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Articles 1 - 3 of 3
Full-Text Articles in Acoustics, Dynamics, and Controls
Derivation And Application Of A Conserved Orbital Energy For The Inverted Pendulum Bipedal Walking Model, Jerry E. Pratt, Sergey V. Drakunov
Derivation And Application Of A Conserved Orbital Energy For The Inverted Pendulum Bipedal Walking Model, Jerry E. Pratt, Sergey V. Drakunov
Publications
We present an analysis of a point mass, point foot, planar inverted pendulum model for bipedal walking. Using this model, we derive expressions for a conserved quantity, the “Orbital Energy”, given a smooth Center of Mass trajectory. Given a closed form Center of Mass Trajectory, the equation for the Orbital Energy is a closed form expression except for an integral term, which we show to be the first moment of area under the Center of Mass path. Hence, given a Center of Mass trajectory, it is straightforward and computationally simple to compute phase portraits for the system. In fact, for …
Vorticity Dynamics And Sound Generation In Two-Dimensional Fluid Flow, Raymond J. Nagem, Guido Sandri, David Uminsky
Vorticity Dynamics And Sound Generation In Two-Dimensional Fluid Flow, Raymond J. Nagem, Guido Sandri, David Uminsky
Mathematics
An approximate solution to the two-dimensional incompressible fluid equations is constructed by expanding the vorticity field in a series of derivatives of a Gaussian vortex. The expansion is used to analyze the motion of a corotating Gaussian vortex pair, and the spatial rotation frequency of the vortex pair is derived directly from the fluid vorticity equation. The resulting rotation frequency includes the effects of finite vortex core size and viscosity and reduces, in the appropriate limit, to the rotation frequency of the Kirchhoff point vortex theory. The expansion is then used in the low Mach number Lighthill equation to derive …
Stream Ambient Noise, Spectrum And Propagation Of Sounds In The Goby Padogobius Martensii: Sound Pressure And Particle Velocity, Marco Lugli, Michael L. Fine
Stream Ambient Noise, Spectrum And Propagation Of Sounds In The Goby Padogobius Martensii: Sound Pressure And Particle Velocity, Marco Lugli, Michael L. Fine
Biology Publications
The most sensitive hearing and peak frequencies of courtship calls of the stream goby, Padogobius martensii, fall within a quiet window at around 100Hz in the ambient noise spectrum. Acoustic pressure was previously measured although Padogobius likely responds to particle motion. In this study a combination pressure (p) and particle velocity (u) detector was utilized to describe ambient noise of the habitat, the characteristics of the goby’s sounds and their attenuation with distance. The ambient noise (AN) spectrum is generally similar for p and u (including the quiet window at noisy locations), although the energy distribution of uspectrum is …