Asymmetric vibrations and chaos in spherical caps under uniform time-varying pressure fields

This paper presents a study on nonlinear asymmetric vibrations in shallow spherical caps under pressure loading. The Novozhilov’s nonlinear shell theory is used for modeling the structural strains. A reduced-order model is developed through the Rayleigh–Ritz method and Lagrange equations. The equations of motion are numerically integrated using an implicit solver. The bifurcation scenario is addressed by varying the external excitation frequency. The occurrence of asymmetric vibrations related to quasiperiodic and chaotic motion is shown through the analysis of time histories, spectra, Poincaré maps, and phase planes

‘Playing a guessing game’: Recognising and responding to anxiety in children with intellectual disability

Background: Children with intellectual disability are at greater risk of developing anxiety than the general population. Limited research has examined the challenges associated with recognising and responding to anxiety in children with intellectual disability, and its perceived impact. Aim: This study aimed to explore anxiety in children with intellectual disability, from the child and parent perspective to better understand how parents and children recognise and respond to anxiety. Method and Procedures: Six children with an intellectual disability (age range: 12–17, four boys) and their mothers participated in a semi-structured interview online. Interviews were transcribed verbatim and interpreted using thematic analysis. Outcome and Results: Mothers elaborated on the difficulties with recognising signs of anxiety due to the impact of the child's primary diagnosis and the overlap of symptoms with co-occurring conditions. Mothers and children discussed the ‘contagious’ effect of anxiety within the household and how this influenced mothers' approaches to managing their child's anxiety. They reported that anxiety limited the meaningful activities in which children and families could engage. Conclusions and Implications: These findings highlight the importance of supporting mothers to recognise their children's anxiety and to assist them with strategies on how best to respond and cope. These findings have implications for future research, and practitioners working in this field

Resonances and nonlinear vibrations of circular cylindrical shells, effects of thermal gradients

In this paper, the results of an experimental campaign focused on the vibrations of shells are presented. More specifically, the goal is to investigate the effect of thermal gradients across the shell thickness on the nonlinear dynamics. The shell is made of polymeric material and an aluminum mass is clamped on one end of the shell; the other shell end is clamped to an electrodynamic shaker, which provides a base harmonic excitation. Tests are performed in a controlled environment where a thermal gradient on the shell thickness is generated by means of a climatic chamber and an internal cartridge heater. Different temperature gradients and base excitation levels have been considered. The nonlinear dynamic scenario is analyzed through amplitude–frequency diagrams, bifurcation diagrams, waterfall diagrams, time histories, Fourier spectra, phase portraits, and Poincaré maps. Results show a strong effect of the temperature on the dynamic response of the shell: subharmonic, quasi-periodic, and chaotic vibrations take place as well as large amplitude vibrations, high sound levels are detected