Nico F. Declercq

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It is known that a handclap in front of the stairs of the great pyramid of Chichen Itza produces a chirp echo which sounds more or less like the sound of a Quetzal bird. The present work describes precise diffraction simulations and attempts to answer the critical question what physical effects cause the formation of the chirp echo. Comparison is made with(More)
One of the most common biological composites is wood material. This natural orthotropic like material is characterized by a high anisotropy determined by the special disposition of the microstructure elements. The anisotropy of wood can be described in various ways using the values of ultrasonic velocities of bulk waves (longitudinal and shear) observed on(More)
Ultrasonic guided waves are capable of rapidly interrogating large, plate-like structures for both nondestructive evaluation and structural health monitoring (SHM) applications. Distributed sparse arrays of inexpensive piezoelectric transducers offer a cost-effective way to automate the interrogation process. However, the sparse nature of the array limits(More)
Strong absorption of sound is often caused by the conversion of sound energy into heat. When this happens, it is not possible to study the interaction of sound with the absorbing material by means of reflected sound characteristics, because there is no reflected sound. Detecting for example the distance that sound travels in a strongly absorbing material,(More)
In electronics, it is well known that filtering devices can be made that are able to decompose a signal instantaneously into a number of real frequency components. This procedure is equivalent to a numerical real time Fourier transform. However, it is also known that an electronic signal can be decomposed not just in real frequency components, but also in(More)
This paper describes the history and the state of the art in radiation mode theory (RMT) in ultrasonics. The RMT originates from electromagnetism in which it has proved to be very efficient in the field of wave guides and discontinuities. In ultrasonics, the RMT made its entrance only a decade ago and has already proved to be very efficient in describing(More)
The anisotropic feature of most crystals, involves a direction dependent wave velocity for each of the possible modes. Paratellurite (Tellurium dioxide) is extraordinary because, for one of the propagation modes, i.e. the quasi shear horizontal (QSH) mode, the anisotropy is exceptional. This results, on the one hand in a very strong directional dependent(More)
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