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A disastrous form of pedestrian behavior is a stampede occurring in an event involving a large crowd in a panic situation. To deal with such stampedes, the possibility to increase the outflow by suitably placing a pillar or some other shaped obstacles in front of the exit has been demonstrated. We present a social force based genetic algorithm to optimize the best design of architectural entities to deal with large crowds. Unlike existing literature, our simulation results indicate that appropriately placing two pillars on both sides but not in front of the door can maximize the escape efficiency. Human experiments using 80 participants correspond well with the simulations. We observed a peculiar property named tangential momentum, the escape speed and the tangential momentum are found to be negatively correlated. The idea to reduce the tangential momentum has practical implications in crowd architectural design. [ABSTRACT FROM AUTHOR]

Abstract: We examined the effect of training history on the load-power relationship in vertical jumping (VJ) by employing external loads ranging from −30% to +30% body weight (BW). Based on previous findings, we hypothesized that (1) the maximum dynamic output (power production and momentum generation) would be within the tested loading interval, and (2) the load-power and load-momentum relations would depend on the subject’s training history. Thirty-one healthy male subjects of different training history (i.e., 9 strength-trained athletes, 12 speed-trained athletes, and 10 sedentary individuals), performed maximum countermovement jumps on a force plate while a pulley system was used to either reduce or increase the subject’s BW. An increase in external loading during VJ resulted in a systematic decrease (p <.001) in power production and momentum generation in all 3 studied groups. We also observed significant Group×Load interactions (p <.01) for the load-power and the load-momentum relationships, probably due to the group differences in slopes of the trend lines that describe the loading-associated changes in power and momentum. The results suggest that, from the evolutionary standpoint, the human muscular system of the lower limbs could be designed to produce the maximum power output against the loads that are well below the mass and inertia of the human body. [Copyright &y& Elsevier]

The standard control problem of the pendubot refers to the task of stabilizing its equilibrium configuration with the highest potential energy. Linearization of the dynamics of the pendubot about this equilibrium results in a completely controllable system and allows a linear controller to be designed for local asymptotic stability. For the underactuated pendubot, the important task is, therefore, to design a controller that will swing up both links and bring the configuration variables of the system within the region of attraction of the desired equilibrium. This paper provides a new method for swing-up control based on a series of rest-to-rest maneuvers of the first link about its vertically upright configuration. The rest-to-rest maneuvers are designed such that each maneuver results in a net gain in energy of the second link. This results in swing-up of the second link and the pendubot configuration reaching the region of attraction of the desired equilibrium. A four-step algorithm is provided for swing-up control followed by stabilization. Simulation results are presented to demonstrate the efficacy of the approach. [ABSTRACT FROM AUTHOR]

Historical, physical, and geometrical relations between two different momenta, characterized here as Cartesian and Lagrangian, are explored. Cartesian momentum is determined by the mass tensor, and gives rise to a kinematical geometry. Lagrangian momentum, which is more general, is given by the fiber derivative, and produces a dynamical geometry. This differs from the kinematical in the presence of a velocity-dependent potential. The relation between trajectories and level surfaces in Hamilton-Jacobi theory can also be Cartesian and kinematical or, more generally, Lagrangian and dynamical. [ABSTRACT FROM AUTHOR]