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Durham, NC, United States

Grant
Agency: Department of Health and Human Services | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2006

DESCRIPTION (provided by applicant): The objective of this application is to develop a general-purpose computer simulator for high intensity focused ultrasound (HIFU) in therapeutic application. A novel computational model is proposed to significantly improve the current modeling capability of therapeutic ultrasound. It will provide the first commercial HIFU simulator to enable the simulation and planning of therapeutic ultrasound protocols. The proposed method is based on the spectral element time-domain (SETD) method recently developed by the research team for linear wave propagation. As in linear wave propagation, it is expected that the SETD method for nonlinear HIFU simulation is also significantly more accurate and more efficient than the conventional finite-difference time-domain (FDTD) method currently being used in research laboratories. In Phase I of this SBIR project, the SETD method will be developed and demonstrated for a quasi-3D HIFU simulator, where the nonlinear acoustic pressure field is assumed 2D axisymmetric, while the temperature field is 3D. The aims in Phase I of this application are to (a) develop the mathematical algorithm of a quasi-3D SETD method for the simulation of high-intensity ultrasound wave interacting with heterogeneous tissue; (b) implement the SETD method for arbitrary quasi-3D heterogeneous media; and (c) perform extensive validation and evaluation of the HIFU simulator with other reference methods. The aims in a follow-up Phase II project are to (a) develop a full 3D SETD algorithm for heterogeneous media; (b) implement the 3D SETD method for realistic therapeutic environment; (c) develop a user-friendly graphic interface environment for practitioners to use the HIFU simulator for design optimization of ultrasound therapeutic protocols; and (d) commercialize this novel therapeutic ultrasound computational tool. This application will develop a general-purpose computer simulator for high intensity focused ultrasound (HIFU) therapeutic planning. Such a computational tool is highly valuable for doctors to plan an HIFU surgery as it gives accurate prediction of what will happen during the surgery by simulating high intensity ultrasound propagation in tissue.


Grant
Agency: Department of Defense | Branch: Navy | Program: SBIR | Phase: Phase I | Award Amount: 70.00K | Year: 2010

Wave Computation Technologies, Inc. (WCT) proposes to develop a new time-domain discontinuous Galerkin software tool for modeling electromagnetic wave propagation through complex material and configurations. This solver combines the discontinuous Galerkin (DG) method with the finite-element time-domain (FETD) method to allow discontinuous discretization of complex geometry and materials. The solver will be implemented for arbitrary anistropoic and dispersive meda, so that novel materials including metamaterials can be included in the design simulation. The DG-FETD solver is highly efficient for complicated problems because it allows independent meshing and resolution for different regions. The WCT team has extensive experience with the relevant computational electromagnetics algorithms, and is in an excellent position to develop such a computational electromagnetics software tool. The proposed time-domain solver will further extend the application domain of the conventional finite element method to include large array of frequency selective surfaces and other complex electromagnetic environments.


Grant
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase II | Award Amount: 500.97K | Year: 2008

Wave Computation Technologies, Inc. (WCT) proposes to develop a new commercial electromagnetic particle-in-cell (EM-PIC) software package based on a 3-D hybrid technique that combines two efficient algorithms, (a) the enlarged cell technique (ECT) and (b) the spectral-element time-domain (SETD) method, as a high-order solver for EM-PIC simulations. This hybrid technique overcomes the well-known limitation of existing EM-PIC solvers due to their stair-stepping approximation. The proposed hybrid method uses domain decomposition to divide the problem into SETD regions with coarse structures and ECT regions with fine structures. As the SETD method has spectral accuracy and the ECT method has second-order accuracy, the overall convergence of this EM-PIC solver is better than second order. In Phase I the team has already developed and demonstrated the prototype of this method. Specifically, we have integrated the ECT with the particle-in-cell calculation, and have achieved the second-order global convergence. The typical computation time for a problem with 5.45 million cells and 1600 time steps is approximately 14 minutes on a desktop computer (Pentium-D 2.8GHz, only 1 CPU is used). This speed is believed to be unprecedented. In Phase II, the proposed 3-D hybrid numerical EM-PIC solver will be integrated into an existing commercial platform to produce a new commercial package, Wavenology PIC. It promises to effectively mitigate spurious effects caused by the stair-stepping approximation in the conventional EM-PIC simulation method. The commercial code will be complete with particle emission and propagation. The algorithm will be scalable, stable and globally at least second order accurate for curved geometries. Issues such as self force, grid heating, non-physical radiation and self heating will be mitigated to globally second-order convergence.


Grant
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2007

We propose to prototype and test a new 3-D hybrid technique that combines two efficient algorithms, (a) the discontinuous Galerkin pseudospectral time-domain (DG-PSTD) method and (b) the boundary conformal finite-difference time-domain (BC-FDTD) method, as a high-order solver for electromagnetic particle-in-cell (EM-PIC) simulations. This hybrid technique overcomes the well-known limitation of existing EM-PIC solvers due to their stair-stepping approximation. The proposed hybrid method uses domain decomposion to divide the problem into DG-PSTD regions with coarse structures and BC-FDTD regions with fine structures. As the DG-PSTD method has spectral accuracy and the BC-FDTD method has second-order accuracy, the overall convergence of this EM-PIC solver is better than second order. The team has already developed the most relevant techniques for the pure electromagnetics problem in an existing commercial prototype, Wavenology EM Pack, and has worked on plasma simulations. The proposed 3-D hybrid numerical EM-PIC solver will be integrated into this commercial prototype. It promises to effectively mitigate spurious effects caused by the stair-stepping approximation in the EM-PIC simulation.


Niu J.,Duke University | Luo M.,Wave Computation Technologies, Inc. | Zhu J.,Xiamen University | Liu Q.H.,Duke University
Optics Express | Year: 2015

Graphene's relatively poor absorption is an essential obstacle for designing graphene-based photonic devices with satisfying photo-responsivity. To enhance the tunable light absorption of graphene, appropriate excitation of localized surface plasmon resonance is considered as a promising approach. In this work, the strategy of incorporating periodic cuboid gold nanoparticle (NP) cluster arrays and cylindrical gold NP arrays with Bragg reflectors into graphene-based photodetectors are theoretically studied by the boundary-integral spectral element method (BI-SEM). With the BI-SEM, the models can be numerically analyzed with excellent accuracy and efficiency. Numerical simulation shows that the proposed structures can effectively engineer the light absorption in graphene by tuning plasmon resonance. In the spectra of 300 nm to 1000 nm, a maximum light absorption of 67.54% is observed for the graphene layer with optimal parameters of the photodetector model. © 2015 Optical Society of America. Source

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