A determination of the dynamic response of softballs

An apparatus is described for measuring the stiffness and coefficient of restitution (COR) of balls with application to softballs. While standardized test methods currently exist to measure these properties, they do not represent the displacement rate and magnitude that occur in play. The apparatus described herein involves impacting a fixed, solid cylindrical surface (matched to the diameter of the bat) with a ball and measuring the impact force during impact and speed of the ball before and after impact. The ratio of the ball speeds determines the COR, while the impact force is used to derive a ball stiffness. For an example of the contribution of the new ball test, the performance of hollow bats, which is sensitive to ball stiffness, was compared. Bat performance showed a much stronger dependence on the proposed ball stiffness than the traditional measure. Finally, it was shown that to achieve similar conditions between impacts with fixed and recoiling objects, the impact speed should be chosen so that the centre of mass energy was the same in the two cases. The method has application to associations wishing an improved method to regulate ball and bat performance.     

Two Teachers' Conceptions of a Reform-Oriented Curriculum: Implications for Mathematics Teacher Development

This paper describes two high school teachers' conceptions of the cooperation and exploration components of a reform-oriented mathematics curriculum. Although the teachers appreciated the themes of cooperation and exploration in theory, their conceptions of these themes with respect to their implementations of the curriculum differed. One teacher viewed the curriculum's problems as open-ended and challenging for students, whereas the other teacher claimed that the problems were overly structured. Each teacher attributed difficulties with students' cooperative work to the amount of structure and direction (too little or too much) offered by the problems. Discussion of such similarities and differences in the teachers' conceptions emphasizes the dynamic, humanistic nature of curriculum implementation and gives rise to important implications for mathematics teacher development in the context of reform. This revised version was published online in July 2006 with corrections to the Cover Date.     

Making a Difference in the Lives of Youth: Mapping Success with the “Six Cs”

Many museums offer specialized programs for young people during out‐of‐school time, yet the consequences of such programs are not well documented. This article explores the potential utility of borrowing a conceptual framework from the youth development literature as a tool for assessment. The authors map findings from three studies of museum youth programs onto the youth development framework as an exercise in understanding the extent to which this model may be useful in developing museum youth programs. Results from this preliminary analysis demonstrate that the framework could serve as a viable tool for program design, and could offer a clear, grounded framework with common language for articulating program impacts often known intuitively and/or anecdotally but not formalized.     

Language Impairment and Reading Disability: Connections and Complexities Introduction to the Special Issue

Researchers and practitioners in the fields of reading and language are well informed about the importance of phonological awareness in beginning reading. The purpose of this special issue of Learning Disabilities Research & Practice is to present recent research that extends the search for language and reading connections beyond the realm of phonological awareness. Many children with language impairment (LI) identified before formal schooling experience persistent difficulty in learning to read. Two interrelated issues are prerequisite for understanding the developmental course of events that might link language and reading (dis)ability in these children. One is an appreciation of exactly what is meant by LI, while the second concerns how LI should be explained. In this introductory article, we explore the complexities of these two issues, in particular the controversy between the domain‐specific perspective and the domain‐general perspective on the nature of specific LI (SLI). Consistent with these perspectives, future studies on possible language‐reading links will need to measure language and related processes in greater breadth and depth, over time, and within a variety of experiential contexts. The five articles in this issue represent a critical first step in this direction.