Composition and Properties of Hot-Pressed SiC-AIN Solid Solutions

High-density SiC-AIN compositions were fabricated from powder mixtures by hot-pressing in the 1700° to 2300°C temperature range. At 2100°C, a 2H solid solution was found from =35 to 100 wt% AlN. The single-phase solid solution samples had steep composition gradients of >10%/μm within the grains. Lattice parameters closely followed Vegard's law. For compositions with <35% AIN, multiphase assemblages were found. Increasing grain size was observed for increasing firing temperature for SiC and AIN. Grain size of the solid solutions was significantly smaller than for SiC or AIN fired to the same temperature. Microhardness values decreased linearly in the solid solution region with increasing AIN content. Flexural strengths of SiC and AIN decreased with increasing firing temperature and increasing grain size. The strengths of SiC, AIN, and the solid solutions were low for materials hot-pressed at 2100°C.     

REINFORCEMENT VERSUS RELATIONSHIP THERAPY FOR SCHIZOPHRENICS.

EVALUATED THE EFFICACY OF REINFORCEMENT VS. RELATIONSHIP THERAPY ON A GROUP OF 22 CHRONIC SCHIZOPHRENICS. THE GROUPS RECEIVED BOTH THERAPIES IN BALANCED ORDER. UNDER REINFORCEMENT THERAPY IMPROVED BEHAVIOR WAS REWARDED WITH POKER CHIPS EXCHANGEABLE FOR MEALS. UNDER RELATIONSHIP THERAPY EACH S MET DAILY FOR 10-13 WK. WITH AN INDIVIDUAL THERAPIST. BEFORE AND AFTER EACH THERAPY, SS WERE RATED FOR SOCIAL BEHAVIOR, WORK COMPETENCE, AND ON CONCEPTUAL AND COMMUNICATION SKILLS. TESTS OF MENTAL EFFICIENCY, ASSOCIATIVE LOOSENESS, WORK SET, SOCIAL SKILLS, AND SELF-CONCEPT WERE ALSO USED. BOTH THERAPIES IMPROVED FUNCTIONING, BUT THERE WERE NO SYSTEMATIC DIFFERENCES BETWEEN THEM. (16 REF.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

HEURISTIC SIMULATION OF PSYCHOLOGICAL DECISION PROCESSES.

ANALYZED AND PROGRAMED COMPLEX THOUGHT PROCESSES USED BY A SKILLED PSYCHOLOGIST DEALING WITH PERSONNEL SELECTION AND PLACEMENT IN A COMPUTER SIMULATION MODEL. HEURISTIC METHODS USED TO LIMIT THE TOTAL POSSIBLE SET OF DECISION BRANCHES IN THE MODEL ARE DEFINED AND ILLUSTRATED. RESEARCH RESULTS INDICATE A STRONG RELATIONSHIP BETWEEN HUMAN AND MACHINE OUTPUT WITH A 94% LEVEL OF AGREEMENT BETWEEN SIMULATED PSYCHOLOGICAL INFERENCES AND HUMAN DECISIONS WITH IDENTICAL ULTIMATE EMPLOYMENT RECOMMENDATIONS IN 22 OF 24 TEST CASES. IMPLICATIONS OF RESEARCH FINDINGS ON PSYCHOLOGICAL INSTRUCTION, EXPERIMENTATION, INFORMATION RETRIEVAL, TEST VALIDATION, AND GENERAL DECISION MAKING ARE DISCUSSED. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chemical Strengthening of Polycrystalline Alumina

Low-expansion solid solution surface layers formed by reaction of Cr₂O₃ and Al₂O₃ were used to chemically strengthen alumina bodies. The surface layers were formed by packing the samples in Cr₂O₃ powder and heating to high temperatures. Fluorides or chlorides were added to the packing material, leading to substantial additional improvement. The flexural strengths of the control samples were increased by refiring in the presence of the products of decomposition of the fluorides. At high concentrations of fluorides in the packing material, the outside dimensions and the weights of the samples decreased during the treatments.     

THREE TYPES OF CITRUS PEEL WASTE AS SOURCES OF COLOR

SUMMARY –Pilot-scale extractions of orange peel color concentrates from whole peel, peel frits and flavedo were reported. Yields of color up to 402, 545 and 669 mg/kg of starting material were obtained from frits, whole peel and flavedo, respectively. Additional color was obtained by acetone treatment of emulsion and this process increased yields by 1% from whole peel, 33% from flavedo and 50% from frits. All three of these waste materials appear to provide good sources of natural orange color. From the standpoint of yield, flavedo was best. Whole peel, although affording the lowest yield of color, offers the advantage of being considerably easier to handle due to lack of emulsion.     

DENTAL FORCES AND MASTICATION*

An engineering approach is presented to the evaluation of forces of mastication. An analysis of the force direction on the teeth is given. Applications of the results are shown to artificial teeth in their placement in a complete denture and in the design of their occlusal surfaces.     

DYNAMIC AND STEADY-STATE RHEOLOGY OF AUSTRALIAN HONEYS AT SUBZERO TEMPERATURES

The rheology of 10 Australian honeys was investigated at temperatures ?15C to 0C by a strain‐controlled rheometer. The honeys exhibited Newtonian behavior irrespective of the temperature, and follow the Cox–Merz rule. G″/G′ and ω are quadratically related, and the crossover frequencies for liquid to solid transformation and relaxation times were obtained. The composition of the honeys correlates well (r² > 0.83) with the viscosity, and with 247 data sets (Australian and Greek honeys), the following equation was obtained: The viscosity of the honeys showed a strong dependence on temperature, and four models were examined to describe this. The models gave good fits (r ² > 0.95), but better fits were obtained for the WLF model using T_g of the honeys and µ_g= 10¹¹ Pa.s. The WLF model with its “universal values” poorly predicted the viscosity, and the implications of the measured rheological behaviors of the honeys in their processing and handling are discussed.     

Infrared Study of Soda-Lime Glass During Hydration and Dehydration

Infrared spectra of two soda-lime silicate glasses were measured after different times of hydration and dehydration. The height of OH and molecular water bands increased proportionally to the square root of time during hydration. The amount of dehydration with time was fit with a diffusion model; the diffusing species was probably molecular water. The rate of dehydration of the two laboratory glasses was many orders of magnitude faster than the rate for a commercial soda-lime glass, consistent with the presence of a transformed layer on the surface of the hydrated laboratory glasses.     

Densities of SiO2-Al2O3 Melts

The densities of binary aluminosilicate melts were measured X-radiographically as a function of Al₂O₃, concentration between 1800° and 2000°C. Within this temperature range, the density curves vary linearly and are parallel from fused SiO₂ to ≊30 to 45 mol% Al₂O₃, depending on the temperature. At higher Al₂O₃ contents, negative deviation from linearity increases with increasing temperature. Recent supplementary research efforts on various aspects of the system SiO₂-Al₂O₃ indicate that the changing coordination and structural role of the aluminum ion may be a primary factor in determining the shapes of the density curves.