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1

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

2

Transonic airfoil design using Cartesian coordinates  

NASA Technical Reports Server (NTRS)

A numerical technique for designing transonic airfoils having a prescribed pressure distribution (the inverse problem) is presented. The method employs the basic features of Jameson's iterative solution for the full potential equation, except that inverse boundary conditions and Cartesian coordinates are used. The method is a direct-inverse approach that controls trailing-edge closure. Examples show the application of the method to design aft-cambered and other airfoils specifically for transonic flight.

Carlson, L. A.

1976-01-01

3

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

4

A Cartesian grid-based unified gas kinetic scheme  

NASA Astrophysics Data System (ADS)

A Cartesian grid-based unified gas kinetic scheme is developed. In this approach, any oriented boundary in a Cartesian grid is represented by many directional boundary points. The numerical flux is evaluated on each boundary point. Then, a boundary flux interpolation method (BFIM) is constructed to distribute the boundary effect to the flow evolution on regular Cartesian grid points. The BFIM provides a general strategy to implement any kind of boundary condition on Cartesian grid. The newly developed technique is implemented in the unified gas kinetic scheme, where the scheme is reformulated into a finite difference format. Several typical test cases are simulated with different geometries. For example, the thermophoresis phenomenon for a plate with infinitesimal thickness immersed in a rarefied flow environment is calculated under different orientations on the same Cartesian grid. These computational results validate the BFIM in the unified scheme for the capturing of different thermal boundary conditions. The BFIM can be extended to the moving boundary problems as well.

Chen, Songze; Xu, Kun

2014-12-01

5

On differential transformations between Cartesian and curvilinear (geodetic) coordinates  

NASA Technical Reports Server (NTRS)

Differential transformations are developed between Cartesian and curvilinear orthogonal coordinates. Only matrix algebra is used for the presentation of the basic concepts. After defining the reference systems used the rotation (R), metric (H), and Jacobian (J) matrices of the transformations between cartesian and curvilinear coordinate systems are introduced. A value of R as a function of H and J is presented. Likewise an analytical expression for J(-1) as a function of H(-2) and R is obtained. Emphasis is placed on showing that differential equations are equivalent to conventional similarity transformations. Scaling methods are discussed along with ellipsoidal coordinates. Differential transformations between elipsoidal and geodetic coordinates are established.

Soler, T.

1976-01-01

6

Cartesian coordinate control for redundant modular robots  

Microsoft Academic Search

The paper focuses on the kinematic control of redundant modular robots for trajectory tracing. Based on the geometric numerical inverse kinematic algorithm developed for modular robots, a new online control method is presented. In this method, the inverse kinematic solution can be optimized through constructing a weighted matrix. Following this approach, some fundamental interpolation algorithms are proposed for Cartesian space

Weihai Chen; I-Ming Chen; Wee Kiat Lim; Guilin Yang

2000-01-01

7

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

8

The Numerical Simulation of Ship Waves Using Cartesian Grid Methods  

E-print Network

The Numerical Simulation of Ship Waves Using Cartesian Grid Methods M. Sussman (Florida State-dimensional spray sheet. 1 Introduction At moderate to high speed, the turbulent flow along the hull of a ship, and complex interac- tions between the ship hull and the free surface, such as transom-stern flows

Sussman, Mark

9

A Cartesian grid embedded boundary method for hyperbolic conservation laws  

E-print Network

A Cartesian grid embedded boundary method for hyperbolic conservation laws Phillip Colella a,*,1-order Godunov algorithm to solve time-dependent hyperbolic systems of conservation laws on irregular domains. Our approach is based on a formally consistent discretization of the conservation laws on a finite

10

A general time element using Cartesian coordinates: Eccentric orbit integration  

NASA Technical Reports Server (NTRS)

A general time element, valid with any arbitrary independent variables, and used with Cartesian coordinates for the integration of the elliptic motion in orbits, is examined. The derivation of the time element from a set of canonical elements of the Delaunay type, developed in the extended phase space, is presented. The application of the method using an example of a transfer orbit for a geosynchronous mission is presented. The eccentric and elliptic anomaly are utilized as the independent variable. The reduction of the in track error resulting from using Cartesian coordinates with the time element is reported.

Janin, G.

1980-01-01

11

The Approach to Steady State Using Homogeneous and Cartesian Coordinates  

PubMed Central

Repeating an arbitrary sequence of RF pulses and magnetic field gradients will eventually lead to a steady-state condition in any magnetic resonance system. While numerical methods can quantify this trajectory, analytic analysis provides significantly more insight and a means for faster calculation. Recently, an analytic analysis using homogeneous coordinates was published. The current work further develops this line of thought and compares the relative merits of using a homogeneous or a Cartesian coordinate system. PMID:23983812

Gochberg, D. F.; Ding, Z.

2013-01-01

12

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

13

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

14

Describing three-dimensional structures with spherical and Cartesian coordinates  

NSDL National Science Digital Library

Analyzing three-dimensional orientation data using a stereonet is an important component of any structural geology course, ideally helping students to visualize structural geometry and serving as a springboard for more advanced topics such as fault and fold kinematics. Rather than teaching my students about stereonets using tracing paper and pushpins, I use the newest version of Rick Allmendinger and NÃstor Cardozo's OSXStereonet program, which includes elegant, interactive three-dimensional view options. Simultaneously, I teach students transformation of orientation data between spherical coordinates and Cartesian coordinates, using MATLAB functions to carry out the conversions. We simultaneously solve problems involving orientation data using OSXStereonet and MATLAB, allowing students to gain an understanding of the mathematics that OSXStereonet carries out behind the scenes while using the visualization capabilities of OSXStereonet to reinforce the three-dimensional concepts. Keywords: Stereonet, OSXStereonet, Matlab, spherical, Cartesian, visualization

Loveless, Jack

15

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

16

3D Euler flow solutions using unstructured Cartesian and prismatic grids  

NASA Technical Reports Server (NTRS)

A hyperbolic prismatic grid generation technique is combined with a background Cartesian grid for the study of inviscid three-dimensional flows. The mathematics of the hyperbolic prismatic grid generation algorithm are described, and some simple inviscid demonstration cases are presented. By combining the simplicity of the Cartesian background grid with the geometric flexibility and computational efficiencies inherent to prismatic grids, this approach shows promise for improving computational aerodynamic simulations.

Melton, John E.; Pandya, Shishir A.; Steger, Joseph L.

1993-01-01

17

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

E-print Network

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

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

19

A finite volume, Cartesian grid method for computational aeroacoustics  

NASA Astrophysics Data System (ADS)

Computational Aeroacoustics (CAA) combines the disciplines from both aeroacoustics and computational fluid dynamics and deals with the sound generation and propagation in association with the dynamics of the fluid flow, and its interaction with the geometry of the surrounding structures. To conduct such computations, it is essential that the numerical techniques for acoustic problems contain low dissipation and dispersion error for a wide range of length and time scales, can satisfy the nonlinear conservation laws, and are capable of dealing with geometric variations. In this dissertation, we first investigate two promising numerical methods for treating convective transport: the dispersion-relation-preservation (DRP) scheme, proposed by Tam and Webb, and the space-time a-epsilon method, developed by Chang. Between them, it seems that for long waves, errors grow slower with the space-time a-epsilon scheme, while for short waves, often critical for acoustics computations, errors accumulate slower with the DRP scheme. Based on these findings, two optimized numerical schemes, the dispersion-relation-preserving (DRP) scheme and the optimized prefactored compact (OPC) scheme, originally developed using the finite difference approach, are recast into the finite volume form so that nonlinear physics can be better handled. Finally, the Cartesian grid, cut-cell method is combined with the high-order finite-volume schemes to offer additional capabilities of handling complex geometry. The resulting approach is assessed against several well identified test problems, demonstrating that it can offer accurate and effective treatment to some important and challenging aspects of acoustic problems.

Popescu, Mihaela

20

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

21

Fast Slant Stack: A notion of Radon Transform for Data in a Cartesian Grid  

E-print Network

Fast Slant Stack: A notion of Radon Transform for Data in a Cartesian Grid which is Rapidly, M. Israeli, J. Wald´en Abstract. We define a notion of Radon Transform for data in an n by n grid = n2 is the number of pixels. This relies on a discrete projection-slice theorem relating this Radon

Averbuch, Amir

22

A Unified Adaptive Cartesian Grid Method for Solid Multiphase Fluid Dynamics with Moving Boundaries  

Microsoft Academic Search

Numerical simulations of flows involving moving boundaries are challenging as they need to address the location and the conditions of the interface that interacts with the flow field. We have developed a unified, marker-based approach, which can treat moving solid and multiphase fluid dynamics using adaptively refined Cartesian grids. The interfaces separating the fluid phases are modeled using a continuous

Eray Uzgoren; Jaeheon Sim; Rajkeshar Singh; Wei Shyy

2007-01-01

23

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

24

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

25

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

26

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

27

Closed-form eigenstructure-based direction finding using arbitrary but identical subarrays on a sparse uniform Cartesian array grid  

Microsoft Academic Search

A sparse uniform Cartesian-grid array suffers cyclic ambiguity in its Cartesian direction-cosine estimates due to the spatial Nyquist sampling theorem. The proposed MUSIC-based or MODE-based algorithm improves and generalizes previous disambiguation schemes that populate the thin array grid with identical subarrays-such as electromagnetic vector sensors, underwater acoustic vector hydrophones, or half-wavelength spaced subarrays

Michael D. Zoltowski; Kainam Thomas Wong

2000-01-01

28

The von Neumann basis in non-Cartesian coordinates: Application to floppy triatomic molecules.  

PubMed

We extend the periodic von Neumann basis to non-Cartesian coordinates. The bound states of two isomerizing triatomic molecules, LiCN/LiNC and HCN/HNC, are calculated using the vibrational Hamiltonian in Jacobi coordinates. The phase space localization of the basis functions leads to a flexible and accurate representation of the Hamiltonian. This results in significant savings compared to a basis localized just in coordinate space. The favorable scaling of the method with dimensionality makes it promising for applications to larger systems. PMID:25527918

Shimshovitz, Asaf; Ba?i?, Zlatko; Tannor, David J

2014-12-21

29

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

2014-01-01

30

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

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

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

33

Cartesian Coordinates  

Microsoft Academic Search

\\u000a René Descartes (1596–1650) is often credited with the invention of the xy-plane, but Pierre de Fermat (1601–1665) was probably the first inventor. In 1636 Fermat was working on a treatise titled\\u000a Ad locus planos et solidos isagoge, which outlined what we now call analytic geometry. Unfortunately, Fermat never published his treatise, although he shared his ideas with other mathematicians such

John Vince

34

A Cartesian grid method for simulation of the unsteady aerodynamics of microscale flapping flight  

NASA Astrophysics Data System (ADS)

Recent improvements in MEMS technology is making it possible to develop microscale mechanical devices capable of operating in gases and liquids at low Reynolds number. In the current work a method has been developed to be able to simulate the operation of such devices computationally. The method imposes arbitrary solid/fluid boundaries on Cartesian grids, thus avoiding complexities with body-fitted grid methods. This thesis explains the numerical approximations used for solving the governing equations, the discretization of the equations, and the implementation of the immersed fluid/solid boundary conditions. The method is validated by comparing computed results of flows over an infinitely thin plate, a cylinder, and a sphere, and it is found that the method predicts both steady and unsteady flows with sufficient accuracy. The method performs similarly whether the solid objects translates through the grid or remains fixed in the grid with an imposed flow field. The method was then used to compute the fluid dynamics and force generation of a microscale flapping cantilever beam propulsion device. Both two-dimensional and three-dimensional flow features were explored, and the investigation showed that the cantilever produces thrust and can therefore potentially be used as a simple propulsion mechanism. Finally, the method was used to simulate an idealized model of fruit fly wing in hovering flight. The computed flow fields and force dynamics compared well with an equivalent experimental model, although some discrepancies were found due to a thicker wing being used in the computations for numerical reasons.

Emblemsvag, Jo-Einar

35

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

36

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

37

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

NASA Astrophysics Data System (ADS)

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

Chen, XinJian

2012-12-01

38

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

PubMed Central

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.

2011-01-01

39

Features of CPB: A Poisson-Boltzmann solver that uses an adaptive cartesian grid.  

PubMed

The capabilities of an adaptive Cartesian grid (ACG)-based Poisson-Boltzmann (PB) solver (CPB) are demonstrated. CPB solves various PB equations with an ACG, built from a hierarchical octree decomposition of the computational domain. This procedure decreases the number of points required, thereby reducing computational demands. Inside the molecule, CPB solves for the reaction-field component (?rf ) of the electrostatic potential (?), eliminating the charge-induced singularities in ?. CPB can also use a least-squares reconstruction method to improve estimates of ? at the molecular surface. All surfaces, which include solvent excluded, Gaussians, and others, are created analytically, eliminating errors associated with triangulated surfaces. These features allow CPB to produce detailed surface maps of ? and compute polar solvation and binding free energies for large biomolecular assemblies, such as ribosomes and viruses, with reduced computational demands compared to other Poisson-Boltzmann equation solvers. The reader is referred to http://www.continuum-dynamics.com/solution-mm.html for how to obtain the CPB software. © 2014 Wiley Periodicals, Inc. PMID:25430617

Fenley, Marcia O; Harris, Robert C; Mackoy, Travis; Boschitsch, Alexander H

2015-02-01

40

Energy-Bounded Flow Approximation on a Cartesian-Product Grid over Rough Terrain  

NASA Astrophysics Data System (ADS)

We construct a method for modelling of three-dimensional, time dependent, compressible fluid flow in a gravitational field on a rotating cartesian-product grid with a spatially rough metric that bounds solutions by the total initial physical energy. Specifically: (1) the total physical energy is an / 2 norm on the model state and (2) this total energy cannot increase provided the timestep does not exceed CFL limits. In particular, the first property means that our measure of the energy is always positive unless the mass, momentum, and internal energy are all everywhere zero. These conditions guarantee that no error can grow unchecked. This is thought to be a desirable property, although only in the case of linear systems is it sufficient for convergence of a consistent approximation to the true solution. The great merit of this choice of norm is that the method is applicable to a wide variety of real physical problems because, even in complex circumstances, the total physical energy is conserved and each component of this energy is in limited supply. We first note that conservation of energy is equivalent to antisymmetry of a particular tendency operator. Energy-bounded approximations of fluid flow are then constructed either from antisymmetric finite difference operators, or from antisymmetric Galerkin operators. The method may be particularly useful when reliability in difficult conditions is needed. For example, when the viscosity must be small in order to simulate flow separation or turbulence, a model of viscous dissipation may be chosen purely from physical considerations, uncompromised by any requirements of numerical stability. We demonstrate this for an "internal hydraulic jump" flow over a bell-shaped mountain, simulating an internal wave as it steepens and breaks to form a turbulent jump.

Purnell, Don K.; Revell, Michael J.

1993-07-01

41

Energy-bounded flow approximation on a cartesian-product grid over rough terrain  

SciTech Connect

We construct a method for modelling of three-dimensional, time dependent, compressible fluid flow in a gravitational field on a rotating cartesian-product grid with a spatially rough metric that bounds solutions by the total initial physical energy. Specifically: (1) the total physical energy is an l{sub 2} norm on the model state and (2) this total energy cannot increase provided the timestep does not exceed CFL limits. In particular, the first property means that our measure of the energy is always positive unless the mass, momentum, and internal energy are all everywhere zero. These conditions guarantee that no error can grow unchecked. This is though to be a desirable property, although only in the case of linear systems is it sufficient for convergence of a consistent approximation to the true solution. The great merit of this choice of norm is that the method is applicable to a wide variety of real physical problems because, even in complex circumstances, the total physical energy is conserved and each component of this energy is in limited supply. We first note that conservation of energy is equivalent to antisymmetry of a particular tendency operator. Energy-bounded approximations of fluid flow are then constructed either from antisymmetric Galerkin operators. The method may be particularly useful when reliability in difficult conditions is needed. For example, when the viscosity must be small in order to simulate flow separation or turbulence, a model of viscuous dissipation may be chosen purely from physical considerations, uncompromised by any requirements of numerical stability. We demonstrate this for an {open_quotes}internal hydraulic jump{close_quotes} flow over a bell-shaped mountain, simulating an internal wave as it steepens and breaks to form a turbulent jump. 15 refs., 6 figs.

Purnell, D.K.; Revell, M.J. [National Institute of Water & Atmospheric Research Ltd., Wellington (New Zealand)] [National Institute of Water & Atmospheric Research Ltd., Wellington (New Zealand)

1993-07-01

42

The 3D wave equation and its Cartesian coordinate stretched perfectly matched embedding A time-domain Green's function performance analysis  

Microsoft Academic Search

A general class of 3D perfectly matched, i.e., reflectionless, Cartesian embeddings (perfectly matched layers in the three coordinate directions) is analyzed with the aid of a combined time-domain Green's function technique and a time-domain, causality-preserving, Cartesian coordinate stretching procedure. It is shown that, for an unbounded embedding of the specified class, the wavefield is, in any 3-rectangular computational solution domain,

Adrianus T. de Hoop; Robert F. Remis; Peter M. van den Berg

2007-01-01

43

The 3D wave equation and its Cartesian coordinate stretched perfectly matched embedding – A time-domain Green’s function performance analysis  

Microsoft Academic Search

A general class of 3D perfectly matched, i.e., reflectionless, Cartesian embeddings (perfectly matched layers in the three coordinate directions) is analyzed with the aid of a combined time-domain Green’s function technique and a time-domain, causality-preserving, Cartesian coordinate stretching procedure. It is shown that, for an unbounded embedding of the specified class, the wavefield is, in any 3-rectangular computational solution domain,

Adrianus T. de Hoop; Robert F. Remis; Peter M. van den Berg

2007-01-01

44

AN ADAPTIVE CARTESIAN GRID METHOD FOR UNSTEADY COMPRESSIBLE FLOW IN IRREGULAR REGIONS \\Lambda  

E-print Network

on a volume­of­fluid approach with a redistribution procedure to maintain conservation while avoiding time Cartesian mesh integration scheme is coupled to a conservative adaptive mesh refinement algorithm.S. Department of Energy by the Lawrence Livermore National Laboratory under contract W­7405­Eng­48. Support

Bell, John B.

45

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

46

Finite-difference ghost-point multigrid methods on Cartesian grids for elliptic problems in arbitrary domains  

NASA Astrophysics Data System (ADS)

In this paper we present a numerical method for solving elliptic equations in an arbitrary domain (described by a level-set function) with general boundary conditions (Dirichlet, Neumann, Robin, etc.) on Cartesian grids, using finite difference discretization and non-eliminated ghost values. A system of Ni+Ng equations in Ni+Ng unknowns is obtained by finite difference discretization on the Ni internal grid points, and second order interpolation to define the conditions for the Ng ghost values. The resulting large sparse linear system is then solved by a multigrid technique. The novelty of the papers can be summarized as follows: general strategy to discretize the boundary condition to second order both in the solution and its gradient; a relaxation of inner equations and boundary conditions by a fictitious time method, inspired by the stability conditions related to the associated time dependent problem (with a convergence proof for the first order scheme); an effective geometric multigrid, which maintains the structure of the discrete system at all grid levels. It is shown that by increasing the relaxation step of the equations associated to the boundary conditions, a convergence factor close to the optimal one is obtained. Several numerical tests, including variable coefficients, anisotropic elliptic equations, and domains with kinks, show the robustness, efficiency and accuracy of the approach.

Coco, Armando; Russo, Giovanni

2013-05-01

47

Evaluation of Cartesian coordinates and radiation doses in points determined with stereo x-ray techniques.  

PubMed

A Fortran computer program STEV (stereo evaluation) is described. The principles of the stereo techniques together with the calculation method of the stereo coordinates are given briefly. The determination of the rectangular coordinates from mean stereo coordinates is described. Radiation doses in anatomical points, during intracavitary and interstitial radiation therapy, are calculated, taking into account a statistical evaluation of the measurement errors. PMID:761457

Storchi, P R; van Kleffens, H J

1979-03-01

48

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

SciTech Connect

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

Walters, W.F.

1985-01-01

49

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

ERIC Educational Resources Information Center

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

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

2005-01-01

50

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

51

77 FR 58416 - Large Scale Networking (LSN); Middleware and Grid Interagency Coordination (MAGIC) Team  

Federal Register 2010, 2011, 2012, 2013, 2014

...Scale Networking (LSN); Middleware and Grid Interagency Coordination (MAGIC) Team...index.php?title=Middleware_And_Grid_Interagency_Coordination_(MAGIC...interests and responsibility for middleware, Grid, and cloud projects. The MAGIC Team...

2012-09-20

52

78 FR 70076 - Large Scale Networking (LSN)-Middleware and Grid Interagency Coordination (MAGIC) Team  

Federal Register 2010, 2011, 2012, 2013, 2014

...Scale Networking (LSN)--Middleware and Grid Interagency Coordination (MAGIC) Team...index.php?title=Middleware_And_Grid_Interagency_Coordination_(MAGIC...interests and responsibility for middleware, Grid, and cloud projects. The MAGIC Team...

2013-11-22

53

78 FR 7464 - Large Scale Networking (LSN)-Middleware And Grid Interagency Coordination (MAGIC) Team  

Federal Register 2010, 2011, 2012, 2013, 2014

...Scale Networking (LSN)--Middleware And Grid Interagency Coordination (MAGIC) Team...index.php?title=Middleware_And_Grid_Interagency_Coordination_(MAGIC...interests and responsibility for middleware, Grid, and cloud projects. The MAGIC Team...

2013-02-01

54

Relationship between Students' Understanding of Functions in Cartesian and Polar Coordinate Systems  

ERIC Educational Resources Information Center

The present study was implemented as a prelude to a study on the generalization of the single variable function concept to multivariate calculus. In the present study we analyze students' mental processes and adjustments, as they are being exposed to single variable calculus with polar coordinates. The results show that there appears to be a…

Montiel, Mariana; Vidakovic, Draga; Kabael, Tangul

2009-01-01

55

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

56

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

57

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

Federal Register 2010, 2011, 2012, 2013, 2014

...Regulatory Commission [Docket No. AD12-5-000] Voltage Coordination on High Voltage Grids; Notice of Staff Workshop Take notice...will hold a Workshop on Voltage Coordination on High Voltage Grids on Thursday, December 1, 2011 from...

