Robust block second order sliding mode control for a quadrotor     

L. Luque-Vega  B. Castillo-Toledo  Alexander G. Loukianov 《Journal of The Franklin Institute》2012,349(2):719-739

This paper presents the design of a controller based on the block control technique combined with the super twisting control algorithm for trajectory tracking of a quadrotor helicopter. A first order exact differentiator is used in order to estimate the virtual control inputs, which simplifies the control law design. In addition, the wind parameter resulting from the aerodynamic forces is also estimated in order to ensure robustness against these unmatched perturbations. The stability and finite time convergence of the exact differentiator have been recently proved by means of Lyapunov functions, and therefore the stability analysis of the proposed controller has been carried out along the same lines. The performance and effectiveness of the proposed controller are tested in a simulation study taking into account external disturbances.  相似文献   

“What could be” in Canadian sport facility environmental sustainability     

Cheryl Mallen  Chris Chard 《Sport Management Review》2012,15(2):230-243

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Comparison of 2D video and electrogoniometry measurements of knee flexion angle during a countermovement jump and landing task     

Erich Petushek  Chris Richter  David Donovan  William P. Ebben  Phillip B. Watts  Randall L. Jensen 《Sports Engineering》2012,15(3):159-166

Quantifying countermovement jump (CMJ) and landing knee flexion angle is important for performance and injury risk assessment. The purpose of the study was to compare electrogoniometer (El-Gon)- and video-derived CMJ and landing knee flexion angle. Twenty-two adults performed three CMJs while knee flexion angle was simultaneously assessed using an El-Gon and video. The average systematic offset (RMSE) of the El-Gon-derived knee flexion angle throughout the entire movement was 7.03°?±?2.69°. Excellent reliability was demonstrated by the El-Gon (ICCavg?=?0.92). Countermovement knee flexion angle, maximum landing knee flexion angle and flexion angle at maximum vertical ground reaction force were 12.0°, 10.9°, and 5.7° higher, respectively, when assessed using El-Gon (p?<?0.001), compared to video. Errors between instruments are likely due to El-Gon crosstalk, misalignment and/or axis determination. The El-Gon is a cost-effective and time-efficient alternative to video analysis for the assessment of knee flexion angle if the error is accounted for and the sensor is precisely attached.  相似文献   

DNS白名单会阻碍IPv6的实施吗？     

John rzozowski  Comcast  洪丹  陈树生 《中国教育网络》2010,(7):31-33

什么是DNS白名单？在当今的公共互联网上使用IPv4地址时,解析程序可以向权威的域名服务器查询并接收IPv4的地址A记录。当一位权威DNS的管理员为指定域添加IPv6地址AAAA记录时,它将像A记录和其他RR一样被解析程序查询和接收。  相似文献   

Learning to use the Internet as a study tool: a review of available resources and exploration of students' priorities     

Bond CS  Fevyer D  Pitt C 《Health information and libraries journal》2006,23(3):189-196

BACKGROUND: The Internet is a valuable information tool, but users often struggle to locate good quality information from within the vast amount of information available. OBJECTIVE: The aim of the study was to identify the online information resources available to assist students develop Internet searching skills, and to explore the students' priorities in online guides. METHODS: A qualitative approach was adopted with two phases. The first was a structured search of available online study skills resources. The second comprised 10 group interviews with a total of 60 students at all stages of five undergraduate health and social care related courses at a UK university. RESULTS: The study found that there were good online guides available, but that, perversely, the better guides tended to require the best searching skills to locate them. A few students were enthusiastic about using online support, however the majority felt that if they had the skills to locate such resources they wouldn't use a study guide to improve these skills, and if they did not have the skills they would not think of using an online guide to develop them. CONCLUSIONS: Students wanted assistance when they had problems or questions, rather than sites that offered structured learning experiences. Personal support rather than virtual support was also considered to be most important to the students in this study.  相似文献   

From special to inclusive education in Macau (SAR)     

Chris Forlin 《International Journal of Inclusive Education》2013,17(4):433-443

The education for learners with special education needs (SEN) in Macau (SAR), China, has gradually transitioned over the past 30 years from a completely segregated approach to a more inclusive one. Following a review of the development of special education and the transition towards inclusion in Macau, consideration is given to the enactment of inclusive education in mainstream schools. Interviews with the leaders in a primary and secondary mainstream government school in Macau outline the ways in which learners with SEN are included in mainstream schools. The discussion focuses on a range of issues regarding the inclusion movement in Macau, including management, schooling and the inclusive model that is applied.  相似文献   

Sustaining technological innovation: The example of videoconferencing in English Schools     

Chris Comber  Tony Lawson 《Education and Information Technologies》2013,18(4):641-659

The main factors associated with technology integration have been the subject of research for over a decade. However, the conditions which sustain technological developments have been less frequently investigated. This paper explores this issue in the context of the use of videoconferencing in schools in England. The research took a multiple case-study approach by returning to schools with a reputation for demonstrating innovative policy and practice in videoconferencing, which were the subject of an earlier investigation. Analysis of developments in the interim five-year period led to the construction of a five-level typology of change. Further analysis identified critical dimensions associated with the sustainability of videoconferencing. These included technical and structural factors, as well as policy frameworks and personnel status. The perceived usefulness and relevance of videoconferencing as a learning technology emerges as a central determinant of sustainability, with the conclusion that for policymakers and schools, videoconferencing has become an ‘orphan’ technology.  相似文献   

Analysing the Role of the Subject Head of Department in Secondary Schools in England and Wales: Towards a theoretical framework     

Chris Turner  Ray Bolam 《School Leadership & Management》2013,33(3):373-388

This paper argues that contingency theory offers a useful basis on which to consider the work of subject heads of department (HoDs) in secondary schools, particularly if they are pro-active in attempting to influence the quality of teaching and learning in their curriculum area. We have developed a provisional model which may shed more light on how HoDs actually work with other departmental staff.  相似文献   

Primary school students' metacognitive beliefs about religious education     

Theo van der Zee  Chris Hermans  Cor Aarnoutse 《Educational Research and Evaluation》2013,19(3):271-293

So far scholars have researched beliefs about knowledge, knowing, and learning mainly in the areas of science and mathematics and among secondary school students. In this article, we explore primary school students' metacognitive beliefs about religious education. The article reports on a study involving 656 fifth- and sixth-grade students. We investigated their metacognitive beliefs, how these beliefs interrelate, and which students agree with which beliefs. In the minds of young students 7 categories are discernible: realistic learning, the transformative power of religion, social learning, intrinsic task value motivation, learning satisfaction motivation, the teacher's empathic orientation to learning, and the teacher's respect for students' contributions. These categories and their interrelationships open up new perspectives for the construction of a metacognitive beliefs system and for an interconnected network of beliefs across domains. We also outline implications for religious education in schools.  相似文献   

The generative paradigm     

Chris Loynes 《Journal of Adventure Education & Outdoor Learning》2013,13(2):113-125

This research highlights the learning of female offenders on a 20-day tailor-made experiential adventure education course (Women in Action) delivered by Outward Bound New Zealand. The aims of the course were to increase self-awareness, to develop an understanding of the concept of choice and self responsibility, to improve communication skills and to effectively influence others. Twenty-seven women were interviewed immediately after the course and 14 of these, three months post-course. Most women indicated that their self-confidence had increased and they had become more self-aware. Key factors in facilitating learning opportunities for the women were the instructors and the course environment both physical and social. The holistic course approach provided physical, creative, emotional and reflective opportunities, enabling all the women to develop personally. The challenge of applying their learning on return to prison was highlighted by some participants.