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Sample records for cartesian coordinate grid

  1. Explicitly computing geodetic coordinates from Cartesian coordinates

    NASA Astrophysics Data System (ADS)

    Zeng, Huaien

    2013-04-01

    This paper presents a new form of quartic equation based on Lagrange's extremum law and a Groebner basis under the constraint that the geodetic height is the shortest distance between a given point and the reference ellipsoid. A very explicit and concise formulae of the quartic equation by Ferrari's line is found, which avoids the need of a good starting guess for iterative methods. A new explicit algorithm is then proposed to compute geodetic coordinates from Cartesian coordinates. The convergence region of the algorithm is investigated and the corresponding correct solution is given. Lastly, the algorithm is validated with numerical experiments.

  2. The 3D Euler solutions using automated Cartesian grid generation

    NASA Technical Reports Server (NTRS)

    Melton, John E.; Enomoto, Francis Y.; Berger, Marsha J.

    1993-01-01

    Viewgraphs on 3-dimensional Euler solutions using automated Cartesian grid generation are presented. Topics covered include: computational fluid dynamics (CFD) and the design cycle; Cartesian grid strategy; structured body fit; grid generation; prolate spheroid; and ONERA M6 wing.

  3. Conversion of Cartesian coordinates from and to Generalized Balanced Ternary addresses

    USGS Publications Warehouse

    van Roessel, Jan W.

    1988-01-01

    Hexagonal grids have several advantages over square grids, such as a greater angular resolution and unambiguous connectivity. The Generalized Balanced Ternary (GBT) system is a spatial addressing method for hexagonal grids in which the hexagons are arranged in hierarchical aggregates, and which accommodates vector operations in GBT space. Efficient algorithms for converting Cartesian coordinates from and to GBT addresses are based on the dual representation of the hexagonal tessellation. The GBT-to-Cartesian algorithm is an order of magnitude faster than the Cartesian-to-GBT algorithm, the latter requiring interpolation and GBT addition for each digit of the generated GBT address.

  4. Unstructured Cartesian/prismatic grid generation for complex geometries

    NASA Technical Reports Server (NTRS)

    Karman, Steve L., Jr.

    1995-01-01

    The generation of a hybrid grid system for discretizing complex three dimensional (3D) geometries is described. The primary grid system is an unstructured Cartesian grid automatically generated using recursive cell subdivision. This grid system is sufficient for computing Euler solutions about extremely complex 3D geometries. A secondary grid system, using triangular-prismatic elements, may be added for resolving the boundary layer region of viscous flows near surfaces of solid bodies. This paper describes the grid generation processes used to generate each grid type. Several example grids are shown, demonstrating the ability of the method to discretize complex geometries, with very little pre-processing required by the user.

  5. Efficient Fluid Dynamic Design Optimization Using Cartesian Grids

    NASA Technical Reports Server (NTRS)

    Dadone, A.; Grossman, B.; Sellers, Bill (Technical Monitor)

    2004-01-01

    This report is subdivided in three parts. The first one reviews a new approach to the computation of inviscid flows using Cartesian grid methods. The crux of the method is the curvature-corrected symmetry technique (CCST) developed by the present authors for body-fitted grids. The method introduces ghost cells near the boundaries whose values are developed from an assumed flow-field model in vicinity of the wall consisting of a vortex flow, which satisfies the normal momentum equation and the non-penetration condition. The CCST boundary condition was shown to be substantially more accurate than traditional boundary condition approaches. This improved boundary condition is adapted to a Cartesian mesh formulation, which we call the Ghost Body-Cell Method (GBCM). In this approach, all cell centers exterior to the body are computed with fluxes at the four surrounding cell edges. There is no need for special treatment corresponding to cut cells which complicate other Cartesian mesh methods.

  6. A Cartesian grid approach with hierarchical refinement for compressible flows

    NASA Technical Reports Server (NTRS)

    Quirk, James J.

    1994-01-01

    Many numerical studies of flows that involve complex geometries are limited by the difficulties in generating suitable grids. We present a Cartesian boundary scheme for two-dimensional, compressible flows that is unfettered by the need to generate a computational grid and so it may be used, routinely, even for the most awkward of geometries. In essence, an arbitrary-shaped body is allowed to blank out some region of a background Cartesian mesh and the resultant cut-cells are singled out for special treatment. This is done within a finite-volume framework and so, in principle, any explicit flux-based integration scheme can take advantage of this method for enforcing solid boundary conditions. For best effect, the present Cartesian boundary scheme has been combined with a sophisticated, local mesh refinement scheme, and a number of examples are shown in order to demonstrate the efficacy of the combined algorithm for simulations of shock interaction phenomena.

  7. Triangle geometry processing for surface modeling and cartesian grid generation

    DOEpatents

    Aftosmis, Michael J. [San Mateo, CA; Melton, John E. [Hollister, CA; Berger, Marsha J. [New York, NY

    2002-09-03

    Cartesian mesh generation is accomplished for component based geometries, by intersecting components subject to mesh generation to extract wetted surfaces with a geometry engine using adaptive precision arithmetic in a system which automatically breaks ties with respect to geometric degeneracies. During volume mesh generation, intersected surface triangulations are received to enable mesh generation with cell division of an initially coarse grid. The hexagonal cells are resolved, preserving the ability to directionally divide cells which are locally well aligned.

  8. Triangle Geometry Processing for Surface Modeling and Cartesian Grid Generation

    NASA Technical Reports Server (NTRS)

    Aftosmis, Michael J. (Inventor); Melton, John E. (Inventor); Berger, Marsha J. (Inventor)

    2002-01-01

    Cartesian mesh generation is accomplished for component based geometries, by intersecting components subject to mesh generation to extract wetted surfaces with a geometry engine using adaptive precision arithmetic in a system which automatically breaks ties with respect to geometric degeneracies. During volume mesh generation, intersected surface triangulations are received to enable mesh generation with cell division of an initially coarse grid. The hexagonal cells are resolved, preserving the ability to directionally divide cells which are locally well aligned.

  9. Topology preserving advection of implicit interfaces on Cartesian grids

    NASA Astrophysics Data System (ADS)

    Qin, Zhipeng; Delaney, Keegan; Riaz, Amir; Balaras, Elias

    2015-06-01

    Accurate representation of implicit interface topology is important for the numerical computation of two phase flow on Cartesian grids. A new method is proposed for the construction of signed distance function by geometrically projecting interface topology onto the Cartesian grid using a multi-level projection framework. The method involves a stepwise improvement in the approximation to the signed distance function based on pointwise, piecewise and locally smooth reconstructions of the interface. We show that this approach provides accurate representation of the projected interface and its topology on the Cartesian grid, including the distance from the interface and the interface normal and curvature. The projected interface can be in the form of either a connected set of marker particles that evolve with Lagrangian advection, or a discrete set of points associated with an implicit interface that evolves with the advection of a scalar function. The signed distance function obtained with geometric projection is independent of the details of the scaler field, in contrast to the conventional approach where advection and reinitialization cannot be decoupled. As a result, errors introduced by reinitialization do not amplify advection errors, which leads to substantial improvement in both volume conservation and topology representation.

  10. Transforming geocentric cartesian coordinates to geodetic coordinates by using differential search algorithm

    NASA Astrophysics Data System (ADS)

    Civicioglu, Pinar

    2012-09-01

    In order to solve numerous practical navigational, geodetic and astro-geodetic problems, it is necessary to transform geocentric cartesian coordinates into geodetic coordinates or vice versa. It is very easy to solve the problem of transforming geodetic coordinates into geocentric cartesian coordinates. On the other hand, it is rather difficult to solve the problem of transforming geocentric cartesian coordinates into geodetic coordinates as it is very hard to define a mathematical relationship between the geodetic latitude (φ) and the geocentric cartesian coordinates (X, Y, Z). In this paper, a new algorithm, the Differential Search Algorithm (DS), is presented to solve the problem of transforming the geocentric cartesian coordinates into geodetic coordinates and its performance is compared with the performances of the classical methods (i.e., Borkowski, 1989; Bowring, 1976; Fukushima, 2006; Heikkinen, 1982; Jones, 2002; Zhang, 2005; Borkowski, 1987; Shu, 2010 and Lin, 1995) and Computational-Intelligence algorithms (i.e., ABC, JDE, JADE, SADE, EPSDE, GSA, PSO2011, and CMA-ES). The statistical tests realized for the comparison of performances indicate that the problem-solving success of DS algorithm in transforming the geocentric cartesian coordinates into geodetic coordinates is higher than those of all classical methods and Computational-Intelligence algorithms used in this paper.

  11. A cartesian grid embedded boundary method for hyperbolic conservation laws

    SciTech Connect

    Colella, Phillip; Graves, Daniel T.; Keen, Benjamin J.; Modiano, David

    2004-10-03

    We present a second-order Godunov algorithm to solve time-dependent hyperbolic systems of conservation laws on irregular domains. Our approach is based on a formally consistent discretization of the conservation laws on a finite-volume grid obtained from intersecting the domain with a Cartesian grid. We address the small-cell stability problem associated with such methods by hybridizing our conservative discretization with a stable, nonconservative discretization at irregular control volumes, and redistributing the difference in the mass increments to nearby cells in a way that preserves stability and local conservation. The resulting method is second-order accurate in L{sup 1} for smooth problems, and is robust in the presence of large-amplitude discontinuities intersecting the irregular boundary.

  12. GSRP/David Marshall: Fully Automated Cartesian Grid CFD Application for MDO in High Speed Flows

    NASA Technical Reports Server (NTRS)

    2003-01-01

    With the renewed interest in Cartesian gridding methodologies for the ease and speed of gridding complex geometries in addition to the simplicity of the control volumes used in the computations, it has become important to investigate ways of extending the existing Cartesian grid solver functionalities. This includes developing methods of modeling the viscous effects in order to utilize Cartesian grids solvers for accurate drag predictions and addressing the issues related to the distributed memory parallelization of Cartesian solvers. This research presents advances in two areas of interest in Cartesian grid solvers, viscous effects modeling and MPI parallelization. The development of viscous effects modeling using solely Cartesian grids has been hampered by the widely varying control volume sizes associated with the mesh refinement and the cut cells associated with the solid surface. This problem is being addressed by using physically based modeling techniques to update the state vectors of the cut cells and removing them from the finite volume integration scheme. This work is performed on a new Cartesian grid solver, NASCART-GT, with modifications to its cut cell functionality. The development of MPI parallelization addresses issues associated with utilizing Cartesian solvers on distributed memory parallel environments. This work is performed on an existing Cartesian grid solver, CART3D, with modifications to its parallelization methodology.

  13. A multilevel Cartesian non-uniform grid time domain algorithm

    SciTech Connect

    Meng Jun; Boag, Amir; Lomakin, Vitaliy; Michielssen, Eric

    2010-11-01

    A multilevel Cartesian non-uniform grid time domain algorithm (CNGTDA) is introduced to rapidly compute transient wave fields radiated by time dependent three-dimensional source constellations. CNGTDA leverages the observation that transient wave fields generated by temporally bandlimited and spatially confined source constellations can be recovered via interpolation from appropriately delay- and amplitude-compensated field samples. This property is used in conjunction with a multilevel scheme, in which the computational domain is hierarchically decomposed into subdomains with sparse non-uniform grids used to obtain the fields. For both surface and volumetric source distributions, the computational cost of CNGTDA to compute the transient field at N{sub s} observation locations from N{sub s} collocated sources for N{sub t} discrete time instances scales as O(N{sub t}N{sub s}logN{sub s}) and O(N{sub t}N{sub s}log{sup 2}N{sub s}) in the low- and high-frequency regimes, respectively. Coupled with marching-on-in-time (MOT) time domain integral equations, CNGTDA can facilitate efficient analysis of large scale time domain electromagnetic and acoustic problems.

  14. An Investigation of Two-Dimensional CAD Generated Models with Body Decoupled Cartesian Grids for DSMC

    SciTech Connect

    OTAHAL,THOMAS J.; GALLIS,MICHAIL A.; BARTEL,TIMOTHY J.

    2000-06-27

    This paper presents an investigation of a technique for using two-dimensional bodies composed of simple polygons with a body decoupled uniform Cmtesian grid in the Direct Simulation Monte Carlo method (DSMC). The method employs an automated grid pre-processing scheme beginning form a CAD geometry definition file, and is based on polygon triangulation using a trapezoid algorithm. A particle-body intersection time comparison is presented between the Icarus DSMC code using a body-fitted structured grid and using a structured body-decoupled Cartesian grid with both linear and logarithmic search techniques. A comparison of neutral flow over a cylinder is presented using the structured body fitted grid and the Cartesian body de-coupled grid.

  15. Cartesian Off-Body Grid Adaption for Viscous Time- Accurate Flow Simulation

    NASA Technical Reports Server (NTRS)

    Buning, Pieter G.; Pulliam, Thomas H.

    2011-01-01

    An improved solution adaption capability has been implemented in the OVERFLOW overset grid CFD code. Building on the Cartesian off-body approach inherent in OVERFLOW and the original adaptive refinement method developed by Meakin, the new scheme provides for automated creation of multiple levels of finer Cartesian grids. Refinement can be based on the undivided second-difference of the flow solution variables, or on a specific flow quantity such as vorticity. Coupled with load-balancing and an inmemory solution interpolation procedure, the adaption process provides very good performance for time-accurate simulations on parallel compute platforms. A method of using refined, thin body-fitted grids combined with adaption in the off-body grids is presented, which maximizes the part of the domain subject to adaption. Two- and three-dimensional examples are used to illustrate the effectiveness and performance of the adaption scheme.

  16. Development and application of a 3D Cartesian grid Euler method

    NASA Technical Reports Server (NTRS)

    Melton, John E.; Aftosmis, Michael J.; Berger, Marsha J.; Wong, Michael D.

    1995-01-01

    This report describes recent progress in the development and application of 3D Cartesian grid generation and Euler flow solution techniques. Improvements to flow field grid generation algorithms, geometry representations, and geometry refinement criteria are presented, including details of a procedure for correctly identifying and resolving extremely thin surface features. An initial implementation of automatic flow field refinement is also presented. Results for several 3D multi-component configurations are provided and discussed.

  17. An adaptive discretization of compressible flow using a multitude of moving Cartesian grids

    NASA Astrophysics Data System (ADS)

    Qiu, Linhai; Lu, Wenlong; Fedkiw, Ronald

    2016-01-01

    We present a novel method for simulating compressible flow on a multitude of Cartesian grids that can rotate and translate. Following previous work, we split the time integration into an explicit step for advection followed by an implicit solve for the pressure. A second order accurate flux based scheme is devised to handle advection on each moving Cartesian grid using an effective characteristic velocity that accounts for the grid motion. In order to avoid the stringent time step restriction imposed by very fine grids, we propose strategies that allow for a fluid velocity CFL number larger than 1. The stringent time step restriction related to the sound speed is alleviated by formulating an implicit linear system in order to find a pressure consistent with the equation of state. This implicit linear system crosses overlapping Cartesian grid boundaries by utilizing local Voronoi meshes to connect the various degrees of freedom obtaining a symmetric positive-definite system. Since a straightforward application of this technique contains an inherent central differencing which can result in spurious oscillations, we introduce a new high order diffusion term similar in spirit to ENO-LLF but solved for implicitly in order to avoid any associated time step restrictions. The method is conservative on each grid, as well as globally conservative on the background grid that contains all other grids. Moreover, a conservative interpolation operator is devised for conservatively remapping values in order to keep them consistent across different overlapping grids. Additionally, the method is extended to handle two-way solid fluid coupling in a monolithic fashion including cases (in the appendix) where solids in close proximity do not properly allow for grid based degrees of freedom in between them.

  18. Euler Technology Assessment program for preliminary aircraft design employing SPLITFLOW code with Cartesian unstructured grid method

    NASA Technical Reports Server (NTRS)

    Finley, Dennis B.

    1995-01-01

    This report documents results from the Euler Technology Assessment program. The objective was to evaluate the efficacy of Euler computational fluid dynamics (CFD) codes for use in preliminary aircraft design. Both the accuracy of the predictions and the rapidity of calculations were to be assessed. This portion of the study was conducted by Lockheed Fort Worth Company, using a recently developed in-house Cartesian-grid code called SPLITFLOW. The Cartesian grid technique offers several advantages for this study, including ease of volume grid generation and reduced number of cells compared to other grid schemes. SPLITFLOW also includes grid adaptation of the volume grid during the solution convergence to resolve high-gradient flow regions. This proved beneficial in resolving the large vortical structures in the flow for several configurations examined in the present study. The SPLITFLOW code predictions of the configuration forces and moments are shown to be adequate for preliminary design analysis, including predictions of sideslip effects and the effects of geometry variations at low and high angles of attack. The time required to generate the results from initial surface definition is on the order of several hours, including grid generation, which is compatible with the needs of the design environment.

  19. A cartesian grid embedded boundary method for the heat equationand poisson's equation in three dimensions

    SciTech Connect

    Schwartz, Peter; Barad, Michael; Colella, Phillip; Ligocki, Terry

    2004-11-02

    We present an algorithm for solving Poisson's equation and the heat equation on irregular domains in three dimensions. Our work uses the Cartesian grid embedded boundary algorithm for 2D problems of Johansen and Colella (1998, J. Comput. Phys. 147(2):60-85) and extends work of McCorquodale, Colella and Johansen (2001, J. Comput. Phys. 173(2):60-85). Our method is based on a finite-volume discretization of the operator, on the control volumes formed by intersecting the Cartesian grid cells with the domain, combined with a second-order accurate discretization of the fluxes. The resulting method provides uniformly second-order accurate solutions and gradients and is amenable to geometric multigrid solvers.

  20. Computing reaching dynamics in motor cortex with Cartesian spatial coordinates

    PubMed Central

    Sejnowski, Terrence J.

    2013-01-01

    How neurons in the primary motor cortex control arm movements is not yet understood. Here we show that the equations of motion governing reaching simplify when expressed in spatial coordinates. In this fixed reference frame, joint torques are the sums of vector cross products between the spatial positions of limb segments and their spatial accelerations and velocities. The consequences that follow from this model explain many properties of neurons in the motor cortex, including directional broad, cosinelike tuning, nonuniformly distributed preferred directions dependent on the workspace, and the rotation of the population vector during arm movements. Remarkably, the torques can be directly computed as a linearly weighted sum of responses from cortical motoneurons, and the muscle tensions can be obtained as rectified linear sums of the joint torques. This allows the required muscle tensions to be computed rapidly from a trajectory in space with a feedforward network model. PMID:23114209

  1. Large-eddy simulation of wind turbine wake interactions on locally refined Cartesian grids

    NASA Astrophysics Data System (ADS)

    Angelidis, Dionysios; Sotiropoulos, Fotis

    2014-11-01

    Performing high-fidelity numerical simulations of turbulent flow in wind farms remains a challenging issue mainly because of the large computational resources required to accurately simulate the turbine wakes and turbine/turbine interactions. The discretization of the governing equations on structured grids for mesoscale calculations may not be the most efficient approach for resolving the large disparity of spatial scales. A 3D Cartesian grid refinement method enabling the efficient coupling of the Actuator Line Model (ALM) with locally refined unstructured Cartesian grids adapted to accurately resolve tip vortices and multi-turbine interactions, is presented. Second order schemes are employed for the discretization of the incompressible Navier-Stokes equations in a hybrid staggered/non-staggered formulation coupled with a fractional step method that ensures the satisfaction of local mass conservation to machine zero. The current approach enables multi-resolution LES of turbulent flow in multi-turbine wind farms. The numerical simulations are in good agreement with experimental measurements and are able to resolve the rich dynamics of turbine wakes on grids containing only a small fraction of the grid nodes that would be required in simulations without local mesh refinement. This material is based upon work supported by the Department of Energy under Award Number DE-EE0005482 and the National Science Foundation under Award number NSF PFI:BIC 1318201.

  2. On the new analytical solution for a well in Cartesian coordinates with MODFLOW comparisons.

    PubMed

    Batu, Vedat

    2014-01-01

    In this paper, the comparison process of Batu (2012) generalized three-dimensional well hydraulics solution for confined aquifers in Cartesian coordinates with MODFLOW is presented. First, a brief description of Batu (2012) solution along with the governing equations and some of its key features are described. The final average drawdown expression in an observation well is given with the conversion expressions from Cartesian to radial coordinates. A generalized comparison using Batu (2012), Hantush (1964), and MODFLOW (Harbaugh et al. 2000), for vertical wells in horizontally isotropic aquifers, that is, ayx  = Ky /Kx  = 1, is presented. Comparisons are also presented with Batu (2012) and MODFLOW for horizontally anisotropic aquifers, that is, ayx  ≠ 1. After that comparisons are presented for horizontal wells between Batu (2012) and MODFLOW. PMID:24236933

  3. Grid-coordinate generation program

    USGS Publications Warehouse

    Cosner, Oliver J.; Horwich, Esther

    1974-01-01

    This program description of the grid-coordinate generation program is written for computer users who are familiar with digital aquifer models. The program computes the coordinates for a variable grid -used in the 'Pinder Model' (a finite-difference aquifer simulator), for input to the CalComp GPCP (general purpose contouring program). The program adjusts the y-value by a user-supplied constant in order to transpose the origin of the model grid from the upper left-hand corner to the lower left-hand corner of the grid. The user has the options of, (1.) choosing the boundaries of the plot; (2.) adjusting the z-values (altitudes) by a constant; (3.) deleting superfluous z-values and (4.) subtracting the simulated surfaces from each other to obtain the decline. Output of this program includes the fixed format CNTL data cards and the other data cards required for input to GPCP. The output from GPCP then is used to produce a potentiometric map or a decline map by means of the CalComp plotter.

  4. A sharp interface finite volume method for elliptic equations on Cartesian grids

    NASA Astrophysics Data System (ADS)

    Oevermann, M.; Scharfenberg, C.; Klein, R.

    2009-08-01

    We present a second order sharp interface finite volume method for the solution of the three-dimensional elliptic equation ∇·(β(x→)∇u(x→))=f(x→) with variable coefficients on Cartesian grids. In particular, we focus on interface problems with discontinuities in the coefficient, the source term, the solution, and the fluxes across the interface. The method uses standard piecewise trilinear finite elements for normal cells and a double piecewise trilinear ansatz for the solution on cells intersected by the interface resulting always in a compact 27-point stencil. Singularities associated with vanishing partial volumes of intersected grid cells are removed by a two-term asymptotic approach. In contrast to the 2D method presented by two of the authors in [M. Oevermann, R. Klein, A Cartesian grid finite volume method for elliptic equations with variable coefficients and embedded interfaces, Journal of Computational Physics 219 (2006) 749-769] we use a minimization technique to determine the unknown coefficients of the double trilinear ansatz. This simplifies the treatment of the different cut-cell types and avoids additional special operations for degenerated interface topologies. The resulting set of linear equations has been solved with a BiCGSTAB solver preconditioned with an algebraic multigrid. In various testcases - including large β-ratios and non-smooth interfaces - the method achieves second order of accuracy in the L∞ and L2 norm.

  5. Linear transformation of anharmonic molecular force constants between normal and Cartesian coordinates.

    PubMed

    Mackie, Cameron J; Candian, Alessandra; Huang, Xinchuan; Lee, Timothy J; Tielens, Alexander G G M

    2015-06-28

    A full derivation of the analytic transformation of the quadratic, cubic, and quartic force constants from normal coordinates to Cartesian coordinates is given. Previous attempts at this transformation have resulted in non-linear transformations; however, for the first time, a simple linear transformation is presented here. Two different approaches have been formulated and implemented, one of which does not require prior knowledge of the translation-rotation eigenvectors from diagonalization of the Hessian matrix. The validity of this method is tested using two molecules H2O and c-C3H2D(+). PMID:26133410

  6. A Cartesian grid embedded boundary method for Poisson`s equation on irregular domains

    SciTech Connect

    Johansen, H.; Colella, P.

    1997-01-31

    The authors present a numerical method for solving Poisson`s equation, with variable coefficients and Dirichlet boundary conditions, on two-dimensional regions. The approach uses a finite-volume discretization, which embeds the domain in a regular Cartesian grid. They treat the solution as a cell-centered quantity, even when those centers are outside the domain. Cells that contain a portion of the domain boundary use conservation differencing of second-order accurate fluxes, on each cell volume. The calculation of the boundary flux ensures that the conditioning of the matrix is relatively unaffected by small cell volumes. This allows them to use multi-grid iterations with a simple point relaxation strategy. They have combined this with an adaptive mesh refinement (AMR) procedure. They provide evidence that the algorithm is second-order accurate on various exact solutions, and compare the adaptive and non-adaptive calculations.

  7. On the diffuse interface method using a dual-resolution Cartesian grid

    NASA Astrophysics Data System (ADS)

    Ding, Hang; Yuan, Cheng-jun

    2014-09-01

    We investigate the applicability and performance of diffuse interface methods on a dual-resolution grid in solving two-phase flows. In the diffuse interface methods, the interface thickness represents a cut-off length scale in resolving the interfacial dynamics, and it was found that an apparent loss of mass occurs when the interface thickness is comparable to the length scale of flows [24]. From the accuracy and mass conservation point of view, it is desirable to have a thin interface in simulations. We propose to use a dual-resolution Cartesian grid, on which a finer resolution is applied to the volume fraction C than that for the velocity and pressure fields. Because the computation of C field is rather inexpensive compared to that required by velocity and pressure fields, dual-resolution grids can significantly increase the resolution of the interface with only a slight increase of computational cost, as compared to the single-resolution grid. The solution couplings between the fine grid for C and the coarse grid (for velocity and pressure) are delicately designed, to make sure that the interpolated velocity is divergence-free at a discrete level and that the mass and surface tension force are conserved. A variety of numerical tests have been performed to validate the method and check its performance. The dual-resolution grid appears to save nearly 70% of the computational time in two-dimensional simulations and 80% in three-dimensional simulations, and produces nearly the same results as the single-resolution grid. Quantitative comparisons are made with previous studies, including Rayleigh Taylor instability, steadily rising bubble, and partial coalescence of a drop into a pool, and good agreement has been achieved. Finally, results are presented for the deformation and breakup of three-dimensional drops in simple shear flows.

  8. Cartesian-Grid Simulations of a Canard-Controlled Missile with a Free-Spinning Tail

    NASA Technical Reports Server (NTRS)

    Murman, Scott M.; Aftosmis, Michael J.; Kwak, Dochan (Technical Monitor)

    2002-01-01

    The proposed paper presents a series of simulations of a geometrically complex, canard-controlled, supersonic missile with free-spinning tail fins. Time-dependent simulations were performed using an inviscid Cartesian-grid-based method with results compared to both experimental data and high-resolution Navier-Stokes computations. At fixed free stream conditions and canard deflections, the tail spin rate was iteratively determined such that the net rolling moment on the empennage is zero. This rate corresponds to the time-asymptotic rate of the free-to-spin fin system. After obtaining spin-averaged aerodynamic coefficients for the missile, the investigation seeks a fixed-tail approximation to the spin-averaged aerodynamic coefficients, and examines the validity of this approximation over a variety of freestream conditions.

  9. Protostellar hydrodynamics: Constructing and testing a spacially and temporally second-order accurate method. 2: Cartesian coordinates

    NASA Technical Reports Server (NTRS)

    Myhill, Elizabeth A.; Boss, Alan P.

    1993-01-01

    In Boss & Myhill (1992) we described the derivation and testing of a spherical coordinate-based scheme for solving the hydrodynamic equations governing the gravitational collapse of nonisothermal, nonmagnetic, inviscid, radiative, three-dimensional protostellar clouds. Here we discuss a Cartesian coordinate-based scheme based on the same set of hydrodynamic equations. As with the spherical coorrdinate-based code, the Cartesian coordinate-based scheme employs explicit Eulerian methods which are both spatially and temporally second-order accurate. We begin by describing the hydrodynamic equations in Cartesian coordinates and the numerical methods used in this particular code. Following Finn & Hawley (1989), we pay special attention to the proper implementations of high-order accuracy, finite difference methods. We evaluate the ability of the Cartesian scheme to handle shock propagation problems, and through convergence testing, we show that the code is indeed second-order accurate. To compare the Cartesian scheme discussed here with the spherical coordinate-based scheme discussed in Boss & Myhill (1992), the two codes are used to calculate the standard isothermal collapse test case described by Bodenheimer & Boss (1981). We find that with the improved codes, the intermediate bar-configuration found previously disappears, and the cloud fragments directly into a binary protostellar system. Finally, we present the results from both codes of a new test for nonisothermal protostellar collapse.

  10. Solving vertical and horizontal well hydraulics problems analytically in Cartesian coordinates with vertical and horizontal anisotropies

    NASA Astrophysics Data System (ADS)

    Batu, Vedat

    2012-01-01

    SummaryA new generalized three-dimensional analytical solution is developed for a partially-penetrating vertical rectangular parallelepiped well screen in a confined aquifer by solving the three-dimensional transient ground water flow differential equation in x- y- z Cartesian coordinates system for drawdown by taking into account the three principal hydraulic conductivities ( Kx, Ky, and Kz) along the x- y- z coordinate directions. The fully penetrating screen case becomes equivalent to the single vertical fracture case of Gringarten and Ramey (1973). It is shown that the new solution and Gringarten and Ramey solution (1973) match very well. Similarly, it is shown that this new solution for a horizontally tiny fully penetrating parallelepiped rectangular parallelepiped screen case match very well with Theis (1935) solution. Moreover, it is also shown that the horizontally tiny partially-penetrating parallelepiped rectangular well screen case of this new solution match very well with Hantush (1964) solution. This new analytical solution can also cover a partially-penetrating horizontal well by representing its screen interval with vertically tiny rectangular parallelepiped. Also the solution takes into account both the vertical anisotropy ( azx = Kz/ Kx) as well as the horizontal anisotropy ( ayx = Ky/ Kx) and has potential application areas to analyze pumping test drawdown data from partially-penetrating vertical and horizontal wells by representing them as tiny rectangular parallelepiped as well as line sources. The solution has also potential application areas for a partially-penetrating parallelepiped rectangular vertical fracture. With this new solution, the horizontal anisotropy ( ayx = Ky/ Kx) in addition to the vertical anisotropy ( azx = Kz/ Kx) can also be determined using observed drawdown data. Most importantly, with this solution, to the knowledge of the author, it has been shown the first time in the literature that some well-known well hydraulics problems can also be solved in Cartesian coordinates with some additional advantages other than the conventional cylindrical coordinates method.

  11. A Fast and Robust Poisson-Boltzmann Solver Based on Adaptive Cartesian Grids

    PubMed Central

    Boschitsch, Alexander H.; Fenley, Marcia O.

    2011-01-01

    An adaptive Cartesian grid (ACG) concept is presented for the fast and robust numerical solution of the 3D Poisson-Boltzmann Equation (PBE) governing the electrostatic interactions of large-scale biomolecules and highly charged multi-biomolecular assemblies such as ribosomes and viruses. The ACG offers numerous advantages over competing grid topologies such as regular 3D lattices and unstructured grids. For very large biological molecules and multi-biomolecule assemblies, the total number of grid-points is several orders of magnitude less than that required in a conventional lattice grid used in the current PBE solvers thus allowing the end user to obtain accurate and stable nonlinear PBE solutions on a desktop computer. Compared to tetrahedral-based unstructured grids, ACG offers a simpler hierarchical grid structure, which is naturally suited to multigrid, relieves indirect addressing requirements and uses fewer neighboring nodes in the finite difference stencils. Construction of the ACG and determination of the dielectric/ionic maps are straightforward, fast and require minimal user intervention. Charge singularities are eliminated by reformulating the problem to produce the reaction field potential in the molecular interior and the total electrostatic potential in the exterior ionic solvent region. This approach minimizes grid-dependency and alleviates the need for fine grid spacing near atomic charge sites. The technical portion of this paper contains three parts. First, the ACG and its construction for general biomolecular geometries are described. Next, a discrete approximation to the PBE upon this mesh is derived. Finally, the overall solution procedure and multigrid implementation are summarized. Results obtained with the ACG-based PBE solver are presented for: (i) a low dielectric spherical cavity, containing interior point charges, embedded in a high dielectric ionic solvent – analytical solutions are available for this case, thus allowing rigorous assessment of the solution accuracy; (ii) a pair of low dielectric charged spheres embedded in a ionic solvent to compute electrostatic interaction free energies as a function of the distance between sphere centers; (iii) surface potentials of proteins, nucleic acids and their larger-scale assemblies such as ribosomes; and (iv) electrostatic solvation free energies and their salt sensitivities – obtained with both linear and nonlinear Poisson-Boltzmann equation – for a large set of proteins. These latter results along with timings can serve as benchmarks for comparing the performance of different PBE solvers. PMID:21984876

  12. Simulating hydrodynamics in a spring-fed estuary using a three-dimensional unstructured Cartesian grid model

    NASA Astrophysics Data System (ADS)

    Chen, XinJian

    2012-12-01

    This paper presents an application of a three-dimensional unstructured Cartesian grid model (Chen, 2011) to a real-world case, namely the Crystal River/Kings Bay system located on the Gulf coast of the Florida peninsula of the United States. Crystal River/Kings Bay is a spring-fed estuarine system which is believed to be the largest natural refuge in the United States for manatees during the coldest days in winter because of the existence of a large amount of discharge out of numerous spring vents at the bottom of Kings Bay. The unstructured Cartesian grid model was used to simulate hydrodynamics, including salinity transport processes and thermodynamics, in the estuary during a 34-month period from April 2007 to February 2010. Although there are some unidentified uncertainties in quantifying flow rates from the spring vents and salinity variations in spring flows, simulated water elevations, salinities, temperatures, and cross-sectional flux all match well or very well with measured real-time field data. This suggests that the unstructured Cartesian grid model can adequately simulate hydrodynamics in a complex shallow water system such as Crystal River/Kings Bay and the numerical theory for the unstructured Cartesian grid model works properly. The successful simulation of hydrodynamics in the estuarine system also suggests that an empirical formula that relates the spring discharge with the water level in Kings Bay and the groundwater level measured in a nearby well is reasonable.

  13. Alternative transformation from Cartesian to geodetic coordinates by least squares for GPS georeferencing applications

    NASA Astrophysics Data System (ADS)

    Soler, T.; Han, J. Y.; Weston, N. D.

    2012-05-01

    The inverse transformation of coordinates, from Cartesian to curvilinear geodetic, or symbolically (x,y,z)?(?,?,h) has been extensively researched in the geodetic literature. However, published formulations require that the application must be deterministically implemented point-by-point individually. Recently, and thanks to GPS technology, scientists have made available thousands of determinations of the coordinates (x,y,z) at a single point perhaps characterized by different observational circumstances such as date, length of occupation time, distance and geometric distribution of reference stations, etc. In this paper a least squares (LS) solution is introduced to determine a unique set of geodetic coordinates, with accompanying accuracy predictions all based on the given sets of individual (x,y,z) GPS-obtained values and their variance-covariance matrices. The (x,y,z) coordinates are used as pseudo-observations with their attached stochastic information in the LS process to simultaneously compute a unique set of (?,?,h) curvilinear geodetic coordinates from different observing scenarios.

  14. From symplectic integrator to Poincare map: Spline expansion of a map generator in Cartesian coordinates

    SciTech Connect

    Warnock, R.L.; Ellison, J.A. |

    1997-08-01

    Data from orbits of a symplectic integrator can be interpolated so as to construct an approximation to the generating function of a Poincare map. The time required to compute an orbit of the symplectic map induced by the generator can be much less than the time to follow the same orbit by symplectic integration. The construction has been carried out previously for full-turn maps of large particle accelerators, and a big saving in time (for instance a factor of 60) has been demonstrated. A shortcoming of the work to date arose from the use of canonical polar coordinates, which precluded map construction in small regions of phase space near coordinate singularities. This paper shows that Cartesian coordinates can also be used, thus avoiding singularities. The generator is represented in a basis of tensor product B-splines. Under weak conditions the spline expansion converges uniformly as the mesh is refined, approaching the exact generator of the Poincare map as defined by the symplectic integrator, in some parallelepiped of phase space centered at the origin.

  15. A Domain-Decomposed Multilevel Method for Adaptively Refined Cartesian Grids with Embedded Boundaries

    NASA Technical Reports Server (NTRS)

    Aftosmis, M. J.; Berger, M. J.; Adomavicius, G.

    2000-01-01

    Preliminary verification and validation of an efficient Euler solver for adaptively refined Cartesian meshes with embedded boundaries is presented. The parallel, multilevel method makes use of a new on-the-fly parallel domain decomposition strategy based upon the use of space-filling curves, and automatically generates a sequence of coarse meshes for processing by the multigrid smoother. The coarse mesh generation algorithm produces grids which completely cover the computational domain at every level in the mesh hierarchy. A series of examples on realistically complex three-dimensional configurations demonstrate that this new coarsening algorithm reliably achieves mesh coarsening ratios in excess of 7 on adaptively refined meshes. Numerical investigations of the scheme's local truncation error demonstrate an achieved order of accuracy between 1.82 and 1.88. Convergence results for the multigrid scheme are presented for both subsonic and transonic test cases and demonstrate W-cycle multigrid convergence rates between 0.84 and 0.94. Preliminary parallel scalability tests on both simple wing and complex complete aircraft geometries shows a computational speedup of 52 on 64 processors using the run-time mesh partitioner.

  16. A Domain-Decomposed Multi-Level Method for Adaptively Refined Cartesian Grids with Embedded Boundaries

    NASA Technical Reports Server (NTRS)

    Aftosmis, M. J.; Berger, M. J.; Adomavicius, G.; Nixon, David (Technical Monitor)

    1998-01-01

    The work presents a new method for on-the-fly domain decomposition technique for mapping grids and solution algorithms to parallel machines, and is applicable to both shared-memory and message-passing architectures. It will be demonstrated on the Cray T3E, HP Exemplar, and SGI Origin 2000. Computing time has been secured on all these platforms. The decomposition technique is an outgrowth of techniques used in computational physics for simulations of N-body problems and the event horizons of black holes, and has not been previously used by the CFD community. Since the technique offers on-the-fly partitioning, it offers a substantial increase in flexibility for computing in heterogeneous environments, where the number of available processors may not be known at the time of job submission. In addition, since it is dynamic it permits the job to be repartitioned without global communication in cases where additional processors become available after the simulation has begun, or in cases where dynamic mesh adaptation changes the mesh size during the course of a simulation. The platform for this partitioning strategy is a completely new Cartesian Euler solver tarcreted at parallel machines which may be used in conjunction with Ames' "Cart3D" arbitrary geometry simulation package.

  17. Features of CPB: A Poisson-Boltzmann Solver that Uses an Adaptive Cartesian Grid

    PubMed Central

    Harris, Robert C.; Mackoy, Travis

    2014-01-01

    The capabilities of an adaptive Cartesian grid (ACG)-based Poisson-Boltzmann (PB) solver (CPB) are demonstrated. CPB solves various PB equations with an ACG, built from a hierarchical octree decomposition of the computational domain. This procedure decreases the number of points required, thereby reducing computational demands. Inside the molecule, CPB solves for the reaction-field component (ϕrf) of the electrostatic potential (ϕ), eliminating the charge-induced singularities in ϕ. CPB can also use a least-squares reconstruction method to improve estimates of ϕ at the molecular surface. All surfaces, which include solvent excluded, Gaussians and others, are created analytically, eliminating errors associated with triangulated surfaces. These features allow CPB to produce detailed surface maps of ϕ and compute polar solvation and binding free energies for large biomolecular assemblies, such as ribosomes and viruses, with reduced computational demands compared to other PBE solvers. The reader is referred to http://www.continuum-dynamics.com/solution-mm.html for how to obtain the CPB software. PMID:25430617

  18. Euler Technology Assessment for Preliminary Aircraft Design: Compressibility Predictions by Employing the Cartesian Unstructured Grid SPLITFLOW Code

    NASA Technical Reports Server (NTRS)

    Finley, Dennis B.; Karman, Steve L., Jr.

    1996-01-01

    The objective of the second phase of the Euler Technology Assessment program was to evaluate the ability of Euler computational fluid dynamics codes to predict compressible flow effects over a generic fighter wind tunnel model. This portion of the study was conducted by Lockheed Martin Tactical Aircraft Systems, using an in-house Cartesian-grid code called SPLITFLOW. The Cartesian grid technique offers several advantages, including ease of volume grid generation and reduced number of cells compared to other grid schemes. SPLITFLOW also includes grid adaption of the volume grid during the solution to resolve high-gradient regions. The SPLITFLOW code predictions of configuration forces and moments are shown to be adequate for preliminary design, including predictions of sideslip effects and the effects of geometry variations at low and high angles-of-attack. The transonic pressure prediction capabilities of SPLITFLOW are shown to be improved over subsonic comparisons. The time required to generate the results from initial surface data is on the order of several hours, including grid generation, which is compatible with the needs of the design environment.

  19. Implementation of the multiconfiguration time-dependent Hatree-Fock method for general molecules on a multiresolution Cartesian grid

    NASA Astrophysics Data System (ADS)

    Sawada, Ryohto; Sato, Takeshi; Ishikawa, Kenichi L.

    2016-02-01

    We report a three-dimensional numerical implementation of the multiconfiguration time-dependent Hartree-Fock method based on a multiresolution Cartesian grid, with no need to assume any symmetry of molecular structure. We successfully compute high-harmonic generation of H2 and H2O . The present implementation will open a way to the first-principles theoretical study of intense-field- and attosecond-pulse-induced ultrafast phenomena in general molecules.

  20. Modelling rapid mass movements using the shallow water equations in Cartesian coordinates

    NASA Astrophysics Data System (ADS)

    Hergarten, S.; Robl, J.

    2015-03-01

    We propose a new method to model rapid mass movements on complex topography using the shallow water equations in Cartesian coordinates. These equations are the widely used standard approximation for the flow of water in rivers and shallow lakes, but the main prerequisite for their application - an almost horizontal fluid table - is in general not satisfied for avalanches and debris flows in steep terrain. Therefore, we have developed appropriate correction terms for large topographic gradients. In this study we present the mathematical formulation of these correction terms and their implementation in the open-source flow solver GERRIS. This novel approach is evaluated by simulating avalanches on synthetic and finally natural topographies and the widely used Voellmy flow resistance law. Testing the results against analytical solutions and the proprietary avalanche model RAMMS, we found a very good agreement. As the GERRIS flow solver is freely available and open source, it can be easily extended by additional fluid models or source areas, making this model suitable for simulating several types of rapid mass movements. It therefore provides a valuable tool for assisting regional-scale natural hazard studies.

  1. X-ray phase-contrast imaging: transmission functions separable in Cartesian coordinates.

    PubMed

    Cao, Guohua; Hamilton, Theron J; Rose-Petruck, Christoph; Diebold, Gerald J

    2007-04-01

    In-line, x-ray phase-contrast imaging is responsive to both phase changes and absorption as the x radiation traverses a body. Expressions are derived for phase-contrast imaging of objects having transmission functions separable in Cartesian coordinates. Starting from the Fresnel-Kirchhoff integral formula for image formation, an expression is found for the phase-contrast image produced by an x-ray source with nonvanishing dimensions. This expression is evaluated in limiting cases where the source-to-object distance is large, where the source acts as a point source, and where the weak phase approximation is valid. The integral expression for the image is evaluated for objects with simple geometrical shapes, showing the influence of the source dimensions on the visibility of phase-contrast features. The expressions derived here are evaluated for cases where the magnification is substantially greater than one as would be employed in biological imaging. Experiments are reported using the in-line phase-contrast imaging method with a microfocus x-ray source and a CCD camera. PMID:17361308

  2. Development of multiphase Navier-Stokes simulation capability for turbulent gas flow over laminar liquid for Cartesian grids

    NASA Astrophysics Data System (ADS)

    Miao, Sha; Hendrickson, Kelli; Liu, Yuming; Subramani, Hariprasad

    2015-11-01

    This work presents a novel and efficient Cartesian-grid based simulation capability for the study of an incompressible, turbulent gas layer over a liquid flow with disparate Reynolds numbers in two phases. This capability couples a turbulent gas-flow solver and a liquid-layer based on a second-order accurate Boundary Data Immersion Method (BDIM) at the deformable interface. The turbulent gas flow solver solves the incompressible Navier-Stokes equations via direct numerical simulation or through turbulence closure (unsteady Reynolds-Averaged Navier-Stokes Models) for Reynolds numbers O(106). In this application, a laminar liquid layer solution is obtained from depth-integrated Navier-Stokes equations utilizing shallow water wave assumptions. The immersed boundary method (BDIM) enforces the coupling at the deformable interface, the boundary conditions to turbulence closure equations and defines the domain geometry on the Cartesian grid. Validations are made for the turbulent gas channel flow over high-viscosity liquid. This simulation capability can be applied to problems in the oil and industrial sector such as channel and pipe flows with heavy oils as well as wind wave generation in shallow waters. Sponsored by the Chevron Energy Technology Company.

  3. Convergence and superconvergence of staggered discontinuous Galerkin methods for the three-dimensional Maxwell’s equations on Cartesian grids

    NASA Astrophysics Data System (ADS)

    Chung, Eric T.; Ciarlet, Patrick; Yu, Tang Fei

    2013-02-01

    In this paper, a new type of staggered discontinuous Galerkin methods for the three dimensional Maxwell’s equations is developed and analyzed. The spatial discretization is based on staggered Cartesian grids so that many good properties are obtained. First of all, our method has the advantages that the numerical solution preserves the electromagnetic energy and automatically fulfills a discrete version of the Gauss law. Moreover, the mass matrices are diagonal, thus time marching is explicit and is very efficient. Our method is high order accurate and the optimal order of convergence is rigorously proved. It is also very easy to implement due to its Cartesian structure and can be regarded as a generalization of the classical Yee’s scheme as well as the quadrilateral edge finite elements. Furthermore, a superconvergence result, that is the convergence rate is one order higher at interpolation nodes, is proved. Numerical results are shown to confirm our theoretical statements, and applications to problems in unbounded domains with the use of PML are presented. A comparison of our staggered method and non-staggered method is carried out and shows that our method has better accuracy and efficiency.

  4. Wave simulation in 2D heterogeneous transversely isotropic porous media with fractional attenuation: A Cartesian grid approach

    NASA Astrophysics Data System (ADS)

    Blanc, Emilie; Chiavassa, Guillaume; Lombard, Bruno

    2014-10-01

    A time-domain numerical modeling of transversely isotropic Biot poroelastic waves is proposed in two dimensions. The viscous dissipation occurring in the pores is described using the dynamic permeability model developed by Johnson-Koplik-Dashen (JKD). Some of the coefficients in the Biot-JKD model are proportional to the square root of the frequency. In the time-domain, these coefficients introduce shifted fractional derivatives of order 1/2, involving a convolution product. Based on a diffusive representation, the convolution kernel is replaced by a finite number of memory variables that satisfy local-in-time ordinary differential equations, resulting in the Biot-DA (diffusive approximation) model. The properties of both the Biot-JKD and the Biot-DA models are analyzed: hyperbolicity, decrease of energy, dispersion. To determine the coefficients of the diffusive approximation, two approaches are analyzed: Gaussian quadratures and optimization methods in the frequency range of interest. The nonlinear optimization is shown to be the better way of determination. A splitting strategy is then applied to approximate numerically the Biot-DA equations. The propagative part is discretized using a fourth-order ADER scheme on a Cartesian grid, whereas the diffusive part is solved exactly. An immersed interface method is implemented to take into account heterogeneous media on a Cartesian grid and to discretize the jump conditions at interfaces. Numerical experiments are presented. Comparisons with analytical solutions show the efficiency and the accuracy of the approach, and some numerical experiments are performed to investigate wave phenomena in complex media, such as multiple scattering across a set of random scatterers.

  5. Augmented weighted diamond form of the linear nodal scheme for Cartesian coordinate systems

    SciTech Connect

    Walters, W.F.

    1985-01-01

    The equations of the high order linear nodal numerical scheme are cast in an augmented weighted difference form for three-dimensional Cartesian nodes. The coupling exhibited by these equations indicate that this new algorithm is simpler and hence faster than previous nodal schemes of this degree of accuracy. A well-logging problem and a fast reactor problem are examined. The new scheme developed here is compared with the classical linear-linear nodal scheme and the diamond difference scheme. For the well-logging problem, it is found that the new scheme is both faster and simpler than the classical linear-linear nodal scheme while sacrificing little in accuracy. Even though the new scheme is more accurate than the diamond difference scheme for the reactor problem, the results indicate that state of the art acceleration methods are needed for nodal schemes.

  6. Characterization of genome-wide ordered sequence-tagged Mycobacterium mutant libraries by Cartesian Pooling-Coordinate Sequencing

    PubMed Central

    Vandewalle, Kristof; Festjens, Nele; Plets, Evelyn; Vuylsteke, Marnik; Saeys, Yvan; Callewaert, Nico

    2015-01-01

    Reverse genetics research approaches require the availability of methods to rapidly generate specific mutants. Alternatively, where these methods are lacking, the construction of pre-characterized libraries of mutants can be extremely valuable. However, this can be complex, expensive and time consuming. Here, we describe a robust, easy to implement parallel sequencing-based method (Cartesian Pooling-Coordinate Sequencing or CP-CSeq) that reports both on the identity as well as on the location of sequence-tagged biological entities in well-plate archived clone collections. We demonstrate this approach using a transposon insertion mutant library of the Mycobacterium bovis BCG vaccine strain, providing the largest resource of mutants in any strain of the M. tuberculosis complex. The method is applicable to any entity for which sequence-tagged identification is possible. PMID:25960123

  7. Early and Late Inhibitions Elicited by a Peripheral Visual Cue on Manual Response to a Visual Target: Are They Based on Cartesian Coordinates?

    ERIC Educational Resources Information Center

    Gawryszewski, Luiz G.; Carreiro, Luiz Renato R.; Magalhaes, Fabio V.

    2005-01-01

    A non-informative cue (C) elicits an inhibition of manual reaction time (MRT) to a visual target (T). We report an experiment to examine if the spatial distribution of this inhibitory effect follows Polar or Cartesian coordinate systems. C appeared at one out of 8 isoeccentric (7[degrees]) positions, the C-T angular distances (in polar…

  8. Hybrid freeform TIR optics construction in Cartesian coordinate system: a new composite ray mapping method

    NASA Astrophysics Data System (ADS)

    Ma, Donglin; Feng, Zexin; Wang, Chengliang; Liang, Rongguang

    2015-09-01

    In this paper, we propose a new composite ray mapping method to design freeform total internal reflective (TIR) optics for LED illumination. We sample the ray intensity distribution into rectangular grids which have the best topological match to those rectangular grids on the target surface. With the multiple-to-one mapping relationships between the source intensity distribution and target irradiance distribution, we can construct the freeform TIR surfaces and freeform refractive surface using Snell's law. Compared to our previous design using uv-θϕ composite ray mapping method, this design approach is expected to have much less surface error and improve the illumination uniformity further because of the better topological match. In addition, due to the overlapping mechanism by multiple-to-one (composite) ray mapping, the method could lead to a more robust freeform optics compared to traditional freeform optics designs.

  9. A Fully Conservative and Entropy Preserving Cut-Cell Method for Incompressible Viscous Flows on Staggered Cartesian Grids

    NASA Astrophysics Data System (ADS)

    Le Chenadec, Vincent; Bay, Yong Yi

    2015-11-01

    The treatment of complex geometries in Computational Fluid Dynamics applications is a challenging endeavor, which immersed boundary and cut-cell techniques can significantly simplify by alleviating the meshing process required by body-fitted meshes. These methods also introduce new challenges, in that the formulation of accurate and well-posed discrete operators is not trivial. A cut-cell method for the solution of the incompressible Navier-Stokes equation is proposed for staggered Cartesian grids. In both scalar and vector cases, the emphasis is set on the structure of the discrete operators, designed to mimic the properties of the continuous ones while retaining a nearest-neighbor stencil. For convective transport, different forms are proposed (divergence, advective and skew-symmetric), and shown to be equivalent when the discrete continuity equation is satisfied. This ensures mass, momentum and kinetic energy conservation. For diffusive transport, conservative and symmetric operators are proposed for both Dirichlet and Neumann boundary conditions. Symmetry ensures the existence of a sink term (viscous dissipation) in the discrete kinetic energy budget, which is beneficial for stability. The accuracy of method is finally assessed in standard test cases.

  10. Balancing Area Coordination: Efficiently Integrating Renewable Energy Into the Grid, Greening the Grid

    SciTech Connect

    Katz, Jessica; Denholm, Paul; Cochran, Jaquelin

    2015-06-01

    Greening the Grid provides technical assistance to energy system planners, regulators, and grid operators to overcome challenges associated with integrating variable renewable energy into the grid. Coordinating balancing area operation can promote more cost and resource efficient integration of variable renewable energy, such as wind and solar, into power systems. This efficiency is achieved by sharing or coordinating balancing resources and operating reserves across larger geographic boundaries.

  11. Direct vibro-elastography FEM inversion in Cartesian and cylindrical coordinate systems without the local homogeneity assumption

    NASA Astrophysics Data System (ADS)

    Honarvar, M.; Lobo, J.; Mohareri, O.; Salcudean, S. E.; Rohling, R.

    2015-05-01

    To produce images of tissue elasticity, the vibro-elastography technique involves applying a steady-state multi-frequency vibration to tissue, estimating displacements from ultrasound echo data, and using the estimated displacements in an inverse elasticity problem with the shear modulus spatial distribution as the unknown. In order to fully solve the inverse problem, all three displacement components are required. However, using ultrasound, the axial component of the displacement is measured much more accurately than the other directions. Therefore, simplifying assumptions must be used in this case. Usually, the equations of motion are transformed into a Helmholtz equation by assuming tissue incompressibility and local homogeneity. The local homogeneity assumption causes significant imaging artifacts in areas of varying elasticity. In this paper, we remove the local homogeneity assumption. In particular we introduce a new finite element based direct inversion technique in which only the coupling terms in the equation of motion are ignored, so it can be used with only one component of the displacement. Both Cartesian and cylindrical coordinate systems are considered. The use of multi-frequency excitation also allows us to obtain multiple measurements and reduce artifacts in areas where the displacement of one frequency is close to zero. The proposed method was tested in simulations and experiments against a conventional approach in which the local homogeneity is used. The results show significant improvements in elasticity imaging with the new method compared to previous methods that assumes local homogeneity. For example in simulations, the contrast to noise ratio (CNR) for the region with spherical inclusion increases from an average value of 1.5-17 after using the proposed method instead of the local inversion with homogeneity assumption, and similarly in the prostate phantom experiment, the CNR improved from an average value of 1.6 to about 20.

  12. Direct vibro-elastography FEM inversion in Cartesian and cylindrical coordinate systems without the local homogeneity assumption.

    PubMed

    Honarvar, M; Lobo, J; Mohareri, O; Salcudean, S E; Rohling, R

    2015-05-01

    To produce images of tissue elasticity, the vibro-elastography technique involves applying a steady-state multi-frequency vibration to tissue, estimating displacements from ultrasound echo data, and using the estimated displacements in an inverse elasticity problem with the shear modulus spatial distribution as the unknown. In order to fully solve the inverse problem, all three displacement components are required. However, using ultrasound, the axial component of the displacement is measured much more accurately than the other directions. Therefore, simplifying assumptions must be used in this case. Usually, the equations of motion are transformed into a Helmholtz equation by assuming tissue incompressibility and local homogeneity. The local homogeneity assumption causes significant imaging artifacts in areas of varying elasticity. In this paper, we remove the local homogeneity assumption. In particular we introduce a new finite element based direct inversion technique in which only the coupling terms in the equation of motion are ignored, so it can be used with only one component of the displacement. Both Cartesian and cylindrical coordinate systems are considered. The use of multi-frequency excitation also allows us to obtain multiple measurements and reduce artifacts in areas where the displacement of one frequency is close to zero. The proposed method was tested in simulations and experiments against a conventional approach in which the local homogeneity is used. The results show significant improvements in elasticity imaging with the new method compared to previous methods that assumes local homogeneity. For example in simulations, the contrast to noise ratio (CNR) for the region with spherical inclusion increases from an average value of 1.5-17 after using the proposed method instead of the local inversion with homogeneity assumption, and similarly in the prostate phantom experiment, the CNR improved from an average value of 1.6 to about 20. PMID:25906038

  13. Computing UV/vis spectra from the adiabatic and vertical Franck-Condon schemes with the use of Cartesian and internal coordinates

    SciTech Connect

    Götze, Jan P.; Karasulu, Bora; Thiel, Walter

    2013-12-21

    We address the effects of using Cartesian or internal coordinates in the adiabatic Franck-Condon (AFC) and vertical Franck-Condon (VFC) approaches to electronic spectra. The adopted VFC approach is a simplified variant of the original approach [A. Hazra, H. H. Chang, and M. Nooijen, J. Chem. Phys. 151, 2125 (2004)], as we omit any contribution from normal modes with imaginary frequency. For our test molecules ranging from ethylene to flavin compounds, VFC offers several advantages over AFC, especially by preserving the properties of the FC region and by avoiding complications arising from the crossing of excited-state potential surfaces or from the failure of the harmonic approximation. The spectral quality for our target molecules is insensitive to the chosen approach. We also explore the effects of Duschinsky rotation and relate the need for internal coordinates to the absence of symmetry elements. When using Duschinsky rotation and treating larger systems without planar symmetry, internal coordinates are found to outperform Cartesian coordinates in the AFC spectral calculations.

  14. Solwnd: A 3D Compressible MHD Code for Solar Wind Studies. Version 1.0: Cartesian Coordinates

    NASA Technical Reports Server (NTRS)

    Deane, Anil E.

    1996-01-01

    Solwnd 1.0 is a three-dimensional compressible MHD code written in Fortran for studying the solar wind. Time-dependent boundary conditions are available. The computational algorithm is based on Flux Corrected Transport and the code is based on the existing code of Zalesak and Spicer. The flow considered is that of shear flow with incoming flow that perturbs this base flow. Several test cases corresponding to pressure balanced magnetic structures with velocity shear flow and various inflows including Alfven waves are presented. Version 1.0 of solwnd considers a rectangular Cartesian geometry. Future versions of solwnd will consider a spherical geometry. Some discussions of this issue is presented.

  15. A Cartesian grid embedded boundary method for solving the Poisson and heat equations with discontinuous coefficients in three dimensions

    SciTech Connect

    Crockett, Robert; Graves, Daniel; Colella, Phillip

    2009-10-23

    We present a method for solving Poisson and heat equations with discon- tinuous coefficients in two- and three-dimensions. It uses a Cartesian cut-cell/embedded boundary method to represent the interface between materi- als, as described in Johansen& Colella (1998). Matching conditions across the interface are enforced using an approximation to fluxes at the boundary. Overall second order accuracy is achieved, as indicated by an array of tests using non-trivial interface geometries. Both the elliptic and heat solvers are shown to remain stable and efficient for material coefficient contrasts up to 106, thanks in part to the use of geometric multigrid. A test of accuracy when adaptive mesh refinement capabilities are utilized is also performed. An example problem relevant to nuclear reactor core simulation is presented, demonstrating the ability of the method to solve problems with realistic physical parameters.

  16. Parallelization of TWOPORFLOW, a Cartesian Grid based Two-phase Porous Media Code for Transient Thermo-hydraulic Simulations

    NASA Astrophysics Data System (ADS)

    Trost, Nico; Jiménez, Javier; Imke, Uwe; Sanchez, Victor

    2014-06-01

    TWOPORFLOW is a thermo-hydraulic code based on a porous media approach to simulate single- and two-phase flow including boiling. It is under development at the Institute for Neutron Physics and Reactor Technology (INR) at KIT. The code features a 3D transient solution of the mass, momentum and energy conservation equations for two inter-penetrating fluids with a semi-implicit continuous Eulerian type solver. The application domain of TWOPORFLOW includes the flow in standard porous media and in structured porous media such as micro-channels and cores of nuclear power plants. In the latter case, the fluid domain is coupled to a fuel rod model, describing the heat flow inside the solid structure. In this work, detailed profiling tools have been utilized to determine the optimization potential of TWOPORFLOW. As a result, bottle-necks were identified and reduced in the most feasible way, leading for instance to an optimization of the water-steam property computation. Furthermore, an OpenMP implementation addressing the routines in charge of inter-phase momentum-, energy- and mass-coupling delivered good performance together with a high scalability on shared memory architectures. In contrast to that, the approach for distributed memory systems was to solve sub-problems resulting by the decomposition of the initial Cartesian geometry. Thread communication for the sub-problem boundary updates was accomplished by the Message Passing Interface (MPI) standard.

  17. A three-dimensional sharp interface Cartesian grid method for solving high speed multi-material impact, penetration and fragmentation problems

    NASA Astrophysics Data System (ADS)

    Kapahi, A.; Sambasivan, S.; Udaykumar, H. S.

    2013-05-01

    This work presents a three-dimensional, Eulerian, sharp interface, Cartesian grid technique for simulating the response of elasto-plastic solid materials to hypervelocity impact, shocks and detonations. The mass, momentum and energy equations are solved along with evolution equations for deviatoric stress and plastic strain using a third-order finite difference scheme. Material deformation occurs with accompanying nonlinear stress wave propagation; in the Eulerian framework the boundaries of the deforming material are tracked in a sharp fashion using level-sets and the conditions on the immersed boundaries are applied by suitable modifications of a ghost fluid approach. The dilatational response of the material is modeled using the Mie-Gruneisen equation of state and the Johnson-Cook model is employed to characterize the material response due to rate-dependent plastic deformation. Details are provided on the treatment of the deviatoric stress ghost state so that physically correct boundary conditions can be applied at the material interfaces. An efficient parallel algorithm is used to handle computationally intensive three-dimensional problems. The results demonstrate the ability of the method to simulate high-speed impact, penetration and fragmentation phenomena in three dimensions.

  18. 76 FR 70721 - Voltage Coordination on High Voltage Grids; Notice of Staff Workshop

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-15

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Voltage Coordination on High Voltage Grids; Notice of Staff Workshop Take notice that the Federal Energy Regulatory Commission will hold a Workshop on Voltage Coordination on High Voltage Grids on Thursday, December...

  19. Coordinated grid and place cell replay during rest.

    PubMed

    Ólafsdóttir, H Freyja; Carpenter, Francis; Barry, Caswell

    2016-06-01

    Hippocampal replay has been hypothesized to underlie memory consolidation and navigational planning, yet the involvement of grid cells in replay is unknown. During replay we found grid cells to be spatially coherent with place cells, encoding locations 11 ms delayed relative to the hippocampus, with directionally modulated grid cells and forward replay exhibiting the greatest coherence with the CA1 area of the hippocampus. This suggests grid cells are engaged during the consolidation of spatial memories to the neocortex. PMID:27089021

  20. Electronic Absolute Cartesian Autocollimator

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.

    2006-01-01

    An electronic absolute Cartesian autocollimator performs the same basic optical function as does a conventional all-optical or a conventional electronic autocollimator but differs in the nature of its optical target and the manner in which the position of the image of the target is measured. The term absolute in the name of this apparatus reflects the nature of the position measurement, which, unlike in a conventional electronic autocollimator, is based absolutely on the position of the image rather than on an assumed proportionality between the position and the levels of processed analog electronic signals. The term Cartesian in the name of this apparatus reflects the nature of its optical target. Figure 1 depicts the electronic functional blocks of an electronic absolute Cartesian autocollimator along with its basic optical layout, which is the same as that of a conventional autocollimator. Referring first to the optical layout and functions only, this or any autocollimator is used to measure the compound angular deviation of a flat datum mirror with respect to the optical axis of the autocollimator itself. The optical components include an illuminated target, a beam splitter, an objective or collimating lens, and a viewer or detector (described in more detail below) at a viewing plane. The target and the viewing planes are focal planes of the lens. Target light reflected by the datum mirror is imaged on the viewing plane at unit magnification by the collimating lens. If the normal to the datum mirror is parallel to the optical axis of the autocollimator, then the target image is centered on the viewing plane. Any angular deviation of the normal from the optical axis manifests itself as a lateral displacement of the target image from the center. The magnitude of the displacement is proportional to the focal length and to the magnitude (assumed to be small) of the angular deviation. The direction of the displacement is perpendicular to the axis about which the mirror is slightly tilted. Hence, one can determine the amount and direction of tilt from the coordinates of the target image on the viewing plane.

  1. Discretization formulas for unstructured grids

    NASA Technical Reports Server (NTRS)

    Baumeister, Kenneth J.

    1988-01-01

    The Galerkin weighted residual technique using linear triangular weight functions is employed to develop finite difference formula in cartesian coordinates for the Laplacian operator, first derivative operators and the function for unstructured triangular grids. The weighted residual coefficients associated with the weak formulation of the Laplacian operator are shown to agree with the Taylor series approach on a global average. In addition, a simple algorithm is presented to determine the Voronoi (finite difference) area of an unstructured grid.

  2. Design and validation of a novel Cartesian biomechanical testing system with coordinated 6DOF real-time load control: application to the lumbar spine (L1-S, L4-L5).

    PubMed

    Kelly, Brian P; Bennett, Charles R

    2013-07-26

    Robotic methods applied to in-vitro biomechanical testing potentially offer more comprehensive evaluations however, standard position control algorithms make real-time load control problematic. This paper describes and evaluates a novel custom developed Cartesian force controlled biomechanical testing system with coordinated 6 degree of freedom (DOF) real-time load control. A custom developed 6-DOF serial manipulator with cascaded force over position control algorithms was designed, assembled, and programmed. Dial gauge tests assessed accuracy of custom linear axes. Standard test input and tuning procedures refined control performance. Two single motion segment units (L4-L5) and lumbar (L1-S) spine segments were tested under continuous pure moment application in flexion-extension, left-right lateral bending and axial rotation to 8Nm under full 6-DOF load control. Mean load control tracking errors between commanded and experimental loads were computed. Global spinal ranges of motion were compared to previously published values for standard non-robotic protocols. Individual linear and rotational axis position control accuracies were equal to or less than 6.35μm and 0.0167° respectively. Pilot pure bending tests demonstrated stable load control performance, as well as load rates, rotational velocities, and ranges of motion comparable to those for standard non-robotic in-vitro tests. Tracking errors for zero commanded forces and all moment controlled axes were less than 0.81±0.68N and 0.18±0.19Nm over all tests, respectively. The Cartesian based system simplified control application and demonstrated robust position and load control that was not limited to single axis or zero commanded loads. In addition to emulating standard biomechanical tests, the novel Cartesian force controlled testing system developed is a promising tool for biomechanical assessments with coordinated dynamic load application and coupled motion response in 6DOF. PMID:23764173

  3. Skeletal octahedral nanoframe with Cartesian coordinates via geometrically precise nanoscale phase segregation in a Pt@Ni core-shell nanocrystal.

