A study of internal and distributed damping for vibrating turbomachiner blades

Internal and distributed damping as possible methods for reducing the vibration response of turbomachine blades and theoretical methods for analyzing damped vibration were studied. It is demonstrated how the Ritz-Galerkin methods may be used to straightforwardly to analyze forced vibrations with damping. This is done directly without requiring the free vibration eigenfunctions. The Galerkin method is an effective technique for these types of problems. The Ritz method has the further advantage of not needing to satisfy the force type boundary conditions, which is particularly important for plates and shells. But proper functionals representing the forcing and damping terms must be developed, and this is done. Two types of damping--viscous and material (hysteretic) are considered. Both distributed and concentrated exciting forces are treated. Numerical results are obtained for cantilevered beams and rectangular plates. Studies showing the rates of convergence of the solutions are made. In the case of the cantilever beam, approximate solutions from the present methods are compared with the exact solutions

The cancer good news project

Abstract presented at the International Social Marketing Conference 2014, 17-18 July 2014, Melbourne, Australi

The Changing Roles of Science Specialists during a Capacity Building Program for Primary School Science

Science education starts at primary school. Yet, recent research shows primary school teachers lack confidence and competence in teaching science (Prinsley & Johnston, 2015). A Victorian state government science specialist initiative responded to this concern by providing professional learning programs to schools across Victoria. Drawing on cultural historical activity theory (CHAT), this paper reports the analysis of transcripts of interviews with 17 science specialists from eleven schools. It presents the various perceived and enacted science specialist roles, and how they changed over time. The CHAT analysis of the transcripts revealed seven different stages describing trajectories of the science specialism. The variation in the trajectories indicate the importance of the influence of the community in the enactment of the science specialism. Affordances, constraints and challenges of implementing the science specialist role are discussed

Control of Material Damping in High-Q Membrane Microresonators

We study the mechanical quality factors of bilayer aluminum/silicon-nitride membranes. By coating ultrahigh-Q Si3N4 membranes with a more lossy metal, we can precisely measure the effect of material loss on Q's of tensioned resonator modes over a large range of frequencies. We develop a theoretical model that interprets our results and predicts the damping can be reduced significantly by patterning the metal film. Using such patterning, we fabricate Al-Si3N4 membranes with ultrahigh Q at room temperature. Our work elucidates the role of material loss in the Q of membrane resonators and informs the design of hybrid mechanical oscillators for optical-electrical-mechanical quantum interfaces

Vibrational modes of circular free plates under tension

The vibrational frequencies of a plate under tension are given by the eigenvalues $\omega$ of the equation $\Delta^2u-\tau\Delta u=\omega u$. This paper determines the eigenfunctions and eigenvalues of this bi-Laplace problem on the ball under natural (free) boundary conditions. In particular, the fundamental modes --- the eigenfunctions of the lowest nonzero eigenvalue --- are identified and found to have simple angular dependence.Comment: 17 pages. To be submitted for publication shortly

Impacto social: el caso Botnia y el impacto social

La lucha social promovida por la ciudad de Gualeguaychú y que curiosamente nació a partir del alerta de ciudadanos de Fray Bentos –informados de la instalación de las pasteras ENCE y BOTNIA- comenzó a partir de mediados de 2003. Un reclamo iniciado por un grupo de vecinos acompañados por el Intendente de la Ciudad, que marcharon a Uruguay a fin de recabar información, dio paso luego a una movilización masiva que durante más de cinco años fue atravesada por este conflicto y sus repercusiones. Entre ellas, la concurrencia por primera vez del Estado Nacional argentino ante la Corte Internacional de Justicia de La Haya (donde no se había ido, por ejemplo, para resolver el conflicto por Malvinas) y el hecho que un Presidente junto a todo su Gabinete y varios Gobernadores, se trasladaran a la ciudad para declarar al reclamo como “Causa Nacional” (llegada del entonces Presidente Kirchner al Corsódromo, el 15 de mayo de 2005). A partir de ahí distintos sectores económicos, políticos y sociales convergieron en la “Asamblea Ciudadana Ambiental de Gualeguaychú” que como movimiento social fue la nave insignia que procesó y diseñó la lucha con un masivo acompañamiento de la sociedad local, fundamentalmente de los sectores medios que emergieron ante un problema local, de tipo ambiental.Eje: Conferencias.Universidad Nacional de La Plat

Marine educators: Linking personal commitment, education and public policy

This thesis reports on a study of the experiences and beliefs of a sample of marine educators from both Canada and Australia. It investigates the educators’ narratives in order to explore their role in regards to their interactions and relationships between and with policy, community and education within the marine education context

