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1

Density functional calculation of many-electron systems in cartesian coordinate grid  

E-print Network

A recently developed density functional method, within Hohenberg-Kohn-Sham framework, is used for faithful description of atoms, molecules in Cartesian coordinate grid, by using an LCAO-MO ansatz. Classical Coulomb potential is obtained by means of a Fourier convolution technique. All two-body potentials (including exchange-correlation (XC)) are constructed directly on real grid, while their corresponding matrix elements are computed from numerical integration. Detailed systematic investigation is made for a representative set of atoms/molecules through a number of properties like total energies, component energies, ionization energies, orbital energies, etc. Two nonlocal XC functionals (FT97 and PBE) are considered for pseudopotential calculation of 35 species while preliminary all-electron results are reported for 6 atoms using the LDA XC density functional. Comparison with literature results, wherever possible, exhibits near-complete agreement. This offers a simple efficient route towards accurate reliable...

Roy, Amlan K

2011-01-01

2

The 3D Euler solutions using automated Cartesian grid generation  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

3

A sharp interface Cartesian grid hydrocode  

NASA Astrophysics Data System (ADS)

Dynamic response of materials to high-speed and high-intensity loading conditions is important in several applications including high-speed flows with droplets, bubbles and particles, and hyper-velocity impact and penetration processes. In such high-pressure physics problems, simulations encounter challenges associated with the treatment of material interfaces, particularly when strong nonlinear waves like shock and detonation waves impinge upon them. To simulate such complicated interfacial dynamics problems, a fixed Cartesian grid approach in conjunction with levelset interface tracking is attractive. In this regard, a sharp interface Cartesian grid-based, Ghost Fluid Method (GFM) is developed for resolving embedded fluid, elasto-plastic solid and rigid (solid) objects in hyper-velocity impact and high-intensity shock loaded environment. The embedded boundaries are tracked and represented by virtue of the level set interface tracking technique. The evolving multimaterial interface and the flow are coupled by meticulously enforcing the boundary conditions and jump relations at the interface. In addition, a tree-based Local Mesh Refinement scheme is employed to efficiently resolve the desired physics. The framework developed is generic and is applicable to interfaces separating a wide range of materials and for a broad spectrum of speeds of interaction (O(km/s)). The wide repertoire of problems solved in this work demonstrates the flexibility, stability and robustness of the method in accurately capturing the dynamics of the embedded interface. Shocks interacting with large ensembles of particles are also computed.

Sambasivan, Shiv Kumar

4

Unstructured Cartesian/prismatic grid generation for complex geometries  

NASA Technical Reports Server (NTRS)

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.

Karman, Steve L., Jr.

1995-01-01

5

Efficient Fluid Dynamic Design Optimization Using Cartesian Grids  

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

6

Partitioned Simulation of Fluid-Structure Interaction on Cartesian Grids  

Microsoft Academic Search

\\u000a This contribution describes recent developments and enhancements of the coupling tool preCICE and the flow solver Peano used\\u000a for our partitioned simualtions of fluid-structure interaction scenarios. Peano brings together hardware efficiency and numerical\\u000a efficiency exploiting advantages of tree-structured adaptive Cartesian computational grids that, in particular, allow for\\u000a a very memory-efficient implementation of parallel adaptive multilevel solvers – an efficiency which

H.-J. Bungartz; J. Benk; B. Gatzhammer; M. Mehl; T. Neckel

7

Triangle Geometry Processing for Surface Modeling and Cartesian Grid Generation  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

8

Triangle geometry processing for surface modeling and cartesian grid generation  

DOEpatents

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.

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

2002-09-03

9

Cartesian to geodetic coordinates conversion on a triaxial ellipsoid  

NASA Astrophysics Data System (ADS)

A new method of transforming Cartesian to geodetic (or planetographic) coordinates on a triaxial ellipsoid is presented. The method is based on simple reasoning coming from essentials of vector calculus. The reasoning results in solving a nonlinear system of equations for coordinates of the point being the projection of a point located outside or inside a triaxial ellipsoid along the normal to the ellipsoid. The presented method has been compared to a vector method of Feltens (J Geod 83:129-137, 2009) who claims that no other methods are available in the literature. Generally, our method turns out to be more accurate, faster and applicable to celestial bodies characterized by different geometric parameters. The presented method also fits to the classical problem of converting Cartesian to geodetic coordinates on the ellipsoid of revolution.

Ligas, Marcin

2012-04-01

10

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

NASA Technical Reports Server (NTRS)

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.

2003-01-01

11

Ghost-Cell Method with far-field coarsening and mesh adaptation for Cartesian grids  

Microsoft Academic Search

Cartesian grid methods for inviscid computational fluid dynamics offer great promise for the development of very rapid conceptual design tools. The present paper deals with a number of new features for Cartesian grid methods which appear to be particularly well suited for this application. A key ingredient is the implementation of non-penetration boundary conditions at solid walls which is based

A. Dadone; B. Grossman

2006-01-01

12

The Numerical Simulation of Ship Waves using Cartesian Grid Methods  

E-print Network

Two different cartesian-grid methods are used to simulate the flow around the DDG 5415. The first technique uses a "coupled level-set and volume-of-fluid" (CLS) technique to model the free-surface interface. The no-flux boundary condition on the hull is imposed using a finite-volume technique. The second technique uses a level-set technique (LS) to model the free-surface interface. A body-force technique is used to impose the hull boundary condition. The predictions of both numerical techniques are compared to whisker-probe measurements of the DDG 5415. The level-set technique is also used to investigate the breakup of a two-dimensional spray sheet.

Sussman, Mark

2014-01-01

13

A Sharp Interface Cartesian Grid Method for Simulating Flows with Complex Moving Boundaries  

Microsoft Academic Search

A Cartesian grid method for computing flows with complex immersed, moving boundaries is presented. The flow is computed on a fixed Cartesian mesh and the solid boundaries are allowed to move freely through the mesh. A mixed Eulerian–Lagrangian framework is employed, which allows us to treat the immersed moving boundary as a sharp interface. The incompressible Navier–Stokes equations are discretized

H. S. Udaykumar; R. Mittal; P. Rampunggoon; A. Khanna

2001-01-01

14

The Numerical Simulation of Ship Waves Using Cartesian-Grid and Volume-of-Fluid Methods  

E-print Network

Cartesian-grid methods in combination with immersed-body and volume-of-fluid methods are ideally suited for simulating breaking waves around ships. A surface panelization of the ship hull is used as input to impose body-boundary conditions on a three-dimensional cartesian grid. The volume-of-fluid portion of the numerical algorithm is used to capture the free-surface interface, including the breaking of waves. The numerical scheme is implemented on a parallel computer. Various numerical issues are discussed, including implementing exit boundary conditions, conserving mass using a novel regridding algorithm, improving resolution through the use of stretched grids, minimizing initial transients, and enforcing hull boundary conditions on cartesian grids. Numerical predictions are compared to experimental measurements of ship models moving with forward speed, including model 5415 and model 5365 (Athena). The ability to model forced-motions is illustrated using a heaving sphere moving with forward speed.

Dommermuth, Douglas G; Wyatt, Donald C; Sussman, Mark; Weymouth, Gabriel D; Yue, Dick K P; Adams, Paul; Hand, Randall

2014-01-01

15

A Cartesian Grid Method for Compressible Inviscid Flows M. Asif Farooq  

E-print Network

point treatment we assume the solid boundary lie in the middle between two grid points in the y to the incompressible Navier-Stokes equations. The popularity of the Cartesian grid method is due to its simplicity modelled by a force term in the incompressible momentum equations [13]. Since this approach is not so

Müller,Bernhard

16

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

SciTech Connect

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.

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

2000-06-27

17

Flutter prediction by an Euler method on non-moving Cartesian grids with gridless boundary conditions  

E-print Network

of transonic flutter is shock oscillations, which must be accounted for to adequately predict stability [3 for the prediction of transonic flutter by the Euler equations on a stationary Cartesian mesh. Local grid refinement of transient flow problems in which surface deflections are small (i.e. flutter calculations) without the need

Liu, Feng

18

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

NASA Technical Reports Server (NTRS)

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.

Buning, Pieter G.; Pulliam, Thomas H.

2011-01-01

19

Ghost-cell method for analysis of inviscid three-dimensional flows on Cartesian-grids  

Microsoft Academic Search

The present paper deals with the implementation of non-penetration boundary conditions at solid walls for three-dimensional inviscid flow computations on Cartesian grids. 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

Andrea Dadone; Bernard Grossman

2007-01-01

20

Development and application of a 3D Cartesian grid Euler method  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

21

The Numerical Simulation of Ship Waves Using Cartesian Grid Methods  

E-print Network

-fitted grids to model the ship hull. For the calculation of ship waves, VOF and level- set methods have certain advantages and disadvantages. VOF uses the volume fraction (F) to track the interface. F = 0 corresponds VOF method. Level-set methods use a level- set function () to model the gas-liquid interface

Sussman, Mark

22

Fully Isotropic Fast Marching Methods on Cartesian Grids  

PubMed Central

The existing Fast Marching methods which are used to solve the Eikonal equation use a locally continuous model to estimate the accumulated cost, but a discontinuous (discretized) model for the traveling cost around each grid point. Because the accumulated cost and the traveling (local) cost are treated differently, the estimate of the accumulated cost at any point will vary based on the direction of the arriving front. Instead we propose to estimate the traveling cost at each grid point based on a locally continuous model, where we will interpolate the traveling cost along the direction of the propagating front. We further choose an interpolation scheme that is not biased by the direction of the front. Thus making the fast marching process truly isotropic. We show the significance of removing the directional bias in the computation of the cost in certain applications of fast marching method. We also compare the accuracy and computation times of our proposed methods with the existing state of the art fast marching techniques to demonstrate the superiority of our method.

Appia, Vikram; Yezzi, Anthony

2014-01-01

23

Active stiffness control of a manipulator in cartesian coordinates  

Microsoft Academic Search

A method of actively controlling the apparent stiffness of a manipulator end effecter is presented. The approach allows the programmer to specify the three transnational and three rotational stiffness of a frame located arbitrarily in hand coordinates. Control of the nominal position of the hand then permits simultaneous position and force control. Stiffness may be changed under program control to

J. Kenneth Salisbury

1980-01-01

24

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

NASA Technical Reports Server (NTRS)

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.

Finley, Dennis B.

1995-01-01

25

Contrast sensitivity functions to stimuli defined in Cartesian, polar and hyperbolic coordinates.  

PubMed

Recent electrophysiological studies indicate that cells in the LGN, V1, V2, and V4 areas in monkeys are specifically sensitive to Cartesian, polar and hyperbolic stimuli. We have characterized the contrast sensitivity functions (CSF) to stimuli defined in these coordinates with the two-alternatives forced-choice paradigm. CSFs to Cartesian, concentric, and hyperbolic stimuli have had similar shapes, with peak sensitivity at approximately 3 c/deg. However, the Cartesian CSF peak sensitivity has been at least 0.1 log units higher than that to stimuli in any other coordinate system. The concentric-Bessel CSF has a low-pass shape, peaking at 1.5 c/deg or below. The radial CSF has a bell shape with maximum sensitivity at 8 c/360 degrees. Only the concentric-Bessel CSF could be explained in terms of the components of maximum amplitude of the Fourier transform. Neural models, which in previous studies predicted the responses to Cartesian and polar Glass patterns, failed to account for the full CSFs data. PMID:15807371

Zana, Y; Cavalcanti, A C G T

2005-01-01

26

Grid-coordinate generation program  

USGS Publications Warehouse

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.

Cosner, Oliver J.; Horwich, Esther

1974-01-01

27

On the New Analytical Solution for a Well in Cartesian Coordinates with MODFLOW Comparisons.  

PubMed

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

Batu, Vedat

2014-11-01

28

Adaptive artificial viscosity for multidimensional gas dynamics for Euler variables in Cartesian coordinates  

Microsoft Academic Search

A method of adaptive artificial viscosity (AAV2D-3D) for the solution of two-and three-dimensional equations of gas dynamics\\u000a for Euler variables in the Cartesian coordinates system is considered. This paper continues works [1, 2]. The computational\\u000a scheme is described in detail and the results of the test case are given.

I. V. Popov; I. V. Fryazinov

2010-01-01

29

Determination of soil pH using a cartesian coordinate laboratory robot and electronic switchbox  

Microsoft Academic Search

A commercially available Cartesian coordinate (gantry style) robot has been programmed to sequentially determine soil\\/water pH (pHw) using a desk?top computer, electronic switchbox, pH meter and a bank of five combination electrodes. All movements of the robot together with pHw data acquisition are orchestrated by the computer. Once the pHw data has been acquired, it is stored in an array

Michael N. Quigley; W. Shaw Reid

1998-01-01

30

Cartesian grid simulations of gas-solids flow systems with complex geometry  

SciTech Connect

Complex geometries encountered in many applications of gas–solids flow need special treatment in most legacy multiphase flow solvers with Cartesian numerical grid. This paper briefly outlines the implementation of a cut cell technique in the open-source multiphase flow solver—MFIX for accurate representation of complex geometries. Specifically, applications of the Cartesian cut cell method to different gas–solids fluidization systems including a small scale bubbling fluidized bed with submerged tube bundle and a complete pilot-scale circulating fluidized bed will be presented. In addition to qualitative predictions on the general flow behaviors inside each system, quantitative comparison with the available experimental data will be presented. Furthermore, some results on extending the current cut-cell technique to Lagrangian–Eulerian simulations will be presented.

Dietiker, Jean-Francois; Li, Tingwen; Garg, Rahul; Mehrdad Shahnam

2013-02-01

31

The Numerical Simulation of Ship Waves Using Cartesian Grid Methods with Adaptive Mesh Refinement  

E-print Network

Cartesian-grid methods with Adaptive Mesh Refinement (AMR) are ideally suited for simulating the breaking of waves, the formation of spray, and the entrainment of air around ships. As a result of the cartesian-grid formulation, minimal input is required to describe the ships geometry. A surface panelization of the ship hull is used as input to automatically generate a three-dimensional model. No three-dimensional gridding is required. The AMR portion of the numerical algorithm automatically clusters grid points near the ship in regions where wave breaking, spray formation, and air entrainment occur. Away from the ship, where the flow is less turbulent, the mesh is coarser. The numerical computations are implemented using parallel algorithms. Together, the ease of input and usage, the ability to resolve complex free-surface phenomena, and the speed of the numerical algorithms provide a robust capability for simulating the free-surface disturbances near a ship. Here, numerical predictions, with and without AMR,...

Dommermuth, Douglas G; Beck, Robert F; O'Shea, Thomas T; Wyatt, Donald C; Olson, Kevin; MacNeice, Peter

2014-01-01

32

Sharp Interface Cartesian Grid Method for High Speed Multi-material Dynamics Problems  

NASA Astrophysics Data System (ADS)

The dynamic response of materials to high-speed and high-intensity loading conditions due to shock waves, detonation waves, high-velocity impact and penetration processes is important in several applications including high-speed flows with droplets, bubbles and particles, and hypervelocity impact and penetration. To simulate such complicated high-pressure physics problems,a fixed Cartesian grid approach in conjunction with level set interface tracking is attractive. In this work, a sharp interface, Cartesian grid-based, Ghost Fluid Method is developed for resolving embedded fluid, elasto-plastic solid and rigid objects in hyper-velocity impact and high-intensity shock loaded environment. The embedded multi-material interface is tracked and represented by virtue of the level set interface tracking technique. The evolving interface and the flow are coupled via the GFM approach by meticulously enforcing the boundary conditions and jump relations exactly at the interface. A reflective boundary condition based approach is used to enforce the conditions on the interface. The subcell position of the interface and the topology of the interface are carefully embedded in the interpolation procedure. In addition, a tree-based Local Mesh Refinement scheme is employed to efficiently resolve the desired physics. The broad range of results presented in this work demonstrates the flexibility and robustness of the current approach.

Sambasivan, Shiv Kumar; Udaykumar, H. S.

2009-11-01

33

Development of a Cartesian-grid finite-volume characteristic flux model for marine applications  

NASA Astrophysics Data System (ADS)

A Finite Volume method based on Characteristic Fluxes for compressible fluids is developed. An explicit cell-centered resolution is adopted, where second-order accuracy is provided by using a MUSCL scheme with Sweby or Superbee limiters for the hyperbolic part. Resolution is performed on a generic unstructured Cartesian grid, where solid boundaries are handled by a Cut-Cell method. Interfaces are explicitely advected in a non-diffusive way, ensuring local mass conservation of each fluid. An improved cell cutting has been developed to handle boundaries of arbitrary geometrical complexity. The mesh density is locally adapted to provide accuracy along these boundaries, which can be fixed or move inside the mesh. Instead of using a polygon clipping algorithm, we use the Voxel traversal algorithm coupled with a local floodfill scanline to intersect 2D or 3D boundary surface meshes with the fixed Cartesian grid. Small cells stability problem near the boundaries is solved using a fully conservative merging method. Inflow and outflow conditions are also implemented in the model. The solver is validated on 2D academic test cases, such as the flow past a cylinder. The latter test cases are performed both in the frame of the body and in a fixed frame where the body is moving across the mesh. Extension to 3D is presently being implemented and first results will be presented at the conference.

Leroy, C.; Le Touzé, D.; Alessandrini, B.

2010-06-01

34

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

SciTech Connect

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.

Johansen, H. [Univ. of California, Berkeley, CA (United States). Dept. of Mechanical Engineering; Colella, P. [Lawrence Berkeley National Lab., CA (United States). Center for Computational Sciences and Engineering

1997-01-31

35

A new DFT method for atoms and molecules in Cartesian grid  

E-print Network

Electronic structure calculation of atoms and molecules, in the past few decades has largely been dominated by density functional methods. This is primarily due to the fact that this can account for electron correlation effects in a rigorous, tractable manner keeping the computational cost at a manageable level. With recent advances in methodological development, algorithmic progress as well as computer technology, larger physical, chemical and biological systems are amenable to quantum mechanical calculations than ever before. Here we report the development of a new method for accurate reliable description of atoms, molecules within the Hohenberg-Kohn-Sham density functional theory (DFT). In a Cartesian grid, atom-centered localized basis set, electron density, molecular orbitals, two-body potentials are directly built on the grid. We employ a Fourier convolution method for classical Coulomb potentials by making an Ewald-type decomposition technique in terms of short- and long-range interactions. One-body ma...

Roy, Amlan K

2013-01-01

36

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

NASA Astrophysics Data System (ADS)

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.

Ding, Hang; Yuan, Cheng-jun

2014-09-01

37

A Cut-Cell Approach for 2D Cartesian Meshes that Preserves Orthogonal Grid Sweep Ordering  

SciTech Connect

In this paper, we present a cut-cell methodology for solving the two-dimensional neutral-particle transport equation on an orthogonal Cartesian grid. We allow the rectangular cell to be subdivided into two polygonal subcells. We ensure that this division (or cut) conserves the volumes of the materials in the subcells and we utilize a step-characteristics (SC) slice balance approach (SBA) to calculate the angular fluxes exiting the cell as well as the average scalar fluxes in each subcell. Solving the discrete ordinates transport equation on an arbitrary mesh has historically been difficult to parallelize while maintaining good parallel efficiency. However on Cartesian meshes, the KBA algorithm maintains good parallel efficiency using a direct solve. The ability to preserve this algorithm was a driving factor in the development of our cut-cell method. This method also provides a more accurate depiction of a material interface in a cell, which leads to more accurate solutions downstream of this cell. As a result, fewer spatial cells can be utilized, resulting in reduced memory requirements. We apply this approach in the 2D/3D discrete ordinates neutral-particle transport code Denovo, where we analyze a 2D 3 x 3 lattice of pincells. We show that, for eigenvalue problems, a significant increase in accuracy for a given mesh size is gained by utilizing the cut-cell, SC equations instead of the standard homogenized-cell, SC equations.

Jarrell, Joshua J [ORNL] [ORNL; Grove, Robert E [ORNL] [ORNL; Evans, Thomas M [ORNL] [ORNL

2011-01-01

38

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

NASA Astrophysics Data System (ADS)

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.

Batu, Vedat

2012-01-01

39

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

PubMed

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

Boschitsch, Alexander H; Fenley, Marcia O

2011-05-10

40

Positivity-preserving Runge-Kutta discontinuous Galerkin method on adaptive Cartesian grid for strong moving shock  

E-print Network

. The Cartesian grids with ghost cell im- mersed boundary method for arbitrarily complex geometries is also Qiu), mgoman@dmu.ac.uk (M Goman), xkl@dmu.ac.uk (X Li), liumeilin.cn@gmail.com (M Liu). 1 #12;solid background mesh and their boundaries are represented by different types of cut cells, or solid bodies

Li, Tiejun

41

Sharp interface Cartesian grid method II: A technique for simulating droplet interactions with surfaces of arbitrary shape  

Microsoft Academic Search

A fixed-grid, sharp interface method is developed to simulate droplet impact and spreading on surfaces of arbitrary shape. A finite-difference technique is used to discretize the incompressible Navier–Stokes equations on a Cartesian grid. To compute flow around embedded solid boundaries, a previously developed sharp interface method for solid immersed boundaries is used. The ghost fluid method (GFM) is used for

H. Liu; S. Krishnan; S. Marella; H. S. Udaykumar

2005-01-01

42

An adaptive discretization of incompressible flow using a multitude of moving Cartesian grids  

NASA Astrophysics Data System (ADS)

We present a novel method for discretizing the incompressible Navier-Stokes equations on a multitude of moving and overlapping Cartesian grids each with an independently chosen cell size to address adaptivity. Advection is handled with first and second order accurate semi-Lagrangian schemes in order to alleviate any time step restriction associated with small grid cell sizes. Likewise, an implicit temporal discretization is used for the parabolic terms including Navier-Stokes viscosity which we address separately through the development of a method for solving the heat diffusion equations. The most intricate aspect of any such discretization is the method used in order to solve the elliptic equation for the Navier-Stokes pressure or that resulting from the temporal discretization of parabolic terms. We address this by first removing any degrees of freedom which duplicately cover spatial regions due to overlapping grids, and then providing a discretization for the remaining degrees of freedom adjacent to these regions. We observe that a robust second order accurate symmetric positive definite readily preconditioned discretization can be obtained by constructing a local Voronoi region on the fly for each degree of freedom in question in order to obtain both its stencil (logically connected neighbors) and stencil weights. Internal curved boundaries such as at solid interfaces are handled using a simple immersed boundary approach which is directly applied to the Voronoi mesh in both the viscosity and pressure solves. We independently demonstrate each aspect of our approach on test problems in order to show efficacy and convergence before finally addressing a number of common test cases for incompressible flow with stationary and moving solid bodies.

English, R. Elliot; Qiu, Linhai; Yu, Yue; Fedkiw, Ronald

2013-12-01

43

A Computer Program To Increase Comprehension of the Cartesian Rectangular Coordinate System in High School Pre-Algebra Students.  

ERIC Educational Resources Information Center

The high percentage of high school pre-algebra students having difficulty learning the abstract concept of graphing ordered pairs on the Cartesian rectangular coordinate system was addressed by the creation and implementation of a computer-managed instructional program. Modules consisted of a pretest, instruction, two practice sessions, and a…

Exley, I. Sheck

44

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

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

45

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

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

46

Coordination in Intelligent Grid Environments  

Microsoft Academic Search

A computational grid is a complex system. The state space of a complex system is very large and it is infeasible to create a rigid infrastructure implementing optimal policies and strategies which take into account the current state of the system. An alternative to a rigid infrastructure is to base the system's reactions on logical inference, planning, and learning, the

Xin Bai; Han Yu; Guoqiang Wang; Yongchang Ji; GABRIELA M. MARINESCU; DAN C. MARINESCU; LADISLAU BÖLÖNI

2005-01-01

47

Differentiating Plasmodium falciparum alleles by transforming Cartesian X,Y data to polar coordinates  

PubMed Central

Background Diagnosis of infectious diseases now benefits from advancing technology to perform multiplex analysis of a growing number of variables. These advances enable simultaneous surveillance of markers characterizing species and strain complexity, mutations associated with drug susceptibility, and antigen-based polymorphisms in relation to evaluation of vaccine effectiveness. We have recently developed assays detecting single nucleotide polymorphisms (SNPs) in the P. falciparum genome that take advantage of post-PCR ligation detection reaction and fluorescent microsphere labeling strategies. Data from these assays produce a spectrum of outcomes showing that infections result from single to multiple strains. Traditional methods for distinguishing true positive signal from background can cause false positive diagnoses leading to incorrect interpretation of outcomes associated with disease treatment. Results Following analysis of Plasmodium falciparum dihydrofolate reductase SNPs associated with resistance to a commonly used antimalarial drug, Fansidar (Sulfadoxine/pyrimethamine), and presumably neutral SNPs for parasite strain differentiation, we first evaluated our data after setting a background signal based on the mean plus three standard deviations for known negative control samples. Our analysis of single allelic controls suggested that background for the absent allele increased as the concentration of the target allele increased. To address this problem, we introduced a simple change of variables from customary (X,Y) (Cartesian) coordinates to planar polar coordinates (X = rcos(?), Y = rsin(?)). Classification of multidimensional fluorescence signals based on histograms of angular and radial data distributions proved more effective than classification based on Cartesian thresholds. Comparison with known diallelic dilution controls suggests that histogram-based classification is effective for major:minor allele concentration ratios as high as 10:1. Conclusion We have observed that the diallelic SNP data resulting from analysis of P. falciparum mutations is more accurately diagnosed when a simple polar transform of the (X,Y) data into (r,?) is used. The development of high through-put methods for genotyping P. falciparum SNPs and the refinement of analytical approaches for evaluating these molecular diagnostic results significantly advance the evaluation of parasite population diversity and antimalarial drug resistance. PMID:20587031

2010-01-01

48

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

NASA Astrophysics Data System (ADS)

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.

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

2007-04-01

49

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

NASA Astrophysics Data System (ADS)

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.

Blanc, Emilie; Chiavassa, Guillaume; Lombard, Bruno

2014-10-01

50

Sharp interface Cartesian grid method II: A technique for simulating droplet interactions with surfaces of arbitrary shape  

NASA Astrophysics Data System (ADS)

A fixed-grid, sharp interface method is developed to simulate droplet impact and spreading on surfaces of arbitrary shape. A finite-difference technique is used to discretize the incompressible Navier-Stokes equations on a Cartesian grid. To compute flow around embedded solid boundaries, a previously developed sharp interface method for solid immersed boundaries is used. The ghost fluid method (GFM) is used for fluid-fluid interfaces. The model accounts for the effects of discontinuities such as density and viscosity jumps and singular sources such as surface tension in both bubble and droplet simulations. With a level-set representation of the propagating interface, large deformations of the boundary can be handled easily. The model successfully captures the essential features of interactions between fluid-fluid and solid-fluid phases during impact and spreading. Moving contact lines are modeled with contact angle hysteresis and contact line motion on non-planar surfaces is computed. Experimental observations and other simulation results are used to validate the calculations.

Liu, H.; Krishnan, S.; Marella, S.; Udaykumar, H. S.

2005-11-01

51

Three-dimensional adaptive Cartesian grid method with conservative interface restructuring and reconstruction  

Microsoft Academic Search

Multiphase flows associated with interfacial dynamics, steep jumps in fluid properties and moving boundaries between different phases pose substantial computational challenges in terms of both modeling as well as computational efficiency. The present work extends a marker-based immersed boundary, or front tracking, technique to model the three-dimensional interfacial dynamics. It tracks the moving boundary using triangulated surface grids and solves

Rajkeshar Singh; Wei Shyy

2007-01-01

52

Coordinated motion control of multiple robotic devices for welding and redundancy coordination through constrained optimization in Cartesian space  

Microsoft Academic Search

The problem of coordinating a positioning table and a seven-axis manipulator is examined. The method described is based on subdivision of tasks. The welding table is coordinated to align the weld point surface normal antiparallel to the direction of gravity. The seven-axis robot (a six-axis Cybotech WV 15 robot and a track) is constrained to move the weld torch along

S. Ahmad; S. Luo

1989-01-01

53

A particle-level set-based sharp interface cartesian grid method for impact, penetration, and void collapse  

NASA Astrophysics Data System (ADS)

An Eulerian, sharp interface, Cartesian grid method is developed for the numerical simulation of the response of materials to impact, shocks and detonations. The mass, momentum, and energy equations are solved along with evolution equations for deviatoric stresses and equivalent plastic strain. These equations are cast in Eulerian conservation law form. The Mie-Grüneisen equation of state is used to obtain pressure and the material is modeled as a Johnson-Cook solid. The ENO scheme is employed to capture shocks in combination with a hybrid particle level set technique to evolve sharp immersed boundaries. The numerical technique is able to handle collisions between multiple materials and can accurately compute the dynamics of the immersed boundaries. Results of calculations for axisymmetric Taylor bar impact and penetration of a Tungsten rod into steel plate show good agreement with moving finite element solutions and experimental results. Qualitative agreement with theory is shown for the void collapse phenomenon in an impacted material containing a spherical void.

Tran, L. B.; Udaykumar, H. S.

2004-01-01

54

Polynesian head form: an interpretation of a factor analysis of Cartesian co-ordinate data.  

