Theoretical study of refraction effects on noise produced by turbulent jets

The transmission of acoustic disturbances from the interior of a jet into the ambient air is studied. The jet is assumed infinitely long with mean velocity profile independent of streamwise location. The noise generator is a sequence of transient sources drifting with the local fluid and confined to a short length of the jet. In Part 1, supersonic jets are considered. Numerical results for mean-square pressure versus angle in the far-field show unexpected peaks which are very sharp. Analysis of simplified models indicates that these are complex quasi-resonant effects which appear to the stationary observer in a high frequency range. The peaks are real for the idealized model, but would be smoothed by mathematical integration over source position, velocity, and frequency. Subsonic jets were considered in part 2, and a preliminary study of the near-field was attempted. Mean-square radial displacements (or mean radial energy flow or space-time correlations of radial pressure gradient) are first found for very simple cases. The most difficult case studied is a sequence of transient sources at the center of a uniform-velocity circular cylindrical jet. Here a numerical triple integration is required and seems feasible although only preliminary results for mean square radial displacement are now available. These preliminary results show disturbances decreasing with increasing radial distance, and with increasing distance upstream and downstream from the source. A trend towards greater downstream disturbances appears even in the near field

Centralized Schools in Ohio

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Asperger's syndrome: learner characteristics and teaching strategies

Students with Asperger's syndrome present a particular challenge for their parents, teachers, and peers. Therefore it is important for teachers working in inclusive settings to become aware of the unique needs of these students. In this paper, challenges for students with Asperger's syndrome are discussed in terms of five aspects; communication, motor clumsiness, obsessional interests, attention and social skills. These characteristics are discussed in a wav that will facilitate teachers' understanding of the difficulties associated with student participation in the school environment. Challenges for teachers are discussed under the headings: inclusive schooling; need for a structured program; behaviour management; communication; and creativity in planning. Adaptive and compensatory strategies for teachers are described which will facilitate learning and participation of students with Asperger's syndrome in the regular classroom

Soil and Drainage

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Planting on Rural School Grounds

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