This thesis analyzes a mathematical model for shell structure acoustics, and develops and implements the adjoint equations for this model. The adjoint equations allow the computation of derivatives with respect to large parameter sets in shape optimization problems where the thickness and mid-surface of the shell are computed so as to generate a radiated sound field subject to broad-band design requirements. The structure and acoustics are modeled, respectively, via the Naghdi shell equations, and thin boundary integral equations, with full coupling at the shell mid-surface. In this way, the three-dimensional structural-acoustic equations can be posed as a problem on the two-dimensional mid-surface of the shell. A wide variety of shapes can thus be explored without re-meshing, and the acoustic field can be computed anywhere in the exterior domain with little additional effort. The problem is discretized using triangular MITC shell elements and piecewise-linear Galerkin boundary elements, coupled with a simple one-to-one scheme. Prior optimization work on coupled shell-acoustics problems has been focused on applications with design requirements over a small range of frequencies. These problems are amenable to a number of simplifying assumptions. In particular, it is often assumed that the structure is dense enough that the air pressure loading can be neglected, or that the structural motions can be expanded in a basis of low-frequency eigenmodes. Optimization of this kind can be done with reasonable success using a small number of shape parameters because simple modal analysis permits a reasonable knowledge of the parts of the design that will require modification. None of these assumptions are made in this thesis. By using adjoint equations, derivatives of the radiated field can be efficiently computed with respect to large numbers of shape parameters, allowing a much richer space of shapes, and thus, a broader range of design problems to be considered. The adjoint equation approach developed in this thesis is applied to the computation of optimal mid-surfaces and shell thicknesses, using a large shape parameter set, proportional in size to the number of degrees of freedom in the underlying finite element discretization.

Nonlinear acoustic media for implementations of parametric generation of low frequencies has so far been restricted to small values of the parameter B/A, typically between 3 and 13. Parametric amplification, defined as the generation of a low difference frequency signal resulting from the nonlinear interactions of two higher frequency fundamentals is enhanced by medium with a large coefficient of nonlinearity and low sound speed. The acoustic properties of a highly nonlinear medium were estimated and introduced in a numerical model, to evaluate the parametric amplification induced by a thin layer of such material in contact with a spherical transducer. The numerical model predicted a significant enhancement of the sound pressure level for the difference frequency component relative to that obtained when the transducer is driven linearly at the difference frequency. A source was then constructed to compare the theoretical predictions with experimental values and an enhancement of 17dB compared to the linear operation of the transducer was measured. The difference between the parametric amplification achieved with the nonlinear medium and the parametric amplification that would be obtained in water is 73dB.

To acquire heat transfer measurements of a high temperature Mach two flow a water-cooled calorimeter was placed in the flow and the water temperature rise was used to calculate the heat transfer rate and the recovery temperature of the gas. In addition, a graphite rod with a stainless steel tube at its core was used to measure the total pressure of the flow. This pressure probe was swept through the flow for two test runs to acquire a stagnation pressure profile of the gas flow. All results were compared to NASA CEA computer simulation code results. The heat transfer and recovery temperature results agreed well with the computer simulation code, while the total pressure results from the probe data agree excellently with the computer simulation code. A sensitivity analysis on the results was also preformed on the results.

Thesis (M.S.M.E.)--University of Washington, 2009. / Includes bibliographical references (p.75-77). Also available on the World Wide Web.

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains viii, 113 p. : ill. (some col.), col. map. Vita. Includes abstract. Includes bibliographical references.

Thesis (M.S.M.E.)--University of Washington, 2009. / Title from Web page (viewed on Feb. 3, 2010). Includes bibliographical references (p.75-77).

Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): Charles W. Therrien, Murali Tummala. Includes bibliographical references (p. 83-84). Also available online.

Thesis (M.S. in Electrical Engineering and M.S. in Engineering Acoustics)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Roberto Cristi, Kevin B. Smith. Includes bibliographical references (p. 91-94). Also available online.

The sound transmission loss of a range of plywood panels was measured to investigate the influence of the orthotropic stiffness of the plywood panels. The plywood panels were tested as single and also double leaf partitions, with a range of stud configurations. A new method was developed for predicting the sound transmission loss of single leaf partitions with both orthotropic and frequency dependent stiffness values. The sound transmission loss was evaluated for two significantly different sample sizes. The observed influence of the sample size on the measured sound transmission loss was profound. The construction of the partition was shown to significantly affect the influence of the sample size on the sound transmission loss. A qualitative analysis based on existing published research of the contributing factors is presented, and methods for adjusting the results for the small sample size for comparison with the large results were developed. The influence of a range of acoustic treatments of lightweight plywood partitions was investigated. The treatments involved internal viscoelastic materials and decoupled mass loaded barriers in various arrangements. The attachment between the treatment and the plywood panel was found to influence the sound transmission loss significantly. A prediction method based on published models was modified to allow the influence of the treatments to be included. Reasonable agreement was achieved between the predicted and measured results for a wide range of samples. A prediction method was developed that accounts for the influence of orthotropic, frequency dependent material parameters. This method utilised an adaptive, numerical integration method to solve an analytical formulation for the sound transmission loss. The influence of the finite sample size was accounted for using an expression for the finite panel radiation impedance. The finite panel radiation impedance was predicted analytically and an approximation was also presented. The presence of a significant source room niche was accounted for by applying an appropriate limit to the integration range of the angle of incidence. The prediction methods developed are compared with the measured transmission loss results from both the small and large test facilities. Good agreement was seen for some of the predicted results. Generally the agreement within the coincidence region was worse than for the rest of the transmission loss curve. The inclusion of orthotropic and frequency dependent stiffness values significantly improved the agreement within the coincidence region.

The motion of tissues within the human body can be investigated by a number of techniques, including ultrasonic echography. The ultrasonic echo patterns from regions of relatively homogeneous tissue bear an ambiguous relationship to their spatial structure, preventing the use of an lmaging system to study the motion of such tissue. This work describes the development and use of a method of analysing the ultrasonic echoes from tissue to investigate their motion. The properties of the echoes from tissue are studied using a theoretical model, and a number of methods of analysing the echoes are suggested. The theoretical model can also be used to simulate the ultrasonic imaging of such tissues. The apparatus for obtaining and analysing the echoes from tissues is described, with an investigation of the errors involved in the digitisation of analogue signals. The methods of echo analysis proposed for the study of tissue motion are evaluated experimentally, using specimens of fixed liver, and the results show that a correlation method of analysis provides the most consistent measure of tissue motion. This method is applied to the analysis of the in vivo motion of soft tissue. The majority of measurements are taken on the livers of normal subjects, with a simultaneous recording of the electrocardiograph. The amplitude, frequency and phase of the motion are measured and the results correlated with the electrocardiograph. The conclusions from this work are that the stochastic properties of the ultrasonic echoes from soft tissues require the use of statistical methods of analysis to study successfully tissue motion. Estimates are made of the extent to which the phenomenon of tissue motion can be used in the characterisation of the pathological state of tissue.