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Full-Text Articles in Engineering
An Autoparametric, Electromagnetic Ambient Vibration Energy Harvester, Johannes Santen, Nitin Kapania, Christopher Lee
An Autoparametric, Electromagnetic Ambient Vibration Energy Harvester, Johannes Santen, Nitin Kapania, Christopher Lee
Christopher Lee
Results are presented for the design and testing of an electromagnetic device to convert ambient mechanical vibration into electricity. The design of the device is based on an L-shaped beam structure which is tuned so that the first two (bending) natural frequencies have a (near) two-to-one ratio. This creates an internal resonance or autoparmetic condition that can result in a nonlinear dynamic response to a sinusoidal (base) displacement excitation over an extended frequency range. This is in contrast to single degree-of-freedom, linear-dynamics based vibration harvesters which convert energy in a very narrow frequency band. Representative measurements of displacement and power …
Markov Chain Monte Carlo-Based Method For Flaw Detection In Beams, Christopher Lee, Ronald Glaser, John Nitao, Tracy Hickling, William Hanley
Markov Chain Monte Carlo-Based Method For Flaw Detection In Beams, Christopher Lee, Ronald Glaser, John Nitao, Tracy Hickling, William Hanley
Christopher Lee
A Bayesian inference methodology using a Markov chain Monte Carlo (MCMC) sampling procedure is presented for estimating the parameters of computational structural models. This methodology combines prior information, measured data, and forward models to produce a posterior distribution for the system parameters of structural models that is most consistent with all available data. The MCMC procedure is based upon a Metropolis-Hastings algorithm that is shown to function effectively with noisy data, incomplete data sets, and mismatched computational nodes/measurement points. A series of numerical test cases based upon a cantilever beam is presented. The results demonstrate that the algorithm is able …
Nonlinear Dynamics And Loop Formation In Kirchoff Rods With Implications To The Mechanics Of Dna And Cables, Sachin Goyal, Noel Perkins, Christopher Lee
Nonlinear Dynamics And Loop Formation In Kirchoff Rods With Implications To The Mechanics Of Dna And Cables, Sachin Goyal, Noel Perkins, Christopher Lee
Christopher Lee
The paper contributes a general dynamical formulation and numerical solution procedure for studying nonlinear and three-dimensional dynamics of Kirchhoffrods. Target applications include the dynamic formation of DNA loops and supercoils as well as loops (hockles) in marine cables. The formulation accommodates non-homogeneous and non-isotropic inextensible rods both with and without coupling of tension and torsion. The utility of this formulation is illustrated by studying the dynamics and quasi-static response of a clamped–clamped rod subject to compression and/or twist. For slow loading rates, the computed quasi-static responses converge to published equilibrium solutions for a benchmark problem. As loading rates increase, new …
A Perching Landing Gear For A Quadcopter, Elsa Culler, Gray Thomas, Christopher Lee
A Perching Landing Gear For A Quadcopter, Elsa Culler, Gray Thomas, Christopher Lee
Christopher Lee
The design, fabrication, and testing of two prototypes of a landing gear mechanism that would allow a quadcopter to grasp and perch upon a branch-like structure are presented. The prototypes are based upon a snapping-claw mechanism that is triggered on the impact of landing. A complaint claw, fabricated using shape deposition manufacturing techniques, can conform to various shapes and contours of perching structures. Results from flight tests with a commercial off-the-shelf quadcopter and zip line tests are presented which demonstrate the performance of the mechanism.