1,721,584 research outputs found
Premises for Effective Teaching and Learning : State of the Art, New Outcomes and Perspectives of Classroom Acoustics
Full text linkMany booklets and standards have already been published on classroom acoustics in several countries, based on studies that were completed up to ten years ago and which were mainly focused on the speech intelligibility of pupils under noisy conditions. In the last decade many studies began to consider the complex speech communication scenario in classrooms, where acoustic requirements are needed for both teachers and pupils. The voice monitoring of teachers has revealed challenging conditions for speaking because of bad acoustics, with consequences on vocal health. Research has underlined the importance of voice support from the room, which has led us to reconsider the optimal reverberation time in classrooms, whose tendency is towards higher values than those for listening. On the other hand, it has been proven that a high reverberation increases the listening effort and decreases reading abilities. Thus, the question of the optimal reverberation time for speaking and listening arises, as well as the need to optimize the design of classrooms to support the voice and control the sound tail. The perceived reverberation is closely related to the perceived acoustical quality, which is recognized as the most important environmental aspect in classrooms. Reverberation also amplifies the noise produced by pupils themselves and affects their well-being. To cope with this, a new device has been introduced to inform pupils on the need to lower their voices and respect others. A summary of the state of the art of classroom acoustics is given in this lecture, together with the new findings on the effects of bad acoustics on pupils' learning and well-being and on teachers' vocal behaviour. A new paradigm on speech communication is needed in classrooms that should involve both teaching and learning. Further work is required to investigate the factors that underpin this complex communication scenario
Input/output decoupling problems for high speed trains
No full textDifferent input/output decoupling problems for a nonlinear model of high speed trains are studied. As it is natural in applications, the input/output decoupling is only one of the requirements, which is to be obtained together with asymptotic stability and asymptotic set point output regulation, in the presence of constant disturbances
On the Role of Convexity/concavity in Vector Fields, Flows and Stability/Stabilizability
No full textThe impact of sound field amplification systems on speech perception of pupils with and without language disorders in natural conditions
Full text linkThe purpose of the study was to investigate in natural conditions the impact of sound field amplification systems (SFAS) on the perception of monosyllabic nonsense words in first to fourth-grade students with and without language disorders in classrooms with different acoustics. One hundred forty-five monolingual primary school pupils were included in the study. Two study groups were formed: pupils with typical language development (TD) (n = 145) and pupils with developmental language disorders (LD) (n = 72). Acoustic measurements were made in twelve classrooms with different reverberation time. Monosyllabic nonsense words perception tests, presented by an examiner, were carried out in classrooms with and without SFAS. The number of errors in the test carried out with SFAS in different acoustic conditions reduced in pupils of Grade 1 with TD (Z = –2.273, p = .023; Z = –1.965, p = .049) and with LD (Z = –2.410, p = .016; Z = –2.156, p = .031). The SFAS installed in large classrooms with long reverberation time significantly increased the number of errors in nonsense monosyllables perception (rS = 0.361, p < .01, rS = 0.229, p < .01). The mean number of errors in children with LD was higher than in children with TD in monosyllabic nonsense words tests carried out with and without SFAS (U = 3194, p < .001; U = 3518.5, p < .001). First-grade students benefit from sound field amplification in perception of monosyllabic nonsense words regardless of classrooms acoustics, and irrespective of the level of language development. The positive effect of SFAS on nonsense word perception was not observed in pupils of Grade 2, 3, and 4 of primary school. Classroom acoustics affects the expected positive impact of SFAS for children older than first graders. Amplification increases speech perception and decreases the number of errors in the reproduction of monosyllabic nonsense words in classrooms with short reverberation time
Dynamic disturbance attenuation and approximate optimal control for fully actuated mechanical systems
No full textThe standard solutions of the L2-disturbance attenuation and optimal control problems hinge upon the computation of the solution of a Hamilton-Jacobi (HJ), Hamilton-Jacobi-Bellman (HJB) respectively, partial differential equation or inequality, which may be difficult or impossible to obtain in closed-form. Herein we focus on the matched disturbance attenuation and on the optimal control problems for fully actuated mechanical systems. We propose a methodology to avoid the solution of the resulting HJ (HJB, respectively) partial differential inequality by means of a dynamic state feedback. It is shown that for planar mechanical systems the solution of the matched disturbance attenuation and the optimal control problems can be given in closed-form. © 2011 AACC American Automatic Control Council
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