    PubMed

    Oh, Aram; Baik, Hionsuck; Choi, Dong Shin; Cheon, Jae Yeong; Kim, Byeongyoon; Kim, Heejin; Kwon, Seong Jung; Joo, Sang Hoon; Jung, Yousung; Lee, Kwangyeol

    2015-03-24

    Catalytic properties of nanoparticles can be significantly enhanced by controlling nanoscale alloying and its structure. In this work, by using a facet-controlled Pt@Ni core-shell octahedron nanoparticle, we show that the nanoscale phase segregation can have directionality and be geometrically controlled to produce a Ni octahedron that is penetrated by Pt atoms along three orthogonal Cartesian axes and is coated by Pt atoms along its edges. This peculiar anisotropic diffusion of Pt core atoms along the ⟨100⟩ vertex, and then toward the ⟨110⟩ edges, is explained via the minimum strain energy for Ni-Ni pair interactions. The selective removal of the Ni-rich phase by etching then results in structurally fortified Pt-rich skeletal PtNi alloy framework nanostructures. Electrochemical evaluation of this hollow nanoframe suggests that the oxygen reduction reaction (ORR) activity is greatly improved compared to conventional Pt catalysts. PMID:25734892

  4. 76 FR 72203 - Voltage Coordination on High Voltage Grids; Notice of Reliability Workshop Agenda

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-22

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Voltage Coordination on High Voltage Grids; Notice of Reliability Workshop Agenda As announced in the Notice of Staff Workshop issued on November 8, 2011, the Commission will hold a workshop on Thursday, December 1,...

  5. Is there continuity between categorical and coordinate spatial relations coding? Evidence from a grid/no-grid working memory paradigm.

    PubMed

    Martin, Romain; Houssemand, Claude; Schiltz, Christine; Burnod, Yves; Alexandre, Frédéric

    2008-01-31

    We ask the question whether the coding of categorical versus coordinate spatial relations depends on different neural networks showing hemispheric specialization or whether there is continuity between these two coding types. The 'continuous spatial coding' hypothesis would mean that the two coding types rely essentially on the same neural network consisting of more general-purpose processes, such as visuo-spatial attention, but with a different weighting of these general processes depending on exact task requirements. With event-related fMRI, we have studied right-handed male subjects performing a grid/no-grid visuo-spatial working memory task inducing categorical and coordinate spatial relations coding. Our data support the 'continuous spatial coding' hypothesis, indicating that, while based on the same fronto-parieto-occipital neural network than categorical spatial relations coding, the coding of coordinate spatial relations relies more heavily on attentional and executive processes, which could induce hemispheric differences similar to those described in the literature. The results also show that visuo-spatial working memory consists of a short-term posterior store with a capacity of up to three elements in the parietal and extrastriate cortices. This store depends on the presence of a visible space categorization and thus can be used for the coding of categorical spatial relations. When no visible space categorization is given or when more than three elements have to be coded, additional attentional and executive processes are recruited, mainly located in the dorso-lateral prefrontal cortex. PMID:18037455

  6. GRID3C: Computer program for generation of C type multilevel, three dimensional and boundary conforming periodic grids

    NASA Technical Reports Server (NTRS)

    Dulikravich, D. S.

    1982-01-01

    A fast computer program, GRID3C, was developed for accurately generating periodic, boundary conforming, three dimensional, consecutively refined computational grids applicable to realistic axial turbomachinery geometries. The method is based on using two functions to generate two dimensional grids on a number of coaxial axisymmetric surfaces positioned between the centerbody and the outer radial boundary. These boundary fitted grids are of the C type and are characterized by quasi-orthogonality and geometric periodicity. The built in nonorthogonal coordinate stretchings and shearings cause the grid clustering in the regions of interest. The stretching parameters are part of the input to GRID3C. In its present version GRID3C can generate and store a maximum of four consecutively refined three dimensional grids. The output grid coordinates can be calculated either in the Cartesian or in the cylindrical coordinate system.

  7. More IMPATIENT: A Gridding-Accelerated Toeplitz-based Strategy for Non-Cartesian High-Resolution 3D MRI on GPUs

    PubMed Central

    Gai, Jiading; Obeid, Nady; Holtrop, Joseph L.; Wu, Xiao-Long; Lam, Fan; Fu, Maojing; Haldar, Justin P.; Hwu, Wen-mei W.; Liang, Zhi-Pei; Sutton, Bradley P.

    2013-01-01

    Several recent methods have been proposed to obtain significant speed-ups in MRI image reconstruction by leveraging the computational power of GPUs. Previously, we implemented a GPU-based image reconstruction technique called the Illinois Massively Parallel Acquisition Toolkit for Image reconstruction with ENhanced Throughput in MRI (IMPATIENT MRI) for reconstructing data collected along arbitrary 3D trajectories. In this paper, we improve IMPATIENT by removing computational bottlenecks by using a gridding approach to accelerate the computation of various data structures needed by the previous routine. Further, we enhance the routine with capabilities for off-resonance correction and multi-sensor parallel imaging reconstruction. Through implementation of optimized gridding into our iterative reconstruction scheme, speed-ups of more than a factor of 200 are provided in the improved GPU implementation compared to the previous accelerated GPU code. PMID:23682203

  8. An orthogonal coordinate grid following the three-dimensional viscous flow over a concave surface

    NASA Technical Reports Server (NTRS)

    Dagenhart, J. R; Saric, W. S.

    1983-01-01

    Swept wings designed for laminar flow control exhibit both centrifugal and crossflow instabilities which produce streamwise vortices that can lead to early transition from laminar to turbulent flow in the presence of Tollmien-Schlichting waves. This paper outlines an iterative algorithm for generation of an orthogonal, curvilinear, coordinate grid following the streamlines of the three-dimensional viscous flow over a swept, concave surface. The governing equations for the metric tensor are derived from the Riemann-Christoffel tensor for an Euclidian geometry. Unit vectors along streamline, normal and binormal directions are determined. The governing equations are not solved directly, but are employed only as compatibility equations. The scale factor for the streamline coordinate is obtained by an iterative integration scheme on a 200 x 100 x 5 grid, while the other two scale factors are determined from definitions. Sample results are obtained which indicate that the compatibility equation error decreases linearly with grid step size. Grids smaller than 200 x 100 x 5 are found to be inadequate to resolve the grid curvature.

  9. Multi-agent coordination algorithms for control of distributed energy resources in smart grids

    NASA Astrophysics Data System (ADS)

    Cortes, Andres

    Sustainable energy is a top-priority for researchers these days, since electricity and transportation are pillars of modern society. Integration of clean energy technologies such as wind, solar, and plug-in electric vehicles (PEVs), is a major engineering challenge in operation and management of power systems. This is due to the uncertain nature of renewable energy technologies and the large amount of extra load that PEVs would add to the power grid. Given the networked structure of a power system, multi-agent control and optimization strategies are natural approaches to address the various problems of interest for the safe and reliable operation of the power grid. The distributed computation in multi-agent algorithms addresses three problems at the same time: i) it allows for the handling of problems with millions of variables that a single processor cannot compute, ii) it allows certain independence and privacy to electricity customers by not requiring any usage information, and iii) it is robust to localized failures in the communication network, being able to solve problems by simply neglecting the failing section of the system. We propose various algorithms to coordinate storage, generation, and demand resources in a power grid using multi-agent computation and decentralized decision making. First, we introduce a hierarchical vehicle-one-grid (V1G) algorithm for coordination of PEVs under usage constraints, where energy only flows from the grid in to the batteries of PEVs. We then present a hierarchical vehicle-to-grid (V2G) algorithm for PEV coordination that takes into consideration line capacity constraints in the distribution grid, and where energy flows both ways, from the grid in to the batteries, and from the batteries to the grid. Next, we develop a greedy-like hierarchical algorithm for management of demand response events with on/off loads. Finally, we introduce distributed algorithms for the optimal control of distributed energy resources, i.e., generation and storage in a microgrid. The algorithms we present are provably correct and tested in simulation. Each algorithm is assumed to work on a particular network topology, and simulation studies are carried out in order to demonstrate their convergence properties to a desired solution.

  10. A level set approach for diffusion and Stefan-type problems with Robin boundary conditions on quadtree/octree adaptive Cartesian grids

    NASA Astrophysics Data System (ADS)

    Papac, Joseph; Helgadottir, Asdis; Ratsch, Christian; Gibou, Frederic

    2013-01-01

    We present a numerical method for simulating diffusion dominated phenomena on irregular domains and free moving boundaries with Robin boundary conditions on quadtree/octree adaptive meshes. In particular, we use a hybrid finite-difference and finite-volume framework that combines the level-set finite difference discretization of Min and Gibou (2007) [13] with the treatment of Robin boundary conditions of Papac et al. (2010) [19] on uniform grids. We present numerical results in two and three spatial dimensions on the diffusion equation and on a Stefan-type problem. In addition, we present an application of this method to the case of the simulation of the Ehrlich-Schwoebel barrier in the context of epitaxial growth.

  11. The adaptive, cut-cell Cartesian approach (warts and all)

    NASA Technical Reports Server (NTRS)

    Powell, Kenneth G.

    1995-01-01

    Solution-adaptive methods based on cutting bodies out of Cartesian grids are gaining popularity now that the ways of circumventing the accuracy problems associated with small cut cells have been developed. Researchers are applying Cartesian-based schemes to a broad class of problems now, and, although there is still development work to be done, it is becoming clearer which problems are best suited to the approach (and which are not). The purpose of this paper is to give a candid assessment, based on applying Cartesian schemes to a variety of problems, of the strengths and weaknesses of the approach as it is currently implemented.

  12. Automatic off-body overset adaptive Cartesian mesh method based on an octree approach

    SciTech Connect

    Peron, Stephanie; Benoit, Christophe

    2013-01-01

    This paper describes a method for generating adaptive structured Cartesian grids within a near-body/off-body mesh partitioning framework for the flow simulation around complex geometries. The off-body Cartesian mesh generation derives from an octree structure, assuming each octree leaf node defines a structured Cartesian block. This enables one to take into account the large scale discrepancies in terms of resolution between the different bodies involved in the simulation, with minimum memory requirements. Two different conversions from the octree to Cartesian grids are proposed: the first one generates Adaptive Mesh Refinement (AMR) type grid systems, and the second one generates abutting or minimally overlapping Cartesian grid set. We also introduce an algorithm to control the number of points at each adaptation, that automatically determines relevant values of the refinement indicator driving the grid refinement and coarsening. An application to a wing tip vortex computation assesses the capability of the method to capture accurately the flow features.

  13. Inverting x,y grid coordinates to obtain latitude and longitude in the vanderGrinten projection

    NASA Technical Reports Server (NTRS)

    Rubincam, D. P.

    1980-01-01

    The latitude and longitude of a point on the Earth's surface are found from its x,y grid coordinates in the vanderGrinten projection. The latitude is a solution of a cubic equation and the longitude a solution of a quadratic equation. Also, the x,y grid coordinates of a point on the Earth's surface can be found if its latitude and longitude are known by solving two simultaneous quadratic equations.

  14. Logarithmic spiral grids for image processing

    NASA Technical Reports Server (NTRS)

    Weiman, C. F. R.; Chaikin, G. M.

    1979-01-01

    A picture digitization grid based on logarithmic spirals rather than Cartesian coordinates is presented. Expressing this curvilinear grid as a conformal exponential mapping reveals useful image processing properties. The mapping induces a computational simplification that suggests parallel architectures in which most geometric transformations are effected by data shifting in memory rather than arithmetic on coordinates. These include fast, parallel noise-free rotation, scaling, and some projective transformations of pixel defined images. Conformality of the mapping preserves local picture-processing operations such as edge detection.

  15. Square grid and pillared square grid coordination polymers - fertile ground for crystal engineering of structure and function.

    PubMed

    Burd, Stephen D; Nugent, Patrick S; Mohameda, Mona H; Elsaidia, Sameh K; Zaworotko, Michael J

    2013-01-01

    Square grid coordination polymers (CPs) based upon four-connected metal centres linked by linear bifunctional ligands such as 4,4'-bipyridine were first reported in 1990 and the study of their pillared variants began in 1995. It was quickly realized by crystal engineers that the modularity of such CPs creates families of related compounds or platforms which in turn affords opportunities for systematic study of structure/function relationships in the context of catalysis, magnetism and porosity. This review covers the historical development of this important class of CPs before addressing recent studies of variants which incorporate 4,4'-bipyridine and related linkers to facilitate control over pore size and inorganic anion pillars to enable strong interactions with polarizable molecules such as CO2. Such pillared CPs offer relatively low cost, high stability and modularity. When these features are coupled with superior performance vs . other classes of porous materials in the context of carbon capture and other gas separations involving CO2, they are likely to gain increased attention in the future. PMID:23945094

  16. Development and Applications of 3D Cartesian CFD Technology

    NASA Technical Reports Server (NTRS)

    Melton, John E.; Berger, Marsha J.; VanDalsem, William (Technical Monitor)

    1994-01-01

    The urgent need for dramatic reductions in aircraft design cycle time is focusing scrutiny upon all aspects of computational fluid dynamics (CFD). These reductions will most likely come not from increased reliance upon user-interactive (and therefore time-expensive) methods, but instead from methods that can be fully automated and incorporated into 'black box' solutions. In comparison with tetrahedral methods, three-dimensional Cartesian grid approaches are in relative infancy, but initial experiences with automated Cartesian techniques are quite promising. Our research is targeted at furthering the development of Cartesian methods so that they can become key elements of a completely automatic grid generation/flow solution procedure applicable to the Euler analysis of complex aircraft geometries.

  17. Flexible Two-Dimensional Square-Grid Coordination Polymers: Structures and Functions

    PubMed Central

    Kajiro, Hiroshi; Kondo, Atsushi; Kaneko, Katsumi; Kanoh, Hirofumi

    2010-01-01

    Coordination polymers (CPs) or metal-organic frameworks (MOFs) have attracted considerable attention because of the tunable diversity of structures and functions. A 4,4′-bipyridine molecule, which is a simple, linear, exobidentate, and rigid ligand molecule, can construct two-dimensional (2D) square grid type CPs. Only the 2D-CPs with appropriate metal cations and counter anions exhibit flexibility and adsorb gas with a gate mechanism and these 2D-CPs are called elastic layer-structured metal-organic frameworks (ELMs). Such a unique property can make it possible to overcome the dilemma of strong adsorption and easy desorption, which is one of the ideal properties for practical adsorbents. PMID:21152303

  18. Software for Automated Generation of Cartesian Meshes

    NASA Technical Reports Server (NTRS)

    Aftosmis, Michael J.; Melton, John E.; Berger, Marshal J.

    2006-01-01

    Cart3D is a collection of computer programs for generating Cartesian meshes [for computational fluid dynamics (CFD) and other applications] in volumes bounded by solid objects. Aspects of Cart3D at earlier stages of development were reported in "Robust and Efficient Generation of Cartesian Meshes for CFD" (ARC-14275), NASA Tech Briefs, Vol. 23, No. 8 (August 1999), page 30. The geometric input to Cart3D comprises surface triangulations like those commonly generated by computer-aided-design programs. Complexly shaped objects can be represented as assemblies of simpler ones. Cart3D deletes all portions of such an assembled object that are not on the exterior surface. Intersections between components are preserved in the resulting triangulation. A tie-breaking routine unambiguously resolves geometric degeneracies. Then taking the intersected surface triangulation as input, the volume mesh is generated through division of cells of an initially coarse hexahedral grid. Cells are subdivided to refine the grid in regions of increased surface curvature and/or increased flow gradients. Cells that become split into multiple unconnected regions by thin pieces of surface are identified.

  19. Molecular tectonics: heterometallic (Ir,Cu) grid-type coordination networks based on cyclometallated Ir(III) chiral metallatectons.

    PubMed

    Xu, Chaojie; Guenet, Aurélie; Kyritsakas, Nathalie; Planeix, Jean-Marc; Hosseini, Mir Wais

    2015-10-11

    A chiral-at-metal Ir(III) organometallic metallatecton was synthesised as a racemic mixture and as enantiopure complexes and combined with Cu(II) to afford a heterobimetallic (Ir,Cu) grid-type 2D coordination network. PMID:26299871

  20. Cartesian Sampling Of FID Data Using Oscillating Gradients

    NASA Astrophysics Data System (ADS)

    Kashmar, G. C.; Nalcioglu, O.

    1988-06-01

    A new method of fast NMR imaging is proposed which uses oscillating gradients and also collects data on Cartesian coordinates. The method is a heuristic attempt at finding an optimal data collection strategy for NMR imaging. It is described in detail and its advantages and disadvantages compared to other methods are analyzed.

  1. A Cartesian embedded boundary method for hyperbolic conservation laws

    SciTech Connect

    Sjogreen, B; Petersson, N A

    2006-12-04

    The authors develop an embedded boundary finite difference technique for solving the compressible two- or three-dimensional Euler equations in complex geometries on a Cartesian grid. The method is second order accurate with an explicit time step determined by the grid size away from the boundary. Slope limiters are used on the embedded boundary to avoid non-physical oscillations near shock waves. They show computed examples of supersonic flow past a cylinder and compare with results computed on a body fitted grid. Furthermore, they discuss the implementation of the method for thin geometries, and show computed examples of transonic flow past an airfoil.

  2. Numerical grid generation; Proceedings of the Symposium on Numerical Generation of Curvilinear Coordinate Systems and Their Use in the Numerical Solution of Partial Differential Equations, Nashville, TN, April 13-16, 1982

    NASA Technical Reports Server (NTRS)

    Thompson, J. F. (Editor)

    1982-01-01

    General curvilinear coordinate systems are considered along with the error induced by coordinate systems, basic differential models for coordinate generation, elliptic grid generation, conformal grid generation, algebraic grid generation, orthogonal grid generation, patched coordinate systems, and solid mechanics applications of boundary fitted coordinate systems. Attention is given to coordinate system control and adaptive meshes, the application of body conforming curvilinear grids for finite difference solution of external flow, the use of solution adaptive grids in solving partial differential equations, adaptive gridding for finite difference solutions to heat and mass transfer problems, and the application of curvilinear coordinate generation techniques to the computation of internal flows. Other topics explored are related to the solution of nonlinear water wave problems using boundary-fitted coordinate systems, the numerical modeling of estuarine hydrodynamics on a boundary-fitted coordinate system, and conformal grid generation for multielement airfoils.

  3. Three-dimensional adaptive grid generation for body-fitted coordinate system

    NASA Astrophysics Data System (ADS)

    Chen, S. C.

    1988-08-01

    This report describes a numerical method for generating 3-D grids for general configurations. The basic method involves the solution of a set of quasi-linear elliptic partial differential equations via pointwise relaxation with a local relaxation factor. It allows specification of the grid spacing off the boundary surfaces and the grid orthogonality at the boundary surfaces. It includes adaptive mechanisms to improve smoothness, orthogonality, and flow resolution in the grid interior.

  4. Three-dimensional adaptive grid generation for body-fitted coordinate system

    NASA Astrophysics Data System (ADS)

    Chen, S. C.

    This report describes a numerical method for generating 3-D grids for general configurations. The basic method involves the solution of a set of quasi-linear elliptic partial differential equations via pointwise relaxation with a local relaxation factor. It allows specification of the grid spacing off the boundary surfaces and the grid orthogonality at the boundary surfaces. It includes adaptive mechanisms to improve smoothness, orthogonality, and flow resolution in the grid interior.

  5. Enabling Design-Oriented Fluid Simulations: Verification with Discontinuous Manufactured Solutions and Automatic Grid Generation with Moving Coordinates

    NASA Astrophysics Data System (ADS)

    Woods, C. Nathan

    Computer simulations of complex mathematical models are a powerful tool for design, but they introduce uncertainties which can lead to poor design choices when simulation data is all that is available. Additionally, computational grid generation can dramatically increases the costs associated with initializing numerical simulations. Proper verification can help quantify the uncertainty in numerical simulations, and a new form of code verification is presented. This is based on the method of manufactured solutions for integral equations, which allows MMS to be used to verify shock-capturing codes. A procedure is presented for numerically evaluating the required integrals, and it is found to completely eliminate numerical error resulting from discontinuous integrand functions. Integral MMS is demonstrated, and it is found to yield convergence rates that differ by less than 5% from those obtained using differential MMS, and which match precisely with the theoretical rates for discontinuous solutions. This indicates that integral MMS can be used for code verification in place of differential MMS, which cannot be used with discontinuous solutions. Moving grids can be used to allow computed fluid motion to generate the computational grid automatically. The unique challenges associated with grid motion are explored, and multiple implementations are discussed. A software library for fluid-mechanical simulation in unsteady coordinates is also introduced. Preliminary verification of both the method and the library is discussed. The use of unsteady coordinates affects accuracy and grid convergence rates in complex ways. This work lays the foundation for future work on the use of moving grids in order to reduce the grid-generation burden for design-oriented computational fluid dynamics.

  6. Rapid Structured Volume Grid Smoothing and Adaption Technique

    NASA Technical Reports Server (NTRS)

    Alter, Stephen J.

    2006-01-01

    A rapid, structured volume grid smoothing and adaption technique, based on signal processing methods, was developed and applied to the Shuttle Orbiter at hypervelocity flight conditions in support of the Columbia Accident Investigation. Because of the fast pace of the investigation, computational aerothermodynamicists, applying hypersonic viscous flow solving computational fluid dynamic (CFD) codes, refined and enhanced a grid for an undamaged baseline vehicle to assess a variety of damage scenarios. Of the many methods available to modify a structured grid, most are time-consuming and require significant user interaction. By casting the grid data into different coordinate systems, specifically two computational coordinates with arclength as the third coordinate, signal processing methods are used for filtering the data [Taubin, CG v/29 1995]. Using a reverse transformation, the processed data are used to smooth the Cartesian coordinates of the structured grids. By coupling the signal processing method with existing grid operations within the Volume Grid Manipulator tool, problems related to grid smoothing are solved efficiently and with minimal user interaction. Examples of these smoothing operations are illustrated for reductions in grid stretching and volume grid adaptation. In each of these examples, other techniques existed at the time of the Columbia accident, but the incorporation of signal processing techniques reduced the time to perform the corrections by nearly 60%. This reduction in time to perform the corrections therefore enabled the assessment of approximately twice the number of damage scenarios than previously possible during the allocated investigation time.

  7. Yin-Yang-Zhong grid: An overset grid system for a sphere

    NASA Astrophysics Data System (ADS)

    Hayashi, Hiroshi; Kageyama, Akira

    2016-01-01

    For numerical simulations inside a sphere, an overset grid system, Yin-Yang-Zhong grid, is proposed. The Yin-Yang-Zhong grid is an extension of the Yin-Yang grid, which is widely used in various simulations in spherical shell geometry. The Yin-Yang grid is itself an overset grid system with two component grids, and a new component grid called Zhong is placed at the center of the Yin-Yang grid. The Zhong grid component is constructed on Cartesian coordinates. Parallelization is intrinsically embedded in the Yin-Yang-Zhong grid system because the Zhong grid points are defined with cuboid blocks that are decomposed domains for parallelization. The computational efficiency approaches the optimum as the process number increases. Quantitative test simulations are performed for a diffusion problem in a sphere with the Yin-Yang-Zhong grid. Correct decay rates are obtained by the simulations. Two other tests in magnetohydrodynamics (MHD) in a sphere are also performed. One is an MHD dynamo simulation, and the other is an MHD relaxation simulation in a sphere.

  8. Variable-coordinate forward modeling of irregular surface based on dual-variable grid

    NASA Astrophysics Data System (ADS)

    Huang, Jian-Ping; Qu, Ying-Ming; Li, Qing-Yang; Li, Zhen-Chun; Li, Guo-Lei; Bu, Chang-Cheng; Teng, Hou-Hua

    2015-03-01

    The mapping method is a forward-modeling method that transforms the irregular surface to horizontal by mapping the rectangular grid as curved; moreover, the wave field calculations move from the physical domain to the calculation domain. The mapping method deals with the irregular surface and the low-velocity layer underneath it using a fine grid. For the deeper high-velocity layers, the use of a fine grid causes local oversampling. In addition, when the irregular surface is transformed to horizontal, the flattened interface below the surface is transformed to curved, which produces inaccurate modeling results because of the presence of ladder-like burrs in the simulated seismic wave. Thus, we propose the mapping method based on the dual-variable finite-difference staggered grid. The proposed method uses different size grid spacings in different regions and locally variable time steps to match the size variability of grid spacings. Numerical examples suggest that the proposed method requires less memory storage capacity and improves the computational efficiency compared with forward modeling methods based on the conventional grid.

  9. Cartesian control of redundant robots

    NASA Technical Reports Server (NTRS)

    Colbaugh, R.; Glass, K.

    1989-01-01

    A Cartesian-space position/force controller is presented for redundant robots. The proposed control structure partitions the control problem into a nonredundant position/force trajectory tracking problem and a redundant mapping problem between Cartesian control input F is a set member of the set R(sup m) and robot actuator torque T is a set member of the set R(sup n) (for redundant robots, m is less than n). The underdetermined nature of the F yields T map is exploited so that the robot redundancy is utilized to improve the dynamic response of the robot. This dynamically optimal F yields T map is implemented locally (in time) so that it is computationally efficient for on-line control; however, it is shown that the map possesses globally optimal characteristics. Additionally, it is demonstrated that the dynamically optimal F yields T map can be modified so that the robot redundancy is used to simultaneously improve the dynamic response and realize any specified kinematic performance objective (e.g., manipulability maximization or obstacle avoidance). Computer simulation results are given for a four degree of freedom planar redundant robot under Cartesian control, and demonstrate that position/force trajectory tracking and effective redundancy utilization can be achieved simultaneously with the proposed controller.

  10. A tensor product B-spline method for numerical grid generation

    SciTech Connect

    Manke, J.

    1989-10-01

    We present a tensor product B-spline method for fast elliptic grid generation. The Cartesian coordinate functions for a block are represented as a sum of tensor product B-spline basis functions defined on the computational domain for the block. The tensor product B-spline basis functions are constructed so that the basis functions and their first partials are continuous on the computational domain for the block. The coordinate functions inherit this smoothness: a grid computed by evaluating the coordinate function along constant parameter lines leads to smooth grid lines with smoothly varying tangents. The expansion coefficients for the coordinates functions are computed by solving the elliptic grid generation equations using collocation. This assures that the computer grid has the smoothness and resolution expected for an elliptic grid with appropriate control. The collocation equations are solved with an ADI solution algorithm analogous to the ADI solution algorithm for the finite difference method. The speed of the method derives from the smoothness of the B-spline basis functions; in effect, a fine grid in the physical domain is obtained by constructing a smooth expansion of the coordinate functions on a coarse grid of knots in the computational domain. Thus, the tensor product B-spline method will be faster than the finite difference method, if a sufficiently smooth fine grid in the physical domain can be obtained for an appropriately coarse grid of knots in the computational domain.

  11. Irreducible Cartesian tensors of highest weight, for arbitrary order

    NASA Astrophysics Data System (ADS)

    Mane, S. R.

    2016-03-01

    A closed form expression is presented for the irreducible Cartesian tensor of highest weight, for arbitrary order. Two proofs are offered, one employing bookkeeping of indices and, after establishing the connection with the so-called natural tensors and their projection operators, the other one employing purely coordinate-free tensor manipulations. Some theorems and formulas in the published literature are generalized from SO(3) to SO(n), for dimensions n ≥ 3.

  12. Non-uniformly sampled grids in double pole coordinate system for freeform reflector construction

    NASA Astrophysics Data System (ADS)

    Ma, Donglin; Pacheco, Shaun; Feng, Zexin; Liang, Rongguang

    2015-08-01

    We propose a new method to design freeform reflectors by nonuniformly sampling the source intensity distribution in double pole coordinate system. In double pole coordinate system, there is no pole for the whole hemisphere because both poles of the spherical coordinate system are moved to southernmost point of the sphere and overlapped together. With symmetric definition of both angular coordinates in the modified double pole coordinate system, a better match between the source intensity distribution and target irradiance distribution can be achieved for reflectors with large acceptance solid angle, leading to higher light efficiency and better uniformity on the target surface. With non-uniform sampling of the source intensity, we can design circular freeform reflector to obtain uniform rectangular illumination pattern. Aided by the feedback optimization, the freeform reflector can achieve the collection efficiency for ideal point source over 0.7 and relative standard deviation (RSD) less than 0.1.

  13. Grid-based methods for diatomic quantum scattering problems: a finite-element, discrete variable representation in prolate spheroidal coordinates

    SciTech Connect

    Tao, Liang; McCurdy, C.W.; Rescigno, T.N.

    2008-11-25

    We show how to combine finite elements and the discrete variable representation in prolate spheroidal coordinates to develop a grid-based approach for quantum mechanical studies involving diatomic molecular targets. Prolate spheroidal coordinates are a natural choice for diatomic systems and have been used previously in a variety of bound-state applications. The use of exterior complex scaling in the present implementation allows for a transparently simple way of enforcing Coulomb boundary conditions and therefore straightforward application to electronic continuum problems. Illustrative examples involving the bound and continuum states of H2+, as well as the calculation of photoionization cross sections, show that the speed and accuracy of the present approach offer distinct advantages over methods based on single-center expansions.

  14. NPSS on NASA's Information Power Grid: Using CORBA and Globus to Coordinate Multidisciplinary Aeroscience Applications

    NASA Technical Reports Server (NTRS)

    Lopez, Isaac; Follen, Gregory J.; Gutierrez, Richard; Foster, Ian; Ginsburg, Brian; Larsson, Olle; Martin, Stuart; Tuecke, Steven; Woodford, David

    2000-01-01

    This paper describes a project to evaluate the feasibility of combining Grid and Numerical Propulsion System Simulation (NPSS) technologies, with a view to leveraging the numerous advantages of commodity technologies in a high-performance Grid environment. A team from the NASA Glenn Research Center and Argonne National Laboratory has been studying three problems: a desktop-controlled parameter study using Excel (Microsoft Corporation); a multicomponent application using ADPAC, NPSS, and a controller program-, and an aviation safety application running about 100 jobs in near real time. The team has successfully demonstrated (1) a Common-Object- Request-Broker-Architecture- (CORBA-) to-Globus resource manager gateway that allows CORBA remote procedure calls to be used to control the submission and execution of programs on workstations and massively parallel computers, (2) a gateway from the CORBA Trader service to the Grid information service, and (3) a preliminary integration of CORBA and Grid security mechanisms. We have applied these technologies to two applications related to NPSS, namely a parameter study and a multicomponent simulation.

  15. Sink or Swim: The Cartesian Diver.

    ERIC Educational Resources Information Center

    Pinkerton, K. David

    2001-01-01

    Presents the activity of Cartesian divers which demonstrates the relationship between pressure, temperature, volume, and buoyancy. Includes both instructor information and student activity sheet. (YDS)

  16. Coordinating the Global Information Grid Initiative with the NG9-1-1 Initiative

    SciTech Connect

    Michael Schmitt

    2008-05-01

    As the Department of Defense develops the Global Information Grid, the Department of Transportation develops the Next Generation 9-1-1 system. Close examinations of these initiatives show that the two are similar in architectures, applications, and communications interoperability. These similarities are extracted from the lowest user level to the highest commander rank that will be involved in each network. Once the similarities are brought into perspective, efforts should be made to collaborate between the two departments.

  17. Cartesian and Non-Cartesian Thinking: Reflections on the Learning of Mathematics.

    ERIC Educational Resources Information Center

    Thomas, R. S. D.

    1987-01-01

    Differences in cognitive structure are approached through consideration of cartesian and non-cartesian knowing. Figuration and configuration are described as two layers of cartesian knowing leading to the third layer, the cognitive structure. Knowing in general is then discussed, with comments on learning in another culture, Botswana. (MNS)

  18. Complex frequency-shifted multi-axial perfectly matched layer for elastic wave modelling on curvilinear grids

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenguo; Zhang, Wei; Chen, Xiaofei

    2014-07-01

    Perfectly matched layer (PML) is an efficient absorbing technique for numerical wave simulations. Since it appeared, various improvements have been made. The complex frequency-shifted PML (CFS-PML) improves the absorbing performance for near-grazing incident waves and evanescent waves. The auxiliary differential equation (ADE) formulation of the PML provides a convenient unsplit-field PML implementation that can be directly used with high order time marching schemes. The multi-axial PML (MPML) stabilizes the PML on anisotropic media. However, these improvements were generally developed for Cartesian grids. In this paper, we extend the ADE CFS-PML to general curvilinear (non-orthogonal) grids for elastic wave modelling. Unlike the common implementations to absorb the waves in the computational space, we apply the damping along the perpendicular direction of the PML layer in the local Cartesian coordinates. Further, we relate the perpendicular and parallel components of the gradient operator in the local Cartesian coordinates to the derivatives in the curvilinear coordinates, to avoid mapping the wavefield to the local Cartesian coordinates. It is thus easy to be incorporated with numerical schemes on curvilinear grids. We derive the PML equations for the interior region and for the free surface separately because the free surface boundary condition modifies the elastic wave equations. We show that the elastic wave modelling on curvilinear grids exhibits anisotropic effects in the computational space, which may lead to unstable simulations. To stabilize the simulation, we adapt the MPML strategy to also absorb the wavefield along the two parallel directions of the PML. We illustrate the stability of this ADE CFS-MPML for finite-difference elastic wave simulations on curvilinear grids by two numerical experiments.

  19. A NEW THREE-DIMENSIONAL SOLAR WIND MODEL IN SPHERICAL COORDINATES WITH A SIX-COMPONENT GRID

    SciTech Connect

    Feng, Xueshang; Zhang, Man; Zhou, Yufen

    2014-09-01

    In this paper, we introduce a new three-dimensional magnetohydrodynamics numerical model to simulate the steady state ambient solar wind from the solar surface to 215 R {sub s} or beyond, and the model adopts a splitting finite-volume scheme based on a six-component grid system in spherical coordinates. By splitting the magnetohydrodynamics equations into a fluid part and a magnetic part, a finite volume method can be used for the fluid part and a constrained-transport method able to maintain the divergence-free constraint on the magnetic field can be used for the magnetic induction part. This new second-order model in space and time is validated when modeling the large-scale structure of the solar wind. The numerical results for Carrington rotation 2064 show its ability to produce structured solar wind in agreement with observations.

  20. Freeform optics construction with nonuniformly sampled grids in modified double-pole coordinate system

    NASA Astrophysics Data System (ADS)

    Ma, Donglin; Pacheco, Shaun; Wang, Chengliang; Liang, Rongguang

    2015-12-01

    The intensity distributions of some light sources have the rotationally symmetric property. We propose a method to design freeform optics by sampling the source intensity distribution nonuniformly in a modified double-pole coordinate system to satisfy the circular emission pattern of the light source. We can greatly improve the smoothness of the designed freeform surfaces and maximize the collection efficiency. We demonstrate the design method with two freeform illumination lenses: one for the light from the multimode filter and the other for the light emitting diode with a hemisphere emitting solid angle. We also demonstrate that the nonuniform sampling algorithm has significant advantages for designing freeform reflectors with superlarge collection angle.

  1. CUDA accelerated uniform re-sampling for non-Cartesian MR reconstruction.

    PubMed

    Feng, Chaolu; Zhao, Dazhe

    2015-01-01

    A grid-driven gridding (GDG) method is proposed to uniformly re-sample non-Cartesian raw data acquired in PROPELLER, in which a trajectory window for each Cartesian grid is first computed. The intensity of the reconstructed image at this grid is the weighted average of raw data in this window. Taking consider of the single instruction multiple data (SIMD) property of the proposed GDG, a CUDA accelerated method is then proposed to improve the performance of the proposed GDG. Two groups of raw data sampled by PROPELLER in two resolutions are reconstructed by the proposed method. To balance computation resources of the GPU and obtain the best performance improvement, four thread-block strategies are adopted. Experimental results demonstrate that although the proposed GDG is more time consuming than traditional DDG, the CUDA accelerated GDG is almost 10 times faster than traditional DDG. PMID:26406102

  2. On automating domain connectivity for overset grids

    NASA Technical Reports Server (NTRS)

    Chiu, Ing-Tsau

    1994-01-01

    An alternative method for domain connectivity among systems of overset grids is presented. Reference uniform Cartesian systems of points are used to achieve highly efficient domain connectivity, and form the basis for a future fully automated system. The Cartesian systems are used to approximated body surfaces and to map the computational space of component grids. By exploiting the characteristics of Cartesian Systems, Chimera type hole-cutting and identification of donor elements for intergrid boundary points can be carried out very efficiently. The method is tested for a range of geometrically complex multiple-body overset grid systems.

  3. Parameter Studies, time-dependent simulations and design with automated Cartesian methods

    NASA Technical Reports Server (NTRS)

    Aftosmis, Michael

    2005-01-01

    Over the past decade, NASA has made a substantial investment in developing adaptive Cartesian grid methods for aerodynamic simulation. Cartesian-based methods played a key role in both the Space Shuttle Accident Investigation and in NASA's return to flight activities. The talk will provide an overview of recent technological developments focusing on the generation of large-scale aerodynamic databases, automated CAD-based design, and time-dependent simulations with of bodies in relative motion. Automation, scalability and robustness underly all of these applications and research in each of these topics will be presented.

  4. A Cartesian cut cell method for rarefied flow simulations around moving obstacles

    NASA Astrophysics Data System (ADS)

    Dechristé, G.; Mieussens, L.

    2016-06-01

    For accurate simulations of rarefied gas flows around moving obstacles, we propose a cut cell method on Cartesian grids: it allows exact conservation and accurate treatment of boundary conditions. Our approach is designed to treat Cartesian cells and various kinds of cut cells by the same algorithm, with no need to identify the specific shape of each cut cell. This makes the implementation quite simple, and allows a direct extension to 3D problems. Such simulations are also made possible by using an adaptive mesh refinement technique and a hybrid parallel implementation. This is illustrated by several test cases, including a 3D unsteady simulation of the Crookes radiometer.

  5. Minimization of deviations of gear real tooth surfaces determined by coordinate measurements

    NASA Technical Reports Server (NTRS)

    Litvin, F. L.; Kuan, C.; Wang, J.-C.; Handschuh, R. F.; Masseth, J.; Maruyama, N.

    1992-01-01

    The deviations of a gear's real tooth surface from the theoretical surface are determined by coordinate measurements at the grid of the surface. A method was developed to transform the deviations from Cartesian coordinates to those along the normal at the measurement locations. Equations are derived that relate the first order deviations with the adjustment to the manufacturing machine-tool settings. The deviations of the entire surface are minimized. The minimization is achieved by application of the least-square method for an overdetermined system of linear equations. The proposed method is illustrated with a numerical example for hypoid gear and pinion.

  6. Turing instabilities on Cartesian product networks

    PubMed Central

    Asllani, Malbor; Busiello, Daniel M.; Carletti, Timoteo; Fanelli, Duccio; Planchon, Gwendoline

    2015-01-01

    The problem of Turing instabilities for a reaction-diffusion system defined on a complex Cartesian product network is considered. To this end we operate in the linear regime and expand the time dependent perturbation on a basis formed by the tensor product of the eigenvectors of the discrete Laplacian operators, associated to each of the individual networks that build the Cartesian product. The dispersion relation which controls the onset of the instability depends on a set of discrete wavelengths, the eigenvalues of the aforementioned Laplacians. Patterns can develop on the Cartesian network, if they are supported on at least one of its constitutive sub-graphs. Multiplex networks are also obtained under specific prescriptions. In this case, the criteria for the instability reduce to compact explicit formulae. Numerical simulations carried out for the Mimura-Murray reaction kinetics confirm the adequacy of the proposed theory. PMID:26245138

  7. Turing instabilities on Cartesian product networks.

    PubMed

    Asllani, Malbor; Busiello, Daniel M; Carletti, Timoteo; Fanelli, Duccio; Planchon, Gwendoline

    2015-01-01

    The problem of Turing instabilities for a reaction-diffusion system defined on a complex Cartesian product network is considered. To this end we operate in the linear regime and expand the time dependent perturbation on a basis formed by the tensor product of the eigenvectors of the discrete Laplacian operators, associated to each of the individual networks that build the Cartesian product. The dispersion relation which controls the onset of the instability depends on a set of discrete wavelengths, the eigenvalues of the aforementioned Laplacians. Patterns can develop on the Cartesian network, if they are supported on at least one of its constitutive sub-graphs. Multiplex networks are also obtained under specific prescriptions. In this case, the criteria for the instability reduce to compact explicit formulae. Numerical simulations carried out for the Mimura-Murray reaction kinetics confirm the adequacy of the proposed theory. PMID:26245138

  8. A transformation-free HOC scheme and multigrid method for solving the 3D Poisson equation on nonuniform grids

    NASA Astrophysics Data System (ADS)

    Ge, Yongbin; Cao, Fujun; Zhang, Jun

    2013-02-01

    A high-order compact (HOC) difference scheme is proposed to solve the three-dimensional (3D) Poisson equation on nonuniform orthogonal Cartesian grids involving no coordinate transformation from the physical space to the computational space. Theoretically, the proposed scheme has third to fourth-order accuracy; its fourth-order accuracy is achieved under uniform grid settings. Then, a multigrid method is developed to solve the linear system arising from this HOC difference scheme and the corresponding multigrid restriction and interpolation operators are constructed using the volume law. Numerical experiments are conducted to show the computed accuracy of the HOC scheme and the computational efficiency of the multigrid method.

  9. Extension of Efficient Low Dissipative High Order Schemes for 3-D Curvilinear Moving Grids

    NASA Technical Reports Server (NTRS)

    Vinokur, Marcel; Yee H. C.; Koga, Dennis (Technical Monitor)

    2000-01-01

    The efficient low dissipative high order schemes proposed by Yee et al. is formulated for 3-D curvilinear moving grids. These schemes consists of a high order base schemes combined with nonlinear characteristic filters. The amount of numerical dissipation is minimized by applying the schemes to the entropy splitting form of the inviscid flux derivatives. The analysis is given for a thermally perfect gas. The main difficulty in the extension of higher order schemes that were formulated in Cartesian coordinates to curvilinear moving grids is the higher order transformed metric evaluations. The higher order numerical evaluation of the transformed metric terms to insure freestream preservation is done in a coordinate invariant manner. The formulation is an improvement over existing formulation of high order scheme in curvilinear moving grids.

  10. A Laplacian Equation Method for Numerical Generation of Boundary-Fitted 3D Orthogonal Grids

    NASA Astrophysics Data System (ADS)

    Theodoropoulos, T.; Bergeles, G. C.

    1989-06-01

    A sethod for generating boundary fitted orthogonal curvilinear grids in 3-dimensional space is described. The mapping between the curvilinear coordinates and the Cartesian coordinates is provided by a set of Laplace equations which, expressed in curvilinear coordinates, involve the components of the metric tensor and are therefore non-linear and coupled. An iterative algorithm is described, which achieves a numerical solution. Grids appropriate for the calculation of flow fields over complex topography or in complex flow passages as those found in turbomachinery, and for other engineering applications can be constructed using the proposed method. Various examples are presented and plotted in perspective, and data for the assessment of the properties of the resulting meshes is provided.

  11. Coordinated learning of grid cell and place cell spatial and temporal properties: multiple scales, attention and oscillations.

    PubMed

    Grossberg, Stephen; Pilly, Praveen K

    2014-02-01

    A neural model proposes how entorhinal grid cells and hippocampal place cells may develop as spatial categories in a hierarchy of self-organizing maps (SOMs). The model responds to realistic rat navigational trajectories by learning both grid cells with hexagonal grid firing fields of multiple spatial scales, and place cells with one or more firing fields, that match neurophysiological data about their development in juvenile rats. Both grid and place cells can develop by detecting, learning and remembering the most frequent and energetic co-occurrences of their inputs. The model's parsimonious properties include: similar ring attractor mechanisms process linear and angular path integration inputs that drive map learning; the same SOM mechanisms can learn grid cell and place cell receptive fields; and the learning of the dorsoventral organization of multiple spatial scale modules through medial entorhinal cortex to hippocampus (HC) may use mechanisms homologous to those for temporal learning through lateral entorhinal cortex to HC ('neural relativity'). The model clarifies how top-down HC-to-entorhinal attentional mechanisms may stabilize map learning, simulates how hippocampal inactivation may disrupt grid cells, and explains data about theta, beta and gamma oscillations. The article also compares the three main types of grid cell models in the light of recent data. PMID:24366136

  12. Coordinated learning of grid cell and place cell spatial and temporal properties: multiple scales, attention and oscillations

    PubMed Central

    Grossberg, Stephen; Pilly, Praveen K.

    2014-01-01

    A neural model proposes how entorhinal grid cells and hippocampal place cells may develop as spatial categories in a hierarchy of self-organizing maps (SOMs). The model responds to realistic rat navigational trajectories by learning both grid cells with hexagonal grid firing fields of multiple spatial scales, and place cells with one or more firing fields, that match neurophysiological data about their development in juvenile rats. Both grid and place cells can develop by detecting, learning and remembering the most frequent and energetic co-occurrences of their inputs. The model's parsimonious properties include: similar ring attractor mechanisms process linear and angular path integration inputs that drive map learning; the same SOM mechanisms can learn grid cell and place cell receptive fields; and the learning of the dorsoventral organization of multiple spatial scale modules through medial entorhinal cortex to hippocampus (HC) may use mechanisms homologous to those for temporal learning through lateral entorhinal cortex to HC (‘neural relativity’). The model clarifies how top-down HC-to-entorhinal attentional mechanisms may stabilize map learning, simulates how hippocampal inactivation may disrupt grid cells, and explains data about theta, beta and gamma oscillations. The article also compares the three main types of grid cell models in the light of recent data. PMID:24366136

  13. Solution-Adaptive Cartesian Cell Approach for Viscous and Inviscid Flows

    NASA Technical Reports Server (NTRS)

    Coirier, William J.; Powell, Kenneth G.

    1996-01-01

    A Cartesian cell-based approach for adaptively refined solutions of the Euler and Navier-Stokes equations in two dimensions is presented. Grids about geometrically complicated bodies are generated automatically, by the recursive subdivision of a single Cartesian cell encompassing the entire flow domain. Where the resulting cells intersect bodies, polygonal cut cells are created using modified polygon-clipping algorithms. The grid is stored in a binary tree data structure that provides a natural means of obtaining cell-to-cell connectivity and of carrying out solution-adaptive mesh refinement. The Euler and Navier-Stokes equations are solved on the resulting grids using a finite volume formulation. The convective terms are upwinded: A linear reconstruction of the primitive variables is performed, providing input states to an approximate Riemann solver for computing the fluxes between neighboring cells. The results of a study comparing the accuracy and positivity of two classes of cell-centered, viscous gradient reconstruction procedures is briefly summarized. Adaptively refined solutions of the Navier-Stokes equations are shown using the more robust of these gradient reconstruction procedures, where the results computed by the Cartesian approach are compared to theory, experiment, and other accepted computational results for a series of low and moderate Reynolds number flows.

  14. Diverse assemblies of the (4,4) grid layers exemplified in Zn(II)/Co(II) coordination polymers with dual linear ligands

    SciTech Connect

    Liu, Guang-Zhen; Li, Xiao-Dong; Xin, Ling-Yun; Li, Xiao-Ling; Wang, Li-Ya

    2013-07-15

    Diverse (4,4) grid layers are exemplified in five two-dimensional coordination polymers with dual µ{sub 2}-bridged ligands, namely, ([Zn(cbaa)(bpp)]·H{sub 2}O){sub n} (1), [Zn{sub 2}(cbaa){sub 2}(bpy)]{sub n} (2), [Co{sub 2}(cbaa){sub 2}(bpp){sub 2}]{sub n} (3), [Co(cbaa)(bpp)]{sub n} (4), and [Co(bdaa)(bpp)(H{sub 2}O){sub 2}]{sub n} (5) (H{sub 2}cbaa=4-carboxybenzeneacetic acid, bpp=1,3-di(4-pyridyl)propane, bpy=4,4′-bipyridyl, and H{sub 2}bdaa=1,4-benzenediacrylic acid). For 1, two (4,4) grid layers with [ZnN{sub 2}O{sub 2}] tetrahedron as the node are held together by lattice water forming a H-bonding bilayer. Individual (4,4) grid layer in 2 is based on (Zn{sub 2}(OCO){sub 4}) paddlewheel unit as the node. Two (4,4) grid layers with (Co{sub 2}O(OCO){sub 2}) dimer as the node are covalently interconnected by organic ligands affording a thick bilayer of 3 with new framework topology. The different entanglements between two coincident (4,4) grid layers with [CoN{sub 2}O{sub 4}] octahedron as the node leads to two 2D→2D interpenetrated structures for 4 and 5. Furthermore, fluorescent properties of 1 and 2 as well as magnetic properties of 3 are investigated. - Graphical abstract: Diverse assemblies of the (4,4) grid layers with different network nodes forms five coordination polymers that are well characterized by IR, TGA, element analysis, fluorescent and magnetic measurement. - Highlights: • Diverse assemblies of the (4,4) grid layers with different structural units as the nodes. • A new topology type with the uninodal 6-connected net of (4{sup 12}.5{sup 2}.6) is found. • Intense fluorescence emissions with a rare blue-shift of 55 nm compared to free carboxylate ligand.

  15. Arbitrary order permanent Cartesian multipolar electrostatic interactions

    NASA Astrophysics Data System (ADS)

    Boateng, H. A.; Todorov, I. T.

    2015-01-01

    Recently, there has been a concerted effort to implement advanced classical potential energy surfaces by adding higher order multipoles to fixed point charge electrostatics in a bid to increase the accuracy of simulations of condensed phase systems. One major hurdle is the unwieldy nature of the expressions which in part has limited developers mostly to including only dipoles and quadrupoles. In this paper, we present a generalization of the Cartesian formulation of electrostatic multipolar interactions that enables the specification of an arbitrary order of multipoles. Specifically, we derive formulas for arbitrary order implementation of the particle mesh Ewald method and give a closed form formula for the stress tensor in the reciprocal space. In addition, we provide recurrence relations for common electrostatic potentials employed in molecular simulations, which allows for the generalization to arbitrary order and guarantees a computational cost that scales as O(p3) for Cartesian multipole interactions of order p.

  16. Surface Generation and Cartesian Mesh Support

    NASA Technical Reports Server (NTRS)

    Haimes, Robert

    2004-01-01

    This document serves as the final report for the grant titled Surface Generation and Cartesian Mesh Support . This completed work was in algorithmic research into automatically generating surface triangulations from CAD geometries. NASA's OVERFLOW and Cart3D simulation packages use surface triangulations as an underlying geometry description and the ability to automatically generate these from CAD files (without translation) substantially reduces both the wall-clock time and expertise required to get geometry out of CAD and into mesh generation. This surface meshing was exercised greatly during the Shuttle investigation during the last year with success. The secondary efforts performed in this grant involve work on a visualization system cut-cell handling for Cartesian Meshes with embedded boundaries.

  17. Adaptation of a matrix parameterization of the middle atmospheric radiative cooling for an arbitrary vertical coordinate grid

    NASA Technical Reports Server (NTRS)

    Akmaev, R. A.; Fomichev, V. I.

    1992-01-01

    Matrices corresponding to a revised vertical grid are shown to be derived from the original grid by integrating the radiative cooling rate over model layers. The method is applied to temperature profiles that represent average or extreme atmospheric conditions and a range of vertical resolutions. The example makes use of the 15-micron CO2 band parameterization proposed by Akmaev and Shved (1982) for the LTE region of the middle atmosphere. Cooling rate errors provided by the present method are not more than 0.11 K/day for a vertical grid spacing of less than 5 km. The matrix transformation method is shown to be valuable for adapting effective matrix parameterizations of middle atmosphere cooling to atmospheric models with arbitrary vertical resolutions.

  18. How do spatial learning and memory occur in the brain? Coordinated learning of entorhinal grid cells and hippocampal place cells.

    PubMed

    Pilly, Praveen K; Grossberg, Stephen

    2012-05-01

    Spatial learning and memory are important for navigation and formation of episodic memories. The hippocampus and medial entorhinal cortex (MEC) are key brain areas for spatial learning and memory. Place cells in hippocampus fire whenever an animal is located in a specific region in the environment. Grid cells in the superficial layers of MEC provide inputs to place cells and exhibit remarkable regular hexagonal spatial firing patterns. They also exhibit a gradient of spatial scales along the dorsoventral axis of the MEC, with neighboring cells at a given dorsoventral location having different spatial phases. A neural model shows how a hierarchy of self-organizing maps, each obeying the same laws, responds to realistic rat trajectories by learning grid cells with hexagonal grid firing fields of multiple spatial scales and place cells with unimodal firing fields that fit neurophysiological data about their development in juvenile rats. The hippocampal place fields represent much larger spaces than the grid cells to support navigational behaviors. Both the entorhinal and hippocampal self-organizing maps amplify and learn to categorize the most energetic and frequent co-occurrences of their inputs. Top-down attentional mechanisms from hippocampus to MEC help to dynamically stabilize these spatial memories in both the model and neurophysiological data. Spatial learning through MEC to hippocampus occurs in parallel with temporal learning through lateral entorhinal cortex to hippocampus. These homologous spatial and temporal representations illustrate a kind of "neural relativity" that may provide a substrate for episodic learning and memory. PMID:22288394

  19. Comparison of iterative and direct solution methods for viscous flow calculations in body-fitted co-ordinates

    NASA Astrophysics Data System (ADS)

    Braaten, M. E.; Shyy, W.

    1986-06-01

    The computational efficiency of iterative and direct solution methods in viscous flows calculated on curvilinear coordinate systems is studied for cases including a series of two-dimensional planar channels with progressive skewness of the grid system and a kidney-shaped channel. The iterative method convergence rate, less rapid than that of the direct method, decreases monotonically with increasing global mesh skewness and Reynolds number, while the direct method is seen as insensitive to these variables. It is shown that the increased complexity of the equations in curvilinear coordinates causes the storage requirements and cost per iteration of the direct method to be higher than in corresponding Cartesian coordinate methods. Therefore, increases in grid size increase CPU time and computer storage needs of the direct method more severely than the iterative method.

  20. Development of a grid-independent approximate Riemannsolver. Ph.D. Thesis - Michigan Univ.

    NASA Technical Reports Server (NTRS)

    Rumsey, Christopher Lockwood

    1991-01-01

    A grid-independent approximate Riemann solver for use with the Euler and Navier-Stokes equations was introduced and explored. The two-dimensional Euler and Navier-Stokes equations are described in Cartesian and generalized coordinates, as well as the traveling wave form of the Euler equations. The spatial and temporal discretization are described for both explicit and implicit time-marching schemes. The grid-aligned flux function of Roe is outlined, while the 5-wave grid-independent flux function is derived. The stability and monotonicity analysis of the 5-wave model are presented. Two-dimensional results are provided and extended to three dimensions. The corresponding results are presented.

  1. A Cartesian Adaptive Level Set Method for Two-Phase Flows

    NASA Technical Reports Server (NTRS)

    Ham, F.; Young, Y.-N.

    2003-01-01

    In the present contribution we develop a level set method based on local anisotropic Cartesian adaptation as described in Ham et al. (2002). Such an approach should allow for the smallest possible Cartesian grid capable of resolving a given flow. The remainder of the paper is organized as follows. In section 2 the level set formulation for free surface calculations is presented and its strengths and weaknesses relative to the other free surface methods reviewed. In section 3 the collocated numerical method is described. In section 4 the method is validated by solving the 2D and 3D drop oscilation problem. In section 5 we present some results from more complex cases including the 3D drop breakup in an impulsively accelerated free stream, and the 3D immiscible Rayleigh-Taylor instability. Conclusions are given in section 6.

  2. Inflow-outflow boundary conditions along arbitrary directions in Cartesian lake models

    NASA Astrophysics Data System (ADS)

    Ramn, C. L.; Corts, A.; Rueda, F. J.

    2015-01-01

    Specifying point sources and sinks of water near boundaries is presented as a flexible approach to prescribe inflows and outflows along arbitrary directions in Cartesian grid lake models. Implementing the approach involves a straightforward modification of the governing equations, to include a first order source term in the continuity and momentum equations. The approach is implemented in a Cartesian grid model and applied to several test cases. First, the flow along a straight flat bottom channel with its axis forming different angles with the grid directions is simulated and the results are compared against well-known analytical solutions. Point-sources are then used to simulate unconfined inflows into a reservoir (a small river entering a reservoir in a jet-like manner), which occur at an angle with the grid directions. The model results are assessed in terms of a mixing ratio between lake and river water, evaluated at a cross section downstream of the inflow boundary. Those results are particularly sensitive to changes in the inflow angle. It is argued that differences in mixing rates near the inflow sections could affect the fate of river-borne substances in model simulations.

  3. Multilevel Error Estimation and Adaptive h-Refinement for Cartesian Meshes with Embedded Boundaries

    NASA Technical Reports Server (NTRS)

    Aftosmis, M. J.; Berger, M. J.; Kwak, Dochan (Technical Monitor)

    2002-01-01

    This paper presents the development of a mesh adaptation module for a multilevel Cartesian solver. While the module allows mesh refinement to be driven by a variety of different refinement parameters, a central feature in its design is the incorporation of a multilevel error estimator based upon direct estimates of the local truncation error using tau-extrapolation. This error indicator exploits the fact that in regions of uniform Cartesian mesh, the spatial operator is exactly the same on the fine and coarse grids, and local truncation error estimates can be constructed by evaluating the residual on the coarse grid of the restricted solution from the fine grid. A new strategy for adaptive h-refinement is also developed to prevent errors in smooth regions of the flow from being masked by shocks and other discontinuous features. For certain classes of error histograms, this strategy is optimal for achieving equidistribution of the refinement parameters on hierarchical meshes, and therefore ensures grid converged solutions will be achieved for appropriately chosen refinement parameters. The robustness and accuracy of the adaptation module is demonstrated using both simple model problems and complex three dimensional examples using meshes with from 10(exp 6), to 10(exp 7) cells.

  4. Material translations in the Cartesian brain.

    PubMed

    Bassiri, Nima

    2012-03-01

    This article reexamines the controversial doctrine of the pineal gland in Cartesian psychophysiology. It argues initially that Descartes' combined metaphysics and natural philosophy yield a distinctly human subject who is rational, willful, but also a living and embodied being in the world, formed in the union and through the dynamics of the interaction between the soul and the body. However, Descartes only identified one site at which this union was staged: the brain, and more precisely, the pineal gland, the small bulb of nervous tissue at the brain's center. The pineal gland was charged with the incredible task of ensuring the interactive mutuality between the soul and body, while also maintaining the necessary ontological incommensurability between them. This article reconsiders the theoretical obligations placed on the pineal gland as the site of the soul-body union, and looks at how the gland was consequently forced to adopt a very precarious ontological status. The article ultimately questions how successfully the Cartesian human could be localized in the pineal gland, while briefly considering the broader historical consequences of the ensuing equivalence of the self and brain. PMID:22326094

  5. Data Grid Management Systems

    NASA Technical Reports Server (NTRS)

    Moore, Reagan W.; Jagatheesan, Arun; Rajasekar, Arcot; Wan, Michael; Schroeder, Wayne

    2004-01-01

    The "Grid" is an emerging infrastructure for coordinating access across autonomous organizations to distributed, heterogeneous computation and data resources. Data grids are being built around the world as the next generation data handling systems for sharing, publishing, and preserving data residing on storage systems located in multiple administrative domains. A data grid provides logical namespaces for users, digital entities and storage resources to create persistent identifiers for controlling access, enabling discovery, and managing wide area latencies. This paper introduces data grids and describes data grid use cases. The relevance of data grids to digital libraries and persistent archives is demonstrated, and research issues in data grids and grid dataflow management systems are discussed.

  6. Tolerating Correlated Failures for Generalized Cartesian Distributions via Bipartite Matching

    SciTech Connect

    Ali, Nawab; Krishnamoorthy, Sriram; Halappanavar, Mahantesh; Daily, Jeffrey A.

    2011-05-05

    Faults are expected to play an increasingly important role in how algorithms and applications are designed to run on future extreme-scale systems. A key ingredient of any approach to fault tolerance is effective support for fault tolerant data storage. A typical application execution consists of phases in which certain data structures are modified while others are read-only. Often, read-only data structures constitute a large fraction of total memory consumed. Fault tolerance for read-only data can be ensured through the use of checksums or parities, without resorting to expensive in-memory duplication or checkpointing to secondary storage. In this paper, we present a graph-matching approach to compute and store parity data for read-only matrices that are compatible with fault tolerant linear algebra (FTLA). Typical approaches only support blocked data distributions with each process holding one block with the parity located on additional processes. The matrices are assumed to be blocked by a cartesian grid with each block assigned to a process. We consider a generalized distribution in which each process can be assigned arbitrary blocks. We also account for the fact that multiple processes might be part of the same failure unit, say an SMP node. The flexibility enabled by our novel application of graph matching extends fault tolerance support to data distributions beyond those supported by prior work. We evaluate the matching implementations and cost to compute the parity and recover lost data, demonstrating the low overhead incurred by our approach.

  7. Grid-based methods for diatomic quantum scattering problems III: Double photoionization of molecular hydrogen in prolate spheroidal coordinates

    SciTech Connect

    Tao, Liang; McCurdy, Bill; Rescigno, Tom

    2010-06-10

    Our previously developed finite-element/ discrete variable representation in prolate spheroidal coordinates is extended to two-electron systems with a study of double ionization of H$_2$ with fixed-nuclei. Particular attention is paid to the development of fast and accurate methods for treating the electron-electron interaction. The use of exterior complex scaling in the implementation offers a simple way of enforcing Coulomb boundary conditions for the electronic double continuum. While the angular distributions calculated in this study are found to be completely consistent with our earlier treatments that employed single-center expansions in spherical coordinates, we find that the magnitude of the integrated cross sections are sensitive to small changes in the initial-state wave function. The present formulation offers significant advantages with respect to convergence and efficiency and opens the way to calculations on more complicated diatomic targets.

  8. Grid-based methods for diatomic quantum scattering problems. III. Double photoionization of molecular hydrogen in prolate spheroidal coordinates

    NASA Astrophysics Data System (ADS)

    Tao, Liang; McCurdy, C. W.; Rescigno, T. N.

    2010-08-01

    Our previously developed finite-element discrete-variable representation in prolate spheroidal coordinates is extended to two-electron systems with a study of double ionization of H2 with fixed nuclei. Particular attention is paid to the development of fast and accurate methods for treating the electron-electron interaction. The use of exterior complex scaling in the implementation offers a simple way of enforcing Coulomb boundary conditions for the electronic double continuum. While the angular distributions calculated in this study are found to be completely consistent with our earlier treatments that employed single-center expansions in spherical coordinates, we find that the magnitude of the integrated cross sections are sensitive to small changes in the initial-state wave function. The present formulation offers significant advantages with respect to convergence and efficiency and opens the way to calculations on more complicated diatomic targets.

  9. Grid-based methods for diatomic quantum scattering problems. III. Double photoionization of molecular hydrogen in prolate spheroidal coordinates

    SciTech Connect

    Tao, Liang; Rescigno, T. N.; McCurdy, C. W.

    2010-08-15

    Our previously developed finite-element discrete-variable representation in prolate spheroidal coordinates is extended to two-electron systems with a study of double ionization of H{sub 2} with fixed nuclei. Particular attention is paid to the development of fast and accurate methods for treating the electron-electron interaction. The use of exterior complex scaling in the implementation offers a simple way of enforcing Coulomb boundary conditions for the electronic double continuum. While the angular distributions calculated in this study are found to be completely consistent with our earlier treatments that employed single-center expansions in spherical coordinates, we find that the magnitude of the integrated cross sections are sensitive to small changes in the initial-state wave function. The present formulation offers significant advantages with respect to convergence and efficiency and opens the way to calculations on more complicated diatomic targets.

  10. Algebraic grid generation

    NASA Technical Reports Server (NTRS)

    Smith, Robert E.; Eriksson, Lars-Erik

    1987-01-01

    Algebraic grid generation is the direct expression of a physical coordinate system as a function of a uniform grid in a rectangular computational coordinate system. Algebraic grid generation is based on mathematical interpolation and is presented in general terms of multivariate transfinite interpolation. The multisurface method and the two-boundary technique are described as univariate procedures that can be applied within the context of transfinite interpolation. A technique for grid clustering is described. Problems that are commonly encountered in three-dimensional grid generation are discussed and approaches for dealing with complex physical domains using multiple computational grid blocks are presented.

  11. A Two-dimensional Cartesian and Axisymmetric Study of Combustion-acoustic Interaction

    NASA Technical Reports Server (NTRS)

    Hood, Caroline; Frendi, Abdelkader

    2006-01-01

    This paper describes a study of a lean premixed (LP) methane-air combustion wave in a two-dimensional Cartesian and axisymmetric coordinate system. Lean premixed combustors provide low emission and high efficiency; however, they are susceptible to combustion instabilities. The present study focuses on the behavior of the flame as it interacts with an external acoustic disturbance. It was found that the flame oscillations increase as the disturbance amplitude is increased. Furthermore, when the frequency of the disturbance is at resonance with a chamber frequency, the instabilities increase. For the axisymmetric geometry, the flame is found to be more unstable compared to the Cartesian case. In some cases, these instabilities were severe and led to flame extinction. In the axisymmetric case, several passive control devices were tested to assess their effectiveness. It is found that an acoustic cavity is better able at controlling the pressure fluctuations in the chamber.

  12. Adaptively Refined Euler and Navier-Stokes Solutions with a Cartesian-Cell Based Scheme

    NASA Technical Reports Server (NTRS)

    Coirier, William J.; Powell, Kenneth G.