PubMed Central

The three dimensional co-ordinates of a large number of landmarks on a series of Polynesian skulls have been obtained by means of a diagraph, and from standard lateral cephalograms. The method is accurate, and a very large amount of data is stored in the concise form of the standardized co-ordinates. A factor analysis of some of these data defines a number of distinct craniofacial segments showing independent variation in positioning, and therefore presumably growth, along defined axes. The segments thus defined relate well to the conclusions of other studies of skull growth and form, and support the view that the basis of cranial variation is the same for all Homo sapiens. It is suggested that the strict independence of the isolated craniofacial segments may be a consequence of the particular method, and may not truly reflect the situation in the growing skull. PMID:7328041

Buranarugsa, M; Houghton, P

1981-01-01

55

Nonlinear finite element and characteristic-based transport methods in the thick diffusion limit in Cartesian coordinates  

NASA Astrophysics Data System (ADS)

We analyze the multi-dimensional, solution-dependent family of discontinuous finite element and characteristic methods in the thick, diffusive limit in Cartesian geometry on an arbitrary grid of polygons or polyhedra. We develop various conditions that must be satisfied by the weight and basis functions in order for an individual spatial discretization to have any chance of succeeding in this limit. In addition, we emphasize the various deviations required by this analysis from the solution-independent families. We provide several specific one and two-dimensional spatial discretizations within this family and analyze them in this limit to validate the results of the general analysis. We stress properties of each method's weight and/or basis functions that result in the method's success or failure in this limit. We further provide several relevant numerical examples for each of the individual methods considered to emphasize the utility and predictive capability of the general analysis. We describe in great detail how the algebraically nonlinear spatial discretization equations are solved. We present a modified Newton-Raphson iterative scheme used to eliminate the basis function coefficients in favor of known quantities. Furthermore, we propose an extension to the transport synthetic acceleration (TSA) algorithm for accelerating source iteration as applied to the class of solution-dependent spatial discretizations. We then test this acceleration scheme on a simple family of problems with variable scattering ratios. Finally, we select two different solution-dependent spatial discretizations contained in these families and analyze them in other limits of interest.

Castrianni, Christopher Lee

56

Sharp Interface Immersed-Boundary\\/Level-Set Cartesian Grid Method for Large-Eddy Simulation of Two-Phase Flows with SurfacePiercing Moving Bodies  

Microsoft Academic Search

A sharp interface Cartesian grid method for the large-eddy simulation of two-phase flows interacting with surface-piercing moving bodies is presented. The method is based on a sharp interface immersed boundary formulation for fluid flows with moving boundaries and a level set based ghost fluid method for two-phase interface treatment. A four-step fractional step method is adopted and a Lagrangian dynamic

Jianming Yang; Frederick Stern

2007-01-01

57

Coordinated motion control of multiple robotic devices for welding and redundancy coordination through constrained optimization in Cartesian space  

Microsoft Academic Search

The authors consider the problem of coordinating multiple motion devices for welding purposes. They focus on the problem of controlling a positioning table and a seven-axis manipulator, given the parametric definition of a trajectory on a weld piece. The problem is complex as there are more than nine axes involved and a number of permutations are possible which achieve the

Shaheen Ahmad; Shengwu Luo

1988-01-01

58

A conservative discretization of the Poisson-Nernst-Planck equations on adaptive Cartesian grids  

NASA Astrophysics Data System (ADS)

In this paper we present a novel hybrid finite-difference/finite-volume method for the numerical solution of the nonlinear Poisson-Nernst-Planck (PNP) equations on irregular domains. The method is described in two spatial dimensions but can be extended to three dimensional problems as well. The boundary of the irregular domain is represented implicitly via the zero level set of a signed distance function and quadtree data structures are used to systematically generate adaptive grids needed to accurately capture the electric double layer near the boundary. To handle the nonlinearity in the PNP equations efficiently, a semi-implicit time integration method is utilized. An important feature of our method is that total number of ions in the system is conserved by carefully imposing the boundary conditions, by utilizing a conservative discretization of the diffusive and, more importantly, the nonlinear migrative flux term. Several numerical experiments are conducted which illustrate that the presented method is first-order accurate in time and second-order accurate in space. Moreover, these tests explicitly indicate that the algorithm is also conservative. Finally we illustrate the applicability of our method in the study of the charging dynamics of porous supercapacitors.

Mirzadeh, Mohammad; Gibou, Frédéric

2014-10-01

59

Coordinates  

NSDL National Science Digital Library

This introduction to the labeling of points on a plane by their Cartesian coordinates can optionally be extended to coordinates in 3-dimensional space, to plane polar coordinates and to 3-dimensional polar coordinates. Students should learn to use Cartesian coordinates (x,y) for defining the position of a point in two dimensions and to use Cartesian coordinates (x,y,z) in 3-dimensional space and learn to appreciate the two ways of defining the z axis. Students should also become familiar with some of the tools and terms used by surveyors such as theodolite, azimuth, elevation, and zenith. Optional items for students familiar with trigonometry and with the theorem of Pythagoras are polar coordinates (r,f ) on the plane, Converting (r,f) to (x,y) and vice versa, at least for r, and Spherical polar coordinates (r,q, f) in 3-dimensional space.

Stern, David

60

Cartesian Diver  

NSDL National Science Digital Library

Students observe Pascal's law, Archimedes' principle and the ideal gas law as a Cartesian diver moves within a closed system. The Cartesian diver is neutrally buoyant and begins to sink when an external pressure is applied to the closed system. A basic explanation and proof of this process is provided in this activity, and supplementary ideas for more extensive demonstrations and independent group activities are presented.

National Science Foundation GK-12 and Research Experience for Teachers (RET) Programs,

61

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

SciTech Connect

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.

Götze, Jan P.; Karasulu, Bora; Thiel, Walter [Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr (Germany)] [Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr (Germany)

2013-12-21

62

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

63

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

PubMed

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. PMID:24359353

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

2013-12-21

64

Global magnetohydrodynamical models of turbulence in protoplanetary disks. I. A cylindrical potential on a Cartesian grid and transport of solids  

Microsoft Academic Search

Aims:We present global 3D MHD simulations of disks of gas and solids, aiming at developing models that can be used to study various scenarios of planet formation and planet-disk interaction in turbulent accretion disks. A second goal is to demonstrate that Cartesian codes are comparable to cylindrical and spherical ones in handling the magnetohydrodynamics of the disk simulations while offering

W. Lyra; A. Johansen; H. Klahr; N. Piskunov

2008-01-01

65

Coordination of Cloud Computing and Smart Power Grids  

E-print Network

Coordination of Cloud Computing and Smart Power Grids Amir-Hamed Mohsenian-Rad and Alberto Leon.mohsenian.rad, alberto.leongarcia}@utoronto.ca Abstract--The emergence of cloud computing has established a trend towards increasing the load at locations where they are built. However, data centers and cloud computing also provide

Mohsenian-Rad, Hamed

66

Cartesian Diver  

NSDL National Science Digital Library

In this quick activity (page 1 of the PDF), learners will build a simple Cartesian Diver in an empty 2-liter bottle. Use this activity to demonstrate the principle of buoyancy, similar to the bladder system many fish rely on to move up and down in their watery environment. Relates to the linked video, DragonflyTV GPS: California Fish.

Twin Cities Public Television, Inc.

2006-01-01

67

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

NASA Technical Reports Server (NTRS)

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.

Deane, Anil E.

1996-01-01

68

Cartesian Diver  

NSDL National Science Digital Library

This activity has students create a Cartesian diver, which will act in some ways like a submarine. Students will adjust the amount of air and water in an inverted test tube (the "diver") so that it at first barely floats in a water-filled bottle. Then, they will squeeze the closed bottle to create higher water pressure, causing the diver to sink. Releasing the bottle allows the diver to float again. Written instructions, a list of materials, and illustrations are included.

2001-06-08

69

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

SciTech Connect

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.

Crockett, Robert; Graves, Daniel; Colella, Phillip

2009-10-23

70

Global magnetohydrodynamical models of turbulence in protoplanetary disks I. A cylindrical potential on a Cartesian grid and transport of solids  

E-print Network

We present global 3D MHD simulations of disks of gas and solids, aiming at developing models that can be used to study various scenarios of planet formation and planet-disk interaction in turbulent accretion disks. A second goal is to show that Cartesian codes are comparable to cylindrical and spherical ones in handling the magnetohydrodynamics of the disk simulations, as the disk-in-a-box models presented here develop and sustain MHD turbulence. We investigate the dependence of the magnetorotational instability on disk scale height, finding evidence that the turbulence generated by the magnetorotational instability grows with thermal pressure. The turbulent stresses depend on the thermal pressure obeying a power law of 0.24+/-0.03, compatible with the value of 0.25 found in shearing box calculations. The ratio of stresses decreased with increasing temperature. We also study the dynamics of boulders in the hydromagnetic turbulence. The vertical turbulent diffusion of the embedded boulders is comparable to the turbulent viscosity of the flow. Significant overdensities arise in the solid component as boulders concentrate in high pressure regions.

W. Lyra; A. Johansen; H. Klahr; N. Piskunov

2007-05-28

71

Global models of turbulence in protoplanetary disks I. A cylindrical potential on a Cartesian grid and transport of solids  

E-print Network

We present global 3D MHD simulations of disks of gas and solids, aiming at developing models that can be used to study various scenarios of planet formation and planet-disk interaction in turbulent accretion disks. A second goal is to show that Cartesian codes are comparable to cylindrical and spherical ones in handling the magnetohydrodynamics of the disk simulations, as the disk-in-a-box models presented here develop and sustain MHD turbulence. We investigate the dependence of the magnetorotational instability on disk scale height, finding evidence that the turbulence generated by the magnetorotational instability grows with thermal pressure. The turbulent stresses depend on the thermal pressure obeying a power law of 0.24+/-0.03, compatible with the value of 0.25 found in shearing box calculations. The ratio of stresses decreased with increasing temperature. We also study the dynamics of boulders in the hydromagnetic turbulence. The vertical turbulent diffusion of the embedded boulders is comparable to the...

Lyra, W; Klahr, H; Piskunov, N

2007-01-01

72

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

73

A comparative study of molecular dynamics in Cartesian and in internal coordinates: dynamical instability in the latter caused by nonlinearity of the equations of motion.  

PubMed

The stability of a general molecular dynamics (MD) integration scheme is examined for simulations in generalized (internal plus external) coordinates (GCs). An analytic expression is derived for the local error in energy during each integration time step. This shows that the explicit dependence of the mass-matrix on GCs, which makes the system's Lagrange equations of motion nonlinear, causes MD simulations in GCs to be less stable than those in Cartesian coordinates (CCs). In terms of CCs, the corresponding mass-matrix depends only on atomic masses and thus atomistic motion is subject to the linear Newton equations, which makes the system more stable. Also investigated are two MD methods in GCs that utilize nonzero elements of the vibrational spectroscopic B-matrices. One updates positions and velocities in GCs that are iteratively adjusted so as to conform to the velocity Verlet equivalent in GCs. The other updates positions in GCs and velocities in CCs that are adjusted to satisfy the internal constraints of the new constrained WIGGLE MD scheme. The proposed methods are applied to an isolated n-octane molecule and their performances are compared with those of several CCMD schemes. The simulation results are found to be consistent with the analytic stability analysis. Finally, a method is presented for computing nonzero elements of B-matrices for external rotations without imposing the Casimir-Eckart conditions. PMID:17279495

Lee, Sang-Ho; Palmo, Kim; Krimm, Samuel

2007-04-30

74

Sharp Interface Immersed-Boundary/Level-Set Cartesian Grid Method for Large-Eddy Simulation of Two-Phase Flows with Surface-Piercing Moving Bodies  

NASA Astrophysics Data System (ADS)

A sharp interface Cartesian grid method for the large-eddy simulation of two-phase flows interacting with surface-piercing moving bodies is presented. The method is based on a sharp interface immersed boundary formulation for fluid flows with moving boundaries and a level set based ghost fluid method for two-phase interface treatment. A four-step fractional step method is adopted and a Lagrangian dynamic Smagorinsky subgrid-scale model is used for large-eddy simulations. The combination of immersed boundary method for solid/fluid boundaries and ghost-fluid method for fluid/fluid interfaces is discussed in detail. A variety of test cases with different scales ranging from bubble dynamics to ship hydrodynamics are performed for verification and validation purpose. Several examples of interest such as water exit and entry of a circular cylinder, landslide generated waves, and ship waves are demonstrated to showcase the accuracy and efficiency of our method. Approaches for extending it to high Reynolds number ship flows by means of wall-layer modeling are also discussed.

Yang, Jianming; Stern, Frederick

2007-11-01

75

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

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

76

George W. Arnold George Arnold was appointed National Coordinator for Smart Grid Interoperability at the  

E-print Network

George W. Arnold George Arnold was appointed National Coordinator for Smart Grid Interoperability the development of standards underpinning the nation's Smart Grid. Dr. Arnold joined NIST in September 2006

Magee, Joseph W.

77

Coordination in Intelligent Grid Environments XIN BAI, HAN YU, GUOQIANG WANG, YONGCHANG JI, GABRIELA M. MARINESCU,  

E-print Network

Coordination in Intelligent Grid Environments XIN BAI, HAN YU, GUOQIANG WANG, YONGCHANG JI's reactions on logical inference, planning, and learning, the quintessential elements of an intelligent system. An intelligent grid is one where societal services exhibit intelligent behavior. A coordination service acting

Bölöni, Ladislau L

78

Opening Remarks by George W. Arnold, National Coordinator for Smart Grid Interoperability  

E-print Network

Opening Remarks by George W. Arnold, National Coordinator for Smart Grid Interoperability Conference on Smart Grid Interoperability Standards January 31, 2011 Introduction Chairman Wellinghoff the opportunity to escribe NIST's and our partners efforts to develop standards for an interoperable d smart grid

Magee, Joseph W.

79

Coordination of the Smart Grid and Distributed Data Centers: A Nested Game-Based Optimization Framework  

E-print Network

Coordination of the Smart Grid and Distributed Data Centers: A Nested Game-Based Optimization pricing policies in the recently proposed smart grid technology can incentivize the cloud computing. On the other hand, distributed data centers also provide opportunities to help the smart grid to improve load

Pedram, Massoud

80

Research on coordinated dispatch of PEV charging and wind power in regional grid  

Microsoft Academic Search

It's a long-term task to improve the ability of wind power accommodation for power grid. With PEVs' (Plug-in Electric Vehicle) rapidly development, the potential coordination between PEVs charging and wind power provides a possibility of multi-resource coordinated utilization on intelligent grid platform. PEVs charging load profile and impacts of different charging modes on grid are studied in this paper. On

Shuguang Song; Xueshan Han; Dayang Yu

2011-01-01

81

Discretization formulas for unstructured grids  

NASA Technical Reports Server (NTRS)

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.

Baumeister, Kenneth J.

1988-01-01

82

NON UNIFORM GRID-BASED COORDINATED ROUTING IN WIRELESS SENSOR NETWORKS  

E-print Network

of Engineering Sandra L. Terell, Dean of The Robert B. Tolouse School of Graduate Studies #12;2 Acknowledgements1 NON UNIFORM GRID-BASED COORDINATED ROUTING IN WIRELESS SENSOR NETWORKS Priyanka Kadiyala, B sister for their unconditional love and support throughout. #12;3 Priyanka Kadiyala, Non-uniform Grid

Akl, Robert

83

Using Coordination to Parallelize Sparse-Grid Methods for 3-D CFD Problems  

Microsoft Academic Search

The good parallel computing properties of sparse-grid solution techniques are investigated.For this, an existing sequential CFD code for a standard 3D problem from computationalaerodynamics is restructured into a parallel application. The restructuring is organized accordingto a master\\/slave protocol. The coordinator modules developed thereby are implementedin the coordination language MANIFOLD and are generally applicable. Performanceresults are given for both the sequential

Kees Everaars; Barry Koren

1998-01-01

84

Grid Operation and Coordination with Wind -2 1.0 Introduction  

E-print Network

1 Grid Operation and Coordination with Wind - 2 1.0 Introduction In this set of notes, we picture provides a view on: Relation between inertial response (kinetic energy), primary reserves, their probable contingencies to determine their prospective most severe single contingencies." We will see most

McCalley, James D.

85

Coordinated Control of DFIG's Rotor and Grid Side Converters During Network Unbalance  

Microsoft Academic Search

This paper proposes a coordinated control of the rotor side converters (RSCs) and grid side converters (GSCs) of doubly-fed induction generator (DFIG) based wind generation systems under unbalanced voltage conditions. System behaviors and operations of the RSC and GSC under unbalanced voltage are illustrated. To provide enhanced operation, the RSC is controlled to eliminate the torque oscillations at double supply

Lie Xu

2008-01-01

86

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

NASA Technical Reports Server (NTRS)

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.

Dulikravich, D. S.

1982-01-01

87

Removing Grid Effect of 3-D Euler Deconvolution using Rotating Coordinate  

NASA Astrophysics Data System (ADS)

A new method for removing grid effect of Euler deconvolution is suggested. Gridding is inevitable process for calculating Euler deconvolution, but in the process of gridding and calculating derivative using FFT, errors are generated like Gibb's phenomenon, edge effect, and circular convolution problem. Solutions which are locations and depths of anomaly bodies are calculated at all window locations, therefore, undesirable, scattered, and too many solutions are achieved and looks like meaningless. In this paper, rotating coordinate technique is used for removing grid effect of Euler deconvolution. Once Euler deconvolution is calculated for locations and depths of anomaly bodies at all window positions, the coordinate is rotated until 90 degree by 15 degree, and re-calculated for locations and depths. The process for removing grid effect is the follows: (1) Rotate the gridded potential data from 0 to 90 degree (2)Calculate the conventional 3-D Euler deconvolution for each data (3)Re-rotate Euler solution(locations and depths) to original coordinate (4) Collocation each solution and remove the solution which is not shown in others. Total 7 solutions can be achieved from these procedures, and common locations and depths results which are shown in all 5 solutions are accepted. The effectiveness of rotating technique is evaluated by using rectangular prism model which has 1km thickness at 5km depth from ground. Random noise also added for verifying the rotating technique. In case of adding noise, the depth accuracy become lower, but location still shows good estimate. This method is also implemented to analysis the tectonic interpretation of the Eastern Asia including Korea, China, and Japan using GRACE and CHAMP satellite gravity and magnetic data

Hwang, J.; Yu, S.; Kim, C.; Min, K.; Kim, J.

2006-12-01

88

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

PubMed Central

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

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

89

CARTESIAN MECHANICS* Sophie Roux  

E-print Network

. T.H. = Fermat, Oeuvres de Fermat. E.N. = Galileo, Le Opere di Galileo Galilei. T.W.B. = Mersenne Galileo.1 The purpose of this paper is not to refute this big picture, but to qualify it from a Cartesian

Boyer, Edmond

90

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

NASA Technical Reports Server (NTRS)

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.

Powell, Kenneth G.

1995-01-01

91

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

NASA Astrophysics Data System (ADS)

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.

Powell, Kenneth G.

1995-10-01

92

Zernike Basis to Cartesian Transformations  

E-print Network

The radial polynomials of the 2D (circular) and 3D (spherical) Zernike functions are tabulated as powers of the radial distance. The reciprocal tabulation of powers of the radial distance in series of radial polynomials is also given, based on projections that take advantage of the orthogonality of the polynomials over the unit interval. They may play a role in the expansion of products of the polynomials into sums, which is demonstrated by some examples. Multiplication of the polynomials by the angular bases (azimuth, polar angle) defines the Zernike functions, for which we derive and tabulate transformations to and from the Cartesian coordinate system centered at the middle of the circle or sphere.

Richard J. Mathar

2008-09-13

93

Accelerating NLTE radiative transfer by means of the Forth-and-Back Implicit Lambda Iteration: A two-level atom line formation in 2D Cartesian coordinates  

NASA Astrophysics Data System (ADS)

State-of-the-art methods in multidimensional NLTE radiative transfer are based on the use of local approximate lambda operator within either Jacobi or Gauss-Seidel iterative schemes. Here we propose another approach to the solution of 2D NLTE RT problems, Forth-and-Back Implicit Lambda Iteration (FBILI), developed earlier for 1D geometry. In order to present the method and examine its convergence properties we use the well-known instance of the two-level atom line formation with complete frequency redistribution. In the formal solution of the RT equation we employ short characteristics with two-point algorithm. Using an implicit representation of the source function in the computation of the specific intensities, we compute and store the coefficients of the linear relations J=a+bS between the mean intensity J and the corresponding source function S. The use of iteration factors in the ‘local’ coefficients of these implicit relations in two ‘inward’ sweeps of 2D grid, along with the update of the source function in other two ‘outward’ sweeps leads to four times faster solution than the Jacobi’s one. Moreover, the update made in all four consecutive sweeps of the grid leads to an acceleration by a factor of 6-7 compared to the Jacobi iterative scheme.

Mili?, Ivan; Atanackovi?, Olga

2014-10-01

94

3D finite volume groundwater and heat transport modeling with non-orthogonal grids, using a coordinate transformation method  

Microsoft Academic Search

Many popular groundwater modeling codes are based on the finite differences or finite volume method for orthogonal grids. In cases of complex subsurface geometries this type of grid either leads to coarse geometric representations or to extremely fine meshes. We use a coordinate transformation method (CTM) to circumvent this shortcoming. In computational fluid dynamics (CFD), this method has been applied

W. Rühaak; V. Rath; A. Wolf; C. Clauser

2008-01-01

95

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

E-print Network

1 How do spatial learning and memory occur in the brain? Coordinated learning of entorhinal grid. The hippocampus and medial entorhinal cortex are key brain areas for spatial learning and memory. Place cells learning; spatial memory; grid cells; place cells; entorhinal cortex; hippocampus; learning; self

Spence, Harlan Ernest

96

Logarithmic spiral grids for image processing  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

97

A nested grid, nonhydrostatic, elastic model using a terrain-following coordinate transformation - The radiative-nesting boundary conditions  

NASA Technical Reports Server (NTRS)

This study presents a nested-grid nonhydrostatic and elastic model using a terrain-following coordinate transformation as well as a unique application of grid-nesting techniques to the time-splitting elastic model. A simulation of the 10-m-high Witch of Agnesi Mountain provides the control to test this new model. The results show that the model produces the same solution as that derived from a simple linear analytic model. It is demonstrated that the new nested-grid model improves model resolution without resorting to the costly method of placing a fine-resolution grid over the entire domain. Since the wave reflection from the boundaries of the fine-grid model is well controlled, the boundary of the nested fine-grid model can be located even at the wave-active region. The model can be used to simulate various weather systems in which scale interactions are important.

Chen, Chaing

1991-01-01

98

Game Coloring the Cartesian Product  

E-print Network

Game Coloring the Cartesian Product of Graphs Xuding Zhu1,2 1DEPARTMENT OF APPLIED MATHEMATICS to each vertex a set of n degree 1 neighbors. If G has game coloring number m and G has acyclic chromatic number k, then the Cartesian product G G has game chromatic number at most k(k+m - 1). As a consequence

Zhu, Xuding

99

Development and Applications of 3D Cartesian CFD Technology  

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

100

On Cartesian trees and range minimum queries  

E-print Network

We present new results on Cartesian trees with applications in range minimum queries and bottleneck edge queries. We introduce a cache-oblivious Cartesian tree for solving the range minimum query problem, a Cartesian tree ...

Demaine, Erik D.

101

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

PubMed Central

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

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

2010-01-01

102

Building proteins from C alpha coordinates using the dihedral probability grid Monte Carlo method.  

PubMed Central

Dihedral probability grid Monte Carlo (DPG-MC) is a general-purpose method of conformational sampling that can be applied to many problems in peptide and protein modeling. Here we present the DPG-MC method and apply it to predicting complete protein structures from C alpha coordinates. This is useful in such endeavors as homology modeling, protein structure prediction from lattice simulations, or fitting protein structures to X-ray crystallographic data. It also serves as an example of how DPG-MC can be applied to systems with geometric constraints. The conformational propensities for individual residues are used to guide conformational searches as the protein is built from the amino-terminus to the carboxyl-terminus. Results for a number of proteins show that both the backbone and side chain can be accurately modeled using DPG-MC. Backbone atoms are generally predicted with RMS errors of about 0.5 A (compared to X-ray crystal structure coordinates) and all atoms are predicted to an RMS error of 1.7 A or better. PMID:7549885

Mathiowetz, A. M.; Goddard, W. A.

1995-01-01

103

A second-order curvilinear to Cartesian transformation of immersed interfaces and  

E-print Network

, structured Cartesian grids, ctitious domains, grid transformation, Front Tracking, VOF, Level-Set, multiphase2 -penalty method) or with phase advection with VOF-PLIC, VOF-TVD, Front-tracking or Level found some examples of ctitious domains on curvilinear grids in the literature. An adaptation of the VOF

Boyer, Edmond

104

Cartesian stiffness control of the JPL\\/Stanford\\/Salisbury hand  

Microsoft Academic Search

To be useful as a dexterous end effector in assembly operations, a multifingered hand must be position-controlled to allow preshaping, and force-controlled to apply and regulate grasp forces. The author describes an implementation of stiffness control on the Salisbury hand, from tendon tension control to coordinated Cartesian object stiffness control. Substantial joint friction effects were observed which were predicted well

G. P. Starr

1988-01-01

105

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)

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.

Thompson, J. F. (editor)

1982-01-01

106

A Cartesian embedded boundary method for hyperbolic conservation laws  

SciTech Connect

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.

Sjogreen, B; Petersson, N A

2006-12-04

107

Rapid Structured Volume Grid Smoothing and Adaption Technique  

NASA Technical Reports Server (NTRS)

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.

Alter, Stephen J.

2006-01-01

108

Coordination  

NSDL National Science Digital Library

Coordination is an organized working together of muscles and groups of muscles aimed at bringing about a purposeful movement such as walking or standing. Coordination involves timing and concentration.

Olivia Worland (Purdue University;Biological Sciences)

2008-06-06

109

Ejs Free Fall Cartesian Model  

NSDL National Science Digital Library

The Ejs Free Fall Cartesian model displays the dynamics of a ball dropped near the surface of Earth onto a platform. The initial conditions for the ball are an initial positive velocity in the x direction and zero initial velocity in the y direction. The coefficient of restitution for the ballâs collision with the platform is less than one. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Free Fall Cartesian model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_newton_FreeFallCartesian.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for Newtonian mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Christian, Wolfgang

2008-06-03

110

Interpenetrating coordination polymers from Cu(I) or Ag(I) and flexible ligands: 2D polyrotaxanes and interpenetrating grids.  

PubMed

The reaction of [Cu(CH3CN)4]NO3 or AgNO3 with flexible ligands 1,4-bis(4-pyridylmethyl)-2,3,5,6-tetrafluorobenzene (bpf) or 4,4'-bis(4-pyridylmethyl)-2,2',3,3',5,5',6,6'-octafluorobiphenyl (bpfb) afforded two types of interpenetrating coordination polymers. The structures of [Cu2(bpf)3(NO3)2]n and [Ag2(bpf)3-(NO3)2]n are 2D polyrotaxane networks in which 1D polymeric chains are aligned in a grid. The structure of {[Cu(bpfb)2]NO3}n is a 2D grid polymer with two-fold parallel interpenetration. PMID:17441069

Kasai, Kayoko; Sato, Mariko

2006-09-18

111

Strong Conservation Form and Grid Generation in Nonsteady Curvilinear Coordinates for Implicit Radiation Hydrodynamics in 2D and 3D  

E-print Network

A generalization of implicit conservative numerics to multiple dimensions requires advanced concepts of tensor analysis and differential geometry and hence a more thorough dedication to mathematical fundamentals than maybe expected at first glance. Hence we begin to discuss fundamental mathematics and physics of RHD with special focus on differential geometric consistency and study numerical methods for nonlinear conservation laws to gain a solid definition of the term conservative. The efforts in tensor analysis will be needed when applying Vinokurs theorem to gain the strong conservation form for conservation laws in general curvilinear coordinates. Moreover, it will be required to slightly reformulate the artificial viscosity for such nonlinear coordinates. Astronomical objects are characterized by fast flows and high propagation speeds on the one hand but astronomical length and time scales on the other hand. Implicit numerical schemes are not affected by the Courant Friedrichs Levy condition which limits explicit schemes to rather impracticably small time steps. Implicit methods however produce algebraic problems that require matrix inversion which is computationally expensive. In order to achieve viable resolution, adaptive grid techniques have been developed. It is desired to treat processes on small length scales like shocks and ionization fronts as well as physics at the extent of the objects dimension itself like large scale convection flows and pulsations. The combination of implicit schemes and adaptive grids allows to resolve astrophysics appropriately at various scales. In the last chapter of this paper we study problem oriented adaptive grid generation in 2D and 3D. We establish three main postulations for an ideal grid and analyze several feasible approaches.

Harald Höller

2012-10-18

112

Non-Cartesian parallel imaging reconstruction.  

PubMed

Non-Cartesian parallel imaging has played an important role in reducing data acquisition time in MRI. The use of non-Cartesian trajectories can enable more efficient coverage of k-space, which can be leveraged to reduce scan times. These trajectories can be undersampled to achieve even faster scan times, but the resulting images may contain aliasing artifacts. Just as Cartesian parallel imaging can be used to reconstruct images from undersampled Cartesian data, non-Cartesian parallel imaging methods can mitigate aliasing artifacts by using additional spatial encoding information in the form of the nonhomogeneous sensitivities of multi-coil phased arrays. This review will begin with an overview of non-Cartesian k-space trajectories and their sampling properties, followed by an in-depth discussion of several selected non-Cartesian parallel imaging algorithms. Three representative non-Cartesian parallel imaging methods will be described, including Conjugate Gradient SENSE (CG SENSE), non-Cartesian generalized autocalibrating partially parallel acquisition (GRAPPA), and Iterative Self-Consistent Parallel Imaging Reconstruction (SPIRiT). After a discussion of these three techniques, several potential promising clinical applications of non-Cartesian parallel imaging will be covered. J. Magn. Reson. Imaging 2014;40:1022-1040. © 2014 Wiley Periodicals, Inc. PMID:24408499

Wright, Katherine L; Hamilton, Jesse I; Griswold, Mark A; Gulani, Vikas; Seiberlich, Nicole

2014-11-01

113

Construction of Perfectly Matched Layer in cylindrical coordinates with non-zero mean flow  

Microsoft Academic Search

Non-reflecting boundary condition is an essential component in developing computational fluid dynamics (CFD) and computational aeroacoustics (CAA) algorithms. Perfectly Matched Layer (PML) is a technique for developing non-reflecting boundary conditions. PML for linearized Euler equations, as well as its extension to the nonlinear Euler and Navier-Stokes equations, have been developed recently for computational grid in the Cartesian coordinates. In this

Sarah Parrish; Fang Hu

2007-01-01

114

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

SciTech Connect

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.

