Effects of gas composition on asynchronous error motion in externally pressurized spindles

Stable, externally pressurized aerostatic spindles exhibit picometer-level vibration as a result of the interaction of the high-pressure working fluid and its path through a spindle's compensation features (e.g., grooves, orifices, pockets, etc.). This vibration presents a challenge as end users seek the lowest possible asynchronous error motion in manufacturing, metrology and data storage applications. This technical brief describes experimental testing to quantify this low-level vibration and its significant variation with both supply gas composition and pressure. Of the gases tested, helium and neon generate the lowest vibration while other gases including air lead to an order of magnitude higher vibration. Vibration levels with carbon dioxide and nitrous oxide are an additional order of magnitude higher. At present, the root cause of the vibration amplitude dependence on supply gas composition is unknown although kinematic viscosity and mean free path length correlate well with the results presented here.     

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.