    1995-01-01

    A Cartesian-cell based scheme with adaptive mesh refinement for solving the Euler and Navier-Stokes equations in two dimensions has been developed and tested. Grids about geometrically complicated bodies were generated automatically, by recursive subdivision of a single Cartesian cell encompassing the entire flow domain. Where the resulting cells intersect bodies, N-sided 'cut' cells were created using polygon-clipping algorithms. The grid was stored in a binary-tree data structure which provided a natural means of obtaining cell-to-cell connectivity and of carrying out solution-adaptive mesh refinement. The Euler and Navier-Stokes equations were solved on the resulting grids using an upwind, finite-volume formulation. The inviscid fluxes were found in an upwinded manner using a linear reconstruction of the cell primitives, providing the input states to an approximate Riemann solver. The viscous fluxes were formed using a Green-Gauss type of reconstruction upon a co-volume surrounding the cell interface. Data at the vertices of this co-volume were found in a linearly K-exact manner, which ensured linear K-exactness of the gradients. Adaptively-refined solutions for the inviscid flow about a four-element airfoil (test case 3) were compared to theory. Laminar, adaptively-refined solutions were compared to accepted computational, experimental and theoretical results.

  13. On automating domain connectivity for overset grids

    NASA Technical Reports Server (NTRS)

    Chiu, Ing-Tsau; Meakin, Robert L.

    1995-01-01

    An alternative method for domain connectivity among systems of overset grids is presented. Reference uniform Cartesian systems of points are used to achieve highly efficient domain connectivity, and form the basis for a future fully automated system. The Cartesian systems are used to approximate body surfaces and to map the computational space of component grids. By exploiting the characteristics of Cartesian systems, Chimera type hole-cutting and identification of donor elements for intergrid boundary points can be carried out very efficiently. The method is tested for a range of geometrically complex multiple-body overset grid systems. A dynamic hole expansion/contraction algorithm is also implemented to obtain optimum domain connectivity; however, it is tested only for geometry of generic shapes.

  14. Fibonacci Grids

    NASA Technical Reports Server (NTRS)

    Swinbank, Richard; Purser, James

    2006-01-01

    Recent years have seen a resurgence of interest in a variety of non-standard computational grids for global numerical prediction. The motivation has been to reduce problems associated with the converging meridians and the polar singularities of conventional regular latitude-longitude grids. A further impetus has come from the adoption of massively parallel computers, for which it is necessary to distribute work equitably across the processors; this is more practicable for some non-standard grids. Desirable attributes of a grid for high-order spatial finite differencing are: (i) geometrical regularity; (ii) a homogeneous and approximately isotropic spatial resolution; (iii) a low proportion of the grid points where the numerical procedures require special customization (such as near coordinate singularities or grid edges). One family of grid arrangements which, to our knowledge, has never before been applied to numerical weather prediction, but which appears to offer several technical advantages, are what we shall refer to as "Fibonacci grids". They can be thought of as mathematically ideal generalizations of the patterns occurring naturally in the spiral arrangements of seeds and fruit found in sunflower heads and pineapples (to give two of the many botanical examples). These grids possess virtually uniform and highly isotropic resolution, with an equal area for each grid point. There are only two compact singular regions on a sphere that require customized numerics. We demonstrate the practicality of these grids in shallow water simulations, and discuss the prospects for efficiently using these frameworks in three-dimensional semi-implicit and semi-Lagrangian weather prediction or climate models.

  15. Cartesian echo planar hybrid scanning with two to eight echoes.

    PubMed

    Kashmar, G; Nalcioglu, O

    1991-01-01

    A method of fast nuclear magnetic resonance (NMR) imaging which uses only square wave gradient shapes and also collects data on Cartesian coordinates in a way similar to the blipped echo planar imaging method (BEPI) is described. The method is a heuristic attempt at finding an optimal data collection strategy for NMR imaging. Its advantages and disadvantages compared to other methods are carefully analyzed. Clinical size anatomical (head and body) images are shown. It is found that the interecho phase-angle discrepancies that are caused bv the B(0) inhomogeneity and by the gradient wave form distortion can largely be eliminated by using the half Fourier method with full Fourier phase map correction, but one phase map is required for each echo. GRASS/FLASH spoiling techniques are incorporated into the method in order to allow multiecho speed increases for scans which would run under 10 s using a single-echo method. The technique can be applied directly to GRASS/FLASH itself, as is demonstrated by a two-echo GRASS scan. The fastest image was 1.9 s. PMID:18222795

  16. A Cartesian, cell-based approach for adaptively-refined solutions of the Euler and Navier-Stokes equations

    NASA Technical Reports Server (NTRS)

    Coirier, William J.; Powell, Kenneth G.

    1994-01-01

    A Cartesian, cell-based approach for adaptively-refined solutions of the Euler and Navier-Stokes equations in two dimensions is developed and tested. Grids about geometrically complicated bodies are generated automatically, by recursive subdivision of a single Cartesian cell encompassing the entire flow domain. Where the resulting cells intersect bodies, N-sided 'cut' cells are created using polygon-clipping algorithms. The grid is stored in a binary-tree structure which provides a natural means of obtaining cell-to-cell connectivity and of carrying out solution-adaptive mesh refinement. The Euler and Navier-Stokes equations are solved on the resulting grids using a finite-volume formulation. The convective terms are upwinded: a gradient-limited, linear reconstruction of the primitive variables is performed, providing input states to an approximate Riemann solver for computing the fluxes between neighboring cells. The more robust of a series of viscous flux functions is used to provide the viscous fluxes at the cell interfaces. Adaptively-refined solutions of the Navier-Stokes equations using the Cartesian, cell-based approach are obtained and compared to theory, experiment, and other accepted computational results for a series of low and moderate Reynolds number flows.

  17. A Cartesian, cell-based approach for adaptively-refined solutions of the Euler and Navier-Stokes equations

    NASA Technical Reports Server (NTRS)

    Coirier, William J.; Powell, Kenneth G.

    1995-01-01

    A Cartesian, cell-based approach for adaptively-refined solutions of the Euler and Navier-Stokes equations in two dimensions is developed and tested. Grids about geometrically complicated bodies are generated automatically, by recursive subdivision of a single Cartesian cell encompassing the entire flow domain. Where the resulting cells intersect bodies, N-sided 'cut' cells are created using polygon-clipping algorithms. The grid is stored in a binary-tree data structure which provides a natural means of obtaining cell-to-cell connectivity and of carrying out solution-adaptive mesh refinement. The Euler and Navier-Stokes equations are solved on the resulting grids using a finite-volume formulation. The convective terms are upwinded: A gradient-limited, linear reconstruction of the primitive variables is performed, providing input states to an approximate Riemann solver for computing the fluxes between neighboring cells. The more robust of a series of viscous flux functions is used to provide the viscous fluxes at the cell interfaces. Adaptively-refined solutions of the Navier-Stokes equations using the Cartesian, cell-based approach are obtained and compared to theory, experiment and other accepted computational results for a series of low and moderate Reynolds number flows.

  18. Stage Cartesian self-calibration: a second method

    NASA Astrophysics Data System (ADS)

    Takac, Michael T.; Whittey, John M.

    1998-12-01

    A physical two-dimensional Cartesian reference has been demonstrated using group theory principles pioneered by Michael Raugh. The first stage Cartesian self-calibration introduction to the microlithographic industry was developed by Stanford University, Hewlett Packard, and IBM San Jose using Leica's LMS-2000 and LMS-2020 platforms. Recently Leica developed a different method based on a similar theory to achieve a Cartesian calibration for their LMS-IPRO x-y metrology system. A review of these methods and a comparison of the results obtained between the methods are presented.

  19. Grid-based Methods in Relativistic Hydrodynamics and Magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Martí, José María; Müller, Ewald

    2015-12-01

    An overview of grid-based numerical methods used in relativistic hydrodynamics (RHD) and magnetohydrodynamics (RMHD) is presented. Special emphasis is put on a comprehensive review of the application of high-resolution shock-capturing methods. Results of a set of demanding test bench simulations obtained with different numerical methods are compared in an attempt to assess the present capabilities and limits of the various numerical strategies. Applications to three astrophysical phenomena are briefly discussed to motivate the need for and to demonstrate the success of RHD and RMHD simulations in their understanding. The review further provides FORTRAN programs to compute the exact solution of the Riemann problem in RMHD, and to simulate 1D RMHD flows in Cartesian coordinates.

  20. Generalized and efficient algorithm for computing multipole energies and gradients based on Cartesian tensors

    NASA Astrophysics Data System (ADS)

    Lin, Dejun

    2015-09-01

    Accurate representation of intermolecular forces has been the central task of classical atomic simulations, known as molecular mechanics. Recent advancements in molecular mechanics models have put forward the explicit representation of permanent and/or induced electric multipole (EMP) moments. The formulas developed so far to calculate EMP interactions tend to have complicated expressions, especially in Cartesian coordinates, which can only be applied to a specific kernel potential function. For example, one needs to develop a new formula each time a new kernel function is encountered. The complication of these formalisms arises from an intriguing and yet obscured mathematical relation between the kernel functions and the gradient operators. Here, I uncover this relation via rigorous derivation and find that the formula to calculate EMP interactions is basically invariant to the potential kernel functions as long as they are of the form f(r), i.e., any Green's function that depends on inter-particle distance. I provide an algorithm for efficient evaluation of EMP interaction energies, forces, and torques for any kernel f(r) up to any arbitrary rank of EMP moments in Cartesian coordinates. The working equations of this algorithm are essentially the same for any kernel f(r). Recently, a few recursive algorithms were proposed to calculate EMP interactions. Depending on the kernel functions, the algorithm here is about 4-16 times faster than these algorithms in terms of the required number of floating point operations and is much more memory efficient. I show that it is even faster than a theoretically ideal recursion scheme, i.e., one that requires 1 floating point multiplication and 1 addition per recursion step. This algorithm has a compact vector-based expression that is optimal for computer programming. The Cartesian nature of this algorithm makes it fit easily into modern molecular simulation packages as compared with spherical coordinate-based algorithms. A software library based on this algorithm has been implemented in C++11 and has been released.

  1. Adjoint Algorithm for CAD-Based Shape Optimization Using a Cartesian Method

    NASA Technical Reports Server (NTRS)

    Nemec, Marian; Aftosmis, Michael J.

    2004-01-01

    Adjoint solutions of the governing flow equations are becoming increasingly important for the development of efficient analysis and optimization algorithms. A well-known use of the adjoint method is gradient-based shape optimization. Given an objective function that defines some measure of performance, such as the lift and drag functionals, its gradient is computed at a cost that is essentially independent of the number of design variables (geometric parameters that control the shape). More recently, emerging adjoint applications focus on the analysis problem, where the adjoint solution is used to drive mesh adaptation, as well as to provide estimates of functional error bounds and corrections. The attractive feature of this approach is that the mesh-adaptation procedure targets a specific functional, thereby localizing the mesh refinement and reducing computational cost. Our focus is on the development of adjoint-based optimization techniques for a Cartesian method with embedded boundaries.12 In contrast t o implementations on structured and unstructured grids, Cartesian methods decouple the surface discretization from the volume mesh. This feature makes Cartesian methods well suited for the automated analysis of complex geometry problems, and consequently a promising approach to aerodynamic optimization. Melvin et developed an adjoint formulation for the TRANAIR code, which is based on the full-potential equation with viscous corrections. More recently, Dadone and Grossman presented an adjoint formulation for the Euler equations. In both approaches, a boundary condition is introduced to approximate the effects of the evolving surface shape that results in accurate gradient computation. Central to automated shape optimization algorithms is the issue of geometry modeling and control. The need to optimize complex, "real-life" geometry provides a strong incentive for the use of parametric-CAD systems within the optimization procedure. In previous work, we presented an effective optimization framework that incorporates a direct-CAD interface. In this work, we enhance the capabilities of this framework with efficient gradient computations using the discrete adjoint method. We present details of the adjoint numerical implementation, which reuses the domain decomposition, multigrid, and time-marching schemes of the flow solver. Furthermore, we explain and demonstrate the use of CAD in conjunction with the Cartesian adjoint approach. The final paper will contain a number of complex geometry, industrially relevant examples with many design variables to demonstrate the effectiveness of the adjoint method on Cartesian meshes.

  2. FIDDLE: A Computer Code for Finite Difference Development of Linear Elasticity in Generalized Curvilinear Coordinates

    NASA Technical Reports Server (NTRS)

    Kaul, Upender K.

    2005-01-01

    A three-dimensional numerical solver based on finite-difference solution of three-dimensional elastodynamic equations in generalized curvilinear coordinates has been developed and used to generate data such as radial and tangential stresses over various gear component geometries under rotation. The geometries considered are an annulus, a thin annular disk, and a thin solid disk. The solution is based on first principles and does not involve lumped parameter or distributed parameter systems approach. The elastodynamic equations in the velocity-stress formulation that are considered here have been used in the solution of problems of geophysics where non-rotating Cartesian grids are considered. For arbitrary geometries, these equations along with the appropriate boundary conditions have been cast in generalized curvilinear coordinates in the present study.

  3. Visual Methods for Model and Grid Validation

    NASA Technical Reports Server (NTRS)

    Pang, Alex

    1998-01-01

    This joint research interchange proposal allowed us to contribute in two directions that are of interest to NASA. These are: (a) data level comparative visualization of experimental and computational fluid flow, and (b) visualization tools for analysis of adaptively refined Cartesian grids.

  4. Frequency-Offset Cartesian Feedback Based on Polyphase Difference Amplifiers

    PubMed Central

    Zanchi, Marta G.; Pauly, John M.; Scott, Greig C.

    2010-01-01

    A modified Cartesian feedback method called “frequency-offset Cartesian feedback” and based on polyphase difference amplifiers is described that significantly reduces the problems associated with quadrature errors and DC-offsets in classic Cartesian feedback power amplifier control systems. In this method, the reference input and feedback signals are down-converted and compared at a low intermediate frequency (IF) instead of at DC. The polyphase difference amplifiers create a complex control bandwidth centered at this low IF, which is typically offset from DC by 200–1500 kHz. Consequently, the loop gain peak does not overlap DC where voltage offsets, drift, and local oscillator leakage create errors. Moreover, quadrature mismatch errors are significantly attenuated in the control bandwidth. Since the polyphase amplifiers selectively amplify the complex signals characterized by a +90° phase relationship representing positive frequency signals, the control system operates somewhat like single sideband (SSB) modulation. However, the approach still allows the same modulation bandwidth control as classic Cartesian feedback. In this paper, the behavior of the polyphase difference amplifier is described through both the results of simulations, based on a theoretical analysis of their architecture, and experiments. We then describe our first printed circuit board prototype of a frequency-offset Cartesian feedback transmitter and its performance in open and closed loop configuration. This approach should be especially useful in magnetic resonance imaging transmit array systems. PMID:20814450

  5. OVERGRID: A Unified Overset Grid Generation Graphical Interface

    NASA Technical Reports Server (NTRS)

    Chan, William M.; Akien, Edwin W. (Technical Monitor)

    1999-01-01

    This paper presents a unified graphical interface and gridding strategy for performing overset grid generation. The interface called OVERGRID has been specifically designed to follow an efficient overset gridding strategy, and contains general grid manipulation capabilities as well as modules that are specifically suited for overset grids. General grid utilities include functions for grid redistribution, smoothing, concatenation, extraction, extrapolation, projection, and many others. Modules specially tailored for overset grids include a seam curve extractor, hyperbolic and algebraic surface grid generators, a hyperbolic volume grid generator, and a Cartesian box grid generator, Grid visualization is achieved using OpenGL while widgets are constructed with Tcl/Tk. The software is portable between various platforms from UNIX workstations to personal computers.

  6. Biangular Coordinates Redux: Discovering a New Kind of Geometry

    ERIC Educational Resources Information Center

    Winkel, Brian; Naylor, Michael

    2010-01-01

    Biangular coordinates specify a point on the plane by two angles giving the intersection of two rays emanating from two fixed poles. This is a dual of Cartesian coordinates wherein a point on the plane is described by two distances. Biangular coordinates, first written about in 1803 in France, were subsequently studied in Britain at the end of the…

  7. Applications of Space-Filling-Curves to Cartesian Methods for CFD

    NASA Technical Reports Server (NTRS)

    Aftosmis, Michael J.; Berger, Marsha J.; Murman, Scott M.

    2003-01-01

    The proposed paper presents a variety novel uses of Space-Filling-Curves (SFCs) for Cartesian mesh methods in 0. While these techniques will be demonstrated using non-body-fitted Cartesian meshes, most are applicable on general body-fitted meshes -both structured and unstructured. We demonstrate the use of single O(N log N) SFC-based reordering to produce single-pass (O(N)) algorithms for mesh partitioning, multigrid coarsening, and inter-mesh interpolation. The intermesh interpolation operator has many practical applications including warm starts on modified geometry, or as an inter-grid transfer operator on remeshed regions in moving-body simulations. Exploiting the compact construction of these operators, we further show that these algorithms are highly amenable to parallelization. Examples using the SFC-based mesh partitioner show nearly linear speedup to 512 CPUs even when using multigrid as a smoother. Partition statistics are presented showing that the SFC partitions are, on-average, within 10% of ideal even with only around 50,000 cells in each subdomain. The inter-mesh interpolation operator also has linear asymptotic complexity and can be used to map a solution with N unknowns to another mesh with M unknowns with O(max(M,N)) operations. This capability is demonstrated both on moving-body simulations and in mapping solutions to perturbed meshes for finite-difference-based gradient design methods.

  8. Applications of Space-Filling-Curves to Cartesian Methods for CFD

    NASA Technical Reports Server (NTRS)

    Aftosmis, M. J.; Murman, S. M.; Berger, M. J.

    2003-01-01

    This paper presents a variety of novel uses of space-filling-curves (SFCs) for Cartesian mesh methods in CFD. While these techniques will be demonstrated using non-body-fitted Cartesian meshes, many are applicable on general body-fitted meshes-both structured and unstructured. We demonstrate the use of single theta(N log N) SFC-based reordering to produce single-pass (theta(N)) algorithms for mesh partitioning, multigrid coarsening, and inter-mesh interpolation. The intermesh interpolation operator has many practical applications including warm starts on modified geometry, or as an inter-grid transfer operator on remeshed regions in moving-body simulations Exploiting the compact construction of these operators, we further show that these algorithms are highly amenable to parallelization. Examples using the SFC-based mesh partitioner show nearly linear speedup to 640 CPUs even when using multigrid as a smoother. Partition statistics are presented showing that the SFC partitions are, on-average, within 15% of ideal even with only around 50,000 cells in each sub-domain. The inter-mesh interpolation operator also has linear asymptotic complexity and can be used to map a solution with N unknowns to another mesh with M unknowns with theta(M + N) operations. This capability is demonstrated both on moving-body simulations and in mapping solutions to perturbed meshes for control surface deflection or finite-difference-based gradient design methods.

  9. Configuration space representation in parallel coordinates

    NASA Technical Reports Server (NTRS)

    Fiorini, Paolo; Inselberg, Alfred

    1989-01-01

    By means of a system of parallel coordinates, a nonprojective mapping from R exp N to R squared is obtained for any positive integer N. In this way multivariate data and relations can be represented in the Euclidean plane (embedded in the projective plane). Basically, R squared with Cartesian coordinates is augmented by N parallel axes, one for each variable. The N joint variables of a robotic device can be represented graphically by using parallel coordinates. It is pointed out that some properties of the relation are better perceived visually from the parallel coordinate representation, and that new algorithms and data structures can be obtained from this representation. The main features of parallel coordinates are described, and an example is presented of their use for configuration space representation of a mechanical arm (where Cartesian coordinates cannot be used).

  10. [The role of the pineal gland in cartesian psychophysiological doctrine].

    PubMed

    López-Muñoz, F; Boya, J

    1992-01-01

    In the present paper, we review the cartesian description of the neuromuscular reflex and the sensorial perception as well as the hypothetical role of the pineal gland on these functions. We analyze the historical bases which support the physiological cartesian doctrine and, from the perspective of our present knowledge, we evaluate the contributions of Descartes to the scientific progress of his time. In the elaborated psychophysiological theory of the french wise, the pineal gland plays a pivotal role, raising the theory that the human soul could be located within this organ. PMID:1343979

  11. String method for calculation of minimum free-energy paths in Cartesian space in freely-tumbling systems.

    PubMed

    Branduardi, Davide; Faraldo-Gómez, José D

    2013-09-10

    The string method is a molecular-simulation technique that aims to calculate the minimum free-energy path of a chemical reaction or conformational transition, in the space of a pre-defined set of reaction coordinates that is typically highly dimensional. Any descriptor may be used as a reaction coordinate, but arguably the Cartesian coordinates of the atoms involved are the most unprejudiced and intuitive choice. Cartesian coordinates, however, present a non-trivial problem, in that they are not invariant to rigid-body molecular rotations and translations, which ideally ought to be unrestricted in the simulations. To overcome this difficulty, we reformulate the framework of the string method to integrate an on-the-fly structural-alignment algorithm. This approach, referred to as SOMA (String method with Optimal Molecular Alignment), enables the use of Cartesian reaction coordinates in freely tumbling molecular systems. In addition, this scheme permits the dissection of the free-energy change along the most probable path into individual atomic contributions, thus revealing the dominant mechanism of the simulated process. This detailed analysis also provides a physically-meaningful criterion to coarse-grain the representation of the path. To demonstrate the accuracy of the method we analyze the isomerization of the alanine dipeptide in vacuum and the chair-to-inverted-chair transition of β-D mannose in explicit water. Notwithstanding the simplicity of these systems, the SOMA approach reveals novel insights into the atomic mechanism of these isomerizations. In both cases, we find that the dynamics and the energetics of these processes are controlled by interactions involving only a handful of atoms in each molecule. Consistent with this result, we show that a coarse-grained SOMA calculation defined in terms of these subsets of atoms yields nearidentical minimum free-energy paths and committor distributions to those obtained via a highly-dimensional string. PMID:24729762

  12. Implicit Approaches for Moving Boundaries in a 3-D Cartesian Method

    NASA Technical Reports Server (NTRS)

    Murman, Scott M.; Aftosmis, Michael J.; Berger, Marsha J.; Kwak, Dochan

    2003-01-01

    This work considers numerical simulation of three-dimensional flows with time-evolving boundaries. Such problems pose a variety of challenges for numerical schemes, and have received a substantial amount of attention in the recent literature. Since such simulations are unsteady, time-accurate solution of the governing equations is required. In special cases, the body motion can be treated by a uniform rigid motion of the computational domain. For the more general situation of relative-body motion, however, this simplification is unavailable and the simulations require a mechanism for ensuring that the mesh evolves with the moving boundaries. This involves a "remeshing" of the computational domain (either localized or global) at each physical timestep, and places a premium on both the speed and robustness of the remeshing algorithms. This work presents a method which includes unsteady flow simulation, rigid domain motion, and relative body motion using a time-evolving Cartesian grid system in three dimensions.

  13. A hybrid Cartesian/immersed boundary method for simulating flows with 3D, geometrically complex, moving bodies

    NASA Astrophysics Data System (ADS)

    Gilmanov, Anvar; Sotiropoulos, Fotis

    2005-08-01

    A numerical method is developed for solving the 3D, unsteady, incompressible Navier-Stokes equations in Cartesian domains containing immersed boundaries of arbitrary geometrical complexity moving with prescribed kinematics. The governing equations are discretized on a hybrid staggered/non-staggered grid layout using second-order accurate finite-difference formulas. The discrete equations are integrated in time via a second-order accurate dual-time-stepping, artificial compressibility iteration scheme. Unstructured, triangular meshes are employed to discretize complex immersed boundaries. The nodes of the surface mesh constitute a set of Lagrangian control points used to track the motion of the flexible body. At every instant in time, the influence of the body on the flow is accounted for by applying boundary conditions at Cartesian grid nodes located in the exterior but in the immediate vicinity of the body by reconstructing the solution along the local normal to the body surface. Grid convergence tests are carried out for the flow induced by an oscillating sphere in a cubic cavity, which show that the method is second-order accurate. The method is validated by applying it to calculate flow in a Cartesian domain containing a rigid sphere rotating at constant angular velocity as well as flow induced by a flapping wing. The ability of the method to simulate flows in domains with arbitrarily complex moving bodies is demonstrated by applying to simulate flow past an undulating fish-like body and flow past an anatomically realistic planktonic copepod performing an escape-like maneuver.

  14. The Cartesian Diver, Surface Tension and the Cheerios Effect

    ERIC Educational Resources Information Center

    Chen, Chi-Tung; Lee, Wen-Tang; Kao, Sung-Kai

    2014-01-01

    A Cartesian diver can be used to measure the surface tension of a liquid to a certain extent. The surface tension measurement is related to the two critical pressures at which the diver is about to sink and about to emerge. After sinking because of increasing pressure, the diver is repulsed to the centre of the vessel. After the pressure is

  15. The Cartesian Diver as an Aid for Teaching Respiratory Physiology

    ERIC Educational Resources Information Center

    Fitch, Greg K.

    2004-01-01

    The mechanism by which air enters the mammalian lung is difficult for many students of physiology. In particular, some students have trouble seeing how pressure can be transmitted through a fluid such as the intrapleural fluid and how the magnitude of that pressure can change. A Cartesian diver, an old-time child's toy, may be used as a visual aid…

  16. The Cartesian Diver, Surface Tension and the Cheerios Effect

    ERIC Educational Resources Information Center

    Chen, Chi-Tung; Lee, Wen-Tang; Kao, Sung-Kai

    2014-01-01

    A Cartesian diver can be used to measure the surface tension of a liquid to a certain extent. The surface tension measurement is related to the two critical pressures at which the diver is about to sink and about to emerge. After sinking because of increasing pressure, the diver is repulsed to the centre of the vessel. After the pressure is…

  17. A Lot of Good Physics in the Cartesian Diver

    ERIC Educational Resources Information Center

    De Luca, Roberto; Ganci, Salvatore

    2011-01-01

    The Cartesian diver experiment certainly occupies a place of honour in old physics textbooks as a vivid demonstration of Archimedes' buoyancy. The original experiment, as described in old textbooks, shows Archimedes buoyancy qualitatively: when the increased weight of the diver is not counterbalanced by Archimedes' buoyancy, the diver sinks. When…

  18. A Lot of Good Physics in the Cartesian Diver

    ERIC Educational Resources Information Center

    De Luca, Roberto; Ganci, Salvatore

    2011-01-01

    The Cartesian diver experiment certainly occupies a place of honour in old physics textbooks as a vivid demonstration of Archimedes' buoyancy. The original experiment, as described in old textbooks, shows Archimedes buoyancy qualitatively: when the increased weight of the diver is not counterbalanced by Archimedes' buoyancy, the diver sinks. When

  19. Generalized and efficient algorithm for computing multipole energies and gradients based on Cartesian tensors.

    PubMed

    Lin, Dejun

    2015-09-21

    Accurate representation of intermolecular forces has been the central task of classical atomic simulations, known as molecular mechanics. Recent advancements in molecular mechanics models have put forward the explicit representation of permanent and/or induced electric multipole (EMP) moments. The formulas developed so far to calculate EMP interactions tend to have complicated expressions, especially in Cartesian coordinates, which can only be applied to a specific kernel potential function. For example, one needs to develop a new formula each time a new kernel function is encountered. The complication of these formalisms arises from an intriguing and yet obscured mathematical relation between the kernel functions and the gradient operators. Here, I uncover this relation via rigorous derivation and find that the formula to calculate EMP interactions is basically invariant to the potential kernel functions as long as they are of the form f(r), i.e., any Green's function that depends on inter-particle distance. I provide an algorithm for efficient evaluation of EMP interaction energies, forces, and torques for any kernel f(r) up to any arbitrary rank of EMP moments in Cartesian coordinates. The working equations of this algorithm are essentially the same for any kernel f(r). Recently, a few recursive algorithms were proposed to calculate EMP interactions. Depending on the kernel functions, the algorithm here is about 4-16 times faster than these algorithms in terms of the required number of floating point operations and is much more memory efficient. I show that it is even faster than a theoretically ideal recursion scheme, i.e., one that requires 1 floating point multiplication and 1 addition per recursion step. This algorithm has a compact vector-based expression that is optimal for computer programming. The Cartesian nature of this algorithm makes it fit easily into modern molecular simulation packages as compared with spherical coordinate-based algorithms. A software library based on this algorithm has been implemented in C++11 and has been released. PMID:26395695

  20. Fast geodetic coordinate transformations

    NASA Astrophysics Data System (ADS)

    Carlson, N. A.

    1980-07-01

    The shape of the earth and its gravity field are well represented by a reference ellipsoid. New algorithms are presented for computationally efficient transformations between geodetic ellipsoidal (altitude, latitude, longitude) and geocentric Cartesian coordinates, including high-accuracy direct approximations and fast iterative exact solution. These algorithms provide significant speed and accuracy advantages over existing techniques. Terrestrial navigation equations based on the new algorithms are developed, and extended to various navigation functions from inertial data processing to Kalman filtering. Applied to a typical GPS/inertial navigator, this mechanization provides a 10% to 15% speed increase over conventional mechanizations.

  1. Grid Interaction Technical Team Roadmap

    SciTech Connect

    2013-06-01

    The mission of the Grid Interaction Technical Team (GITT) is to support a transition scenario to large scale grid-connected vehicle charging with transformational technology, proof of concept and information dissemination. The GITT facilitates technical coordination and collaboration between vehicle-grid connectivity and communication activities among U.S. DRIVE government and industry partners.

  2. A finite volume Fokker-Planck collision operator in constants-of-motion coordinates

    NASA Astrophysics Data System (ADS)

    Xiong, Z.; Xu, X. Q.; Cohen, B. I.; Cohen, R.; Dorr, M. R.; Hittinger, J. A.; Kerbel, G.; Nevins, W. M.; Rognlien, T.

    2006-04-01

    TEMPEST is a 5D gyrokinetic continuum code for edge plasmas. Constants of motion, namely, the total energy E and the magnetic moment μ, are chosen as coordinate s because of their advantage in minimizing numerical diffusion in advection operato rs. Most existing collision operators are written in other coordinates; using them by interpolating is shown to be less satisfactory in maintaining overall numerical accuracy and conservation. Here we develop a Fokker-Planck collision operator directly in (E,μ) space usin g a finite volume approach. The (E, μ) grid is Cartesian, and the turning point boundary represents a straight line cutting through the grid that separates the ph ysical and non-physical zones. The resulting cut-cells are treated by a cell-mergin g technique to ensure a complete particle conservation. A two dimensional fourth or der reconstruction scheme is devised to achieve good numerical accuracy with modest number of grid points. The new collision operator will be benchmarked by numerical examples.

  3. A Cartesian quasi-classical model to nonequilibrium quantum transport: The Anderson impurity model

    NASA Astrophysics Data System (ADS)

    Li, Bin; Levy, Tal J.; Swenson, David W. H.; Rabani, Eran; Miller, William H.

    2013-03-01

    We apply the recently proposed quasi-classical approach for a second quantized many-electron Hamiltonian in Cartesian coordinates [B. Li and W. H. Miller, J. Chem. Phys. 137, 154107 (2012), 10.1063/1.4757935] to correlated nonequilibrium quantum transport. The approach provides accurate results for the resonant level model for a wide range of temperatures, bias, and gate voltages, correcting the flaws of our recently proposed mapping using action-angle variables. When electron-electron interactions are included, a Gaussian function scheme is required to map the two-electron integrals, leading to quantitative results for the Anderson impurity model. In particular, we show that the current mapping is capable of capturing quantitatively the Coulomb blockade effect and the temperature dependence of the current below and above the blockade.

  4. Polar versus Cartesian velocity models for maneuvering target tracking with IMM

    NASA Astrophysics Data System (ADS)

    Laneuville, Dann

    This paper compares various model sets in different IMM filters for the maneuvering target tracking problem. The aim is to see whether we can improve the tracking performance of what is certainly the most widely used model set in the literature for the maneuvering target tracking problem: a Nearly Constant Velocity model and a Nearly Coordinated Turn model. Our new challenger set consists of a mixed Cartesian position and polar velocity state vector to describe the uniform motion segments and is augmented with the turn rate to obtain the second model for the maneuvering segments. This paper also gives a general procedure to discretize up to second order any non-linear continuous time model with linear diffusion. Comparative simulations on an air defence scenario with a 2D radar, show that this new approach improves significantly the tracking performance in this case.

  5. Simulations of 6-DOF Motion with a Cartesian Method

    NASA Technical Reports Server (NTRS)

    Murman, Scott M.; Aftosmis, Michael J.; Berger, Marsha J.; Kwak, Dochan (Technical Monitor)

    2003-01-01

    Coupled 6-DOF/CFD trajectory predictions using an automated Cartesian method are demonstrated by simulating a GBU-32/JDAM store separating from an F-18C aircraft. Numerical simulations are performed at two Mach numbers near the sonic speed, and compared with flight-test telemetry and photographic-derived data. Simulation results obtained with a sequential-static series of flow solutions are contrasted with results using a time-dependent flow solver. Both numerical methods show good agreement with the flight-test data through the first half of the simulations. The sequential-static and time-dependent methods diverge over the last half of the trajectory prediction. after the store produces peak angular rates. A cost comparison for the Cartesian method is included, in terms of absolute cost and relative to computing uncoupled 6-DOF trajectories. A detailed description of the 6-DOF method, as well as a verification of its accuracy, is provided in an appendix.

  6. Equipartition Principle for Internal Coordinate Molecular Dynamics

    PubMed Central

    Jain, Abhinandan; Park, In-Hee; Vaidehi, Nagarajan

    2012-01-01

    The principle of equipartition of (kinetic) energy for all-atom Cartesian molecular dynamics states that each momentum phase space coordinate on the average has ½kT of kinetic energy in a canonical ensemble. This principle is used in molecular dynamics simulations to initialize velocities, and to calculate statistical properties such as entropy. Internal coordinate molecular dynamics (ICMD) models differ from Cartesian models in that the overall kinetic energy depends on the generalized coordinates and includes cross-terms. Due to this coupled structure, no such equipartition principle holds for ICMD models. In this paper we introduce non-canonical modal coordinates to recover some of the structural simplicity of Cartesian models and develop a new equipartition principle for ICMD models. We derive low-order recursive computational algorithms for transforming between the modal and physical coordinates. The equipartition principle in modal coordinates provides a rigorous method for initializing velocities in ICMD simulations thus replacing the ad hoc methods used until now. It also sets the basis for calculating conformational entropy using internal coordinates. PMID:23341754

  7. Frequency-Offset Cartesian Feedback for MRI Power Amplifier Linearization

    PubMed Central

    Zanchi, Marta Gaia; Stang, Pascal; Kerr, Adam; Pauly, John Mark; Scott, Greig Cameron

    2011-01-01

    High-quality magnetic resonance imaging (MRI) requires precise control of the transmit radio-frequency field. In parallel excitation applications such as transmit SENSE, high RF power linearity is essential to cancel aliased excitations. In widely-employed class AB power amplifiers, gain compression, cross-over distortion, memory effects, and thermal drift all distort the RF field modulation and can degrade image quality. Cartesian feedback (CF) linearization can mitigate these effects in MRI, if the quadrature mismatch and DC offset imperfections inherent in the architecture can be minimized. In this paper, we present a modified Cartesian feedback technique called “frequency-offset Cartesian feedback” (FOCF) that significantly reduces these problems. In the FOCF architecture, the feedback control is performed at a low intermediate frequency rather than DC, so that quadrature ghosts and DC errors are shifted outside the control bandwidth. FOCF linearization is demonstrated with a variety of typical MRI pulses. Simulation of the magnetization obtained with the Bloch equation demonstrates that high-fidelity RF reproduction can be obtained even with inexpensive class AB amplifiers. Finally, the enhanced RF fidelity of FOCF over CF is demonstrated with actual images obtained in a 1.5 T MRI system. PMID:20959264

  8. Plasticity of Intermediate Mechanics Students' Coordinate System Choice

    ERIC Educational Resources Information Center

    Sayre, Eleanor C.; Wittman, Michael C.

    2008-01-01

    We investigate the interplay between mathematics and physics resources in intermediate mechanics students. In the mechanics course, the selection and application of coordinate systems is a consistent thread. At the University of Maine, students often start the course with a strong preference to use Cartesian coordinates, in accordance with their…

  9. Plasticity of Intermediate Mechanics Students' Coordinate System Choice

    ERIC Educational Resources Information Center

    Sayre, Eleanor C.; Wittman, Michael C.

    2008-01-01

    We investigate the interplay between mathematics and physics resources in intermediate mechanics students. In the mechanics course, the selection and application of coordinate systems is a consistent thread. At the University of Maine, students often start the course with a strong preference to use Cartesian coordinates, in accordance with their

  10. SU-E-I-41: Non-Cartesian MR Image Reconstruction with Integrated Gradient Non-Linearity Correction

    SciTech Connect

    Tao, S; Trzasko, JD; Polley, TW; Shu, Y; Bernstein, MA

    2014-06-01

    Purpose: Nonlinearities in the spatial encoding gradients of MRI systems cause geometric distortion in images. Typically, this is retrospectively corrected via image-domain interpolation (a.k.a., “gradwarp”) albeit with a loss of spatial resolution. For non-Cartesian MRI, the latter problem is exaggerated by noise and undersampling artifact. In this study, we describe a novel correction strategy that accounts for gradient nonlinearities during — rather than after — non-Cartesian MRI reconstruction, and demonstrate that this approach mitigates the resolution loss that can occur with standard methods. Methods: To test the proposed method, the American College of Radiology (ACR) quality control phantom was scanned on at 1.5 T (General Electric, v16.0, “zoom” gradient) using a 1.6x undersampled 3D non- Cartesian Shells trajectory (GRE, FOV=24 cm3, 120 shells, 16552 shots, 512 readout, matrix=2403). Image reconstruction was first performed via standard k-space density-compensated gridding and retrospectively corrected via cubic spline interpolation. Image reconstruction was then separately performed using a k-space and image-domain densitycompensated type-3 non-uniform fast Fourier transform (NUFFT), which provides a direct mapping between non-Cartesian k-space samples and warped image space voxel locations. Thus, no separate distortion correction procedure is needed for the proposed approach. The gradient distortion field was determined using vendor provided calibration data. Results: Phantom scan results show that both processing approaches successfully correct geometric distortion. However, visual inspection of the ACR phantom spatial resolution inserts shows that the proposed strategy preserves the resolution of the nominal (uncorrected) reconstruction while “gradwarp” imparts marked spatial blurring (especially for the 1.0 and 1.1 mm inserts) and thus resolution loss. Conclusion: We've presented a novel reconstruction strategy for non-Cartesian MRI that corrects for gradient nonlinearities during — rather than after — reconstruction, and thus better preserves image resolution than traditional interpolation-based methods. This approach is expected to be especially advantageous when imaging with non-standard magnet geometries. NIH RR018898; NIH EB10065.

  11. Three-Dimensional Deformable Grid Electromagnetic Particle-in-cell for Parallel Computers

    NASA Technical Reports Server (NTRS)

    Wang, J.; Kondrashov, D.; Liewer, P. C.; Karmesin, S. R.

    1998-01-01

    We describe a new parallel, non-orthogonal grid, three-dimensional electromagnetic particle-in-cell (EMPIC) code based on a finite-volume formulation. This code uses a logically Cartesian grid of deformable hexahedral cells, a discrete surface integral (DSI) algorithm to calculate the electromagnetic field, and a hybrid logical-physical space algorithm to push particles.

  12. High Energy Boundary Conditions for a Cartesian Mesh Euler Solver

    NASA Technical Reports Server (NTRS)

    Pandya, Shishir; Murman, Scott; Aftosmis, Michael

    2003-01-01

    Inlets and exhaust nozzles are common place in the world of flight. Yet, many aerodynamic simulation packages do not provide a method of modelling such high energy boundaries in the flow field. For the purposes of aerodynamic simulation, inlets and exhausts are often fared over and it is assumed that the flow differences resulting from this assumption are minimal. While this is an adequate assumption for the prediction of lift, the lack of a plume behind the aircraft creates an evacuated base region thus effecting both drag and pitching moment values. In addition, the flow in the base region is often mis-predicted resulting in incorrect base drag. In order to accurately predict these quantities, a method for specifying inlet and exhaust conditions needs to be available in aerodynamic simulation packages. A method for a first approximation of a plume without accounting for chemical reactions is added to the Cartesian mesh based aerodynamic simulation package CART3D. The method consists of 3 steps. In the first step, a components approach where each triangle is assigned a component number is used. Here, a method for marking the inlet or exhaust plane triangles as separate components is discussed. In step two, the flow solver is modified to accept a reference state for the components marked inlet or exhaust. In the third step, the flow solver uses these separated components and the reference state to compute the correct flow condition at that triangle. The present method is implemented in the CART3D package which consists of a set of tools for generating a Cartesian volume mesh from a set of component triangulations. The Euler equations are solved on the resulting unstructured Cartesian mesh. The present methods is implemented in this package and its usefulness is demonstrated with two validation cases. A generic missile body is also presented to show the usefulness of the method on a real world geometry.

  13. [Cartesian misunderstanding as a cause of therapeutic failure].

    PubMed

    Isler, H

    1986-01-01

    Headache patients disassociate themselves from their own automatic responses, relying on the traditional separation of body and mind. On the other hand, patients who obtain voluntary control of automatic functions by biofeedback training modify not only vegetative but also voluntary behaviour patterns, losing "neurotic" traits. The basic misconception of the separation of body and mind, Cartesian dualism, is now ingrained in our culture. In the 17th century Descartes asserted that concepts applied to the soul must be entirely different from those used for the body in order to improve comprehension of the immortality of the soul. This dualism also led to "enlightenment" and to many later social and philosophical developments. But his basic neurophysiology was obsolete when he wrote it down. Other models from mainstream natural philosophy were better compatible with observation and experiments. Gassendi assumed a "body soul" consisting of energy as the functional principle of the nervous system, and Willis accommodated a series of anticipations of 19th century discoveries within this model. No comparable progress resulted from Descartes' own medieval model. Cartesian dualism has become untenable in view of recent neuropsychology but it still obstructs our management of functional patients. Instead of reinforcing the delusion of separation of psyche and soma, we ought to encourage patients to understand that their malfunctioning organs are on-line with their emotions, and with their mind. PMID:2420000

  14. Cartesian grid simulations of bubbling fluidized beds with a horizontal tube bundle

    SciTech Connect

    Li, Tingwen; Dietiker, Jean-Francois; Zhang, Yongmin; Shahnam, Mehrdad

    2011-12-01

    In this paper, the flow hydrodynamics in a bubbling fluidized bed with submerged horizontal tube bundle was numerically investigated with an open-source code: Multiphase Flow with Interphase eXchange (MFIX). A newly implemented cut-cell technique was employed to deal with the curved surface of submerged tubes. A series of 2D simulations were conducted to study the effects of gas velocity and tube arrangement on the flow pattern. Hydrodynamic heterogeneities on voidage, particle velocity, bubble fraction, and frequency near the tube circumferential surface were successfully predicted by this numerical method, which agrees qualitatively with previous experimental findings and contributes to a sounder understanding of the non-uniform heat transfer and erosion around a horizontal tube. A 3D simulation was also conducted. Significant differences between 2D and 3D simulations were observed with respect to bed expansion, bubble distribution, voidage, and solids velocity profiles. Hence, the 3D simulation is needed for quantitative prediction of flow hydrodynamics. On the other hand, the flow characteristics and bubble behavior at the tube surface are similar under both 2D and 3D simulations as far as the bubble frequency and bubble phase fraction are concerned. Comparison with experimental data showed that qualitative agreement was obtained in both 2D and 3D simulations for the bubble characteristics at the tube surface.

  15. Scaling laws and accurate small-amplitude stationary solution for the motion of a planar vortex filament in the Cartesian form of the local induction approximation

    NASA Astrophysics Data System (ADS)

    Van Gorder, Robert A.

    2013-04-01

    We provide a formulation of the local induction approximation (LIA) for the motion of a vortex filament in the Cartesian reference frame (the extrinsic coordinate system) which allows for scaling of the reference coordinate. For general monotone scalings of the reference coordinate, we derive an equation for the planar solution to the derivative nonlinear Schrödinger equation governing the LIA. We proceed to solve this equation perturbatively in small amplitude through an application of multiple-scales analysis, which allows for accurate computation of the period of the planar vortex filament. The perturbation result is shown to agree strongly with numerical simulations, and we also relate this solution back to the solution obtained in the arclength reference frame (the intrinsic coordinate system). Finally, we discuss nonmonotone coordinate scalings and their application for finding self-intersections of vortex filaments. These self-intersecting vortex filaments are likely unstable and collapse into other structures or dissipate completely.

  16. Compact-range coordinate system established using a laser tracker.

    SciTech Connect

    Gallegos, Floyd H.; Bryce, Edwin Anthony

    2006-12-01

    Establishing a Cartesian coordinate reference system for an existing Compact Antenna Range using the parabolic reflector is presented. A SMX (Spatial Metrix Corporation) M/N 4000 laser-based coordinate measuring system established absolute coordinates for the facility. Electric field characteristics with positional movement correction are evaluated. Feed Horn relocation for alignment with the reflector axis is also described. Reference points are established for follow-on non-laser alignments utilizing a theodolite.

  17. An Adaptively-Refined, Cartesian, Cell-Based Scheme for the Euler and Navier-Stokes Equations. Ph.D. Thesis - Michigan Univ.

    NASA Technical Reports Server (NTRS)

    Coirier, William John

    1994-01-01

    A Cartesian, cell-based scheme for solving the Euler and Navier-Stokes equations in two dimensions is developed and tested. Grids about geometrically complicated bodies are generated automatically, by recursive subdivision of a single Cartesian cell encompassing the entire flow domain. Where the resulting cells intersect bodies, polygonal 'cut' cells are created. The geometry of the cut cells is computed using polygon-clipping algorithms. The grid is stored in a binary-tree data structure which provides a natural means of obtaining cell-to-cell connectivity and of carrying out solution-adaptive refinement. The Euler and Navier-Stokes equations are solved on the resulting grids using a finite-volume formulation. The convective terms are upwinded, with a limited linear reconstruction of the primitive variables used to provide input states to an approximate Riemann solver for computing the fluxes between neighboring cells. A multi-stage time-stepping scheme is used to reach a steady-state solution. Validation of the Euler solver with benchmark numerical and exact solutions is presented. An assessment of the accuracy of the approach is made by uniform and adaptive grid refinements for a steady, transonic, exact solution to the Euler equations. The error of the approach is directly compared to a structured solver formulation. A non smooth flow is also assessed for grid convergence, comparing uniform and adaptively refined results. Several formulations of the viscous terms are assessed analytically, both for accuracy and positivity. The two best formulations are used to compute adaptively refined solutions of the Navier-Stokes equations. These solutions are compared to each other, to experimental results and/or theory for a series of low and moderate Reynolds numbers flow fields. The most suitable viscous discretization is demonstrated for geometrically-complicated internal flows. For flows at high Reynolds numbers, both an altered grid-generation procedure and a different formulation of the viscous terms are shown to be necessary. A hybrid Cartesian/body-fitted grid generation approach is demonstrated. In addition, a grid-generation procedure based on body-aligned cell cutting coupled with a viscous stensil-construction procedure based on quadratic programming is presented.

  18. Extending geometric conservation law to cell-centered finite difference methods on moving and deforming grids

    NASA Astrophysics Data System (ADS)

    Liao, Fei; Ye, Zhengyin

    2015-12-01

    Despite significant progress in recent computational techniques, the accurate numerical simulations, such as direct-numerical simulation and large-eddy simulation, are still challenging. For accurate calculations, the high-order finite difference method (FDM) is usually adopted with coordinate transformation from body-fitted grid to Cartesian grid. But this transformation might lead to failure in freestream preservation with the geometric conservation law (GCL) violated, particularly in high-order computations. GCL identities, including surface conservation law (SCL) and volume conservation law (VCL), are very important in discretization of high-order FDM. To satisfy GCL, various efforts have been made. An early and successful approach was developed by Thomas and Lombard [6] who used the conservative form of metrics to cancel out metric terms to further satisfy SCL. Visbal and Gaitonde [7] adopted this conservative form of metrics for SCL identities and satisfied VCL identity through invoking VCL equation to acquire the derivative of Jacobian in computation on moving and deforming grids with central compact schemes derived by Lele [5]. Later, using the metric technique from Visbal and Gaitonde [7], Nonomura et al. [8] investigated the freestream and vortex preservation properties of high-order WENO and WCNS on stationary curvilinear grids. A conservative metric method (CMM) was further developed by Deng et al. [9] with stationary grids, and detailed discussion about the innermost difference operator of CMM was shown with proof and corresponding numerical test cases. Noticing that metrics of CMM is asymmetrical without coordinate-invariant property, Deng et al. proposed a symmetrical CMM (SCMM) [12] by using the symmetric forms of metrics derived by Vinokur and Yee [10] to further eliminate asymmetric metric errors with stationary grids considered only. The research from Abe et al. [11] presented new asymmetric and symmetric conservative forms of time metrics and Jacobian on three-dimensional moving and deforming mesh. Moreover, Abe et al. [14] discussed the symmetrical and asymmetrical geometric interpretations of metrics and Jacobian. By deriving sufficient conditions for the conservative form of VCL, Sjögreen et al. [13] generalized their previous GCL treatment for stationary grids to moving and deforming grids with a new form of time metrics and Jacobian. Recently, Liao et al. [1] focused on the discretization and geometric interpretations of metrics and Jacobian in cell-centered finite difference methods (CCFDM), where the geometric conservation of multiblock interfaces, the treatment of singular axis and simplification of multiblock boundary condition are discussed in detail.

  19. Progress Towards a Cartesian Cut-Cell Method for Viscous Compressible Flow

    NASA Technical Reports Server (NTRS)

    Berger, Marsha; Aftosmis, Michael J.

    2011-01-01

    The proposed paper reports advances in developing a method for high Reynolds number compressible viscous flow simulations using a Cartesian cut-cell method with embedded boundaries. This preliminary work focuses on accuracy of the discretization near solid wall boundaries. A model problem is used to investigate the accuracy of various difference stencils for second derivatives and to guide development of the discretization of the viscous terms in the Navier-Stokes equations. Near walls, quadratic reconstruction in the wall-normal direction is used to mitigate mesh irregularity and yields smooth skin friction distributions along the body. Multigrid performance is demonstrated using second-order coarse grid operators combined with second-order restriction and prolongation operators. Preliminary verification and validation for the method is demonstrated using flat-plate and airfoil examples at compressible Mach numbers. Simulations of flow on laminar and turbulent flat plates show skin friction and velocity profiles compared with those from boundary-layer theory. Airfoil simulations are performed at laminar and turbulent Reynolds numbers with results compared to both other simulations and experimental data

  20. Parallel domain connectivity algorithm for unsteady flow computations using overlapping and adaptive grids

    NASA Astrophysics Data System (ADS)

    Sitaraman, Jayanarayanan; Floros, Matthew; Wissink, Andrew; Potsdam, Mark

    2010-06-01

    This paper describes the algorithms and functionality of a new module developed to support overset grid assembly associated with performing time-dependent and adaptive moving body calculations of external aerodynamic flows using a multi-solver paradigm (i.e. different CFD solvers in different parts of the computational domain). We use the term "domain connectivity" in this paper to denote all the procedures that are involved in an overset grid assembly, and the module developed is referred henceforth as the domain-connectivity module. The domain-connectivity module coordinates the data transfer between different solvers applied in different parts of the computational domain - body fitted structured or unstructured to capture viscous near-wall effects, and Cartesian adaptive mesh refinement to capture effects away from the wall. The execution of the CFD solvers and the domain-connectivity module are orchestrated by a Python-based computational infrastructure. The domain-connectivity module is fully parallel and performs all its operations (identification of grid overlaps and determination of data interpolation strategy) on the partitioned grid data. In addition, the domain connectivity procedures are completely automated such that no user intervention or manual input is necessary. The capabilities and performance of the package are presented for several test problems, including flow over a NACA 0015 wing and an AGARD A2 slotted airfoil, hover simulation of a scaled V-22 rotor, and dynamic simulation of a UH-60A rotor in forward flight. A modification to the algorithm for improved domain connectivity solutions in problems with tight tolerances as well as heterogeneous grid clustering is also presented.

  1. Enhanced Elliptic Grid Generation

    NASA Technical Reports Server (NTRS)

    Kaul, Upender K.

    2007-01-01

    An enhanced method of elliptic grid generation has been invented. Whereas prior methods require user input of certain grid parameters, this method provides for these parameters to be determined automatically. "Elliptic grid generation" signifies generation of generalized curvilinear coordinate grids through solution of elliptic partial differential equations (PDEs). Usually, such grids are fitted to bounding bodies and used in numerical solution of other PDEs like those of fluid flow, heat flow, and electromagnetics. Such a grid is smooth and has continuous first and second derivatives (and possibly also continuous higher-order derivatives), grid lines are appropriately stretched or clustered, and grid lines are orthogonal or nearly so over most of the grid domain. The source terms in the grid-generating PDEs (hereafter called "defining" PDEs) make it possible for the grid to satisfy requirements for clustering and orthogonality properties in the vicinity of specific surfaces in three dimensions or in the vicinity of specific lines in two dimensions. The grid parameters in question are decay parameters that appear in the source terms of the inhomogeneous defining PDEs. The decay parameters are characteristic lengths in exponential- decay factors that express how the influences of the boundaries decrease with distance from the boundaries. These terms govern the rates at which distance between adjacent grid lines change with distance from nearby boundaries. Heretofore, users have arbitrarily specified decay parameters. However, the characteristic lengths are coupled with the strengths of the source terms, such that arbitrary specification could lead to conflicts among parameter values. Moreover, the manual insertion of decay parameters is cumbersome for static grids and infeasible for dynamically changing grids. In the present method, manual insertion and user specification of decay parameters are neither required nor allowed. Instead, the decay parameters are determined automatically as part of the solution of the defining PDEs. Depending on the shape of the boundary segments and the physical nature of the problem to be solved on the grid, the solution of the defining PDEs may provide for rates of decay to vary along and among the boundary segments and may lend itself to interpretation in terms of one or more physical quantities associated with the problem.

  2. The Overgrid Interface for Computational Simulations on Overset Grids

    NASA Technical Reports Server (NTRS)

    Chan, William M.; Kwak, Dochan (Technical Monitor)

    2002-01-01

    Computational simulations using overset grids typically involve multiple steps and a variety of software modules. A graphical interface called OVERGRID has been specially designed for such purposes. Data required and created by the different steps include geometry, grids, domain connectivity information and flow solver input parameters. The interface provides a unified environment for the visualization, processing, generation and diagnosis of such data. General modules are available for the manipulation of structured grids and unstructured surface triangulations. Modules more specific for the overset approach include surface curve generators, hyperbolic and algebraic surface grid generators, a hyperbolic volume grid generator, Cartesian box grid generators, and domain connectivity: pre-processing tools. An interface provides automatic selection and viewing of flow solver boundary conditions, and various other flow solver inputs. For problems involving multiple components in relative motion, a module is available to build the component/grid relationships and to prescribe and animate the dynamics of the different components.

  3. Adaptive Learning in Cartesian Product of Reproducing Kernel Hilbert Spaces

    NASA Astrophysics Data System (ADS)

    Yukawa, Masahiro

    2015-11-01

    We propose a novel adaptive learning algorithm based on iterative orthogonal projections in the Cartesian product of multiple reproducing kernel Hilbert spaces (RKHSs). The task is estimating/tracking nonlinear functions which are supposed to contain multiple components such as (i) linear and nonlinear components, (ii) high- and low- frequency components etc. In this case, the use of multiple RKHSs permits a compact representation of multicomponent functions. The proposed algorithm is where two different methods of the author meet: multikernel adaptive filtering and the algorithm of hyperplane projection along affine subspace (HYPASS). In a certain particular case, the sum space of the RKHSs is isomorphic to the product space and hence the proposed algorithm can also be regarded as an iterative projection method in the sum space. The efficacy of the proposed algorithm is shown by numerical examples.

  4. Internal coordinate molecular dynamics: a foundation for multiscale dynamics.

    PubMed

    Vaidehi, Nagarajan; Jain, Abhinandan

    2015-01-29

    Internal coordinates such as bond lengths, bond angles, and torsion angles (BAT) are natural coordinates for describing a bonded molecular system. However, the molecular dynamics (MD) simulation methods that are widely used for proteins, DNA, and polymers are based on Cartesian coordinates owing to the mathematical simplicity of the equations of motion. However, constraints are often needed with Cartesian MD simulations to enhance the conformational sampling. This makes the equations of motion in the Cartesian coordinates differential-algebraic, which adversely impacts the complexity and the robustness of the simulations. On the other hand, constraints can be easily placed in BAT coordinates by removing the degrees of freedom that need to be constrained. Thus, the internal coordinate MD (ICMD) offers an attractive alternative to Cartesian coordinate MD for developing multiscale MD method. The torsional MD method is a special adaptation of the ICMD method, where all the bond lengths and bond angles are kept rigid. The advantages of ICMD simulation methods are the longer time step size afforded by freezing high frequency degrees of freedom and performing a conformational search in the more important low frequency torsional degrees of freedom. However, the advancements in the ICMD simulations have been slow and stifled by long-standing mathematical bottlenecks. In this review, we summarize the recent mathematical advancements we have made based on spatial operator algebra, in developing a robust long time scale ICMD simulation toolkit useful for various applications. We also present the applications of ICMD simulations to study conformational changes in proteins and protein structure refinement. We review the advantages of the ICMD simulations over the Cartesian simulations when used with enhanced sampling methods and project the future use of ICMD simulations in protein dynamics. PMID:25517406

  5. Internal Coordinate Molecular Dynamics: A Foundation for Multiscale Dynamics

    PubMed Central

    2015-01-01

    Internal coordinates such as bond lengths, bond angles, and torsion angles (BAT) are natural coordinates for describing a bonded molecular system. However, the molecular dynamics (MD) simulation methods that are widely used for proteins, DNA, and polymers are based on Cartesian coordinates owing to the mathematical simplicity of the equations of motion. However, constraints are often needed with Cartesian MD simulations to enhance the conformational sampling. This makes the equations of motion in the Cartesian coordinates differential-algebraic, which adversely impacts the complexity and the robustness of the simulations. On the other hand, constraints can be easily placed in BAT coordinates by removing the degrees of freedom that need to be constrained. Thus, the internal coordinate MD (ICMD) offers an attractive alternative to Cartesian coordinate MD for developing multiscale MD method. The torsional MD method is a special adaptation of the ICMD method, where all the bond lengths and bond angles are kept rigid. The advantages of ICMD simulation methods are the longer time step size afforded by freezing high frequency degrees of freedom and performing a conformational search in the more important low frequency torsional degrees of freedom. However, the advancements in the ICMD simulations have been slow and stifled by long-standing mathematical bottlenecks. In this review, we summarize the recent mathematical advancements we have made based on spatial operator algebra, in developing a robust long time scale ICMD simulation toolkit useful for various applications. We also present the applications of ICMD simulations to study conformational changes in proteins and protein structure refinement. We review the advantages of the ICMD simulations over the Cartesian simulations when used with enhanced sampling methods and project the future use of ICMD simulations in protein dynamics. PMID:25517406

  6. Multi-fault Tolerance for Cartesian Data Distributions

    SciTech Connect

    Ali, Nawab; Krishnamoorthy, Sriram; Halappanavar, Mahantesh; Daily, Jeffrey A.

    2013-06-01

    Faults are expected to play an increasingly important role in how algorithms and applications are designed to run on future extreme-scale sys- tems. Algorithm-based fault tolerance (ABFT) is a promising approach that involves modications to the algorithm to recover from faults with lower over- heads than replicated storage and a signicant reduction in lost work compared to checkpoint-restart techniques. Fault-tolerant linear algebra (FTLA) algo- rithms employ additional processors that store parities along the dimensions of a matrix to tolerate multiple, simultaneous faults. Existing approaches as- sume regular data distributions (blocked or block-cyclic) with the failures of each data block being independent. To match the characteristics of failures on parallel computers, we extend these approaches to mapping parity blocks in several important ways. First, we handle parity computation for generalized Cartesian data distributions with each processor holding arbitrary subsets of blocks in a Cartesian-distributed array. Second, techniques to handle corre- lated failures, i.e., multiple processors that can be expected to fail together, are presented. Third, we handle the colocation of parity blocks with the data blocks and do not require them to be on additional processors. Several al- ternative approaches, based on graph matching, are presented that attempt to balance the memory overhead on processors while guaranteeing the same fault tolerance properties as existing approaches that assume independent fail- ures on regular blocked data distributions. The evaluation of these algorithms demonstrates that the additional desirable properties are provided by the pro- posed approach with minimal overhead.

  7. Nonlinear Accelerator with Transverse Motion Integrable in Normalized Polar Coordinates

    SciTech Connect

    Nagaitsev, S.; Kharkov, Y.; Morozov, I.A.; Zolkin, T.V.; /Chicago U.

    2012-05-01

    Several families of nonlinear accelerator lattices with integrable transverse motion were suggested recently. One of the requirements for the existence of two analytic invariants is a special longitudinal coordinate dependence of fields. This paper presents the particle motion analysis when a problem becomes integrable in the normalized polar coordinates. This case is distinguished from the others: it yields an exact analytical solution and has a uniform longitudinal coordinate dependence of the fields (since the corresponding nonlinear potential is invariant under the transformation from the Cartesian to the normalized coordinates). A number of interesting features are revealed: while the frequency of radial oscillations is independent of the amplitude, the spread of angular frequencies in a beam is absolute. A corresponding spread of frequencies of oscillations in the Cartesian coordinates is evaluated via the simulation of transverse Schottky noise.

  8. A Cartesian classical second-quantized many-electron Hamiltonian, for use with the semiclassical initial value representation

    NASA Astrophysics Data System (ADS)

    Li, Bin; Miller, William H.

    2012-10-01

    A new classical model for the general second-quantized many-electron Hamiltonian in Cartesian coordinates and momenta is presented; this makes semiclassical (SC) calculations using an initial value representation (IVR) more useful than the classical Hamiltonian in action-angle variables given earlier by Miller and White [J. Chem. Phys. 84, 5059-5066 (1986)], 10.1063/1.450655. If only 1-electron terms are included in this Hamiltonian, the classical equations of motion for the Cartesian variables are linear, and the SC-IVR gives exact results for the propagator (and thus for transition probabilities, the energy spectrum, etc.), as confirmed by analytic proof and numerical calculations. Though this new Hamiltonian is not exact when 2-electron interactions are included, we observe good results for the SC-IVR transition probabilities for times that are not too long. Test calculations, for example, show that the SC-IVR is accurate for times long enough to obtain good result for the eigenvalue spectrum (i.e., the energy levels of the electronic system).

  9. Cartesian stiffness for wrist joints: analysis on the Lie group of 3D rotations and geometric approximation for experimental evaluation.

    PubMed

    Campolo, Domenico

    2013-01-01

    This paper is concerned with the analysis and the numerical evaluation from experimental measurements of the static, Cartesian stiffness of wrist joints, in particular the human wrist. The primary aim is to extend from Euclidean spaces to so(3), the group of rigid body rotations, previous methods for assessing the end-point stiffness of the human arm, typically performed via a robotic manipulandum. As a first step, the geometric definition of Cartesian stiffness from current literature is specialised to the group so(3). Emphasis is placed on the choice of the unique, natural, affine connection on so(3) which guarantees symmetry of the stiffness matrix in presence of conservative fields for any configuration, also out of equilibrium. As the main contribution of this study, a coordinate-independent approximation based on the geometric notion of geodesics is proposed which provides a working equation for evaluating stiffness directly from experimental measurements. Finally, a graphical representation of the stiffness is discussed which extends the ellipse method often used for end-point stiffness visualisation and which is suitable to compare stiffness matrices evaluated at different configurations. PMID:22224937

  10. Constructing the ASCI computational grid

    SciTech Connect

    BEIRIGER,JUDY I.; BIVENS,HUGH P.; HUMPHREYS,STEVEN L.; JOHNSON,WILBUR R.; RHEA,RONALD E.

    2000-06-01

    The Accelerated Strategic Computing Initiative (ASCI) computational grid is being constructed to interconnect the high performance computing resources of the nuclear weapons complex. The grid will simplify access to the diverse computing, storage, network, and visualization resources, and will enable the coordinated use of shared resources regardless of location. To match existing hardware platforms, required security services, and current simulation practices, the Globus MetaComputing Toolkit was selected to provide core grid services. The ASCI grid extends Globus functionality by operating as an independent grid, incorporating Kerberos-based security, interfacing to Sandia's Cplant{trademark},and extending job monitoring services. To fully meet ASCI's needs, the architecture layers distributed work management and criteria-driven resource selection services on top of Globus. These services simplify the grid interface by allowing users to simply request ''run code X anywhere''. This paper describes the initial design and prototype of the ASCI grid.

  11. Cartesian formulation of the mobile block Hessian approach to vibrational analysis in partially optimized systems

    NASA Astrophysics Data System (ADS)

    Ghysels, A.; Van Neck, D.; Waroquier, M.

    2007-10-01

    Partial optimization is a useful technique to reduce the computational load in simulations of extended systems. In such nonequilibrium structures, the accurate calculation of localized vibrational modes can be troublesome, since the standard normal mode analysis becomes inappropriate. In a previous paper [A. Ghysels et al., J. Chem. Phys. 126, 224102 (2007)], the mobile block Hessian (MBH) approach was presented to deal with the vibrational analysis in partially optimized systems. In the MBH model, the nonoptimized regions of the system are represented by one or several blocks, which can move as rigid bodies with respect to the atoms of the optimized region. In this way unphysical imaginary frequencies are avoided and the translational/rotational invariance of the potential energy surface is fully respected. In this paper we focus on issues concerning the practical numerical implementation of the MBH model. The MBH normal mode equations are worked out for several coordinate choices. The introduction of a consistent group-theoretical notation facilitates the treatment of both the case of a single block and the case of multiple blocks. Special attention is paid to the formulation in terms of Cartesian variables, in order to provide a link with the standard output of common molecular modeling programs.

  12. Extending a CAD-Based Cartesian Mesh Generator for the Lattice Boltzmann Method

    SciTech Connect

    Cantrell, J Nathan; Inclan, Eric J; Joshi, Abhijit S; Popov, Emilian L; Jain, Prashant K

    2012-01-01

    This paper describes the development of a custom preprocessor for the PaRAllel Thermal Hydraulics simulations using Advanced Mesoscopic methods (PRATHAM) code based on an open-source mesh generator, CartGen [1]. PRATHAM is a three-dimensional (3D) lattice Boltzmann method (LBM) based parallel flow simulation software currently under development at the Oak Ridge National Laboratory. The LBM algorithm in PRATHAM requires a uniform, coordinate system-aligned, non-body-fitted structured mesh for its computational domain. CartGen [1], which is a GNU-licensed open source code, already comes with some of the above needed functionalities. However, it needs to be further extended to fully support the LBM specific preprocessing requirements. Therefore, CartGen is being modified to (i) be compiler independent while converting a neutral-format STL (Stereolithography) CAD geometry to a uniform structured Cartesian mesh, (ii) provide a mechanism for PRATHAM to import the mesh and identify the fluid/solid domains, and (iii) provide a mechanism to visually identify and tag the domain boundaries on which to apply different boundary conditions.