2011-11-15

58

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

59

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

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

G-GPE Squares on a coordinate grid  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: In the picture below a square is outlined whose vertices lie on the coordinate grid points: The area of this particular square is 16 square units. For ...

62

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

63

Recognizing Patterns In Log-Polar Coordinates  

NASA Technical Reports Server (NTRS)

Log-Hough transform is basis of improved method for recognition of patterns - particularly, straight lines - in noisy images. Takes advantage of rotational and scale invariance of mapping from Cartesian to log-polar coordinates, and offers economy of representation and computation. Unification of iconic and Hough domains simplifies computations in recognition and eliminates erroneous quantization of slopes attributable to finite spacing of Cartesian coordinate grid of classical Hough transform. Equally efficient recognizing curves. Log-Hough transform more amenable to massively parallel computing architectures than traditional Cartesian Hough transform. "In-place" nature makes it possible to apply local pixel-neighborhood processing.

Weiman, Carl F. R.

1992-01-01

64

Cartesian-space time delay compensation in leader-follower coordination of two manipulators using exponential time functions  

Microsoft Academic Search

Coordinated control of two manipulators carrying a common object using discrete position feedback is developed and tested using a multiprocessor architecture and two PUMA robot arms. Leader-follower coordination is used because of its computational efficiency. Computation and other timing delays incur the loss of two sampling intervals. A class of predictive filters is designed to compensate for these delays. These

Z. S. Tumeh

1992-01-01

65

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

66

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

67

An Augmented Lagrangian Based Compressed Sensing Reconstruction for Non-Cartesian Magnetic Resonance Imaging without Gridding and Regridding at Every Iteration  

PubMed Central

Background Non-Cartesian trajectories are used in a variety of fast imaging applications, due to the incoherent image domain artifacts they create when undersampled. While the gridding technique is commonly utilized for reconstruction, the incoherent artifacts may be further removed using compressed sensing (CS). CS reconstruction is typically done using conjugate-gradient (CG) type algorithms, which require gridding and regridding to be performed at every iteration. This leads to a large computational overhead that hinders its applicability. Methods We sought to develop an alternative method for CS reconstruction that only requires two gridding and one regridding operation in total, irrespective of the number of iterations. This proposed technique is evaluated on phantom images and whole-heart coronary MRI acquired using 3D radial trajectories, and compared to conventional CS reconstruction using CG algorithms in terms of quantitative vessel sharpness, vessel length, computation time, and convergence rate. Results Both CS reconstructions result in similar vessel length (P?=?0.30) and vessel sharpness (P?=?0.62). The per-iteration complexity of the proposed technique is approximately 3-fold lower than the conventional CS reconstruction (17.55 vs. 52.48 seconds in C++). Furthermore, for in-vivo datasets, the convergence rate of the proposed technique is faster (60±13 vs. 455±320 iterations) leading to a ?23-fold reduction in reconstruction time. Conclusions The proposed reconstruction provides images of similar quality to the conventional CS technique in terms of removing artifacts, but at a much lower computational complexity. PMID:25215945

Akçakaya, Mehmet; Nam, Seunghoon; Basha, Tamer A.; Kawaji, Keigo; Tarokh, Vahid; Nezafat, Reza

2014-01-01

68

Cartesian-Space Time Delay Compensation in Leader-Follower Coordination of Two Manipulators using Periodic Time Functions  

Microsoft Academic Search

Different approaches in multi-manipulator control can be classified into those which adopt a leader-follower operation and those which use indistinguished control. Although leader-follower coordination is more efficient to implement, its performance is more susceptible to the leader arm controller performance. In this paper coordinated control of two manipulators carrying a common object using discrete position feedback is developed and tested

Zuheir S. Thmeh

1992-01-01

69

Concurrent Negotiation and Coordination for Grid Resource Coallocation  

Microsoft Academic Search

Bolstering resource coallocation is essential for realizing the Grid vision, because computationally intensive applications often require multiple computing resources from different administrative domains. Given that resource providers and consumers may have different requirements, successfully obtaining commitments through concurrent negotiations with multiple resource providers to simultaneously access several resources is a very challenging task for consumers. The impetus of this paper

Kwang Mong Sim; Benyun Shi

2010-01-01

70

A new vertical coordinate system for a 3D unstructured-grid model  

NASA Astrophysics Data System (ADS)

We present a new vertical coordinate system for cross-scale applications. Dubbed LSC2 (Localized Sigma Coordinates with Shaved Cell), the new system allows each node of the grid to have its own vertical grid, while still maintaining reasonable smoothness across horizontal and vertical dimensions. Furthermore, the staircase created by the mismatch of vertical levels at adjacent nodes is eliminated with a simple shaved-cell like approach using the concept of degenerate prisms. The new system is demonstrated to have the benefits of both terrain-following and Z-coordinate systems, while minimizing their adverse effects. We implement LSC2 in a 3D unstructured-grid model (SELFE) and demonstrate its superior performance with test cases on lake and ocean stratification.

Zhang, Yinglong J.; Ateljevich, Eli; Yu, Hao-Cheng; Wu, Chin H.; Yu, Jason C. S.

2015-01-01

71

Cartesian Bicategories II  

E-print Network

The notion of cartesian bicategory, introduced by Carboni and Walters for locally ordered bicategories, is extended to general bicategories. It is shown that a cartesian bicategory is a symmetric monoidal bicategory.

Carboni, A; Walters, R F C; Wood, R J

2007-01-01

72

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

PubMed

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

Kelly, Brian P; Bennett, Charles R

2013-07-26

73

Electronic Absolute Cartesian Autocollimator  

NASA Technical Reports Server (NTRS)

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

Leviton, Douglas B.

2006-01-01

74

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

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

75

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

NASA Technical Reports Server (NTRS)

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

Rubincam, D. P.

1980-01-01

76

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

77

Ultrahigh resolution absolute Cartesian electronic autocollimator  

Microsoft Academic Search

The development of a compact, ultra-high resolution, electronic autocollimator with excellent readout stability, linearity, and coordinate orthogonality is presented. This optical metrology tool relies on new advances in Cartesian optical encoders based on pattern recognition technology. Readout instabilities characteristic of conventional electronic autocollimators whose lateral effect photodetectors and operational amplifiers exhibit temporal and thermal drifts, are absent in this new

Douglas B. Leviton

2003-01-01

78

The soft grid  

E-print Network

The grid in architecture is a systematic organization of space. The means that architects use to organize space are, almost by definition, rigid and totalizing. The Cartesian grid, which will serve as the antagonist of the ...

Kardasis, Ari (Ari David)

2011-01-01

79

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

SciTech Connect

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

Peron, Stephanie, E-mail: stephanie.peron@onera.fr [ONERA - The French Aerospace Lab, F-92322 Chatillon (France)] [ONERA - The French Aerospace Lab, F-92322 Chatillon (France); Benoit, Christophe, E-mail: christophe.benoit@onera.fr [ONERA - The French Aerospace Lab, F-92322 Chatillon (France)] [ONERA - The French Aerospace Lab, F-92322 Chatillon (France)

2013-01-01

80

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

81

Filling the Void: Interpolating in Cartesian Cut Cells  

Microsoft Academic Search

The majority of scientific visualization algorithms are finite-element based. For Cartesian meshes, the definition of the boundary conditions around the body leads to inaccurate visualization data due to the nature of the grid (it is not compatible with finite-element based algorithms). In this paper, we present an algorithm to generate an intermediate, 3D, body- fitted mesh that links the Cartesian

A. Hendriks; M. J. Aftosmis?

82

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

83

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

84

Dispersive tsunami wave modeling by parallel computation with variable nested-grids in spherical coordinates  

NASA Astrophysics Data System (ADS)

Due to development of offshore tsunami observation technologies, frequency dispersion on tsunami propagation has been often observed in the recent tsunamis such as the 2004 Indian Ocean and 2011 Tohoku tsunamis. The dispersive propagation of tsunamis can be simulated with the Boussinesq model, but which demands a lot of computation resources. On the other hand, rapid progress is being made in parallel computing technology. In this study, we investigated a parallelized approach using OpenMP and MPI for dispersive tsunami wave modeling. Our new parallel code solves either the linear or nonlinear Boussinesq-type dispersive water equations in spherical coordinates. A variable nested-grid scheme was employed to increase spatial resolution in the target region. Tsunami inundation on land can be also predicted with the code. This new code was named 'JAGURS'. JAGURS stands for that the 'JA'MSTEC improved the former code developed by 'G'eoscience Australia and 'UR'S Corporation (Jakeman et al., 2011) which uses 'S'atake (2002)'s kernel. By applying JAGURS, the dispersive tsunami modeling was implemented for the 2011 Tohoku earthquake. The finest topographic grid interval was 0.22 arc-second (about 5m) along the longitude and latitude directions in coastal area. A good agreement was shown between the dispersive wave modeling and the tsunami waveforms observed in offshore. The dispersive model predicted the similar inundation area with that derived from the non-dispersive model.

BABA, T.; Takahashi, N.; Kaneda, Y.; Ando, K.; Matsuoka, D.; Kato, T.

2013-12-01

85

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

86

Determining the role of geospatial technologies for stigmergic coordination in situation management: Implications of the wireless grid  

Microsoft Academic Search

Abs tract—Geospatial technologies in conjunction with wireless grids will offer a context for locating and coordinating team activities in such a way that the nature of each team member's effort may be known and understood by other members. This constructed group knowledge enables teams to respond to unforeseen and emergent contingencies and act in concert through the active interpretation of

Janet Marsden

2011-01-01

87

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

88

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

89

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 reduction 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.

2004-01-01

90

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

91

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

92

CARTESIAN CONTROL OF VGT MANIPULATORS  

E-print Network

-2979 Phone: (740) 593-1096 Fax: (740) 593-0476 E-mail: bobw@bobcat.ent.ohiou.edu #12;CARTESIAN CONTROL OF VGT bobw@bobcat.ent.ohiou.edu ABSTRACT This paper introduces a novel method for Cartesian trajectory

Williams II, Robert L.

93

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

E-print Network

California, Los Angeles, CA, USA {yanzhiwa, xuelin, pedram}@usc.edu Abstract--The emergence of cloud pricing policies in the recently proposed smart grid technology can incentivize the cloud computing system of the smart grid, the cloud computing system, and other load devices. A nested two stage game

Pedram, Massoud

94

Ultrahigh-resolution Cartesian absolute optical encoder  

NASA Astrophysics Data System (ADS)

A new optical encoder which measures absolute, true-Cartesian displacement with ultra-high sensitivity and linearity has been developed at NASA"s Goddard Space Flight Center. The device is the two-dimensional analog of recently developed linear and rotary encoders based on optical pattern recognition. In this encoder, a glass scale carrying absolute Cartesian position information travels with the payload in an X-Y motion system. Because the scale comprises the entire measurement coordinate system in a monolithic form, motion control axes can be skew to one another to an arbitrary degree and can exhibit substantial lateral drift with no effect on the correctness of X-Y readout, thus eliminating challenges of orthogonal mounting for motion axes and challenges of mounting independent encoders parallel to the directions of travel for each constituent X and Y axis. Prototype devices with ranges of 30 x 30 mm and 150 x 150 mm with 5 nm and 50 nm resolutions, respectively, have been built in the laboratory. Performance data from the Cartesian encoder in the Point Target Assembly for the optical calibration stimulus for Hubble Space Telescope"s Wide Field Camera 3 are presented.

Leviton, Douglas B.; Kirk, Jeff; Lobsinger, Luke

2003-11-01

95

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

96

A tensor product b-spline method for 3D multi-block elliptic grid generation  

SciTech Connect

We formulate a tensor product b-spline method for multi-block numerical grid generation. The Cartesian coordinate functions for a block are represented as a sum of tensor product b-spline basis functions defined on a parameter space for the block. The tensor product b-spline basis functions are constructed so that the basis functions and their first partials are continuous on the parameter space. The coordinate functions inherit this smoothness: a grid computed by evaluating the coordinate functions along constant parameter lines leads to smooth grid lines with smoothly varying tangents. The expansion coefficients for the coordinate functions are computed by solving the usual elliptic grid generation equations using simple collocation. This assures that the computed grid has the smoothness and resolution expected for an elliptic grid with appropriate control. An important result of the formulation is that the dimension of the collocation equations is the number of distinct knots for the tensor product b-spline basis functions. Combining this results with the smoothness of the b-spline representation makes it possible to reduce the dimension of the tensor product method with respect to the finite difference method, simply by using fewer knots than grid points. We formulate the expansion of the Cartesian coordinate functions as a sum of tensor product b-spline basis functions, and then we derive the collocation and boundary condition equations for the usual elliptic grid generation equations. We investigate the structure of the system of equations for the expansion coefficients and then formulate a solution algorithm to compute the coefficients. Finally, we describe the implementation of the method in a 2D multi-block grid code and discuss the performance of the method for several grids. 3 refs., 11 figs.

Manke, J.W.

1988-12-01

97

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

98

A tensor product b-spline method for 3D multi-block elliptic grid generation  

Microsoft Academic Search

We formulate a tensor product b-spline method for multi-block numerical grid generation. The Cartesian coordinate functions for a block are represented as a sum of tensor product b-spline basis functions defined on a parameter space for the block. The tensor product b-spline basis functions are constructed so that the basis functions and their first partials are continuous on the parameter

Manke

1988-01-01

99

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

100

Ultrahigh resolution absolute Cartesian electronic autocollimator  

NASA Astrophysics Data System (ADS)

The development of a compact, ultra-high resolution, electronic autocollimator with excellent readout stability, linearity, and coordinate orthogonality is presented. This optical metrology tool relies on new advances in Cartesian optical encoders based on pattern recognition technology. Readout instabilities characteristic of conventional electronic autocollimators whose lateral effect photodetectors and operational amplifiers exhibit temporal and thermal drifts, are absent in this new technology. An autocollimator with a form factor similar to conventional alignment telescopes has been demonstrated with an angular resolution of 0.02 arcseconds peak-to-peak and less than 0.01 arcseconds rms. Various optical metrology applications for the laboratory and for space flight, including cryostatic ones, are described.

Leviton, Douglas B.

2003-11-01

101

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

102

The coordinated automatic voltage control of the Italian transmission Grid-part II: control apparatuses and field performance of the consolidated hierarchical system  

Microsoft Academic Search

The hierarchical voltage control system, currently fully exploited in the Italian transmission grid and presented in Part I, improves voltage quality, network security and operation efficiency. This coordinated automatic system, operated by the Italian ISO (GRTN), is subdivided into three hierarchical control levels, requiring unconventional regulation apparatuses. They are the Voltage and Reactive Power Regulator (REPORT) at the power plant

Sandro Corsi; Massimo Pozzi; Marino Sforna; Giuseppe Dell' Olio

2004-01-01

103

A direct procedure for interpolation on a structured curvilinear two-dimensional grid  

NASA Technical Reports Server (NTRS)

A direct procedure is presented for locally bicubic interpolation on a structured, curvilinear, two-dimensional grid. The physical (Cartesian) space is transformed to a computational space in which the grid is uniform and rectangular by a generalized curvilinear coordinate transformation. Required partial derivative information is obtained by finite differences in the computational space. The partial derivatives in physical space are determined by repeated application of the chain rule for partial differentiation. A bilinear transformation is used to analytically transform the individual quadrilateral cells in physical space into unit squares. The interpolation is performed within each unit square using a piecewise bicubic spline.

Zingg, David W.; Yarrow, Maurice

1989-01-01

104

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

105

Cartesian control of redundant robots  

NASA Technical Reports Server (NTRS)

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

Colbaugh, R.; Glass, K.

1989-01-01

106

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. PMID:24408499

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

2014-11-01

107

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

108

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

109

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

110

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

NASA Astrophysics Data System (ADS)

Diverse (4,4) grid layers are exemplified in five two-dimensional coordination polymers with dual ?2-bridged ligands, namely, {[Zn(cbaa)(bpp)]·H2O}n (1), [Zn2(cbaa)2(bpy)]n (2), [Co2(cbaa)2(bpp)2]n (3), [Co(cbaa)(bpp)]n (4), and [Co(bdaa)(bpp)(H2O)2]n (5) (H2cbaa=4-carboxybenzeneacetic acid, bpp=1,3-di(4-pyridyl)propane, bpy=4,4?-bipyridyl, and H2bdaa=1,4-benzenediacrylic acid). For 1, two (4,4) grid layers with [ZnN2O2] tetrahedron as the node are held together by lattice water forming a H-bonding bilayer. Individual (4,4) grid layer in 2 is based on {Zn2(OCO)4} paddlewheel unit as the node. Two (4,4) grid layers with {Co2O(OCO)2} dimer as the node are covalently interconnected by organic ligands affording a thick bilayer of 3 with new framework topology. The different entanglements between two coincident (4,4) grid layers with [CoN2O4] octahedron as the node leads to two 2D?2D interpenetrated structures for 4 and 5. Furthermore, fluorescent properties of 1 and 2 as well as magnetic properties of 3 are investigated.

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

2013-07-01

111

Discrepancy of Cartesian Products of Arithmetic Progressions  

E-print Network

Discrepancy of Cartesian Products of Arithmetic Progressions Benjamin Doerr # + Anand Srivastav discrepancy of the hypergraph H of cartesian products of d arithmetic progressions in the [N ] d --lattice ([N ] = {0, 1, . . . , N - 1}). The study of such higher dimensional arithmetic progressions is motivated

Srivastav, Anand

112

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

113

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

PubMed

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

Grossberg, Stephen; Pilly, Praveen K

2014-02-01

114

Skull evolution in the rhinocerotidae (Mammalia, Perissodactyla): Cartesian transformations and functional interpretations  

Microsoft Academic Search

Cartesian transformation, applied as a landmark morphometric method, is used to investigate some of the evolutionary shape changes leading to the skulls of the modern rhinoceroses. The early Oligocene genusSubhyracodon serves as the primitive shape from which the extant genera (Dicerorhinus, Rhinocerso, Diceros, andCeratotherium) have been transformed. Coordinate data for 21 landmarks, defined in lateral view, are analyzed by the

Gerald S. Bales

1996-01-01

115

Discrepancy of Cartesian Products of Arithmetic Progressions  

E-print Network

Discrepancy of Cartesian Products of Arithmetic Progressions Benjamin Doerr #3; y Anand Srivastav: arithmetic progressions, discrepancy, harmonic analysis, locally compact abelian groups. Abstract We arithmetic progressions is motivated by a multi-dimensional version of van der Waerden's theorem, namely

Doerr, Benjamin

116

Concept Cartesianism, Concept Pragmatism, and Frege Cases  

Microsoft Academic Search

This paper concerns the dialectal role of Frege Cases in the debate between Concept Cartesians and Concept Pragmatists. I\\u000a take as a starting point Christopher Peacocke’s argument that, unlike Cartesianism, his ‘Fregean’ Pragmatism can account for\\u000a facts about the rationality and epistemic status of certain judgments. I argue that since this argument presupposes that the\\u000a rationality of thoughts turn on

Bradley Rives

2009-01-01

117

Recommended coordinate systems for thin spherocylindrical lenses.  

PubMed

Because the set of thin spherocylindrical lenses forms a vector space, any such lens can be expressed in terms of its cartesian coordinates with respect to whatever set of basis lenses we may choose. Two types of cartesian coordinate systems have become prominent, those having coordinates associated with the lens power matrix and those having coordinates associated with the Humphrey Vision Analyzer. This paper emphasizes the value of a particular cartesian coordinate system of the latter type, and the cylindrical coordinate system related to it, by showing how it can simplify the trigonometry of adding lenses and how it preserves symmetry in depicting the sets of all spherical lenses, all Jackson crossed-cylinders, and all cylindrical lenses. It also discusses appropriate coordinates for keeping statistics on lenses and shows that an easy extension of the lens vector space to include general optical systems is not possible. PMID:8515971

Deal, F C; Toop, J

1993-05-01

118

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

NASA Technical Reports Server (NTRS)

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

Rumsey, Christopher Lockwood

1991-01-01

119

A spectral element shallow water model on spherical geodesic grids  

NASA Astrophysics Data System (ADS)

The spectral element method for the two-dimensional shallow water equations on the sphere is presented. The equations are written in conservation form and the domains are discretized using quadrilateral elements obtained from the generalized icosahedral grid introduced previously (Giraldo FX. Lagrange-Galerkin methods on spherical geodesic grids: the shallow water equations. Journal of Computational Physics 2000; 160: 336-368). The equations are written in Cartesian co-ordinates that introduce an additional momentum equation, but the pole singularities disappear. This paper represents a departure from previously published work on solving the shallow water equations on the sphere in that the equations are all written, discretized, and solved in three-dimensional Cartesian space. Because the equations are written in a three-dimensional Cartesian co-ordinate system, the algorithm simplifies into the integration of surface elements on the sphere from the fully three-dimensional equations. A mapping (Song Ch, Wolf JP. The scaled boundary finite element method - alias consistent infinitesimal finite element cell method - for diffusion. International Journal for Numerical Methods in Engineering 1999; 45: 1403-1431) which simplifies these computations is described and is shown to contain the Eulerian version of the method introduced previously by Giraldo (Journal of Computational Physics 2000; 160: 336-368) for the special case of triangular elements. The significance of this mapping is that although the equations are written in Cartesian co-ordinates, the mapping takes into account the curvature of the high-order spectral elements, thereby allowing the elements to lie entirely on the surface of the sphere. In addition, using this mapping simplifies all of the three-dimensional spectral-type finite element surface integrals because any of the typical two-dimensional planar finite element or spectral element basis functions found in any textbook (for example, Huebner et al. The Finite Element Method for Engineers. Wiley, New York, 1995; Karniadakis GE, Sherwin SJ. Spectral/hp Element Methods for CFD. Oxford University Press, New York, 1999; and Szabó B, Babu\\vska I. Finite Element Analysis. Wiley, New York, 1991) can be used. Results for six test cases are presented to confirm the accuracy and stability of the new method. Published in 2001 by John Wiley & Sons, Ltd.

