Current Issue : July - September Volume : 2015 Issue Number : 3 Articles : 4 Articles
Anexact solution for free vibrations of a series of uniformEuler-Bernoulli beams connected byKelvin-Voigt is developed.Thebeams\nhave the same length and end conditions but can have different material or geometric properties. An example of five concentric\nbeams connected by viscoelastic layers is considered...
The analysis of acoustic emissions generated by the interaction between the wind and a building�s\nfacade of approximately 90 m high, located in the city of Montevideo, is presented. There is a helipad\non the roof of the building. It is surrounded by a perforated plate (4.87 m high). Once the\nbuilding was finished, complaints about the noise annoyance were expressed by some neighbors\nand working population in the building. Measurements of sound pressure levels on the site have\nbeen done. Also the possible acoustic sources were physically characterized. The noise source was\nidentified: the acoustical emissions were associated with a phenomenon caused by wind speeds\nabove 20 m/s from different directions, generating high sounds pressure levels in octave band of\n4000 Hz, after its passage through the perforated plate on the contour of the roof. These studies\nwere complemented by measurements in wind tunnel using a physical model built with the same\nplate installed in the building, which allowed verifying the results....
The experiment involves creating a sound wave that propagates down a pipe with 8 transducers\nattached at equally spaced intervals of 0.01016 m. The numerical methodââ?¬â?the Cross Correlation\nMethod, used to solve for the phase component, creates a high correlation value, but the speed of\nsound varies immensely. The method involves a Fast Fourier Transform (FFT) of the collected data,\nwhich is used to find the phase of the sound wave, and the slope of the position versus time\ngraph, which is used to calculate the speed of sound. This high correlation value shows that the\ndata are correct, but the numerical method for analyzing the data is incorrect....
In nuclear reactors cooled by liquid metals, ultrasound is the only type of field that allows obtaining\nimages of the reactor cores and diagnostics of the integrity of the fuel assemblies. The article\ndiscusses the features of the practical realization of ultrasonic imaging systems based on phased\narrays and offers an alternative solution of imaging on the basis of the acoustic lenses of refractive\nand diffraction types. Using lenses eliminates many of the technical and technological problems\nassociated with the development of multi-element phased arrays. It is shown that lens systems allow\nusing traditional methods of transformation of acoustic fields into the visible images by 2D\npiezo matrix and a more promising way of acoustooptical transformation based on coherent optical\ninterferometry....
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