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Describing the plastic deformation of aluminium softball bats   总被引:1,自引:1,他引:0  
Hollow aluminium bats were introduced over 30 years ago to provide improved durability over wooden bats. Since their introduction, however, interest in hollow bats has focused almost exclusively around their hitting performance. The aim of this study was to take advantage of the progress that has been made in predicting bat performance using finite elements and apply it to describe bat durability. Accordingly, the plastic deformation from a ball impact of a single-wall aluminum bat was numerically modelled. The bat deformation from the finite-element analysis was then compared with experiment using a high-speed bat test machine. The ball was modelled as an isotropic, homogeneous, viscoelastic sphere. The viscoelastic parameters of the ball model were found from instrumented, high-speed, rigid-wall ball impacts. The rigid-wall ball impacts were modelled numerically and showed good agreement with the experimentally obtained response. The strain response of the combined bat-ball model was verified with a strain-gauged bat at intermediate ball impact speeds in the elastic range. The strain response of the bat-ball model exhibited positive correlation with the experimental measurements. High-speed bat-ball impacts were performed experimentally and simulated numerically at increasing impact speeds which induced correspondingly increased dent sizes in the bat. The plastic deformation from the numerical model found good agreement with experiment provided the aluminium work hardening and strain rate effects were appropriately described. The inclusion of strain rate effects was shown to have a significant effect on the bat deformations produced in the finite-element simulations. They also helped explain the existence of high bat stresses found in many performance models.  相似文献   
23.
This paper will explore some issues raised by an evaluation of a Scottish video making project which works with young people in trouble or 'at risk' in school. In the paper we reflect on the problems of evaluating work with troubled and troublesome pupils and on the difficulties of both collecting and presenting appropriate evidence. It offers a contribution to continuing debates over educational exclusion and inclusion and to the research literature on strategies for supporting young people in school. The paper also raises key questions about the planning and evaluating of support services for young people by schools.  相似文献   
24.
The purpose of this study was to assess the validity of predicting the maximal oxygen uptake (VO2(max)) of sedentary men from sub-maximal VO2 values obtained during a perceptually regulated exercise test. Thirteen healthy, sedentary males aged 29-52 years completed five graded exercise tests on a cycle ergometer. The first and fifth test involved a graded exercise test to determine VO2(max). The two maximal graded exercise tests were separated by three sub-maximal graded exercise tests, perceptually regulated at 3-min RPE intensities of 9, 11, 13, 15, and 17 on the Borg ratings of perceived exertion (RPE) scale, in that order. After confirmation that individual linear regression models provided the most appropriate fit to the data, the regression lines for the perceptual ranges 9-17, 9-15, and 11-17 were extrapolated to RPE 20 to predict VO2(max). There were no significant differences between VO2(max) values from the graded exercise tests (mean 43.9 ml x kg(-1) x min(-1), s = 6.3) and predicted VO2(max) values for the perceptual ranges 9-17 (40.7 ml x kg(-1) x min(-1), s = 2.2) and RPE 11-17 (42.5 ml x kg(-1) x min(-1), s = 2.3) across the three trials. The predicted VO2(max) from the perceptual range 9-15 was significantly lower (P < 0.05) (37.7 ml x kg(-1) x min(-1), s = 2.3). The intra-class correlation coefficients between actual and predicted VO2(max) for RPE 9-17 and RPE 11-17 across trials ranged from 0.80 to 0.87. Limits of agreement analysis on actual and predicted VO2 values (bias +/- 1.96 x S(diff)) were 3.4 ml x kg(-1) x min(-1) (+/- 10.7), 2.4 ml x kg(-1) x min(-1) (+/- 9.9), and 3.7 ml x kg(-1) x min(-1) (+/- 12.8) (trials 1, 2, and 3, respectively) of RPE range 9-17. Results suggest that a sub-maximal, perceptually guided graded exercise test provides acceptable estimates of VO2(max) in young to middle-aged sedentary males.  相似文献   
25.
The Heritage Lottery Fund has, over the past 13 years, given £4billion to heritage projects of all kinds. As the Fund has matured a greater emphasis has been placed on the evaluation of the social and economic outcomes of this funding. In 2004 we reported on progress with evaluation of the programmes targeted at particular types of heritage (Clark, 2004 Clark, K. 2004. Why fund heritage? The role of research in the Heritage Lottery Fund. Cultural Trends, 52: 6585.  [Google Scholar]). The greater challenge has been to evaluate the outcomes from the Fund's generic programmes, which can fund any type of heritage and which between them account for over two-thirds of total funding. This article reviews the Fund's experience over the last 3 years in developing and implementing an evaluation system using the Public (or Cultural) Value framework. It presents some initial results from the research so far completed and reviews how far the framework has been useful in suggesting research priorities and organizing findings.  相似文献   
26.
