Eccentricity effects on acoustic radiation from a spherical source suspended within a thermoviscous fluid sphere.

Acoustic radiation from a spherical source undergoing angularly periodic axisymmetric harmonic surface vibrations while eccentrically suspended within a thermoviscous fluid sphere, which is immersed in a viscous thermally conducting unbounded fluid medium, is analyzed in an exact fashion. The formulation uses the appropriate wave-harmonic field expansions along with the translational addition theorem for spherical wave functions and the relevant boundary conditions to develop a closed-form solution in form of infinite series. The analytical results are illustrated with a numerical example in which the vibrating source is eccentrically positioned within a chemical fluid sphere submerged in water. The modal acoustic radiation impedance load on the source and the radiated far-field pressure are evaluated and discussed for representative values of the parameters characterizing the system. The proposed model can lead to a better understanding of dynamic response of an underwater acoustic lens. It is equally applicable in miniature transducer analysis and design with applications in medical ultrasonics.

Unsteady Effects of Shock Wave Induced Separation

The aim of this series is to publish promptly and in detailed form new material from the field of Numerical Fluid Mechanics and Multidisciplinary Design ...

CHANGES IN PREDICTED MOS DEVICE CHARACTERISTICS DUE TO THE USE OF TWO DIMENSIONAL SOURCE/DRAIN PROFILES.

Two-dimensional MOS device simulation programs such as MINIMOS left bracket 1 right bracket are limited in their validity due to assumptions made in defining the initial two-dimensional source/drain profiles. The two options available to define source/drain regions both construct a two-dimensional profile from one-dimensional profiles normal to the surface. Inaccuracies in forming these source/drain profiles can be expected to effect predicted device characteristics as channel dimensions of the device are reduced. This paper examines these changes by interfacing numerically similated two dimensional source/drain profiles to MINIMOS and comparing predicted I//D-V//D characteristics with 2-D interfacing, 2-D profiles constructed from interfaced 1-D profiles and MINIMOS self generated profiles. Data obtained for simulations of 3 mu m N and P channel devices are presented.