Michael Schmitt

2008-05-01

115

Sink or Swim: The Cartesian Diver.  

ERIC Educational Resources Information Center

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)

Pinkerton, K. David

2001-01-01

116

Spherical polar co-ordinate calculations of induced fields in the retina and head for applied magnetic fields at 50 Hz  

NASA Astrophysics Data System (ADS)

This paper sets out to explore the effects of voxel resolution, from 2 mm down to 0.1 mm for Cartesian co-ordinates and the differences between Cartesian and spherical polar co-ordinates for a standardized test-bed model of the eye. This model was taken from the work of Yoriyaz et al (2005 Radiat. Prot. Dosim. 115 316-9) who have developed a detailed geometric description of the eye including choroid, retina, sclera, lens, cornea, anterior chamber, vitreous humour and optic nerve for ophthalmic brachytherapy. The spherical co-ordinate model has radial and angular steplengths of 0.1 mm and 0.25°, respectively. The current density averaged over 1 cm2 and the 99th percentile value of the induced electric field have been calculated in the retina and central nervous system for uniform magnetic fields. The Cartesian co-ordinate calculations proceed in a sequence of grids at 2, 1, 0.5, 0.2 and 0.1 mm resolution with the potentials from the previous calculation at a coarser grid providing the boundary conditions on the finer grid. The 0.2 mm grid provides the boundary conditions for the spherical polar calculations. Comparisons are made with the International Commission on Non-Ionizing Radiation Protection reference levels.

Dimbylow, Peter

2011-07-01

117

Adjoint Formulation for an Embedded-Boundary Cartesian Method  

NASA Technical Reports Server (NTRS)

Many problems in aerodynamic design can be characterized by smooth and convex objective functions. This motivates the use of gradient-based algorithms, particularly for problems with a large number of design variables, to efficiently determine optimal shapes and configurations that maximize aerodynamic performance. Accurate and efficient computation of the gradient, however, remains a challenging task. In optimization problems where the number of design variables dominates the number of objectives and flow- dependent constraints, the cost of gradient computations can be significantly reduced by the use of the adjoint method. The problem of aerodynamic optimization using the adjoint method has been analyzed and validated for both structured and unstructured grids. The method has been applied to design problems governed by the potential, Euler, and Navier-Stokes equations and can be subdivided into the continuous and discrete formulations. Giles and Pierce provide a detailed review of both approaches. Most implementations rely on grid-perturbation or mapping procedures during the gradient computation that explicitly couple changes in the surface shape to the volume grid. The solution of the adjoint equation is usually accomplished using the same scheme that solves the governing flow equations. Examples of such code reuse include multistage Runge-Kutta schemes coupled with multigrid, approximate-factorization, line-implicit Gauss-Seidel, and also preconditioned GMRES. The development of the adjoint method for aerodynamic optimization problems on Cartesian grids has been limited. In contrast to implementations on structured and unstructured grids, Cartesian grid methods decouple the surface discretization from the volume grid. This feature makes Cartesian methods well suited for the automated analysis of complex geometry problems, and consequently a promising approach to aerodynamic optimization. Melvin e t 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 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.

Nemec, Marian; Aftosmis, Michael J.; Murman, Scott M.; Pulliam, Thomas H.

2004-01-01

118

Index integral representations for connection between cartesian, cylindrical, and spheroidal systems  

SciTech Connect

In this paper, we present two new index integral representations for connection between cartesian, cylindrical, and spheroidal coordinate systems in terms of Bessel, MacDonald, and conical functions. Our result is mainly motivated by solution of the boundary value problems in domains composed of both cartesian and hyperboloidal boundaries, and the need for new integral representations that facilitate the transformation between these coordinates. As a by-product, the special cases of our results will produce new proofs to known index integrals and provide some new integral identities.

Passian, Ali [ORNL; Koucheckian, Sherwin [University of South Florida, Tampa; Yakubovich, Semyon [University of Porto, Portugal

2011-01-01

119

Two-boundary grid generation for the solution of the three dimensional compressible Navier-Stokes equations. Ph.D. Thesis - Old Dominion Univ.  

NASA Technical Reports Server (NTRS)

A grid generation technique called the two boundary technique is developed and applied for the solution of the three dimensional Navier-Stokes equations. The Navier-Stokes equations are transformed from a cartesian coordinate system to a computational coordinate system, and the grid generation technique provides the Jacobian matrix describing the transformation. The two boundary technique is based on algebraically defining two distinct boundaries of a flow domain and the distribution of the grid is achieved by applying functions to the uniform computational grid which redistribute the computational independent variables and consequently concentrate or disperse the grid points in the physical domain. The Navier-Stokes equations are solved using a MacCormack time-split technique. Grids and supersonic laminar flow solutions are obtained for a family of three dimensional corners and two spike-nosed bodies.

Smith, R. E.

1981-01-01

120

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

NASA Technical Reports Server (NTRS)

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.

Aftosmis, Michael

2005-01-01

121

Simple Coordinates Game  

NSDL National Science Digital Library

In this activity, students enter in coordinates then the applet places a house at that location, or the location is decided first then the student must enter in the coordinates of the house. This activity allows students to practice with coordinates and ordered pairs in the Cartesian coordinate system. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.

2010-01-01

122

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

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

123

3-Hydroxynaphthalene-2-carboxylic acid supported grid-like structure of cadmium chloride coordination polymer with 1,3-bis(4-pyridyl)propane  

NASA Astrophysics Data System (ADS)

Inclusion of 3-hydroxynaphthalene-2-carboxylic acid in grid-like structure of a coordination-polymer 1 formed from 1,3-bis(4-pyridyl)propane (LL) with cadmium(II) chloride is described. Components of the grid are comprised of cyclic secondary building blocks of 4 + 4 condensation of LLs and cadmium ions. Guest 3-Hydroxynaphthalene-2-carboxylic acid (Hnap) molecules possess intramolecular hydrogen bonds and Csbnd H⋯? and Osbnd H⋯Cl interactions with host coordination polymer. Among four pyridyl rings coordinated to each cadmium ion, two pyridyl rings are distinguishable from other two pyridyl rings as they are involved in Csbnd H⋯Cl interactions. 1H NMR experiments show that Hnap has a role in formation of grid-like structure. A similar reaction of chelating ligand 2,2?-bipyridine and Hnap with cadmium chloride led to a mono-nuclear complex bis(2,2?-bipyridine)-bis(3-hydroxynaphthalene-2-carboxylato)cadmium(II) (2) which was structurally characterized.

Phukan, Nithi; Baruah, Jubaraj B.

2014-11-01

124

SUPRA-CONVERGENCE OF LINEAR EQUATIONS ON IRREGULAR CARTESIAN GRIDS  

E-print Network

the first order error terms. Also in [7], a Lax- Wendroff type scheme with an artificial viscosity on the error terms and establish the second order bounds for the error for Re(s) 0, where s is the vari- able

Soatto, Stefano

125

Enhanced Elliptic Grid Generation  

NASA Technical Reports Server (NTRS)

Method and system for generating an elliptic grid in generalized coordinates in two or three dimensions, where one or more decay parameters near a boundary segment of a grid are determined as part of the grid solution, rather than being prescribed initially by a user. The decay parameters may vary with one or more generalized coordinates and determine the rate(s) at which separation distances between adjacent grid lines change as one moves toward or away from a grid boundary segment.

Kaul, Upender K. (Editor)

2007-01-01

126

Time-independent and time-dependent calculations on one and two-photon ionization of diatomic molecules with a grid-based method in prolate spheroidal coordinates  

NASA Astrophysics Data System (ADS)

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. 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. The time-independent and time-dependent calculations of photoionizaton cross sections for H2^+, as well as time-independent results for the two-electron H2 target, show that the efficiency and accuracy of the present approach offers distinct advantages over methods based on single-center expansions.

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

2009-05-01

127

Cartesian Divers: Experimenting with Pressure and Density  

NSDL National Science Digital Library

Ocean FEST is a program of hands-on, ocean-themed science activities for students in grades 3-6 and/or their families. Our goals are to: (1) educate participants about ocean and earth science issues that are relevant to their communities; and (2) inspire students--especially those from underrepresented groups--to pursue careers in the ocean and earth sciences. This activity has students make predictions and conduct experiments with their own Cartesian diver.

2012-01-01

128

Coordinated learning of grid cell and place cell spatial and temporal properties: Multiple scales, attention, and oscillations  

E-print Network

or more firing fields, that match neurophysiological data about their development in juvenile rats. Both article for a special issue on: Space and the Brain T. Hartley, C. Lever, N. Burgess, and J. O'Keefe, Eds model proposes how entorhinal grid cells and hippocampal place cells may develop as spatial categories

Spence, Harlan Ernest

129

AMR Simulations of Magnetohydrodynamic Problems by the CESE Method in Curvilinear Coordinates  

NASA Astrophysics Data System (ADS)

The objective of this paper is to present new extensions of the space - time conservation element and solution element (CESE) method for simulations of magnetohydrodynamic (MHD) problems in general curvilinear coordinates by using an adaptive mesh refinement (AMR) grid system. By transforming the governing MHD equations from the physical space ( x, y, z) to the computational space ( ?, ?,?) while retaining the form of conservation, the CESE method is established for MHD in the curvilinear coordinates. Utilizing the parallel AMR package PARAMESH, we present the first implementation of applying the AMR CESE method for MHD (AMR-CESE-MHD) in both Cartesian and curvilinear coordinates. To show the validity and capabilities of the AMR-CESE-MHD code, a suite of numerical tests in two and three dimensions including ideal MHD and resistive MHD are carried out, with two of them in both Cartesian and curvilinear coordinates. Numerical tests show that our results are highly consistent with those obtained previously by other authors, and the results under both coordinate systems confirm each other very well.

Jiang, Chaowei; Feng, Xueshang; Zhang, Jian; Zhong, Dingkun

2010-12-01

130

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

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

131

Structured background grids for generation of unstructured grids by advancing front method  

NASA Technical Reports Server (NTRS)

A new method of background grid construction is introduced for generation of unstructured tetrahedral grids using the advancing-front technique. Unlike the conventional triangular/tetrahedral background grids which are difficult to construct and usually inadequate in performance, the new method exploits the simplicity of uniform Cartesian meshes and provides grids of better quality. The approach is analogous to solving a steady-state heat conduction problem with discrete heat sources. The spacing parameters of grid points are distributed over the nodes of a Cartesian background grid by interpolating from a few prescribed sources and solving a Poisson equation. To increase the control over the grid point distribution, a directional clustering approach is used. The new method is convenient to use and provides better grid quality and flexibility. Sample results are presented to demonstrate the power of the method.

Pirzadeh, Shahyar

1991-01-01

132

Strong Conservation Form and Grid Generation in Nonsteady Curvilinear Coordinates for Implicit Radiation Hydrodynamics in 2D and 3D  

E-print Network

A generalization of implicit conservative numerics to multiple dimensions requires advanced concepts of tensor analysis and differential geometry and hence a more thorough dedication to mathematical fundamentals than maybe expected at first glance. Hence we begin to discuss fundamental mathematics and physics of RHD with special focus on differential geometric consistency and study numerical methods for nonlinear conservation laws to gain a solid definition of the term conservative. The efforts in tensor analysis will be needed when applying Vinokurs theorem to gain the strong conservation form for conservation laws in general curvilinear coordinates. Moreover, it will be required to slightly reformulate the artificial viscosity for such nonlinear coordinates. Astronomical objects are characterized by fast flows and high propagation speeds on the one hand but astronomical length and time scales on the other hand. Implicit numerical schemes are not affected by the Courant Friedrichs Levy condition which limits...

Höller, Harald

2012-01-01

133

Material translations in the Cartesian brain.  

PubMed

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

Bassiri, Nima

2012-03-01

134

Data Grid Management Systems  

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

135

Tolerating Correlated Failures for Generalized Cartesian Distributions via Bipartite Matching  

SciTech Connect

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.

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

2011-05-05

136

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

NASA Technical Reports Server (NTRS)

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.

Hood, Caroline; Frendi, Abdelkader

2006-01-01

137

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

NASA Technical Reports Server (NTRS)

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.

Coirier, William J.; Powell, Kenneth G.

1995-01-01

138

Senior Year Project Design and Implementation of a Cartesian Router  

E-print Network

ECED 4902 Senior Year Project Design and Implementation of a Cartesian Router Students: Edward A Submitted: 2001/12/03 #12;Abstract The goal of this project was to design and implement a Cartesian router. Unfortunately, the discrete logic router proved to be too large for two students with full course

Hughes, Larry

139

A breakthrough in neuroscience needs a “Nebulous Cartesian System”  

Microsoft Academic Search

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

Erol Ba?ar; Bahar Güntekin

2007-01-01

140

Self-Modifying Cartesian Genetic Programming Simon Harding  

E-print Network

of Cartesian Genetic Programming that includes self-modification operations. One advantage of this approachSelf-Modifying Cartesian Genetic Programming Simon Harding Dept. of Computer Science Memorial-writing, multi- cell- ularity, or genetic regulation. In many cases it has been difficult to produce general

Fernandez, Thomas

141

Fibonacci Grids  

NASA Technical Reports Server (NTRS)

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.

Swinbank, Richard; Purser, James

2006-01-01

142

Dig That Grid!  

NSDL National Science Digital Library

In this lesson, students will use their knowledge of coordinates and coordinate pairs in a real life situation as they become archaeologists excavating a dig site. They will measure their site, label the grids with correct coordinates and use coordinate pairs to record the location of the artifacts they discover.

Driggers, Diane

2012-06-05

143

Evaluation of gridded Scanning ARM Cloud Radar reflectivity observations and vertical Doppler velocity retrievals  

NASA Astrophysics Data System (ADS)

The Scanning ARM Cloud Radars (SACR's) provide continuous atmospheric observations aspiring to capture the 3-D cloud-scale structure. Sampling clouds in 3-D is challenging due to their temporal-spatial scales, the need to sample the sky at high elevations and cloud radar limitations. Thus, a common scan strategy is to repetitively slice the atmosphere from horizon to horizon as clouds advect over the radar (Cross-Wind Range Height Indicator - CWRHI). Here, the processing and gridding of the SACR CW-RHI scans are presented. First, the SACR sample observations from the ARM Oklahoma (SGP) and Cape-Cod (PVC) sites are post-processed (detection mask, velocity de-aliasing and gaseous attenuation correction). The resulting radial Doppler moment fields are then mapped to Cartesian coordinates with time as one of the dimension. The Cartesian-gridded Doppler velocity fields are next decomposed into the horizontal wind velocity contribution and the vertical Doppler velocity component. For validation purposes, all gridded and retrieved fields are compared to collocated zenith pointing ARM cloud radar measurements. We consider that the SACR sensitivity loss with range, the cloud type observed and the research purpose should be considered in determining the gridded domain size. Our results also demonstrate that the gridded SACR observations resolve the main features of low and high stratiform clouds. It is established that the CW-RHI observations complemented with processing techniques could lead to robust 3-D clouds dynamical representations up to 25-30° off zenith. The proposed gridded products are expected to advance our understanding of 3-D cloud morphology, dynamics, anisotropy and lead to more realistic 3-D radiative transfer calculations.

Lamer, K.; Tatarevic, A.; Jo, I.; Kollias, P.

2013-11-01

144

A comparative study of the parabolized Navier-Stokes code using various grid-generation techniques  

NASA Technical Reports Server (NTRS)

The parabolized Navier-Stokes (PNS) equations are used to calculate the flow-field characteristics about the hypersonic research aircraft X-24C. A comparison of the results obtained using elliptic, hyperbolic and algebraic grid generators is presented. The outer bow shock is treated as a sharp discontinuity, and the discontinuities within the shock layer are captured. Surface pressures and heat-transfer results at angles of attack of 6 deg and 20 deg, obtained using the three grid generators, are compared. The PNS equations are marched downstream over the body in both Cartesian and cylindrical base coordinate systems, and the results are compared. A robust marching procedure is demonstrated by successfully using large marching-step sizes with the implicit shock fitting procedure. A correlation is found between the marching-step size, Reynolds number and the angle of attack at fixed values of smoothing and stability coefficients for the marching scheme.

Kaul, U. K.; Chaussee, D. S.

1985-01-01

145

A comparative study of the parabolized Navier-Stokes code using various grid-generation techniques  

NASA Technical Reports Server (NTRS)

The parabolized Navier-Stokes (PNS) equations are used to calculate the flow-field characteristics about the hypersonic research aircraft X-24C. A comparison of the results obtained using elliptic, hyperbolic, and algebraic grid generators is presented. The outer bow shock is treated as a sharp discontinuity, and the discontinuities within the shock layer are captured. Surface pressures and heat-transfer results at angles of attack of 6 deg and 20 deg, obtained using the three grid generators, are compared. The PNS equations are marched downstream over the body in both Cartesian and cylindrical base coordinate systems, and the results are compared. A robust marching procedure is demonstrated by successfully using large marching step sizes with the implicit shock fitting procedure. A correlation is found between the marching step size, Reynolds number, and the angle of attack at fixed values of smoothing and stability coefficients for the marching scheme.

Kaul, U. K.; Chaussee, D. S.

1984-01-01

146

Twenty-five years of natural coordinates  

Microsoft Academic Search

In the early eighties, the author and co-workers created and further developed the natural coordinates to describe the motion\\u000a of 2-D and 3-D multibody systems. Natural coordinates do not need angles or angular parameters to define orientation, leading\\u000a to constant inertia matrices and to the simplest form of the constraint equations. Natural coordinates are composed by the\\u000a Cartesian coordinates of

Javier García de Jalón

2007-01-01

147

The Structure of Integral Dimensions: Contrasting Topological and Cartesian Representations  

E-print Network

The Structure of Integral Dimensions: Contrasting Topological and Cartesian Representations Matt structure that has never been questioned but may not be psychologically meaningful for integral dimensions dimensions are surprisingly structured, despite their holistic, unanalyzed nature. Keywords: integral

Goldstone, Robert

148

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

NASA Technical Reports Server (NTRS)

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.

Nemec, Marian; Aftosmis, Michael J.

2004-01-01

149

C. R. WORTHINGTON 783 Fourier transform of t(r) is T(R) and, using Cartesian  

E-print Network

C. R. WORTHINGTON 783 Fourier transform of t(r) is T(R) and, using Cartesian coordinates, T(X, Y, Z can write, after omitting the weight factors, the Fourier transform T(X, Y) as T(X, Y) = sinc ¢rAX sinc 7ryoY, (29) and T(/), Z = l~c, is given by T(1) -- sinc 7rzol/c. (30) The Fourier transform T(X, Y

Rossmann, Michael G.

150

Bondage number of grid graphs  

E-print Network

The bondage number $b(G)$ of a nonempty graph $G$ is the cardinality of a smallest set of edges whose removal from $G$ results in a graph with domination number greater than the domination number of $G$. Here we study the bondage number of some grid-like graphs. In this sense, we obtain some bounds or exact values of the bondage number of some Cartesian product, strong product or direct product of two paths.

Dettlaff, Magda; Yero, Ismael G

2012-01-01

151

A study on the extension of a VOF\\/PLIC based method to a curvilinear co-ordinate system  

Microsoft Academic Search

The conventional volume-of-fluid method has the potential to deal with large free surface deformation on a fixed Cartesian grid. However, when free-surface flows are within or over complex geometries of industrial relevance, such as free-surface flows over offshore oil platforms, it is advantageous to extend the method originally written in Cartesian forms into non-Cartesian forms. In the present study, an

W. Jang; J. Jilesen; F. S. Lien; H. Ji

2008-01-01

152

Hybrid impedance control in constraint coordinates using a disturbance observer  

Microsoft Academic Search

Many contact tasks are more easily defined in terms of constraint equations (and therefore constraint coordinates), rather than either Cartesian or joint coordinates. Deburring and grinding are examples of two such tasks. Hybrid impedance control has been a popular force control algorithm for these tasks. This paper gives a procedure to specify orthogonal subspaces in constraint coordinates. It is then

Robert Bickel; Masayoshi Tomizuka; Wankyun Chung

1996-01-01

153

76 FR 46279 - Smart Grid Advisory Committee  

Federal Register 2010, 2011, 2012, 2013

...Standards and Technology Smart Grid Advisory Committee...SUMMARY: The Smart Grid Advisory Committee...by calling into a central phone number. DATES: The SGAC...National Coordinator for Smart Grid...

2011-08-02

154

77 FR 38768 - Smart Grid Advisory Committee  

Federal Register 2010, 2011, 2012, 2013

...to review updates on the Smart Grid Interoperability Panel...subcommittee and the August Smart Grid Workshop in Boulder...by calling into a central phone number. DATES: The SGAC...National Coordinator for Smart Grid...

2012-06-29

155

OVERGRID: A Unified Overset Grid Generation Graphical Interface  

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

156

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

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

157

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

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

158

Cartesian-based control of a deformable robot manipulator  

NASA Technical Reports Server (NTRS)

A control scheme for the 6-DOF Cincinnati-Milacron T3 robot arm is developed and demonstrated by means of numerical simulations. The arm is modeled as an open-loop articulated system with both actuators and position and velocity sensors at each joint, and a Cartesian-frame control algorithm is constructed in which (1) an adaptive scheme decouples the end-effector subsystem from the complex highly nonlinear main system and (2) a servo scheme drives the reduced system to follow a presumed end-effector trajectory on the basis of the Cartesian-frame feedback gains. The velocity transformation used to transfer the control forces from the Cartesian frame to joint-based space is explained, and the simulation results are presented in extensive graphs and diagrams. The control is found to respond well to system-topology changes and robot-environment impacts.

Chang, C. W.

1990-01-01

159

Locally refined discrete velocity grids for stationary rarefied flow simulations  

NASA Astrophysics Data System (ADS)

Most of deterministic solvers for rarefied gas dynamics use discrete velocity (or discrete ordinate) approximations of the distribution function on a Cartesian grid. This grid must be sufficiently large and fine to describe the distribution functions at every space position in the computational domain. For 3-dimensional hypersonic flows, like in re-entry problems, this induces much too dense velocity grids that cannot be practically used, for memory storage requirements. In this article, we present an approach to generate automatically a locally refined velocity grid adapted to a given simulation. This grid contains much less points than a standard Cartesian grid and allows us to make realistic 3-dimensional simulations at a reduced cost, with a comparable accuracy.

Baranger, C.; Claudel, J.; Hérouard, N.; Mieussens, L.

2014-01-01

160

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

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

161

Robust Control of Robot Manipulators in Cartesian Space  

Microsoft Academic Search

In this paper, we consider the problem of designing a robust control scheme that will enable the end-effector of a robot manipulator to track a specified trajectory in Cartesian space. The control system is robust in the sense that the trajectory is tracked in the presence of uncertainties such as payload variations and joint friction. The robust control scheme uses

P. Misra; R. V. Patel; C. A. Balafoutis

1988-01-01

162

The Structure of Integral Dimensions: Contrasting Topological and Cartesian Representations  

ERIC Educational Resources Information Center

Diverse evidence shows that perceptually integral dimensions, such as those composing color, are represented holistically. However, the nature of these holistic representations is poorly understood. Extant theories, such as those founded on multidimensional scaling or general recognition theory, model integral stimulus spaces using a Cartesian

Jones, Matt; Goldstone, Robert L.

2013-01-01

163

A Lot of Good Physics in the Cartesian Diver  

ERIC Educational Resources Information Center

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…

De Luca, Roberto; Ganci, Salvatore

2011-01-01

164

Reading Rembrandt: The influence of Cartesian dualism on Dutch art  

Microsoft Academic Search

In this essay, I aim to identify and analyze the influence of Cartesian dualism on Rembrandt's pictorial representations of the self. My thesis is that Descartes and Rembrandt share concerns about philosophy's exploration of human nature, concerns rooted in mind–body dualism. Descartes's corpus bears witness to a growing skepticism about the relation between matter and extension. Likewise, Rembrandt's anatomy lessons

J. Lenore Wright

2007-01-01

165

Self Modifying Cartesian Genetic Programming: Fibonacci, Squares, Regression and Summing  

E-print Network

the subsequent genetic expression [1, 2]. The concept of self-modification can be a unifying way of looking that by utilizing self-modification opera- tions within an existing computational method (a form of geneticSelf Modifying Cartesian Genetic Programming: Fibonacci, Squares, Regression and Summing Simon

Fernandez, Thomas

166

The Cartesian Diver, Surface Tension and the Cheerios Effect  

ERIC Educational Resources Information Center

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…

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

2014-01-01

167

Polar versus Cartesian velocity models for maneuvering target tracking with IMM  

NASA Astrophysics Data System (ADS)

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.

Laneuville, Dann

168

High-order, finite-volume methods in mapped coordinates  

NASA Astrophysics Data System (ADS)

We present an approach for constructing finite-volume methods for flux-divergence forms to any order of accuracy defined as the image of a smooth mapping from a rectangular discretization of an abstract coordinate space. Our approach is based on two ideas. The first is that of using higher-order quadrature rules to compute the flux averages over faces that generalize a method developed for Cartesian grids to the case of mapped grids. The second is a method for computing the averages of the metric terms on faces such that freestream preservation is automatically satisfied. We derive detailed formulas for the cases of fourth-order accurate discretizations of linear elliptic and hyperbolic partial differential equations. For the latter case, we combine the method so derived with Runge-Kutta time discretization and demonstrate how to incorporate a high-order accurate limiter with the goal of obtaining a method that is robust in the presence of discontinuities and underresolved gradients. For both elliptic and hyperbolic problems, we demonstrate that the resulting methods are fourth-order accurate for smooth solutions.

Colella, P.; Dorr, M. R.; Hittinger, J. A. F.; Martin, D. F.

2011-04-01

169

Moving overlapping grids with adaptive mesh refinement for high-speed reactive and non-reactive flow  

Microsoft Academic Search

We consider the solution of the reactive and non-reactive Euler equations on two-dimensional domains that evolve in time. The domains are discretized using moving overlapping grids. In a typical grid construction, boundary-fitted grids are used to represent moving boundaries, and these grids overlap with stationary background Cartesian grids. Block-structured adaptive mesh refinement (AMR) is used to resolve fine-scale features in

William D. Henshaw; Donald W. Schwendeman

2006-01-01

170

Simulations of 6-DOF Motion with a Cartesian Method  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

171

Calculation of steady and unsteady transonic flow using a Cartesian mesh and gridless boundary conditions with application to aeroelasticity  

NASA Astrophysics Data System (ADS)

A numerical method for the solution of inviscid compressible flow using an array of embedded Cartesian meshes in conjunction with gridless surface boundary conditions is developed. The gridless boundary treatment is implemented by means of a least squares fitting of the conserved flux variables using a cloud of nodes in the vicinity of the surface geometry. The method allows for accurate treatment of the surface boundary conditions using a grid resolution an order of magnitude coarser than required of typical Cartesian approaches. Additionally, the method does not suffer from issues associated with thin body geometry or extremely fine cut cells near the body. Unlike some methods that consider a gridless (or "meshless") treatment throughout the entire domain, multi-grid acceleration can be effectively incorporated and issues associated with global conservation are alleviated. The "gridless" surface boundary condition provides for efficient and simple problem set up since definition of the body geometry is generated independently from the field mesh, and automatically incorporated into the field discretization of the domain. The applicability of the method is first demonstrated for steady flow of single and multi-element airfoil configurations. Using this method, comparisons with traditional body-fitted grid simulations reveal that steady flow solutions can be obtained accurately with minimal effort associated with grid generation. The method is then extended to unsteady flow predictions. In this application, flow field simulations for the prescribed oscillation of an airfoil indicate excellent agreement with experimental data. Furthermore, it is shown that the phase lag associated with shock oscillation is accurately predicted without the need for a deformable mesh. Lastly, the method is applied to the prediction of transonic flutter using a two-dimensional wing model, in which comparisons with moving mesh simulations yield nearly identical results. As a result, applicability of the method to transient and vibrating fluid-structure interaction problems is established in which the requirement for a deformable mesh is eliminated.

Kirshman, David

172

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

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

173

Zeno's First Paradox of Motion: A Cartesian Perspective  

E-print Network

into the labyrinth of the continuum." 5 7 Leibniz also felt that only part of motion was real, the part which is force or power. As Wilson reports, this view of motion is something Leibniz believed he had recognized about the true nature of motion that Zeno did...Zeno's First Paradox of Motion: A Cartesian Perspective Lori Bolster University of Dayton Before I introduce some of Descartes' perspective into a discussion of Zeno's First Paradox of Motion, I would first like to restate in general what Zeno...

Balster, Lori

2002-06-01

174

Compact-range coordinate system established using a laser tracker.  

SciTech Connect

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.

Gallegos, Floyd H.; Bryce, Edwin Anthony

2006-12-01

175

The total bondage number of grid graphs  

E-print Network

The total domination number of a graph $G$ without isolated vertices is the minimum number of vertices that dominate all vertices in $G$. The total bondage number $b_t(G)$ of $G$ is the minimum number of edges whose removal enlarges the total domination number. This paper considers grid graphs. An $(n,m)$-grid graph $G_{n,m}$ is defined as the cartesian product of two paths $P_n$ and $P_m$. This paper determines the exact values of $b_t(G_{n,2})$ and $b_t(G_{n,3})$, and establishes some upper bounds of $b_t(G_{n,4})$.