Giraldo, Francis X.

2001-04-01

120

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

Microsoft Academic Search

We present a comprehensive error estimation of four spatial discretization schemes of the two-dimensional Discrete Ordinates (SN) equations on Cartesian grids utilizing a Method of Manufactured Solution (MMS) benchmark suite based on variants of Larsens benchmark featuring different orders of smoothness of the underlying exact solution. The considered spatial discretization schemes include the arbitrarily high order transport methods of the

Sebastian Schunert; Yousry Y. Azmy; Damien Fournier

2011-01-01

121

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

122

Decentralized coordination through digital technology, dynamic pricing, and Customer-Driven control: the GridWise testbed demonstration project  

SciTech Connect

The project highlights the idea that technology-enabled decentralized coordination can achieve the same, or better, economic and reliability benefits when compared to utility-focused centralized physical and economic control. Among the design's unique features was a retail double auction with five-minute market-clearing intervals that included residential customers as direct, active market participants. (author)

Chassin, David P.; Kiesling, Lynne

2008-10-15

123

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

124

Solution-Adaptive Cartesian Cell Approach for Viscous and Inviscid Flows  

NASA Technical Reports Server (NTRS)

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

Coirier, William J.; Powell, Kenneth G.

1996-01-01

125

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

SciTech Connect

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

Tao, Liang; McCurdy, Bill; Rescigno, Tom

2010-06-10

126

Accurate and Robust Fluid Analysis Using Cubic Interpolation with Volume\\/Area Coordinates (CIVA) Method on Unstructured Grids  

Microsoft Academic Search

This paper concerns the cubic interpolation with volume\\/area coordinates (CIVA) method, which is an extension of the cubic interpolation profile (CIP) to a triangular or tetrahedral mesh system, implemented in an unstructured and fixed (Eulerian) mesh-based finite-volume solver. First, we briefly explain the accuracy of and the results of stability analysis by CIVA. Then, to demonstrate the accuracy and robustness

Nobuatsu Tanaka; Toshiteru Yamasaki; Takaya Taguchi

2004-01-01

127

Automated Parameter Studies Using a Cartesian Method  

Microsoft Academic Search

A modular process for performing general parametric studies about an aerodynamic configuration using a Cartesian method is described. A novel part of this process is the automatic handling of general control surfaces deflections based upon simple, user- specified inputs. The article focuses on the use of aerodynamic databases in the design process. Database fly-through is used to develop and analyze

Scott M. Murman; Michael J. Aftosmis; Marian Nemec

128

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

129

Development of a 2-D black-oil reservoir simulator using a unique grid-block system  

E-print Network

effective in reducing the grid orientation effect than the Cartesian grid. The HGB grid performs better by consistently giving a smaller relative difference between HGB parallel grid and HGB diagonal grid in pore volume recovered (6.0, 4.5, 3.3, and 2...

Chong, Emeline E

2006-04-12

130

Accurate and Robust Fluid Analysis Using Cubic Interpolation with Volume/Area Coordinates (CIVA) Method on Unstructured Grids  

NASA Astrophysics Data System (ADS)

This paper concerns the cubic interpolation with volume/area coordinates (CIVA) method, which is an extension of the cubic interpolation profile (CIP) to a triangular or tetrahedral mesh system, implemented in an unstructured and fixed (Eulerian) mesh-based finite-volume solver. First, we briefly explain the accuracy of and the results of stability analysis by CIVA. Then, to demonstrate the accuracy and robustness of the algorithm, we solve two-dimensional benchmark problems of incompressible lid-driven recirculating flow in square and triangular cavities. In addition, a two-dimensional vortex-driven flow is solved in order to analyze the conservative property of CIVA. Finally, an example of an industrial application of CIVA method is described. These numerical experiments demonstrate the high capability of the method and that it is sufficiently robust for complex industrial applications.

Tanaka, Nobuatsu; Yamasaki, Toshiteru; Taguchi, Takaya

131

Adaptation of a k-epsilon Model to a C artesian Grid Based Methodology  

Microsoft Academic Search

Despite the high cost of memory and CPU time required to resolve the boundary layer, a viscous unstructured grid solver has many advantages over a structured grid solver such as the convenience in automated grid generation and vortex capturing by solution adaption. In present study, an unstructured Cartesian grid solver is developed on the basis of the existing viscous solver,

Stephen M. Ruffin; Jae-Doo Lee

132

Arbitrary order permanent Cartesian multipolar electrostatic interactions.  

PubMed

Recently, there has been a concerted effort to implement advanced classical potential energy surfaces by adding higher order multipoles to fixed point charge electrostatics in a bid to increase the accuracy of simulations of condensed phase systems. One major hurdle is the unwieldy nature of the expressions which in part has limited developers mostly to including only dipoles and quadrupoles. In this paper, we present a generalization of the Cartesian formulation of electrostatic multipolar interactions that enables the specification of an arbitrary order of multipoles. Specifically, we derive formulas for arbitrary order implementation of the particle mesh Ewald method and give a closed form formula for the stress tensor in the reciprocal space. In addition, we provide recurrence relations for common electrostatic potentials employed in molecular simulations, which allows for the generalization to arbitrary order and guarantees a computational cost that scales as O(p(3)) for Cartesian multipole interactions of order p. PMID:25612699

Boateng, H A; Todorov, I T

2015-01-21

133

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

NASA Astrophysics Data System (ADS)

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

Ramón, C. L.; Cortés, A.; Rueda, F. J.

2015-01-01

134

A Cartesian Adaptive Level Set Method for Two-Phase Flows  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

135

Discrepancy of Cartesian Products of Arithmetic Progressions  

Microsoft Academic Search

We determine the combinatorial discrepancy of the hypergraph H of cartesian products of d arithmetic progressions in the (N)d-lattice ((N )= {0, 1,...,N 1}). The study of such higher dimensional arithmetic progressions is motivated by a multi-dimensional version of van der Waerden's theorem, namely the Gallai-theorem (1933). We solve the discrepancy problem for d-dimensional arithmetic progressions by proving disc(H )=

Benjamin Doerr; Anand Srivastav; Petra Wehr

2004-01-01

136

Adaptive grid shallow water modeling  

Microsoft Academic Search

Adaptive grid generation procedure is coupled with the solver of the shallow water equations. The theory of harmonic maps is used as a theoretical framework for grid generation. The problem of constructing harmonic coordinates on the surface of the graph of control function is formulated. The projection of these coordinates onto a physical region produces an adaptive-harmonic grid. Modification of

Sergey A. Ivanenko; Galina V. Muratova

2000-01-01

137

FUTURE POWER GRID INITIATIVE Future Power Grid  

E-print Network

FUTURE POWER GRID INITIATIVE Future Power Grid Control Paradigm OBJECTIVE This project line power) after contingencies - Coordinate voltage resources to improve voltage security margin) to quickly stabilize system - Modify AGC to only focus on restoring tie line power to scheduled values

138

76 FR 46279 - Smart Grid Advisory Committee  

Federal Register 2010, 2011, 2012, 2013, 2014

...National Institute of Standards and Technology Smart Grid Advisory Committee AGENCY: Department...SUMMARY: The Smart Grid Advisory Committee (SGAC or Committee...Office of the National Coordinator for Smart Grid Interoperability, National...

2011-08-02

139

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

140

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

141

A HIGH-RESOLUTION ROTATED GRID METHOD FOR CONSERVATION LAWS WITH EMBEDDED GEOMETRIES  

E-print Network

-dimensional problems. The numerical challenge associated with a Cartesian grid embedded boundary approach is the so, Germany (helzel@iam.uni-bonn.de). The research of this author was supported by the German Science Foun

LeVeque, Randy

142

Biangular Coordinates Redux: Discovering a New Kind of Geometry  

ERIC Educational Resources Information Center

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

Winkel, Brian; Naylor, Michael

2010-01-01

143

A CUDA-based reverse gridding algorithm for MR reconstruction.  

PubMed

MR raw data collected using non-Cartesian method can be transformed on Cartesian grids by traditional gridding algorithm (GA) and reconstructed by Fourier transform. However, its runtime complexity is O(K×N(2)), where resolution of raw data is N×N and size of convolution window (CW) is K. And it involves a large number of matrix calculation including modulus, addition, multiplication and convolution. Therefore, a Compute Unified Device Architecture (CUDA)-based algorithm is proposed to improve the reconstruction efficiency of PROPELLER (a globally recognized non-Cartesian sampling method). Experiment shows a write-write conflict among multiple CUDA threads. This induces an inconsistent result when synchronously convoluting multiple k-space data onto the same grid. To overcome this problem, a reverse gridding algorithm (RGA) was developed. Different from the method of generating a grid window for each trajectory as in traditional GA, RGA calculates a trajectory window for each grid. This is what "reverse" means. For each k-space point in the CW, contribution is cumulated to this grid. Although this algorithm can be easily extended to reconstruct other non-Cartesian sampled raw data, we only implement it based on PROPELLER. Experiment illustrates that this CUDA-based RGA has successfully solved the write-write conflict and its reconstruction speed is 7.5 times higher than that of traditional GA. PMID:22898698

Yang, Jingzhu; Feng, Chaolu; Zhao, Dazhe

2013-02-01

144

Graphing Equations on the Cartesian Plane: Slope  

NSDL National Science Digital Library

The lesson teaches students about an important characteristic of lines: their slope. Slope can be determined either in graphical or algebraic form. Slope can also be described as positive, negative, zero, or undefined. Students get an explanation of when and how these different types of slope occur. Finally, students learn how slope relates to parallel and perpendicular lines. When two lines are parallel, they have the same slope and when they are perpendicular their slopes are negative reciprocals of one another. Prerequisite knowledge: Students must know how to graph points on the Cartesian plane. They must be familiar with the x- and y- axes on the plane in both the positive and negative directions.

VU Bioengineering RET Program, School of Engineering,; Mckelvey, Aubrey

2007-01-01

145

Three-dimensional Cartesian finite element method for the time dependent Schrödinger equation of molecules in laser fields  

Microsoft Academic Search

A finite element (FE) method in three-dimensional Cartesian coordinates is described to solve the time dependent Schro¨dinger equation for H+2, H2, and H+3 in the presence of time dependent electromagnetic fields. The ionization rates and harmonic generation spectra have been calculated for these molecules for field directions parallel or perpendicular to the molecular axis. Nonlinear optical susceptibilities of H+2 have

Hengtai Yu; André D. Bandrauk

1995-01-01

146

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)= T(X, Y)T(Z). This is a simplification in the computation of the diffraction intensity I(~:, l). One can write, after omitting the weight factors, the Fourier transform T(X, Y) as T(X, Y) = sinc ¢r

Rossmann, Michael G.

147

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

148

On connectivity of the Cartesian product of two graphs  

Microsoft Academic Search

In this paper, sufficient conditions for the Cartesian product of two graphs to be maximum edge-connected, maximum point-connected, super edge-connected or super point-connected are presented. As a corollary, some graphs with these properties are obtained. Furthermore, the relationship between super point-connectivity and super edge-connectivity on the Cartesian product of graphs is pointed out.

Wen-sz Chiue; Bih-sheue Shieh

1999-01-01

149

Plasticity of Intermediate Mechanics Students' Coordinate System Choice  

ERIC Educational Resources Information Center

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…

Sayre, Eleanor C.; Wittman, Michael C.

2008-01-01

150

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

PubMed Central

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

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

2014-01-01

151

Impact of uncoordinated and coordinated charging of plug-in electric vehicles on substation transformer in smart grid with charging stations  

Microsoft Academic Search

With the rapidly growing interest in smart grid technology, plug-in electric vehicles (PEVs) are expected to become more popular as low emission replacement for the petroleum based vehicles. Significant PEVs charging activities will mostly take place in customer's premises, public or corporate car parks and electric charging stations. Therefore, utilities are concern about the possible detrimental impacts of these sizeable

Amir S. Masoum; Ahmed Abu-Siada; Syed Islam

2011-01-01

152

77 FR 71169 - Smart Grid Advisory Committee Meeting  

Federal Register 2010, 2011, 2012, 2013, 2014

...National Institute of Standards and Technology Smart Grid Advisory Committee Meeting AGENCY...SUMMARY: The Smart Grid Advisory Committee (SGAC or Committee...cybersecurity coordination and the NIST Smart Grid Program Plan. The agenda may...

2012-11-29

153

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

154

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

PubMed

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

Branduardi, Davide; Faraldo-Gómez, José D

2013-09-10

155

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

PubMed Central

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

Branduardi, Davide; Faraldo-Gómez, José D.

2014-01-01

156

Frequency-Offset Cartesian Feedback Based on Polyphase Difference Amplifiers  

PubMed Central

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

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

2010-01-01

157

ASAM v2.7: a compressible atmospheric model with a Cartesian cut cell approach  

NASA Astrophysics Data System (ADS)

In this work, the fully compressible, nonhydrostatic atmospheric model ASAM is presented. A cut cell approach is used to include obstacles and orography into the Cartesian grid. Discretization is realized by a mixture of finite differences and finite volumes and a state limiting is applied. An implicit time integration scheme ensures numerical stability around small cells. To make the model applicable for atmospheric problems, physical parameterizations like a Smagorinsky subgrid scale model, a two-moment bulk microphysics scheme, precipitation and vertical surface fluxes by a constant flux layer or a more complex soil model are implemented. Results for three benchmark test cases from the literature are shown. A sensitivity study regarding the development of a convective boundary layer together with island effects at Barbados is carried out to show the capability to perform real case simulations with ASAM.

Jähn, M.; Knoth, O.; König, M.; Vogelsberg, U.

2014-07-01

158

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

159

Database Oriented Grid Middlewares  

Microsoft Academic Search

Abstract—Efficient management of massive data sets is a key aspect in typical grid and e-science applications. To this end, the benefits of employing database technologies in such applications has been identified since the early days of grid computing, which aims at enabling coordinated resource shar- ing, knowledge generation and problem solving in dynamic, multi-institutional virtual organizations through a distributed, scalable,

Efthymia Tsamoura; Anastasios Gounaris

2009-01-01

160

A Survey of Self Modifying Cartesian Genetic Programming  

NASA Astrophysics Data System (ADS)

Self-Modifying Cartesian Genetic Programming (SMCGP) is a general purpose, graph-based, developmental form of Cartesian Genetic Programming. In addition to the usual computational functions found in CGP, SMCGP includes functions that can modify the evolved program at run time. This means that programs can be iterated to produce an infinite sequence of phenotypes from a single evolved genotype. Here, we discuss the results of using SMCGP on a variety of different problems, and see that SMCGP is able to solve tasks that require scalability and plasticity. We demonstrate how SMCGP is able to produce results that would be impossible for conventional, static Genetic Programming techniques.

Harding, Simon; Banzhaf, Wolfgang; Miller, Julian F.

161

White paper of NIST and SG-CG on standardization of Smart Grids White paper on standardization of Smart Grids  

E-print Network

White paper of NIST and SG-CG on standardization of Smart Grids White paper on standardization of Smart Grids published by NIST & Smart Grid Co-ordination Group 1 #12;White paper of NIST and SG-CG on standardization of Smart Grids INTRODUCTION Europe and the US have identified Smart Grids as a major means

162

An Adaptively Refined Cartesian Mesh Solver for the Euler Equations  

Microsoft Academic Search

A method for adaptive refinement of a Cartesian mesh for the solution of the steady Euler equations is presented. The algorithm creates an initial uniform mesh and cuts the body out of that mesh. The mesh is then refined based on body curvature. Next, the solution is converged to a steady state using a linear reconstruction and Roe's approximate Riemann

Darren Dezeeuw; Kenneth G. Powell

1993-01-01

163

Recurrence relations for the Cartesian derivatives of the Zernike polynomials.  

PubMed

A recurrence relation for the first-order Cartesian derivatives of the Zernike polynomials is derived. This relation is used with the Clenshaw method to determine an efficient method for calculating the derivatives of any linear series of Zernike polynomials. PMID:24695132

Stephenson, Philip C L

2014-04-01

164

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

165

The Cartesian Diver as an Aid for Teaching Respiratory Physiology  

ERIC Educational Resources Information Center

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

Fitch, Greg K.

2004-01-01

166

The Category of Categories is Cartesian Closed Maarten M Fokkinga  

E-print Network

The Category of Categories is Cartesian Closed Maarten M Fokkinga CWI, Amsterdam, and University) = (x.F).G ; 1 #12; : A Ã? B C in C and x y = (x, y). ; A, A , . . . vary over objects of A (i A (mapping an object to A and a morphism to idA ), then we can summarize all four definitions of ^ by y. (x

Fokkinga, Maarten M.

167

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

168

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

169

Grid management  

NASA Technical Reports Server (NTRS)

A computational environment that allows many Computational Fluid Dynamics (CFD) engineers to work on the same project exists in the Special Project Office (SPO). This environment enables several users to carry out the task of grid generation. The grid management system, used by the engineers, is described in a brief overview. The topics will include the grid file naming system, the grid-generation procedure, grid storage, and the grid format standard.

Hwang, Danny

1992-01-01

170

Synthesis, structure and host-guest properties of (Et4N)2[Sn(IV)Ca(II)(chloranilate)4], a new type of robust microporous coordination polymer with a 2D square grid structure.  

PubMed

Reaction of chloranilic acid with SnCl(4), Ca(NO(3))(2) and Et(4)NBF(4) in aqueous acetone yields (Et(4)N)(2)[Sn(IV)Ca(II)(can)(4)]. 2 Me(2)CO which contains 2D coordination polymer sheets of composition [Sn(IV)Ca(II)(can)(4)](2-). Both metals are 8-coordinate and act as 4-connecting nodes to form a square grid containing "square" holes. The anionic sheets are electrostatically bound together by Et(4)N(+) cations, which align the sheets so that holes are arranged directly above and below each other, generating channels perpendicular to the sheets. The acetone is easily removed, after which single crystal character is retained. Crystallographic studies indicate that (Et(4)N)(2)[Sn(IV)Ca(II)(can)(4)] is able to sorb one molecule per square hole of either acetonitrile, or CS(2). Gas sorption measurements indicate that at a pressure of 2000 kPa each square cavity sorbs two CO(2) molecules at 273 K, approximately one molecule of N(2) at 195 K and approximately 2.4 molecules of H(2) at 77 K. PMID:21918755

Abrahams, Brendan F; Grannas, Martin J; Hudson, Timothy A; Hughes, Steven A; Pranoto, Naomi H; Robson, Richard

2011-12-01

171

Building Cartesian Trees from Free Trees Brian C. Dean Raghuveer Mohan  

E-print Network

Building Cartesian Trees from Free Trees Brian C. Dean Raghuveer Mohan July 6, 2011 Abstract One can build a Cartesian tree from an n-element sequence in O(n) time, and from an n-node free tree in O connect these results together by describing an "adaptive" Cartesian tree construction algorithm running

Dean, Brian C.

172

General noncommuting curvilinear coordinates and fluid Mechanics  

E-print Network

We show that restricting the states of a charged particle to the lowest Landau level introduces noncommutativity between general curvilinear coordinate operators. The cartesian, circular cylindrical and spherical polar coordinates are three special cases of our quite general method. The connection between U(1) gauge fields defined on a general noncommuting curvilinear coordinates and fluid mechanics is explained. We also recognize the Seiberg-Witten map from general noncommuting to commuting variables as the quantum correspondence of the Lagrange to Euler map in fluid mechanics.

S. A. Alavi

2006-08-16

173

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

PubMed

We apply the recently proposed quasi-classical approach for a second quantized many-electron Hamiltonian in Cartesian coordinates [B. Li and W. H. Miller, J. Chem. Phys. 137, 154107 (2012)] to correlated nonequilibrium quantum transport. The approach provides accurate results for the resonant level model for a wide range of temperatures, bias, and gate voltages, correcting the flaws of our recently proposed mapping using action-angle variables. When electron-electron interactions are included, a Gaussian function scheme is required to map the two-electron integrals, leading to quantitative results for the Anderson impurity model. In particular, we show that the current mapping is capable of capturing quantitatively the Coulomb blockade effect and the temperature dependence of the current below and above the blockade. PMID:23514468

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

2013-03-14

174

Internal coordinate molecular dynamics: a foundation for multiscale dynamics.  

PubMed

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

Vaidehi, Nagarajan; Jain, Abhinandan

2015-01-29

175

Nonlinear Accelerator with Transverse Motion Integrable in Normalized Polar Coordinates  

SciTech Connect

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

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

2012-05-01

176

Schwinger, Pegg and Barnett approaches and a relationship between angular and Cartesian quantum descriptions II: Phase Spaces  

E-print Network

Following the discussion -- in state space language -- presented in a preceding paper, we work on the passage from the phase space description of a degree of freedom described by a finite number of states (without classical counterpart) to one described by an infinite (and continuously labeled) number of states. With that it is possible to relate an original Schwinger idea to the Pegg and Barnett approach to the phase problem. In phase space language, this discussion shows that one can obtain the Weyl-Wigner formalism, for both Cartesian {\\em and} angular coordinates, as limiting elements of the discrete phase space formalism.

