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61.
Ioannis Papadopoulos 《Science & Education》2014,23(1):61-77
This paper describes a classroom experiment where students use techniques found in the history of mathematics to learn about an important mathematical idea. More precisely, sixth graders in a primary school follow Archimedes’s method of exhaustion in order to compute the number π. Working in a computer environment, students inscribe and circumscribe regular polygons inside and around a circle in order to find the approximate area of the circle. They then compute the ratio of that approximation to the area of a square with side-length equal to the radius of the circle. This ratio indicates how many times larger the area of the circle is than the area of the square. Mirroring Archimedes’s findings, students discover that as they increase the number of sides in their polygons, the numerical results they obtain convince them that this number is almost equal to 3.14. 相似文献
62.
In most real-life bilateral teleoperators the available physical parameters are uncertain and the communications exhibit variable time-delays. In order to confront these situations and only assuming that a bound of the time-delays is known, the present work reports an adaptive controller which ensures asymptotic convergence of both position errors and velocities to zero, provided that a sufficient condition on the control gains is met. Compared to previous related works that only treated constant time-delays, the stability analysis does not rely on the cascade interconnection structure of the local and remote nonlinear dynamics and the linear interconnection map. Instead, the paper employs a different Lyapunov candidate function that incorporates a strictly positive term, the local and remote position error. Some simulations, in free space and interacting with a rigid wall, and experiments, using two nonlinear manipulators, illustrate the performance of the proposed control scheme in the presence of uncertain parameters and variable time-delays. 相似文献
63.
The present study investigated the reasons of parents request for the initial evaluation to determine their children’s special educational needs (SEN) and the state authorities’ response in the Greek educational system. For the needs of the present study, 250 case files were randomly selected from a state Centre for Differential Diagnosis and Support, which is responsible for the identification, evaluation and intervention for students with SEN. Various data were recorded, such as parental reason for requesting the evaluation, the official designation for each case, whether the parent accepted the evaluation results and whether any individualised intervention plan or other recommendations were specified. The analysis suggested that most cases involved students with learning disabilities, although a certain degree of disagreement in the classification of students was observed. For the majority of cases, parents accepted the official diagnosis; however, the state centre did not offer an intervention plan to benefit the students in the majority of the cases. Implications based on the present study findings are considered. 相似文献
64.
Eleni A. Kortianou Ioannis G. Nasis Stavroula T. Spetsioti Andreas M. Daskalakis Ioannis Vogiatzis 《Cardiopulmonary Physical Therapy Journal》2010,21(3):12-19
Physical training is beneficial and should be included in the comprehensive management of all patients with COPD independently of disease severity. Different rehabilitative strategies and training modalities have been proposed to optimize exercise tolerance. Interval exercise training has been used as an effective alternative modality to continuous exercise in patients with moderate and severe COPD.Although in healthy elderly individuals and patients with chronic heart failure there is evidence that this training modality is superior to continuous exercise in terms of physiological training effects, in patients with COPD, there is not such evidence. Nevertheless, in patients with COPD application of interval training has been shown to be equally effective to continuous exercise as it induces equivalent physiological training effects but with less symptoms of dyspnea and leg discomfort during training.The main purpose of this review is to summarize previous studies of the effectiveness of interval training in COPD and also to provide arguments in support of the application of interval training to overcome the respiratory and peripheral muscle limiting factors of exercise capacity. To this end we make recommendations on how best to implement interval training in the COPD population in the rehabilitation setting so as to maximize training effects.Key Words: interval exercise training, chronic obstructive pulmonary disease, exercise tolerance, pulmonary rehabilitation 相似文献