http://hdl.handle.net/1903/1655 2013-05-22T16:09:44Z 2013-05-22T16:09:44Z Govindarajan, Bharath http://hdl.handle.net/1903/11846 2011-08-18T02:30:13Z 2011-08-01T00:00:00Z

Title: Evaluation of Particle Clustering Algorithms in the Prediction of Brownout Dust Clouds Authors: Govindarajan, Bharath Abstract: A study of three Lagrangian particle clustering methods has been conducted with application to the problem of predicting brownout dust clouds that develop when rotorcraft land over surfaces covered with loose sediment. A significant impediment in performing such particle modeling simulations is the extremely large number of particles needed to obtain dust clouds of acceptable fidelity. Computing the motion of each and every individual sediment particle in a dust cloud (which can reach into tens of billions per cubic meter) is computationally prohibitive. The reported work involved the development of computationally efficient clustering algorithms that can be applied to the simulation of dilute gas-particle suspensions at low Reynolds numbers of the relative particle motion. The Gaussian distribution, k-means and Osiptsov's clustering methods were studied in detail to highlight the nuances of each method for a prototypical flow field that mimics the highly unsteady, two-phase vortical particle flow obtained when rotorcraft encounter brownout conditions. It is shown that although clustering algorithms can be problem dependent and have bounds of applicability, they offer the potential to significantly reduce computational costs while retaining the overall accuracy of a brownout dust cloud solution.

2011-08-01T00:00:00Z Shapiro, Benjamin Zinn, B. T. http://hdl.handle.net/1903/9440 2009-10-02T02:35:18Z 1997-01-01T00:00:00Z

Title: High-Frequency Nonlinear Vibrational Control Authors: Shapiro, Benjamin; Zinn, B. T. Abstract: This paper discusses the feasibility of high-frequency nonlinear vibrational control. Such control has the advantage that it does not require state measurement and processing capabilities that are required in conventional feedback control. Bellman et al. [1] investigated nonlinear systems controlled by linear vibrational controllers and proved that vibrational control is not feasible if the Jacobian matrix has a positive trace. This paper extends previous work to include nonlinear vibrational controllers. A stability criteria is derived for nonlinear systems with nonlinear controllers, and it is shown that a nonlinear vibrational controller can stabilize a system even if the Jacobian matrix has a positive trace.

1997-01-01T00:00:00Z Shapiro, Benjamin http://hdl.handle.net/1903/9438 2009-10-02T02:35:15Z 2005-04-01T00:00:00Z

Title: Workshop on Control of Micro- and Nano-Scale Systems Authors: Shapiro, Benjamin

2005-04-01T00:00:00Z Shapiro, Benjamin Chaudhary, Satej http://hdl.handle.net/1903/9437 2009-10-02T02:35:20Z 2006-07-01T00:00:00Z

Title: Arbitrary Steering of Multiple Particles Independently in an Electro-Osmotically Driven Microfluidic System Authors: Shapiro, Benjamin; Chaudhary, Satej Abstract: We demonstrate how to use feedback control of microflows to steer multiple particles independently in planar microfluidic systems driven by electro-osmotic actuation. This technique enables the handling of biological materials, such as cells, bacteria, DNA, and drug packets, in a hand-held format using simple and easy-to-fabricate actuators. The feedback loop consists of a vision system which identifies the positions of the particles in real-time, a control algorithm that computes the actuator (electrode) inputs based on information received from the vision system, and a set of electrodes (actuators) that create the required flow through electro-osmotic forces to steer all the particles along their desired trajectories and correct for particle position errors and thermal noise. Here, we focus on the development of control algorithms to achieve the steering of particles: vision system implementation, fabrication of devices, and experimental validation is addressed in other publications. In particular, steering of a single (yeast cell) particle has been demonstrated experimentally in our prior research and we have recently demonstrated experimental steering of three particles independently. In this paper, we develop the control algorithms for steering multiple particles independently and we validate our control techniques using simulations with realistic sources of initial position errors and thermal noise. In this study, we assume perfect measurement and actuation.

2006-07-01T00:00:00Z