Evaluating the Effectiveness of a ‘Real‐World’ Shared Reading Intervention for Preschool Children and Their Families: A Randomised Controlled Trial

Background Shared reading interventions can impact positively on preschool children's language development and on their caregiver's attitudes/behaviours towards reading. However, a number of barriers may discourage families from engaging with these interventions, particularly families from lower socio‐economic status (SES) backgrounds. We investigated how families from such backgrounds responded to an intervention designed explicitly to overcome these barriers. Methods In a preregistered cluster randomised controlled trial, 85 lower SES families and their 3‐year‐old to 4‐year‐old children from 10 different preschools were randomly allocated to take part in The Reader's Shared Reading programme (intervention) or an existing ‘Story Time’ group at a library (control) once a week for 8 weeks. Three outcome measures were assessed at baseline and post intervention: (1) attendance, (2) enjoyment of the reading groups and (3) caregivers' knowledge of, attitudes and behaviours towards reading. A fourth − children's vocabulary – was assessed at baseline and 4 weeks post intervention. Results Families were significantly more likely to attend the intervention group and rated it more favourably, compared with the control group. However, there were no significant effects on caregivers' knowledge, attitudes and behaviours or on children's language. Conclusion The intervention was only successful in engaging families from disadvantaged backgrounds in shared reading. Implications for the use, duration and intensity of shared reading interventions are discussed

MAGIC-2D simulations of high efficiency hollow beam klystrons

Results from MAGIC-2D simulations of hollow beam, 800 MHz klystrons, with efficiencies on the order of 85% are presented. Such tubes employ the core oscillation method of electron bunching, which allows for most electrons in the beam to be contained within the bunch at the output cavity. By moving towards hollow beam geometries, the bunch at the output cavity presents a favourable phase and spatial profile for energy extraction, and thus, the overall tube efficiency can be maximised

On the global nonlinear instability of the rotating-disk flow over a finite domain

Direct numerical simulations based on the incompressible nonlinear Navier–Stokes equations of the flow over the surface of a rotating disk have been conducted. An impulsive disturbance was introduced and its development as it travelled radially outwards and ultimately transitioned to turbulence has been analysed. Of particular interest was whether the nonlinear stability is related to the linear stability properties. Specifically three disk-edge conditions were considered; (i) a sponge region forcing the flow back to laminar flow, (ii) a disk edge, where the disk was assumed to be infinitely thin, and (iii) a physically-realistic disk edge of finite thickness. This work expands on the linear simulations presented by Appelquist et al. (J. Fluid. Mech., vol. 765, 2015, pp. 612-631), where, for case (i), this configuration was shown to be globally linearly unstable when the sponge region effectively models the influence of the turbulence on the flow field. In contrast, case (ii) was mentioned there to be linearly globally stable, and here, where nonlinearity is included, it is shown that both case (ii) and (iii) are nonlinearly globally unstable. The simulations show that the flow can be globally linearly stable if the linear wavepacket has a positive front velocity. However, in the same flow field, a nonlinear global instability can emerge, which is shown to depend on the outer turbulent region generating a linear inward-travelling mode that sustains a transition-front within the domain. The results show that the front position does not approach the critical Reynolds number for the local absolute instability, R = 507. Instead, the front approaches R = 583 and both the temporal frequency and spatial growth rate correspond to a global mode originating at this position.Swedish Research Counci

Numerical design of high efficiency klystrons using core oscillation bunching

1-D and 2-D numerical simulations of 800 MHz klystrons with efficiencies approaching 90% are presented. While traditional klystrons employ monotonic electron bunching along their lengths, the core oscillation method allows for an improved bunch shape at the output cavity, facilitating maximum energy extraction. The core oscillation bunching scheme proves an attractive method for attaining high efficiency operation in klystrons, which can be used to reduce the power consumption of future particle accelerators

On the effects of suction and injection on the absolute instability of the rotating-disk boundary layer

In this paper we are concerned with the theoretical behavior of the laminar von Kármán boundary-layer flow, extending the work presented by Lingwood [J. Fluid Mech. 299, 17 (1995); 314, 373 (1996)] to the flow with mass transfer at the surface of the disk. It is known that, within specific regions of the parameter space, the flow is absolutely unstable in the radial direction, i.e. disturbances grow in time at every radial location within these regions. Uniform suction through the disk is shown to delay the onset of absolute instability, while uniform injection promotes the onset. By comparing suction and injection velocities of the same magnitude, it is shown that suction has a greater stabilizing effect on the absolute instability than the destabilizing effect of injection. Suction is also strongly stabilizing to both stationary and travelling inviscidly unstable branch-1 modes; injection is destabilizing. Stationary viscously unstable branch-2 modes are strongly stabilized and destabilized by suction and injection, respectively, but travelling branch-2 modes are shown to be much less sensitive to mass transfer through the disk

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