M. Ruzzi; D. Galetti

2002-02-07

177

The Overgrid Interface for Computational Simulations on Overset Grids  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

178

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

179

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

Microsoft Academic Search

We solve the incompressible Navier-Stokes equations on moving overset grids. Near dynamically deforming boundaries we use thin, body-fitted grids and cover most of the computational domain with fixed Cartesian grids. Large scale deformation of the flow boundaries can be handled efficiently without global regridding. We'll discuss a velocity-pressure formulation of the Navier-Stokes equations for domains with elastic boundaries. Time permitting,

Petri Fast

2001-01-01

180

Constructing the ASCI computational grid  

SciTech Connect

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

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

2000-06-01

181

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

182

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

183

ONMCGP: Orthogonal Neighbourhood Mutation Cartesian Genetic Programming for Evolvable Hardware  

NASA Astrophysics Data System (ADS)

Evolvable Hardware is facing the problems of scalability and stalling effect. This paper proposed a novel Orthogonal Neighbourhood Mutation (ONM) operator in Cartesian genetic programming (CGP), to reduce the stalling effect in CGP and improve the efficiency of the algorithms.The method incorporates with Differential Evolution strategy. Demonstrated by experiments on benchmark, the proposed Orthogonal Neighbourhood Search can jump out of Local optima, reduce the stalling effect in CGP and the algorithm convergence faster.

I, Fuchuan N.; I, Yuanxiang L.; E, Peng K.

2014-03-01

184

Solving real-valued optimisation problems using cartesian genetic programming  

Microsoft Academic Search

Classical Evolutionary Programming (CEP) and Fast Evo- lutionary Programming (FEP) have been applied to real- valued function optimisation. Both of these techniques di- rectly evolve the real-values that are the arguments of the real-valued function. In this paper we have applied a form of genetic programming called Cartesian Genetic Program- ming (CGP) to a number of real-valued optimisation bench- mark

James Alfred Walker; Julian Francis Miller

2007-01-01

185

Quality-based generation of weather radar Cartesian products  

NASA Astrophysics Data System (ADS)

Weather radar data volumes are commonly processed to obtain various 2-D Cartesian products based on the transfer from polar to Cartesian representations through a certain interpolation method. In this research, an algorithm of the spatial interpolation of polar reflectivity data with respect to QI (quality index) data is applied to find the Cartesian reflectivity as PPI (plan position indicator) product and generate a corresponding QI field. On this basis, quality-based versions of standard algorithms for the generation of the following products have been developed: ETOP (echo top), MAX (maximum of reflectivity), and VIL (vertically integrated liquid water). Moreover, as an example of a higher-level product, a CONVECTION (detection of convection) has been defined as a specific combination of the above-listed standard products. A corresponding QI field is determined for each generated product, taking into account the quality of the pixels from which a given product was determined and how large a fraction of the investigated heights was scanned. Examples of such quality-based products are presented in the paper.

O?ródka, K.; Szturc, J.

2014-11-01

186

Frequency-Offset Cartesian Feedback for MRI Power Amplifier Linearization  

PubMed Central

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

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

2011-01-01

187

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

NASA Technical Reports Server (NTRS)

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

Liu, Yen; Vinokur, Marcel

1997-01-01

188

An Efficient Means of Adaptive Refinement Within Systems of Overset Grids  

NASA Technical Reports Server (NTRS)

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

Meakin, Robert L.

1996-01-01

189

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

PubMed

We provide a formulation of the local induction approximation (LIA) for the motion of a vortex filament in the Cartesian reference frame (the extrinsic coordinate system) which allows for scaling of the reference coordinate. For general monotone scalings of the reference coordinate, we derive an equation for the planar solution to the derivative nonlinear Schrödinger equation governing the LIA. We proceed to solve this equation perturbatively in small amplitude through an application of multiple-scales analysis, which allows for accurate computation of the period of the planar vortex filament. The perturbation result is shown to agree strongly with numerical simulations, and we also relate this solution back to the solution obtained in the arclength reference frame (the intrinsic coordinate system). Finally, we discuss nonmonotone coordinate scalings and their application for finding self-intersections of vortex filaments. These self-intersecting vortex filaments are likely unstable and collapse into other structures or dissipate completely. PMID:23679541

Van Gorder, Robert A

2013-04-01

190

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

NASA Technical Reports Server (NTRS)

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

Coirier, William John

1994-01-01

191

Ontology-Based Resource Matching in the Grid - The Grid Meets the Semantic Web  

Microsoft Academic Search

The Grid is an emerging technology for enabling resource sharing and coordinated problem solving in dynamic multi-institutional virtual organizations. In the Grid environment, shared resources and users typically span different orga- nizations. The resource matching problem in the Grid involves assigning resources to tasks in order to satisfy task requirements and resource policies. These require- ments and policies are often

Hongsuda Tangmunarunkit; Stefan Decker; Carl Kesselman

2003-01-01

192

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.

193

High Energy Boundary Conditions for a Cartesian Mesh Euler Solver  

NASA Technical Reports Server (NTRS)

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

Pandya, Shishir; Murman, Scott; Aftosmis, Michael

2003-01-01

194

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

NASA Technical Reports Server (NTRS)

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

Berger, Marsha; Aftosmis, Michael J.

2011-01-01

195

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

196

AN ADAPTIVE CARTESIAN GRID METHOD FOR UNSTEADY COMPRESSIBLE FLOW IN IRREGULAR REGIONS \\Lambda  

E-print Network

Richard B. Pember, John B. Bell, Lawrence Livermore National Laboratory, P.O. Box 808, L­316, Livermore Berkeley, CA 94720 William Y. Crutchfield, and Michael L. Welcome Lawrence Livermore National Laboratory, P.S. Department of Energy by the Lawrence Livermore National Laboratory under contract W­7405­Eng­48. Support

Bell, John B.

197

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

198

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

PubMed

A new classical model for the general second-quantized many-electron Hamiltonian in Cartesian coordinates and momenta is presented; this makes semiclassical (SC) calculations using an initial value representation (IVR) more useful than the classical Hamiltonian in action-angle variables given earlier by Miller and White [J. Chem. Phys. 84, 5059-5066 (1986)]. If only 1-electron terms are included in this Hamiltonian, the classical equations of motion for the Cartesian variables are linear, and the SC-IVR gives exact results for the propagator (and thus for transition probabilities, the energy spectrum, etc.), as confirmed by analytic proof and numerical calculations. Though this new Hamiltonian is not exact when 2-electron interactions are included, we observe good results for the SC-IVR transition probabilities for times that are not too long. Test calculations, for example, show that the SC-IVR is accurate for times long enough to obtain good result for the eigenvalue spectrum (i.e., the energy levels of the electronic system). PMID:23083148

Li, Bin; Miller, William H

2012-10-21

199

An Accuracy Assessment of Cartesian-Mesh Approaches for the Euler Equations  

Microsoft Academic Search

A critical assessment of the accuracy of Cartesian-mesh approaches for steady, transonic solutions of the Euler equations of gas dynamics is made. An exact solution of the Euler equations (Ringleb's flow) is used not only to infer the order of the truncation error of the Cartesian-mesh approaches, but also to compare the magnitude of the discrete error directly to that

William J. Coirier; Kenneth G. Powell

1995-01-01

200

The comoving-frame equation of radiative transfer in a curvilinear coordinate system  

NASA Astrophysics Data System (ADS)

The comoving-frame equation of radiative transfer and moment equations are derived in orthogonal, curvilinear coordinates, inclusive of terms of order v/c. The equation of radiative transfer, which contains the terms due to the effect of curvature of coordinate lines explicitly as well as those of Doppler shift and aberration, is the generalization of Castor's equation for spherical symmetry and of Buchler's equation for Cartesian coordinates. The moment equations agree with Buchler's.

Kaneko, N.; Morita, K.; Maekawa, M.

1984-12-01

201

Highly Energy-Conservative Finite Difference Method for the Cylindrical Coordinate System  

Microsoft Academic Search

A highly energy-conservative second-order-accurate finite difference method for the cylindrical coordinate system is developed. It is rigorously proved that energy conservation in discretized space is satisfied when appropriate interpolation schemes are used. This argument holds not only for an unequally spaced mesh but also for an equally spaced mesh on cylindrical coordinates but not on Cartesian coordinates. Numerical tests are

Koji Fukagata; Nobuhide Kasagi

2002-01-01

202

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

203

Equatorial Coordinates Model  

NSDL National Science Digital Library

The Equatorial Coordinates model displays the position of a star in equatorial (Right Ascension/Declination --- RA/Dec) coordinates. The horizon is shown along with the four cardinal directions (N, E, S, and W). The Latitude slider changes the latitude of the observer which is shown by the change in the (teal) celestial pole relative to the northern horizon. The position of the star can be changed by using the Right Ascension and Declination sliders. Once these coordinates are selected, pressing the play button will put the star, celestial grid, and the equatorial coordinates in motion to simulate the 23 hour and 56 minute motion of stars in the night sky. Equatorial Coordinates model is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_astronomy_EquatorialCoordinates.jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the plot and selecting "Open EJS Model" from the pop-up menu item.

Belloni, Mario; Timberlake, Todd

2009-11-14

204

Grids = Structure.  

ERIC Educational Resources Information Center

Proposes that narrow columns provide a flexible system of organization for designers. Notes that grids serve the content on the pages, help to develop a layout that will clearly direct the reader to information; and prevent visual monotony. Concludes when grid layouts are used, school publications look as good as professional ones. (PM)

Barrington, Linda; Carter, Jacky

2003-01-01

205

The National Grid Project: A system overview  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

206

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

207

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

208

MESH2D GRID GENERATOR DESIGN AND USE  

SciTech Connect

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

Flach, G.; Smith, F.

2012-01-20

209

Grid2003 and Open Science Grid Ruth Pordes  

E-print Network

for CDF, D0, SDSS, U.S CMS, BTeV..) U.S. CMS Trillium: PPDG Coordinator, iVDGL Management, April 16th 2004&C U.S. ATLAS Computing SDSS Trillium LIGO* ** * * Grid TelemetryUofBuffalo * BTeV Virtual Data Toolkit Anzar Afaq, Eileen Berman, James Annis, Lothar Bauerdick, Michael Ernst, Ian Fisk, Lisa Giacchetti, Greg

Wisconsin at Madison, University of

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

Multiples Grid  

NSDL National Science Digital Library

This problem reinforces a learner's understanding of factors and multiples. Students are presented with the hundred grid or parts of the grid where specific numbers have been shaded and must find out which factors have been chosen in order to produce the shading. A link to a spreadsheet which shades the squares according to the chosen factors, can be used by students to check their hypotheses. The Teachers' Notes page offers rationale, suggestions for implementation, discussion questions, and ideas for extension and support.

212

A Group Selection Pattern Applied to Grid Resource Management  

Microsoft Academic Search

A key challenge in grid computing is the achievement of efficient and self-organized resource management. Grids are often large scale, heterogeneous, and unpredictable systems. Introducing group structures can help to distribute coordination efforts, but higher levels of adaptation and learning in the coordination protocols are still required in order to cope with system complexity. We provide a solution based on

Isaac Chao; Oscar Ardaiz; Ramon Sangüesa

2009-01-01

213

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

214

Introduction to grid generation systems in turbomachinery  

NASA Astrophysics Data System (ADS)

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

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

215

A Grid-based Spatial Association Mining Method  

Microsoft Academic Search

The grid is a distributed computing infrastructure that supports the sharing and coordinated use of various resources in virtual organizations. The grid can be used for compute intensive tasks and data intensive applications. Data mining algorithms are intensive compute and data, and spatial data are heterogeneous, multidimensional and stored at various places. Therefore, the grid can provide a computing and

Xiaohui Zhao; Yu Fang

2007-01-01

216

The Granular Sea Ice Model in Spherical Coordinates and Its Application to a Global Climate Model  

Microsoft Academic Search

The granular sea ice model (GRAN) from Tremblay and Mysak is converted from Cartesian to spherical coordinates. In this conversion, the metric terms in the divergence of the deviatoric stress and in the strain rates are included. As an application, the GRAN is coupled to the global Earth System Climate Model from the University of Victoria. The sea ice model

Jan Sedlacek; Jean-François Lemieux; Lawrence A. Mysak; L. Bruno Tremblay; David M. Holland

2007-01-01

217

Coordinate Dependence of Variability Analysis Dagmar Sternad1,2,3  

E-print Network

actions. For example, Morasso [1] studied planar reaching movements and showed that translation and rotation of the start and target positions evoked systematic variation of joint kinematics (angles of shoulder and elbow) but much less variation of hand kinematics (Cartesian coordinates of the hand

Sternad, Dagmar

218

Static Aeroelastic Analysis with an Inviscid Cartesian Method  

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

219

Static Aeroelastic Analysis with an Inviscid Cartesian Method  

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

220

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

221

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

E-print Network

, it is significant that?save Smith?s? none of the essays focused on medicine or technology, or other larger cultural trends that may have help shaping cultural styles and influenced the approach to understanding and representing nature. Jorge Secada. Cartesian... on our intellect and our knowledge of the essences of substances. Despite Descartes? formulation of this anti-Aristotelian phi- losophy, Secada contends that it is not difficult to trace the Scholas- tic origins of Cartesian metaphysics. To begin with...

Luciano Boschiero

2002-01-01

222

Grid Game  

NSDL National Science Digital Library

With this interactive Shockwave applet students practice recognizing various types of numbers, including factors, multiples, and prime numbers. Each level presents several grids of numbers, each with a specific rule. Users select all numbers in the grid that satisfy the rule. Level 1 involves parity (odd/even) and multiplication facts of 2, 3, 4, 5 and 10. Level 2 includes multiplication facts up to 10 x 10, primes, and square numbers. Level 3 also covers powers of 2, triangle numbers less than 100, and lower cube numbers. A Key Ideas window explains each type of number. Cross Number puzzle printouts are available for further practice.

2000-01-01

223

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

224

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

225

Geoboard - Coordinate  

NSDL National Science Digital Library

This interactive Java applet lets users explore the coordinate plane through the use of a Geoboard. The user places bands on the board where each peg is at an integer coordinate. Once a band has been placed, the applet outputs the perimeter and area of the shape or, if bands are placed as line segments, the applet outputs the distance and slope of the segment.

1999-01-01

226

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

227

Multiscale geometric modeling of macromolecules I: Cartesian representation.  

PubMed

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

2014-01-01

228

Multiscale geometric modeling of macromolecules I: Cartesian representation  

SciTech Connect

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.

Xia, Kelin [Department of Mathematics, Michigan State University, MI 48824 (United States)] [Department of Mathematics, Michigan State University, MI 48824 (United States); Feng, Xin [Department of Computer Science and Engineering, Michigan State University, MI 48824 (United States)] [Department of Computer Science and Engineering, Michigan State University, MI 48824 (United States); Chen, Zhan [Department of Mathematics, Michigan State University, MI 48824 (United States)] [Department of Mathematics, Michigan State University, MI 48824 (United States); Tong, Yiying [Department of Computer Science and Engineering, Michigan State University, MI 48824 (United States)] [Department of Computer Science and Engineering, Michigan State University, MI 48824 (United States); Wei, Guo-Wei, E-mail: wei@math.msu.edu [Department of Mathematics, Michigan State University, MI 48824 (United States) [Department of Mathematics, Michigan State University, MI 48824 (United States); Department of Biochemistry and Molecular Biology, Michigan State University, MI 48824 (United States)

2014-01-15

229

Multiscale geometric modeling of macromolecules I: Cartesian representation  

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

230

Technical Note: Algebraic iterative image reconstruction using a cylindrical image grid for tetrahedron beam computed tomography  

PubMed Central

Purpose: To accelerate iterative algebraic reconstruction algorithms using a cylindrical image grid. Methods: Tetrahedron beam computed tomography (TBCT) is designed to overcome the scatter and detector problems of cone beam computed tomography (CBCT). Iterative algebraic reconstruction algorithms have been shown to mitigate approximate reconstruction artifacts that appear at large cone angles, but clinical implementation is limited by their high computational cost. In this study, a cylindrical voxelization method on a cylindrical grid is developed in order to take advantage of the symmetries of the cylindrical geometry. The cylindrical geometry is a natural fit for the circular scanning trajectory employed in volumetric CT methods such as CBCT and TBCT. This method was implemented in combination with the simultaneous algebraic reconstruction technique (SART). Both two- and three-dimensional numerical phantoms as well as a patient CT image were utilized to generate the projection sets used for reconstruction. The reconstructed images were compared to the original phantoms using a set of three figures of merit (FOM). Results: The cylindrical voxelization on a cylindrical reconstruction grid was successfully implemented in combination with the SART reconstruction algorithm. The FOM results showed that the cylindrical reconstructions were able to maintain the accuracy of the Cartesian reconstructions. In three dimensions, the cylindrical method provided better accuracy than the Cartesian methods. At the same time, the cylindrical method was able to provide a speedup factor of approximately 40 while also reducing the system matrix storage size by 2 orders of magnitude. Conclusions: TBCT image reconstruction using a cylindrical image grid was able to provide a significant improvement in the reconstruction time and a more compact system matrix for storage on the hard drive and in memory while maintaining the image quality provided by the Cartesian voxelization on a Cartesian grid. PMID:23927323

Kim, Joshua; Ionascu, Dan; Zhang, Tiezhi

2013-01-01

231

Easing The Calculation Of Bolt-Circle Coordinates  

NASA Technical Reports Server (NTRS)

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

Burley, Richard K.

1995-01-01

232

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

233

Magnetohydrodynamic Modeling of Solar System Processes on Geodesic Grids  

NASA Astrophysics Data System (ADS)

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

2013-04-01

234

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

NASA Astrophysics Data System (ADS)

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

Kuczy?ski, Pawe?; Bia?ecki, Ryszard

2014-06-01

235

A Vertical Grid Module for Baroclinic Models of the Atmosphere  

SciTech Connect

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

Drake, John B [ORNL

2008-04-01

236

Safe Grid  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

237

FUTURE POWER GRID INITIATIVE GridOPTICSTM  

E-print Network

FUTURE POWER GRID INITIATIVE GridOPTICSTM : A Software Framework for Power System Operations technologies needed to support the operations and planning of the future power grid » provide a framework for integrating novel new operations and planning technologies with external power grid systems, including energy

238

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

239

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

240

An analysis of a collision situation in polar coordinates  

NASA Astrophysics Data System (ADS)

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

Wolski, Adam; Banachowicz, Andrzej

2014-05-01

241

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.

2014-09-18

242

Random subspaces for encryption based on a private shared Cartesian frame  

SciTech Connect

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

Bartlett, Stephen D. [School of Physics, University of Sydney, New South Wales 2006 (Australia); Hayden, Patrick [School of Computer Science, McGill University, Montreal (Canada); Spekkens, Robert W. [Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 (Canada)

2005-11-15

243

GridMan: A grid manipulation system  

NASA Technical Reports Server (NTRS)

GridMan is an interactive grid manipulation system. It operates on grids to produce new grids which conform to user demands. The input grids are not constrained to come from any particular source. They may be generated by algebraic methods, elliptic methods, hyperbolic methods, parabolic methods, or some combination of methods. The methods are included in the various available structured grid generation codes. These codes perform the basic assembly function for the various elements of the initial grid. For block structured grids, the assembly can be quite complex due to a large number of clock corners, edges, and faces for which various connections and orientations must be properly identified. The grid generation codes are distinguished among themselves by their balance between interactive and automatic actions and by their modest variations in control. The basic form of GridMan provides a much more substantial level of grid control and will take its input from any of the structured grid generation codes. The communication link to the outside codes is a data file which contains the grid or section of grid.

Eiseman, Peter R.; Wang, Zhu

1992-01-01

244

Algebraic grid generation for wing-fuselage bodies  

NASA Technical Reports Server (NTRS)

An algebraic procedure for the generation of boundary-fitted grids about wing-fuselage configurations is presented. A wing-fuselage configuration is specified by cross sections and mathematically represented by Coons' patches. A configuration is divided into sections so that several grid blocks that either adjoin each other or partially overlap each other can be generated, and each grid has six surfaces that map into a computational cube. Grids are first determined on the six boundary surfaces and then in the interior. Grid curves that are on the surface of the configuration are derived using plane-patch intersections, and single-valued functions relating approximate arc lengths along the curves to computational coordinates define the distribution of grid points. The two-boundary technique and transfinite interpolation are used to determine the boundary surface grids that are not on the configuration, and transfinite interpolation with linear blending functions is used to determine the interior grids.

Smith, R. E.; Everton, E. L.; Kudlinski, R. A.

1984-01-01

245

Implicit time-accurate solutions on unstructured dynamic grids  

NASA Astrophysics Data System (ADS)

In this paper an unstructured multigrid algorithm is used as an iterative solution procedure for the discrete equations arising from an implicit time discretization of the unsteady Euler equations on tetrahedral grids. To calculate unsteady flows due to oscillating boundaries, a novel grid movement algorithm is introduced in which an elliptic equation with a non-linear diffusion coefficient is used to define the displacement of interior grid nodes. This allows large grid displacements to be calculated in a single step. The multigrid technique uses an edge-collapsing algorithm to generate a sequence of grids, and a pseudo-time-stepping smoother. On the coarser grids, no grid motion is used. Instead, surface normals are rotated consistently and transfer/interpolation weights are based on the time-averaged grid co-ordinates. A 2D NACA0012 test case is used to validate the programme. 3D results are presented for the M6 wing and a full aircraft configuration.

Crumpton, P. I.; Giles, M. B.

