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

Beatriz B. Gomes  Filipe A.V. Conceição  David R. Pendergast  Ross H. Sanders  Mário A.P. Vaz  João Paulo Vilas-Boas 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(4):394-403

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.  相似文献   

Equating Exams as a Prerequisite for Maintaining Standards: Experience with Dutch centralised secondary examinations     

René V. J. Alberts 《Assessment in Education: Principles, Policy & Practice》2001,8(3):353-367

National examinations in The Netherlands play an important role both as school-leaving exams and in providing access to tertiary education. For most subjects the exams consist of two parts: a part internal to the school which is constructed, set and marked by the individual schoolteacher; and a central part which is constructed by Cito, the Dutch National Institute for Educational Measurement, but administered and marked by the schools. For many years, and until the 1990s, the procedures for the construction of the exams and for setting cut-off scores remained largely unchanged. In the 1990s, in response to concerns over standards, studies were conducted which demonstrated the necessity and feasibility of using equating procedures. Acting upon the outcomes, the State Secretary for Education and Science provided funds for introducing and maintaining equating as a standard procedure in central exams. From 1994 onwards, more and more exams have involved formal equating procedures.  相似文献   

The Teaching of the Mathematical Disciplines in Sixteenth-Century Spain*     

Víctor Navarro-Brotóns 《Science & Education》2006,15(2-4):209-233

This essay examines some aspects of the teaching of mathematics and its applications in three of the principal sixteenth century Spanish universities (Salamanca, Valencia and Alcalá) and in other institutions sponsored by the monarchy, such as the “Casa de la Contratación” (House of Trade) of Seville and the so-called Academy of Mathematics of Madrid. All three of the above universities had chairs of mathematics. In the Casa de la Contratación and other nautical schools the teaching of mathematics was oriented toward providing the foundations of navigation (nautical astronomy, instruments and maps, etc.). The Academy of Mathematics was oriented mainly towards subjects related to cosmography and navigation. Although the different areas of the teaching of mathematics imposed conditions on the discourses and practices of the mathematical disciplines, they did not impede the circulation of persons, knowledge, and practices among these areas. This work has partially financed by grants from Spanish Ministry of Science and Technology (BHA 2000–1456) and from Ministry of Education and Science (BHA2003-08394-(02-01).  相似文献   

Teaching social studies to high school students with academic handicaps in a mainstreamed setting: effects of a computerized study guide     

S V Horton  T C Lovitt  A Givens  R Nelson 《Journal of learning disabilities》1989,22(2):102-107

This research investigated the effectiveness of a computerized study guide, in comparison to a notetaking condition, as a method to increase textbook comprehension among students with learning disabilities and remedial education pupils enrolled in a ninth-grade world geography class. Results indicated that the computerized study guide produced significantly higher performance than notetaking for both groups of students. There was no significant difference in the performance of the two groups within treatments. Several practical issues concerning the implementation of computerized study guides in secondary programs serving students with academic handicaps are discussed.  相似文献   

Self-esteem and Academic Achievement Among Adolescents   总被引：1，自引：0，他引：1  

M. Alves-Martins  F. Peixoto  M. Gouveia-Pereira  V. Amaral  I. Pedro 《教育心理学》2002,22(1):51-62

The main purpose of this research is to analyse what strategies are pursued in order to protect self-esteem when it is threatened by a negative self-evaluation of school competence. Participants were 838 secondary-school students from the seventh to the ninth grades. Data were collected using Harter's Self-Perception Profile for Adolescents, together with a Scale of Attitudes towards School. Our results show that there are significant differences between the self-esteem enjoyed by successful and unsuccessful students in the seventh grade; such differences disappear in the eighth and ninth grades. They also reveal success-related differences in domain-specific self-evaluation. We also found that students with low levels of academic achievement attribute less importance to school-related areas and reveal less favourable attitudes towards school. We discuss these results in terms of Harter's self-esteem model and Robinson and Tayler's self-esteem protection model.  相似文献   

Book reviews     

Neil?CameronEmail author  Sandra?StotskyEmail author 《Academic Questions》2003,16(3):84-95

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The deterioration and mobilization effects of trauma on social support: childhood maltreatment and adulthood military violence in a Palestinian community sample     

Punamäki RL  Komproe I  Qouta S  El-Masri M  de Jong JT 《Child abuse & neglect》2005,29(4):351-373

OBJECTIVES: To show that exposure to childhood maltreatment deteriorates, whereas exposure to adulthood military violence mobilizes social support; second, to show that associations between traumatic events and mental health problems are mediated through social support and, subsequently, adulthood military violence is associated with low level and childhood maltreatment with high level of mental health symptoms; third, to explore whether the moderating (protecting) effect of sufficient and satisfactory social support would differ among victims of childhood maltreatment and adulthood military violence. METHOD: The participants were a random-sample of Palestinian men and women (n=585) of 16-60 years of age. Exposure to military violence in adulthood was assessed by the Harvard Trauma Questionnaire (HTQ_I), and to childhood maltreatment by a 13-item questionnaire developed for the study. A Social Network Schedule was applied to assess the function, source, and satisfaction with social support, and the Revised SCL90-R Symptoms Checklist to assess mental health symptoms. RESULTS: Findings supported our hypothesis that exposure to childhood maltreatment was associated with low levels of social support, whereas exposure to adulthood military violence was associated with high levels of social support. Contrary to our second hypothesis, both childhood maltreatment and adulthood military violence were associated with high levels of mental health symptoms. Finally, high level and satisfactory social support moderated the association between exposure to military violence in adulthood and mental health symptoms, but not between childhood maltreatment and mental health symptoms. CONCLUSION: The findings emphasize that the nature of trauma, that is, whether familial or political, determines the availability of protective resources versus vulnerability, which should be considered when tailoring interventions to trauma victims.  相似文献   

An ecological perspective on learner-constructed learning spaces     

Crina Damşa  Monika Nerland  Zacharias E. Andreadakis 《British journal of educational technology : journal of the Council for Educational Technology》2019,50(5):2075-2089

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Innovation and Resistance to Change in Bolivian Schools     

Talavera  María Luisa 《Prospects》2002,32(3)

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In context: Some recent Australian writing for adolescents     

I. V. Hansen 《Children‘s Literature in Education》1989,20(3):151-163

He has taught in schools in Australia and England and for over 25 years has been involved in teacher education.  相似文献