A rational approach to the synthesis of one-dimensional acoustic filters

The velocity ratio algorithm developed from a heuristic study of transfer matrix multiplication has been employed to bring out the relative effects of the elements constituting a linear, one-dimensional acoustic filter, the overall dimensions of which are fixed, and synthesize a suitable straight-through configuration for a low-pass, wide-band, non-dissipative acoustic filter. The potential of the foregoing approach in applications to the rational design of practical acoustic filters such as automotive mufflers is indicated.

Two-dimensional NMR spectra of oriented molecules

Abstract is not available.

New nondestructive method for three-dimensional photoelasticity

A new set of equations describing completely the optical phenomena in a model involving continuous rotation of secondary axes and secondary principal-stress differences are obtained. These are solved by Peano-Baker method using experimentally determined characteristic parameters for several wavelengths of light. Experimental verifications are obtained for a rectangular bar subjected to combined torsion and tension. Paper was presented at Third SESA International Congress on Experimental Mechanics held in Los Angeles, CA on May 13–18, 1973.

Shape-Dependent Confinement in Ultrasmall Zero-, One-, and Two-Dimensional PbS Nanostructures

Spatial dimensionality affects the degree of confinement when an electron-hole pair is squeezed from one or more dimensions approaching the bulk exciton Bohr radius (alpha(B)) limit. The etectron-hole interaction in zero-dimensional (0D) dots, one-dimensional (1D) rods/wires, and two-dimensional (2D) wells/sheets should be enhanced by the increase in confinement dimensions in the order 0D > 1D > 2D. We report the controlled synthesis of PbS nanomateriats with 0D, 1D, and 2D forms retaining at least one dimension in the strongly confined regime far below alpha(B) (similar to 10 nm for PbS) and provide evidence through varying the exciton-phonon coupling strength that the degree of confinement is systematically weakened by the loss of confinement dimension. Geometry variations show distinguishable far-field optical polarizations, which could find useful applications in polarization-sensitive devices.

Quasi-three-dimensional elastic stresses in rotating disks

A method is presented to obtain stresses and displacements in rotating disks by taking into account the effect of out-of-plane restraint conditions at the hub. The stresses and displacements are obtained in a non-dimensional form, presented in the form of graphs and compared with the generalized plane stress solution.

A new nondestructive method for three-dimensional photoelasticity

A new set of equations describing completely the optical phenomena in a model involving continuous rotation of secondary axes and secondary principal-stress differences are obtained. These are solved by Peano-Baker method using experimentally determined characteristic parameters for several wavelengths of light. Experimental verifications are obtained for a rectangular bar subjected to combined torsion and tension.

Quasi-three-dimensional elastic stresses in rotating disks

A method is presented to obtain stresses and displacements in rotating disks by taking into account the effect of out-of-plane restraint conditions at the hub. The stresses and displacements are obtained in a non-dimensional form, presented in the form of graphs and compared with the generalized plane stress solution.

Determination of the optically equivalent model in three-dimensional photoelasticity

Any stressed photoelastic medium can be reduced to an optically equivalent model consisting of a linear retarder, with retardation 1 and principal axis at azimuth 1, and a pure rotator of power 2. The paper describes two simple methods to determine these quantities experimentally. Further, a method is described to overcome the problem of rotational effects in scattered-light investigations. This new method makes use of the experimentally determined characteristic parameters

Line tension of a two dimensional gas-liquid interface

In two dimensional (2D) gas-liquid systems, the reported simulation values of line tension are known to disagree with the existing theoretical estimates. We find that while the simulation erred in truncating the range of the interaction potential, and as a result grossly underestimated the actual value, the earlier theoretical calculation was also limited by several approximations. When both the simulation and the theory are improved, we find that the estimate of line tension is in better agreement with each other. The small value of surface tension suggests increased influence of noncircular clusters in 2D gas-liquid nucleation, as indeed observed in a recent simulation.

Three-dimensional corner reflector of arbitrary apex angle

A method of analysing a 3-dimensional corner reflector antenna of arbitrary apex angle is given. Expressions have been obtained for the far field of the 3-dimensional corner reflector fed by a dipole. The radiation resistance and the directive gain of the antenna have been calculated. The method described is applicable even when the feed dipole is arbitrarily oriented. It is found that the radiation along a prescribed direction can be circularly polarised (right or left) by suitably orienting the feed dipole.

Possibility of a condensed phase of excitons because of phonon induced exciton-exciton pairing

In this paper we study the phonon-induced exciton-exciton interaction. It is found that the interaction can be attractive under certain conditions. Taking into account this attractive interaction, the pairing of excitons with opposite momenta is studied and the excitation spectrum determined. The results are similar to a system of bosons. There appears to be some possibility of superfluid behaviour.

Iterative solution of a class of linear equations with application to reconstruction of three-dimensional object arrays

An iterative algorithm baaed on probabilistic estimation is described for obtaining the minimum-norm solution of a very large, consistent, linear system of equations AX = g where A is an (m times n) matrix with non-negative elements, x and g are respectively (n times 1) and (m times 1) vectors with positive components.

Two-dimensional heat conduction with phase change in a semi-infinite mould

Analytical solution of a 2-dimensional problem of solidification of a superheated liquid in a semi-infinite mould has been studied in this paper. On the boundary, the prescribed temperature is such that the solidification starts simultaneously at all points of the boundary. Results are also given for the 2-dimensional ablation problem. The solution of the heat conduction equation has been obtained in terms of multiple Laplace integrals involving suitable unknown fictitious initial temperatures. These fictitious initial temperatures have interesting physical interpretations. By choosing suitable series expansions for fictitious initial temperatures and moving interface boundary, the unknown quantities can be determined. Solidification thickness has been calculated for short time and effect of parameters on the solidification thickness has been shown with the help of graphs.

Crystal structure and semiconductor-metal transition of the quasi-two-dimensional transition metal oxide, La2NiO4

Abstract is not available.