  13. Radially Dependent Large Scale Dynamos in Global Cylindrical Shear Flows and the Local Cartesian Limit

    NASA Astrophysics Data System (ADS)

    Ebrahimi, F.; Blackman, E. G.

    2016-03-01

    For cylindrical differentially rotating plasmas, we study large-scale magnetic field generation from finite amplitude non-axisymmetric perturbations by comparing numerical simulations with quasi-linear analytic theory. When initiated with a vertical magnetic field of either zero or finite net flux, our global cylindrical simulations exhibit the magnetorotational instability (MRI) and large scale dynamo growth of radially alternating mean fields, averaged over height and azimuth. This dynamo growth is explained by our analytic calculations of a non-axisymmetric fluctuation-induced EMF that is sustained by azimuthal shear of the fluctuating fields. The standard "Ω effect" (shear of the mean field by differential rotation) is unimportant. For the MRI case, we express the large-scale dynamo field as a function of differential rotation. The resulting radially alternating large-scale fields may have implications for angular momentum transport in disks and corona. To connect with previous work on large scale dynamos with local linear shear and identify the minimum conditions needed for large scale field growth, we also solve our equations in local Cartesian coordinates. We find that large scale dynamo growth in a linear shear flow without rotation can be sustained by shear plus non-axisymmetric fluctuations-even if not helical, a seemingly previously unidentified distinction. The linear shear flow dynamo emerges as a more restricted version of our more general new global cylindrical calculations.

  14. Radially dependent large-scale dynamos in global cylindrical shear flows and the local cartesian limit

    NASA Astrophysics Data System (ADS)

    Ebrahimi, F.; Blackman, E. G.

    2016-06-01

    For cylindrical differentially rotating plasmas, we study large-scale magnetic field generation from finite amplitude non-axisymmetric perturbations by comparing numerical simulations with quasi-linear analytic theory. When initiated with a vertical magnetic field of either zero or finite net flux, our global cylindrical simulations exhibit the magnetorotational instability (MRI) and large-scale dynamo growth of radially alternating mean fields, averaged over height and azimuth. This dynamo growth is explained by our analytic calculations of a non-axisymmetric fluctuation-induced electromotive force that is sustained by azimuthal shear of the fluctuating fields. The standard `Ω effect' (shear of the mean field by differential rotation) is unimportant. For the MRI case, we express the large-scale dynamo field as a function of differential rotation. The resulting radially alternating large-scale fields may have implications for angular momentum transport in discs and corona. To connect with previous work on large-scale dynamos with local linear shear and identify the minimum conditions needed for large-scale field growth, we also solve our equations in local Cartesian coordinates. We find that large-scale dynamo growth in a linear shear flow without rotation can be sustained by shear plus non-axisymmetric fluctuations - even if not helical, a seemingly previously unidentified distinction. The linear shear flow dynamo emerges as a more restricted version of our more general new global cylindrical calculations.

  15. A comparison of coordinate systems for use in determining a radiotherapy delineation margin for whole breast

    NASA Astrophysics Data System (ADS)

    Pogson, E. M.; Bell, L.; Batumalai, V.; Koh, E. S.; Delaney, G.; Metcalfe, P.; Holloway, L.

    2014-03-01

    Cartesian co-ordinates, traditionally used for radiotherapy margins, calculated at 6 points, may not adequately represent changes in inter-observer contour variation as necessary to define a delineation margin. As a first step, this study compared the standard deviation (SD) in contour delineation using Polar and Cartesian co-ordinates for whole breast. Whole breast Clinical Target Volumes (CTV) were delineated by eight observers for 9 patients. The SD of contour position was determined for Polar co-ordinates at 1° increments for 5 slices and averaged across all patients. The mean centre of mass (COM) was used as the origin for the right breast, for the left the COM was shifted 1cm superiorly to avoid clipping. The SD was determined for Cartesian co-ordinates for medial-lateral and anterior-posterior positions. At slice Z=0cm considering Polar co-ordinates, the SD peaked medially reaching 3.55cm at 15° for the right breast, and 1.44cm at 171° for the left. The SD of the remaining slices maintained a similar distribution, with variation in the peak occurring within 10° of the Z=0cm positions. By comparison, for Cartesian co-ordinates at slice Z=0cm, the largest SD in the medial-lateral and anterior-posterior directions was 0.54/0.57cm and 1.03/0.67cm respectively for right/left breasts. The SD for inter-observer variation for whole breast varies with anatomical position. The maximum SD determined with Polar co-ordinates was greater than with Cartesian coordinates. A delineation margin may thus need to vary with angle over the entire structure and Cartesian co-ordinates may not be the best approach for margin determination for whole breast.

  16. 76 FR 46279 - Smart Grid Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-02

    ... National Institute of Standards and Technology Smart Grid Advisory Committee AGENCY: Department of Commerce, National Institute of Standards and Technology ACTION: Notice of open meeting. SUMMARY: The Smart Grid... should be sent to Office of the National Coordinator for Smart Grid Interoperability, National...

  17. TIGGERC: Turbomachinery Interactive Grid Generator for 2-D Grid Applications and Users Guide

    NASA Technical Reports Server (NTRS)

    Miller, David P.

    1994-01-01

    A two-dimensional multi-block grid generator has been developed for a new design and analysis system for studying multiple blade-row turbomachinery problems. TIGGERC is a mouse driven, interactive grid generation program which can be used to modify boundary coordinates and grid packing and generates surface grids using a hyperbolic tangent or algebraic distribution of grid points on the block boundaries. The interior points of each block grid are distributed using a transfinite interpolation approach. TIGGERC can generate a blocked axisymmetric H-grid, C-grid, I-grid or O-grid for studying turbomachinery flow problems. TIGGERC was developed for operation on Silicon Graphics workstations. Detailed discussion of the grid generation methodology, menu options, operational features and sample grid geometries are presented.

  18. Some studies on generalized coordinate sets for polyatomic molecules

    NASA Astrophysics Data System (ADS)

    Li, Wenjin; Ma, Ao

    2015-12-01

    Generalized coordinates are widely used in various analyses of the trajectories of polyatomic molecules from molecular dynamics simulations, such as normal mode analysis and force distribution analysis. Here, we presented detailed discussions on the properties of some specific sets of generalized coordinates, which separate translational, rotational, and vibrational motions of a molecule from one another once the trajectories of dynamical systems are known. Efficient methods were suggested for estimating the transformation matrix between generalized and Cartesian coordinates. Some properties of the well-known BAT coordinates (bond length, angle, and torsional coordinates) were discussed as well.

  19. An Efficient Means of Adaptive Refinement Within Systems of Overset Grids

    NASA Technical Reports Server (NTRS)

    Meakin, Robert L.

    1996-01-01

    An efficient means of adaptive refinement within systems of overset grids is presented. Problem domains are segregated into near-body and off-body fields. Near-body fields are discretized via overlapping body-fitted grids that extend only a short distance from body surfaces. Off-body fields are discretized via systems of overlapping uniform Cartesian grids of varying levels of refinement. a novel off-body grid generation and management scheme provides the mechanism for carrying out adaptive refinement of off-body flow dynamics and solid body motion. The scheme allows for very efficient use of memory resources, and flow solvers and domain connectivity routines that can exploit the structure inherent to uniform Cartesian grids.

  20. Efficient grid generation

    NASA Technical Reports Server (NTRS)

    Seki, Rycichi

    1989-01-01

    Because the governing equations in fluid dynamics contain partial differentials and are too difficult in most cases to solve analytically, these differentials are generally replaced by finite difference terms. These terms contain terms in the solution at nearby states. This procedure discretizes the field into a finite number of states. These states, when plotted, form a grid, or mesh, of points. It is at these states, or field points, that the solution is found. The optimum choice of states, the x, y, z coordinate values, minimizes error and computational time. But the process of finding these states is made more difficult by complex boundaries, and by the need to control step size differences between the states, that is, the need to control the spacing of field points. One solution technique uses a different set of state variables, which define a different coordinate system, to generate the grid more easily. A new method, developed by Dr. Joseph Steger, combines elliptic and hyperbolic partial differential equations into a mapping function between the physical and computational coordinate systems. This system of equations offers more control than either equation provides alone. The Steger algorithm was modified in order to allow bodies with stronger concavities to be used, offering the possibility of generating a single grid about multiple bodies. Work was also done on identifying areas where grid breakdown occurs.

  1. Exact Integrations of Polynomials and Symmetric Quadrature Formulas over Arbitrary Polyhedral Grids

    NASA Technical Reports Server (NTRS)

    Liu, Yen; Vinokur, Marcel

    1997-01-01

    This paper is concerned with two important elements in the high-order accurate spatial discretization of finite volume equations over arbitrary grids. One element is the integration of basis functions over arbitrary domains, which is used in expressing various spatial integrals in terms of discrete unknowns. The other consists of quadrature approximations to those integrals. Only polynomial basis functions applied to polyhedral and polygonal grids are treated here. Non-triangular polygonal faces are subdivided into a union of planar triangular facets, and the resulting triangulated polyhedron is subdivided into a union of tetrahedra. The straight line segment, triangle, and tetrahedron are thus the fundamental shapes that are the building blocks for all integrations and quadrature approximations. Integrals of products up to the fifth order are derived in a unified manner for the three fundamental shapes in terms of the position vectors of vertices. Results are given both in terms of tensor products and products of Cartesian coordinates. The exact polynomial integrals are used to obtain symmetric quadrature approximations of any degree of precision up to five for arbitrary integrals over the three fundamental domains. Using a coordinate-free formulation, simple and rational procedures are developed to derive virtually all quadrature formulas, including some previously unpublished. Four symmetry groups of quadrature points are introduced to derive Gauss formulas, while their limiting forms are used to derive Lobatto formulas. Representative Gauss and Lobatto formulas are tabulated. The relative efficiency of their application to polyhedral and polygonal grids is detailed. The extension to higher degrees of precision is discussed.

  2. A flux-coordinate independent field-aligned approach to plasma turbulence simulations

    NASA Astrophysics Data System (ADS)

    Hariri, F.; Ottaviani, M.

    2013-11-01

    This work illustrates a new approach to field-aligned coordinates for plasma turbulence simulations which is not based on flux variables. The method employs standard Cartesian or polar coordinates to discretize the fields. Parallel derivatives are computed directly along a coordinate that follows the local field, and poloidal derivatives are computed in the original Cartesian frame. Several advantages of this approach are presented. The tests on a drift-wave model demonstrate that the method is well suited to exploit the flute property of small parallel gradients by minimizing the number of degrees of freedom needed to treat a given problem in an accurate and efficient manner.

  3. A HYBRID SOLAR WIND MODEL OF THE CESE+HLL METHOD WITH A YIN-YANG OVERSET GRID AND AN AMR GRID

    SciTech Connect

    Feng Xueshang; Zhang Shaohua; Xiang Changqing; Yang Liping; Jiang Chaowei; Wu, S. T.

    2011-06-10

    A hybrid three-dimensional (3D) MHD model for solar wind study is proposed in the present paper with combined grid systems and solvers. The computational domain from the Sun to Earth space is decomposed into the near-Sun and off-Sun domains, which are respectively constructed with a Yin-Yang overset grid system and a Cartesian adaptive mesh refinement (AMR) grid system and coupled with a domain connection interface in the overlapping region between the near-Sun and off-Sun domains. The space-time conservation element and solution element method is used in the near-Sun domain, while the Harten-Lax-Leer method is employed in the off-Sun domain. The Yin-Yang overset grid can avoid well-known singularity and polar grid convergence problems and its body-fitting property helps achieve high-quality resolution near the solar surface. The block structured AMR Cartesian grid can automatically capture far-field plasma flow features, such as heliospheric current sheets and shock waves, and at the same time, it can save significant computational resources compared to the uniformly structured Cartesian grid. A numerical study of the solar wind structure for Carrington rotation 2069 shows that the newly developed hybrid MHD solar wind model successfully produces many realistic features of the background solar wind, in both the solar corona and interplanetary space, by comparisons with multiple solar and interplanetary observations.

  4. Grid Work

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Pointwise Inc.'s, Gridgen Software is a system for the generation of 3D (three dimensional) multiple block, structured grids. Gridgen is a visually-oriented, graphics-based interactive code used to decompose a 3D domain into blocks, distribute grid points on curves, initialize and refine grid points on surfaces and initialize volume grid points. Gridgen is available to U.S. citizens and American-owned companies by license.

  5. Crystal structures of [Ln(NO3)3(μ2-bpydo)2], where Ln = Ce, Pr or Nd, and bpydo = 4,4′-bi­pyridine N,N′-dioxide: layered coordination networks containing 44 grids

    PubMed Central

    Stromyer, Michael L.; Lilly, Cassandra P.; Dillner, Adam J.; Knaust, Jacqueline M.

    2016-01-01

    Three isostructural coordination networks of Ce, Pr, and Nd nitrate with 4,4′-bi­pyridine N,N′-dioxide (bpydo) are reported, namely poly[[tris­(nitrato-κ2 O,O′)cerium(III)]-bis­(μ2-4,4′-bi­pyridine N,N′-dioxide-κ2 N:N′)], [Ce(NO3)3(C10H8N2O2)2], poly[[tris­(nitrato-κ2 O,O′)praeseodymium(III)]-bis­(μ2-4,4′-bi­pyridine N,N′-dioxide-κ2 N:N′)], [Pr(NO3)3(C10H8N2O2)2], and poly[[tris(nitrato-κ2 O,O′)neodymium(III)]-bis­(μ2-4,4′-bi­pyridine N,N′-dioxide-κ2 N:N′], [Nd(NO3)3(C10H8N2O2)2]. All three compounds are isostructural to the previously reported La analogue. The asymmetric unit of [Ln(NO3)3(μ2-bpydo)2] contains one lanthanide cation, two bpydo ligands, and three nitrate anions. Both bpydo ligands act as end-to-end μ2-bridges and display nearly ideal cis and gauche conformations, respectively. The bpydo ligands link the ten-coordinate Ln III cations, forming inter­digitating 44 grid-like layers extending parallel to (-101), where inter­digitation of layers is promoted by C—H⋯O inter­actions between nitrate anions and bpydo ligands. The inter­digitated layers are linked to sets of neighboring layers via further C—H⋯O and π–π inter­actions. PMID:26870578

  6. Crystal structures of [Ln(NO3)3(μ2-bpydo)2], where Ln = Ce, Pr or Nd, and bpydo = 4,4'-bi-pyridine N,N'-dioxide: layered coordination networks containing 4(4) grids.

    PubMed

    Stromyer, Michael L; Lilly, Cassandra P; Dillner, Adam J; Knaust, Jacqueline M

    2016-01-01

    Three isostructural coordination networks of Ce, Pr, and Nd nitrate with 4,4'-bi-pyridine N,N'-dioxide (bpydo) are reported, namely poly[[tris-(nitrato-κ(2) O,O')cerium(III)]-bis-(μ2-4,4'-bi-pyridine N,N'-dioxide-κ(2) N:N')], [Ce(NO3)3(C10H8N2O2)2], poly[[tris-(nitrato-κ(2) O,O')praeseodymium(III)]-bis-(μ2-4,4'-bi-pyridine N,N'-dioxide-κ(2) N:N')], [Pr(NO3)3(C10H8N2O2)2], and poly[[tris(nitrato-κ(2) O,O')neodymium(III)]-bis-(μ2-4,4'-bi-pyridine N,N'-dioxide-κ(2) N:N'], [Nd(NO3)3(C10H8N2O2)2]. All three compounds are isostructural to the previously reported La analogue. The asymmetric unit of [Ln(NO3)3(μ2-bpydo)2] contains one lanthanide cation, two bpydo ligands, and three nitrate anions. Both bpydo ligands act as end-to-end μ2-bridges and display nearly ideal cis and gauche conformations, respectively. The bpydo ligands link the ten-coordinate Ln (III) cations, forming inter-digitating 4(4) grid-like layers extending parallel to (-101), where inter-digitation of layers is promoted by C-H⋯O inter-actions between nitrate anions and bpydo ligands. The inter-digitated layers are linked to sets of neighboring layers via further C-H⋯O and π-π inter-actions. PMID:26870578

  7. General formulation of vibronic spectroscopy in internal coordinates

    NASA Astrophysics Data System (ADS)

    Baiardi, Alberto; Bloino, Julien; Barone, Vincenzo

    2016-02-01

    Our general platform integrating time-independent and time-dependent evaluations of vibronic effects at the harmonic level for different kinds of absorption and emission one-photon, conventional and chiral spectroscopies has been extended to support various sets of internal coordinates. Thanks to the implementation of analytical first and second derivatives of different internal coordinates with respect to cartesian ones, both vertical and adiabatic models are available, with the inclusion of mode mixing and, possibly, Herzberg-Teller contributions. Furthermore, all supported non-redundant sets of coordinates are built from a fully automatized algorithm using only a primitive redundant set derived from a bond order-based molecular topology. Together with conventional stretching, bending, and torsion coordinates, the availability of additional coordinates (including linear and out-of-plane bendings) allows a proper treatment of specific systems, including, for instance, inter-molecular hydrogen bridges. A number of case studies are analysed, showing that cartesian and internal coordinates are nearly equivalent for semi-rigid systems not experiencing significant geometry distortions between initial and final electronic states. At variance, delocalized (possibly weighted) internal coordinates become much more effective than their cartesian counterparts for flexible systems and/or in the presence of significant geometry distortions accompanying electronic transitions.

  8. GridPV Toolbox

    SciTech Connect

    Broderick, Robert; Quiroz, Jimmy; Grijalva, Santiago; Reno, Matthew; Coogan, Kyle

    2014-07-15

    Matlab Toolbox for simulating the impact of solar energy on the distribution grid. The majority of the functions are useful for interfacing OpenDSS and MATLAB, and they are of generic use for commanding OpenDSS from MATLAB and retrieving GridPV Toolbox information from simulations. A set of functions is also included for modeling PV plant output and setting up the PV plant in the OpenDSS simulation. The toolbox contains functions for modeling the OpenDSS distribution feeder on satellite images with GPS coordinates. Finally, example simulations functions are included to show potential uses of the toolbox functions.

  9. GridPV Toolbox

    Energy Science and Technology Software Center (ESTSC)

    2014-07-15

    Matlab Toolbox for simulating the impact of solar energy on the distribution grid. The majority of the functions are useful for interfacing OpenDSS and MATLAB, and they are of generic use for commanding OpenDSS from MATLAB and retrieving GridPV Toolbox information from simulations. A set of functions is also included for modeling PV plant output and setting up the PV plant in the OpenDSS simulation. The toolbox contains functions for modeling the OpenDSS distribution feedermore » on satellite images with GPS coordinates. Finally, example simulations functions are included to show potential uses of the toolbox functions.« less

  10. Shared Memory Parallelism for 3D Cartesian Discrete Ordinates Solver

    NASA Astrophysics Data System (ADS)

    Moustafa, Salli; Dutka-Malen, Ivan; Plagne, Laurent; Ponçot, Angélique; Ramet, Pierre

    2014-06-01

    This paper describes the design and the performance of DOMINO, a 3D Cartesian SN solver that implements two nested levels of parallelism (multicore+SIMD) on shared memory computation nodes. DOMINO is written in C++, a multi-paradigm programming language that enables the use of powerful and generic parallel programming tools such as Intel TBB and Eigen. These two libraries allow us to combine multi-thread parallelism with vector operations in an efficient and yet portable way. As a result, DOMINO can exploit the full power of modern multi-core processors and is able to tackle very large simulations, that usually require large HPC clusters, using a single computing node. For example, DOMINO solves a 3D full core PWR eigenvalue problem involving 26 energy groups, 288 angular directions (S16), 46 × 106 spatial cells and 1 × 1012 DoFs within 11 hours on a single 32-core SMP node. This represents a sustained performance of 235 GFlops and 40:74% of the SMP node peak performance for the DOMINO sweep implementation. The very high Flops/Watt ratio of DOMINO makes it a very interesting building block for a future many-nodes nuclear simulation tool.

  11. Static Aeroelastic Analysis with an Inviscid Cartesian Method

    NASA Technical Reports Server (NTRS)

    Rodriguez, David L.; Aftosmis, Michael J.; Nemec, Marian; Smith, Stephen C.

    2014-01-01

    An embedded-boundary, Cartesian-mesh flow solver is coupled with a three degree-of-freedom structural model to perform static, aeroelastic analysis of complex aircraft geometries. The approach solves a nonlinear, aerostructural system of equations using a loosely-coupled strategy. An open-source, 3-D discrete-geometry engine is utilized to deform a triangulated surface geometry according to the shape predicted by the structural model under the computed aerodynamic loads. The deformation scheme is capable of modeling large deflections and is applicable to the design of modern, very-flexible transport wings. The coupling interface is modular so that aerodynamic or structural analysis methods can be easily swapped or enhanced. After verifying the structural model with comparisons to Euler beam theory, two applications of the analysis method are presented as validation. The first is a relatively stiff, transport wing model which was a subject of a recent workshop on aeroelasticity. The second is a very flexible model recently tested in a low speed wind tunnel. Both cases show that the aeroelastic analysis method produces results in excellent agreement with experimental data.

  12. Static Aeroelastic Analysis with an Inviscid Cartesian Method

    NASA Technical Reports Server (NTRS)

    Rodriguez, David L.; Aftosmis, Michael J.; Nemec, Marian; Smith, Stephen C.

    2014-01-01

    An embedded-boundary Cartesian-mesh flow solver is coupled with a three degree-offreedom structural model to perform static, aeroelastic analysis of complex aircraft geometries. The approach solves the complete system of aero-structural equations using a modular, loosely-coupled strategy which allows the lower-fidelity structural model to deform the highfidelity CFD model. The approach uses an open-source, 3-D discrete-geometry engine to deform a triangulated surface geometry according to the shape predicted by the structural model under the computed aerodynamic loads. The deformation scheme is capable of modeling large deflections and is applicable to the design of modern, very-flexible transport wings. The interface is modular so that aerodynamic or structural analysis methods can be easily swapped or enhanced. This extended abstract includes a brief description of the architecture, along with some preliminary validation of underlying assumptions and early results on a generic 3D transport model. The final paper will present more concrete cases and validation of the approach. Preliminary results demonstrate convergence of the complete aero-structural system and investigate the accuracy of the approximations used in the formulation of the structural model.

  13. MAGNETIC GRID

    DOEpatents

    Post, R.F.

    1960-08-01

    An electronic grid is designed employing magnetic forces for controlling the passage of charged particles. The grid is particularly applicable to use in gas-filled tubes such as ignitrons. thyratrons, etc., since the magnetic grid action is impartial to the polarity of the charged particles and, accordingly. the sheath effects encountered with electrostatic grids are not present. The grid comprises a conductor having sections spaced apart and extending in substantially opposite directions in the same plane, the ends of the conductor being adapted for connection to a current source.

  14. A second-order Cartesian method for the simulation of electropermeabilization cell models

    NASA Astrophysics Data System (ADS)

    Leguèbe, M.; Poignard, C.; Weynans, L.

    2015-07-01

    In this paper, we present a new finite differences method to simulate electropermeabilization models, like the model of Neu and Krassowska or the recent model of Kavian et al. These models are based on the evolution of the electric potential in a cell embedded in a conducting medium. The main feature lies in the transmission of the voltage potential across the cell membrane: the jump of the potential is proportional to the normal flux thanks to the well-known Kirchoff law. An adapted scheme is thus necessary to accurately simulate the voltage potential in the whole cell, notably at the membrane separating the cell from the outer medium. We present a second-order finite differences scheme in the spirit of the method introduced by Cisternino and Weynans for elliptic problems with immersed interfaces. This is a Cartesian grid method based on the accurate discretization of the fluxes at the interface, through the use of additional interface unknowns. The main novelty of our present work lies in the fact that the jump of the potential is proportional to the flux, and therefore is not explicitly known. The original use of interface unknowns makes it possible to discretize the transmission conditions with enough accuracy to obtain a second-order spatial convergence. We prove the second-order spatial convergence in the stationary linear one-dimensional case, and the first-order temporal convergence for the dynamical non-linear model in one dimension. We then perform numerical experiments in two dimensions that corroborate these results.

  15. Beyond grid security

    NASA Astrophysics Data System (ADS)

    Hoeft, B.; Epting, U.; Koenig, T.

    2008-07-01

    While many fields relevant to Grid security are already covered by existing working groups, their remit rarely goes beyond the scope of the Grid infrastructure itself. However, security issues pertaining to the internal set-up of compute centres have at least as much impact on Grid security. Thus, this talk will present briefly the EU ISSeG project (Integrated Site Security for Grids). In contrast to groups such as OSCT (Operational Security Coordination Team) and JSPG (Joint Security Policy Group), the purpose of ISSeG is to provide a holistic approach to security for Grid computer centres, from strategic considerations to an implementation plan and its deployment. The generalised methodology of Integrated Site Security (ISS) is based on the knowledge gained during its implementation at several sites as well as through security audits, and this will be briefly discussed. Several examples of ISS implementation tasks at the Forschungszentrum Karlsruhe will be presented, including segregation of the network for administration and maintenance and the implementation of Application Gateways. Furthermore, the web-based ISSeG training material will be introduced. This aims to offer ISS implementation guidance to other Grid installations in order to help avoid common pitfalls.

  16. Multiscale geometric modeling of macromolecules I: Cartesian representation

    SciTech Connect

    Xia, Kelin; Feng, Xin; Chen, Zhan; Tong, Yiying; Wei, Guo-Wei; Department of Biochemistry and Molecular Biology, Michigan State University, MI 48824

    2014-01-15

    This paper focuses on the geometric modeling and computational algorithm development of biomolecular structures from two data sources: Protein Data Bank (PDB) and Electron Microscopy Data Bank (EMDB) in the Eulerian (or Cartesian) representation. Molecular surface (MS) contains non-smooth geometric singularities, such as cusps, tips and self-intersecting facets, which often lead to computational instabilities in molecular simulations, and violate the physical principle of surface free energy minimization. Variational multiscale surface definitions are proposed based on geometric flows and solvation analysis of biomolecular systems. Our approach leads to geometric and potential driven Laplace–Beltrami flows for biomolecular surface evolution and formation. The resulting surfaces are free of geometric singularities and minimize the total free energy of the biomolecular system. High order partial differential equation (PDE)-based nonlinear filters are employed for EMDB data processing. We show the efficacy of this approach in feature-preserving noise reduction. After the construction of protein multiresolution surfaces, we explore the analysis and characterization of surface morphology by using a variety of curvature definitions. Apart from the classical Gaussian curvature and mean curvature, maximum curvature, minimum curvature, shape index, and curvedness are also applied to macromolecular surface analysis for the first time. Our curvature analysis is uniquely coupled to the analysis of electrostatic surface potential, which is a by-product of our variational multiscale solvation models. As an expository investigation, we particularly emphasize the numerical algorithms and computational protocols for practical applications of the above multiscale geometric models. Such information may otherwise be scattered over the vast literature on this topic. Based on the curvature and electrostatic analysis from our multiresolution surfaces, we introduce a new concept, the polarized curvature, for the prediction of protein binding sites.

  17. Multiscale geometric modeling of macromolecules I: Cartesian representation

    PubMed Central

    Xia, Kelin; Feng, Xin; Chen, Zhan; Tong, Yiying; Wei, Guo Wei

    2013-01-01

    This paper focuses on the geometric modeling and computational algorithm development of biomolecular structures from two data sources: Protein Data Bank (PDB) and Electron Microscopy Data Bank (EMDB) in the Eulerian (or Cartesian) representation. Molecular surface (MS) contains non-smooth geometric singularities, such as cusps, tips and self-intersecting facets, which often lead to computational instabilities in molecular simulations, and violate the physical principle of surface free energy minimization. Variational multiscale surface definitions are proposed based on geometric flows and solvation analysis of biomolecular systems. Our approach leads to geometric and potential driven Laplace-Beltrami flows for biomolecular surface evolution and formation. The resulting surfaces are free of geometric singularities and minimize the total free energy of the biomolecular system. High order partial differential equation (PDE)-based nonlinear filters are employed for EMDB data processing. We show the efficacy of this approach in feature-preserving noise reduction. After the construction of protein multiresolution surfaces, we explore the analysis and characterization of surface morphology by using a variety of curvature definitions. Apart from the classical Gaussian curvature and mean curvature, maximum curvature, minimum curvature, shape index, and curvedness are also applied to macromolecular surface analysis for the first time. Our curvature analysis is uniquely coupled to the analysis of electrostatic surface potential, which is a by-product of our variational multiscale solvation models. As an expository investigation, we particularly emphasize the numerical algorithms and computational protocols for practical applications of the above multiscale geometric models. Such information may otherwise be scattered over the vast literature on this topic. Based on the curvature and electrostatic analysis from our multiresolution surfaces, we introduce a new concept, the polarized curvature, for the prediction of protein binding sites. PMID:24327772

  18. Consistent finite-volume discretization of hydrodynamic conservation laws for unstructured grids

    SciTech Connect

    Burton, D.E.

    1994-10-17

    We consider the conservation properties of a staggered-grid Lagrange formulation of the hydrodynamics equations (SGH). Hydrodynamics algorithms are often formulated in a relatively ad hoc manner in which independent discretizations are proposed for mass, momentum, energy, and so forth. We show that, once discretizations for mass and momentum are stated, the remaining discretizations are very nearly uniquely determined, so there is very little latitude for variation. As has been known for some time, the kinetic energy discretization must follow directly from the momentum equation; and the internal energy must follow directly from the energy currents affecting the kinetic energy. A fundamental requirement (termed isentropicity) for numerical hydrodynamics algorithms is the ability to remain on an isentrope in the absence of heating or viscous forces and in the limit of small timesteps. We show that the requirements of energy conservation and isentropicity lead to the replacement of the usual volume calculation with a conservation integral. They further forbid the use of higher order functional representations for either velocity or stress within zones or control volumes, forcing the use of a constant stress element and a constant velocity control volume. This, in turn, causes the point and zone coordinates to formally disappear from the Cartesian formulation. The form of the work equations and the requirement for dissipation by viscous forces strongly limits the possible algebraic forms for artificial viscosity. The momentum equation and a center-of-mass definition lead directly to an angular momentum conservation law that is satisfied by the system. With a few straightforward substitutions, the Cartesian formulation can be converted to a multidimensional curvilinear one. The formulation in 2D symmetric geometry preserves rotational symmetry.

  19. High-order conservative reconstruction schemes for finite volume methods in cylindrical and spherical coordinates

    NASA Astrophysics Data System (ADS)

    Mignone, A.

    2014-08-01

    High-order reconstruction schemes for the solution of hyperbolic conservation laws in orthogonal curvilinear coordinates are revised in the finite volume approach. The formulation employs a piecewise polynomial approximation to the zone-average values to reconstruct left and right interface states from within a computational zone to arbitrary order of accuracy by inverting a Vandermonde-like linear system of equations with spatially varying coefficients. The approach is general and can be used on uniform and non-uniform meshes although explicit expressions are derived for polynomials from second to fifth degree in cylindrical and spherical geometries with uniform grid spacing. It is shown that, in regions of large curvature, the resulting expressions differ considerably from their Cartesian counterparts and that the lack of such corrections can severely degrade the accuracy of the solution close to the coordinate origin. Limiting techniques and monotonicity constraints are revised for conventional reconstruction schemes, namely, the piecewise linear method (PLM), third-order weighted essentially non-oscillatory (WENO) scheme and the piecewise parabolic method (PPM). The performance of the improved reconstruction schemes is investigated in a number of selected numerical benchmarks involving the solution of both scalar and systems of nonlinear equations (such as the equations of gas dynamics and magnetohydrodynamics) in cylindrical and spherical geometries in one and two dimensions. Results confirm that the proposed approach yields considerably smaller errors, higher convergence rates and it avoid spurious numerical effects at a symmetry axis.

  20. Overture: The grid classes

    SciTech Connect

    Brislawn, K.; Brown, D.; Chesshire, G.; Henshaw, W.

    1997-01-01

    Overture is a library containing classes for grids, overlapping grid generation and the discretization and solution of PDEs on overlapping grids. This document describes the Overture grid classes, including classes for single grids and classes for collections of grids.

  1. One-way Wavefield Extrapolation in Riemannian Coordinates

    NASA Astrophysics Data System (ADS)

    Sava, P. C.; Shragge, J. C.; Fomel, S. B.

    2004-12-01

    Images of crustal and lithospheric-scale structure can be created through seismic wavefield extrapolation, which extends surface-recorded data to depth through application of a wave-equation operator. The one-way extrapolation operators are derived from the acoustic wave-equation dispersion relation, and are usually defined in a Cartesian coordinate system with a vertical extrapolation axis. However, in this formulation there is an assumption that a vertical extrapolation axis can handle all wavefield propagation effects. In particular, there are numerous seismic imaging experiments where challenges such as incorporating rough topography, modeling overturning waves, and accounting for spherical Earth effects make extrapolation in Cartesian coordinates impractical. Riemannian wavefield extrapolation (RWE) (Sava and Fomel, 2004) is a generalization of the downward continuation concept to coordinate systems that incorporate geometrical or wave propagation effects. For example, geometrical effects such as topography can be directly incorporated into the coordinate system, and wavefield extrapolation commenced directly from relief (Shragge and Sava, AGU 2004). Another example is modeling path propagation effects directly in the coordinate system enabling accurate one-way wavefield extrapolation, even in situations where wavefields overturn. The method is implemented with a mixed domain solution involving both Fourier and space-domain finite differences. The algorithm is modestly more costly than wavefield extrapolation performed on a Cartesian computational mesh.

  2. Simplified Cartesian basis model for intrapolyad emission intensities in the bent-to-linear electronic transition of acetylene.

    PubMed

    Park, G Barratt; Steeves, Adam H; Baraban, Joshua H; Field, Robert W

    2015-02-01

    The acetylene emission spectrum from the trans-bent electronically excited state to the linear ground electronic X? state has attracted considerable attention because it grants FranckCondon access to local bending vibrational levels of the X? state with large-amplitude motion along the acetylene ? vinylidene isomerization coordinate. For emission from the ground vibrational level of the state, there is a simplifying set of FranckCondon propensity rules that gives rise to only one zero-order bright state per conserved vibrational polyad of the X? state. Unfortunately, when the upper level involves excitation in the highly admixed ungerade bending modes, ?4? and ?6?, the simplifying FranckCondon propensity rule breaks down--as long as the usual polar basis (with v and l quantum numbers) is used to describe the degenerate bending vibrations of the X? state--and the intrapolyad intensities result from complicated interference patterns between many zero-order bright states. In this article, we show that, when the degenerate bending levels are instead treated in the Cartesian two-dimensional harmonic oscillator basis (with vx and vy quantum numbers), the propensity for only one zero-order bright state (in the Cartesian basis) is restored, and the intrapolyad intensities are simple to model, as long as corrections are made for anharmonic interactions. As a result of trans ? cis isomerization in the state, intrapolyad emission patterns from overtones of ?4? and ?6? evolve as quanta of trans bend (?3?) are added, so the emission intensities are not only relevant to the ground-state acetylene ? vinylidene isomerization, they are also a direct reporter of isomerization in the electronically excited state. PMID:25625552

  3. Grid technologies empowering drug discovery.

    PubMed

    Chien, Andrew; Foster, Ian; Goddette, Dean

    2002-10-15

    Grid technologies enable flexible coupling and sharing of computers, instruments and storage. Grids can provide technical solutions to the volume of data and computational demands associated with drug discovery by delivering larger computing capability (flexible resource sharing), providing coordinated access to large data resources and enabling novel online exploration (coupling computing, data and instruments online). Here, we illustrate this potential by describing two applications: the use of desktop PC grid technologies for virtual screening, and distributed X-ray structure reconstruction and online visualization. PMID:12546902

  4. An FDTD scheme on a face-centered-cubic (FCC) grid for the solution of the wave equation

    NASA Astrophysics Data System (ADS)

    Potter, M. E.; Lamoureux, M.; Nauta, M. D.

    2011-07-01

    A method is proposed to improve the numerical dispersion characteristics for simulations of the scalar wave equation in 3D using the FDTD method. The improvements are realized by choosing a face-centered-cubic (FCC) grid instead of the typical Cartesian (Yee) grid, which exhibits non-physical distortions of the wavefront due to the FD stencil. FCC grids are the logical extension of hexagonal grids in 2D, and have been shown previously to provide optimal sampling of space based on close packing of spheres (highest density). The difference equations are developed for the wave equation on this alternative grid, and the dispersion relationship and stability for grids of equal and non-equal aspect ratios are derived. A comparison is made between FCC and Cartesian formulations, based upon having an equal volume density of gridpoints in each method (i.e. the computational storage requirements of each method would be the same for the same simulated space). The comparison shows that the FCC grid exhibits a much more isotropic dispersion relation than the Cartesian grid of equivalent density. Furthermore, for an equivalent density, the FCC method has a more relaxed stability criterion by a factor of approximately 1.35, resulting in a further reduction in computational resources.

  5. 77 FR 71169 - Smart Grid Advisory Committee Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-29

    ... recommendations from the Committee's report and to receive presentations on cybersecurity coordination and the... cybersecurity coordination and the NIST Smart Grid Program Plan. The agenda may change to accommodate...

  6. Comparison of Cartesian and Non-Cartesian Real-Time MRI Sequences at 1.5T to Assess Velar Motion and Velopharyngeal Closure during Speech

    PubMed Central

    Freitas, Andreia C.; Wylezinska, Marzena; Birch, Malcolm J.; Petersen, Steffen E.; Miquel, Marc E.

    2016-01-01

    Dynamic imaging of the vocal tract using real-time MRI has been an active and growing area of research, having demonstrated great potential to become routinely performed in the clinical evaluation of speech and swallowing disorders. Although many technical advances have been made in regards to acquisition and reconstruction methodologies, there is still no consensus in best practice protocols. This study aims to compare Cartesian and non-Cartesian real-time MRI sequences, regarding image quality and temporal resolution trade-off, for dynamic speech imaging. Five subjects were imaged at 1.5T, while performing normal phonation, in order to assess velar motion and velopharyngeal closure. Data was acquired using both Cartesian and non-Cartesian (spiral and radial) real-time sequences at five different spatial-temporal resolution sets, between 10 fps (1.7×1.7×10 mm3) and 25 fps (1.5×1.5×10 mm3). Only standard scanning resources provided by the MRI scanner manufacturer were used to ensure easy applicability to clinical evaluation and reproducibility. Data sets were evaluated by comparing measurements of the velar structure, dynamic contrast-to-noise ratio and image quality visual scoring. Results showed that for all proposed sequences, FLASH spiral acquisitions provided higher contrast-to-noise ratio, up to a 170.34% increase at 20 fps, than equivalent bSSFP Cartesian acquisitions for the same spatial-temporal resolution. At higher frame rates (22 and 25 fps), spiral protocols were optimal and provided higher CNR and visual scoring than equivalent radial protocols. Comparison of dynamic imaging at 10 and 22 fps for radial and spiral acquisitions revealed no significant difference in CNR performance, thus indicating that temporal resolution can be doubled without compromising spatial resolution (1.9×1.9 mm2) or CNR. In summary, this study suggests that the use of FLASH spiral protocols should be preferred over bSSFP Cartesian for the dynamic imaging of velopharyngeal closure, as it allows for an improvement in CNR and overall image quality without compromising spatial-temporal resolution. PMID:27073905

  7. Grid oscillators

    NASA Technical Reports Server (NTRS)

    Popovic, Zorana B.; Kim, Moonil; Rutledge, David B.

    1988-01-01

    Loading a two-dimensional grid with active devices offers a means of combining the power of solid-state oscillators in the microwave and millimeter-wave range. The grid structure allows a large number of negative resistance devices to be combined. This approach is attractive because the active devices do not require an external locking signal, and the combining is done in free space. In addition, the loaded grid is a planar structure amenable to monolithic integration. Measurements on a 25-MESFET grid at 9.7 GHz show power-combining and frequency-locking without an external locking signal, with an ERP of 37 W. Experimental far-field patterns agree with theoretical results obtained using reciprocity.

  8. The National Grid Project: A system overview

    NASA Technical Reports Server (NTRS)

    Gaither, Adam; Gaither, Kelly; Jean, Brian; Remotigue, Michael; Whitmire, John; Soni, Bharat; Thompson, Joe; Dannenhoffer,, John; Weatherill, Nigel

    1995-01-01

    The National Grid Project (NGP) is a comprehensive numerical grid generation software system that is being developed at the National Science Foundation (NSF) Engineering Research Center (ERC) for Computational Field Simulation (CFS) at Mississippi State University (MSU). NGP is supported by a coalition of U.S. industries and federal laboratories. The objective of the NGP is to significantly decrease the amount of time it takes to generate a numerical grid for complex geometries and to increase the quality of these grids to enable computational field simulations for applications in industry. A geometric configuration can be discretized into grids (or meshes) that have two fundamental forms: structured and unstructured. Structured grids are formed by intersecting curvilinear coordinate lines and are composed of quadrilateral (2D) and hexahedral (3D) logically rectangular cells. The connectivity of a structured grid provides for trivial identification of neighboring points by incrementing coordinate indices. Unstructured grids are composed of cells of any shape (commonly triangles, quadrilaterals, tetrahedra and hexahedra), but do not have trivial identification of neighbors by incrementing an index. For unstructured grids, a set of points and an associated connectivity table is generated to define unstructured cell shapes and neighboring points. Hybrid grids are a combination of structured grids and unstructured grids. Chimera (overset) grids are intersecting or overlapping structured grids. The NGP system currently provides a user interface that integrates both 2D and 3D structured and unstructured grid generation, a solid modeling topology data management system, an internal Computer Aided Design (CAD) system based on Non-Uniform Rational B-Splines (NURBS), a journaling language, and a grid/solution visualization system.

  9. An accuracy assessment of Cartesian-mesh approaches for the Euler equations

    NASA Technical Reports Server (NTRS)

    Coirier, William J.; Powell, Kenneth G.

    1995-01-01

    A critical assessment of the accuracy of Cartesian-mesh approaches for steady, transonic solutions of the Euler equations of gas dynamics is made. An exact solution of the Euler equations (Ringleb's flow) is used not only to infer the order of the truncation error of the Cartesian-mesh approaches, but also to compare the magnitude of the discrete error directly to that obtained with a structured mesh approach. Uniformly and adaptively refined solutions using a Cartesian-mesh approach are obtained and compared to each other and to uniformly refined structured mesh results. The effect of cell merging is investigated as well as the use of two different K-exact reconstruction procedures. The solution methodology of the schemes is explained and tabulated results are presented to compare the solution accuracies.

  10. Radiation heat transfer model using Monte Carlo ray tracing method on hierarchical ortho-Cartesian meshes and non-uniform rational basis spline surfaces for description of boundaries

    NASA Astrophysics Data System (ADS)

    Kuczyński, Paweł; Białecki, Ryszard

    2014-06-01

    The paper deals with a solution of radiation heat transfer problems in enclosures filled with nonparticipating medium using ray tracing on hierarchical ortho-Cartesian meshes. The idea behind the approach is that radiative heat transfer problems can be solved on much coarser grids than their counterparts from computational fluid dynamics (CFD). The resulting code is designed as an add-on to OpenFOAM, an open-source CFD program. Ortho-Cartesian mesh involving boundary elements is created based upon CFD mesh. Parametric non-uniform rational basis spline (NURBS) surfaces are used to define boundaries of the enclosure, allowing for dealing with domains of complex shapes. Algorithm for determining random, uniformly distributed locations of rays leaving NURBS surfaces is described. The paper presents results of test cases assuming gray diffusive walls. In the current version of the model the radiation is not absorbed within gases. However, the ultimate aim of the work is to upgrade the functionality of the model, to problems in absorbing, emitting and scattering medium projecting iteratively the results of radiative analysis on CFD mesh and CFD solution on radiative mesh.

  11. Grid generation on surfaces in 3 dimensions

    NASA Technical Reports Server (NTRS)

    Eiseman, Peter R.

    1986-01-01

    The development of a surface grid generation algorithm was initiated. The basic adaptive movement technique of mean-value-relaxation was extended from the viewpoint of a single coordinate grid over a surface described by a single scalar function to that of a surface more generally defined by vector functions and covered by a collection of smoothly connected grids. Within the multiconnected assemblage, the application of control was examined in several instances.

  12. Grid scans: A transfer map diagnostic

    SciTech Connect

    Emma, P.; Spence, W.

    1991-05-01

    A beam line transfer map diagnostic is described which uses induced betatron oscillations to search for focusing errors and geometric aberrations. A grid is produced graphically in normalized phase space coordinates with the beta match quantified from this grid. Application to the SLC electron damping Ring-To-Linac (RTL) transport line is presented. 1 ref., 4 figs.

  13. Unstructured Grid Generation Techniques and Software

    NASA Technical Reports Server (NTRS)

    Posenau, Mary-Anne K. (Editor)

    1993-01-01

    The Workshop on Unstructured Grid Generation Techniques and Software was conducted for NASA to assess its unstructured grid activities, improve the coordination among NASA centers, and promote technology transfer to industry. The proceedings represent contributions from Ames, Langley, and Lewis Research Centers, and the Johnson and Marshall Space Flight Centers. This report is a compilation of the presentations made at the workshop.

  14. Random subspaces for encryption based on a private shared Cartesian frame

    SciTech Connect

    Bartlett, Stephen D.; Hayden, Patrick; Spekkens, Robert W.

    2005-11-15

    A private shared Cartesian frame is a novel form of private shared correlation that allows for both private classical and quantum communication. Cryptography using a private shared Cartesian frame has the remarkable property that asymptotically, if perfect privacy is demanded, the private classical capacity is three times the private quantum capacity. We demonstrate that if the requirement for perfect privacy is relaxed, then it is possible to use the properties of random subspaces to nearly triple the private quantum capacity, almost closing the gap between the private classical and quantum capacities.

  15. [Mental interiority in the early-modern age. The "Cartesian theater"].

    PubMed

    Gillot, Pascale

    2010-01-01

    This paper looks into the notion of mental interiority in the early-modern age and, more specifically, into the Cartesian conception of the mind as an "inner theater". The main claim emphasizes a close connexion at work between the representative theory of the mind, associated with internalism, on the one hand, and a "neuropsychological" view on the other hand. Cartesian mentalism, in so far as it is based upon a disjunction between representation and resemblance, can therefore not be separated from the general project, already at work in the Dioptrique, of an intra-cerebral localization of the mental. PMID:20533801

  16. Approximations to wire grid inductance.

    SciTech Connect

    Warne, Larry Kevin; Johnson, William Arthur; Merewether, Kimball O.

    2004-06-01

    By using a multipole-conformal mapping expansion for the wire currents we examine the accuracy of approximations for the transfer inductance of a one dimensional array of wires (wire grid). A simple uniform fit is constructed by introduction of the decay factor from bipolar coordinates into existing formulas for this inductance.

  17. COMPARISON OF THE ACCURACY OF VARIOUS SPATIAL DISCRETIZATION SCHEMES OF THE DISCRETE ORDINATES EQUATIONS IN 2D CARTESIAN GEOMETRY

    SciTech Connect

    Sebastian Schunert; Yousry Y. Azmy; Damien Fournier

    2011-05-01

    We present a comprehensive error estimation of four spatial discretization schemes of the two-dimensional Discrete Ordinates (SN) equations on Cartesian grids utilizing a Method of Manufactured Solution (MMS) benchmark suite based on variants of Larsen’s benchmark featuring different orders of smoothness of the underlying exact solution. The considered spatial discretization schemes include the arbitrarily high order transport methods of the nodal (AHOTN) and characteristic (AHOTC) types, the discontinuous Galerkin Finite Element method (DGFEM) and the recently proposed higher order diamond difference method (HODD) of spatial expansion orders 0 through 3. While AHOTN and AHOTC rely on approximate analytical solutions of the transport equation within a mesh cell, DGFEM and HODD utilize a polynomial expansion to mimick the angular flux profile across each mesh cell. Intuitively, due to the higher degree of analyticity, we expect AHOTN and AHOTC to feature superior accuracy compared with DGFEM and HODD, but at the price of potentially longer grind times and numerical instabilities. The latter disadvantages can result from the presence of exponential terms evaluated at the cell optical thickness that arise from the semianalytical solution process. This work quantifies the order of accuracy and the magnitude of the error of all four discretization methods for different optical thicknesses, scattering ratios and degrees of smoothness of the underlying exact solutions in order to verify or contradict the aforementioned intuitive expectation.

  18. An assessment of unstructured grid technology for timely CFD analysis

    NASA Technical Reports Server (NTRS)

    Kinard, Tom A.; Schabowski, Deanne M.

    1995-01-01

    An assessment of two unstructured methods is presented in this paper. A tetrahedral unstructured method USM3D, developed at NASA Langley Research Center is compared to a Cartesian unstructured method, SPLITFLOW, developed at Lockheed Fort Worth Company. USM3D is an upwind finite volume solver that accepts grids generated primarily from the Vgrid grid generator. SPLITFLOW combines an unstructured grid generator with an implicit flow solver in one package. Both methods are exercised on three test cases, a wing, and a wing body, and a fully expanded nozzle. The results for the first two runs are included here and compared to the structured grid method TEAM and to available test data. On each test case, the set up procedure are described, including any difficulties that were encountered. Detailed descriptions of the solvers are not included in this paper.

  19. Advances in Distance-Based Hole Cuts on Overset Grids

    NASA Technical Reports Server (NTRS)

    Chan, William M.; Pandya, Shishir A.

    2015-01-01

    An automatic and efficient method to determine appropriate hole cuts based on distances to the wall and donor stencil maps for overset grids is presented. A new robust procedure is developed to create a closed surface triangulation representation of each geometric component for accurate determination of the minimum hole. Hole boundaries are then displaced away from the tight grid-spacing regions near solid walls to allow grid overlap to occur away from the walls where cell sizes from neighboring grids are more comparable. The placement of hole boundaries is efficiently determined using a mid-distance rule and Cartesian maps of potential valid donor stencils with minimal user input. Application of this procedure typically results in a spatially-variable offset of the hole boundaries from the minimum hole with only a small number of orphan points remaining. Test cases on complex configurations are presented to demonstrate the new scheme.

  20. Numerical solution of the full potential equation using a chimera grid approach

    NASA Technical Reports Server (NTRS)

    Holst, Terry L.

    1995-01-01

    A numerical scheme utilizing a chimera zonal grid approach for solving the full potential equation in two spatial dimensions is described. Within each grid zone a fully-implicit approximate factorization scheme is used to advance the solution one interaction. This is followed by the explicit advance of all common zonal grid boundaries using a bilinear interpolation of the velocity potential. The presentation is highlighted with numerical results simulating the flow about a two-dimensional, nonlifting, circular cylinder. For this problem, the flow domain is divided into two parts: an inner portion covered by a polar grid and an outer portion covered by a Cartesian grid. Both incompressible and compressible (transonic) flow solutions are included. Comparisons made with an analytic solution as well as single grid results indicate that the chimera zonal grid approach is a viable technique for solving the full potential equation.

  1. MESH2D GRID GENERATOR DESIGN AND USE

    SciTech Connect

    Flach, G.; Smith, F.

    2012-01-20

    Mesh2d is a Fortran90 program designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j{sub 0}) coordinates along index i are permitted to undulate or otherwise vary. Mesh2d also assigns an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations. The overall mesh is constructed from grid zones that are typically then subdivided into a collection of smaller grid cells. The grid zones usually correspond to distinct materials or larger-scale geometric shapes. The structured grid zones are identified through uppercase indices (I,J). Subdivision of zonal regions into grid cells can be done uniformly, or nonuniformly using either a polynomial or geometric skewing algorithm. Grid cells may be concentrated backward, forward, or toward both ends. Figure 1 illustrates the above concepts in the context of a simple four zone grid.

  2. A mixed volume grid approach for the Euler and Navier-Stokes equations

    NASA Technical Reports Server (NTRS)

    Coirier, William J.; Jorgenson, Philip C. E.

    1996-01-01

    An approach for solving the compressible Euler and Navier-Stokes equations upon meshes composed of nearly arbitrary polyhedra is described. Each polyhedron is constructed from an arbitrary number of triangular and quadrilateral face elements, allowing the unified treatment of tetrahedral, prismatic, pyramidal, and hexahedral cells, as well the general cut cells produced by Cartesian mesh approaches. The basics behind the numerical approach and the resulting data structures are described. The accuracy of the mixed volume grid approach is assessed by performing a grid refinement study upon a series of hexahedral, tetrahedral, prismatic, and Cartesian meshes for an analytic inviscid problem. A series of laminar validation cases are made, comparing the results upon differing grid topologies to each other, to theory, and experimental data. A computation upon a prismatic/tetrahedral mesh is made simulating the laminar flow over a wall/cylinder combination.

  3. Dynamic coordination of a self-reconfigurable manipulator system

    NASA Technical Reports Server (NTRS)

    Kim, Sungbok; Lee, Sukhan

    1991-01-01

    The authors present the dynamic coordination of a self-reconfigurable manipulator system capable of changing its mechanical structure according to given task requirements. The self-reconfiguration is achieved by reconfiguring the topology of a dual-arm system through serial, parallel, and bracing structures. Particular emphasis is placed on the dynamic coordination of two arms having three different dual-arm topologies. The authors develop the Cartesian space dynamic models of a dual-arm system of three dual-arm topologies and derive the kinematic and dynamic constraints imposed on two arms in cooperation. Dual-arm dynamic manipulabilities are defined to quantify the dynamic performance of three dual-arm topologies in terms of the efficiency of generating Cartesian accelerations. A methodology of selecting serial, parallel, and bracing structures based on dual-arm dynamic manipulabilities is provided.

  4. Coordinate transformation by minimizing correlations between parameters

    NASA Technical Reports Server (NTRS)

    Kumar, M.

    1972-01-01

    This investigation was to determine the transformation parameters (three rotations, three translations and a scale factor) between two Cartesian coordinate systems from sets of coordinates given in both systems. The objective was the determination of well separated transformation parameters with reduced correlations between each other, a problem especially relevant when the sets of coordinates are not well distributed. The above objective is achieved by preliminarily determining the three rotational parameters and the scale factor from the respective direction cosines and chord distances (these being independent of the translation parameters) between the common points, and then computing all the seven parameters from a solution in which the rotations and the scale factor are entered as weighted constraints according to their variances and covariances obtained in the preliminary solutions. Numerical tests involving two geodetic reference systems were performed to evaluate the effectiveness of this approach.

  5. Solving Partial Differential Equations on Overlapping Grids

    SciTech Connect

    Henshaw, W D

    2008-09-22

    We discuss the solution of partial differential equations (PDEs) on overlapping grids. This is a powerful technique for efficiently solving problems in complex, possibly moving, geometry. An overlapping grid consists of a set of structured grids that overlap and cover the computational domain. By allowing the grids to overlap, grids for complex geometries can be more easily constructed. The overlapping grid approach can also be used to remove coordinate singularities by, for example, covering a sphere with two or more patches. We describe the application of the overlapping grid approach to a variety of different problems. These include the solution of incompressible fluid flows with moving and deforming geometry, the solution of high-speed compressible reactive flow with rigid bodies using adaptive mesh refinement (AMR), and the solution of the time-domain Maxwell's equations of electromagnetism.

  6. Introduction to grid generation systems in turbomachinery

    NASA Astrophysics Data System (ADS)

    Camarero, R.; Ozell, B.; Reggio, M.; Caron, A.

    Body-fitted curvilinear grid generation for the numerical simulation of three dimensional flow in turbomachines is introduced. The grids yield coordinate curves aligned with the domain boundaries. The numerical scheme for the governing equations is carried out on a rectangular mesh, giving a simpler and more accurate algorithm since bondaries coincide with coordinate grids, and no interpolation is required. The geometric complexity, through the transformation, is imbedded into the coefficients of the governing equations, affording the possibility of writing generalized codes applicable to a variety of geometries. This results in a great saving in the code development effort.

  7. An improved method for calculating self-motion coordinates for redundant manipulators

    SciTech Connect

    Reister, D.B.

    1997-04-01

    For a redundant manipulator, the objective of redundancy resolution is to follow a specified path in Cartesian space and simultaneously perform another task (for example, maximize an objective function or avoid obstacles) at every point along the path. The conventional methods have several drawbacks: a new function must be defined for each task, the extended Jacobian can be singular, closed cycles in Cartesian space may not yield closed cycles in joint space, and the objective is point-wise redundancy resolution (to determine a single point in joint space for each point in Cartesian space). The author divides the redundancy resolution problem into two parts: (1) calculate self-motion coordinates for all possible positions of a manipulator at each point along a Cartesian path and (2) determination of optimal self-motion coordinates that maximize an objective function along the path. This paper will discuss the first part of the problem. The path-wise approach overcomes all of the drawbacks of conventional redundancy resolution methods: no need to define a new function for each task, extended Jacobian cannot be singular, and closed cycles in extended Cartesian space will yield closed cycles in joint space.

  8. Supporting Generative Thinking about Number Lines, the Cartesian Plane, and Graphs of Linear Functions

    ERIC Educational Resources Information Center

    Earnest, Darrell Steven

    2012-01-01

    This dissertation explores fifth and eighth grade students' interpretations of three kinds of mathematical representations: number lines, the Cartesian plane, and graphs of linear functions. Two studies were conducted. In Study 1, I administered the paper-and-pencil Linear Representations Assessment (LRA) to examine students'…

  9. Embodying Learning: Post-Cartesian Pedagogy and the Academic Study of Religion

    ERIC Educational Resources Information Center

    Lelwica, Michelle Mary

    2009-01-01

    This paper explores the concept and practice of "embodied pedagogy" as an alternative to the Cartesian approach to knowledge that is tacitly embedded in traditional modes of teaching and learning about religion. My analysis highlights a class I co-teach that combines the study of Aikido (a Japanese martial art) with seminar-style discussions of…

  10. "Mens Sana in Corpore Sano": Cartesian Dualism and the Marginalisation of Sex Education

    ERIC Educational Resources Information Center

    Paechter, Carrie

    2004-01-01

    Cartesian dualism has left a heavy legacy in terms of how we think about ourselves, so that we treat humans as minds within bodies rather than mind/body unities. This has far-reaching effects on our conceptualisation of the sex/gender distinction and on the relationship between bodies and identities. Related to this is a dualism that is embedded…

  11. Supporting Generative Thinking about Number Lines, the Cartesian Plane, and Graphs of Linear Functions

    ERIC Educational Resources Information Center

    Earnest, Darrell Steven

    2012-01-01

    This dissertation explores fifth and eighth grade students' interpretations of three kinds of mathematical representations: number lines, the Cartesian plane, and graphs of linear functions. Two studies were conducted. In Study 1, I administered the paper-and-pencil Linear Representations Assessment (LRA) to examine students'

  12. Real-time cartesian force feedback control of a teleoperated robot

    NASA Technical Reports Server (NTRS)

    Campbell, Perry

    1989-01-01

    Active cartesian force control of a teleoperated robot is investigated. An economical microcomputer based control method was tested. Limitations are discussed and methods of performance improvement suggested. To demonstrate the performance of this technique, a preliminary test was performed with success. A general purpose bilateral force reflecting hand controller is currently being constructed based on this control method.

  13. Cartesian Meshing Impacts for PWR Assemblies in Multigroup Monte Carlo and Sn Transport

    NASA Astrophysics Data System (ADS)

    Manalo, K.; Chin, M.; Sjoden, G.

    2014-06-01

    Hybrid methods of neutron transport have increased greatly in use, for example, in applications of using both Monte Carlo and deterministic transport to calculate quantities of interest, such as flux and eigenvalue in a nuclear reactor. Many 3D parallel Sn codes apply a Cartesian mesh, and thus for nuclear reactors the representation of curved fuels (cylinder, sphere, etc.) are impacted in the representation of proper fuel inventory (both in deviation of mass and exact geometry representation). For a PWR assembly eigenvalue problem, we explore the errors associated with this Cartesian discrete mesh representation, and perform an analysis to calculate a slope parameter that relates the pcm to the percent areal/volumetric deviation (areal corresponds to 2D and volumetric to 3D, respectively). Our initial analysis demonstrates a linear relationship between pcm change and areal/volumetric deviation using Multigroup MCNP on a PWR assembly compared to a reference exact combinatorial MCNP geometry calculation. For the same multigroup problems, we also intend to characterize this linear relationship in discrete ordinates (3D PENTRAN) and discuss issues related to transport cross-comparison. In addition, we discuss auto-conversion techniques with our 3D Cartesian mesh generation tools to allow for full generation of MCNP5 inputs (Cartesian mesh and Multigroup XS) from a basis PENTRAN Sn model.

  14. Interactive grid generation program for CAP-TSD

    NASA Technical Reports Server (NTRS)

    Bland, Samuel R.

    1990-01-01

    A grid generation program for use with the CAP-TSD transonic small disturbance code is described. The program runs interactively in FORTRAN on the Sun Workstation. A fifth-degree polynomial is used to map the grid index onto the computational coordinate. The grid is plotted to aid in the assessment of its quality and may be saved on file in NAMELIST format.

  15. Grid systems for Earth radiation budget experiment applications

    NASA Technical Reports Server (NTRS)

    Brooks, D. R.

    1981-01-01

    Spatial coordinate transformations are developed for several global grid systems of interest to the Earth Radiation Budget Experiment. The grid boxes are defined in terms of a regional identifier and longitude-latitude indexes. The transformations associate longitude with a particular grid box. The reverse transformations identify the center location of a given grid box. Transformations are given to relate the rotating (Earth-based) grid systems to solar position expressed in an inertial (nonrotating) coordinate system. The FORTRAN implementations of the transformations are given, along with sample input and output.

  16. Wave-equation migration in generalized coordinate systems

    NASA Astrophysics Data System (ADS)

    Shragge, Jeffrey

    Wave-equation migration using one-way wavefield extrapolation operators is commonly used in industry to generate images of complex geologic structure from 3D seismic data. By design, most conventional wave-equation approaches restrict propagation to downward continuation, where wavefields are recursively extrapolated to depth on Cartesian meshes. In practice, this approach is limited in high-angle accuracy and is restricted to down-going waves, which precludes the use of some steep dip and all turning wave components important for imaging targets in such areas as steep salt body flanks. This thesis discusses a strategy for improving wavefield extrapolation based on extending wavefield propagation to generalized coordinate system geometries that are more conformal to the wavefield propagation direction and permit imaging with turning waves. Wavefield propagation in non-Cartesian coordinates requires properly specifying the Laplacian operator in the governing Helmholtz equation. By employing differential geometry theory, I demonstrate how generalized a Riemannian wavefield extrapolation (RWE) procedure can be developed for any 3D non-orthogonal coordinate system, including those constructed by smoothing ray-based coordinate meshes formed from a suite of traced rays. I present 2D and 3D generalized RWE propagation examples illustrating the improved steep-dip propagation afforded by the coordinate transformation. One consequence of using non-Cartesian coordinates, though, is that the corresponding 3D extrapolation operators have up to 10 non-stationary coefficients, which can lead to imposing (and limiting) computer memory constraints for realistic 3D applications. To circumvent this difficulty, I apply the generalized RWE theory to analytic coordinate systems, rather than numerically generated meshes. Analytic coordinates offer the advantage of having straightforward analytic dispersion relationships and easy-to-implement extrapolation operators that add little computational overhead. In particular, I demonstrate that the dispersion relationship for 2D elliptical geometry introduces only an effective velocity model stretch, permitting the use of existing high-order Cartesian extrapolators. The results of elliptical coordinate shot-profile migration tests demonstrate the improvements in steep dip reflector imaging facilitated by the coordinate system transformation approach. I extend the analytic coordinate system approach to 3D geometries using tilted elliptical-cylindrical (TEC) meshes. I demonstrate that propagation in a TEC coordinate system is equivalent to wavefield extrapolation in elliptically anisotropic media, which is easily handled by existing industry practice. TEC coordinates also allow steep dip propagation in both the inline and cross-line directions by virtue of the associated elliptical and tilting Cartesian geometries. Observing that a TEC coordinate system conforms closely to the shape of a line-source impulse response, I develop an TEC-coordinate, inline-delay-source migration strategy that enables the efficient migration of individual sail-line data. I argue that this strategy is more robust than 3D plane-wave migration because of the reduced migration aperture requirements and, commonly, a lower number of total migration runs. Synthetic imaging tests on a 3D wide-azimuth data set demonstrate the imaging advantages offered by the TEC coordinate transformation, especially in the cross-line direction. Field data tests on a Gulf of Mexico data set similarly indicate the advantage of TEC coordinates.

  17. TBGG- INTERACTIVE ALGEBRAIC GRID GENERATION

    NASA Technical Reports Server (NTRS)

    Smith, R. E.

    1994-01-01

    TBGG, Two-Boundary Grid Generation, applies an interactive algebraic grid generation technique in two dimensions. The program incorporates mathematical equations that relate the computational domain to the physical domain. TBGG has application to a variety of problems using finite difference techniques, such as computational fluid dynamics. Examples include the creation of a C-type grid about an airfoil and a nozzle configuration in which no left or right boundaries are specified. The underlying two-boundary technique of grid generation is based on Hermite cubic interpolation between two fixed, nonintersecting boundaries. The boundaries are defined by two ordered sets of points, referred to as the top and bottom. Left and right side boundaries may also be specified, and call upon linear blending functions to conform interior interpolation to the side boundaries. Spacing between physical grid coordinates is determined as a function of boundary data and uniformly spaced computational coordinates. Control functions relating computational coordinates to parametric intermediate variables that affect the distance between grid points are embedded in the interpolation formulas. A versatile control function technique with smooth cubic spline functions is also presented. The TBGG program is written in FORTRAN 77. It works best in an interactive graphics environment where computational displays and user responses are quickly exchanged. The program has been implemented on a CDC Cyber 170 series computer using NOS 2.4 operating system, with a central memory requirement of 151,700 (octal) 60 bit words. TBGG requires a Tektronix 4015 terminal and the DI-3000 Graphics Library of Precision Visuals, Inc. TBGG was developed in 1986.