1997-12-01

246

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

247

A Cartesian cut cell method for shallow water flows with moving boundaries  

Microsoft Academic Search

A new computational method for the calculation of shallow water flows with moving physical boundaries is presented. The procedure can cope with shallow water problems having arbitrarily complex geometries and moving boundary elements. Although the method provides a fully boundary-fitted capability, no mesh generation is required in the conventional sense. Solid regions are simply cut out of a background Cartesian

D. M Causon; D. M Ingram; C. G Mingham

2001-01-01

248

GENERIC POINTS IN THE CARTESIAN POWERS OF THE MORSE DYNAMICAL SYSTEM  

E-print Network

GENERIC POINTS IN THE CARTESIAN POWERS OF THE MORSE DYNAMICAL SYSTEM by Emmanuel Lesigne, Anthony Quas & M´at´e Wierdl Abstract. -- The symbolic dynamical system associated with the Morse sequence in the fourth power of the system, but not in lower powers. We exhibit various examples and counterexamples

Quas, Anthony

249

FLUTTER PREDICTION BY A CARTESIAN MESH EULER METHOD WITH SMALL PERTURBATION GRIDLESS BOUNDARY CONDITIONS  

E-print Network

FLUTTER PREDICTION BY A CARTESIAN MESH EULER METHOD WITH SMALL PERTURBATION GRIDLESS BOUNDARY of California, Irvine Abstract A method for the prediction of transonic flutter by the Euler equations for efficient and accurate solution of transient problems in which surface deflections are small (i.e. flutter

Liu, Feng

250

Juan Huarte de San Juan in cartesian and modern psycholinguistics: an encounter with Noam Chomsky  

Microsoft Academic Search

This article presents Noam Chomsky's standpoint on the relevance of Juan Huarte de San Juan's work Examen de ingenios para las ciencias (The Examination of Men's Wits, 1575-1594) for Cartesian lin- guistics and cognitive science. Huartian conceptions relevant to psycholinguistics and to Chomskian generativism include: (a) the generative quality of human understanding, (b) qualitative differences between human and animal capacity,

Javier Virués Ortega

2005-01-01

251

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

252

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

E-print Network

A Cartesian Robot for RFID Signal Distribution Model Verification Aliasgar Kutiyanawala instrumentation cost, i.e., a minimum number of surface-embedded passive RFID transponders. Our previous results were based on the assumption that the signal distribution model of an individual RFID transponder can

Kulyukin, Vladimir

253

Relative end-effector control using Cartesian position based visual servoing  

Microsoft Academic Search

This paper presents a complete design methodology for Cartesian position based visual servo control for robots with a single camera mounted at the end-effector. Position based visual servo control requires the explicit calculation of the relative position and orientation (POSE) of the workpiece object with respect to the camera. This is accomplished using image plane measurements of a number of

William J. Wilson; Carol C. Williams Hulls; Graham S. Bell

1996-01-01

254

Advanced Techniques for the Creation and Propagation of Modules in Cartesian Genetic Programming  

E-print Network

Advanced Techniques for the Creation and Propagation of Modules in Cartesian Genetic Programming The choice of an appropriate hardware representation model is key to successful evolution of digital circuits. A recent approach towards scalable hardware evolution is based on the automated cre- ation of modules from

Fernandez, Thomas

255

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

Microsoft Academic Search

The purpose of this work is the development and testing of a new family of methods for calculating the spatial dependence of the neutron density in nuclear systems described in two-dimensional Cartesian geometry. The energy and angular dependence of the neutron density is approximated using the multigroup and discrete ordinates techniques respectively. The basic approach is to (1) approximate the

Pevey

1982-01-01

256

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

Microsoft Academic Search

The purpose of this work is the development and testing of a new family of methods for calculating the spatial dependence of the neutron density in nuclear systems described in two-dimensional Cartesian geometry. The energy and angular dependence of the neutron density is approximated using the multigroup and discrete ordinates techniques, respectively. The resulting FORTRAN computer code is designed to

Pevey

1982-01-01

257

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

258

GridDaen: A Data Grid Engine  

Microsoft Academic Search

The volume of datasets in scie ntific computing domain is increasing ex- plosively and data is becoming the center of scientific computing. Data Grid is an emerging technology to provide uniform access and management of the large scale distributed scientific datasets. In this paper, the GridDaen system, a new Data Grid middleware, which provides uniform APIs and GUI to access

Nong Xiao; Dongsheng Li; Wei Fu; Bin Huang; Xicheng Lu

2003-01-01

259

A distributed control framework for smart grid development: Energy\\/water system optimal operation and electric grid integration  

Microsoft Academic Search

In this work, we propose a conceptual distributed control framework for electrical grid integrated with distributed renewable energy generation systems in order to enable the development of the so-called “smart electrical grid”. First, we introduce the key elements and their interactions in the proposed control architecture and discuss the design of the distributed control systems which are able to coordinate

Wei Qi; Jinfeng Liu; Panagiotis D. Christofides

2011-01-01

260

Symplectic integration of closed chain rigid body dynamics with internal coordinate equations of motion  

NASA Astrophysics Data System (ADS)

Internal coordinate molecular dynamics (ICMD) is a recent efficient method for modeling polymer molecules which treats them as chains of rigid bodies rather than ensembles of point particles as in Cartesian MD. Unfortunately, it is readily applicable only to linear or tree topologies without closed flexible loops. Important examples violating this condition are sugar rings of nucleic acids, proline residues in proteins, and also disulfide bridges. This paper presents the first complete numerical solution of the chain closure problem within the context of ICMD. The method combines natural implicit fixation of bond lengths and bond angles by the choice of internal coordinates with explicit constraints similar to Cartesian dynamics used to maintain the chain closure. It is affordable for large molecules and makes possible 3-5 times faster dynamics simulations of molecular systems with flexible rings, including important biological objects like nucleic acids and disulfide-bonded proteins.

Mazur, Alexey K.

1999-07-01

261

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

262

Development of Mathematical Concepts of Two-Dimensional Space in Grid Environments: An Exploratory Study.  

ERIC Educational Resources Information Center

Investigated the development among fourth-graders of two-dimensional space concepts within a mathematics unit on grids, coordinates, and rectangles. Found that students' knowledge of grid and coordinate systems related to levels of competence in number sense, spatial-geometric relationships, and the ability to discriminate and integrate the two…

Sarama, Julie; Clements, Douglas H.; Swaminathan, Sudha; McMillen, Sue; Gonzalez Gomez, Rosa M.

2003-01-01

263

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

264

Grid generation and its application to separated flows  

NASA Technical Reports Server (NTRS)

A method for the computation of recirculating flows on a nonorthogonal boundary-fitted coordinate system is presented. The algebraic grid generation technique is used to generate grids in a flow field of arbitrary shape. Computations are performed by using the set of governing equations transformed for use on a generalized curvilinear coordinate system. Turbulent flow computations were made by using the k-epsilon model for most of the flow cases. Three pressure correction algorithms - SIMPLE, SIMPLEC, and PISO - were incorporated for use on a nonorthogonal grid. Comparisons were made on the basis of numerical stability and accuracy. The present method was found to be efficient for computations of recirculating flows.

Maruszewski, J. P.; Amano, R. S.

1992-01-01

265

Grid Coverage for Surveillance and Target Location in Distributed Sensor Networks  

Microsoft Academic Search

We present novel grid coverage strategies for effective surveillance and target location in distributed sensor networks. We represent the sensor field as a grid (two or three-dimensional) of points (coordinates) and use the term target location to refer to the problem of locating a target at a grid point at any instant in time. We first present an integer linear

Krishnendu Chakrabarty; S. Sitharama Iyengar; Hairong Qi; Eungchun Cho

2002-01-01

266

Parallel Grid Manipulations in Earth Science Calculations  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

267

Vertical Scan (V-SCAN) for 3-D Grid Adaptive Mesh Refinement for an atmospheric Model Dynamical Core  

Microsoft Academic Search

One of the major building blocks of a rigorous representation of cloud evolution in global atmospheric models is a parallel adaptive grid MPI-based communication library (an Adaptive Blocks for Locally Cartesian Topologies library -- ABLCarT), which manages the block-structured data layout, handles ghost cell updates among neighboring blocks and splits a block as refinements occur. The library has several modules

N. G. Andronova; D. Vandenberg; R. Oehmke; Q. F. Stout; J. E. Penner

2009-01-01

268

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

269

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

270

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

271

Exploring predistortion training algorithms in a Cartesian feedback-trained digital predistortion system for RF power amplifier linearization  

E-print Network

A Cartesian feedback-trained digital predistortion system for RF power amplifier linearization offers many advantages with its combination of two different linearization techniques. This thesis describes such a system, ...

Huang, Jeffrey B

2006-01-01

272

Augmented Lagrangian with variable splitting for faster non-Cartesian L1-SPIRiT MR image reconstruction.  

PubMed

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

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

2014-02-01

273

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

274

(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

275

(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

276

A spectral nodal method for one-group X,Y,Z-cartesian geometry discrete ordinates problems  

Microsoft Academic Search

The solution of one-group discrete ordinates SN problems with linearly anisotropic scattering in x, y, z - cartesian geometry has been studied by using SGF-CN “spectral Green's function-constant nodal’ method, developed first by De Barros and Larsen (1990–1992) for one dimensional and two dimensional x, y - cartesian geometries. The solutions of SN transverse - integrated nodal equations in which

F. Anli; S. Güngör

1996-01-01

277

An adaptive grid method for computing the high speed 3D viscous flow about a re-entry vehicle  

NASA Technical Reports Server (NTRS)

An algebraic solution adaptive grid generation method that allows adapting the grid in all three coordinate directions is presented. Techniques are described that maintain the integrity of the original vehicle definition for grid point movement on the vehicle surface and that avoid grid cross over in the boundary layer portion of the grid lying next to the vehicle surface. The adaptive method is tested by computing the Mach 6 hypersonic three dimensional viscous flow about a proposed Martian entry vehicle.

Bockelie, Michael J.; Smith, Robert E.

1992-01-01

278

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

279

caGrid: design and implementation of the core architecture of the cancer biomedical informatics grid  

Microsoft Academic Search

Motivation: The complexity of cancer is prompting researchers to find new ways to synthesize information from diverse data sources and to carry out coordinated research efforts that span multiple institutions. There is a need for standard applications, common data models, and softwareinfrastructuretoenablemoreefficientaccesstoandsharingof distributedcomputationalresourcesincancerresearch.Toaddressthis need the National Cancer Institute (NCI) has initiated a national-scale effort, called the cancer Biomedical Informatics Grid

Joel H. Saltz; Scott Oster; Shannon Hastings; Stephen Langella; Tahsin M. Kurç; William Sanchez; Manav Kher; Arumani Manisundaram; Krishnakant Shanbhag; Peter A. Covitz

2006-01-01

280

Noniterative three-dimensional grid generation using parabolic partial differential equations  

NASA Technical Reports Server (NTRS)

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

Edwards, T. A.

1985-01-01

281

Grid Computing Portals Lecture  

NSDL National Science Digital Library

Grid Computing Lecture~~Grid portals: purpose, application-based portals, historical examples, GPDK, Gridport, etc., OGCE2/gridsphere portal, portal implementation, portlets, JSR 168, portlet source and deployment files.

Ferner, Clayton; Wilkinson, Barry

2011-07-05

282

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

283

Off the Grid  

NSDL National Science Digital Library

Students learn and discuss the advantages and disadvantages of renewable and non-renewable energy sources. They also learn about our nation's electric power grid and what it means for a residential home to be "off the grid."

Integrated Teaching And Learning Program

284

Smart Power Grid  

NSDL National Science Digital Library

This video segment adapted from NOVA scienceNOW provides an overview of the existing United States power grid, and envisions a smart power grid that would prevent problems, such as blackouts, and reduce energy waste and pollution.

WGBH Educational Foundation

2011-03-31

285

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

NASA Astrophysics Data System (ADS)

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

Hamilton, Nicholas; Cal, Raúl Bayoán

2015-01-01

286

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

287

Grid Computing Lecture - Globus 4.0 grid services  

NSDL National Science Digital Library

Grid Computing Lecture~~Globus 4.0 grid services: Using Web services for grid computing, stateful web services, Grid computing standards, Open Grid Services Architecture (OGSA), Web Services Resource Framework (WSRF), programming GT 4.0 grid services, GT 4.0 container.

Ferner, Clayton; Wilkinson, Barry

2011-07-05

288

Interactive grid adaption  

NASA Technical Reports Server (NTRS)

An interactive grid adaption method is developed, discussed and applied to the unsteady flow about an oscillating airfoil. The user is allowed to have direct interaction with the adaption of the grid as well as the solution procedure. Grid points are allowed to adapt simultaneously to several variables. In addition to the theory and results, the hardware and software requirements are discussed.

Abolhassani, Jamshid S.; Everton, Eric L.

1990-01-01

289

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

290

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

291

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

292

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

293

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

PubMed

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

Omar, Mohamed A

2014-01-01

294

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

PubMed Central

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

Omar, Mohamed A.

2014-01-01

295

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

296

Grid quality improvement by a grid adaptation technique  

NASA Technical Reports Server (NTRS)

A grid adaptation technique is presented which improves grid quality. The method begins with an assessment of grid quality by defining an appropriate grid quality measure. Then, undesirable grid properties are eliminated by a grid-quality-adaptive grid generation procedure. The same concept has been used for geometry-adaptive and solution-adaptive grid generation. The difference lies in the definition of the grid control sources; here, they are extracted from the distribution of a particular grid property. Several examples are presented to demonstrate the versatility and effectiveness of the method.

Lee, K. D.; Henderson, T. L.; Choo, Y. K.

1991-01-01

297

Navigation in Grid Space with the NAS Grid Benchmarks  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

298

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

299

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

300

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

NASA Technical Reports Server (NTRS)

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

Aldridge, Hal A.; Juang, Jer-Nan

1997-01-01

301

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

302

From Cartesian to polar: a new POLICRYPS geometry for realizing circular optical diffraction gratings.  

PubMed

We report on the realization of a liquid crystal (LC)-based optical diffraction grating showing a polar symmetry of the director alignment. This has been obtained as a natural evolution of the POLICRYPS technique, which enables the realization of highly efficient, switchable, planar diffraction gratings. Performances exhibited in the Cartesian geometry are extended to the polar one by exploiting the spherical aberration produced by simple optical elements. This enables producing the required highly stable polar pattern that allows fabricating a circular optical diffraction grating. Results are promising for their possible application in fields in which a rotational structure of the optical beam is needed. PMID:25361314

Alj, Domenico; Caputo, Roberto; Umeton, Cesare

2014-11-01

303

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

304

Cartesian Diver  

NSDL National Science Digital Library

In this demonstration, learners observe the effects of density and pressure. A "diver" constructed out of a piece of straw and Blu-Tack will bob inside a bottle filled with water. This highly visual demonstration works best when learners can try moving the diver up and down themselves. This activity can also be related to how animals, like whales, dive in deep waters. This activity guide includes a helpful video that demonstrates each step of the demonstration.

Physics, Institute O.

2012-06-26

305

Cartesian Divers  

NSDL National Science Digital Library

This activity gives students a hands-on look at the effects of increased water pressure and shows them how submarines work. Using a balloon and plastic water bottle, students create a neutrally buoyant diver. Then they squeeze the bottle to see how increased pressure compresses the balloon, making it heavier and causing it to sink. The activity includes an extension that has students further explore how animals use their swim bladders to dive and rise. Students can find out with a balloon and a bottle of water how a submarine, which is buoyant to start with, becomes heavier and dives down into the water.

306

Let's Learn Coordinates  

NSDL National Science Digital Library

Locate the Aliens or Help the Robot by understanding the four quadrants and the coordinates. Locate the Aliens By understanding the coordinates and quadrants, find the aliens. Direct the Robot Through the Maze Use your quadrant and coordinate knowledge to guide the Robot. Billy Bug s Quest for Grub Help Billy get to the right coordinates to feed. ...

Clark, Mr

2012-10-31

307

Improved representation of topographic effects by a vertical adaptive grid in Vector-Ocean-Model (VOM). Part II: Simulations in unstructured adaptive grids  

NASA Astrophysics Data System (ADS)

A static adaptive grid approximates the topography and defines the vertical resolution in Vector-Ocean-Model (VOM). The adaptation to topography creates unstructured grids, which are organised in a one-dimensional vector by column-wise storage of only wet cells. The model's name reflects this data structure. The intention of VOM is better resolving flow and stratification near topographic boundaries in Z-coordinates. This is the second part of a publication that describes the generation of adaptive grids (part I), and simulations with VOM in unstructured grids (this part). Adaptive grids generated for a synthetic topography in part I include shelf, continental slope, and ocean. Three of those grids are here utilised in upwelling simulations. Under the same forcing increased vertical resolution at seabed and slopes yields a significant increase in flow energy as compared to coarser grids. Results allow explaining the surface intensification of a continental slope jet by vertical displacements of water masses in the seabed Ekman layer. Results in unstructured grids are almost identical to reference simulations in equidistant grids where the respective smallest grid size of unstructured grids was used. Negative effects of grids on predicted flow and stratification are absent also over particularly rough topography, as demonstrated by using vertical velocity as most sensitive indicator. In a further simulation an overflow governed by the advection of water mass properties is presented to demonstrate the conservation properties of the model. After 5 months of simulation the predicted domain average temperature deviated by 10 -8 from the initial temperature field. Compared to equidistant grids the advection/diffusion scheme looses about one order of magnitude in accuracy when used in an unstructured grid. The results of VOM, being defined in Z-coordinates, are void of coordinate transformation errors. In an arbitrary topography unforced zero-flow remains quiescent in a stratification that only varies in the vertical. VOM due to its depth-independent vertical resolution appears particularly suitable for simulations of ocean-shelf exchange.

Backhaus, Jan O.; Harms, Ingo; Hübner, Udo

308

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

309

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

310

World Community Grid  

NSDL National Science Digital Library

Hosted by IBM, the World Community Grid is an ambitious public-computing network developed to bolster humanitarian research around the world. The Grid gains its power through a vast network of computers, all contributing small pieces to large research projects while they are idle. At present the Grid is supporting the Institute for Systems Biology's Human Proteome Folding Project, which will ultimately contribute to disease prevention by developing a greater understanding of the shapes of human proteins. In addition to information about this ongoing project, the Grid website contains downloadable Request for Proposals documents, and a section for Project Archives. The site also provides simple instructions for joining the Grid; several online forums; and Grid statistics including current member totals.

311

The Swiss ATLAS Grid  

Microsoft Academic Search

In this paper the technical solutions, the usage and the future development of the Swiss ATLAS Grid are presented. In 2009\\u000a the Swiss ATLAS Grid consists of four clusters with about 2000 shared computing cores and about 250 TB of disk space. It is\\u000a based on middlewares provided by the NorduGrid Collaboration and the EGEE project. It supports multiple virtual

Eric Cogneras; Szymon Gadomski; Sigve Haug; Peter Z. Kunszt; Sergio Maffioletti; Riccardo Murri; Cyril Topfel

2009-01-01

312

Grid Graph Reachability Problems  

Microsoft Academic Search

We study the complexity of restricted versions ofst- connectivity, which is the standard complete problem for NL. Grid graphs are a useful tool in this regard, since reachability on grid graphs is logspace-equivalent to reachability in general planar digraphs, and reachability on certain classes of grid graphs gives natural examples of problems that are hard forNC1 underAC0 reductions but are

Eric Allender; David A. Mix; Barringtony Tanmoy; Sambuddha Roy

313

Grids, Clouds, and Virtualization  

Microsoft Academic Search

\\u000a This chapter introduces and puts in context Grids, Clouds, and Virtualization. Grids promised to deliver computing power on\\u000a demand. However, despite a decade of active research, no viable commercial grid computing provider has emerged. On the other\\u000a hand, it is widely believed—especially in the Business World—that HPC will eventually become a commodity. Just as some commercial\\u000a consumers of electricity have

Massimo Cafaro; Giovanni Aloisio

2011-01-01

314

Grid Computing Security Lecture  

NSDL National Science Digital Library

Grid Computing Lecture~~Security: secure connection, authentication and authorization, password authentication, symmetric (secret) and asymmetric (public/private) key cyptography, RSA algorithm.

Ferner, Clayton; Wilkinson, Barry

2011-07-05

315

Algebraic grid generation about wing-fuselage bodies  

NASA Technical Reports Server (NTRS)

An algebraic procedure for the generation of boundary-fitted grids about wing-fuselage configurations is presented. A wing-fuselage configuration is specified by cross sections and mathematically represented by Coons' patches. A configuration is divided into sections so that several grid blocks that either adjoin each other or partially overlap each other can be generated. Each grid has six exterior surfaces that map into a computational cube. Grids are first determined on the six boundary surfaces and then in the interior. Grid curves that are on the surface of the configuration are derived from the intersection of planes with the Coons' patch definition. Single-valued functions relating approximate arc lengths along the grid curves to a computational coordinate define the distribution of grid points. The two-boundary technique and transfinite interpolation are used to determine the boundary surface grids that are not on the configuration, and transfinite interpolation with linear blending functions is used to determine the interior grid.

Smith, R. E.

