Is passive drag dependent on the interaction of kayak design and paddler weight in flat-water kayaking?

Abstract

Drag is one of the major factors that influences kayaking performance. To focus on the drag of the kayak’s hull shape and the paddlers’ weight per se, the passive drag (D_p) was measured on a flat-water sprint course for one paddler with added weights. D_p was measured by an electromechanical towing device using a load cell, at incremental and constant velocities from 2.78 to 5.56 m/s. Three kayaks of different sizes and shapes (Nelo® K1 Quattro-M, ML, and L) were used and the paddlers’ body weight was adjusted with weights so the total paddler weight in the kayak was 65, 75, and 85 kg. The mean D_p increased by the power function of D = kvⁿ (mean R² = .990; SD .006). The D_p went from 21.37?±?1.29 N at 2.78 m/s to 89.32?±?6.43 N at 5.56 m/s. For the two lighter weighted kayaks (65 and 75 kg), the lowest D_p was observed with different kayak sizes (M, ML, or L) depending on the target velocity. The manufacturers suggest that paddlers should select a kayak size according to their body weight to minimise drag; however, the results of this study suggest that target velocities, and thus competition distance should also be factored into kayak selection.     

Can educational experiments both test a theory and inform practice?

This article feeds into debate about the feasibility and usefulness of educational experiments by discussing methodological issues arising out of a study which sought causal links between teaching and learning of one aspect of French as a foreign language. The study involved two small‐scale experiments which tested a hypothesis regarding the learning of second language grammar within a particular theoretical, and its related pedagogical, framework (Input Processing and Processing Instruction respectively), and has been described in full elsewhere. The current article uses that example to suggest some circumstances (contextual, methodological and theoretical) within which educational experiments may be able to both test a learning theory and inform educational practice. It is argued that despite the complexities and limits of small‐scale educational experiments, an experimental design which combined a range of methods was able to generate new and useful (in a range of senses) substantive knowledge.     

Peer assessment of oral presentations: effects of student gender,university affiliation and participation in the development of assessment criteria

Peer assessment provides a useful mechanism to develop many positive qualities in students studying in higher education (HE). Potential influences on peer‐awarded marks include student qualities such as gender, HE background (e.g. university affiliation) and participation in the development of the assessment criteria. Many studies that have investigated peer assessment have placed great emphasis on marks from a single tutor, or very few tutors, from a single university. This study examined grades awarded by 11 tutors (affiliated with four universities) to oral presentations delivered on a residential field course by second‐year undergraduate students from two universities studying environmental or biological disciplines. Student assessors awarded marks of fairly high precision (correlating strongly with tutor grades) but averaged 5% higher than their tutors (i.e. of only moderate accuracy). Marginally higher marks (circa 1.6%) were awarded by student assessors to speakers studying at the same university. Gender influences were detected as males tended to grade other male speakers very slightly more highly than female speakers. Marks from females were unaffected by speaker gender. Students who participated in the development of the assessment criteria did not achieve higher grades for their presentations. However, when these ‘participants’ were assessing, they awarded lower marks than their peers (i.e. closer to, but not as low as, those awarded by tutors). Lower marks were also awarded during the middle of sessions, possibly resulting from factors associated with motivation and attention of speakers and markers. Overall, the potential biases in marking by naive assessors examined in this study may influence the validity of marks generated by peer assessment schemes, but the experience of this type of assessment had positive effects on those involved.     

Supervision of Doctoral Students in the Natural Sciences: expectations and experiences

Within the natural sciences and engineering, literature relating to postgraduate education, in particular the process of completing a doctorate, remains generally scarce. That which does exist emphasises the role of the supervisor in effecting successful completion and points to a wide range of activities performed by supervisors. There remains, however, little by way of accounts of the actual experiences of supervisors or students when engaged in the process of doctoral supervision. It is these experiences which form the basis of this paper which focuses upon doctoral students and their supervisors in the disciplines of physics, mathematics and engineering science. Data for the paper have been collected, as part of an ESRC funded project, by means of in‐depth interviews with students and supervisors in nine universities in England. In particular, we address students expectations of PhD supervision, the extent to which expectations have been met, and within the context of the ‘career’ of the PhD, the ways in which supervision changes as the doctoral process progresses. Important issues relating to the need for training for PhD supervisors and their capacity to meet the expectations of their students are raised, together with those which question the relationship between the PhD and the culture of academic work.     

La géométrie projective à l'école

Sans résuméTravail effectué dans le cadre du groupe de recherche en didactique de la mathématique du Conseil National des Recherches.     

Can higher education compensate for society? Modelling the determinants of academic success at university

This paper examines the role that social characteristics play in determining the academic success of students who begin university with roughly similar entry grades. The data used were drawn from the administrative records of over 38,000 UK-domiciled undergraduate students from one British university between 1998 and 2009. Results show that the characteristics of entrants have varied only slightly over this period and intake is still largely in favour of ‘traditional’ entrants: namely those from professional occupational backgrounds, the privately educated and those of traditional age. The relationship between background characteristics and eventual academic success also reflects patterns seen at earlier education stages. However, when prior attainment was taken into account, the link between degree outcome and many social characteristics does diminish – notably for students who were privately educated and who came from professional occupational groups. This suggests that once students have overcome barriers to admission, it is entry grades rather than social characteristics that may most strongly influence eventual academic success.     

Predicting acceptance of diversity in pre-kindergarten classrooms

This study examined classroom-level contributors to an acceptance of diversity in publicly supported pre-kindergarten classrooms across 11 states. Classroom composition, process quality, and teacher characteristics were examined as predictors of diversity-promoting practices as measured by the ECERS-R, acceptance of diversity construct. Findings reveal that emotional climate, bilingual classrooms, family poverty levels within classrooms, and Latino teacher ethnicity are predictive of diversity-promoting classrooms; while classroom-level ethnic sameness to teacher prohibits diversity-promoting practices in pre-kindergarten classrooms.     

Associations between peer bullying and classroom concentration: evidence for mediation by perceived personal safety and relationship with teacher

Being bullied is associated with a psycho-social maladjustment during childhood. One hitherto largely overlooked correlate is disrupted classroom concentration. Using data collected from 364 9–11-year-old children attending seven junior schools in the UK, we tested a model in which children’s perceived safety in two contexts (classroom and playground) and their perceived relationship with their teacher were hypothesised to mediate the association between being bullied and classroom concentration. Two analytical approaches to testing multiple mediation – product of coefficients and bootstrapping – supported the model. None of the mediation effects was moderated by sex but they were by year; in all cases the mediation effect was stronger in the older children than in the younger children (but still significant among the latter). These data suggest mechanisms through which bullying might have its effects on classroom concentration. The practical and theoretical implications are discussed.     

The influence of personality characteristics on children's intrinsic reading motivation

Research suggests that children's motivation to read is influenced by their level of reading skill and reading self-concept. However, it is possible that characteristics unrelated to reading, such as underlying personality characteristics, may also influence children's motivation to read. The current study examined the extent to which children's intrinsic reading motivation was predicted by their reading skill, reading self-concept, and personality characteristics. Two hundred and ninety five children (aged 10–11) completed questionnaires measuring reading motivation, reading self-concept, personality characteristics, and also completed a reading assessment. It was found that personality explained significant variance in intrinsic reading motivation after accounting for reading skill and reading self-concept. Furthermore, personality factors accounted for similar amounts of variance in intrinsic reading motivation as reading self-concept and skill. The implications for improving children's motivation to read are discussed, in addition to the importance of tailoring educational and motivational strategies to individuals.