  18. TIGGERC: Turbomachinery interactive grid generator energy distributor and restart code

    NASA Technical Reports Server (NTRS)

    Miller, David P.

    1992-01-01

    A two dimensional multi-block grid generator was developed for a new design and analysis system for studying multi-blade row turbomachinery problems with an axisymmetric viscous/inviscid 'average passage' through flow code. TIGGERC is a mouse driven, fully interactive grid generation program which can be used to modify boundary coordinates and grid packing. TIGGERC generates grids using a hyperbolic tangent or algebraic distribution of grid points on the block boundaries and the interior points of each block grid are distributed using a transfinite interpolation approach. TIGGERC generates a blocked axisymmetric H grid, C grid, I grid, or O grid for studying turbomachinery flow problems. TIGGERC was developed for operation on small high speed graphic workstations.

  19. Safe Grid

    NASA Technical Reports Server (NTRS)

    Chow, Edward T.; Stewart, Helen; Korsmeyer, David (Technical Monitor)

    2003-01-01

    The biggest users of GRID technologies came from the science and technology communities. These consist of government, industry and academia (national and international). The NASA GRID is moving into a higher technology readiness level (TRL) today; and as a joint effort among these leaders within government, academia, and industry, the NASA GRID plans to extend availability to enable scientists and engineers across these geographical boundaries collaborate to solve important problems facing the world in the 21 st century. In order to enable NASA programs and missions to use IPG resources for program and mission design, the IPG capabilities needs to be accessible from inside the NASA center networks. However, because different NASA centers maintain different security domains, the GRID penetration across different firewalls is a concern for center security people. This is the reason why some IPG resources are been separated from the NASA center network. Also, because of the center network security and ITAR concerns, the NASA IPG resource owner may not have full control over who can access remotely from outside the NASA center. In order to obtain organizational approval for secured remote access, the IPG infrastructure needs to be adapted to work with the NASA business process. Improvements need to be made before the IPG can be used for NASA program and mission development. The Secured Advanced Federated Environment (SAFE) technology is designed to provide federated security across NASA center and NASA partner's security domains. Instead of one giant center firewall which can be difficult to modify for different GRID applications, the SAFE "micro security domain" provide large number of professionally managed "micro firewalls" that can allow NASA centers to accept remote IPG access without the worry of damaging other center resources. The SAFE policy-driven capability-based federated security mechanism can enable joint organizational and resource owner approved remote access from outside of NASA centers. A SAFE enabled IPG can enable IPG capabilities to be available to NASA mission design teams across different NASA center and partner company firewalls. This paper will first discuss some of the potential security issues for IPG to work across NASA center firewalls. We will then present the SAFE federated security model. Finally we will present the concept of the architecture of a SAFE enabled IPG and how it can benefit NASA mission development.

  20. MAGNETOHYDRODYNAMIC MODELING OF SOLAR SYSTEM PROCESSES ON GEODESIC GRIDS

    SciTech Connect

    Florinski, V.; Guo, X.; Balsara, D. S.; Meyer, C.

    2013-04-01

    This report describes a new magnetohydrodynamic numerical model based on a hexagonal spherical geodesic grid. The model is designed to simulate astrophysical flows of partially ionized plasmas around a central compact object, such as a star or a planet with a magnetic field. The geodesic grid, produced by a recursive subdivision of a base platonic solid (an icosahedron), is free from control volume singularities inherent in spherical polar grids. Multiple populations of plasma and neutral particles, coupled via charge-exchange interactions, can be simulated simultaneously with this model. Our numerical scheme uses piecewise linear reconstruction on a surface of a sphere in a local two-dimensional 'Cartesian' frame. The code employs Haarten-Lax-van-Leer-type approximate Riemann solvers and includes facilities to control the divergence of the magnetic field and maintain pressure positivity. Several test solutions are discussed, including a problem of an interaction between the solar wind and the local interstellar medium, and a simulation of Earth's magnetosphere.

  1. Crystal structure of a two-dimensional grid-type iron(II) coordination polymer: poly[[di­aqua­tetra-μ-cyanido-diargentate(I)iron(II)] trans-1,2-bis(pyridin-2-yl)ethyl­ene disolvate

    PubMed Central

    Othong, Jintana; Wannarit, Nanthawat; Pakawatchai, Chaveng; Youngme, Sujittra

    2014-01-01

    In the title compound, {[Ag2Fe(CN)4(H2O)2]·2C12H10N2}n, the asymmetric unit contains one FeII cation, two water mol­ecules, two di­cyanido­argentate(I) anions and two uncoordinating 1,2-bis­(pyridin-2-yl)ethyl­ene (2,2′-bpe) mol­ecules. Each FeII atom is six-coordinated in a nearly regular octa­hedral geometry by four N atoms from di­cyanido­argentate(I) bridges and two coordinating water mol­ecules. The FeII atoms are bridged by di­cyanido­argentate(I) units to give a two-dimensional layer with square-grid spaces. The inter­grid spaces with inter­layer distance of 6.550 (2) Å are occupied by 2,2′-bpe guest mol­ecules which form O—H⋯N hydrogen bonds to the host layers. This leads to an extended three-dimensional supra­molecular architecture. The structure of the title compound is compared with some related compounds containing di­cyanido­argentate(I) ligands and N-donor organic co-ligands. PMID:25249868

  2. Engineering of Services and Business Models for Grid Applications

    NASA Astrophysics Data System (ADS)

    Falkner, Jürgen; Weisbecker, Anette

    In the context of using grid applications in medicine and bioinformatics a combination of classic biomedical services like the analysis of biomaterial with grid services is quite common. Services for customers in those fields need to comprise both and offer an easy way to use these combined services. Within the German project Services@MediGRID, methods for the systematic development of complex customer services including the use of grid applications are developed. In coordination with this service engineering approach for grid applications, commercial business models are derived for a set of biomedical grid services.

  3. Easing The Calculation Of Bolt-Circle Coordinates

    NASA Technical Reports Server (NTRS)

    Burley, Richard K.

    1995-01-01

    Bolt Circle Calculation (BOLT-CALC) computer program used to reduce significant time consumed in manually computing trigonometry of rectangular Cartesian coordinates of holes in bolt circle as shown on blueprint or drawing. Eliminates risk of computational errors, particularly in cases involving many holes or in cases in which coordinates expressed to many significant digits. Program assists in many practical situations arising in machine shops. Written in BASIC. Also successfully compiled and implemented by use of Microsoft's QuickBasic v4.0.

  4. Determination of Ship Approach Parameters in the Polar Coordinates System

    NASA Astrophysics Data System (ADS)

    Banachowicz, Andrzej; Wolski, Adam

    2014-06-01

    An essential aspect of the safety of navigation is avoiding collisions with other vessels and natural or man made navigational obstructions. To solve this kind of problem the navigator relies on automatic anti-collision ARPA systems, or uses a geometric method and makes radar plots. In both cases radar measurements are made: bearing (or relative bearing) on the target position and distance, both naturally expressed in the polar coordinates system originating at the radar antenna. We first convert original measurements to an ortho-Cartesian coordinate system. Then we solve collision avoiding problems in rectangular planar coordinates, and the results are transformed to the polar coordinate system. This article presents a method for an analysis of a collision situation at sea performed directly in the polar coordinate system. This approach enables a simpler geometric interpretation of a collision situation

  5. Mean square optimal NUFFT approximation for efficient non-Cartesian MRI reconstruction

    NASA Astrophysics Data System (ADS)

    Yang, Zhili; Jacob, Mathews

    2014-05-01

    The fast evaluation of the discrete Fourier transform of an image at non-uniform sampling locations is key to efficient iterative non-Cartesian MRI reconstruction algorithms. Current non-uniform fast Fourier transform (NUFFT) approximations rely on the interpolation of oversampled uniform Fourier samples. The main challenge is high memory demand due to oversampling, especially when multidimensional datasets are involved. The main focus of this work is to design an NUFFT algorithm with minimal memory demands. Specifically, we introduce an analytical expression for the expected mean square error in the NUFFT approximation based on our earlier work. We then introduce an iterative algorithm to design the interpolator and scale factors. Experimental comparisons show that the proposed optimized NUFFT scheme provides considerably lower approximation errors than the previous designs [1] that rely on worst case error metrics. The improved approximations are also seen to considerably reduce the errors and artifacts in non-Cartesian MRI reconstruction.

  6. Adaptive nonlinear vibration control of a Cartesian flexible manipulator driven by a ballscrew mechanism

    NASA Astrophysics Data System (ADS)

    Qiu, Zhi-cheng

    2012-07-01

    A flexible Cartesian manipulator is a coupling system with a moving rigid body and flexible structures. Thus, vibration suppression problem must be solved to guarantee the stability and control accuracy. A characteristic model based nonlinear golden section adaptive control (CMNGSAC) algorithm is implemented to suppress the vibration of a flexible Cartesian smart material manipulator driven by a ballscrew mechanism using an AC servomotor. The system modeling is derived to recognize the dynamical characteristics. The closed loop stability is analyzed based on the model. Also, an experimental setup is constructed to verify the adopted method. Experimental comparison studies are conducted for modal frequencies' identification and active vibration control of the flexible manipulator. The active vibration control experiments include set-point vibration control responses, vibration suppression under resonant excitation and simultaneous translating and vibration suppression using different control methods. The experimental results demonstrate that the controller can suppress both the larger and the lower amplitude vibration near the equilibrium point effectively.

  7. Aerodynamic Design of Complex Configurations Using Cartesian Methods and CAD Geometry

    NASA Technical Reports Server (NTRS)

    Nemec, Marian; Aftosmis, Michael J.; Pulliam, Thomas H.

    2003-01-01

    The objective for this paper is to present the development of an optimization capability for the Cartesian inviscid-flow analysis package of Aftosmis et al. We evaluate and characterize the following modules within the new optimization framework: (1) A component-based geometry parameterization approach using a CAD solid representation and the CAPRI interface. (2) The use of Cartesian methods in the development Optimization techniques using a genetic algorithm. The discussion and investigations focus on several real world problems of the optimization process. We examine the architectural issues associated with the deployment of a CAD-based design approach in a heterogeneous parallel computing environment that contains both CAD workstations and dedicated compute nodes. In addition, we study the influence of noise on the performance of optimization techniques, and the overall efficiency of the optimization process for aerodynamic design of complex three-dimensional configurations. of automated optimization tools. rithm and a gradient-based algorithm.

  8. Direct simulation of multi-phase MHD flows on an unstructured Cartesian adaptive system

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Ni, Ming-Jiu

    2014-08-01

    An approach for direct simulation of the multi-phase magnetohydrodynamics (MHD) flows has been developed in the present study on an unstructured Cartesian adaptive system. The approach is based on the volume-of-fluid (VOF) method for capturing the interface with the adaptive mesh refinement (AMR) technique used to well resolve the interface and the boundary layer. The Lorentz force is calculated using the consistent and conservative scheme, which is specially designed on a Cartesian adaptive mesh to conserve the physical conservation laws. The continuous-surface-tension (CSF) formulation is adopted for surface tension calculation. Moreover, the interfacial flows driven by thermal Marangoni effects at multifluid interfaces are also studied with a special numerical treatment presented. The method is able to simulate bubble motion in liquid metal under magnetic field irrespective of high density ratio and electric conductivity ratio. The proposed scheme for multi-phase MHD flows is validated by experimental results as well as analytical solutions.

  9. The NMR multi-transmit phased array: a Cartesian feedback approach.

    PubMed

    Hoult, D I; Kolansky, G; Kripiakevich, D; King, S B

    2004-11-01

    The use of Cartesian feedback is proposed to solve the problem of using an array of coils for the purposes of transmission in magnetic resonance imaging. The difficulties caused by direct and sample-mediated coil interactions are briefly examined, and the known solutions of using power-mismatched pre-amplifiers and transmitters noted. It is then shown that, without loss of transmitter efficiency, a high effective impedance may be created in series with each coil in the array by the use of Cartesian negative feedback. A bench experiment is described that confirms the theory. The solution is also viable for signal reception and is more efficacious than pre-amplifier damping, albeit over a smaller bandwidth. PMID:15504683

  10. On the Use of Parmetric-CAD Systems and Cartesian Methods for Aerodynamic Design

    NASA Technical Reports Server (NTRS)

    Nemec, Marian; Aftosmis, Michael J.; Pulliam, Thomas H.

    2004-01-01

    Automated, high-fidelity tools for aerodynamic design face critical issues in attempting to optimize real-life geometry arid in permitting radical design changes. Success in these areas promises not only significantly shorter design- cycle times, but also superior and unconventional designs. To address these issues, we investigate the use of a parmetric-CAD system in conjunction with an embedded-boundary Cartesian method. Our goal is to combine the modeling capabilities of feature-based CAD with the robustness and flexibility of component-based Cartesian volume-mesh generation for complex geometry problems. We present the development of an automated optimization frame-work with a focus on the deployment of such a CAD-based design approach in a heterogeneous parallel computing environment.

  11. Mean square optimal NUFFT approximation for efficient non-Cartesian MRI reconstruction

    PubMed Central

    Yang, Zhili; Jacob, Mathews

    2014-01-01

    The fast evaluation of the discrete Fourier transform of an image at non-uniform sampling locations is key to efficient iterative non-Cartesian MRI reconstruction algorithms. Current non-uniform fast Fourier transform (NUFFT) approximations rely on the interpolation of oversampled uniform Fourier samples. The main challenge is high memory demand due to oversampling, especially when multi-dimensional datasets are involved. The main focus of this work is to design an NUFFT algorithm with minimal memory demands. Specifically, we introduce an analytical expression for the expected mean square error in the NUFFT approximation based on our earlier work. We then introduce an iterative algorithm to design the interpolator and scale factors.Experimental comparisons show that the proposed optimized NUFFT scheme provides considerably lower approximation errors than our previous scheme that rely on worst case error metrics. The improved approximations are also seen to considerably reduce the errors and artifacts in non-Cartesian MRI reconstruction. PMID:24637054

  12. Mean square optimal NUFFT approximation for efficient non-Cartesian MRI reconstruction.

    PubMed

    Yang, Zhili; Jacob, Mathews

    2014-05-01

    The fast evaluation of the discrete Fourier transform of an image at non-uniform sampling locations is key to efficient iterative non-Cartesian MRI reconstruction algorithms. Current non-uniform fast Fourier transform (NUFFT) approximations rely on the interpolation of oversampled uniform Fourier samples. The main challenge is high memory demand due to oversampling, especially when multidimensional datasets are involved. The main focus of this work is to design an NUFFT algorithm with minimal memory demands. Specifically, we introduce an analytical expression for the expected mean square error in the NUFFT approximation based on our earlier work. We then introduce an iterative algorithm to design the interpolator and scale factors. Experimental comparisons show that the proposed optimized NUFFT scheme provides considerably lower approximation errors than the previous designs [1] that rely on worst case error metrics. The improved approximations are also seen to considerably reduce the errors and artifacts in non-Cartesian MRI reconstruction. PMID:24637054

  13. The Cartesian clock metaphor for pineal gland operation pervades the origin of modern chronobiology.

    PubMed

    Barrera-Mera, B; Barrera-Calva, E

    1998-01-01

    In theoretical descriptions formulated during the 1600s, R. Descartes attributed a clock-like role to the pineal gland. He established the belief that pineal function underlies the laws of the universe that determine the cyclic sleep-awake states in man. Recent reports about pineal circadian pacemakers now validate the brilliant accuracy of Cartesian thought, in relation to the relevant role of the pineal gland. PMID:9861610

  14. Cartesian path control of a two-degree-of-freedom robot manipulator

    NASA Technical Reports Server (NTRS)

    Nguyen, Charles C.; Pooran, Farhad J.

    1988-01-01

    The problem of cartesian trajectory control of a closed-kinematic chain mechanism robot manipulator with possible space station applications is considered. The study was performed by both computer simulation and experimentation for tracking of three different paths: a straight line, a sinusoid and a circle. Linearization and pole placement methods are employed to design controller gains. Results show that the controllers are robust and there are good agreements between simulation and experimentation. Excellent tracking quality and small overshoots are also evident.

  15. Algorithm For Modeling Coordinates Of Corners Of Buildings Determined With RTN GNSS Technology Using Vectors Translation Method

    NASA Astrophysics Data System (ADS)

    Krzyżek, Robert

    2015-09-01

    The paper presents an innovative solution which increases the reliability of determining the coordinates of corners of building structures in the RTN GNSS mode. Having performed the surveys of the base points in real time, it is proposed to use the method of line-line intersection, which results in capturing the Cartesian coordinates X, Y of the corners of buildings. The coordinates which were obtained in this way, are subjected to an innovative solution called the method of vectors translation. This method involves modeling the coordinates obtained by the algorithm developed by the author. As a result, we obtain the Cartesian coordinates X and Y of the corners of building structures, the accuracy and reliability of determining which is on a very high level.

  16. Density- and wavefunction-normalized Cartesian spherical harmonics for l ≤ 20

    DOE PAGESBeta

    Michael, J. Robert; Volkov, Anatoliy

    2015-03-01

    The widely used pseudoatom formalism in experimental X-ray charge-density studies makes use of real spherical harmonics when describing the angular component of aspherical deformations of the atomic electron density in molecules and crystals. The analytical form of the density-normalized Cartesian spherical harmonic functions for up to l ≤ 7 and the corresponding normalization coefficients were reported previously by Paturle & Coppens. It was shown that the analytical form for normalization coefficients is available primarily forl ≤ 4. Only in very special cases it is possible to derive an analytical representation of the normalization coefficients for 4 < l ≤ 7.more » In most cases for l > 4 the density normalization coefficients were calculated numerically to within seven significant figures. In this study we review the literature on the density-normalized spherical harmonics, clarify the existing notations, use the Paturle–Coppens method in the Wolfram Mathematicasoftware to derive the Cartesian spherical harmonics for l ≤ 20 and determine the density normalization coefficients to 35 significant figures, and computer-generate a Fortran90 code. The article primarily targets researchers who work in the field of experimental X-ray electron density, but may be of some use to all who are interested in Cartesian spherical harmonics.« less

  17. Density- and wavefunction-normalized Cartesian spherical harmonics for l ≤ 20

    SciTech Connect

    Michael, J. Robert; Volkov, Anatoliy

    2015-03-01

    The widely used pseudoatom formalism in experimental X-ray charge-density studies makes use of real spherical harmonics when describing the angular component of aspherical deformations of the atomic electron density in molecules and crystals. The analytical form of the density-normalized Cartesian spherical harmonic functions for up to l ≤ 7 and the corresponding normalization coefficients were reported previously by Paturle & Coppens. It was shown that the analytical form for normalization coefficients is available primarily forl ≤ 4. Only in very special cases it is possible to derive an analytical representation of the normalization coefficients for 4 < l ≤ 7. In most cases for l > 4 the density normalization coefficients were calculated numerically to within seven significant figures. In this study we review the literature on the density-normalized spherical harmonics, clarify the existing notations, use the Paturle–Coppens method in the Wolfram Mathematicasoftware to derive the Cartesian spherical harmonics for l ≤ 20 and determine the density normalization coefficients to 35 significant figures, and computer-generate a Fortran90 code. The article primarily targets researchers who work in the field of experimental X-ray electron density, but may be of some use to all who are interested in Cartesian spherical harmonics.

  18. The NCRC Grid Scheduling Environment

    SciTech Connect

    Indiviglio, Frank M; Maxwell, Don E

    2011-01-01

    In support of the NCRC, a joint computing center between NOAA and ORNL, a grid-based scheduling infrastructure was designed to allow geographically separate computing resources to be used as production resources in climate and weather research workflows. These workflows require job coordination between the two centers in order to provide a complete workflow of data staging, computation, post-analysis and archival. This paper details the design, implementation and initial production phase of the infrastructure and lessons learned from the process.

  19. A computer program for converting rectangular coordinates to latitude-longitude coordinates

    USGS Publications Warehouse

    Rutledge, A.T.

    1989-01-01

    A computer program was developed for converting the coordinates of any rectangular grid on a map to coordinates on a grid that is parallel to lines of equal latitude and longitude. Using this program in conjunction with groundwater flow models, the user can extract data and results from models with varying grid orientations and place these data into grid structure that is oriented parallel to lines of equal latitude and longitude. All cells in the rectangular grid must have equal dimensions, and all cells in the latitude-longitude grid measure one minute by one minute. This program is applicable if the map used shows lines of equal latitude as arcs and lines of equal longitude as straight lines and assumes that the Earth 's surface can be approximated as a sphere. The program user enters the row number , column number, and latitude and longitude of the midpoint of the cell for three test cells on the rectangular grid. The latitude and longitude of boundaries of the rectangular grid also are entered. By solving sets of simultaneous linear equations, the program calculates coefficients that are used for making the conversion. As an option in the program, the user may build a groundwater model file based on a grid that is parallel to lines of equal latitude and longitude. The program reads a data file based on the rectangular coordinates and automatically forms the new data file. (USGS)

  20. Augmented Lagrangian with Variable Splitting for Faster Non-Cartesian L1-SPIRiT MR Image Reconstruction

    PubMed Central

    Weller, Daniel S.; Ramani, Sathish; Fessler, Jeffrey A.

    2013-01-01

    SPIRiT (iterative self-consistent parallel imaging reconstruction), and its sparsity-regularized variant L1-SPIRiT, are compatible with both Cartesian and non-Cartesian MRI sampling trajectories. However, the non-Cartesian framework is more expensive computationally, involving a nonuniform Fourier transform with a nontrivial Gram matrix. We propose a novel implementation of the regularized reconstruction problem using variable splitting, alternating minimization of the augmented La-grangian, and careful preconditioning. Our new method based on the alternating direction method of multipliers converges much faster than existing methods because of the preconditioners' heightened effectiveness. We demonstrate such rapid convergence substantially improves image quality for a fixed computation time. Our framework is a step forward towards rapid non-Cartesian L1-SPIRiT reconstructions. PMID:24122551

  1. A Vertical Grid Module for Baroclinic Models of the Atmosphere

    SciTech Connect

    Drake, John B

    2008-04-01

    The vertical grid of an atmospheric model assigns dynamic and thermo- dynamic variables to grid locations. The vertical coordinate is typically not height but one of a class of meteorological variables that vary with atmo- spheric conditions. The grid system is chosen to further numerical approx- imations of the boundary conditions so that the system is terrain following at the surface. Lagrangian vertical coordinates are useful in reducing the numerical errors from advection processes. That the choices will effect the numercial properties and accuracy is explored in this report. A MATLAB class for Lorentz vertical grids is described and applied to the vertical struc- ture equation and baroclinic atmospheric circulation. A generalized meteo- rolgoical coordinate system is developed which can support σ, isentropic θ vertical coordinate, or Lagrangian vertical coordinates. The vertical atmo- spheric column is a MATLAB class that includes the kinematic and ther- modynamic variables along with methods for computing geopoentials and terms relevant to a 3D baroclinc atmospheric model.

  2. Development of a fractional-step method for the unsteady incompressible Navier-Stokes equations in generalized coordinate systems

    NASA Technical Reports Server (NTRS)

    Rosenfeld, Moshe; Kwak, Dochan; Vinokur, Marcel

    1992-01-01

    A fractional step method is developed for solving the time-dependent three-dimensional incompressible Navier-Stokes equations in generalized coordinate systems. The primitive variable formulation uses the pressure, defined at the center of the computational cell, and the volume fluxes across the faces of the cells as the dependent variables, instead of the Cartesian components of the velocity. This choice is equivalent to using the contravariant velocity components in a staggered grid multiplied by the volume of the computational cell. The governing equations are discretized by finite volumes using a staggered mesh system. The solution of the continuity equation is decoupled from the momentum equations by a fractional step method which enforces mass conservation by solving a Poisson equation. This procedure, combined with the consistent approximations of the geometric quantities, is done to satisfy the discretized mass conservation equation to machine accuracy, as well as to gain the favorable convergence properties of the Poisson solver. The momentum equations are solved by an approximate factorization method, and a novel ZEBRA scheme with four-color ordering is devised for the efficient solution of the Poisson equation. Several two- and three-dimensional laminar test cases are computed and compared with other numerical and experimental results to validate the solution method. Good agreement is obtained in all cases.

  3. Cartesian contrivances

    NASA Astrophysics Data System (ADS)

    Kemp, Martin

    1998-08-01

    If matter fills the Universe, making everything happen by its interactions, what does it all look like? René Descartes may have been over-mechanistic in his view, but his efforts to visualize the invisible created striking images.

  4. caGrid 1.0 : an enterprise Grid infrastructure for biomedical research.

    SciTech Connect

    Oster, S.; Langella, S.; Hastings, S.; Ervin, D.; Madduri, R.; Phillips, J.; Kurc, T.; Siebenlist, F.; Covitz, P.; Shanbhag, K.; Foster, I.; Saltz, J.; Mathematics and Computer Science; The Ohio State Univ.; National Cancer Inst. Centerfor Bioinformatics; SemanticBits

    2008-03-01

    To develop software infrastructure that will provide support for discovery, characterization, integrated access, and management of diverse and disparate collections of information sources, analysis methods, and applications in biomedical research. Design: An enterprise Grid software infrastructure, called caGrid version 1.0 (caGrid 1.0), has been developed as the core Grid architecture of the NCI-sponsored cancer Biomedical Informatics Grid (caBIG{trademark}) program. It is designed to support a wide range of use cases in basic, translational, and clinical research, including (1) discovery, (2) integrated and large-scale data analysis, and (3) coordinated study. Measurements: The caGrid is built as a Grid software infrastructure and leverages Grid computing technologies and the Web Services Resource Framework standards. It provides a set of core services, toolkits for the development and deployment of new community provided services, and application programming interfaces for building client applications. Results: The caGrid 1.0 was released to the caBIG community in December 2006. It is built on open source components and caGrid source code is publicly and freely available under a liberal open source license. The core software, associated tools, and documentation can be downloaded from the following URL: Grid>.

  5. An analysis of a collision situation in polar coordinates

    NASA Astrophysics Data System (ADS)

    Wolski, Adam; Banachowicz, Andrzej

    2014-05-01

    Avoiding collisions with other vessels and natural or artificial navigational obstructions is an important element of navigation safety. This problem is automatically solved in anti-collision ARPA systems, or geometrically as radar plots. In both cases we use radar measurements: bearing (or relative bearing) on the target position and distance, both naturally localized in the polar coordinates system with the origin at the radar antenna. We convert original measurements to an ortho-Cartesian coordinate system. Then we solve a collision avoiding problem in the new system, and then transform the results to the polar coordinate system. This article presents a method for an analysis of a collision situation performed directly in the polar coordinate system. This approach enables a simpler geometric interpretation of a collision situation.

  6. COORDINATED AV.

    ERIC Educational Resources Information Center

    CLEAVES, PAUL C.; AND OTHERS

    THE INSTRUCTIONAL MATERIALS CENTER IS LOCATED IN THE LOCAL HIGH SCHOOL AND SUPPLIES ALL SCHOOLS IN THE AREA. AUDIOVISUAL EQUIPMENT ORDERS, AFTER SELECTIONS ARE MADE BY THE CLASSROOM TEACHER, ARE PROCESSED BY THE CENTER, CONFIRMED AND DELIVERED BY TRUCK THREE TIMES EACH WEEK. EACH SCHOOL HAS A BUILDING COORDINATOR WHO CHECKS THE ORDERS INTO THE…

  7. Nurbs and grid generation

    SciTech Connect

    Barnhill, R.E.; Farin, G.; Hamann, B.

    1995-12-31

    This paper provides a basic overview of NURBS and their application to numerical grid generation. Curve/surface smoothing, accelerated grid generation, and the use of NURBS in a practical grid generation system are discussed.

  8. Smart Grid Risk Management

    NASA Astrophysics Data System (ADS)

    Abad Lopez, Carlos Adrian

    Current electricity infrastructure is being stressed from several directions -- high demand, unreliable supply, extreme weather conditions, accidents, among others. Infrastructure planners have, traditionally, focused on only the cost of the system; today, resilience and sustainability are increasingly becoming more important. In this dissertation, we develop computational tools for efficiently managing electricity resources to help create a more reliable and sustainable electrical grid. The tools we present in this work will help electric utilities coordinate demand to allow the smooth and large scale integration of renewable sources of energy into traditional grids, as well as provide infrastructure planners and operators in developing countries a framework for making informed planning and control decisions in the presence of uncertainty. Demand-side management is considered as the most viable solution for maintaining grid stability as generation from intermittent renewable sources increases. Demand-side management, particularly demand response (DR) programs that attempt to alter the energy consumption of customers either by using price-based incentives or up-front power interruption contracts, is more cost-effective and sustainable in addressing short-term supply-demand imbalances when compared with the alternative that involves increasing fossil fuel-based fast spinning reserves. An essential step in compensating participating customers and benchmarking the effectiveness of DR programs is to be able to independently detect the load reduction from observed meter data. Electric utilities implementing automated DR programs through direct load control switches are also interested in detecting the reduction in demand to efficiently pinpoint non-functioning devices to reduce maintenance costs. We develop sparse optimization methods for detecting a small change in the demand for electricity of a customer in response to a price change or signal from the utility, dynamic learning methods for scheduling the maintenance of direct load control switches whose operating state is not directly observable and can only be inferred from the metered electricity consumption, and machine learning methods for accurately forecasting the load of hundreds of thousands of residential, commercial and industrial customers. These algorithms have been implemented in the software system provided by AutoGrid, Inc., and this system has helped several utilities in the Pacific Northwest, Oklahoma, California and Texas, provide more reliable power to their customers at significantly reduced prices. Providing power to widely spread out communities in developing countries using the conventional power grid is not economically feasible. The most attractive alternative source of affordable energy for these communities is solar micro-grids. We discuss risk-aware robust methods to optimally size and operate solar micro-grids in the presence of uncertain demand and uncertain renewable generation. These algorithms help system operators to increase their revenue while making their systems more resilient to inclement weather conditions.

  9. Grid Labeling Using A Marked Grid

    NASA Astrophysics Data System (ADS)

    Dunn, Stanley M.; Keizer, Richard L.

    1989-03-01

    Accurate grid labeling is a key step in recovering 3-D surfaces from structured light images. Knowledge of the real world (projector and camera geometry, surface continuity and smoothness, etc.) can be used to derive a set of local and global constraints which the grid labels must satisfy. Propagation of these constraints eliminates all but a small set of possible grid labels, but ambiguous solutions may still remain. This paper discusses a method of eliminating grid labeling ambiguity by adding constraints introduced by placing markers within the grid pattern. Grid labeling is based on geometric and topological constraints. Geometric constraints are global constraints on grid labels arising from knowledge of the camera and projector geometry, from assumed opaqueness of the object, and from knowledge of the work volume. Topological constraints are local constraints on grid labels arising from the sequential ordering of grid labels along a single grid stripe in the camera image, and from the assumption that a continuous (smooth) network of grid stripes in the camera image indicates a continuous (smooth) three-dimensional surface. This last assumption may be sometimes violated due to infrequent "viewing accidents" which may be caused by surface irregularities such as occluding contours or creases or by image processing errors. A problem with previous methods is the possible ambiguity of the recovered surface. This ambiguity occurs when more than one globally consistent set of grid labels is obtained, and consequently more than one object surface is possible. Our results show that the locations of the grid markers provide additional constraints to guide the grid labeling. We will present results of using several algorithms for labeling grids in structured light images. We will show that the additional constraints can be easily included into constraint propagation algorithms previously used for grid labeling.

  10. A practical adaptive-grid method for complex fluid-flow problems

    NASA Technical Reports Server (NTRS)

    Nakahashi, K.; Deiwert, G. S.

    1984-01-01

    A practical solution, adaptive-grid method utilizing a tension and torsion spring analogy is proposed for multidimensional fluid flow problems. The tension spring, which connects adjacent grid points to each other, controls grid spacings. The torsion spring, which is attached to each grid node, controls inclinations of coordinate lines and grid skewness. A marching procedure was used that results in a simple tridiagonal system of equations at each coordinate line to determine grid-point distribution. Multidirectional adaptation is achieved by successive applications of one-dimensional adaptation. Examples of applications for axisymmetric afterbody flow fields and two dimensional transonic airfoil flow fields are shown.

  11. Interactive grid generation for turbomachinery flow field simulations

    NASA Technical Reports Server (NTRS)

    Choo, Yung K.; Eiseman, Peter R.; Reno, Charles

    1988-01-01

    The control point form of algebraic grid generation presented provides the means that are needed to generate well structured grids for turbomachinery flow simulations. It uses a sparse collection of control points distributed over the flow domain. The shape and position of coordinate curves can be adjusted from these control points while the grid conforms precisely to all boundaries. An interactive program called TURBO, which uses the control point form, is being developed. Basic features of the code are discussed and sample grids are presented. A finite volume LU implicit scheme is used to simulate flow in a turbine cascade on the grid generated by the program.

  12. Interactive grid generation for turbomachinery flow field simulations

    NASA Technical Reports Server (NTRS)

    Choo, Yung K.; Reno, Charles; Eiseman, Peter R.

    1988-01-01

    The control point form of algebraic grid generation presented provides the means that are needed to generate well structured grids of turbomachinery flow simulations. It uses a sparse collection of control points distributed over the flow domain. The shape and position of coordinate curves can be adjusted from these control points while the grid conforms precisely to all boundaries. An interactive program called TURBO, which uses the control point form, is being developed. Basic features of the code are discussed and sample grids are presented. A finite volume LU implicit scheme is used to simulate flow in a turbine cascade on the grid generated by the program.

  13. System Wide Joint Position Sensor Fault Tolerance in Robot Systems Using Cartesian Accelerometers

    NASA Technical Reports Server (NTRS)

    Aldridge, Hal A.; Juang, Jer-Nan

    1997-01-01

    Joint position sensors are necessary for most robot control systems. A single position sensor failure in a normal robot system can greatly degrade performance. This paper presents a method to obtain position information from Cartesian accelerometers without integration. Depending on the number and location of the accelerometers. the proposed system can tolerate the loss of multiple position sensors. A solution technique suitable for real-time implementation is presented. Simulations were conducted using 5 triaxial accelerometers to recover from the loss of up to 4 joint position sensors on a 7 degree of freedom robot moving in general three dimensional space. The simulations show good estimation performance using non-ideal accelerometer measurements.

  14. Efficient and Robust Cartesian Mesh Generation for Building-Cube Method

    NASA Astrophysics Data System (ADS)

    Ishida, Takashi; Takahashi, Shun; Nakahashi, Kazuhiro

    In this study, an efficient and robust Cartesian mesh generation method for Building-Cube Method (BCM) is proposed. It can handle “dirty” geometry data whose surface has cracks, overlaps, and reverse of triangle. BCM mesh generation is implemented by two procedures; cube generation and cell generation in each cube. The cell generation procedure in this study is managed in each cube individually, and parallelized by OpenMP. Efficiency of the parallelized BCM mesh generation is demonstrated for several three-dimensional test cases using a multi-core PC.

  15. CAD-Based Aerodynamic Design of Complex Configurations using a Cartesian Method

    NASA Technical Reports Server (NTRS)

    Nemec, Marian; Aftosmis, Michael J.; Pulliam, Thomas H.

    2003-01-01

    A modular framework for aerodynamic optimization of complex geometries is developed. By working directly with a parametric CAD system, complex-geometry models are modified nnd tessellated in an automatic fashion. The use of a component-based Cartesian method significantly reduces the demands on the CAD system, and also provides for robust and efficient flowfield analysis. The optimization is controlled using either a genetic or quasi-Newton algorithm. Parallel efficiency of the framework is maintained even when subject to limited CAD resources by dynamically re-allocating the processors of the flow solver. Overall, the resulting framework can explore designs incorporating large shape modifications and changes in topology.

  16. Adjoint Sensitivity Computations for an Embedded-Boundary Cartesian Mesh Method and CAD Geometry

    NASA Technical Reports Server (NTRS)

    Nemec, Marian; Aftosmis,Michael J.

    2006-01-01

    Cartesian-mesh methods are perhaps the most promising approach for addressing the issues of flow solution automation for aerodynamic design problems. In these methods, the discretization of the wetted surface is decoupled from that of the volume mesh. This not only enables fast and robust mesh generation for geometry of arbitrary complexity, but also facilitates access to geometry modeling and manipulation using parametric Computer-Aided Design (CAD) tools. Our goal is to combine the automation capabilities of Cartesian methods with an eficient computation of design sensitivities. We address this issue using the adjoint method, where the computational cost of the design sensitivities, or objective function gradients, is esseutially indepeudent of the number of design variables. In previous work, we presented an accurate and efficient algorithm for the solution of the adjoint Euler equations discretized on Cartesian meshes with embedded, cut-cell boundaries. Novel aspects of the algorithm included the computation of surface shape sensitivities for triangulations based on parametric-CAD models and the linearization of the coupling between the surface triangulation and the cut-cells. The objective of the present work is to extend our adjoint formulation to problems involving general shape changes. Central to this development is the computation of volume-mesh sensitivities to obtain a reliable approximation of the objective finction gradient. Motivated by the success of mesh-perturbation schemes commonly used in body-fitted unstructured formulations, we propose an approach based on a local linearization of a mesh-perturbation scheme similar to the spring analogy. This approach circumvents most of the difficulties that arise due to non-smooth changes in the cut-cell layer as the boundary shape evolves and provides a consistent approximation tot he exact gradient of the discretized abjective function. A detailed gradient accurace study is presented to verify our approach. Thereafter, we focus on a shape optimization problem for an Apollo-like reentry capsule. The optimization seeks to enhance the lift-to-drag ratio of the capsule by modifyjing the shape of its heat-shield in conjunction with a center-of-gravity (c.g.) offset. This multipoint and multi-objective optimization problem is used to demonstrate the overall effectiveness of the Cartesian adjoint method for addressing the issues of complex aerodynamic design. This abstract presents only a brief outline of the numerical method and results; full details will be given in the final paper.

  17. Analysis of local anharmonicity using Gaussian model potentials and cartesian oscillator basis sets: example, HCN.

    PubMed

    Schmidt, P P

    2005-12-22

    This paper examines local anharmonic vibrations in molecules using an analysis that starts with an ab initio potential energy surface, fits a model potential constructed of Gaussian basis functions, and proceeds to a quantum mechanical analysis of the anharmonic modes using Cartesian harmonic oscillator basis functions in a variational calculation. The objective of this work is to suggest methods, with origins in nuclear and molecular (electronic) quantum mechanics, that should be useful for the accurate analysis of the local anharmonic motions of hydrogen, and perhaps other atoms or small molecular fragments, residing in molecularly complicated but otherwise harmonic environments. PMID:16354032

  18. Anisotropy of the Reynolds stress tensor in the wakes of wind turbine arrays in Cartesian arrangements with counter-rotating rotors

    NASA Astrophysics Data System (ADS)

    Hamilton, Nicholas; Cal, Raúl Bayoán

    2015-01-01

    A 4 × 3 wind turbine array in a Cartesian arrangement was constructed in a wind tunnel setting with four configurations based on the rotational sense of the rotor blades. The fourth row of devices is considered to be in the fully developed turbine canopy for a Cartesian arrangement. Measurements of the flow field were made with stereo particle-image velocimetry immediately upstream and downstream of the selected model turbines. Rotational sense of the turbine blades is evident in the mean spanwise velocity W and the Reynolds shear stress - v w ¯ . The flux of kinetic energy is shown to be of greater magnitude following turbines in arrays where direction of rotation of the blades varies. Invariants of the normalized Reynolds stress anisotropy tensor (η and ξ) are plotted in the Lumley triangle and indicate that distinct characters of turbulence exist in regions of the wake following the nacelle and the rotor blade tips. Eigendecomposition of the tensor yields principle components and corresponding coordinate system transformations. Characteristic spheroids representing the balance of components in the normalized anisotropy tensor are composed with the eigenvalues yielding shapes predicted by the Lumley triangle. Rotation of the coordinate system defined by the eigenvectors demonstrates trends in the streamwise coordinate following the rotors, especially trailing the top-tip of the rotor and below the hub. Direction of rotation of rotor blades is shown by the orientation of characteristic spheroids according to principle axes. In the inflows of exit row turbines, the normalized Reynolds stress anisotropy tensor shows cumulative effects of the upstream turbines, tending toward prolate shapes for uniform rotational sense, oblate spheroids for streamwise organization of rotational senses, and a mixture of characteristic shapes when the rotation varies by row. Comparison between the invariants of the Reynolds stress anisotropy tensor and terms from the mean mechanical energy equation indicate correlation between the degree of anisotropy and the regions of the wind turbine wakes where turbulence kinetic energy is produced. The flux of kinetic energy into the momentum-deficit area of the wake from above the canopy is associated with prolate characteristic spheroids. Flux upward into the wake from below the rotor area is associated with oblate characteristic spheroids. Turbulence in the region of the flow directly following the nacelle of the wind turbines demonstrates greater isotropy than regions following the rotor blades. The power and power coefficients for wind turbines indicate that flow structures on the order of magnitude of the spanwise turbine spacing that increase turbine efficiency depending on particular array configuration.

  19. North RTL grid scan'' studies

    SciTech Connect

    Emma, P.

    1990-10-17

    This study was made in response to screen measurements which indicated an emittance growth of nearly a factor of two within the North RTL or linac girder-1. Betatron oscillations are induced at the beginning of the North RTL to search for gross geometric aberrations arising within the RTL or sector-2 of the linac. The oscillations are induced horizontally and vertically with two X or two Y dipole correctors stepped in a nested loop fashion. In both cases the full set of RTL and first girder sector-2 linac beam position monitors (BPMs) are sampled in X and Y for each corrector setting. Horizontal (or vertical) data from pairs of BPMs are then transformed to phase space coordinates by the linear transformation constructed assuming the transport optics between the BPMs is known. A second transformation is then made to normalized phase space coordinates by using Twiss parameters consistent with the assumed transport optics. By careful choice of initial Twiss parameters the initial grid can be made square for convenience in graphical interpretation. A linear grid'' is then fitted to the transformed data points for each pair of BPMs. The area of each grid is calculated and linearity qualitatively evaluated. Furthermore, although not the focus of this study, the beta match at each BPM can be quantified. 6 figs.

  20. North RTL 'Grid Scan' Studies

    SciTech Connect

    Emma, P.; /SLAC

    2007-02-26

    This study was made in response to screen measurements which indicated an emittance growth of nearly a factor of two within the North RTL or linac girder-1. Betatron oscillations are induced at the beginning of the North RTL to search for gross geometric aberrations arising within the RTL or sector-2 of the linac. The oscillations are induced horizontally and vertically with two X or two Y dipole correctors stepped in a nested loop fashion. In both cases the full set of RTL and first girder sector-2 linac beam position monitors (BPMs) are sampled in X and Y for each corrector setting. Horizontal (or vertical) data from pairs of BPMs are then transformed to phase space coordinates by the linear transformation constructed assuming the transport optics between the BPMs is known. A second transformation is then made to normalized phase space coordinates by using Twiss parameters consistent with the assumed transport optics. By careful choice of initial Twiss parameters the initial grid can be made square for convenience in graphical interpretation. A linear ''grid'' is then fitted to the transformed data points for each pair of BPMs. The area of each grid is calculated and linearity qualitatively evaluated. Furthermore, although not the focus of this study, the beta match at each BPM can be quantified.

  1. GridMate - The Grid Matlab Extension

    NASA Astrophysics Data System (ADS)

    Jejkal, Thomas

    Matlab is a powerful tool for rapid prototyping and algorithm development and application in various scientific fields. In the meanwhile Matlab is even able to run functions in parallel on a network of machines, but it is still difficult to run Matlab functions on Grid resources. For this purpose GridMate was developed at Forschungszentrum Karlsruhe. The aim of GridMate is to run arbitrary Matlab functions in parallel without struggling with special extensions or licenses. On one hand GridMate uses the Matlab Runtime Environment to run Matlab functions remotely integrated in WSRF-compliant Web services. On the other hand GridMate offers a Matlab toolbox to integrate a Web service client seamlessly into an application. It allows parallel access to the deployed Web services at Grid and Cloud Computing resources and hides the technological complexity. In first tests GridMate was able to scale almost linear.

  2. Systematic and Deterministic Graph-Minor Embedding of Cartesian Products of Complete Graphs

    NASA Astrophysics Data System (ADS)

    Zaribafiyan, Arman; Marchand, Dominic J. J.; Changiz Rezaei, Seyed Saeed

    The limited connectivity of current and next-generation quantum annealers motivates the need for efficient graph-minor embedding methods. The overhead of the widely used heuristic techniques is quickly proving to be a significant bottleneck for real-world applications. To alleviate this obstacle, we propose a systematic deterministic embedding method that exploits the structures of both the input graph of the specific combinatorial optimization problem and the quantum annealer. We focus on the specific case of the Cartesian product of two complete graphs, a regular structure that occurs in many problems. We first divide the problem by embedding one of the factors of the Cartesian product in a repeatable unit. The resulting simplified problem consists of placing copies of this unit and connecting them together appropriately. Aside from the obvious speed and efficiency advantages of a systematic deterministic approach, the embeddings produced can be easily scaled for larger processors and show desirable properties with respect to the number of qubits used and the chain length distribution.

  3. A Grid portal for Earth Observation community

    NASA Astrophysics Data System (ADS)

    Aloisio, G.; Cafaro, M.; Cartenì, G.; Epicoco, I.; Quarta, G.

    2005-03-01

    Earth Observation techniques offer many powerful instruments for Earth planet study, urban development planning, military intelligence helping and so on. Terabytes of EO and geospatial data about lands, oceans, glaciers, cities, etc. are continuously downloaded through remote-sensing infrastructures and stored into heterogeneous, distributed repositories usually belonging to different virtual organizations. A problem-solving environment can be a viable solution to handle, coordinate and share heterogeneous and distributed resources. Moreover, grid computing is an emerging technology to solve large-scale problems in dynamic, multi-institutional Virtual Organizations coordinated by sharing resources such as high-performance computers, observation devices, data and databases over high-speed networks, etc. In this paper we present the Italian Grid for Earth Observation (I-GEO) project, a pervasive environment based on grid technology to help the integration and processing of Earth Observation data, providing a tool to share and access data, applications and computational resources among several organizations.

  4. Computer coordination of limb motion for a three-legged walking robot

    NASA Technical Reports Server (NTRS)

    Klein, C. A.; Patterson, M. R.

    1980-01-01

    Coordination of the limb motion of a vehicle which could perform assembly and maintenance operations on large structures in space is described. Manipulator kinematics and walking robots are described. The basic control scheme of the robot is described. The control of the individual arms are described. Arm velocities are generally described in Cartesian coordinates. Cartesian velocities are converted to joint velocities using the Jacobian matrix. The calculation of a trajectory for an arm given a sequence of points through which it is to pass is described. The free gait algorithm which controls the lifting and placing of legs for the robot is described. The generation of commanded velocities for the robot, and the implementation of those velocities by the algorithm are discussed. Suggestions for further work in the area of robot legged locomotion are presented.

  5. Phase-space distributions in quasi-polar coordinates and the fractional Fourier transform.

    PubMed

    Alieva, T; Bastiaans, M J

    2000-12-01

    The ambiguity function and Cohen's class of bilinear phase-space distributions are represented in a quasipolar coordinate system instead of in a Cartesian system. Relationships between these distributions and the fractional Fourier transform are derived; in particular, derivatives of the ambiguity function are related to moments of the fractional power spectra. A simplification is achieved for the description of underspread signals, for optical beam characterization, and for the generation of signal-adaptive phase-space distributions. PMID:11140493

  6. Parallel Grid Manipulations in Earth Science Calculations

    NASA Technical Reports Server (NTRS)

    Sawyer, W.; Lucchesi, R.; daSilva, A.; Takacs, L. L.

    1999-01-01

    The National Aeronautics and Space Administration (NASA) Data Assimilation Office (DAO) at the Goddard Space Flight Center is moving its data assimilation system to massively parallel computing platforms. This parallel implementation of GEOS DAS will be used in the DAO's normal activities, which include reanalysis of data, and operational support for flight missions. Key components of GEOS DAS, including the gridpoint-based general circulation model and a data analysis system, are currently being parallelized. The parallelization of GEOS DAS is also one of the HPCC Grand Challenge Projects. The GEOS-DAS software employs several distinct grids. Some examples are: an observation grid- an unstructured grid of points at which observed or measured physical quantities from instruments or satellites are associated- a highly-structured latitude-longitude grid of points spanning the earth at given latitude-longitude coordinates at which prognostic quantities are determined, and a computational lat-lon grid in which the pole has been moved to a different location to avoid computational instabilities. Each of these grids has a different structure and number of constituent points. In spite of that, there are numerous interactions between the grids, e.g., values on one grid must be interpolated to another, or, in other cases, grids need to be redistributed on the underlying parallel platform. The DAO has designed a parallel integrated library for grid manipulations (PILGRIM) to support the needed grid interactions with maximum efficiency. It offers a flexible interface to generate new grids, define transformations between grids and apply them. Basic communication is currently MPI, however the interfaces defined here could conceivably be implemented with other message-passing libraries, e.g., Cray SHMEM, or with shared-memory constructs. The library is written in Fortran 90. First performance results indicate that even difficult problems, such as above-mentioned pole rotation- a sparse interpolation with little data locality between the physical lat-lon grid and a pole rotated computational grid- can be solved efficiently and at the GFlop/s rates needed to solve tomorrow's high resolution earth science models. In the subsequent presentation we will discuss the design and implementation of PILGRIM as well as a number of the problems it is required to solve. Some conclusions will be drawn about the potential performance of the overall earth science models on the supercomputer platforms foreseen for these problems.

  7. Comprehensive Smart Grid Planning in a Regulated Utility Environment

    NASA Astrophysics Data System (ADS)

    Turner, Matthew; Liao, Yuan; Du, Yan

    2015-06-01

    This paper presents the tools and exercises used during the Kentucky Smart Grid Roadmap Initiative in a collaborative electric grid planning process involving state regulators, public utilities, academic institutions, and private interest groups. The mandate of the initiative was to assess the existing condition of smart grid deployments in Kentucky, to enhance understanding of smart grid concepts by stakeholders, and to develop a roadmap for the deployment of smart grid technologies by the jurisdictional utilities of Kentucky. Through involvement of many important stakeholder groups, the resultant Smart Grid Deployment Roadmap proposes an aggressive yet achievable strategy and timetable designed to promote enhanced availability, security, efficiency, reliability, affordability, sustainability and safety of the electricity supply throughout the state while maintaining Kentucky's nationally competitive electricity rates. The models and methods developed for this exercise can be utilized as a systematic process for the planning of coordinated smart grid deployments.

  8. On constructing three-dimensional overlapping grids with CMPGRD

    NASA Technical Reports Server (NTRS)

    Henshaw, William D.; Chesshire, Geoffrey; Henderson, Michael E.

    1992-01-01

    Techniques for the construction of three-dimensional composite overlapping grids, using the grid construction program CMPGRD, are described. The overlapping approach can be used to generate grids for regions of complicated geometry. The grids can be constructed to be smooth and free from coordinate singularities. The ability to create smooth grids for complicated regions is an important first step towards the accurate numerical solution of partial differential equations. The creation of grids for surfaces defined by cross-sections such as an airplane wing is described. A method for integrating the patched surfaces generated by a computer aided design (CAD) package with the CMPGRD program is described. Additionally, the creation of grids in regions where surfaces intersect is described.

  9. Parallel grid population

    DOEpatents

    Wald, Ingo; Ize, Santiago

    2015-07-28

    Parallel population of a grid with a plurality of objects using a plurality of processors. One example embodiment is a method for parallel population of a grid with a plurality of objects using a plurality of processors. The method includes a first act of dividing a grid into n distinct grid portions, where n is the number of processors available for populating the grid. The method also includes acts of dividing a plurality of objects into n distinct sets of objects, assigning a distinct set of objects to each processor such that each processor determines by which distinct grid portion(s) each object in its distinct set of objects is at least partially bounded, and assigning a distinct grid portion to each processor such that each processor populates its distinct grid portion with any objects that were previously determined to be at least partially bounded by its distinct grid portion.

  10. Documentation of program AFTBDY to generate coordinate system for 3D after body using body fitted curvilinear coordinates, part 1

    NASA Technical Reports Server (NTRS)

    Kumar, D.

    1980-01-01

    The computer program AFTBDY generates a body fitted curvilinear coordinate system for a wedge curved after body. This wedge curved after body is being used in an experimental program. The coordinate system generated by AFTBDY is used to solve 3D compressible N.S. equations. The coordinate system in the physical plane is a cartesian x,y,z system, whereas, in the transformed plane a rectangular xi, eta, zeta system is used. The coordinate system generated is such that in the transformed plane coordinate spacing in the xi, eta, zeta direction is constant and equal to unity. The physical plane coordinate lines in the different regions are clustered heavily or sparsely depending on the regions where physical quantities to be solved for by the N.S. equations have high or low gradients. The coordinate distribution in the physical plane is such that x stays constant in eta and zeta direction, whereas, z stays constant in xi and eta direction. The desired distribution in x and z is input to the program. Consequently, only the y-coordinate is solved for by the program AFTBDY.

  11. General formulation of the vibrational kinetic energy operator in internal bond-angle coordinates

    NASA Astrophysics Data System (ADS)

    Frederick, John H.; Woywod, Clemens

    1999-10-01

    A general formulation of the vibrational kinetic energy operator expressed in internal bond-angle coordinates is presented. This formulation is based on Podolsky's expression for the covariant form of the Laplace-Beltrami operator. When a valid set of internal bond-angle coordinates is employed, it is possible to adapt a systematic approach to solve for the Jacobian determinant governing the coordinate transformation from Cartesian coordinates. In the general case of an arbitrary N-atom system, this Jacobian always factorizes to a simple form. This allows one to evaluate all the terms that contribute to V̂', the effective potential that arises from transforming the kinetic energy operator to internal coordinates. We discuss restrictions on the choice of internal vibrational coordinates that may be included in a valid set. We then provide tabular information from which the vibrational kinetic energy operator for any molecular system can be constructed directly with no matrix inversion or chain rule manipulation required.

  12. Rapid analysis of scattering from periodic dielectric structures using accelerated Cartesian expansions

    SciTech Connect

    Baczewski, Andrew David; Miller, Nicholas C.; Shanker, Balasubramaniam

    2012-03-22

    Here, the analysis of fields in periodic dielectric structures arise in numerous applications of recent interest, ranging from photonic bandgap structures and plasmonically active nanostructures to metamaterials. To achieve an accurate representation of the fields in these structures using numerical methods, dense spatial discretization is required. This, in turn, affects the cost of analysis, particularly for integral-equation-based methods, for which traditional iterative methods require Ο(Ν2) operations, Ν being the number of spatial degrees of freedom. In this paper, we introduce a method for the rapid solution of volumetric electric field integral equations used in the analysis of doubly periodic dielectric structures. The crux of our method is the accelerated Cartesian expansion algorithm, which is used to evaluate the requisite potentials in Ο(Ν) cost. Results are provided that corroborate our claims of acceleration without compromising accuracy, as well as the application of our method to a number of compelling photonics applications.

  13. Validation of Inlet and Exhaust Boundary Conditions for a Cartesian Method

    NASA Technical Reports Server (NTRS)

    Pandya, Shishir A.; Murman, Scott M.; Aftosmis, Michael J.

    2004-01-01

    Inlets and exhaust nozzles are often omitted in aerodynamic simulations of aircraft due to the complexities involved in the modeling of engine details and flow physics. However, the omission is often improper since inlet or plume flows may have a substantial effect on vehicle aerodynamics. A method for modeling the effect of inlets and exhaust plumes using boundary conditions within an inviscid Cartesian flow solver is presented. This approach couples with both CAD systems and legacy geometry to provide an automated tool suitable for parameter studies. The method is validated using two and three-dimensional test problems which are compared with both theoretical and experimental results. The numerical results demonstrate excellent agreement with theory and available data, even for extremely strong jets and very sensitive inlets.

  14. Accelerated Cartesian expansions for the rapid solution of periodic multiscale problems

    SciTech Connect

    Baczewski, Andrew David; Dault, Daniel L.; Shanker, Balasubramaniam

    2012-07-03

    We present an algorithm for the fast and efficient solution of integral equations that arise in the analysis of scattering from periodic arrays of PEC objects, such as multiband frequency selective surfaces (FSS) or metamaterial structures. Our approach relies upon the method of Accelerated Cartesian Expansions (ACE) to rapidly evaluate the requisite potential integrals. ACE is analogous to FMM in that it can be used to accelerate the matrix vector product used in the solution of systems discretized using MoM. Here, ACE provides linear scaling in both CPU time and memory. Details regarding the implementation of this method within the context of periodic systems are provided, as well as results that establish error convergence and scalability. In addition, we also demonstrate the applicability of this algorithm by studying several exemplary electrically dense systems.

  15. Accelerated Cartesian expansions for the rapid solution of periodic multiscale problems

    DOE PAGESBeta

    Baczewski, Andrew David; Dault, Daniel L.; Shanker, Balasubramaniam

    2012-07-03

    We present an algorithm for the fast and efficient solution of integral equations that arise in the analysis of scattering from periodic arrays of PEC objects, such as multiband frequency selective surfaces (FSS) or metamaterial structures. Our approach relies upon the method of Accelerated Cartesian Expansions (ACE) to rapidly evaluate the requisite potential integrals. ACE is analogous to FMM in that it can be used to accelerate the matrix vector product used in the solution of systems discretized using MoM. Here, ACE provides linear scaling in both CPU time and memory. Details regarding the implementation of this method within themore » context of periodic systems are provided, as well as results that establish error convergence and scalability. In addition, we also demonstrate the applicability of this algorithm by studying several exemplary electrically dense systems.« less

  16. Numerical Simulation of Rolling-Airframes Using a Multi-Level Cartesian Method

    NASA Technical Reports Server (NTRS)

    Murman, Scott M.; Aftosmis, Michael J.; Berger, Marsha J.; Kwak, Dochan (Technical Monitor)

    2002-01-01

    A supersonic rolling missile with two synchronous canard control surfaces is analyzed using an automated, inviscid, Cartesian method. Sequential-static and time-dependent dynamic simulations of the complete motion are computed for canard dither schedules for level flight, pitch, and yaw maneuver. The dynamic simulations are compared directly against both high-resolution viscous simulations and relevant experimental data, and are also utilized to compute dynamic stability derivatives. The results show that both the body roll rate and canard dither motion influence the roll-averaged forces and moments on the body. At the relatively, low roll rates analyzed in the current work these dynamic effects are modest, however the dynamic computations are effective in predicting the dynamic stability derivatives which can be significant for highly-maneuverable missiles.

  17. Visual SLAM Using Variance Grid Maps

    NASA Technical Reports Server (NTRS)

    Howard, Andrew B.; Marks, Tim K.

    2011-01-01

    An algorithm denoted Gamma-SLAM performs further processing, in real time, of preprocessed digitized images acquired by a stereoscopic pair of electronic cameras aboard an off-road robotic ground vehicle to build accurate maps of the terrain and determine the location of the vehicle with respect to the maps. Part of the name of the algorithm reflects the fact that the process of building the maps and determining the location with respect to them is denoted simultaneous localization and mapping (SLAM). Most prior real-time SLAM algorithms have been limited in applicability to (1) systems equipped with scanning laser range finders as the primary sensors in (2) indoor environments (or relatively simply structured outdoor environments). The few prior vision-based SLAM algorithms have been feature-based and not suitable for real-time applications and, hence, not suitable for autonomous navigation on irregularly structured terrain. The Gamma-SLAM algorithm incorporates two key innovations: Visual odometry (in contradistinction to wheel odometry) is used to estimate the motion of the vehicle. An elevation variance map (in contradistinction to an occupancy or an elevation map) is used to represent the terrain. The Gamma-SLAM algorithm makes use of a Rao-Blackwellized particle filter (RBPF) from Bayesian estimation theory for maintaining a distribution over poses and maps. The core idea of the RBPF approach is that the SLAM problem can be factored into two parts: (1) finding the distribution over robot trajectories, and (2) finding the map conditioned on any given trajectory. The factorization involves the use of a particle filter in which each particle encodes both a possible trajectory and a map conditioned on that trajectory. The base estimate of the trajectory is derived from visual odometry, and the map conditioned on that trajectory is a Cartesian grid of elevation variances. In comparison with traditional occupancy or elevation grid maps, the grid elevation variance maps are much better for representing the structure of vegetated or rocky terrain.

  18. Grasp of Consciousness and Performance in Mathematics Making Explicit the Ways of Thinking in Solving Cartesian Product Problems

    ERIC Educational Resources Information Center

    Soares, Maria Tereza Carneiro; Moro, Maria Lucia Faria; Spinillo, Alina Galvao

    2012-01-01

    This study examines the relationship between the grasp of consciousness of the reasoning process in Grades 5 and 8 pupils from a public and a private school, and their performance in mathematical problems of Cartesian product. Forty-two participants aged from 10 to 16 solved four problems in writing and explained their solution procedures by

  19. Advancing Smart Grid Interoperability and Implementing NIST's Interoperability Roadmap

    SciTech Connect

    Basso,T.; DeBlasio, R.

    2010-04-01

    The IEEE American National Standards project P2030TM addressing smart grid interoperability and the IEEE 1547 series of standards addressing distributed resources interconnection with the grid have been identified in priority action plans in the Report to NIST on the Smart Grid Interoperability Standards Roadmap. This paper presents the status of the IEEE P2030 development, the IEEE 1547 series of standards publications and drafts, and provides insight on systems integration and grid infrastructure. The P2030 and 1547 series of standards are sponsored by IEEE Standards Coordinating Committee 21.

  20. Dynamic Power Grid Simulation

    SciTech Connect

    Top, Philip; Woodward, Carol; Smith, Steve; Banks, Lawrence; Kelley, Brian

    2015-09-14

    GridDyn is a part of power grid simulation toolkit. The code is designed using modern object oriented C++ methods utilizing C++11 and recent Boost libraries to ensure compatibility with multiple operating systems and environments.

  1. Method of grid generation

    DOEpatents

    Barnette, Daniel W.

    2002-01-01

    The present invention provides a method of grid generation that uses the geometry of the problem space and the governing relations to generate a grid. The method can generate a grid with minimized discretization errors, and with minimal user interaction. The method of the present invention comprises assigning grid cell locations so that, when the governing relations are discretized using the grid, at least some of the discretization errors are substantially zero. Conventional grid generation is driven by the problem space geometry; grid generation according to the present invention is driven by problem space geometry and by governing relations. The present invention accordingly can provide two significant benefits: more efficient and accurate modeling since discretization errors are minimized, and reduced cost grid generation since less human interaction is required.

  2. Geo-spatial grid-based transformations of precipitation estimates using spatial interpolation methods

    NASA Astrophysics Data System (ADS)

    Teegavarapu, Ramesh S. V.; Meskele, Tadesse; Pathak, Chandra S.

    2012-03-01

    Geo-spatial interpolation methods are often necessary in instances where the precipitation estimates available from multisensor source data on a specific spatial grid need to be transformed to another grid with a different spatial grid or orientation. The study involves development and evaluation of spatial interpolation or weighting methods for transforming hourly multisensor precipitation estimates (MPE) available in the form of 44 km2 HRAP (hydrologic rainfall analysis project) grid to a Cartesian 22 km2 radar (NEXt generation RADar:NEXRAD) grid. Six spatial interpolation weighting methods are developed and evaluated to assess their suitability for transformation of precipitation estimates in space and time. The methods use distances and areal extents of intersection segments of the grids as weights in the interpolation schemes. These methods were applied to transform precipitation estimates from HRAP to NEXRAD grids in the South Florida Water Management District (SFWMD) region in South Florida, United States. A total of 192 rain gauges are used as ground truth to assess the quality of precipitation estimates obtained from these interpolation methods. The rain gauge data in the SFWMD region were also used for radar data bias correction procedures. To help in the assessment, several error measures are calculated and appropriate weighting functions are developed to select the most accurate method for the transformation. Three local interpolation methods out of six methods were found to be competitive and inverse distance based on four nearest neighbors (grids) was found to be the best for the transformation of data.

  3. IPG Power Grid Overview

    NASA Technical Reports Server (NTRS)

    Hinke, Thomas

    2003-01-01

    This presentation will describe what is meant by grids and then cover the current state of the IPG. This will include an overview of the middleware that is key to the operation of the grid. The presentation will then describe some of the future directions that are planned for the IPG. Finally the presentation will conclude with a brief overview of the Global Grid Forum, which is a key activity that will contribute to the successful availability of grid components.

