R1-soar: an experiment in knowledge-intensive programming in a problem-solving architecture

This paper presents an experiment in knowledge-intensive programming within a general problem-solving production-system architecture called Soar. In Soar, knowledge is encoded within a set of problem spaces, which yields a system capable of reasoning from first principles. Expertise consists of additional rules that guide complex problem-space searches and substitute for expensive problem-space operators. The resulting system uses both knowledge and search when relevant. Expertise knowledge is acquired either by having it programmed, or by a chunking mechanism that automatically learns new rules reflecting the results implicit in the knowledge of the problem spaces. The approach is demonstrated on the computer-system configuration task, the task performed by the expert system R1.     

Electroform replication used for multiple x-ray mirror production

Work done to produce x-ray mirrors via electroform replication is reported. Several advances have been made over previous work. We have produced lower grazing incidence angle (30 min) mirrors, obtained quantitative measurements up to higher energies (6.40 keV), produced about four times as many replicas from one mandrel, and obtained angular resolutions better than other work done with replicated metal mirrors.     

An experimental investigation into the formation of an equiaxed zone in ingot casting: Pb-Sb alloy system

An experimental investigation was undertaken to obtain a better understanding of the phenomenon of equiaxed zone formation in ingot castings with particular attention to the thermal conditions during dendritic growth and the mechanism of columnar-to-equiaxed transition. Thermal conditions during dendritic growth were measured in the laboratory-scale Pb-Sb castings. Solidification was also directly observed in castings of the cyclohexanol-phenol red system. A close correlation was noted between the general behaviour of the thermal history curves, especially when taken on the centreline of the ingots, and the resulting macrostructure. The dendritic solidification front was found to grow with considerable solute undercooling and also with a slight, but positive, temperature gradient ahead of the front in the bulk liquid. Moreover, the dendritic front temperature was also noted to increase with distance from the mould wall surface, the nominal rate of advance of the front being sensitive to the solute content and the cooling rate. Heterogeneous nucleation ahead of the columnar front was believed to have played a major role in equiaxed zone formation. However, columnar-to-equiaxed transition was observed not to take place immediately when the equiaxed crystals formed, but some time later, equiaxed dendrites growing at a somewhat higher temperature than the columnar dendritic front. Finally, combining the information gained from thermal analysis data with the observations made upon non-metallic castings, a novel picture of how columnar-to-equiaxed transition takes place has been proposed.Associate Professor of Physical Metallurgy.     

Porosity of detonation-deposited chromium carbide-base coatings

Conclusions The variation of the open porosity of a coating as a function of detonation-deposition process conditions matches that of the quality of the coating as assessed by other parameters. The open porosity of a coating is strongly affected by its surface roughness, and consequently estimates of _op may be high. The size of a specimen for open porosity testing should not be greater than 1.2 times the barrel bore. Under optimum conditions the visible porosity of coatings does not exceed 1%.Translated from Poroshkovaya Metallurgiya, No. 7(259), pp. 17–20, July, 1984.