Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 64-68). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 64-68). Also available on the Internet.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 94-97). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 161-168). Available also in a digital version from Dissertation Abstracts.

by Andrew E. Yagle, Bernard C. Levy. / "September, 1983." / Bibliography p. 18-19. / Supported by the Air Force Office of Scientific Research under Grant AFOSR-82-0135

Analisamos um problema de transmissão de ondas viscoelásticas. Isto é, estudamos a propagação da onda sobre materiais consistindo de componentes elástica e viscoelástica em um conjunto aberto, conexo e limitado com fronteira suave e fronteira com condições de transmissão. Mostramos que para este tipo de material a dissipação produzida pela parte viscoelástica é suficientemente forte para produzir decaimento exponencial da solução, não importando quão pequeno seja o tamanho da parte viscoelástica. / We consider a transmission problem of viscoelastic waves. That is, we study the wave propagations over materials consisting of elastic and viscoelastic components in a bounded, open connected set with smooth boundary and transmission boundary conditions. We show that for this type decay of the solution, no matter how small is its size.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 211-213. / by Si, Boon-Ing. / M.S.

No description available.

The vibrational energy propagating in straight fluid-filled elastic pipes is carried by the structure as well as by the internal fluid. Part of the energy in the system may also transfer from one medium to the other as propagation occurs. For various types of harmonic disturbance, this study demonstrates that, whether the propagating energy is predominantly conveyed in the shell or in the fluid, large attenuations of the total power flow may be achieved by using an active control approach. As the shell and fluid motions are fully coupled, the implementation of intrusive sources/sensors in the acoustic field can be also avoided. The approach is based on using radial control forces applied to the outer shell wall and error sensors observing the structural motion. A broad analytical study gives insight into the control mechanisms. The cylindrical shell is assumed to be infinite, in vacuo or filled with water. The first disturbance source investigated is a propagating free wave of circumferential order n=0 or n= 1. The control forces are appropriate harmonic line forces radially applied to the structure. The radial displacement of the shell wall at discrete locations downstream of the control forces is minimized using linear quadratic optimal control theory. The attenuation of the total power flow in the system after control is used to study the impact of the fluid on the performance of the control approach. Results for the shell in vacuo are presented for comparison. Considering the breathing mode (n=O), the fluid decreases the control performance when the disturbance is a structural-type incident wave. Significant reductions of the transmitted power flow can be achieved when the disturbance is a fluid-type of wave. Regarding the beam mode (n=1), the fluid increases the control performance below the first acoustic cut-off frequency and decreases it above this frequency. / Ph. D.