We examine optical pulse propagation through a 30-period, GaAs/AlAs, one-dimensional, periodic structure at the photonic band-edge transmission resonance. We predict theoretically-and demonstrate experimentally-an approximate energy, momentum, and form invariance of the transmitted pulse, as well as large group index ͑up to 13.5͒. The group index is tunable and many orders of magnitude more sensitive to variation in material refractive index than for bulk material. We interpret this observation in terms of timedependent electromagnetic states of the pulse-crystal system. ͓S1063-651X͑96͒50108-X͔

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A senior design team from the Milwaukee School of Engineering assisted the Milwaukee Harbor District with a trash collecting solution for the Kinnickinnic River. The design objectives were: the use of solar panels to generate charge for the continuous operation of the trash solution, an innovative and cost-efficient way to clear debris blockages from the conveyor, low cost, and a design that can operate as autonomously as possible to require the least amount of human intervention. The Kinnickinnic River experiences a reverse flow and a substantial rise in water level during and after storms. The need for a trash solution in the section of the river that passes underneath Becker St. in downtown Milwaukee is due to the extreme pollution that has collected over the years. The city of Milwaukee, through the Harbor District and other non-profit organizations, have made plans to beautify the areas that have suffered from the residual pollution and simultaneously launch a promotional campaign to raise environmental awareness. Through school programs and the reality of the team’s trash solution in the river, the Kinnickinnic River will once again flourish in both flora and fauna. The team has created a design that will fit the river’s needs taking into consideration the solar energy available and various flow simulations. A full design solution with design details and specifications for manufacturing will be submitted to the Harbor District of Milwaukee for their review. The current design makes use of a floating platform base, 24 solar panels, eight lead acid batteries, a DC motor to run a conveyor belt to pull trash out of the water and to run a rake system to aid in pushing trash onto the conveyor, a gearbox to produce the necessary torque, a boom and cable system to catch trash further in the river, and a dumpster located on a dock in front of the trash collector. Finite Element Analysis and Computational Fluid Dynamics simulations were run to test the designs developed for the conveyor mechanism and the raking system and to test the amount of force placed on the trash collector by the water and air velocities. Further simulations may be run to test more components of the trash collector as needed. A prototype of the conveyor and rake system was produced to simulate the functionality of the design. Additionally, the selected solar panels for the design were tested using a data collector and analyzed to ensure power to the design would be enough.

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