Simulation of ultrasonic lamb wave generation, propagation and detection for an air coupled robotic scanner

A computer simulator, to facilitate the design and assessment of a reconfigurable, air-coupled ultrasonic scanner is described and evaluated. The specific scanning system comprises a team of remote sensing agents, in the form of miniature robotic platforms that can reposition non-contact Lamb wave transducers over a plate type of structure, for the purpose of non-destructive evaluation (NDE). The overall objective is to implement reconfigurable array scanning, where transmission and reception are facilitated by different sensing agents which can be organised in a variety of pulse-echo and pitch-catch configurations, with guided waves used to generate data in the form of 2-D and 3-D images. The ability to reconfigure the scanner adaptively requires an understanding of the ultrasonic wave generation, its propagation and interaction with potential defects and boundaries. Transducer behaviour has been simulated using a linear systems approximation, with wave propagation in the structure modelled using the local interaction simulation approach (LISA). Integration of the linear systems and LISA approaches are validated for use in Lamb wave scanning by comparison with both analytic techniques and more computationally intensive commercial finite element/difference codes. Starting with fundamental dispersion data, the paper goes on to describe the simulation of wave propagation and the subsequent interaction with artificial defects and plate boundaries, before presenting a theoretical image obtained from a team of sensing agents based on the current generation of sensors and instrumentation

Capitalismo si, pero ¿cual?.

La caída del comunismo en Europa del Este es la más grande transformación del mundo económico y político desde la Segunda Guerra Mundial. Nada tan importante pudo imaginarse. Pero esta transformación ha padecido una lectura política simplista y hasta peligrosa. Consecuencia de lo que yo llamo ideología primitiva: es la idea de que existe una muralla muy definida entre los principios del comunismo y las reglas que preceden la economía capitalista de libre empresa.Según esta ideología, ahora los países víctimas del comunismo, caminan hacia el nirvana del capitalismo puro y duro. De los principios del socialismo de Marx y Lenin pasaremos a los formulados por Adam Smith y David Ricardo sobre el capitalismo en su forma más clásica

A DIVIDA EXTERNA: UMA CHANCE DE SOLUÇÃO?

Não há resumo

Economic aspects of the bee industry /

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