Longitudinal analysis of semiconductor lasers with low reflectivity facets

An analysis is made of longitudinal effects in semiconductor lasers with low facet reflectivities. For this purpose, a self-consistent model is used based on the beam propagation method, which takes into account both the lateral and longitudinal dimension. The calculations show that longitudinal effects have a significant influence on the output fields in the laser.     

Improved coupled-mode theory of anisotropic optical waveguides

A coupled-mode equation for anisotropic waveguide systems of arbitrary cross section and general dielectric distribution is derived. Numerical results comparing the exact calculations to those of the method of Hardy et al. (Opt. Lett., vol.11, 742-4, 1986) show that the same accuracy can be obtained not only for TE, but also for TM mode coupling in the case of anisotropic waveguides, and the improved coupled-mode theory is applicable to the situation when moderately strong coupling occurs under the condition where the edge-to-edge separation of two coupled guides D₂ is about 0.1 μm     

The fourth amendment and emerging communications technologies

The key US Supreme Court case that addresses the constitutionality of government surveillance is nearly four decades old. This overview considers how technological developments have strained the prevailing legal framework and highlights areas for reform.     

An environment for developing fault-tolerant software

An environment that supports execution of programs using both N-version programming and recovery blocks in a uniform manner is described. For N-version programming, the system offers an easy and flexible way of specifying the target machines for the separate versions. The basic unit of fault tolerance supported by this system is at the procedure or function level. Each such program unit can be packaged as its own task, and different fault tolerance techniques can subsequently be employed, even within the same application. The environment also allows versions to be written in different programming languages and executed on different machines. This enhances the independence between the different versions, making the fault tolerance techniques more effective. This environment has been developed for use on Unix-based hosts and currently runs on a network of Sun and DEC workstations     

Shear deformation under impact conditions

The deformation behavior that results from falling weight impact testing with flat-headed darts is analyzed in terms of elasticity and plasticity. From a comparison of the time and temperature dependence of the yield stress that is observed during a falling weight test with the same dependences of the yield stress during simple shear tests, it is concluded that the use of flat-headed darts results in strong shear loading. Consequently most of the plastic deformation takes place by shear flow. Of practical interest is that this leads to a simple dependence of the yield stress during the impact test and the impact energy on the plate thickness. Furthermore, for a number of cases this result allows a direct conversion of temperature effects to time effects. In practice this means that it is possible to simulate the impact behavior at very high impact rates simply by performing impact tests at lower temperatures.