Percolation and the resistive transition of the critical temperature Tc of Nb3Sn

The relationship between the distribution of the critical temperature, the percolation function, and the resistive transition of the critical temperature is explored for polycrystalline Nb₃Sn. In the neighborhood of the critical temperature, Nb₃Sn is assumed to be a random mixture of superconducting and normal grains. Percolation concepts are applied to a study of the resistivity. A general analysis is made showing that the onset and shape of the resistive transition for composite conductors are determined by the percolation function and the distribution of the critical temperature. An approximate form of the percolation function is determined based on a linear FEM analysis. Example resistive transitions are calculated for an assumed normal distribution of the critical temperature. An argument is presented that relates grain orientation and strain dependence in Nb₃Sn. It is noted that a dependence of the distribution of T_c with strain, in addition to the usual shift in T_c with strain, would be the result of a strain dependence that is a function of grain orientation. The analysis shows the extent to which the slope of the resistive transition is a measure of the distribution of the critical temperature, and therefore a measure of the grain orientation strain sensitivity. Finally, a method is described to determine the percolation function experimentally.     

Physical, Mental, and Social Catastrophic Cognitions as Prognostic Factors in Cognitive-Behavioral and Pharmacological Treatments for Panic Disorder.

The authors explored the prognostic value of 3 different types of catastrophic cognitions in the treatment of panic disorder with and without mild-to-moderate agoraphobia using a sample of 143 participants who received either cognitive-behavioral therapy (CBT) or imipramine in a randomized controlled trial. Stronger fears of social catastrophes both prior to and following treatment with CBT or imipramine were associated with a poorer outcome. In contrast, cognitions involving physical or mental catastrophes were unrelated to outcome, regardless of whether these thoughts were measured prior to or following treatment. These findings are consistent with the notion that although the intensity of physical catastrophe cognitions may best discriminate between panic disorder and other anxiety disorders, it is the intensity of social catastrophe cognitions that is most closely tied to success in treating this disorder. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interpreting the Good Life: Growth Memories in the Lives of Mature, Happy People.

In 2 studies, the authors examined autobiographical memories for the presence of 2 growth orientations that were expected to correspond differentially to maturity and well-being, which are considered to be key facets of "the good life" by L. A. King (2001). Mature participants emphasized integrative memories (conceptual integration and learning), whereas happy participants emphasized intrinsic memories (humanistic concerns). Both kinds of growth memories correlated more strongly with eudaimonic than with hedonic measures of well-being. Growth memories were largely independent of Big Five traits in relation to maturity and well-being. Finally, older participants were more likely than younger participants to have greater maturity (marginally) and well-being, but this was in part explained by older participants' greater tendency to have growth memories. The discussion considers the role of growth memories in the intentional cultivation of the good life. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Uncertainties in Small-Angle Measurement Systems Used to Calibrate Angle Artifacts

We have studied a number of effects that can give rise to errors in small-angle measurement systems when they are used to calibrate artifacts such as optical polygons. Of these sources of uncertainty, the most difficult to quantify are errors associated with the measurement of imperfect, non-flat faces of the artifact, causing the instrument to misinterpret the average orientation of the surface. In an attempt to shed some light on these errors, we have compared autocollimator measurements to angle measurements made with a Fizeau phase-shifting interferometer. These two instruments have very different operating principles and implement different definitions of the orientation of a surface, but (surprisingly) we have not yet seen any clear differences between results obtained with the autocollimator and with the interferometer. The interferometer is in some respects an attractive alternative to an autocollimator for small-angle measurement; it implements an unambiguous and robust definition of surface orientation in terms of the tilt of a best-fit plane, and it is easier to quantify likely errors of the interferometer measurements than to evaluate autocollimator uncertainty.     

Overconfidence in Interval Estimates.

Judges were asked to make numerical estimates (e.g., "In what year was the first flight of a hot air balloon?"). Judges provided high and low estimates such that they were X% sure that the correct answer lay between them. They exhibited substantial overconfidence: The correct answer fell inside their intervals much less than X% of the time. This contrasts with choices between 2 possible answers to a question, which showed much less overconfidence. The authors show that overconfidence in interval estimates can result from variability in setting interval widths. However, the main cause is that subjective intervals are systematically too narrow given the accuracy of one's information-sometimes only 40% as large as necessary to be well calibrated. The degree of overconfidence varies greatly depending on how intervals are elicited. There are also substantial differences among domains and between male and female judges. The authors discuss the possible psychological mechanisms underlying this pattern of findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Using Ordinal Optimization Approach to Improve Efficiency of Selection Procedures

Indifference-zone selection procedures have been widely studied and applied to determine the sample sizes for selecting a good design among k alternative designs. However, efficiency is still a key concern for using simulation to solve ranking and selection problems. Ordinal optimization has emerged as an effective technique to improve efficiency of simulation and optimization. In this paper, we incorporate the concept of ordinal optimization with ranking-and-selection methodology and propose using a normal approximation to estimate the probability of correct selection. The proposed procedure takes into account not only the sample variances but also the difference of sample means when determining the sample sizes. Furthermore, the procedure is valid with the variance reduction technique of common random numbers. An experimental performance evaluation demonstrates the efficiency of the new procedure.     

Simulating ion beam extraction from a single aperture triode acceleration column: a comparison of the beam transport codes IGUN and PBGUNS with test stand data

Ion beam extraction from two different ion sources with single aperture triode extraction columns was simulated with the particle beam transport codes PBGUNS and IGUN. For each ion source, the simulation results are compared to experimental data generated on well-equipped test stands. Both codes reproduced the qualitative behavior of the extracted ion beams to incremental and scaled changes to the extraction electrode geometry observed on the test stands. Numerical values of optimum beam currents and beam emittance generated by the simulations also agree well with test stand data.     

Survival Skills for The is Professional

IS professionals can only dream of the days when technical brilliance alone was enough to ensure a successful career. Now business acumen and a strong understanding of customer expectations are vital to long-term career survival. Based on their study of 75 experienced IS professionals, the authors present guidelines for fostering the development of customer-oriented IS professionals.