1986-01-01

316

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

317

Flexible Residential Smart Grid Simulation Framework  

NASA Astrophysics Data System (ADS)

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

Xiang, Wang

318

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

319

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

320

The Grid Economy  

Microsoft Academic Search

This work identifies challenges in managing resources in a Grid computing environment and proposes computational economy as a metaphor for effective management of resources and application scheduling. It identifies distributed resource management challenges and requirements of economy-based Grid systems, and discusses various representative economy-based systems, both historical and emerging, for cooperative and competitive trading of resources such as CPU cycles,

RAJKUMAR BUYYA; DAVID ABRAMSON; SRIKUMAR VENUGOPAL

2005-01-01

321

Grid Graph Reachability Problems  

Microsoft Academic Search

We study the complexity of reachability problems on various classes of grid graphs. Reachability on certain classes of grid graphs gives natural examples of problems that are hard for NC1 under AC0 reductions but are not known to be hard far L; they thus give insight into the structure of L. In addition to explicating the structure of L, another

Eric Allender; David A. Mix Barrington; Tanmoy Chakraborty; Samir Datta; Sambuddha Roy

2006-01-01

322

Grid Database Service Specification  

Microsoft Academic Search

Data management systems are central to many applications across multiple domains, and play a significant role in many others. Web services provide implementation neutral facilities for describing, invoking and orchestrating collections of networked resources. The Open Grid Services Architecture (OGSA) extends Web Services with consistent interfaces for creating, managing and exchanging information among Grid Services, which are dynamic computational artefacts

James Clerk Maxwell; Susan Malaika; Gavin McCance; James Magowan; Norman W. Paton; Greg Riccardi

2002-01-01

323

Decentral Smart Grid Control  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

324

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

325

Modeling and Simulation of the EV Charging in a Residential Distribution Power Grid  

E-print Network

and coordinate the EV charging locally and at the substation level to mitigate the impact of EV charging from to shape the peak load of EV charging in the smart grid. Authors in [7] delayed the EV charging schedule

Al Faruque, Mohammad Abdullah

326

Data Grid Implementations  

SciTech Connect

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

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

2002-02-27

327

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

328

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

329

Fibonacci (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 Klavzar 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 simultaneously gen- eralize several interconnection networks, notably hypercubes, Fibonacci cubes, and postal

Klavzar, Sandi

330

Fibonacci (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 Klavzar 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 generalize several interconnection networks, notably hypercubes, Fibonacci cubes, and postal networks

Klavzar, Sandi

331

MultiStencils Fast Marching Methods: A Highly Accurate Solution to the Eikonal Equation on Cartesian Domains  

Microsoft Academic Search

A wide range of computer vision applications require an accurate solution of a particular Hamilton-Jacobi (HJ) equation known as the Eikonalequation. In this paper, we propose an improved version of the fast marching method (FMM) that is highly accurate for both 2D and 3D Cartesian domains. The new method is called multistencils fast marching (MSFM), which computes the solution at

M. Sabry Hassouna; Aly A. Farag

2007-01-01

332

The application of spectral nodal methods to discrete ordinates and diffusion problems in Cartesian geometry for neutron multiplying systems  

Microsoft Academic Search

We describe in this paper the recent advances in spectral nodal methods applied to discrete ordinates (SN) and diffusion problems in Cartesian geometry for neutron multiplying systems. We divide this paper into three major parts. Part I and II deal with SN and diffusion eingenvalue problems. In Part III we describe the progress of spectral nodal methods applied to time-dependent

Dany S. Dominguez; Carlos R. G. Hernández

2003-01-01

333

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

334

Validation of Inlet and Exhaust Boundary Conditions for a Cartesian Method  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

335

DOMINO: A fast 3D cartesian discrete ordinates solver for reference PWR simulations and SPN validation  

SciTech Connect

As part of its activity, EDF R and D is developing a new nuclear core simulation code named COCAGNE. This code relies on DIABOLO, a Simplified PN (SPN) method to compute the neutron flux inside the core for eigenvalue calculations. In order to assess the accuracy of SPN calculations, we have developed DOMINO, a new 3D Cartesian SN solver. The parallel implementation of DOMINO is very efficient and allows to complete an eigenvalue calculation involving around 300 x 10{sup 9} degrees of freedom within a few hours on a single shared-memory supercomputing node. This computation corresponds to a 26-group S{sub 8} 3D PWR core model used to assess the SPN accuracy. At the pin level, the maximal error for the SP{sub 5} DIABOLO fission production rate is lower than 0.2% compared to the S{sub 8} DOMINO reference for this 3D PWR core model. (authors)

Courau, T.; Moustafa, S.; Plagne, L.; Poncot, A. [EDF R and D, 1, Av du General de Gaulle, F92141 Clamart cedex (France)

2013-07-01

336

Ion-ion collision dynamics in two-dimensional Cartesian space  

SciTech Connect

Ion-ion collision dynamics are studied by direct solution of the time-dependent Schroedinger and Dirac equations on a two-dimensional Cartesian lattice. The time-dependent Dirac equation is solved in both its two- and four-component forms using difference offsetting on the lattice to mitigate the fermion doubling pathology. For Pd{sup 46+} on Pd{sup 45+}, which energetically corresponds to U{sup 92+} on U{sup 91+} in a three-dimensional space, total inelastic probabilities are calculated at a fixed ion velocity and several impact parameters. In this intermediate energy range, the total inelastic probabilities from the Schroedinger and two- and four-component Dirac equations are in reasonable agreement, although the detailed collision dynamics reveal interesting differences. (c) 2000 The American Physical Society.

Pindzola, M. S. [Department of Physics, Auburn University, Auburn, Alabama 36849 (United States)] [Department of Physics, Auburn University, Auburn, Alabama 36849 (United States)

2000-09-01

337

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

338

An exponential discontinuous scheme for discrete-ordinate calculations in Cartesian geometries  

SciTech Connect

We describe a new nonlinear spatial differencing scheme for solving the discrete-ordinate transport equations, called the exponential discontinuous (ED) scheme in one, two and three dimensional Cartesian geometries. The ED scheme is much easier to derive and less computationally expensive than the recently developed nonlinear characteristic (NC) scheme and is nearly as accurate for deep penetration shielding problems. Like the nonlinear characteristic scheme, the exponential discontinuous scheme produces strictly positive angular fluxes given positive discrete-ordinate sources. However, the ED scheme can be less accurate than even the linear discontinuous (LD) scheme for certain types of problems. Numerical results are provided to show the accuracy and positivity of the ED scheme.

Wareing, T.A.

1997-10-01

339

Non-relativistic model of the laws of gravitation and electromagnetism, invariant under the change of inertial and non-inertial coordinate systems  

E-print Network

Under the classical non-relativistic consideration of the space-time we propose the model of the laws of gravitation and Electrodynamics, invariant under the galilean transformations and moreover, under every change of non-inertial cartesian coordinate system. Being in the frames of non-relativistic model of the space-time, we adopt some general ideas of the General Theory of Relativity, like the assumption of covariance of the most general physical laws in every inertial and non-inertial coordinate system and equivalence of factious forces in non-inertial coordinate systems and the force of gravitation.

Poliakovsky, Arkady

2015-01-01

340

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

341

Finite-surface method for the Maxwell equations in generalized coordinates  

NASA Technical Reports Server (NTRS)

A finite-surface technique for the Maxwell equations in generalized nonorthogonal coordinates is developed. It directly applies the integral Faraday's and Ampere's laws to faces of primary and secondary grid cells, respectively. The technique features an accurate treatment of matching conditions at a material interface, grid singularities, and radiation conditions at outer boundaries.

Vinokur, Marcel; Yarrow, Maurice

1993-01-01

342

Accurate American Option Pricing by Grid Stretching and High Order Finite Differences  

E-print Network

Accurate American Option Pricing by Grid Stretching and High Order Finite Differences Cornelis W as a grid stretching in space by means of an analytic coordinate transformation. This transformation is made time-dependent for pricing American options following the optimal exercise boundary. Numerical pricing

Vuik, Kees

343

Trends in life science grid: from computing grid to knowledge grid  

PubMed Central

Background Grid computing has great potential to become a standard cyberinfrastructure for life sciences which often require high-performance computing and large data handling which exceeds the computing capacity of a single institution. Results This survey reviews the latest grid technologies from the viewpoints of computing grid, data grid and knowledge grid. Computing grid technologies have been matured enough to solve high-throughput real-world life scientific problems. Data grid technologies are strong candidates for realizing "resourceome" for bioinformatics. Knowledge grids should be designed not only from sharing explicit knowledge on computers but also from community formulation for sharing tacit knowledge among a community. Conclusion Extending the concept of grid from computing grid to knowledge grid, it is possible to make use of a grid as not only sharable computing resources, but also as time and place in which people work together, create knowledge, and share knowledge and experiences in a community. PMID:17254294

Konagaya, Akihiko

2006-01-01

344

Movement coordination during conversation.  

PubMed

Behavioral coordination and synchrony contribute to a common biological mechanism that maintains communication, cooperation and bonding within many social species, such as primates and birds. Similarly, human language and social systems may also be attuned to coordination to facilitate communication and the formation of relationships. Gross similarities in movement patterns and convergence in the acoustic properties of speech have already been demonstrated between interacting individuals. In the present studies, we investigated how coordinated movements contribute to observers' perception of affiliation (friends vs. strangers) between two conversing individuals. We used novel computational methods to quantify motor coordination and demonstrated that individuals familiar with each other coordinated their movements more frequently. Observers used coordination to judge affiliation between conversing pairs but only when the perceptual stimuli were restricted to head and face regions. These results suggest that observed movement coordination in humans might contribute to perceptual decisions based on availability of information to perceivers. PMID:25119189

Latif, Nida; Barbosa, Adriano V; Vatiokiotis-Bateson, Eric; Castelhano, Monica S; Munhall, K G

2014-01-01

345

The open science grid  

SciTech Connect

The U.S. LHC Tier-1 and Tier-2 laboratories and universities are developing production Grids to support LHC applications running across a worldwide Grid computing system. Together with partners in computer science, physics grid projects and active experiments, we will build a common national production grid infrastructure which is open in its architecture, implementation and use. The Open Science Grid (OSG) model builds upon the successful approach of last year's joint Grid2003 project. The Grid3 shared infrastructure has for over eight months provided significant computational resources and throughput to a range of applications, including ATLAS and CMS data challenges, SDSS, LIGO, and biology analyses, and computer science demonstrators and experiments. To move towards LHC-scale data management, access and analysis capabilities, we must increase the scale, services, and sustainability of the current infrastructure by an order of magnitude or more. Thus, we must achieve a significant upgrade in its functionalities and technologies. The initial OSG partners will build upon a fully usable, sustainable and robust grid. Initial partners include the US LHC collaborations, DOE & NSF Laboratories and Universities & Trillium Grid projects. The approach is to federate with other application communities in the U.S. to build a shared infrastructure open to other sciences and capable of being modified and improved to respond to needs of other applications, including CDF, D0, BaBar, and RHIC experiments. We describe the application-driven, engineered services of the OSG, short term plans and status, and the roadmap for a consortium, its partnerships and national focus.

Pordes, R.; /Fermilab

2004-12-01

346

76 FR 1153 - Atlantic Grid Operations A LLC, Atlantic Grid Operations B LLC, Atlantic Grid Operations C LLC...  

Federal Register 2010, 2011, 2012, 2013, 2014

...OF ENERGY Federal Energy Regulatory Commission [Docket No. EL11-13-000] Atlantic Grid Operations A LLC, Atlantic Grid Operations B LLC, Atlantic Grid Operations C LLC, Atlantic Grid Operations D LLC and Atlantic Grid Operations E...

2011-01-07

347

The TeraGrid  

NSDL National Science Digital Library

A project of the National Science Foundation, the TeraGrid is "a multi-year effort to build and deploy the world's largest, fastest, distributed infrastructure for open scientific research." This paper, published in September 2002, describes the activities and ongoing projects that will ultimately lead to the project's completion. TeraGrid, as the name implies, is based on principles of grid computing. It will eventually consist of a massive network of computers spread out over several sites that can work simultaneously and independently on scientific applications. Many specifications and design objectives are outlined in the paper, offering some insight into the ambitious project.

Catlett, Charlie.

2002-01-01

348

Parallel grid library for rapid and flexible simulation development  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

349

What is the grid? a three point checklist  

Microsoft Academic Search

Grids have moved from the obscurely academic to the highly popular. We read about Compute Grids, Data Grids, Science Grids, Access Grids, Knowledge Grids, Bio Grids, Sensor Grids, Cluster Grids, Campus Grids, Tera Grids, and Commodity Grids. The skeptic can be forgiven for wondering if there is more to the Grid than, as one wag put it, a \\

I. Foster

2002-01-01

350

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

351

Geometric Computations by Broadcasting Automata on the Integer Grid  

E-print Network

-oriented grid environment. The method is based on the generation of nodal patterns in the environment via sequences of discrete waves. The power of the primitives is illustrated by giv- ing solutions to two. This leads to the question of how to co-ordinate these robots in their task whilst retaining their simplicity

Potapov, Igor

352

The coordinator and coordinator programming language (COPL)  

SciTech Connect

As parallel architectures become more specialized for specific purposes, a distributed system with a network of heterogeneous parallel architectures will be very effective in order to satisfy a variety of parallel computational needs. Because such a system may be both complex and diverse, we cannot expect a homogeneous operating system to take care of all the heterogeneity of the proposed network and the related massive parallelism. The coordinator is defined as a system layer between the operating system and applications, and a common homogeneous interface is provided for users through heterogeneous coordinator services built on heterogeneous operating system kernels which provide a basic set of functions. The coordinator is a hierarchical system which manages jobs/processes/processors and may be based on a variety of implementation strategies. A new concurrent programming language, COPL (COordinator Programming Language), suitable for programming hierarchical resource management systems, was designed as a vehicle to implement the coordinator. COPL can be used effectively for concurrent programming in a combination of shared-memory-based multiprocessing and distributed processing without shared memory.

Jung, Cul-Doo.

1988-01-01

353

Generation of orthogonal grids by boundary grid relaxation  

NASA Technical Reports Server (NTRS)

Two elliptic grid generation schemes that yield orthogonal grids are presented (FGBR and UBGR). With the UBGR scheme, the grid points on the flow boundaries are automatically determined by the algorithm, while the FBGR scheme at most one half of the boundary grid points may be prespecified and the remainder of boundary grid points are determined automatically. Numerical examples show their capability of easy stretching, clustering and shock fitting while maintaining orthogonality of grid. The present method can be implemented into existing elliptic grid generation programs with relatively minor modifications.

Nakamura, S.

1983-01-01

354

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

355

Using Grid Benchmarks for Dynamic Scheduling of Grid Applications  

NASA Technical Reports Server (NTRS)

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

Frumkin, Michael; Hood, Robert

2003-01-01

356

Three-dimensional adaptive coordinate transformations for the Fourier modal method.  

PubMed

The concepts of adaptive coordinates and adaptive spatial resolution have proved to be a valuable tool to improve the convergence characteristics of the Fourier Modal Method (FMM), especially for metallo-dielectric systems. Yet, only two-dimensional adaptive coordinates were used so far. This paper presents the first systematic construction of three-dimensional adaptive coordinate and adaptive spatial resolution transformations in the context of the FMM. For that, the construction of a three-dimensional mesh for a periodic system consisting of two layers of mutually rotated, metallic crosses is discussed. The main impact of this method is that it can be used with any classic FMM code that is able to solve the large FMM eigenproblem. Since the transformation starts and ends in a Cartesian mesh, only the transformed material tensors need to be computed and entered into an existing FMM code. PMID:24515140

Küchenmeister, Jens

2014-01-27

357

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

358

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.

359

Space Development Grid Portal  

NASA Technical Reports Server (NTRS)

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

Vaziri, Arsi

2004-01-01

360

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

361

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

362

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

363

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

364

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

365

A Java commodity grid kit  

Microsoft Academic Search

In this paper we report on the features of the Java Commodity Grid Kit. The Java CoG Kit provides middleware for accessing Grid functionality from the Java framework. Java CoG Kit middleware is general enough to design a variety of advanced Grid applications with quite different user requirements. Access to the Grid is established via Globus protocols, allowing the Java

Gregor Von Laszewski; Ian T. Foster; Jarek Gawor

2001-01-01

366

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

367

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

368

Generalized harmonic spatial coordinates and hyperbolic shift conditions  

E-print Network

We propose a generalization of the condition for harmonic spatial coordinates analogous to the generalization of the harmonic time slices introduced by Bona et al., 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 blow-ups. Finally, we perform a series of numerical experiments to illustrate the behavior of this shift condition.

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

2005-10-24

369

Basal Ganglia Outputs Map Instantaneous Position Coordinates during Behavior.  

PubMed

The basal ganglia (BG) are implicated in many movement disorders, yet how they contribute to movement remains unclear. Using wireless in vivo recording, we measured BG output from the substantia nigra pars reticulata (SNr) in mice while monitoring their movements with video tracking. The firing rate of most nigral neurons reflected Cartesian coordinates (either x- or y-coordinates) of the animal's head position during movement. The firing rates of SNr neurons are either positively or negatively correlated with the coordinates. Using an egocentric reference frame, four types of neurons can be classified: each type increases firing during movement in a particular direction (left, right, up, down), and decreases firing during movement in the opposite direction. Given the high correlation between the firing rate and the x and y components of the position vector, the movement trajectory can be reconstructed from neural activity. Our results therefore demonstrate a quantitative and continuous relationship between BG output and behavior. Thus, a steady BG output signal from the SNr (i.e., constant firing rate) is associated with the lack of overt movement, when a stable posture is maintained by structures downstream of the BG. Any change in SNr firing rate is associated with a change in position (i.e., movement). We hypothesize that the SNr output quantitatively determines the direction, velocity, and amplitude of voluntary movements. By changing the reference signals to downstream position control systems, the BG can produce transitions in body configurations and initiate actions. PMID:25673860

Barter, Joseph W; Li, Suellen; Sukharnikova, Tatyana; Rossi, Mark A; Bartholomew, Ryan A; Yin, Henry H

2015-02-11

370

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

371

Integrating Renewable Electricity on the Grid  

NASA Astrophysics Data System (ADS)

The demand for carbon-free electricity is driving a growing movement of adding renewable energy to the grid. Renewable Portfolio Standards mandated by states and under consideration by the federal government envision a penetration of 20-30% renewable energy in the grid by 2020 or 2030. The renewable energy potential of wind and solar far exceeds these targets, suggesting that renewable energy ultimately could grow well beyond these initial goals. The grid faces two new and fundamental technological challenges in accommodating renewables: location and variability. Renewable resources are concentrated at mid-continent far from population centers, requiring additional long distance, high-capacity transmission to match supply with demand. The variability of renewables due to the characteristics of weather is high, up to 70% for daytime solar due to passing clouds and 100% for wind on calm days, much larger than the relatively predictable uncertainty in load that the grid now accommodates by dispatching conventional resources in response to demand. Solutions to the challenges of remote location and variability of generation are needed. The options for DC transmission lines, favored over AC lines for transmission of more than a few hundred miles, need to be examined. Conventional high voltage DC transmission lines are a mature technology that can solve regional transmission needs covering one- or two-state areas. Conventional high voltage DC has drawbacks, however, of high loss, technically challenging and expensive conversion between AC and DC, and the requirement of a single point of origin and termination. Superconducting DC transmission lines lose little or no energy, produce no heat, and carry higher power density than conventional lines. They operate at moderate voltage, allowing many "on-ramps" and "off-ramps" in a single network and reduce the technical and cost challenges of AC to DC conversion. A network of superconducting DC cables overlaying the existing patchwork of conventional transmission lines would create an interstate highway system for electricity that moves large amounts of renewable electric power efficiently over long distances from source to load. Research and development is needed to identify the technical challenges associated with DC superconducting transmission and how it can be most effectively deployed. The challenge of variability can be met (i) by switching conventional generation capacity in or out in response to sophisticated forecasts of weather and power generation, (ii) by large scale energy storage in heat, pumped hydroelectric, compressed air or stationary batteries designed for the grid, or (iii) by national balancing of regional generation deficits and excesses using long distance transmission. Each of these solutions to variability has merit and each requires significant research and development to understand its capacity, performance, cost and effectiveness. The challenge of variability is likely to be met by a combination of these three solutions; the interactions among them and the appropriate mix needs to be explored. The long distances from renewable sources to demand centers span many of the grid's physical, ownership and regulatory boundaries. This introduces a new feature to grid structure and operation: national and regional coordination. The grid is historically a patchwork of local generation resources and load centers that has been built, operated and regulated to meet local needs. Although it is capable of sharing power across moderate distances, the arrangements for doing so are cumbersome and inefficient. The advent of renewable electricity with its enormous potential and inherent regional and national character presents an opportunity to examine the local structure of the grid and establish coordinating principles that will not only enable effective renewable integration but also simplify and codify the grid's increasingly regional and national character.

Crabtree, George; Misewich, Jim; Ambrosio, Ron; Clay, Kathryn; DeMartini, Paul; James, Revis; Lauby, Mark; Mohta, Vivek; Moura, John; Sauer, Peter; Slakey, Francis; Lieberman, Jodi; Tai, Humayun

2011-11-01

372

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

373

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

374

The BioGRID interaction database: 2015 update.  

PubMed

The Biological General Repository for Interaction Datasets (BioGRID: http://thebiogrid.org) is an open access database that houses genetic and protein interactions curated from the primary biomedical literature for all major model organism species and humans. As of September 2014, the BioGRID contains 749 912 interactions as drawn from 43 149 publications that represent 30 model organisms. This interaction count represents a 50% increase compared to our previous 2013 BioGRID update. BioGRID data are freely distributed through partner model organism databases and meta-databases and are directly downloadable in a variety of formats. In addition to general curation of the published literature for the major model species, BioGRID undertakes themed curation projects in areas of particular relevance for biomedical sciences, such as the ubiquitin-proteasome system and various human disease-associated interaction networks. BioGRID curation is coordinated through an Interaction Management System (IMS) that facilitates the compilation interaction records through structured evidence codes, phenotype ontologies, and gene annotation. The BioGRID architecture has been improved in order to support a broader range of interaction and post-translational modification types, to allow the representation of more complex multi-gene/protein interactions, to account for cellular phenotypes through structured ontologies, to expedite curation through semi-automated text-mining approaches, and to enhance curation quality control. PMID:25428363

Chatr-Aryamontri, Andrew; Breitkreutz, Bobby-Joe; Oughtred, Rose; Boucher, Lorrie; Heinicke, Sven; Chen, Daici; Stark, Chris; Breitkreutz, Ashton; Kolas, Nadine; O'Donnell, Lara; Reguly, Teresa; Nixon, Julie; Ramage, Lindsay; Winter, Andrew; Sellam, Adnane; Chang, Christie; Hirschman, Jodi; Theesfeld, Chandra; Rust, Jennifer; Livstone, Michael S; Dolinski, Kara; Tyers, Mike

2015-01-28

375

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

376

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

377

NREL Smart Grid Projects  

SciTech Connect

Although implementing Smart Grid projects at the distribution level provides many advantages and opportunities for advanced operation and control, a number of significant challenges must be overcome to maintain the high level of safety and reliability that the modern grid must provide. For example, while distributed generation (DG) promises to provide opportunities to increase reliability and efficiency and may provide grid support services such as volt/var control, the presence of DG can impact distribution operation and protection schemes. Additionally, the intermittent nature of many DG energy sources such as photovoltaics (PV) can present a number of challenges to voltage regulation, etc. This presentation provides an overview a number of Smart Grid projects being performed by the National Renewable Energy Laboratory (NREL) along with utility, industry, and academic partners. These projects include modeling and analysis of high penetration PV scenarios (with and without energy storage), development and testing of interconnection and microgrid equipment, as well as the development and implementation of advanced instrumentation and data acquisition used to analyze the impacts of intermittent renewable resources. Additionally, standards development associated with DG interconnection and analysis as well as Smart Grid interoperability will be discussed.

