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Julie Marshall 《International Journal of Disability, Development & Education》1997,44(4):341-365
Knowledge about paediatric speech and language difficulties, training for and contact with children with such problems and views on service developments were explored using a written questionnaire, completed by 84 Tanzanian health and education professionals. Additionally, two sets of interviews were carried out, one with a subset of questionnaire respondents and another with a group of 14 health/education planners and administrators. Results showed that whilst only 41 % of respondents had received training about speech and language difficulties, 68% considered themselves to be responsible for assisting children with such problems. Levels of knowledge were significantly higher in the special education group, but were not significantly related to training, exposure to speech and language therapists, or professional responsibility. However, knowledge levels were significantly related to daily contact with children with speech and language difficulties. No evidence of research or planning for children with such difficulties was discovered. Views on service provision favoured educational over health‐based provision. Qualitative information on attitudes and beliefs about speech and language difficulties did not contradict previous data on disabilities. The implications for Tanzania and other similar countries are discussed. Improvements to the questionnaire are discussed. More data are needed in order to facilitate appropriate service development. 相似文献
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G. Welch R. Purves D. Hargreaves N. Marshall 《British Educational Research Journal》2011,37(2):285-315
The article reports an Economic and Social Research Council‐funded study of the early career experiences of secondary school music teachers in England, set within a wider national picture of decreasing age‐related pupil engagement with school music, career perceptions of music teaching, variable patterns of teacher recruitment and possible mismatches between the musical biographies of young people and intending music teachers. Qualitative and quantitative data were collected from a short‐term longitudinal survey (first questionnaire: n = 74, second questionnaire: n = 29), supplemented by case studies (n = 6) and open‐ended, written questions (n = 20). Analyses suggest that only a half of the newly qualified participants chose to teach full‐time in a mainstream, state‐funded school music classroom. Of these, the majority were faced with a range of early career challenges stemming from curricular, extra‐curricular and non‐curricular school expectations. These included the need to balance their existing musical performer identity with that of being a new teacher. 相似文献
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Robert B. Anderson Julius A. Marshall Andrea L’Afflitto 《Journal of The Franklin Institute》2021,358(12):6281-6308
In classical model reference adaptive control (MRAC), the adaptive rates must be tuned to meet multiple competing objectives. Large adaptive rates guarantee rapid convergence of the trajectory tracking error to zero. However, large adaptive rates may also induce saturation of the actuators and excessive overshoots of the closed-loop system’s trajectory tracking error. Conversely, low adaptive rates may produce unsatisfactory trajectory tracking performances. To overcome these limitations, in the classical MRAC framework, the adaptive rates must be tuned through an iterative process. Alternative approaches require to modify the plant’s reference model or the reference command input. This paper presents the first MRAC laws for nonlinear dynamical systems affected by matched and parametric uncertainties that constrain both the closed-loop system’s trajectory tracking error and the control input at all times within user-defined bounds, and enforce a user-defined rate of convergence on the trajectory tracking error. By applying the proposed MRAC laws, the adaptive rates can be set arbitrarily large and both the plant’s reference model and the reference command input can be chosen arbitrarily. The user-defined rate of convergence of the closed-loop plant’s trajectory is enforced by introducing a user-defined auxiliary reference model, which converges to the trajectory tracking error obtained by applying the classical MRAC laws before its transient dynamics has decayed, and steering the trajectory tracking error to the auxiliary reference model at a rate of convergence that is higher than the rate of convergence of the plant’s reference model. The ability of the proposed MRAC laws to prescribe the performance of the closed-loop system’s trajectory tracking error and control input is guaranteed by barrier Lyapunov functions. Numerical simulations illustrate both the applicability of our theoretical results and their effectiveness compared to other techniques such as prescribed performance control, which allows to constrain both the rate of convergence and the maximum overshoot on the trajectory tracking error of uncertain systems. 相似文献
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