  4. An overset grid method for the study of reflex tearing.

    PubMed

    Maki, K L; Braun, R J; Driscoll, T A; King-Smith, P E

    2008-09-01

    We present an overset grid method to simulate the evolution of human tear film thickness subject to reflex tearing. The free-surface evolution is governed by a single fourth-order non-linear equation derived from lubrication theory with specified film thickness and volume flux at each end. The model arises from considering the limiting case where the surfactant is strongly affecting the surface tension. In numerical simulations, the overset grid is composed of fine boundary grids near the upper and lower eyelids to capture localized capillary thinning referred to as 'black lines' and a Cartesian grid covers the remaining domain. Numerical studies are performed on a non-linear test problem to confirm the accuracy and convergence of the scheme. The computations on the tear film model show qualitative agreement with in vivo tear film thickness measurements. Furthermore, the role of the black lines in the presence of tear supply from the lid margins, reflex tearing, was found to be more subtle than a barrier to tear fluid flow between the anterior of the eye and the meniscus at the lid margin. During reflex tearing, tears may flow through the region normally containing the black line and drift down over the cornea under the influence of gravity. PMID:18628245

  5. Efficient parallel seismic simulations including topography and 3-D material heterogeneities on locally refined composite grids

    NASA Astrophysics Data System (ADS)

    Petersson, Anders; Rodgers, Arthur

    2010-05-01

    The finite difference method on a uniform Cartesian grid is a highly efficient and easy to implement technique for solving the elastic wave equation in seismic applications. However, the spacing in a uniform Cartesian grid is fixed throughout the computational domain, whereas the resolution requirements in realistic seismic simulations usually are higher near the surface than at depth. This can be seen from the well-known formula h ≤ L-P which relates the grid spacing h to the wave length L, and the required number of grid points per wavelength P for obtaining an accurate solution. The compressional and shear wave lengths in the earth generally increase with depth and are often a factor of ten larger below the Moho discontinuity (at about 30 km depth), than in sedimentary basins near the surface. A uniform grid must have a grid spacing based on the small wave lengths near the surface, which results in over-resolving the solution at depth. As a result, the number of points in a uniform grid is unnecessarily large. In the wave propagation project (WPP) code, we address the over-resolution-at-depth issue by generalizing our previously developed single grid finite difference scheme to work on a composite grid consisting of a set of structured rectangular grids of different spacings, with hanging nodes on the grid refinement interfaces. The computational domain in a regional seismic simulation often extends to depth 40-50 km. Hence, using a refinement ratio of two, we need about three grid refinements from the bottom of the computational domain to the surface, to keep the local grid size in approximate parity with the local wave lengths. The challenge of the composite grid approach is to find a stable and accurate method for coupling the solution across the grid refinement interface. Of particular importance is the treatment of the solution at the hanging nodes, i.e., the fine grid points which are located in between coarse grid points. WPP implements a new, energy conserving, coupling procedure for the elastic wave equation at grid refinement interfaces. When used together with our single grid finite difference scheme, it results in a method which is provably stable, without artificial dissipation, for arbitrary heterogeneous isotropic elastic materials. The new coupling procedure is based on satisfying the summation-by-parts principle across refinement interfaces. From a practical standpoint, an important advantage of the proposed method is the absence of tunable numerical parameters, which seldom are appreciated by application experts. In WPP, the composite grid discretization is combined with a curvilinear grid approach that enables accurate modeling of free surfaces on realistic (non-planar) topography. The overall method satisfies the summation-by-parts principle and is stable under a CFL time step restriction. A feature of great practical importance is that WPP automatically generates the composite grid based on the user provided topography and the depths of the grid refinement interfaces. The WPP code has been verified extensively, for example using the method of manufactured solutions, by solving Lamb's problem, by solving various layer over half- space problems and comparing to semi-analytic (FK) results, and by simulating scenario earthquakes where results from other seismic simulation codes are available. WPP has also been validated against seismographic recordings of moderate earthquakes. WPP performs well on large parallel computers and has been run on up to 32,768 processors using about 26 Billion grid points (78 Billion DOF) and 41,000 time steps. WPP is an open source code that is available under the Gnu general public license.

  6. Comparison of coordinate-invariant and coordinate-aligned upwinding for the Euler equations

    NASA Technical Reports Server (NTRS)

    Hartwich, Peter M.

    1993-01-01

    A floating-shock fitting method for the Euler equations has been developed that uses one-sided spatial differences along and across streamlines. This method has been applied to unsteady shocked flow in a duct with a ramp, to supercritical flow over a circular cylinder, and to transonic flow over airfoils. Compared to methods using coordinate-aligned upwind differencing, the coordinate-invariant upwinding generally required fewer grid points to produce crisp shocks and shears. For transonic airfoils, coordinate-invariant upwind differencing advances the agreement between computations and experiment, and it reduces the grid dependency of the computed results for strong shocks. The computational expenditure is comparable to that of coordinate-aligned upwind methods for the Euler equations.

  7. Chimera Grid Tools

    NASA Technical Reports Server (NTRS)

    Chan, William M.; Rogers, Stuart E.; Nash, Steven M.; Buning, Pieter G.; Meakin, Robert

    2005-01-01

    Chimera Grid Tools (CGT) is a software package for performing computational fluid dynamics (CFD) analysis utilizing the Chimera-overset-grid method. For modeling flows with viscosity about geometrically complex bodies in relative motion, the Chimera-overset-grid method is among the most computationally cost-effective methods for obtaining accurate aerodynamic results. CGT contains a large collection of tools for generating overset grids, preparing inputs for computer programs that solve equations of flow on the grids, and post-processing of flow-solution data. The tools in CGT include grid editing tools, surface-grid-generation tools, volume-grid-generation tools, utility scripts, configuration scripts, and tools for post-processing (including generation of animated images of flows and calculating forces and moments exerted on affected bodies). One of the tools, denoted OVERGRID, is a graphical user interface (GUI) that serves to visualize the grids and flow solutions and provides central access to many other tools. The GUI facilitates the generation of grids for a new flow-field configuration. Scripts that follow the grid generation process can then be constructed to mostly automate grid generation for similar configurations. CGT is designed for use in conjunction with a computer-aided-design program that provides the geometry description of the bodies, and a flow-solver program.

  8. Cartesian and polar Schmidt bases for down-converted photons. How high dimensional entanglement protects the shared information from non-ideal measurements

    NASA Astrophysics Data System (ADS)

    Miatto, F. M.; Brougham, T.; Yao, A. M.

    2012-07-01

    We derive an analytical form of the Schmidt modes of spontaneous parametric down-conversion (SPDC) biphotons in both Cartesian and polar coordinates. We show that these correspond to Hermite-Gauss (HG) or Laguerre-Gauss (LG) modes only for a specific value of their width, and we show how such value depends on the experimental parameters. The Schmidt modes that we explicitly derive allow one to set up an optimised projection basis that maximises the mutual information gained from a joint measurement. The possibility of doing so with LG modes makes it possible to take advantage of the properties of orbital angular momentum eigenmodes. We derive a general entropic entanglement measure using the Rényi entropy as a function of the Schmidt number, K, and then retrieve the von Neumann entropy, S. Using the relation between S and K we show that, for highly entangled states, a non-ideal measurement basis does not degrade the number of shared bits by a large extent. More specifically, given a non-ideal measurement which corresponds to the loss of a fraction of the total number of modes, we can quantify the experimental parameters needed to generate an entangled SPDC state with a sufficiently high dimensionality to retain any given fraction of shared bits.

  9. FermiGrid

    SciTech Connect

    Yocum, D.R.; Berman, E.; Canal, P.; Chadwick, K.; Hesselroth, T.; Garzoglio, G.; Levshina, T.; Sergeev, V.; Sfiligoi, I.; Sharma, N.; Timm, S.; /Fermilab

    2007-05-01

    As one of the founding members of the Open Science Grid Consortium (OSG), Fermilab enables coherent access to its production resources through the Grid infrastructure system called FermiGrid. This system successfully provides for centrally managed grid services, opportunistic resource access, development of OSG Interfaces for Fermilab, and an interface to the Fermilab dCache system. FermiGrid supports virtual organizations (VOs) including high energy physics experiments (USCMS, MINOS, D0, CDF, ILC), astrophysics experiments (SDSS, Auger, DES), biology experiments (GADU, Nanohub) and educational activities.

  10. Grid Architecture 2

    SciTech Connect

    Taft, Jeffrey D.

    2016-01-01

    The report describes work done on Grid Architecture under the auspices of the Department of Electricity Office of Electricity Delivery and Reliability in 2015. As described in the first Grid Architecture report, the primary purpose of this work is to provide stakeholder insight about grid issues so as to enable superior decision making on their part. Doing this requires the creation of various work products, including oft-times complex diagrams, analyses, and explanations. This report provides architectural insights into several important grid topics and also describes work done to advance the science of Grid Architecture as well.

  11. Reentry-Vehicle Shape Optimization Using a Cartesian Adjoint Method and CAD Geometry

    NASA Technical Reports Server (NTRS)

    Nemec, Marian; Aftosmis, Michael J.

    2006-01-01

    A DJOINT solutions of the governing flow equations are becoming increasingly important for the development of efficient analysis and optimization algorithms. A well-known use of the adjoint method is gradient-based shape. Given an objective function that defines some measure of performance, such as the lift and drag functionals, its gradient is computed at a cost that is essentially independent of the number of design variables (e.g., geometric parameters that control the shape). Classic aerodynamic applications of gradient-based optimization include the design of cruise configurations for transonic and supersonic flow, as well as the design of high-lift systems. are perhaps the most promising approach for addressing the issues of flow solution automation for aerodynamic design problems. In these methods, the discretization of the wetted surface is decoupled from that of the volume mesh. This not only enables fast and robust mesh generation for geometry of arbitrary complexity, but also facilitates access to geometry modeling and manipulation using parametric computer-aided design (CAD). In previous work on Cartesian adjoint solvers, Melvin et al. developed an adjoint formulation for the TRANAIR code, which is based on the full-potential equation with viscous corrections. More recently, Dadone and Grossman presented an adjoint formulation for the two-dimensional Euler equations using a ghost-cell method to enforce the wall boundary conditions. In Refs. 18 and 19, we presented an accurate and efficient algorithm for the solution of the adjoint Euler equations discretized on Cartesian meshes with embedded, cut-cell boundaries. Novel aspects of the algorithm were the computation of surface shape sensitivities for triangulations based on parametric-CAD models and the linearization of the coupling between the surface triangulation and the cut-cells. The accuracy of the gradient computation was verified using several three-dimensional test cases, which included design variables such as the free stream parameters and the planform shape of an isolated wing. The objective of the present work is to extend our adjoint formulation to problems involving general shape changes. Factors under consideration include the computation of mesh sensitivities that provide a reliable approximation of the objective function gradient, as well as the computation of surface shape sensitivities based on a direct-CAD interface. We present detailed gradient verification studies and then focus on a shape optimization problem for an Apollo-like reentry vehicle. The goal of the optimization is to enhance the lift-to-drag ratio of the capsule by modifying the shape of its heat-shield in conjunction with a center-of-gravity (c.g.) offset. This multipoint and multi-objective optimization problem is used to demonstrate the overall effectiveness of the Cartesian adjoint method for addressing the issues of complex aerodynamic design.

  12. A Highly Accurate Technique for the Treatment of Flow Equations at the Polar Axis in Cylindrical Coordinates Using Series Expansions

    NASA Astrophysics Data System (ADS)

    Constantinescu, G. S.; Lele, S. K.

    2002-11-01

    Numerical methods for solving the flow equations in cylindrical or spherical coordinates should be able to capture the behavior of the exact solution near the regions where the particular form of the governing equations is singular. In this work we focus on the treatment of these numerical singularities for finite-difference methods by reinterpreting the regularity conditions developed in the context of pseudo-spectral methods. A generally applicable numerical method for treating the singularities present at the polar axis, when nonaxisymmetric flows are solved in cylindrical coordinates using highly accurate finite-difference schemes (e.g., Pade schemes) on nonstaggered grids, is presented. Governing equations for the flow at the polar axis are derived using series expansions near r=0. The only information needed to calculate the coefficients in these equations are the values of the flow variables and their radial derivatives at the previous iteration (or time) level. These derivatives, which are multivalued at the polar axis, are calculated without dropping the accuracy of the numerical method using a mapping of the flow domain from (0, R)*(0, 2?) to (- R, R)*(0, ?), where R is the radius of the computational domain. This allows the radial derivatives to be evaluated using high-order differencing schemes (e.g., compact schemes) at points located on the polar axis. The accuracy of the method is checked by comparison with the theoretical solution corresponding to a circular compressible forced jet in the regime of linear growth. The proposed technique is illustrated by results from simulations of laminar-forced jets and turbulent compressible jets using large eddy simulation (LES) methods. In terms of the general robustness of the numerical method and smoothness of the solution close to the polar axis, the present results compare very favorably to similar calculations in which the equations are solved in Cartesian coordinates at the polar a xis, or in which the singularity is removed by employing a staggered mesh in the radial direction without a mesh point at r=0, following the method proposed recently by Mohseni and Colonius [1]. Extension of the method described here for incompressible flows or for any other set of equations that is solved on a nonstaggered mesh in cylindrical or spherical coordinates with finite-difference schemes of various levels of accuracy is immediate.

  13. DSMC Grid Methodologies for Computing Low-Density, Hypersonic Flows About Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Wilmoth, Richard G.; LeBeau, Gerald J.; Carlson, Ann B.

    1996-01-01

    Two different grid methodologies are studied for application to DSMC simulations about reusable launch vehicles. One method uses an unstructured, tetrahedral grid while the other uses a structured, variable-resolution Cartesian grid. The relative merits of each method are discussed in terms of accuracy, computational efficiency, and overall ease of use. Both methods are applied to the computation of a low-density, hypersonic flow about a winged single-stage-to-orbit reusable launch vehicle concept at conditions corresponding to an altitude of 120 km. Both methods are shown to give comparable results for both surface and flowfield quantities as well as for the overall aerodynamic behavior. For the conditions simulated, the flowfield about the vehicle is very rarefied but the DSMC simulations show significant departure from free-molecular predictions for the surface friction and heat transfer as well as certain aerodynamic quantities.

  14. Understanding The Smart Grid

    SciTech Connect

    2007-11-15

    The report provides an overview of what the Smart Grid is and what is being done to define and implement it. The electric industry is preparing to undergo a transition from a centralized, producer-controlled network to a decentralized, user-interactive one. Not only will the technology involved in the electric grid change, but the entire business model of the industry will change too. A major objective of the report is to identify the changes that the Smart Grid will bring about so that industry participants can be prepared to face them. A concise overview of the development of the Smart Grid is provided. It presents an understanding of what the Smart Grid is, what new business opportunities or risks might come about due to its introduction, and what activities are already taking place regarding defining or implementing the Smart Grid. This report will be of interest to the utility industry, energy service providers, aggregators, and regulators. It will also be of interest to home/building automation vendors, information technology vendors, academics, consultants, and analysts. The scope of the report includes an overview of the Smart Grid which identifies the main components of the Smart Grid, describes its characteristics, and describes how the Smart Grid differs from the current electric grid. The overview also identifies the key concepts involved in the transition to the Smart Grid and explains why a Smart Grid is needed by identifying the deficiencies of the current grid and the need for new investment. The report also looks at the impact of the Smart Grid, identifying other industries which have gone through a similar transition, identifying the overall benefits of the Smart Grid, and discussing the impact of the Smart Grid on industry participants. Furthermore, the report looks at current activities to implement the Smart Grid including utility projects, industry collaborations, and government initiatives. Finally, the report takes a look at key technology providers involved in the Smart Grid and provides profiles on them including contact information, company overviews, technology reviews, and key Smart Grid activities.

  15. Noniterative three-dimensional grid generation using parabolic partial differential equations

    NASA Technical Reports Server (NTRS)

    Edwards, T. A.

    1985-01-01

    A new algorithm for generating three-dimensional grids has been developed and implemented which numerically solves a parabolic partial differential equation (PDE). The solution procedure marches outward in two coordinate directions, and requires inversion of a scalar tridiagonal system in the third. Source terms have been introduced to control the spacing and angle of grid lines near the grid boundaries, and to control the outer boundary point distribution. The method has been found to generate grids about 100 times faster than comparable grids generated via solution of elliptic PDEs, and produces smooth grids for finite-difference flow calculations.

  16. Decentralized Service Allocation in a Broker Overlay Based Grid

    NASA Astrophysics Data System (ADS)

    Azab, Abdulrahman; Meling, Hein

    Grid computing is based on coordinated resource sharing in a dynamic environment of multi-institutional virtual organizations. Data exchanges, and service allocation, are challenging problems in the field of Grid computing. This is due to the decentralization of Grid systems. Building decentralized Grid systems with efficient resource management and software component mechanisms is a need for achieving the required efficiency and usability of Grid systems. In this work, a decentralized Grid system model is presented in which, the system is divided into virtual organizations each controlled by a broker. An overlay network of brokers is responsible for global resource management and managing allocation of services. Experimental results show that, the system achieves dependable performance with various loads of services, and broker failures.

  17. Navigation in Grid Space with the NAS Grid Benchmarks

    NASA Technical Reports Server (NTRS)

    Frumkin, Michael; Hood, Robert; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    We present a navigational tool for computational grids. The navigational process is based on measuring the grid characteristics with the NAS Grid Benchmarks (NGB) and using the measurements to assign tasks of a grid application to the grid machines. The tool allows the user to explore the grid space and to navigate the execution at a grid application to minimize its turnaround time. We introduce the notion of gridscape as a user view of the grid and show how it can be me assured by NGB, Then we demonstrate how the gridscape can be used with two different schedulers to navigate a grid application through a rudimentary grid.

  18. Grid enabled Service Support Environment - SSE Grid

    NASA Astrophysics Data System (ADS)

    Goor, Erwin; Paepen, Martine

    2010-05-01

    The SSEGrid project is an ESA/ESRIN project which started in 2009 and is executed by two Belgian companies, Spacebel and VITO, and one Dutch company, Dutch Space. The main project objectives are the introduction of a Grid-based processing on demand infrastructure at the Image Processing Centre for earth observation products at VITO and the inclusion of Grid processing services in the Service Support Environment (SSE) at ESRIN. The Grid-based processing on demand infrastructure is meant to support a Grid processing on demand model for Principal Investigators (PI) and allow the design and execution of multi-sensor applications with geographically spread data while minimising the transfer of huge volumes of data. In the first scenario, 'support a Grid processing on demand model for Principal Investigators', we aim to provide processing power close to the EO-data at the processing and archiving centres. We will allow a PI (non-Grid expert user) to upload his own algorithm, as a process, and his own auxiliary data from the SSE Portal and use them in an earth observation workflow on the SSEGrid Infrastructure. The PI can design and submit workflows using his own processes, processes made available by VITO/ESRIN and possibly processes from other users that are available on the Grid. These activities must be user-friendly and not requiring detailed knowledge about the underlying Grid middleware. In the second scenario we aim to design, implement and demonstrate a methodology to set up an earth observation processing facility, which uses large volumes of data from various geographically spread sensors. The aim is to provide solutions for problems that we face today, like wasting bandwidth by copying large volumes of data to one location. We will avoid this by processing the data where they are. The multi-mission Grid-based processing on demand infrastructure will allow developing and executing complex and massive multi-sensor data (re-)processing applications more efficiently. A workflow can be built and submitted for execution on multiple loosely coupled Grids (e.g. at VITO and at ESRIN). It is ensured that the data are processed where they are located. For this purpose the project aims to upgrade the Service Support Environment (SSE) to integrate multi-Grid processing services to be used by the PI for the systematic processing or reprocessing of EO data. For both scenarios described above, two processing modes will be available. In near real-time (NRT), or 'subscription mode', processing, the execution of a workflow is started but suspended a certain step where the workflow waits until certain data are present on the Grid. As soon as the data become available from the sensors, the execution is resumed automatically. In 'historical mode' it is assumed that the data are already present. An other main objective of the SSEGrid project is to propose new or amended versions of 'Web Processing Service' protocols that may be able to bridge geo-spatial Service Oriented Architectures and Open Grid Services Architectures. In this context we will propose the Grid Web Processing Service as an extension of the OGC WPS service to allow for the dynamic deployment of user processes (workflows or Grid processes) and auxiliary data, for the discovery of user auxiliary data, for the query of process status and process audit (execution trace, log file) and for the notification of process completion or failure.

  19. Coordinate systems integration for development of malaysian craniofacial database.

    PubMed

    Rajion, Zainul; Suwardhi, Deni; Setan, Halim; Chong, Albert; Majid, Zulkepli; Ahmad, Anuar; Rani Samsudin, Ab; Aziz, Izhar; Wan Harun, W A R

    2005-01-01

    This study presents a data registration method for craniofacial spatial data of different modalities. The data consists of three dimensional (3D) vector and raster data models. The data is stored in object relational database. The data capture devices are Laser scanner, CT (Computed Tomography) scan and CR (Close Range) Photogrammetry. The objective of the registration is to transform the data from various coordinate systems into a single 3-D Cartesian coordinate system. The standard error of the registration obtained from multimodal imaging devices using 3D affine transformation is in the ranged of 1-2 mm. This study is a step forward for storing the spatial craniofacial data in one reference system in database. PMID:17281397

  20. Securing smart grid technology

    NASA Astrophysics Data System (ADS)

    Chaitanya Krishna, E.; Kosaleswara Reddy, T.; Reddy, M. YogaTeja; Reddy G. M., Sreerama; Madhusudhan, E.; AlMuhteb, Sulaiman

    2013-03-01

    In the developing countries electrical energy is very important for its all-round improvement by saving thousands of dollars and investing them in other sector for development. For Growing needs of power existing hierarchical, centrally controlled grid of the 20th Century is not sufficient. To produce and utilize effective power supply for industries or people we should have Smarter Electrical grids that address the challenges of the existing power grid. The Smart grid can be considered as a modern electric power grid infrastructure for enhanced efficiency and reliability through automated control, high-power converters, modern communications infrastructure along with modern IT services, sensing and metering technologies, and modern energy management techniques based on the optimization of demand, energy and network availability and so on. The main objective of this paper is to provide a contemporary look at the current state of the art in smart grid communications as well as critical issues on smart grid technologies primarily in terms of information and communication technology (ICT) issues like security, efficiency to communications layer field. In this paper we propose new model for security in Smart Grid Technology that contains Security Module(SM) along with DEM which will enhance security in Grid. It is expected that this paper will provide a better understanding of the technologies, potential advantages and research challenges of the smart grid and provoke interest among the research community to further explore this promising research area.

  1. Time-Accurate Computation of Viscous Flow Around Deforming Bodies Using Overset Grids

    SciTech Connect

    Fast, P; Henshaw, W D

    2001-04-02

    Dynamically evolving boundaries and deforming bodies interacting with a flow are commonly encountered in fluid dynamics. However, the numerical simulation of flows with dynamic boundaries is difficult with current methods. We propose a new method for studying such problems. The key idea is to use the overset grid method with a thin, body-fitted grid near the deforming boundary, while using fixed Cartesian grids to cover most of the computational domain. Our approach combines the strengths of earlier moving overset grid methods for rigid body motion, and unstructured grid methods for Aow-structure interactions. Large scale deformation of the flow boundaries can be handled without a global regridding, and in a computationally efficient way. In terms of computational cost, even a full overset grid regridding is significantly cheaper than a full regridding of an unstructured grid for the same domain, especially in three dimensions. Numerical studies are used to verify accuracy and convergence of our flow solver. As a computational example, we consider two-dimensional incompressible flow past a flexible filament with prescribed dynamics.

  2. Rapid analysis of scattering from periodic dielectric structures using accelerated Cartesian expansions

    DOE PAGESBeta

    Baczewski, Andrew David; Miller, Nicholas C.; Shanker, Balasubramaniam

    2012-03-22

    Here, the analysis of fields in periodic dielectric structures arise in numerous applications of recent interest, ranging from photonic bandgap structures and plasmonically active nanostructures to metamaterials. To achieve an accurate representation of the fields in these structures using numerical methods, dense spatial discretization is required. This, in turn, affects the cost of analysis, particularly for integral-equation-based methods, for which traditional iterative methods require Ο(Ν2) operations, Ν being the number of spatial degrees of freedom. In this paper, we introduce a method for the rapid solution of volumetric electric field integral equations used in the analysis of doubly periodic dielectricmore » structures. The crux of our method is the accelerated Cartesian expansion algorithm, which is used to evaluate the requisite potentials in Ο(Ν) cost. Results are provided that corroborate our claims of acceleration without compromising accuracy, as well as the application of our method to a number of compelling photonics applications.« less

  3. On the Use of CAD and Cartesian Methods for Aerodynamic Optimization

    NASA Technical Reports Server (NTRS)

    Nemec, M.; Aftosmis, M. J.; Pulliam, T. H.

    2004-01-01

    The objective for this paper is to present the development of an optimization capability for Curt3D, a Cartesian inviscid-flow analysis package. We present the construction of a new optimization framework and we focus on the following issues: 1) Component-based geometry parameterization approach using parametric-CAD models and CAPRI. A novel geometry server is introduced that addresses the issue of parallel efficiency while only sparingly consuming CAD resources; 2) The use of genetic and gradient-based algorithms for three-dimensional aerodynamic design problems. The influence of noise on the optimization methods is studied. Our goal is to create a responsive and automated framework that efficiently identifies design modifications that result in substantial performance improvements. In addition, we examine the architectural issues associated with the deployment of a CAD-based approach in a heterogeneous parallel computing environment that contains both CAD workstations and dedicated compute engines. We demonstrate the effectiveness of the framework for a design problem that features topology changes and complex geometry.

  4. Sadness as a passion of the soul: a psychopathological consideration of the Cartesian concept of melancholy.

    PubMed

    López-Muñoz, Francisco; Rubio, Gabriel; Molina, Juan D; Alamo, Cecilio

    2011-04-25

    The relationship between the "passions" (emotions or feelings) and psychopathology has been a constant throughout the history of medicine. In this context, melancholy was considered a perversion of the soul (corruption of the passions). One of the most influential authors on this subject was René Descartes, who discussed it in his work The Treatise on the Passions of the Soul (1649). Descartes believed that "passions" were sensitive movements that the soul experienced due to its union with the body (res extensa). According to this theory, the soul was located in the pineal gland, where it was actively involved in overseeing the functions of the "human machine" and kept its dysfunctions under control, by circulating animal spirits. Descartes described sadness as one of "the six primitive passions of the soul", which leads to melancholy if not remedied. Cartesian theories had a great deal of influence on the way that mental pathologies were considered throughout the entire 17th century (Spinoza, Willis, Pitcairn) and during much of the 18th century (Le Cat, Tissot). From the 19th century onwards, emotional symptomatology finally began to be used in diagnostic criteria for mood disorders. PMID:21315810

  5. A community benchmark for 2-D Cartesian compressible convection in the Earth's mantle

    NASA Astrophysics Data System (ADS)

    King, Scott D.; Lee, Changyeol; van Keken, Peter E.; Leng, Wei; Zhong, Shijie; Tan, Eh; Tosi, Nicola; Kameyama, Masanori C.

    2010-01-01

    Benchmark comparisons are an essential tool to verify the accuracy and validity of computational approaches to mantle convection. Six 2-D Cartesian compressible convection codes are compared for steady-state constant and temperature-dependent viscosity cases as well as time-dependent constant viscosity cases. In general we find good agreement between all codes when comparing average flow characteristics such as Nusselt number and rms velocity. At Rayleigh numbers near 106 and dissipation numbers between 0 and 2, the results differ by approximately 1 per cent. Differences in discretization and use of finite volumes versus finite elements dominate the differences. There is a small systematic difference between the use of the anelastic liquid approximation (ALA) compared to that of the truncated ALA. In determining the onset of time-dependence, there was less agreement between the codes with a spread in the Rayleigh number where the first bifurcation occurs ranging from 7.79 × 105 to 1.05 × 106.

  6. Viability of Bioprinted Cellular Constructs Using a Three Dispenser Cartesian Printer

    PubMed Central

    Dennis, SG.; Trusk, T.; Richards, D.; Jia, J.; Tan, Y.; Mei, Y.; Fann, S.; Markwald, R.; Yost, M.

    2016-01-01

    Tissue engineering has centralized its focus on the construction of replacements for non-functional or damaged tissue. The utilization of three-dimensional bioprinting in tissue engineering has generated new methods for the printing of cells and matrix to fabricate biomimetic tissue constructs. The solid freeform fabrication (SFF) method developed for three-dimensional bioprinting uses an additive manufacturing approach by depositing droplets of cells and hydrogels in a layer-by-layer fashion. Bioprinting fabrication is dependent on the specific placement of biological materials into three-dimensional architectures, and the printed constructs should closely mimic the complex organization of cells and extracellular matrices in native tissue. This paper highlights the use of the Palmetto Printer, a Cartesian bioprinter, as well as the process of producing spatially organized, viable constructs while simultaneously allowing control of environmental factors. This methodology utilizes computer-aided design and computer-aided manufacturing to produce these specific and complex geometries. Finally, this approach allows for the reproducible production of fabricated constructs optimized by controllable printing parameters. PMID:26436877

  7. Progress Towards a Cartesian Cut-Cell Method for Viscous Compressible Flow

    NASA Technical Reports Server (NTRS)

    Berger, Marsha; Aftosmis, Michael J.

    2012-01-01

    We present preliminary development of an approach for simulating high Reynolds number steady compressible flow in two space dimensions using a Cartesian cut-cell finite volume method. We consider both laminar and turbulent flow with both low and high cell Reynolds numbers near the wall. The approach solves the full Navier-Stokes equations in all cells, and uses a wall model to address the resolution requirements near boundaries and to mitigate mesh irregularities in cut cells. We present a quadratic wall model for low cell Reynolds numbers. At high cell Reynolds numbers, the quadratic is replaced with a newly developed analytic wall model stemming from solution of a limiting form of the Spalart-Allmaras turbulence model which features a forward evaluation for flow velocity and exactly matches characteristics of the SA turbulence model in the field. We develop multigrid operators which attain convergence rates similar to inviscid multigrid. Investigations focus on preliminary verification and validation of the method. Flows over flat plates and compressible airfoils show good agreement with both theoretical results and experimental data. Mesh convergence studies on sub- and transonic airfoil flows show convergence of surface pressures with wall spacings as large as approx.0.1% chord. With the current analytic wall model, one or two additional refinements near the wall are required to obtain mesh converged values of skin friction.

  8. Viability of Bioprinted Cellular Constructs Using a Three Dispenser Cartesian Printer.

    PubMed

    Dennis, Sarah Grace; Trusk, Thomas; Richards, Dylan; Jia, Jia; Tan, Yu; Mei, Ying; Fann, Stephen; Markwald, Roger; Yost, Michael

    2015-01-01

    Tissue engineering has centralized its focus on the construction of replacements for non-functional or damaged tissue. The utilization of three-dimensional bioprinting in tissue engineering has generated new methods for the printing of cells and matrix to fabricate biomimetic tissue constructs. The solid freeform fabrication (SFF) method developed for three-dimensional bioprinting uses an additive manufacturing approach by depositing droplets of cells and hydrogels in a layer-by-layer fashion. Bioprinting fabrication is dependent on the specific placement of biological materials into three-dimensional architectures, and the printed constructs should closely mimic the complex organization of cells and extracellular matrices in native tissue. This paper highlights the use of the Palmetto Printer, a Cartesian bioprinter, as well as the process of producing spatially organized, viable constructs while simultaneously allowing control of environmental factors. This methodology utilizes computer-aided design and computer-aided manufacturing to produce these specific and complex geometries. Finally, this approach allows for the reproducible production of fabricated constructs optimized by controllable printing parameters. PMID:26436877

  9. Development of a new two-dimensional Cartesian geometry nodal multigroup discrete-ordinates method

    SciTech Connect

    Pevey, R.E.

    1982-07-01

    The purpose of this work is the development and testing of a new family of methods for calculating the spatial dependence of the neutron density in nuclear systems described in two-dimensional Cartesian geometry. The energy and angular dependence of the neutron density is approximated using the multigroup and discrete ordinates techniques, respectively. The resulting FORTRAN computer code is designed to handle an arbitrary number of spatial, energy, and angle subdivisions. Any degree of scattering anisotropy can be handled by the code for either external source or fission systems. The basic approach is to (1) approximate the spatial variation of the neutron source across each spatial subdivision as an expansion in terms of a user-supplied set of exponential basis functions; (2) solve analytically for the resulting neutron density inside each region; and (3) approximate this density in the basis function space in order to calculate the next iteration flux-dependent source terms. In the general case the calculation is iterative due to neutron sources which depend on the neutron density itself, such as scattering interactions.

  10. Static Analysis of Large-Scale Multibody System Using Joint Coordinates and Spatial Algebra Operator

    PubMed Central

    Omar, Mohamed A.

    2014-01-01

    Initial transient oscillations inhibited in the dynamic simulations responses of multibody systems can lead to inaccurate results, unrealistic load prediction, or simulation failure. These transients could result from incompatible initial conditions, initial constraints violation, and inadequate kinematic assembly. Performing static equilibrium analysis before the dynamic simulation can eliminate these transients and lead to stable simulation. Most exiting multibody formulations determine the static equilibrium position by minimizing the system potential energy. This paper presents a new general purpose approach for solving the static equilibrium in large-scale articulated multibody. The proposed approach introduces an energy drainage mechanism based on Baumgarte constraint stabilization approach to determine the static equilibrium position. The spatial algebra operator is used to express the kinematic and dynamic equations of the closed-loop multibody system. The proposed multibody system formulation utilizes the joint coordinates and modal elastic coordinates as the system generalized coordinates. The recursive nonlinear equations of motion are formulated using the Cartesian coordinates and the joint coordinates to form an augmented set of differential algebraic equations. Then system connectivity matrix is derived from the system topological relations and used to project the Cartesian quantities into the joint subspace leading to minimum set of differential equations. PMID:25045732

  11. Static analysis of large-scale multibody system using joint coordinates and spatial algebra operator.

    PubMed

    Omar, Mohamed A

    2014-01-01

    Initial transient oscillations inhibited in the dynamic simulations responses of multibody systems can lead to inaccurate results, unrealistic load prediction, or simulation failure. These transients could result from incompatible initial conditions, initial constraints violation, and inadequate kinematic assembly. Performing static equilibrium analysis before the dynamic simulation can eliminate these transients and lead to stable simulation. Most exiting multibody formulations determine the static equilibrium position by minimizing the system potential energy. This paper presents a new general purpose approach for solving the static equilibrium in large-scale articulated multibody. The proposed approach introduces an energy drainage mechanism based on Baumgarte constraint stabilization approach to determine the static equilibrium position. The spatial algebra operator is used to express the kinematic and dynamic equations of the closed-loop multibody system. The proposed multibody system formulation utilizes the joint coordinates and modal elastic coordinates as the system generalized coordinates. The recursive nonlinear equations of motion are formulated using the Cartesian coordinates and the joint coordinates to form an augmented set of differential algebraic equations. Then system connectivity matrix is derived from the system topological relations and used to project the Cartesian quantities into the joint subspace leading to minimum set of differential equations. PMID:25045732

  12. Efficient procedure for the numerical calculation of harmonic vibrational frequencies based on internal coordinates

    SciTech Connect

    Miliordos, Evangelos; Xantheas, Sotiris S.

    2013-08-15

    We propose a general procedure for the numerical calculation of the harmonic vibrational frequencies that is based on internal coordinates and Wilson’s GF methodology via double differentiation of the energy. The internal coordinates are defined as the geometrical parameters of a Z-matrix structure, thus avoiding issues related to their redundancy. Linear arrangements of atoms are described with a dummy atom of infinite mass. The procedure has been automated in FORTRAN90 and its main advantage lies in the nontrivial reduction of the number of single point energy calculations needed for the construction of the Hessian matrix when compared to the corresponding number using double differentiation in Cartesian coordinates. For molecules of C1 symmetry the computational savings amount to 36! − 30, where N is the number of atoms, with additional savings when symmetry is present. Typical applications for small and medium size molecules in their minimum and transition state geometries as well as hydrogen bonded clusters are presented. In all cases the frequencies based on internal coordinates differ on average by < 1 cm-1 from those obtained from Cartesian coordinates.

  13. A breakthrough in neuroscience needs a "Nebulous Cartesian System" Oscillations, quantum dynamics and chaos in the brain and vegetative system.

    PubMed

    Başar, Erol; Güntekin, Bahar

    2007-04-01

    The Cartesian System is a fundamental conceptual and analytical framework related and interwoven with the concept and applications of Newtonian Dynamics. In order to analyze quantum processes physicist moved to a Probabilistic Cartesian System in which the causality principle became a probabilistic one. This means the trajectories of particles (obeying quantum rules) can be described only with the concept of cloudy wave packets. The approach to the brain-body-mind problem requires more than the prerequisite of modern physics and quantum dynamics. In the analysis of the brain-body-mind construct we have to include uncertain causalities and consequently multiple uncertain causalities. These multiple causalities originate from (1) nonlinear properties of the vegetative system (e.g. irregularities in biochemical transmitters, cardiac output, turbulences in the vascular system, respiratory apnea, nonlinear oscillatory interactions in peristalsis); (2) nonlinear behavior of the neuronal electricity (e.g. chaotic behavior measured by EEG), (3) genetic modulations, and (4) additional to these physiological entities nonlinear properties of physical processes in the body. The brain shows deterministic chaos with a correlation dimension of approx. D(2)=6, the smooth muscles approx. D(2)=3. According to these facts we propose a hyper-probabilistic approach or a hyper-probabilistic Cartesian System to describe and analyze the processes in the brain-body-mind system. If we add aspects as our sentiments, emotions and creativity to this construct, better said to this already hyper-probabilistic construct, this "New Cartesian System" is more than hyper-probabilistic, it is a nebulous system, we can predict the future only in a nebulous way; however, despite this chain of reasoning we can still provide predictions on brain-body-mind incorporations. We tentatively assume that the processes or mechanisms of the brain-body-mind system can be analyzed and predicted similar to the metaphor of "finding the walking path in a cloudy or foggy day". This is meant by stating "The Nebulous Cartesian System" (NCS). Descartes, at his time undertaking his genius step, did not possess the knowledge of today's physiology and modern physics; we think that the time has come to consider such a New Cartesian System. To deal with this, we propose the utilization of the Heisenberg S-Matrix and a modified version of the Feynman Diagrams which we call "Brain Feynman Diagrams". Another metaphor to consider within the oscillatory approach of the NCS is the "string theory". We also emphasize that fundamental steps should be undertaken in order to create the own dynamical framework of the brain-body-mind incorporation; suggestions or metaphors from physics and mathematics are useful; however, the grammar of the brains intrinsic language must be understood with the help of a new biologically founded, adaptive-probabilistic Cartesian system. This new Cartesian System will undergo mutations and transcend to the philosophy of Henri Bergson in parallel to the Evolution theory of Charles Darwin to open gateways for approaching the brain-body-mind problem. PMID:17049654

  14. Choice of coordinates on a toroidal magnetic surface

    SciTech Connect

    Skovoroda, A. A.

    2008-11-15

    Construction of global angular coordinates on an arbitrarily shaped toroidal surface is considered. It is shown that global orthogonal, isothermal, and semigeodesic geometric coordinates can always be introduced on a toroidal surface. Such coordinates can be rather efficient in solving problems of plasma equilibrium and stability in a magnetic field. At the same time, it is impossible to introduce global geodesic coordinates and coordinates based on curvature lines. It is proposed to use a magnetic analogy to search for transformations of global angular geometric coordinates that simplify the expression for the length element on an arbitrary toroidal surface. An algorithm for the computation of such coordinates is offered. With this approach, a 'virtual' magnetic field such that its force lines, as well as the lines orthogonal to them, are closed is searched for on the toroidal surface. These lines comprise a geometric coordinate grid on an actual magnetic surface formed by the actual magnetic field.

  15. A New Method for Accurate Treatment of Flow Equations in Cylindrical Coordinates Using Series Expansions

    NASA Technical Reports Server (NTRS)

    Constantinescu, G.S.; Lele, S. K.

    2000-01-01

    The motivation of this work is the ongoing effort at the Center for Turbulence Research (CTR) to use large eddy simulation (LES) techniques to calculate the noise radiated by jet engines. The focus on engine exhaust noise reduction is motivated by the fact that a significant reduction has been achieved over the last decade on the other main sources of acoustic emissions of jet engines, such as the fan and turbomachinery noise, which gives increased priority to jet noise. To be able to propose methods to reduce the jet noise based on results of numerical simulations, one first has to be able to accurately predict the spatio-temporal distribution of the noise sources in the jet. Though a great deal of understanding of the fundamental turbulence mechanisms in high-speed jets was obtained from direct numerical simulations (DNS) at low Reynolds numbers, LES seems to be the only realistic available tool to obtain the necessary near-field information that is required to estimate the acoustic radiation of the turbulent compressible engine exhaust jets. The quality of jet-noise predictions is determined by the accuracy of the numerical method that has to capture the wide range of pressure fluctuations associated with the turbulence in the jet and with the resulting radiated noise, and by the boundary condition treatment and the quality of the mesh. Higher Reynolds numbers and coarser grids put in turn a higher burden on the robustness and accuracy of the numerical method used in this kind of jet LES simulations. As these calculations are often done in cylindrical coordinates, one of the most important requirements for the numerical method is to provide a flow solution that is not contaminated by numerical artifacts. The coordinate singularity is known to be a source of such artifacts. In the present work we use 6th order Pade schemes in the non-periodic directions to discretize the full compressible flow equations. It turns out that the quality of jet-noise predictions using these schemes is especially sensitive to the type of equation treatment at the singularity axis. The objective of this work is to develop a generally applicable numerical method for treating the singularities present at the polar axis, which is particularly suitable for highly accurate finite-differences schemes (e.g., Pade schemes) on non-staggered grids. The main idea is to reinterpret the regularity conditions developed in the context of pseudo-spectral methods. A set of exact equations at the singularity axis is derived using the appropriate series expansions for the variables in the original set of equations. The present treatment of the equations preserves the same level of accuracy as for the interior scheme. We also want to point out the wider utility of the method, proposed here in the context of compressible flow equations, as its extension for incompressible flows or for any other set of equations that are solved on a non-staggered mesh in cylindrical coordinates with finite-differences schemes of various level of accuracy is straightforward. The robustness and accuracy of the proposed technique is assessed by comparing results from simulations of laminar forced-jets and turbulent compressible jets using LES with similar calculations in which the equations are solved in Cartesian coordinates at the polar axis, or in which the singularity is removed by employing a staggered mesh in the radial direction without a mesh point at r = 0.

  16. ESA SpaceGRID

    NASA Astrophysics Data System (ADS)

    Perry, C. H.; Dunkin, S.; Grande, M.; Pike, C. D.; Stewart, B.; Beco, S.; SpaceGRID Consortium

    SpaceGRID is an ESA study aimed at identifying the potential benefits of "Grids" to the ESA community and defining a road map for the implementation of this technol- ogy within ESA. Grid technology is an emerging computing infrastructure that is intended to provide uniform access to a set of distributed, networked resources that would otherwise be incompatible. Depending on the Grid application, the resources may be large-scale computational systems, data-archives or shared facilities constituting a collaborative working environment. The SpaceGRID study spans a broad range of domains including Earth Observation, various aspects of spacecraft engineering and Solar System research (solar, STP and planetary). In this presentation we provide an overview of the aims of the SpaceGRID study and report on the requirements analysis for the Solar System research field.

  17. Solar cell grid patterns

    NASA Technical Reports Server (NTRS)

    Yasui, R. K.; Berman, P. A. (Inventor)

    1976-01-01

    A grid pattern is described for a solar cell of the type which includes a semiconductive layer doped to a first polarity and a top counter-doped layer. The grid pattern comprises a plurality of concentric conductive grids of selected geometric shapes which are centered about the center of the exposed active surface of the counter-doped layer. Connected to the grids is one or more conductors which extend to the cell's periphery. For the pattern area, the grids and conductors are arranged in the pattern to minimize the maximum distance which any injected majority carriers have to travel to reach any of the grids or conductors. The pattern has a multiaxes symmetry with respect to the cell center to minimize the maximum temperature differentials between points on the cell surface and to provide a more uniform temperature distribution across the cell face.

  18. Calculation of Water Entry Problem for Free-falling Bodies Using a Developed Cartesian Cut Cell Mesh

    NASA Astrophysics Data System (ADS)

    Wenhua, Wang; Yanying, Wang

    2010-05-01

    This paper describes the development of free surface capturing method on Cartesian cut cell mesh to water entry problem for free-falling bodies with body-fluid interaction. The incompressible Euler equations for a variable density fluid system are presented as governing equations and the free surface is treated as a contact discontinuity by using free surface capturing method. In order to be convenient for dealing with the problem with moving body boundary, the Cartesian cut cell technique is adopted for generating the boundary-fitted mesh around body edge by cutting solid regions out of a background Cartesian mesh. Based on this mesh system, governing equations are discretized by finite volume method, and at each cell edge inviscid flux is evaluated by means of Roe's approximate Riemann solver. Furthermore, for unsteady calculation in time domain, a time accurate solution is achieved by a dual time-stepping technique with artificial compressibility method. For the body-fluid interaction, the projection method of momentum equations and exact Riemann solution are applied in the calculation of fluid pressure on the solid boundary. Finally, the method is validated by test case of water entry for free-falling bodies.

  19. Even-odd mode excitation for stability investigation of Cartesian feedback amplifier used in parallel transmit array.

    PubMed

    Shooshtary, S; Solbach, K

    2015-08-01

    A 7 Tesla Magnetic Resonance Imaging (MRI) system with parallel transmission (pTx) for 32 near-magnet Cartesian feedback loop power amplifiers (PA) with output power of 1kW is under construction at Erwin L. Hahn Institute for Magnetic Resonance Imaging. Variation of load impedance due to mutual coupling of neighborhood coils in the array may lead to instability of the Cartesian feedback loop amplifier. MRI safety requires unconditional stability of the PAs at any load. In order to avoid instability in the pTx system, conditions and limits of stability have to be investigated for every possible excitation mode for the coil array. In this work, an efficient method of stability check for an array of two transmit channels (Tx) with Cartesian feedback loop amplifier and a selective excitation mode for the coil array is proposed which allows extension of stability investigations to a large pTx array with any arbitrary excitation mode for the coil array. PMID:26736573

  20. A grid amplifier

    NASA Technical Reports Server (NTRS)

    Kim, Moonil; Weikle, Robert M., II; Hacker, Jonathan B.; Delisio, Michael P.; Rutledge, David B.; Rosenberg, James J.; Smith, R. P.

    1991-01-01

    A 50-MESFET grid amplifier is reported that has a gain of 11 dB at 3.3 GHz. The grid isolates the input from the output by using vertical polarization for the input beam and horizontal polarization for the transmitted output beam. The grid unit cell is a two-MESFET differential amplifier. A simple calibration procedure allows the gain to be calculated from a relative power measurement. This grid is a hybrid circuit, but the structure is suitable for fabrication as a monolithic wafer-scale integrated circuit, particularly at millimeter wavelengths.

  1. Challenges facing production grids

    SciTech Connect

    Pordes, Ruth; /Fermilab

    2007-06-01

    Today's global communities of users expect quality of service from distributed Grid systems equivalent to that their local data centers. This must be coupled to ubiquitous access to the ensemble of processing and storage resources across multiple Grid infrastructures. We are still facing significant challenges in meeting these expectations, especially in the underlying security, a sustainable and successful economic model, and smoothing the boundaries between administrative and technical domains. Using the Open Science Grid as an example, I examine the status and challenges of Grids operating in production today.

  2. Collaboration in a Wireless Grid Innovation Testbed by Virtual Consortium

    NASA Astrophysics Data System (ADS)

    Treglia, Joseph; Ramnarine-Rieks, Angela; McKnight, Lee

    This paper describes the formation of the Wireless Grid Innovation Testbed (WGiT) coordinated by a virtual consortium involving academic and non-academic entities. Syracuse University and Virginia Tech are primary university partners with several other academic, government, and corporate partners. Objectives include: 1) coordinating knowledge sharing, 2) defining key parameters for wireless grids network applications, 3) dynamically connecting wired and wireless devices, content and users, 4) linking to VT-CORNET, Virginia Tech Cognitive Radio Network Testbed, 5) forming ad hoc networks or grids of mobile and fixed devices without a dedicated server, 6) deepening understanding of wireless grid application, device, network, user and market behavior through academic, trade and popular publications including online media, 7) identifying policy that may enable evaluated innovations to enter US and international markets and 8) implementation and evaluation of the international virtual collaborative process.

  3. On Efficient Parallel Implementation of Moving Body Overset Grid Methods

    NASA Technical Reports Server (NTRS)

    Wissink, Andrew M.; Meakin, Robert L.; Warmbrodt, William (Technical Monitor)

    1997-01-01

    An investigation into the parallel performance of moving-body overset grid methods will be presented. Parallel versions of the OVERFLOW flow solver, DCF3D domain connectivity software, and SIXDO six-degree-of-freedom routine are coupled with an automatic load balance routine and tested for 3D Navier-Stokes calculations on the IBM SP2. The primary source of parallel inefficiency in moving and problems are the domain connectivity costs with DCF 3D. Although this algorithm constitutes a relatively low fraction of the total solution cost (e.g. 10-20%) in calculations on serial machines, the consequently cause a significant degradation in the overall parallel performance. The paper will highlight some approaches for improving the scalability of DCF3D. The paper will present results of a proposed new load balancing scheme that seeks more equal distribution of the inter-grid boundary points in order to more evenly load balance the donor search costs associated with DCF3D. Some preliminary results will also be given from a new solution-adaption algorithm coupled with OVERFLOW which incorporates overset cartesian grids with various levels of refinement. The measured parallel performance from a descending delta-wing configuration and a generic store-separation from a wing/pylon case will be presented.

  4. SAGE - MULTIDIMENSIONAL SELF-ADAPTIVE GRID CODE

    NASA Technical Reports Server (NTRS)

    Davies, C. B.

    1994-01-01

    SAGE, Self Adaptive Grid codE, is a flexible tool for adapting and restructuring both 2D and 3D grids. Solution-adaptive grid methods are useful tools for efficient and accurate flow predictions. In supersonic and hypersonic flows, strong gradient regions such as shocks, contact discontinuities, shear layers, etc., require careful distribution of grid points to minimize grid error and produce accurate flow-field predictions. SAGE helps the user obtain more accurate solutions by intelligently redistributing (i.e. adapting) the original grid points based on an initial or interim flow-field solution. The user then computes a new solution using the adapted grid as input to the flow solver. The adaptive-grid methodology poses the problem in an algebraic, unidirectional manner for multi-dimensional adaptations. The procedure is analogous to applying tension and torsion spring forces proportional to the local flow gradient at every grid point and finding the equilibrium position of the resulting system of grid points. The multi-dimensional problem of grid adaption is split into a series of one-dimensional problems along the computational coordinate lines. The reduced one dimensional problem then requires a tridiagonal solver to find the location of grid points along a coordinate line. Multi-directional adaption is achieved by the sequential application of the method in each coordinate direction. The tension forces direct the redistribution of points to the strong gradient region. To maintain smoothness and a measure of orthogonality of grid lines, torsional forces are introduced that relate information between the family of lines adjacent to one another. The smoothness and orthogonality constraints are direction-dependent, since they relate only the coordinate lines that are being adapted to the neighboring lines that have already been adapted. Therefore the solutions are non-unique and depend on the order and direction of adaption. Non-uniqueness of the adapted grid is acceptable since it makes possible an overall and local error reduction through grid redistribution. SAGE includes the ability to modify the adaption techniques in boundary regions, which substantially improves the flexibility of the adaptive scheme. The vectorial approach used in the analysis also provides flexibility. The user has complete choice of adaption direction and order of sequential adaptions without concern for the computational data structure. Multiple passes are available with no restraint on stepping directions; for each adaptive pass the user can choose a completely new set of adaptive parameters. This facility, combined with the capability of edge boundary control, enables the code to individually adapt multi-dimensional multiple grids. Zonal grids can be adapted while maintaining continuity along the common boundaries. For patched grids, the multiple-pass capability enables complete adaption. SAGE is written in FORTRAN 77 and is intended to be machine independent; however, it requires a FORTRAN compiler which supports NAMELIST input. It has been successfully implemented on Sun series computers, SGI IRIS's, DEC MicroVAX computers, HP series computers, the Cray YMP, and IBM PC compatibles. Source code is provided, but no sample input and output files are provided. The code reads three datafiles: one that contains the initial grid coordinates (x,y,z), one that contains corresponding flow-field variables, and one that contains the user control parameters. It is assumed that the first two datasets are formatted as defined in the plotting software package PLOT3D. Several machine versions of PLOT3D are available from COSMIC. The amount of main memory is dependent on the size of the matrix. The standard distribution medium for SAGE is a 5.25 inch 360K MS-DOS format diskette. It is also available on a .25 inch streaming magnetic tape cartridge in UNIX tar format or on a 9-track 1600 BPI ASCII CARD IMAGE format magnetic tape. SAGE was developed in 1989, first released as a 2D version in 1991 and updated to 3D in 1993.

  5. Newton's "de Gravitatione" Argument: Cartesian Relationalist Dynamics and the Structure of Space and Time

    NASA Astrophysics Data System (ADS)

    Slowik, Edward Steven

    What properties must space, or the modern notion of space-time, possess to allow the development of a coherent description of the natural world? My dissertation explores various aspects of this problem, both as they developed historically in a famous dispute between Descartes and Newton, and as they appear in more modern approaches to mechanics. In an early paper, De gravitatione, Newton presented an argument against Descartes' theory of space and time that has generated much controversy. Descartes had postulated a theory that regards space and time as formed merely from the relations among material bodies; yet, on the other hand, he had appealed to a particle's velocity in his theory of motion. Newton objected, claiming that, in order to define velocity or motion coherently, the natural world must possess a means of identifying the same spatial locations over time (i.e., the places passed by an object must remain fixed in time if the notion of a "change in distance" is to be rendered coherent). However, if space is viewed as a special form of entity with an independent existence, as Newton believed, then the enduring spatial locations required for determining "velocity" make sense. Although philosophers for many years were receptive to Descartes' "relationalist" philosophy, modern research has tended to favor Newton's side of the dispute, for most physical theories rely upon notions of "velocity" or "acceleration" that require an independent space-time backdrop. Nevertheless, not all coherent theories meet Newton's demands--the modern theory of machines (i.e., connected gears) does not; thus, I explore the possibility that Newton's argument could be answered in this vein. My thesis traces through these concerns in great detail, concluding that, despite the appeal of Descartes' rejection of space as an independent entity, Cartesian science is unable to completely resolve the dilemma posed by Newton's argument.

  6. Security for grids

    SciTech Connect

    Humphrey, Marty; Thompson, Mary R.; Jackson, Keith R.

    2005-08-14

    Securing a Grid environment presents a distinctive set of challenges. This paper groups the activities that need to be secured into four categories: naming and authentication; secure communication; trust, policy, and authorization; and enforcement of access control. It examines the current state of the art in securing these processes and introduces new technologies that promise to meet the security requirements of Grids more completely.

  7. Geometric grid generation

    NASA Technical Reports Server (NTRS)

    Ives, David

    1995-01-01

    This paper presents a highly automated hexahedral grid generator based on extensive geometrical and solid modeling operations developed in response to a vision of a designer-driven one day turnaround CFD process which implies a designer-driven one hour grid generation process.

  8. Absolute flatness testing of skip-flat interferometry by matrix analysis in polar coordinates.

    PubMed

    Han, Zhi-Gang; Yin, Lu; Chen, Lei; Zhu, Ri-Hong

    2016-03-20

    A new method utilizing matrix analysis in polar coordinates has been presented for absolute testing of skip-flat interferometry. The retrieval of the absolute profile mainly includes three steps: (1) transform the wavefront maps of the two cavity measurements into data in polar coordinates; (2) retrieve the profile of the reflective flat in polar coordinates by matrix analysis; and (3) transform the profile of the reflective flat back into data in Cartesian coordinates and retrieve the profile of the sample. Simulation of synthetic surface data has been provided, showing the capability of the approach to achieve an accuracy of the order of 0.01 nm RMS. The absolute profile can be retrieved by a set of closed mathematical formulas without polynomial fitting of wavefront maps or the iterative evaluation of an error function, making the new method more efficient for absolute testing. PMID:27140578

  9. Data Grid Implementations

    SciTech Connect

    Moore, Reagan W.; Studham, Ronald S.; Rajasekar, Arcot; Watson, Chip; Stockinger, Heinz; Kunszt, Peter; Charlie Catlett and Ian Foster

    2002-02-27

    Data grids link distributed, heterogeneous storage resources into a coherent data management system. From a user perspective, the data grid provides a uniform name space across the underlying storage systems, while supporting retrieval and storage of files. In the high energy physics community, at least six data grids have been implemented for the storage and distribution of experimental data. Data grids are also being used to support projects as diverse as digital libraries (National Library of Medicine Visible Embryo project), federation of multiple astronomy sky surveys (NSF National Virtual Observatory project), and integration of distributed data sets (Long Term Ecological Reserve). Data grids also form the core interoperability mechanisms for creating persistent archives, in which data collections are migrated to new technologies over time. The ability to provide a uniform name space across multiple administration domains is becoming a critical component of national-scale, collaborative projects.

  10. The SIM astronmetric grid

    NASA Technical Reports Server (NTRS)

    Swartz, R.

    2002-01-01

    The Space Interferometry Mission (SIM) is fundamentally a one-dimensional instrument with a 15-degree field-of-regard. Mission objectives require a global reference grid of thousands of well-understood stars with positions known to 4 microarcseconds which will be used to establish the instrument baseline vector during scientific observations. This accuracy will be achieved by frequently observing a set of stars throughout the mission and performing a global fit of the observations to determine position, proper motion and parallax for each star. Each star will be observed approximately 200 times with about 6.5 stars per single instrument field on the sky. We describe the nature of the reference grid, the candidate objects, and the results of simulations demonstrating grid performance, including estimates of the grid robustness when including effects such as instrument drift and possible contamination of the grid star sample by undetected binaries.

  11. Flexible Residential Smart Grid Simulation Framework

    NASA Astrophysics Data System (ADS)

    Xiang, Wang

    Different scheduling and coordination algorithms controlling household appliances' operations can potentially lead to energy consumption reduction and/or load balancing in conjunction with different electricity pricing methods used in smart grid programs. In order to easily implement different algorithms and evaluate their efficiency against other ideas, a flexible simulation framework is desirable in both research and business fields. However, such a platform is currently lacking or underdeveloped. In this thesis, we provide a simulation framework to focus on demand side residential energy consumption coordination in response to different pricing methods. This simulation framework, equipped with an appliance consumption library using realistic values, aims to closely represent the average usage of different types of appliances. The simulation results of traditional usage yield close matching values compared to surveyed real life consumption records. Several sample coordination algorithms, pricing schemes, and communication scenarios are also implemented to illustrate the use of the simulation framework.

  12. A conservative approach for flow field calculations on multiple grids

    NASA Technical Reports Server (NTRS)

    Kathong, Monchai; Tiwari, Surendra N.

    1988-01-01

    In the computation of flow fields about complex configurations, it is very difficult to construct body-fitted coordinate systems. An alternative approach is to use several grids at once, each of which is generated independently. This procedure is called the multiple grids or zonal grids approach and its applications are investigated in this study. The method follows the conservative approach and provides conservation of fluxes at grid interfaces. The Euler equations are solved numerically on such grids for various configurations. The numerical scheme used is the finite-volume technique with a three-state Runge-Kutta time integration. The code is vectorized and programmed to run on the CDC VPS-32 computer. Some steady state solutions of the Euler equations are presented and discussed.

  13. Decentral Smart Grid Control

    NASA Astrophysics Data System (ADS)

    Schäfer, Benjamin; Matthiae, Moritz; Timme, Marc; Witthaut, Dirk

    2015-01-01

    Stable operation of complex flow and transportation networks requires balanced supply and demand. For the operation of electric power grids—due to their increasing fraction of renewable energy sources—a pressing challenge is to fit the fluctuations in decentralized supply to the distributed and temporally varying demands. To achieve this goal, common smart grid concepts suggest to collect consumer demand data, centrally evaluate them given current supply and send price information back to customers for them to decide about usage. Besides restrictions regarding cyber security, privacy protection and large required investments, it remains unclear how such central smart grid options guarantee overall stability. Here we propose a Decentral Smart Grid Control, where the price is directly linked to the local grid frequency at each customer. The grid frequency provides all necessary information about the current power balance such that it is sufficient to match supply and demand without the need for a centralized IT infrastructure. We analyze the performance and the dynamical stability of the power grid with such a control system. Our results suggest that the proposed Decentral Smart Grid Control is feasible independent of effective measurement delays, if frequencies are averaged over sufficiently large time intervals.

  14. A Highly Accurate Technique for the Treatment of Flow Equations at the Polar Axis in Cylindrical Coordinates using Series Expansions. Appendix A

    NASA Technical Reports Server (NTRS)

    Constantinescu, George S.; Lele, S. K.

    2001-01-01

    Numerical methods for solving the flow equations in cylindrical or spherical coordinates should be able to capture the behavior of the exact solution near the regions where the particular form of the governing equations is singular. In this work we focus on the treatment of these numerical singularities for finite-differences methods by reinterpreting the regularity conditions developed in the context of pseudo-spectral methods. A generally applicable numerical method for treating the singularities present at the polar axis, when nonaxisymmetric flows are solved in cylindrical, coordinates using highly accurate finite differences schemes (e.g., Pade schemes) on non-staggered grids, is presented. Governing equations for the flow at the polar axis are derived using series expansions near r=0. The only information needed to calculate the coefficients in these equations are the values of the flow variables and their radial derivatives at the previous iteration (or time) level. These derivatives, which are multi-valued at the polar axis, are calculated without dropping the accuracy of the numerical method using a mapping of the flow domain from (0,R)*(0,2pi) to (-R,R)*(0,pi), where R is the radius of the computational domain. This allows the radial derivatives to be evaluated using high-order differencing schemes (e.g., compact schemes) at points located on the polar axis. The proposed technique is illustrated by results from simulations of laminar-forced jets and turbulent compressible jets using large eddy simulation (LES) methods. In term of the general robustness of the numerical method and smoothness of the solution close to the polar axis, the present results compare very favorably to similar calculations in which the equations are solved in Cartesian coordinates at the polar axis, or in which the singularity is removed by employing a staggered mesh in the radial direction without a mesh point at r=0, following the method proposed recently by Mohseni and Colonius (1). Extension of the method described here for incompressible flows or for any other set of equations that are solved on a non-staggered mesh in cylindrical or spherical coordinates with finite-differences schemes of various level of accuracy is immediate.

  15. Parallel grid library for rapid and flexible simulation development

    NASA Astrophysics Data System (ADS)

    Honkonen, I.; von Alfthan, S.; Sandroos, A.; Janhunen, P.; Palmroth, M.

    2013-04-01

    We present an easy to use and flexible grid library for developing highly scalable parallel simulations. The distributed cartesian cell-refinable grid (dccrg) supports adaptive mesh refinement and allows an arbitrary C++ class to be used as cell data. The amount of data in grid cells can vary both in space and time allowing dccrg to be used in very different types of simulations, for example in fluid and particle codes. Dccrg transfers the data between neighboring cells on different processes transparently and asynchronously allowing one to overlap computation and communication. This enables excellent scalability at least up to 32 k cores in magnetohydrodynamic tests depending on the problem and hardware. In the version of dccrg presented here part of the mesh metadata is replicated between MPI processes reducing the scalability of adaptive mesh refinement (AMR) to between 200 and 600 processes. Dccrg is free software that anyone can use, study and modify and is available at https://gitorious.org/dccrg. Users are also kindly requested to cite this work when publishing results obtained with dccrg. Catalogue identifier: AEOM_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEOM_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: GNU Lesser General Public License version 3 No. of lines in distributed program, including test data, etc.: 54975 No. of bytes in distributed program, including test data, etc.: 974015 Distribution format: tar.gz Programming language: C++. Computer: PC, cluster, supercomputer. Operating system: POSIX. The code has been parallelized using MPI and tested with 1-32768 processes RAM: 10 MB-10 GB per process Classification: 4.12, 4.14, 6.5, 19.3, 19.10, 20. External routines: MPI-2 [1], boost [2], Zoltan [3], sfc++ [4] Nature of problem: Grid library supporting arbitrary data in grid cells, parallel adaptive mesh refinement, transparent remote neighbor data updates and load balancing. Solution method: The simulation grid is represented by an adjacency list (graph) with vertices stored into a hash table and edges into contiguous arrays. Message Passing Interface standard is used for parallelization. Cell data is given as a template parameter when instantiating the grid. Restrictions: Logically cartesian grid. Running time: Running time depends on the hardware, problem and the solution method. Small problems can be solved in under a minute and very large problems can take weeks. The examples and tests provided with the package take less than about one minute using default options. In the version of dccrg presented here the speed of adaptive mesh refinement is at most of the order of 106 total created cells per second. http://www.mpi-forum.org/. http://www.boost.org/. K. Devine, E. Boman, R. Heaphy, B. Hendrickson, C. Vaughan, Zoltan data management services for parallel dynamic applications, Comput. Sci. Eng. 4 (2002) 90-97. http://dx.doi.org/10.1109/5992.988653. https://gitorious.org/sfc++.

  16. Grid Computing Education Support

    SciTech Connect

    Steven Crumb

    2008-01-15

    The GGF Student Scholar program enabled GGF the opportunity to bring over sixty qualified graduate and under-graduate students with interests in grid technologies to its three annual events over the three-year program.

  17. Space Development Grid Portal

    NASA Technical Reports Server (NTRS)

    Vaziri, Arsi

    2004-01-01

    This viewgraph presentation provides information on the development of a portal to provide secure and distributed grid computing for Payload Operations Integrated Center and Mission Control Center ground services.

  18. IDL Grid Web Portal

    NASA Astrophysics Data System (ADS)

    Massimino, P.; Costa, A.

    2008-08-01

    Image Data Language is a software for data analysis, visualization and cross-platform application development. The potentiality of IDL is well-known in the academic scientific world, especially in the astronomical environment where thousands of procedures are developed by using IDL. The typical use of IDL is the interactive mode but it is also possible to run IDL programs that do not require any interaction with the user, submitting them in batch or background modality. Through the interactive mode the user immediately receives images or other data produced in the running phase of the program; in batch or background mode, the user will have to wait for the end of the program, sometime for many hours or days to obtain images or data that IDL produced as output: in fact in Grid environment it is possible to access to or retrieve data only after completion of the program. The work that we present gives flexibility to IDL procedures submitted to the Grid computer infrastructure. For this purpose we have developed an IDL Grid Web Portal to allow the user to access the Grid and to submit IDL programs granting a full job control and the access to images and data generated during the running phase, without waiting for their completion. We have used the PHP technology and we have given the same level of security that Grid normally offers to its users. In this way, when the user notices that the intermediate program results are not those expected, he can stop the job, change the parameters to better satisfy the computational algorithm and resubmit the program, without consuming the CPU time and other Grid resources. The IDL Grid Web Portal allows you to obtain IDL generated images, graphics and data tables by using a normal browser. All conversations from the user and the Grid resources occur via Web, as well as authentication phases. The IDL user has not to change the program source much because the Portal will automatically introduce the appropriate modification before submitting the IDL program to the Grid. When the user wishes, he will be able to check the status of his program and outputs, if any, because the Portal will assign the users a specific and univocal session identification number. This Web portal runs in the Trinacria Grid Virtual Laboratory and fully exploits the power of this grid in terms of CPU and data storage.

