Ming Lin - Academia.edu (original) (raw)

Papers by Ming Lin

2009 IEEE International Conference on Robotics and Automation, 2009

2010 Abstracts IEEE International Conference on Plasma Science, 2010

In this work, we study the pulling effect of the A6 magnetron using a conformal finite-difference... more In this work, we study the pulling effect of the A6 magnetron using a conformal finite-difference time-domain (CFDTD) method as implemented in VORPAL [1]. We can accurately calculate the frequency shifts of the A6 magnetron due to the pulling effect of the output loading and also study the resulting mode competition. A tapered output waveguide and a coupling slot have been added to the A6 magnetron and the perfectly matching layer (PML) boundary condition has been successfully applied at the output of the waveguide. Here, we use a mesh grid of 100×100 with Dey-Mittra technique [2, 3] and a total simulation time up to 1000 ns so that we can preserve the frequency accuracy of 99.8% for the model [4]. The pulling effect can be studied via measuring the frequency shift of the constructed model with the loading changed by varying the size of the coupling slot, i.e., changing the slot coupling. The cases of the slot coupling angle ∗F equal to 0.5, 1, 2, 4, 8 and 16 Degrees are simulated. The simulation results show that the frequency spectra are very sensitive to the strength of the output coupling. The frequencies of some modes are shifted due to the coupling and some mode destruction has been observed. It is found that the resonance peak of the π mode is very weak in the case of Ψ Degrees and disappears in the cases corresponding to larger coupling angles. However, the resonance peak of the 2π mode exits in all of the cases and is more robust compared to the π mode resonance. The resonances of both π and 2π modes are blue shifted, i.e., shifted to the higher frequency regime. By comparison, the frequency shift of the π mode is larger than that of the 2π mode. Based on these simulation results, we can conclude that the waveguide coupling of the A6 magnetron is unfavorable to the π mode oscillation. However, the 2π mode oscillation is not too sensitive to the waveguide coupling- - as the π mode does. This could possibly explain why the operation of the A6 magnetron favors the 2π mode.

31st Aerospace Sciences Meeting, 1993

We present exploratory tests of a new optical method which measures directly two components of th... more We present exploratory tests of a new optical method which measures directly two components of the 3D power spectrum of the refractive-index fluctuation. The method was applied to a Mach 2 turbulent shear layer. Length scales of 0.1 mm to 1.0 mm were resolved within a shear-layer thickness ranging from 5 mm to 10 mm. At low-to-moderate wavenumbers, the spectral

Proceedings of the 2007 ACM symposium on Solid and physical modeling - SPM '07, 2007

Proceedings of the fifteenth annual symposium on Computational geometry - SCG '99, 1999

2010 Abstracts IEEE International Conference on Plasma Science, 2010

The feasibility of modeling a multistage depressed collector using a conformal finite-difference ... more The feasibility of modeling a multistage depressed collector using a conformal finite-difference time-domain particle-incell code has been studied. A feedback mechanism is implemented to provide stable time-dependent voltages for each stage of the depressed collector. An arbitrary space-time dependent spent beam distribution can be given in our time domain simulations. We demonstrate the design of a five stage depressed collector

Proceedings of the 1997 Particle Accelerator Conference (Cat. No.97CH36167), 1998

ABSTRACT We present a novel approach for interactive navigation and planning of multiple agents i... more ABSTRACT We present a novel approach for interactive navigation and planning of multiple agents in crowded scenes with moving obstacles. Our formulation uses a pre-computed roadmap that provides macroscopic, global connectivity for way-finding and combines it with fast ...

We develop an algorithm to decouple a multi-robot path planning problem into subproblems whose so... more We develop an algorithm to decouple a multi-robot path planning problem into subproblems whose solutions can be executed sequentially. Given an external path planner for general configuration spaces, our algorithm finds an execution sequence that minimizes the dimension of the highest-dimensional subproblem over all possible execution sequences. If the external planner is complete (at least up to this minimum dimension), then our algorithm is complete because it invokes the external planner only for spaces of dimension at most this minimum. Our algorithm can decouple and solve path planning problems with many robots, even with incomplete external planners. We show scenarios involving 16 to 65 robots, where our algorithm solves planning problems of dimension 32 to 130 using a PRM planner for at most eight dimensions. 1

