Creep Behavior of Nickel-Copper Solid Solution Alloys below 0. 55 Tm

In two recent creep studies of inhomogeneous nickelcopper solid solution alloys,i.e. cast weld metal with solidification-induced composition gradients^[1] and nickelcopper laminate composites with controlled composition gradients across the layers,^[2] the creep rates at an intermediate temperature (500 °C) were shown to decrease with an increase in homogenization. The creep behavior in inhomogeneous alloy systems reflects the composite effects of position-dependent creep properties as controlled by solid solution alloy content. To utilize composite modeling techniques in creep analyses of materials with composition gradients, creep data of homogeneous materials as a function of alloy content are required. Therefore, this study was undertaken to evaluate the creep behavior of nickel-copper solid solution alloys at intermediate temperatures and to provide a base set of data to evaluate the effect of gradients described above.^[1,2] I. D. CHOI, formerly Graduate Research Assistant, Colorado School of Mines.     

Judgments of the lucky across development and culture.

For millennia, human beings have believed that it is morally wrong to judge others by the fortuitous or unfortunate events that befall them or by the actions of another person. Rather, an individual's own intended, deliberate actions should be the basis of his or her evaluation, reward, and punishment. In a series of studies, the authors investigated whether such rules guide the judgments of children. The first 3 studies demonstrated that children view lucky others as more likely than unlucky others to perform intentional good actions. Children similarly assess the siblings of lucky others as more likely to perform intentional good actions than the siblings of unlucky others. The next 3 studies demonstrated that children as young as 3 years believe that lucky people are nicer than unlucky people. The final 2 studies found that Japanese children also demonstrate a robust preference for the lucky and their associates. These findings are discussed in relation to M. J. Lerner's (1980) just-world theory and J. Piaget's (1932/1965) immanent-justice research and in relation to the development of intergroup attitudes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exploring Variability and Performance in a Sub-200-mV Processor

In this study, we explore the design of a subthreshold processor for use in ultra-low-energy sensor systems. We describe an 8-bit subthreshold processor that has been designed with energy efficiency as the primary constraint. The processor, which is functional below V_dd=200 mV, consumes only 3.5 pJ/inst at V_dd=350 mV and, under a reverse body bias, draws only 11 nW at V_dd=160 mV. Process and temperature variations in subthreshold circuits can cause dramatic fluctuations in performance and energy consumption and can lead to robustness problems. We investigate the use of body biasing to adapt to process and temperature variations. Test-chip measurements show that body biasing is particularly effective in subthreshold circuits and can eliminate performance variations with minimal energy penalties. Reduced performance is also problematic at low voltages, so we investigate global and local techniques for improving performance while maintaining energy efficiency.     

Recent results of fracture experiments on carbon steel welded pipes

Several pipe fracture experiments were conducted with circumferential cracks in the center of ferritic nuclear pipe welds. These experiments involved either submerged arc or shielded metal arc welds with either through-wall cracks or internal surface cracks. The pipe diameters varied from 940 mm (37 inches) to 152 mm (6 inches), and thickness from 10·9 mm (0·43 inches) to 86·6 mm (3·41 inches). Some of the through-wall and surface-cracked pipe experiments were conducted under constant internal pressure and four-point bending. The test temperature was 288°C (550°F). The results of these experiments are compared with limit-load analyses, the ASME, Section XI, article IWB-3650 criterion, and more elaborate elastic-plastic fracture mechanical analysis.     

Investigation of the Impacts of Gamma Radiolysis on an Advanced TALSPEAK Separation

The advanced TALSPEAK process is a selective solvent extraction that utilizes 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) to separate lanthanide elements from trivalent actinides, which are held back in the aqueous phase by N-hydroxylethyl-N,N’,N’-ethylenediamine triacetic acid (HEDTA) buffered by citric acid. Gamma irradiation of an experiment containing Eu(III) and Am(III) as representative lanthanide and actinide elements resulted in higher distribution ratios of both and separation factors which decreased in an exponential fashion with increasing dose. Analysis of the reagents showed that the HEDTA concentration also decreased in an exponential fashion, strongly suggesting that degradation was correlated with loss of separation selectivity. In contrast, the concentration of citrate was unaffected, and while the concentration of HEH[EHP] did decrease, its dose-dependent kinetic profile indicated that it was not limiting partitioning. A second set of experiments were conducted using a citrate concentration that was 7.5 X higher, with the expectation that citrate would protect the HEDTA by scavenging radiolytically formed OH radicals. HEDTA degradation was significantly mitigated at higher gamma doses, but the Eu-Am separation was worse than in the low citrate experiments, presumably because at the high citrate concentrations, the Eu-citrate complexes formed in abundances competitive with the Am complexes, and are more effectively held back in the aqueous phase.     

Fractionation of non-Brownian rod-like particle suspensions in a viscoplastic fluid

In this work we explore a fractionation technique for non-Brownian rod-like particle suspensions based upon the control of the threshold for motion in a yield stress fluid. The principle is demonstrated by observing the motion of particles under the influence of a centrifugal force in a weak gel. Here we develop calibration curves of the force required to initiate motion in a gel under numerous configurations of the particles. Demonstration separations of bidisperse suspensions are reported. Here we achieve complete separation of dilute suspensions based upon length, diameter, or density. The method is then applied to an industrially important suspension, that is a polydispersed papermaking fibre suspension, in which a length-based fractionation is reported.     

Limitations of classical methods for measuring surface tension in visco-elastic liquids

The surface tension of a water/detergent mixture and a visco-elastic waterborne paint sample were measured using the classical ring method in which a thin free liquid film (lamella) is formed between the ring and the parent liquid. Lamella tension was measured during the stretching of the lamella. Measurements of water/surfactant mixtures have shown essentially classical behavior of lamella tension (independence of tension on deformation). Measurements of a waterborne paint formulation, however, have shown that after stretching of the lamella, the lamella tension decreases. The lamella tension of the paint sample increases after contraction of the lamella. Comparison of experimental results with rheological properties of the paint have shown that bulk visco-elastic properties of liquid are found in both the bulk sample and the lamella. The conclusion is that for the study of surface properties of visco-elastic liquids such as waterborne paints, the applicability of classical methods is limited. Therefore, it was necessary to develop new methods and approaches to study the properties of these materials. These methods are described in this paper.     

Growth rates of Salmonella and Escherichia coli O157:H7 in irradiated beef.

Ground beef was irradiated to 0, 2, or 4 kGy and then inoculated with a mixed culture of four serotypes of salmonellae or five strains of Escherichia coli O157:H7. The ground beef was stored at either 15 or 25 degrees C, and the growth of the inoculated bacteria was monitored over time. Growth parameters were determined for both the salmonellae and the E. coli O157:H7 using the Gompertz equation. There was no significant difference in lag phase duration or generation time, irrespective of the dose to which the ground beef had previously been exposed. Furthermore, the lag phase durations and generation times determined in this study did not differ significantly from previously published values. This suggests that, although irradiation eliminates a significant portion of the spoilage microflora in ground beef, the absence of this microflora provides no competitive advantage to the growth of salmonellae or E. coli O157:H7 in ground beef.