Hu, Fu-Tao; Xu, Jun-Ming

2011-01-01

176

Importance of Grid Center Arrangement  

NASA Astrophysics Data System (ADS)

In Digital Elevation Modeling, grid size is accepted to be the most important parameter. Despite the point density and/or scale of the source data, it is freely decided by the user. Most of the time, arrangement of the grid centers are ignored, even most GIS packages omit the choice of grid center coordinate selection. In our study; importance of the arrangement of grid centers is investigated. Using the analogy between "Raster Grid DEM" and "Bitmap Image", importance of placement of grid centers in DEMs are measured. The study has been conducted on four different grid DEMs obtained from a half ellipsoid. These grid DEMs are obtained in such a way that they are half grid size apart from each other. Resulting grid DEMs are investigated through similarity measures. Image processing scientists use different measures to investigate the dis/similarity between the images and the amount of different information they carry. Grid DEMs are projected to a finer grid in order to co-center. Similarity measures are then applied to each grid DEM pairs. These similarity measures are adapted to DEM with band reduction and real number operation. One of the measures gives function graph and the others give measure matrices. Application of similarity measures to six grid DEM pairs shows interesting results. These four different grid DEMs are created with the same method for the same area, surprisingly; thirteen out of 14 measures state that, the half grid size apart grid DEMs are different from each other. The results indicated that although grid DEMs carry mutual information, they have also additional individual information. In other words, half grid size apart constructed grid DEMs have non-redundant information.; Joint Probability Distributions Function Graphs

Pasaogullari, O.; Usul, N.

2012-12-01

177

Coil Compression for Accelerated Imaging with Cartesian Sampling  

PubMed Central

MRI using receiver arrays with many coil elements can provide high signal-to-noise ratio and increase parallel imaging acceleration. At the same time, the growing number of elements results in larger datasets and more computation in the reconstruction. This is of particular concern in 3D acquisitions and in iterative reconstructions. Coil compression algorithms are effective in mitigating this problem by compressing data from many channels into fewer virtual coils. In Cartesian sampling there often are fully sampled k-space dimensions. In this work, a new coil compression technique for Cartesian sampling is presented that exploits the spatially varying coil sensitivities in these non-subsampled dimensions for better compression and computation reduction. Instead of directly compressing in k-space, coil compression is performed separately for each spatial location along the fully-sampled directions, followed by an additional alignment process that guarantees the smoothness of the virtual coil sensitivities. This important step provides compatibility with autocalibrating parallel imaging techniques. Its performance is not susceptible to artifacts caused by a tight imaging fieldof-view. High quality compression of in-vivo 3D data from a 32 channel pediatric coil into 6 virtual coils is demonstrated. PMID:22488589

Zhang, Tao; Pauly, John M.; Vasanawala, Shreyas S.; Lustig, Michael

2012-01-01

178

Parallel large-eddy simulations of turbulent flows with complex moving boundaries on fixed Cartesian grids  

E-print Network

. INTRODUCTION Today with the advent of inexpensive parallel computers state-of-the-art modeling strategies is obtained from the solution of the filtered Navier-Stokes equations, where the effect of the unresolved by the finite- difference operators. The resulting subgrid scale (SGS) stresses are modeled using the Lagrangian

Yang, Jianming

179

An Embedded Cartesian Grid Euler Solver with Radial Basis Function for  

E-print Network

with global con- servation are greatly mitigated. Several two and three-dimensional problems are presented of Aeronautics and Astronautics, Inc., with permission. #12;I. Introduction Mesh generation is one of the most a challenge to generate a mesh around complex configuration. Recently, there is renewed interest in using

Liu, Feng

180

Anisotropic Fast-Marching on cartesian grids using Lattice Basis Reduction  

E-print Network

in numerous applications, such as motion planning control problems [19], modeling of bio-medical phenom- ena to the identity matrix). Lattice Basis Reduction [14] is a concept from discrete mathematics, discussed the small numerical cost of the algorithm and show an accuracy competitive in general, an remarkable in test

Paris-Sud XI, Université de

181

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

SciTech Connect

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.

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

2011-12-01

182

Kinematic and Dynamic Simulation of Rigid and Flexible Systems with Fully Cartesian Coordinates  

Microsoft Academic Search

\\u000a Multibody systems are quite often a complex combination or assembly of mechanical elements with very different mechanical\\u000a behavior: rigid or flexible, linear or non-linear, etc. Sometimes it can be very difficult to carry out an efficient dynamic\\u000a simulation with a single software package.\\u000a \\u000a \\u000a In practical applications, some bodies are so small and rigid that flexibility effects can be neglected safely,

J. Garcia Jalon; J. Cuadrado; A. Avello; J. M. Jimenez

183

Enhanced Elliptic Grid Generation  

NASA Technical Reports Server (NTRS)

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.

Kaul, Upender K.

2007-01-01

184

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

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

185

Accelerated MRI with CIRcular Cartesian UnderSampling (CIRCUS): a variable density Cartesian sampling strategy for compressed sensing and parallel imaging  

PubMed Central

Purpose This study proposes and evaluates a novel method for generating efficient undersampling patterns for 3D Cartesian acquisition with compressed sensing (CS) and parallel imaging (PI). Methods Image quality achieved with schemes that accelerate data acquisition, including CS and PI, are sensitive to the design of the specific undersampling scheme used. Ideally random sampling is required to recover MR images from undersampled data with CS. In practice, pseudo-random sampling schemes are usually applied. Radial or spiral sampling either for Cartesian or non-Cartesian acquisitions has been using because of its favorable features such as interleaving flexibility. In this study, we propose to undersample data on the ky-kz plane of the 3D Cartesian acquisition by circularly selecting sampling points in a way that maintains the features of both random and radial or spiral sampling. Results The proposed sampling scheme is shown to outperform conventional random and radial or spiral samplings for 3D Cartesian acquisition and is found to be comparable to advanced variable-density Poisson-Disk sampling (vPDS) while retaining interleaving flexibility for dynamic imaging, based on the results with retrospective undersampling. Our preliminary results with the prospective implementation of the proposed undersampling strategy demonstrated its favorable features. Conclusions The proposed undersampling patterns for 3D Cartesian acquisition possess the desirable properties of randomization and radial or spiral trajectories. It provides easy implementation, flexible sampling, and high accuracy of image reconstruction with CS and PI. PMID:24649436

Saloner, David

2014-01-01

186

A Cartesian Robot for RFID Signal Distribution Model Verification Aliasgar Kutiyanawala Vladimir Kulyukin  

E-print Network

A Cartesian Robot for RFID Signal Distribution Model Verification Aliasgar Kutiyanawala Vladimir (tags). These surfaces assist localization in mobile devices and intel- ligent walkers for the elderly the design of a Cartesian robot for verifying the localization probability of a given PRF surface

Kulyukin, Vladimir

187

Consent: a Cartesian ideal? Human neural transplantation in Parkinson's disease.  

PubMed

The grafting of human embryonic cells in Parkinson's disease is an innovative and hopefully useful therapeutic approach. However, it still concerns a very small number of patients and is only suggested as a research protocol. We present here a study of the problems of information and consent to research within the framework of this disease in which the efficacy of medical treatment is shortlived. The only French center to use this treatment (Hôpital H. Mondor in Créteil) has received authorization from the Comité Consultatif National d'Ethique (Consultative National Committee on Ethics). Eleven patients were treated between 1991 and 1998. The study of the results of a questionnaire sent to those patients showed the difficulties met in evaluating the perception of information despite intact intellectual capacities in people "prepared to risk everything." In France, the duty to inform patients during research procedures is regulated by the Huriet Act. However, it is not easy to guarantee genuine consent when preliminary information is given to patients psychologically impaired by the slow and ineluctable course of their disease. In these borderline cases, a valid consent seems to be a myth in terms of pure autonomy when considered with the Cartesian aim of elimination of uncertainty. The relevance of this concept of genuine consent probably makes more sense as aiming at a Cartesian ideal which is perhaps more in the spirit rather than in the letter. It is in that same spirit that, from the outset, we propose to define t he practical ways of answering the patients' request for information, even sometimes after consent has been given. PMID:12809343

Lopes, Manuel; Meningaud, Jean-Paul; Behin, Anthony; Hervé, Christian

2003-01-01

188

Multi-fault Tolerance for Cartesian Data Distributions  

SciTech Connect

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.

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

2013-06-01

189

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

PubMed

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

Campolo, Domenico

2013-01-01

190

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

SciTech Connect

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.

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

2012-01-01

191

A pseudo-spectral method for the simulation of poro-elastic seismic wave propagation in 2D polar coordinates using domain decomposition  

SciTech Connect

We present a novel numerical approach for the comprehensive, flexible, and accurate simulation of poro-elastic wave propagation in 2D polar coordinates. An important application of this method and its extensions will be the modeling of complex seismic wave phenomena in fluid-filled boreholes, which represents a major, and as of yet largely unresolved, computational problem in exploration geophysics. In view of this, we consider a numerical mesh, which can be arbitrarily heterogeneous, consisting of two or more concentric rings representing the fluid in the center and the surrounding porous medium. The spatial discretization is based on a Chebyshev expansion in the radial direction and a Fourier expansion in the azimuthal direction and a Runge–Kutta integration scheme for the time evolution. A domain decomposition method is used to match the fluid–solid boundary conditions based on the method of characteristics. This multi-domain approach allows for significant reductions of the number of grid points in the azimuthal direction for the inner grid domain and thus for corresponding increases of the time step and enhancements of computational efficiency. The viability and accuracy of the proposed method has been rigorously tested and verified through comparisons with analytical solutions as well as with the results obtained with a corresponding, previously published, and independently benchmarked solution for 2D Cartesian coordinates. Finally, the proposed numerical solution also satisfies the reciprocity theorem, which indicates that the inherent singularity associated with the origin of the polar coordinate system is adequately handled.

Sidler, Rolf, E-mail: rsidler@gmail.com [Center for Research of the Terrestrial Environment, University of Lausanne, CH-1015 Lausanne (Switzerland)] [Center for Research of the Terrestrial Environment, University of Lausanne, CH-1015 Lausanne (Switzerland); Carcione, José M. [Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), Borgo Grotta Gigante 42c, 34010 Sgonico, Trieste (Italy)] [Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), Borgo Grotta Gigante 42c, 34010 Sgonico, Trieste (Italy); Holliger, Klaus [Center for Research of the Terrestrial Environment, University of Lausanne, CH-1015 Lausanne (Switzerland)] [Center for Research of the Terrestrial Environment, University of Lausanne, CH-1015 Lausanne (Switzerland)

2013-02-15

192

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

NASA Technical Reports Server (NTRS)

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.

Miller, David P.

1994-01-01

193

Implementation of Vehicle to Grid Infrastructure Using Fuzzy Logic Controller  

Microsoft Academic Search

With high penetration of electric vehicles (EVs), stability of the electric grid becomes a challenging task. A greater penetration level would demand a proper coordination amongst the various EVs as they charge or discharge to the grid. Coordination here refers to controlling the charging and discharging patterns of different EVs depending on their individual battery states and the present grid

Mukesh Singh; Praveen Kumar; Indrani Kar

2012-01-01

194

Shared Memory Parallelism for 3D Cartesian Discrete Ordinates Solver  

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

195

Beyond grid security  

NASA Astrophysics Data System (ADS)

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.

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

2008-07-01

196

TeraGrid  

NSDL National Science Digital Library

TeraGrid is an open scientific discovery infrastructure combining leadership class resources at nine partner sites to create an integrated, persistent computational resource. Using high-performance network connections, the TeraGrid integrates high-performance computers, data resources and tools, and high-end experimental facilities around the country. These integrated resources include more than 102 teraflops of computing capability and more than 15 petabytes (quadrillions of bytes) of online and archival data storage with rapid access and retrieval over high-performance networks. Through the TeraGrid, researchers can access over 100 discipline-specific databases. With this combination of resources, the TeraGrid is the world's largest, most comprehensive distributed cyberinfrastructure for open scientific research. TeraGrid is coordinated through the Grid Infrastructure Group (GIG) at the University of Chicago, working in partnership with the Resource Provider sites: Indiana University, Oak Ridge National Laboratory, National Center for Supercomputing Applications, Pittsburgh Supercomputing Center, Purdue University, San Diego Supercomputer Center, Texas Advanced Computing Center, University of Chicago/Argonne National Laboratory, and the National Center for Atmospheric Research.

197

The distinguishing chromatic number of Cartesian products of two complete graphs  

E-print Network

a question of Choi, Hartke and Kaul whether there are some other graphs for which this equality holds. Key determined in [8, 12]. Choi, Hartke and Kaul [6] studied the distinguishing chromatic number of Cartesian

Klavzar, Sandi

198

Steven Nadler, Occasionalism: Causation Among the Cartesians New York: Oxford University Press, 2011. xi + 215 pp.  

E-print Network

as an ad hoc response to the problem of mind-body interaction. Cartesian dualism to mind-body relations (106, 121). The first chapter of the collection takes claims that mind and body have radically different natures: the former

McDonough, Jeffrey

199

Grid Resource Negotiation: Survey with a Machine Learning Perspective  

Microsoft Academic Search

Grid computing can be defined as coordinated re- source sharing and problem solving in dynamic, multi- institutional collaborations (1). As more Grids are de- ployed worldwide, the number of multi-institutional col- laborations is rapidly growing. However, for Grid comput- ing to realize its full potential, it is expected that Grid par- ticipants are able to use one another resources. Resource

Cyril Briquet; Pierre-arnoul De Marneffe

2006-01-01

200

Multiscale geometric modeling of macromolecules I: Cartesian representation  

PubMed Central

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

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

2013-01-01

201

Engineering Process Coordination based on A Service Event Notification Model  

E-print Network

Engineering Process Coordination based on A Service Event Notification Model Jian Cao1, Jie Wang2 notification model based on grid service to coordinate different applications and human. The model takes for supporting process coordination. In this model, an event noti- fication server composed of a group of grid

Stanford University

202

Overture: The grid classes  

SciTech Connect

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.

Brislawn, K.; Brown, D.; Chesshire, G.; Henshaw, W. [and others

1997-01-01

203

A coarse-grid projection method for accelerating incompressible flow computations  

NASA Astrophysics Data System (ADS)

We present a coarse-grid projection (CGP) method for accelerating incompressible flow computations, which is applicable to methods involving Poisson equations as incompressibility constraints. The CGP methodology is a modular approach that facilitates data transfer with simple interpolations and uses black-box solvers for the Poisson and advection-diffusion equations in the flow solver. After solving the Poisson equation on a coarsened grid, an interpolation scheme is used to obtain the fine data for subsequent time stepping on the full grid. A particular version of the method is applied here to the vorticity-stream function, primitive variable, and vorticity-velocity formulations of incompressible Navier-Stokes equations. We compute several benchmark flow problems on two-dimensional Cartesian and non-Cartesian grids, as well as a three-dimensional flow problem. The method is found to accelerate these computations while retaining a level of accuracy close to that of the fine resolution field, which is significantly better than the accuracy obtained for a similar computation performed solely using a coarse grid. A linear acceleration rate is obtained for all the cases we consider due to the linear-cost elliptic Poisson solver used, with reduction factors in computational time between 2 and 42. The computational savings are larger when a suboptimal Poisson solver is used. We also find that the computational savings increase with increasing distortion ratio on non-Cartesian grids, making the CGP method a useful tool for accelerating generalized curvilinear incompressible flow solvers.

San, Omer; Staples, Anne E.

2013-01-01

204

Smart Grid Impact on Intelligent Buildings  

E-print Network

OF DIRECTORS 3 Making?the?Grid?Smart Smart?grid?features?expand?energy? efficiency?beyond?the?grid?into? buildings?by?coordinating?low?priority? energy?consuming?devices?to?take? advantage?of?the?most?desirable? energy?sources Smart...?and?the?following?CABA?Members?funded?this?Research?Project: Ruby?Sponsor: Emerald?Sponsors Diamond?Sponsors Source:?CABA?s?Smart?Grid?Impact?on? Intelligent?Buildings Focus?of?the?Study Smart?Grid?Commercial?Buildings?Business?Opportunities =??Focus?of?this?study (On?Site) Incl. Net Zero Energy...

Zimmer, R. J.

2013-01-01

205

Coordination polymers  

Microsoft Academic Search

This paper is a review of the metal complex forming coordination polymers. A polymer–metal complex is composed of synthetic polymer and metal ions bound to the polymer ligand by a coordinate bond. A polymer ligand contains anchoring sites like nitrogen, oxygen or sulphur obtained either by the polymerization of monomer possessing the coordinating site or by a chemical reaction between

T. Kaliyappan; P. Kannan

2000-01-01

206

Grid oscillators  

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

207

3-D simultaneous inversion for velocity and reflector geometry using multiple classes of arrivals in a spherical coordinate frame  

NASA Astrophysics Data System (ADS)

The two key requirements in conducting 3-D simultaneous traveltime tomography on real data at the regional and global scale with multiple classes of arrival time information are (1) it needs an efficient and accurate arrival tracking algorithm for multiply transmitted, reflected (or refracted) and converted waves in a 3-D variable velocity model with embedded velocity discontinuities (or subsurface interfaces), and (2) a subdimensional inversion solver is required which can easily search for different types of model parameters to balance the trade-off between the different types of model parameter updated in the simultaneous inversion process. For these purposes, we first extend a popular grid/cell-based wavefront expanding ray tracing algorithm (the multistage irregular shortest-path ray tracing method), which previously worked only in Cartesian coordinate at the local scale, to spherical coordinates appropriate to the regional or global scale. We then incorporated a fashionable inversion solver (the subspace method) to formulate a simultaneous inversion algorithm, in which the multiple classes of arrivals (including direct and reflected arrivals from different velocity discontinuities) can be used to simultaneously update both the velocity fields and the reflector geometries. Numerical tests indicate that the new inversion method is both applicable and flexible in terms of computational efficiency and solution accuracy, and is not sensitive to a modest level of noise in the traveltime data. It offers several potential benefits over existing schemes for real data seismic imaging.

Huang, Guo-jiao; Bai, Chao-ying; Li, Xing-wang; Greenhalgh, Stewart

2014-01-01

208

Solutions to Maxwell's Equations using Spheroidal Coordinates  

E-print Network

Analytical solutions to the wave equation in spheroidal coordinates in the short wavelength limit are considered. The asymptotic solutions for the radial function are significantly simplified, allowing scalar spheroidal wave functions to be defined in a form which is directly reminiscent of the Laguerre-Gaussian solutions to the paraxial wave equation in optics. Expressions for the Cartesian derivatives of the scalar spheroidal wave functions are derived, leading to a new set of vector solutions to Maxwell's equations. The results are an ideal starting point for calculations of corrections to the paraxial approximation.

Zeppenfeld, Martin

2009-01-01

209

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

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

210

An assessment of unstructured grid technology for timely CFD analysis  

NASA Technical Reports Server (NTRS)

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.

Kinard, Tom A.; Schabowski, Deanne M.

1995-01-01

211

Grid Characteristics and Uses: A Grid Definition  

Microsoft Academic Search

This paper discusses the concept of grid towards achieving a complete definition using main grid characteristics and uses found in literature. Ten definitions extracted from main literature sources have been studied allowing the extraction of grid characteristics while grid uses are defined in terms of the dierent types of application support provided by grids. A grid definition is proposed using

Miguel L. Bote-lorenzo; Yannis A. Dimitriadis; Eduardo Gómez-sánchez

2003-01-01

212

Coordinate transformation by minimizing correlations between parameters  

NASA Technical Reports Server (NTRS)

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.

Kumar, M.

1972-01-01

213

Testing Grid Application Workflows Using TTCN-3  

Microsoft Academic Search

The collective and coordinated usage of distributed re- sources for problem solution within dynamic virtual orga- nizations can be realized with the Grid computing technol- ogy. For distributing and solving a task, a Grid application involves a complex workflow of dividing a task into smaller sub-tasks, scheduling and submitting jobs for solving those sub-tasks, and eventually collecting and combining the

Thomas Rings; Helmut Neukirchen; Jens Grabowski

2008-01-01

214

Direct comparison of 3D spiral vs. Cartesian gradient-echo coronary magnetic resonance angiography.  

PubMed

While 3D thin-slab coronary magnetic resonance angiography (MRA) has traditionally been performed using a Cartesian acquisition scheme, spiral k-space data acquisition offers several potential advantages. However, these strategies have not been directly compared in the same subjects using similar methodologies. Thus, in the present study a comparison was made between 3D coronary MRA using Cartesian segmented k-space gradient-echo and spiral k-space data acquisition schemes. In both approaches the same spatial resolution was used and data were acquired during free breathing using navigator gating and prospective slice tracking. Magnetization preparation (T(2) preparation and fat suppression) was applied to increase the contrast. For spiral imaging two different examinations were performed, using one or two spiral interleaves, during each R-R interval. Spiral acquisitions were found to be superior to the Cartesian scheme with respect to the signal-to-noise ratio (SNR) and contrast-to-noise-ratio (CNR) (both P < 0.001) and image quality. The single spiral per R-R interval acquisition had the same total scan duration as the Cartesian acquisition, but the single spiral had the best image quality and a 2.6-fold increase in SNR. The double-interleaf spiral approach showed a 50% reduction in scanning time, a 1.8-fold increase in SNR, and similar image quality when compared to the standard Cartesian approach. Spiral 3D coronary MRA appears to be preferable to the Cartesian scheme. The increase in SNR may be "traded" for either shorter scanning times using multiple consecutive spiral interleaves, or for enhanced spatial resolution. PMID:11590656

Börnert, P; Stuber, M; Botnar, R M; Kissinger, K V; Koken, P; Spuentrup, E; Manning, W J

2001-10-01

215

C[squared] = Creative Coordinates  

ERIC Educational Resources Information Center

"C[squared] = Creative Coordinates" is an engaging group of tasks that fosters the integration of mathematics and art to create meaningful understanding. The project lets students illustrate of find an image, then plot points to map their design on a grid. The project usually takes about a week to complete. When it is finished, students who are…

McHugh, Shelley R.

2007-01-01

216

Simulation of sharp gas-liquid interface using VOF method and adaptive grid local refinement around the interface  

Microsoft Academic Search

The volume of fluid (VOF) method is used to perform two-phase simulations (gas-liquid). The governing Navier-Stokes conservation equations of the flow field are numerically solved on two-dimensional axisymmetric or three-dimensional unstructured grids, using Cartesian velocity components, following the finite volume approximation and a pressure correction method. A new method of adaptive grid local refinement is developed in order to enhance

A. Theodorakakos; G. Bergeles

2004-01-01

217

Solving Partial Differential Equations on Overlapping Grids  

SciTech Connect

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.

Henshaw, W D

2008-09-22

218

A Multi-chromosome Approach to Standard and Embedded Cartesian Genetic Programming  

E-print Network

A Multi-chromosome Approach to Standard and Embedded Cartesian Genetic Programming Genetic in the form of modules. In this paper, we introduce for the first time a new multi-chromosome approach to CGP also propose a multi-chromosome evolutionary strategy which selects the best chromosomes from

Fernandez, Thomas

219

An improved hybrid Cartesian\\/immersed boundary method for fluid solid flows  

Microsoft Academic Search

SUMMARY An improved hybrid Cartesian\\/immersed boundary method is proposed based on ghost point treatment. A second-order Taylor series expansion is used to evaluate the values at the ghost points, and an inverse distance weighting method to interpolate the values due to its properties of preserving local extrema and smooth reconstruction. The present method effectively eliminates numerical instabilities caused by matrix

Tong Gao; Yu-Heng Tseng; Xi-Yun Lu

2007-01-01

220

An accurate cartesian method for incompress-ible flows with moving boundaries  

E-print Network

are spatially discretized onto a fixed Cartesian mesh. The body is taken into account via the ghost-cell method, especially when the solid presents complex boundaries. These studies can be divided in two cat- egories, there are the Ghost Fluid method [12] or the Immersed Boundary method [24]. The current work focuses on the immersed

Boyer, Edmond

221

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

ERIC Educational Resources Information Center

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…

Lelwica, Michelle Mary

2009-01-01

222

PHYSICS OF FLUIDS 25, 044105 (2013) Onset of buoyancy-driven convection in Cartesian  

E-print Network

PHYSICS OF FLUIDS 25, 044105 (2013) Onset of buoyancy-driven convection in Cartesian the onset of buoyancy-driven convection relevant to subsurface carbon dioxide sequestration in confined and may help with understanding the onset of buoyancy-driven convection in real systems where lateral

Firoozabadi, Abbas

223

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

ERIC Educational Resources Information Center

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…

Paechter, Carrie

2004-01-01

224

Cartesian thrust allocation algorithm with variable direction thrusters, turn rate limits and singularity avoidance  

E-print Network

thrust slowly and/or reverse the direction of the generated thrust, minimizing the power consumptionCartesian thrust allocation algorithm with variable direction thrusters, turn rate limits Abstract-- The literature on thrust allocation algorithms that is currently available usually focuses

Johansen, Tor Arne

225

Investigating the Effects of Density and Volume of a Cartesian Diver  

NSDL National Science Digital Library

This activity is an inquiry investigation where students gather data on why the Cartesian diver sinks or floats. They then develop a new question and then conduct a new investigation by changing one variable and repeat the altered experiment and record their conclusions.

Lee Anne Garhofer Ames Elementary School St. Paul, MN 55106

226

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

227

3D Cable-Based Cartesian Metrology System Robert L. Williams II  

E-print Network

-257, 2004 Keywords: metrology, cable-based metrology, cables, wires, string pots, rapid prototyping. Their six-cable parallel wire mechanism is based on a (non-inverted) Stewart Platform. No analytical3D Cable-Based Cartesian Metrology System Robert L. Williams II Ohio University Athens, Ohio James

Williams II, Robert L.

228

Interactive grid generation program for CAP-TSD  

NASA Technical Reports Server (NTRS)

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.

Bland, Samuel R.

1990-01-01

229

TBGG- INTERACTIVE ALGEBRAIC GRID GENERATION  

NASA Technical Reports Server (NTRS)

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.

Smith, R. E.

1994-01-01

230

Determination of Ship Approach Parameters in the Polar Coordinates System  

NASA Astrophysics Data System (ADS)

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

Banachowicz, Andrzej; Wolski, Adam

2014-06-01

231

MAGNETOHYDRODYNAMIC MODELING OF SOLAR SYSTEM PROCESSES ON GEODESIC GRIDS  

SciTech Connect

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.

Florinski, V. [Department of Physics, University of Alabama, Huntsville, AL 35899 (United States)] [Department of Physics, University of Alabama, Huntsville, AL 35899 (United States); Guo, X. [Center for Space Plasma and Aeronomic Research, University of Alabama, Huntsville, AL 35899 (United States)] [Center for Space Plasma and Aeronomic Research, University of Alabama, Huntsville, AL 35899 (United States); Balsara, D. S.; Meyer, C. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)] [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)

2013-04-01

232

Engineering of Services and Business Models for Grid Applications  

NASA Astrophysics Data System (ADS)

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.

Falkner, Jürgen; Weisbecker, Anette

233

Technology for a NASA Space-Based Science Operations Grid  

NASA Technical Reports Server (NTRS)

This viewgraph representation presents an overview of a proposal to develop a space-based operations grid in support of space-based science experiments. The development of such a grid would provide a dynamic, secure and scalable architecture based on standards and next-generation reusable software and would enable greater science collaboration and productivity through the use of shared resources and distributed computing. The authors propose developing this concept for use on payload experiments carried aboard the International Space Station. Topics covered include: grid definitions, portals, grid development and coordination, grid technology and potential uses of such a grid.

Bradford, Robert N.; Redman, Sandra H.

2003-01-01

234

Hybrid Simulation of EMIC Waves in Curvilinear Coordinates  

NASA Astrophysics Data System (ADS)

Electromagnetic Ion Cyclotron (EMIC) waves play an important role in the Earth's Radiation Belts dynamics. Theoretical work has suggested EMIC waves may contribute significantly to Relativistic Electron Precipitation (REP) by pitch-angle scattering. We will be self-consistently simulating the EMIC instability, wave propagation, and wave-particle interaction using a hybrid code, in which ions are treated as super particles and electrons as a massless fluid. While most of the numerical simulations on EMIC waves have been done in Cartesian coordinates, we will carry on our simulation in generalized orthogonal curvilinear coordinates. The generalized coordinates fit better especially for geometries that have irregular boundary shapes, which is often the case in the Earth's radiation belts. An energy-conserving particle mover in curvilinear coordinates will be presented, as well as reflection boundary conditions for particles. We will also discuss the power spectrum method in Fourier space used to analyze the waves. Simulation results in different coordinates (e.g. Cartesian and dipole) of different dimensions (1D and 2D) will be presented to compare with linear theory.

Hu, Y.; Denton, R.

2008-12-01

235

Plasticity of intermediate mechanics studentsâ coordinate system choice  

NSDL National Science Digital Library

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 prior physics and mathematics classes. In small-group interviews and in homework help sessions, we ask students to define a coordinate system and set up the equations of motion for a simple pendulum for which polar coordinates are more appropriate. We analyze video data from several encounters using a combination of Process/Object theory and Resource Theory. We find that students sometimes persist in using an inappropriate Cartesian system. Furthermore, students often derive (rather than recall) the details of the polar coordinate system, indicating that their knowledge is far from solid. To describe our work more precisely, we define a scale of plasticity and several heuristics for defining resources and their plasticity.

Sayre, Eleanor C.; Wittmann, Michael C.

2010-03-11

236

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

USGS Publications Warehouse

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)

Rutledge, A.T.

