical strength to the scaffold

Hardware verification at Computational Logic, Inc.

The following topics are covered in viewgraph form: (1) hardware verification; (2) Boyer-Moore logic; (3) core RISC; (4) the FM8502 fabrication, implementation specification, and pinout; (5) hardware description language; (6) arithmetic logic generator; (7) near term expected results; (8) present trends; (9) future directions; (10) collaborations and technology transfer; and (11) technology enablers

Enhanced Computer Graphics for Decision Makers

Words need a context to be understood. Visual patterns also need a context to convey their meaning. When patterns represent quantities in business graphics, decision makers (DMs) depend on contrasting visual contexts to discern patterns and discover relationships. Depending on the context in which DMs see trends, differences between two trends may point to a problem, to continuity, or to an opportunity. Can enhancing the context in computer graphics help DMs visualize problems? To answer this research question, three experiments were done in the field on computer graphics. One hundred five DMs tried 17 different contexts for time-series trends displayed on a microcomputer monitor. The research objective was to find out whether changing the context in graphics affected the decision efficiency (accuracy/response time) of DMs in determining relationships among trends. Essential for measuring the effect were interactive computer programs that displayed random trends in graphics of differing contexts, collected the DMs\u27 answers to questions about the trends, and graded 1133 graphics based on the answers, response times, and trend data. The experimental results supported the hypothesis that computers can enhance the visual context surrounding time-series trends so that DMs can better visualize problems. Results were based on comparisons of DMs\u27 decision efficiencies between trial graphics with differing contextual enhancements and based on answers to questions about the trial graphics. The results were tested with nonparametric statistics at the 0.05 significance level. Specific findings were: (1) Computer-supplied forecasts, as an enhancement, significantly helped DMs discover differences among trends. (2) Although not statistically significant, stratified presentation of trends and fading chartjunk tended to increase DMs\u27 efficiencies. (3) Adding two colors, as an enhancement, made no difference in efficiency over black and white. (4) Paired trends in windows did not affect efficiency significantly. (5) Sequentially traced trends and composites of enhancements did not affect efficiency significantly. (6) DMs preferred stratified trends most and had the most confidence in graphics with fading context. They least liked and had the least confidence in black-and-white graphics

Automorphisms of graphs of cyclic splittings of free groups

We prove that any isometry of the graph of cyclic splittings of a finitely generated free group $F_N$ of rank $N\ge 3$ is induced by an outer automorphism of $F_N$. The same statement also applies to the graphs of maximally-cyclic splittings, and of very small splittings.Comment: 22 pages, 5 figures. Small modifications. To appear in Geometriae Dedicat