Hambrick, J.

2012-01-01

378

On the Coordinate System of Space-Weather HMI Active Region Patches (SHARPs): A Technical Note  

E-print Network

We describe the coordinate systems of two streams of HMI active region vector data. A distinction is made between (a) the 2D grid on which the field vector is measured (or sampled), and (b) the 3D coordinate established at each grid point, in which the field vector is presented. The HMI data reduction can involve coordinate changes on both, with those performed on the former termed "remapping", the latter "vector transformation". Relevant pipeline procedures are described. Useful examples are given for data analysis.

,

2013-01-01

379

Ion Accelerator With Negatively Biased Decelerator Grid  

NASA Technical Reports Server (NTRS)

Three-grid ion accelerator in which accelerator grid is biased at negative potential and decelerator grid downstream of accelerator grid biased at smaller negative potential. This grid and bias arrangement reduces frequency of impacts, upon accelerator grid, of charge-exchange ions produced downstream in collisions between accelerated ions and atoms and molecules of background gas. Sputter erosion of accelerator grid reduced.

Brophy, John R.

1994-01-01

380

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

381

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

382

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

383

The variational nodal method: A three-dimensional transport method in Cartesian, triangular, and hexagonal geometries  

SciTech Connect

The variational nodal method (VNM) has been generalized to three dimensions and used to solve a set of five criticality problems, in Cartesian, triangular, and hexagonal geometries. The code is implemented within the IDF 3D neutronics production code on a Cray-XMP. The first four benchmarks are taken from Takeda and Ikeda, and the last is a simplified sixth-core model of the Experimental Breeder Reactor II (EBR-II). Comparisons are made to various S[sub N] codes, the other nodal methods, and Monte Carlo reference solutions. The VNM is based on a variational principle whose Euler-Lagrange equation is the even-parity transport equation. Nodal balance is imposed through the odd-parity fluxes used as a Lagrange multiplier on nodal interfaces. Even- and odd-parity fluxes are expanded in a classical Ritz procedure with complete sets of orthogonal polynomials in space and angle. The VNM is cast in response matrix form, and the even- and odd-parity fluxes are replaced by partial current moments on the nodal interfaces.

Carrico, C.B.; Palmiotti, G. (Argonne National Lab., IL (United States)); Lewis, E.E. (Northwestern Univ., Evanston, IL (United States)); Mills, M.

1992-01-01

384

Coordination sequences and coordination waves in matter  

SciTech Connect

A possible way of partitioning a space into polycubes (n-dimensional modifications of Golomb polyominoes, which are generally nonconvex) is used as a basic model of ordered matter structure. It is suggested that layer-by-layer growth of a structure, occurring along the geodetics of the digraph of a net defined by the local rules of bonding of polycubes, justifies the phenomenological laws of shaping (self-similarity during the growth, independence of the polyhedron shape on the 'seed,' the symmetry of the growth polyhedron, etc.). Specific results of the analysis of number sequences of the increase in coordination circles for planar periodic partitions of model and real crystal structures, as well as the preliminary results of investigation of standing coordination topological waves, revealed for the first time in computer experiments, are reported.

Rau, V. G., E-mail: vgrau@mail.ru; Pugaev, A. A.; Rau, T. F. [Vladimir State Pedagogical University (Russian Federation)

2006-01-15

385

Information Power Grid Posters  

NASA Technical Reports Server (NTRS)

This document is a summary of the accomplishments of the Information Power Grid (IPG). Grids are an emerging technology that provide seamless and uniform access to the geographically dispersed, computational, data storage, networking, instruments, and software resources needed for solving large-scale scientific and engineering problems. The goal of the NASA IPG is to use NASA's remotely located computing and data system resources to build distributed systems that can address problems that are too large or complex for a single site. The accomplishments outlined in this poster presentation are: access to distributed data, IPG heterogeneous computing, integration of large-scale computing node into distributed environment, remote access to high data rate instruments,and exploratory grid environment.

Vaziri, Arsi

2003-01-01

386

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

387

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

388

Enabling Campus Grids with Open Science Grid Technology  

NASA Astrophysics Data System (ADS)

The Open Science Grid is a recognized key component of the US national cyber-infrastructure enabling scientific discovery through advanced high throughput computing. The principles and techniques that underlie the Open Science Grid can also be applied to Campus Grids since many of the requirements are the same, even if the implementation technologies differ. We find five requirements for a campus grid: trust relationships, job submission, resource independence, accounting, and data management. The Holland Computing Center's campus grid at the University of Nebraska-Lincoln was designed to fulfill the requirements of a campus grid. A bridging daemon was designed to bring non-Condor clusters into a grid managed by Condor. Condor features which make it possible to bridge Condor sites into a multi-campus grid have been exploited at the Holland Computing Center as well.

Weitzel, Derek; Bockelman, Brian; Fraser, Dan; Pordes, Ruth; Swanson, David

2011-12-01

389

The Coordinate Plane  

NSDL National Science Digital Library

This is a set of three, one-page problems about how astronomers use coordinate systems. Learners will plot a constellation on a coordinate plane and/or plot the route of Mars Science Lab (MSL aka Curiosity) on the surface of Mars. Options are presented so that students may learn about the MSL mission through a NASA press release or about the coordinate plane by viewing a NASA eClips video [7 min.]. This activity is part of the Space Math multi-media modules that integrate NASA press releases, NASA archival video, and mathematics problems targeted at specific math standards commonly encountered in middle school.

2014-03-19

390

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

391

An overset grid method for global geomagnetic induction  

NASA Astrophysics Data System (ADS)

A new finite difference solution to the global geomagnetic induction problem is developed and tested, based on a modified Lorenz gauge of the magnetic vector and electric scalar potentials and implementing a novel, overset `Yin-Yang' grid that avoids unnecessary mesh refinement at the geographic poles. Previously used in whole-earth mantle convection models, the overset grid is built from a pair of partially overlapping mid-latitude latitude-longitude (lat/lon) grids, one of which is rotated with respect to the other for complete coverage of the sphere. Because of this symmetry, only one set of finite difference templates is required for global discretization of the governing Maxwell equations, a redundancy that is exploited for computational efficiency and multithreaded parallelization. Comparisons between solutions obtained by the proposed method show excellent agreement with those obtained by independent integral equation methods for 1-D, 2-D and 3-D problem geometries. The computational footprint of the method is minimized through a (non-symmetric) matrix-free BiCG-STAB iterative solver which computes finite difference matrix coefficients `on the fly' as needed, rather than pulling stored values from memory. Scaling of the matrix-free BiCG-STAB algorithm with problem size shows behaviour similar to that seen with the (symmetric) QMR algorithm used in the Cartesian case from which the present algorithm is based. The proposed method may therefore provide a competitive addition to the existing body of global-scale geomagnetic induction modelling algorithms, allowing for resource-efficient forward modelling as the kernel for large-scale computing such as inversion of geomagnetic response functions, computational hypothesis testing and parametric studies of mantle geodynamics and physiochemical state.

Weiss, Chester J.

2014-07-01

392

FUTURE POWER GRID INITIATIVE GridOPTICSTM Power Networking,  

E-print Network

FUTURE POWER GRID INITIATIVE GridOPTICSTM Power Networking, Equipment, and Technology (powerNET) Testbed OBJECTIVE A lot of interest in research, improvements, and testing surrounds the power grid to these activities. Specifically, » power system equipment is expensive and has a high knowledge barrier

393

Embedding grids into grids: Techniques for large compression ratios  

Microsoft Academic Search

We return to the problem of embedding 2-dimensional (h ?á w ) guest grid graphs into 2dimensional (h ?á w ) host grid graphs, where w < w , and h is the smallest integer such thathw h w . This 2-dimensional problem has many applications in computer science including the simulationof one grid of processors by another of different

John A. Ellis

1996-01-01

394

Grid Interoperability: An Experiment in Bridging Grid Islands  

Microsoft Academic Search

In the past decade Grid computing has matured considerably. A number of groups have built, operated, and expanded large testbed and production Grids. These Grids have inevitably been designed to meet the needs of a limited set of initial stakeholders, resulting in varying and sometimes ad-hoc specifications. As the use of e-Science becomes more common, this inconsistency is increasingly problematic

Blair Bethwaite; David Abramson; Ashley Buckle

2008-01-01

395

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

396

Local Coordinates Model  

NSDL National Science Digital Library

The Local Coordinates model displays the position of a star in local (Altitude/Azimuth) coordinates. The horizon is shown along with the four cardinal directions (N, E, S, and W). The latitude of the observer is set at 35.5 degrees which sets the location of the north celestial pole (teal) relative to the northern horizon. The position of the star can be changed by using the Altitude and Azimuth sliders. The Local Coordinates 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_astronomy_Local Coordinates.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.

Belloni, Mario; Timberlake, Todd

2010-01-02

397

HR COMMUNICATIONS Program Coordinator  

E-print Network

HR COMMUNICATIONS Program Coordinator 51518 9254 04 VACANT University Business Administrator II TECHNOLOGY/ HR DATA MANAGEMENT/ COMMUNICATIONS RECORDS BENEFITS TIME & LABOR EMPLOYEE DATA MANAGEMENT EMPLOYMENT FACILITIES SATELLITE OFFICE EMPLOYEE & LABOR RELATIONS Director, Admin Svcs 55607 9250A 07 VACANT

Ronquist, Fredrik

398

Coordination Mechanisms George Christodoulou  

E-print Network

Coordination Mechanisms George Christodoulou Elias Koutsoupias Akash Nanavati§ Abstract We of Athens. Email: elias@di.uoa.gr § Computer Science Department, University of California Los Angeles. Email

Koutsoupias, Elias

399

APEC Smart Grid Initiative  

SciTech Connect

This brief paper describes the activities of the Asia Pacific Economic Cooperation (APEC) Smart Grid Initiative (ASGI) which is being led by the U.S. and developed by the APEC Energy Working Group. In the paper, I describe the origin of the initiative and briefly mention the four major elements of the initiative along with existing APEC projects which support it.

Bloyd, Cary N.

2012-03-01

400

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

401

Condor and the Grid  

Microsoft Academic Search

SUMMARY Since 1984, the Condor project has helped ordinary users to do extraordinary computing. Today, the project continues to explore the social and technical problems of cooperative computing on scales ranging from the desktop to the world-wide computational grid. In this chapter, we provide the history and philosophy of the Condor project and describe how it has interacted with other

Douglas Thain; Todd Tannenbaum; Miron Livny

2002-01-01

402

Condor and the grid  

Microsoft Academic Search

SUMMARY Since 1984, the Condor project has helped ordinary users to do extraordinary computing. Today, the project continues to explore the social and technical problems of cooperative computing on scales ranging from the desktop to the world-wide computational grid. In this chapter, we provide the history and philosophy of the Condor project and describe how it has interacted with other

Douglas Thain; Todd Tannenbaum; Miron Livny

2003-01-01

403

Stability of elastic grid shells  

E-print Network

The elastic grid shell is a solution that combines double curvature and ease of mounting. This structural system, based on the deformation of an initially at grid without shear stiffness was invented more than fifty years ...

Mesnil, Romain, M. Eng. Massachusetts Institute of Technology

2013-01-01

404

Luminescent lanthanide coordination polymers  

SciTech Connect

One-dimensional lanthanide coordination polymers with the formula Ln(isonicotinate){sub 3}(H{sub 2}O){sub 2} (Ln = Ce, Pr, Nd, Sm, Eu, Tb; 1a-f) were synthesized by treating nitrate or perchlorate salts of Ln(III) with 4-pyridinecarboxaldehyde under hydro(solvo)thermal conditions. Single-crystal and powder X-ray diffraction studies indicate that these lanthanide coordination polymers adopt two different structures. While Ce(III), Pr(III), and Nd(III) complexes adopt a chain structure with alternating Ln-(carboxylate){sub 2}-Ln and Ln-(carboxylate){sub 4}-Ln linkages, Sm(III), Eu(III), and Tb(III) complexes have a doubly carboxylate-bridged infinite-chain structure with one chelating carboxylate group on each metal center. In both structures, the lanthanide centers also bind to two water molecules to yield an eight-coordinate, square antiprismatic geometry. The pyridine nitrogen atoms of the isonicotinate groups do not coordinate to the metal centers in these lanthanide(III) complexes; instead, they direct the formation of Ln(III) coordination polymers via hydrogen bonding with coordinated water molecules. Photoluminescence measurements show that Tb(isonicotinate){sub 3}(H{sub 2}O){sub 2} is highly emissive at room temperature with a quantum yield of {approximately}90%. These results indicate that highly luminescent lanthanide coordination polymers can be assembled using a combination of coordination and hydrogen bonds. Crystal data for 1a: monoclinic space group P2{sub 1}/c, a = 9.712(2) {angstrom}, b = 19.833(4) {angstrom}, c = 11.616(2) {angstrom}, {beta} = 111.89(3){degree}, Z = 4. Crystal data for 1f: monoclinic space group C2/c, a = 20.253(4) {angstrom}, b = 11.584(2) {angstrom}, c = 9.839(2) {angstrom}, {beta} = 115.64(3){degree}, Z = 8.

Ma, L.; Evans, O.R.; Foxman, B.M.; Lin, W.

1999-12-13

405

Particle transport with unstructured grid on GPU  

NASA Astrophysics Data System (ADS)

The method of discontinuous finite element discrete ordinates which involves inverting an operator by iteratively sweeping across a mesh from multiple directions is commonly used to solve the time-dependent particle transport equation. Graphics Processing Unit (GPU) provides great faculty in solving scientific applications. The particle transport with unstructured grid bringing forward several challenges while implemented on GPU. This paper presents an efficient implementation of particle transport with unstructured grid under 2D cylindrical Lagrange coordinates system on a fine-grained data level parallelism GPU platform from three aspects. The first one is determining the sweep order of elements from different angular directions. The second one is mapping the sweep calculation onto the GPU thread execution model. The last one is efficiently using the on-chip memory to improve performance. As to the authors' knowledge, this is the first implementation of a general purpose particle transport simulation with unstructured grid on GPU. Experimental results show that the performance speedup of NVIDIA M2050 GPU with double precision floating operations ranges from 11.03 to 17.96 compared with the serial implementation on Intel Xeon X5355 and Core Q6600.

Gong, Chunye; Liu, Jie; Huang, Haowei; Gong, Zhenghu

2012-03-01

406

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

SciTech Connect

The purpose of this work is the development and testing of a new family of methods for calculating the spatial dependence of the neutron density in nuclear systems described in two-dimensional Cartesian geometry. The energy and angular dependence of the neutron density is approximated using the multigroup and discrete ordinates techniques respectively. The basic approach is to (1) approximate the spatial variation of the neutron source across each spatial subdivision as an expansion in terms of a user-supplied set of exponential basis functions; (2) solve analytically for the resulting neutron density inside each region; and (3) approximate this density in the basis function space in order to calculate the next iteration flux-dependent source terms. The three methods which were developed differ in the detail of the spatial description: (1) the first method expands the two-dimensional intranode neutron flux as two separable one-dimensional expansions in the x- and y-dimensions and represents the edge fluxes as constant; (2) the second method is the same as the first in the interior of each node, but represents the edge fluxes as one-dimensional expansions in the basis function set; and (3) the third method is the same as the second on the edges, but represents the interior flux shape in a full two-dimensional expansion in the x- and y-dependent basis functions. In order to test the accuracy versus computer time of the three methods, five sample problems were run and the results compared with those of the finite-difference code DOT4.2.

Pevey, R.E.

1982-01-01

407

75 FR 55947 - Coordinated Communications  

Federal Register 2010, 2011, 2012, 2013, 2014

...109 [Notice 2010-17] Coordinated Communications AGENCY: Federal Election Commission...regulations regarding coordinated communications. The Commission is issuing these...other issues involving the coordinated communications rules. DATES: These rules are...

2010-09-15

408

Smart Grid - a reliability perspective  

Microsoft Academic Search

Increasing complexity of power grids, growing demand, and requirement for greater grid reliability, security and efficiency as well as environmental and energy sustainability concerns continue to highlight the need for a quantum leap in harnessing communication and information technologies. This leap toward a ¿smarter¿ grid is now widely referred to as \\

Khosrow Moslehi; Ranjit Kumar

2010-01-01

409

Job Scheduling for Computational Grids  

Microsoft Academic Search

Grid computing is a method to execute computational jobs requiring a signifi- cant amount of computing resources and\\/or large sets of data. Contrary to large heteroge- neous distributed systems, a Computational Grid has many independent resource providers with different access policies. In addition to the size of such a Grid, the diversity of those policies leads to a very complex

Uwe Schwiegelshohn; Ramin Yahyapour

2006-01-01

410

Spectral methods on arbitrary grids  

NASA Technical Reports Server (NTRS)

Stable and spectrally accurate numerical methods are constructed on arbitrary grids for partial differential equations. These new methods are equivalent to conventional spectral methods but do not rely on specific grid distributions. Specifically, we show how to implement Legendre Galerkin, Legendre collocation, and Laguerre Galerkin methodology on arbitrary grids.

Carpenter, Mark H.; Gottlieb, David

1995-01-01

411

Enabling Applications on the Grid - A GridLab Overview  

NSDL National Science Digital Library

This paper on computational grid technology is scheduled to be published in the International Journal of High Performance Computing Applications in August 2003. The first part of the paper discusses the great potential of grid computing in scientific and business scenarios, as well as the challenges that must be overcome if it is to be more widely adopted. A specific grid architecture, called GridLab, is initially mentioned, but the second part of the paper goes into more detail about the system's design and implementation. The GridLab project is funded by the European Union.

Allen, Gabrielle.; Davis, Kelly.; Dolkas, Konstantinos N.; Doulamis, Nikolaos D.; Goodale, Tom.; Kielmann, Thilo.

2003-01-01

412

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

413

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

414

Cloud Computing for the Grid: GridControl: A Software Platform to Support the Smart Grid  

SciTech Connect

GENI Project: Cornell University is creating a new software platform for grid operators called GridControl that will utilize cloud computing to more efficiently control the grid. In a cloud computing system, there are minimal hardware and software demands on users. The user can tap into a network of computers that is housed elsewhere (the cloud) and the network runs computer applications for the user. The user only needs interface software to access all of the cloud’s data resources, which can be as simple as a web browser. Cloud computing can reduce costs, facilitate innovation through sharing, empower users, and improve the overall reliability of a dispersed system. Cornell’s GridControl will focus on 4 elements: delivering the state of the grid to users quickly and reliably; building networked, scalable grid-control software; tailoring services to emerging smart grid uses; and simulating smart grid behavior under various conditions.

None

2012-02-08

415

Workforce needs for smart grid technologies  

Microsoft Academic Search

The electrical power grids are going through some major changes and investments to secure reliable grid operation and more efficient and sustainable energy use. Smart grid technologies are key enablers to develop future grids. Securing a qualified workforce to adapt to the game changers in our industry, deploying smart grid technologies and managing the grid is essential to achieving industry

Damir Novosel

2011-01-01

416

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

417

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

418

Stability assessment of a multi-port power electronic interface for hybrid micro-grid applications  

NASA Astrophysics Data System (ADS)

Migration to an industrial society increases the demand for electrical energy. Meanwhile, social causes for preserving the environment and reducing pollutions seek cleaner forms of energy sources. Therefore, there has been a growth in distributed generation from renewable sources in the past decade. Existing regulations and power system coordination does not allow for massive integration of distributed generation throughout the grid. Moreover, the current infrastructures are not designed for interfacing distributed and deregulated generation. In order to remedy this problem, a hybrid micro-grid based on nano-grids is introduced. This system consists of a reliable micro-grid structure that provides a smooth transition from the current distribution networks to smart micro-grid systems. Multi-port power electronic interfaces are introduced to manage the local generation, storage, and consumption. Afterwards, a model for this micro-grid is derived. Using this model, the stability of the system under a variety of source and load induced disturbances is studied. Moreover, pole-zero study of the micro-grid is performed under various loading conditions. An experimental setup of this micro-grid is developed, and the validity of the model in emulating the dynamic behavior of the system is verified. This study provides a theory for a novel hybrid micro-grid as well as models for stability assessment of the proposed micro-grid.

Shamsi, Pourya

419

Using the LibCF/GRIDSPEC extensions to interpret data on mosaic grids with CDAT  

NASA Astrophysics Data System (ADS)

Increasingly earth system models perform computations on grids that are not describable as simple, rectangular arrays (e.g. lon by lat), instead requiring a mosaic of interacting, logically rectangular tiles. Such grids are developed for a variety of reasons that include removal of coordinate singularities that may degrade numerical reliability in a region of interest (e.g. the north pole in an ocean model) and increasing the uniformity of numerical precision over the globe. Coupled earth system models, typically characterized by independent coordinate reference systems for modeling atmosphere, ocean, ice, and terrestrial processes, are themselves examples of such mosaic grids. GRIDSPEC is a proposed set of conventions to the Climate and Forecast library (LibCF) describing data on mosaic grids developed by V. Balaji et al. (Geophysical Fluid Dynamics Laboratory). It supports unstructured assemblies of structured grids, including the cubed-sphere and tripolar meshes. Here we review a GRIDSPEC NetCDF format based on host, contact, grid, and data files. We will show how mosaic grids can be created from the ground up using a C API and the Python Climate Data Anaysis Tools (CDAT) for visualization. As an application we use GRIDSPEC to regrid cubed-sphere data onto a longitude-latitude grid.

Kindig, D.; Pletzer, A.; Balaji, V.; Hankin, S. C.; Hartnett, E. J.; Doutriaux, C.; Painter, J.; Sobol, A.; Wrobel, M.

