Vacuum interrupter, high reliability component of distribution switches, circuit breakers and contactors

The use of vacuum interrupters(VIs)as the current interruption component for switches,circuit breakers,reclosers and contactors operating at distribution voltages has escalated since their introduction in the mid-1950’s.This electrical product has developed a dominating position for switching and protecting distribution circuits.VIs are even being introduced into switching products operating at transmission voltages.Among the reasons for the VI’s popularity are its compactness,its range of application,its low cost,its superb electrical and mechanical life and its ease of application.Its major advantage is its well-established reliability.In this paper we show how this reliability has been achieved by design,by mechanical life testing and by electrical performance testing.We introduce the“sealed for life”concept for the VI’s integrity.We discuss this in terms of what is meant by a practical leak rate for VIs with a life of over 30 years.We show that a simple high voltage withstand test is an easy and effective method for monitoring the long-term vacuum integrity.Finally we evaluate the need for routine inspection of this electrical product when it is used in adverse ambient environments.     

Development and validation of the preschool learning behaviors scale

This article presents the design, national standardization, and validation of the Preschool Learning Behaviors Scale (McDermott, Green, Francis, & Stott, 2000). A normative sample (N = 100) of 3‐ to 5–1/2‐year‐olds was configured to the U.S. Census, wherewith factor analyses yielded distinct and reliable dimensions of Competence Motivation, Attention/Persistence, and Attitude Toward Learning. The solution was invariant in an independent national sample (N = 170) and generalizable across child sex, age, ethnicity, and parent education level. Three‐week stability and interobserver agreement were supported with a local Head Start sample (N = 52). Bivariate and canonical correlations demonstrated validity convergence with indices of social skills, divergence from behavior problems, and substantial independence from cognitive ability. Implications and future research are considered. © 2002 Wiley Periodicals, Inc.     

The Interplay of Psychology and Mathematics Education: From the Attraction of Psychology to the Discovery of the Social

It is a rather safe statement to claim that the social dimensions of the scientific process are accepted in a fair share of studies in the philosophy of science. It is a somewhat safe statement to claim that the social dimensions are now seen as an essential element in the understanding of what human cognition is and how it functions. But it would be a rather unsafe statement to claim that the social is fully accepted in the philosophy of mathematics. And we are not quite sure what kind of statement it is to claim that the social dimensions in theories of mathematics education are becoming more prominent, compared to the psychological dimensions. In our contribution we will focus, after a brief presentation of the above claims, on this particular domain to understand the successes and failures of the development of theories of mathematics education that focus on the social and not primarily on the psychological.     

提心吊胆的华尔街

The war in Iraq, terrorism, rising oil prices-and now the threat of higher interest rates-are all preying on the market. There comes a point in virtually every bull market when     

Does calibration reduce variability in the assessment of accounting learning outcomes?

Reliable, consistent assessment process that produces comparable assessment grades between assessors and institutions is a core activity and an ongoing challenge with which universities have failed to come to terms. In this paper, we report results from an experiment that tests the impact of an intervention designed to reduce grader variability and develop a shared understanding of national threshold learning standards by a cohort of reviewers. The intervention involved consensus moderation of samples of accounting students’ work, with a focus on three research questions. First, what is the quantifiable difference in grader variability on the assessment of learning outcomes in ‘application skills’ and ‘judgement’? Second, does participation in the workshops lead to reduced disparity in the assessment of the students’ learning outcomes in ‘application skills’ and ‘judgement’? Third, does participation in the workshops lead to greater confidence by reviewers in their ability to assess students’ skills in application skills and judgement? Our findings suggest consensus moderation does reduce variability across graders and also builds grader confidence.