2009 IEEE International Conference on Robotics and Automation, 2009

2010 Abstracts IEEE International Conference on Plasma Science, 2010

In this work, we study the pulling effect of the A6 magnetron using a conformal finite-difference... more In this work, we study the pulling effect of the A6 magnetron using a conformal finite-difference time-domain (CFDTD) method as implemented in VORPAL [1]. We can accurately calculate the frequency shifts of the A6 magnetron due to the pulling effect of the output loading and also study the resulting mode competition. A tapered output waveguide and a coupling slot have been added to the A6 magnetron and the perfectly matching layer (PML) boundary condition has been successfully applied at the output of the waveguide. Here, we use a mesh grid of 100×100 with Dey-Mittra technique [2, 3] and a total simulation time up to 1000 ns so that we can preserve the frequency accuracy of 99.8% for the model [4]. The pulling effect can be studied via measuring the frequency shift of the constructed model with the loading changed by varying the size of the coupling slot, i.e., changing the slot coupling. The cases of the slot coupling angle ∗F equal to 0.5, 1, 2, 4, 8 and 16 Degrees are simulated. The simulation results show that the frequency spectra are very sensitive to the strength of the output coupling. The frequencies of some modes are shifted due to the coupling and some mode destruction has been observed. It is found that the resonance peak of the π mode is very weak in the case of Ψ Degrees and disappears in the cases corresponding to larger coupling angles. However, the resonance peak of the 2π mode exits in all of the cases and is more robust compared to the π mode resonance. The resonances of both π and 2π modes are blue shifted, i.e., shifted to the higher frequency regime. By comparison, the frequency shift of the π mode is larger than that of the 2π mode. Based on these simulation results, we can conclude that the waveguide coupling of the A6 magnetron is unfavorable to the π mode oscillation. However, the 2π mode oscillation is not too sensitive to the waveguide coupling- - as the π mode does. This could possibly explain why the operation of the A6 magnetron favors the 2π mode.

31st Aerospace Sciences Meeting, 1993

We present exploratory tests of a new optical method which measures directly two components of th... more We present exploratory tests of a new optical method which measures directly two components of the 3D power spectrum of the refractive-index fluctuation. The method was applied to a Mach 2 turbulent shear layer. Length scales of 0.1 mm to 1.0 mm were resolved within a shear-layer thickness ranging from 5 mm to 10 mm. At low-to-moderate wavenumbers, the spectral

Proceedings of the 2007 ACM symposium on Solid and physical modeling - SPM '07, 2007

Proceedings of the fifteenth annual symposium on Computational geometry - SCG '99, 1999

2010 Abstracts IEEE International Conference on Plasma Science, 2010

The feasibility of modeling a multistage depressed collector using a conformal finite-difference ... more The feasibility of modeling a multistage depressed collector using a conformal finite-difference time-domain particle-incell code has been studied. A feedback mechanism is implemented to provide stable time-dependent voltages for each stage of the depressed collector. An arbitrary space-time dependent spent beam distribution can be given in our time domain simulations. We demonstrate the design of a five stage depressed collector

Proceedings of the 1997 Particle Accelerator Conference (Cat. No.97CH36167), 1998

ABSTRACT We present a novel approach for interactive navigation and planning of multiple agents i... more ABSTRACT We present a novel approach for interactive navigation and planning of multiple agents in crowded scenes with moving obstacles. Our formulation uses a pre-computed roadmap that provides macroscopic, global connectivity for way-finding and combines it with fast ...

We develop an algorithm to decouple a multi-robot path planning problem into subproblems whose so... more We develop an algorithm to decouple a multi-robot path planning problem into subproblems whose solutions can be executed sequentially. Given an external path planner for general configuration spaces, our algorithm finds an execution sequence that minimizes the dimension of the highest-dimensional subproblem over all possible execution sequences. If the external planner is complete (at least up to this minimum dimension), then our algorithm is complete because it invokes the external planner only for spaces of dimension at most this minimum. Our algorithm can decouple and solve path planning problems with many robots, even with incomplete external planners. We show scenarios involving 16 to 65 robots, where our algorithm solves planning problems of dimension 32 to 130 using a PRM planner for at most eight dimensions. 1