1989-01-01

237

Gravitational attraction of local crustal masses in spherical coordinates  

NASA Astrophysics Data System (ADS)

The gravitational attractions of terrestrial masses and condensed terrestrial masses were modeled in local regions of gravity stations in different ways. These differences in the models included the type of coordinate frame (Cartesian versus spherical), grid spacing (30 vs 3 arcseconds), and the shape of the terrain ("flat-topped" vs "sloped-topped" prisms). The effect of each of these variables is quantified for its overall impact on Helmert gravity anomalies. The combined effect of removing the masses and restoring the condensed masses is also compared to classical terrain corrections for suitability in computing Helmert anomalies. Some detailed conclusions are drawn from these test computations. The effect of the Earth's curvature has both a near-field effect (due to the differences in volume and shape between rectangular and spherical prisms) and a far-field effect (due to physical location of masses below the horizon). The near-field effect can achieve 0.4 mGal in the Rocky mountains, and affect the geoid by up to 7.5 cm. Additionally, the approximation of the terrain by flat-topped prisms (even at fine spacings such as 3 arcseconds) is inappropriate for terrain near the station, where errors of 20 mGal have been computed using 30-arcsecond data. It is concluded that when 30-arcsecond terrain is allowed to have a more curved (bilinear) prism top, its gravitational attraction is a significantly closer approximation of 3-arcsecond terrain, even for the prism surrounding the station, as compared to the case of 30-arcsecond flat-topped prisms. It is suggested that classical terrain corrections, for many reasons, should not be used to compute Helmert anomalies. Considering only the accuracy, and not the speed, of the computations, the following conclusions are drawn: terrain effects computed inside a local "cap" should be done exclusively in spherical coordinates with a 3-arcsecond Digital Elevation Model (DEM) out to 0.2: radius, and then a 30-arcsecond DEM from 0.2 out to 3.5:. In all cases, bilinearly shaped prism tops should be used.

Smith, D. A.; Robertson, D. S.; Milbert, D. G.

2001-03-01

238

Aerodynamic Design of Complex Configurations Using Cartesian Methods and CAD Geometry  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

239

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

NASA Technical Reports Server (NTRS)

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.

Nguyen, Charles C.; Pooran, Farhad J.

1988-01-01

240

“Mens Sana in Corpore Sano”: Cartesian dualism and the marginalisation of sex education  

Microsoft Academic Search

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 in how we think

Carrie Paechter

2004-01-01

241

(p, r)cubes as Cartesian products Sandi Klavzar a,b,c Yoomi Rho d  

E-print Network

Fibonacci (p, r)­cubes as Cartesian products Sandi KlavŸzar a,b,c Yoomi Rho d a Faculty The Fibonacci (p, r)­cube # (p,r) n is the subgraph of Qn induced on binary words of length n in which there are at most r consecutive ones and at least p zeros between two substrings of ones. These cubes simultaneously

Klavzar, Sandi

242

(p, r)cubes as Cartesian products Sandi Klavzar a,b,c Yoomi Rho d  

E-print Network

Fibonacci (p, r)­cubes as Cartesian products Sandi KlavŸzar a,b,c Yoomi Rho d a Faculty The Fibonacci (p, r)­cube # (p,r) n is the subgraph of Qn induced on binary words of length n in which there are at most r consecutive ones and there are at least p zeros between two substrings of ones. These cubes

Klavzar, Sandi

243

A case for using grid architecture for state public health informatics: the Utah perspective  

Microsoft Academic Search

This paper presents the rationale for designing and implementing the next-generation of public health information systems using grid computing concepts and tools. Our attempt is to evaluate all grid types including data grids for sharing information and computational grids for accessing computational resources on demand. Public health is a broad domain that requires coordinated uses of disparate and heterogeneous information

Catherine J Staes; Wu Xu; Samuel D LeFevre; Ronald C Price; Scott P Narus; Adi Gundlapalli; Robert Rolfs; Barry Nangle; Matthew Samore; Julio C Facelli

2009-01-01

244

Symmetric positive semi-definite Cartesian Tensor fiber orientation distributions (CT-FOD).  

PubMed

A novel method for estimating a field of fiber orientation distribution (FOD) based on signal de-convolution from a given set of diffusion weighted magnetic resonance (DW-MR) images is presented. We model the FOD by higher order Cartesian tensor basis using a parametrization that explicitly enforces the positive semi-definite property to the computed FOD. The computed Cartesian tensors, dubbed Cartesian Tensor-FOD (CT-FOD), are symmetric positive semi-definite tensors whose coefficients can be efficiently estimated by solving a linear system with non-negative constraints. Next, we show how to use our method for converting higher-order diffusion tensors to CT-FODs, which is an essential task since the maxima of higher-order tensors do not correspond to the underlying fiber orientations. Finally, we propose a diffusion anisotropy index computed directly from CT-FODs using higher order tensor distance measures thus consolidating the whole analysis pipeline of diffusion imaging solely using CT-FODs. We evaluate our method qualitatively and quantitatively using simulated DW-MR images, phantom images, and human brain real dataset. The results conclusively demonstrate the superiority of the proposed technique over several existing multi-fiber reconstruction methods. PMID:22890050

Weldeselassie, Yonas T; Barmpoutis, Angelos; Atkins, M Stella

2012-08-01

245

The Grid  

NSDL National Science Digital Library

The class forms a "Presidential Task Force" for a week, empowered by the president to find answers and make recommendations concerning the future of the national power grid. Task force members conduct daily debriefings with their research team and prepare a report and presentation of their findings for the president, using an actual policy document as a guide. Although this activity is geared towards fifth-grade and older students and Internet research capabilities are required, some portions may be appropriate for younger students.

Integrated Teaching And Learning Program

246

Basic equations for non-reacting Newtonian fluids in curvilinear, non-orthogonal, and accelerated coordinate systems  

Microsoft Academic Search

Procedures for writing the basic fluid mechanical equations for a Newtonian fluid relative to a non-inertial reference frame of general non-orthogonal and curvilinear coordinates are reported. The constitutive equations are also discussed and refer to a compressible Newtonian fluid. A survey of non-Cartesian tensor analysis is provided. The flow distribution around finite cambered swept wings is discussed.

K. Robert; R. Grundmann

1976-01-01

247

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

NASA Technical Reports Server (NTRS)

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.

Rosenfeld, Moshe; Kwak, Dochan; Vinokur, Marcel

1992-01-01

248

The NCRC Grid Scheduling Environment  

SciTech Connect

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.

Indiviglio, Frank M [ORNL; Maxwell, Don E [ORNL

2011-01-01

249

Commodity Grid Kit  

NSDL National Science Digital Library

Commodity Grid (CoG) Kits allow Grid users, Grid application developers, and Grid administrators to use, program, and administer Grids from a higher-level framework. The Java and Python CoG Kits are good examples. These kits allow for easy and rapid Grid application development. They encourage collaborative code reuse and avoid the duplication of effort among problem solving environments, science portals, Grid middleware, and collaboratory pilots.

Von Laszewski, Gregor

250

caGrid 1.0 : an enterprise Grid infrastructure for biomedical research.  

SciTech Connect

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>.

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

251

Smart Grid Interoperability Panel  

E-print Network

Standards. ” This document describes the purpose and scope of the Catalog, as well as the process and procedures for the management of the SGIP Catalog of Standards (CoS). Procedures are described for the management of the lifecycle of an entry into the Catalog, from its proposed inclusion, to its approval for inclusion, its periodic review for relevance and its possible deprecation and removal from the Catalog. Note that the SGIP Catalog of Standards is anticipated to provide a key but not exclusive source of input to the NIST process for coordinating the development of a framework of protocols and model standards for the Smart Grid under its Energy Independence and Security Act (EISA) of 2007 responsibilities. The Catalog is a compendium of standards and practices considered to be relevant for the development and deployment of a robust and interoperable Smart Grid. The Catalog may contain multiple entries that may accomplish the same goals and are functionally equivalent; similarly a single Catalog entry may contain optional elements that need not be included in all implementations. In

unknown authors

252

An update on the classical and quantum harmonic oscillators on the sphere and the hyperbolic plane in polar coordinates  

E-print Network

A simple derivation of the classical solutions of a nonlinear model describing a harmonic oscillator on the sphere and the hyperbolic plane is presented in polar coordinates. These solutions are then related to those in cartesian coordinates, whose form was previously guessed. In addition, the nature of the classical orthogonal polynomials entering the bound-state radial wavefunctions of the corresponding quantum model is identified.

Quesne, C

2014-01-01

253

Cluster and Grid Computing  

NSDL National Science Digital Library

* Overview of grid computing, * Basic Internet technologies: IP, HTTP, UDP, TCP, * Security, * Web Services and Enabling technologies, * Grid service concepts,* Resource Management, * Discovery and Information Services, * Parallel programming techniques suitable for a Grid, * Cluster computing and basic message passing techniques

Apon, Amy

254

Sampling microcanonical ensembles of trajectories using harmonic approximation in internal coordinates  

NASA Astrophysics Data System (ADS)

In this paper, we modify quasiclassical harmonic sampling of microcanonical ensembles of trajectories by using the curvilinear internal coordinates. The harmonic approximation in the curvilinear normal coordinates provides a more realistic description of the PES than in the conventional rectilinear ones at finite displacements. Therefore, the sampling of vibrations in the internal coordinates significantly improves the quality of the sampling in a block-box fashion, providing more realistic displacements and reducing the errors in the potential energy. In particular, the sampling of large-amplitude torsion vibrations, which is non-realistic in the Cartesian modes, becomes accurate or acceptable in the curvilinear modes.

Rybkin, Vladimir V.; Ekström, Ulf

2014-08-01

255

Grid und Cloud Computing.  

E-print Network

??In dieser Arbeit werden die theoretischen Konzepte und mögliche praktische Anwendungsmöglichkeiten von Grid- und Cloud-Computing dargestellt. Als erster Teil der Arbeit wird zuerst auf Grids… (more)

Shahi Barogh, Bahareh

2010-01-01

256

Parallel adaptive Cartesian upwind methods for shock-driven multiphysics simulation  

SciTech Connect

The multiphysics fluid-structure interaction simulation of shock-loaded thin-walled structures requires the dynamic coupling of a shock-capturing flow solver to a solid mechanics solver for large deformations. By combining a Cartesian embedded boundary approach with dynamic mesh adaptation a generic software framework for such flow solvers has been constructed that allows easy exchange of the specific hydrodynamic finite volume upwind scheme and coupling to various explicit finite element solid dynamics solvers. The paper gives an overview of the computational approach and presents first simulations that couple the software to the general purpose solid dynamics code DYNA3D.

Deiterding, Ralf [ORNL] [ORNL

2011-01-01

257

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

NASA Technical Reports Server (NTRS)

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.

Nemec, Marian; Aftosmis,Michael J.

2006-01-01

258

Efficient and Robust Cartesian Mesh Generation for Building-Cube Method  

NASA Astrophysics Data System (ADS)

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.

Ishida, Takashi; Takahashi, Shun; Nakahashi, Kazuhiro

259

A review of "Cartesian Metaphysics: The Late Scholastic Origins of Modern Philosophy." by Jorge Secada  

E-print Network

originated from Late Scho- lastic thought. In fact, the aim of Secada?s book is ?to offer a uni- fied reading of Descartes? metaphysics against the background of Scholastic philosophy? (1), thus opening the way for a thorough and contextual account... and thought. The issues dealt with here and in Part Two are at the core of the Cartesian metaphysical and natural philosophical views that came to replace the Scholastic traditions from which they were born, and which are explained in Part One of Secada...

Luciano Boschiero

2002-01-01

260

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

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

261

MIT Physics 8.02: Vector Fields Visualizations - Coordinate Systems  

NSDL National Science Digital Library

This item is an interactive 3D Shockwave simulation that illustrates the different types of coordinate systems often used in studying electromagnetism: cartesian, cylindrical (polar), and spherical. Each system has a distinct set of principle axes, represented by the three surfaces. Users may toggle among the three systems, move each system in any direction, and control the observation point in the three different principle directions. This item is part of a collection of visualizations developed by the MIT TEAL project to supplement an introductory course in calculus-based electricity and magnetism. Lecture notes, labs, and presentations are also available as part of MIT's Open Courseware Repository: MIT Open Courseware: Electricity and Magnetism

2010-03-31

262

Nonlinear and linear local cartesian relative motion state models for J2 pertubed elliptical orbits  

NASA Astrophysics Data System (ADS)

Formulating a relative motion model between artificial satellites keeps a very actual interest in order to achieve devices adapted to autonomous rendezvous operating or formation flying control. Scanning the existing models field leads to distinguish them according to their nature -- linear or nonlinear -- the relative state variables -- local cartesian or curvilinear variables, relative orbital elements, classical or not -- the reference state variables -- inertial cartesian or spherical variables, orbital elements -- the pertubations taken into account -- drag, J2, ... -- and other assumptions as eccentricity of the reference satellite. The historical Clohessy-Wiltshire and Tschauner-Hempel models have been outclassed by improved linear models that include J2 pertubation [1, 2, 3] or drag [4] but do not take rigorously into account the perturbed dynamics of the reference local frame. As far as this fundamental point is concerned, Kechichian's nonlinear model [5] provides an interesting but complex formulation because of a non optimal derivation method. More over, it does not take full advantage of the Lagrange conditions [6] implied by orbital elements definition which allows simplifications without loss of generality. These elements are presented in this article to reach an improved relative motion nonlinear model under J2 perturbation assumption which results are validated by comparison with those produced by a nonlinear equinoctial propagator. A linear model is also proposed.

Theron, A.; Kara-Zaitri, M.; Arzelier, D.; Louembet, C.

2009-10-01

263

Two-dimensional central-upwind schemes for curvilinear grids and application to gas dynamics with angular momentum  

Microsoft Academic Search

In this work we present new second order semi-discrete central schemes for systems of hyperbolic conservation laws on curvilinear grids. Our methods generalise the two-dimensional central-upwind schemes developed by Kurganov and Tadmor (1). In these schemes we account for area and volume changes in the numerical ux functions due to the non-cartesian geometries. In case of vectorial conservation laws we

Tobias F. Illenseer; Wolfgang J. Duschl

2009-01-01

264

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

NASA Technical Reports Server (NTRS)

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.

Kumar, D.

1980-01-01

265

Induced current bio-impedance technique for monitoring cryosurgery procedure in a two-dimensional head model using generalized coordinate systems.  

PubMed

In the noninvasive bio-impedance technique, small amplitude currents are applied to the body and the developing potentials on its surface are measured. This noninvasive technique is used to monitor physiological and pathological processes, which alter the values or the spatial distribution of the electrical impedance inside the human body. A possible application of the bio-impedance technique is monitoring brain cryosurgery procedure--a surgical technique that employs freezing to destroy undesirable tissues. A numerical solver was developed to evaluate the ability of an induced-current bio-impedance system to monitor the growth of the frozen tissue inside the head in simulation. The forward-problem bio-impedance solver, which is based on the finite volume method in generalized two-dimensional (2-D) coordinate systems, was validated by a comparison to a known analytical solution for body-fitted and Cartesian meshing grids. The sensitivity of the developed surface potential to the ice-ball area was examined using a 2-D head model geometry, and was found to range between 0.8 x 10(-2) and 1.68 x 10(-2) (relative potential difference/mm2), depending on the relative positioning of the excitation coil and the head. The maximal sensitivity was achieved when the coil was located at the geometrical center of the model. PMID:16042004

Gergel, Alexander; Zlochiver, Sharon; Rosenfeld, Moshe; Abboud, Shimon

2005-07-01

266

Visual SLAM Using Variance Grid Maps  

NASA Technical Reports Server (NTRS)

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.

Howard, Andrew B.; Marks, Tim K.

2011-01-01

267

Cartesian SENSE and k-t SENSE reconstruction using commodity graphics hardware.  

PubMed

This study demonstrates that modern commodity graphics cards (GPUs) can be used to perform fast Cartesian SENSE and k-t SENSE reconstruction. Specifically, the SENSE inversion is accelerated by up to two orders of magnitude and is no longer the time-limiting step. The achieved reconstruction times are now well below the acquisition times, thus enabling real-time, interactive SENSE imaging, even with a large number of receive coils. The fast GPU reconstruction is also beneficial for datasets that are not acquired in real time. We demonstrate that it can be used for interactive adjustment of regularization parameters for k-t SENSE in the same way that one would adjust window and level settings. This enables a new way of performing imaging reconstruction, where the user chooses the setting of tunable reconstruction parameters, in real time, depending on the context in which the images are interpreted. PMID:18306398

Hansen, Michael S; Atkinson, David; Sorensen, Thomas S

2008-03-01

268

Investigation of Radar Propagation in Buildings: A 10 Billion Element Cartesian-Mesh FETD Simulation  

SciTech Connect

In this paper large scale full-wave simulations are performed to investigate radar wave propagation inside buildings. In principle, a radar system combined with sophisticated numerical methods for inverse problems can be used to determine the internal structure of a building. The composition of the walls (cinder block, re-bar) may effect the propagation of the radar waves in a complicated manner. In order to provide a benchmark solution of radar propagation in buildings, including the effects of typical cinder block and re-bar, we performed large scale full wave simulations using a Finite Element Time Domain (FETD) method. This particular FETD implementation is tuned for the special case of an orthogonal Cartesian mesh and hence resembles FDTD in accuracy and efficiency. The method was implemented on a general-purpose massively parallel computer. In this paper we briefly describe the radar propagation problem, the FETD implementation, and we present results of simulations that used over 10 billion elements.

Stowell, M L; Fasenfest, B J; White, D A

2008-01-14

269

Best of Both Worlds: Uniform sampling in Cartesian and Cayley Molecular Assembly Configuration Space  

E-print Network

EASAL (efficient atlasing and sampling of assembly landscapes) is a recently reported geometric method for representing, visualizing, sampling and computing integrals over the potential energy landscape tailored for small molecular assemblies. EASAL's efficiency arises from the fact that small assembly landscapes permit the use of so-called Cayley parameters (inter-atomic distances) for geometric representation and sampling of the assembly configuration space regions; this results in their isolation, convexification, customized sampling and systematic traversal using a comprehensive topological roadmap, ensuring reasonable coverage of crucial but narrow regions of low effective dimension. However, this alone is inadequate for accurate computation of configurational entropy and other integrals, required for estimation of both free energy and kinetics - where it is essential to obtain uniform sampling in appropriate cartesian or moduli space parameterization. Standard adjustment of Cayley sampling via the Jacob...

Ozkan, Aysegul

2014-01-01

270

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

NASA Technical Reports Server (NTRS)

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.

Hartwich, Peter M.

1993-01-01

271

A Parallel Cartesian Approach for External Aerodynamics of Vehicles with Complex Geometry  

NASA Technical Reports Server (NTRS)

This workshop paper presents the current status in the development of a new approach for the solution of the Euler equations on Cartesian meshes with embedded boundaries in three dimensions on distributed and shared memory architectures. The approach uses adaptively refined Cartesian hexahedra to fill the computational domain. Where these cells intersect the geometry, they are cut by the boundary into arbitrarily shaped polyhedra which receive special treatment by the solver. The presentation documents a newly developed multilevel upwind solver based on a flexible domain-decomposition strategy. One novel aspect of the work is its use of space-filling curves (SFC) for memory efficient on-the-fly parallelization, dynamic re-partitioning and automatic coarse mesh generation. Within each subdomain the approach employs a variety reordering techniques so that relevant data are on the same page in memory permitting high-performance on cache-based processors. Details of the on-the-fly SFC based partitioning are presented as are construction rules for the automatic coarse mesh generation. After describing the approach, the paper uses model problems and 3- D configurations to both verify and validate the solver. The model problems demonstrate that second-order accuracy is maintained despite the presence of the irregular cut-cells in the mesh. In addition, it examines both parallel efficiency and convergence behavior. These investigations demonstrate a parallel speed-up in excess of 28 on 32 processors of an SGI Origin 2000 system and confirm that mesh partitioning has no effect on convergence behavior.

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

2001-01-01

272

the Smart Grid  

E-print Network

Technology (NIST) promotes the U.S. economy and public welfare by providing technical leadership for the Nation’s measurement and standards infrastructure. ITL develops tests, test methods, reference data, proof of concept implementations, and technical analysis to advance the development and productive use of information technology (IT). ITL’s responsibilities include the development of technical, physical, administrative, and management standards and guidelines for the cost-effective security and privacy of sensitive unclassified information in federal computer systems. This National Institute of Standards and Technology Interagency Report (NISTIR) discusses ITL’s research, guidance, and outreach efforts in computer security and its collaborative activities with industry, government, and academic organizations. National Institute of Standards and Technology Interagency Report 7628, vol. 2 69 pages (August 2010) Certain commercial entities, equipment, or materials may be identified in this report in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose. ACKNOWLEDGMENTS This report was developed by members of the Smart Grid Interoperability Panel–Cyber Security Working Group (SGIP-CSWG), formerly the Cyber Security Coordination Task Group (CSCTG), and during its development was chaired by Annabelle Lee of the Federal Energy Regulatory Commission (FERC), formerly of NIST. The CSWG is now chaired by Marianne

The Smart; Grid Interoperability

2010-01-01

273

Calculation of steady and unsteady transonic flow using a Cartesian mesh and gridless boundary conditions with application to aeroelasticity  

Microsoft Academic Search

A numerical method for the solution of inviscid compressible flow using an array of embedded Cartesian meshes in conjunction with gridless surface boundary conditions is developed. The gridless boundary treatment is implemented by means of a least squares fitting of the conserved flux variables using a cloud of nodes in the vicinity of the surface geometry. The method allows for

David Kirshman

2003-01-01

274

A Simplified Cartesian-Computed Torque Controller for Highly Geared Systems and Its Application to an Experimental Climbing Robot  

Microsoft Academic Search

A simplified Cartesian computed torque (SCCT) control scheme and its application to an experimental climbing robot named LIBRA is presented. SCCT control is developed ex- ploiting some of the characteristics of highly geared mobile robots. The effectiveness of the method is shown by simulation and experimental results using the LIBRA robot. SCCT control is shown to have improved performance, over

Steven Dubowsky; Constantinos Mavroidis

1999-01-01

275

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

Microsoft Academic Search

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

Domenico Campolo

2011-01-01

276

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

ERIC Educational Resources Information Center

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…

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

2012-01-01

277

Advancing Smart Grid Interoperability and Implementing NIST's Interoperability Roadmap  

SciTech Connect

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.

Basso,T.; DeBlasio, R.

2010-04-01

278

An orthogonal terrain-following coordinate and its preliminary tests using 2-D idealized advection experiments  

NASA Astrophysics Data System (ADS)

We have designed an orthogonal curvilinear terrain-following coordinate (the orthogonal ? coordinate, or the OS coordinate) to reduce the advection errors in the classic ? coordinate. First, we rotate the basis vectors of the z coordinate in a specific way in order to obtain the orthogonal, terrain-following basis vectors of the OS coordinate, and then add a rotation parameter b to each rotation angle to create the smoother vertical levels of the OS coordinate with increasing height. Second, we solve the corresponding definition of each OS coordinate through its basis vectors; and then solve the 3-D coordinate surfaces of the OS coordinate numerically, therefore the computational grids created by the OS coordinate are not exactly orthogonal and its orthogonality is dependent on the accuracy of a numerical method. Third, through choosing a proper b, we can significantly smooth the vertical levels of the OS coordinate over a steep terrain, and, more importantly, we can create the orthogonal, terrain-following computational grids in the vertical through the orthogonal basis vectors of the OS coordinate, which can reduce the advection errors better than the corresponding hybrid ? coordinate. However, the convergence of the grid lines in the OS coordinate over orography restricts the time step and increases the numerical errors. We demonstrate the advantages and the drawbacks of the OS coordinate relative to the hybrid ? coordinate using two sets of 2-D linear advection experiments.

Li, Y.; Wang, B.; Wang, D.; Li, J.; Dong, L.

2014-08-01

279

Method of grid generation  

DOEpatents

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.

Barnette, Daniel W. (Veguita, NM)

2002-01-01

280

IPG Power Grid Overview  

NASA Technical Reports Server (NTRS)

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.

Hinke, Thomas

2003-01-01

281

Conversation and Coordinative Structures  

Microsoft Academic Search

People coordinate body postures and gaze patterns during conversation. We review literature showing that (1) action embodies cognition, (2) postural coordination emerges spontaneously when two people converse, (3) gaze patterns influence postural coordination, (4) gaze coordination is a function of common ground knowledge and visual information that conversants believe they share, and (5) gaze coordination is causally related to mutual

Kevin Shockley; Daniel C. Richardson; Rick Dalec

2009-01-01

282

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

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

283

FermiGrid  

SciTech Connect

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.

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

284

Focus Sensitive Coordination  

E-print Network

This thesis investigates the role of the Focus Sensitive Operators (FSOs) even and also when found inside of a coordination. Coordinations of this form are called Focus Sensitive Coordinations (FSC) and include or even, ...

Hulsey, Sarah McNearney

2008-01-01

285

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

SciTech Connect

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.

Miliordos, Evangelos; Xantheas, Sotiris S.

2013-08-15

286

Which grids are Hamiltonian  

SciTech Connect

A complete grid G/sub m,n/ is a graph having m x n pertices that are connected to form a rectangular lattice in the plane, i.e., all edges of G/sub m,n/ connect vertices along horizontal or vertical lines. A grid is a subgraph of a complete grid. As an illustration, complete grids describe the basic pattern of streets in most cities. This paper examines the existence of Hamiltonian cycles in complete grids and complete grids with one or two vertices removed. It is determined for most values of m,n greater than or equal to 1, which grids G/sub m,n/ - (u) and G/sub m,n/ - (u,v) are Hamiltonian. 12 figures. (RWR)

Hedetniemi, S. M.; Hedetniemi, S. T.; Slater, P. J.

1980-01-01

287

Smart Grid Communications: Overview of Research Challenges, Solutions, and Standardization Activities  

E-print Network

Optimization of energy consumption in future intelligent energy networks (or Smart Grids) will be based on grid-integrated near-real-time communications between various grid elements in generation, transmission, distribution and loads. This paper discusses some of the challenges and opportunities of communications research in the areas of smart grid and smart metering. In particular, we focus on some of the key communications challenges for realizing interoperable and future-proof smart grid/metering networks, smart grid security and privacy, and how some of the existing networking technologies can be applied to energy management. Finally, we also discuss the coordinated standardization efforts in Europe to harmonize communications standards and protocols.

Fan, Zhong; Gormus, Sedat; Efthymiou, Costas; Kalogridis, Georgios; Sooriyabandara, Mahesh; Zhu, Ziming; Lambotharan, Sangarapillai; Chin, Woon Hau

2011-01-01

288

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

NASA Technical Reports Server (NTRS)

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.

Nemec, Marian; Aftosmis, Michael J.

2006-01-01

289

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

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

290

Choice of coordinates on a toroidal magnetic surface  

NASA Astrophysics Data System (ADS)

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.

Skovoroda, A. A.

2008-11-01

291

Dynamic fisheye grids for binary black hole simulations  

NASA Astrophysics Data System (ADS)

We present a new warped gridding scheme adapted to simulating gas dynamics in binary black hole spacetimes. The grid concentrates grid points in the vicinity of each black hole to resolve the smaller scale structures there, and rarefies grid points away from each black hole to keep the overall problem size at a practical level. In this respect, our system can be thought of as a ‘double’ version of the fisheye coordinate system, used before in numerical relativity codes for evolving binary black holes. The gridding scheme is constructed as a mapping between a uniform coordinate system—in which the equations of motion are solved—to the distorted system representing the spatial locations of our grid points. Since we are motivated to eventually use this system for circumbinary disc calculations, we demonstrate how the distorted system can be constructed to asymptote to the typical spherical polar coordinate system, amenable to efficiently simulating orbiting gas flows about central objects with little numerical diffusion. We discuss its implementation in the Harm3d code, tailored to evolve the magnetohydrodynamics equations in curved spacetimes. We evaluate the performance of the system’s implementation in Harm3d with a series of tests, such as the advected magnetic field loop test, magnetized Bondi accretion, and evolutions of hydrodynamic discs about a single black hole and about a binary black hole. Like we have done with Harm3d, this gridding scheme can be implemented in other unigrid codes as a (possibly) simpler alternative to adaptive mesh refinement.

Zilhão, Miguel; Noble, Scott C.

2014-03-01

292

Interaction and Coordination for Distributed Grid Computing Department Computer Science  

E-print Network

University Arkansas Little Rock Little Rock, AR 72204 James Sinnamon Department Computer Science Australian growth network capability doubles every nine months), opens many distributed applications services

Tang, Peiyi

293

Enabling Autonomic Grid Applications: Dynamic Composition, Coordination and Interaction  

Microsoft Academic Search

The increasing complexity, heterogeneity and dynamism of networks, systems and applications have made our computational and information infras- tructure brittle, unmanageable and insecure. This has necessitated the investiga- tion of an alternate paradigm for system and application design, which is based on strategies used by biological systems to deal with similar challenges of complex- ity, heterogeneity, and uncertainty, i.e. autonomic

Zhen Li; Manish Parashar

2004-01-01

294

Coordinated Variable Structure Switching Attacks for Smart Grid  

E-print Network

The effective modeling and analysis of large-scale power system disturbances especially those stemming from intentional attack represents an open engineering and research problem. Challenges stem from the need to develop intelligent models of cyber...

Liu, Shan

2013-02-11

295

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

NASA Technical Reports Server (NTRS)

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.

Berger, Marsha; Aftosmis, Michael J.

2012-01-01

296

Efficient and stable numerical method for evaluation of Zernike polynomials and their Cartesian derivatives  

NASA Astrophysics Data System (ADS)

Our work is focused on a problem of numerical evaluation of Zernike polynomials and their Cartesian partial derivatives. Since the direct calculation using explicit definition relations is relatively slow and it is numerically instable for higher orders of evaluated polynomials there is a need for a more effective and stable method. In recent years several recurrent methods were developed for numerical evaluation of Zernike polynomials. These methods are numerically stable up to very high orders and they are much faster than direct calculation. In our work a brief review of the existing methods for calculation of Zernike polynomials is given and then an analogous recurrence method for evaluation of x and y partial derivatives of Zernike polynomials is proposed. The numerical stability of this method and the comparison of computation time with respect to the direct method is presented using computer simulations. The proposed method can be used e.g. in optical modeling for expressing the shape of optical surfaces or in optical measurement methods based on the wavefront gradient measurements (Shack-Hartmann wavefront sensor, pyramidal sensor or shearing interferometry), where modal wavefront reconstruction using Zernike polynomials is often used.

