Fruits of (Acanthaceae) explosively launch small (2.5 mm diameter × 0.46 mm thick), disc-shaped seeds at velocities over 15 m s, reaching distances of up to 7 m. Through high-speed video analysis, we observe that seeds fly with extraordinary backspin of up to 1660 Hz. By modelling the seeds as spinning discs, we show that flying with backspin is stable against gyroscopic precession. This stable backspin orientation minimizes the frontal area during flight, decreasing drag force on the seeds and thus increasing dispersal distance. From high-speed video of the seeds' flight, we experimentally determine drag forces that are 40% less than those calculated for a sphere of the same volume and density. This reduces the energy costs for seed dispersal by up to a factor of five.
Metropolitan areas with high traffic demand are often served by a system of two or more airports whose arrival and departure operations are highly interdependent. Such an airport system is referred to as a metroplex. A temporal-spatial framework for evaluating concepts for improving metroplex operations was developed. In this framework, concepts for metroplex operations were defined by their spatial and temporal impacts on operations. These impacts were evaluated parametrically with a generic metroplex model. The experiment revealed that temporal scheduling and route segregation are the two most important integrated concepts for reducing delays in the terminal area airspace. These two concepts were then incorporated to form an experiment matrix, and their effects were tested in a metroplex model based on the New York terminal area airspace. Simulation analyses showed a nearly 80% reduction in queueing delay for arrival flights when the scheduling and route structural design were combined and more than 60% reduction with scheduling alone.
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