Based on the theory of continuously distributed dislocations, the equilibrium equations for both edge-and screw-dislocation pile-ups in materials composed of soft and hard phases are formulated in terms of a singular integral equation. The integral equation is solved exactly by using the Wiener-Hopf technique with Mellin transforms. The dislocation distribution function is found in explicit form. It is shown that the number of dislocations in the piled-up array can be determined directly from the Mellin transform of the distribution function without its inverse transform.

If an obstacle exists in the vicinity of the free surface of a half-space and a stress field is applied in such a manner that dislocations are pushed towards the obstacle, an array of dislocations then piles up into an equilibrium distribution against the obstacle. The distributions of dislocations are obtained by the Wiener--Hopf technique for the edge and screw dislocations. The total strength of dislocations (Burgers vector multiplied by the number of dislocations) distributed in the distance L is calculated as 0.9211' (1-I').,.AL/G for edge dislocations and 2.,.AL/G for screw dislocations, where G, I' are the shear modulus and Poisson ratio respectively and.,.A is the applied stress. The result can be applied to crack problems. The above two numbers for the total strength of dislocations give the crack openings at the free surface for the extensional mode and the antiplane shear mode of fracture, respectively.

We present a flexible and dynamically programmable optical filter based on an all fiber Michelson Gires-Turnois interferometer (MGTI). Arbitrary filter transfer functions can be accomplished by dynamically adjusting the reflectance of fiber loop mirrors.

Electric-field-assisted assembly is used to position ultra-thin, micron-sized sheets of alternative materials in high density arrays on silicon substrates. Dielectrophoretic forces induced on the solution-suspended polarizable sheets by a spatially varying, non-uniform electric field attract and align the sheets to lithographically defined assembly electrodes on the substrate. Studying the assembly of 10 µm long, 100 nm thick chromium sheets fabricated in three different widths of 1.2, 2.4, and 3.0 µm showed that the maximum array density decreases with increasing width. This result provides insight into the assembly of sheets composed of doped semiconductor device layers and junctions.

All-optical techniques for microwave and radio frequency (RF) signal processing has attracted considerable attention in recent years. An important optical component in these all-optical signal processing techniques is the optical filter. Tunable optical filters with a variety of transfer functions have been proposed. However, adjustability of the optical filter transfer function is required to provide an extra degree of control. This adjustability of the shape of the transfer function has not been addressed adequately in the literature. In this paper, we report on the theoretical basis for an allfiber based adjustable transfer function optical filter. In particular, we model the optical filter using FO-circuit transfer matrices and Jones matrices to fully describe the state of polarization changes of the optical signals through the optical filter. The filter is based on an all fiber Michelson Gires-Turnois interferometer (MGTI). The Gires-Turnois resonators (GTRs) required for the formation of the MGTI are realized by pairs of fiber-loop mirrors (FLMs) in the two arms of the Michelson interferometer. The optical reflectivity of the GTRs is control via adjustment of the polarization in the fiber loop mirrors. We show that arbitrary transfer functions can be realized by adjusting the reflectivity of the FLMs as well as the cavity length of the fiber based GTRs.