The sweet spot of a cricket bat for low speed impacts

The impact location of a cricket ball on a cricket bat has a large influence on the resulting rebound velocity of the ball. To measure this, a cricket bat was swung in a pendulum motion towards a cricket ball suspended in space. The position of the ball was modified so that it impacted the bat at 24 different positions on the face of the bat. This included six positions longitudinally and four positions laterally. The speed of the bat and each rebound were measured by a radar gun so that the apparent coefficient of restitution (ACOR) could be calculated. Impacts occurring centrally and 1?cm either side of the midline produced significantly higher rebound speeds and ACOR??s than impacts occurring 2 and 3cm off centre (p?<?0.01). Impacts occurring 15?C20?cm from the base of the bat produced the highest rebound speeds (p?<?0.01) and impacts occurring 20?C30?cm from the base of the bat produced the highest ACOR values. Implications for higher speed impacts and game scenarios are discussed.     

Effects of swing-weight on swing speed and racket power

Measurements are presented of the speed at which six different rods could be swung by four male students. Three of the rods had the same mass but their swing-weight (i.e. moment of inertia) differed by large factors. The other three rods had the same swing-weight but different masses. Our primary objective was to quantify the effects of mass and swing-weight on swing speed. The result has a direct bearing on whether baseball, tennis, cricket and golf participants should choose a heavy or light implement to impart maximum speed to a ball. When swinging with maximum effort, swing speed (V) was found to decrease as swing-weight (Io) increased, according to the relation V = C/Ion, where C is a different constant for each participant and n = 0.27 when Io > 0.03 kg x m2. Remarkably similar results were obtained previously with softball bats (where n = 0.25) and golf clubs (where n = 0.26). Swing speed remained approximately constant as swing mass increased (when keeping swing-weight fixed). The implications for racket power are discussed.     

OCLC records for federal depository documents: A preliminary investigation

A representative sample of 300 printed monographs and analyzed serials distributed to depository libraries was searched in the OCLC online system to determine when, how, and by whom depository documents are likely to be cataloged. Particular attention was paid to differences between dates of distribution and cataloging for sales publications, for all titles cataloged by the Government Printing Office, and for those cataloged by the Library of Congress. Patterns relating to document distribution as well as to cataloging practices were discernible from survey results and are presented here. Major findings may be summarized as follows: 1) not all depository monographs are cataloged by the Government Printing Office; 2) sales publications are cataloged quickly, often before distribution by GPO; 3) the quality of cataloging records for depository documents available on OCLC is generally high; 4) the Library of Congress catalogs relatively few depository documents and is comparatively slow to do so; and 5) many different types of OCLC member libraries catalog federal depository documents, often before GPO does. The article concludes with a discussion of implications for future changes in documents cataloging policies among depository libraries, and argues for greater inclusion of documents records in the many online, public-access catalogs currently being planned or used.     

小脑作用并不小

"在我们的颅后窝内,附着于拱形颅骨半球下的脑干上,有一团棒球大小的豆状灰白色脑组织,这就是小脑."     

Relationships between computational thinking and the quality of computer programs

Education and Information Technologies - Computational thinking – the ability to reformulate and solve problems in ways that can be undertaken by computers – has been heralded as a...     

The Interplay of Teacher and Student Actions in the Teaching and Learning of Geometric Proof

Proof and reasoning are fundamental aspects of mathematics. Yet, how to help students develop the skills they need to engage in this type of higher-order thinking remains elusive. In order to contribute to the dialogue on this subject, we share results from a classroom-based interpretive study of teaching and learning proof in geometry. The goal of this research was to identify factors that may be related to the development of proof understanding. In this paper, we identify and interpret students' actions, teacher's actions, and social aspects that are evident in a classroom in which students discuss mathematical conjectures, justification processes and student-generated proofs. We conclude that pedagogical choices made by the teacher, as manifested in the teacher's actions, are key to the type of classroom environment that is established and, hence, to students' opportunities to hone their proof and reasoning skills. More specifically, the teacher's choice to pose open-ended tasks (tasks which are not limited to one specific solution or solution strategy), engage in dialogue that places responsibility for reasoning on the students, analyze student arguments, and coach students as they reason, creates an environment in which participating students make conjectures, provide justifications, and build chains of reasoning. In this environment, students who actively participate in the classroom discourse are supported as they engage in proof development activities. By examining connections between teacher and student actions within a social context, we offer a first step in linking teachers' practice to students' understanding of proof.     

A generative theory of textbook design: Using annotated illustrations to foster meaningful learning of science text

In three experiments, college students read a text explaining how lightning works and then took problem-solving transfer tests. Some students (integrated group) also viewed illustrations depicting the major stages in the formation of lightning that (a) were placed adjacent to corresponding text paragraphs and (b) contained annotations repeating the verbal cause-and-effect information from the text. Other students (separated group) viewed the same illustrations (a) on a separate page and (b) without annotations, after they had finished reading the text. The integrated group generated approximately 50% more creative solutions on transfer problems than the separated group, and this pattern was stronger for students who lacked experience in meteorology than for high-experience students. The positive effects of integrated illustrations depended on incorporating annotations (i.e., captions and labels) into the illustrations rather than placing illustrations close to corresponding paragraphs. Results were interpreted in light of a generative theory of multimedia learning which posits that meaningful learning requires constructing connections between visual and verbal representations of a system.     

MANAGING STRESS AMONG ADULT WOMEN STUDENTS IN COMMUNITY COLLEGES

Stress management for adult women students in community colleges is essential because of the enormous demands they face from family, career, and financial responsibilities. Community colleges and adult educators must help adult women students identify their major sources of stress as well as provide strategies to alleviate those stressors. An extensive review of the literature and a campus-based study found high levels of stress resulting from parenting, nancial, and health concerns. Age was also found to be an important stress factor. Recommendations for helping adult women students are discussed.     

Mixing metaphors: The school as patsy 1

Despite the frequent juxtaposition of the terms "risk taking" and "change" in literature on school reform, we know very little about risk-taking behavior. Research conducted in the field of a psychology of risk-taking behavior has identified three essential elements of risk: (a) loss, (b) significance of loss, and (c) uncertainty (Yates &; Stone, 1992). In this case study, teacher risk taking was examined in the context of the development of a school-within-a-school (SWS) program, targeting sophomores at high risk for dropping out of school. Findings indicate that a psychology of risk-taking behavior provides a useful lens for understanding teacher risk taking in the context of this SWS innovation. The study also finds that the three essential elements of risk may not be sufficient to explain teacher risk taking. Constructs of emotion and gain, which appeared to be embedded in loss and significance of loss, need further identification and study. In addition, social interactions, organizational processes, and group or organizational values also appeared to influence collective risk-taking behavior. It is possible that a sociology of risk-taking behavior is an emerging construct that needs greater exploration.