In the years since Michael Brown’s death, the hashtag #HandsUpDontShoot has been criticized for supposedly misrepresenting forensic evidence as framed by the Department of Justice. However, an expressive pull has kept alive both the hashtag and the sentiment behind it. The images of #HandsUpDontShoot are compelling in that they offer a glimpse into lived experiences that are often dismissed, ignored, or refuted. In this essay, I trace the aesthetic features of the #HandsUpDontShoot images, which foreground shocking juxtapositions between nonviolent protesters and militarized police forces, to the hashtag’s historical analogue: antilynching photography. Antilynching photography often utilized the aesthetic techniques of remediation, recontextualization, and juxtaposition—aesthetic features used prominently in today’s digital and remix cultures. By noting #HandsUpDontShoot’s use of these same techniques, I illuminate the ways in which Twitter’s connective affordances shape the viewer’s encounter with the images to engender ethical witnessing by affectively linking Brown’s death to shared material experiences of racial minorities. Such encounters propel witnesses beyond distanced objectification and toward an embodied reckoning of those experiences.  相似文献   
27.
This article draws on findings from my doctoral research to exemplify some of the difficulties I encountered when interviewing 20 female professors11. In the UK context, the title of ‘professor’ is reserved for full professors only – that is, those with either an established or personal chair. and subsequently writing about their life histories. In this article, I discuss how I addressed the issues of representing and positioning my participants, and I reflect on the power dynamics present in the research process. The article contends that by drawing on Bourdieu and Wacquant's [An Invitation to Reflexive Sociology. Chicago, IL: University of Chicago Press] understanding of reflexivity and feminist interpretations of their work including McNay [“Gender, Habitus and the Field: Pierre Bourdieu and the Limits of Reflexivity.” Theory Culture Society 16: 95] and Adkins [“Reflexivity Freedom or Habit of Gender?” Theory Culture Society 20: 21], valuable research can be produced, despite the difficulties. A related aim of this paper is to reflect back after four years in an academic post on my position as a novice researcher, and some of the associated issues facing doctoral students, particularly the problems with researching upwards [Walford, G. 2011 Walford, G. 2011. “Researching the Powerful.” British Educational Research Association on-line resource. Accessed March 17, 2014. www.bera.ac.uk/system/files/Researching%20the%20Powerful.pdf [Google Scholar]. “Researching the Powerful. British Educational Research Association On-line Resource.” Accessed March 17, 2014. www.bera.ac.uk/system/files/Researching%20the%20Powerful.pdfWalford 2011].  相似文献   
28.
Robust academic research on the topic of students involved in the sex industry is in its infancy, yet the relationship appears consistent and permanent. This paper draws on findings from the largest study into the stripping industry in the United Kingdom to explore the relationships between students, sex work and consumption. To make sense of the relationship between students and participation in the sex industry, a deeper understanding of other social and cultural processes is needed. In this discussion we argue that the following points are relevant and interlinked: changes to the nature of sexual commerce and sexual consumption as they become part of the marketplace; changes in social attitudes and the rise of ‘respectability’ in sexual commerce; the ‘pleasure dynamic’ amongst students; and changes in the higher education structure that place students as consumers as well as financially fragile. We set out a future research agenda given that this relationship is set to grow as the individual bares the cost of higher education.  相似文献   
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Three of the most prevalent developmental disorders (DDs) are autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD) and fetal alcohol spectrum disorder (FASD). As part of a study screening for DDs in Greater Manchester, UK, a unique opportunity was taken to explore parents' experiences of receiving reports about their child's previously unrecognised DD. Six parents out of a possible 16 took part in interviews, which were analysed thematically. Findings drawn from parental responses revealed a number of barriers to accessing support for their child's additional needs, including perceived resistance from schools, particularly for quiet, well-behaved girls, and difficulty in accessing assessment or referrals. There needs to be greater awareness of additional needs in children without externalising behaviours, the presence of gender-specific differences in the presentation of DDs, and FASD as a commonly occurring DD. Ultimately, better support for children with DDs would reduce the burden of unmet needs for the children and their families, and for wider services.  相似文献   
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