Search

A real time dynamic biomechanical model of the human elbow joint has been used as the first step in the process of calculating time varying joint position from the electromyograms (EMGs) of eight muscles crossing the joint. Since calculation of position has a high sensitivity to errors in the model torque calculation, a genetic algorithm (GA) neural network (NN) has been developed for automatic error reduction in the dynamic model. Genetic algorithms are used to design many neural network structures during a preliminary trial effort, and then each network's performance is ranked to choose a trained network that represents the most accurate result. Experimental results from three subjects have shown model error reduction in 84.2% of the data sets from a subject on which the model had been trained, and 52.6% of the data sets from the subjects on which the model had not been trained. Furthermore, the GA networks reduced the error standard deviation across all subjects, showing that progress in error reduction was made evenly across all data sets.

Monolithically integrated 2*2 semiconductor laser amplifier gate switch arrays have been fabricated and evaluated. Net positive chip gain, high extinction ratio, and high electrical isolation between the integrated laser amplifiers are reported.

Monolithically integrated 4×4 semiconductor laser amplifier gate switch arrays comprising 24 integrated laser amplifiers have been fabricated and evaluated. Net positive optical gain between fibres, high extinction ratio, and low crosstalk are reported.

Optical bistability at 5 mW input power at 840 nm is reported in Al0.06Ga0.94As etalons grown by metalorganic vapor phase epitaxy, having an epitaxially grown high‐reflecting back mirror. The devices have been switched from the high‐reflecting to the low‐reflecting state with pulses from a laser diode operating at 778 nm with 10 pJ switching energy. The devices could be thermally stable for as long as 200 μs. The experimental results are compared with a simple theoretical model.

Nonlinear Fabry–Perot etalons of GaAs have been fabricated with metalorganic vapor phase epitaxy technology. The etalons operate in reflection mode, and have an epitaxially grown, rear dielectric mirror consisting of a stack of alternating AlAs/GaAlAs layers. Optical logic functions using a HeNe laser and optical bistability at room temperature are reported. Low switching powers and improved etalon uniformity are obtained.

Optical bistability with 10 mW input power is reported in a thermally stable, nonlinear AlGaAs etalon. A 3‐μm‐thick silver layer, which serves both as high‐reflecting mirror and heat sink, makes it possible to operate the device at arbitrary duty cycles and pulse lengths up to 0.5 s, without any regenerative pulsations, at room temperature. The device operation depends on the plasma‐induced electronic nonlinearity, and switching times are typically 10 ns. Device performance is compared with results from a numerical model which takes diffraction, diffusion, and heat conduction into account.