  19. Implementing Production Grids

    NASA Technical Reports Server (NTRS)

    Johnston, William E.; Ziobarth, John (Technical Monitor)

    2002-01-01

    We have presented the essence of experience gained in building two production Grids, and provided some of the global context for this work. As the reader might imagine, there were a lot of false starts, refinements to the approaches and to the software, and several substantial integration projects (SRB and Condor integrated with Globus) to get where we are today. However, the point of this paper is to try and make it substantially easier for others to get to the point where Information Power Grids (IPG) and the DOE Science Grids are today. This is what is needed in order to move us toward the vision of a common cyber infrastructure for science. The author would also like to remind the readers that this paper primarily represents the actual experiences that resulted from specific architectural and software choices during the design and implementation of these two Grids. The choices made were dictated by the criteria laid out in section 1. There is a lot more Grid software available today that there was four years ago, and various of these packages are being integrated into IPG and the DOE Grids. However, the foundation choices of Globus, SRB, and Condor would not be significantly different today than they were four years ago. Nonetheless, if the GGF is successful in its work - and we have every reason to believe that it will be - then in a few years we will see that the 28 functions provided by these packages will be defined in terms of protocols and MIS, and there will be several robust implementations available for each of the basic components, especially the Grid Common Services. The impact of the emerging Web Grid Services work is not yet clear. It will likely have a substantial impact on building higher level services, however it is the opinion of the author that this will in no way obviate the need for the Grid Common Services. These are the foundation of Grids, and the focus of almost all of the operational and persistent infrastructure aspects of Grids.

  20. Random array grid collimator

    DOEpatents

    Fenimore, E.E.

    1980-08-22

    A hexagonally shaped quasi-random no-two-holes touching grid collimator. The quasi-random array grid collimator eliminates contamination from small angle off-axis rays by using a no-two-holes-touching pattern which simultaneously provides for a self-supporting array increasng throughput by elimination of a substrate. The presentation invention also provides maximum throughput using hexagonally shaped holes in a hexagonal lattice pattern for diffraction limited applications. Mosaicking is also disclosed for reducing fabrication effort.

  1. Grid in Geosciences

    NASA Astrophysics Data System (ADS)

    Petitdidier, Monique; Schwichtenberg, Horst

    2010-05-01

    The worldwide Earth science community covers a mosaic of disciplines and players such as academia, industry, national surveys, international organizations, and so forth. It provides a scientific basis for addressing societal issues, which require that the Earth science community utilize massive amounts of data, both in real and remote time. This data is usually distributed among many different organizations and data centers. These facts, the utilization of massive, distributed data amounts, explain the interest of the Earth science community for Grid technology, also noticeable by the variety of applications ported and tools developed. In parallel to the participation in EGEE, other projects involving ES disciplines were or have been carried out as related projects to EGEE (Enabling Grids for E-sciencE) such as CYCLOPS, SEEGrid, EELA2, EUASIA or outside e.g., in the framework of WGISS/CEOS. Numerous applications in atmospheric chemistry, meteorology, seismology, hydrology, pollution, climate and biodiversity were deployed successfully on Grid. In order to fulfill requirements of risk management, several prototype applications have been deployed using OGC (Open geospatial Consortium) components with Grid middleware. Examples are in hydrology for flood or Black Sea Catchment monitoring, and in fire monitoring. Meteorological, pollution and climate applications are based on meteorological models ported on Grid such as MM5 (Mesoscale Model), WRF (Weather Research and Forecasting), RAMS (Regional Atmospheric Modeling System) or CAM (Community Atmosphere Model). Seismological applications on Grid are numerous in locations where their occurrence is important and computer resources too small; then interfaces and gateways have been developed to facilitate the access to data and specific software and avoid work duplication. A portal has been deployed for commercial seismological software, Geocluster, for academic users. In this presentation examples of such applications will be presented to point out the potentiality of Grid for research and operation. Grid provides large amount of compute resources but is also an interesting e-collaboration platform, important for geosciences projects.

  2. Movement and Coordination

    MedlinePlus

    ... will seem to be continually on the go—running, kicking, climbing, jumping. His attention span, which was ... his coordination. In the months ahead, your child’s running will become smoother and more coordinated. He’ll ...

  3. Exploring Hypersonic, Unstructured-Grid Issues through Structured Grids

    NASA Technical Reports Server (NTRS)

    Mazaheri, Ali R.; Kleb, Bill

    2007-01-01

    Pure-tetrahedral unstructured grids have been shown to produce asymmetric heat transfer rates for symmetric problems. Meanwhile, two-dimensional structured grids produce symmetric solutions and as documented here, introducing a spanwise degree of freedom to these structured grids also yields symmetric solutions. The effects of grid skewness and other perturbations of structured-grids are investigated to uncover possible mechanisms behind the unstructured-grid solution asymmetries. By using controlled experiments around a known, good solution, the effects of particular grid pathologies are uncovered. These structured-grid experiments reveal that similar solution degradation occurs as for unstructured grids, especially for heat transfer rates. Non-smooth grids within the boundary layer is also shown to produce large local errors in heat flux but do not affect surface pressures.

  4. Using Grid Benchmarks for Dynamic Scheduling of Grid Applications

    NASA Technical Reports Server (NTRS)

    Frumkin, Michael; Hood, Robert

    2003-01-01

    Navigation or dynamic scheduling of applications on computational grids can be improved through the use of an application-specific characterization of grid resources. Current grid information systems provide a description of the resources, but do not contain any application-specific information. We define a GridScape as dynamic state of the grid resources. We measure the dynamic performance of these resources using the grid benchmarks. Then we use the GridScape for automatic assignment of the tasks of a grid application to grid resources. The scalability of the system is achieved by limiting the navigation overhead to a few percent of the application resource requirements. Our task submission and assignment protocol guarantees that the navigation system does not cause grid congestion. On a synthetic data mining application we demonstrate that Gridscape-based task assignment reduces the application tunaround time.

  5. Generation of Surface Coordinates by Elliptic Partial Differential Equations

    NASA Technical Reports Server (NTRS)

    Warsi, Z. U. A.

    1985-01-01

    The problem of generating spatial coordinates by numerical methods through carefully selected mathematical models is of current interest both in mechanics and physics. The problem of generation of a desired system of coordinates in a given surface was considered, which essentially is an effort directed to the problem of grid generation in a two-dimensional non-Euclidean space. The mathematical model selected for this purpose is based on the formulae of Gauss for a surface. The proposed equations can be used to generate a new coordinate system from the data of an already given coordinate system in a surface. If the coefficients of the first and second fundamental forms have been given, then the proposed equations can be used to generate a surface satisfying the given data (surface fitting). The proposed equations can also be used to generate surfaces in the space between two arbitrary given surfaces, thus providing 3D grids in an Euclidean space.

  6. On the use of a high order overlapping grid method for coupling in CFD/CAA

    NASA Astrophysics Data System (ADS)

    Desquesnes, G.; Terracol, M.; Manoha, E.; Sagaut, P.

    2006-12-01

    This paper presents a theoretical analysis and two applications of a high-order overlapping grid method for coupling Cartesian and curvilinear grids, developed in order to simulate aerodynamic noise. First, the overlapping grid method based on Lagrange interpolating polynomials is described and a theoretical analysis of the interpolation operator is then carried out. It shows that the interpolation generates spurious modes that depend on the wavenumbers of the signal. Besides it also gives the optimal conditions in which interpolation can be applied. Then an application to the simulation of the aeroacoustic noise generated by the vortex shedding behind a cylinder is presented. During this simulation, it appears that interpolation can create some spurious acoustic modes in regions where hydrodynamic fluctuations are significant, as predicted by the theoretical analysis. It is shown that these spurious modes disappear when a refined Cartesian grid is used (26 points per wavelength of the vortex shedding were found to be adequate in this study). At last, the simulation of the aerodynamic noise of a three element high-lift wing profile has then been carried out. For this application, the main acoustic source at the slat trailing edge is represented analytically. The propagation of the generated acoustic wave is simulated with a mean flow at rest and with a steady turbulent mean flow computed by RANS. The first application allows us to assess the method by comparing the results to a reference solution. The second one shows that the influence of a non-uniform mean flow on the directivity of an acoustic source can be observed in complex geometries. This application therefore shows that the proposed coupling method is well adapted to complex geometries that are usually met in industrial applications.

  7. Grid generation strategies for turbomachinery configurations

    NASA Astrophysics Data System (ADS)

    Lee, K. D.; Henderson, T. L.

    1991-01-01

    Turbomachinery flow fields involve unique grid generation issues due to their geometrical and physical characteristics. Several strategic approaches are discussed to generate quality grids. The grid quality is further enhanced through blending and adapting. Grid blending smooths the grids locally through averaging and diffusion operators. Grid adaptation redistributes the grid points based on a grid quality assessment. These methods are demonstrated with several examples.

  8. GRIDS: Grid-Scale Rampable Intermittent Dispatchable Storage

    SciTech Connect

    2010-09-01

    GRIDS Project: The 12 projects that comprise ARPA-E’s GRIDS Project, short for “Grid-Scale Rampable Intermittent Dispatchable Storage,” are developing storage technologies that can store renewable energy for use at any location on the grid at an investment cost less than $100 per kilowatt hour. Flexible, large-scale storage would create a stronger and more robust electric grid by enabling renewables to contribute to reliable power generation.

  9. Arc Length Based Grid Distribution For Surface and Volume Grids

    NASA Technical Reports Server (NTRS)

    Mastin, C. Wayne

    1996-01-01

    Techniques are presented for distributing grid points on parametric surfaces and in volumes according to a specified distribution of arc length. Interpolation techniques are introduced which permit a given distribution of grid points on the edges of a three-dimensional grid block to be propagated through the surface and volume grids. Examples demonstrate how these methods can be used to improve the quality of grids generated by transfinite interpolation.

  10. Processing Coordination Ambiguity

    ERIC Educational Resources Information Center

    Engelhardt, Paul E.; Ferreira, Fernanda

    2010-01-01

    We examined temporarily ambiguous coordination structures such as "put the butter in the bowl and the pan on the towel." Minimal Attachment predicts that the ambiguous noun phrase "the pan" will be interpreted as a noun-phrase coordination structure because it is syntactically simpler than clausal coordination. Constraint-based theories assume…

  11. The Benefits of Grid Networks

    ERIC Educational Resources Information Center

    Tennant, Roy

    2005-01-01

    In the article, the author talks about the benefits of grid networks. In speaking of grid networks the author is referring to both networks of computers and networks of humans connected together in a grid topology. Examples are provided of how grid networks are beneficial today and the ways in which they have been used.

  12. Unstructured Grids on NURBS Surfaces

    NASA Technical Reports Server (NTRS)

    Samareh-Abolhassani, Jamshid

    1993-01-01

    A simple and efficient computational method is presented for unstructured surface grid generation. This method is built upon an advancing front technique combined with grid projection. The projection technique is based on a Newton-Raphson method. This combined approach has been successfully implemented for structured and unstructured grids. In this paper, the implementation for unstructured grid is discussed.

  13. Smart Grid Integration Laboratory

    SciTech Connect

    Troxell, Wade

    2011-12-22

    The initial federal funding for the Colorado State University Smart Grid Integration Laboratory is through a Congressionally Directed Project (CDP), DE-OE0000070 Smart Grid Integration Laboratory. The original program requested in three one-year increments for staff acquisition, curriculum development, and instrumentation all which will benefit the Laboratory. This report focuses on the initial phase of staff acquisition which was directed and administered by DOE NETL/ West Virginia under Project Officer Tom George. Using this CDP funding, we have developed the leadership and intellectual capacity for the SGIC. This was accomplished by investing (hiring) a core team of Smart Grid Systems engineering faculty focused on education, research, and innovation of a secure and smart grid infrastructure. The Smart Grid Integration Laboratory will be housed with the separately funded Integrid Laboratory as part of CSU's overall Smart Grid Integration Center (SGIC). The period of performance of this grant was 10/1/2009 to 9/30/2011 which included one no cost extension due to time delays in faculty hiring. The Smart Grid Integration Laboratory's focus is to build foundations to help graduate and undergraduates acquire systems engineering knowledge; conduct innovative research; and team externally with grid smart organizations. Using the results of the separately funded Smart Grid Workforce Education Workshop (May 2009) sponsored by the City of Fort Collins, Northern Colorado Clean Energy Cluster, Colorado State University Continuing Education, Spirae, and Siemens has been used to guide the hiring of faculty, program curriculum and education plan. This project develops faculty leaders with the intellectual capacity to inspire its students to become leaders that substantially contribute to the development and maintenance of Smart Grid infrastructure through topics such as: (1) Distributed energy systems modeling and control; (2) Energy and power conversion; (3) Simulation of electrical power distribution system that integrates significant quantities of renewable and distributed energy resources; (4) System dynamic modeling that considers end-user behavior, economics, security and regulatory frameworks; (5) Best practices for energy management IT control solutions for effective distributed energy integration (including security with the underlying physical power systems); (6) Experimental verification of effects of various arrangements of renewable generation, distributed generation and user load types along with conventional generation and transmission. Understanding the core technologies for enabling them to be used in an integrated fashion within a distribution network remains is a benefit to the future energy paradigm and future and present energy engineers.

  14. Numerical methods for solid mechanics on overlapping grids: Linear elasticity

    NASA Astrophysics Data System (ADS)

    Appelö, Daniel; Banks, Jeffrey W.; Henshaw, William D.; Schwendeman, Donald W.

    2012-07-01

    This paper presents a new computational framework for the simulation of solid mechanics on general overlapping grids with adaptive mesh refinement (AMR). The approach, described here for time-dependent linear elasticity in two and three space dimensions, is motivated by considerations of accuracy, efficiency and flexibility. We consider two approaches for the numerical solution of the equations of linear elasticity on overlapping grids. In the first approach we solve the governing equations numerically as a second-order system (SOS) using a conservative finite-difference approximation. The second approach considers the equations written as a first-order system (FOS) and approximates them using a second-order characteristic-based (Godunov) finite-volume method. A principal aim of the paper is to present the first careful assessment of the accuracy and stability of these two representative schemes for the equations of linear elasticity on overlapping grids. This is done by first performing a stability analysis of analogous schemes for the first-order and second-order scalar wave equations on an overlapping grid. The analysis shows that non-dissipative approximations can have unstable modes with growth rates proportional to the inverse of the mesh spacing. This new result, which is relevant for the numerical solution of any type of wave propagation problem on overlapping grids, dictates the form of dissipation that is needed to stabilize the scheme. Numerical experiments show that the addition of the indicated form of dissipation and/or a separate filter step can be used to stabilize the SOS scheme. They also demonstrate that the upwinding inherent in the Godunov scheme, which provides dissipation of the appropriate form, stabilizes the FOS scheme. We then verify and compare the accuracy of the two schemes using the method of analytic solutions and using problems with known solutions. These latter problems provide useful benchmark solutions for time dependent elasticity. We also consider two problems in which exact solutions are not available, and use a posterior error estimates to assess the accuracy of the schemes. One of these two problems is additionally employed to demonstrate the use of dynamic AMR and its effectiveness for resolving elastic “shock” waves. Finally, results are presented that compare the computational performance of the two schemes. These demonstrate the speed and memory efficiency achieved by the use of structured overlapping grids and optimizations for Cartesian grids.

  15. Symmetrizing grids, radial basis functions, and Chebyshev and Zernike polynomials for the D4 symmetry group; Interpolation within a squircle, Part I

    NASA Astrophysics Data System (ADS)

    Li, Shan; Boyd, John P.

    2014-02-01

    A domain is invariant under the eight-element D4 symmetry group if it is unchanged by reflection with respect to the x and y axes and also the diagonal line x=y. Previous treatments of group theory for spectral methods have generally demanded a semester's worth of group theory. We show this is unnecessary by providing explicit recipes for creating grids, etc. We show how to decompose an arbitrary function into six symmetry-invariant components, and thereby split the interpolation problem into six independent subproblems. We also show how to make symmetry-invariant basis functions from products of Chebyshev polynomials, from Zernike polynomials and from radial basis functions (RBFs) of any species. These recipes are completely general, and apply to any domain that is invariant under the dihedral group D4. These concepts are illustrated by RBF pseudospectral solutions of the Poisson equation in a domain bounded by a squircle, the square-with-rounded corners defined by x2ν+y2ν-1=0 where here ν=2. We also apply Chebyshev polynomials to compute eigenmodes of the Helmholtz equation on the square and show each mode belongs to one and only one of the six D4 classes. [F. Albert Cotton, in: Chemical Applications of Group Theory, John Wiley, New York, 1963, p. vii]Cartesian coordinates. Znm(x,y), the Zernike polynomials. Radial basis functions (RBFs). We shall show how to rearrange each basis into six disjoint sets which are eigenfunctions of the operations of the group. We shall then explain how the interpolation problem with N points can be split into four problems of size N/8 and two problems of size N/4 with an enormous reduction of cost.First, though, we shall provide a brief overview of the D4 symmetry group.

  16. Compressed Sensing Of Complex Sinusoids Off The Grid

    NASA Astrophysics Data System (ADS)

    Ping, Cheng; Liu, Shi; Jiaqun, Zhao

    2015-07-01

    To solve off-grid problem in compressed sensing, a new reconstruction algorithm for complex sinusoids is proposed. The compressed sensing reconstruction problem is transformed into a joint optimized problem. Based on coordinate descent approach and linear estimator, a new iteration algorithm is proposed. The results of experiments verify the effectiveness of the proposed method.

  17. PDEs on moving surfaces via the closest point method and a modified grid based particle method

    NASA Astrophysics Data System (ADS)

    Petras, A.; Ruuth, S. J.

    2016-05-01

    Partial differential equations (PDEs) on surfaces arise in a wide range of applications. The closest point method (Ruuth and Merriman (2008) [20]) is a recent embedding method that has been used to solve a variety of PDEs on smooth surfaces using a closest point representation of the surface and standard Cartesian grid methods in the embedding space. The original closest point method (CPM) was designed for problems posed on static surfaces, however the solution of PDEs on moving surfaces is of considerable interest as well. Here we propose solving PDEs on moving surfaces using a combination of the CPM and a modification of the grid based particle method (Leung and Zhao (2009) [12]). The grid based particle method (GBPM) represents and tracks surfaces using meshless particles and an Eulerian reference grid. Our modification of the GBPM introduces a reconstruction step into the original method to ensure that all the grid points within a computational tube surrounding the surface are active. We present a number of examples to illustrate the numerical convergence properties of our combined method. Experiments for advection-diffusion equations that are strongly coupled to the velocity of the surface are also presented.

  18. A unified formulation for the three-dimensional shallow water equations using orthogonal co-ordinates: theory and application

    NASA Astrophysics Data System (ADS)

    Kernkamp, Herman W. J.; Petit, Henri A. H.; Gerritsen, Herman; de Goede, Erik D.

    2005-12-01

    In this paper, the formulations of the primitive equations for shallow water flow in various horizontal co-ordinate systems and the associated finite difference grid options used in shallow water flow modelling are reviewed. It is observed that horizontal co-ordinate transformations do not affect the chosen co-ordinate system and representation in the vertical, and are the same for the three- and two-dimensional cases. A systematic derivation of the equations in tensor notation is presented, resulting in a unified formulation for the shallow water equations that covers all orthogonal horizontal grid types of practical interest. This includes spherical curvilinear orthogonal co-ordinate systems on the globe. Computational efficiency can be achieved in a single computer code. Furthermore, a single numerical algorithmic code implementation satisfies. All co-ordinate system specific metrics are determined as part of a computer-aided model grid design, which supports all four orthogonal grid types. Existing intuitive grid design and visual interpretation is conserved by appropriate conformal mappings, which conserve spherical orthogonality in planar representation. A spherical curvilinear co-ordinate solution of wind driven steady channel flow applying a strongly distorted grid is shown to give good agreement with a regular spherical co-ordinate model approach and the solution based on a β-plane approximation. Especially designed spherical curvilinear boundary fitted model grids are shown for typhoon surge propagation in the South China Sea and for ocean-driven flows through Malacca Straits. By using spherical curvilinear grids the number of grid points in these single model grid applications is reduced by a factor of 50-100 in comparison with regular spherical grids that have the same horizontal resolution in the area of interest. The spherical curvilinear approach combines the advantages of the various grid approaches, while the overall computational effort remains acceptable for very large model domains.

  19. GridLAB-D/SG

    Energy Science and Technology Software Center (ESTSC)

    2011-08-30

    GridLAB-D is a new power system simulation tool that provides valuable information to users who design and operate electric power transmission and distribution systems, and to utilities that wish to take advantage of the latest smart grid technology. This special release of GridLAB-D was developed to study the proposed Smart Grid technology that is used by Battelle Memorial Institute in the AEP gridSMART demonstration project in Northeast Columbus, Ohio.

  20. Movement Coordination during Conversation

    PubMed Central

    Latif, Nida; Barbosa, Adriano V.; Vatiokiotis-Bateson, Eric; Castelhano, Monica S.; Munhall, K. G.

    2014-01-01

    Behavioral coordination and synchrony contribute to a common biological mechanism that maintains communication, cooperation and bonding within many social species, such as primates and birds. Similarly, human language and social systems may also be attuned to coordination to facilitate communication and the formation of relationships. Gross similarities in movement patterns and convergence in the acoustic properties of speech have already been demonstrated between interacting individuals. In the present studies, we investigated how coordinated movements contribute to observers’ perception of affiliation (friends vs. strangers) between two conversing individuals. We used novel computational methods to quantify motor coordination and demonstrated that individuals familiar with each other coordinated their movements more frequently. Observers used coordination to judge affiliation between conversing pairs but only when the perceptual stimuli were restricted to head and face regions. These results suggest that observed movement coordination in humans might contribute to perceptual decisions based on availability of information to perceivers. PMID:25119189

  1. An Approach for Dynamic Grids

    NASA Technical Reports Server (NTRS)

    Slater, John W.; Liou, Meng-Sing; Hindman, Richard G.

    1994-01-01

    An approach is presented for the generation of two-dimensional, structured, dynamic grids. The grid motion may be due to the motion of the boundaries of the computational domain or to the adaptation of the grid to the transient, physical solution. A time-dependent grid is computed through the time integration of the grid speeds which are computed from a system of grid speed equations. The grid speed equations are derived from the time-differentiation of the grid equations so as to ensure that the dynamic grid maintains the desired qualities of the static grid. The grid equations are the Euler-Lagrange equations derived from a variational statement for the grid. The dynamic grid method is demonstrated for a model problem involving boundary motion, an inviscid flow in a converging-diverging nozzle during startup, and a viscous flow over a flat plate with an impinging shock wave. It is shown that the approach is more accurate for transient flows than an approach in which the grid speeds are computed using a finite difference with respect to time of the grid. However, the approach requires significantly more computational effort.

  2. NREL Smart Grid Projects

    SciTech Connect

    Hambrick, J.

    2012-01-01

    Although implementing Smart Grid projects at the distribution level provides many advantages and opportunities for advanced operation and control, a number of significant challenges must be overcome to maintain the high level of safety and reliability that the modern grid must provide. For example, while distributed generation (DG) promises to provide opportunities to increase reliability and efficiency and may provide grid support services such as volt/var control, the presence of DG can impact distribution operation and protection schemes. Additionally, the intermittent nature of many DG energy sources such as photovoltaics (PV) can present a number of challenges to voltage regulation, etc. This presentation provides an overview a number of Smart Grid projects being performed by the National Renewable Energy Laboratory (NREL) along with utility, industry, and academic partners. These projects include modeling and analysis of high penetration PV scenarios (with and without energy storage), development and testing of interconnection and microgrid equipment, as well as the development and implementation of advanced instrumentation and data acquisition used to analyze the impacts of intermittent renewable resources. Additionally, standards development associated with DG interconnection and analysis as well as Smart Grid interoperability will be discussed.

  3. An Adaptive Unstructured Grid Method by Grid Subdivision, Local Remeshing, and Grid Movement

    NASA Technical Reports Server (NTRS)

    Pirzadeh, Shahyar Z.

    1999-01-01

    An unstructured grid adaptation technique has been developed and successfully applied to several three dimensional inviscid flow test cases. The approach is based on a combination of grid subdivision, local remeshing, and grid movement. For solution adaptive grids, the surface triangulation is locally refined by grid subdivision, and the tetrahedral grid in the field is partially remeshed at locations of dominant flow features. A grid redistribution strategy is employed for geometric adaptation of volume grids to moving or deforming surfaces. The method is automatic and fast and is designed for modular coupling with different solvers. Several steady state test cases with different inviscid flow features were tested for grid/solution adaptation. In all cases, the dominant flow features, such as shocks and vortices, were accurately and efficiently predicted with the present approach. A new and robust method of moving tetrahedral "viscous" grids is also presented and demonstrated on a three-dimensional example.

  4. Finite-surface method for the Maxwell equations in generalized coordinates

    NASA Technical Reports Server (NTRS)

    Vinokur, Marcel; Yarrow, Maurice

    1993-01-01

    A finite-surface technique for the Maxwell equations in generalized nonorthogonal coordinates is developed. It directly applies the integral Faraday's and Ampere's laws to faces of primary and secondary grid cells, respectively. The technique features an accurate treatment of matching conditions at a material interface, grid singularities, and radiation conditions at outer boundaries.

  5. The Computing Grids

    NASA Astrophysics Data System (ADS)

    Govoni, P.

    2009-12-01

    Since the beginning of the millennium, High Energy Physics research institutions like CERN and INFN pioneered several projects aimed at exploiting the synergy among computing power, storage and network resources, and creating an infrastructure of distributed computing on a worldwide scale. In the year 2000, after the Monarch project [ http://monarc.web.cern.ch/MONARC/], DataGrid started [ http://eu-datagrid.web.cern.ch/eu-datagrid/] aimed at providing High Energy Physics with the computing power needed for the LHC enterprise. This program evolved into the EU DataGrid project, that implemented the first actual prototype of a Grid middleware running on a testbed environment. The next step consisted in the application to the LHC experiments, with the LCG project [ http://lcg.web.cern.ch/LCG/], in turn followed by the EGEE [ http://www.eu-egee.org/] and EGEE II programs.

  6. Information Power Grid Posters

    NASA Technical Reports Server (NTRS)

    Vaziri, Arsi

    2003-01-01

    This document is a summary of the accomplishments of the Information Power Grid (IPG). Grids are an emerging technology that provide seamless and uniform access to the geographically dispersed, computational, data storage, networking, instruments, and software resources needed for solving large-scale scientific and engineering problems. The goal of the NASA IPG is to use NASA's remotely located computing and data system resources to build distributed systems that can address problems that are too large or complex for a single site. The accomplishments outlined in this poster presentation are: access to distributed data, IPG heterogeneous computing, integration of large-scale computing node into distributed environment, remote access to high data rate instruments,and exploratory grid environment.

  7. Gravity inversion in spherical coordinates using tesseroids

    NASA Astrophysics Data System (ADS)

    Uieda, Leonardo; Barbosa, Valeria C. F.

    2014-05-01

    Satellite observations of the gravity field have provided geophysicists with exceptionally dense and uniform coverage of data over vast areas. This enables regional or global scale high resolution geophysical investigations. Techniques like forward modeling and inversion of gravity anomalies are routinely used to investigate large geologic structures, such as large igneous provinces, suture zones, intracratonic basins, and the Moho. Accurately modeling such large structures requires taking the sphericity of the Earth into account. A reasonable approximation is to assume a spherical Earth and use spherical coordinates. In recent years, efforts have been made to advance forward modeling in spherical coordinates using tesseroids, particularly with respect to speed and accuracy. Conversely, traditional space domain inverse modeling methods have not yet been adapted to use spherical coordinates and tesseroids. In the literature there are a range of inversion methods that have been developed for Cartesian coordinates and right rectangular prisms. These include methods for estimating the relief of an interface, like the Moho or the basement of a sedimentary basin. Another category includes methods to estimate the density distribution in a medium. The latter apply many algorithms to solve the inverse problem, ranging from analytic solutions to random search methods as well as systematic search methods. We present an adaptation for tesseroids of the systematic search method of "planting anomalous densities". This method can be used to estimate the geometry of geologic structures. As prior information, it requires knowledge of the approximate densities and positions of the structures. The main advantage of this method is its computational efficiency, requiring little computer memory and processing time. We demonstrate the shortcomings and capabilities of this approach using applications to synthetic and field data. Performing the inversion of gravity and gravity gradient data, simultaneously or separately, is straight forward and requires no changes to the existing algorithm. Such feature makes it ideal for inverting the multicomponent gravity gradient data from the GOCE satellite. An implementation of our adaptation is freely available in the open-source modeling and inversion package Fatiando a Terra (http://www.fatiando.org).

  8. Grid Data Management and Customer Demands at MeteoSwiss

    NASA Astrophysics Data System (ADS)

    Rigo, G.; Lukasczyk, Ch.

    2010-09-01

    Data grids constitute the required input form for a variety of applications. Therefore, customers increasingly expect climate services to not only provide measured data, but also grids of these with the required configurations on an operational basis. Currently, MeteoSwiss is establishing a production chain for delivering data grids by subscription directly from the data warehouse in order to meet the demand for precipitation data grids by governmental, business and science customers. The MeteoSwiss data warehouse runs on an Oracle database linked with an ArcGIS Standard edition geodatabase. The grids are produced by Unix-based software written in R called GRIDMCH which extracts the station data from the data warehouse and stores the files in the file system. By scripts, the netcdf-v4 files are imported via an FME interface into the database. Currently daily and monthly deliveries of daily precipitation grids are available from MeteoSwiss with a spatial resolution of 2.2km x 2.2km. These daily delivered grids are a preliminary based on 100 measuring sites whilst the grid of the monthly delivery of daily sums is calculated out of about 430 stations. Crucial for the absorption by the customers is the understanding of and the trust into the new grid product. Clearly stating needs which can be covered by grid products, the customers require a certain lead time to develop applications making use of the particular grid. Therefore, early contacts and a continuous attendance as well as flexibility in adjusting the production process to fulfill emerging customer needs are important during the introduction period. Gridding over complex terrain can lead to temporally elevated uncertainties in certain areas depending on the weather situation and coverage of measurements. Therefore, careful instructions on the quality and use and the possibility to communicate the uncertainties of gridded data proofed to be essential especially to the business and science customers who require near-real-time datasets to build up trust in the product in different applications. The implementation of a new method called RSOI for the daily production allowed to bring the daily precipitation field up to the expectations of customers. The main use of the grids were near-realtime and past event analysis in areas scarcely covered with stations, and inputs for forecast tools and models. Critical success factors of the product were speed of delivery and at the same time accuracy, temporal and spatial resolution, and configuration (coordinate system, projection). To date, grids of archived precipitation data since 1961 and daily/monthly precipitation gridsets with 4h-delivery lag of Switzerland or subareas are available.

  9. Integrating Renewable Electricity on the Grid

    NASA Astrophysics Data System (ADS)

    Crabtree, George; Misewich, Jim; Ambrosio, Ron; Clay, Kathryn; DeMartini, Paul; James, Revis; Lauby, Mark; Mohta, Vivek; Moura, John; Sauer, Peter; Slakey, Francis; Lieberman, Jodi; Tai, Humayun

    2011-11-01

    The demand for carbon-free electricity is driving a growing movement of adding renewable energy to the grid. Renewable Portfolio Standards mandated by states and under consideration by the federal government envision a penetration of 20-30% renewable energy in the grid by 2020 or 2030. The renewable energy potential of wind and solar far exceeds these targets, suggesting that renewable energy ultimately could grow well beyond these initial goals. The grid faces two new and fundamental technological challenges in accommodating renewables: location and variability. Renewable resources are concentrated at mid-continent far from population centers, requiring additional long distance, high-capacity transmission to match supply with demand. The variability of renewables due to the characteristics of weather is high, up to 70% for daytime solar due to passing clouds and 100% for wind on calm days, much larger than the relatively predictable uncertainty in load that the grid now accommodates by dispatching conventional resources in response to demand. Solutions to the challenges of remote location and variability of generation are needed. The options for DC transmission lines, favored over AC lines for transmission of more than a few hundred miles, need to be examined. Conventional high voltage DC transmission lines are a mature technology that can solve regional transmission needs covering one- or two-state areas. Conventional high voltage DC has drawbacks, however, of high loss, technically challenging and expensive conversion between AC and DC, and the requirement of a single point of origin and termination. Superconducting DC transmission lines lose little or no energy, produce no heat, and carry higher power density than conventional lines. They operate at moderate voltage, allowing many "on-ramps" and "off-ramps" in a single network and reduce the technical and cost challenges of AC to DC conversion. A network of superconducting DC cables overlaying the existing patchwork of conventional transmission lines would create an interstate highway system for electricity that moves large amounts of renewable electric power efficiently over long distances from source to load. Research and development is needed to identify the technical challenges associated with DC superconducting transmission and how it can be most effectively deployed. The challenge of variability can be met (i) by switching conventional generation capacity in or out in response to sophisticated forecasts of weather and power generation, (ii) by large scale energy storage in heat, pumped hydroelectric, compressed air or stationary batteries designed for the grid, or (iii) by national balancing of regional generation deficits and excesses using long distance transmission. Each of these solutions to variability has merit and each requires significant research and development to understand its capacity, performance, cost and effectiveness. The challenge of variability is likely to be met by a combination of these three solutions; the interactions among them and the appropriate mix needs to be explored. The long distances from renewable sources to demand centers span many of the grid's physical, ownership and regulatory boundaries. This introduces a new feature to grid structure and operation: national and regional coordination. The grid is historically a patchwork of local generation resources and load centers that has been built, operated and regulated to meet local needs. Although it is capable of sharing power across moderate distances, the arrangements for doing so are cumbersome and inefficient. The advent of renewable electricity with its enormous potential and inherent regional and national character presents an opportunity to examine the local structure of the grid and establish coordinating principles that will not only enable effective renewable integration but also simplify and codify the grid's increasingly regional and national character.

  10. Computational fluid dynamics for propulsion technology: Geometric grid visualization in CFD-based propulsion technology research

    NASA Technical Reports Server (NTRS)

    Ziebarth, John P.; Meyer, Doug

    1992-01-01

    The coordination is examined of necessary resources, facilities, and special personnel to provide technical integration activities in the area of computational fluid dynamics applied to propulsion technology. Involved is the coordination of CFD activities between government, industry, and universities. Current geometry modeling, grid generation, and graphical methods are established to use in the analysis of CFD design methodologies.

  11. Distributed Accounting on the Grid

    NASA Technical Reports Server (NTRS)

    Thigpen, William; Hacker, Thomas J.; McGinnis, Laura F.; Athey, Brian D.

    2001-01-01

    By the late 1990s, the Internet was adequately equipped to move vast amounts of data between HPC (High Performance Computing) systems, and efforts were initiated to link together the national infrastructure of high performance computational and data storage resources together into a general computational utility 'grid', analogous to the national electrical power grid infrastructure. The purpose of the Computational grid is to provide dependable, consistent, pervasive, and inexpensive access to computational resources for the computing community in the form of a computing utility. This paper presents a fully distributed view of Grid usage accounting and a methodology for allocating Grid computational resources for use on a Grid computing system.

  12. Essential Grid Workflow Monitoring Elements

    SciTech Connect

    Gunter, Daniel K.; Jackson, Keith R.; Konerding, David E.; Lee,Jason R.; Tierney, Brian L.

    2005-07-01

    Troubleshooting Grid workflows is difficult. A typicalworkflow involves a large number of components networks, middleware,hosts, etc. that can fail. Even when monitoring data from all thesecomponents is accessible, it is hard to tell whether failures andanomalies in these components are related toa given workflow. For theGrid to be truly usable, much of this uncertainty must be elim- inated.We propose two new Grid monitoring elements, Grid workflow identifiersand consistent component lifecycle events, that will make Gridtroubleshooting easier, and thus make Grids more usable, by simplifyingthe correlation of Grid monitoring data with a particular Gridworkflow.

  13. Basal Ganglia Outputs Map Instantaneous Position Coordinates during Behavior

    PubMed Central

    Barter, Joseph W.; Li, Suellen; Sukharnikova, Tatyana; Rossi, Mark A.; Bartholomew, Ryan A.

    2015-01-01

    The basal ganglia (BG) are implicated in many movement disorders, yet how they contribute to movement remains unclear. Using wireless in vivo recording, we measured BG output from the substantia nigra pars reticulata (SNr) in mice while monitoring their movements with video tracking. The firing rate of most nigral neurons reflected Cartesian coordinates (either x- or y-coordinates) of the animal's head position during movement. The firing rates of SNr neurons are either positively or negatively correlated with the coordinates. Using an egocentric reference frame, four types of neurons can be classified: each type increases firing during movement in a particular direction (left, right, up, down), and decreases firing during movement in the opposite direction. Given the high correlation between the firing rate and the x and y components of the position vector, the movement trajectory can be reconstructed from neural activity. Our results therefore demonstrate a quantitative and continuous relationship between BG output and behavior. Thus, a steady BG output signal from the SNr (i.e., constant firing rate) is associated with the lack of overt movement, when a stable posture is maintained by structures downstream of the BG. Any change in SNr firing rate is associated with a change in position (i.e., movement). We hypothesize that the SNr output quantitatively determines the direction, velocity, and amplitude of voluntary movements. By changing the reference signals to downstream position control systems, the BG can produce transitions in body configurations and initiate actions. PMID:25673860

  14. Basal ganglia outputs map instantaneous position coordinates during behavior.

    PubMed

    Barter, Joseph W; Li, Suellen; Sukharnikova, Tatyana; Rossi, Mark A; Bartholomew, Ryan A; Yin, Henry H

    2015-02-11

    The basal ganglia (BG) are implicated in many movement disorders, yet how they contribute to movement remains unclear. Using wireless in vivo recording, we measured BG output from the substantia nigra pars reticulata (SNr) in mice while monitoring their movements with video tracking. The firing rate of most nigral neurons reflected Cartesian coordinates (either x- or y-coordinates) of the animal's head position during movement. The firing rates of SNr neurons are either positively or negatively correlated with the coordinates. Using an egocentric reference frame, four types of neurons can be classified: each type increases firing during movement in a particular direction (left, right, up, down), and decreases firing during movement in the opposite direction. Given the high correlation between the firing rate and the x and y components of the position vector, the movement trajectory can be reconstructed from neural activity. Our results therefore demonstrate a quantitative and continuous relationship between BG output and behavior. Thus, a steady BG output signal from the SNr (i.e., constant firing rate) is associated with the lack of overt movement, when a stable posture is maintained by structures downstream of the BG. Any change in SNr firing rate is associated with a change in position (i.e., movement). We hypothesize that the SNr output quantitatively determines the direction, velocity, and amplitude of voluntary movements. By changing the reference signals to downstream position control systems, the BG can produce transitions in body configurations and initiate actions. PMID:25673860

  15. Modeling groundwater flow by lattice Boltzmann method in curvilinear coordinates

    NASA Astrophysics Data System (ADS)

    Budinski, Ljubomir; Fabian, Julius; Stipic, Matija

    2015-07-01

    In order to promote the use of the lattice Boltzmann method (LBM) for the simulation of isotropic groundwater flow in a confined aquifer with arbitrary geometry, Poisson's equation was transformed into a curvilinear coordinate system. With the metric function between the physical and the computational domain established, Poisson's equation written in Cartesian coordinates was transformed in curvilinear coordinates. Following, the appropriate equilibrium function for the D2Q9 square lattice has been defined. The resulting curvilinear formulation of the LBM for groundwater flow is capable of modeling flow in domains of complex geometry with the opportunity of local refining/coarsening of the computational mesh corresponding to the complexity of the flow pattern and the required accuracy. Since the proposed form of the LBM uses the transformed equation of flow implemented in the equilibrium function, finding a solution does not require supplementary procedures along the curvilinear boundaries, nor in the zones requiring mesh density adjustments. Thus, the basic concept of the LBM is completely maintained. The improvement of the proposed LBM over the previously published classical methods is completely verified by three examples with analytical solutions. The results demonstrate the advantages of the proposed curvilinear LBM in modeling groundwater flow in complex flow domains.

  16. Adapted harmonic coordinates

    SciTech Connect

    Bel, L.; Coll, B. )

    1993-06-01

    The authors obtain the necessary and sufficient conditions that a timelike congruence has to satisfy to admit three independent adapted harmonic coordinates of space, proving in the process that if it does then these coordinates are unique up to a linear transformation with constant coefficients. As a particular example it is proven that irrotational pure Born (i.e. not Killing) congruences never admit a system of adapted harmonic coordinates of space. 8 refs.

  17. Ion Accelerator With Negatively Biased Decelerator Grid

    NASA Technical Reports Server (NTRS)

    Brophy, John R.

    1994-01-01

    Three-grid ion accelerator in which accelerator grid is biased at negative potential and decelerator grid downstream of accelerator grid biased at smaller negative potential. This grid and bias arrangement reduces frequency of impacts, upon accelerator grid, of charge-exchange ions produced downstream in collisions between accelerated ions and atoms and molecules of background gas. Sputter erosion of accelerator grid reduced.

  18. The BioGRID interaction database: 2015 update

    PubMed Central

    Chatr-aryamontri, Andrew; Breitkreutz, Bobby-Joe; Oughtred, Rose; Boucher, Lorrie; Heinicke, Sven; Chen, Daici; Stark, Chris; Breitkreutz, Ashton; Kolas, Nadine; O'Donnell, Lara; Reguly, Teresa; Nixon, Julie; Ramage, Lindsay; Winter, Andrew; Sellam, Adnane; Chang, Christie; Hirschman, Jodi; Theesfeld, Chandra; Rust, Jennifer; Livstone, Michael S.; Dolinski, Kara; Tyers, Mike

    2015-01-01

    The Biological General Repository for Interaction Datasets (BioGRID: http://thebiogrid.org) is an open access database that houses genetic and protein interactions curated from the primary biomedical literature for all major model organism species and humans. As of September 2014, the BioGRID contains 749 912 interactions as drawn from 43 149 publications that represent 30 model organisms. This interaction count represents a 50% increase compared to our previous 2013 BioGRID update. BioGRID data are freely distributed through partner model organism databases and meta-databases and are directly downloadable in a variety of formats. In addition to general curation of the published literature for the major model species, BioGRID undertakes themed curation projects in areas of particular relevance for biomedical sciences, such as the ubiquitin-proteasome system and various human disease-associated interaction networks. BioGRID curation is coordinated through an Interaction Management System (IMS) that facilitates the compilation interaction records through structured evidence codes, phenotype ontologies, and gene annotation. The BioGRID architecture has been improved in order to support a broader range of interaction and post-translational modification types, to allow the representation of more complex multi-gene/protein interactions, to account for cellular phenotypes through structured ontologies, to expedite curation through semi-automated text-mining approaches, and to enhance curation quality control. PMID:25428363

  19. The BioGRID interaction database: 2015 update.

    PubMed

    Chatr-Aryamontri, Andrew; Breitkreutz, Bobby-Joe; Oughtred, Rose; Boucher, Lorrie; Heinicke, Sven; Chen, Daici; Stark, Chris; Breitkreutz, Ashton; Kolas, Nadine; O'Donnell, Lara; Reguly, Teresa; Nixon, Julie; Ramage, Lindsay; Winter, Andrew; Sellam, Adnane; Chang, Christie; Hirschman, Jodi; Theesfeld, Chandra; Rust, Jennifer; Livstone, Michael S; Dolinski, Kara; Tyers, Mike

    2015-01-01

    The Biological General Repository for Interaction Datasets (BioGRID: http://thebiogrid.org) is an open access database that houses genetic and protein interactions curated from the primary biomedical literature for all major model organism species and humans. As of September 2014, the BioGRID contains 749,912 interactions as drawn from 43,149 publications that represent 30 model organisms. This interaction count represents a 50% increase compared to our previous 2013 BioGRID update. BioGRID data are freely distributed through partner model organism databases and meta-databases and are directly downloadable in a variety of formats. In addition to general curation of the published literature for the major model species, BioGRID undertakes themed curation projects in areas of particular relevance for biomedical sciences, such as the ubiquitin-proteasome system and various human disease-associated interaction networks. BioGRID curation is coordinated through an Interaction Management System (IMS) that facilitates the compilation interaction records through structured evidence codes, phenotype ontologies, and gene annotation. The BioGRID architecture has been improved in order to support a broader range of interaction and post-translational modification types, to allow the representation of more complex multi-gene/protein interactions, to account for cellular phenotypes through structured ontologies, to expedite curation through semi-automated text-mining approaches, and to enhance curation quality control. PMID:25428363

  20. Marshall Space Flight Center surface modeling and grid generation applications

    NASA Astrophysics Data System (ADS)

    Williams, Robert W.; Benjamin, Theodore G.; Cornelison, Joni W.

    1995-03-01

    The Solid Rocket Motors (SRM) used by NASA to propel the Space Shuttle employ gimballing nozzles as a means for vehicular guidance during launch and ascent. Gimballing a nozzle renders the pressure field of the exhaust gases nonaxisymmetric. This has two effects: (1) it exerts a torque and side load on the nozzle; and (2) the exhaust gases flow circumferentially in the aft-dome region, thermally loading the flexible boot, case-to-nozzle joint, and casing insulation. The use of CFD models to simulate such flows is imperative in order to assess SRM design. The grids for these problems were constructed by obtaining information from drawings and tabulated coordinates. The 2D axisymmetric grids were designed and generated using the EZ-Surf and GEN2D surface and grid generation codes. These 2D grids were solved using codes such as FDNS, GASP, and MINT. These axisymmetric grids were rotated around the center-line to form 3D nongimballed grids. These were then gimballed around the pivot point and the gaps or overlaps resurfaced to obtain the final domains, which contained approximately 366,000 grid points. The 2D solutions were then rotated and manipulated as appropriate for geometry and used as initial guesses in the final solution. The analyses were used in answering questions about flight criteria.

  1. Marshall Space Flight Center surface modeling and grid generation applications

    NASA Technical Reports Server (NTRS)

    Williams, Robert W.; Benjamin, Theodore G.; Cornelison, Joni W.

    1995-01-01

    The Solid Rocket Motors (SRM) used by NASA to propel the Space Shuttle employ gimballing nozzles as a means for vehicular guidance during launch and ascent. Gimballing a nozzle renders the pressure field of the exhaust gases nonaxisymmetric. This has two effects: (1) it exerts a torque and side load on the nozzle; and (2) the exhaust gases flow circumferentially in the aft-dome region, thermally loading the flexible boot, case-to-nozzle joint, and casing insulation. The use of CFD models to simulate such flows is imperative in order to assess SRM design. The grids for these problems were constructed by obtaining information from drawings and tabulated coordinates. The 2D axisymmetric grids were designed and generated using the EZ-Surf and GEN2D surface and grid generation codes. These 2D grids were solved using codes such as FDNS, GASP, and MINT. These axisymmetric grids were rotated around the center-line to form 3D nongimballed grids. These were then gimballed around the pivot point and the gaps or overlaps resurfaced to obtain the final domains, which contained approximately 366,000 grid points. The 2D solutions were then rotated and manipulated as appropriate for geometry and used as initial guesses in the final solution. The analyses were used in answering questions about flight criteria.

  2. Grid cell spatial tuning reduced following systemic muscarinic receptor blockade.

    PubMed

    Newman, Ehren L; Climer, Jason R; Hasselmo, Michael E

    2014-06-01

    Grid cells of the medial entorhinal cortex exhibit a periodic and stable pattern of spatial tuning that may reflect the output of a path integration system. This grid pattern has been hypothesized to serve as a spatial coordinate system for navigation and memory function. The mechanisms underlying the generation of this characteristic tuning pattern remain poorly understood. Systemic administration of the muscarinic antagonist scopolamine flattens the typically positive correlation between running speed and entorhinal theta frequency in rats. The loss of this neural correlate of velocity, an important signal for the calculation of path integration, raises the question of what influence scopolamine has on the grid cell tuning as a read out of the path integration system. To test this, the spatial tuning properties of grid cells were compared before and after systemic administration of scopolamine as rats completed laps on a circle track for food rewards. The results show that the spatial tuning of the grid cells was reduced following scopolamine administration. The tuning of head direction cells, in contrast, was not reduced by scopolamine. This is the first report to demonstrate a link between cholinergic function and grid cell tuning. This work suggests that the loss of tuning in the grid cell network may underlie the navigational disorientation observed in Alzheimer's patients and elderly individuals with reduced cholinergic tone. PMID:24493379

  3. Unlocking the smart grid

    SciTech Connect

    Rokach, Joshua Z.

    2010-10-15

    The country has progressed in a relatively short time from rotary dial phones to computers, cell phones, and iPads. With proper planning and orderly policy implementation, the same will happen with the Smart Grid. Here are some suggestions on how to proceed. (author)

  4. APEC Smart Grid Initiative

    SciTech Connect

    Bloyd, Cary N.

    2012-03-01

    This brief paper describes the activities of the Asia Pacific Economic Cooperation (APEC) Smart Grid Initiative (ASGI) which is being led by the U.S. and developed by the APEC Energy Working Group. In the paper, I describe the origin of the initiative and briefly mention the four major elements of the initiative along with existing APEC projects which support it.

  5. NSTAR Smart Grid Pilot

    SciTech Connect

    Rabari, Anil; Fadipe, Oloruntomi

    2014-03-31

    NSTAR Electric & Gas Corporation (“the Company”, or “NSTAR”) developed and implemented a Smart Grid pilot program beginning in 2010 to demonstrate the viability of leveraging existing automated meter reading (“AMR”) deployments to provide much of the Smart Grid functionality of advanced metering infrastructure (“AMI”), but without the large capital investment that AMI rollouts typically entail. In particular, a central objective of the Smart Energy Pilot was to enable residential dynamic pricing (time-of-use “TOU” and critical peak rates and rebates) and two-way direct load control (“DLC”) by continually capturing AMR meter data transmissions and communicating through customer-sited broadband connections in conjunction with a standardsbased home area network (“HAN”). The pilot was supported by the U.S. Department of Energy’s (“DOE”) through the Smart Grid Demonstration program. NSTAR was very pleased to not only receive the funding support from DOE, but the guidance and support of the DOE throughout the pilot. NSTAR is also pleased to report to the DOE that it was able to execute and deliver a successful pilot on time and on budget. NSTAR looks for future opportunities to work with the DOE and others in future smart grid projects.

  6. Changing from computing grid to knowledge grid in life-science grid.

    PubMed

    Talukdar, Veera; Konar, Amit; Datta, Ayan; Choudhury, Anamika Roy

    2009-09-01

    Grid computing has a great potential to become a standard cyber infrastructure for life sciences that often require high-performance computing and large data handling, which exceeds the computing capacity of a single institution. Grid computer applies the resources of many computers in a network to a single problem at the same time. It is useful to scientific problems that require a great number of computer processing cycles or access to a large amount of data.As biologists,we are constantly discovering millions of genes and genome features, which are assembled in a library and distributed on computers around the world.This means that new, innovative methods must be developed that exploit the re-sources available for extensive calculations - for example grid computing.This survey reviews the latest grid technologies from the viewpoints of computing grid, data grid and knowledge grid. Computing grid technologies have been matured enough to solve high-throughput real-world life scientific problems. Data grid technologies are strong candidates for realizing a "resourceome" for bioinformatics. Knowledge grids should be designed not only from sharing explicit knowledge on computers but also from community formulation for sharing tacit knowledge among a community. By extending the concept of grid from computing grid to knowledge grid, it is possible to make use of a grid as not only sharable computing resources, but also as time and place in which people work together, create knowledge, and share knowledge and experiences in a community. PMID:19579217

  7. An overset grid method for global geomagnetic induction

    NASA Astrophysics Data System (ADS)

    Weiss, Chester J.

    2014-07-01

    A new finite difference solution to the global geomagnetic induction problem is developed and tested, based on a modified Lorenz gauge of the magnetic vector and electric scalar potentials and implementing a novel, overset `Yin-Yang' grid that avoids unnecessary mesh refinement at the geographic poles. Previously used in whole-earth mantle convection models, the overset grid is built from a pair of partially overlapping mid-latitude latitude-longitude (lat/lon) grids, one of which is rotated with respect to the other for complete coverage of the sphere. Because of this symmetry, only one set of finite difference templates is required for global discretization of the governing Maxwell equations, a redundancy that is exploited for computational efficiency and multithreaded parallelization. Comparisons between solutions obtained by the proposed method show excellent agreement with those obtained by independent integral equation methods for 1-D, 2-D and 3-D problem geometries. The computational footprint of the method is minimized through a (non-symmetric) matrix-free BiCG-STAB iterative solver which computes finite difference matrix coefficients `on the fly' as needed, rather than pulling stored values from memory. Scaling of the matrix-free BiCG-STAB algorithm with problem size shows behaviour similar to that seen with the (symmetric) QMR algorithm used in the Cartesian case from which the present algorithm is based. The proposed method may therefore provide a competitive addition to the existing body of global-scale geomagnetic induction modelling algorithms, allowing for resource-efficient forward modelling as the kernel for large-scale computing such as inversion of geomagnetic response functions, computational hypothesis testing and parametric studies of mantle geodynamics and physiochemical state.

  8. Grid generation research at OSU

    NASA Technical Reports Server (NTRS)

    Nakamura, S.

    1992-01-01

    In the last two years, effort was concentrated on: (1) surface modeling; (2) surface grid generation; and (3) 3-D flow space grid generation. The surface modeling shares the same objectives as the surface modeling in computer aided design (CAD), so software available in CAD can in principle be used for solid modeling. Unfortunately, however, the CAD software cannot be easily used in practice for grid generation purposes, because they are not designed to provide appropriate data base for grid generation. Therefore, we started developing a generalized surface modeling software from scratch, that provides the data base for the surface grid generation. Generating surface grid is an important step in generating a 3-D space for flow space. To generate a surface grid on a given surface representation, we developed a unique algorithm that works on any non-smooth surfaces. Once the surface grid is generated, a 3-D space can be generated. For this purpose, we also developed a new algorithm, which is a hybrid of the hyperbolic and the elliptic grid generation methods. With this hybrid method, orthogonality of the grid near the solid boundary can be easily achieved without introducing empirical fudge factors. Work to develop 2-D and 3-D grids for turbomachinery blade geometries was performed, and as an extension of this research we are planning to develop an adaptive grid procedure with an interactive grid environment.

  9. Grid-independent large-eddy simulation (LES) of turbulent flow around a circular cylinder using explicit filtering

    NASA Astrophysics Data System (ADS)

    Singh, Satbir; You, Donghyun

    2013-11-01

    The explicit filtering technique has the potential to provide grid-independent and error-quantified large-eddy-simulation (LES) solutions. recently obtained grid-independent LES solutions for turbulent channel flow using one-dimensional discrete filter functions implemented on Cartesian grids. Many complex flow configurations, however, employ arbitrary shape grids, for which it is difficult to design such discrete filter functions. In the present work, we employ an elliptic differential filter to solve explicit-filter LES equations on arbitrary shaped grids. The coefficients of the elliptic filter are determined by comparing its filtering characteristics with those of a Gausian filter. The elliptic filter is applied to a homogeneous isotropic turbulence flow field and the coefficient is adjusted until a filtered energy spectra similar to that of the Gaussian filter is obtained. The filter coefficients thus obtained are then employed to solve explicit-filter LES equations for turbulent channel flow at Re? = 395 and turbulent flow over a circular cylinder at ReD = 3900 . Grid-independent solutions are obtained for both flow configurations.

  10. Women's collective constructions of embodied practices through memory work: Cartesian dualism in memories of sweating and pain.

    PubMed

    Gillies, Val; Harden, Angela; Johnson, Katherine; Reavey, Paula; Strange, Vicki; Willig, Carla

    2004-03-01

    The research presented in this paper uses memory work as a method to explore six women's collective constructions of two embodied practices, sweating and pain. The paper identifies limitations in the ways in which social constructionist research has theorized the relationship between discourse and materiality, and it proposes an approach to the study of embodiment which enjoins, rather than bridges, the discursive and the non-discursive. The paper presents an analysis of 25 memories of sweating and pain which suggests that Cartesian dualism is central to the women's accounts of their experiences. However, such dualism does not operate as a stable organizing principle. Rather, it offers two strategies for the performance of a split between mind and body. The paper traces the ways in which dualism can be both functional and restrictive, and explores the tensions between these two forms. The paper concludes by identifiying opportunities and limitations associated with memory work as a method for studying embodiment. PMID:15035700

  11. Free-breathing whole-heart coronary MRA: motion compensation integrated into 3D cartesian compressed sensing reconstruction.

    PubMed

    Forman, Christoph; Grimm, Robert; Hutter, Jana Maria; Maier, Andreas; Hornegger, Joachim; Zenge, Michael O

    2013-01-01

    Respiratory motion remains a major challenge for whole-heart coronary magnetic resonance angiography (CMRA). Recently, iterative reconstruction has been augmented with non-rigid motion compensation to correct for the effects of respiratory motion. The major challenge of this approach is the estimation of dense deformation fields. In this work, the application of such a motion-compensated reconstruction is proposed for accelerated 3D Cartesian whole-heart CMRA. Without the need for extra calibration data or user interaction, the nonrigid deformations due to respiratory motion are directly estimated on the acquired image data. In-vivo experiments on 14 healthy volunteers were performed to compare the proposed method with the result of a navigator-gated reference scan. While reducing the acquisition time by one third, the reconstructed images resulted in equivalent vessel sharpness of 0.44 +/- 0.06 mm(-1) and 0.45 +/- 0.05 mm(-1), respectively. PMID:24579187

  12. Code Development of Linearized Euler Equation on Block-Structured Cartesian Mesh Combined with Immersed Boundary Method

    NASA Astrophysics Data System (ADS)

    Fukushima, Yuuma; Sasaki, Daisuke; Nakahashi, Kazuhiro

    Recently, acoustic analysis using the Linearized Euler Equation (LEE) on multi-block structured or unstructured mesh is focused. However, mesh generation around complicated geometries takes time on structured mesh and cost of high order calculation gets larger on unstructured mesh. In this research, a LEE code for aeroacoustic analysis is developed on block structured Cartesian mesh of Building-Cube Method. To make an accurate calculation, the Immersed Boundary Method is implemented for wall boundary treatment and high order Lagrange interpolation is implemented at the Cube boundary for data exchange. This code is validated through acoustics scattering problems around cylinders and the calculational errors are compared. The results show good agreement with analytical solutions and the usability of these methods.

  13. Pedagogical tools to explore Cartesian mind-body dualism in the classroom: philosophical arguments and neuroscience illusions

    PubMed Central

    Hamilton, Scott; Hamilton, Trevor J.

    2015-01-01

    A fundamental discussion in lower-level undergraduate neuroscience and psychology courses is Descartes’s “radical” or “mind-body” dualism. According to Descartes, our thinking mind, the res cogitans, is separate from the body as physical matter or substance, the res extensa. Since the transmission of sensory stimuli from the body to the mind is a physical capacity shared with animals, it can be confused, misled, or uncertain (e.g., bodily senses imply that ice and water are different substances). True certainty thus arises from within the mind and its capacity to doubt physical stimuli. Since this doubting mind is a thinking thing that is distinct from bodily stimuli, truth and certainty are reached through the doubting mind as cogito ergo sum, or the certainty of itself as it thinks: hence Descartes’s famous maxim, I think, therefore I am. However, in the last century of Western philosophy, with nervous system investigation, and with recent advances in neuroscience, the potential avenues to explore student’s understanding of the epistemology and effects of Cartesian mind-body dualism has expanded. This article further explores this expansion, highlighting pedagogical practices and tools instructors can use to enhance a psychology student’s understanding of Cartesian dualistic epistemology, in order to think more critically about its implicit assumptions and effects on learning. It does so in two ways: first, by offering instructors an alternative philosophical perspective to dualistic thinking: a mind-body holism that is antithetical to the assumed binaries of dualistic epistemology. Second, it supplements this philosophical argument with a practical component: simple mind-body illusions that instructors may use to demonstrate contrary epistemologies to students. Combining these short philosophical and neuroscience arguments thereby acts as a pedagogical tool to open new conceptual spaces within which learning may occur. PMID:26321981

  14. Pedagogical tools to explore Cartesian mind-body dualism in the classroom: philosophical arguments and neuroscience illusions.

    PubMed

    Hamilton, Scott; Hamilton, Trevor J

    2015-01-01

    A fundamental discussion in lower-level undergraduate neuroscience and psychology courses is Descartes's "radical" or "mind-body" dualism. According to Descartes, our thinking mind, the res cogitans, is separate from the body as physical matter or substance, the res extensa. Since the transmission of sensory stimuli from the body to the mind is a physical capacity shared with animals, it can be confused, misled, or uncertain (e.g., bodily senses imply that ice and water are different substances). True certainty thus arises from within the mind and its capacity to doubt physical stimuli. Since this doubting mind is a thinking thing that is distinct from bodily stimuli, truth and certainty are reached through the doubting mind as cogito ergo sum, or the certainty of itself as it thinks: hence Descartes's famous maxim, I think, therefore I am. However, in the last century of Western philosophy, with nervous system investigation, and with recent advances in neuroscience, the potential avenues to explore student's understanding of the epistemology and effects of Cartesian mind-body dualism has expanded. This article further explores this expansion, highlighting pedagogical practices and tools instructors can use to enhance a psychology student's understanding of Cartesian dualistic epistemology, in order to think more critically about its implicit assumptions and effects on learning. It does so in two ways: first, by offering instructors an alternative philosophical perspective to dualistic thinking: a mind-body holism that is antithetical to the assumed binaries of dualistic epistemology. Second, it supplements this philosophical argument with a practical component: simple mind-body illusions that instructors may use to demonstrate contrary epistemologies to students. Combining these short philosophical and neuroscience arguments thereby acts as a pedagogical tool to open new conceptual spaces within which learning may occur. PMID:26321981

  15. Self-gravitational Force Calculation of Second-order Accuracy for Infinitesimally Thin Gaseous Disks in Polar Coordinates

    NASA Astrophysics Data System (ADS)

    Wang, Hsiang-Hsu; Yen, David C. C.; Taam, Ronald E.

    2015-11-01

    Investigating the evolution of disk galaxies and the dynamics of proto-stellar disks can involve the use of both a hydrodynamical and a Poisson solver. These systems are usually approximated as infinitesimally thin disks using two-dimensional Cartesian or polar coordinates. In Cartesian coordinates, the calculations of the hydrodynamics and self-gravitational forces are relatively straightforward for attaining second-order accuracy. However, in polar coordinates, a second-order calculation of self-gravitational forces is required for matching the second-order accuracy of hydrodynamical schemes. We present a direct algorithm for calculating self-gravitational forces with second-order accuracy without artificial boundary conditions. The Poisson integral in polar coordinates is expressed in a convolution form and the corresponding numerical complexity is nearly linear using a fast Fourier transform. Examples with analytic solutions are used to verify that the truncated error of this algorithm is of second order. The kernel integral around the singularity is applied to modify the particle method. The use of a softening length is avoided and the accuracy of the particle method is significantly improved.

  16. IEEE Smart Grid Series of Standards IEEE 2030 (Interoperability) and IEEE 1547 (Interconnection) Status: Preprint

    SciTech Connect

    Basso, T.; DeBlasio, R.

    2012-04-01

    The IEEE American National Standards smart grid publications and standards development projects IEEE 2030, which addresses smart grid interoperability, and IEEE 1547TM, which addresses distributed resources interconnection with the grid, have made substantial progress since 2009. The IEEE 2030TM and 1547 standards series focus on systems-level aspects and cover many of the technical integration issues involved in a mature smart grid. The status and highlights of these two IEEE series of standards, which are sponsored by IEEE Standards Coordinating Committee 21 (SCC21), are provided in this paper.

  17. Interface procedures for overlapping grids

    NASA Technical Reports Server (NTRS)

    Mastin, C. W.

    1985-01-01

    Interpolation at grid boundaries is studied for the purpose of solving partial differential equations using either implicit or conservative explicit finite-difference methods on multi-component overlapping grid systems.

  18. Team coordination dynamics.

    PubMed

    Gorman, Jamie C; Amazeen, Polemnia G; Cooke, Nancy J

    2010-07-01

    Team coordination consists of both the dynamics of team member interaction and the environmental dynamics to which a team is subjected. Focusing on dynamics, an approach is developed that contrasts with traditional aggregate-static concepts of team coordination as characterized by the shared mental model approach. A team coordination order parameter was developed to capture momentary fluctuations in coordination. Team coordination was observed in three-person uninhabited air vehicle teams across two experimental sessions. The dynamics of the order parameter were observed under changes of a team familiarity control parameter. Team members returned for the second session to either the same (Intact) or different (Mixed) team. 'Roadblock' perturbations, or novel changes in the task environment, were introduced in order to probe the stability of team coordination. Nonlinear dynamic methods revealed differences that a traditional approach did not: Intact and Mixed team coordination dynamics looked very different; Mixed teams were more stable than Intact teams and explored the space of solutions without the need for correction. Stability was positively correlated with the number of roadblock perturbations that were overcome successfully. The novel and non-intuitive contribution of a dynamical analysis was that Mixed teams, who did not have a long history working together, were more adaptive. Team coordination dynamics carries new implications for traditional problems such as training adaptive teams. PMID:20587302

  19. IVS Technology Coordinator Report

    NASA Technical Reports Server (NTRS)

    Whitney, Alan

    2013-01-01

    This report of the Technology Coordinator includes the following: 1) continued work to implement the new VLBI2010 system, 2) the 1st International VLBI Technology Workshop, 3) a VLBI Digital- Backend Intercomparison Workshop, 4) DiFX software correlator development for geodetic VLBI, 5) a review of progress towards global VLBI standards, and 6) a welcome to new IVS Technology Coordinator Bill Petrachenko.

  20. Social Postural Coordination

    ERIC Educational Resources Information Center

    Varlet, Manuel; Marin, Ludovic; Lagarde, Julien; Bardy, Benoit G.

    2011-01-01

    The goal of the current study was to investigate whether a visual coupling between two people can produce spontaneous interpersonal postural coordination and change their intrapersonal postural coordination involved in the control of stance. We examined the front-to-back head displacements of participants and the angular motion of their hip and…

  1. On Reaction Coordinate Optimality.

    PubMed

    Krivov, Sergei V

    2013-01-01

    The following question is addressed: how to establish that a constructed reaction coordinate is optimal, i.e., that it provides an accurate description of dynamics. It is shown that the reaction coordinate is optimal if its cut free energy profile, determined using length-weighted transitions, is constant, i.e., it is position and sampling interval independent. The observation leads to a number of interesting results. In particular, the equilibrium flux between two boundary states can be computed exactly as diffusion on a free energy profile associated with the coordinate. The mean square displacement, for the trajectory projected onto the coordinate, grows linear with time. That for the same trajectory projected onto a suboptimal coordinate grows slower than linear with time. The results are illustrated on a number of model systems, Sierpinski gasket, FIP35 protein, and beta3s peptide. PMID:26589017

  2. Ion Engine Grid Gap Measurements

    NASA Technical Reports Server (NTRS)

    Soulas, Gerge C.; Frandina, Michael M.