Novák, Pavel; Novák, Jí?í

2013-05-01

297

Non-Cartesian MRI Reconstruction With Automatic Regularization Via Monte-Carlo SURE  

PubMed Central

Magnetic resonance image (MRI) reconstruction from undersampled k-space data requires regularization to reduce noise and aliasing artifacts. Proper application of regularization however requires appropriate selection of associated regularization parameters. In this work, we develop a data-driven regularization parameter adjustment scheme that minimizes an estimate (based on the principle of Stein’s unbiased risk estimate—SURE) of a suitable weighted squared-error measure in k-space. To compute this SURE-type estimate, we propose a Monte-Carlo scheme that extends our previous approach to inverse problems (e.g., MRI reconstruction) involving complex-valued images. Our approach depends only on the output of a given reconstruction algorithm and does not require knowledge of its internal workings, so it is capable of tackling a wide variety of reconstruction algorithms and nonquadratic regularizers including total variation and those based on the ?1-norm. Experiments with simulated and real MR data indicate that the proposed approach is capable of providing near mean squared-error (MSE) optimal regularization parameters for single-coil undersampled non-Cartesian MRI reconstruction. PMID:23591478

Weller, Daniel S.; Nielsen, Jon-Fredrik; Fessler, Jeffrey A.

2013-01-01

298

On the Use of CAD and Cartesian Methods for Aerodynamic Optimization  

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

299

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

PubMed

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

Ba?ar, Erol; Güntekin, Bahar

2007-04-01

300

A Unified Coordinate System for Solving the Three-Dimensional Euler Equations  

Microsoft Academic Search

Two general coordinate systems have been used extensively in computational fluid dynamics: the Eulerian and the Lagrangian. The Eulerian coordinates cause excessive numerical diffusion across flow discontinuities, slip lines in particular. The Lagrangian coordinates, on the other hand, can resolve slip lines sharply but cause severe grid deformation, resulting in large errors and even breakdown of the computation. Recently, Hui

W. H. Hui; S. Kudriakov

2001-01-01

301

Improving coordination between regional power markets  

NASA Astrophysics Data System (ADS)

Restructuring of the electric power industry---both in the United States and elsewhere---has fostered the development of regional wholesale power markets closely integrated with power grid operations. The natural focus of the system optimizations used in these markets has been on maximizing the value of in-system resources. Where cross-border flows are possible, accommodations are made, but relative to the optimization such adjustments are ad hoc. Cross-border flows are growing, however, and present an increasing challenge to transmission system operators. Industry efforts at interregional coordination have focused on practical barriers to trade between regions; academic research has addressed some of the engineering challenges of coordinating separate regional grid optimizations. The existing research has for the most part neglected a number of issues traditionally of interest to economists. The present research uses the methods of experimental economics to examine the consequences of a market design to promote more efficient use of interconnections.

Giberson, Michael A.

302

Generalized k-space decomposition with chemical shift correction for non-Cartesian water-fat imaging.  

PubMed

Chemical-shift artifacts associated with non-Cartesian imaging are more complex to model and less clinically acceptable than the bulk fat shift that occurs with conventional spin-warp Cartesian imaging. A novel k-space based iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) approach is introduced that decomposes multiple species while simultaneously correcting distortion of off-resonant species. The new signal model accounts for the additional phase accumulated by off-resonant spins at each point in the k-space acquisition trajectory. This phase can then be corrected by adjusting the decomposition matrix for each k-space point during the final IDEAL processing step with little increase in reconstruction time. The technique is demonstrated with water-fat decomposition using projection reconstruction (PR)/radial, spiral, and Cartesian spin-warp imaging of phantoms and human subjects, in each case achieving substantial correction of chemical-shift artifacts. Simulations of the point-spread-function (PSF) for off-resonant spins are examined to show the nature of the chemical-shift distortion for each acquisition. Also introduced is an approach to improve the signal model for species which have multiple resonant peaks. Many chemical species, including fat, have multiple resonant peaks, although such species are often approximated as a single peak. The improved multipeak decomposition is demonstrated with water-fat imaging, showing a substantial improvement in water-fat separation. PMID:18429018

Brodsky, Ethan K; Holmes, James H; Yu, Huanzhou; Reeder, Scott B

2008-05-01

303

Collaboration in a Wireless Grid Innovation Testbed by Virtual Consortium  

NASA Astrophysics Data System (ADS)

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.

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

304

Which coordinate system for modelling path integration?  

PubMed

Path integration is a navigation strategy widely observed in nature where an animal maintains a running estimate, called the home vector, of its location during an excursion. Evidence suggests it is both ancient and ubiquitous in nature, and has been studied for over a century. In that time, canonical and neural network models have flourished, based on a wide range of assumptions, justifications and supporting data. Despite the importance of the phenomenon, consensus and unifying principles appear lacking. A fundamental issue is the neural representation of space needed for biological path integration. This paper presents a scheme to classify path integration systems on the basis of the way the home vector records and updates the spatial relationship between the animal and its home location. Four extended classes of coordinate systems are used to unify and review both canonical and neural network models of path integration, from the arthropod and mammalian literature. This scheme demonstrates analytical equivalence between models which may otherwise appear unrelated, and distinguishes between models which may superficially appear similar. A thorough analysis is carried out of the equational forms of important facets of path integration including updating, steering, searching and systematic errors, using each of the four coordinate systems. The type of available directional cue, namely allothetic or idiothetic, is also considered. It is shown that on balance, the class of home vectors which includes the geocentric Cartesian coordinate system, appears to be the most robust for biological systems. A key conclusion is that deducing computational structure from behavioural data alone will be difficult or impossible, at least in the absence of an analysis of random errors. Consequently it is likely that further theoretical insights into path integration will require an in-depth study of the effect of noise on the four classes of home vectors. PMID:19962387

Vickerstaff, Robert J; Cheung, Allen

2010-03-21

305

Replication strategy in Peer-to-Peer Geospatial Data Grid  

Microsoft Academic Search

Data Grid provides distributed resources for dealing with large-scale applications that generate huge volume data sets, while the Peer-to-Peer architecture provides the maximum autonomy and scalability. Combing their features, we have built a P2P Data Grid prototype as a high-available coordinated platform for storing, processing, and mining the massive Geospatial data. Replication strategy is the most challenging issue in building

Yin Dafei; Chen Bin; Huang Zhou; Lin Xin; Zhang Ke; Fang Yu

2007-01-01

306

Operation of Power Grids with High Penetration of Wind Power  

Microsoft Academic Search

The integration of wind power into the power grid poses many challenges due to its highly uncertain nature. This dissertation involves two main components related to the operation of power grids with high penetration of wind energy: wind-thermal stochastic dispatch and wind-thermal coordinated bidding in short-term electricity markets. In the first part, a stochastic dispatch (SD) algorithm is proposed that

Ali Taleb Al-Awami

2010-01-01

307

Online scheduling in grids  

Microsoft Academic Search

This paper addresses nonclairvoyant and non- preemptive online job scheduling in Grids. In the applied basic model, the Grid system consists of a large number of identical processors that are divided into several machines. Jobs are independent, they have a fixed degree of parallelism, and they are submitted over time. Further, a job can only be executed on the processors

Andrei Tchernykh; Ramin Yahyapour

2008-01-01

308

Security for grids  

SciTech Connect

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.

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

2005-08-14

309

GridFlow: Workflow Management for Grid Computing  

Microsoft Academic Search

Grid computing is becoming a mainstream technology for large-scale distributed resource sharing and system integration. Workflow management is emerging as one of the most important grid services. In this work, a workflow management system for grid computing, called GridFlow, is presented, including a user portal and services of both g lobal grid workflow management and local grid sub-workflow scheduling. Simulation,

Junwei Cao; Stephen A. Jarvis; Subhash Saini; Graham R. Nudd

2003-01-01

310

A conservative approach for flow field calculations on multiple grids  

NASA Technical Reports Server (NTRS)

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.

Kathong, Monchai; Tiwari, Surendra N.

1988-01-01

311

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)

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.

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

2001-01-01

312

Hand Eye Coordination  

E-print Network

This paper describes a simple method of converting visual coordinates to arm coordinates which does not require knowledge of the position of the camera(s). Comparisons are made to other methods and two camera, three ...

Speckert, Glen

313

Evolution of Dynamic Coordination  

E-print Network

5 Evolution of Dynamic Coordination Evan Balaban, Shimon Edelman, Sten Grillner, Uri Grodzinski comparative biology provide for furthering scienti¿c un- derstanding of the evolution of dynamic coordination structures, neural functions, and behavioral coordination. Below we present an overview of neural machinery

Jarvis, Erich D.

314

Processing Coordination Ambiguity  

ERIC Educational Resources Information Center

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…

Engelhardt, Paul E.; Ferreira, Fernanda

2010-01-01

315

MISCELLANEA Spherical Coordinates  

E-print Network

and to denote polar coordinates. Most American calculus texts also utilize in spherical coordinates coordinate. There is however a much more serious problem. Several of the most commonly used calculus texts overnight from driving on the left to driving on the right! We argue that the conflict between the different

316

AUSTRALASIAN JOURNAL OF COMBINATORICS Volume 41 (2008), Pages 15–28 Average firefighting on infinite grids  

E-print Network

In the Firefighter Problem, a fire breaks out at a vertex of a graph G, then f firefighters protect f vertices. At each subsequent time step, the fire spreads from each “burned ” vertex to all of its unprotected neighbours, then f firefighters “protect ” f unburned vertices. Once a vertex is protected or burned, it remains so from then onward. A common objective is to determine the minimum number f, such that if f vertices are protected at each time step, then the fire can be contained on a graph G. In this paper, average firefighting is introduced: the number of vertices protected in each time step is allowed to vary. If the number of firefighters used is periodic and the average number (per time step) is strictly greater than 3/2, then a fire on the Cartesian grid can be contained. Similar results are also determined for the triangular and strong grids. 1

M. E. Messinger

317

myGrid: personalised bioinformatics on the information grid  

Microsoft Academic Search

Motivation: The my Grid project aims to exploit Grid technology, with an emphasis on the Information Grid, and provide middleware layers that make it appropriate for the needs of bioinformatics. my Grid is building high level services for data and application integration such as resource discovery, workflow enactment and distributed query processing. Additional services are provided to support the scientific

Robert D. Stevens; Alan J. Robinson; Carole A. Goble

2003-01-01

318

Ligand directed self-assembly of polymetallic [n x n] grids: rational routes to large functional molecular subunits?  

PubMed

Poly-(n)-topic ligands with a linear arrangement of coordination pockets self-assemble, generally in high yield, to produce square [n x n] grid complexes. Oligomeric, non-grid intermediates, identified by structural studies, have shown alternative construction pathways, but have also indicated possible mechanistic routes to grid assembly. Various factors are considered critical to grid formation, including reaction pH, metal ion identity, CFSE, and metal ion redox behaviour. Ultimately the design of the ligand is pivotal to successful grid self-assembly, and the size of the [n x n] grid is largely limited only by the synthetic limitations of the ligands themselves. PMID:18354761

Dawe, Louise N; Abedin, Tareque S M; Thompson, Laurence K

2008-04-01

319

Distributed Adaptive Grid Hierarchy  

NSDL National Science Digital Library

DAGH (which stands for Distributed Adaptive Grid Hierarchy) was developed as a computational toolkit for the Binary Black Hole NSF Grand Challenge Project. It provides the framework to solve systems of partial differential equations using adaptive finite difference methods.

320

The gridded electromagnet probe  

E-print Network

We attempted to measure the anisotropy in the electron distribution function in magnetized plasma by exploiting the adiabatic invariance of the electron's magnetic moment with a probe comprising a grid, a collector, and ...

Shadman, K. (Khashayar), 1972-

2003-01-01

321

Grid Computing Education Support  

SciTech Connect

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.

Steven Crumb

2008-01-15

322

Implementing Production Grids  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

323

IDL Grid Web Portal  

NASA Astrophysics Data System (ADS)

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.

Massimino, P.; Costa, A.

2008-08-01

324

Grid and Percent It  

NSDL National Science Digital Library

This lesson begins with a basic visual used in many textbooks: a 10 Ã 10 grid as a model for demonstrating percent as "parts per hundred" with a worksheet of these grids to print for each student. The lesson goes on to extend the model to solve various percentage problems. Especially valuable is the illustration of each problem and the thorough explanation that accompanies it.

2002-01-01

325

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)

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 x2?+y2?-1=0 where here ?=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.

Li, Shan; Boyd, John P.

2014-02-01

326

Exploring Hypersonic, Unstructured-Grid Issues through Structured Grids  

NASA Technical Reports Server (NTRS)

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.

Mazaheri, Ali R.; Kleb, Bill

2007-01-01

327

Numerical methods for solid mechanics on overlapping grids: Linear elasticity  

NASA Astrophysics Data System (ADS)

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.

Appelö, Daniel; Banks, Jeffrey W.; Henshaw, William D.; Schwendeman, Donald W.

2012-07-01

328

Petri Net Modeling of Cyber-Physical Attacks on Smart Grid  

Microsoft Academic Search

This paper investigates the use of Petri nets for mod- eling coordinated cyber-physical attacks on the smart grid. Petri nets offer more flexibility and expressiveness than traditional at- tack trees to represent the actions of simultaneous attackers. How- ever, Petri net models for attacks on very large critical infrastruc- tures such as the smart grid require a great amount of

Thomas M. Chen; Juan Carlos Sanchez-Aarnoutse; John Buford

2011-01-01

329

GRIDS: Grid-Scale Rampable Intermittent Dispatchable Storage  

SciTech Connect

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.

None

2010-09-01

330

FUTURE POWER GRID INITIATIVE Future Power Grid  

E-print Network

DHRC with remedial action schemes (RAS) - Optimal voltage control for improved voltage stability - Use » The proposed control paradigm will - Improve transient stability and restore system conditions (frequency & tie line power) after contingencies - Coordinate voltage resources to improve voltage security margin

331

Unstructured Grids on NURBS Surfaces  

NASA Technical Reports Server (NTRS)

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.

Samareh-Abolhassani, Jamshid

1993-01-01

332

Distributed Geo-rectification of Satellite Images using Grid Computing  

E-print Network

with a defined array of coordinates [25]. Figure 1 illustrates the geo-rectification process. A satellite image1 Distributed Geo-rectification of Satellite Images using Grid Computing Y.M. Teo* , S.C. Tay** , and J.P. Gozali* * Department of Computer Science ** Centre for Remote Imaging, Sensing and Processing

Teo, Yong-Meng

333

Different gridding methods and their influence on surface wave tomography  

NASA Astrophysics Data System (ADS)

Seismic waveform data of 106 broadband digital stations in South China between 1999 and 2012 were initially collected. Then surface-wave waveforms for shallow and moderate focal-depth events with magnitude Ms ? 5.0 were analyzed. We processed Rayleigh waves and obtained their group velocities by using frequency-time analysis method. Checker-board tests were used to choose an appropriate grid size for following inversions. To accommodate the possible sutures, Chenzhou-Linwu fault and Jingxian-Anhua fault between Cathaysian and Yangtze blocks in South China, we set up two meshes to test the effects of different model parameterizations. One mesh had the regular grids with boundaries parallel to latitude or longitude (regular grid) and another mesh used grids with boundaries approximately parallel or perpendicular to the strike of Chenzhou-Linwu fault (slant grid). The different meshes were utilized by coordinate transformation. Ray coverage density and azimuth coverage of two gridding methods were compared, and the slant grid shows a better ray coverage uniformity along the fault strike than the regular grid, but azimuth coverage for both meshes are similar. After inverting the path-averaged group times by means of a damped least-squares approach, we have acquired location-dependent group velocities on a 1.5°×1.5° grid and constructed Rayleigh wave group velocity maps at periods from 10 to 100s. Resolution and covariance matrices have been computed in order to evaluate the quality of the results. Similarly, slant grid has some improvements in group velocity images at various periods on some major characters. Results above indicate that the trial of slant gridding method is reasonable.

Wang, Minling; Zhang, Zhongjie; Chen, Yun; Xu, Yihe; Teng, Jiwen

2014-05-01

334

Modeling and Supporting Grid Scheduling  

Microsoft Academic Search

Abstract\\\\ \\\\ Grid resource management systems and schedulers are important components for building Grids. They are responsible for the\\u000a selection and allocation of Grid resources to current and future applications. Thus, they are important building blocks for\\u000a making Grids available to user communities. In this paper we briefly analyze the requirements of Grid resource management\\u000a and provide a classification of schedulers. Then,

Andrea Pugliese; Domenico Talia; Ramin Yahyapour

2007-01-01

335

Adaptive Grid Workflow Scheduling Algorithm  

Microsoft Academic Search

\\u000a The scheduling policy and algorithm of grid workflow determine the effectiveness and efficiency of grid workflow tasks, which\\u000a is the key technology in grid workflow. Based on the definition of grid workflow tasks dynamic ready queue, critical factor,\\u000a dynamic factor and prior factor, the grid workflow tasks selection algorithm, resource selection algorithm and tasks allocation\\u000a algorithm are presented, which constitute

Shaohua Zhang; Yujin Wu; Ning Gu

2004-01-01

336

Grids for electric storage batteries  

SciTech Connect

A grid array for use in assembling a multicell electric battery comprises a plurality of grids preferably arranged in two spaced parallel lines, adapted to provide a plate for every cell of the battery. Each grid is connected to one or more adjacent grids by a combination of integral bridge pieces and sufficient temporary links to maintain all the grids of the array in their desired configuration.

Hayes, M. H.; Pearson, E. J.

1985-07-09

337

21me Congrs Franais de Mcanique Bordeaux, 26 au 30 aot 2013 A second order finite-volume scheme on cartesian grids for  

E-print Network

�es pr�s de la fronti�re avec le solide, nous r�solvons un probl�me de Riemann ad hoc qui tient compte des conditions aux limites � imposer. Pour �viter les oscillations de pression pr�s du solide, nous'angle entre la normale au solide et celle � la cellule de la grille cart�sienne. Le sch�ma est simple � impl

Boyer, Edmond

338

Tax Coordination and Unemployment  

Microsoft Academic Search

This paper analyses the implications of unemployment for fiscal competition and tax coordination among small open economies.\\u000a Unemployment is modeled as resulting from wage bargaining. The analysis focuses on the effect of labour and capital tax coordination\\u000a on welfare. We show that, while coordinated capital and labour tax increases unambiguously raise welfare if labour markets\\u000a are competitive, different results emerge

Clemens Fuest; Bernd Huber

1999-01-01

339

Generalized harmonic spatial coordinates and hyperbolic shift conditions  

NASA Astrophysics Data System (ADS)

We propose a generalization of the condition for harmonic spatial coordinates analogous to the generalization of the harmonic time slices introduced by Bona , and closely related to dynamic shift conditions recently proposed by Lindblom and Scheel, and Bona and Palenzuela. These generalized harmonic spatial coordinates imply a condition for the shift vector that has the form of an evolution equation for the shift components. We find that in order to decouple the slicing condition from the evolution equation for the shift it is necessary to use a rescaled shift vector. The initial form of the generalized harmonic shift condition is not spatially covariant, but we propose a simple way to make it fully covariant so that it can be used in coordinate systems other than Cartesian. We also analyze the effect of the shift condition proposed here on the hyperbolicity of the evolution equations of general relativity in 1+1 dimensions and 3+1 spherical symmetry, and study the possible development of blowups. Finally, we perform a series of numerical experiments to illustrate the behavior of this shift condition.

Alcubierre, Miguel; Corichi, Alejandro; González, José A.; Núñez, Darío; Reimann, Bernd; Salgado, Marcelo

2005-12-01

340

Accelerating NLTE radiative transfer by means of the Forth-and-Back Implicit Lambda Iteration: A two-level atom line formation in 2D Cartesian coordinates  

E-print Network

State-of-the-art methods in multidimensional NLTE radiative transfer are based on the use of local approximate lambda operator within either Jacobi or Gauss-Seidel iterative schemes. Here we propose another approach to the solution of 2D NLTE RT problems, Forth-and-Back Implicit Lambda Iteration (FBILI), developed earlier for 1D geometry. In order to present the method and examine its convergence properties we use the well-known instance of the two-level atom line formation with complete frequency redistribution. In the formal solution of the RT equation we employ short characteristics with two-point algorithm. Using an implicit representation of the source function in the computation of specific intensities, we compute and store the coefficients of the linear relations J = a + bS between the mean intensity J and the corresponding source function S. The use of iteration factors in the 'local' coefficients of these implicit relations in two 'inward' directions, along with the update of the source function in o...

Milic, Ivan

2014-01-01

341

1. (a)Derive the three dimensional heat diffusion equation in Cartesian coordinates (14%), and @)describe the three kinds of boundary conditions generally  

E-print Network

,2, 3, and 4.(20%) Adiabatic #12;5. Waste heat of exhaust hot' air from a manufacturing process may air is 77'C in cross flow with a velocity'of 10 mls over the tube. The inlet and outlet temperatures o.023Re ~r 0'4 if the flow is turbulent. (2). For external air flow, you may use the Churchill

Huang, Haimei

342

An Adaptive Unstructured Grid Method by Grid Subdivision, Local Remeshing, and Grid Movement  

NASA Technical Reports Server (NTRS)

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.

Pirzadeh, Shahyar Z.

1999-01-01

343

Coordinating Coordination Failures in Keynesian Models  

Microsoft Academic Search

This paper focuses on the importance of strategic complementarities in agents' payoff functions as a basis for macroeconomic coordination failures. Strategic complementarities arise when the optimal strategy of an agent depends positively upon the strategies of the other agents. The authors first analyze an abst ract game and find that multiple equilibria and a multiplier process may arise when strategic

Russell Cooper; Andrew John

1988-01-01

344

An arbitrary curvilinear coordinate particle in cell method  

NASA Astrophysics Data System (ADS)

A new approach to the kinetic simulation of plasmas in complex geometries, based on the Particle-in-Cell (PIC) simulation method, is explored. In this method, called the Arbitrary Curvilinear Coordinate PIC (ACC-PIC) method, all essential PIC operations are carried out on a uniform, unitary square logical domain and mapped to a nonuniform, boundary fitted physical domain. We utilize an elliptic grid generation technique known as Winslow's method to generate boundary-fitted physical domains. We have derived the logical grid macroparticle equations of motion based on a canonical transformation of Hamilton's equations from the physical domain to the logical. These equations of motion are not seperable, and therefore unable to be integrated using the standard Leapfrog method. We have developed an extension of the semi-implicit Modified Leapfrog (ML) integration technique to preserve the symplectic nature of the logical grid particle mover. We constructed a proof to show that the ML integrator is symplectic for systems of arbitrary dimension. We have constructed a generalized, curvilinear coordinate formulation of Poisson's equations to solve for the electrostatic fields on the uniform logical grid. By our formulation, we supply the plasma charge density on the logical grid as a source term. By the formulations of the logical grid particle mover and the field equations, the plasma particles are weighted to the uniform logical grid and the self-consistent mean fields obtained from the solution of the Poisson equation are interpolated to the particle position on the logical grid. This process eliminates the complexity associated with the weighting and interpolation processes on the nonuniform physical grid. In this work, we explore the feasibility of the ACC-PIC method as a first step towards building a production level, time-adaptive-grid, 3d electromagnetic ACC-PIC code. We begin by combining the individual components to construct a 1d, electrostatic ACC-PIC code on a stationary nonuniform grid. Several standard physics tests were used to validate the accuracy of our method in comparison with a standard uniform grid PIC code. We then extend the code to two spatial dimensions and repeat the physics tests on a rectangular domain with both orthogonal and nonorthogonal meshing in comparison with a standard 2d uniform grid PIC code. As a proof of principle, we then show the time evolution of an electrostatic plasma oscillation on an annular domain obtained using Winslow's method.

Fichtl, Christopher A.

345

Grid Data Management and Customer Demands at MeteoSwiss  

NASA Astrophysics Data System (ADS)

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.

Rigo, G.; Lukasczyk, Ch.

2010-09-01

346

The Global Grid  

E-print Network

This paper puts forward the vision that a natural future stage of the electricity network could be a grid spanning the whole planet and connecting most of the large power plants in the world: this is the "Global Grid". The main driving force behind the Global Grid will be the harvesting of remote renewable sources, and its key infrastructure element will be the high capacity long transmission lines. Wind farms and solar power plants will supply load centers with green power over long distances. This paper focusses on the introduction of the concept, showing that a globally interconnected network can be technologically feasible and economically competitive. We further highlight the multiple opportunities emerging from a global electricity network such as smoothing the renewable energy supply and electricity demand, reducing the need for bulk storage, and reducing the volatility of the energy prices. We also discuss possible investment mechanisms and operating schemes. Among others, we envision in such a system...

Chatzivasileiadis, Spyros; Andersson, Göran

2012-01-01

347

The Computing Grids  

NASA Astrophysics Data System (ADS)

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.

Govoni, P.

2009-12-01

348

Numerical Solution of Turbulent Flow Problems in General Geometry.  

National Technical Information Service (NTIS)

Turbulent flow of fluid was computed satisfactorily with the Imperial College TEACH program for a wide spectrum of problems. TEACH geometry is restricted to rectangular grids in Cartesian or cylindrical coordinates. The TURF program being developed at KAP...

E. L. Wachspress

1979-01-01

349

Social Postural Coordination  

ERIC Educational Resources Information Center

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…

Varlet, Manuel; Marin, Ludovic; Lagarde, Julien; Bardy, Benoit G.

2011-01-01

350

Mean value coordinates  

Microsoft Academic Search

We derive a generalization of barycentric coordinates which allows a vertex in a planar triangulation to be expressed as a convex combination of its neighbouring vertices. The coordinates are motivated by the Mean Value Theorem for harmonic functions and can be used to simplify and improve methods for parameterization and morphing.

Michael S. Floater

2003-01-01

351

6. Coordination and control.  

PubMed

Any complex operation requires a system for management. In most societies, disaster management is the responsibility of the government. Coordination and control is a system that provides the oversight for all of the disaster management functions. The roles and responsibilities of a coordination and control centre include: (1) planning; (2) maintenance of inventories; (3) activation of the disaster response plan; (4) application of indicators of function; (5) surveillance; (6) information management; (7) coordination of activities of the BSFs; (8) decision-making; (9) priority setting; (10) defining overarching goal and objectives for interventions; (11) applying indicators of effectiveness; (12) applying indicators of benefit and impact; (13) exercising authority; (14) managing resources; (15) initiating actions; (16) preventing influx of unneeded resources; (17) defining progress; (18) providing information; (19) liasing with responding organisations; and (20) providing quality assurance. Coordination and control is impossible without communications. To accomplish coordination and control, three factors must be present: (1) mandate; (2) power and authority; and (3) available resources. Coordination and control is responsible for the evaluation of the effectiveness and benefits/impacts of all interventions. Coordination and control centres (CCCs) are organised hierarchically from the on-scene CCCs (incident command) to local provincial to national CCCs. Currently, no comprehensive regional and international CCCs have been universally endorsed. Systems such as the incident command system, the unified command system, and the hospital incident command system are described as are the humanitarian reform movement and the importance of coordination and control in disaster planning and preparedness. PMID:24785803

2014-05-01

352

Heliospheric coordinate systems  

Microsoft Academic Search

This article gives an overview and reference to the most common coordinate systems currently used in space science. While coordinate systems used in near-Earth space physics have been described in previous work we extend that description to systems used for physical observations of the Sun and the planets and to systems based on spacecraft location. For all systems, we define

M. Fränz; D. Harper

2002-01-01

353

Computational fluid dynamics for propulsion technology: Geometric grid visualization in CFD-based propulsion technology research  

NASA Technical Reports Server (NTRS)

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.

Ziebarth, John P.; Meyer, Doug

1992-01-01

354

Processing coordination ambiguity.  

PubMed

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 that interpretations are the result of a constraint-satisfaction process, which predicts that frequency or context can bias the parser to initially pursue a more complex interpretation.The results showed an initial preference for noun-phrase coordination, despite the fact that sentential coordination is more frequent in imperative structures. These data suggest that the parser uses a syntactic simplicity heuristic for building initial structural analyses. PMID:21313991

Engelhardt, Paul E; Ferreira, Fernanda

2010-01-01

355

An arbitrary curvilinear-coordinate method for particle-in-cell modeling  

NASA Astrophysics Data System (ADS)

A new approach to kinetic simulation of plasmas in complex geometries, based on the particle-in-cell (PIC) simulation method, is explored. In the two-dimensional (2D) electrostatic version of our method, called the arbitrary curvilinear-coordinate PIC method, all essential PIC operations are carried out in 2D on a uniform grid on the unit square logical domain, and mapped to a nonuniform boundary-fitted grid on the physical domain. As the resulting logical grid equations of motion are not separable, we have developed an extension of the semi-implicit modified leapfrog integration technique to preserve the symplectic nature of the logical grid particle mover. A generalized, curvilinear-coordinate formulation of Poisson's equations to solve for the electrostatic fields on the uniform logical grid is also developed. By our formulation, we compute the plasma charge density on the logical grid based on the particles' positions on the logical domain. That is, the plasma particles are weighted to the uniform logical grid and the self-consistent mean electrostatic fields obtained from the solution of the logical grid Poisson equation are interpolated to the particle positions on the logical grid. This process eliminates the complexity associated with the weighting and interpolation processes on the nonuniform physical grid and allows us to run the PIC method on arbitrary boundary-fitted meshes.

Fichtl, C. A.; Finn, J. M.; Cartwright, K. L.

2012-01-01

356

Distributed Accounting on the Grid  

NASA Technical Reports Server (NTRS)

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.

