Multiple necking of tungsten fibers in a brass-tungsten composite

A model composite system, brass-tungsten, was used to study the effect of multiple necking of metal fibers, strain rate, and fiber surface condition on the ductility and deformation behavior of uniaxial metal matrix composites. Low volume percent (<20 vol pct) composites were made using brass (90 Cu-10 Zn) powders and tungsten wires. Tungsten wires contained in plastically deformed composites exhibited numerous necks per length of wire, with an average spacing between necks of 3 to 5 wire diameters. Composite ductility was shown to increase with decreasing multiple neck spacing and increasing percent reduction-in-area at the necks and was generally independent of strain rate. The multiple necking of tungsten wires in a brass matrix was found to result from local strain hardening of the brass matrix in the vicinity of each neck enabling the matrix to control composite deformation locally. Degrading the brass-tungsten interfacial bond by electropolishing the tungsten wires and coating them with graphite had no effect on the multiple necking phenomenon and composite ductility.     

Different rule systems for counting behavior acquired in meaningful and rote contexts of learning.

In a series of 3 experiments, 68 undergraduates learned to a criterion of 2 errorless trials to recite the 1st 12 or 18 responses in a pattern based on Base 3. In Exp I, the pattern was presented as letters (w, d, r, dw, dd,?.?.?.) or as numerals (0, 1, 2, 10, 11,?.?.?.). In Exps II and III, the pattern was presented as letters, and Ss were given a letter-to-digit conversion list (w?=?0, d?=?1, r?=?2) either before or after learning. On a posttest, Ss who knew that the pattern related to numerals during learning performed better on transfer tasks such as addition or further counting in Base 3. Results suggest that different rule systems were acquired even though the same levels of performance on the behavioral objective were achieved. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unconstrained Inverse Electrocardiography: Epicardial Potentials

The inverse problem in electrocardiography is attacked via the development of a model appropriate for the computation of epicardial potentials from a knowledge of heart and torso geometry as well as surface potentials. The model takes the form of an integral equation of the first kind in which the kernel is interpreted as a Green's function. A theoretical investigation of system independence in the presence of error is developed, and two techniques for the theoretical consideration of system independence are examined. Application of these two techniques to concentric spherical systems indicates that spheres with ratios of inner-to-outer radii less than 0.5 contain less than twenty independent parameters in the presence of realistic noise levels. The number of independent parameters deteriorates rapidly as this ratio falls below 0.5. These results suggest that it is not feasible to determine epicardial potentials from torso potentials by using unconstrained solutions.     

A Computer-Aided Graphical Procedure for Scheduling Preventive Maintenance of Electric Power Generating Units

This article attempts to show how computer graphics can assist in computerized development of project-type schedules as exemplified by preventive maintenance scheduling in the electric power industry. The method is equally applicable to the scheduling of maintenance activities in general or, with modification, to devising shift schedules for personnel such as police, nurses, and toll collectors who must provide 24-hour service with changing demand levels. A hand procedure currently used by electric utilities for creating preventive maintenance shutdown schedules for generator units is first described. A mixed integer programming model of the problem is given which is computationally intractable for any realistic-size problems. The same problem using man-machine interaction via a graphics terminal to overcome the computational limitations of the mathematical formulation is then described and illustrated. A proposed extension to improve the speed of solution is also described.     

Design and analysis of research using time series.

Develops a time-series methodology for approaching data in a range of research settings and presents a design package using the time series as a method to eliminate major sources of rival hypotheses. A mathematical model with special considerations for application is offered which maximizes the utility of time-series data for generating and testing hypotheses. (21 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wall and ceiling protection for heating appliances

An evaluation was made of the effects of radiant heat transfer from hot stove and chimney pipes to unprotected and protected room walls and ceilings. Pipe surface temperatures were 350° C (662° F) for normal operation, and 400–450° C (752–842° F) to simulate overfire conditions. Unprotected ceilings at 457 mm (18 in.) clearance met code recommended temperature rise limits for normal operation, but protection was needed for overfire exposures. Some protected walls allowed for clearance reductions to 76 mm (3 in.) for all exposures, while others needed at least 304 mm (12 in.) for normal and 457 mm (18 in.) for overfire exposures.Recommendations for model building code specifications for wall and ceiling protection are provided. Reference: Joseph J. Loftus and Richard D. Peacock, Wall and Ceiling Protection for Heating Appliances,Fire Technology, Vol. 21, No. 3, August 1985, p. 213.This paper is a contribution of the National Bureau of Standards and is not subject to copyright.     

Brain areas controlling thermoregulatory grooming prone extension, locomotion, and tail vasodilation in rats.

In an experiment with 134 male Long-Evans rats, localized diathermic warming elicited the principal hyperthermic responses of the rat: grooming, body extension, locomotion, and tail vasodilation. Failure of diathermy to elicit nonthermoregulatory responses evoked by electrical stimulation ruled out nonspecific excitation. The largest zone extended from the septal area through the preoptic area and hypothalamus into the midbrain, and a smaller zone was located in the medulla. Grooming, extension, and locomotion were obtained from differentiated though partially overlapping subareas, all of which elicited vasodilation. Fewer than 3% of the electrodes induced all responses, while the remainder produced incomplete combinations, indicating that the rat's hyperthermic repertoire results from largely independent channels from thermal detector to motor effector, and does not require an integrative center or mutually excitatory collaterals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Encounter groups: Comparisons and ethical considerations.

Examines the evolution and nature of encounter groups, and whether or not there are any differences in the relative effectiveness of various encounter groups. Numerous ethical considerations are discussed, and some ethical guidelines for group leaders are suggested. (62 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)