The analysis of acoustic waves generated by a transient normal point load applied on a fluid–solid interface is presented. The closed-form exact solution of the wave motion is obtained by using integral transform techniques. The obtained analytical solution provides necessary theoretical background for optimization of fluid-coupled ultrasonic and acoustic wave detection in experiments. Numerical simulation (elastodynamic finite integration technique) is performed to verify the obtained analytical solution. Detailed descriptions of leaky Rayleigh and Scholte wave solutions are presented. A simplified solution to isolate the contributions of leaky Rayleigh and Scholte waves generated by a transient point load is proposed, and closed-form formulations for displacement and stress components are then presented. The simplified solution is compared to the exact solution for two configurations: water/concrete and air/concrete. The excitation effectiveness of leaky Rayleigh waves for the air/concrete configuration is studied, which has practical significance to air-coupled sensing in civil engineering structures.
This paper deals with the elastodynamic finite integration technique for axisymmetric wave propagation in a homogeneous and heterogeneous cylindrical medium ͑CEFIT͒. This special variant of a finite difference time domain ͑FDTD͒ scheme offers a suitable method to calculate real three-dimensional problems in a two-dimensional staggered grid. In order to test the accuracy of the numerical CEFIT code, problems for which analytical solutions are available are presented. These solutions involve wave propagation in an elastic plate, the scattering of a plane longitudinal wave by a spherical obstacle, and ultrasound generation by a thermoelastic laser source. For the latter problem experimental results are included. The CEFIT code also allows the treatment of more complicated problems. Further possible applications are the investigation of elastic waves generated in an acoustic microscope, the simulation of impact-echo measurements in multi-layer systems, axisymmetric wave propagation in arbitrary bodies of revolution, the calculation of elastic wave fields of longitudinal wave transducers with a circular aperture, and the investigation of multi-layer models for particulates.
Standard-Nutzungsbedingungen:Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden.Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen.Sofern die Verfasser die Dokumente unter Open-Content-Lizenzen (insbesondere CC-Lizenzen) zur Verfügung gestellt haben sollten, gelten abweichend von diesen Nutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte. www.econstor.eu DOI 10.1007/s12651-009-0020-z R E S E A R C H P A P E R ZAF (2010) ing on eligible individuals' social origin. In this article we explore the question why there is a correlation between social origin and choice of field of study. Using data from the Saxon survey of high school graduate candidates, we model the decision process of high school students regarding postsecondary education about three month prior to graduation. Our empirical results prove that the effect of social origin on the choice of field of study is the result of an individual decision structured by status maintenance motive, by expected costs for the different types of higher education and training, by individual ability level, by expected success probabilities as well as by the socio-cultural distance to tertiary education. These determinants of the choice of field of study explains the effect of social origin and, therefore for the aggregate, the persistent social inequality of opportunities in the access to field of study.
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