Thigpen, William; Hacker, Thomas J.; McGinnis, Laura F.; Athey, Brian D.

2001-01-01

357

Essential Grid Workflow Monitoring Elements  

SciTech Connect

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.

Gunter, Daniel K.; Jackson, Keith R.; Konerding, David E.; Lee,Jason R.; Tierney, Brian L.

2005-07-01

358

Marshall Space Flight Center surface modeling and grid generation applications  

NASA Astrophysics Data System (ADS)

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.

Williams, Robert W.; Benjamin, Theodore G.; Cornelison, Joni W.

1995-03-01

359

The BioGRID Interaction Database: 2011 update  

PubMed Central

The Biological General Repository for Interaction Datasets (BioGRID) is a public database that archives and disseminates genetic and protein interaction data from model organisms and humans (http://www.thebiogrid.org). BioGRID currently holds 347?966 interactions (170?162 genetic, 177?804 protein) curated from both high-throughput data sets and individual focused studies, as derived from over 23?000 publications in the primary literature. Complete coverage of the entire literature is maintained for budding yeast (Saccharomyces cerevisiae), fission yeast (Schizosaccharomyces pombe) and thale cress (Arabidopsis thaliana), and efforts to expand curation across multiple metazoan species are underway. The BioGRID houses 48 831 human protein interactions that have been curated from 10 247 publications. Current curation drives are focused on particular areas of biology to enable insights into conserved networks and pathways that are relevant to human health. The BioGRID 3.0 web interface contains new search and display features that enable rapid queries across multiple data types and sources. An automated Interaction Management System (IMS) is used to prioritize, coordinate and track curation across international sites and projects. BioGRID provides interaction data to several model organism databases, resources such as Entrez-Gene and other interaction meta-databases. The entire BioGRID 3.0 data collection may be downloaded in multiple file formats, including PSI MI XML. Source code for BioGRID 3.0 is freely available without any restrictions. PMID:21071413

Stark, Chris; Breitkreutz, Bobby-Joe; Chatr-aryamontri, Andrew; Boucher, Lorrie; Oughtred, Rose; Livstone, Michael S.; Nixon, Julie; Van Auken, Kimberly; Wang, Xiaodong; Shi, Xiaoqi; Reguly, Teresa; Rust, Jennifer M.; Winter, Andrew; Dolinski, Kara; Tyers, Mike

2011-01-01

360

The BioGRID Interaction Database: 2011 update.  

PubMed

The Biological General Repository for Interaction Datasets (BioGRID) is a public database that archives and disseminates genetic and protein interaction data from model organisms and humans (http://www.thebiogrid.org). BioGRID currently holds 347,966 interactions (170,162 genetic, 177,804 protein) curated from both high-throughput data sets and individual focused studies, as derived from over 23,000 publications in the primary literature. Complete coverage of the entire literature is maintained for budding yeast (Saccharomyces cerevisiae), fission yeast (Schizosaccharomyces pombe) and thale cress (Arabidopsis thaliana), and efforts to expand curation across multiple metazoan species are underway. The BioGRID houses 48,831 human protein interactions that have been curated from 10,247 publications. Current curation drives are focused on particular areas of biology to enable insights into conserved networks and pathways that are relevant to human health. The BioGRID 3.0 web interface contains new search and display features that enable rapid queries across multiple data types and sources. An automated Interaction Management System (IMS) is used to prioritize, coordinate and track curation across international sites and projects. BioGRID provides interaction data to several model organism databases, resources such as Entrez-Gene and other interaction meta-databases. The entire BioGRID 3.0 data collection may be downloaded in multiple file formats, including PSI MI XML. Source code for BioGRID 3.0 is freely available without any restrictions. PMID:21071413

Stark, Chris; Breitkreutz, Bobby-Joe; Chatr-Aryamontri, Andrew; Boucher, Lorrie; Oughtred, Rose; Livstone, Michael S; Nixon, Julie; Van Auken, Kimberly; Wang, Xiaodong; Shi, Xiaoqi; Reguly, Teresa; Rust, Jennifer M; Winter, Andrew; Dolinski, Kara; Tyers, Mike

2011-01-01

361

O`ahu Grid Study: Validation of Grid Models  

E-print Network

O`ahu Grid Study: Validation of Grid Models Prepared for the U.S. Department of Energy Office............................................................................................................. 1 2 Model Validation.................................................................. 8 2.2.2 Dynamic Data Model

362

Metagenomics Smart power grid  

E-print Network

Metagenomics Smart power grid The new weapons workhorse Laser on Mars LOS ALAMOS SCIENCE: Microorganisms in the soil perform services that are essential to the survival of all plant and animal life of these microorganisms are understood by science today. Can we rapidly learn about the other 99 percent? Vibrant Science

363

Bar-grid oscillators  

Microsoft Academic Search

Grid oscillators are an attractive way of obtaining high power levels from the solid-state devices, since potentially the output powers of thousands of individual devices can be combined. The active devices do not require an external locking signal, and the power combining is done in free space. Thirty-six transistors were mounted on parallel brass bars, which provide a stable bias

ZOYA BASTA POPOVIC; ROBERT M. WEIKLE; MOONIL KIM; KENT A. POTTER; DAVID B. RUTLEDGE

1990-01-01

364

Times Tables Grid Game  

NSDL National Science Digital Library

This Flash applet provides targeted practice of multiplication facts. After a player selects which group(s) of multiples to practice, the applet displays products one at a time, and the player locates a cell on a blank grid that identifies a possible factor pair. Users may choose to play timed or untimed, and must complete a round with no more than 5 errors.

2013-01-01

365

Grid generation research at OSU  

NASA Technical Reports Server (NTRS)

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.

Nakamura, S.

1992-01-01

366

y 0 grid_size..:= x 0 grid_size..:=  

E-print Network

E = Youngs modulus D = flexural rigidity g = average gravity _load = density of the load _mantley 0 grid_size..:= x 0 grid_size..:= Calculate elastic plate flexure grid_size floor 1000 valid for choice of valid) (See Eq. 2.6) D _mantle _infill-( ) g 0.25 := Determine the 3-D flexural parameter

Watts, A. B. "Tony"

367

IEEE Smart Grid Series of Standards IEEE 2030 (Interoperability) and IEEE 1547 (Interconnection) Status: Preprint  

SciTech Connect

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.

Basso, T.; DeBlasio, R.

2012-04-01

368

Women's collective constructions of embodied practices through memory work: Cartesian dualism in memories of sweating and pain.  

PubMed

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

Gillies, Val; Harden, Angela; Johnson, Katherine; Reavey, Paula; Strange, Vicki; Willig, Carla

2004-03-01

369

Uranyl ion coordination  

USGS Publications Warehouse

A review of the known crystal structures containing the uranyl ion shows that plane-pentagon coordination is equally as prevalent as plane-square or plane-hexagon. It is suggested that puckered-hexagon configurations of OH - or H2O about the uranyl group will tend to revert to plane-pentagon coordination. The concept of pentagonal coordination is invoked for possible explanations of the complex crystallography of the natural uranyl hydroxides and the unusual behavior of polynuclear ions in hydrolyzed uranyl solutions.

Evans, H.T., Jr.

1963-01-01

370

Interface procedures for overlapping grids  

NASA Technical Reports Server (NTRS)

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.

Mastin, C. W.

1985-01-01

371

Explicit Generation of Orthogonal Grids for Ocean Models  

NASA Astrophysics Data System (ADS)

Several explicit methods are proposed for generating global orthogonal curvilinear grids for ocean modelling. The methods are based on the conformal properties of stereographic and Mercator map projections and have been developed with the specific object of removing the North Pole from the ocean domain. Some of the configurations, in addition to overcoming the pole problem, have very attractive resolution properties in the polar regions. Two of the constructions are geometrical in nature, while a third is based on the superposition of potential fields generated by discrete coordinate poles. The methods described here differ from those commonly employed in engineering problems in that grid line control is exercised by the placement of a finite number of singularities, and no specific condition is placed upon the fitting of coordinate lines to physical boundaries. The grids produced are accordingly of global construction and have smooth variations in grid size. Being of analytical or semi-analytical formulation, the grids may be generated quickly and without the need for advanced software.

Murray, Ross J.

1996-07-01

372

Understanding social motor coordination.  

PubMed

Recently there has been much interest in social coordination of motor movements, or as it is referred to by some researchers, joint action. This paper reviews the cognitive perspective's common coding/mirror neuron theory of joint action, describes some of its limitations and then presents the behavioral dynamics perspective as an alternative way of understanding social motor coordination. In particular, behavioral dynamics' ability to explain the temporal coordination of interacting individuals is detailed. Two experiments are then described that demonstrate how dynamical processes of synchronization are apparent in the coordination underlying everyday joint actions such as martial art exercises, hand-clapping games, and conversations. The import of this evidence is that emergent dynamic patterns such as synchronization are the behavioral order that any neural substrate supporting joint action (e.g., mirror systems) would have to sustain. PMID:20817320

Schmidt, R C; Fitzpatrick, Paula; Caron, Robert; Mergeche, Joanna

2011-10-01

373

Corrected geomagnetic pole coordinates  

Microsoft Academic Search

A new method for the accurate calculation of the corrected geomagnetic pole coordinates is developed. The results are compared with those obtained by previous methods, and maximum divergence was found to be approximately 1-deg.

Iu. L. Sverdlov; T. N. Khorkova

1982-01-01

374

Biorepository Coordinating Committee (BCC)  

Cancer.gov

Based on the findings of an NCI analysis of NCI-supported biorepositories, the National Cancer Advisory Board (NCAB) approved in November 2004 the formation of a trans-NCI committee, called the NCI Biorepository Coordinating Committee (BCC).

375

Kairoscope : coordinating time socially  

E-print Network

If everyone says time is relative, why is it still so rigidly defined? There have been many attempts to address the issue of coordinating schedules, but each of these attempts runs into an issue of rigidity: in order to ...

Martin, Reed Eric

2010-01-01

376

Vocational Education Curriculum Coordination.  

ERIC Educational Resources Information Center

Discusses the history, current structure, publications and communications strategies, information services for educators, and national information search procedures of the National Network for Curriculum Coordination in Vocational and Technical Education (NNCCVTE). (JL)

Bjorner, Susan

1982-01-01

377

Detecting Faults in Computational Grids  

Microsoft Academic Search

In this paper we will first present a basic definition and a brief history of grid computing since its inception during the last decade. We will then look at a review of the most common faults occurring within the grid environment as identified by a survey of grid computing users. Two papers addressing fault detection are then reviewed for comparison.

Russ Wakefield

378

Power Grid Issues  

NSDL National Science Digital Library

Tampa Electric (1) offers animated illustrations that show how electricity is created and distributed. The first lets the user see the main components of a power plant, while the second outlines what is involved in transmission from the power plant to the destination. A less flashy but more detailed description of the electricity generation process is provided by the Energy Information Administration (2). This site goes more into different generation methods, such as coal, nuclear, and solar power. A few Energy Information Sheets and other resources are also available. Fuel cells are commonly discussed in terms of alternative fuel vehicles, but they might find their way into the power grid before they become standard in cars. This possibility is explored in an eight-page article (3) that highlights examples of hydrogen-powered energy systems. A similar topic is addressed in a February 2003 article in Popular Science (4). However, instead of dealing with large-scale fuel cell power plants, the article introduces fuel cells that can produce enough energy for a single family. Equipping every home with such a cell could make transmission lines obsolete, but the fact that this is currently infeasible is acknowledged. A research paper from Washington State University (5) identifies a number of risks to the power grid that could be exploited by terrorists. The authors propose specific research areas on which to focus in order to mitigate these risks, mainly dealing with communications and grid control. Related to this paper is an April 2003 article describing security measures that are being implemented to strengthen the computer systems used to operate generators and other grid components (6). The additional measures were necessary because of known weaknesses that made the systems vulnerable to intrusions. Since coal is one of the cheapest and widely available natural resources, Los Alamos National Laboratory is researching ways to make coal burning generators cleaner. The Clean Coal Technology project began several years ago, and this is one of several reports discussing a particular aspect of the project (7). The Integrated Energy and Communications System Architecture (8) is an initiative to combine the development of the power grid with advanced distributed computing technologies. The goal is to create a more efficient grid with capabilities of self-healing and intelligent management. An overview of the initiative is given on its Web site, as well as a more detailed white paper.

Leske, Cavin.

379

Ideal hydrodynamics outside and inside a black hole: Hamiltonian description in Painlevé-Gullstrand coordinates  

NASA Astrophysics Data System (ADS)

We show that when the Painlevé-Gullstrand coordinates are used in their Cartesian version, the Hamiltonian of relativistic ideal hydrodynamics in the vicinity of a nonrotating black hole differs by only one simple term from the corresponding Hamiltonian in a flat spacetime. The interior region of the black hole is also described in a unified way, because there is no singularity on the event horizon in Painlevé-Gullstrand coordinates. We present the exact solution describing the steady accretion of extremely hard matter (? ? n 2) onto a moving black hole up to the central singularity. In the local induction approximation, we derive the equation of motion for a thin vortex filament against the background of such an accretion flow. We explicitly calculate the Hamiltonian for a fluid with an ultrarelativistic equation of state, ? ? n 4/3, and solve the problem of a centrally symmetric steady flow of such matter.

Ruban, V. P.

2014-07-01

380

Pathwise coordinate optimization  

Microsoft Academic Search

We consider ``one-at-a-time'' coordinate-wise descent algorithms for a class of convex optimization problems. An algorithm of this kind has been proposed for the $L_1$-penalized regression (lasso) in the literature, but it seems to have been largely ignored. Indeed, it seems that coordinate-wise algorithms are not often used in convex optimization. We show that this algorithm is very competitive with the

Jerome Friedman; Trevor Hastie; Holger Höfling; Robert Tibshirani

2007-01-01

381

Dynamics of Interpersonal Coordination  

Microsoft Academic Search

Everyday human actions often occur in a social context. Past psychological research has found that the motor behavior of socially\\u000a situated individuals tends to be coordinated. Our research performed over the last 20 years has sought to understand how the\\u000a mutuality, accommodation, and synchrony found in everyday interactional coordination can be understood using a dynamical theory\\u000a of behavioral order, namely

Richard C. Schmidt; Michael J. Richardson

382

Elliptic surface grid generation in three-dimensional space  

NASA Technical Reports Server (NTRS)

A methodology for surface grid generation in three dimensional space is described. The method solves a Poisson equation for each coordinate on arbitrary surfaces using successive line over-relaxation. The complete surface curvature terms were discretized and retained within the nonhomogeneous term in order to preserve surface definition; there is no need for conventional surface splines. Control functions were formulated to permit control of grid orthogonality and spacing. A method for interpolation of control functions into the domain was devised which permits their specification not only at the surface boundaries but within the interior as well. An interactive surface generation code which makes use of this methodology is currently under development.

Kania, Lee

1992-01-01

383

Grid integrated distributed PV (GridPV).  

SciTech Connect

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.

Reno, Matthew J.; Coogan, Kyle [Georgia Institute of Technology, Atlanta, GA

2013-08-01

384

Gridded electron reversal ionizer  

NASA Technical Reports Server (NTRS)

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.

Chutjian, Ara (Inventor)

1993-01-01

385

Image processing for calibrating a coordinate measurement set-up  

NASA Astrophysics Data System (ADS)

Image processing was used to efficiently calibrate a measurement set-up composed of multiple translation and rotation stages, and a sensing element fixed to a cantilever. Using the dimensions of individual devices to estimate the sensor position proved tedious: positioning and alignment errors between components accumulate and some physical dimensions are unknown or hard to measure. Defining a coordinate mapping via image processing seemed a convenient alternative and indeed typically yielded a measurement accuracy of less than 220 µm pixel width. The measurement rig was used to gather the magnetic field data of circular paths in a plane around electric conductors with a variety of cross-sections. To be of use in subsequent analysis steps, measurements had to be mapped by the calibration above onto both a cylinder and a Cartesian coordinate system. Additional error sources not accessible to visual inspection were identified when a calibration rod was measured. Correction of these errors completed the data preparation. As a proof of the concept, the centroid location and the integral current—two basic parameters of the current density which caused the magnetic field readings—were computed.

Hofer, Dominik; Zagar, Bernhard G.

2014-11-01

386

New coordinates for the amplitude parameter space of continuous gravitational waves  

NASA Astrophysics Data System (ADS)

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.

Whelan, John T.; Prix, Reinhard; Cutler, Curt J.; Willis, Joshua L.

2014-03-01

387

Adaptive grid optical tomography  

Microsoft Academic Search

Image-based modeling of semi-transparent, dynamic phenomena is a challenging task. We present an optical tomogra- phy method that uses an adaptive grid for the reconstruction of a three-dimensional density function from its projections. The proposed method is applied to reconstruct thin smoke and flames volumetrically from synchronized multi-video recordings. Our adaptive reconstruction algorithm computes a time-varying volumetric model, that enables

Ivo Ihrke; Marcus A. Magnor

2006-01-01

388

Grid Application Programming Environments  

Microsoft Academic Search

One challenge of building future grid systems is to provide suitable application programming interfaces and environments. In this chapter, we identify functional and non-functional properties for such environments. We then review three existing systems that have been co-developed by the authors with respect to the identied properties: ProActive, Ibis, and GAT. Apparently, no currently existing system is able to address

Thilo Kielmann; André Merzky; Henri E. Bal; Françoise Baude; Denis Caromel; Fabrice Huet

2004-01-01

389

Wireless Communications in Smart Grid  

NASA Astrophysics Data System (ADS)

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.

Bojkovic, Zoran; Bakmaz, Bojan

390

Advanced Techniques for Constrained Internal Coordinate Molecular Dynamics  

PubMed Central

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

Wagner, Jeffrey R.; Balaraman, Gouthaman S.; Niesen, Michiel J. M.; Larsen, Adrien B.; Jain, Abhinandan; Vaidehi, Nagarajan

2013-01-01

391

Sinusoidal grid definition  

E-print Network

This note shortly describes the sinusoidal equal-area grid on which the MERIS level 2 products are spatially binned. The average size of the grid bins is equal to 1/12°, leading to 2160 rows in latitude, i.e. 1080 latitude rows in each hemisphere (the equatorial line is located between two rows of bins). This discretisation corresponds to roughly 9.277 km. Just below and above the equatorial line, the rows have 4320 bins. This number decreases regularly from the equator to the poles where the last latitude row have only 3 bins. For each row, the left side of the first bin is always aligned with longitude-180 ° while the right side of the last bin is aligned with longitude +180°, covering all the latitude row area. The number of bins per row is always an integer number, computed in order to have the bin cell size as close as possible to 9.277 km, so that the effective longitudinal bin size may vary from one row to the next one. Applying this simple rules from South to North pole leads to a total of 5,940,422 bins. The pseudo-code below can be used to build the sinusoidal grid, i.e. to link the index of each bin (n) to its geolocation in longitude and latitude (bin_lon[n], bin_lat[n]).

Gilbert Barrot Acri-st; Issue /jan

392

TRMM Gridded Text Products  

NASA Technical Reports Server (NTRS)

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.

Stocker, Erich Franz

2007-01-01

393

Coordinated Control and Optimization of Virtual Power Plants for Energy and Frequency Regulation Services in Electricity Markets  

E-print Network

co-located Flywheel Energy Storage System (FESS). The coordination of the VPP is implemented through power electronics?based controllers. A five-bus system test case demonstrates the technical feasibility of VPPs to respond to grid frequency deviation...

Zhang, Fan

2012-02-14

394

Progress in Grid Generation: From Chimera to DRAGON Grids  

NASA Technical Reports Server (NTRS)

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.

Liou, Meng-Sing; Kao, Kai-Hsiung

1994-01-01

395

An accelerated time-domain finite-difference simulation scheme for 3D transient-electromagnetic modeling using multi-grid concepts  

NASA Astrophysics Data System (ADS)

Explicit time stepping schemes for the solution of three-dimensional electromagnetic (EM) field simulations have a high computational time demand. The fact that the transient-electromagnetic field is smoothed gradually in space with time allows for a reduced spatial sampling rate of the EM field. Based on concepts known from multi-grid (MG) methods, we have developed a restriction operator in order to map the EM field from a fine to a coarser finite-difference mesh during a forward field simulation. Two advantages follow. First, the grid size can be reduced. Field restriction involves reducing the number of grid nodes by a factor of two for each Cartesian direction. Second, as can be seen from the Courant-Friedrichs-Levy condition, the larger grid spacing allows for proportionally larger time step sizes. The initial simulation grid is identical to the mesh defining the distribution of the electrical conductivity over the model. After field restriction, a material averaging scheme is employed in order to calculate the underlying effective medium on the new (coarse) simulation grid. Test results on the scheme appear quite promising with up to a factor of ten reduction in solution run time, compared to a scheme that uses a constant grid. Key to the accuracy of the approach is knowledge of the proper time range to restrict the fields. Experiments for an adequate restriction criteria involve a spatial Fourier transform of the EM field to estimate the decay rate of the high frequency contents of the field.

Commer, M.; Newman, G. A.

2005-12-01

396

Modeling and Expression of Vector Data in the Hexagonal Discrete Global Grid System  

NASA Astrophysics Data System (ADS)

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.

Tong, X. C.; Ben, J.; Liu, Y. Y.; Zhang, Y. S.

2013-10-01

397

Implementation of the equation of radiative transfer on block-structured grids for modeling light propagation in tissue.  

PubMed

We present the first algorithm for solving the equation of radiative transfer (ERT) in the frequency domain (FD) on three-dimensional block-structured Cartesian grids (BSG). This algorithm allows for accurate modeling of light propagation in media of arbitrary shape with air-tissue refractive index mismatch at the boundary at increased speed compared to currently available structured grid algorithms. To accurately model arbitrarily shaped geometries the algorithm generates BSGs that are finely discretized only near physical boundaries and therefore less dense than fine grids. We discretize the FD-ERT using a combination of the upwind-step method and the discrete ordinates (S(N)) approximation. The source iteration technique is used to obtain the solution. We implement a first order interpolation scheme when traversing between coarse and fine grid regions. Effects of geometry and optical parameters on algorithm performance are evaluated using numerical phantoms (circular, cylindrical, and arbitrary shape) and varying the absorption and scattering coefficients, modulation frequency, and refractive index. The solution on a 3-level BSG is obtained up to 4.2 times faster than the solution on a single fine grid, with minimal increase in numerical error (less than 5%). PMID:21258514

Montejo, Ludguier D; Klose, Alexander D; Hielscher, Andreas H

2010-01-01

398

Implementation of the equation of radiative transfer on block-structured grids for modeling light propagation in tissue  

PubMed Central

We present the first algorithm for solving the equation of radiative transfer (ERT) in the frequency domain (FD) on three-dimensional block-structured Cartesian grids (BSG). This algorithm allows for accurate modeling of light propagation in media of arbitrary shape with air-tissue refractive index mismatch at the boundary at increased speed compared to currently available structured grid algorithms. To accurately model arbitrarily shaped geometries the algorithm generates BSGs that are finely discretized only near physical boundaries and therefore less dense than fine grids. We discretize the FD-ERT using a combination of the upwind-step method and the discrete ordinates (SN) approximation. The source iteration technique is used to obtain the solution. We implement a first order interpolation scheme when traversing between coarse and fine grid regions. Effects of geometry and optical parameters on algorithm performance are evaluated using numerical phantoms (circular, cylindrical, and arbitrary shape) and varying the absorption and scattering coefficients, modulation frequency, and refractive index. The solution on a 3-level BSG is obtained up to 4.2 times faster than the solution on a single fine grid, with minimal increase in numerical error (less than 5%). PMID:21258514

Montejo, Ludguier D.; Klose, Alexander D.; Hielscher, Andreas H.

2010-01-01

399

The impact of smart grid residential energy management schemes on the carbon footprint of the household electricity consumption  

Microsoft Academic Search

Smart grid provides remarkable opportunities for residential energy management. Residential energy management covers a large number of devices and techniques, from basic components, such as energy saving light bulbs to more complex methods, such as coordinating the household load. With the use of smart meters, smart grid enables two-way communication between the utilities and their consumers, where energy management becomes

Melike Erol-Kantarci; Hussein T. Mouftah

2010-01-01

400

Coordinate Standard Measurement Development  

SciTech Connect

A Shelton Precision Interferometer Base, which is used for calibration of coordinate standards, was improved through hardware replacement, software geometry error correction, and reduction of vibration effects. Substantial increases in resolution and reliability, as well as reduction in sampling time, were achieved through hardware replacement; vibration effects were reduced substantially through modification of the machine component dampening and software routines; and the majority of the machine's geometry error was corrected through software geometry error correction. Because of these modifications, the uncertainty of coordinate standards calibrated on this device has been reduced dramatically.

Hanshaw, R.A.

2000-02-18

401

SORMA - Building an Open Grid Market for Grid Resource Allocation  

Microsoft Academic Search

The demand for computing and storage resources in a Grid network increases in both academic and industrial application domains.\\u000a Participants in a network (i.e. companies or research institutes) try to selfishly maximize their individual benefit from\\u000a participating in the Grid. Setting the right incentives for suppliers and requesters for an efficient usage of the limited\\u000a Grid resources will motivate the

Dirk Neumann; Jochen Stoesser; Arun Anandasivam; Nikolay Borissov

2007-01-01

402

From Grid Islands to a World Wide Grid  

Microsoft Academic Search

\\u000a The World Wide Web has become a phenomenon that now influences our everyday life in any possible areas and disciplines. This\\u000a chapter describes a potential roadmap establishing its grid equivalent, a scientific, workflow-oriented, computational World\\u000a Wide Grid (WWG). In order to achieve such a WWG, this chapter suggests three major steps. First, create uniform meta-brokers\\u000a and connect existing production grids

P. Kacsuk; T. Kiss

403

Data Management in the GridRPC GridRPC Data Management API  

E-print Network

Data Management in the GridRPC Issues Conclusion GridRPC Data Management API Implementations, Le Mahec, Nakada GridRPC DM API: Implem. and Interop. Issues (1/13) #12;Data Management in the GridRPC Issues Conclusion Goal GridRPC DM types: Reminder 1 Data Management in the GridRPC Goal GridRPC DM types

Caniou, Yves

404

Multidimensional discretization of conservation laws for unstructured polyhedral grids  

SciTech Connect

To the extent possible, a discretized system should satisfy the same conservation laws as the physical system. The author considers the conservation properties of a staggered-grid Lagrange formulation of the hydrodynamics equations (SGH) which is an extension of a ID scheme due to von Neumann and Richtmyer (VNR). The term staggered refers to spatial centering in which position, velocity, and kinetic energy are centered at nodes, while density, pressure, and internal energy are at cell centers. Traditional SGH formulations consider mass, volume, and momentum conservation, but tend to ignore conservation of total energy, conservation of angular momentum, and requirements for thermodynamic reversibility. The author shows that, once the mass and momentum discretizations have been specified, discretization for other quantities are dictated by the conservation laws and cannot be independently defined. The spatial discretization method employs a finite volume procedure that replaces differential operators with surface integrals. The method is appropriate for multidimensional formulations (1D, 2D, 3D) on unstructured grids formed from polygonal (2D) or polyhedral (3D) cells. Conservation equations can then be expressed in conservation form in which conserved currents are exchanged between control volumes. In addition to the surface integrals, the conservation equations include source terms derived from physical sources or geometrical considerations. In Cartesian geometry, mass and momentum are conserved identically. Discussion of volume conservation will be temporarily deferred. The author shows that the momentum equation leads to a form-preserving definition for kinetic energy and to an exactly conservative evolution equation for internal energy. Similarly, the author derives a form-preserving definition and corresponding conservation equation for a zone-centered angular momentum.

Burton, D.E.

1994-08-22

405

Study on the grid-based distributed virtual geo-environment (DVGE-G)  

NASA Astrophysics Data System (ADS)

It is publicly considered that the next generational Internet technology is grid computing, which supports the sharing and coordinated use of diverse resources in dynamic virtual organizations from geographically and organizationally distributed components. Grid computing characters strong computing ability and broad width information exchange. After analyzing the characteristic of grid computing, this paper expatiates on current application status of grid computing with middleware technology on DVGE-G and the problems it faces. Cooperating with IBM, Microsoft and HP, Globus Toolkit as a standard for grid computing is widely used to develop application on grid, which can run on Unix and Windows operation systems. On the basis of "the five-tiers sandglass structure" and web services technology, Globus presented Open Grid Services Architecture (OGSA), which centered on grid services. According to the characteristic of DVGE-G and the development of current grid computing, this paper put forward the Grid-Oriented Distributed Network Model for DVGE-G. Virtual group is corresponding with the Virtual Organization in OGSA service, which is easier and more directly for the dynamic virtual groups in GDNM to utilize the grid source and communication each other. The GDNM is not only more advantage to the distributed database consistency management, but also it is more convenient to the virtual group users acquiring the DVGE-G data information, The architecture of DVGE-G designed in this paper is based on OGSA and web services, which is keep to "the five-tiers sandglass structure" of the OGSA. This architecture is more convenient to utilizing grid service and decreasing the conflict with the grid environment. At last, this paper presents the implementation of DVGE-G and the interfaces of Grid Service.

Tang, Lu-liang; Li, Qing-quan

2005-10-01

406

The Volume Grid Manipulator (VGM): A Grid Reusability Tool  

NASA Technical Reports Server (NTRS)

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.

Alter, Stephen J.

1997-01-01

407

Adventures in Computational Grids  

NASA Technical Reports Server (NTRS)

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.

