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 of sex-trait stereotypes among young children in the United Staes, England, and Ireland

The Sex Stereotype Measure II (SSM II), a 32-item revision of the Williams, Bennett, and Best Sex Stereotype Measure, was developed to assess children's knowledge of conventional, sex-trait stereotypes defined by American university students. The procedure employed brief stories and human figure silhouettes which were individually administered to 5- and 8-year-old children in the United States, England, and Ireland and group administered to 11-year-olds in the United States. In the United States, knowledge of sex-trait stereotypes was found to develop in a linear fashion between the ages of 5 and 11, with more male traits than female traits being known at each age level. Cross-nationally, there was a high degree of similarity in the nature of the sex stereotypes being learned by the children in the 3 countries, although the rate of learning appeared slower among the Irish children. In all countries there was a clear progression in sex-stereotype learning from age 5 to age 8. English boys had greater knowledge of stereotypes than English girls, but this was not true in Ireland and the United States. Generally, knowledge of male stereotype traits appeared to develop earlier while knowledge of the female traits increased more rapidly between ages 5 and 8. The similarity in sex-stereotype learning in the 3 countries is discussed, and studies in progress in other countries of greater cultural diversity are noted.     

Child abuse potential inventory and parenting behavior: Relationships with high-risk correlates

The primary purpose of this research was to examine the construct validity of the Child Abuse Potential Inventory by comparing maltreating and high-risk parents' CAP Inventory abuse scores to their behavior during interactions with their children. A second purpose was to determine the degree to which CAP Inventory scores and parenting behavior were related to several known correlates of abuse, as measured by parent and teacher reports. Participants (n = 41) included abusive and high-risk parents and their children referred to a treatment group. Correlational analyses revealed that CAP Inventory scores and observed parenting style yielded highly related findings, supporting construct validity of the CAP Inventory. However, the CAP Inventory and observed behavior index showed a different pattern of relationships to the risk correlates. Implications for assessment of risk status are discussed and recommendations are provided for continued research.     

An Onto-Semiotic Analysis of Combinatorial Problems and the Solving Processes by University Students

In this paper we describe an ontological and semiotic model for mathematical knowledge, using elementary combinatorics as an example. We then apply this model to analyze the solving process of some combinatorial problems by students with high mathematical training, and show its utility in providing a semiotic explanation for the difficulty of combinatorial reasoning. We finally analyze the implications of the theoretical model and type of analysis presented for mathematics education research and practice.     

Familiarity with Latin and Greek anatomical terms and course performance in undergraduates

Commonly used technical anatomy and physiology (A&P) terms are predominantly rooted in Latin and Greek vocabulary, so it is commonly inferred that a solid grounding in Latin and Greek roots of medical terminology will improve student learning in anatomy and related disciplines. This study examines the association of etymological knowledge of A&P terms and A&P course performance among 446 undergraduates in their first semester of the study of human gross anatomy and physiology, with a more detailed analysis of the characteristics of 52 students who filled out surveys about their prior knowledge and experiences related to medicine or anatomy. In both data sets, there was only a weak positive correlation between the performance on a quiz of Latin and Greek medical terms and the students' performance on regular assignments. The presumption that familiarity with Latin and Greek word roots has a strong influence on successful learning of anatomy is not supported by these data. Future research should address whether or not there are particular skills associated with using etymological knowledge in improving A&P course performance.     

Teacher–student negotiations during context-based chemistry reform: A case study

Teachers participating in curricular reforms, especially reforms based on constructivism, are expected to bring about change in their teaching approach. This is often a difficult, complex and intensive process, and demands a radical reculturing of the classroom. This is also the case for social constructivist reforms in chemistry education, which are based on a context-based approach. Educational change is a social and interactional process, and during this change teachers will engage in negotiations with their students about the reform. These teacher–student negotiations have a profound impact on the succeeding of the reform. This study explores the teacher–student interactions during the reform that shape and alter the context-based chemistry approach. We focused on two teachers, of whom it was found in an earlier study that one of them succeeded in implementing the reform, while the other one struggled. By following them for one school year, in which in-depth qualitative data was collected through various instruments, we developed insights about the teacher–student negotiations that influenced the educational reform. Three themes emerged from the data: “agency of learning,” “vulnerability,” and “care.” The differences that were found between the teachers regarding these themes help explain why and how the reform can become a success and why the reform often fails to change classroom practice.     

Design and testing of a frictionless mechanical inerter device using living-hinges

In this paper a novel type of frictionless mechanical inerter device is presented, where instead of gears, motion of the flywheel is achieved using living-hinges. The design is a type of pivoted flywheel inerter inspired in part by the Dynamic Anti-resonant Vibration Isolator (DAVI) concept, which was first developed in the 1960s. Unlike the DAVI, it will be shown that the pivoted flywheel inerter has the advantage of producing balanced forces. Furthermore the use of living-hinges eliminates the need for gears or other frictional elements in the inerter mechanism. To demonstrate the utility of the new concept, a bench-top experiment was performed using a small-scale living-hinge inerter manufactured using polypropylene hinges. By estimating the experimental system parameters, the transmissibility results from the experiment could be compared to a mathematical model. These results showed that the living-hinge inerter provided an isolation effect of at least three orders of magnitude in terms of the maximum amplitude reduction from the uncontrolled system compared to that with the inerter added. Although friction was eliminated, the living-hinges did introduce additional damping, and this was found to correspond to an increase in the equivalent damping ratio for the uncontrolled system of 1.2%. It is shown that the living-hinge inerter developed in this paper fits all of the essential conditions required to be a practical inerter device. Furthermore, as it operates without mechanical friction, or fluid flow, it represents a new paradigm in experimental inerter technology.