High-Temperature Testing Techniques for Brittle Refractory Materials

The evaluation of brittle refractory materials calls for special techniques that are different from those normally used for ductile materials. Techniques have been developed at the N.A.C.A. Lewis Flight Propulsion Laboratory to evaluate brittle materials as turbine blades in jet engines and in creep, stress rupture, and thermal shock. The type of equipment and the procedure for creep and stress-rupture testing are described. A parameter is given by which the thermal-shock resistance of brittle materials is related to their physical properties. A simple apparatus has been devised to verify experimentally conclusions given by this parameter. Another apparatus is described that simulates the thermal-shock conditions encountered in a jet engine. The final testing of materials in a jet engine is described.     

PREDICTION OF CREATIVITY AND OTHER PERFORMANCE MEASURES FROM BIOGRAPHICAL INFORMATION AMONG PHARMACEUTICAL SCIENTISTS.

A 160-ITEM BIOGRAPHICAL INVENTORY WAS ADMINISTERED TO 157 PHARMACEUTICAL SCIENTISTS WHO WERE RANDOMLY ASSIGNED TO 2 GROUPS OF 79 AND 78 SS. EACH ALTERNATIVE FROM EACH ITEM IN THE INVENTORY WAS CORRELATED WITH 19 CRITERION MEASURES OBTAINED ON EACH OF THE SCIENTISTS. THESE PRIMARILY INVOLVED RATINGS OF CREATIVITY, QUANTITY OF WORK PRODUCED, SKILL WITH PEOPLE, ETC., OBTAINED FROM SUPERVISORS, PEERS, AND SUBORDINATES. REMARKABLY LITTLE RELATIONSHIP EXISTED BETWEEN SUPERVISORY AND PEER RATINGS OF THE SCIENTISTS ON MOST VARIABLES. USING A DOUBLE CROSS-VALIDATION DESIGN, INVENTORY PREDICTOR KEYS WERE DEVELOPED FOR EACH OF THE CRITERION RATINGS AND APPLIED ACROSS TO THE NEW INDEPENDENT SAMPLE. SIGNIFICANT CROSS VALIDITIES WERE OBTAINED, NOTABLY IN THE PREDICTION OF THE CREATIVITY CRITERION, WHERE CORRELATIONS OF .36 AND .42 RESULTED ACROSS THE 2 SUBSAMPLES. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Salt and Aging Time Effects on the Viability of Trichinella spiralis in Heavy Dry-cured Hams and Shoulders

SUMMARY: 28 pigs weighing approximately 100 lb were dosed with 10,000 to 15,000 excysted trichina larvae, grown to 285 lb and sacrificed. Fresh lean samples from one ham and shoulder per carcass were digested in a pepsine-HCI solution and microscopically examined to determine infection rates. 24 of the more heavily infected hams and shoulders then were selected for further observations. The hams and shoulders were dry-cured for 2 days per lb, using an 8% cure applied in 3 equal applications at 5-day intervals. The cure contained salt, sugar, potassium nitrate and sodium nitrite. After curing, the meat was placed in salt equalization for 30 days, smoked for 24 hr at 100°F and aged at 75°F until termination of the study. Cored lean samples were taken from 8 hams and shoulders at weekly intervals after salt equalization and analyzed for salt concentrations and viability. Viable trichinae persisted throughout curing, salt equalization, smoking and 2 weeks of aging. Samples taken from hams and shoulders after 3 weeks of aging were found to be free of any live trichinae. Similar lean samples were taken at this time and force fed to rats for 5 days. After 8 weeks on a commercial ration the rats were sacrificed, artificially digested and examined. No trichina larvae could be recovered.     

The Ontolingua Server: a tool for collaborative ontology construction

Reusable ontologies are becoming increasingly important for tasks such as information integration, knowledge-level interoperation and knowledge-base development. We have developed a set of tools and services to support the process of achieving consensus on commonly shared ontologies by geographically distributed groups. These tools make use of the World Wide Web to enable wide access and provide users with the ability to publish, browse, create and edit ontologies stored on anontology server. Users can quickly assemble a new ontology from a library of modules. We discuss how our system was constructed, how it exploits existing protocols and browsing tools, and our experience supporting hundreds of users. We describe applications using our tools to achieve consensus on ontologies and to integrate information.The Ontolingua Server may be accessed through the URLhttp://ontolingua.stanford.edu     

Relative Energies of Tilt Boundaries in Aluminum Oxide

The relative grain boundary energy and surface diffusion coefficient of aluminum oxide were determined by observing the thermal grooving behavior of a series of bi-crystals containing symmetric tilt boundaries. The relative energy for high tilt angles (30° to 150°) was roughly constant and equal to 0.54. The variation of relative energy with tilt angle was consistent with a dislocation core model for grain boundaries. The surface diffusion coefficient was:    
The agreement of this value for a vacuum etch with previous data for etches in air ruled out the oxygen ion as a possible rate-controlling diffusion species.     

Adsorption of Tagged Phosphute Ions on Glass Surfaces as Related to Alkaline Attack

A preliminary investigation has been made of various factors involved in the sorption of phosphate ions on glass surfaces, particularly with reference to a possible utilization of phosphate sorption as an indicator of alkaline attack of the surface. Sorption has been measured by means of a tracer technique using radioactive phosphorus as trisodium phosphate, and tests have been made with two types of soft glass and with Pyrex-brand glass, with and without alkaline pretreatments. Radioautographs have been prepared to determine the distribution of sorbed phosphate on soft-glass specimens treated in various ways. The sorption of phosphate ions from dilute alkaline solutions at room temperature on fused soft glass and Pyrex-brand glass has been found to be very slight, on the order of one-thousandth of a μ gm. per sq. in. (roughly equivalent to a thousandth of a monomolecular layer on the macrosurface). Treatment of soft glass for a few minutes in sodium hydroxide solution at 80°C. results in a multifold increase in subsequent sorption of phosphate ions at room temperature. A much longer alkaline pretreatment is required in the case of Pyrex-brand glass, but a similar increase in sorption is found. The different results obtained with soda-lime and borosilicate glasses may be explained on the basis of different types of nonadsorbing surface films. Zinc ions in the alkaline pretreatment solution appear to cause an increase in subsequent sorption, and it is proposed that adsorption of polyvalent cations facilitates the adsorption of phosphate ions.     

Elastic and Flow Properties of Dense, Pure Oxide Refractories

Mechanical properties, including creep rates, were measured for slip-cast magnesia, hydrostatically pressed magnesia, thoria, zircon, and mullite. None equaled alumina or zirconia in strength, rigidity, or creep resistance. Although mullite was found to have good properties, magnesia showed the best properties of the oxides tested. Thoria was very weak, zircon was highly plastic above 1000°C. Elastic and flow properties were determined primarily by the crystal structure and atomic bonding of the oxides and secondarily by grain boundary conditions.