    2004-01-01

    A simple technique for measuring the grid gap of an ion engine s ion optics during startup and steady-state operation was demonstrated with beam extraction. The grid gap at the center of the ion optics assembly was measured with a long distance microscope that was focused onto an alumina pin that protruded through the center accelerator grid aperture and was mechanically attached to the screen grid. This measurement technique was successfully applied to a 30 cm titanium ion optics assembly mounted onto an NSTAR engineering model ion engine. The grid gap and each grid s movement during startup from room temperature to both full and low power were measured. The grid gaps with and without beam extraction were found to be significantly different. The grid gaps at the ion optics center were both significantly smaller than the cold grid gap and different at the two power levels examined. To avoid issues associated with a small grid gap during thruster startup with titanium ion optics, a simple method was to operate the thruster initially without beam extraction to heat the ion optics. Another possible method is to apply high voltage to the grids prior to igniting the discharge because power deposition to the grids from the plasma is lower with beam extraction than without. Further testing would be required to confirm this approach.

  3. Spectral methods on arbitrary grids

    NASA Technical Reports Server (NTRS)

    Carpenter, Mark H.; Gottlieb, David

    1995-01-01

    Stable and spectrally accurate numerical methods are constructed on arbitrary grids for partial differential equations. These new methods are equivalent to conventional spectral methods but do not rely on specific grid distributions. Specifically, we show how to implement Legendre Galerkin, Legendre collocation, and Laguerre Galerkin methodology on arbitrary grids.

  4. Conformational Motions and Functionally Key Residues for Vitamin B12 Transporter BtuCD–BtuF Revealed by Elastic Network Model with a Function-Related Internal Coordinate

    PubMed Central

    Su, Ji-Guo; Zhang, Xiao; Zhao, Shu-Xin; Li, Xing-Yuan; Hou, Yan-Xue; Wu, Yi-Dong; Zhu, Jian-Zhuo; An, Hai-Long

    2015-01-01

    BtuCD–BtuF from Escherichia coli is a binding protein-dependent adenosine triphosphate (ATP)-binding cassette (ABC) transporter system that uses the energy of ATP hydrolysis to transmit vitamin B12 across cellular membranes. Experimental studies have showed that during the transport cycle, the transporter undergoes conformational transitions between the “inward-facing” and “outward-facing” states, which results in the open–closed motions of the cytoplasmic gate of the transport channel. The opening–closing of the channel gate play critical roles for the function of the transporter, which enables the substrate vitamin B12 to be translocated into the cell. In the present work, the extent of opening of the cytoplasmic gate was chosen as a function-related internal coordinate. Then the mean-square fluctuation of the internal coordinate, as well as the cross-correlation between the displacement of the internal coordinate and the movement of each residue in the protein, were calculated based on the normal mode analysis of the elastic network model to analyze the function-related motions encoded in the structure of the system. In addition, the key residues important for the functional motions of the transporter were predicted by using a perturbation method. In order to facilitate the calculations, the internal coordinate was introduced as one of the axes of the coordinate space and the conventional Cartesian coordinate space was transformed into the internal/Cartesian space with linear approximation. All the calculations were carried out in this internal/Cartesian space. Our method can successfully identify the functional motions and key residues for the transporter BtuCD–BtuF, which are well consistent with the experimental observations. PMID:26247943

  5. Conformational Motions and Functionally Key Residues for Vitamin B12 Transporter BtuCD-BtuF Revealed by Elastic Network Model with a Function-Related Internal Coordinate.

    PubMed

    Su, Ji-Guo; Zhang, Xiao; Zhao, Shu-Xin; Li, Xing-Yuan; Hou, Yan-Xue; Wu, Yi-Dong; Zhu, Jian-Zhuo; An, Hai-Long

    2015-01-01

    BtuCD-BtuF from Escherichia coli is a binding protein-dependent adenosine triphosphate (ATP)-binding cassette (ABC) transporter system that uses the energy of ATP hydrolysis to transmit vitamin B12 across cellular membranes. Experimental studies have showed that during the transport cycle, the transporter undergoes conformational transitions between the "inward-facing" and "outward-facing" states, which results in the open-closed motions of the cytoplasmic gate of the transport channel. The opening-closing of the channel gate play critical roles for the function of the transporter, which enables the substrate vitamin B12 to be translocated into the cell. In the present work, the extent of opening of the cytoplasmic gate was chosen as a function-related internal coordinate. Then the mean-square fluctuation of the internal coordinate, as well as the cross-correlation between the displacement of the internal coordinate and the movement of each residue in the protein, were calculated based on the normal mode analysis of the elastic network model to analyze the function-related motions encoded in the structure of the system. In addition, the key residues important for the functional motions of the transporter were predicted by using a perturbation method. In order to facilitate the calculations, the internal coordinate was introduced as one of the axes of the coordinate space and the conventional Cartesian coordinate space was transformed into the internal/Cartesian space with linear approximation. All the calculations were carried out in this internal/Cartesian space. Our method can successfully identify the functional motions and key residues for the transporter BtuCD-BtuF, which are well consistent with the experimental observations. PMID:26247943

  6. Data location-aware job scheduling in the grid. Application to the GridWay metascheduler

    NASA Astrophysics Data System (ADS)

    Delgado Peris, Antonio; Hernandez, Jose; Huedo, Eduardo; Llorente, Ignacio M.

    2010-04-01

    Grid infrastructures constitute nowadays the core of the computing facilities of the biggest LHC experiments. These experiments produce and manage petabytes of data per year and run thousands of computing jobs every day to process that data. It is the duty of metaschedulers to allocate the tasks to the most appropriate resources at the proper time. Our work reviews the policies that have been proposed for the scheduling of grid jobs in the context of very data-intensive applications. We indicate some of the practical problems that such models will face and describe what we consider essential characteristics of an optimum scheduling system: aim to minimise not only job turnaround time but also data replication, flexibility to support different virtual organisation requirements and capability to coordinate the tasks of data placement and job allocation while keeping their execution decoupled. These ideas have guided the development of an enhanced prototype for GridWay, a general purpose metascheduler, part of the Globus Toolkit and member of the EGEE's RESPECT program. Current GridWay's scheduling algorithm is unaware of data location. Our prototype makes it possible for job requests to set data needs not only as absolute requirements but also as functions for resource ranking. As our tests show, this makes it more flexible than currently used resource brokers to implement different data-aware scheduling algorithms.

  7. Grid integrated distributed PV (GridPV).

    SciTech Connect

    Reno, Matthew J.; Coogan, Kyle

    2013-08-01

    This manual provides the documentation of the MATLAB toolbox of functions for using OpenDSS to simulate the impact of solar energy on the distribution system. The majority of the functions are useful for interfacing OpenDSS and MATLAB, and they are of generic use for commanding OpenDSS from MATLAB and retrieving information from simulations. A set of functions is also included for modeling PV plant output and setting up the PV plant in the OpenDSS simulation. The toolbox contains functions for modeling the OpenDSS distribution feeder on satellite images with GPS coordinates. Finally, example simulations functions are included to show potential uses of the toolbox functions. Each function in the toolbox is documented with the function use syntax, full description, function input list, function output list, example use, and example output.

  8. Cloud Computing for the Grid: GridControl: A Software Platform to Support the Smart Grid

    SciTech Connect

    2012-02-08

    GENI Project: Cornell University is creating a new software platform for grid operators called GridControl that will utilize cloud computing to more efficiently control the grid. In a cloud computing system, there are minimal hardware and software demands on users. The user can tap into a network of computers that is housed elsewhere (the cloud) and the network runs computer applications for the user. The user only needs interface software to access all of the cloud’s data resources, which can be as simple as a web browser. Cloud computing can reduce costs, facilitate innovation through sharing, empower users, and improve the overall reliability of a dispersed system. Cornell’s GridControl will focus on 4 elements: delivering the state of the grid to users quickly and reliably; building networked, scalable grid-control software; tailoring services to emerging smart grid uses; and simulating smart grid behavior under various conditions.

  9. Grid pulse generator

    NASA Astrophysics Data System (ADS)

    Jansweijer, P. P. M.; Vanes, J. T.

    A fast pulse generator was designed for the grid of the injector of the electron accelerator MEA in order to shoot the electrons emitted by the cathode into the bundle pipe where they are accelerated. The generator delivers a high voltage pulse of maximum 6000 V with a rise tile smaller than 50 ns. This results in a slow rate of more than 120,000 V/microsecond. A current of 8 A is required to charge the 60 pF capacity of the grid up to 6000 V is 50 ns. The maximul pulse length is 50 microseconds with a 500 Hz pulse repetition frequency. During these 5 microseconds the pulse amplitude stability is better than 0.1 percent.

  10. Quantum grid infrared photodetectors

    SciTech Connect

    Rokhinson, L.P.; Chen, C.J.; Tsui, D.C.; Vawter, G.A.; Choi, K.K.

    1999-02-01

    In this letter we introduce a quantum well infrared photodetector (QWIP) structure, which we refer to as the quantum grid infrared photodetector (QGIP). In an ideal structure, a grid pattern with very narrow linewidth is created in the QWIP active region to achieve lateral electron confinement, thereby improving its absorption as well as transport characteristics. In order to realize this detector structure, we have fabricated QGIPs with line patterns of lithographical linewidths w{sub l} ranging from 0.1 to 4 {mu}m, allowing for possible sidewall depletion. Low-damage reactive ion beam etching was employed to produce vertical sidewalls. From the experimental data, although the best detector performance occurs at w{sub l}{approx}1.5 {mu}m, the detector starts to improve when w{sub l}{lt}0.5 {mu}m, indicating a possible quantum confinement effect. {copyright} {ital 1999 American Institute of Physics.}

  11. Gridded electron reversal ionizer

    NASA Technical Reports Server (NTRS)

    Chutjian, Ara (Inventor)

    1993-01-01

    A gridded electron reversal ionizer forms a three dimensional cloud of zero or near-zero energy electrons in a cavity within a filament structure surrounding a central electrode having holes through which the sample gas, at reduced pressure, enters an elongated reversal volume. The resultant negative ion stream is applied to a mass analyzer. The reduced electron and ion space-charge limitations of this configuration enhances detection sensitivity for material to be detected by electron attachment, such as narcotic and explosive vapors. Positive ions may be generated by generating electrons having a higher energy, sufficient to ionize the target gas and pulsing the grid negative to stop the electron flow and pulsing the extraction aperture positive to draw out the positive ions.

  12. Smart Grid Demonstration Project

    SciTech Connect

    Miller, Craig; Carroll, Paul; Bell, Abigail

    2015-03-11

    The National Rural Electric Cooperative Association (NRECA) organized the NRECA-U.S. Department of Energy (DOE) Smart Grid Demonstration Project (DE-OE0000222) to install and study a broad range of advanced smart grid technologies in a demonstration that spanned 23 electric cooperatives in 12 states. More than 205,444 pieces of electronic equipment and more than 100,000 minor items (bracket, labels, mounting hardware, fiber optic cable, etc.) were installed to upgrade and enhance the efficiency, reliability, and resiliency of the power networks at the participating co-ops. The objective of this project was to build a path for other electric utilities, and particularly electrical cooperatives, to adopt emerging smart grid technology when it can improve utility operations, thus advancing the co-ops’ familiarity and comfort with such technology. Specifically, the project executed multiple subprojects employing a range of emerging smart grid technologies to test their cost-effectiveness and, where the technology demonstrated value, provided case studies that will enable other electric utilities—particularly electric cooperatives— to use these technologies. NRECA structured the project according to the following three areas: Demonstration of smart grid technology; Advancement of standards to enable the interoperability of components; and Improvement of grid cyber security. We termed these three areas Technology Deployment Study, Interoperability, and Cyber Security. Although the deployment of technology and studying the demonstration projects at coops accounted for the largest portion of the project budget by far, we see our accomplishments in each of the areas as critical to advancing the smart grid. All project deliverables have been published. Technology Deployment Study: The deliverable was a set of 11 single-topic technical reports in areas related to the listed technologies. Each of these reports has already been submitted to DOE, distributed to co-ops, and posted for universal access at www.nreca.coop/smartgrid. This research is available for widespread distribution to both cooperative members and non-members. These reports are listed in Table 1.2. Interoperability: The deliverable in this area was the advancement of the MultiSpeak™ interoperability standard from version 4.0 to version 5.0, and improvement in the MultiSpeak™ documentation to include more than 100 use cases. This deliverable substantially expanded the scope and usability of MultiSpeak, ™ the most widely deployed utility interoperability standard, now in use by more than 900 utilities. MultiSpeak™ documentation can be accessed only at www.multispeak.org. Cyber Security: NRECA’s starting point was to develop cyber security tools that incorporated succinct guidance on best practices. The deliverables were: cyber security extensions to MultiSpeak,™ which allow more security message exchanges; a Guide to Developing a Cyber Security and Risk Mitigation Plan; a Cyber Security Risk Mitigation Checklist; a Cyber Security Plan Template that co-ops can use to create their own cyber security plans; and Security Questions for Smart Grid Vendors.

  13. Neural coding of image structure and contrast polarity of Cartesian, hyperbolic, and polar gratings in the primary and secondary visual cortex of the tree shrew.

    PubMed

    Poirot, Jordan; De Luna, Paolo; Rainer, Gregor

    2016-04-01

    We comprehensively characterize spiking and visual evoked potential (VEP) activity in tree shrew V1 and V2 using Cartesian, hyperbolic, and polar gratings. Neural selectivity to structure of Cartesian gratings was higher than other grating classes in both visual areas. From V1 to V2, structure selectivity of spiking activity increased, whereas corresponding VEP values tended to decrease, suggesting that single-neuron coding of Cartesian grating attributes improved while the cortical columnar organization of these neurons became less precise from V1 to V2. We observed that neurons in V2 generally exhibited similar selectivity for polar and Cartesian gratings, suggesting that structure of polar-like stimuli might be encoded as early as in V2. This hypothesis is supported by the preference shift from V1 to V2 toward polar gratings of higher spatial frequency, consistent with the notion that V2 neurons encode visual scene borders and contours. Neural sensitivity to modulations of polarity of hyperbolic gratings was highest among all grating classes and closely related to the visual receptive field (RF) organization of ON- and OFF-dominated subregions. We show that spatial RF reconstructions depend strongly on grating class, suggesting that intracortical contributions to RF structure are strongest for Cartesian and polar gratings. Hyperbolic gratings tend to recruit least cortical elaboration such that the RF maps are similar to those generated by sparse noise, which most closely approximate feedforward inputs. Our findings complement previous literature in primates, rodents, and carnivores and highlight novel aspects of shape representation and coding occurring in mammalian early visual cortex. PMID:26843607

  14. 76 FR 1153 - Atlantic Grid Operations A LLC, Atlantic Grid Operations B LLC, Atlantic Grid Operations C LLC...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-07

    ... Energy Regulatory Commission Atlantic Grid Operations A LLC, Atlantic Grid Operations B LLC, Atlantic Grid Operations C LLC, Atlantic Grid Operations D LLC and Atlantic Grid Operations E LLC; Notice of... (Commission) Rules of Practice and Procedure, 18 CFR 385.207, and Order No. 679,\\1\\ Atlantic Grid Operations...

  15. TRMM Gridded Text Products

    NASA Technical Reports Server (NTRS)

    Stocker, Erich Franz

    2007-01-01

    NASA's Tropical Rainfall Measuring Mission (TRMM) has many products that contain instantaneous or gridded rain rates often among many other parameters. However, these products because of their completeness can often seem intimidating to users just desiring surface rain rates. For example one of the gridded monthly products contains well over 200 parameters. It is clear that if only rain rates are desired, this many parameters might prove intimidating. In addition, for many good reasons these products are archived and currently distributed in HDF format. This also can be an inhibiting factor in using TRMM rain rates. To provide a simple format and isolate just the rain rates from the many other parameters, the TRMM product created a series of gridded products in ASCII text format. This paper describes the various text rain rate products produced. It provides detailed information about parameters and how they are calculated. It also gives detailed format information. These products are used in a number of applications with the TRMM processing system. The products are produced from the swath instantaneous rain rates and contain information from the three major TRMM instruments: radar, radiometer, and combined. They are simple to use, human readable, and small for downloading.

  16. Grid generation for turbomachinery problems

    NASA Technical Reports Server (NTRS)

    Steinhoff, J.; Reddy, K. C.

    1986-01-01

    The development of a computer code to generate numerical grids for complex internal flow systems such as the fluid flow inside the space shuttle main engine is outlined. The blending technique for generating a grid for stator-rotor combination at a particular radial section is examined. The computer programs which generate these grids are listed in the Appendices. These codes are capable of generating grids at different cross sections and thus providng three dimensional stator-rotor grids for the turbomachinery of the space shuttle main engine.

  17. Wireless Communications in Smart Grid

    NASA Astrophysics Data System (ADS)

    Bojkovic, Zoran; Bakmaz, Bojan

    Communication networks play a crucial role in smart grid, as the intelligence of this complex system is built based on information exchange across the power grid. Wireless communications and networking are among the most economical ways to build the essential part of the scalable communication infrastructure for smart grid. In particular, wireless networks will be deployed widely in the smart grid for automatic meter reading, remote system and customer site monitoring, as well as equipment fault diagnosing. With an increasing interest from both the academic and industrial communities, this chapter systematically investigates recent advances in wireless communication technology for the smart grid.

  18. Compass Coordinate System

    NASA Astrophysics Data System (ADS)

    Wei, Ziqing; Liu, Guangming; Wu, Fumei

    2013-04-01

    This presentation addresses the definition and realization of the Compass Coordinate System, which is utilized by the BeiDou/Compass satellite navigation system. The definition follows the criteria described by the IERS Technical Note No.21. The reference ellipsoid used is the GRS80 ellipsoid except that the IERS recommended value of 3986004.418´108m3s-2 is adopted for the Earth's gravitational constant. The realization has been done in such a way that the system is closely aligned to the ITRF 2008. The relationship between the Compass Coordinate System and the China Geodetic Coordinate System 2000 (CGCS 2000) is also outlined in the presentation.

  19. Progress in Grid Generation: From Chimera to DRAGON Grids

    NASA Technical Reports Server (NTRS)

    Liou, Meng-Sing; Kao, Kai-Hsiung

    1994-01-01

    Hybrid grids, composed of structured and unstructured grids, combines the best features of both. The chimera method is a major stepstone toward a hybrid grid from which the present approach is evolved. The chimera grid composes a set of overlapped structured grids which are independently generated and body-fitted, yielding a high quality grid readily accessible for efficient solution schemes. The chimera method has been shown to be efficient to generate a grid about complex geometries and has been demonstrated to deliver accurate aerodynamic prediction of complex flows. While its geometrical flexibility is attractive, interpolation of data in the overlapped regions - which in today's practice in 3D is done in a nonconservative fashion, is not. In the present paper we propose a hybrid grid scheme that maximizes the advantages of the chimera scheme and adapts the strengths of the unstructured grid while at the same time keeps its weaknesses minimal. Like the chimera method, we first divide up the physical domain by a set of structured body-fitted grids which are separately generated and overlaid throughout a complex configuration. To eliminate any pure data manipulation which does not necessarily follow governing equations, we use non-structured grids only to directly replace the region of the arbitrarily overlapped grids. This new adaptation to the chimera thinking is coined the DRAGON grid. The nonstructured grid region sandwiched between the structured grids is limited in size, resulting in only a small increase in memory and computational effort. The DRAGON method has three important advantages: (1) preserving strengths of the chimera grid; (2) eliminating difficulties sometimes encountered in the chimera scheme, such as the orphan points and bad quality of interpolation stencils; and (3) making grid communication in a fully conservative and consistent manner insofar as the governing equations are concerned. To demonstrate its use, the governing equations are discretized using the newly proposed flux scheme, AUSM+, which will be briefly described herein. Numerical tests on representative 2D inviscid flows are given for demonstration. Finally, extension to 3D is underway, only paced by the availability of the 3D unstructured grid generator.

  20. The Fourier method for tri-atomic systems in the search for the optimal coordinate system

    NASA Astrophysics Data System (ADS)

    Katz, Gil; Yamashita, Koichi; Zeiri, Yehuda; Kosloff, Ronnie

    2002-03-01

    The Fourier grid method has been implemented on four tri-atomic coordinate systems. The explicit forms of the kinetic-energy operators are presented and the method of implementation described. The coordinates tested are the perimetric, Eckart, Jacobi, and conformal Euclidean. A comparative study was carried out using propagation techniques to obtain the lowest vibrational eigenvalues on the H3+ and the van der Waals NaṡṡṡFH molecules for J=0. Converged eigenvalues were obtained for all the coordinate systems tested. The wavepacket representation methods were also compared for the nonadiabatic photodissociation dynamics of the NaṡṡṡFH. When the coordinate systems matched the topology of the potential-energy surface, significant reduction in the grid size was obtained. The analysis has led to a method for evaluating grid efficiency and optimization based on a classical phase space approach.

  1. GridTool: A surface modeling and grid generation tool

    NASA Technical Reports Server (NTRS)

    Samareh-Abolhassani, Jamshid

    1995-01-01

    GridTool is designed around the concept that the surface grids are generated on a set of bi-linear patches. This type of grid generation is quite easy to implement, and it avoids the problems associated with complex CAD surface representations and associated surface parameterizations. However, the resulting surface grids are close to but not on the original CAD surfaces. This problem can be alleviated by projecting the resulting surface grids onto the original CAD surfaces. GridTool is designed primary for unstructured grid generation systems. Currently, GridTool supports VGRID and FELISA systems, and it can be easily extended to support other unstructured grid generation systems. The data in GridTool is stored parametrically so that once the problem is set up, one can modify the surfaces and the entire set of points, curves and patches will be updated automatically. This is very useful in a multidisciplinary design and optimization process. GridTool is written entirely in ANSI 'C', the interface is based on the FORMS library, and the graphics is based on the GL library. The code has been tested successfully on IRIS workstations running IRIX4.0 and above. The memory is allocated dynamically, therefore, memory size will depend on the complexity of geometry/grid. GridTool data structure is based on a link-list structure which allows the required memory to expand and contract dynamically according to the user's data size and action. Data structure contains several types of objects such as points, curves, patches, sources and surfaces. At any given time, there is always an active object which is drawn in magenta, or in their highlighted colors as defined by the resource file which will be discussed later.

  2. Normalized ion distribution function in expanding sheaths of 2D grid electrodes

    NASA Astrophysics Data System (ADS)

    Yi, Changho; Namkung, Won; Cho, Moohyun

    2016-04-01

    Ion distributions in expanding collisionless sheaths of two-dimensional (2D) grid electrodes were studied by using XOOPIC (particle-in-cell) simulations when short pulses of negative high-voltage were applied to electrodes immersed in plasmas. 2D grid electrodes consist of a periodic array of cylindrical electrodes, and the opening ratio of the grid electrodes is defined by the ratio of the spacing between cylindrical electrodes to the periodic length of the grid electrodes. In this paper, we introduce a normalized ion distribution function in normalized coordinates, and it is shown by simulation that the normalized ion distribution function depends only on the opening ratio of the grid electrodes. When the opening ratio of the grid electrodes is fixed, the ion distribution in expanding sheaths can be easily found in various conditions using only a single run of a PIC simulation, and the computation time can be significantly reduced.

  3. Using a radial ultrasound probe's virtual origin to compute midsagittal smoothing splines in polar coordinates.

    PubMed

    Heyne, Matthias; Derrick, Donald

    2015-12-01

    Tongue surface measurements from midsagittal ultrasound scans are effectively arcs with deviations representing tongue shape, but smoothing-spline analysis of variances (SSANOVAs) assume variance around a horizontal line. Therefore, calculating SSANOVA average curves of tongue traces in Cartesian Coordinates [Davidson, J. Acoust. Soc. Am. 120(1), 407-415 (2006)] creates errors that are compounded at tongue tip and root where average tongue shape deviates most from a horizontal line. This paper introduces a method for transforming data into polar coordinates similar to the technique by Mielke [J. Acoust. Soc. Am. 137(5), 2858-2869 (2015)], but using the virtual origin of a radial ultrasound transducer as the polar origin-allowing data conversion in a manner that is robust against between-subject and between-session variability. PMID:26723359

  4. Coordinated education in dietetics.

    PubMed

    Lewis, M N; Beaudette, T M

    1977-06-01

    Details essential in implementing coordinated education in the preparation of the professional dietitian are described. Consideration is given to semantics, with clarification of terms posing problems in the smooth evolution of coordinated programs. Four phases of transition from the traditional to the coordinated process are illustrated: (a) Integration of the clinical phase into the undergraduate years; (b) interrelation of subject matter among departmental courses; (c) trans-disciplinary coordination; and (d) on-going evaluation of the curriculum in terms of professional practice. Also addressed are barriers to change in professional education. The ultimate goals are a balance between standardization and accountability and a climate in which academia has the liberty to meet demands in an innovative fashion. PMID:864150

  5. Developmental coordination disorder

    MedlinePlus

    Physical education and perceptual motor training (combining movement with tasks that require thinking, like math or reading) are the best ways to treat coordination disorder. Using a computer to ... Encouraging physical activity is important to prevent obesity.

  6. Modeling and Expression of Vector Data in the Hexagonal Discrete Global Grid System

    NASA Astrophysics Data System (ADS)

    Tong, X. C.; Ben, J.; Liu, Y. Y.; Zhang, Y. S.

    2013-10-01

    The Discrete Global Grid System (DGGS) is a new type of global spatial data model and is the extension of the plane grid on a sphere. The hexagon is usually used in the construction of DGGS for its advantageous geometric structure. The paper principally focuses on the issue of modeling and expression of vector data in the hexagon DGGS. The precision of vector data is the basis of data recording and data expression, and data with different precision fall into the grid cells of corresponding sizes, making the gridding data themselves contain the precision and scale information. The present method of data recording is reserved, as far as possible, in the data recording process, and only the geometric information of vectors is substituted by the one-dimension coding of grids. This approach is more simple and effective than the digital coordinate recording method. The gridding expression of vector data differs from the traditional technique, mainly due to the subdivision of the durative space by grids as well as the obedience of the subdivision special rules, among which the point expression should activate the corresponding grid cells in the light of the point coordinates. Linear expression should activate the corresponding grid cells of every coordinate as well as the connected grids between every two node cells, and area expression should express both the boundary and internal regions by virtue of grid cells. For spherical expression, vector data have to solve the cell filling problem, but also the extension from planum to sphere. This paper puts forward a reasonable sphere extension approach, in which the vector data expression on the spherical grids was accomplished by the dismantling of vector data on different extended areas and the multi-times transformation. Besides, the algorithm in connection with the vector data was verified through experiments for its effect and efficiency. Moreover, the distance and direction of vector data on the grids would change in the mapping process from planum to sphere girds, leading to an inaccurate spherical gridding expression. So, the effects on the rectilinear direction in grids of the hexagon from the planum-sphere mapping process was investigated, and accuracy control of the spherical expression was processed to make sure that the drawing error of the spherical grids for vector data should be limited within one cell.

  7. Luminescent lanthanide coordination polymers

    SciTech Connect

    Ma, L.; Evans, O.R.; Foxman, B.M.; Lin, W.

    1999-12-13

    One-dimensional lanthanide coordination polymers with the formula Ln(isonicotinate){sub 3}(H{sub 2}O){sub 2} (Ln = Ce, Pr, Nd, Sm, Eu, Tb; 1a-f) were synthesized by treating nitrate or perchlorate salts of Ln(III) with 4-pyridinecarboxaldehyde under hydro(solvo)thermal conditions. Single-crystal and powder X-ray diffraction studies indicate that these lanthanide coordination polymers adopt two different structures. While Ce(III), Pr(III), and Nd(III) complexes adopt a chain structure with alternating Ln-(carboxylate){sub 2}-Ln and Ln-(carboxylate){sub 4}-Ln linkages, Sm(III), Eu(III), and Tb(III) complexes have a doubly carboxylate-bridged infinite-chain structure with one chelating carboxylate group on each metal center. In both structures, the lanthanide centers also bind to two water molecules to yield an eight-coordinate, square antiprismatic geometry. The pyridine nitrogen atoms of the isonicotinate groups do not coordinate to the metal centers in these lanthanide(III) complexes; instead, they direct the formation of Ln(III) coordination polymers via hydrogen bonding with coordinated water molecules. Photoluminescence measurements show that Tb(isonicotinate){sub 3}(H{sub 2}O){sub 2} is highly emissive at room temperature with a quantum yield of {approximately}90%. These results indicate that highly luminescent lanthanide coordination polymers can be assembled using a combination of coordination and hydrogen bonds. Crystal data for 1a: monoclinic space group P2{sub 1}/c, a = 9.712(2) {angstrom}, b = 19.833(4) {angstrom}, c = 11.616(2) {angstrom}, {beta} = 111.89(3){degree}, Z = 4. Crystal data for 1f: monoclinic space group C2/c, a = 20.253(4) {angstrom}, b = 11.584(2) {angstrom}, c = 9.839(2) {angstrom}, {beta} = 115.64(3){degree}, Z = 8.

  8. New coordinates for the amplitude parameter space of continuous gravitational waves

    NASA Astrophysics Data System (ADS)

    Whelan, John T.; Prix, Reinhard; Cutler, Curt J.; Willis, Joshua L.

    2014-03-01

    The parameter space for continuous gravitational waves (GWs) can be divided into amplitude parameters (signal amplitude, inclination and polarization angles describing the orientation of the source, and an initial phase) and phase-evolution parameters (signal frequency and frequency derivatives, and parameters such as sky position which determine the Doppler modulation of the signal). The division is useful in part because of the existence of a set of functions known as the Jaranowski-Królak-Schutz (JKS) coordinates, which are a set of four coordinates on the amplitude parameter space such that the GW signal can be written as a linear combination of four template waveforms (which depend on the phase-evolution parameters) with the JKS coordinates as coefficients. We define a new set of coordinates on the amplitude parameter space, with the same properties, which can be more closely connected to the physical amplitude parameters. These naturally divide into two pairs of Cartesian-like coordinates on two-dimensional subspaces, one corresponding to left- and the other to right-circular polarization. We thus refer to these as circular polarization factored (CPF) coordinates. The corresponding two sets of polar coordinates (known as CPF-polar) can be related in a simple way to the physical parameters. A further coordinate transformation can be made, within each subspace, between CPF and so-called root-radius coordinates, whose radial coordinate is the fourth root of the radial coordinate in CPF-polar coordinates. We illustrate some simplifying applications for these various coordinate systems, such as a calculation of the Jacobian for the transformation between JKS or CPF coordinates and the physical amplitude parameters (amplitude, inclination, polarization and initial phase); a demonstration that the Jacobian between root-radius coordinates and the physical parameters is a constant; an illustration of the signal coordinate singularities associated with left- and right-circular polarization, which correspond to the origins of the two two-dimensional subspaces; and an elucidation of the form of the log-likelihood ratio between hypotheses of Gaussian noise with and without a continuous GW signal. These are used to illustrate some of the prospects for approximate evaluation of a Bayesian detection statistic defined by marginalization over the physical parameter space. Additionally, in the presence of simplifying assumptions about the observing geometry, we are able, using CPF-polar coordinates, to explicitly evaluate the integral for the Bayesian detection statistic, and compare it to the approximate results.

  9. Stagnant lid convection in 3D-Cartesian geometry: Scaling laws and applications to icy moons and dwarf planets

    NASA Astrophysics Data System (ADS)

    Deschamps, Frédéric; Lin, Ja-Ren

    2014-04-01

    We conducted numerical experiments of stagnant lid thermal convection in 3D-Cartesian geometry, and use these experiments to derive parameterizations for the average internal temperature, heat flux, and stagnant lid thickness. Our experiments suggest that the non-dimensional temperature jump across the bottom thermal boundary layer (TBL) is well described by (1 -θm) = 1.23 (ΔTv / ΔT) , where θm is the non-dimensional average temperature of the convective sublayer, and ΔTv / ΔT a viscous temperature scale defined as the inverse of the logarithmic temperature derivative of viscosity. Due to the presence of the stagnant lid at the top of the fluid, the frequency of the time-variations of the surface heat flux is much lower than those of the bottom heat flux. The Nusselt number, measuring the heat transfer, is well explain by Nu = 1.46 Ram0.270 (ΔTv / ΔT)1.21 , where Ram is the effective Rayleigh number. This result indicates that the heat flux through the outer ice shells of large icy moons and dwarf planets is larger than that predicted by scalings in 2D-Cartesian geometry by 20-40%. We then apply our parameterizations to the dynamics of the outer ice I shells of icy moons and dwarf planets. As pointed out in previous studies, our calculations indicate that the presence of volatile in the primordial ocean of these bodies strongly reduces the vigor of convection within their outer ice I shell, the heat transfer through these shells, and the tectonic activity at their surface. Furthermore, thicker ice I layers may be achieved in bodies having low (0.7 m/s2) gravity acceleration (e.g., Pluto), than in bodies having larger (1.3 m/s2 and more) gravity acceleration (e.g., Europa, Ganymede, and Titan). Decrease in the surface temperature increases the thickness of the stagnant lid, which may result in a stronger lithosphere, and thus in fewer tectonic activity. Our parameterizations may also be used as boundary conditions at zero curvature to build parameterizations in spherical geometry.

  10. Grid crusher apparatus and method

    SciTech Connect

    McDaniels, J.D. Jr.

    1994-01-11

    A grid crusher apparatus and method are provided for a nuclear fuel rod consolidation system. Spacer grids are crushed within a basket which is then placed in a storage canister. The grid crusher apparatus has a ram assembly and a basket driving mechanism. The ram assembly has a sleeve ram and a central ram. The sleeve ram surrounds the central ram which is longitudinally movable within the sleeve ram. The central ram protrudes from the sleeve ram at a ram contact end and is retractable upon application of a preselected force to the central ram so that the central ram is flush with the sleeve ram at the ram contact end. The basket driving mechanism is configured to move the basket containing a spacer grid towards the ram contact end so that the spacer grid is crushed within the basket. The spacer grid is crushed by the combination of successive forces from the central ram and the sleeve ram, respectively. Essentially, the central portion of the spacer grid is crushed first, and then the remaining outer portion of the spacer grid is crushed to complete the crushing action of the spacer grid. The foregoing process is repeated for other spacer grids until the basket reaches a predetermined allowable capacity, and then the basket is stored in a storage canister. 11 figs.

  11. A study of overflow simulations using MPAS-Ocean: Vertical grids, resolution, and viscosity

    NASA Astrophysics Data System (ADS)

    Reckinger, Shanon M.; Petersen, Mark R.; Reckinger, Scott J.

    2015-12-01

    MPAS-Ocean is used to simulate an idealized, density-driven overflow using the dynamics of overflow mixing and entrainment (DOME) setup. Numerical simulations are carried out using three of the vertical coordinate types available in MPAS-Ocean, including z-star with partial bottom cells, z-star with full cells, and sigma coordinates. The results are first benchmarked against other models, including the MITgcm's z-coordinate model and HIM's isopycnal coordinate model, which are used to set the base case used for this work. A full parameter study is presented that looks at how sensitive overflow simulations are to vertical grid type, resolution, and viscosity. Horizontal resolutions with 50 km grid cells are under-resolved and produce poor results, regardless of other parameter settings. Vertical grids ranging in thickness from 15 m to 120 m were tested. A horizontal resolution of 10 km and a vertical resolution of 60 m are sufficient to resolve the mesoscale dynamics of the DOME configuration, which mimics real-world overflow parameters. Mixing and final buoyancy are least sensitive to horizontal viscosity, but strongly sensitive to vertical viscosity. This suggests that vertical viscosity could be adjusted in overflow water formation regions to influence mixing and product water characteristics. Lastly, the study shows that sigma coordinates produce much less mixing than z-type coordinates, resulting in heavier plumes that go further down slope. Sigma coordinates are less sensitive to changes in resolution but as sensitive to vertical viscosity compared to z-coordinates.

  12. Advanced Techniques for Constrained Internal Coordinate Molecular Dynamics

    PubMed Central

    Wagner, Jeffrey R.; Balaraman, Gouthaman S.; Niesen, Michiel J. M.; Larsen, Adrien B.; Jain, Abhinandan; Vaidehi, Nagarajan

    2013-01-01

    Internal coordinate molecular dynamics (ICMD) methods provide a more natural description of a protein by using bond, angle and torsional coordinates instead of a Cartesian coordinate representation. Freezing high frequency bonds and angles in the ICMD model gives rise to constrained ICMD (CICMD) models. There are several theoretical aspects that need to be developed in order to make the CICMD method robust and widely usable. In this paper we have designed a new framework for 1) initializing velocities for non-independent CICMD coordinates, 2) efficient computation of center of mass velocity during CICMD simulations, 3) using advanced integrators such as Runge-Kutta, Lobatto and adaptive CVODE for CICMD simulations, and 4) cancelling out the “flying ice cube effect” that sometimes arises in Nosé-Hoover dynamics. The Generalized Newton-Euler Inverse Mass Operator (GNEIMO) method is an implementation of a CICMD method that we have developed to study protein dynamics. GNEIMO allows for a hierarchy of coarse-grained simulation models based on the ability to rigidly constrain any group of atoms. In this paper, we perform tests on the Lobatto and Runge-Kutta integrators to determine optimal simulation parameters. We also implement an adaptive coarse graining tool using the GNEIMO Python interface. This tool enables the secondary structure-guided “freezing and thawing” of degrees of freedom in the molecule on the fly during MD simulations, and is shown to fold four proteins to their native topologies. With these advancements we envision the use of the GNEIMO method in protein structure prediction, structure refinement, and in studying domain motion. PMID:23345138

  13. Coordinate Representations for Interference Reduction in Motor Learning

    PubMed Central

    Yeo, Sang-Hoon; Wolpert, Daniel M.; Franklin, David W.

    2015-01-01

    When opposing force fields are presented alternately or randomly across trials for identical reaching movements, subjects learn neither force field, a behavior termed ‘interference’. Studies have shown that a small difference in the endpoint posture of the limb reduces this interference. However, any difference in the limb’s endpoint location typically changes the hand position, joint angles and the hand orientation making it ambiguous as to which of these changes underlies the ability to learn dynamics that normally interfere. Here we examine the extent to which each of these three possible coordinate systems—Cartesian hand position, shoulder and elbow joint angles, or hand orientation—underlies the reduction in interference. Subjects performed goal-directed reaching movements in five different limb configurations designed so that different pairs of these configurations involved a change in only one coordinate system. By specifically assigning clockwise and counter-clockwise force fields to the configurations we could create three different conditions in which the direction of the force field could only be uniquely distinguished in one of the three coordinate systems. We examined the ability to learn the two fields based on each of the coordinate systems. The largest reduction of interference was observed when the field direction was linked to the hand orientation with smaller reductions in the other two conditions. This result demonstrates that the strongest reduction in interference occurred with changes in the hand orientation, suggesting that hand orientation may have a privileged role in reducing motor interference for changes in the endpoint posture of the limb. PMID:26067480

  14. Evaluating the Information Power Grid using the NAS Grid Benchmarks

    NASA Technical Reports Server (NTRS)

    VanderWijngaartm Rob F.; Frumkin, Michael A.

    2004-01-01

    The NAS Grid Benchmarks (NGB) are a collection of synthetic distributed applications designed to rate the performance and functionality of computational grids. We compare several implementations of the NGB to determine programmability and efficiency of NASA's Information Power Grid (IPG), whose services are mostly based on the Globus Toolkit. We report on the overheads involved in porting existing NGB reference implementations to the IPG. No changes were made to the component tasks of the NGB can still be improved.

  15. TASMANIAN Sparse Grids Module

    Energy Science and Technology Software Center (ESTSC)

    2013-09-20

    Sparse Grids are the family of methods of choice for multidimensional integration and interpolation in low to moderate number of dimensions. The method is to select extend a one dimensional set of abscissas, weights and basis functions by taking a subset of all possible tensor products. The module provides the ability to create global and local approximations based on polynomials and wavelets. The software has three components, a library, a wrapper for the library thatmore » provides a command line interface via text files ad a MATLAB interface via the command line tool.« less

  16. TASMANIAN Sparse Grids Module

    SciTech Connect

    and Drayton Munster, Miroslav Stoyanov

    2013-09-20

    Sparse Grids are the family of methods of choice for multidimensional integration and interpolation in low to moderate number of dimensions. The method is to select extend a one dimensional set of abscissas, weights and basis functions by taking a subset of all possible tensor products. The module provides the ability to create global and local approximations based on polynomials and wavelets. The software has three components, a library, a wrapper for the library that provides a command line interface via text files ad a MATLAB interface via the command line tool.

  17. Adventures in Computational Grids

    NASA Technical Reports Server (NTRS)

    Walatka, Pamela P.; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    Sometimes one supercomputer is not enough. Or your local supercomputers are busy, or not configured for your job. Or you don't have any supercomputers. You might be trying to simulate worldwide weather changes in real time, requiring more compute power than you could get from any one machine. Or you might be collecting microbiological samples on an island, and need to examine them with a special microscope located on the other side of the continent. These are the times when you need a computational grid.

  18. Provably optimal parallel transport sweeps on regular grids

    SciTech Connect

    Adams, M. P.; Adams, M. L.; Hawkins, W. D.; Smith, T.; Rauchwerger, L.; Amato, N. M.; Bailey, T. S.; Falgout, R. D.

    2013-07-01

    We have found provably optimal algorithms for full-domain discrete-ordinate transport sweeps on regular grids in 3D Cartesian geometry. We describe these algorithms and sketch a 'proof that they always execute the full eight-octant sweep in the minimum possible number of stages for a given P{sub x} x P{sub y} x P{sub z} partitioning. Computational results demonstrate that our optimal scheduling algorithms execute sweeps in the minimum possible stage count. Observed parallel efficiencies agree well with our performance model. An older version of our PDT transport code achieves almost 80% parallel efficiency on 131,072 cores, on a weak-scaling problem with only one energy group, 80 directions, and 4096 cells/core. A newer version is less efficient at present-we are still improving its implementation - but achieves almost 60% parallel efficiency on 393,216 cores. These results conclusively demonstrate that sweeps can perform with high efficiency on core counts approaching 10{sup 6}. (authors)

  19. Stress boundary conditions with the staggered grid: a numerical investigation

    NASA Astrophysics Data System (ADS)

    Duretz, Thibault; May, Dave

    2014-05-01

    In this study, we investigate the numerical properties of the finite-difference method employing dynamic boundary conditions (BC). Stress BC's are gaining popularity in the geodynamic modelling community since the use of a free surface (stress-free BC) is required to model the dynamic evolution of topography. Additionnaly, normal stress BC's might also be used to prescribe known lithospheric rheological models as a dynamic forcing. Under this constraints, boundary velocities are not fixed, they thus vary through time in reaction to stress equilibria within the domain. Dynamic BC's were implemented on a regular Cartesian mesh using a standart staggered grid discretisation. The numerical properties of the scheme were quantified by means of a convergence study and error analysis. Integrated errors owing to the numerical method were evaluated using analytical and manufactured full flow-field solutions and associated convergence rates were derived. Finally, we present two lithospheric-scale applications. The first model depicts the topographic evolution of a linear-viscous lithosphere subjected to the rise of a mantle plume, employing a staircase type free surface. The second model shows the pattern of strain localisation in a thermally activated power law crust subjected to normal stress loading.

  20. SEXIE 3.0 — an updated computer program for the calculation of coordination shells and geometries

    NASA Astrophysics Data System (ADS)

    Tabor-Morris, Anne E.; Rupp, Bernhard

    1994-08-01

    We report a new version of our FORTRAN program SEXIE (ACBV). New features permit interfacing to related programs for EXAFS calculations (FEFF by J.J. Rehr et al.) and structure visualization (SCHAKAL by E. Keller). The code has been refined and the basis transformation matrix from fractional to cartesian coordinates has been corrected and made compatible with IUCr (International Union for Crystallography) standards. We discuss how to determine the correct space group setting and atom position input. New examples for Unix script files are provided.

  1. The Volume Grid Manipulator (VGM): A Grid Reusability Tool

    NASA Technical Reports Server (NTRS)

    Alter, Stephen J.

    1997-01-01

    This document is a manual describing how to use the Volume Grid Manipulation (VGM) software. The code is specifically designed to alter or manipulate existing surface and volume structured grids to improve grid quality through the reduction of grid line skewness, removal of negative volumes, and adaption of surface and volume grids to flow field gradients. The software uses a command language to perform all manipulations thereby offering the capability of executing multiple manipulations on a single grid during an execution of the code. The command language can be input to the VGM code by a UNIX style redirected file, or interactively while the code is executing. The manual consists of 14 sections. The first is an introduction to grid manipulation; where it is most applicable and where the strengths of such software can be utilized. The next two sections describe the memory management and the manipulation command language. The following 8 sections describe simple and complex manipulations that can be used in conjunction with one another to smooth, adapt, and reuse existing grids for various computations. These are accompanied by a tutorial section that describes how to use the commands and manipulations to solve actual grid generation problems. The last two sections are a command reference guide and trouble shooting sections to aid in the use of the code as well as describe problems associated with generated scripts for manipulation control.

  2. Multi-grid calculation of transonic potential flows

    NASA Technical Reports Server (NTRS)

    Caughey, D. A.; Shmilovich, A.

    1985-01-01

    The finite-volume method discussed by Jameson and Caughey (1977), and Caughey and Jameson (1979, 1980) has made it possible to calculate the transonic potential flow past any configuration for which a suitable boundary-conforming coordinate grid can be constructed. However, computations for practical three-dimensional problems have remained quite expensive in terms of the required computer time. The reason for this is primarily related to the large number of grid cells necessary for adequate resolution in these complex three-dimensional problems, taking into account the large number of iterations required to achieve even modest convergence on these fine grids. The present chapter provides a description of work directed at removing this latter difficulty by making use of the multigrid method. Attention is given to finite-volume formulation, multigrid iteration, geometrical aspects, and computed results.

  3. Spatial grid services for adaptive spatial query optimization

    NASA Astrophysics Data System (ADS)

    Gao, Bingbo; Xie, Chuanjie; Sheng, Wentao

    2008-10-01

    Spatial information sharing and integration has now become an important issue of Geographical Information Science (GIS). Web Service technologies provide a easy and standard way to share spatial resources over network, and grid technologies which aim at sharing resources such as data, storage, and computational powers can help the sharing go deeper. However, the dynamic characteristic of grid brings complexity to spatial query optimization which is more stressed in GIS domain because spatial operations are both CPU intensive and data intensive. To address this problem, a new grid framework is employed to provide standard spatial services which can also manage and report their state information to the coordinator which is responsible for distributed spatial query optimization.

  4. Prepares Overset Grids for Processing

    Energy Science and Technology Software Center (ESTSC)

    1998-04-22

    Many large and complex computational problems require multiple, structured, generically overlapped (overset) grids to obtain numerical solutions in a timely manner. BREAKUP significantly reduces required compute times by preparing overset grids for processing on massively parallel computers. BREAKUP subdivides the original grids for use on a user-specified number of parallel processors. Grid-to-grid and intragrid communications are maintained in the parallel environment via connectivity tables generated by BREAKUP. The subgrids are formed to be statically loadmore » balanced and to incur a minimum of communication between the subgrids. When the output of BREAKUP is submitted to an appropriately modified flow solver, subgrid solutions will be updated simultaneously. This contrasts to the much less efficient solution method of updating each original grid sequentially as done in the past.« less

  5. Prepares Overset Grids for Processing

    SciTech Connect

    1998-04-22

    Many large and complex computational problems require multiple, structured, generically overlapped (overset) grids to obtain numerical solutions in a timely manner. BREAKUP significantly reduces required compute times by preparing overset grids for processing on massively parallel computers. BREAKUP subdivides the original grids for use on a user-specified number of parallel processors. Grid-to-grid and intragrid communications are maintained in the parallel environment via connectivity tables generated by BREAKUP. The subgrids are formed to be statically load balanced and to incur a minimum of communication between the subgrids. When the output of BREAKUP is submitted to an appropriately modified flow solver, subgrid solutions will be updated simultaneously. This contrasts to the much less efficient solution method of updating each original grid sequentially as done in the past.

  6. Using the LibCF/GRIDSPEC extensions to interpret data on mosaic grids with CDAT

    NASA Astrophysics Data System (ADS)

    Kindig, D.; Pletzer, A.; Balaji, V.; Hankin, S. C.; Hartnett, E. J.; Doutriaux, C.; Painter, J.; Sobol, A.; Wrobel, M.

    2010-12-01

    Increasingly earth system models perform computations on grids that are not describable as simple, rectangular arrays (e.g. lon by lat), instead requiring a mosaic of interacting, logically rectangular tiles. Such grids are developed for a variety of reasons that include removal of coordinate singularities that may degrade numerical reliability in a region of interest (e.g. the north pole in an ocean model) and increasing the uniformity of numerical precision over the globe. Coupled earth system models, typically characterized by independent coordinate reference systems for modeling atmosphere, ocean, ice, and terrestrial processes, are themselves examples of such mosaic grids. GRIDSPEC is a proposed set of conventions to the Climate and Forecast library (LibCF) describing data on mosaic grids developed by V. Balaji et al. (Geophysical Fluid Dynamics Laboratory). It supports unstructured assemblies of structured grids, including the cubed-sphere and tripolar meshes. Here we review a GRIDSPEC NetCDF format based on host, contact, grid, and data files. We will show how mosaic grids can be created from the ground up using a C API and the Python Climate Data Anaysis Tools (CDAT) for visualization. As an application we use GRIDSPEC to regrid cubed-sphere data onto a longitude-latitude grid.

  7. LDCM Grid Prototype (LGP)

    NASA Technical Reports Server (NTRS)

    Weinstein, Beth; Lubelczyk, Jeff

    2006-01-01

    The LGP successfully demonstrated that grid technology could be used to create a collaboration among research scientists, their science development machines, and distributed data to create a science production system in a nationally distributed environment. Grid technology provides a low cost and effective method of enabling production of science products by the science community. To demonstrate this, the LGP partnered with NASA GSFC scientists and used their existing science algorithms to generate virtual Landsat-like data products using distributed data resources. LGP created 48 output composite scenes with 4 input scenes each for a total of 192 scienes processed in parallel. The demonstration took 12 hours, which beat the requirement by almost 50 percent, well within the LDCM requirement to process 250 scenes per day. The LGP project also showed the successful use of workflow tools to automate the processing. Investing in this technology has led to funding for a ROSES ACCESS proposal. The proposal intends to enable an expert science user to produce products from a number of similar distributed instrument data sets using the Land Cover Change Community-based Processing and Analysis System (LC-ComPS) Toolbox. The LC-ComPS Toolbox is a collection of science algorithms that enable the generation of data with ground resolution on the order of Landsat-class instruments.

  8. Grid Task Execution

    NASA Technical Reports Server (NTRS)

    Hu, Chaumin

    2007-01-01

    IPG Execution Service is a framework that reliably executes complex jobs on a computational grid, and is part of the IPG service architecture designed to support location-independent computing. The new grid service enables users to describe the platform on which they need a job to run, which allows the service to locate the desired platform, configure it for the required application, and execute the job. After a job is submitted, users can monitor it through periodic notifications, or through queries. Each job consists of a set of tasks that performs actions such as executing applications and managing data. Each task is executed based on a starting condition that is an expression of the states of other tasks. This formulation allows tasks to be executed in parallel, and also allows a user to specify tasks to execute when other tasks succeed, fail, or are canceled. The two core components of the Execution Service are the Task Database, which stores tasks that have been submitted for execution, and the Task Manager, which executes tasks in the proper order, based on the user-specified starting conditions, and avoids overloading local and remote resources while executing tasks.

  9. Smart Grid Enabled EVSE

    SciTech Connect

    None, None

    2014-10-15

    The combined team of GE Global Research, Federal Express, National Renewable Energy Laboratory, and Consolidated Edison has successfully achieved the established goals contained within the Department of Energy’s Smart Grid Capable Electric Vehicle Supply Equipment funding opportunity. The final program product, shown charging two vehicles in Figure 1, reduces by nearly 50% the total installed system cost of the electric vehicle supply equipment (EVSE) as well as enabling a host of new Smart Grid enabled features. These include bi-directional communications, load control, utility message exchange and transaction management information. Using the new charging system, Utilities or energy service providers will now be able to monitor transportation related electrical loads on their distribution networks, send load control commands or preferences to individual systems, and then see measured responses. Installation owners will be able to authorize usage of the stations, monitor operations, and optimally control their electricity consumption. These features and cost reductions have been developed through a total system design solution.

  10. Grid-Enabled Measures

    PubMed Central

    Moser, Richard P.; Hesse, Bradford W.; Shaikh, Abdul R.; Courtney, Paul; Morgan, Glen; Augustson, Erik; Kobrin, Sarah; Levin, Kerry; Helba, Cynthia; Garner, David; Dunn, Marsha; Coa, Kisha

    2011-01-01

    Scientists are taking advantage of the Internet and collaborative web technology to accelerate discovery in a massively connected, participative environment —a phenomenon referred to by some as Science 2.0. As a new way of doing science, this phenomenon has the potential to push science forward in a more efficient manner than was previously possible. The Grid-Enabled Measures (GEM) database has been conceptualized as an instantiation of Science 2.0 principles by the National Cancer Institute with two overarching goals: (1) Promote the use of standardized measures, which are tied to theoretically based constructs; and (2) Facilitate the ability to share harmonized data resulting from the use of standardized measures. This is done by creating an online venue connected to the Cancer Biomedical Informatics Grid (caBIG®) where a virtual community of researchers can collaborate together and come to consensus on measures by rating, commenting and viewing meta-data about the measures and associated constructs. This paper will describe the web 2.0 principles on which the GEM database is based, describe its functionality, and discuss some of the important issues involved with creating the GEM database, such as the role of mutually agreed-on ontologies (i.e., knowledge categories and the relationships among these categories— for data sharing). PMID:21521586

  11. Time-dependent thermocapillary convection in a Cartesian cavity - Numerical results for a moderate Prandtl number fluid

    NASA Technical Reports Server (NTRS)

    Peltier, L. J.; Biringen, S.

    1993-01-01

    The present numerical simulation explores a thermal-convective mechanism for oscillatory thermocapillary convection in a shallow Cartesian cavity for a Prandtl number 6.78 fluid. The computer program developed for this simulation integrates the two-dimensional, time-dependent Navier-Stokes equations and the energy equation by a time-accurate method on a stretched, staggered mesh. Flat free surfaces are assumed. The instability is shown to depend upon temporal coupling between large scale thermal structures within the flow field and the temperature sensitive free surface. A primary result of this study is the development of a stability diagram presenting the critical Marangoni number separating steady from the time-dependent flow states as a function of aspect ratio for the range of values between 2.3 and 3.8. Within this range, a minimum critical aspect ratio near 2.3 and a minimum critical Marangoni number near 20,000 are predicted below which steady convection is found.

  12. A semi-implicit spectral method for compressible convection of rotating and density-stratified flows in Cartesian geometry

    NASA Astrophysics Data System (ADS)

    Cai, Tao

    2016-04-01

    In this paper, we have described a 'stratified' semi-implicit spectral method to study compressible convection in Cartesian geometry. The full set of compressible hydrodynamic equations are solved in conservative forms. The numerical scheme is accurate and efficient, based on fast Fourier/sin/cos spectral transforms in the horizontal directions, Chebyshev spectral transform or second-order finite difference scheme in the vertical direction, and second order semi-implicit scheme in time marching of linear terms. We have checked the validity of both the fully pseudo-spectral scheme and the mixed finite-difference pseudo-spectral scheme by studying the onset of compressible convection. The difference of the critical Rayleigh number between our numerical result and the linear stability analysis is within two percent. Besides, we have computed the Mach numbers with different Rayleigh numbers in compressible convection. It shows good agreement with the numerical results of finite difference methods and finite volume method. This model has wide application in studying laminar and turbulent flow. Illustrative examples of application on horizontal convection, gravity waves, and long-lived vortex are given in this paper.

  13. Progress in the Simulation of Steady and Time-Dependent Flows with 3D Parallel Unstructured Cartesian Methods

    NASA Technical Reports Server (NTRS)

    Aftosmis, M. J.; Berger, M. J.; Murman, S. M.; Kwak, Dochan (Technical Monitor)

    2002-01-01

    The proposed paper will present recent extensions in the development of an efficient Euler solver for adaptively-refined Cartesian meshes with embedded boundaries. The paper will focus on extensions of the basic method to include solution adaptation, time-dependent flow simulation, and arbitrary rigid domain motion. The parallel multilevel method makes use of on-the-fly parallel domain decomposition to achieve extremely good scalability on large numbers of processors, and is coupled with an automatic coarse mesh generation algorithm for efficient processing by a multigrid smoother. Numerical results are presented demonstrating parallel speed-ups of up to 435 on 512 processors. Solution-based adaptation may be keyed off truncation error estimates using tau-extrapolation or a variety of feature detection based refinement parameters. The multigrid method is extended to for time-dependent flows through the use of a dual-time approach. The extension to rigid domain motion uses an Arbitrary Lagrangian-Eulerlarian (ALE) formulation, and results will be presented for a variety of two- and three-dimensional example problems with both simple and complex geometry.

  14. Cartesian theories on the passions, the pineal gland and the pathogenesis of affective disorders: an early forerunner.

    PubMed

    López-Muñoz, F; Alamo, C

    2011-03-01

    The relationship between physical and functional alterations in the pineal gland, the 'passions' (emotions or feelings) and psychopathology has been a constant throughout the history of medicine. One of the most influential authors on this subject was René Descartes, who discussed it in his work The Treatise on the Passions of the Soul (1649). Descartes believed that 'passions' were sensitive movements that the soul, located in the pineal gland, experienced due to its union with the body, by circulating animal spirits. Descartes described sadness as one of the six primitive passions of the soul, which leads to melancholy if not remedied. Cartesian theories had a great deal of influence on the way that mental pathologies were considered throughout the entire 17th century and during much of the 18th century, but the link between the pineal gland and psychiatric disorders it was definitively highlighted in the 20th century, with the discovery of melatonin in 1958. The recent development of a new pharmacological agent acting through melatonergic receptors (agomelatine) has confirmed the close link between the pineal gland and affective disorders. PMID:20836904

  15. On unstructured grids and solvers

    NASA Technical Reports Server (NTRS)

    Barth, T. J.

    1990-01-01

    The fundamentals and the state-of-the-art technology for unstructured grids and solvers are highlighted. Algorithms and techniques pertinent to mesh generation are discussed. It is shown that grid generation and grid manipulation schemes rely on fast multidimensional searching. Flow solution techniques for the Euler equations, which can be derived from the integral form of the equations are discussed. Sample calculations are also provided.

  16. OGC and Grid Interoperability in enviroGRIDS Project

    NASA Astrophysics Data System (ADS)

    Gorgan, Dorian; Rodila, Denisa; Bacu, Victor; Giuliani, Gregory; Ray, Nicolas

    2010-05-01

    EnviroGRIDS (Black Sea Catchment Observation and Assessment System supporting Sustainable Development) [1] is a 4-years FP7 Project aiming to address the subjects of ecologically unsustainable development and inadequate resource management. The project develops a Spatial Data Infrastructure of the Black Sea Catchment region. The geospatial technologies offer very specialized functionality for Earth Science oriented applications as well as the Grid oriented technology that is able to support distributed and parallel processing. One challenge of the enviroGRIDS project is the interoperability between geospatial and Grid infrastructures by providing the basic and the extended features of the both technologies. The geospatial interoperability technology has been promoted as a way of dealing with large volumes of geospatial data in distributed environments through the development of interoperable Web service specifications proposed by the Open Geospatial Consortium (OGC), with applications spread across multiple fields but especially in Earth observation research. Due to the huge volumes of data available in the geospatial domain and the additional introduced issues (data management, secure data transfer, data distribution and data computation), the need for an infrastructure capable to manage all those problems becomes an important aspect. The Grid promotes and facilitates the secure interoperations of geospatial heterogeneous distributed data within a distributed environment, the creation and management of large distributed computational jobs and assures a security level for communication and transfer of messages based on certificates. This presentation analysis and discusses the most significant use cases for enabling the OGC Web services interoperability with the Grid environment and focuses on the description and implementation of the most promising one. In these use cases we give a special attention to issues such as: the relations between computational grid and the OGC Web service protocols, the advantages offered by the Grid technology - such as providing a secure interoperability between the distributed geospatial resource -and the issues introduced by the integration of distributed geospatial data in a secure environment: data and service discovery, management, access and computation. enviroGRIDS project proposes a new architecture which allows a flexible and scalable approach for integrating the geospatial domain represented by the OGC Web services with the Grid domain represented by the gLite middleware. The parallelism offered by the Grid technology is discussed and explored at the data level, management level and computation level. The analysis is carried out for OGC Web service interoperability in general but specific details are emphasized for Web Map Service (WMS), Web Feature Service (WFS), Web Coverage Service (WCS), Web Processing Service (WPS) and Catalog Service for Web (CSW). Issues regarding the mapping and the interoperability between the OGC and the Grid standards and protocols are analyzed as they are the base in solving the communication problems between the two environments: grid and geospatial. The presetation mainly highlights how the Grid environment and Grid applications capabilities can be extended and utilized in geospatial interoperability. Interoperability between geospatial and Grid infrastructures provides features such as the specific geospatial complex functionality and the high power computation and security of the Grid, high spatial model resolution and geographical area covering, flexible combination and interoperability of the geographical models. According with the Service Oriented Architecture concepts and requirements of interoperability between geospatial and Grid infrastructures each of the main functionality is visible from enviroGRIDS Portal and consequently, by the end user applications such as Decision Maker/Citizen oriented Applications. The enviroGRIDS portal is the single way of the user to get into the system and the portal faces a unique style of the graphical user interface. Main reference for further information: [1] enviroGRIDS Project, http://www.envirogrids.net/

  17. Optimizing Vibrational Coordinates To Modulate Intermode Coupling.

    PubMed

    Zimmerman, Paul M; Smereka, Peter

    2016-04-12

    The choice of coordinate system strongly affects the convergence properties of vibrational structure computations. Two methods for efficient generation of improved vibrational coordinates are presented and justified by analysis of a model anharmonic two-mode Hessian and numerical computations on polyatomic molecules. To produce optimal coordinates, metrics which quantify off-diagonal couplings over a grid of Hessian matrices are minimized through unitary rotations of the vibrational basis. The first proposed metric minimizes the total squared off-diagonal coupling, and the second minimizes the total squared change in off-diagonal coupling. In this procedure certain anharmonic modes tend to localize, for example X-H stretches. The proposed methods do not rely on prior fitting of the potential energy, vibrational structure computations, or localization metrics, so they are unique from previous vibrational coordinate generation algorithms and are generally applicable to polyatomic molecules. Fitting the potential to the approximate n-mode representation in the optimized bases for all-trans polyenes shows that off-diagonal anharmonic couplings are substantially reduced by the new choices of coordinate system. Convergence of vibrational energies is examined in detail for ethylene, and it is shown that coupling-optimized modes converge in vibrational configuration interaction computations to within 1 cm(-1) using only 3-mode couplings, where normal modes require 4-mode couplings for convergence. Comparison of the vibrational configuration interaction convergence with respect to excitation level for the two proposed metrics shows that minimization of the total off-diagonal coupling is most effective for low-cost vibrational structure computations. PMID:26914536

  18. Flexible microporous coordination polymers

    SciTech Connect

    Uemura, Kazuhiro; Matsuda, Ryotaro; Kitagawa, Susumu . E-mail: kitagawa@sbchem.kyoto-u.ac.jp

    2005-08-15

    In a decade, many porous coordination polymers have been synthesized, providing a variety of properties ranging from storage, separation and exchange of guests in their cavities, magnetism, conductivity and catalysis by their frameworks. Recent advent of flexible porous coordination polymers, which exhibit elastic guest accommodation in contrast to rigid three-dimensional (3-D) frameworks of conventional porous materials, have acquired a position as a new class of porous materials. Such flexible porous properties induce highly selective guest accommodation and magnetic modulation, which could now be a unique class of practical materials. In this review, we introduce recent flexible porous coordination polymers (3-17) and their functional properties, categorizing with the four types of pores with framework deformation.

  19. Metastable postural coordination dynamics.

    PubMed

    James, Eric G

    2013-08-26

    The present study examined the coordination dynamics of the head and center of mass (COM) using accelerometry in quiet 1 and 2 leg stance with and without vision. The root mean square jerk of effectors was greater in 1 leg stance and without vision, and was greater for the head in 2 leg stance and greater at the COM for 1 leg stance. The coordination of the COM and head was more variable in 1 leg stance with vision than in the other stance and vision combinations. Both grouped and individual participant data showed metastable coordination dynamics with the presence of ghost attractors on both axes of motion that varied with the task. The findings indicated that stance and visual information conditions acted as control parameters, with increments in task difficulty increasing relative phase variability until a bifurcation in the metastable dynamics occurred in 1 leg stance without vision. PMID:23769730

  20. Recent Progress on the Parallel Implementation of Moving-Body Overset Grid Schemes

    NASA Technical Reports Server (NTRS)

    Wissink, Andrew; Allen, Edwin (Technical Monitor)

    1998-01-01

    Viscous calculations about geometrically complex bodies in which there is relative motion between component parts is one of the most computationally demanding problems facing CFD researchers today. This presentation documents results from the first two years of a CHSSI-funded effort within the U.S. Army AFDD to develop scalable dynamic overset grid methods for unsteady viscous calculations with moving-body problems. The first pan of the presentation will focus on results from OVERFLOW-D1, a parallelized moving-body overset grid scheme that employs traditional Chimera methodology. The two processes that dominate the cost of such problems are the flow solution on each component and the intergrid connectivity solution. Parallel implementations of the OVERFLOW flow solver and DCF3D connectivity software are coupled with a proposed two-part static-dynamic load balancing scheme and tested on the IBM SP and Cray T3E multi-processors. The second part of the presentation will cover some recent results from OVERFLOW-D2, a new flow solver that employs Cartesian grids with various levels of refinement, facilitating solution adaption. A study of the parallel performance of the scheme on large distributed- memory multiprocessor computer architectures will be reported.