Dynamics of the martial arts high front kick     

Henrik S⊘rensen  Morten Zacho  Erik B. Simonsen  Poul Dyhre‐Poulsen  Klaus Klausen 《Journal of sports sciences》2013,31(6):483-495

Fast unloaded movements (i.e. striking, throwing and kicking) are typically performed in a proximo‐distal sequence, where initially high proximal segments accelerate while distal segments lag behind, after which proximal segments decelerate while distal segments accelerate. The aims of this study were to examine whether proximal segment deceleration is performed actively by antagonist muscles or is a passive consequence of distal segment movement, and whether distal segment acceleration is enhanced by proximal segment deceleration. Seventeen skilled taekwon‐do practitioners were filmed using a high‐speed camera while performing a high front kick. During kicking, EMG recordings were obtained from five major lower extremity muscles. Based on the kinematic data, inverse dynamics computations were performed yielding muscle moments and motion‐dependent moments. The results indicated that thigh deceleration was caused by motion‐dependent moments arising from lower leg motion and not by active deceleration. This was supported by the EMG recordings. Lower leg acceleration was caused partly by a knee extensor muscle moment and partly by a motion‐dependent moment arising from thigh angular velocity. Thus, lower leg acceleration was not enhanced by thigh deceleration. On the contrary, thigh deceleration, although not desirable, is unavoidable because of lower leg acceleration.  相似文献   

Who's Responsible for the Digital Divide? Public Perceptions and Policy Implications     

Dmitry Epstein  Erik C. Nisbet  Tarleton Gillespie 《The Information Society》2013,29(2):92-104

Addressing the reasons for—and the solutions to—the “digital divide” has been on the public agenda since the emergence of the Internet. However, the term has meant quite different things, depending on the audience and the context, and these competing interpretations may in fact orient toward different policy outcomes. The goals of this article are twofold. First, the authors unpack the term “digital divide” and examine how it has been deployed and interpreted across a range of academic and policy discourses. Second, through a framing experiment embedded within a nationally representative survey, the authors demonstrate how presenting respondents with two different conceptual frames of the digital divide may lead to different perceptions of who is most accountable for addressing the issue. From this, they discuss the dynamic relationship between the construction and communication of policy discourse and the public understanding of the digital divide, as well as implications for effective communication about the digital divide and information and communication technology policy to the general public.  相似文献   

The Debate     

Erik P. Bucy 《The Information Society》2013,29(5)

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Recollection of a mentor     

Hans Erik Wennberg 《TechTrends》2003,47(1):2-3

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Learning from instruction: the case of mathematics     

Erik De Corte 《Learning Inquiry》2007,1(1):19-30

Starting from a brief analysis of adaptive competence in mathematics, this article describes a series of research-based characteristics of the kind of learning processes that should be elicited in students to facilitate and support in them the progressive acquisition of such competence. Four major characteristics are discussed in some detail: learning is constructive, self-regulated, situated or contextual, and collaborative. A rather new approach to transfer of learning is then presented in which transfer is conceived as the preparation for future learning. Throughout the article it is argued that, notwithstanding the progress made in research on learning from instruction, numerous and complex issues and problems remain for continued inquiry.  相似文献   

An evaluation of vocational education in Swedish upper secondary schools     

Rune Axelsson  Erik Wallin 《Studies in Educational Evaluation》1984,10(1):89-93

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Primary teachers’ experiences with weekly education outside the classroom during a year     

Erik Mygind  Mads Bølling  Karen Seierøe Barfod 《Education 3-13》2019,47(5):599-611

The aim of the present study was through semi-structured interviews to explore udeskole teacher’s perceptions of motivational factors and challenges while teaching regularly outside the classroom on a weekly basis during a year. Six females and two male udeskole teachers participated and answered an interview guide containing five themes about their motivations, student relations, teaching experiences, challenges and recognition. Udeskole was perceived to have substantial potentials to improve both academic learning and life skills and ‘the common third’, i.e. teacher–pupil relations, was mentioned as a value added to the indoor teaching. Health and safety issues were not perceived as barriers.  相似文献   

Vacuum interrupter, high reliability component of distribution switches, circuit breakers and contactors   总被引：1，自引：0，他引：1  

SLADE Paul G LI Wang-pei MAYO Stephen SMITH R. Kirkland TAYLOR Erik D 《浙江大学学报(A卷英文版)》2007,8(3):335-342

The use of vacuum interrupters(VIs)as the current interruption component for switches,circuit breakers,reclosers and contactors operating at distribution voltages has escalated since their introduction in the mid-1950’s.This electrical product has developed a dominating position for switching and protecting distribution circuits.VIs are even being introduced into switching products operating at transmission voltages.Among the reasons for the VI’s popularity are its compactness,its range of application,its low cost,its superb electrical and mechanical life and its ease of application.Its major advantage is its well-established reliability.In this paper we show how this reliability has been achieved by design,by mechanical life testing and by electrical performance testing.We introduce the“sealed for life”concept for the VI’s integrity.We discuss this in terms of what is meant by a practical leak rate for VIs with a life of over 30 years.We show that a simple high voltage withstand test is an easy and effective method for monitoring the long-term vacuum integrity.Finally we evaluate the need for routine inspection of this electrical product when it is used in adverse ambient environments.  相似文献   

Distinct Age‐Related Differences in Temporal Discounting and Risk Taking in Adolescents and Young Adults     

Erik de Water  Antonius H. N. Cillessen  Anouk Scheres 《Child development》2014,85(5):1881-1897

Age‐related differences in temporal discounting (TD) and risk taking, and their association, were examined in adolescents and young adults (n = 337) aged 12–27 years. Since monetary rewards are typically used in TD and risk‐taking tasks, the association between monetary reward valuation and age and decision making in these tasks was explored as well. TD declined linearly with age, with a particularly sharp decline from 15 to 16 years. In contrast, risk taking was not correlated with age and TD. Reward valuation was not associated with TD and risk taking, and age‐related differences in TD remained significant after controlling for reward valuation. Together, these findings suggest that risk taking and TD are two separate constructs with distinct age‐related differences in adolescence and young adulthood.  相似文献   

E‐mail communication in workplace romantic relationships     

Shelly R.A. Hovick  Renee A. Meyers  C. Erik Timmerman 《Communication Studies》2013,64(4):468-482

This study examined workplace romantic relationship partners’ e‐mail practices and perceptions. Results suggest that the relationship may play an integral role in determining participants' uses and perceptions of e‐mail Workplace romantic couples used e‐mail as frequently as face‐to‐face communication to interact with romantic partners and rated it as both rich and important Participants used e‐mail for both work‐related and social tasks. In addition, participants used business e‐mail addresses for communicating with relational partners and perceived that few organizational policies existed regarding its use. Theoretically, these findings suggest the importance of studying the relationship as a factor that affects e‐mail practices and perceptions. Practically, results indicated that e‐mail may present an additional channel for enhancing communication and connectedness in workplace romantic relationships, and that organizations may need to reflect more carefully about policies concerning e‐mail use in the workplace.  相似文献