Impacto social: el caso Botnia y el impacto social

La lucha social promovida por la ciudad de Gualeguaychú y que curiosamente nació a partir del alerta de ciudadanos de Fray Bentos –informados de la instalación de las pasteras ENCE y BOTNIA- comenzó a partir de mediados de 2003. Un reclamo iniciado por un grupo de vecinos acompañados por el Intendente de la Ciudad, que marcharon a Uruguay a fin de recabar información, dio paso luego a una movilización masiva que durante más de cinco años fue atravesada por este conflicto y sus repercusiones. Entre ellas, la concurrencia por primera vez del Estado Nacional argentino ante la Corte Internacional de Justicia de La Haya (donde no se había ido, por ejemplo, para resolver el conflicto por Malvinas) y el hecho que un Presidente junto a todo su Gabinete y varios Gobernadores, se trasladaran a la ciudad para declarar al reclamo como “Causa Nacional” (llegada del entonces Presidente Kirchner al Corsódromo, el 15 de mayo de 2005). A partir de ahí distintos sectores económicos, políticos y sociales convergieron en la “Asamblea Ciudadana Ambiental de Gualeguaychú” que como movimiento social fue la nave insignia que procesó y diseñó la lucha con un masivo acompañamiento de la sociedad local, fundamentalmente de los sectores medios que emergieron ante un problema local, de tipo ambiental.Eje: Conferencias.Universidad Nacional de La Plat

Impacto social: el caso Botnia y el impacto social

La lucha social promovida por la ciudad de Gualeguaychú y que curiosamente nació a partir del alerta de ciudadanos de Fray Bentos –informados de la instalación de las pasteras ENCE y BOTNIA- comenzó a partir de mediados de 2003. Un reclamo iniciado por un grupo de vecinos acompañados por el Intendente de la Ciudad, que marcharon a Uruguay a fin de recabar información, dio paso luego a una movilización masiva que durante más de cinco años fue atravesada por este conflicto y sus repercusiones. Entre ellas, la concurrencia por primera vez del Estado Nacional argentino ante la Corte Internacional de Justicia de La Haya (donde no se había ido, por ejemplo, para resolver el conflicto por Malvinas) y el hecho que un Presidente junto a todo su Gabinete y varios Gobernadores, se trasladaran a la ciudad para declarar al reclamo como “Causa Nacional” (llegada del entonces Presidente Kirchner al Corsódromo, el 15 de mayo de 2005). A partir de ahí distintos sectores económicos, políticos y sociales convergieron en la “Asamblea Ciudadana Ambiental de Gualeguaychú” que como movimiento social fue la nave insignia que procesó y diseñó la lucha con un masivo acompañamiento de la sociedad local, fundamentalmente de los sectores medios que emergieron ante un problema local, de tipo ambiental.Eje: Conferencias.Universidad Nacional de La Plat

Passive targeted energy transfers and strong modal interactions in the dynamics of a thin plate with strongly nonlinear attachments

We study Targeted Energy Transfers (TETs) and nonlinear modal interactions attachments occurring in the dynamics of a thin cantilever plate on an elastic foundation with strongly nonlinear lightweight attachments of different configurations in a more complicated system towards industrial applications. We examine two types of shock excitations that excite a subset of plate modes, and systematically study, nonlinear modal interactions and passive broadband targeted energy transfer phenomena occurring between the plate and the attachments. The following attachment configurations are considered: (i) a single ungrounded, strongly (essentially) nonlinear single-degree-of-freedom (SDOF) attachment – termed nonlinear energy sink (NES); (ii) a set of two SDOF NESs attached at different points of the plate; and (iii) a single multi-degree-of-freedom (MDOF) NES with multiple essential stiffness nonlinearities. We perform parametric studies by varying the parameters and locations of the NESs, in order to optimize passive TETs from the plate modes to the attachments, and we showed that the optimal position for the NES attachments are at the antinodes of the linear modes of the plate. The parametric study of the damping coefficient of the SDOF NES showed that TETs decreasing with lower values of the coefficient and moreover we showed that the threshold of maximum energy level of the system with strong TETs occured in discrete models is by far beyond the limits of the engineering design of the continua. We examine in detail the underlying dynamical mechanisms influencing TETs by means of Empirical Mode Decomposition (EMD) in combination with Wavelet Transforms. This integrated approach enables us to systematically study the strong modal interactions occurring between the essentially nonlinear NESs and different plate modes, and to detect the dominant resonance captures between the plate modes and the NESs that cause the observed TETs. Moreover, we perform comparative studies of the performance of different types of NESs and of the linear Tuned-Mass-Dampers (TMDs) attached to the plate instead of the NESs. Finally, the efficacy of using this type of essentially nonlinear attachments as passive absorbers of broadband vibration energy is discussed