2010-12-01

420

Generator Coordinate Truncations  

E-print Network

We investigate the accuracy of several schemes to calculate ground-state correlation energies using the generator coordinate technique. Our test-bed for the study is the $sd$ interacting boson model, equivalent to a 6-level Lipkin-type model. We find that the simplified projection of a triaxial generator coordinate state using the $S_3$ subgroup of the rotation group is not very accurate in the parameter space of the Hamiltonian of interest. On the other hand, a full rotational projection of an axial generator coordinate state gives remarkable accuracy. We also discuss the validity of the simplified treatment using the extended Gaussian overlap approximation (top-GOA), and show that it works reasonably well when the number of boson is four or larger.

K. Hagino; G. F. Bertsch; P. -G. Reinhard

2003-04-17

421

GridTool: A surface modeling and grid generation tool  

NASA Technical Reports Server (NTRS)

GridTool is designed around the concept that the surface grids are generated on a set of bi-linear patches. This type of grid generation is quite easy to implement, and it avoids the problems associated with complex CAD surface representations and associated surface parameterizations. However, the resulting surface grids are close to but not on the original CAD surfaces. This problem can be alleviated by projecting the resulting surface grids onto the original CAD surfaces. GridTool is designed primary for unstructured grid generation systems. Currently, GridTool supports VGRID and FELISA systems, and it can be easily extended to support other unstructured grid generation systems. The data in GridTool is stored parametrically so that once the problem is set up, one can modify the surfaces and the entire set of points, curves and patches will be updated automatically. This is very useful in a multidisciplinary design and optimization process. GridTool is written entirely in ANSI 'C', the interface is based on the FORMS library, and the graphics is based on the GL library. The code has been tested successfully on IRIS workstations running IRIX4.0 and above. The memory is allocated dynamically, therefore, memory size will depend on the complexity of geometry/grid. GridTool data structure is based on a link-list structure which allows the required memory to expand and contract dynamically according to the user's data size and action. Data structure contains several types of objects such as points, curves, patches, sources and surfaces. At any given time, there is always an active object which is drawn in magenta, or in their highlighted colors as defined by the resource file which will be discussed later.

Samareh-Abolhassani, Jamshid

1995-01-01

422

Accelerated Cartesian expansions - A fast method for computing of potentials of the form R- ? for all real ?  

NASA Astrophysics Data System (ADS)

The need to compute potentials of the form R- ? for ? ? 1 occur in a variety of areas ranging from electromagnetics to biophysics to molecular dynamics to astrophysics, etc. For instance, Coulomb, London, Lennard-Jones, H-bonds are of the form ?=1, 5, 6 (and 12), 10, respectively. For a systems with N source/observation points, the cost of computing these potentials scales proportional to O(N2). Methods to overcome this computational bottleneck have been a popular research topic for quite some time. For instance, the fast multipole method (FMM) and their cousins—tree codes—have revolutionized the computation of electrostatic potentials ( ? = 1). These methods rely on a hierarchical decomposition of the computational domain, i.e, construction of a regular oct-tree decomposition, and exploits the principle of divide and conquer to compute potentials at each observation point. This paper presents two methods, in the vein of FMM, albeit based on Cartesian tensors. The salient features of the first are as follows: (i) it relies on totally symmetric tensors and (ii) the errors are independent of the height of the tree. The second method is presented specifically for ? = 1, and relies on traceless totally symmetric Cartesian tensors. Using the relationship between traceless Cartesian tensors and spherical harmonics, it will be shown that this technique has the same computational cost as the classical FMM. Generalization of the second method for ? ? 1 is trivial; however, one needs to use totally symmetric tensors instead. Finally, in the whole computation scheme, only the translation operator (that used to traverse across the tree) depends on ?. Convergence of the proposed method is proven for all ??R. Numerical results that validate the cost and accuracy are presented for several potential functions; these include those typically encountered in the analysis of physical systems (Coulombic, Lennard-Jones, Lattice gas).

Shanker, B.; Huang, H.

2007-09-01

423

Spatial grid services for adaptive spatial query optimization  

NASA Astrophysics Data System (ADS)

Spatial information sharing and integration has now become an important issue of Geographical Information Science (GIS). Web Service technologies provide a easy and standard way to share spatial resources over network, and grid technologies which aim at sharing resources such as data, storage, and computational powers can help the sharing go deeper. However, the dynamic characteristic of grid brings complexity to spatial query optimization which is more stressed in GIS domain because spatial operations are both CPU intensive and data intensive. To address this problem, a new grid framework is employed to provide standard spatial services which can also manage and report their state information to the coordinator which is responsible for distributed spatial query optimization.

Gao, Bingbo; Xie, Chuanjie; Sheng, Wentao

2008-10-01

424

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

425

43rd AIAA Aerospace Sciences Meeting and Exhibit, 1013, January 2005, Reno, Nevada A Hybrid Cartesian Grid and Gridless Method for  

E-print Network

43rd AIAA Aerospace Sciences Meeting and Exhibit, 10­13, January 2005, Reno, Nevada A Hybrid for Applied Computational Sciences, Senior Member AIAA. Director, Center for Applied Computational Sciences, Associate Fellow AIAA. Professor, Institute for Computational Sciences and Informatics, Member AIAA

Löhner, Rainald

426

Block coordination copolymers  

DOEpatents

The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

Koh, Kyoung Moo; Wong-Foy, Antek G.; Matzger, Adam J.; Benin, Annabelle I.; Willis, Richard R.

2012-12-04

427

Block coordination copolymers  

DOEpatents

The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

Koh, Kyoung Moo; Wong-Foy, Antek G; Matzger, Adam J; Benin, Annabelle I; Willis, Richard R

2012-11-13

428

Coordinating Texas Water Research  

E-print Network

centers. #12;"Texas Panel on Water" Potential Activities 1. Regularly convene a panel of experts 2. ReviewCoordinating Texas Water Research Jay Banner and Eric Hersh Environmental Science Institute and Jackson School of Geosciences, The University of Texas at Austin CIESS Water Forum III October 14, 2013

Yang, Zong-Liang

429

Block coordination copolymers  

DOEpatents

The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

Koh, Kyoung Moo; Wong-Foy, Antek G; Matzger, Adam J; Benin, Annabelle I; Willis, Richard R

2014-11-11

430

Sex Equity Coordinator's Handbook.  

ERIC Educational Resources Information Center

This guidebook was designed to assist sex equity coordinators in the Los Angeles Community College District in promoting the recruitment, retention, and placement of students in vocational programs that are non-traditional for their sex. The guidebook's first ten chapters present: (1) outlines of relevant legislation and legal guidelines for…

Rubenstein, Dorothy; Sillman, Donna

431

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

432

Palantír: Coordinating Distributed Workspaces  

Microsoft Academic Search

Distributed software development suffers from limited collaboration capabilities, as developers are unable to easily coordinate their efforts across physical boundaries. Different fields, such as CSCW and groupware, have at- tempted to bridge this gap, but few of the approaches developed so far have been incorporated in current soft- ware development environments. Configuration Manage- ment (CM) systems are vital to any

Anita Sarma; André Van Der Hoek

2002-01-01

433

Coordinating author Maurizio Cocchi  

E-print Network

1 #12;2 Coordinating author Maurizio Cocchi Etaflorence Renewable Energies www.etaflorence.it Contributing authors Lars Nikolaisen Danish Technological Institute www.dti.dk Martin Junginger, Chun been taken when compiling the report, the authors disclaim any legal liability or responsibility

434

Coordinating chiral ionic liquids.  

PubMed

A practical synthesis of novel coordinating chiral ionic liquids with an amino alcohol structural motif was developed starting from commercially available amino alcohols. These basic chiral ionic liquids could be successfully applied as catalysts in the asymmetric alkylation of aldehydes and gave high enantioselectivities of up to 91% ee. PMID:24163003

Vasiloiu, Maria; Leder, Sonja; Gaertner, Peter; Mereiter, Kurt; Bica, Katharina

2013-12-14

435

Evaluating the Information Power Grid using the NAS Grid Benchmarks  

NASA Technical Reports Server (NTRS)

The NAS Grid Benchmarks (NGB) are a collection of synthetic distributed applications designed to rate the performance and functionality of computational grids. We compare several implementations of the NGB to determine programmability and efficiency of NASA's Information Power Grid (IPG), whose services are mostly based on the Globus Toolkit. We report on the overheads involved in porting existing NGB reference implementations to the IPG. No changes were made to the component tasks of the NGB can still be improved.

VanderWijngaartm Rob F.; Frumkin, Michael A.

2004-01-01

436

Journal of Grid Computing From Grids to Cloud Federations  

E-print Network

1 23 Journal of Grid Computing From Grids to Cloud Federations ISSN 1570-7873 Volume 11 Number 1 J Grid Computing (2013) 11:63-81 DOI 10.1007/s10723-012-9238-z Cloud Platform Datastore Support Navraj Computing (2013) 11:63­81 DOI 10.1007/s10723-012-9238-z Cloud Platform Datastore Support Navraj Chohan

Krintz, Chandra

437

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

438

Density-conserving shape factors for particle simulations in cylindrical and spherical coordinates  

NASA Technical Reports Server (NTRS)

It is established that a particle-to-grid weighting which is based on both conventional particle-in-cell (PIC) and cloud-in-cell (CIC) shape factors will yield nonuniform grid densities, even in the case of uniform particle distributions, in both cylindrical and spherical coordinates. In view of this, alternative density-conserving weighting schemes are discussed which encompass modified PIC and CIC weighting. These alternative shape factors are mathematically no more complicated than the conventional nondensity-conserving expressions.

Ruyten, Wilhelmus M.

1993-01-01

439

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

440

A grid quality manipulation system  

NASA Technical Reports Server (NTRS)

A grid quality manipulation system is described. The elements of the system are the measures by which quality is assessed, the computer graphic display of those measures, and the local grid manipulation to provide a response to the viewed quality indication. The display is an overlaid composite where the region is first covered with colors to reflect the values of the quality indicator, the grid is then placed on top of those colors, and finally a control net is placed on top of everything. The net represents the grid in terms of the control point form of algebraic grid generation. As a control point is moved, both the grid and the colored quality measures also move. This is a real time dynamic action so that the consequences of the manipulation are continuously seen.

Lu, Ning; Eiseman, Peter R.

1991-01-01

441

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

442

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

443

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

444

Grid Integration of Robotic Telescopes  

E-print Network

Robotic telescopes and grid technology have made significant progress in recent years. Both innovations offer important advantages over conventional technologies, particularly in combination with one another. Here, we introduce robotic telescopes used by the Astrophysical Institute Potsdam as ideal instruments for building a robotic telescope network. We also discuss the grid architecture and protocols facilitating the network integration that is being developed by the German AstroGrid-D project. Finally, we present three user interfaces employed for this purpose.

F. Breitling; T. Granzer; H. Enke

2009-03-23

445

Transistor oscillator and amplifier grids  

Microsoft Academic Search

Although quasi-optical techniques are applicable to a large variety of solid-state devices, special attention is given to transistors, which are attractive because they can be used as either amplifiers or oscillators. Experimental results for MESFET bar-grid and planar grid oscillators are presented. A MESFET grid amplifier that receives only vertically polarized waves at the input and radiates horizontally polarized waves

ROBERT M. WEIKLE; MOONIL KIM; JONATHAN B. HACKER; MICHAEL P. DE LISIO; ZOYA B. POPOVIC; DAVID B. RUTLEDGE

1992-01-01

446

The edutain@grid Project  

Microsoft Academic Search

edutain@grid is an exciting and ground breaking new project making use of Grid technology. The project will identify and define\\u000a a new class of applications that are highly significant for Grid computing but have not been studied in the past, which we\\u000a characterise as Real-Time Online Interactive Applications (ROIA). The distinctive features that make ROIA unique include large\\u000a user concurrency

Thomas Fahringer; Christoph Anthes; Alexis Arragon; Arton Lipaj; Jens Müller-iden; Christopher J. Rawlings; Radu Prodan; Mike Surridge

2007-01-01

447

Modelling the vertical thermal stratification in the North Sea - advantages of using adaptive coordinates  

NASA Astrophysics Data System (ADS)

The seasonal stratification in the North Sea which is characterised by a sharp summer thermocline oscillating on semi-diurnal (tidal and inertial) timescales has been studied in a numerical model (GETM) of the coupled system North Sea / Baltic Sea. The setup includes three nested grids: a 4 nm one for the North Atlantic, a 1 nm grid for the North Sea / Baltic Sea and a 600 m grid for the southern North Sea. The model results are analysed for the period 2003-2012. To validate the modelling system, point measurements but also vertical Scanfish-transect covering the entire North Sea are used. To assess the impact of the vertical coordinate system, a twin experiment is started: a) a run with fixed sigma-coordinates and b) a run with adaptive coordinates with an adaptation towards stratification. The differences are quantified in terms of Potential Energy Anomaly, bottom and surface temperature differences and numerical mixing. The results indicate that the adaptive coordinates show an excellent performance in reproducing the location of the thermocline and the temperature gradient across the thermocline. Whereas the sigma coordinates also match the thermocline-location, its vertical gradient is significantly underestimated. In the vicinity of the thermocline the adaptive coordinates allow for a vertical grid spacing of down to 5-10 cm, which is hardly feasible in classical vertical coordinate systems. Additionally, the minimum vertical viscosity/diffusivity at the thermocline is one order of magnitude lower than for sigma coordinates. Transforming the vertical gradient and diffusivity into a vertical flux gives higher values for sigma coordinates and allow for an higher exchange across the thermocline. Here the results for the adaptive coordinates show the expected blocking behaviour. The better representation of vertical gradients by using adaptive coordinates reduces the numerical mixing and thus the artificial effects of the numerics. Since the adaptive coordinates are spatially and temporal varying, they allow for the oscillation of the coordinate lines with the moving thermocline due to internal waves or internal tides. This gives lower values of numerical mixing. The total stratified area during the summer does not vary much between the two runs. Only in the southern part of the North Sea significant differences are visible. Our results show that vertical adaptive coordinates are beneficial in modelling regions with spatial and temporal varying stratification. Although the adaptive coordinates introduce computational overhead of roughly 10% for hydrodynamic runs, this is compensated by the excellent performance in reproducing vertical gradients. Moreover, the overhead is negligible in biogeochemical applications where most of the computational time is spend in the advection routines.

Gräwe, Ulf; Holtermann, Peter; Klingbeil, Knut; Burchard, Hans

2013-04-01

448

New Global Bathymetry and Topography Model Grids  

NASA Astrophysics Data System (ADS)

A new version of the "Smith and Sandwell" global marine topography model is available in two formats. A one-arc-minute Mercator projected grid covering latitudes to +/- 80.738 degrees is available in the "img" file format. Also available is a 30-arc-second version in latitude and longitude coordinates from pole to pole, supplied as tiles covering the same areas as the SRTM30 land topography data set. The new effort follows the Smith and Sandwell recipe, using publicly available and quality controlled single- and multi-beam echo soundings where possible and filling the gaps in the oceans with estimates derived from marine gravity anomalies observed by satellite altimetry. The altimeter data have been reprocessed to reduce the noise level and improve the spatial resolution [see Sandwell and Smith, this meeting]. The echo soundings database has grown enormously with new infusions of data from the U.S. Naval Oceanographic Office (NAVO), the National Geospatial-intelligence Agency (NGA), hydrographic offices around the world volunteering through the International Hydrographic Organization (IHO), and many other agencies and academic sources worldwide. These new data contributions have filled many holes: 50% of ocean grid points are within 8 km of a sounding point, 75% are within 24 km, and 90% are within 57 km. However, in the remote ocean basins some gaps still remain: 5% of the ocean grid points are more than 85 km from the nearest sounding control, and 1% are more than 173 km away. Both versions of the grid include a companion grid of source file numbers, so that control points may be mapped and traced to sources. We have compared the new model to multi-beam data not used in the compilation and find that 50% of differences are less than 25 m, 95% of differences are less than 130 m, but a few large differences remain in areas of poor sounding control and large-amplitude gravity anomalies. Land values in the solution are taken from SRTM30v2, GTOPO30 and ICESAT data. GEBCO has agreed to adopt this model and begin updating it in 2009. Ongoing tasks include building an uncertainty model and including information from the latest IBCAO map of the Arctic Ocean.

Smith, W. H.; Sandwell, D. T.; Marks, K. M.

2008-12-01

449

Introduction to CamGrid  

E-print Network

details (2) Responsibility of individual pools to authenticate local submitters. Need to trust root on remote machine, especially for Standard Universe. There’s no shared FS across CamGrid, but Parrot (from the Condor project) is a nice user-space file... Introduction to CamGrid Mark Calleja Cambridge eScience Centre www.escience.cam.ac.uk Why grids? The idea comes from electricity grids: you don’t care which power station your kettle’s using. Also, there are lots of underutilised resources around...

Calleja, Mark

2008-06-26

450

Abstract A Self-Organising Federation of Alchemi Desktop Grids  

E-print Network

Desktop grids presents a next generation platform for aggregating the idle processing cycles of desktop computers. However, in order to efficiently harness the power of millions of desktop computers, the systems or middlewares that can support high level of efficiency, scalability, robustness and manageability are required. In this paper, we propose a scalable and self-organising desktop grid system, Alchemi-Federation, which uses a Peer-to-Peer (P2P) network model for discovering and coordinating the provisioning of distributed Alchemi grids. Alchemi grids self-organise based on a structured P2P routing overlay that maintains a d-dimensional index for resource discovery. The unique features of Alchemi-Federation are: (i) Internet-based federation of distributed Alchemi grids; (ii) implementation of a P2P publish/subscribe based resource indexing service that makes the system highly scalable; and (iii) implementation of a P2P tuple space-based distributed load-balancing algorithm. 1

Rajiv Ranjan; Xingchen Chu; Carlos A. Queiroz; Aaron Harwood; Rajkumar Buyya

451

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. 

452

Conformal Fermi Coordinates  

E-print Network

Fermi Normal Coordinates (FNC) are a useful frame for isolating the locally observable, physical effects of a long-wavelength spacetime perturbation. Their cosmological application, however, is hampered by the fact that they are only valid on scales much smaller than the horizon. We introduce a generalization that we call Conformal Fermi Coordinates (CFC). CFC preserve all the advantages of FNC, but in addition are valid outside the horizon. They allow us to calculate the coupling of long- and short-wavelength modes on all scales larger than the sound horizon of the cosmological fluid, starting from the epoch of inflation until today, by removing the complications of the second order Einstein equations to a large extent, and eliminating all gauge ambiguities. As an application, we present a calculation of the effect of long-wavelength tensor modes on small scale density fluctuations. We recover previous results, but clarify the physical content of the individual contributions in terms of locally measurable ef...

Dai, Liang; Schmidt, Fabian

2015-01-01

453

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

454

Grid Task Execution  

NASA Technical Reports Server (NTRS)

IPG Execution Service is a framework that reliably executes complex jobs on a computational grid, and is part of the IPG service architecture designed to support location-independent computing. The new grid service enables users to describe the platform on which they need a job to run, which allows the service to locate the desired platform, configure it for the required application, and execute the job. After a job is submitted, users can monitor it through periodic notifications, or through queries. Each job consists of a set of tasks that performs actions such as executing applications and managing data. Each task is executed based on a starting condition that is an expression of the states of other tasks. This formulation allows tasks to be executed in parallel, and also allows a user to specify tasks to execute when other tasks succeed, fail, or are canceled. The two core components of the Execution Service are the Task Database, which stores tasks that have been submitted for execution, and the Task Manager, which executes tasks in the proper order, based on the user-specified starting conditions, and avoids overloading local and remote resources while executing tasks.

Hu, Chaumin

2007-01-01

455

Three-dimensional surface grid generation for calculation of thermal radiation shape factors  

NASA Technical Reports Server (NTRS)

A technique is described to generate three dimensional surface grids suitable for calculating shape factors for thermal radiative heat transfer. The surface under consideration is approximated by finite triangular elements generated in a special manner. The grid is generated by dividing the surface into a two dimensional array of nodes. Each node is defined by its coordinates. Each set of four adjacent nodes is used to construct two triangular elements. Each triangular element is characterized by the vector representation of its vertices. Vector algebra is used to calculate all desired geometric properties of grid elements. The properties are used to determine the shape factor between the element and an area element in space. The grid generation can be graphically displayed using any software with three dimensional features. DISSPLA was used to view the grids.

Aly, Hany M.

1992-01-01

456

Spherical Polar Coordinates  

NSDL National Science Digital Library

This applet displays a point or an volume in three dimensions using spherical coordinates. The user can change the radius and angles and move the point of view. It should be noted that the author uses a different naming convention for the angles than is common for physics in the United States, using θ for the azimuthal angle and φ for the polar angle. This is part of a large collection of physics and math applets by the author.

Reddy, Surendranath

2011-06-17

457

Online Market Coordination  

Microsoft Academic Search

The aim of this paper is to deal with the problem of coordination for online markets where a seller registers to an online\\u000a market to sell an item. The seller and the owner of the market then form an alliance to generate revenue through online sales.\\u000a However, the efficiency and stability of the alliance highly relies on the contract that

Masabumi Furuhata; Dongmo Zhang; Laurent Perrussel

2008-01-01

458

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

459

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

460

Data mining on grids. Maarten Altorf  

E-print Network

Miner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.2 WekaG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4.3 Weka4WS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 4.4 DataMiningGrid . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 4.5 GridWeka 2. The follow- ing applications are taken into consideration: GridMiner, WekaG, Weka4WS, DataMiningGrid and GridWeka

Emmerich, Michael

461

Smart Grid Technologies: Communication Technologies and Standards  

Microsoft Academic Search

For 100 years, there has been no change in the basic structure of the electrical power grid. Experiences have shown that the hierarchical, centrally controlled grid of the 20th Century is ill-suited to the needs of the 21st Century. To address the challenges of the existing power grid, the new concept of smart grid has emerged. The smart grid can

Vehbi C. Gungor; Dilan Sahin; Taskin Kocak; Salih Ergut; Concettina Buccella; Carlo Cecati; Gerhard P. Hancke

2011-01-01

462