We present a generalization of the modified smooth particle hydrodynamics simulation technique capable of simulating static and dynamic liquid crystalline behavior. This generalization is then implemented in the context of the Qian-Sheng description of nematodynamics. To test the method, we first use it to simulate switching in both a Fréedericksz setup and a chiral hybrid aligned nematic cell. In both cases, the results obtained give excellent agreement with previously published results. We then apply the technique in a three-dimensional simulation of the switching dynamics of the post aligned bistable nematic device.

We use a novel mesh-free simulation approach to study the post aligned bistable nematic (PABN) cell.By employing the Qian-Sheng formalism for liquid crystals along with a smooth representation of the surface posts, we have been able to identify two distinct stable configurations. The three-dimensional order field configurations of these states and their elastic free energies are consistent with both experimental results and previous simulation attempts. However, alternative states suggested in previous studies do not appear to remain stable when finite post curvature is considered.

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Abstract. The output current of an avalanche photodiodes (APD's) fluctuates in the absence of light as well as in its presence. The noise in APD's current arises from three sources: randomness in the number and in the positions at which dark carrier pairs are generated, randomness in the photon arrival number, and randomness in the carrier multiplication process. A Monte Carlo model has been used to estimate the excess noise factor in thin p + -i-n + GaAs avalanche photodiodes. As this approach is computation intensive, simple parallel algorithm considering heterogeneous cluster based on MPICH was designed and implemented. Very good performance gain was achieved. It was found that APD model provides very good fits to the measured gain and noise and as such provides an accurate picture of the device operation. In this way, various device structures can be analyzed prior to their experimental realization. Through "computer experiments" like this outlined here, the effect of various geometries and material compositions on device performance can be assessed and optimal designs achieved.