Walatka, Pamela P.; Biegel, Bryan A. (Technical Monitor)

2002-01-01

408

A development of grid generation procedure for multicomponent aerodynamic configuration  

NASA Technical Reports Server (NTRS)

Two approaches for solving the transonic flow in a multi-block grid were explored. The first approach examines a method involving "zonal decomposition" wherein block boundaries are treated as true boundary surfaces separating interfacing grids. The issues investigated involve techniques for matching solutions at a block boundary. A feasibility study was completed and the results are presented. The second approach involves overlapping grids for differencing across a block boundary near an artificially induced coordinate singularity occurring at a fictitious corner. This approach selects a set of neighboring nodes for the fictitious corner such that the resulting physical cells for a node are topologically the same as any other node on the airfoil surface.

Chen, H. C.

1981-01-01

409

Adaptive-coordinate real-space electronic-structure calculations for atoms, molecules, and solids  

SciTech Connect

We report the development of a real-space approach to electronic-structure calculations which utilizes adaptive curvilinear coordinates. A regular real-space mesh would be desirable from computational considerations because it produces a sparse, local, and highly structured Hamiltonian, which enables the effective use of iterative numerical methods and parallel-computer architectures. However, a regular real-space mesh has equal resolution everywhere. This results in an inefficient distribution of mesh points, since actual physical systems are inhomogeneous. To remedy this inherent inefficiency without losing the computational advantages of a regular mesh, we use a {ital regular} mesh in {ital curvilinear} coordinates, which is mapped by a change of coordinates to an {ital adaptive} mesh in {ital Cartesian} coordinates. We discuss in detail the choices involved in the implementation of the method, including the form and optimization of the coordinate transformation, the expression for the discretized Laplacian, the regularization of the ionic potential for all-electron calculations, the method of calculating the forces, and the algorithms used. Band-structure calculations have been implemented by adding a phase shift at periodic boundary conditions. We report all-electron calculations for atoms and molecules with 1s and 2p valence electrons, and pseudopotential calculations for molecules and solids. {copyright} {ital 1997} {ital The American Physical Society}

Modine, N.A.; Zumbach, G.; Kaxiras, E. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States)] [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States)

1997-04-01

410

Mackenzie Broughton Unit Coordinator  

E-print Network

.broughton@ttu.edu. Employer Resources RECRUITING ENGINEERING STUDENTS As an engineering company recruiting at Texas Tech, weMackenzie Broughton Unit Coordinator Career Services mackenzie.broughton@ttu.edu Employer Resources anywhere, the Whitacre College of Engineering is committed to making your recruitment experiences on our

Gelfond, Michael

411

Coordination and Integration  

Microsoft Academic Search

A strong coordination (i. e. the configuration of data flows and the division of planning tasks to modules) of APS modules is a prerequisite to achieve consistent plans for the different planning levels and for each entity of the supply chain. The same data should be used for each de-centralized planning task and decision. APS can be seen as “add-ons”

Jens Rohde

412

Coordinated Program in Dietetics  

E-print Network

_tuiton_fee.html umdnJ FinAnciAl Aid Phone: 973-972-4376 Web: www.umdnj.edu/studentfinancialaid imporTAnT conTAcT inFormATion UMDNJ-BSHS Coordinated Program in Dietetics 2nd Bachelor's Degree #12;Students who

Cheng, Mei-Fang

413

Brent Warner Coordinator  

E-print Network

food system?Our food system? #12;"We put fast food on every corner, we put junk food in our schools, weBrent Warner Coordinator Canadian Agritourism Working Group (CATWG) Local FoodLocal Food ! #12;· less and less money spent on food as a percentage of income except in 2009 up 4.4% You have

Peak, Derek

414

Communication Gestion et coordination  

E-print Network

Communication Gestion et coordination de patrouilles environnementales Développement de stratégies et d'outils de communication en développement durable Communication des politiques, programmes et travail interdisciplinaire, la communication et l'esprit critique. Au final, les diplômés pourront exercer

Spino, Claude

415

Biochemistry 448 Course Coordinator  

E-print Network

Biochemistry 448 Course Coordinator Dr Scott Covey scott.covey@ubc.ca 604-822-1949 Course Description This is an independent biochemistry driven research project performed under the supervision independent research and lab work. Although biochemistry honours students have priority majors student can

Strynadka, Natalie

416

Coordinated stasis: An overview  

Microsoft Academic Search

Coordinated stasis, as defined herein, represents an empirical pattern, common in the fossil record, wherein groups of coexisting species lineages display concurrent stability over extended intervals of geologic time separated by episodes of relatively abrupt change. In marine benthic fossil assemblages, where the pattern was first recognized, the majority of species lineages (60 to more than 80%) are present in

Carlton E. Brett; Linda C. Ivany; Kenneth M. Schopf

1996-01-01

417

Origins of Coordinate Searching.  

ERIC Educational Resources Information Center

Reviews the origins of post-coordinate searching and emphasizes that the focal point should be on the searcher, not on the item being indexed. Highlights include the history of the term information retrieval; edge notched punch cards; the "peek-a-boo" system; the Uniterm system; and using computers to search for information. (LRW)

Kilgour, Frederick G.

1997-01-01

418

On unstructured grids and solvers  

NASA Technical Reports Server (NTRS)

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.

Barth, T. J.

1990-01-01

419

LDCM Grid Prototype (LGP)  

NASA Technical Reports Server (NTRS)

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.

Weinstein, Beth; Lubelczyk, Jeff

2006-01-01

420

Grid Generation Techniques Utilizing the Volume Grid Manipulator  

NASA Technical Reports Server (NTRS)

This paper presents grid generation techniques available in the Volume Grid Manipulation (VGM) code. The VGM code is designed to manipulate existing line, surface and volume grids to improve the quality of the data. It embodies an easy to read rich language of commands that enables such alterations as topology changes, grid adaption and smoothing. Additionally, the VGM code can be used to construct simplified straight lines, splines, and conic sections which are common curves used in the generation and manipulation of points, lines, surfaces and volumes (i.e., grid data). These simple geometric curves are essential in the construction of domain discretizations for computational fluid dynamic simulations. By comparison to previously established methods of generating these curves interactively, the VGM code provides control of slope continuity and grid point-to-point stretchings as well as quick changes in the controlling parameters. The VGM code offers the capability to couple the generation of these geometries with an extensive manipulation methodology in a scripting language. The scripting language allows parametric studies of a vehicle geometry to be efficiently performed to evaluate favorable trends in the design process. As examples of the powerful capabilities of the VGM code, a wake flow field domain will be appended to an existing X33 Venturestar volume grid; negative volumes resulting from grid expansions to enable flow field capture on a simple geometry, will be corrected; and geometrical changes to a vehicle component of the X33 Venturestar will be shown.

Alter, Stephen J.

1998-01-01

421

NAS Grid Benchmarks: A Tool for Grid Space Exploration  

Microsoft Academic Search

We present a benchmark suite for computational grids in this paper. It is based on the NAS Parallel Benchmarks (NPB) and is called the NAS Grid Benchmark (NGB). We present NGB as a data flow graph encapsulating an instance of an NPB code in each graph node, which communicates with other nodes by sending\\/receiving initialization data. These nodes may be

Michael A. Frumkin; Rob F. Van Der Wijngaart

2001-01-01

422

Book Review: The Digital Cast of Being: Metaphysics, Mathematics, Cartesianism, Cybernetics, Capitalism, Communication Michael Eldred Piscataway, New Jersey: Transaction Books, 2009  

E-print Network

Book Reviews 37 The Digital Cast of Being: Metaphysics, Mathematics, Cartesianism, Cybernetics, Capitalism, Communication Michael Eldred Piscataway, New Jersey: Transaction Books, 2009 ISBN: Review by Shawn Loht, Mercer University... In this text Australian-German scholar Michael Eldred analyzes the "cast" or disclosure of being in its digital manifestation. The goal of the work, stated in Chapter One, is to clarify this digital cast ontologically and to uncover what must be given...

Loht, Shawn

2009-09-01

423

NAS Grid Benchmarks: A Tool for Grid Space Exploration  

NASA Technical Reports Server (NTRS)

We present an approach for benchmarking services provided by computational Grids. It is based on the NAS Parallel Benchmarks (NPB) and is called NAS Grid Benchmark (NGB) in this paper. We present NGB as a data flow graph encapsulating an instance of an NPB code in each graph node, which communicates with other nodes by sending/receiving initialization data. These nodes may be mapped to the same or different Grid machines. Like NPB, NGB will specify several different classes (problem sizes). NGB also specifies the generic Grid services sufficient for running the bench-mark. The implementor has the freedom to choose any specific Grid environment. However, we describe a reference implementation in Java, and present some scenarios for using NGB.

Frumkin, Michael; VanderWijngaart, Rob F.; Biegel, Bryan (Technical Monitor)

2001-01-01

424

Shared Activity Coordination  

NASA Technical Reports Server (NTRS)

Interacting agents that interleave planning and execution must reach consensus on their commitments to each other. In domains where agents have varying degrees of interaction and different constraints on communication and computation, agents will require different coordination protocols in order to efficiently reach consensus in real time. We briefly describe a largely unexplored class of real-time, distributed planning problems (inspired by interacting spacecraft missions), new challenges they pose, and a general approach to solving the problems. These problems involve self-interested agents that have infrequent communication but collaborate on joint activities. We describe a Shared Activity Coordination (SHAC) framework that provides a decentralized algorithm for negotiating the scheduling of shared activities in a dynamic environment, a soft, real-time approach to reaching consensus during execution with limited communication, and a foundation for customizing protocols for negotiating planner interactions. We apply SHAC to a realistic simulation of interacting Mars missions and illustrate the simplicity of protocol development.

Clement, Bradley J.; Barrett, Anthony C.

2003-01-01

425

Plant Breeding Coordinating Committee  

NSDL National Science Digital Library

To view additional success stories click on the link in the left menu Please click here to report your plant breeding success stories.  Click on TCAP logo to see the Economic impact of USDA-NIFA small grains CAPsThe Plant Breeding Coordinating Committee (SCC 080) is the USDA-sponsored advisory group of representatives from land grant universities.  The Plant Breeding Coordinating Committee represents national plant breeding with a focus on education in the broader sense, including providing information to the public and administrators, and encouraging the development of formal educational opportunities, continuing education, and lifelong learning. Mission: To provide a forum for leadership on issues and opportunities of strategic importance to national core competency in plant breeding research and education Membership: The PBCC members will consist of the representatives of the SCC-080 committee and others by request. 

426

The Open Science Grid  

SciTech Connect

The Open Science Grid (OSG) provides a distributed facility where the Consortium members provide guaranteed and opportunistic access to shared computing and storage resources. OSG provides support for and evolution of the infrastructure through activities that cover operations, security, software, troubleshooting, addition of new capabilities, and support for existing and engagement with new communities. The OSG SciDAC-2 project provides specific activities to manage and evolve the distributed infrastructure and support its use. The innovative aspects of the project are the maintenance and performance of a collaborative (shared & common) petascale national facility over tens of autonomous computing sites, for many hundreds of users, transferring terabytes of data a day, executing tens of thousands of jobs a day, and providing robust and usable resources for scientific groups of all types and sizes. More information can be found at the OSG web site: www.opensciencegrid.org.

Pordes, Ruth; /Fermilab; Kramer, Bill; Olson, Doug; / /LBL, Berkeley; Livny, Miron; Roy, Alain; /Wisconsin U., Madison; Avery, Paul; /Florida U.; Blackburn, Kent; /Caltech; Wenaus, Torre; /Brookhaven; Wurthwein, Frank; /UC, San Diego; Gardner, Rob; Wilde, Mike; /Chicago U. /Indiana U.

2007-06-01

427

General Coordinates Game  

NSDL National Science Digital Library

This interactive Java applet allows users to plot a "house" on a -10 by 10 coordinate plane. A "view" mode allows users to enter an ordered pair and move the house to that location. The "guess" mode randomly plots the house on the plane and the user must enter the ordered pair for its location. An optional scoring feature allows users to keep track of the number correct.

2005-01-01

428

Proposal of Smart Storage for Ubiquitous Power Grid  

NASA Astrophysics Data System (ADS)

Penetrating large amount of renewable energy sources into power system, battery energy storage performs an important role for smoothing their natural intermittency, ensuring grid-wide frequency stability, and suppressing voltage rise caused by reverse power flow. The ubiquitous power grid concept has been proposed as a smart grid in Japanese context, where the total battery capacity can be optimized by coordinating renewable energy sources, controllable distributed generators, and controllable loads on demand side, for example, heat pump based water heater with heat storage, and plug-in hybrid vehicle or electric vehicle with onboard battery, and so on. In this paper, we propose an autonomous distributed vehicle-to-grid (V2G) control scheme. The proposed V2G control has droop characteristics against power system frequency measurement at 200/100V plug-in terminal, and battery state-of-charge (SOC) is balanced within designable range by restraining V2G gain according to estimated SOC. Of course, the convenience for vehicle user is considered by V1G charge, which is one-way charging control for plug-out. Self terminal frequency measurement algorithm, model based battery SOC estimation method, and the proposed autonomous distributed V2G control are implemented to automotive power electronics circuit and electric control unit. These concepts are summarized as Smart Storage in ubiquitous power grid applications.

Ota, Yutaka; Taniguchi, Haruhito; Nakajima, Tatsuhito; Liyanage, Kithsiri M.; Baba, Junpei; Yokoyama, Akihiko

429

Hipparchus' coordinate system  

NASA Astrophysics Data System (ADS)

In his "Histoire de l'Astronomie Ancienne" Delambre concludes unequivocally that Hipparchus knew and used a definite system of celestial spherical coordinates, namely the right ascension and declination system that we use today. The basis of Delambre's conclusion was disarmingly simple: he pointed out that in the "Commentary to Aratus" Hipparchus actually quotes the positions of numerous stars directly in right ascension and declination (or more often its complement, polar distance). Nearly two centuries later, in his "A History of Ancient Mathematical Astronomy", Neugebauer not only completely ignores Delambre's conclusion on this issue, but goes further to propose his own, as we shall see quite fanciful, theory that begins "From the Commentary to Aratus, it is quite obvious that at Hipparchus' time a definite system of spherical coordinates for stellar positions did not yet exist." and concludes "...nowhere in Greek astronomy before the catalogue of stars in the Almagest is it attested that orthogonal spherical coordinates are used to determine stellar positions." Today it is clear that Neugebauer's theory is conventionally accepted. It is the purpose of this paper to offer fresh arguments that Delambre was correct.

Duke, Dennis W.

2002-07-01

430

Towards an Autonomic Wisdom Grid  

Microsoft Academic Search

Multi agent systems, Grid technology, Semantic Web, Autonomic Com- puting, and Web Intelligence paradigms are modern approaches in information technologies, which we put together in our research effort described in this pa- per to create a new-generation infrastructure called the Autonomic Wisdom Grid (AWG) with the mission to maintain, share, discover, and expand knowledge in geographically distributed environments. This paper

Peter Brezany; Ivan Janciak; Andrzej Goscinski; A. Min Tjoa

431

Intelligent automated surface grid generation  

NASA Technical Reports Server (NTRS)

The goal of our research is to produce a flexible, general grid generator for automated use by other programs, such as numerical optimizers. The current trend in the gridding field is toward interactive gridding. Interactive gridding more readily taps into the spatial reasoning abilities of the human user through the use of a graphical interface with a mouse. However, a sometimes fruitful approach to generating new designs is to apply an optimizer with shape modification operators to improve an initial design. In order for this approach to be useful, the optimizer must be able to automatically grid and evaluate the candidate designs. This paper describes and intelligent gridder that is capable of analyzing the topology of the spatial domain and predicting approximate physical behaviors based on the geometry of the spatial domain to automatically generate grids for computational fluid dynamics simulators. Typically gridding programs are given a partitioning of the spatial domain to assist the gridder. Our gridder is capable of performing this partitioning. This enables the gridder to automatically grid spatial domains of wide range of configurations.

Yao, Ke-Thia; Gelsey, Andrew

1995-01-01

432

LAPS Grid generation and adaptation  

NASA Astrophysics Data System (ADS)

LAPS uses a common-data framework in which a general purpose grid generation and adaptation package in toroidal and simply connected domains is implemented. The initial focus is on implementing the Winslow/Laplace-Beltrami method for generating non-overlapping block structured grids. This is to be followed by a grid adaptation scheme based on Monge-Kantorovich optimal transport method [Delzanno et al., J. Comput. Phys,227 (2008), 9841-9864], that equidistributes application-specified error. As an initial set of applications, we will lay out grids for an axisymmetric mirror, a field reversed configuration, and an entire poloidal cross section of a tokamak plasma reconstructed from a CMOD experimental shot. These grids will then be used for computing the plasma equilibrium and transport in accompanying presentations. A key issue for Monge-Kantorovich grid optimization is the choice of error or monitor function for equi-distribution. We will compare the Operator Recovery Error Source Detector (ORESD) [Lapenta, Int. J. Num. Meth. Eng,59 (2004) 2065-2087], the Tau method and a strategy based on the grid coarsening [Zhang et al., AIAA J,39 (2001) 1706-1715] to find an ``optimal'' grid.

Pagliantini, Cecilia; Delzanno, Gia Luca; Guo, Zehua; Srinivasan, Bhuvana; Tang, Xianzhu; Chacon, Luis

2011-11-01

433

Grid Integration of Wind Farms  

Microsoft Academic Search

This article gives an overview of grid integration of wind farms with respect to impact on voltage quality and power system stability. The recommended procedure for assessing the impact of wind turbines on voltage quality in distribution grids is presented. The procedure uses the power quality characteristic data of wind turbines to determine the impact on slow voltage variations, flicker,

John Olav Giæver Tande

2003-01-01

434

Evolutionary Computing within Grid Environment  

Microsoft Academic Search

Evolutionary computing (EC) techniques such as genetic algorithm (GA), genetic programming (GP), evolutionary programming (EP) and evolution strategies (ES) mimic nature through natural selection to perform complex optimisation processes that require more than one solutions. Grid-enabled environment provides suitable framework for EC techniques due to its computational and data capabilities. In addition, the semantic and knowledge Grids aid in the

Ashutosh Tiwari; Gokop Goteng; Rajkumar Roy

2007-01-01

435

Grid generation in three dimensions by Poisson equations with control of cell size and skewness at boundary surfaces  

NASA Technical Reports Server (NTRS)

An algorithm for generating computational grids about arbitrary three-dimensional bodies is developed. The elliptic partial differential equation (PDE) approach developed by Steger and Sorenson and used in the NASA computer program GRAPE is extended from two to three dimensions. Forcing functions which are found automatically by the algorithm give the user the ability to control mesh cell size and skewness at boundary surfaces. This algorithm, as is typical of PDE grid generators, gives smooth grid lines and spacing in the interior of the grid. The method is applied to a rectilinear wind-tunnel case and to two body shapes in spherical coordinates.

Sorenson, R. L.; Steger, J. L.

1983-01-01

436

Single particle calculations for a Woods Saxon potential with triaxial deformations, and large Cartesian oscillator basis (new version code)  

NASA Astrophysics Data System (ADS)

We present a new version of the computer program which solves the Schrödinger equation of the stationary states for an average nuclear potential of Woods-Saxon type. In this work, we take specifically into account triaxial (i.e. ellipsoidal) nuclear surfaces. The deformation is specified by the usual Bohr parameters. The calculations are carried out in two stages. In the first, one calculates the representative matrix of the Hamiltonian in the Cartesian oscillator basis. In the second stage one diagonalizes this matrix with the help of subroutines of the EISPACK library. This new version calculates all the eigenvalues up to a given cutoff energy, and gives the components of the corresponding eigenfunctions. For a more convenient handling, these results are stored simultaneously in the computer memory, and on a files. Program summaryTitle of program:Triaxial2007 Catalogue identifier:ADSK_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADSK_v2_0 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Summary of revision:One input file instead two. Reduced number of input parameters. Storage of eigenvalues and eigenvectors in memory in a very simple way which makes the code very convenient to the user. Reasons for the new version: More convenient handling of the eigenvectors Catalogue number old version: ADSK Catalogue number new version:ADSK_v2_0 Journal: Computer Physics Commun. 156 (2004) 241-282 Licensing provisions: none Computer: PC Pentium 4, 2600 MHz Hard disk: 40 Gb RAM: 256 Mb Swap file: 4 Gb Operating system: WINDOWS XP Software used: Compaq Visual FORTRAN (with full optimizations in the settings project options) Programming language used:Fortran 77/90 (double precision) Number of bits in a word: 32 No. of lines in distributed program, including test data, etc.:4058 No. of bytes in distributed program, including test data, etc.:75 590 Distribution format:tar.gz Nature of the problem: The single particle energies and the single particle wave functions are calculated from one-body Hamiltonian including a central field of Woods-Saxon type, a spin-orbit interaction, and the Coulomb potential for the protons. We consider only ellipsoidal (triaxial) shapes. The deformation of the nuclear shape is fixed by the usual Bohr parameters (?,?). Method of solution: The representative matrix of the Hamiltonian is built by means of the Cartesian basis of the anisotropic harmonic oscillator, and then diagonalized by a set of subroutines of the EISPACK library. Two quadrature methods of Gauss are employed to calculate, respectively, the integrals of the matrix elements of the Hamiltonian, and the integral defining the Coulomb potential. Restrictions: There are two restrictions for the code: The number of the major shells of the basis does not have to exceed N=26. For the largest values of N (˜23-26), the diagonalization takes the major part of the running time, but the global run-time remains reasonable. Typical running time: (With full optimization in the project settings of the Compaq Visual Fortran on Windows XP) With N=23, for the neutrons case, and for both parities, the running time is about 40 sec on the P4 computer at 2.6 GHz. In this case, the calculation of the matrix elements takes only about 17 sec. If all unbound states are required, the runtime becomes larger.

Mohammed-Azizi, B.; Medjadi, D. E.

2007-05-01

437

Grid Programming in Java and Python  

NSDL National Science Digital Library

Introduction to Grids, the Globus Toolkit, and the Commodity Grid (CoG) Kit. Using and programming grids with the Java and Python CoG Kits, including secure access to remote resources, remote job submission and data access.

Von Laszewski, Gregor; Jackson, Keith

438

Single grid accelerator for an ion thrustor  

NASA Technical Reports Server (NTRS)

A single grid accelerator system for an ion thrustor is discussed. A layer of dielectric material is interposed between this metal grid and the chamber containing an ionized propellant for protecting the grid against sputtering erosion.

Margosian, P. M.; Nakanishi, S. (inventors)

1973-01-01

439

Optimizing solar-cell grid geometry  

NASA Technical Reports Server (NTRS)

Trade-off analysis and mathematical expressions calculate optimum grid geometry in terms of various cell parameters. Determination of the grid geometry provides proper balance between grid resistance and cell output to optimize the energy conversion process.

Crossley, A. P.

1969-01-01

440

WIRELESS GRIDS: APPROACHES, ARCHITECTURES, AND TECHNICAL CHALLENGES  

E-print Network

Grid computing and grid topologies are attracting a growing amount of attention. Originating as a concept for sharing computing resources among wired participants, the grid concept is gradually been extended into the ...

Agarwal, Ashish

2004-04-02

441

Wireless Grids: Approaches, Architectures and Technical Challenges  

E-print Network

Grid computing and grid topologies are attracting a growing amount of attention. Originating as a concept for sharing computing resources among wired participants, the grid concept is gradually been ...

Agarwal, Ashish

2004-12-10

442

Statistical Computations with AstroGrid and the Grid  

E-print Network

We outline our first steps towards marrying two new and emerging technologies; the Virtual Observatory (e.g, AstroGrid) and the computational grid. We discuss the construction of VOTechBroker, which is a modular software tool designed to abstract the tasks of submission and management of a large number of computational jobs to a distributed computer system. The broker will also interact with the AstroGrid workflow and MySpace environments. We present our planned usage of the VOTechBroker in computing a huge number of n-point correlation functions from the SDSS, as well as fitting over a million CMBfast models to the WMAP data.

Robert C Nichol; Garry Smith; Christopher J Miller; Chris Genovese; Larry Wasserman; Brent Bryan; Alexander Gray; Jeff Schneider; Andrew W Moore

2005-11-15

443

Statistical Computations with AstroGrid and the Grid  

E-print Network

We outline our first steps towards marrying two new and emerging technologies; the Virtual Observatory (e.g, AstroGrid) and the computational grid. We discuss the construction of VOTechBroker, which is a modular software tool designed to abstract the tasks of submission and management of a large number of computational jobs to a distributed computer system. The broker will also interact with the AstroGrid workflow and MySpace environments. We present our planned usage of the VOTechBroker in computing a huge number of n-point correlation functions from the SDSS, as well as fitting over a million CMBfast models to the WMAP data.

Nichol, R C; Miller, C J; Genovese, C; Wasserman, L; Bryan, B; Gray, A; Schneider, J; Moore, A W; Nichol, Robert C; Smith, Garry; Miller, Christopher J; Genovese, Chris; Wasserman, Larry; Bryan, Brent; Gray, Alexander; Schneider, Jeff; Moore, Andrew W

2005-01-01

444

Work Coordination Engine  

NASA Technical Reports Server (NTRS)

The Work Coordination Engine (WCE) is a Java application integrated into the Service Management Database (SMDB), which coordinates the dispatching and monitoring of a work order system. WCE de-queues work orders from SMDB and orchestrates the dispatching of work to a registered set of software worker applications distributed over a set of local, or remote, heterogeneous computing systems. WCE monitors the execution of work orders once dispatched, and accepts the results of the work order by storing to the SMDB persistent store. The software leverages the use of a relational database, Java Messaging System (JMS), and Web Services using Simple Object Access Protocol (SOAP) technologies to implement an efficient work-order dispatching mechanism capable of coordinating the work of multiple computer servers on various platforms working concurrently on different, or similar, types of data or algorithmic processing. Existing (legacy) applications can be wrapped with a proxy object so that no changes to the application are needed to make them available for integration into the work order system as "workers." WCE automatically reschedules work orders that fail to be executed by one server to a different server if available. From initiation to completion, the system manages the execution state of work orders and workers via a well-defined set of events, states, and actions. It allows for configurable work-order execution timeouts by work-order type. This innovation eliminates a current processing bottleneck by providing a highly scalable, distributed work-order system used to quickly generate products needed by the Deep Space Network (DSN) to support space flight operations. WCE is driven by asynchronous messages delivered via JMS indicating the availability of new work or workers. It runs completely unattended in support of the lights-out operations concept in the DSN.

Zendejas, Silvino; Bui, Tung; Bui, Bach; Malhotra, Shantanu; Chen, Fannie; Kim, Rachel; Allen, Christopher; Luong, Ivy; Chang, George; Sadaqathulla, Syed

2009-01-01

445

National Smart Water Grid  

SciTech Connect

The United States repeatedly experiences floods along the Midwest's large rivers and droughts in the arid Western States that cause traumatic environmental conditions with huge economic impact. With an integrated approach and solution these problems can be alleviated. Tapping into the Mississippi River and its tributaries, the world's third largest fresh water river system, during flood events will mitigate the damage of flooding and provide a new source of fresh water to the Western States. The trend of increased flooding on the Midwest's large rivers is supported by a growing body of scientific literature. The Colorado River Basin and the western states are experiencing a protracted multi-year drought. Fresh water can be pumped via pipelines from areas of overabundance/flood to areas of drought or high demand. Calculations document 10 to 60 million acre-feet (maf) of fresh water per flood event can be captured from the Midwest's Rivers and pumped via pipelines to the Colorado River and introduced upstream of Lake Powell, Utah, to destinations near Denver, Colorado, and used in areas along the pipelines. Water users of the Colorado River include the cities in southern Nevada, southern California, northern Arizona, Colorado, Utah, Indian Tribes, and Mexico. The proposed start and end points, and routes of the pipelines are documented, including information on right-of-ways necessary for state and federal permits. A National Smart Water Grid{trademark} (NSWG) Project will create thousands of new jobs for construction, operation, and maintenance and save billions in drought and flood damage reparations tax dollars. The socio-economic benefits of NWSG include decreased flooding in the Midwest; increased agriculture, and recreation and tourism; improved national security, transportation, and fishery and wildlife habitats; mitigated regional climate change and global warming such as increased carbon capture; decreased salinity in Colorado River water crossing the US-Mexico border; and decreased eutrophication (excessive plant growth and decay) in the Gulf of Mexico to name a few. The National Smart Water Grid{trademark} will pay for itself in a single major flood event.

Beaulieu, R A

2009-07-13

446

Martian surface coordinates  

NASA Technical Reports Server (NTRS)

The resolution of the pictures from the Mariner 9 mission determines the distribution of the control points, as well as the gaps in the planet-wide control net. After discussing the photogrammetric equations and the computational method used to establish the planet-wide control net and the secondary net, the camera stations and the assumed physical properties of Mars are considered. Subsequent paragraphs contain a description of the control points, their measurements, and a discussion of how distortions are removed. Finally, results of the computations are given, with tables of coordinates for the control points.

Davies, M. E.; Arthur, D. W. G.

1973-01-01

447

A nonhydrostatic, isopycnal-coordinate ocean model for internal waves  

NASA Astrophysics Data System (ADS)

We present a nonhydrostatic ocean model with an isopycnal (density-following) vertical coordinate system. The primary motivation for the model is the proper treatment of nonhydrostatic dispersion and the formation of nonlinear internal solitary waves. The nonhydrostatic, isopycnal-coordinate formulation may be preferable to nonhydrostatic formulations in z- and ? -coordinates because it improves computational efficiency by reducing the number of vertical grid points and eliminates spurious diapycnal mixing and solitary-wave amplitude loss due to numerical diffusion of scalars. The model equations invoke a mild isopycnal-slope approximation to remove small metric terms associated with diffusion and nonhydrostatic pressure from the momentum equations and to reduce the pressure Poisson equation to a symmetric linear system. Avoiding this approximation requires a costlier inversion of a non-symmetric linear system. We demonstrate that the model is capable of simulating nonlinear internal solitary waves for simplified and physically-realistic ocean-scale problems with a reduced number of layers.

Vitousek, Sean; Fringer, Oliver B.

2014-11-01

448